U.S. patent application number 17/079555 was filed with the patent office on 2021-02-11 for co-extruded, multi-layered battery separator.
The applicant listed for this patent is CELGARD, LLC. Invention is credited to Ronald W. Call, C. William Fulk, JR., Khuy V. Nguyen, Lie Shi, Xiaomin Zhang.
Application Number | 20210043904 17/079555 |
Document ID | / |
Family ID | 1000005170316 |
Filed Date | 2021-02-11 |
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United States Patent
Application |
20210043904 |
Kind Code |
A1 |
Call; Ronald W. ; et
al. |
February 11, 2021 |
CO-EXTRUDED, MULTI-LAYERED BATTERY SEPARATOR
Abstract
A battery separator comprises a co-extruded, microporous
membrane having at least two layers made of extrudable polymers and
having: a uniform thickness defined by a standard deviation of
<0.80 microns (.mu.m); or an interply adhesion as defined by a
peel strength >60 grams.
Inventors: |
Call; Ronald W.; (Rock Hill,
SC) ; Fulk, JR.; C. William; (New Bern, NC) ;
Shi; Lie; (Matthews, NC) ; Zhang; Xiaomin;
(Charlotte, NC) ; Nguyen; Khuy V.; (Charlotte,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CELGARD, LLC |
Charlotte |
NC |
US |
|
|
Family ID: |
1000005170316 |
Appl. No.: |
17/079555 |
Filed: |
October 26, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15979679 |
May 15, 2018 |
10818899 |
|
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17079555 |
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11560911 |
Nov 17, 2006 |
10003058 |
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15979679 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 48/10 20190201;
B29C 48/307 20190201; B29C 48/0018 20190201; B29C 48/21 20190201;
B29K 2067/00 20130101; B29K 2105/16 20130101; B29K 2105/06
20130101; B29K 2023/065 20130101; B29K 2023/06 20130101; B29K
2029/04 20130101; H01M 50/411 20210101; B29L 2028/00 20130101; B29K
2031/00 20130101; B29C 48/17 20190201; B29K 2105/256 20130101; B29K
2067/006 20130101; B29K 2077/00 20130101; B29K 2081/04 20130101;
B29K 2105/0032 20130101; B29C 48/305 20190201; B29K 2023/0633
20130101; B29K 2105/0026 20130101; B29K 2027/16 20130101; B29C
48/32 20190201; B29L 2009/00 20130101; B29K 2023/0683 20130101;
B29K 2027/08 20130101; B29C 48/022 20190201; B29K 2027/18 20130101;
B29C 48/13 20190201; B29C 48/08 20190201; B29K 2023/0625 20130101;
B29K 2059/00 20130101; B29C 48/0012 20190201; B29C 48/30 20190201;
H01M 50/449 20210101; B29C 48/16 20190201; B29K 2023/12 20130101;
B29K 2105/0008 20130101; B29K 2105/04 20130101; H01M 10/0525
20130101 |
International
Class: |
H01M 2/16 20060101
H01M002/16; B29C 48/32 20060101 B29C048/32; B29C 48/305 20060101
B29C048/305; B29C 48/08 20060101 B29C048/08; B29C 48/10 20060101
B29C048/10; B29C 48/30 20060101 B29C048/30 |
Claims
1. A battery separator comprising: a co-extruded, microporous
membrane having at least two layers made of extrudable polymers and
having a uniform thickness defined by a standard deviation of
<0.80 .mu.m, wherein the co-extruded, microporous membrane has a
thickness from 8 to 25 microns.
2. (canceled)
3. (canceled)
4. The battery separator of claim 1 wherein an extrudable polymer
of one of said at least two layers is the same or different than an
extrudable polymer of another of said at least two layers.
5. The battery separator according to claim 1 wherein at least one
of said extrudable polymers is a thermoplastic polymer.
6. The battery separator according to claim 1 wherein at least one
of said extrudable polymers is selected from the group consisting
of: polyolefins, polyamides, polyvinylidenes, copolymers of the
foregoing, and blends thereof.
7. The battery separator according to claim 1 wherein at least one
of said extrudable polymers further comprises a material added
thereto.
8. The battery separator according to claim 7 wherein said material
is selected from the group of materials adapted to do at least one
of the following: lower the melting temperature of the extrudable
polymers; improve the melt integrity of the membrane; improve the
strength of toughness of the membrane; improve the antistatic
properties of the membrane; improve the surface wettability of the
separator; improve the surface tribology performance of the
separator; improve the processing of the extrudable polymers;
improve the flame of the membrane; facilitate nucleation of the
extrudable polymers; color the layer of the membrane; and
combinations thereof.
9. A battery separator comprising: a co-extruded, microporous
membrane having at least two layers made of extrudable polymers and
having an interply adhesion as defined by a peel strength >60
grams.
10. The battery separator according to claim 9 wherein at least one
of said extrudable polymers is a thermoplastic polymer.
11. The battery separator of claim 9 wherein an extrudable polymer
of one of said at least two layers is the same or different than an
extrudable polymer of another of said at least two layers.
