BATTERY SEPARATORS COMPRISING CHEMICAL ADDITIVES
FIELD OF INVENTION
The present embodiments relate generally to non- woven webs, and specifically,
to non-woven webs that can be used as battery separators for batteries, such as lead acid
batteries.
BACKGROUND
10 Batteries convert stored chemical energy into electrical energy and are commonly
used as energy sources. Typically, a battery comprises one or more electrochemical cells
including a negative electrode, a positive electrode, an electrolyte, and a battery
separator. Battery separators are a critical component in many batteries. The battery
separator mechanically and electrically isolates the negative and positive electrodes,
15 while also allowing ions in the electrolyte to move between the electrodes.
Battery separators should be chemically, mechanically, and electrochemically
stable under the strongly reactive environpartiments in the battery during operation,
should not adversely interact with the electrolyte and/or electrode materials, and have no
deleterious effect on of the battery’s performance (e.g., energy production, cycle life,
20 safety). For example, the battery separator should not degrade, leach harmful
components, react in a negative way with the electrode materials, allow short circuits to
form between the electrodes, and/or crack or break during battery assembly and/or
operation. Though many battery separators exist, improvements in the stability of
battery separators and/or battery separators that lead to enhanced battery performance are
25 needed.
SUMMARY
In one set of embodiments, battery separators are provided. In one embodiment,
a battery separator comprises a non-woven web comprising a plurality of glass fibers
30 having an average diameter of greater than or equal to about 0.1 microns and less than or
equal to about 15 microns, wherein the glass fibers are present in an amount of greater
than or equal to about 2 wt.% and less than or equal to about 95 wt.% of the non-woven
web, and one or more sulfate salts, wherein the one or more sulfate salts are present in an
2
amount of greater than or equal to about 0.1 wt.% and less than or equal to 30 wt.% of
the battery separator prior to contact with a battery electrolyte.
In another embodiment, a battery separator comprises a non-woven web
comprising a plurality of glass fibers having an average diameter of greater than or equal
to about 0.1 microns and less than or equal to about 15 microns, w 5 herein the glass fibers
are present in an amount of greater than or equal to about 2 wt.% and less than or equal
to about 95 wt.% of the non-woven web, and one or more antioxidants, wherein the
antioxidants are present in an amount of greater than or equal to about 0.05 wt.% and
less than or equal to about 5 wt.% of the battery separator.
10 In one embodiment, a battery separator comprises a non-woven web comprising a
plurality of glass fibers having an average diameter of greater than or equal to about 0.1
microns and less than or equal to about 15 microns, wherein the glass fibers are present
in an amount of greater than or equal to about 2 wt.% and less than or equal to about 95
wt.% of the non-woven web and a plurality of synthetic fibers, wherein the synthetic
15 fibers are present in an amount of greater than or equal to about 1 wt.% and less than or
equal to about 80 wt.% of the non-woven web. The battery separator also comprises a
plurality of inorganic particles, wherein the inorganic particles are resistant to sulfuric
acid, and wherein the inorganic particles are present in the non-woven web in an amount
of greater than or equal to about 10 wt.% and less than or equal to about 80 wt.% of the
20 non-woven web, and one or more rubbers, wherein the one or more rubbers are present
in the battery separator in an amount of greater than or equal to about 3 wt.% and less
than or equal to about 80 wt.% of the battery separator.
Other advantages and novel features of the present invention will become
apparent from the following detailed description of various non-limiting embodiments of
25 the invention when considered in conjunction with the accompanying figures. In cases
where the present specification and a document incorporated by reference include
conflicting and/or inconsistent disclosure, the present specification shall control. If two
or more documents incorporated by reference include conflicting and/or inconsistent
disclosure with respect to each other, then the document having the later effective date
30 shall control.
BRIEF DESCRIPTION OF THE DRAWINGS
Non-limiting embodiments of the present invention will be described by way of
3
example with reference to the accompanying figure, which is schematic and is not
intended to be drawn to scale. In the figure, each identical or nearly identical component
illustrated is typically represented by a single numeral. For purposes of clarity, not every
component is labeled, nor is every component of each embodiment of the invention
shown where illustration is not necessary to allow those 5 of ordinary skill in the art to
understand the invention. In the figures:
FIG. 1 is a schematic diagram of a battery separator including a non-woven web
according to one set of embodiments;
FIG. 2A is a schematic diagram showing a cross section of a non-woven web
10 including a plurality of fibers according to one set of embodiments;
FIG. 2B is a schematic diagram showing a cross section of a non-woven web
including fibers that are partially coated with a resin including an additive according to
one set of embodiments;
FIG. 2C is a schematic diagram showing a cross section of a non-woven web in
15 which substantially all of the fibers are coated with a resin including an additive
according to one set of embodiments;
FIG. 2D is a schematic diagram showing a cross section of a non-woven web that
is partially coated with an additive according to one set of embodiments;
FIG. 3A is a schematic diagram of the thickness and overall thickness of a planar
20 layer that can be included in a battery separator according to one set of embodiments;
FIG. 3B is a schematic diagram of the thickness and overall thickness of a nonplanar
layer that can be included in a battery separator according to one set of
embodiments;
FIGs. 4A-4D are schematic diagrams showing different battery arrangements
25 according to one set of embodiments; and
FIGs. 5A-5D are schematics of a battery separator and an electrode, according to
one set of embodiments.
DETAILED DESCRIPTION
30 Battery separators are provided. In some embodiments, the battery separators
may comprise a non-woven web including one or more chemical additives. The
chemical additives may impart beneficial properties, such as enhanced separator stability
and/or battery performance. In some embodiments, the chemical additive(s) may confer
4
resistance to oxidation, heavy metal deposition, and/or formation of short circuits. For
example, a lead acid battery separator may comprise a non-woven web that includes one
or more sulfate salts. The sulfate salts may prevent internal shorts by inhibiting the
dissolution of metallic compounds, such as lead sulfate, within the separator. As another
example, a lead acid battery separator may comprise 5 rubber and/or one or more
antioxidants. The rubber may scavenge certain heavy metals (e.g., antimony) that might
otherwise deposit on the surface of a battery electrode and reduce battery performance.
The antioxidant may prevent degradation of the non-woven web in the caustic battery
environment by inhibiting the oxidation of organic material in the non-woven web. The
10 respective characteristics and amounts of the chemical additive(s) may be selected to
impart desirable properties while having relatively minimal or no adverse effects on
another property of the battery separator and/or the overall battery.
In some embodiments, a battery separator described herein may comprise a layer
having a relatively low apparent density; for example, the density that includes any
15 unoccupied space within the outermost boundaries of the layer may be relatively low.
The low apparent density may be attributed to, at least in part, the geometry of the layer.
For instance, in some embodiments, the layer may include undulations and/or have at
least one non-planar surface (e.g., a corrugated layer; an embossed layer), as described in
more detail below. In some embodiments, a battery comprising a layer having a
20 relatively low apparent density may have desirable properties, including relatively low
electrical resistance and/or relatively high capacity.
The battery separators described herein may be well suited for a variety of battery
types, including lead acid batteries.
In a typical battery, the battery separator primarily functions to electrically and
25 mechanically isolate the negative electrode and positive electrode, while allowing ionic
conduction. However, the presence of the battery separator between the electrodes can
affect battery performance (e.g., electrical resistance, lifetime). For instance, the battery
separator generally increases the resistance to ion movement between the electrodes
compared to the electrolyte alone and thus increases the electrical resistance of the
30 battery. Moreover, the battery separator can reduce the amount of electrolyte between
the electrodes compared to the electrolyte alone for a given volume between the
electrodes), due to the volume occupied by the battery separator. This reduction of
electrolyte can limit the battery capacity.
5
In general, the chemical (e.g., composition, stability, wettability), structural (e.g.,
porosity, pore size, thickness, permeability), and/or mechanical (e.g., strength, stiffness)
properties of the battery separator can affect battery performance (e.g. electrical
resistance, lifetime). In some battery applications, a trade-off exists between the
properties of the battery separator that provide sufficient 5 isolation and/or ion movement,
and battery performance. For instance, a battery separator having a sufficient porosity to
allow for ion mobility may be brittle and result in early battery failure due to damage to
the separator. The balance of separator and battery performance is further aggravated in
battery applications that utilize highly reactive operating conditions, such as lead acid
10 batteries. In such applications, the chemical, mechanical, and electrochemical stability
of the battery separator may be important design parameters to be balanced with
separator and battery performance. Often, conventional battery separators are designed
to have desirable stability, separation performance, or battery performance at the expense
of one or more other properties such as stability, separation performance, and/or battery
15 performance. For example, some conventional battery separators have attempted to
minimize the influence of the battery separator on capacity and electrical resistance by
reducing the mass of the battery separator to increase the volume porosity. However, the
tradeoff between mass and mechanical stability can limit this approach. Accordingly,
there is a need for improved battery separators.
20 In the present disclosure, battery separators are provided. In some embodiments,
a battery separator may include a layer (e.g., non-woven web) comprising one or more
chemical additives, and/or that has at least one non-planar surface (e.g., a shaped layer,
or a layer that includes undulations or other surface topography, as described herein).
Such a layer may be used alone, or in combination with an additional layer, in a battery
25 separator as described herein. The chemical additive(s) and/or layer shape/topography
can be used to impart desirable properties to the battery separator and/or overall battery
(e.g. stability, separation performance, battery performance). For instance, in some
embodiments involving a battery comprising a layer that includes undulations and/or has
at least one non-planar surface (i.e., a non-planar layer) positioned between two
30 electrodes, the shape of the layer may increase the void volume between the electrodes
resulting in a decrease in electrical resistance and dendrite formation. In certain
embodiments, these desirable properties can be imparted while having little or no
adverse effects on another property of the battery separator and/or overall battery.
6
In some such embodiments, a battery separator comprising a layer (e.g., nonwoven
web) described herein does not suffer from one or more limitations of certain
existing battery separators. For instance, in some embodiments involving a battery
separator that includes a beneficial component that is susceptible to an adverse
interaction with a species (e.g., acid generated radical) in the 5 electrolyte, the battery
separator may include a chemical additive (e.g., an antioxidant) capable of complexing
and/or neutralizing the adverse species. The inclusion of such a chemical additive can
allow the battery separator to include an adequate percentage of the susceptible
component (e.g., rubber) without (or minimally) negatively impacting battery
10 performance. As described further below, such a battery separator may include, in some
embodiments, a non-woven web comprising glass fibers and one or more chemical
additives (e.g., sulfate salts, rubber, antioxidants). In certain embodiments, the nonwoven
web may optionally include a binder resin, synthetic fibers, inorganic particles,
and/or other components as described herein.
15 A non-limiting example of a battery separator including a non-woven web is
shown schematically in FIG. 1. In some embodiments, a battery separator 5 may include
a non-woven web 6. In some embodiments, a non-woven web 6 includes one or more
chemical additives. In certain embodiments, non-woven web 6 may be a non-planar
layer. In some instances, the battery separator may be a non-woven web that is a non20
planar layer including one or more chemical additive(s). In some embodiments, the
battery separator may be a single layer (e.g., the separator does not include layers 7 or 8
in FIG. 1). For instance, the battery separator may be formed of a single non-woven
web.
In other embodiments, the battery separator may comprise multiple layers. The
25 multi-layer battery separator may include at least one non-woven web (e.g., at least two
non-woven webs, at least three non-woven webs). In some embodiments, the at least one
non-woven web may have one or more non-planar surfaces and/or may include one or
more chemical additive(s), as described herein. In some embodiments, in addition to
non-woven web 6, the battery separator may include an optional layer 7 and/or 8 (e.g.,
30 additional layers), which may be adjacent the non-woven web. The additional layer may
be planar or non-planar as described herein.
For instance, in one particular embodiment, the battery separator may comprise a
non-planar, non-woven layer 6, a layer 7 (e.g., non-woven web) (that may, for example,
7
allow even pressure distribution of non-woven layer 6 in a battery configuration), and a
non-woven web 8. In some such cases, layer 7 may be a non-planar, non-woven layer
having a relatively high Gurley stiffness (e.g., greater than or equal to about 500 mg and
less than or equal to about 5000 mg, greater than or equal to about 800 to less than or
equal to about 1200 mg). Such a layer may have, in some 5 embodiments, substantially
the same or similar attributes as non-woven layer 6 (e.g., chemical stability, volume
porosity). However, other configurations are also possible. In some embodiments in
which non-woven layer 6 is non-planar, layer 7 may be a planar layer. For instance, in
one embodiment, layer 7 may be the planar version of non-woven layer 6. In other
10 embodiments, optional layer 7 and/or 8 may be a non-planar layer. In general, any layer
of the battery separator may be non-planar and/or may include one or more chemical
additives, as described herein.
In general, a layer within a battery separator, including any optional layer(s) (e.g.,
additional layer(s)) should be stable in a battery environment, have sufficient porosity to
15 allow for sufficient ionic conduction, and have a suitable thickness. For instance, in a
lead acid battery, the layer(s) may have an acid weight loss of less than 5% according to
the standard BCI 03-A. As used herein, acid weight loss refers to the percent of weight
loss due to acid erosion, as described in more detail below. In certain embodiments, the
layer(s), including the optional layer(s), may have a porosity of greater than or equal to
20 about 10% and less than or equal to about 99% (e.g., greater than or equal to about 65%
and less than or equal to about 95%) and a thickness of greater than or equal to about 0.1
mm and less than or equal to about 3 mm (e.g., greater than or equal to about 0.1 mm and
less than or equal to about 3 mm). It should be appreciated, however, that other ranges
of acid weight loss, porosity, and/or thickness are possible.
25 In some embodiments, one or more optional layers (e.g., additional layers) may
be a non-woven web. For instance, in some embodiments a second non-woven web may
be present in the battery separator. In certain embodiments, the optional layer may be a
planar layer having a relatively low apparent density (e.g., an open layer), as described
herein. Non-limiting examples of optional/additional layers include non-woven webs
30 formed of long, coarsely drawn individual glass fibers (e.g., having a fiber diameter of
greater than about 13 microns) bonded with an adhesive in the parallel direction (e.g., a
sliver), rovings (e.g., a long fiber adhesive-bonded non-woven web used for insulation),
braids, spacer fabrics (e.g., layers separated by a system of rigid support members
8
running perpendicular to the outer surfaces), corduroy fabrics, ribbed knits, porous
membranes, functionalized needle punched and hydroentangled non-woven webs, and
nets (e.g., synthetic expanded mesh). Woven webs can also be used. In other
embodiments, one or more optional layers (e.g., additional layers) may be an extruded
layer (e.g., a non-fibrous layer). Other types 5 of layers are also possible.
As used herein, when a layer is referred to as being “adjacent” another layer, it
can be directly adjacent to the layer, or an intervening layer also may be present. A layer
that is “directly adjacent” another layer means that no intervening layer is present.
In some embodiments, one or more layer in the battery separator may be
10 designed to be discrete from another layer. That is, the components (e.g., fibers) from
one layer do not substantially intermingle (e.g., do not intermingle at all) with
components (e.g., fibers) from another layer. For example, with respect to FIG. 1, in one
set of embodiments, fibers from non-woven web 6 do not substantially intermingle with
fibers of optional layer 8. Discrete layers may be joined by any suitable process
15 including, for example, lamination, thermo-dot bonding, calendering, ultrasonic
processes, or by adhesives, as described in more detail below. It should be appreciated,
however, that certain embodiments may include one or more layers that are not discrete
with respect to one another.
It should be understood that the configurations of the layers shown in the figures
20 are by way of example only, and that in other embodiments, battery separators including
other configurations of layers may be possible. For example, while the optional layers
are shown in a specific order in FIG. 1, other configurations are also possible. For
example, optional layer 7 may be positioned between the non-woven web and optional
layer 8. Furthermore, in some embodiments, additional layers may be present in addition
25 to the ones shown in the figures. It should also be appreciated that not all components
shown in the figures need be present in some embodiments.
As described herein, a battery separator comprising a non-woven web may
include one or more chemical additives. The chemical additive(s) may be associated
with the non-woven web in any suitable manner. The chemical additive(s) may be, for
30 example, immobilized on at least a portion of the non-woven web and/or on or within a
carrier (e.g., a coating, a particle) present in the non-woven web. For example, in some
embodiments an additive is encapsulated (e.g., partially or fully) within a coating on at
least a portion of the non-woven web. In some embodiments, the chemical additive(s)
9
may be part of a binder resin that is coated on the non-woven web. In certain
embodiments, the chemical additive(s) may be coated on at least portions of the nonwoven
web without a resin. In some instances, the chemical additive(s) may be noncovalently
attached (e.g., adsorbed) to one or more components of the non-woven web,
such as fibers, a resin, and/or inorganic particles 5 within the non-woven web. Covalent
attachment or ionic attachment of a chemical additive to a portion of the non-woven web
is also possible. In some cases, a chemical additive is attached to a portion of a fiber
web through electrostatic interactions. Other configurations are also possible.
A non-limiting example of a non-woven web coated with a chemical additive is
10 shown in FIG. 2. Examples of chemical additives are provided below. As shown
illustratively in FIG. 2A, a non-woven web 10, shown in cross-section, may include a
plurality of fibers 15 (e.g., glass fibers, glass fibers and synthetic fibers). In some
instances, non-woven web 10 may also comprise a plurality of inorganic particles 18
(e.g., sulfuric acid-resistant inorganic particles). In embodiments in which the chemical
15 additive is part of a binder resin, all or portions of the non-woven web may be coated
with a binder resin comprising chemical additive 22 distributed therein, which is shown
illustratively in FIGs. 2B-2C. The binder resin, with chemical additive distributed
within, may remain on the non-woven web after the non-woven web has been coated and
dried. In other embodiments, all or portions of the non-woven web may be coated with
20 chemical additive 22 absent a binder resin, as shown illustratively in FIG. 2D.
In one set of embodiments, a coating including a chemical additive may be
formed on one or more sides or surfaces of the non-woven web. In other embodiments,
the chemical additive may be applied to the non-woven web to produce a coating 20 on
at least a portion of the fibers and/or other components (e.g., inorganic particles) in the
25 interior of the non-woven web (i.e., through the thickness of the non-woven web). In
certain embodiments, substantially all of the fibers of the non-woven web may be coated
with the chemical additive, as illustrated in FIG. 2C. However, in some embodiments,
not all fibers and/or other components of the non-woven web are coated, e.g., as
illustrated in FIG. 2B. In some embodiments, regardless of whether the surface and/or
30 interior of the non-woven web are coated, the chemical additive and/or binder resin
components may absorb into the surface of the fibers and/or other components of the
non-woven web. In some embodiments, at least one of coated non-woven webs 25, 30,
and 40, shown in FIGs. 2B, 2C, and 2D, respectively, may be included in a battery
10
separator and may have enhanced chemical stability and battery performance as
described herein.
A design of a battery separator that produces desirable separator performance,
battery performance, and/or chemical stability is difficult to achieve for batteries having
highly reactive operating conditions. For instance, i 5 n some embodiments, battery
separators having the requisite chemical stability may only be formed from a limited
number of materials and/or may be required to have a certain structure. Conversely,
separators that produce excellent battery performance may be susceptible to degradation
and/or adverse chemical reaction in a highly reactive battery environment. Certain
10 features of a battery separator described herein will now be described in the context of an
exemplary application: lead acid batteries. Lead acid batteries are used herein as one
example of a battery that has highly reactive operating conditions. It should be
understood, however, that the battery separators described herein may be suitable for a
wide variety of applications and are not limited to use in lead acid batteries.
15 Lead acid batteries comprise a positive electrode comprising lead dioxide (PbO2),
and negative electrode comprising metallic lead, and an electrolyte comprising a high
molarity aqueous sulfuric acid solution. In some embodiments, the positive electrode
and/or negative electrode may contain a lead alloy comprising a heavy metal, such as
antimony for processing into grids and/or plates. The caustic battery environment may
20 lead to reactions that liberate at least a portion of the heavy metal from one or more
electrodes into the electrolyte. The heavy metal may undergo subsequent reactions in the
electrolyte and/or deposit on the surface of an electrode, adversely altering battery
performance. For example, antimony may be released from the positive electrode as the
grid material is oxidized or corroded, migrate to the negative electrode due to the
25 attraction of heavy metals to the negative plate, and deposit on the surface of the negative
electrode in metallic form as it is attracted by electrochemical potential. The presence of
the antimony on the negative electrode may alter the voltage at which the electrolysis of
water occurs in the lead acid battery. As a result, during charging of the battery,
electrolysis of water may occur more readily at an electrode having heavy metal deposits
30 and more water consumption (or loss) may occur during battery operation. Increased
water consumption may lead to high sulfuric acid concentration that may preclude
effective recharging, reduced electrolyte quantity in cell, and/or accelerate grid
corrosion. This may also necessitate more frequent maintenance of battery through
11
watering. The highly acidic environment can also produce radicals that are capable of
degrading organic material, such as an organic material (e.g., fibers, filler, binder or
resin) in the battery separator.
