U.S. patent application number 15/643153 was filed with the patent office on 2017-10-26 for resin composition, filler-containing resin film for non-aqueous electrolyte secondary battery, and method for producing filler-containing resin film for non-aqueous electrolyte secondary battery.
The applicant listed for this patent is KUREHA CORPORATION. Invention is credited to Tamito IGARASHI, Yusaku INABA, Yuki SAKAI, Aya TAKEUCHI.
Application Number | 20170306174 15/643153 |
Document ID | / |
Family ID | 49783082 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170306174 |
Kind Code |
A1 |
INABA; Yusaku ; et
al. |
October 26, 2017 |
RESIN COMPOSITION, FILLER-CONTAINING RESIN FILM FOR NON-AQUEOUS
ELECTROLYTE SECONDARY BATTERY, AND METHOD FOR PRODUCING
FILLER-CONTAINING RESIN FILM FOR NON-AQUEOUS ELECTROLYTE SECONDARY
BATTERY
Abstract
An object of the present invention is to provide a
filler-containing resin film in which shedding of inorganic
materials or the like is suppressed, a resin composition that can
be used in production of the filler-containing resin film, and a
method for producing the filler-containing resin film. The
filler-containing resin film of the present invention is a
filler-containing resin film comprising: a vinylidene fluoride
copolymer obtained by copolymerizing vinylidene fluoride and a
compound represented by formula (1) (in formula (1), R.sup.1,
R.sup.2, and R.sup.3 are each independently hydrogen atoms,
chlorine atoms, or alkyl groups having from 1 to 5 carbons; and X'
is an atomic group having a molecular weight of 472 or less and
having a main chain configured from 1 to 19 atoms); and an
insulating inorganic filler. The resin film is produced by applying
onto a substrate and then drying a resin composition containing the
vinylidene fluoride copolymer, the insulating inorganic filler, and
an organic solvent. ##STR00001##
Inventors: |
INABA; Yusaku; (Tokyo,
JP) ; IGARASHI; Tamito; (Tokyo, JP) ; SAKAI;
Yuki; (Tokyo, JP) ; TAKEUCHI; Aya; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KUREHA CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
49783082 |
Appl. No.: |
15/643153 |
Filed: |
July 6, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14409014 |
Dec 18, 2014 |
|
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PCT/JP2013/067216 |
Jun 24, 2013 |
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15643153 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 60/10 20130101;
H01M 2/145 20130101; H01M 2220/20 20130101; C08K 2003/2227
20130101; H01M 10/052 20130101; H01M 2/1653 20130101; C08K 3/22
20130101; C09D 127/16 20130101; H01M 2/1646 20130101; H01M 2/1686
20130101; H01M 2/1673 20130101; H01M 2/166 20130101; Y02P 70/50
20151101; Y02P 70/54 20151101; Y02E 60/122 20130101; C09D 7/61
20180101; C09D 127/16 20130101; C08K 3/00 20130101; C08K 3/22
20130101; C08L 27/16 20130101 |
International
Class: |
C09D 127/16 20060101
C09D127/16; C08K 3/22 20060101 C08K003/22; C09D 7/12 20060101
C09D007/12; H01M 2/14 20060101 H01M002/14; H01M 2/16 20060101
H01M002/16; H01M 2/16 20060101 H01M002/16; H01M 2/16 20060101
H01M002/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2012 |
JP |
2012-145518 |
Claims
1. A separator resin film for insulating a positive electrode and a
negative electrode in a non-aqueous electrolyte secondary battery,
wherein the separator resin film comprises a fluororesin film
formed from a resin composition, the resin composition comprising a
vinylidene fluoride copolymer obtained by copolymerizing vinylidene
fluoride and a compound represented by formula (2) below; an
insulating inorganic filler; and an organic solvent, the
fluororesin film comprising 50 parts by mass or more of the
insulating inorganic filler with respect to 100 parts by mass of
the whole of the fluororesin film, ##STR00007## wherein R.sup.1,
R.sup.2, and R.sup.3 are each independently hydrogen atoms,
chlorine atoms, or alkyl groups having from 1 to 5 carbons; and
X''' is an atomic group having a molecular weight of 456 or less
and having a main chain configured from 1 to 18 atoms.
2. The separator resin film according to claim 1, wherein the
insulating inorganic filler is at least any one of alumina and
silicon dioxide.
3. A non-aqueous electrolyte secondary battery comprising the
separator resin film according to claim 1.
4. A non-aqueous electrolyte secondary battery comprising the
separator resin film according to claim 2.
Description
[0001] This is a Division of application Ser. No. 14/409,014 filed
Dec. 18, 2014, which in turn is a National Stage Entry of
PCT/JP2013/067216 filed Jun. 24, 2013, which claims the benefit of
Japanese Patent Application No. 2012-145518 filed Jun. 28, 2012.
The disclosure of the prior applications is hereby incorporated by
reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a resin composition, a
filler-containing resin film for a non-aqueous electrolyte
secondary battery, and a method for producing a filler-containing
resin film for a non-aqueous electrolyte secondary battery.
BACKGROUND OF THE INVENTION
[0003] Recently, electronic technology has been remarkably
developed, and various appliances have been made smaller and
lighter. Along with the miniaturization and reduction in weight of
electronic appliances, miniaturization and reduction in weight of
batteries, serving as power sources of these electronic appliances,
have been demanded. As batteries that have small volume and mass
but are capable of providing large amounts of energy, non-aqueous
electrolyte secondary batteries using lithium have been used. In
addition, it has been proposed to use non-aqueous electrolyte
secondary batteries as power sources for hybrid cars, electric
cars, and the like, and the non-aqueous electrolyte secondary
batteries have been put into practical use.
