TECHNICAL FIELD
[0001] This application claims priority from Korean Patent
Application No. 10-2020-0045542, filed on April 14, 2020, the
disclosure of which is incorporated by reference herein.
10 [0002] The present invention relates to a pouch type battery
case and a pouch type secondary battery, and more particularly,
to a pouch type battery case, in which formability is improved
by improving tensile strength and elongation, and a pouch type
secondary battery.
15 BACKGROUND ART
[0003] In general, types of secondary batteries include a
nickel cadmium battery, a nickel hydride battery, a lithium
ion battery, and a lithium ion polymer battery. These
secondary batteries are not only applied and used in small
20 products such as digital cameras, P-DVDs, MP3Ps, mobile phones,
PDAs, portable game devices, power tools, and E-bikes, but are
also applied and used in large products requiring high output,
such as electric vehicles and hybrid vehicles, and a power
storage device and a power storage device for backup which
25 store surplus generated power or renewable energy.
2
[0004] In order to prepare such a secondary battery, first,
a positive electrode collector and a negative electrode
collector are respectively coated with electrode active
material slurries to prepare a positive electrode and a
5 negative electrode, and the positive electrode and the negative
electrode are then stacked on both sides of a separator to
form an electrode assembly having a predetermined shape. Then,
after the electrode assembly is accommodated in a battery case
and an electrolyte solution is injected, the battery case is
10 sealed.
[0005] The secondary battery is classified into a pouch type,
a can type, and the like, according to a material of a case
for accommodating the electrode assembly. The pouch type
accommodates the electrode assembly in a pouch formed of a
15 flexible polymer material. In addition, the can type
accommodates the electrode assembly in a case formed of a
material such as metal or plastic.
[0006] The pouch, which is a case of the pouch type secondary
battery, is prepared by press working of a flexible pouch film
20 laminate to form a cup portion. Then, when the cup portion is
formed, the electrode assembly is accommodated in an
accommodating space of the cup portion and a sealing portion
is sealed to prepare a secondary battery.
[0007] Drawing in the press working is performed by inserting
25 the pouch film laminate into press equipment and applying a
3
pressure to the pouch film laminate with a punch to stretch
the pouch film laminate. The pouch film laminate is composed
of a plurality of layers, and a gas barrier layer disposed
therein is formed of metal. However, a conventional pouch
5 film laminate had a limitation in forming a deeper cup portion,
and also had a limitation in reducing a radius of filleting
when edges of a bottom portion and edges of an open portion of
the cup portion are filleted. Furthermore, the conventional
pouch film laminate had a limitation in forming an outer wall
10 of the cup portion close to vertical. Accordingly, there was
a problem in that a dead space of the secondary battery was
increased and a size of the electrode assembly was decreased
to reduce energy efficiency to volume.
DISCLOSURE OF THE INVENTION
15 TECHNICAL PROBLEM
[0008] An aspect of the present invention provides a pouch
type battery case, in which formability is improved by
improving tensile strength and elongation, and a pouch type
secondary battery.
20 [0009] The object of the present invention is not limited to
the aforesaid, but other objects not described herein will be
clearly understood by those skilled in the art from
descriptions below.
TECHNICAL SOLUTION
25 [0010] According to an aspect of the present invention, there
4
is provided a pouch type battery case accommodating an
electrode assembly therein which is formed by stacking a
positive electrode, a separator, and a negative electrode,
wherein the pouch type battery case includes a pouch film
5 laminate including: a sealant layer formed of a first polymer
that is an innermost layer; a surface protection layer formed
of a second polymer that is an outermost layer; and a gas
barrier layer laminated between the surface protection layer
and the sealant layer and formed of an aluminum alloy film
10 having a thickness of 60 μm to 100 μm and a grain size of 10
μm to 13 μm. Also, the aluminum alloy film may include iron
in an amount of 1.2 wt% to 1.7 wt%.
[0011] Furthermore, the aluminum alloy film may include iron
in an amount of 1.3 wt% to 1.7 wt%.
15 [0012] Also, the aluminum alloy film may include silicon in
an amount of 0.2 wt% or less.
