FIELD
The present invention relates generally to battery separators, and, more particularly, to battery separators comprising ribs.
BACKGROUND
Battery separators may be employed in a variety of applications to prevent direct contact between electrodes. Some battery separators include ribs. However, some ribs exhibit undesirable thermal instability and/or have structures that allow for undesirably low electrolyte diffusion.
Accordingly, improved battery separator designs are needed.
SUMMARY
Battery separators, related components, and related methods are generally described.
In some embodiments, a battery separator is provided. The battery separator comprises a porous layer and a plurality of ribs disposed on the porous layer. The ribs comprise a polymer, the ribs comprise a filler, and the plurality of ribs forms a discrete component of the battery separator.
In some embodiments, a battery separator comprises a porous layer and a plurality of ribs disposed on the porous layer. The ribs exhibit a mass loss of less than or equal to 2% upon exposure to a temperature of 160 °C for 13 minutes and the plurality of ribs forms a discrete component of the battery separator.
In some embodiments, a battery separator comprises a porous layer and a plurality of ribs disposed on the porous layer. The ribs are porous and the plurality of ribs forms a discrete component of the battery separator.
In some embodiments, a method is provided. The method comprises passing a fluid comprising a polymer through a screen comprising a plurality of orifices onto a porous layer and cooling the fluid to form ribs comprising the polymer disposed on the porous layer.
Other advantages and novel features of the present invention will become apparent from the following detailed description of various non-limiting embodiments of 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 shall control.
BRIEF DESCRIPTION OF THE DRAWINGS
Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In the figures:
FIG. 1 shows a battery separator comprising a plurality of ribs, in accordance with some embodiments;
FIG. 2 shows a battery separator comprising a first porous layer and a second porous layer, in accordance with some embodiments;
FIG. 3 shows a battery separator comprising a first plurality of ribs and a second plurality of ribs on a side of the battery separator opposite that on which the first plurality of ribs is disposed, in accordance with some embodiments;
FIG. 4 shows a method of passing a fluid through a screen onto a porous layer, in accordance with some embodiments;
FIG. 5 shows flow of a fluid through a rotating cylindrical screen that is deposited onto a porous layer translating therebeneath, in accordance with some embodiments;
FIG. 6 shows micrographs of ribs after exposure to heat, in accordance with some embodiments;
FIG. 7 shows micrographs of ribs after exposure to sulfuric acid, in accordance with some embodiments;
FIG. 8 is a chart showing the amount of iron leached into an electrolyte from two pluralities of ribs, in accordance with some embodiments;

FIG. 9 is a chart showing C20, CIO, and CI capacities for batteries comprising different battery separators, in accordance with some embodiments;
FIGs. 10 and 11 show micrographs of battery separators, in accordance with some embodiments;
FIG. 12 is a chart showing the porosity of the battery separators as a function of the amount of pore-forming additive present in the fluid from which their ribs were formed, in accordance with some embodiments;
FIGs. 13 and 14 are charts showing the weight loss for battery separators upon exposure to oxidative fluids, in accordance with some embodiments;
FIG. 15 is a chart showing heat flow during differential scanning calorimetry analysis of various materials, in accordance with some embodiments; and
FIG. 16 is a chart showing the end of discharge voltage as a function of the number of cycles for various batteries, in accordance with some embodiments.
DETAILED DESCRIPTION
Battery separators comprising ribs are generally described. In some embodiments, the ribs have one or more features that enhance the performance of the battery separator.
As one example, in some embodiments, a battery separator comprises ribs that comprise a polymer and a filler. Some fillers may enhance the thermal stability of the ribs in which they are positioned by serving as portions of the ribs that do not melt and/or degrade at temperatures typically experienced by the ribs. Some fillers may advantageously reduce the electrical resistance of the battery separator of which they form a part by serving as portions of the battery separator that have a relatively high dielectric constant.
As a second example, in some embodiments, a battery separator comprises ribs that are porous. The porosity may promote diffusion of electrolyte through the ribs and/or the battery separator, which may reduce the electrical resistance of the battery separator and/or may enhance ion mobility through the battery separator. In some embodiments, the presence of porosity in ribs may enhance one or more properties of a battery in which the battery separator is positioned. For instance, porosity may increase electrolyte availability between battery plates, enhance charge acceptance, and/or reduce electrical resistance across the battery as a whole.

As a third example, in some embodiments, a battery separator comprises ribs that are thermally stable. Such ribs may undergo minimal or no degradation and/or structural change when exposed to the heated conditions typically present during fabrication (e.g., during a cast on strap process) and/or operation (e.g., during cycling).
Some embodiments relate to methods of fabricating battery separators. A method of fabricating a battery separator may comprise passing a fluid through a screen comprising a plurality of orifices onto a porous layer. The fluid may then be cooled to form ribs comprising one or more components present in the fluid. Advantageously, this method may allow for the formation of ribs in a manner that is facile, rapid, and relatively inexpensive.
FIG. 1 shows one non-limiting embodiment of a battery separator comprising a plurality of ribs. In FIG. 1, the battery separator 100 comprises a porous layer 200 and a plurality of ribs 300 disposed on the porous layer. Some battery separators described herein, like that shown in FIG. 1, are leaf separators. It is also possible for a battery separator described herein to be a folded separator, a pocket separator, a z-fold separator, a sleeve separator, a corrugated separator, a C-wrap separator, or a U-wrap separator.
In some embodiments, like the embodiment shown in FIG. 1, a battery separator includes exactly one porous layer and includes a plurality of ribs on exactly one side thereof. It is also possible for a battery separator to include two or more porous layers (e.g., as shown in FIG. 2, which depicts a battery separator comprising a first porous layer 202 and a second porous layer 252) and/or to include ribs on two opposing sides thereof (e.g., as shown in FIG. 3, which depicts a battery separator comprising a first plurality of ribs 304 and a second plurality of ribs 354 on a side of the battery separator opposite that on which the first plurality of ribs is disposed). When a battery separator comprises two pluralities of ribs positioned on different surfaces thereof, the two pluralities of ribs may be mirror images of each other (e.g., as shown in FIG. 3) or may differ from mirror images of each other in one or more ways. For instance, pluralities of ribs positioned on opposing sides of a battery separator may have different shapes, have different repeat periods, be positioned at different locations, and/or have different compositions. In some embodiments, a battery separator comprises a first plurality of ribs on one side thereof that is suitable for being positioned adjacent to a negative electrode and a second plurality of ribs on an opposite side thereof that is suitable for being positioned adjacent to a positive electrode.

In some embodiments, a plurality of ribs forms a discrete component of a battery separator in which it is positioned. Discrete components of battery separators may be components that are clearly separate from any other components to which they are adjacent. For instance, a component of a battery separator that is a discrete component may be separated from other components of the battery separator to which it is adjacent by an interface. As another example, a component of a battery separator that is a discrete component may have a different chemical composition than other components of the battery separator to which it is adjacent and/or a different structure (e.g., porosity) than other components of the battery separator to which it is adjacent. As a third example, in some embodiments, a component of a battery separator that is a discrete component is not integrally connected to any other components of the battery separator and/or may be separable from other components of the battery separator (i.e., those it is discrete from) without the use of specialized tools. Some pluralities of ribs that are discrete components of battery separators may be layers that are not coextruded with any other layers (e.g., any porous layers in the battery separators).
Some pluralities of ribs described herein comprise at least two ribs that are not directly topologically connected by a material having the same composition as the ribs. In other words, for at least two ribs in the plurality of ribs, there may not exist any pathway therebetween that passes exclusively through portions of the battery separator formed from the same material as the ribs. With respect to FIG. 1, and in embodiments in which the porous layer shown in FIG. 1 has a different composition from the plurality of ribs shown in FIG. 1, the ribs 400 and 450 are not directly topologically connected by a material having the same composition as the ribs. As can be seen in FIG. 1, any pathway connecting the ribs 400 and 450 must pass outside the battery separator and/or through the porous layer having a different composition from these ribs.
The ribs described herein may have a variety of suitable designs. For instance, some pluralities of ribs may comprise continuous ribs (e.g., ribs lacking termini positioned at locations other than the edges of the surface of the battery separator on which they are positioned), some pluralities of ribs may comprise discontinuous ribs (e.g., ribs comprising termini positioned at locations other than the edges of the surface of the battery separator on which they are positioned), and some pluralities of ribs may comprise both continuous ribs and discontinuous ribs. Ribs, whether continuous or discontinuous, may comprise cross-sections having a variety of suitable shapes. Non-limiting examples of suitable cross-sections (e.g., in the plane parallel to