[0004] Generally, a non-aqueous electrolyte secondary battery has a
positive electrode, a negative electrode, and a separator provided
therebetween for insulating the positive electrode and the negative
electrode. Conventionally, a porous film of a polyolefin-based
polymer has been used as a separator used in the non-aqueous
electrolyte secondary battery.
[0005] In the non-aqueous electrolyte secondary batteries, due to
ions (in the case of a lithium-ion secondary battery, lithium ion
(Li.sup.+)) moving between a positive electrode and a negative
electrode through a separator, charging and discharging are
possible. Therefore, the separator is required to not inhibit ions
from moving freely, and a porous film having a plurality of
microscopic holes has been used as the separator.
[0006] In addition, the separator is required to have a so-called
shutdown function. The shutdown function is a function that
improves safety of the non-aqueous electrolyte secondary battery
by, in the case where a fine short circuit has occurred in a
battery, inhibiting the movement of ions by blocking the holes in
the part where the short circuit occurred in order to make the
battery lose the function at the part. In the porous film of a
polyolefin-based polymer, the shutdown function is achieved by, in
the case where a fine short circuit occurred in the battery,
melting the part where the short circuit occurred by increasing the
temperature and thereby blocking the holes.
[0007] However, for example, if the battery temperature exceeds
150.degree. C. due to an instant increase in temperature, the
separator may instantly shrink and the part of the short circuit of
the positive electrode and the negative electrode may expand. In
this case, the battery temperature may reach several hundred
degrees Celsius or higher, and it has been a safety problem of the
non-aqueous electrolyte secondary battery.
[0008] To enhance the safety of the non-aqueous electrolyte
secondary battery at high temperatures, it has been proposed to
provide a porous film containing an inorganic material in between a
conventional separator, such as a porous film of a polyolefin-based
polymer, and a positive or negative electrode.
[0009] For example, it has been proposed to use a specific
.alpha.-alumina when an inorganic oxide porous film having
insulating properties is formed (e.g. see Patent Document 1).
Patent Document 1 proposes to form an inorganic oxide porous film
by applying an inorganic oxide slurry formed from .alpha.-alumina,
a binder, and a solvent on an electrode or a separator, and drying
the slurry. Furthermore, Patent Document 1 provides examples of
various resins, as a binder, including polyvinylidene fluoride
(PVDF).
[0010] The primary purpose of the invention described in Patent
Document 1 is to provide an inorganic oxide porous material for use
in a lithium-ion secondary battery that is thermally stable and
highly uniform and has a suitable porosity from the perspective of
electrical conductivity of lithium ion.
[0011] However, the investigation of the adhesion between an
inorganic material and a binder resin that constitute a porous film
containing the inorganic material was not sufficient.
CITATION LIST
Patent Literature
[0012] Patent Document 1: Japanese Unexamined Patent Application
Publication No. 2012-004103A
SUMMARY OF INVENTION
Technical Problem
[0013] When a porous film containing an inorganic material is
provided between a conventional separator and a positive or
negative electrode, the inorganic material is required not to be
peeled off.
[0014] However, resins that have been conventionally used with
inorganic materials such as polyvinylidene fluoride have
insufficient adhesion toward inorganic materials.
[0015] An object of the present invention is to provide a
filler-containing resin film in which shedding of inorganic
materials or the like is suppressed.
[0016] Furthermore, another object of the present invention is to
provide a resin composition that can be used in production of the
filler-containing resin film, and a method for producing the
filler-containing resin film.
Solution to Problem
[0017] As a result of diligent research to achieve the above
described objects, the present inventors have found that the above
described problems can be solved by using a particular vinylidene
fluoride copolymer, and thus completed the present invention.
[0018] That is, the resin composition of the present invention is a
resin composition comprising: a vinylidene fluoride copolymer
obtained by copolymerizing vinylidene fluoride and a compound
represented by formula (1) below; an insulating inorganic filler;
and an organic solvent.
[0019] The filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention is a
filler-containing resin film for a non-aqueous electrolyte
secondary battery comprising: a vinylidene fluoride copolymer
obtained by copolymerizing vinylidene fluoride and a compound
represented by formula (1) below; and an insulating inorganic
filler.
[0020] The method for producing a filler-containing resin film for
a non-aqueous electrolyte secondary battery of the present
invention is a method for producing a filler-containing resin film
for a non-aqueous electrolyte secondary battery, the method
comprising the steps of: applying a resin composition containing: a
vinylidene fluoride copolymer obtained by copolymerizing vinylidene
fluoride and a compound represented by formula (1) below, an
insulating inorganic filler, and an organic solvent on a substrate;
and drying the resin composition.
##STR00002##
In formula (1), R.sup.1, R.sup.2, and R.sup.3 are each
independently hydrogen atoms, chlorine atoms, or alkyl groups
having from 1 to 5 carbons; and X' is an atomic group having a
molecular weight of 472 or less and having a main chain configured
from 1 to 19 atoms. The substrate is preferably an electrode or a
separator.
[0021] Furthermore, in the present invention, the compound
represented by formula (1) above is preferably a compound
represented by formula (2) below:
##STR00003##
In formula (2), R.sup.1, R.sup.2, and R.sup.3 are each
independently hydrogen atoms, chlorine atoms, or alkyl groups
having from 1 to 5 carbons; and X''' is an atomic group having a
molecular weight of 456 or less and having a main chain configured
from 1 to 18 atoms.
Effect of the Invention
[0022] Since the filler-containing resin film for a non-aqueous
electrolyte secondary battery produced by using the resin
composition of the present invention has sufficient air
permeability, the film does not inhibit ions from moving between a
positive electrode and a negative electrode. Furthermore, since the
insulating inorganic filler adheres to the vinylidene fluoride
copolymer with sufficient strength in the resin film, shedding of
the insulating inorganic filler is suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a cross sectional schematic diagram illustrating a
structure of a non-aqueous electrolyte secondary battery containing
a filler-containing resin film of the present invention.