During discharge of the lead acid batteries, the following half reactions occur at
the negative electrode and positive 5 electrode, respectively.
Pb0 + HSO4
- PbSO4 + H+ +2e- (negative electrode)
PbO2 + 3H+ + HSO4
- + 2e- PbSO4 + 2H2O (positive electrode)
10 Without being bound by theory, it is believed that discharging of the battery results in a
change in the sulfate ion concentration in the electrolyte due to the consumption of the
sulfate to form lead sulfate at the negative electrode and positive electrodes.
Accordingly, the change in sulfate ion concentration increases the solubility of other
sulfate compounds in the battery, such as the lead sulfate produced at the negative
15 electrode and positive electrode. In some instances, at least a portion of the lead sulfate
formed at the electrodes may dissolve in the electrolyte and diffuse within the battery
separator (e.g., a non-woven web within the separator). Charging of batteries produces
the reverse reaction at the electrodes and results in an increase in the sulfate ion
concentration in the electrolyte. Accordingly, the solubility of the other sulfate species,
20 such as lead sulfate, decreases. It is believed that the decrease in solubility may cause
lead from dissolved lead sulfate in the battery separator and/or elsewhere to precipitate.
The lead sulfate can precipitate to form metallic lead in dendrite form when sulfate
content in the electrolyte increases as the battery is recharged. In certain embodiments,
recharging of the battery may lead to the production of dendrites in the form of a
25 continuous lead (Pb) pathway from the negative electrode to positive electrode through
the battery separator, resulting in a short circuit.
It is also believed that the PbO2 and metallic lead, which is formed from PbSO4
during charging, are more loosely bound to the positive and negative electrode,
respectively, than the PbO2 and metallic lead that has not undergone an electrochemical
30 reaction. It is believed that cycling of the battery results in shedding of the active
material in the electrode due to this loss of cohesiveness of the active material. The end
of battery cycle life may come from the shedding of the active mass.
12
In some embodiments, a battery separator that produces desirable separation
and/or battery performance may include certain chemical additives to further enhance the
separator’s chemical stability and/or performance in a battery, such as a lead acid battery.
For instance, in some embodiments, a battery separator including a non-woven web
comprising glass fibers may include one or more sulfate salts. T 5 he sulfate salts may be
present in amount of, for example, greater than or equal to about 0.1 wt.% and less than
about 30 wt.% (e.g., greater than or equal to about 0.5 wt.% and less than about 5 wt.% )
of the battery separator and/or the non-woven web. In some embodiments, the sulfate
salt may be a solid. For instance, the non-woven web and/or battery separator may
10 comprise sulfate salt particles.
Without being bound by theory, it is believed that sulfate salts present in (e.g.,
originating from) the non-woven web and/or battery separator may prevent or reduce the
solubilization of lead sulfate through the common ion effect. That is, the sulfate salts
may reduce the lead sulfate solubility during the discharging and charging processes,
15 thereby reducing or preventing the amount of lead dendrites, as described in more detail
below.
Due to the relatively high concentration of sulfuric acid in the electrolyte of lead
acid batteries, the sulfate salt within the non-woven web and/or battery separator may
have a relatively low solubility in the bulk electrolyte. In some such embodiments, a
20 relatively high percentage of the sulfate salt in the non-woven web (e.g., greater than or
equal to about 20%, greater than or equal to about 30%, greater than or equal to about
40%, greater than or equal to about 50%, greater than or equal to about 60%, greater than
or equal to about 70%, greater than or equal to about 80%, greater than or equal to about
90%, greater than or equal to about 95%) may not dissolve (e.g., may be in solid form)
25 and/or may remain within the non-woven web and/or battery separator (e.g., in solid or
dissolved form) prior to operation of the battery and/or during battery discharge. In
some such instances, solid sulfate salt within the non-woven web and/or battery separator
may dissolve in the electrolyte, but the electrolyte containing the dissolved sulfate salt
may remain within the pores of the battery separator, also referred to herein as the local
30 electrolyte.
When the concentration of sulfate ion in the bulk electrolyte is relatively low
(e.g., when the state of charge of the battery is low, the concentration of sulfate ion
within the local electrolyte may remain relatively high. In some instances, the relatively
13
high concentration of sulfate ion in the local electrolyte may be a result of the dissolved
sulfate salt originating from the non-woven web and/or battery separator remaining in
the battery separator. In such embodiments, a concentration gradient of sulfate salt may
exist between the local electrolyte and the bulk electrolyte.
In certain instances, such as during discharge, a relatively 5 low concentration of
sulfate ions in the bulk electrolyte may result in a low concentration of sulfate ions in the
local electrolyte. The low concentration of sulfate ion in the local electrolyte may cause
at least a portion of the solid sulfate salt in the non-woven web/and or battery separator
to dissolve into the local electrolyte, thereby increasing the concentration of sulfate ion
10 in the local electrolyte, such that the local electrolyte has a relatively high concentration
of sulfate ion.
In embodiments in which the local electrolyte has a relatively high concentration
of sulfate ion, lead sulfate may have a relative low solubility within the local electrolyte
(e.g., the electrolyte in the pores of non-woven web and/or battery separator). This
15 reduced solubilization of lead sulfate within the non-woven web and/or battery separator
can result in the reduction or prevention of lead dendrites at or in the non-woven web
and/or battery separator.
As described herein, in some embodiments a battery separator includes a dried
non-woven web having a certain amount of sulfate salts incorporated therein. For
20 instance, the sulfate salts may be present in the battery separator prior to the separator’s
contact with or exposure to an electrolyte (e.g., present in the battery separator prior to
the separator being incorporated into a battery). In some cases, the sulfate salts’ ability
to reduce the solubilization of lead sulfate may be more effective when the sulfate salts
are present in the battery separator prior to the separator’s contact with or exposure to an
25 electrolyte (e.g., present in the battery separator prior to the separator being incorporated
into a battery), compared to sulfate salts originating from (or added to) the bulk
electrolyte solution directly. It is believed that sulfate salts incorporated into the
separator may be more effective in resisting dendrite formation, since the sulfate salts
may have a higher local concentration within the battery separator (e.g., in the local
30 electrolyte) compared to when the sulfate salt originates from or is added to the bulk
electrolyte directly.
In certain embodiments, a lower concentration of sulfate salts may be used to
achieve the desired result (e.g., preventing dendrite formation) when the sulfate salts are
14
present in the battery separator and/or non-woven web prior to the separator’s contact
with or exposure to an electrolyte (e.g., present in the battery separator prior to the
separator being incorporated into a battery), compared to a concentration required when
the sulfate salts are originating from (or added to) the bulk electrolyte directly. It may be
desirable for a battery to include lower concentrations of sulfate 5 salts to reduce certain
undesirable effects of sulfate salts in the electrolyte, such as self-discharge.
In some embodiments, the total weight percentage of sulfate salts in the non-woven web
and/or battery separator (e.g., prior to the non-woven web’s or separator’s contact with a
battery electrolyte) may be greater than or equal to about 0.1 wt.%, greater than or equal
10 to about 0.2 wt.%, greater than or equal to about 0.5 wt.%, greater than or equal to about
0.8 wt.%, greater than or equal to about 1 wt.%, greater than or equal to about 2 wt.%,
greater than or equal to about 3 wt.%, greater than or equal to about 5 wt.%, greater than
or equal to about 8 wt.%, greater than or equal to about 10 wt.%, greater than or equal to
about 12 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 18
15 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 22 wt.%, or
greater than or equal to about 25 wt.%. In some cases, the total weight percentage of
sulfate salts in the non-woven web and/or battery separator (e.g., prior to the non-woven
web’s or separator’s contact with a battery electrolyte) may be less than or equal to about
30 wt.%, less than or equal to about 28 wt.%, less than or equal to about 25 wt.%, less
20 than or equal to about 22 wt.%, less than or equal to about 20 wt.%, less than or equal to
about 18 wt.%, less than or equal to about 15 wt.%, less than or equal to about 12 wt.%,
less than or equal to about 10 wt.%, less than or equal to about 8 wt.%, less than or equal
to about 5 wt.%, less than or equal to about 4 wt.%, less than or equal to about 3 wt.%,
less than or equal to about 2 wt.%, or less than or equal to about 1 wt.%.
25 Combinations of the above-referenced ranges are also possible (e.g., a total
weight percentage of sulfate salts of greater than or equal to about 0.1 wt.% and less than
about 30 wt.%, greater than or equal to about 1 wt.% and less than about 10 wt.%,
greater than or equal to about 0.5 wt.% and less than about 5 wt.%). Other ranges are
also possible. The total weight percentage of sulfate salts in the non-woven web and/or
30 battery separator is based on the dry solids and can be determined prior to adding the
sulfate salts to the non-woven web and/or battery separator. In some embodiments, the
sulfate salt may be part of a resin that is coated on the non-woven web. In some
embodiments, the sulfate salt may be coated onto or incorporated with another
15
component of the non-woven web and/or battery separator (e.g., silica particles, fibers).
In certain embodiments, the total percentage of sulfate salts in the dry solids of the
binder resin may include one or more of the above-referenced ranges.
In general, any sulfate salt suitable for including in the battery separator may be
used. In some embodiments, a suitable sulfate salt may be 5 more soluble in the particular
electrolyte chosen for a battery than lead sulfate. For instance, the sulfate salt may have
a higher solubility product constant in the electrolyte than lead sulfate. In some
embodiments, a sulfate salt incorporated in a battery separator described herein does not
adversely affect battery performance by, e.g., interfering with an electrochemical
10 reaction in the battery and/or adversely interacting with a battery component.
Additionally, the sulfate salt may be water-soluble. Non-limiting examples of sulfate
salts that may be utilized include sodium sulfate, magnesium sulfate, calcium sulfate,
aluminum sulfate, cobalt sulfate, potassium sulfate, and combinations thereof. In certain
embodiments, sulfate salts comprising divalent cations (e.g., magnesium sulfate, calcium
15 sulfate) may be used. In some instances, divalent cations may interact with surfactants
and/or may coagulate emulsion binder resins, thereby reducing resin migration in the
non-woven web.
In some embodiments, the sulfate salt may be in the form of a particle. The
average particle size (e.g., average diameter, or average cross-sectional dimension) of the
20 sulfate salt particles included in a non-woven web and/or separator described herein may
be, for example, greater than or equal to about 0.01 micron, greater than or equal to about
0.05 micron, greater than or equal to about 0.1 micron, greater than or equal to about 0.5
micron, greater than or equal to about 1 micron, greater than or equal to about 3 microns,
greater than or equal to about 5 microns, greater than or equal to about 10 microns,
25 greater than or equal to about 20 microns, greater than or equal to about 30 microns,
greater than or equal to about 40 microns, greater than or equal to about 50 microns,
greater than or equal to about 60 microns, greater than or equal to about 70 microns,
greater than or equal to about 80 microns, or greater than or equal to about 90 microns.
The particles may have an average particle size of, for example, less than or equal to
30 about 100 microns, less than or equal to about 90 microns, less than or equal to about 80
microns, less than or equal to about 70 microns, less than or equal to about 60 microns,
less than or equal to about 50 microns, less than or equal to about 40 microns, less than
or equal to about 30 microns, less than or equal to about 20 microns, less than or equal to
16
about 10 microns, less than or equal to about 5 microns, or less than or equal to about 1
microns. Combinations of the above-referenced ranges are also possible (e.g., greater
than or equal to about 1 micron and less than or equal to about 50 microns, greater than
or equal to about 3 micron and less than or equal to about 20 microns). Other ranges are
also possible. Particle sizes described herein (e.g., average particle 5 sizes) refer to ones
measured by dynamic light scattering.
In some embodiments, a battery separator including a non-woven web
comprising one or more sulfate salts may reduce dendrite formation, and accordingly,
may increase the lifetime of the battery separator, compared to a battery separator
10 lacking the one or more sulfate salts, all other factors being equal. As described herein,
the sulfate salts may be present in the battery separator prior to the separator’s contact
with or exposure to an electrolyte (e.g., present in the battery separator prior to the
separator being incorporated into a battery). The increase in lifetime of the battery
and/or reduction in dendrite formation may be measured indirectly by the percent loss of
15 breakdown voltage (BDV) of a battery separator comprising sulfate salts after exposure
to lead electroplating conditions.
The breakdown voltage has its ordinary meaning in the art and refers to the
minimum voltage that causes a portion of the battery separator to become electrically
conductive. In general, the breakdown voltage is a measure of the dielectric strength of
20 the dry battery separator. Briefly, the breakdown voltage can be measured by applying
100V, using 10 cm by 10 cm electrodes, across the battery separator and then increasing
the voltage applied across the separator until a current of 18 mA is produced. The
applied voltage at which electrical conductivity occurs is the breakdown voltage. In
general, the breakdown voltage of a battery separator without a short will be relatively
25 high. However, a short (e.g., due to dendrite formation) will produce a relatively low
breakdown voltage. The loss in breakdown voltage is the percent decrease in the
breakdown voltage after exposure of the battery separator to certain conditions (e.g.,
electroplating conditions).
In some embodiments, the percent loss of BDV of a battery separator comprising
30 sulfate salts after exposure to lead electroplating conditions may be less than or equal to
about 30 %, less than or equal to about 25%, less than or equal to about 20%, less than
or equal to about 15%, less than or equal to about 10%, less than or equal to about 8%,
less than or equal to about 5%, less than or equal to about 3%, less than or equal to about
17
3%, or less than or equal to about 1%. In some cases, the percent loss of BDV of a
battery separator comprising sulfate salts after exposure to lead electroplating conditions
may be greater than or equal to about 0%, greater than or equal to about 0.05%, greater
than or equal to about 0.1%, greater than or equal to about 0.2%, greater than or equal to
about 0.5%, greater than or equal to about 1%, greater 5 than or equal to about 2%, greater
than or equal to about 3%, greater than or equal to about 4%, greater than or equal to
about 5%, greater than or equal to about 6%, greater than or equal to about 8%, greater
than or equal to about 10%, greater than or equal to about 12%, or greater than or equal
to about 15%. Combinations of the above-referenced ranges are also possible (e.g.,
10 greater than or equal to about 0% and less than about 20%). Other ranges are also
possible.
The loss in breakdown voltage may be determined by measuring the breakdown
voltage of the battery separator before and after exposing the battery separator to lead
electroplating conditions. Electroplating conditions result in a relatively high
15 concentration of dissolved lead, resulting in an increased probability of dendrite
formation. Briefly, electroplating conditions using the following protocol can be used.
The battery separator can be incorporated into an electrochemical cell including standard
lead foil electrodes as the negative electrode and positive electrode and the
electrochemical cell can be operated under overcharging conditions. The separator (e.g.,
20 in leaf form) may be positioned between the negative electrode and positive electrode to
separate the plates. The electrochemical cell can be filled with distilled water. The cell
can be charged at 7 A (i.e., 20 mA/cm2) for 15 minutes. The voltage and temperature of
the cell can be monitored at one minute intervals. After 15 minutes, the electroplating
can be stopped. The separator can be removed from the assembly of electrodes and
25 washed with distilled water. The separator can be dried at 80 °C in an oven for 20
minutes. The breakdown voltage may then be determined as described above and
compared with the breakdown voltage prior to exposure to electroplating conditions to
determine the percent loss in BDV.
Methods of adding a sulfate compound to a non-woven web and/or battery
30 separator are described in more detail below.
In another set of embodiments, a battery separator includes one or more heavy
metal scavengers such as a rubber. The heavy metal scavenger may be present in certain
embodiments in which one or more electrodes of the battery comprises a heavy metal
18
(e.g., a lead antimony alloy electrode). The heavy metal scavenger (e.g., a rubber) may
prevent or reduce the amount of heavy metals depositing on the one or more electrodes.
In some embodiments, the battery separator and/or a non-woven web within the battery
separator may comprise a rubber as a heavy metal scavenger. The rubber may dissolve
in the electrolyte and may scavenge or bind with heavy 5 metals, such as Sb, thereby
removing the heavy metal before it irreversibly deposits on an electrode surface (e.g.,
negative electrode surface) and/or before it increases water consumption. In some such
cases, a battery separator including a non-woven web comprising a rubber (e.g. rubber
particles) as described herein may increase antimony suppression and/or reduce water
10 consumption during operation of a battery including the battery separator, compared to a
battery including a separator lacking the rubber or having a lower concentration of the
rubber, all other factors being equal.
In some embodiments, the water consumption of a battery separator comprising a
rubber may be less than or equal to about 10 g/AH, less than or equal to about 9 g/AH,
15 less than or equal to about 8 g/AH, less than or equal to about 7 g/AH, less than or equal
to about 6 g/AH, less than or equal to about 5 g/AH, less than or equal to about 4 g/AH,
less than or equal to about 3 g/AH, less than or equal to about 2 g/AH, or less than or
equal to about 1 g/AH. In some instances, the water consumption of a battery separator
comprising a rubber may be greater than or equal to about 0.5 g/AH, greater than or
20 equal to about 1 g/AH, greater than or equal to about 2 g/AH, greater than or equal to
about 3 g/AH, greater than or equal to about 4 g/AH, greater than or equal to about 5
g/AH, greater than or equal to about 6 g/AH, greater than or equal to about 7 g/AH, or
greater than or equal to about 8 g/AH. Combinations of the above-referenced ranges are
also possible (e.g., greater than or equal to about 1 g/AH and less than or equal to about
25 10 g/AH, greater than or equal to about 2 g/AH and less than or equal to about 5 g/AH).
Water consumption may be determined by following the VRLA SLI Batteries (AGM)
Requirements test, VDA Requirement Specification AGM: 2010-03 Method 9.10, e.g.,
using H8 European Automotive battery with a capacity of 100AH.
The antimony suppression produced by a battery separator may be determined by
30 determining the recharge efficiency (i.e., capacity taken in vs. capacity taken out) using
the protocol described in “Antimony Suppression Analysis”, R. Wimberly and G.
Brilmyer in “The Battery Man”, August 2000, pp. 28-35. In some embodiments, the
recharge efficiency of a battery comprising a battery separator comprising a non-woven
19
web including a rubber may be greater than or equal to about 6%, greater than or equal to
about 7%, greater than or equal to about 8%, greater than or equal to about 9%, greater
than or equal to about 10%, greater than or equal to about 12%, greater than or equal to
about 15%, greater than or equal to about 18%, greater than or equal to about 20%,
greater than or equal to about 22%, greater than or 5 equal to about 25%, greater than or
equal to about 28%, greater than or equal to about 30%, or greater than or equal to about
40%. In some cases, the recharge efficiency of a battery comprising a battery separator
comprising a non-woven web including a rubber may be less than or equal to about 40
%, less than or equal to about 38%, less than or equal to about 35%, less than or equal to
10 about 32%, less than or equal to about 30%, less than or equal to about 28%, less than or
equal to about 25%, less than or equal to about 22%, less than or equal to about 20%,
less than or equal to about 18%, less than or equal to about 15%, less than or equal to
about 12%, less than or equal to about 10%, or less than or equal to about 8%.
Combinations of the above-referenced ranges are also possible. In some embodiments,
15 the recharge efficiency is greater than or equal to about 6% (e.g., greater than or equal to
about 10%).
In general, any suitable rubber that is able to scavenge antimony and that does not
adversely affect battery performance may be used. Non-limiting examples of suitable
rubbers include natural rubbers (e.g., smoked sheet, pale crepes, blanket crepes, brown
20 crepes, amber or flat bark crepes, Hevea brasiliensis rubber, latex of natural rubber) and
synthetic rubbers (e.g., styrene-butadiene rubbers, polybutyldiene, polyisoprene, styrene
butadiene, nitrile, butyl, ethylene-propylene, silicone, polysulfide, polyacrylate). In
some cases, the rubber may be cured. In other cases, the rubber may be uncured. In
some embodiments, the rubber may in the form of, or may be included in, a binder resin,
25 and the rubber may be used to bind one or more components of the non-woven web
together. In other embodiments, the rubber does not serve to bind components of the
non-woven web together and may function primarily as a heavy metal scavenger and/or
carrier for another chemical additive (e.g., an antioxidant).
In some embodiments, the rubber may be in the form of a particle. The average
30 particle size (e.g., average diameter, or average cross-sectional dimension) of the rubber
particles included in a non-woven web and/or separator described herein may be, for
example, greater than or equal to about 1 micron, greater than or equal to about 3
microns, greater than or equal to about 5 microns, greater than or equal to about 10
20
microns, greater than or equal to about 20 microns, greater than or equal to about 30
microns, greater than or equal to about 40 microns, greater than or equal to about 50
microns, greater than or equal to about 60 microns, greater than or equal to about 70
microns, greater than or equal to about 80 microns, or greater than or equal to about 90
microns. The particles may have an average particle size 5 of, for example, less than or
equal to about 100 microns, less than or equal to about 90 microns, less than or equal to
about 80 microns, less than or equal to about 70 microns, less than or equal to about 60
microns, less than or equal to about 50 microns, less than or equal to about 40 microns,
less than or equal to about 30 microns, less than or equal to about 20 microns, less than
10 or equal to about 10 microns, or less than or equal to about 5 microns. Combinations of
the above-referenced ranges are also possible (e.g., greater than or equal to about 1
micron and less than or equal to about 100 microns, greater than or equal to about 3
micron and less than or equal to about 20 microns). Other ranges are also possible.