the porous layer on which the ribs are disposed) include circular cross-sections, oval cross-sections, diamond cross-sections, rectangular cross-sections, square cross-sections, line segment cross-sections, and star cross-sections (e.g., five-pointed, six-pointed, seven-pointed, higher-pointed).
In some embodiments, a plurality of ribs (that may be continuous or discontinuous) has a structure that can be characterized by one or more symmetry operators. For instance, in some embodiments, a plurality of ribs has a structure that can be mapped relatively closely to a two-dimensional lattice, such as a two-dimensional lattice having rectangular symmetry, tetragonal symmetry, or hexagonal symmetry. The mapping may be sufficiently close such that the standard deviation of the centers of gravity of the ribs from the lattice points may be less than or equal to 10%, less than or equal to 5%, less than or equal to 2%, or less than or equal to 1% of the nearest neighbor distance of the lattice points. In some embodiments, a plurality of ribs comprises a structure that is periodic in one or two dimensions. For example, the plurality of ribs may comprise a waved structure and/or a sinusoidal structure. As another example, a plurality of ribs may comprise a structural motif that is repeated in one or two dimensions, non-limiting examples of which include diamonds and triangles.
As described elsewhere herein, some embodiments relate to methods for fabricating battery separators. The methods may comprise forming ribs on porous layers. In some embodiments, a method comprises forming ribs on a porous layer from a fluid comprising one or more components to be included in the ribs. The fluid may be disposed on the porous layer and then cooled to form the ribs. In some embodiments, the fluid is disposed on the porous layer by passing it through a screen comprising a plurality of orifices. A porous layer may be positioned on the opposing side of the screen, and may receive the fluid passed through the orifices. In some embodiments, the shape of the ribs may be influenced by and/or substantially the same as the shapes of the orifices through which the fluid passed.
FIG. 4 shows one non-limiting embodiment of a method of passing a fluid through a screen onto a porous layer. In FIG. 4, a fluid 406 is passed through a screen 506 onto a porous layer 206. As shown in FIG. 4, the fluid may pass through the orifices in a screen and/or the orifices in the screen may direct the fluid to deposit on the porous layer in select locations. The screens described herein may have a variety of suitable shapes. As one non-limiting example, in some embodiments, a screen has a shape that has a hollow center. The fluid may be fed into the

hollow center and then passed outwardly through the screen. One example of a screen having this shape is a cylindrical screen.
For screens of any shape, a method may comprise removing (e.g., by scraping, by squeegeeing) excess amounts of a fluid to be passed through the screen from a side of the screen opposite a porous layer onto which the fluid is to be deposited. For instance, fluid may be supplied to the screen at a rate and/or in an amount that is larger than suitable for deposition onto the porous layer. Removing the excess fluid from the screen in such embodiments may assist with the deposition of the fluid onto the porous layer in a manner that is controlled and/or that results in the deposition of an appropriate amount of fluid having an appropriate morphology onto the porous layer. In embodiments in which fluid is passed through the screen from a hollow center outwards, the fluid removal may be performed on an interior surface of the screen. In other words, excess fluid may be removed from an interior of the screen.
In some embodiments, a method comprising passing a fluid through a screen onto a porous layer comprises moving the screen and/or the porous layer. Either or both of these movements may occur while fluid is passing through the screen. As one example, in some embodiments, a porous layer may be translated on a side of the screen opposing the fluid, such as beneath the screen, while fluid is being passed through the screen. As the porous layer translates, the fluid may be deposited onto different portions of the porous layer. In some such embodiments, the porous layer may be translated beneath the screen in a roll-to-roll manner. As another example, in some embodiments, the screen is rotated while fluid is being passed therethrough. For instance, a screen comprising a hollow center may be rotated around a hollow central axis. As the screen rotates, different portions of the screen may be positioned in different locations around the rotational axis. This may result in a flow through the screen that, for a particular position opposite the screen, varies over time. When the porous layer translates adjacent a rotating screen, the fluid may deposit such that it forms a spatially-varying pattern thereon.
FIG. 5 shows one non-limiting example of flow of a fluid through a rotating cylindrical screen that is deposited onto a porous layer translating therebeneath. As can be seen from FIG. 5, as orifices and solid portions of the screen pass beneath the source of fluid flowing therethrough (not shown), the orifices allow fluid to flow through the screen and the solid portions of the screen block fluid flow therethrough. This causes portions of fluid to be

deposited on the porous layer that are not topologically connected by a material having the same composition as the fluid. In FIG. 5, the porous layer is labeled as the "base web" and the screen is labeled as the "rotary coating head". FIG. 5 also further depicts a bottom roller positioned beneath the porous layer.
In some embodiments, one or more processes are performed on a fluid deposited on a porous layer after deposition thereon. Such process may be performed to transform the fluid, and/or one or more components thereof, into a plurality of ribs. As one example, in some embodiments, the fluid may be cured. Curing may comprise heating the fluid to promote the reaction of one or more components therein to form a solid material. The heating may comprise exposure to radiation (e.g., infrared radiation, ultraviolet radiation, gamma radiation, and/or microwave radiation). As another example, in some embodiments, the fluid may be cooled. For instance, the fluid may be cooled from a temperature at which it is deposited to a temperature at which the fluid solidifies and/or may be cooled after the performance of a curing process that occurs at an elevated temperature.
As described elsewhere herein, in some embodiments, a battery separator comprises a plurality of ribs. The ribs described herein may have a variety of chemical compositions. Further details regarding some possible chemical compositions for ribs are provided below.
In some embodiments, a plurality of ribs comprises one or more polymers. Polymers may make up a variety of suitable amounts of the ribs described herein. In some embodiments, one or more polymers make up greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%, greater than or equal to 55 wt%, greater than or equal to 60 wt%, greater than or equal to 65 wt%, greater than or equal to 70 wt%, greater than or equal to 75 wt%, greater than or equal to 80 wt%, greater than or equal to 85 wt%, greater than or equal to 90 wt%, or greater than or equal to 95 wt% of the ribs in a plurality of ribs. In some embodiments, one or more polymers make up less than or equal to 100 wt%, less than or equal to 95 wt%, less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 75 wt%, less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 55 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30

wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% of the ribs in a plurality of ribs. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 wt% and less than or equal to 100 wt%, greater than or equal to 10 wt% and less than or equal to 90 wt%, greater than or equal to 20 wt% and less than or equal to 80 wt%, or greater than or equal to 30 wt% and less than or equal to 50 wt%). Other ranges are also possible. In some embodiments, one or more polymers make up identically 100 wt% of the ribs in a plurality of ribs.
Each polymer present in a plurality of ribs may independently make up a wt% of the ribs in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the polymers together in a plurality of ribs may make up a wt% of the ribs in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more polymers individually in an amount in one or more of the above-referenced ranges and/or may comprise a combination of polymers that are present together in an amount in one or more of the above-referenced ranges.
Non-limiting examples of suitable polymers include poly(acrylate)s, poly(ester)s, poly(alpha olefins), and poly(styrene). The polymers may comprise homopolymers and/or copolymers and/or terpolymers comprising one or more of the above types of polymers and/or monomers from one or more of the above types of polymers (e.g., poly(styrene)-poly(acrylate) copolymers). In some embodiments, the plurality of ribs comprises an amorphous polymer and/or comprises a blend of polymers that is amorphous.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more polymers having one or more of the above-described compositions.
Polymers suitable for incorporation into the ribs described herein may have a variety of suitable degrees of polymerization. In some embodiments, a polymer present in ribs in a plurality of ribs has a degree of polymerization of greater than or equal to 500, greater than or equal to 750, greater than or equal to 1000, greater than or equal to 1250, greater than or equal to 1500, greater than or equal to 1750, greater than or equal to 2000, greater than or equal to 2250, greater than or equal to 2500, greater than or equal to 2750, greater than or equal to 3000, greater than or equal to 3500, greater than or equal to 4000, greater than or equal to 4500, greater than or