[0024] FIG. 2 shows the result of a cycle test of a laminated cell
obtained in Working Example 3 of the present invention.
DESCRIPTION OF EMBODIMENTS
[0025] Next, the present invention will be described in further
detail.
[0026] The resin composition of the present invention is a resin
composition comprising: a vinylidene fluoride copolymer obtained by
copolymerizing vinylidene fluoride and a compound represented by
formula (1) below; an insulating inorganic filler; and an organic
solvent.
[0027] [Vinylidene fluoride copolymer] The vinylidene fluoride
copolymer used in the present invention is a copolymer obtained by
copolymerizing vinylidene fluoride and a compound represented by
formula (1) below.
##STR00004##
In formula (1), R.sup.1, R.sup.2, and R.sup.3 are each
independently hydrogen atoms, chlorine atoms, or alkyl groups
having from 1 to 5 carbons; and X' is an atomic group having a
molecular weight of 472 or less and having a main chain configured
from 1 to 19 atoms. The vinylidene fluoride copolymer used in the
present invention is a polymer containing a structural unit derived
from vinylidene fluoride and a structural unit derived from the
compound represented by formula (1) above. In addition, the
vinylidene fluoride copolymer may further contain a structural unit
derived from another monomer.
[0028] Since the vinylidene fluoride copolymer used in the present
invention contains a structural unit derived from the compound
represented by formula (1) above, the vinylidene fluoride copolymer
exhibits excellent adhesion. The compound represented by formula
(1) above is preferably a compound represented by formula (2)
below. Since, in the vinylidene fluoride copolymer using the
compound represented by formula (1) above, a carboxyl group
functioning as an adhesive functional group is present via a spacer
on a main chain of the vinylidene fluoride polymer, degree of
freedom of the arrangement of the carboxyl group is high.
Therefore, the functional group can be easily arranged at a
position where the functional group can easily exhibit its adhesion
imparting properties, and the present inventors conceived that the
vinylidene fluoride copolymer used in the present invention
exhibits excellent adhesion toward inorganic fillers. Furthermore,
the compound represented by formula (1) above contains, in addition
to a carboxyl group, a carbonyl group. The present inventors
conceived that, since the carbonyl group can be coordinated to a
metal atom, the vinylidene fluoride copolymer obtained by using the
compound has excellent adhesion particularly toward metals, metal
oxides, and the like.
##STR00005##
In formula (2), R.sup.1, R.sup.2, and R.sup.3 are each
independently hydrogen atoms, chlorine atoms, or alkyl groups
having from 1 to 5 carbons; and X''' is an atomic group having a
molecular weight of 456 or less and having a main chain configured
from 1 to 18 atoms. In formulas (1) and (2) above, although
R.sup.1, R.sup.2, and R.sup.3 described above are each
independently hydrogen atoms, chlorine atoms, or alkyl groups
having from 1 to 5 carbons, from the perspective of polymerization
reactivity, in particular, R.sup.1 and R.sup.2 are preferably
substituents with small steric hindrance, and R.sup.1 and R.sup.2
are preferably hydrogens or alkyl groups having from 1 to 3
carbons, and are more preferably hydrogens or methyl groups.
[0029] In formula (1) above, although the molecular weight of the
atomic group represented by X' is 472 or less, the molecular weight
is preferably 172 or less. Furthermore, the lower limit of the
molecular weight of the atomic group represented by X' is not
particularly limited; however, X' is typically in a form of
--CH.sub.2-- and, that is, the molecular weight thereof is 14.
[0030] Furthermore, in formula (2) above, although the molecular
weight of the atomic group represented by X''' is 456 or less, the
molecular weight is preferably 156 or less. Furthermore, the lower
limit of the molecular weight of the atomic group represented by
X''' is not particularly limited; however, X''' is typically in a
form of --CH.sub.2-- and, that is, the molecular weight thereof is
14.
[0031] From the perspective of polymerizability, the molecular
weight of the atomic group represented by X' or X''' is preferably
in the range described above.
[0032] In the atomic group represented by X' in formula (1) above,
the main chain of the atomic group is composed of 1 to 19 atoms,
preferably composed of 1 to 14 atoms, and more preferably composed
of 1 to 9 atoms.
[0033] Furthermore, in the atomic group represented by X''' in
formula (2) above, the main chain of the atomic group is composed
of 1 to 18 atoms, preferably composed of 1 to 13 atoms, and more
preferably composed of 1 to 8 atoms.
[0034] From the perspective of polymerizability, the number of
atoms on the main chain is preferably in the range described
above.
[0035] Note that, in formulas (1) and (2) above, the "number of
atoms on the main chain" means the number of atoms on the backbone
of the chain that connects a carboxyl group written on the right
side of X' or X''' and a group (R.sup.1R.sup.2C.dbd.CR.sup.3--CO--
(in formula (1)); or R.sup.1R.sup.2C.dbd.CR.sup.3--COO-- (in
formula (2))) written on the left side of X' or X''' and that
contains a minimum number of atoms.
[0036] Note that the number of atoms on the main chain of
2-acryloyloxyethyl succinate (AES) and 2-carboxyethyl acrylate
(CEA) used in working examples are as below.
[0037] AES corresponds to a compound represented by formula (1) and
a compound represented by formula (2). When the compound
represented by formula (1) is AES, the atomic group represented by
X' is --OCH.sub.2CH.sub.2O--(CO)--CH.sub.2CH.sub.2--. The number of
atoms on the main chain of the atomic group is the number of atoms
on a backbone of the straight chain. That is, an oxygen atom that
constitutes a carbonyl group or a hydrogen atom that constitutes a
methylene group is not included in the number of atoms on the main
chain. That is, the backbone of the main chain is --OCCO--C--CC--,
and the number of atoms thereof is 7. In the same manner, when the
compound represented by formula (2) is AES, the number of atoms on
the main chain of the atomic group represented by X''' is 6.