12. The battery separator according to claim 9 wherein at least one
of said extrudable polymers is selected from the group consisting
of: polyolefins, polyacetals, polyamides, polyesters, polysulfides,
polyvinyl alcohols, polyvinyl esters, polyvinylidenes, copolymers
of the foregoing, and blends thereof.
13. The battery separator according to claim 9 wherein at least one
of said extrudable polymers further comprises a material added
thereto.
14. The battery separator according to claim 13 wherein said
material is selected from the group of materials adapted to do at
least one of the following: lower the melting temperature of the
extrudable polymers; improve the melt integrity of the membrane;
improve the strength of toughness of the membrane; improve the
antistatic properties of the membrane; improve the surface
wettability of the separator; improve the surface tribology
performance of the separator; improve the processing of the
extrudable polymers; improve the flame retardancy of the membrane;
facilitate nucleation of the extrudable polymers; color the layer
of the membrane; and combinations thereof.
15.-18. (canceled)
19. The battery separator according to claim 1 wherein said
membrane is a dry-stretched membrane.
20. The battery separator according to claim 9 wherein said
membrane is a dry-stretched membrane.
21. A lithium ion battery comprising the battery separator of claim
1.
22. A lithium ion battery comprising the battery separator of claim
9.
23. (canceled)
24. The battery separator of claim 4 wherein the extrudable polymer
of one of said at least two layers is different than an extrudable
polymer of another of said at least two layers, and wherein
dissimilar polymer refers to: polymers having dissimilar chemical
natures (e.g., PE and PP, or PE and a co-polymer of PE are polymers
having dissimilar chemical natures), and/or polymer having the same
chemical nature (e.g., PP1 and PP2, or PP and a co-polymer of PP
are polymers having similar chemical natures) but dissimilar
properties (e.g., two PE's or PP's having differing properties
(e.g., density, molecular weights, molecular weight distributions,
rheology, additives (composition and/or percentage), etc.).
25. The battery separator of claim 4 wherein an extrudable polymer
of one of said at least two layers is polymerically dissimilar from
an extrudable polymer of another of said at least two layers.
26. The battery separator of claim 4, wherein the extrudable
polymer of the one of said at least two layers comprises a first
polypropylene, and wherein the extrudable polymer of the another of
said at least two layers comprises a second polypropylene, said
second polypropylene having a density, molecular weight, molecular
weight distribution, rheology, additives (composition and/or
percentage), and/or the like different from said first
polypropylene.
27. The battery separator of claim 11 wherein the extrudable
polymer of one of said at least two layers is different than an
extrudable polymer of another of said at least two layers, and
wherein dissimilar polymer refers to: polymers having dissimilar
chemical natures (e.g., PE and PP, or PE and a co-polymer of PE are
polymers having dissimilar chemical natures), and/or polymer having
the same chemical nature (e.g., PP1 and PP2, or PP and a co-polymer
of PP are polymers having similar chemical natures) but dissimilar
properties (e.g., two PE's or PP's having differing properties
(e.g., density, molecular weights, molecular weight distributions,
rheology, additives (composition and/or percentage), etc.).
28. The battery separator of claim 11 wherein an extrudable polymer
of one of said at least two layers is polymerically dissimilar from
an extrudable polymer of another of said at least two layers.
29. The battery separator of claim 11, wherein the extrudable
polymer of the one of said at least two layers comprises a first
polypropylene, and wherein the extrudable polymer of the another of
said at least two layers comprises a second polypropylene, said
second polypropylene having a density, molecular weight, molecular
weight distribution, rheology, additives (composition and/or
percentage), and/or the like different from said first
polypropylene.
30. The battery separator according to claim 4 wherein said
membrane is a dry-stretched membrane.
31. The battery separator according to claim 11 wherein said
membrane is a dry-stretched membrane.
32. A lithium ion battery comprising the battery separator of claim
4.
33. A lithium ion battery comprising the battery separator of claim
11.
34. A membrane comprising: a co-extruded, microporous membrane
having at least two layers made of extrudable polymers and having a
uniform thickness defined by a standard deviation of <0.80
.mu.m, wherein the co-extruded, microporous membrane has a
thickness from 8 to 25 microns.
35. The membrane of claim 34 wherein an extrudable polymer of one
of said at least two layers is the same or different than an
extrudable polymer of another of said at least two layers.
36. The membrane according to claim 34 wherein at least one of said
extrudable polymers is a thermoplastic polymer.
37. The membrane according to claim 34 wherein at least one of said
extrudable polymers is selected from the group consisting of:
polyolefins, polyvinylidenes, copolymers of the foregoing, and
blends thereof.
38. The membrane according to claim 34 wherein at least one of said
extrudable polymers further comprises a material added thereto.