equal to 5000, greater than or equal to 6000, or greater than or equal to 7500. In some embodiments, a polymer present in ribs in a plurality of ribs has a degree of polymerization of less than or equal to 10000, less than or equal to 7500, less than or equal to 6000, less than or equal to 5000, less than or equal to 4500, less than or equal to 4000, less than or equal to 3500, less than or equal to 3000, less than or equal to 2750, less than or equal to 2500, less than or equal to 2250, less than or equal to 2000, less than or equal to 1750, less than or equal to 1500, less than or equal to 1250, less than or equal to 1000, or less than or equal to 750. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 500 and less than or equal to 10000, greater than or equal to 1000 and less than or equal to 5000, or greater than or equal to 2000 and less than or equal to 3000). Other ranges are also possible.
Gel permeation chromatography may be employed to determine the degree of polymerization of a polymer present in the ribs described herein. The gel permeation chromatography may be performed on polymer that has been extracted from the ribs.
Each polymer present in a plurality of ribs may independently have a degree of polymerization in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the polymers together in a plurality of ribs may have a degree of polymerization in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more polymers individually having a degree of polymerization in one or more of the above-referenced ranges and/or may comprise a combination of polymers that together have a degree of polymerization in one or more of the above-referenced ranges.
In some embodiments, a plurality of ribs comprises one or more fillers. Fillers may make up a variety of suitable amounts of the ribs described herein. In some embodiments, one or more fillers make up greater than or equal to 0 wt%, greater than or equal to 1 wt%, greater than or equal to 2.5 wt%, greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, greater than or equal to 17.5 wt%, greater than or equal to 20 wt%, greater than or equal to 22.5 wt%, greater than or equal to 25 wt%, greater than or equal to 27.5 wt%, greater than or equal to 30 wt%, greater than or equal to 32.5 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal

to 70 wt%, or greater than or equal to 80 wt% of the ribs in a plurality of ribs. In some embodiments, one or more fillers make up less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 32.5 wt%, less than or equal to 30 wt%, less than or equal to 27.5 wt%, less than or equal to 25 wt%, less than or equal to 22.5 wt%, less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, less than or equal to 2.5 wt%, or less than or equal to 1 wt% of the ribs in a plurality of ribs. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 90 wt%, greater than or equal to 1 wt% and less than or equal to 30 wt%, greater than or equal to 10 wt% and less than or equal to 35 wt%, or greater than or equal to 15 wt% and less than or equal to 25 wt%). Other ranges are also possible. In some embodiments, one or more fillers make up identically 0 wt% of the ribs in a plurality of ribs.
Each filler present in a plurality of ribs may independently make up a wt% of the ribs in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the fillers together in a plurality of ribs may make up a wt% of the ribs in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more fillers individually in an amount in one or more of the above-referenced ranges and/or may comprise a combination of fillers that are present together in an amount in one or more of the above-referenced ranges.
Fillers suitable for use in the ribs described herein may include chemically inert materials. For instance, in some embodiments, filler present in a plurality of ribs comprise a ceramic and/or glass. In some embodiments, a filler comprises a carbonate salt, silica, titanium dioxide, china clay, and/or multani mitti. Non-limiting examples of suitable carbonate salts include calcium carbonate and magnesium carbonate. Non-limiting examples of suitable types of silica include fumed silica, precipitated silica, hydrophilic silica, hydrophobic silica, mineral silica, and wollastonite silica.

When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more fillers having one or more of the above-described compositions.
Fillers suitable for incorporation into the ribs described herein may have a variety of suitable specific surface areas. In some embodiments, a filler present in ribs in a plurality of ribs has a specific surface area of greater than or equal to 10 m2/g, greater than or equal to 20 m2/g, greater than or equal to 50 m2/g, greater than or equal to 75 m2/g, greater than or equal to 100 m2/g, greater than or equal to 125 m2/g, greater than or equal to 150 m2/g, greater than or equal to 175 m2/g, greater than or equal to 200 m2/g, greater than or equal to 250 m2/g, greater than or equal to 300 m2/g, greater than or equal to 350 m2/g, greater than or equal to 400 m2/g, greater than or equal to 450 m2/g, greater than or equal to 500 m2/g, greater than or equal to 600 m2/g, greater than or equal to 700 m2/g, greater than or equal to 800 m2/g, greater than or equal to 950 m2/g, greater than or equal to 1250 m2/g, greater than or equal to 1500 m2/g, or greater than or equal to 1750 m2/g. In some embodiments, a filler present in ribs in a plurality of ribs has a specific surface area of less than or equal to 2000 m2/g, less than or equal to 1750 m2/g, less than or equal to 1500 m2/g, less than or equal to 1250 m2/g, less than or equal to 950 m2/g, less than or equal to 800 m2/g, less than or equal to 700 m2/g, less than or equal to 600 m2/g, less than or equal to 500 m2/g, less than or equal to 450 m2/g, less than or equal to 400 m2/g, less than or equal to 350 m2/g, less than or equal to 300 m2/g, less than or equal to 250 m2/g, less than or equal to 200 m2/g, less than or equal to 175 m2/g, less than or equal to 150 m2/g, less than or equal to 125 m2/g, less than or equal to 100 m2/g, less than or equal to 75 m2/g, less than or equal to 50 m2/g, or less than or equal to 20 m2/g. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 m2/g and less than or equal to 2000 m2/g, greater than or equal to 20 m2/g and less than or equal to 950 m2/g, greater than or equal to 100 m2/g and less than or equal to 500 m2/g, or greater than or equal to 150 m2/g and less than or equal to 300 m2/g). Other ranges are also possible.
The specific surface area may be determined in accordance with section 10 of Battery Council International Standard BCIS-03 A (2009), "Recommended Battery Materials Specifications Valve Regulated Recombinant Batteries", section 10 being "Standard Test Method for Surface Area of Recombinant Battery Separator Mat". Following this technique, the specific surface area is measured via adsorption analysis using a BET surface analyzer (e.g.,

Micromeritics Gemini III 2375 Surface Area Analyzer) with nitrogen gas; the sample amount is between 0.5 and 0.6 grams in a 3/4" tube; and, the sample is allowed to degas at 100 °C for a minimum of 3 hours.
Each filler present in a plurality of ribs may independently have a specific surface area in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the fillers together in a plurality of ribs may have a specific surface area in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more fillers individually having a specific surface area in one or more of the above-referenced ranges and/or may comprise a combination of fillers that together have a specific surface area in one or more of the above-referenced ranges.
Fillers suitable for incorporation into the ribs described herein may have a variety of suitable specific pore volumes. In some embodiments, a filler present in ribs in a plurality of ribs has a specific pore volume of greater than or equal to 0.2 cm3/g, greater than or equal to 0.3 cm3/g, greater than or equal to 0.4 cm3/g, greater than or equal to 0.5 cm3/g, greater than or equal to 0.6 cm3/g, greater than or equal to 0.8 cm3/g, greater than or equal to 1 cm3/g, greater than or equal to 1.25 cm3/g, greater than or equal to 1.5 cm3/g, greater than or equal to 1.75 cm3/g, greater than or equal to 2 cm3/g, greater than or equal to 2.25 cm3/g, greater than or equal to 2.5 cm3/g, or greater than or equal to 2.75 cm3/g. In some embodiments, a filler present in ribs in a plurality of ribs has a specific pore volume of less than or equal to 3 cm3/g, less than or equal to 2.75 cm3/g, less than or equal to 2.5 cm3/g, less than or equal to 2.25 cm3/g, less than or equal to
2 cm3/g, less than or equal to 1.75 cm3/g, less than or equal to 1.5 cm3/g, less than or equal to
1.25 cm3/g, less than or equal to 1 cm3/g, less than or equal to 0.8 cm3/g, less than or equal to 0.6
cm3/g, less than or equal to 0.5 cm3/g, less than or equal to 0.4 cm3/g, or less than or equal to 0.3
cm3/g. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal
to 0.2 cm3/g and less than or equal to 3 cm3/g, greater than or equal to 0.5 cm3/g and less than or
equal to 2 cm3/g, or greater than or equal to 1 cm3/g and less than or equal to 1.5 cm3/g). Other
ranges are also possible.
The specific pore volume of a filler may be determined in accordance with ASTM F316-
03 (2019).