[0038] CEA corresponds to a compound represented by formula (1) and
a compound represented by formula (2). When the compound
represented by formula (1) is CEA, the number of atoms on the main
chain of the atomic group represented by X' is 3, and when the
compound represented by formula (2) is CEA, the number of atoms on
the main chain of the atomic group represented by X''' is 2.
[0039] Furthermore, the number of atoms on the main chain of
acryloyloxyethyl phthalic acid is as below. Acryloyloxyethyl
phthalic acid is a compound represented by formula (B) below, and
corresponds to a compound represented by formula (1) and a compound
represented by formula (2). When the compound represented by
formula (1) is acryloyloxyethyl phthalic acid, the atomic group
represented by X' is represented by formula (B') below. The number
of atoms on the main chain of the atomic group is the number of
atoms on the backbone of the chain that connects, with a minimum
number of atoms, a carboxyl group bonded to the atomic group and a
group (CH.sub.2.dbd.CH--CO--) written on the left side. That is, in
formula (B') below, the number of atoms on the backbone of the
chain connecting the carboxyl group and the group
(CH.sub.2.dbd.CH--CO--) written on the left is considered to be 7
which is the number of atoms shown in formula (B'-1), or 11 which
is the number of atoms shown in formula (B'-2); however, in this
case, the number of atoms on the main chain is 7, which is the
smaller number. In the same manner, when the compound represented
by formula (2) is acryloyloxyethyl phthalic acid, the number of
atoms on the main chain of the atomic group represented by X''' is
6.
[0040] Furthermore, in the case of a compound having a plurality of
carboxyl groups, the number of atoms on the main chain is as below.
For example, in a compound having a plurality of carboxyl groups,
there are chains that respectively connect, with a minimum number
of atoms, the carboxyl group and the group written on the left
side; however, the number of atoms on the main chain is the
smallest value of the numbers of atoms on the backbones of these
chains. That is, in a compound having two carboxyl groups, there is
a chain for each of the carboxyl groups (hereinafter called
"carboxyl group A" and "carboxyl group B" for convenience) that
connects, with a minimum number of atoms, the carboxyl group and
the group written on the left side; however, for example, in the
case where the number of atoms of the backbone of the chain
connecting, with a minimum number of atoms, the group written on
the left side and carboxyl group A is 3 and the number of atoms of
the backbone of the chain connecting, with a minimum number of
atoms, the group written on the left side and carboxyl group B is
6, the number of atoms on the main chain in the compound is 3. As a
specific example, a compound represented by formula (C) below will
be described. The compound represented by formula (C) below
corresponds to a compound represented by formula (1) and a compound
represented by formula (2). The compound represented by formula (C)
has two carboxyl groups. When the compound represented by formula
(1) is the compound represented by formula (C), the number of atoms
on the backbone of the chain connecting the carboxyl group and the
group (CH.sub.2.dbd.CH--CO--) written on the left side with a
minimum number of atoms is considered to be 5 which is the number
of atoms shown in formula (C-1), or 7 which is the number of atoms
shown in formula (C-2); however, in this case, the number of atoms
on the main chain is 5, which is a smaller number of atoms on the
backbone. In the same manner, when the compound represented by
formula (2) is the compound represented by formula (C), the number
of atoms on the main chain of the atomic group represented by X'''
is 4.
##STR00006##
Note that, in the present invention, (meth)acryl and (meth)acrylate
mean acryl and/or methacryl and acrylate and/or methacrylate,
respectively.
[0041] Examples of the compound represented by formula (2) above
include 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate,
acryloyloxyethyl succinate, methacryloyloxyethyl succinate,
acryloyloxyethyl phthalic acid, methacryloyloxyethyl phthalic acid,
and the like. Of these, 2-carboxyethyl acrylate, 2-carboxyethyl
methacrylate, acryloyloxyethyl succinate, and methacryloyloxyethyl
succinate are preferable from the perspective of having excellent
copolymerizability with vinylidene fluoride.
[0042] The vinylidene fluoride copolymer used in the present
invention preferably contains from 0.01 to 10 mol %, more
preferably from 0.02 to 7 mol %, and particularly preferably from
0.03 to 4 mol %, of a structural unit derived from the compound
represented by formula (1) above (provided that the total of a
structural unit derived from vinylidene fluoride and a structural
unit derived from the compound represented by formula (1) is 100
mol %). Furthermore, the vinylidene fluoride copolymer preferably
contains from 90 to 99.99 mol %, more preferably from 93 to 99.98
mol %, and particularly preferably from 96 to 99.97 mol %, of a
structural unit derived from vinylidene fluoride.
[0043] Note that, in the vinylidene fluoride copolymer used in the
present invention, the content of the structural unit derived from
the compound represented by formula (1) and the content of the
structural unit derived from vinylidene fluoride can be typically
determined by .sup.1H NMR spectrum of the vinylidene fluoride
copolymer or by neutralization titration.
[0044] Furthermore, examples of the other monomer include
fluorine-based monomers or hydrocarbon-based monomers, such as
ethylene and propylene, that are copolymerizable with vinylidene
fluoride, and monomers that are copolymerizable with the compound
represented by formula (1) above. Examples of the fluorine-based
monomer that is copolymerizable with vinylidene fluoride include
vinyl fluoride, trifluoroethylene, tetrafluoroethylene,
chlorotrifluoroethylene, hexafluoropropylene,
perfluoroalkylvinylether exemplified by perfluoromethylvinylether,
and the like. Examples of the monomer that is copolymerizable with
the compound represented by formula (1) above include (meth)acrylic
acid, alkyl meth(acrylate) compounds exemplified by methyl
(meth)acrylate, and the like. Note that the other monomer may be
used alone or in a combination of two or more types thereof.