39. The membrane according to claim 38 wherein said material is
selected from the group of materials adapted to do at least one of
the following: lower the melting temperature of the extrudable
polymers; improve the melt integrity of the membrane; improve the
strength of toughness of the membrane; improve the antistatic
properties of the membrane; improve the surface wettability of the
separator; improve the surface tribology performance of the
separator; improve the processing of the extrudable polymers;
improve the flame of the membrane; facilitate nucleation of the
extrudable polymers; color the layer of the membrane; and
combinations thereof.
40. A membrane comprising: a co-extruded, microporous membrane
having at least two layers made of extrudable polymers and having
an interply adhesion as defined by a peel strength >60
grams.
41. The membrane according to claim 40 wherein at least one of said
extrudable polymers is a thermoplastic polymer.
42. The membrane of claim 40 wherein an extrudable polymer of one
of said at least two layers is the same or different than an
extrudable polymer of another of said at least two layers.
43. The membrane according to claim 40 wherein at least one of said
extrudable polymers is selected from the group consisting of:
polyolefins, polyacetals, polyamides, polyesters, polysulfides,
polyvinyl alcohols, polyvinyl esters, polyvinylidenes, copolymers
of the foregoing, and blends thereof.
44. The membrane according to claim 40 wherein at least one of said
extrudable polymers further comprises a material added thereto.
45. The membrane according to claim 44 wherein said material is
selected from the group of materials adapted to do at least one of
the following: lower the melting temperature of the extrudable
polymers; improve the melt integrity of the membrane; improve the
strength of toughness of the membrane; improve the antistatic
properties of the membrane; improve the surface wettability of the
separator; improve the surface tribology performance of the
separator; improve the processing of the extrudable polymers;
improve the flame retardancy of the membrane; facilitate nucleation
of the extrudable polymers; color the layer of the membrane; and
combinations thereof.
46. The membrane according to claim 34 wherein said membrane is a
dry-stretched membrane.
47. The membrane according to claim 40 wherein said membrane is a
dry-stretched membrane.
48. A lithium ion battery comprising the membrane of claim 34.
49. A lithium ion battery comprising the membrane of claim 40.
50. The membrane of claim 35 wherein the extrudable polymer of one
of said at least two layers is different than an extrudable polymer
of another of said at least two layers, and wherein dissimilar
polymer refers to: polymers having dissimilar chemical natures
(e.g., PE and PP, or PE and a co-polymer of PE are polymers having
dissimilar chemical natures), and/or polymer having the same
chemical nature (e.g., PP1 and PP2, or PP and a co-polymer of PP
are polymers having similar chemical natures) but dissimilar
properties (e.g., two PE's or PP's having differing properties
(e.g., density, molecular weights, molecular weight distributions,
rheology, additives (composition and/or percentage), etc.).
51. The membrane of claim 35 wherein an extrudable polymer of one
of said at least two layers is polymerically dissimilar from an
extrudable polymer of another of said at least two layers.
52. The membrane of claim 35, wherein the extrudable polymer of the
one of said at least two layers comprises a first polypropylene,
and wherein the extrudable polymer of the another of said at least
two layers comprises a second polypropylene, said second
polypropylene having a density, molecular weight, molecular weight
distribution, rheology, additives (composition and/or percentage),
and/or the like different from said first polypropylene.
53. The membrane of claim 42 wherein the extrudable polymer of one
of said at least two layers is different than an extrudable polymer
of another of said at least two layers, and wherein dissimilar
polymer refers to: polymers having dissimilar chemical natures
(e.g., PE and PP, or PE and a co-polymer of PE are polymers having
dissimilar chemical natures), and/or polymer having the same
chemical nature (e.g., PP1 and PP2, or PP and a co-polymer of PP
are polymers having similar chemical natures) but dissimilar
properties (e.g., two PE's or PP's having differing properties
(e.g., density, molecular weights, molecular weight distributions,
rheology, additives (composition and/or percentage), etc.).
54. The membrane of claim 42 wherein an extrudable polymer of one
of said at least two layers is polymerically dissimilar from an
extrudable polymer of another of said at least two layers.
55. The membrane of claim 42, wherein the extrudable polymer of the
one of said at least two layers comprises a first polypropylene,
and wherein the extrudable polymer of the another of said at least
two layers comprises a second polypropylene, said second
polypropylene having a density, molecular weight, molecular weight
distribution, rheology, additives (composition and/or percentage),
and/or the like different from said first polypropylene.
56. The membrane according to claim 35 wherein said membrane is a
dry-stretched membrane.
57. The membrane according to claim 42 wherein said membrane is a
dry-stretched membrane.
58. A lithium ion battery comprising the membrane of claim 35.
59. A lithium ion battery comprising the membrane of claim 42.
Description
RELATED APPLICATION
[0001] This application is a divisional application claiming the
benefit of co-pending U.S. patent application Ser. No. 15/979,679,
filed May 15, 2018, which claims priority to U.S. application Ser.
No. 11/560,911 filed Nov. 17, 2006, now U.S. Pat. No. 10,003,058,
Issued Jun. 19, 2018, the references which are incorporated
herein.
FIELD OF THE INVENTION
[0002] The battery separator disclosed herein is a co-extruded,
multi-layered battery separator. One embodiment of this separator
may be used in lithium ion batteries.