In some embodiments, the choice of average particle size of the rubber particles
15 may depend at least in part on the method in which the rubber particles are added to the
non-woven web. For example, in some embodiments, fine rubber particles (e.g., less
than or equal to about 20 microns) may be used when the rubber particles are added to
the non-woven web via electrostatic attraction of the rubber particles to one or more
oppositely charged component(s) of the non-woven web. Methods of adding a rubber
20 compound to a non-woven web and/or battery separator are described in more detail
below.
In some embodiments, the total weight percentage of rubbers in the non-woven
web and/or battery separator may be greater than or equal to about 1 wt.%, greater than
or equal to about 2 wt.%, greater than or equal to about 5 wt.%, greater than or equal to
25 about 10 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 20
wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 30 wt.%,
greater than or equal to about 35 wt.%, greater than or equal to about 40 wt.%, greater
than or equal to about 45 wt.%, greater than or equal to about 50 wt.%, greater than or
equal to about 55 wt.%, greater than or equal to about 60 wt.%, or greater than or equal
30 to about 65 wt.%.
In some cases, the total weight percentage of rubbers in the non-woven web
and/or battery separator may be less than or equal to about 70 wt.%, less than or equal to
about 65 wt.%, less than or equal to about 60 wt.%, less than or equal to about 55 wt.%,
21
less than or equal to about 50 wt.%, less than or equal to about 45 wt.%, less than or
equal to about 40 wt.%, less than or equal to about 35 wt.%, less than or equal to about
30 wt.%, less than or equal to about 25 wt.%, less than or equal to about 20 wt.%, less
than or equal to about 15 wt.%, less than or equal to about 10 wt.%, less than or equal to
about 8 wt.%, less than or equal to about 5 wt.%, less 5 than or equal to about 3 wt.%, less
than or equal to about 2 wt.%, or less than or equal to about 1 wt.%. Combinations of
the above-referenced ranges are also possible (e.g., a total weight percentage of rubbers
of greater than or equal to about 1 wt.% and less than about 70 wt.%, greater than or
equal to about 2 wt.% and less than about 20 wt.%). Other ranges are also possible.
10 The total weight percentage of rubbers in the non-woven web and/or battery
separator is based on the dry solids and can be determined prior to adding the rubbers to
the non-woven web and/or battery separator.
One or more rubbers may be present in any suitable form in the non-woven web.
In some embodiments, the rubber may be part of a resin that is coated on at least portions
15 of the non-woven web. In other embodiments, the rubber may be coated on at least
portions of the non-woven web without a resin.
In some embodiments, a rubber (e.g., rubber particles) included in a non-woven
web and/or battery separator described herein includes one or more antioxidants, as
described in more detail below.
20 As noted above, in some embodiments, a non-woven web may include one or
more antioxidants. The antioxidant(s) may reduce or prevent oxidation of organic
material (e.g., synthetic fibers, binder resin, and other chemical additives such as a
rubber) in the non-woven web and/or battery separator. In general, oxidation can
degrade the non-woven web and reduces the mechanical integrity of the battery
25 separator. In lead acid batteries, any carbon-based polymer (e.g., rubber, polyethylene)
in the non-woven web and/or battery separator containing carbon–carbon single bonds
across its main chain may be susceptible to oxidative damage. The carbon-carbon single
bonds may be susceptible to thermo-oxidative cleavage, as a consequence of their ability
to undergo free-radical cleavage reactions. Some carbon-based polymers in the non30
woven web and/or battery separator may break down in an oxidative environment and
form alkoxy radicals followed by hydroperoxide and peroxy radicals. The formation of
these radicals can reduce the performance of the battery.
22
In some instances, an antioxidant described herein may reduce the rate of
oxidation of organic material in the non-woven web and/or battery separator. In certain
embodiments, the combination of a rubber and an antioxidant may have a synergistic
effect on chemical stability and/or battery performance. For instance, the antioxidant
may prevent oxidation of the rubber, which scavenges heavy metals 5 that might otherwise
adversely affect battery performance.
In some embodiments, a battery separator comprising a non-woven web
including one or more antioxidants may be resistant to oxidation and, accordingly, may
have a relatively long life time (e.g., a long time to failure). In some embodiments, the
10 time to failure of the battery separator may be greater than or equal to about 5 hours,
greater than or equal to about 10 hours, greater than or equal to about 25 hours, greater
than or equal to about 50 hours, greater than or equal to about 100 hours, greater than or
equal to about 250 hours, greater than or equal to about 500 hours, greater than or equal
to about 750 hours, greater than or equal to about 1,000 hours, greater than or equal to
15 about 1,250 hours, greater than or equal to about 1,500 hours, or greater than or equal to
about 1,750 hours. In certain embodiments, the time to failure of the battery separator
may be less than or equal to about 2,000 hours, less than or equal to about 1,750 hours,
less than or equal to about 1,500 hours, less than or equal to about 1,250 hours, less than
or equal to about 1,000 hours, less than or equal to about 750 hours, less than or equal to
20 about 500 hours, less than or equal to about 250 hours, less than or equal to about 100
hours, or less than or equal to about 50 hours. Combinations of the above-referenced
ranges are also possible (e.g., greater than about 5 hours and less than or equal to about
2,000 hours, greater than about 100 hours and less than or equal to about 1,000 hours).
Other values are also possible. The time to failure may be measured by performing an
25 electrochemical oxidation test according to the standard IS 6071-1986. Briefly, in an
electrochemical oxidation test, the battery separator is exposed to overcharging
conditions. As a result, oxygen evolves at the positive electrode, which produces
oxidizing conditions that can degrade the battery separator. Failure is defined as the time
at when the measured voltage across the battery separator is 0V.
30 In some embodiments, a battery separator comprising a non-woven web
including one or more antioxidants may have better mechanical stability over time
compared to a battery separator lacking the one or more antioxidants, all other factors
being equal. For instance, in some embodiments, the tensile strength in the machine
23
direction of a battery separator comprising a non-woven web including one or more
antioxidants, after exposure to hydrogen peroxide as defined in the protocol BCIS 03B
Rev Mar 2010 Method 22 Chemical/Oxidation Resistance by Hydrogen Peroxide, may
be of greater than or equal to about 10 kg/cm2, greater than or equal to about 15 kg/cm2,
greater than or equal to about 20 kg/cm2, greater than or equal to about 30 kg/cm2 5 ,
greater than or equal to about 40 kg/cm2, greater than or equal to about 50 kg/cm2,
greater than or equal to about 60 kg/cm2, greater than or equal to about 70 kg/cm2, or
greater than or equal to about 75 kg/cm2. In some instances, the tensile strength may be
less than or equal to about 80 kg/cm2, less than or equal to about 70 kg/cm2, less than or
equal to about 60 kg/cm2, less than or equal to about 50 kg/cm210 , less than or equal to
about 40 kg/cm2, less than or equal to about 30 kg/cm2, less than or equal to about 20
kg/cm2, or less than or equal to about 15 kg/cm2. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 10 kg/cm2and less than or
equal to about 80 kg/cm2, greater than or equal to about 15 kg/cm2and less than or equal
to about 60 kg/cm215 ). The tensile strength may be determined using BCIS 03B Rev Mar
2010 Method 4.
In some embodiments, the puncture strength (or puncture resistance) of a battery
separator comprising a non-woven web including one or more antioxidants, or the
puncture strength (or puncture resistance) of the non-woven web itself, after exposure to
20 hydrogen peroxide as defined in the protocol BCIS 03B Rev Mar 2010 Method 22, may
be greater than or equal to about 1 N, greater than or equal to about 1.5 N, greater than or
equal to about 2 N, greater than or equal to about 3 N, greater than or equal to about 5 N,
greater than or equal to about 8 N, greater than or equal to about 10 N, greater than or
equal to about 12N, or greater than or equal to about 15 N. In some instances, the
25 puncture strength (or puncture resistance) may be less than or equal to about 20 N, less
than or equal to about 18 N, less than or equal to about 15 N, less than or equal to about
12 N, less than or equal to about 10 N, less than or equal to about 8 N, less than or equal
to about 5 N, or less than or equal to about 3 N. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 1 N and less than or equal to
30 about 20 N, greater than or equal to about 1.5 N and less than or equal to about 15 N).
The puncture strength may be determined using protocol BCIS 03B Rev Mar 2010
Method 9. The puncture resistance may be determined using BCIS 03B Rev Mar 2010
Method 10.
24
In some embodiments, at least a portion of the antioxidant may be immobilized
on at least a portion of the non-woven web and/or within a carrier (e.g., rubber particle)
present in the non-woven web. In some instances, substantially all of the antioxidant
included in a battery separator may be immobilized on at least a portion of the nonwoven
web or within a carrier (e.g., a rubber particle) 5 present in the non-woven web,
e.g., as opposed to within an electrolyte present in the pores of the battery separator. In
some embodiments, an antioxidant that is immobilized with respect to the non-woven
web and/or a carrier may be retained in or on the non-woven web and/or carrier during
and/or after use (e.g., cycling of a battery including the non-woven web). For instance,
10 in some embodiments, a substantial amount of the antioxidant may remain in or on the
non-woven web after extended battery operation (e.g., during the lifetime of the battery)
and/or after subjecting the non-woven web to the electrolyte. In other embodiments, at
least a portion of the antioxidant is not immobilized on the non-woven web and/or
on/within a carrier after exposure to the electrolyte, and in such embodiments, the
15 antioxidant may leach out of the non-woven web and into the electrolyte.
In certain embodiments, immobilization of the antioxidant on at least a portion of
the non-woven web and/or on/in a carrier (e.g., a rubber particle) may protect the nonwoven
web and/or particle from adverse interactions with species in the electrolyte.
Without being bound by theory, the immobilized antioxidant may neutralize oxidants
20 that are in close proximity to organic material in the non-woven and/or battery separator.
In certain embodiments, the immobilized antioxidant may alter the local concentration of
oxidants in the vicinity of the organic material. Immobilization may prevent or reduce
the amount of antioxidant that diffuses into the electrolyte. Conversely, a mobile
antioxidant (i.e., an antioxidant that is not immobilized in or on the web) may diffuse
25 into the electrolyte, and in some cases, may react with oxidants in the bulk electrolyte.
In some such embodiments, a relatively high concentration of mobile antioxidant may be
needed to neutralize enough oxidants to protect the non-woven web and/or battery
separator from adverse interactions, compared to a relatively lower concentration of
antioxidant that is immobilized on/within the non-woven web. In some instances, at
30 least a portion of the antioxidant (e.g., substantially all) included in a battery separator
may be immobilized on at least a portion of the non-woven web and/or in a carrier
present in the non-woven web. In some cases, the antioxidant may be sterically trapped
25
within a part of a resin that is immobilized on the non-woven web and/or sterically
trapped in a carrier present in the non-woven web.
In general, any suitable antioxidant may be used. Non-limiting examples of
antioxidants include sulfur compounds (e.g., glutathione, 2-mercaptobenzimidazole,
sulfonamide), phenols (e.g., butylatedhydroxytoluene, but 5 lyatedhydroxyanisole,
styrenated phenol), hydroquinoline, amines (e.g., phenlyenediamines, 2,6-di-tert-butyl-4-
methylphenol, scetone/diphenylamine condensates, octylated diphenylamine, 4,4'-
di(dimethylbenzyl)diphenylamine, polymerized 1,2-dihydro-2,2,4-trimethylquinolline,
N-iso-propyl-N-p-phenylenediamine, p-Phenylenediamine, diaryl-phenylenediamines,
10 N,N'-bis-(1-Ethyl-3-methylpentyl) p-phenylenediamine, N,N'-bis-(1-Methyl Heptyl) pphenylenediamine,
N,N'-bis-(1,4-dimethyl pentyl) p-phenylenediamine, analinehydroquinone-
o-toluidine reaction products, xylidines-hydroquinone-o-toluidine reaction
products, N-isopropyl-N'-phenyl-p-phenylenediamine, n-1,3-dimethyl butyl-N'-
phenylene-p-phenylenediamine, n,1-methyl heptyl-N'-[henyl-p-phenylenediamine]),
15 vitamins and vitamin analogs (e.g., vitamin A, vitamin C, vitamin E), phosphorous
compounds (e.g., phytic acid, tris(nonylphenyl) phosphite), ubiquinol, uric acid,
melatonin, butyl zimate, isobutyl niclate, methyl niclate, and combinations thereof
In some embodiments, the total weight percentage of antioxidants in the nonwoven
web and/or battery separator may be greater than or equal to about 0.05 wt.%,
20 greater than or equal to about 0.06 wt.%, greater than or equal to about 0.08 wt.%,
greater than or equal to about 0.1 wt.%, greater than or equal to about 0.2 wt.%, greater
than or equal to about 0.5 wt.%, greater than or equal to about 0.8 wt.%, greater than or
equal to about 1 wt.%, greater than or equal to about 1.5 wt.%, greater than or equal to
about 2 wt.%, greater than or equal to about 2.5 wt.%, greater than or equal to about 3
25 wt.%, greater than or equal to about 3.5 wt.%, greater than or equal to about 4 wt.%, or
greater than or equal to about 4.5 wt.%. In some cases, the total weight percentage of
antioxidants in the non-woven web and/or battery separator may be less than or equal to
about 5 wt.%, less than or equal to about 4.5 wt.%, less than or equal to about 4 wt.%,
less than or equal to about 3.5 wt.%, less than or equal to about 3 wt.%, less than or
30 equal to about 2.5 wt.%, less than or equal to about 2 wt.%, less than or equal to about
1.5 wt.%, less than or equal to about 1 wt.%, less than or equal to about 0.8 wt.%, less
than or equal to about 0.5 wt.%, less than or equal to about 0.2 wt.%, or less than or
equal to about 0.1 wt.%. Combinations of the above-referenced ranges are also possible
26
(e.g., a total weight percentage of antioxidants of greater than or equal to about 0.05
wt.% and less than about 5 wt.%, greater than or equal to about 0.1 wt.% and less than
about 1 wt.%). Other ranges are also possible. The total weight percentage of
antioxidants in the non-woven web and/or battery separator is based on the dry solids of
the non-woven web and/or battery separator, and can be 5 determined prior to adding the
antioxidant to the non-woven web and/or battery separator.
In some embodiments, an antioxidant may be included in a rubber (e.g., rubber
particles) present in a non-woven web. A rubber (e.g., rubber particles) may have any
suitable weight percentage of antioxidant included therein. For instance, in some
10 embodiments, the weight percentage of antioxidant in the rubber may be greater than or
equal to about 0.01 wt.%, greater than or equal to about 0.02 wt.%, greater than or equal
to about 0.03 wt.%, greater than or equal to about 0.04 wt.%, greater than or equal to
about 0.06 wt.%, greater than or equal to about 0.08 wt.%, greater than or equal to about
0.1 wt.%, greater than or equal to about 0.2 wt.%, greater than or equal to about 0.5
15 wt.%, or greater than or equal to about 1 wt.%. In some instances, the weight percentage
of antioxidant in the rubber may be less than or equal to about 2 wt.%, less than or equal
to about 1.5 wt.%, less than or equal to about 1.2 wt.%, less than or equal to about 1
wt.%, less than or equal to about 0.8 wt.%, less than or equal to about 0.6 wt.%, less than
or equal to about 0.5 wt.%, or less than or equal to about 0.4 wt.%. Combinations of the
20 above-referenced ranges are also possible (e.g., greater than or equal to about 0.01 wt.%
and less than or equal to about 2 wt.%, greater than or equal to about 0.1 wt.% and less
than or equal to about 1 wt.%). Other values of weight percentage of antioxidant in the
resin are also possible. The weight percentage of antioxidant in the rubber is based on
the dry rubber and can be determined prior to incorporating the rubber into the non25
woven web.
It should be understood that a battery separator described herein can contain any
suitable number and/or types of additives. In some embodiments, a battery separator
may comprise two or more of the same type of chemical additives. For instance, a
nonwoven web may comprise two sulfate salts (e.g., calcium sulfate and magnesium
30 sulfate), two antioxidants, or two rubbers. In some embodiments, a battery separator
may comprise a non-woven web comprising different types of chemical additives. For
instance, a battery separator may comprise a non-woven web comprising two different
types of chemical additives (e.g., rubber and antioxidant, rubber and sulfate salt, or
27
sulfate salt and antioxidant) or three different types of chemical additives (e.g., rubber,
antioxidant, and sulfate salt). Other combinations are also possible.
In one example, a battery separator may include a non-woven web comprising a
sulfate salt (e.g., magnesium sulfate, calcium sulfate) and a rubber (e.g., natural rubber).
In some such embodiments, the non-woven and/or battery separator 5 may include greater
than or equal to about 0.5 wt.% and less than or equal to about 15 wt.% of a rubber and
greater than or equal to about 1 wt.% and less than or equal to about 10 wt.% of a sulfate
salt. The non-woven may also include glass fibers (e.g., greater than or equal to about 5
wt.% and less than or equal to about 50 wt.%), synthetic fibers (greater than or equal to
10 about 15 wt.% and less than or equal to about 35 wt.%), inorganic particles (greater than
or equal to about 30 wt.% and less than or equal to about 60 wt.%), and optionally binder
resin (greater than or equal to about 0.5 wt.% and less than or equal to about 15 wt.%).
The synthetic fibers may include multi-component fibers, such as bi-component fibers
(e.g., greater than or equal to about 15 wt.% and less than or equal to about 25 wt.%),
15 and/or monocomponent fibers (greater than or equal to about 5 wt.% and less than or
equal to about 15 wt.%) that have a relatively large average diameter (e.g., greater than
or equal to about 5 microns and less than or equal to about 20 microns). The inorganic
particles (e.g., silica) may have a relatively small particle size (e.g., greater than or equal
to about 4 microns and less than or equal to about 12 microns), and/or, in some
20 embodiments, may have a relatively high surface area (e.g., greater than or equal to about
10 m2/g and less than or equal to about 2,000 m2/g, greater than or equal to about 400
m2/g and less than or equal to about 600 m2/g). In some instances, the battery separator
including a non-woven web comprising a sulfate salt and a rubber may have a basis
weight of greater than or equal to about 30 g/m2 and less than or equal to about 500 g/m2
(e.g., greater than or equal to about 50 g/m2 and less than or equal to about 150 g/m225 ). In
some cases, the non-woven web may be a planar non-woven web.
In certain embodiments, the battery separator may include a non-woven web (e.g.
a planar non-woven web or a non-woven web including at least one non-planar surface)
and an additional layer that has at least one non-planar surface (e.g., includes
30 undulations). As used herein a “non-planar layer” refers to a layer that includes repeated
undulations and/or has at least one non-planar surface. An undulating layer (i.e., a layer
that includes undulations) refers to a layer that includes repeated bends that distorts both
the top and bottom face of the layer in a similar manner. For instance, a cross-section of
28
a bend or curve of the layer will have a top line 56 that is parallel to the bottom line 57,
e.g., as shown in FIG. 3B. In some embodiments, the size or amplitude of the bends or
curves may be on the order of the thickness of the layer (e.g., 0.1-2 times the thickness of
the layer) or greater, as described in more detail below. The bends or curves in the
undulating layer may be irregular or regular. In some 5 embodiments, the undulating layer
may have a wavelike form. Examples of such layers include corrugated layers, pleated
layers, and crimped layers, amongst others.
As described herein, a battery separator may comprise a layer having a relatively
low apparent density. As used herein, apparent density has its ordinary meaning in the
10 art and may be represented by the following equation.
Apparent density (g/m2×mm) = Basis weight (g/m2) ÷ Overall thickness (mm)
As illustrated by the equation, apparent density is a measure of the mass of the layer
15 divided by the volume (i.e., area times overall thickness) of the layer that includes any
unoccupied space within the outermost boundaries of the layer, also referred to as voids.