[0045] For cases where the vinylidene fluoride copolymer used in
the present invention contains a structural unit derived from the
other monomer, the vinylidene fluoride copolymer preferably
contains from 0.01 to 10 mol % of a structural unit derived from
the other monomer relative to 100 mol % of structural units derived
from all the monomers constituting the copolymer.
[0046] The vinylidene fluoride copolymer used in the present
invention can be obtained by copolymerizing vinylidene fluoride,
the compound represented by formula (1) above and, as necessary,
the other monomer.
[0047] The method of copolymerizing the vinylidene fluoride
copolymer used in the present invention is not particularly
limited; however, the method such as suspension polymerization,
emulsion polymerization, and solution polymerization are generally
used. From the perspectives of ease of post treatment and the like,
aqueous suspension polymerization and emulsion polymerization are
preferable, and aqueous suspension polymerization is particularly
preferable.
[0048] In suspension polymerization using water as a dispersing
medium, a suspending agent, such as methylcellulose, methoxylated
methylcellulose, propoxylated methylcellulose,
hydroxyethylcellulose, hydroxypropylcellulose, polyvinyl alcohol,
polyethylene oxide, and gelatin, may be used by adding in a range
of 0.005 to 1.0 parts by mass, and preferably in a range of 0.01 to
0.4 parts by mass, per 100 parts by mass of all the monomers used
in the copolymerization (vinylidene fluoride, the compound
represented by formula (1), and the other monomer that is
copolymerized as necessary).
[0049] As a polymerization initiator, diisopropyl
peroxydicarbonate, di-n-propyl peroxydicarbonate,
di-n-heptafluoropropyl peroxydicarbonate, isobutyryl peroxide,
di(chlorofluoroacyl)peroxide, di(perfluoroacyl)peroxide, t-butyl
peroxypivalate, and the like can be used. The used amount thereof
is from 0.05 to 5 parts by mass, and preferably from 0.15 to 2
parts by mass, per 100 parts by mass of all the monomers used in
the copolymerization (vinylidene fluoride, the compound represented
by formula (1), and the other monomer that is copolymerized as
necessary).
[0050] Furthermore, the degree of polymerization of the resulting
vinylidene fluoride copolymer can be adjusted by adding a chain
transfer agent, such as ethyl acetate, methyl acetate, diethyl
carbonate, acetone, ethanol, n-propanol, acetaldehyde,
propylaldehyde, ethylpropionate, and carbon tetrachloride. In the
case of using a chain transfer agent, the used amount of the chain
transfer agent is typically from 0.1 to 5 parts by mass, and
preferably from 0.5 to 3 parts by mass, per 100 parts by mass of
all the monomers used in the copolymerization (vinylidene fluoride,
the compound represented by formula (1), and the other monomer that
is copolymerized as necessary).
[0051] Furthermore, the charged amount of all the monomer used in
the copolymerization (vinylidene fluoride, the compound represented
by formula (1), and the other monomer that is copolymerized as
necessary) is, in terms of a ratio "total mass of the
monomers":"mass of water", typically from 1:1 to 1:10, and
preferably from 1:2 to 1:5.
[0052] The polymerization temperature T is appropriately selected
depending on the 10 hour half-life temperature T.sub.10 of the
polymerization initiator. The polymerization temperature T is
typically selected from a range of T.sub.10-25.degree.
C..ltoreq.T.ltoreq.T.sub.10+25.degree. C. For example, T.sub.10 of
t-butyl peroxypivalate is 54.6.degree. C., and T.sub.10 of
diisopropyl peroxydicarbonate is 40.5.degree. C. (see a product
catalog from NOF Corporation). Therefore, in the polymerization
using t-butyl peroxypivalate and diisopropyl peroxydicarbonate as
polymerization initiators, the polymerization temperatures T are
each appropriately selected from a range of 29.6.degree.
C..ltoreq.T.ltoreq.79.6.degree. C. and a range of 15.5.degree.
C..ltoreq.T.ltoreq.65.5.degree. C. Although the polymerization time
is not particularly limited, the polymerization time is preferably
100 hours or less from the perspective of productivity. The
polymerization is typically performed under increased pressure, and
preferably at 2.0 to 8.0 MPa-G.
[0053] By performing aqueous suspension polymerization under the
conditions described above, vinylidene fluoride, the compound
represented by formula (1), and the other monomer that is
copolymerized as necessary can be easily copolymerized to obtain
the vinylidene fluoride copolymer of the present invention.
[0054] The vinylidene fluoride copolymer used in the present
invention preferably has an inherent viscosity (logarithmic
viscosity at 30.degree. C. of a solution in which 4 g of a resin is
dissolved in 1 L of N,N-dimethylformamide; hereinafter the same) in
a range of 0.5 to 5.0 dL/g, and more preferably in a range of 1.0
to 4.0 dL/g. As long as the viscosity is in the range described
above, the vinylidene fluoride copolymer can be suitably used in
the production of the filler-containing resin film.
[0055] The inherent viscosity .eta..sub.i can be determined by
dissolving 80 mg of vinylidene fluoride copolymer in 20 mL of
N,N-dimethylformamide, measuring the mixture using a Ubbelohde
viscometer in a thermoregulated bath at 30.degree. C., and
performing calculation using the following equation.
.eta..sub.i=(1/C)ln(.eta./.eta..sub.0)
Here, .eta. is the viscosity of the polymer solution, .eta..sub.0
is the viscosity of the N,N-dimethylformamide alone of the solvent,
and C is 0.4 g/dL.