BACKGROUND OF THE INVENTION
[0003] Multi-layered battery separators are disclosed in, for
example, U.S. Pat. Nos.: 4,650,730; 5,240,655; 5,281,491;
5,691,047; 5,691,077; 5,952,120; 6,080,507; 6,878,226; and U.S.
Patent Publication No. 20020136945.
[0004] While several of the foregoing references mention that
multi-layered separators may be made by a co-extrusion process, in
commercial practice, the co-extrusion process has been difficult to
implement on a commercial basis. Particularly, the products of
previous co-extrusion trials have been fraught with uniformity
issues that have inhibited the commercialization of products made
by that process. These issues, it is believed, arise from the
intricacies associated with simultaneously extruding at least two
dissimilar polymers through a narrow orifice die. Accordingly, the
prior attempts to produce a co-extruded, multi-layered battery
separator have yielded non-uniform product. As such, no
co-extruded, multi-layered battery separators are commercially
available.
[0005] Therefore, there is a need for a co-extruded, multi-layered
battery separator having uniform physical properties.
SUMMARY OF THE INVENTION
[0006] A battery separator comprises a co-extruded, microporous
membrane having at least two layers made of extrudable polymers and
having: a uniform thickness defined by a standard deviation of
<0.80 microns (.mu.m); or an interply adhesion as defined by a
peel strength >60 grams.
DESCRIPTION OF THE INVENTION
[0007] The instant battery separator shall be described with regard
to use in secondary lithium ion batteries (e.g., those used in cell
phones, laptop computers, and other devices requiring a
light-weight charge storage device). It being understood, however,
that the invention is not so limited and the instant battery
separator may be used in other battery systems (e.g., NiMH, NiCd,
alkaline, primary lithium, to name a few).
[0008] In general, battery separators for use in lithium ion
batteries are microporous membranes having the following typical
physical properties: thickness--less than 5 mils (125 .mu.m), or
less than 2 mils (50 .mu.m), or less than 1 mil (25 .mu.m), the
practical lower limit is about 1/3 mil (8 .mu.m); puncture
strength--greater than 400 grams, or greater than 550 grams;
average pore sizes--0.005-10.000 .mu.m, or 0.01-5.00 .mu.m, or
0.05-2.00 .mu.m; Gurley values (ASTM-D726(B))--5-100 seconds, or
10-60 seconds.
[0009] The instant battery separator is a co-extruded,
multi-layered battery separator. Co-extruded refers to a process
where polymers are simultaneously brought together in an extrusion
die and exit from the die in a form, here a generally planar
structure, having at least two discrete layers joined together at
the interface of the discrete layers by, for example, a commingling
of the polymers forming the interface of the discrete layers. The
extrusion die may be either a flat sheet (or slot) die or a blown
film (or annular) die. The co-extrusion process shall be described
in greater detail below. Multi-layered refers to a separator having
at least two layers. Multi-layered may also refer to structures
with 3, 4, 5, 6, 7, or more layers. Each layer is formed by a
separate polymer feed stream into the extrusion die. The layers may
be of differing thicknesses. Most often, at least two of the feed
streams are of dissimilar polymers. Dissimilar polymer refers to:
polymers having dissimilar chemical natures (e.g., PE and PP, or PE
and a co-polymer of PE are polymers having dissimilar chemical
natures); and/or polymer having the same chemical nature but
dissimilar properties (e.g., two PE's having differing properties
(e.g., density, molecular weights, molecular weight distributions,
rheology, additives (composition and/or percentage), etc.))
However, the polymers may be the same or identical.
[0010] The polymers that may be used in the instant battery
separator are those that are extrudable. Such polymers are
typically referred to as thermoplastic polymers. Exemplary
thermoplastic polymers include, but are not limited to:
polyolefins, polyacetals (or polyoxymethylenes), polyamides,
polyesters, polysulfides, polyvinyl alcohols, polyvinyl esters, and
polyvinylidenes. Polyolefins include, but are not limited to:
polyethylene (including, for example, LDPE, LLDPE, HDPE, UHDPE),
polybutylene, polymethylpentane, co-polymers thereof, and blends
thereof. Polyamides (nylons) include, but are not limited to:
polyamide 6, polyamide 66, Nylon 10,10,polyphthalamide (PPA),
co-polymers thereof, and blends thereof. Polyesters include, but
are not limited to: polyester terephalthalate, polybutyl
terephalthalate, co-polymers thereof, and blends thereof.
Polysulfides include, but are not limited to, polyphenyl sulfide,
co-polymers thereof, and blends thereof. Polyvinyl alcohols
include, but are not limited to: ethylene-vinyl alcohol,
co-polymers thereof, and blends thereof. Polyvinyl esters include,
but are not limited to, polyvinyl acetate, ethylene vinyl acetate,
co-polymers thereof, and blends thereof. Polyvinylidenes include,
but are not limited to: fluorinated polyvinylidenes (e.g.,
polyvinylidene chloride, polyvinylidene), co-polymers thereof, and
blends thereof.