Each filler present in a plurality of ribs may independently have a specific pore volume in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the fillers together in a plurality of ribs may have a specific pore volume in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more fillers individually having a specific pore volume in one or more of the above-referenced ranges and/or may comprise a combination of fillers that together have a specific pore volume in one or more of the above-referenced ranges.
Fillers suitable for incorporation into the ribs described herein may have a variety of suitable average diameters. In some embodiments, a filler present in ribs in a plurality of ribs has an average diameter of greater than or equal to 0.01 micron, greater than or equal to 0.02 microns, greater than or equal to 0.05 microns, greater than or equal to 0.075 microns, greater than or equal to 0.1 micron, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 7.5 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, greater than or equal to 50 microns, or greater than or equal to 60 microns. In some embodiments, a filler present in ribs in a plurality of ribs has an average diameter of less than or equal to 75 microns, less than or equal to 60 microns, less than or equal to 50 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 7.5 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.75 microns, less than or equal to 0.5 microns, less than or equal to 0.2 microns, less than or equal to 0.1 micron, less than or equal to 0.075 microns, less than or equal to 0.05 microns, or less than or equal to 0.02 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.01 micron and less than or equal to 75 microns, greater than or equal to 1 micron and less than or equal to 60 microns, greater than or equal to 4 microns and less than or equal to

12 microns, or greater than or equal to 10 microns and less than or equal to 30 microns). Other ranges are also possible.
Each filler present in a plurality of ribs may independently have an average diameter in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the fillers together in a plurality of ribs may have an average diameter in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more fillers individually having an average diameter in one or more of the above-referenced ranges and/or may comprise a combination of fillers that together have an average diameter in one or more of the above-referenced ranges.
In some embodiments, a plurality of ribs comprises one or more plasticizers. When present, such plasticizers may be covalently-bonded to one or more other species also present in the ribs (e.g., to one or more polymers therein) or lack such covalent bonds. Plasticizers may make up a variety of suitable amounts of the ribs described herein. In some embodiments, one or more plasticizers make up greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%, or greater than or equal to 55 wt% of the ribs in a plurality of ribs. In some embodiments, one or more plasticizers make up less than or equal to 60 wt%, less than or equal to 55 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% of the ribs in a plurality of ribs. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 wt% and less than or equal to 60 wt%, greater than or equal to 20 wt% and less than or equal to 50 wt%, or greater than or equal to 30 wt% and less than or equal to 40 wt%). Other ranges are also possible.
Each plasticizer present in a plurality of ribs may independently make up a wt% of the ribs in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the plasticizers together in a plurality of ribs may make up a wt% of the ribs in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one

or more plasticizers individually in an amount in one or more of the above-referenced ranges and/or may comprise a combination of plasticizers that are present together in an amount in one or more of the above-referenced ranges.
Non-limiting examples of suitable plasticizers include non-volatile organic compounds, sulfates of alkylsulfite acids, esters of alkylsulfite acids, alcohols, phenols, diesters of ortho-phthalic acids, epoxy esters of unsaturated fatty acids (e.g., plant-derived epoxy esters of unsaturated fatty acids, epoxidized butyl esters of unsaturated fatty acids, epoxidized n-hexyl esters of unsaturated fatty acids), reaction products of phthalic anhydrides, reaction products of oxo alcohols (e.g., comprising greater than or equal to 4 and less than or equal to 13 carbon atoms).
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise one or more plasticizers having one or more of the above-described compositions.
In some embodiments, ribs in a plurality of ribs comprise relatively low (or zero) amounts of species that may leach deleteriously therefrom upon exposure to one or more oxidative fluids for one or more periods of time. Non-limiting examples of such species include leachable plasticizers. Three non-limiting examples of oxidative fluids into which relatively low (or zero) amounts of species may leach are: (1) sulfuric acid having a specific gravity of 1.260, (2) sulfuric acid having a specific gravity of 1.260 comprising potassium dichromate; and (3) sulfuric acid having a specific gravity of 1.260 comprising hydrogen peroxide. Two non-limiting examples of time periods over which the relatively low (or zero) amounts of species may leach are: (1) 3 hours; and (2) 24 hours.
The amount of species that leach from the ribs upon exposure to an oxidative fluid in a plurality of ribs may be determined by exposing the plurality of ribs to the relevant oxidative fluid and then measuring the amount of weight loss during this process. The amount of weight lost is taken to be equivalent to the amount of leachable species initially present. For the amount of species that leaches from the ribs over 3 hours, these measurements may be made in accordance with BCIS-03B-23, BCIS-03B-24, and BCIS-03B-22 (2015) for the oxidative fluids of sulfuric acid having a specific gravity of 1.260, sulfuric acid having a specific gravity of 1.260 comprising potassium dichromate, and sulfuric acid having a specific gravity of 1.260 further comprising hydrogen peroxide, respectively. For the amount of species that leaches from the

ribs over 24 hours, these measurements may be made in accordance with the same testing standards described in the preceding sentence modified such that the exposure to the oxidative fluid occurs for 24 hours instead of 3 hours.
Species that leach from the ribs upon exposure to an oxidative fluid may make up less than or equal to 5 wt%, less than or equal to 4.5 wt%, less than or equal to 4 wt%, less than or equal to 3.5 wt%, less than or equal to 3 wt%, less than or equal to 2.5 wt%, less than or equal to 2 wt%, less than or equal to 1.5 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.2 wt%, or less than or equal to 0.1 wt% of the ribs. Species that leach from the ribs upon exposure to an oxidative fluid may make up greater than or equal to 0 wt%, greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 1.5 wt%, greater than or equal to 2 wt%, greater than or equal to 2.5 wt%, greater than or equal to 3 wt%, greater than or equal to 3.5 wt%, greater than or equal to 4 wt%, or greater than or equal to 4.5 wt% of the ribs. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 5 wt% and greater than or equal to 0 wt%, less than or equal to 2 wt% and greater than or equal to 0 wt%, or less than or equal to 1 wt% and greater than or equal to 0 wt%). Other ranges are also possible. In some embodiments, species that leach from the ribs upon exposure to sulfuric acid having a specific gravity of 1.260 make up identically 0 wt% of the ribs.
A battery separator may comprise an amount of species that leach from the ribs in one or more of the above-referenced ranges as measured under one or more of the following conditions: (1) exposure to sulfuric acid having a specific gravity of 1.260 for 3 hours; (2) exposure to sulfuric acid having a specific gravity of 1.260 comprising potassium dichromate for 3 hours; (3) exposure to sulfuric acid having a specific gravity of 1.260 comprising hydrogen peroxide for 3 hours; (4) exposure to acid having a specific gravity of 1.260 for 24 hours; (5) exposure to sulfuric acid having a specific gravity of 1.260 comprising potassium dichromate for 24 hours; and (6) exposure to sulfuric acid having a specific gravity of 1.260 comprising hydrogen peroxide for 24 hours.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently be described by one or more of the conditions in the preceding paragraph and/or both pluralities of ribs may together comprise an

amount of species that are described by one or more of the conditions in the preceding paragraph.
In some embodiments, a relatively low amount of iron ions may be leached from a plurality of ribs upon exposure to a volume of 98% sulfuric acid. The amount of iron ions leached from the plurality of ribs may be less than or equal to 100 ppm, less than or equal to 90 ppm, less than or equal to 80 ppm, less than or equal to 70 ppm, less than or equal to 60 ppm, less than or equal to 55 ppm, less than or equal to 50 ppm, less than or equal to 45 ppm, less than or equal to 40 ppm, less than or equal to 35 ppm, less than or equal to 30 ppm, less than or equal to 25 ppm, less than or equal to 20 ppm less than or equal to 15 ppm, less than or equal to 10 ppm, or less than or equal to 5 ppm. The amount of iron ions leached from the plurality of ribs may be greater than or equal to 0 ppm, greater than or equal to 5 ppm, greater than or equal to 10 ppm, greater than or equal to 15 ppm, greater than or equal to 20 ppm, greater than or equal to 25 ppm, greater than or equal to 30 ppm, greater than or equal to 35 ppm, greater than or equal to 40 ppm, greater than or equal to 45 ppm, greater than or equal to 50 ppm, greater than or equal to 55 ppm, greater than or equal to 60 ppm, greater than or equal to 70 ppm, greater than or equal to 80 ppm, or greater than or equal to 90 ppm. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 100 ppm and greater than or equal to 0 ppm, less than or equal to 60 ppm and greater than or equal to 0 ppm, less than or equal to 30 ppm and greater than or equal to 0 ppm, or less than or equal to 25 ppm and greater than or equal to 0 ppm). Other ranges also apply. In some embodiments, identically 0 ppm of iron ions leaches from the plurality of ribs upon exposure to 98% sulfuric acid.
The leaching of iron ions from ribs upon exposure to 98% sulfuric acid may be determined in accordance with IS 6071 (1986).
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently leach an amount of iron ions therefrom upon exposure to 98% sulfuric acid in one or more of the above-referenced ranges and/or both pluralities of ribs may together leach an amount of iron ions therefrom upon exposure to 98% sulfuric acid in one or more of the above-referenced ranges.
In some embodiments, a relatively low amount of chloride ions may be leached from a plurality of ribs upon exposure to a volume of 98% sulfuric acid. The amount of chloride ions leached from the plurality of ribs may be less than or equal to 100 ppm, less than or equal to 80