[0056] Furthermore, the vinylidene fluoride copolymer has an
absorbance ratio (A.sub.R), represented by formula (I) below
obtained by infrared absorption spectroscopy, preferably in a range
of 0.01 to 5.0, and more preferably in a range of 0.05 to 3.0. If
A.sub.R is less than 0.01, the adhesion to the filler contained in
the filler-containing resin film may be insufficient. On the other
hand, if A.sub.R exceeds 5.0, anti-electrolyte property of the
vinylidene fluoride copolymer tends to decrease. Note that the
infrared absorption spectroscopy of the polymer is performed by
obtaining an infrared absorption spectrum of a film that is
produced by subjecting the polymer to hot pressing. Specifically,
the vinylidene fluoride copolymer is subjected to hot pressing at
200.degree. C. to produce a pressed sheet of 30 mm.times.30 mm.
Thereafter, the IR spectrum of the pressed sheet in a range of 1500
cm.sup.-1 to 4000 cm.sup.-1 is obtained using the infrared
spectrophotometer FT-730 (manufactured by HORIBA, Ltd.).
A.sub.R=A.sub.1700-1800/A.sub.3023 (I)
In the equation (I) above, A.sub.1700-1800 is the absorbance
detected in a range of 1700 to 1800 cm.sup.-1 assigned to the
stretching vibration of a carbonyl group. A.sub.3023 is the
absorbance detected around 3023 cm.sup.-1 assigned to the
stretching vibration of CH. A.sub.R is a measure indicating the
content of carbonyl groups that are present in the vinylidene
fluoride copolymer.
[0057] Furthermore, in the vinylidene fluoride copolymer used in
the present invention, the randomness of structural units derived
from the compound represented by formula (1) is preferably 40% or
greater, more preferably 50% or greater, and particularly
preferably 60% or greater. Although details of this are not known,
if the randomness is in the range described above, uniformity of
the polymer chain is enhanced, so that the carboxyl groups can
exhibit the adhesion imparting ability more efficiently, which is
preferable.
[0058] Note that, in the present invention, the randomness is an
indicator that indicates how much degree the structural units that
is derived from the compound represented by formula (1) and that is
present in the vinylidene fluoride copolymer used in the present
invention are dispersed in the polymer chain. A lower randomness
indicates that the structural units derived from the compound
represented by formula (1) tend to be present more continuously, in
other words, the vinylidene fluoride copolymer tends to have a
chain in which compounds represented by formula (1) are polymerized
with each other (hereinafter, also referred to as a polymer chain
derived from the compound represented by formula (1)). On the other
hand, a higher randomness indicates that the structural units
derived from the compound represented by formula (1) tend to be
present more independently, in other words, the structural units
derived from the compound represented by formula (1) tend to be
discontinuous and bonded to structural units derived from
vinylidene fluoride.
[0059] The randomness of the vinylidene fluoride copolymer used in
the present invention can be determined by dividing the content
[mol %] of polymer chains derived from the compound represented by
formula (1) by the content [mol %] of structural units derived from
the compound represented by formula (1) (randomness [%]=content
[mol %] of polymer chains derived from compound represented by
formula (1)/content [mol %] of structural units derived from
compound represented by formula (1).times.100). Note that the mole
percentage (mol %) is relative to the content of structural units
derived from vinylidene fluoride taken as 100 mol %. Furthermore,
the content of polymer chains derived from the compound represented
by formula (1) can be determined by .sup.19F NMR spectroscopy, and
the content of structural units derived from the compound
represented by formula (1) can be determined by, for example,
.sup.1H NMR spectroscopy or neutralization titration.
[0060] For example, for cases where the vinylidene fluoride
copolymer used in the present invention is a copolymer of
vinylidene fluoride and acryloyloxyethyl succinate, the randomness
can be determined by the method described below. In a .sup.19F NMR
spectrum, a peak of CF.sub.2 adjacent to the acryloyloxyethyl
succinate unit is observed around -94 ppm. The mole percentage (mol
%) of the acryloyloxyethyl succinate chains is determined from an
integral ratio of this peak to all the peaks in the spectrum. The
randomness can be determined as a ratio of the mole percentage (mol
%) of the acryloyloxyethyl succinate chain to the mole percentage
(mol %) of all the structural units derived from the
acryloyloxyethyl succinate in the polymer determined by .sup.1H NMR
spectroscopy, neutralization titration, or the like (randomness
[%]=mole percentage (mol %) of acryloyloxyethyl succinate
chains/mole percentage (mol %) of all structural units derived from
acryloyloxyethyl succinate.times.100).
[0061] Note that, for carboxyethyl acrylate (CEA) used in Working
Example 2, the randomness can be calculated by the same measurement
method described above.
[0062] An example of the method for producing a vinylidene fluoride
copolymer used in the present invention having the randomness in
the range described above is a method that adds a compound
represented by formula (1) continuously while the suspension
polymerization described above or the like is being performed.
[0063] [Insulating Inorganic Filler]
[0064] The insulating inorganic filler used in the present
invention is not particularly limited, and a conventionally used
insulating inorganic filler can be used as a resin film provided
between a separator and a positive or negative electrode of a
non-aqueous electrolyte secondary battery.
[0065] Examples of the insulating inorganic filler include oxides
such as silicon dioxide (SiO.sub.2), alumina (Al.sub.2O.sub.3),
titanium dioxide (TiO.sub.2), calcium oxide (CaO), strontium oxide
(SrO), barium oxide (BaO), magnesium oxide (MgO); hydroxides such
as magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide
(Ca(OH).sub.2), aluminum hydroxide (Al(OH).sub.3); carbonates such
as calcium carbonate (CaCO.sub.3); sulfates such as barium sulfate;
nitrides; clay minerals; and the like. The insulating inorganic
filler may be used alone or in a combination of two or more types
thereof.
[0066] The insulating inorganic filler is preferably alumina or
silicon dioxide from the perspectives of safety of the battery and
stability of the coating liquid.