[0011] Various materials may be added to the polymers. These
materials are added to modify or enhance the performance or
properties of an individual layer or the overall separator. Such
materials include, but are not limited to:
[0012] Materials to lower the melting temperature of the polymer
may be added. Typically, the multi-layered separator includes a
layer designed to close its pores at a predetermined temperature to
block the flow of ions between the electrodes of the battery. This
function is commonly referred to as `shutdown.` In one embodiment,
a trilayer separator has a middle shutdown layer. To lower the
shutdown temperature of the layer, materials, with a melting
temperature less than the polymer to which they are mixed, may be
added to the polymer. Such materials include, but are not limited
to: materials with a melting temperature less than 125.degree. C.,
for example, polyolefins or polyolefin oligomers. Such materials
include, but are not limited to: polyolefin waxes (polyethylene
wax, polypropylene wax, polybutene wax, and blends thereof). These
materials may be loaded into the polymer at a rate of 5-50wt % of
the polymer. Shutdown s obtainable in one embodiment. Shutdown
temperatures below 130.degree. C. are obtainable in other
embodiments.
[0013] Materials to improve the melt integrity of the membrane may
be added. Melt integrity refers to the ability of the membrane to
limit its loss or deterioration of its physical dimension at
elevated temperatures such that the electrodes remain physically
separated. Such materials include mineral fillers. Mineral fillers
include, but are not limited to: talc, kaolin, synthetic silica,
diatomaceous earth, mica, nanoclay, boron nitride, silicon dioxide,
titanium dioxide, barium sulfate, calcium carbonate, aluminum
hydroxide, magnesium hydroxide and the like, and blends thereof.
Such materials may also include, but are not limited to, fine
fibers. Fine fibers include glass fibers and chopped polymer
fibers. Loading rates range from 1-60 wt % of the polymer of the
layer. Such materials may also include high melting point or high
viscosity organic materials, e.g., PTFE and UHMWPE. Such materials
may also include cross-linking or coupling agents.
[0014] Materials to improve the strength or toughness of the
membrane may be added. Such materials include elastomers.
Elastomers include, but are not limited to: ethylene-propylene
(EPR), ethylene-propylene-diene (EPDM), styrene-butadiene (SBR),
styrene isoprene (SIR), ethylidene norbornene (ENB), epoxy, and
polyurethane and blends thereof. Such materials may also include,
but are not limited to, fine fibers. Fine fibers include glass
fibers and chopped polymer fibers. Loading rates range from 2-30 wt
% of the polymer of the layer. Such materials may also include
cross-linking or coupling agents or high viscosity or high melting
point materials.
[0015] Materials to improve the antistatic properties of the
membrane may be added. Such materials include, for example,
antistatic agents. Antistatic agents include, but are not limited
to, glycerol monostreates, ethoxylated amines, polyethers (e.g.,
Pelestat 300, commercially available from Sanyo Chemical Industrial
of Japan). Loading rates range from 0.001-10 wt % of the polymer of
the layer.
[0016] Materials to improve the surface wettability of the
separator may be added. Such materials include, for example,
wetting agents. Wetting agents include, but are not limited to,
ethoxylated alcohols, primary polymeric carboxylic acids, glycols
(e.g., polypropylene glycol and polyethylene glycols), polyolefin
functionalized with maleic anhydride, acrylic acid, glycidyl
methacrylate. Loading rates range from 0.01-10wt % of the polymer
of the layer.
[0017] Materials to improve the surface tribology performance of
the separator may be added. Such materials include lubricants.
Lubricants include, for example, fluoropolymers (e.g.,
polyvinylidene fluoride, polytetrafluoroethylene, low molecular
weight fluoropolymers), slip agents (e.g., oleamide, stearamide,
erucamide, Kemamide.RTM., calcium stearate, silicone. Loading rates
range from 0.001-10wt % of the polymer of the layer.
[0018] Materials to improve the polymer processing may be added.
Such materials include, for example, fluoropolymers, boron nitride,
polyolefin waxes. Loading rates range from 100 ppm to 10 wt % of
the polymer of the layer.
[0019] Materials to improve the flame retardant nature of the
membrane may be added. Such materials include, for example,
brominated flame retardants, ammonium phosphate, ammonium
hydroxide, alumina trihydrate, and phosphate ester.
[0020] Materials to facilitate nucleation of the polymer may be
added. Such materials include nucleating agents. Nucleating agents
include, but are not limited to, sodium benzoate, dibenzylidene
sorbitol (DBS) and it chemical derivatives. Loading rates are
conventional.
[0021] Materials to color the layers may be added. Such materials
are conventional.