ppm, less than or equal to 60 ppm, less than or equal to 50 ppm, less than or equal to 40 ppm, less than or equal to 30 ppm, less than or equal to 25 ppm, less than or equal to 20 ppm less than or equal to 15 ppm, less than or equal to 10 ppm, or less than or equal to 5 ppm. The amount of chloride ions leached from the plurality of ribs may be greater than or equal to 0 ppm, greater than or equal to 5 ppm, greater than or equal to 10 ppm, greater than or equal to 15 ppm, greater than or equal to 20 ppm, greater than or equal to 25 ppm, greater than or equal to 30 ppm, greater than or equal to 40 ppm, greater than or equal to 50 ppm, greater than or equal to 60 ppm, or greater than or equal to 80 ppm. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 100 ppm and greater than or equal to 0 ppm, less than or equal to 30 ppm and greater than or equal to 0 ppm, less than or equal to 20 ppm and greater than or equal to 0 ppm, or less than or equal to 10 ppm and greater than or equal to 0 ppm). Other ranges also apply. In some embodiments, identically 0 ppm of chloride ions leaches from the plurality of ribs upon exposure to 98% sulfuric acid.
The leaching of chloride ions from ribs upon exposure to 98% sulfuric acid may be determined in accordance with BCIS-03A (2015).
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently leach an amount of chloride ions therefrom upon exposure to 98% sulfuric acid in one or more of the above-referenced ranges and/or both pluralities of ribs may together leach an amount of chloride ions therefrom upon exposure to 98% sulfuric acid in one or more of the above-referenced ranges.
In some embodiments, ribs in a plurality of ribs are formed from a fluid comprising one or more species that are described above (e.g., one or more polymers, one or more fillers, one or more plasticizers). Such species may be present in the fluid in one or more of the ranges described above with respect to the amount that these species may make up of ribs in a plurality of ribs. In some embodiments, one or more such species may be present in the form of particulates dispersed and/or suspended in the fluid (e.g., polymer particles, filler particles, plasticizer particles). Such particles may be uniformly or non-uniformly dispersed through the fluid.
It is also possible for the fluid to comprise one or more species that are removed from the fluid during rib formation. For instance, the fluid may comprise a species that evaporates, outgasses, and/or undergoes a chemical reaction (e.g., a chemical reaction resulting in

outgassing) during rib formation. This species may be removed upon deposition of the fluid onto a porous layer and/or during one or more subsequent steps (e.g., during a curing step). One example of a species having this property is a solvent, such as an aqueous solvent. Another example of a species having this property is a pore-forming additive. The pore-forming additive may undergo a reaction to produce a gas and/or outgas during a curing process performed after a fluid to be transformed into a plurality of ribs is deposited on a porous layer. During the reaction and/or outgassing, the pore-forming additive may expand greatly in size. This expansion may push apart the fluid and/or a reaction product of the fluid forming during the curing process, leaving behind a plurality of pores in the resultant ribs.
Pore-forming additives may be present in a variety of amounts in fluids from which ribs are formed. In some embodiments, one or more pore-forming additives make up greater than or equal to 0.05 wt%, greater than or equal to 0.075 wt%, greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 1.5 wt%, greater than or equal to 2 wt%, greater than or equal to 2.5 wt%, greater than or equal to 3 wt%, greater than or equal to 4 wt%, greater than or equal to 5 wt%, greater than or equal to 6 wt%, greater than or equal to 8 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, greater than or equal to 17.5 wt%, greater than or equal to 20 wt%, or greater than or equal to 25 wt% of a fluid from which a plurality of ribs is formed. In some embodiments, one or more pore-forming additives make up less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 8 wt%, less than or equal to 6 wt%, less than or equal to 5 wt%, less than or equal to 4 wt%, less than or equal to 3 wt%, less than or equal to 2.5 wt%, less than or equal to 2 wt%, less than or equal to 1.5 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.2 wt%, less than or equal to 0.1 wt%, or less than or equal to 0.075 wt% of a fluid from which a plurality of ribs is formed. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.05 wt% and less than or equal to 30 wt%, greater than or equal to 0.05 wt% and less than or equal to 20 wt%, greater than or equal to 0.5 wt% and less than or equal to 10 wt%, or greater than or equal to 1 wt% and less than or equal to 5 wt%). Other ranges are also possible.

Each pore-forming additive present in a fluid from which a plurality of ribs is formed may independently make up a wt% of the fluid in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the pore-forming additives together in a fluid from which a plurality of ribs is formed may make up a wt% of the fluid in one or more of the above-referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each fluid from which a plurality of ribs is formed may independently comprise one or more pore-forming additives individually in an amount in one or more of the above-referenced ranges and/or may comprise a combination of pore-forming additives that are present together in an amount in one or more of the above-referenced ranges.
Pore-forming additives suitable for use in the fluids from which ribs may be formed may include a variety of suitable materials, non-limiting examples of which include azodicarbonamide, microspheres comprising a polymeric shell,
dinitrosopentamethylenetetramine, 4-methylbenzenesulfohydrazide, 4-toluene sulfohydrazide, p,p-oxybisbenzenesulfonylhydrazide. Polymer(s) present in a pore-forming additive and/or a polymeric shell of a microsphere may comprise homopolymers and/or copolymers. In some embodiments, pore-forming additive and/or a polymeric shell of a microsphere comprises repeat units that are polymerized ethylenically unsaturated species. Such species may include nitrile-containing monomers (e.g., acrylonitrile, methacrylonitrile, a-chloroacrylonitrile, a-ethoxyacrylonitrile, fumaronitrile, crotonitrile), acrylic esters (e.g., methyl acrylate, ethyl acrylate), methacrylic esters (e.g., methyl methacrylate, isobomyl methacrylate, ethyl methacrylate, hydroxyethylmethacrylate), vinyl halides (e.g., vinyl chloride, vinylidene chloride) vinyl pyridine, vinyl esters (e.g., vinyl acetate), styrenes (e.g., styrene, halogenated styrenes, a-methyl styrene), dienes (e.g., butadiene, isoprene, chloroprene), unsaturated carboxylic compounds (e.g., acrylic acid, methacrylic acid, salts thereof), acrylamide, and/or N-substituted maleimides. Additionally, one non-limiting example of a suitable microsphere comprising a polymeric shell is expancel.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently be formed from a fluid comprising one or more pore-forming additives having one or more of the above-described compositions.
In some embodiments, pore-forming additives suitable for incorporation into the fluids from which ribs may be formed described herein may be particulate. In such embodiments, the

particles may have a variety of suitable average diameters. In some embodiments, one or more pore-forming additives has an average diameter of greater than or equal to 0.05 microns, greater than or equal to 0.075 microns, greater than or equal to 0.1 micron, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 1.5 microns, greater than or equal to 2 microns, greater than or equal to 2.5 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 12.5 microns, greater than or equal to 15 microns, greater than or equal to 17.5 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, or greater than or equal to 40 microns. In some embodiments, one or more pore-forming additives has an average diameter of less than or equal to 50 microns, less than or equal to 40 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 8 microns, less than or equal to 6 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, less than or equal to 2.5 microns, less than or equal to 2 microns, less than or equal to 1.5 microns, less than or equal to 1 micron, less than or equal to 0.75 microns, less than or equal to 0.5 microns, less than or equal to 0.2 microns, less than or equal to 0.1 micron, or less than or equal to 0.075 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.05 microns and less than or equal to 50 microns, greater than or equal to 0.05 microns and less than or equal to 20 microns, greater than or equal to 0.5 microns and less than or equal to 10 microns, or greater than or equal to 1 micron and less than or equal to 5 microns). Other ranges are also possible.
As used herein, the average diameter of a plurality of particles is the average of the diameters of the particles in the plurality of particles. The diameter of each particle in a plurality of particles is equivalent to the largest cross-sectional diameter of the particle.
Each pore-forming additive present in a fluid from which a plurality of ribs is formed may independently have an average diameter in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the pore-forming additives together in a fluid from which a plurality of ribs is formed may have an average diameter in one or more of the above-