[0067] The average particle size of the insulating inorganic filler
is preferably from 5 nm to 2 .mu.m, and more preferably from 10 nm
to 1 .mu.m.
[0068] A commercially available product may be used as the
insulating inorganic filler used in the present invention. For
example, commercially available high purity alumina particles such
as AKP3000 (manufactured by Sumitomo Chemical Co., Ltd.) can be
used.
[0069] [Organic Solvent]
[0070] As the organic solvent used in the present invention, an
organic solvent that can dissolve the vinylidene fluoride copolymer
is used, and a solvent having a polarity is preferably used.
Specific examples of the organic solvent include
N-methyl-2-pyrrolidone, N,N-dimethylformamide,
N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide,
dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate,
trimethyl phosphate, acetone, 2-butanone, cyclohexanone, and the
like. N-methyl-2-pyrrolidone, N,N-dimethylformamide, acetone, and
2-butanone are preferable. Furthermore, the non-aqueous solvent may
be used alone or in a combination of two or more types thereof.
[0071] [Resin Composition]
[0072] The resin composition of the present invention contains the
vinylidene fluoride copolymer, the insulating inorganic filler, and
the organic solvent described above.
[0073] The vinylidene fluoride copolymer contained in the resin
composition of the present invention exhibits strong adhesion
toward the insulating inorganic filler. Therefore, it is preferable
to produce the filler-containing resin film for a non-aqueous
electrolyte secondary battery using the resin composition of the
present invention since the insulating inorganic filler does not
peel off from the obtained resin film.
[0074] The resin composition of the present invention preferably
contains from 0.5 to 80 parts by mass of the vinylidene fluoride
copolymer and from 99.5 to 20 parts by mass of the insulating
inorganic filler, and more preferably contains from 1 to 50 parts
by mass of the vinylidene fluoride copolymer and from 99 to 50
parts by mass of the insulating inorganic filler per 100 parts
total mass of the vinylidene fluoride copolymer and the insulating
inorganic filler in the resin composition.
[0075] Furthermore, the resin composition of the present invention
preferably contains from 50 to 4900 parts by mass, and more
preferably from 200 to 1900 parts by mass, of the organic solvent
per 100 parts total mass of the vinylidene fluoride copolymer and
the insulating inorganic filler in the resin composition.
[0076] The preparation method of the resin composition of the
present invention is not particularly limited, and, for example,
the resin composition may be obtained by adding and stirring the
vinylidene fluoride copolymer and the insulating inorganic filler
in the organic solvent in order to dissolve the vinylidene fluoride
copolymer and to disperse the insulating inorganic filler. In
addition, the resin composition may also be prepared by preparing a
solution in which the vinylidene fluoride copolymer is dissolved by
adding and stirring the vinylidene fluoride polymer in a part of
the organic solvent; preparing a dispersion liquid in which the
insulating inorganic filler is dispersed by adding and stirring the
insulating inorganic filler in the rest of the organic solvent; and
mixing the solution and the dispersion liquid.
[0077] In order to adjust the viscosity of the resin composition
and/or adhesion between the vinylidene fluoride copolymer and the
insulating inorganic filler of the present invention, another
vinylidene fluoride copolymer may be blended in addition to the
vinylidene fluoride copolymer described above.
[0078] The resin composition of the present invention may contain,
as necessary, various additives such as organic fillers, dispersing
agents, electrolyte solutions, electrolytes, electrolyte polymers,
and the like.
[0079] [Filler-Containing Resin Film for Non-Aqueous Electrolyte
Secondary Battery]
[0080] The filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention contains the
vinylidene fluoride copolymer and the insulating inorganic filler
described above.
[0081] The filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention can be used
as a separator auxiliary layer that is provided, generally, in
between a separator and a positive or negative electrode
constituting the non-aqueous electrolyte secondary battery.
[0082] Since the vinylidene fluoride copolymer used in the present
invention has superior heat resistance compared to polyolefin which
constitutes conventional separators, the safety of a non-aqueous
electrolyte secondary battery containing the filler-containing
resin film of the present invention is enhanced.
[0083] The filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention is
preferable in that the insulating inorganic filler does not peel
off.
[0084] The filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention preferably
contains from 0.5 to 80 parts by mass of the vinylidene fluoride
copolymer and from 99.5 to 20 parts by mass of the insulating
inorganic filler, and more preferably contains from 1 to 50 parts
by mass of the vinylidene fluoride copolymer and from 99 to 50
parts by mass of the insulating inorganic filler, per 100 parts by
mass of the resin film.
[0085] The thickness of the filler-containing resin film for a
non-aqueous electrolyte secondary battery of the present invention
is typically from 0.1 to 30 .mu.m, and preferably from 0.5 to 5
.mu.m, from the perspectives of coatability and ionic
conductivity.
[0086] Furthermore, as described below, the filler-containing resin
film for a non-aqueous electrolyte secondary battery of the present
invention is generally formed on an electrode or a separator. For
cases where the resin film is formed on a separator, the Gurley air
permeability of a separator on which the filler-containing resin
film for a non-aqueous electrolyte secondary battery of the present
invention is provided is typically from 50 to 1000 s/100 mL, and
preferably from 80 to 800 s/100 mL. If the Gurley air permeability
is in the range described above, it is preferable that the
conductivity of the lithium ion is ensured. When the Gurley air
permeability is in the range described above, it is assumed that
the filler-containing resin film for a non-aqueous electrolyte
secondary battery has a porous structure.
[0087] [Method for Producing Filler-Containing Resin Film for
Non-Aqueous Electrolyte Secondary Battery]
[0088] The method for producing the filler-containing resin film
for a non-aqueous electrolyte secondary battery of the present
invention is characterized by, generally, applying and drying the
resin composition described above on a substrate.