[0022] In the manufacture of the instant battery separator, the
polymers are co-extruded to form a multi-layered, nonporous
precursor, and then the precursor is processed to form the
micropores. Micropores may be formed by a `wet` process or a `dry`
process. The wet process (also referred as: solvent extraction,
phase inversion, thermally induced phase separation (TIPS), or gel
extraction) generally involves: the addition of a removable
material prior to the formation of the precursor, and subsequently
removing that material, for example, by an extraction process to
form the pores. The dry process (also referred to as the Celgard
process) generally involves: extruding a precursor (not including
any removal material for pore formation); annealing the precursor;
and stretching the precursor to form the micropores. The instant
invention will be discussed hereinafter with regard to the dry
process.
[0023] To obtain the uniform dimensional properties of the instant
co-extruded, multi-layered battery separator, an extrusion die
having a specific shear rate was used. It was determined that the
shear rate of the die must be at a minimum 4/sec at a throughput of
18-100 lbs/hr (8.2-45.4 Kg/hr) per layer. In one embodiment, the
shear rate was .gtoreq.8/sec at a throughput of 18-100 lbs/hr
(8.2-45.4 Kg/hr) per layer. All other parameters are those
conventionally known.
EXAMPLES
[0024] The foregoing invention is further illustrated in the
following examples. Table 1 illustrates 11 samples made according
to the foregoing discussion of the invention. Table 2 illustrates
the use of various materials to improve the melt integrity of the
separator to a separator without such material. Table 3 illustrates
the use of other of the foregoing materials to improve various
properties of the separator. The test procedures used in compiling
the information in the Tables is set out below.
Test Procedures
[0025] Gurley: Gurley was measured by two methods. In the first
method defined as the Japanese Industrial Standard Gurley (JIS
Gurley), Gurley is measured using the OHKEN permeability tester.
JIS Gurley is defined as the time in seconds required for 100 cc of
air to pass through one square inch of film at constant pressure of
4.8 inches of H.sub.2O. In the second method, Gurley is measured
according to the ASTM D-726 procedure and is defined as the time in
seconds required for 10 cc of air to pass through one square inch
of film at constant pressure of 4.8 inches of H.sub.2O.
[0026] Tensile properties: MD and TD Tensile strength is measured
using Instron Model 4201 according to ASTM-882 procedure.
[0027] Puncture strength: Puncture strength is measured using
Instron Model 4442 based on ASTM D3763. The units of puncture
strength are newtons. The measurements are made across the width of
stretched product and the averaged puncture energy (puncture
strength) is defined as the force required to puncture the test
sample.
[0028] Peel Strength or Adhesion: Intra-layer adhesion is tested
using the Chatillon TCD-200 Peel Force Tester.
[0029] Shrinkage: Shrinkage is measured at 90.degree. C. for 60
minutes using a modified ASTM D-2732-96 procedure.
[0030] Thickness: The membrane thickness values are measured using
the Emveco Microgage 210-A precision micrometer according to ASTM
D374. Thickness values are reported in units of micrometers
(.mu.m). 20 individual micrometer readings taken across the width
of the sample are averaged.
[0031] Porosity: The porosity of the microporous film is measured
by method ASTM D2873.
[0032] High Temperature Melt Integrity: High Temperature Melt
Integrity is measured using Thermal Mechanical Analysis (TMA). The
TMA compression probe is used to measure the thickness change of a
separator under compression at a constant load of 125 gm as the
temperature is scanned from 25 to 300.degree. C. at a rate of
5.degree. C./min. The percentage of thickness retained at
250.degree. C. is defined as the high temperature melting
integrity.
[0033] Wettability: One drop of a typical lithium ion electrolyte
is placed on a sample of the membrane. The change in appearance of
sample from opaque to nearly transparent is recorded. For the
wettable separator, appearance should be nearly uniform translucent
with no opaque areas. A non-wettable sample retains its
opacity.
[0034] ER (Electrical Resistance): The units of electrical
resistance are ohm-cm.sup.2. The separator resistance is
characterized by cutting small pieces of separators from the
finished material and then placing them between two blocking
electrodes. The separators are completely saturated with the
battery electrolyte with 1.0M LiPF.sub.6 salt in EC/EMC solvent of
3:7 ratio by volume. The resistance, R (.OMEGA.) of the separator
is measured by 4-probe AC impedance technique. In order to reduce
the measurement error on the electrode/separator interface,
multiple measurements are needed by adding more separator layers.
Based on the multiple layer measurements, the electrical (ionic)
resistance, R.sub.s (.OMEGA.) of the separator saturated with
electrolyte is then calculated by the formula,
R s = .rho. s l A ( 1 ) ##EQU00001##
where .rho..sub.s is the ionic resistivity of the separator in
.OMEGA.-cm, A is the electrode area in cm.sup.2 and / is the
thickness of the separator membrane in cm. The ratio .rho..sub.s/A
is the slope calculated for the variation of separator resistance
(.DELTA.R) with multiple separator layers (.DELTA..delta.) which is
given by,
slope = .rho. s A = .DELTA. R .DELTA. .delta. . ( 2 )
##EQU00002##
Also see U.S. patent application Ser. No. 11/400,465 filed Apr. 7,
2006, test procedure related to `ionic resistance`, incorporated
herein by reference.