referenced ranges. When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each fluid from which a plurality of ribs is formed may independently comprise one or more pore-forming additives individually having an average diameter in one or more of the above-referenced ranges and/or may comprise a combination of pore-forming additives that together have an average diameter in one or more of the above-referenced ranges.
The ribs described herein may have a variety of suitable morphologies and physical properties. Further details regarding such properties are provided below.
Pluralities of ribs may cover a variety of suitable percentages of a surface of a porous layer on which they are disposed. In some embodiments, a plurality of ribs covers greater than or equal to 0.05%, greater than or equal to 0.075%, greater than or equal to 0.1%, greater than or equal to 0.2%, greater than or equal to 0.5%, greater than or equal to 0.75%, greater than or equal to 1%>, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 7.5%, greater than or equal to 10%, greater than or equal to 12.5%, greater than or equal to 15%, greater than or equal to 17.5%, greater than or equal to 20%, greater than or equal to 22.5%, greater than or equal to 25%, greater than or equal to 27.5%, greater than or equal to 30%, greater than or equal to 32.5%, greater than or equal to 35%, or greater than or equal to 37.5% of a surface of a porous layer on which it is disposed. In some embodiments, a plurality of ribs covers less than or equal to 40%, less than or equal to 37.5%, less than or equal to 35%, less than or equal to 32.5%, less than or equal to 30%, less than or equal to 27.5%, less than or equal to 25%o, less than or equal to 22.5%, less than or equal to 20%, less than or equal to 17.5%, less than or equal to 15%, less than or equal to 12.5%, less than or equal to 10%, less than or equal to 7.5%o, less than or equal to 5%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.75%, less than or equal to 0.5%, less than or equal to 0.2%, less than or equal to 0.1%, or less than or equal to 0.075%> of a surface of a porous layer on which it is disposed. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.05%) and less than or equal to 40%, greater than or equal to 10% and less than or equal to 15%, or greater than or equal to 20% and less than or equal to 30%). Other ranges are also possible.
The ranges described above may refer to the percentage of the surface area of the porous layer on which the ribs are disposed that is in direct contact with the ribs. Additionally, when a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces),

each plurality of ribs may independently cover a percentage of a porous layer on which it is disposed in one or more of the above-referenced ranges.
Pluralities of ribs may have a variety of suitable average heights. In some embodiments, the average height of the ribs in a plurality of ribs is greater than or equal to 0.05 mm, greater than or equal to 0.075 mm, greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.3 mm, greater than or equal to 0.4 mm, greater than or equal to 0.5 mm, greater than or equal to 0.6 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, greater than or equal to 1.75 mm, greater than or equal to 2 mm, greater than or equal to 2.25 mm, greater than or equal to 2.5 mm, or greater than or equal to 2.75 mm. In some embodiments, the average height of the ribs in a plurality of ribs is less than or equal to 3 mm, less than or equal to 2.75 mm, less than or equal to 2.5 mm, less than or equal to 2.25 mm, less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, less than or equal to 0.6 mm, less than or equal to 0.5 mm, less than or equal to 0.4 mm, less than or equal to 0.3 mm, less than or equal to 0.2 mm, less than or equal to 0.1 mm, or less than or equal to 0.075 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.05 mm and less than or equal to 3 mm, greater than or equal to 0.5 mm and less than or equal to 2 mm, or greater than or equal to 0.6 mm and less than or equal to 1 mm). Other ranges are also possible.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having an average height in one or more of the above-referenced ranges.
Pluralities of ribs may have a variety of suitable average widths. The average width of the ribs in a plurality of ribs may be an average of the widths of the ribs therein. In some embodiments, the average width of the ribs in a plurality of ribs is greater than or equal to 0.05 mm, greater than or equal to 0.075 mm, greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, greater than or equal to 1.75 mm, greater than or equal to 2 mm, greater than or equal to 2.25 mm, greater than or equal to 2.5 mm, greater than or equal to 2.75 mm, greater than or equal to 3 mm, greater than or equal to 3.5 mm, greater than or equal to 4 mm, or greater than or equal to 4.5 mm. In some embodiments, the average width of the ribs

in a plurality of ribs is less than or equal to 5 mm, less than or equal to 4.5 mm, less than or equal to 4 mm, less than or equal to 3.5 mm, less than or equal to 3 mm, less than or equal to 2.75 mm, less than or equal to 2.5 mm, less than or equal to 2.25 mm, less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, less than or equal to 0.5 mm, less than or equal to 0.2 mm, less than or equal to 0.1 mm, or less than or equal to 0.075 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.05 mm and less than or equal to 5 mm, greater than or equal to 0.05 mm and less than or equal to 2.5 mm, greater than or equal to 0.5 mm and less than or equal to 5 mm, greater than or equal to 1 mm and less than or equal to 5 mm, greater than or equal to 1.5 mm and less than or equal to 3 mm, or greater than or equal to 2 mm and less than or equal to 2.5 mm). Other ranges are also possible.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having an average width in one or more of the above-referenced ranges. The external ribs configured to face the negative battery plate may have a smaller average width than the ribs configured to face the positive battery plate. In some embodiments, ribs configured to face the negative battery plate have an average width of greater than or equal to 0.05 mm and less than or equal to 2.5 mm. In some embodiments, ribs configured to face the positive battery plate have an average width of greater than or equal to 0.5 mm and less than or equal to 2.5 mm.
Pluralities of ribs may have a variety of suitable average aspect ratios. The aspect ratio of a rib may be equivalent to the ratio of its length to its width. The average aspect ratios of the ribs in a plurality of ribs may be an average of the aspect ratios of the ribs therein. In some embodiments, the average aspect ratio of the ribs in a plurality of ribs is greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 8, greater than or equal to 9, greater than or equal to 10, greater than or equal to 12.5, greater than or equal to 15, greater than or equal to 17.5, greater than or equal to 20, greater than or equal to 25, greater than or equal to 30, or greater than or equal to 35. In some embodiments, the average aspect ratio of the ribs in a plurality of ribs is less than or equal to 40, less than or equal to 35, less than or equal to 30, less than or equal to 25, less than or equal to 20, less than or equal to 17.5, less than or equal to 15, less than or equal to 12.5, less than or equal to 10, less than or

equal to 9, less than or equal to 8, less than or equal to 7, less than or equal to 6, less than or equal to 5, less than or equal to 4, less than or equal to 3, or less than or equal to 2. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 40, greater than or equal to 5 and less than or equal to 8, or greater than or equal to 10 and less than or equal to 20). Other ranges are also possible. In some embodiments, the average aspect ratio of the ribs in a plurality of ribs is identically 1 (e.g., when the ribs are dots or squares).
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having an average aspect ratio in one or more of the above-referenced ranges.
Pluralities of ribs may have a variety of suitable average spacings. In some embodiments, a plurality of ribs comprises ribs having an average spacing of greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 5 mm, greater than or equal to 7.5 mm, greater than or equal to 10 mm, greater than or equal to 12.5 mm, greater than or equal to 15 mm, greater than or equal to 17.5 mm, greater than or equal to 20 mm, or greater than or equal to 22.5 mm. In some embodiments, a plurality of ribs comprises ribs having an average spacing of less than or equal to 25 mm, less than or equal to 22.5 mm, less than or equal to 20 mm, less than or equal to 17.5 mm, less than or equal to 15 mm, less than or equal to 12.5 mm, less than or equal to 10 mm, less than or equal to 7.5 mm, less than or equal to 5 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, less than or equal to 0.5 mm, or less than or equal to 0.2 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 mm and less than or equal to 25 mm, greater than or equal to 0.1 mm and less than or equal to 12.5 mm, or greater than or equal to 2 mm and less than or equal to 25 mm). Other ranges are also possible.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having an average spacing in one or more of the above-referenced ranges.
In some embodiments, it may be advantageous for a battery separator to comprise two pluralities of ribs on opposite external surfaces having different average spacings. The external ribs configured to face the negative battery plate may have a smaller average spacing than the

ribs configured to face the positive battery plate. In some embodiments, ribs configured to face the negative battery plate have an average spacing of greater than or equal to 0.1 mm and less than or equal to 12.5 mm. In some embodiments, ribs configured to face the positive battery plate have an average spacing of greater than or equal to 2 mm and less than or equal to 25 mm.
Pluralities of ribs may have a variety of suitable frequencies. In some embodiments, a plurality of ribs comprises ribs having a frequency in the machine direction of greater than or equal to 20 ribs/m, greater than or equal to 30 ribs/m, greater than or equal to 40 ribs/m, greater than or equal to 50 ribs/m, greater than or equal to 60 ribs/m, greater than or equal to 70 ribs/m, greater than or equal to 80 ribs/m, greater than or equal to 90 ribs/m, greater than or equal to 100 ribs/m, greater than or equal to 125 ribs/m, greater than or equal to 150 ribs/m, greater than or equal to 175 ribs/m, greater than or equal to 200 ribs/m, greater than or equal to 250 ribs/m, greater than or equal to 300 ribs/m, greater than or equal to 400 ribs/m, greater than or equal to 500 ribs/m, or greater than or equal to 750 ribs/m. In some embodiments, a plurality of ribs comprises ribs having a frequency in the machine direction of less than or equal to 1000 ribs/m, less than or equal to 750 ribs/m, less than or equal to 500 ribs/m, less than or equal to 400 ribs/m, less than or equal to 300 ribs/m, less than or equal to 250 ribs/m, less than or equal to 200 ribs/m, less than or equal to 175 ribs/m, less than or equal to 150 ribs/m, less than or equal to 125 ribs/m, less than or equal to 100 ribs/m, less than or equal to 90 ribs/m, less than or equal to 80 ribs/m, less than or equal to 70 ribs/m, less than or equal to 60 ribs/m, less than or equal to 50 ribs/m, less than or equal to 40 ribs/m, or less than or equal to 30 ribs/m. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 20 ribs/m and less than or equal to 1000 ribs/m, greater than or equal to 50 ribs/m and less than or equal to 500 ribs/m, or greater than or equal to 80 ribs/m and less than or equal to 250 ribs/m). Other ranges are also possible.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having a frequency in one or more of the above-referenced ranges.
Pluralities of ribs may be oriented in a variety of suitable manners. In some embodiments, an average angle of the direction of the length of the rib to the machine direction may be greater than or equal to 0°, greater than or equal to 5°, greater than or equal to 10°, greater than or equal to 15°, greater than or equal to 20°, greater than or equal to 25°, greater than or equal to 30°, greater than or equal to 35°, greater than or equal to 40°, greater than or