[0013] Furthermore, the aluminum alloy film may have a grain
size of 10.5 μm to 12.5 μm.
[0014] Also, the aluminum alloy film may have alloy number
20 AA8021.
[0015] Furthermore, the gas barrier layer may have a thickness
of 70 μm to 90 μm.
[0016] Also, a thickness of the sealant layer may be 0.6 times
to 1.2 times the thickness of the gas barrier layer, for
25 example, may be in a range of 30 μm to 90 μm.
5
[0017] Furthermore, the first polymer may include
polypropylene (PP).
[0018] Also, the surface protection layer may have a thickness
of 6 μm to 25 μm.
5 [0019] Furthermore, the second polymer may include
polyethylene terephthalate (PET).
[0020] Also, the pouch type battery case may further include
a drawing assistance layer which is formed of a third polymer
and is laminated between the surface protection layer and the
10 gas barrier layer.
[0021] Furthermore, the drawing assistance layer may have a
thickness of 20 μm to 50 μm.
[0022] Also, the third polymer may include Nylon.
[0023] Furthermore, the pouch film laminate may have a total
15 thickness of 180 μm or more, for example, 180 μm to 210 μm.
[0024] Also, the pouch film laminate may have a tensile
strength, which is measured while the pouch film laminate is
pulled at a tensile speed of 50 mm/min after being cut to a
size of 15 mm × 80 mm, of 200 N/15mm to 300 N/15mm, and may
20 have an elongation of 105% to 150%.
[0025] According to another aspect of the present invention,
there is provided a pouch type secondary battery including an
electrode assembly therein which is formed by stacking a
positive electrode, a separator, and a negative electrode; and
25 a pouch type battery case accommodating the electrode assembly,
6
wherein the battery case includes: a sealant layer formed of
a first polymer that is an innermost layer; a surface
protection layer formed of a second polymer that is an
outermost layer; and a gas barrier layer laminated between the
5 surface protection layer and the sealant layer and formed of
an aluminum alloy film having a thickness of 60 μm to 100 μm
and a grain size of 10 μm to 13 μm.
[0026] Other specific details of the present invention are
included in the detailed description and drawings.
10 ADVANTAGEOUS EFFECTS
[0027] According to the embodiments of the present invention,
at least the following effects may be achieved.
[0028] A pouch type battery case according to the present
invention improves tensile strength, elongation, and toughness
15 of a pouch film laminate by using the pouch film laminate
including an aluminum alloy film having specific thickness and
grain size as a gas barrier layer. If the pouch film laminate
is used, since a forming depth may be increased without
occurrence of pinholes or cracks during forming of a cup
20 portion and a radius of curvature of an edge of the cup portion
may be reduced, an accommodating space volume of a battery
assembly may be increased.
[0029] Also, since the pouch film laminate according to the
present invention has excellent puncture strength, it may more
25 effectively protect an internal electrode assembly even if it
7
is under great pressure from the outside or is damaged by being
pierced by a sharp object.
[0030] The effects according to the present invention are not
limited to the contents as exemplified above, but more various
5 effects are included in the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is an assembly view of a secondary battery
according to an embodiment of the present invention;
[0032] FIG. 2 is a cross-sectional view of a pouch film
10 laminate according to an embodiment of the present invention;
[0033] FIG. 3 is a graph illustrating iron and silicon
contents of an aluminum alloy with alloy number AA8079 and an
aluminum alloy with alloy number AA8021;
[0034] FIG. 4 is a graph illustrating tensile strength,
15 elongation, and grain size of the aluminum alloy with alloy
number AA8079 and the aluminum alloy with alloy number AA8021;
[0035] FIG. 5 is magnified scanning electron microscope (SEM)
images of grains of a thin film of the aluminum alloy with
alloy number AA8021 used in Example 1 and a thin film of the
20 aluminum alloy with alloy number AA8079 used in Comparative
Example 3;
[0036] FIG. 6 is a graph of the results of testing tensile
strength and elongation of pouch film laminates according to
Preparation Example, Comparative Example 1, and Comparative
25 Example 2 of the present invention; and
8
[0037] FIG. 7 is a graph of the results of testing puncture
strength of the pouch film laminates according to Preparation
Example, Comparative Example 1, and Comparative Example 2 of
the present invention.