[0035] Pin Removal: The pin removal test simulates the cell winding
process. Pin Removal force is the force in grams required to pull
the pin from the center of jelly roll after winding. A battery
winding machine was used to wind the separator around a pin (or
core or mandrel). The pin is a two (2) piece cylindrical mandrel
with a 0.16 inch diameter and a smooth exterior surface. Each piece
has a semicircular cross section. The separator, discussed below,
is taken up on the pin. The initial force (tangential) on the
separator is 0.5 kgf and thereafter the separator is wound at a
rate of ten (10) inches in twenty four (24) seconds. During
winding, a tension roller engages the separator being wound on the
mandrel. The tension roller comprises a 5/8'' diameter roller
located on the side opposite the separator feed, a 3/4'' pneumatic
cylinder to which 1 bar of air pressure is applied (when engaged),
and a 1/4'' rod interconnecting the roller and the cylinder. The
separator consists of two (2) 30 mm (width).times.10'' pieces of
the membrane being tested. Five (5) of these separators are tested,
the results averaged, and the averaged value is reported. Each
piece is spliced onto a separator feed roll on the winding machine
with a 1'' overlap. From the free end of the separator, i.e.,
distal the spliced end, ink marks are made at 1/2'' and 7''. The
1/2'' mark is aligned with the far side of the pin (i.e., the side
adjacent the tension roller), the separator is engaged between the
pieces of the pin, and winding is begun with the tension roller
engaged. When the 7'' mark is about 1/2'' from the jellyroll
(separator wound on the pin), the separator is cut at that mark,
and the free end of the separator is secured to the jellyroll with
a piece of adhesive tape (1'' wide, 1/2'' overlap). The jellyroll
(i.e., pin with separator wound thereon) is removed from the
winding machine. An acceptable jellyroll has no wrinkles and no
telescoping. The jellyroll is placed in a tensile strength tester
(i.e., Chatillon Model TCD 500-MS from Chatillon Inc., Greensboro,
N.C.) with a load cell (50 lbs.times.0.02b; Chatillon DFGS 50). The
strain rate is 2.5 inches per minute and data from the load cell is
recorded at a rate of 100 points per second. The peak force is
reported as the pin removal force. Also see: U.S. Pat. No.
6,692,867, incorporated herein by reference.
[0036] Dielectric Breakdown: Voltage is increased on a sample until
a dielectric breakdown of the material is observed. Dielectric
Breakdown is expressed in volts. A separator is placed between two
electrodes and a voltage is applied across the electrodes. The
voltage is increased until dielectric breakdown of the separator is
observed. Strong separators show high failure voltage. Any
non-uniformity can lead to a low failure voltage.
[0037] Aquapore Size: Pore size is measured using the Aquapore
available through PMI (Porous Materials Inc.). Pore size is
expressed in microns, .mu.m.
[0038] Mixed Penetration: Mixed penetration is the force required
to create a short through a separator and is expressed in
kilogram-force, kgf. Mixed penetration is the force required to
create a short through a separator due to mixed penetration. In
this test one starts with a base of a first metal plate, on top of
this plate is placed a sheet of cathode material, on top of cathode
is placed a separator, and on top of the separator is placed a
sheet of anode material. A ball tip of 3 mm is then provided
attached to a force gauge. The ball tip is connected to the first
metal plate by a resistance meter. Pressure is applied to the ball
tip, which is recorded on the force gauge. Once force is applied,
there builds up an anode mix and a cathode mix on either side of
the separator. When the resistance falls dramatically it indicates
a short through the separator due to mixed penetration. Mixed
penetration measures the strength of the separator and resistance
towards mixed penetration. This has been found to more accurately
simulate the behavior of a real cell. It is a better indicator than
puncture strength of how a separator will behave in a cell. This
test is used to indicate the tendency of separators to allow
short-circuits during battery assembly. Also see U.S. patent
application Ser. No. 11/400,465 filed Apr. 7, 2006, incorporated
herein by reference.
TABLE-US-00001 TABLE 1 Examples of Bilayer & Trilayer
Microporous Membrane Sample Celgard Sample Sample Sample Sample
Sample Sample Sample Sample Sample Sample Sample Number 2300 .RTM.