The overall thickness is measured according to BCIS-03A under 10kPa as
described in more detail below. The voids of the layer are accounted for in the overall
thickness. FIG. 3 shows the difference between overall thickness and thickness for a
20 layer having planar surfaces (e.g., planar layer 50) and a layer having at least one nonplanar
surface and/or that includes undulations (e.g.., non-planar layer 55). The overall
thickness 60, as well as thickness 61, of the planar layer is measured along surfaces 51
and 52 as shown in FIG. 3A. The overall thickness and thickness for the planar layer are
the same. FIG.3B shows planar layer 50 after undergoing a shaping process (e.g.,
25 corrugation, embossing, pleating) to form a non-planar layer 55, which has the same
thickness 61 as planar layer 50. The thickness 61 of non-planar layer 55 is also
measured from surfaces 51 and 52. The overall thickness 60, however, is measured from
outermost surfaces 56 and 57, which are the most external surfaces of the layer. As
shown in FIG. 3B, the overall thickness takes into account voids 58 in the layer. Thus,
30 the thickness of the layer refers to the thickness of the material used to form the layer
while the overall thickness refers to the spatial thickness of the layer.
In some embodiments, the apparent density of a layer may be lowered by
increasing the overall thickness of the layer as shown illustratively in FIG. 3 (or by
29
increasing the overall thickness of the layer by a factor larger than a factor of the layer’s
increase in basis weight). For example, planar layer 50 may have an overall thickness of
2 mm prior to any shaping process. After subjecting the layer to a shaping process, the
layer may have a non-planar surface and/or undulations in the layer. The non-planar
layer may have an overall thickness 60 (e.g., 10 mm) greater 5 than the overall thickness
60 of the layer prior to shaping. In this example, the basis weight of layer 55 in FIG. 3B
would be greater than the basis weight of layer 50 in FIG. 3A for the same size/area layer
(e.g., 10 cm x 10 cm); however, as long as the proportional increase in thickness of layer
55 is larger than its proportional increase in basis weight, the apparent density of layer 55
10 would be lower than its apparent density prior to shaping (e.g., layer 50 of FIG. 3A). For
example, layer 55 of FIG. 3B having an increase in overall thickness by a factor of 5
(e.g., 2 mm to 10 mm) and an increase in basis weight by a factor of about 1.33 (e.g., 300
g/m2 to 400 g/m2), would have an apparent density that is lower by a factor of 3.75 (e.g.,
150 g/m2mm to 40 g/m2mm) compared to that for layer 50 of FIG. 3A.
15 In some embodiments, a battery separator including a layer having a relatively
low apparent density may result in a battery arrangement having a relatively high total
void volume between the electrodes. As used herein, total void volume of a layer has its
ordinary meaning in the art and refers to the empty (i.e., void) volume, e.g., that is
capable of being filled with matter (e.g., an electrolyte). The total void volume includes
20 the internal void volume and the external void volume. The internal void volume refers
to the volume within the internal voids (e.g., pores) in the layer itself; that is the empty
(i.e., void) volume within the outermost boundaries of the layer, e.g., that is capable of
being filled with matter (e.g., an electrolyte). The external void volume refers to the
volume within the external voids (e.g., the volume under a bend in the layer) formed as a
25 result of the shape of the layer. The total void volume percentage, also referred to as the
total volume porosity, may be determined using the following formula:
% Total Volume Porosity = 100 – (Basis weight / (Matter density x overall thickness))
30 where matter density refers to the density of the components forming the separator/layer
(e.g., fibers), e.g., as measured by BCIS-03A, Sept-09 Method 11. For example, the
matter density for a battery separator containing only glass fibers would be the density of
the glass fibers. The matter density of a battery separator comprising a mixture of fibers,
30
inorganic particles, and binder resin would be would be a weighted average of the
density of each material in the battery separator.
The internal volume porosity percent may be determined according to the
standard BCIS-03B – Method 6, which is a volume displacement method.
Non-limiting examples of void volumes within battery 5 separators comprising a
conventional planar layer, a conventional ribbed layer, or non-planar layers of the present
disclosure are shown in FIG. 4. FIG. 4A shows a cross-section of a battery arrangement
comprising a conventional planar battery separator 70 positioned between and in direct
contact with a negative electrode 75 and a positive electrode 80. When a battery
10 separator is configured between (e.g., in direct contact with) a negative electrode and a
positive electrode, the external void volume refers to the volume between the negative
electrode and the surface of the battery separator closest to the negative electrode, and
the volume between the positive electrode and the surface of the battery separator closest
to the positive electrode that is void prior to addition of the electrolyte. In FIG. 4A, the
15 entire surface area of the negative electrode and the positive electrode are in contact with
the planar battery separator. Thus, in this illustration, the total volume porosity is equal
to the internal void volume (i.e., internal volume porosity) of the battery separator. In
embodiments in which the total volume porosity of the battery separator is equal to the
internal volume porosity of the battery separator, the majority of ion movement occurs
20 within the battery separator.
FIG. 4B shows a cross-section of a battery arrangement comprising a
conventional battery separator 85 comprising ribs 90 on the top and the bottom surfaces
of planar layer 88. Ribs, as shown in FIG. 4B, are material added to at least one surface
of the battery separator in a discontinuous arrangement (e.g., the rib material does not
25 form a continuous sheet of material along the whole surface of the layer on which the
ribs are positioned). The ribs act as a spacer between the battery separator and the
positive electrode and/or negative electrode, and creates unoccupied space (e.g., voids)
between the surface of the layer and the surface of the negative electrode and/or positive
electrode. This unoccupied space can be used to increase the volume of electrolyte
30 between the electrodes. Movement of ions in the unoccupied space (e.g., “freely”
moving ions) is not hindered by the battery separator and thus serves to lower electrical
resistance. The unoccupied space may also serve to minimize dendrite formation
because it is easier for dendrites to grow on solid material, such as the fibers of the
31
separator where there are more potential points of attachment, than to grow in a liquid
(e.g., electrolyte) where there is active ionic conduction. However, since ribs are
additional material added to at least one surface of the battery separator, some
conventional ribs may block at least a portion of the separator’s pores and increase the
electrical resistance of the battery separator. Conventional 5 ribs may also reduce the
surface area of the electrode(s) that is/are in direct contact with the battery separator.
The reduction in contact area between the electrode and the separator may result in nonuniform
pressure distribution across the electrodes and may increase shedding of active
material from areas of the electrode that are not in contact with the ribs.
10 Referring back to FIG. 4B, battery separator 85 may be positioned between
negative electrode 75 and positive electrode 80, such that the ribs are in contact with
electrodes but the top and bottom surfaces of planar layer 88 are not in direct contact
with the electrodes. The presence of the ribs creates voids 92 that can allow ions within
the void volume to move “freely” without interference of portions of the battery
15 separator. In this configuration, the void volume will depend on the size (e.g., height,
width) of the ribs. In some instances, ribs 90 may block portions 94 of layer 88 and
hinder the movement of ions through those portions of the layer. Moreover, since the
ribs have a different surface area than layer 88, and may have a different composition
than layer 88, the chemical stability and/or mechanical properties of the ribs may differ
20 from those of the layer. That is, ribs may change the overall chemical stability and
mechanical properties of the battery separator. The use of ribs can also be costly since
additional material used to form the ribs and an additional process step of adding the ribs
to the separator are typically needed.
In some embodiments, a battery separator described herein having at least one
25 non-planar surface and/or including undulations may have advantages of a separator
including ribs (e.g., increase in void volume and freely moving ions), but without (or
reduced degree of) certain limitations of the ribs (e.g., electrical resistance and/or
shedding of active material from areas of the electrode that are not in contact with the
ribs). It is noted that a non-planar layer and/or a surface that includes undulations, as
30 described herein, does not encompass a planar layer including ribs alone like that shown
in FIG. 4B, though a non-planar layer and/or a surface that includes undulations is not
precluded from including ribs.
32
Examples of a battery separator including a layer having at least one non-planar
surface and/or including undulations are shown in FIGs.4C-4D. As shown illustratively
in these figures, each of the battery separators may be a layer having two non-planar
(opposing) faces. In some instances, the layer may have a patterned shape. For instance,
layer 100 may comprise a regular pattern as in FIG. 4C. In 5 certain embodiments, layer
105 may have an irregular pattern as shown in FIG.4D. In both FIGs. 4C and 4D, the
undulating layers include repeated bends and/or curves that distort both the top and
bottom face of the layer in a similar manner. Regardless of whether the pattern or shape
of the non-planar layer is regular or irregular, the shape of the layer may create voids 110
10 that can allow “free” ion movement.
In some embodiments, the shape of the layer may be produced by a process that
does not negatively influence the chemical stability and/or mechanical properties of the
battery separator (e.g., ion conductivity, chemical stability, mechanical strength).
The shaping of the layer/separator may result in different amounts of surface
15 contact area, i.e., the area of the layer/battery separator in contact with a positive and/or
negative electrode (or in direct contact with a planar surface positioned adjacent the
battery separator). In some embodiments, the surface contact area percentage of a
layer/battery separator may be greater than or equal to about 5%, greater than or equal to
about 10%, greater than or equal to about 20%, greater than or equal to about 30%,
20 greater than or equal to about 40%, greater than or equal to about 50%, greater than or
equal to about 60%, greater than or equal to about 70%, greater than or equal to about
75%, greater than or equal to about 80%, or greater than or equal to about 90%. In some
instances, the surface contact area percentage may be less than 100%, less than or equal
to about 90%, less than or equal to about 80%, less than or equal to about 75%, less than
25 or equal to about 70%, less than or equal to about 60%, less than or equal to about 50%,
less than or equal to about 40%, less than or equal to about 30%, less than or equal to
about 20%, or less than or equal to about 15%. Combination of the above-referenced
ranges are also possible (e.g., greater than or equal to about 10% and less than or equal to
about 30%). Other values are also possible. In some embodiments, both sides/surfaces
30 of the battery separator may have percentages of surface contact area within one or more
of the above-referenced ranges. In certain embodiments, the percentage surface contact
area may be measured while applying a pressure of 10 kPa to the layer/battery separator.
33
In other embodiments, the percentage surface contact area may be measured without
applying any pressure to the layer/battery separator.
Any suitable method may be used to incorporate a chemical additive into a nonwoven
web and/or battery separator. In some embodiments, a coating method is used to
form a coating comprising a chemical 5 additive on the non-woven web. In some
embodiments, a coating process involves introducing a resin (e.g., a binder resin) to a
pre-formed fiber layer (e.g., a pre-formed non-woven web formed by a wet-laid process).
In some embodiments in which the chemical additive(s) are added to the binder resin, as
the fiber layer is passed along an appropriate screen or wire, different components
10 included in the resin, such as an sulfate salts, rubber, and/or antioxidants described
herein, which may be in the form of separate emulsions, are added to the fiber layer
using a suitable technique. In some cases, each component of the binder resin is mixed
as an emulsion prior to being combined with the other components and/or fiber layer. In
some embodiments, the emulsion/components included in the binder resin may be pulled
15 through the fiber layer using, for example, gravity and/or vacuum. In some
embodiments, one or more of the components included in the binder resin may be diluted
with softened water and pumped into the fiber layer. In some embodiments, a binder
resin may be applied to a fiber slurry prior to introducing the slurry into a headbox. For
example, the binder resin may be introduced (e.g., injected) into the fiber slurry and
20 impregnated with and/or precipitated on to the fibers.
In some embodiments, the binder resin comprising one or more chemical
additives may be applied to the non-woven web using a non-compressive coating
technique. The non-compressive coating technique may coat the non-woven web, while
not substantially decreasing the thickness of the web. In other embodiments, the binder
25 resin may be applied to the non-woven web using a compressive coating technique.
Non-limiting examples of coating methods include the use of a slot die coater, gravure
coating, screen coating, size press coating (e.g., a two roll-type or a metering blade type
size press coater), film press coating, blade coating, roll-blade coating, air knife coating,
roll coating, foam application, reverse roll coating, bar coating, curtain coating,
30 champlex coating, brush coating, Bill-blade coating, short dwell-blade coating, lip
coating, gate roll coating, gate roll size press coating, melt coating, dip coating, knife roll
coating, spin coating, spray coating, gapped roll coating, roll transfer coating, padding
saturant coating, and saturation impregnation. Other coating methods are also possible.
34
After applying the binder resin to the non-woven web, the binder resin may be
dried by any suitable method. Non-limiting examples of drying methods include the use
of an infrared dryer, hot air oven, steam-heated cylinder, through air dryer, hot air float
oven, or any suitable type of dryer familiar to those of ordinary skill in the art.
The binder resin may coat any suitable 5 portion of the non-woven web. In some
embodiments, the coating of binder resin may be formed such that the surfaces of the
non-woven web are coated without substantially coating the interior of the non-woven
web. In some instances, a single surface of the non-woven web may be coated. For
example, a top surface or layer of the non-woven web may be coated. In other instances,
10 more than one surface or layer of the non-woven web may be coated (e.g., the top and
bottom surfaces or layers). In other embodiments, at least a portion of the interior of the
non-woven web may be coated without substantially coating at least one surface or layer
of the non-woven web. For example, a middle layer of a non-woven web may be coated,
but one or more layers adjacent to the middle layer may not be coated. The coating may
15 also be formed such that at least one surface or layer of the non-woven web and the
interior of the non-woven web are coated. In some embodiments, the entire web is
coated with the binder resin.
In some embodiments, at least a portion of the fibers and/or other components of
the non-woven web may be coated without substantially blocking the pores of the non20
woven web. In some instances, substantially all of the fibers and/or other components of
the non-woven web may be coated without substantially blocking the pores. Coating the
non-woven web using the binder resins described herein may add strength and/or
flexibility to the non-woven web, and leaving the pores substantially unblocked may be
important for maintaining or improving ion conductivity.
25 In some embodiments, the chemical additive(s) may be added to the fibers at the
wet end and/or deposited on the fibers and/or other components of the non-woven web
prior to addition of any binder resin. In some embodiments, chemical additive(s), such
as those described herein, may be added to the fiber slurry. In certain embodiments, the
chemical additive(s) may be coated on the fibers and/or other components of the non30
woven web using a beater addition method. Briefly, in a beater addition method, at least
a portion of the fibers and/or other components of the non-woven web are coated with a
charged molecule that has an opposite charge (e.g., positive or negative) from the
chemical additive to be added. The charged chemical additive is then brought into
35
contact with the oppositely charged non-woven web components, such that an
electrostatic interaction forms.
In some embodiments, the non-woven web may include more than one coating.
For example, at least a portion of the non-woven web may be coated with a chemical
additive and then at least a portion of the non-woven w 5 eb may be coated with a binder
resin.
In some embodiments a method of forming a coated non-woven web includes
applying a pre-polymerized and/or uncured resin including one or more chemical
additives to a non-woven web. In other embodiments, at least portions of the resin (or
10 components of the resin) may be polymerized or cured after applying the resin to the
non-woven web.
Various shaping techniques can be used to form a non-planar or shaped layer
described herein. In some embodiments, a shaping technique that allows the geometry of
the layer to be controlled without negatively affecting another beneficial property of the
15 layer (e.g., volume porosity) may be used. The shape or geometry of the layer may be
altered during and/or after fabrication of the layer. Non-limiting examples of suitable
processes include, but are not limited to, corrugation, pleating, embossing creping, and
micrexing.
As described herein, shaping of a layer may result in the formation of a non20
planar layer (a layer that includes repeated undulations and/or has at least one non-planar
surface). The undulating layer may include repeated bends and/or curves (e.g., waves,
pleats) that distort both the top and bottom face of the layer in a similar manner. In some
embodiments, the average size or amplitude of the bends or curves (e.g., waves, pleats)
may be on the order of the average thickness of the layer (e.g., at least 0.1, at least 0.2
25 times, at least 0.5 times, at least 1 time, at least 2 times) the thickness of the layer, or
greater (e.g., at least 4, at least 6, at least 8, at least 10 times the average thickness of the
layer). The average size or amplitude of the bends or curves (e.g., waves, pleats) may be,
in some instances, less than or equal to 20 times, less than or equal to 15 times, less than
or equal to 10 times, less than or equal to 8 times, less than or equal to 5 times, less than
30 or equal to 3 times, less than or equal to 2 times, or less than or equal to 1 time the
average thickness of the layer. Combinations of the above-referenced ranges are also
possible (e.g., average size or amplitude of at least 1 time and less than or equal to 10
times the average thickness of the layer). Other ranges are also possible.
36
The frequency of bends and/or curves (e.g., waves, pleats) in a layer may also
vary. In some embodiments, a layer described herein (e.g., a non-planar layer, an
undulating layer) may have at least 1 bend/100 mm, at least 10 bends/100 mm, at least
50 bends/100 mm, at least 100 bends/100 mm, at least 200 bends/100 mm, at least 300
bends/100 mm, at least 400 bends/100 mm, a 5 t least 500 bends/100 mm, at least 600
bends/100 mm, at least 700 bends/100 mm, at least 800 bends/100 mm, or at least 900
bends/100 mm. In certain embodiments, a layer described herein (e.g., a non-planar
layer, an undulating layer) may have less than or equal to 1000 bends/100 mm, less than
or equal to 900 bends/100 mm, less than or equal to 800 bends/100 mm, less than or
10 equal to 700 bends/100 mm, less than or equal to 600 bends/100 mm, less than or equal
to 500 bends/100 mm, less than or equal to 400 bends/100 mm, less than or equal to 300
bends/100 mm, less than or equal to 200 bends/100 mm, less than or equal to 100
bends/100 mm, less than or equal to 50 bends/100 mm, or less than or equal to 10
bends/100 mm.at least 100 bends/100 mm and less than or equal to 1000 bends/100
15 mm).It should appreciated that the ranges above for bends can also be applied to curves,
waves, pleats or other repeated units of shape (e.g., embossed patterns) as described
herein.
The percent surface area of the layer that is shaped (i.e., the percent surface area
that is non-planar, or at a non-zero angle (e.g., at an angle of greater than or equal to
20 about 5 degrees, at an angle of greater than or equal to about 10 degrees , at an angle of
greater than or equal to about 15 degrees), with respect to the plane of the layer) may
also vary. In some embodiments, the percent surface area of the layer that is shaped may
be greater than or equal to about 5%, greater than or equal to about 10%, greater than or
equal to about 20%, greater than or equal to about 30%, greater than or equal to about
25 40%, greater than or equal to about 50%, greater than or equal to about 60%, greater than
or equal to about 70%, greater than or equal to about 75%, greater than or equal to about
80%, or greater than or equal to about 90%. In some instances, the percent surface area
of the layer that is shaped may be less than 100%, less than or equal to about 90%, less
than or equal to about 80%, less than or equal to about 75%, less than or equal to about
30 70%, less than or equal to about 60%, less than or equal to about 50%, less than or equal
to about 40%, less than or equal to about 30%, less than or equal to about 20%, or less
than or equal to about 15%. Combination of the above-referenced ranges are also
possible (e.g., greater than or equal to about 10% and less than or equal to about 30%).In
37
some embodiments, both sides/surfaces of the layer may have percentages within one or
more of the above-referenced ranges. The percent surface area of the layer that is shaped
may be occupied by bends, curves, waves, pleats or other repeated units of shape as
described herein.
In some embodiments, corrugation or pleating may 5 be used to shape a layer (e.g.,
non-woven web). The corrugation or pleating may be performed in the machine
direction or cross direction. In some embodiments, corrugation or pleating may result in
bends, curves, waves or pleats within the layer having an amplitude, frequency and/or
percent surface area of coverage as described herein.
10 In some embodiments, embossing may be used to shape a layer. Several different
techniques may be used to emboss the layer. For example, pressure may be applied to a
layer using a roll system to form surface features (e.g., indentations) having a specific
pattern. In some instances, the layer may be formed on a wire (e.g., inclined table, flat
table, rotoformer, round former) that has a mesh pattern. The mesh pattern may generate
15 zones with more or less pulp and, accordingly, may produce an uneven thickness profile
(e.g., indentations) across the layer. In some such embodiments, the indendations may
be in the form of a mesh pattern, and may have a depth and/or a percent area coverage in
the layer in one or more ranges described herein. In embodiments in which the layer is a
wet laid layer, the layer may be embossed during the wet stage using a dandy roll with a
20 defined pattern. An embossed layer may comprise repeated units of one or more shape
(e.g., square indentations). The repeated units may have a defined shape, which may be,
for example, substantially circular, square, rectangular, trapezoidal, polygonal, or oval in
cross-section and/or in plan view (i.e., viewed from above). The shapes may be regular
or irregular. Any suitable shape may be embossed onto the layer.
25 In certain embodiments, the plurality of indentations in an embossed layer may
be arranged to form a pattern. In some embodiments, the pattern of indentations may be
simple, such as a checkerboard pattern, or more complex like a honeycomb pattern. In
other cases, for example, the pattern may be cubic, hexagonal, and/or polygonal. The
pattern of indentations may be regular or irregular.
30 In embodiments in which a layer described herein includes a non-planar surface
(e.g., an embossed surface), the average size or depth of the surface features (e.g.,
indentations) in the layer may be at least at least 0.05 times, at least 0.1 times, at least 0.2
times, at least 0.5 times, at least 1 time, at least 2 times, at least 4 times, at least 6 times,
38
or at least 8 times the average thickness of the layer. The average size or depth of the
surface features (e.g., indentations) in the layer may be less than or equal to 10 times,
less than or equal to 8 times, less than or equal to 5 times, less than or equal to 3 times,
less than or equal to 2 times, or less than or equal to 1 time the average thickness of the
layeraverage size or depth of at least 0.1 times and l 5 ess than or equal to 4 times the
average thickness of the layer). Other ranges are also possible.