5 MODE FOR CARRYING OUT THE INVENTION
[0038] Advantages and features of the present invention, and
implementation methods thereof will be clarified through
following embodiments described with reference to the
accompanying drawings. The present invention may, however, be
10 embodied in different forms and should not be construed as
limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
present invention to those skilled in the art. Further, the
15 present invention is only defined by scopes of claims. Like
reference numerals refer to like elements throughout.
[0039] Unless defined otherwise, all terms (including
technical and scientific terms) used herein may be intended to
have meanings understood by those skilled in the art. In
20 addition, terms defined in general dictionaries should not be
interpreted abnormally or exaggeratedly, unless clearly
specifically defined.
[0040] The terminology used herein is for the purpose of
describing particular example embodiments only and is not
25 intended to be limiting of the present invention. In the
9
specification, the terms of a singular form may include plural
forms unless referred to the contrary. It will be further
understood that the terms "comprises" and/or "comprising" when
used in this specification, specify the presence of stated
5 components, but do not preclude the presence or addition of
one or more other components.
[0041] Hereinafter, preferred embodiments of the present
invention will be described in detail with reference to the
accompanying drawings.
10 [0042] FIG. 1 is an assembly view of a secondary battery 1
according to an embodiment of the present invention.
[0043] According to an embodiment of the present invention,
since toughness is increased by improving tensile strength and
elongation of a pouch film laminate 135, formability may be
15 improved when the pouch film laminate 135 is formed to prepare
a pouch type battery case 13. Also, since the pouch film
laminate has excellent puncture strength, it may more
effectively protect an internal electrode assembly even if it
is under great pressure from the outside or is damaged by being
20 pierced by a sharp object.
[0044] For this purpose, the pouch type battery case 13
according to an embodiment of the present invention is the
pouch type battery case 13 accommodating an electrode assembly
10 which is formed by stacking a positive electrode, a
25 separator, and a negative electrode, and includes the pouch
10
film laminate 135 including a sealant layer 1351 formed of a
first polymer as an innermost layer; a surface protection layer
1353 formed of a second polymer as an outermost layer; and a
gas barrier layer 1352 laminated between the surface protection
5 layer 1353 and the sealant layer 1351 and formed of an aluminum
alloy film having a thickness of 60 μm to 100 μm and a grain
size of 10 μm to 13 μm.
[0045] The secondary battery 1 according to the embodiment of
the present invention includes the electrode assembly 10 which
10 is formed by stacking a positive electrode, a separator, and
a negative electrode; and the pouch type battery case 13
accommodating the electrode assembly 10, wherein the battery
case 13 includes the pouch film laminate 135 including: the
sealant layer 1351 formed of a first polymer as an innermost
15 layer; the surface protection layer 1353 formed of a second
polymer as an outermost layer; and the gas barrier layer 1352
laminated between the surface protection layer 1353 and the
sealant layer 1351 and formed of an aluminum alloy film having
a thickness of 60 μm to 100 μm and a grain size of 10 μm to 13
20 μm.
[0046] The electrode assembly 10 is formed by sequentially
stacking a positive electrode, a separator, and a negative
electrode. First, a slurry, in which an electrode active
material, a binder, and a conductive material are mixed, is
25 applied to a positive electrode collector and a negative
11
electrode collector to prepare the positive electrode and the
negative electrode, and, after the electrode assembly 10 having
a predetermined shape is formed by stacking the positive
electrode and the negative electrode on both sides of the
5 separator, the electrode assembly 10 is inserted into the
battery case 13, and the battery case 13 is sealed after
injecting an electrolyte solution.
[0047] Specifically, the electrode assembly 10 includes two
types of electrodes, such as the positive electrode and the
10 negative electrode, and the separator disposed between the
electrodes to insulate the electrodes from each other. The
electrode assembly 10 includes a stacked type, a jelly-rolltype, and a stack and folding type. The two types of
electrodes, that is, the positive electrode and the negative
15 electrode, have a structure in which active material slurries
are applied to electrode collectors in the form of a metal
foil or metal mesh including aluminum and copper, respectively.