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 PP/PE/P PP/PE/ PP/PE PP/PE/PP
PP/PE/PP PP/PE/PP PP/PE/PP PP/PE/PP PE/PP/PE PE/PP/PE PE/PP/PE
PE/PP/PE PE/PE/PE Des- PP 60% PP 65% PP 65% PP 65% PP 65% PP 65% PP
58% PP 42% PP 42% PP 42% PP 0% PP cription Thickness, 26.9 15.7 9.5
13.0 15.7 18.6 19.9 9.4 9.8 16.5 17.2 17.1 .mu.m Thickness 0.72
0.46 0.37 0.46 0.45 0.65 0.55 0.49 0.45 0.51 0.60 0.54 std dev JIS
Gurley, 540 485 391 427 550 560 -- 283 195 373 517 364 second
Shrinkage 2.7 0.8 0.7 0.9 1.6 1.6 1.5 2.8 5.4 1.7 3.7 7.2 @
90.degree. C. for 1 hour, % Elongation 52/ 73/ 88/ 90/ 79/ 73/ 99/
87/ 63/ 68/ 77/ 75/ at break in 478 928 36 93 416 963 116 964 869
1031 967 1022 MD/TD, % Modulus in 5170/ 5425/ 5166/ 4724/ 5764/
5959/ 2969/ 2957/ 3645/ 2833/ 3846/ 2979/ MD/TD, 2421 3413 5880
5507 4431 4021 2348 1866 2409 1766 1973 2266 kg/cm.sup.2 Tensile
1925 2133 2115 1749 2075 2006 1830 2077 1891 1923 1740 1925
strength in MD, kg/cm.sup.2 Tensile 146 193 187 181 154 170 163 199
188 176 157 120 strength in TD, kg/cm.sup.2 Puncture 502 373 for
177 252 365 421 357 183 154 255 243 283 Strength, g PP side/ 218
for PE side ER, ohm- 1.92 2.05 1.31 1.87 1.70 2.00 2.30 1.11 0.89
1.42 1.81 1.63 cm.sup.2 Mixed 130 110 89 112 105 123 122 70 67 104
118 103 Pene- tration, kgf Dielectric 2900 2082 823 1563 2337 2,341
2,568 754 1040 1476 1769 1564 Break- down, volts Porosity, 40.3 38
30 38 34 41 40 36 43 43 37 44 %
TABLE-US-00002 TABLE 2 Examples of Polymer Blends with Ceramic
TiO.sub.2 to Improve Melting Integrity Comparison #1 Sample #1
Sample #2 Sample #3 Sample #4 Description PE/PE/PE PE/PP/PE
PP/PE/PP PP/PE/PP PE/PE/PE trilayer trilayer PE trilayer PE
trilayer PE trilayer 65% in 35% 58% thickness in thickness in
thickness Additive no additives 30% TiO2 in 20% TiO2 in 20% TiO2 in
20% TiO2 in the middle the middle the middle the middle layer layer
layer layer Thickness, .mu.m/thickness 17.1/0.54 17.8/0.40
15.3/0.61 15.9/0.44 15.5/0.46 std dev JIS Gurley, sec 364 500 400
267 193 Shrinkage @ 90.degree. C. for 1 7.2 5.3 2.2 1.6 4.6 hour, %
Tensile strength in TD, 120 110 148 180 100 kg/cm.sup.2 Puncture
strength, g 283 310 288 257 265 ER, ohm-cm.sup.2 1.63 1.76 2.60
1.53 1.08 Mix Penetration, kgf 103 102 99 104 87 Dielectric
Breakdown, volts 1564 1586 1973 1643 1179 Porosity, % 43.5 43.5
41.5 45.0 46.6 Aquapore Size, .mu.m 0.055 0.030/0.057 --
0.035/0.091 0.064 Peel Strength or Adhesion, >60 >60 >60
>60 >60 g High Temperature Melt 0% 13% 15% 20% 10% Integrity
@250.degree. C. by TMA
TABLE-US-00003 TABLE 3 Examples of Polymer Blends Comparison Sample
Sample Sample Sample Sample Sample Sample Sample Sample Number #1
#1 #2 #3 #4 #5 #6 #7 #8 Description PP/PE/PP PP/PE/PP PP/PE/PP
PP/PE/PP PE/PE/PE PE/PE/PE PP/PE/PP PP/PE/PP PP/PE/PP trilayer
trilayer with trilayer with trilayer trilayer with trilayer with
trilayer trilayer trilayer without 5% 5000 ppm with 2% 15% PE wax
30% PE with 10% with 20% with 10% additives ethoxylated Kemamide
.RTM. antistatic in the middle wax in the talc in talc in talc in
alcohols in in the outside additive layer to middle outside outside
outside the middle layers to Pelestat lower the layer to PP layer
PP layer PP layer layer to improve pin 300 in the shutdown lower
shut and 20% and 25% and 25% improve removal outside temperature
down TiO2 in TiO2 in TiO2 in wettability performance layer
temperature the the the middle middle middle PE layer PE layer PE
layer to to to improve improve improve melt melt melt integrity
integrity integrity Thickness, (.mu.m) 16.0 15.5 15.5 17.3 20.6
20.3 18.3 18.0 17.5 Gurley, sec 35 35 35 37 13 13-25 56 60 44
Wettable No Yes -- -- -- -- -- -- -- Shutdown 130 130 130 130 127
124 130 130 130 Temp,.degree. C. High 0% 0% 0% 0% 0% 0% >20%
>20% >20% Temperature Melt Integrity @ 250.degree. C. Pin
Removal, g 9100 -- 8400 -- -- -- -- -- --
[0039] The present invention may be embodied in other forms without
departing from the spirit and the essential attributes thereof,
and, accordingly, reference should be made to the appended claims,
rather than to the foregoing specification, as indicated the scope
of the invention.
* * * * *