In embodiments in which a layer described herein includes a non-planar surface
(e.g., an embossed surface), the average size or depth of the surface features (e.g.,
indentations) in the layer may be at least 0.05 times, at least 0.1 times, at least 0.2 times,
10 at least 0.5 times, at least 1 time the overall thickness of the layer. The average size or
depth of the surface features (e.g., indentations) in the layer may be less than or equal to
1 time, less than or equal to 0.5 times, less than or equal to 0.2 times, or less than or
equal to 0.1 times the overall thickness of the layer.average size or depth of at least 0.1
times and less than or equal to 1 times the overall thickness of the layer). Other ranges
15 are also possible.
The frequency of indentations in a layer may also vary. In some embodiments, a
layer described herein (e.g., an embossed layer) may have at least 1 indentation/100
mm2, at least 2 indentations/100 mm2, at least 5 indentations/100 mm2, at least 10
indentations/100 mm2, at least 20 indentations/10 mm2, at least 30 indentations/100 mm2,
at least 40 indentations/100 mm2, at least 50 indentations/100 mm220 , at least 60
indentations/100 mm2, at least 70 indentations/100 mm2, at least 80 indentations/100
mm2, or at least 90 indentations/100 mm2. In certain embodiments, a layer described
herein (e.g., an embossed layer) may have less than or equal to 100 indentations/100
mm2, less than or equal to 90 indentations/100 mm2, less than or equal to 80
indentations/100 mm2, less than or equal to 70 indentations/100 mm225 , less than or equal
to 60 indentations/100 mm2, less than or equal to 50 indentations/100 mm2, less than or
equal to 40 indentations/100 mm2, less than or equal to 30 indentations/100 mm2, less
than or equal to 20 indentations/100 mm2, less than or equal to 10 indentations/100 mm2,
less than or equal to 5 indentations/100 mm2, or less than or equal to 2 indentations/100
mm2at least 10 indentations/100 mm2 30 and less than or equal to 100 indentations/100
mm2The percent surface area of the layer that is embossed (i.e., the percent surface area
that is indented) may also vary. In some embodiments, the percent surface area of the
layer that is embossed may be greater than or equal to about 5%, greater than or equal to
39
about 10%, greater than or equal to about 20%, greater than or equal to about 30%,
greater than or equal to about 40%, greater than or equal to about 50%, greater than or
equal to about 60%, greater than or equal to about 70%, greater than or equal to about
75%, greater than or equal to about 80%, or greater than or equal to about 90%. In some
instances, the percent surface area of the layer that 5 is embossed may be less than 100%,
less than or equal to about 90%, less than or equal to about 80%, less than or equal to
about 75%, less than or equal to about 70%, less than or equal to about 60%, less than or
equal to about 50%, less than or equal to about 40%, less than or equal to about 30%,
less than or equal to about 20%, or less than or equal to about 15%. Combination of the
10 above-referenced ranges are also possible (e.g., greater than or equal to about 10% and
less than or equal to about 30%). Other values are also possible. In some embodiments,
both sides/surfaces of the layer may have percentages within one or more of the abovereferenced
ranges.
In some embodiments, creping may be used to shape the layer. In some
15 embodiments, creping refers to the generation of a 3D structure of a flat wet sheet using
a quick change of speed and angle of the sheet path from a smooth roll. In some
embodiments, creping may be used to form an irregular shape in the layer, such as an
irregular wave pattern. In some embodiments, creping may be used to form a regular
shape. In some embodiments, creping may result in bends, curves, waves or patterns
20 within the layer having an amplitude, frequency and/or percent surface area of coverage
as described herein.
In some embodiments, micrexing may be used to shape the layer. Micrex is
similar to creping but is performed on a fully dried sheet. In some embodiments,
micrexing may be used to form an irregular shape in the layer, such as an irregular wave
25 pattern. In some embodiments, microexing may be used to form a regular shape. In
some embodiments, micrexing may result in bends, curves, waves or patterns within the
layer having an amplitude, frequency and/or percent surface area of coverage as
described herein.
It should be appreciated that while in some embodiments a layer may be shaped,
30 e.g., corrugated, pleated, embossed, creped, and/or micrexed, in some embodiments, a
layer described herein (e.g., a shaped layer, a non-woven layer) is not corrugated, not
pleated, not embossed, not creped, and/or not micrexed. Additionally, it should be
understood that in certain embodiments, more than one shaping technique can be used to
40
form a layer and/or separator described herein (e.g., corrugation and embossing). Shaped
layers that include additives are also possible. Other configurations are also possible.
In some embodiments, a non-woven web may include glass fibers (e.g.,
microglass fibers, chopped strand glass fibers, or a combination thereof). Microglass
fibers and chopped strand glass fibers are known to t 5 hose of ordinary skill in the art.
One of ordinary skill in the art is able to determine whether a glass fiber is microglass or
chopped strand by observation (e.g., optical microscopy, electron microscopy).
Microglass fibers may also have chemical differences from chopped strand glass fibers.
In some cases, though not required, chopped strand glass fibers may contain a greater
10 content of calcium or sodium than microglass fibers. For example, chopped strand glass
fibers may be close to alkali free with high calcium oxide and alumina content.
Microglass fibers may contain 10-15% alkali (e.g., sodium, magnesium oxides) and have
relatively lower melting and processing temperatures. The terms refer to the
technique(s) used to manufacture the glass fibers. Such techniques impart the glass
15 fibers with certain characteristics. In general, chopped strand glass fibers are drawn from
bushing tips and cut into fibers in a process similar to textile production. Chopped strand
glass fibers are produced in a more controlled manner than microglass fibers, and as a
result, chopped strand glass fibers will generally have less variation in fiber diameter and
length than microglass fibers. Microglass fibers are drawn from bushing tips and further
20 subjected to flame blowing or rotary spinning processes. In some cases, fine microglass
fibers may be made using a remelting process. In this respect, microglass fibers may be
fine or coarse. As used herein, fine microglass fibers are less than or equal to 1 micron
in diameter and coarse microglass fibers are greater than or equal to 1 micron in
diameter.
25 The microglass fibers may have small diameters. For instance, in some
embodiments, the average diameter of the microglass fibers may be less than or equal to
about 10 microns, less than or equal to about 9 microns, less than or equal to about 7
microns, less than or equal to about 5 microns, less than or equal to about 3 microns, or
less than or equal to about 1 micron. In some instances, the microglass fibers may have
30 an average fiber diameter of greater than or equal to about 0.1 microns, greater than or
equal to about 0.3 microns, greater than or equal to about 1 micron, greater than or equal
to about 3 microns, or greater than or equal to about 7 microns. Combinations of the
above-referenced ranges are also possible (e.g., greater than or equal to about 0.1
41
microns and less than or equal to about 10 microns, greater than or equal to about 0.1
microns and less than or equal to about 5 microns, greater than or equal to about 0.3
microns and less than or equal to about 3 microns). Other values of average fiber
diameter are also possible. Average diameter distributions for microglass fibers are
generally log-normal. However, it can be appreciated that 5 microglass fibers may be
provided in any other appropriate average diameter distribution (e.g., Gaussian
distribution).
In some embodiments, the average length of microglass fibers may be less than
or equal to about 10 mm, less than or equal to about 10 mm, less than or equal to about 8
10 mm, less than or equal to about 6 mm, less than or equal to about 5 mm, less than or
equal to about 4 mm, less than or equal to about 3 mm, or less than or equal to about 2
mm. In certain embodiments, the average length of microglass fibers may be greater
than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or equal
to about 4 mm, greater than or equal to about 5 mm, greater than equal to about 6 mm, or
15 greater than or equal to about 8 mm. Combinations of the above referenced ranges are
also possible (e.g., microglass fibers having an average length of greater than or equal to
about 4 mm and less than about 6 mm). Other ranges are also possible.
In other embodiments, the microglass fibers may vary significantly in length as a
result of process variations. For instance, in some embodiments, the average aspect
20 ratios (length to diameter ratio) of the microglass fibers in a non-woven web may be
greater than or equal to about 100, greater than or equal to about 200, greater than or
equal to about 300, greater than or equal to about 1000, greater than or equal to about
3,000, greater than or equal to about 6,000, greater than or equal to about 9,000. In some
instances, the microglass fibers may have an average aspect ratio of less than or equal to
25 about 10,000, less than or equal to about 5,000, less than or equal to about 2,500, less
than or equal to about 600, or less than or equal to about 300. Combinations of the
above-referenced ranges are also possible (e.g., greater than or equal to about 200 and
less than or equal to about 2,500). Other values of average aspect ratio are also possible.
It should be appreciated that the above-noted dimensions are not limiting and that the
30 microglass fibers may also have other dimensions.
In general, chopped strand glass fibers may have an average fiber diameter that is
greater than the diameter of the microglass fibers. For instance, in some embodiments,
the average diameter of the chopped strand glass fibers may be greater than or equal to
42
about 5 microns, greater than or equal to about 7 microns, greater than or equal to about
9 microns, greater than or equal to about 11 microns, or greater than or equal to about 20
microns. In some instances, the chopped strand glass fibers may have an average fiber
diameter of less than or equal to about 30 microns, less than or equal to about 25
microns, less than or equal to about 15 microns, l 5 ess than or equal to about 12 microns,
or less than or equal to about 10 microns. Combinations of the above-referenced ranges
are also possible (e.g., greater than or equal to about 5 microns and less than or equal to
about 12 microns). Other values of average fiber diameter are also possible. Chopped
strand diameters tend to follow a normal distribution. Though, it can be appreciated that
10 chopped strand glass fibers may be provided in any appropriate average diameter
distribution (e.g., Gaussian distribution).
In some embodiments, chopped strand glass fibers may have a length in the range
of between about 0.125 inches and about 1 inch (e.g., about 0.25 inches, or about 0.5
inches). In some embodiments, the average length of chopped strand glass fibers may be
15 less than or equal to about 1 inch, less than or equal to about 0.8 inches, less than or
equal to about 0.6 inches, less than or equal to about 0.5 inches, less than or equal to
about 0.4 inches, less than or equal to about 0.3 inches, or less than or equal to about 0.2
inches. In certain embodiments, the average length of chopped strand glass fibers may
be greater than or equal to about 0.125 inches, greater than or equal to about 0.2 inches,
20 greater than or equal to about 0.4 inches, greater than or equal to about 0.5 inches,
greater than equal to about 0.6 inches, or greater than or equal to about 0.8 inches.
Combinations of the above referenced ranges are also possible (e.g., chopped strand
glass fibers having an average length of greater than or equal to about 0.125 inches and
less than about 1 inch). Other ranges are also possible.
25 It should be appreciated that the above-noted dimensions are not limiting and that
the microglass and/or chopped strand fibers, as well as the other fibers described herein,
may also have other dimensions.
In some embodiments, the average diameter of the glass fibers in the non-woven
web may be greater than or equal to about 0.1 microns, greater than or equal to about 0.3
30 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1
micron, greater than or equal to about 2 microns, greater than or equal to about 3
microns, greater than or equal to about 5 microns, greater than or equal to about 7
microns, greater than or equal to about 9 microns, greater than or equal to about 10
43
microns, or greater than or equal to about 12 microns. In some instances, the average
diameter of the glass fibers in the non-woven web may have an average fiber diameter of
less than or equal to about 15 microns, less than or equal to about 12 microns, less than
or equal to about 10 microns, less than or equal to about 8 microns, less than or equal to
about 5 microns, less than or equal to about 3 microns, or 5 less than or equal to about 1
micron. Combinations of the above-referenced ranges are also possible (e.g., greater
than or equal to about 0.1 microns and less than or equal to about 15 microns, greater
than or equal to about 0.1 microns and less than or equal to about 10 microns, greater
than or equal to about 0.1 microns and less than or equal to about 5 microns, greater than
10 or equal to about 0.3 microns and less than or equal to about 3 microns).
In some embodiments, the average length of the glass fibers in the non-woven
web may be less than or equal to about 50 mm, less than or equal to about 40 mm, less
than or equal to about 30 mm, less than or equal to about 25 mm, less than or equal to
about 20 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less
15 than or equal to about 10 mm, less than or equal to about 8 mm, less than or equal to
about 5 mm, less than or equal to about 3 mm, or less than or equal to about 1 mm. In
certain embodiments, the average length diameter of the glass fibers in the non-woven
web may be greater than or equal to about 0.05 mm, greater than or equal to about 0.1
mm, greater than or equal to about 0.2 mm, greater than or equal to about 0.5 mm,
20 greater than equal to about 1 mm, greater than or equal to about 5 mm, greater than equal
to about 10 mm, greater than or equal to about 15 mm, greater than equal to about 20
mm, greater than or equal to about 30 mm, or greater than or equal to about 40 mm.
Combinations of the above referenced ranges are also possible (e.g., greater than or equal
to about 0.05 mm and less than about 50 mm, greater than or equal to about 1 mm and
25 less than about 25 mm, greater than or equal to about 0.1 mm and less than about 12 mm,
greater than or equal to about 0.2 mm and less than about 6 mm, greater than or equal to
about 0.5 mm and less than about 3 mm). Other ranges are also possible.
A non-woven web may include a suitable percentage of glass fibers. In some
embodiments, the weight percentage of glass fibers in the non-woven web may be
30 greater than or equal to about 2 wt.%, greater than or equal to about 5 wt.%, greater than
or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal
to about 30 wt.%, greater than or equal to about 40 wt.%, greater than or equal to about
50 wt.%, greater than or equal to about 60 wt.%, greater than or equal to about 70 wt.%,
44
greater than or equal to about 80 wt.%, or greater than or equal to about 90 wt.%. In
some embodiments, the weight percentage of the glass fibers in the non-woven web may
be less than or equal to about 95 wt.%, less than or equal to about 90 wt.%, less than or
equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about
60 wt.%, less than or equal to about 50 wt.%, less 5 than or equal to about 40 wt.%, less
than or equal to about 30 wt.%, less than or equal to about 20 wt.%, less than or equal to
about10 wt.%, or less than or equal to about 5 wt.%. Combinations of the abovereferenced
ranges are also possible (e.g., greater than about 2 wt.% and less than or equal
to about 95 wt.%, greater than about 5 wt.% and less than or equal to about 50 wt.%,
10 greater than about 10 wt.% and less than or equal to about 50 wt.%, greater than about 10
wt.% and less than or equal to about 30 wt.%). Other ranges are also possible. In some
embodiments, a non-woven web includes the above-noted ranges of glass fibers with
respect to the total weight of fibers in the non-woven web and/or the battery separator.
In some embodiments, a non-woven web described herein includes one or more
15 synthetic fibers. Synthetic fibers may include any suitable type of synthetic polymer.
Examples of suitable synthetic fibers include polyester, polyaramid, polyimide,
polyolefin (e.g., polyethylene), polypropylene, Kevlar, nomex, halogenated polymers
(e.g., polyethylene terephthalate), acrylics, polyphenylene oxide, polyphenylene sulfide,
and combinations thereof. In some embodiments, the synthetic fibers are organic
20 polymer fibers. Synthetic fibers may also include multi-component fibers (i.e., fibers
having multiple compositions such as bi-component fibers). The non-woven web may
also include combinations of more than one type of composition of synthetic fiber. It
should be understood that other compositions of synthetic fiber types may also be used.
In some embodiments, synthetic fibers may be staple fibers, which may be
25 synthetic fibers that are cut to a suitable average length and are appropriate for
incorporation into a wet-laid or dry-laid process for forming a non-woven web. In some
cases, groups of staple fibers may be cut to have a particular length with only slight
variations in length between individual fibers.
In some embodiments, synthetic fibers may be binder fibers, as described in more
30 detail below.
Non-woven webs including combinations of different types of synthetic fibers are
also possible.
45
A non-woven web may include a suitable percentage of synthetic fibers. In some
embodiments, the weight percentage of synthetic fibers in the non-woven web may be
0%, greater than or equal to about 1 wt.%, greater than or equal to about 5 wt.%, greater
than or equal to about 10 wt.%, greater than or equal to about 15 wt.%, greater than or
equal to about 20 wt.%, greater than or equal to a 5 bout 30 wt.%, greater than or equal to
about 40 wt.%, greater than or equal to about 50 wt.%, greater than or equal to about 60
wt.%, or greater than or equal to about 70 wt.%. In some embodiments, the weight
percentage of the synthetic fibers in the non-woven web may be less than or equal to
about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%,
10 less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or
equal to about 30 wt.%, less than or equal to about 20 wt.%, less than or equal to about
10 wt.%, or less than or equal to about 5 wt.%. Combinations of the above-referenced
ranges are also possible (e.g., greater than about 1 wt.% and less than or equal to about
80 wt.%, greater than about 1 wt.% and less than or equal to about 50 wt.%, greater than
15 about 5 wt.% and less than or equal to about 50 wt.%, greater than about 5 wt.% and less
than or equal to about 30 wt.%, greater than about 10 wt.% and less than or equal to
about 40 wt.%, greater than about 15 wt.% and less than or equal to about 25 wt.%).
Other ranges are also possible. In some embodiments, a non-woven web includes the
above-noted ranges of synthetic fibers with respect to the total weight of fibers in the
20 non-woven web and/or the battery separator.
In general, synthetic fibers may have any suitable dimensions. For instance, in
some embodiments, the synthetic fibers may have an average diameter of greater than or
equal to about 0.5 micron, greater than or equal to about 1 micron, greater than or equal
to about 2 microns, greater than or equal to about 4 microns, greater than or equal to
25 about 6 microns, greater than or equal to about 8 microns, greater than or equal to about
10 microns, greater than or equal to about 12 microns, greater than or equal to about 15
microns, greater than or equal to about 20 microns, greater than or equal to about 30
microns, or greater than or equal to about 40 microns. In some cases, the synthetic fibers
may have an average diameter of less than or equal to about 50 microns, less than or
30 equal to about 40 microns, less than or equal to about 30 microns, less than or equal to
about 20 microns, less than or equal to about 15 microns, less than or equal to about 12
microns, less than or equal to about 10 microns, than or equal to about 8 microns, less
than or equal to about 6 microns, less than equal to about 4 microns, or less than or equal
46
to about 2 microns. Combinations of the above referenced ranges are also possible (e.g.,
greater than or equal to about 0.5 microns and less than about 50 microns, greater than or
equal to about 5 microns and less than about 20 microns). Other ranges are also
possible.
In some embodiments, synthetic fibers may have an average 5 length of greater
than or equal to about 0.25 mm, greater than or equal to about 0.5 mm, greater than or
equal to about 1 mm, greater than or equal to about 3 mm, greater than or equal to about
5 mm, greater than or equal to about 10 mm, greater than or equal to about 25 mm,
greater than or equal to about 50 mm, greater than or equal to about 75 mm, greater than
10 or equal to about 100 mm, greater than or equal to about 150 mm, greater than or equal
to about 200 mm, or greater than or equal to about 250 mm. In some instances, synthetic
fibers may have an average length of less than or equal to about 300 mm, less than or
equal to about 250 mm, less than or equal to about 200 mm, less than or equal to about
150 mm, less than or equal to about 100 mm, less than or equal to about 76 mm, less
15 than or equal to about 50 mm, less than or equal to about 25 mm, less than or equal to
about 20 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less
than or equal to about 10 mm, less than or equal to about 9 mm, less than or equal to
about 6 mm, less than or equal to about 4 mm, less than or equal to about 2 mm, or less
than or equal to about 1 mm. Combinations of the above-referenced ranges are also
20 possible (e.g., greater than or equal to about 0.5 mm and less than or equal to about 300
mm, greater than or equal to about 0.25 mm and less than or equal to about 76 mm,
greater than or equal to about 1 mm and less than or equal to about 12 mm, greater than
or equal to about 3 mm and less than or equal to about 9 mm). Other values of average
fiber length are also possible.
25 As described herein, in some embodiments, at least a portion of the synthetic
fibers may be binder fibers. The binder fibers may be mono-component (i.e., having a
single composition) or multi-component (i.e., having multiple compositions such as a bicomponent
fiber). The non-woven web may include a suitable percentage of monocomponent
fibers and/or multi-component fibers. In some embodiments, all of the
30 synthetic fibers are mono-component fibers. In some embodiments, at least a portion of
the synthetic fibers are multi-component fibers. In some embodiments, the non-woven
web may comprise a residue from a binder fiber.
47
An example of a multi-component fiber is a bi-component fiber which includes a
first material and a second material that is different from the first material. The different
components of a multi-component fiber may exhibit a variety of spatial arrangements.