The active material slurry may be typically formed by stirring
a granular active material, a conductive material, and a binder
20 in a state in which a solvent is added. The solvent is removed
in a subsequent process.
[0048] As illustrated in FIG. 1, the electrode assembly 10
includes an electrode tab 11. The electrode tab 11 is
connected to each of the positive electrode and the negative
25 electrode of the electrode assembly 10 and protrudes from one
12
side of the electrode assembly 10 to the outside so that it
becomes a path through which electrons may move between the
inside and the outside of the electrode assembly 10. The
current collector of the electrode assembly 10 is composed of
5 a portion to which the electrode active material is applied
and an end portion to which the electrode active material is
not applied, that is, an uncoated portion. The electrode tab
11 may be formed by cutting the uncoated portion or may be
formed by connecting a separate conductive member to the
10 uncoated portion by ultrasonic welding or the like. As
illustrated in FIG. 1, the electrode tabs 11 may protrude side
by side from one side of the electrode assembly 10 in the same
direction, but are not limited thereto and may protrude in
different directions, respectively.
15 [0049] An electrode lead 12 is connected to the electrode tab
11 of the electrode assembly 10 by spot welding or the like.
In addition, a portion of the electrode lead 12 is surrounded
by an insulating portion 14. The insulating portion 14 is
limitedly located at a sealing portion 134, to which a first
20 case 131 and a second case 132 of the battery case 13 are
thermally fused, to adhere the electrode lead 12 to the battery
case 13. In addition, the insulating portion 14 prevents flow
of electricity generated from the electrode assembly 10 to the
battery case 13 through the electrode lead 12, and maintains
25 sealing of the battery case 13. Thus, the insulating portion
13
14 is formed of an insulator having non-conductivity which
does not conduct electricity well. In general, as the
insulating portion 14, an insulating tape, which is easy to be
attached to the electrode lead 12 and is relatively thin, is
5 widely used, but the present invention is not limited thereto
and various members may be used as long as they may insulate
the electrode lead 12.
[0050] One end of the electrode lead 12 is connected to the
electrode tab 11, and the other end thereof protrudes to the
10 outside of the battery case 13. That is, the electrode lead
12 includes a positive electrode lead 121, which has one end
connected to a positive electrode tab 111 and extends in a
protruding direction of the positive electrode tab 111, and a
negative electrode lead 122 which has one end connected to a
15 negative electrode tab 112 and extends in a protruding
direction of the negative electrode tab 112. As illustrated
in FIG. 1, the other ends of both of the positive electrode
lead 121 and the negative electrode lead 122 protrude to the
outside of the battery case 13. Accordingly, the electricity
20 generated inside the electrode assembly 10 may be supplied to
the outside. Also, since the positive electrode tab 111 and
the negative electrode tab 112 are formed to respectively
protrude in various directions, the positive electrode lead
121 and the negative electrode lead 122 may also respectively
25 extend in various directions.
14
[0051] Materials of the positive electrode lead 121 and the
negative electrode lead 122 may be different from each other.
That is, the positive electrode lead 121 may be formed of an
aluminum (Al) material that is the same as the positive
5 electrode collector, and the negative electrode lead 122 may
be formed of a copper (Cu) material or nickel (Ni)-coated
copper material that is the same as the negative electrode
collector. Since a portion of the electrode lead 12 protruding
to the outside of the battery case 13 becomes a terminal
10 portion, it is electrically connected to an external terminal.