equal to 45°, greater than or equal to 50°, greater than or equal to 55°, greater than or equal to 60°, greater than or equal to 65°, greater than or equal to 70°, greater than or equal to 75°, greater than or equal to 80°, or greater than or equal to 85°. In some embodiments, an average angle of the direction of the length of the rib to the machine direction may be less than or equal to 90°, less than or equal to 85°, less than or equal to 80°, less than or equal to 75°, less than or equal to 70°, less than or equal to 65°, less than or equal to 60°, less than or equal to 55°, less than or equal to 50°, less than or equal to 45°, less than or equal to 40°, less than or equal to 35°, less than or equal to 30°, less than or equal to 25°, less than or equal to 20°, less than or equal to 15°, less than or equal to 10°, or less than or equal to 5°. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0° and less than or equal to 90°, greater than or equal to 0° and less than or equal to 45°, or greater than or equal to 0° and less than or equal to 15°). Other ranges are also possible. In some embodiments, the average angle of the direction of the length of the ribs to the machine direction is identically 0°. In some embodiments, the average angle of the direction of the length of the ribs to the machine direction is identically 90°.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having an average angle to the machine direction in one or more of the above-referenced ranges.
Pluralities of ribs may have a variety of average porosities. In some embodiments, an average porosity of the ribs in a plurality of ribs is greater than or equal to 0%, greater than or equal to 5%, greater than or equal to 10%, greater than or equal to 15%, greater than or equal to 20%), greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, or greater than or equal to 85%). In some embodiments, the average porosity of the ribs in a plurality of ribs less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, less than or equal to 70%, less than or equal to 65%, less than or equal to 60%, less than or equal to 55%), less than or equal to 50%, less than or equal to 45%, less than or equal to 40%, less than or equal to 35%, less than or equal to 30%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, or less than or equal to 5%. Combinations of the above-referenced

ranges are also possible (e.g., greater than or equal to 0% and less than or equal to 90%, greater than or equal to 20% and less than or equal to 80%>, or greater than or equal to 30% and less than or equal to 70%). Other ranges are also possible. In some embodiments, the average porosity of the ribs in a plurality of ribs is identically 0%.
The average porosity of the ribs in a plurality of ribs may be determined by: (1) measuring the average porosity of a porous layer on which ribs are disposed and the ribs together in accordance with BCIS-03B (2015); (2) measuring the average porosity of the porous layer alone in accordance with BCIS-03B (2015); and (3) computing the average porosity of the ribs based on these two measurements.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having an average porosity in one or more of the above-referenced ranges.
In some embodiments, ribs in a plurality of ribs are relatively thermally stable. In some embodiments, ribs in a plurality of ribs may exhibit relatively low amounts of mass loss upon exposure to heat. The ribs in the plurality of ribs may lose less than or equal to 5%, less than or equal to 4.5%, less than or equal to 4%, less than or equal to 3.5%, less than or equal to 3%, less than or equal to 2.5%, less than or equal to 2%, less than or equal to 1.5%, less than or equal to 1%>, less than or equal to 0.75%, less than or equal to 0.5%, less than or equal to 0.2%, or less than or equal to 0.1% of their mass upon exposure to a temperature of 160 °C for 13 minutes. The ribs in the plurality of ribs may lose greater than or equal to 0%, greater than or equal to 0.1%>, greater than or equal to 0.2%, greater than or equal to 0.5%, greater than or equal to 0.75%), greater than or equal to 1%, greater than or equal to 1.5%, greater than or equal to 2%, greater than or equal to 2.5%, greater than or equal to 3%, greater than or equal to 3.5%, greater than or equal to 4%, or greater than or equal to 4.5% of their mass upon exposure to a temperature of 160 °C for 13 minutes. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 5% and greater than or equal to 0%, less than or equal to 4% and greater than or equal to 0%, less than or equal to 2% and greater than or equal to 0%, or less than or equal to 1% and greater than or equal to 0%). Other ranges are also possible. In some embodiments, the ribs in a plurality of ribs lose identically 0% of their mass upon exposure to a temperature of 160 °C for 13 minutes.

The exposure of the plurality of ribs to the temperature of 160 °C for 13 minutes and the measurement of any associated mass loss may be determined by heating a sample of the plurality of ribs in a thermogravimetric analyzer to 160 °C, holding it at 160 °C therein, and employing the thermogravimetric analyzer to measure the mass loss.
When a battery separator comprises two pluralities of ribs (e.g., disposed on opposite external surfaces), each plurality of ribs may independently comprise ribs having a thermal stability in one or more of the above-referenced ranges.
As described elsewhere herein, in some embodiments, a battery separator comprises a porous layer. A variety of suitable types of porous layers may be employed, some of which may be fibrous and some of which may be non-fibrous. For instance, some battery separators may comprise one or more of the following types of porous layers: non-woven fiber webs (e.g., wet laid non-woven fiber webs, non-wet laid non-woven fiber webs), membranes (e.g., extruded membranes, sintered membranes, cast membranes), woven layers, knitted layers, and braided layers. Additionally, although it should be noted that non-fibrous porous layers may have any of the properties described elsewhere herein with respect to porous layers, some exemplary non-fibrous porous layers include membranes having a porosity of greater than or equal to 30% and less than or equal to 70% and a mean flow pore size of greater than or equal to 0.05 microns and less than or equal to 1 micron, sintered membranes having a porosity of greater than or equal to 25%) and less than or equal to 60%> and a mean flow pore size of greater than or equal to 2.5 microns and less than or equal to 75 microns, and cast membranes having a porosity of greater than or equal to 25% and less than or equal to 50% and a mean flow pore size of greater than or equal to 0.05 microns and less than or equal to 1 micron.
Battery separators that comprise two or more porous layers may comprise two or more porous layers of the same type and/or may comprise two or more porous layers of different types. Porous layers of different types may have similar properties and porous layers of the same type may have different properties. Accordingly, references herein to porous layers should be understood to refer to porous layers of any suitable type of porous layer and references to porous layer properties should be understood to refer to the properties of any suitable type of porous layer unless otherwise specified.
Additionally, porous layers within a battery separator comprising two or more porous layers may be arranged as desired. For instance, a battery separator may comprise any of the

above-described porous layers in one or more of the following positions: an outermost layer in the battery separator (e.g., in a battery separator for which a plurality of ribs does not form one of the outermost layers), a layer directly adjacent to a plurality of ribs, and a layer that is both not an outermost layer and not directly adjacent to a plurality of ribs.
Layers and battery separator components disposed on each other as described herein and/or shown in the figures herein may be directly disposed on each other or may be indirectly disposed on each other. In other words, as used herein, when a layer and/or component is referred to as being "disposed on" or "adjacent" another layer and/or component, it can be directly disposed on or adjacent the layer and/or component, or it may be disposed on one or more intervening layers and/or components disposed on the other layer and/or component. A layer and/or component that is "directly disposed on", "directly adjacent" or "in contact with" another layer and/or component means that it is disposed on the other layer and/or component in a manner such that no intervening layer and/or component is present.
In some embodiments, a porous layer is fibrous. Fibers in a porous fibrous layer may have a variety of suitable average fiber diameters. In some embodiments, fibers in a porous fibrous layer have an average fiber diameter of greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 7.5 microns, greater than or equal to 10 microns, or greater than or equal to 15 microns. In some embodiments, fibers in a porous fibrous layer have an average fiber diameter of less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 7.5 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, or less than or equal to 0.75 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 20 microns, greater than or equal to 0.5 microns and less than or equal to 5 microns, or greater than or equal to 0.5 microns and less than or equal to 2 microns). Other ranges are also possible.
Each type of fiber present in a fibrous porous layer may independently have an average fiber diameter in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the fibers together in a fibrous porous layer may have an average fiber diameter in one or more of the above-referenced ranges. When a battery separator comprises two or more fibrous porous layers, each fibrous porous layer may independently comprise fibers