For example, multi-component fibers may be arranged in a core-sheath configuration
(e.g., a first material may be a sheath material that surrounds 5 a second material which is a
core material), a side by side configuration (e.g., a first material may be arranged
adjacent to a second material), a segmented pie arrangement (e.g., different materials
may be arranged adjacent to one another in a wedged configuration), a tri-lobal
arrangement (e.g., a tip of a lobe may have a material different from the lobe) and an
10 arrangement of localized regions of one component in a different component (e.g.,
“islands in sea”).
In some embodiments, for a core-sheath configuration, a multi-component fiber,
such as a bi-component fiber, may include a sheath of a first material that surrounds a
core comprising a second material. In such an arrangement, for some embodiments, the
15 melting point of the first material may be lower than the melting point of the second
material. Accordingly, at a suitable step during manufacture of a non-woven web (e.g.,
drying), the first material comprising the sheath may be melted (e.g., may exhibit a phase
change) while the second material comprising the core remains unaltered (e.g., may
exhibit no phase change). For instance, an outer sheath portion of a multi-component
20 fiber may have a melting temperature between about 50 ºC and about 200 ºC (e.g., 180
ºC) and an inner core of the multi-component fiber may have a melting temperature
above 200 ºC. As a result, when the fiber is subjected to a temperature during drying,
e.g., at 180 ºC, then the outer sheath of the fiber may melt while the core of the fiber
does not melt.
25 Examples of suitable multi-component fibers include polyolefin (e.g.,
polyethylene / PET, coPET (e.g., melt amorphous, melt crystalline) / PET, and
polyethylene / polypropylene. In this listing of multi-component fibers, the convention
is to list the material having the lower melting temperature (e.g., first material) separated
from the material having the higher melting temperature (e.g., second material) with a
30 “/". Other suitable compositions are known to those of skill in the art. In some
embodiments, the binder fiber may include a vinyl compounds (e.g., polyvinyl alcohol).
In some embodiments, the weight percentage of multi-component fibers (e.g., bicomponent
fibers) in the non-woven web may be 0%, greater than or equal to about 1
48
wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 10 wt.%,
greater than or equal to about 15 wt.%, greater than or equal to about 20 wt.%, greater
than or equal to about 30 wt.%, greater than or equal to about 40 wt.%, greater than or
equal to about 50 wt.%, greater than or equal to about 60 wt.%, or greater than or equal
to about 70 wt.%. In some embodiments, the weight percentage 5 of the multi-component
fibers (e.g., bi-component fibers) in the non-woven web may be less than or equal to
about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%,
less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or
equal to about 30 wt.%, less than or equal to about 20 wt.%, less than or equal to about
10 10 wt.%, or less than or equal to about 5 wt.%. Combinations of the above-referenced
ranges are also possible (e.g., greater than about 5 wt.% and less than or equal to about
30 wt.%). Other ranges are also possible. In some embodiments, a non-woven web
includes the above-noted ranges of multi-component fibers (e.g., bi-component fibers)
with respect to the total weight of fibers in the non-woven web and/or the battery
15 separator.
In general, a non-woven web and/or separator may include any suitable binder
resin. Features of the binder resin may include resistance to the battery environment
(e.g., acid electrolyte, oxidation), the ability to be applied in the form of a water soluble
emulsion or dispersion, even flow characteristics on the non-woven web upon drying,
20 thermal stability, and/or the ability to thermally cure above 100 °C within 1 minute. The
binder resin may comprise a thermoplastic, a thermoset, or a combination thereof. For
example, the binder resin may include one or more of the following resins: natural
rubber, acrylic, latex emulsion, styrene-acrylic, synthetic rubber (e.g., styrene butadiene
rubber), styrene acrylonitrile, and combinations thereof. In some embodiments, the resin
25 may be provided as an aqueous solvent-based system. In some such embodiments, the
binder resin may be an emulsion or dispersion. In certain embodiments, the binder resin
may be provided as a non-aqueous solvent-based system. In some embodiments, one or
more of the polymers in the resin may comprise aryl pendant groups. These aryl groups
may impart stiffness and steric hindrance on to the main chain, providing excellent
30 chemical and electrochemical resistance.
The amount of resin in a non-woven web may vary. For example, the weight
percentage of binder resin in the non-woven web and/or battery separator may be
between 0 wt.% and 40 wt.%. In some embodiments, the weight percentage of resin in
49
the non-woven web may be greater than or equal to about 2 wt.%, greater than or equal
to about 5 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 15
wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%,
greater than or equal to about 30 wt.%, greater than or equal to about 35 wt.%, greater
than or equal to about 40 wt.%, or greater than or 5 equal to about 45 wt.%. In some cases,
the weight percentage of resin in the non-woven web may be less than or equal to about
50 wt.%, less than or equal to about 45 wt.%, less than or equal to about 40 wt.%, less
than or equal to about 35 wt.%, less than or equal to about 30 wt.%, less than or equal to
about 25 wt.%, less than or equal to about 20 wt.%, less than or equal to about 15 wt.%,
10 less than or equal to about 10 wt.%, or less than or equal to about 5 wt.%. Combinations
of the above-referenced ranges are also possible (e.g., greater than or equal to about 2
wt.% and less than about 40 wt.%, greater than or equal to about 5 wt.% and less than
about 40 wt.%, greater than or equal to about 5 wt.% and less than about 20 wt.%,
greater than or equal to about 10 wt.% and less than about 20 wt.%). Other ranges are
15 also possible. The weight percentage of binder resin in the entire non-woven web and/or
battery separator is based on the dry solids and can be determined prior to coating the
non-woven web.
To form a binder resin containing one or more chemical additives and/or other
components of the non-woven web (e.g., inorganic particles), the chemical additive(s)
20 and/or other components to be included in the binder resin may first be added in a
specific amount to a solution or suspension (e.g., water or other solvent). In some
embodiments, an emulsion is formed. A binder resin (and any optional additives) may
then be combined and mixed with the solution/suspension/emulsion containing the
chemical additive(s) and/or other components. It should be understood that this method
25 of binder resin formulation is not limiting and other methods of resin formulation are
possible. A binder resin containing chemical additive(s) and/or other components
therein may be added to the non-woven web in any suitable manner (e.g., in the wet state
or in the dry state) after the non-woven web is formed and/or during formation of the
non-woven web.
30 In some embodiments, the non-woven web may comprise inorganic particles. In
some embodiments, inorganic particles in the non-woven web may result in one or more
of the following advantages: reduce the pore size of the non-woven without significantly
altering the volume porosity of the non-woven web, increase the wicking and wettability
50
of the non-woven web, absorb more electrolyte compared to a similar non-woven web
that lacks inorganic particles (all other factors being equal), e.g., due to the wetting
properties of the inorganic particles, and/or scavenge harmful contaminants such as
heavy metal ions. For instance, in some embodiments inorganic particles having very
fine pores may create enhanced capillary forces to absorb electrolyte 5 and the trapping of
contaminants may be due, at least in part, to this capillary action. In some embodiments,
the inorganic particles may coat the fibers of the non-woven and serve to reduce the pore
size and/or the variation in pore size of the non-woven web.
Non-limiting examples of inorganic particles include silica (e.g., fumed,
10 ground/mineral, fused, precipitated, agglomerated), clay, talc, diatoms (e.g.,
diatomaceous earth), zeolites, TiO2, rice husk ash, other ashes, and combinations thereof.
In some embodiments, the inorganic particles are substantially non-porous. For certain
battery types, a suitable inorganic particle may be resistant to sulfuric acid and/or may
have a suitable surface area.
15 In some embodiments, the weight percentage of inorganic particles in the nonwoven
web and/or battery separator may be greater than or equal to about 10 wt.%,
greater than or equal to about 20 wt.%, greater than or equal to about 30 wt.%, greater
than or equal to about 40 wt.%, greater than or equal to about 50 wt.%, greater than or
equal to about 60 wt.%, or greater than or equal to about 70 wt.%. In some cases, the
20 weight percentage of inorganic particle in the non-woven web and/or battery separator
may be less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than
or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to
about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%,
or less than or equal to about 15 wt.%. Combinations of the above-referenced ranges are
25 also possible (e.g., greater than or equal to about 10 wt.% and less than about 80 wt.%,
greater than or equal to about 30 wt.% and less than about 60 wt.%). Other ranges are
also possible. The weight percentage of inorganic particles in the entire non-woven web
and/or battery separator is based on the dry solids and can be determined prior to forming
the non-woven web.
30 In some embodiments, the inorganic particles (e.g., silica) may have a relatively
high surface area and/or may be porous. In certain embodiments, inorganic particles
with a high surface area may resist stratification, or layering of acid, during recharge as a
51
function of gravity. In some embodiments, the inorganic particles may be chemically
inert and stable in acid. The inorganic particles may also be thermally stable.
In some embodiments, the inorganic particles included in a nonwoven web and/or
separator described herein may be chosen to have a particular range of average surface
area. The average surface area of the inorganic particles may 5 be, for example, greater
than or equal to about 10 m2/g, greater than or equal to about 50 m2/g, greater than or
equal to about 100 m2/g, greater than or equal to about 200 m2/g, greater than or equal to
about 400 m2/g, greater than or equal to about 600 m2/g, greater than or equal to about
800 m2/g, greater than or equal to about 1,000 m2/g, greater than or equal to about 1,250
m2/g, greater than or equal to about 1,500 m210 /g, or greater than or equal to about 1,750
m2/g. In some embodiments, the average surface area of the inorganic particles may be
less than or equal to about 2,000 m2/g, less than or equal to about 1,750 m2/g, less than or
equal to about 1,500 m2/g, less than or equal to about 1,250 m2/g, less than or equal to
about 1,000 m2/g, less than or equal to about 900 m2/g, less than or equal to about 800
m2/g, less than or equal to about 600 m2/g, less than or equal to about 400 m215 /g, less than
or equal to about 200 m2/g, less than or equal to about 100 m2/g, or less than or equal to
about 50 m2/g. Combinations of the above-referenced ranges are also possible (e.g.,
greater than or equal to about 10 m2/g and less than or equal to about 2,000 m2/g, greater
than or equal to about 50 m2/g and less than or equal to about 1,000 m2/g, greater than or
equal to about 100 m2/g and less than or equal to about 600 m220 /g, greater than or equal to
about 400 m2/g and less than or equal to about 600 m2/g). Other ranges are also possible.
As determined herein, surface area is measured according to BCIS-03A, Sept -09
revision, Method 8 (e.g., using a 0.5 gram sample).
In some embodiments, the average particle size (e.g., average diameter, or
25 average cross-sectional dimension) of the inorganic particles included in a non-woven
web and/or separator described herein may be, for example, greater than about 1 micron,
greater than or equal to about 3 microns, greater than or equal to about 5 microns, greater
than or equal to about 10 microns, greater than or equal to about 20 microns, greater than
or equal to about 30 microns, greater than or equal to about 40 microns, greater than or
30 equal to about 50 microns, greater than or equal to about 60 microns, greater than or
equal to about 70 microns, greater than or equal to about 80 microns, or greater than or
equal to about 90 microns. The particles may have an average particle size of, for
example, less than or equal to about 100 microns, less than or equal to about 90 microns,
52
less than or equal to about 80 microns, less than or equal to about 70 microns, less than
or equal to about 60 microns, less than or equal to about 50 microns, less than or equal to
about 40 microns, less than or equal to about 30 microns, less than or equal to about 20
microns, less than or equal to about 10 microns, or less than or equal to about 5 microns.
Combinations of the above-referenced ranges are also possible 5 (e.g., greater than or
equal to about 1 micron and less than or equal to about 100 microns, greater than or
equal to about 3 micron and less than or equal to about 10 microns). Other ranges are
also possible.
In some embodiments, the inorganic particles included in a nonwoven web and/or
10 battery separator may be resistant to sulfuric acid. As used herein, particles that are
resistant to sulfuric acid refer to inorganic particles that have an acid weight loss of less
than 20% (e.g., less than 15%, less than 10%, less than 5%) of the total weight of the
particles after a three-hour reflux in 1.260 SG sulfuric acid using the BCIS-03A Mar
2010 method 13. The weight of the inorganic particles is measured prior to and after
15 such sulfuric acid exposure to determine percent of weight lost (e.g., % acid weight loss
= [weight of particles before exposure – weight of particles after exposure]/weight of
particles before exposure*100). In some embodiments, inorganic particles having a total
weight loss of less than 20%, less than 15%, less than 10%, or less than 5% are used in a
non-woven web and/or battery separator described herein.
20 In general, any suitable process may be used to add the inorganic particles to the
non-woven web and/or battery separator. In some embodiments, the inorganic particles
are added with the fibers in the fiber slurry during formation of the non-woven web.
Alternatively, the inorganic particles may be added into the binder resin. In certain
embodiments, inorganic particles may be added to both the fiber slurry and the binder
25 resin.
In some embodiments, the non-woven web and/or battery separator may
comprise ribs as shown in FIG. 4B. One of ordinary skill in the art would understand
that ribs are additional material that is added to one or more surfaces of one or more
layers of the battery separator (e.g., a surface of a non-woven web described herein), and
30 that ribs are discrete from the layer(s) on which the ribs are added (e.g., a distinguishable
interface exists between the rib material and the layer on which the rib material is added)
as illustrated in FIG. 4B. For instance, the ribs are typically added in a secondary step
after the layer (e.g., non-woven web) has been formed. In certain embodiments, one or
53
more of the chemical additives described herein, may be added to the ribs in the wt. %’s
described earlier.
In general, any suitable material that is resistant to the battery environment may
be used to form the ribs. Non-limiting examples of rib material includes thermoplastics,
such as plastisol (e.g., polyvinylchloride blended with a plasticizer, pol 5 yacrylates),
polyolefins (e.g., polyethylene, polypropylene, polybutylene, copolyethylene-octene,
polyethylenevinylacetate), polyester, polystyrene, acrylonitrile-butadiene-styrene (ABS),
polyvinylchloride, polyimides, polyurethanes, and thermosets, such as polyurethanes,
polyacrylates, polyepoxides, reactive plastisols, phenolic resin, polyimides, rubber (e.g.,
10 natural, synthetic), and combinations thereof.
In general, the ribs may have any suitable shape and be arranged in any suitable
pattern as described in PCT/IB/064420 filed Sept. 11, 2014, entitled Battery Separator
with Ribs and a Method of Casting the Ribs on the Separator, which is incorporated
herein by reference in its entirety. For example, the ribs may be in the form of lines
15 (e.g., continuous, discontinuous) or dots arranged in rows on top of one or more layers of
the battery separator. In some embodiments, ribs may not be present on the battery
separator.
In some embodiments, the battery separator including a non-woven web
comprising one or more chemical additives and/or non-planar layer may have desirable
20 structural properties.
In some embodiments, the basis weight of one or more layers of the battery
separator (e.g., the non-woven web and/or the overall battery separator) may range from
between about 25 g/m2 and about 1,200 g/m2. For instance, in some embodiments, the
basis weight of one or more layers of the battery separator (e.g., the non-woven web
and/or the overall battery separator) may be greater than or equal to about 25 g/m225 ,
greater than or equal to about 40 g/m2, greater than or equal to about 60 g/m2, greater
than or equal to about 80 g/m2, greater than or equal to about 100 g/m2, greater than or
equal to about 150 g/m2, greater than or equal to about 200 g/m2, greater than or equal to
about 250 g/m2, greater than or equal to about 300 g/m2, or greater than or equal to about
350 g/m230 . In some cases, the basis weight of one or more layers of the battery separator
(e.g., the non-woven web and/or the overall battery separator) may be less than or equal
to about 400 g/m2, less than or equal to about 350 g/m2, less than or equal to about 300
g/m2, less than or equal to about 250 g/m2, less than or equal to about 200 g/m2, less than
54
or equal to about 150 g/m2, less than or equal to about 100 g/m2, less than or equal to
about 75 g/m2, or less than or equal to about 50 g/m2. Combinations of the abovereferenced
ranges are also possible (e.g., greater than or equal to about 25 g/m2 and less
than or equal to about 400 g/m2, greater than or equal to about 80 g/m2 and less than or
equal to about 300 g/m2). Other ranges are also possible. A 5 s determined herein, the
basis weight of the non-woven web and/or battery separator is measured according to the
BCIS-03A, Sept -09, Method 3.
In certain embodiments, the basis weight of one or more layers of the battery
separator (e.g., the non-woven web and/or the overall battery separator) may be higher
10 than the above-recited range. In some embodiments, a non-planar (e.g., shaped) nonwoven
web or battery separator may have a greater basis weight compared to a similar
non-woven web in planar form (e.g., prior to shaping), as described herein. For instance,
in some embodiments, the basis weight of the non-woven web and/or battery separator
may be greater than or equal to about 500 g/m2, greater than or equal to about 600 g/m2,
greater than or equal to about 800 g/m2, or greater than or equal to about 1,000 g/m215 . In
some cases, the basis weight of one or more layers of the battery separator (e.g., the nonwoven
web and/or the overall battery separator) may be less than or equal to about 1,200
g/m2, less than or equal to about 1,000 g/m2, less than or equal to about 800 g/m2, less
than or equal to about 600 g/m2, or less than or equal to about 500 g/m2. Combinations
20 of the above-referenced ranges are also possible (e.g., greater than or equal to about 25
g/m2 and less than or equal to about 1,200 g/m2, greater than or equal to about 100 g/m2
and less than or equal to about 375 g/m2). Other ranges are also possible. As determined
herein, the basis weight of the non-woven web and/or battery separator is measured
according to the BCIS-03A Sept -09 Method 3.
25 Thickness, as referred to herein, is determined according to BCIS 03-A Sept-09,
Method 10 using 10 kPa pressure. The thickness of one or more layers of the battery
separator (e.g., the non-woven web and/or the overall battery separator) may be between
about 0.05 mm and about 3 mm. In some embodiments, the thickness of the non-woven
web and/or battery separator may be greater than or equal to about 0.05 mm, greater than
30 or equal to about 0.1 mm, greater than or equal to about 0.2 mm, greater than or equal to
about 0.3 mm, greater than or equal to about 0.5 mm, greater than or equal to about 0.8
mm, greater than or equal to about 1 mm, greater than or equal to about 1.2 mm, greater
than or equal to about 1.5 mm, greater than or equal to about 1.8 mm, greater than or
55
equal to about 2 mm, or greater than or equal to about 2.5 mm. In certain embodiments,
the thickness of one or more layers of the battery separator (e.g., the non-woven web
and/or the overall battery separator) may be less than or equal to about 3 mm, less than
or equal to about 2.8 mm, less than or equal to about 2.5 mm, less than or equal to about
2.0 mm, less than or equal to about 1.8 mm, less 5 than or equal to about 1.5 mm, less than
or equal to about 1.2 mm, less than or equal to about 1 mm, less than or equal to about
0.8 mm, less than or equal to about 0.6 mm, less than or equal to about 0.4 mm, or less
than or equal to about 0.2 mm. Combinations of the above-referenced ranges are also
possible (e.g., greater than about 0.05 mm and less than or equal to about 3 mm, greater
10 than about 0.1 mm and less than or equal to about 1 mm). Other ranges are also possible.
The overall thickness of one or more layers of the battery separator (e.g., the nonwoven
web and/or the overall battery separator) described herein may vary, for example,
between about 0.05 mm and about 30 mm. In some embodiments, the overall thickness
of the non-woven web and/or battery separator may be greater than or equal to about
15 0.05 mm, greater than or equal to about 0.1 mm, greater than or equal to about 0.5 mm,
greater than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or
equal to about 3 mm, greater than or equal to about 5 mm, greater than or equal to about
8 mm, greater than or equal to about 10 mm, greater than or equal to about 12 mm,
greater than or equal to about 15 mm, greater than or equal to about 20 mm, or greater
20 than or equal to about 25 mm. In certain embodiments, the overall thickness of one or
more layers of the battery separator (e.g., the non-woven web and/or the overall battery
separator) may be less than or equal to about 30 mm, less than or equal to about 28 mm,
less than or equal to about 25 mm, less than or equal to about 20 mm, less than or equal
to about 18 mm, less than or equal to about 15 mm, less than or equal to about 12 mm,
25 less than or equal to about 10 mm, less than or equal to about 8 mm, less than or equal to
about 6 mm, less than or equal to about 3 mm, less than or equal to about 2 mm, less than
or equal to about 1 mm, or less than or equal to about 0.5 mm. Combinations of the
above-referenced ranges are also possible (e.g., greater than about 0.05 mm and less than
or equal to about 30 mm, greater than about 0.5 mm and less than or equal to about 3
30 mm). Overall thickness, as referred to herein, is determined according to BCIS 03-A
Sept-09, Method 10 using 10 kPa pressure.