[0052] The battery case 13 is formed by forming a pouch film
laminate which is formed of a flexible material. Hereinafter,
the battery case 13 will be described as a pouch. The battery
case 13 accommodates the electrode assembly 10 so that the
15 portion of the electrode lead 12, that is, the terminal portion
is exposed and is sealed. As illustrated in FIG. 1, the
battery case 13 includes the first case 131 and the second
case 132. A cup portion 133 is formed in the second case 132
to provide an accommodation space 1331 capable of accommodating
20 the electrode assembly 10, and the first case 131 covers the
accommodation space 1331 from the top so that the electrode
assembly 10 is not separated to the outside of the battery
case 13. In this case, as illustrated in FIG. 1, the cup
portion 133 provided with the accommodation space 1331 may
25 also be formed in the first case 131 to accommodate the
15
electrode assembly 10 from the top. The first case 131 and
the second case 132 may be prepared by connecting one sides
thereof to each other as illustrated in FIG. 1, but the present
invention is not limited thereto and the first case 131 and
5 the second case 132 may be prepared in various ways, for
example, the first case 131 and the second case 132 are
separated from each other and prepared separately.

CLAIMS
1. A pouch type battery case accommodating an electrode
assembly therein which is formed by stacking a positive
5 electrode, a separator, and a negative electrode, the pouch
type battery case comprising a pouch film laminate including:
a sealant layer formed of a first polymer that is an
innermost layer;
a surface protection layer formed of a second polymer
10 that is an outermost layer; and
a gas barrier layer laminated between the surface
protection layer and the sealant layer and formed of an
aluminum alloy film having a thickness of 60 μm to 100 μm and
a grain size of 10 μm to 13 μm.
15
2. The pouch type battery case of claim 1, wherein the
aluminum alloy film comprises iron in an amount of 1.2 wt% to
1.7 wt%.
20 3. The pouch type battery case of claim 1, wherein the
aluminum alloy film comprises iron in an amount of 1.3 wt% to
1.7 wt%.
4. The pouch type battery case of claim 1, wherein the
25 aluminum alloy film comprises silicon in an amount of 0.2 wt%
43
or less.
5. The pouch type battery case of claim 2, wherein the
aluminum alloy film has a grain size of 10.5 μm to 12.5 μm.
5
6. The pouch type battery case of claim 1, wherein the
aluminum alloy film has alloy number AA8021.
7. The pouch type battery case of claim 1, wherein the gas
10 barrier layer has a thickness of 70 μm to 90 μm.
8. The pouch type battery case of claim 1, wherein a
thickness of the sealant layer is 0.6 times to 1.2 times a
thickness of the gas barrier layer.
15
9. The pouch type battery case of claim 1, wherein the
sealant layer has a thickness of 30 μm to 90 μm.
10. The pouch type battery case of claim 1, wherein the first
20 polymer comprises polypropylene (PP).
11. The pouch type battery case of claim 1, wherein the
surface protection layer has a thickness of 6 μm to 25 μm.
25 12. The pouch type battery case of claim 1, wherein the
44
second polymer comprises polyethylene terephthalate (PET).
13. The pouch type battery case of claim 1, further
comprising a drawing assistance layer formed of a third polymer
5 and laminated between the surface protection layer and the gas
barrier layer.
14. The pouch type battery case of claim 13, wherein the
drawing assistance layer has a thickness of 20 μm to 50 μm.
10
15. The pouch type battery case of claim 13, wherein the
third polymer comprises Nylon.
16. The pouch type battery case of claim 1, wherein the pouch
15 film laminate has a total thickness of 180 μm or more.
17. The pouch type battery case of claim 1, wherein the pouch
film laminate has a tensile strength, measured while the pouch
film laminate is pulled at a tensile speed of 50 mm/min after
20 being cut to a size of 15 mm × 80 mm, of 200 N/15mm to 300
N/15mm, and has an elongation of 105% to 150%.
18. The pouch type battery case of claim 1, wherein the pouch
film laminate has a puncture strength of 30 N or more.
25
45
19. A pouch type secondary battery comprising an electrode
assembly therein which is formed by stacking a positive
electrode, a separator, and a negative electrode; and a pouch
type battery case accommodating the electrode assembly, the
5 battery case comprising a pouch film laminate including:
a sealant layer formed of a first polymer that is an
innermost layer;
a surface protection layer formed of a second polymer
that is an outermost layer; and
10 a gas barrier layer laminated between the surface
protection layer and the sealant layer and formed of an
aluminum alloy film having a thickness of 60 μm to 100 μm and
a grain size of 10 μm to 13 μm.