having an average fiber diameter in one or more of the above-referenced ranges and/or may comprise a combination of fibers that together have an average fiber diameter in one or more of the above-referenced ranges.
Fibers in a porous fibrous layer may have a variety of suitable average fiber lengths. In some embodiments, fibers in a porous fibrous layer have an average fiber length of greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 5 mm, greater than or equal to 7.5 mm, greater than or equal to 10 mm, greater than or equal to 20 mm, greater than or equal to 50 mm, greater than or equal to 60 mm, or greater than or equal to 75 mm. In some embodiments, fibers in a porous fibrous layer have an average fiber length of less than or equal to 90 mm, less than or equal to 75 mm, less than or equal to 60 mm, less than or equal to 50 mm, less than or equal to 20 mm, less than or equal to 10 mm, less than or equal to 7.5 mm, less than or equal to 5 mm, or less than or equal to 2 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 mm and less than or equal to 90 mm). Other ranges are also possible.
Each type of fiber present in a fibrous porous layer may independently have an average fiber length in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the fibers together in a fibrous porous layer may have an average fiber length in one or more of the above-referenced ranges. When a battery separator comprises two or more fibrous porous layers, each fibrous porous layer may independently comprise fibers having an average fiber length in one or more of the above-referenced ranges and/or may comprise a combination of fibers that together have an average fiber length in one or more of the above-referenced ranges.
Fibrous porous layers described herein may comprise fibers of a variety of suitable types. For instance, fibrous porous layers may comprise glass fibers (e.g., microglass fibers, chopped strand glass fibers), types of inorganic fibers other than glass fibers (e.g., rock wool fibers), natural fibers, and/or synthetic fibers (e.g., monocomponent synthetic fibers, multicomponent synthetic fibers).
Glass fibers may make up a variety of suitable percentages of the porous layers described herein. In some embodiments, glass fibers make up greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%,

greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt% of the fibers present in a fibrous porous layer. In some embodiments, glass fibers make up less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, or less than or equal to 7.5 wt% of the fibers present in a fibrous porous layer. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 5 wt% and less than or equal to 100 wt%, or greater than or equal to 5 wt% and less than or equal to 50 wt%). Other ranges are also possible. In some embodiments, glass fibers make up identically 100 wt% of the fibers in a fibrous porous layer.
Each type of glass fiber present in a fibrous porous layer may independently make up a wt% of the fibrous porous layer in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the types of glass fibers together in a fibrous porous layer may make up a wt% of the fibrous porous layer in one or more of the above-referenced ranges. When a battery separator comprises two or more fibrous porous layers, each fibrous porous layer may independently comprise one or more types of glass fibers individually in an amount in one or more of the above-referenced ranges and/or may comprise a combination of types of glass fibers that are present together in an amount in one or more of the above-referenced ranges.
Glass fibers present in a porous layer may have a variety of suitable average fiber diameters. In some embodiments, a porous layer comprises glass fibers having an average fiber diameter of greater than or equal to 0.1 micron, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 1.5 microns, greater than or equal to 2 microns, greater than or equal to 2.5 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7.5 microns, greater than or equal to 10 microns, greater than or equal to 12.5 microns, greater than or equal to 15 microns, or greater than or equal to 17.5 microns. In some embodiments, a porous layer comprises glass fibers having an average fiber diameter of less than

or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 7.5 microns, less than or equal to 5 microns, less than or equal to 3 microns, less than or equal to 2.5 microns, less than or equal to 2 microns, less than or equal to 1.5 microns, less than or equal to 1 micron, less than or equal to 0.75 microns, less than or equal to 0.5 microns, or less than or equal to 0.2 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 20 microns). Other ranges are also possible.
Each type of glass fiber present in a fibrous porous layer may independently have an average fiber diameter in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the glass fibers together in a fibrous porous layer may have an average fiber diameter in one or more of the above-referenced ranges. When a battery separator comprises two or more fibrous porous layers, each fibrous porous layer may independently comprise glass fibers having an average fiber diameter in one or more of the above-referenced ranges and/or may comprise a combination of glass fibers that together have an average fiber diameter in one or more of the above-referenced ranges.
Glass fibers present in a porous layer may have a variety of suitable average fiber lengths. In some embodiments, a porous layer comprises glass fibers having an average fiber length of greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 5 mm, greater than or equal to 7.5 mm, greater than or equal to 10 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, greater than or equal to 30 mm, greater than or equal to 40 mm, greater than or equal to 50 mm, greater than or equal to 60 mm, greater than or equal to 70 mm, or greater than or equal to 80 mm. In some embodiments, a porous layer comprises glass fibers having an average fiber length of less than or equal to 90 mm, less than or equal to 80 mm, less than or equal to 70 mm, less than or equal to 60 mm, less than or equal to 50 mm, less than or equal to 40 mm, less than or equal to 30 mm, less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 10 mm, less than or equal to 7.5 mm, less than or equal to 5 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, less than or equal to 0.5 mm, or less than or equal to 0.2 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 mm and less than or equal to 90 mm). Other ranges are also possible.

Each type of glass fiber present in a fibrous porous layer may independently have an average fiber length in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the glass fibers together in a fibrous porous layer may have an average fiber length in one or more of the above-referenced ranges. When a battery separator comprises two or more fibrous porous layers, each fibrous porous layer may independently comprise glass fibers having an average fiber length in one or more of the above-referenced ranges and/or may comprise a combination of glass fibers that together have an average fiber length in one or more of the above-referenced ranges.
As described above, some porous layers comprise glass fibers that are microglass fibers. Suitable microglass fibers may be fibers drawn from bushing tips and further subjected to flame blowing or rotary spinning processes. In some cases, microglass fibers may be made using a remelting process. The microglass fibers may be microglass fibers for which alkali metal oxides (e.g., sodium oxides, magnesium oxides) make up 10-20 wt% of the fibers. Such fibers may have relatively lower melting and processing temperatures. Non-limiting examples of microglass fibers are M glass fibers according to Man Made Vitreous Fibers by Nomenclature Committee of TFMA Inc. March 1993, Page 45 and C glass fibers (e.g., Lauscha C glass fibers, JM 253 C glass fibers). It should be understood that a plurality of microglass fibers may comprise one or more of the types of microglass fibers described herein.
Microglass fibers may make up a variety of suitable percentages of the porous layers described herein. In some embodiments, microglass fibers make up greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 45 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt% of the fibers present in a fibrous porous layer. In some embodiments, microglass fibers make up less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, or less

than or equal to 7.5 wt% of the fibers present in a fibrous porous layer. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 5 wt% and less than or equal to 100 wt%, or greater than or equal to 5 wt% and less than or equal to 50 wt%). Other ranges are also possible. In some embodiments, microglass fibers make up identically 100 wt% of the fibers in a fibrous porous layer.
Each type of microglass fiber present in a fibrous porous layer may independently make up a wt% of the fibrous porous layer in one or more of the above-referenced ranges. Additionally, in some embodiments, all of the types of microglass fibers together in a fibrous porous layer may make up a wt% of the fibrous porous layer in one or more of the above-referenced ranges. When a battery separator comprises two or more fibrous porous layers, each fibrous porous layer may independently comprise one or more types of microglass fibers individually in an amount in one or more of the above-referenced ranges and/or may comprise a combination of types of microglass fibers that are present together in an amount in one or more of the above-referenced ranges.

WE CLAIM:

1. A battery separator, comprising:
a porous layer; and
a plurality of ribs disposed on the porous layer, wherein: the ribs comprise a polymer, the ribs comprise a filler, and the plurality of ribs forms a discrete component of the battery separator.
2. A battery separator, comprising:
a porous layer; and
a plurality of ribs disposed on the porous layer, wherein:
the ribs exhibit a mass loss of less than or equal to 2% upon exposure to a temperature of 160 °C for 13 minutes, and
the plurality of ribs forms a discrete component of the battery separator.
3. A battery separator, comprising:
a porous layer; and
a plurality of ribs disposed on the porous layer, wherein: the ribs are porous, and the plurality of ribs forms a discrete component of the battery separator.
4. A method for fabricating a battery separator, comprising:
passing a fluid comprising a polymer through a screen comprising a plurality of orifices onto a porous layer; and
cooling the fluid to form ribs comprising the polymer disposed on the porous layer.