In some embodiments, a non-woven web and/or battery separator described
herein may have an apparent density of, for example, between about 40 g/m2/mm and
56
about 300 g/m2/mm. For instance, in some embodiments, the apparent density of one or
more layers of the battery separator (e.g., the non-woven web and/or the overall battery
separator) may be less than or equal to about less than or equal to about 300 g/m2/mm,
less than or equal to about less than or equal to about 275 g/m2/mm, less than or equal to
about 250 g/m2/mm, less than or equal to about less than or equal to about 225 g/m2 5 /mm,
less than or equal to about 200 g/m2/mm, less than or equal to about 175 g/m2/mm, less
than or equal to about 150 g/m2/mm, less than or equal to about 125 g/m2/mm, less than
or equal to about 100 g/m2/mm, less than or equal to about 75 g/m2/mm, or less than or
equal to about 50 g/m2/mm. In some cases, the apparent density of one or more layers of
10 the battery separator (e.g., the non-woven web and/or the overall battery separator) may
be greater than or equal to about 40 g/m2/mm, greater than or equal to about 60
g/m2/mm, greater than or equal to about 80 g/m2/mm, greater than or equal to about 100
g/m2/mm, greater than or equal to about 150 g/m2/mm, greater than or equal to about 200
g/m2/mm, greater than or equal to about 250 g/m2/mm, greater than or equal to about 300
g/m2/mm, or greater than or equal to about 350 g/m215 /mm. Combinations of the abovereferenced
ranges are also possible (e.g., greater than or equal to about 40 g/m2/mm and
less than or equal to about 300 g/m2/mm greater than or equal to about 80 g/m2/mm and
less than or equal to about 150 g/m2/mm). Other ranges are also possible. As
determined herein, the apparent density of one or more layers of the battery separator
20 (e.g., the non-woven web and/or the overall battery separator) is measured by dividing
the basis weight determined according to BCIS-03A Sept-09, Method 3 of the nonwoven
web (and/or battery separator) by the overall thickness of the non-woven web
(and/or battery separator) determined according to BCIS 03-A Sept-09, Method 10 under
10kPa.
25 In some embodiments, one or more layers of the battery separator (e.g., the nonwoven
web and/or the overall battery separator) described herein may have an internal
volume porosity of greater than or equal to about 80%, greater than or equal to about
82%, greater than or equal to about 84%, greater than or equal to about 86%, greater than
or equal to about 88%, greater than or equal to about 90%, greater than or equal to about
30 92%, greater than or equal to about 94%, or greater than or equal to about 96%. In some
cases, one or more layers of the battery separator (e.g., the non-woven web and/or the
overall battery separator) may have an internal volume porosity of less than or equal to
about 99%, less than or equal to about 98 %, less than or equal to about 96%, less than
57
or equal to about 94%, less than or equal to about 92%, less than or equal to about 90%,
less than or equal to about 88%, less than or equal to about 86%, less than or equal to
about 84%, or less than or equal to about 82%. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 80% and less than about
98%, greater than or equal to about 90% and less than a 5 bout 96%). Other ranges are also
possible.
In some embodiments, one or more layers of the battery separator (e.g., the nonwoven
web and/or the overall battery separator) described herein may have a total
volume porosity of greater than or equal to about 80%, greater than or equal to about
10 82%, greater than or equal to about 84%, greater than or equal to about 86%, greater than
or equal to about 88%, greater than or equal to about 90%, greater than or equal to about
92%, greater than or equal to about 94%, or greater than or equal to about 96%. In some
cases, the total volume porosity may have a volume porosity of less than or equal to
about 99%, less than or equal to about 98%, less than or equal to about 96%, less than or
15 equal to about 94%, less than or equal to about 92%, less than or equal to about 90%,
less than or equal to about 88%, less than or equal to about 86%, less than or equal to
about 84%, or less than or equal to about 82%. Combinations of the above-referenced
ranges are also possible (e.g., greater than or equal to about 80% and less than about
98%, greater than or equal to about 80% and less than about 98%). Other ranges are also
20 possible.
One or more layers of the battery separator (e.g., the non-woven web and/or the
overall battery separator) may exhibit a suitable mean flow pore size for ionic
conduction. In some embodiments, the mean flow pore size of the non-woven web
and/or battery separator may be less than or equal to about 60 microns, less than or equal
25 to about 50 microns, less than or equal to about 45 microns, less than or equal to about
40 microns, less than or equal to about 30 microns, less than or equal to about 25
microns, less than or equal to about 20 microns, less than or equal to about 15 microns,
less than or equal to about 10 microns, or less than or equal to about 5 microns, less than
or equal to about 3 microns, less than or equal to about 2 microns, less than or equal to
30 about 1 micron, less than or equal to about 0.8 microns, less than or equal to about 0.5
microns, or less than or equal to about 0.2 microns. In other embodiments, the mean
flow pore size may be greater than or equal to about 0.1 microns, greater than or equal to
about 0.2 microns, greater than or equal to about 0.5 microns, greater than or equal to
58
about 0.8 microns, greater than or equal to about 1 micron, greater than or equal to about
2 microns, greater than or equal to about 5 microns, greater than or equal to about 10
microns, greater than or equal to about 15 microns, greater than or equal to about 20
microns, greater than or equal to about 25 microns, greater than or equal to about 30
microns, greater than or equal to about 35 microns, g 5 reater than or equal to about 50
microns or greater than or equal to about 60 microns. Combinations of the abovereferenced
ranges are also possible (e.g., greater than or equal to about 0.1 microns and
less than or equal to about 60 microns, greater than or equal to about 0.2 microns and
less than or equal to about 30 microns). Other values and ranges of mean flow pore size
10 are also possible. Mean flow pore size, as determined herein, is measured according to
the standard BCIS-03A, Sept -09, Method 6.
In some embodiments, a non-woven web and/or battery separator described
herein may have desirable mechanical strength characteristics. For example, the nonwoven
web and/or battery separator may be sufficiently strong to be used as a leaf and/or
15 an envelope separator. In some embodiments, one or more layers of the battery separator
(e.g., the non-woven web and/or the overall battery separator) may have a tensile
strength in the machine direction of greater than or equal to about 10 kg/cm2, greater than
or equal to about 15 kg/cm2, greater than or equal to about 20 kg/cm2, greater than or
equal to about 30 kg/cm2, greater than or equal to about 40 kg/cm2, greater than or equal
to about 50 kg/cm2, greater than or equal to about 60 kg/cm220 , greater than or equal to
about 70 kg/cm2, or greater than or equal to about 75 kg/cm2. In some instances, the
tensile strength in the machine direction may be less than or equal to about 80 kg/cm2,
less than or equal to about 70 kg/cm2, less than or equal to about 60 kg/cm2, less than or
equal to about 50 kg/cm2, less than or equal to about 40 kg/cm2, less than or equal to
about 30 kg/cm2, less than or equal to about 20 kg/cm225 , or less than or equal to about 15
kg/cm2. Combinations of the above-referenced ranges are also possible (e.g., greater
than or equal to about 10 kg/cm2and less than or equal to about 80 kg/cm2, greater than
or equal to about 15 kg/cm2and less than or equal to about 60 kg/cm2). The tensile
strength in the machine direction may be determined using the standard BCIS 03B Rev
30 Mar 2010 Method 4.
In some embodiments, the puncture strength (or puncture resistance) of a battery
separator and/or a non-woven web described herein may be greater than or equal to
about 1 N, greater than or equal to about 1.5 N, greater than or equal to about 2 N,
59
greater than or equal to about 3 N, greater than or equal to about 5 N, greater than or
equal to about 8 N, greater than or equal to about 10 N, greater than or equal to about
12N, or greater than or equal to about 15 N. In some instances, the puncture strength (or
puncture resistance) may be less than or equal to about 20 N, less than or equal to about
18 N, less than or equal to about 15 N, less 5 than or equal to about 12 N, less than or
equal to about 10 N, less than or equal to about 8 N, less than or equal to about 5 N, or
less than or equal to about 3 N. Combinations of the above-referenced ranges are also
possible (e.g., greater than or equal to about 1 N and less than or equal to about 20 N,
greater than or equal to about 1.5 N and less than or equal to about 15 N). The puncture
10 strength may be determined using protocol BCIS 03B Rev Mar 2010 Method 9. The
puncture resistance may be determined using BCIS 03B Rev Mar 2010 Method 10.
In some embodiments, the puncture strength (or puncture resistance) of one or more
layers of the battery separator (e.g., the non-woven web and/or the overall battery
separator) described herein
15 In some embodiments, the Gurley stiffness of one or more layers of the battery
separator (e.g., the non-woven web and/or the overall battery separator) described
herein, or an additional layer described herein, may be greater than or equal to about 500
mg, greater than or equal to about 800 mg, greater than or equal to about 1,000 mg,
greater than or equal to about 1,250 mg, greater than or equal to about 1,500 mg, greater
20 than or equal to about 1,750 mg, greater than or equal to about 2,000 mg, greater than or
equal to about 2,500 mg, , greater than or equal to about 3,000 mg, greater than or equal
to about 3,500 mg, or greater than or equal to about 4,000 mg. In some instances, the
Gurley stiffness may be less than or equal to about 5,000 mg, less than or equal to about
4,500 mg, less than or equal to about 4,000 mg, less than or equal to about 3,500 mg, less
25 than or equal to about 3,000 mg, less than or equal to about 2,500 mg, less than or equal
to about 2,000 mg, less than or equal to about 1,800 mg, less than or equal to about 1,500
mg, less than or equal to about 1,200 mg, or less than or equal to about 1,000 mg.
Combinations of the above-referenced ranges are also possible (e.g., greater than or
equal to about 500 mg and less than or equal to about 5000 mg, greater than or equal to
30 about 800 to less than or equal to about 1200 mg). The Gurley stiffness may be
determined using TAPPI T543 om-94 in the machine direction.
60
In some embodiments, a battery separator including a non-woven web including
one or more chemical additives and/or non-planar layers may have enhanced battery
performance.
In some embodiments, a battery comprising a battery separator and/or one or
more layers of the battery separator (e.g., the non-woven web)5 described herein may have
a relatively low electrical resistance. For instance, in some embodiments, the electrical
resistance may be less than or equal to about 1 cm2, less than or equal to about 0.8
cm2, less than or equal to about 0.6 cm2, less than or equal to about 0.4 cm2, less
than or equal to about 0.2 cm2, less than or equal to about 0.1 cm2, less than or equal
to about 0.08 cm2, less than or equal to about 0.06 cm210 , less than or equal to about
0.04 cm2, less than or equal to about 0.02 cm2, less than or equal to about 0.01
cm2, less than or equal to about 0.008 cm2, or less than or equal to about 0.005
cm2. In certain embodiments, the electrical resistance may be greater than or equal to
about 0.001 cm2, greater than or equal to about 0.003 cm2, greater than or equal to
about 0.005 cm2, greater than or equal to about 0.008 cm215 , greater than or equal to
about 0.01 cm2, greater than or equal to about 0.05 cm2, greater than or equal to
about 0.08 cm2, greater than or equal to about 0.1 cm2, greater than or equal to
about 0.3 cm2, greater than or equal to about 0.5 cm2, or greater than or equal to
about 0.8 cm2. Combinations of the above-referenced ranges are also possible (e.g.,
greater than about 0.001 cm2 and less than or equal to about 1 cm220 , greater than
about 0.01 cm2 and less than or equal to about 0.5 cm2). Other ranges are also
possible. The electrical resistance may be measured according to the standard IS 6071-
1986 or standard BCIS-03B method 3.
In some embodiments, the electrical resistance per thickness of the battery
separator may be less than or equal to about 0.15 (cm225 )/mm, less than or equal to
about 0.12 (cm2)/mm, less than or equal to about 0.1 (cm2)/mm, less than or equal
to about 0.09 (cm2)/mm, less than or equal to about 0.08 (cm2)/mm, less than or
equal to about 0.07 (cm2)/mm, less than or equal to about 0.06 (cm2)/mm, less than
or equal to about 0.05 (cm2)/mm, less than or equal to about 0.04 (cm2)/mm, or less
than or equal to about 0.03 (cm230 )/mm. In certain embodiments, the electrical resistance
may be greater than or equal to about 0.02 (cm2)/mm, greater than or equal to about
0.03 (cm2)/mm, greater than or equal to about 0.04 (cm2)/mm, greater than or equal
to about 0.05 (cm2)/mm, greater than or equal to about 0.06 (cm2)/mm, greater than
61
or equal to about 0.07 (cm2)/mm, greater than or equal to about 0.08 (cm2)/mm,
greater than or equal to about 0.09 (cm2)/mm, greater than or equal to about 0.1
(cm2)/mm, or greater than or equal to about 0.12 (cm2)/mm. Combinations of the
above-referenced ranges are also possible (e.g., greater than about 0.02 (cm2)/mm and
less than or equal to about 0.07 (cm2)/mm, greater than about 0.02 (cm2 5 )/mm and
less than or equal to about 0.04 (cm2)/mm). Other ranges are also possible. The
electrical resistance may be measured according to the standard IS 6071-1986 or
standard BCIS-03B method 3.
In some embodiments, one or more layers of the battery separator (e.g., the non10
woven web and/or the overall battery separator) described herein may have a relatively
long life time (e.g., a long time to failure). In some embodiments, the time to failure of
the battery separator may be greater than or equal to about 5 hours, greater than or equal
to about 10 hours, greater than or equal to about 25 hours, greater than or equal to about
50 hours, greater than or equal to about 100 hours, greater than or equal to about 250
15 hours, greater than or equal to about 500 hours, greater than or equal to about 750 hours,
greater than or equal to about 1,000 hours, greater than or equal to about 1,250 hours,
greater than or equal to about 1,500 hours, or greater than or equal to about 1,750 hours.
In certain embodiments, the time to failure of the battery separator may be less than or
equal to about 2,000 hours, less than or equal to about 1,750 hours, less than or equal to
20 about 1,500 hours, less than or equal to about 1,250 hours, less than or equal to about
1,000 hours, less than or equal to about 750 hours, less than or equal to about 500 hours,
less than or equal to about 250 hours, less than or equal to about 100 hours, or less than
or equal to about 50 hours. Combinations of the above-referenced ranges are also
possible (e.g., greater than about 5 hours and less than or equal to about 2,000 hours,
25 greater than about 100 hours and less than or equal to about 1,000 hours). Other values
are also possible. The time to failure of the battery separator may be measured according
to the standard IS 6071-1986. Failure is defined as the time at which the measured
voltage across the battery separator reaches 0V.
In some embodiments, loss of capacity of a battery including a battery separator
30 and/or one or more layers of the battery separator (e.g., the non-woven web)described
herein, after 18 weeks of cyclic testing (1530 cycles) with a 17% depth of discharge
partial state of charge (i.e., PSOC), may be less than 30% of 20 hour capacity, less than
25% of 20 hour capacity, less than 20% of 20 hour capacity, less than 18% of 20 hour
62
capacity, less than 15% of 20 hour capacity, less than 12% of 20 hour capacity, or less
than 10% of 20 hour capacity. The 17% depth of discharge PSOC may be measured
according to the VRLA SLI Batteries (AGM) Requirements and test, VDA Requirement
Specification AGM: 2010-03 Method 9.9.3, e.g., using a European H8 size battery, 100
5 AH capacity.
In some embodiments, a battery described herein at 50% state of charge and
0°C, and including a battery separator and/or one or more layers of the battery separator
(e.g., the non-woven web)described herein, may accept (i.e., have a charge acceptance
of) greater than or equal to about 5 A per 100 AH of capacity, greater than or equal to
10 about 10 A per 100 AH of capacity, greater than or equal to about 15 A per 100 AH of
capacity, greater than or equal to about 20 A per 100 AH of capacity, greater than or
equal to about 25 A per 100 AH of capacity, greater than or equal to about 35 A per 100
AH of capacity, greater than or equal to about 40 A per 100 AH of capacity, or greater
than or equal to about 45 A per 100 AH of capacity, e.g., after 10 minutes of charging at
15 14.4 V. In some instances, the charge acceptance may be less than or equal to about 50
A per 100 AH of capacity, less than or equal to about 45 A/ per 100 AH of capacity, less
than or equal to about 40 A per 100 AH of capacity, less than or equal to about 35 A per
100 AH of capacity, less than or equal to about 30 A per 100 AH of capacity, less than or
equal to about 25 A per 100 AH of capacity, less than or equal to about 20 A per 100 AH
20 of capacity, or less than or equal to about 15 A per 100 AH of capacity. Combinations of
the above-referenced ranges are also possible. The charge acceptance (i.e., effective
amount of charge being accepted by the battery during charging) may be measured
according to the VRLA SLI Batteries (AGM) Requirements and test, VDA Requirement
Specification AGM: 2010-03 Method 9.5, e.g., using a European H8 size battery, 100
25 AH capacity.
In some embodiments, the dynamic charge acceptance (i.e., the charge
acceptance at different states of charge) of a battery including a battery separator
described herein may be 1 A/AH of total battery capacity (20 hr) at greater than or equal
to about 10% state of charge, at greater than or equal to about 15% state of charge, at
30 greater than or equal to about 20% state of charge, at greater than or equal to about 25%
state of charge, at greater than or equal to about 30% state of charge, at greater than or
equal to about 35% state of charge, at greater than or equal to about 40% state of charge,
at greater than or equal to about 50% state of charge, at greater than or equal to about
63
60% state of charge, or at greater than or equal to about at 75% state of charge. In some
instances, the dynamic charge acceptance may be 1 A/AH of total battery capacity (20
hr) at less than or equal to about at 80% state of charge, at less than or equal to about
70% state of charge, at less than or equal to about 60% state of charge, at less than or
equal to about 50% state of charge, at less than or equal 5 to about 45% state of charge, at
less than or equal to about 40% state of charge, at less than or equal to about 35% state
of charge, at less than or equal to about 30% state of charge, at less than or equal to about
25% state of charge, at less than or equal to about 20% state of charge, or at less than or
equal to about 15% state of charge. Combinations of the above-referenced ranges are
10 also possible. The dynamic charge acceptance may be measured according to VRLA
SLI Batteries (AGM) Requirements and test, VDA Requirement Specification AGM:
2010-03 Method 9.6.
It should be appreciated that although some of the parameters and characteristics
noted above are described with respect to non-woven webs, the same parameters and
15 characteristics (including the values and ranges for such parameters and characteristics)
may also be applied to a battery separator including the non-woven web.
In some embodiments, a separator described herein may be used in a battery (e.g.,
lead acid battery). The battery may comprise a negative plate, a positive plate, and a
battery separator (e.g., including a non-woven web described herein) disposed between
20 the negative and positive plates.
It is to be understood that the other components of the battery that are not
explicitly discussed herein can be conventional battery components. Positive plates and
negative plates can be formed of conventional lead acid battery plate materials. For
example, in container formatted batteries, plates can include grids that include a
25 conductive material, which can include, but is not limited to, lead, lead alloys, graphite,
carbon, carbon foam, titanium, ceramics (such as Ebonex®), laminates and composite
materials. The grids are typically pasted with active materials. The pasted grids are
typically converted to positive and negative battery plates by a process called
"formation." Formation involves passing an electric current through an assembly of
30 alternating positive and negative plates with separators between adjacent plates while the
assembly is in a suitable electrolyte (e.g., to convert pasted oxide to active materials).
As a specific example, positive plates may contain lead dioxide as the active
material, and negative plates may contain lead as the active material. Plates can also
64
contain one or more reinforcing materials, such as chopped organic fibers (e.g., having
an average length of 0.125 inch or more), chopped glass fibers, metal sulfate(s) (e.g.,
nickel sulfate, copper sulfate), red lead (e.g., a Pb304-containing material), litharge,
paraffin oil, and/or expander(s). In some embodiments, an expander contains barium
sulfate, carbon black and lignin sulfonate as the primary 5 components. The components
of the expander(s) can be pre- mixed or not pre-mixed. Expanders are commercially
available from, for example, Hammond Lead Products (Hammond, IN) and Atomized
Products Group, Inc. (Garland, TX).
An example of a commercially available expander is the Texex® expander
10 (Atomized Products Group, Inc.). In certain embodiments, the expander(s), metal
sulfate(s) and/or paraffin are present in positive plates, but not negative plates. In some
embodiments, positive plates and/or negative plates contain fibrous material or other
glass compositions.
A battery can be assembled using any desired technique. For example, separators
15 may be wrapped around plates (e.g., positive electrode, negative electrode). The positive
plates, negative plates and separators are then assembled in a case using conventional
lead acid battery assembly methods. The battery separators may be used, for example, as
a leaf separator, as shown illustratively in FIGs. 5A and 5C, or an envelope separator
(i.e., the separator is sealed on three sides) as shown illustratively in FIGs. 5B and 5D.
20 FIG. 5 is a schematic diagram showing a cross-section of a battery separator 120 and a
plate 125. The thickness 130 and overall thickness 135 of each separator as the terms are
used herein are also shown in FIGs. 5A-5D. In certain embodiments, separators are
compressed after they are assembled in the case, i.e., the thickness of the separators are
reduced after they are placed into the case. An electrolyte (e.g., sulfuric acid) is then
25 disposed in the case. It should be understood that the shapes (e.g., planar, non-planar) of
the battery separators shown in FIG. 5 are non-limiting and the battery separators
described herein may have any suitable shape. That is, the battery separators may be
planar as shown in FIGs. 5C-5D or non-planar as shown in FIGs. 5A-5B, and non-planar
battery separators may have the same or a different shape as separator 120 shown
30 illustratively in FIGs. 5A-D. In some embodiments, a combination of planar and nonplanar
layers may be used in separator.
The electrolyte can include other compositions. For example, the electrolyte can
include liquids other than sulfuric acid, such as a hydroxide (e.g., potassium hydroxide).
65
In some embodiments, the electrolyte includes one or more additives, including but not
limited to a mixture of an iron chelate and a magnesium salt or chelate, organic polymers
and lignin and/or organic molecules, and phosphoric acid. In some embodiments, the
electrolyte is sulfuric acid. In some embodiments, the specific gravity of the sulfuric
acid is between 1.21 g/cm3 and 1.32 g/cm3, or between 1.28 g/cm3 and 1.31 g/cm3 5 . In
certain embodiments the specific gravity of the sulfuric acid is 1.26 g/cm3. In certain
embodiments the specific gravity of the sulfuric acid is about 1.3 g/cm3.
In some embodiments, the battery separators (including the non-woven webs
described herein) may be used in lead acid batteries including valve-regulated batteries
10 (e.g., absorbent glass mat batteries) and flooded batteries. For example, in some
embodiments, the battery separators may be used in flooded battery applications. In
some such embodiments, the battery separator may be a enveloped separator that is
wrapped around one or more plate (e.g., positive plate(s), positive and negative plate(s)).
In some such embodiments, the battery separator may comprise a non-woven web
15 bonded to a web/layer including glass fibers and resin. In some such cases, the battery
separator may be wrapped around the plate, such that the glass layer faces and/or is in
contact with the plate. In other cases, the battery separator may be wrapped around the
plate, such that the glass layer is on a side opposite the plate. The glass layer may serve
to stabilize the active material in the electrode(s) and minimize shedding. In certain
20 embodiments, the battery separator does not include a web including glass fibers and
resin. In some such embodiments, the glass fibers in a non-woven web described herein
may serve to stabilize the active material in the electrode(s) and minimize shedding. In
some embodiments in which a battery separator described herein is used in a flooded
battery, the plates may include a glass layer embedded on to the plate that serves to
25 decrease shedding of the plate and/or may comprise carbon based additives that increase
the conductance of the plate (e.g., graphene, graphite) and/or have a high surface area
(e.g., greater than or equal to about 500 m2/g and less than or equal to about 5,000 m2/g).
A enveloped battery separator, as described herein, may be wrapped around such a plate.
In some embodiments, a carbon-impregnated non-woven web may be positioned
30 adjacent to the plate. In some embodiments, a battery separator may be used in a flooded
battery comprising various additives in the electrolyte solution.
As described herein, a non-woven web may form all or part of a battery separator.
In some embodiments, one or more additional layers or components are included with
66
the non-woven web (e.g., disposed adjacent to the non-woven web, contacting one or
both sides of the non-woven web). In some instances, an additional layer is a fibrous
layer. Non-limiting examples of fibrous additional layers include a meltblown layer, a
wet laid layer (e.g., a glass fiber wet laid layer), a spunbond layer, an extruded layer, or
an electrospun layer. In some embodiments, multiple 5 non-woven webs in accordance
with embodiments may be layered together in forming a multi-layer sheet for use in a
battery separator. In other embodiments, an additional layer may be a non-fibrous layer.
For example, the layer may be a polymeric layer formed by an extrusion process (e.g., a
membrane such as a PE membrane). Other configurations are also possible.
10 In some embodiments two or more layers of a web may be formed separately,
and combined by any suitable method such as lamination, collation, or by use of
adhesives. The two or more layers may be formed using different processes, or the same
process. For example, each of the layers may be independently formed by a wet laid
process, a non-wet laid process, or any other suitable process.
15 In some embodiments, two or more layers may be formed by the same process.
In some instances, the two or more layers may be formed simultaneously.
Different layers may be adhered together by any suitable method. For instance,
layers may be adhered by an adhesive and/or melt-bonded to one another on either side.
Lamination and calendering processes may also be used. In some embodiments, an
20 additional layer may be formed from any type of fiber or blend of fibers via an added
headbox or a coater and appropriately adhered to another layer.
A battery separator may include any suitable number of layers, e.g., at least 2, at
least 3, at least 4, at least 5, at least 6, at least 7 layers. In some embodiments, a battery
separator may include up to 10 layers.
25 Non-woven webs described herein may be produced using suitable processes,
such as a wet laid process. In general, a wet laid process involves mixing together fibers
of one or more type; for example, glass fibers of one type may be mixed together with
glass fibers of another type, and/or with fibers of a different type (e.g., synthetic fibers),
to provide a fiber slurry. The slurry may be, for example, an aqueous-based slurry. In
30 certain embodiments, fibers, are optionally stored separately, or in combination, in
various holding tanks prior to being mixed together.
For instance, a first fiber may be mixed and pulped together in one container and
a second fiber may be mixed and pulped in a separate container. The first fibers and the
67
second fibers may subsequently be combined together into a single fibrous mixture.
Appropriate fibers may be processed through a pulper before and/or after being mixed
together. In some embodiments, combinations of fibers are processed through a pulper
and/or a holding tank prior to being mixed together. It can be appreciated that other
components (e.g., inorganic particles) may also be 5 introduced into the mixture.
Furthermore, it should be appreciated that other combinations of fibers types may be
used in fiber mixtures, such as the fiber types described herein.
In certain embodiments, two or more layers are formed by a wet laid process.
For example, a first dispersion (e.g., a pulp) containing fibers in a solvent (e.g., an
10 aqueous solvent such as water) can be applied onto a wire conveyor in a papermaking
machine (e.g., a fourdrinier or, a round former, or a rotoformer) to form first layer
supported by the wire conveyor. A second dispersion (e.g., another pulp) containing
fibers in a solvent (e.g., an aqueous solvent such as water) is applied onto the first layer
either at the same time or subsequent to deposition of the first layer on the wire.
15 Vacuum is continuously applied to the first and second dispersions of fibers during the
above process to remove the solvent from the fibers, thereby resulting in an article
containing first and second layers. The article thus formed is then dried and, if
necessary, further processed by using known methods to form multi-layered non-woven
webs.
20 Any suitable method for creating a fiber slurry may be used. In some
embodiments, further additives are added to the slurry to facilitate processing. The
temperature may also be adjusted to a suitable range, for example, between 33 ºF and
100 ºF (e.g., between 50 ºF and 85 ºF). In some cases, the temperature of the slurry is
maintained. In some instances, the temperature is not actively adjusted.
25 In some embodiments, the wet laid process uses similar equipment as in a
conventional papermaking process, for example, a hydropulper, a former or a headbox, a
dryer, and an optional converter. A non-woven web can also be made with a laboratory
handsheet mold in some instances. As discussed above, the slurry may be prepared in
one or more pulpers. After appropriately mixing the slurry in a pulper, the slurry may be
30 pumped into a headbox where the slurry may or may not be combined with other
slurries. Other additives may or may not be added. The slurry may also be diluted with
additional water such that the final concentration of fiber is in a suitable range, such as
for example, between about 0.1% and 0.5% by weight.
68
In some cases, the pH of the fiber slurry may be adjusted as desired. For
instance, fibers of the slurry may be dispersed under acidic or neutral conditions.
Before the slurry is sent to a headbox, the slurry may optionally be passed
through centrifugal cleaners and/or pressure screens for removing unfiberized material.
The slurry may or may not be passed through additional 5 equipment such as refiners or
deflakers to further enhance the dispersion of the fibers. For example, deflakers may be
useful to smooth out or remove lumps or protrusions that may arise at any point during
formation of the fiber slurry. Fibers may then be collected on to a screen or wire at an
appropriate rate using any suitable equipment, e.g., a fourdrinier, a rotoformer, a
10 cylinder/round former, or an inclined wire fourdrinier.
As described herein, in some embodiments, a binder resin, which may optionally
contain one or more chemical additives, is added to a pre-formed fiber layer (e.g., a preformed
non-woven web formed by a wet-laid process). For instance, as the fiber layer is
passed along an appropriate screen or wire, different components included in the binder
15 resin (e.g., chemical additives, inorganic particles, rubber), which may be in the form of
separate emulsions, are added to the fiber layer using a suitable technique. In some
cases, each component of the binder resin is mixed as an emulsion prior to being
combined with the other components and/or fiber layer. The components included in the
resin may be pulled through the fiber layer using, for example, gravity and/or vacuum.
20 In some embodiments, one or more of the components included in the binder resin may
be diluted with softened water and pumped into the fiber layer. In some embodiments, a
resin may be applied to a fiber slurry prior to introducing the slurry into a headbox. For
example, the resin may be introduced (e.g., injected) into the fiber slurry and
impregnated with and/or precipitated on to the fibers.
25 During or after formation of a non-woven web, the non-woven web may be
further processed according to a variety of known techniques. Optionally, additional
layers can be formed and/or added to a non-woven web using processes such as
lamination, co-pleating, or collation. For example, in some cases, two layers are formed
into a composite article by a wet laid process, and the composite article is then combined
30 with a third layer by any suitable process (e.g., lamination, co-pleating, or collation). It
can be appreciated that a non-woven web or a composite article formed by the processes
described herein may be suitably tailored not only based on the components of each fiber
layer, but also according to the effect of using multiple fiber layers of varying properties
69
in appropriate combination to form non-woven webs having the characteristics described
herein.
In some embodiments, a non-woven web can be post-processed such as subjected
to a shaping process as described herein.
5
EXAMPLES
The following examples are intended to illustrate certain embodiments of the
present invention, but are not to be construed as limiting and do not exemplify the full
scope of the invention.
10
EXAMPLE 1
This example demonstrates the reduction in dendrite formation in batteries
including a battery separator comprising a non-woven web including sodium sulfate salt
in the non-woven web (e.g., prior to introduction of the separator into the battery),
15 compared to a) a similar battery including a separator lacking the sulfate salt, but
including sulfate ion in the electrolyte (water), and b) a conventional battery separator.
The non-woven webs of battery separator 1 contained about 20% glass fibers,
about 20% polyester fibers, about 15% resin, and about 45% precipitated silica. Various
amounts of sodium sulfate were added to battery separator 1 (e.g., the non-woven web),
20 and/or to the electrolyte (water). The non-woven webs of battery separator 2 included
about 1% sodium sulfate, about 18.5% glass fibers, about 10% polyester fibers, about
14% resin, about 18% bi-component fiber, about 6% rubber, and about 32.5%
precipitated silica. The conventional battery separator (i.e., battery separator 3) was an
extruded (non-fibrous) polyethylene separator containing 40% precipitated silica, 45%
25 polyethylene polymer, and 15% oil.
The battery separators were exposed to electroplating conditions and the
breakdown voltage was determined as described herein. The results are shown in table
1.
30 Table 1. Breakdown Voltage for Various Battery Separators
Separator 3 3 1 1 1 1 1 1 2 2
Na2SO4
in the
separator
in
grams/cel
- - - 0.024 0.06 - - - 0.12 0.12
70
l
Na2SO4in
the water
in
gram/cell
- 0.5 - - - 0.06 0.12 0.5 - 0.5
% Loss in
BDV
88 82 70 78 33 85 47 25 28 0
The results show that addition of sodium sulfate to a fiber web is beneficial in
preventing lead dendrite shorting. The results suggest that addition of sodium sulfate
confined to the interior of the separator (separator 2) at a concentration of 0.12% is as
effective as a direct addition of 0.5% sodium sulfate to the electrolyte 5 (separator 1) in
terms of a relatively low % loss in BDV. Moreover, when sodium sulfate was present in
both the electrolyte and the non-woven web, there was no loss in breakdown voltage
(separator 2).
10
EXAMPLE 2
This example demonstrates the reduction in water consumption in a battery
separator including a non-woven web including rubber compared to a conventional
battery separator comprising rubber. The battery separator including a non-woven web
15 including rubber (i.e., battery separator 2 from Example 1) had a lower water
consumption than a conventional extruded (non-fibrous) polyethylene separator
comprising rubber (i.e., battery separator 3 from Example 1).
The water consumption of the battery separators were measured using 2V (75Ah)
cell including 5 positive lead dioxide electrodes and 6 negative lead electrodes. Positive
20 electrode grids contained 2.5 % antimony . The size of the electrode was 124 mm by
142 mm by 2.5 mm for the positive electrode and 124 mm by 142 mm by 2.2 mm for the
negative electrode. The positive electrode weighed about 245 g and the negative
electrode weighed about 210 g. The volume of sulfuric acid (1.27 g/cc density) in the
cell was about 787 cm3. The test was performed using test protocol IEC 60095. Briefly,
25 the electrochemical cells were weighed prior to charging. Then the electrochemical cell
was charged at 14.4V for a period of 500 hours at 40°C. The weight of the cells was
noted at the end of the test.
71
Table 2: Water consumption for Various Battery Separators
Separator details Water consumption g/Ah
Battery separator 2 2.5
Battery separator 3 3.3
EXAMPLE 3
This example describes the mechanical and performance 5 properties of a singlelayer
corrugated battery separator and multi-layer corrugated battery separators. Five
multi-layer battery separators including a corrugated layer were formed that varied in the
number and type of additional layers. The battery separators including the corrugated
layer had increased total volume porosity and strength while maintaining a similar
10 electrical resistance compared to a planar single layer battery separator.
The planar battery separator was a non-woven web that contained about 20%
glass fibers, about 20% polyester fibers, about 15% resin, and about 45% precipitated
silica.
The battery separator in Experiment A contained the corrugated version of the
15 planar non-woven web that was bonded to additional layer 1. The planar layer was
corrugated by passing the planar non-woven web between two heated corrugating rollers.
The two rollers were arranged such that there was an inter-meshing of the teeth of the
rollers which forced the layer into flutes. Additional layer 1 was a wet-laid non-woven
web that contained about 24.5% glass fibers, about 15% polyester fibers, about 10%
20 resin, and about 50.5% precipitated silica using acid resistant copolymer latex.
Additional layer 1 had a basis weight of about 120 g/m2 and thickness of about 0.3 mm.
In Experiment B, the battery separator contained the corrugated non-woven web
of Experiment A bonded to additional layer 2. Additional layer 2 was a wet-laid glass
mat comprising glass fibers and binder resin. The glass mat had a basis weight of 50
g/m2 25 and a thickness of 0.4 mm at 3.5 kPa.
In Experiment C, the battery separator contained the corrugated non-woven web
of Experiment A bonded on both sides to additional layer 1 used in Experiment A.
In Experiment D, the battery separator contained the corrugated non-woven web
of Experiment A bonded on both sides to additional layer 2 used in Experiment B.
30 In Experiment E, the battery separator contained the corrugated non-woven web
of Experiment A bonded on one side to additional layer 2 used in Experiment B and to
additional layer 1 used in Experiment A on the other side.
72
Various properties of each of the battery separators is shown in Table 1.
Table 1. Properties of Various Battery Separators
Test Units Planar
Separator
A B C D E
Overall Thickness mm 1.6 2.81 3.15 3.18 3.48 5.92
Basis Wt. g/m2 230 313 280 454 311 781
Apparent Density g/m2/mm 143 111 88 143 88 131
Total Porosity % 57 68 66 69 74 73
Resistance ·cm2 0.1 0.102 0.113 0.124 0.105 0.185
Resistance/Thickness ·cm2/mm 0.063 0.036 0.036 0.039 0.030 0.031
Puncture Strength N 7.99 11.54 10.64 16.44 17.7 21.64
Each of the battery separators including the corrugated layer had increased total
volume porosity and puncture strength while having a similar electrical 5 resistance as that
for the planar single layer battery separator. Each of the battery separators from
experiments A, B, D, and E had a lower apparent density than the planar single layer
battery separator.

CLAIMS:CLAIMS
1. A battery separator, comprising:
a non-woven web comprising:
a plurality of glass fibers having an average diameter 5 of greater than or
equal to about 0.1 microns and less than or equal to about 15 microns, wherein
the glass fibers are present in an amount of greater than or equal to about 2 wt.%
and less than or equal to about 95 wt.% of the non-woven web; and
one or more sulfate salts, wherein the one or more sulfate salts are present
10 in an amount of greater than or equal to about 0.1 wt.% and less than or equal to
30 wt.% of the battery separator prior to contact with a battery electrolyte.
2. A battery separator, comprising:
a non-woven web comprising:
15 a plurality of glass fibers having an average diameter of greater than or
equal to about 0.1 microns and less than or equal to about 15 microns, wherein
the glass fibers are present in an amount of greater than or equal to about 2 wt.%
and less than or equal to about 95 wt.% of the non-woven web; and
one or more antioxidants, wherein the antioxidants are present in an
20 amount of greater than or equal to about 0.05 wt.% and less than or equal to
about 5 wt.% of the battery separator.
3. A battery separator, comprising:
a non-woven web comprising:
25 a plurality of glass fibers having an average diameter of greater than or
equal to about 0.1 microns and less than or equal to about 15 microns, wherein
the glass fibers are present in an amount of greater than or equal to about 2 wt.%
and less than or equal to about 95 wt.% of the non-woven web;
a plurality of synthetic fibers, wherein the synthetic fibers are present in
30 an amount of greater than or equal to about 1 wt.% and less than or equal to about
80 wt.% of the non-woven web;
a plurality of inorganic particles, wherein the inorganic particles are
resistant to sulfuric acid, and wherein the inorganic particles are present in the
74
non-woven web in an amount of greater than or equal to about 10 wt.% and less
than or equal to about 80 wt.% of the non-woven web; and
one or more rubbers, wherein the one or more rubbers are present in the
battery separator in an amount of greater than or equal to about 3 wt.% and less
than or equal to about 80 wt.% 5 of the battery separator.
4. A battery separator as in any preceding claim wherein the non-woven web
comprises, a plurality of synthetic fibers, wherein the synthetic fibers are present in an
amount of greater than or equal to about 1 wt.% and less than or equal to about 80 wt.%
10 of the non-woven web; and
5. A battery separator as in any preceding claim, wherein the non-woven web
comprises a plurality of synthetic fibers, wherein the synthetic fibers are present in an
amount of greater than or equal to about 5 wt.% and less than or equal to about 50 wt.%
15 of the non-woven web.
6. A battery separator as in any preceding claim, wherein the non-woven web
comprises a plurality of inorganic particles, wherein the inorganic particles are resistant
to sulfuric acid, and wherein the inorganic particles are present in an amount of greater
20 than or equal to about 30 wt.% and less than or equal to about 60 wt.% of the non-woven
web.
7. A battery separator as in any preceding claim, wherein non-woven web further
comprises a binder resin.
25
8. A battery separator as in any preceding claim, wherein the non-woven web
comprises one or more sulfate salts, wherein the one or more sulfate salts are present in
an amount of greater than or equal to about 0.5 wt.% and less than or equal to 5 wt.% of
the non-woven web.
30
9. A battery separator as in any preceding claim, wherein the non-woven web
comprises one or more antioxidants, wherein the antioxidants are present in an amount of
75
greater than or equal to about 0.1 wt.% and less than or equal to about1 wt.% of the nonwoven
web.
10. A battery separator as in any preceding claim, wherein the non-woven web
comprises one or more rubbers, wherein the one or 5 more rubbers are present in an
amount of greater than or equal to about 2 wt.% and less than or equal to about 20 wt.%
of the non-woven web.
11. A battery separator as in any preceding claim, wherein the battery separator is a
10 lead acid battery separator.
12. A battery separator as in any preceding claim, wherein the rubber is a natural
rubber.
15 13. A battery separator as in any preceding claim, wherein the rubber is in particulate
form.
14. A battery separator as in any preceding claim, wherein the sulfuric acid resistant
inorganic particles have a surface area of greater than or equal to about 10 m2/g and less
than or equal to about 2,000 m220 /g.
15. A battery separator as in any preceding claim, wherein the thickness of the
battery separator is greater than or equal to about 0.1 mm and less than or equal to about
1 mm.
25
16. A battery separator as in any preceding claim, wherein the pore size of the battery
separator is greater than or equal to about 0.2 microns and less than or equal to about 30
microns.
30 17. A battery separator as in any preceding claim, wherein the puncture strength of
the battery separator is greater than or equal to about 1.5 N and less than or equal to
about 15 N.
76
18. A battery separator as in any preceding claim, wherein the tensile strength of the
battery separator is greater than or equal to about 15 kg/cm2 and less than or equal to
about 60 kg/cm2.
19. A lead acid battery comprising the battery separator 5 of any preceding claim.