[0089] As the substrate, an electrode or a separator is typically
used. The electrode and the separator is not particularly limited
and an electrode and a separator that are used for non-aqueous
electrolyte secondary batteries can be used.
[0090] When producing the filler-containing resin film for a
non-aqueous electrolyte secondary battery of the present invention,
first, the resin composition is applied onto the substrate. For
cases where the substrate is a separator, the coating is applied
onto at least one surface of the separator, and may be performed on
both sides of the separator. Furthermore, for cases where the
substrate is an electrode, typically, the coating is applied onto a
surface of the electrode mixture layer side of the electrodes,
which is a surface adjacent to a separator when a non-aqueous
electrolyte secondary battery is assembled.
[0091] Furthermore, the method of applying is not particularly
limited, and examples thereof include a method of applying the
resin composition on the substrate using a bar coater, die coater,
comma coater, gravure coater such as a direct gravure, reverse
gravure, reverse kiss gravure, off set gravure, or similar gravure
coater, reverse roll coater, micro gravure coater, air knife
coater, dip coater, and the like.
[0092] When the filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention is produced,
drying is performed after the applying.
[0093] Drying is performed in order to remove the organic solvent
in the resin composition applied onto the substrate, and is
typically performed at a temperature of 40 to 200.degree. C. for 2
seconds to 10 minutes. Furthermore, the pressure at the drying is
not particularly limited; however, typically, the drying is
performed under atmospheric pressure or reduced pressure.
[0094] By applying and drying the resin composition on the
substrate as described above, the filler-containing resin film for
a non-aqueous electrolyte secondary battery can be obtained.
[0095] Electrodes and separators that can be used in the present
invention will be described below.
[0096] (Electrode)
[0097] For cases where the substrate on which the resin composition
is applied is an electrode, the electrode may be a positive
electrode or a negative electrode; however, from the perspective of
enhancing oxidation resistance, the electrode is more preferably a
positive electrode.
[0098] The positive electrode is not particularly limited as long
as the positive electrode contains a positive electrode active
material that involves in a positive electrode reaction and has a
current collecting function; however, in many cases, the positive
electrode is composed of a positive electrode mixture layer
containing a positive electrode active material and a positive
electrode current collector that, as well as functioning as a
current collector, serves to hold the positive electrode mixture
layer.
[0099] Furthermore, the negative electrode is not particularly
limited as long as the negative electrode contains a negative
electrode active material that involves in a negative electrode
reaction and has a current collecting function; however, in many
cases, the negative electrode is composed of a negative electrode
mixture layer containing a negative electrode active material and a
negative electrode current collector that, as well as functioning
as a current collector, serves to hold the negative electrode
mixture layer.
[0100] Note that, in the present specification, a positive
electrode and negative electrode may be comprehensively described
as "electrodes", a positive electrode mixture layer and negative
electrode mixture layer may be comprehensively described as
"electrode mixture layers", and a positive electrode current
collector and negative electrode current collector may be
comprehensively described as "current collectors".
[0101] In the present invention, for cases where the
filler-containing resin film for a non-aqueous electrolyte
secondary battery is formed on an electrode, the resin composition
is typically applied onto the electrode mixture layer.
[0102] In the present invention, the electrode mixture layer
contains an electrode active material and a binding agent, and as
necessary, the electrode mixture layer can further contain a
conductivity promoter.
[0103] Here, the compounding ratio of the electrode active
material, the binding agent, and the conductivity promoter in the
electrode mixture layer can be a generally used compounding ratio
used in conventionally known non-aqueous electrolyte secondary
batteries such as lithium-ion secondary batteries; however, the
compounding ratio can be appropriately adjusted depending on the
type of the electrolyte secondary battery.
[0104] The thickness of the electrode mixture layer is typically
from 20 to 250 .mu.m.
[0105] The electrode active material used in the non-aqueous
electrolyte secondary battery of the present invention is not
particularly limited, and a conventionally known electrode active
material for negative electrodes and a conventionally known
electrode active material for positive electrodes can be used.
[0106] Here, if the non-aqueous electrolyte secondary battery is a
lithium-ion secondary battery, the positive electrode active
material constituting the positive electrode mixture layer is
preferably a lithium-based positive electrode active material
containing at least lithium.
[0107] Examples of the lithium-based positive electrode active
material include composite metal chalcogen compounds represented by
general formula: LiMY.sub.2 (M represents at least one type of
transition metals such as Co, Ni, Fe, Mn, Cr, and V; Y represents a
chalcogen element such as O and S) such as LiCoO.sub.2,
LiNi.sub.xCo.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1), composite metal
oxides having a spinel structure such as LiMn.sub.2O.sub.4;
olivin-type lithium compounds such as LiFePO.sub.4; and the like.
Note that a commercially available product may be used as the
positive electrode active material.
[0108] The specific surface area of the positive electrode active
material is preferably from 0.05 to 50 m.sup.2/g.
[0109] On the other hand, examples of the negative electrode active
material constituting the negative electrode mixture layer include
carbon materials, metal/alloy materials, metal oxides, and the
like. Of these, carbon materials are preferable.
[0110] As the carbon material, artificial graphite, natural
graphite, non-graphitizable carbon, easily graphitizable carbon, or
the like is used. Furthermore, the carbon material may be used
alone or in a combination of two or more types thereof.
[0111] When such a carbon material is used, the energy density of
the battery can be increased.
[0112] The artificial graphite can be obtained by, for example,
carbonizing an organic material, heat treating the material at
higher temperature, and crushing and sieving the material. The
non-graphitizable carbon can be obtained by, for example, calcining
a material derived from petroleum pitch at 1000 to 1500.degree.
C.
[0113] Note that a commercially available product may be used as
these negative electrode active materials.
[0114] The specific surface area of the negative electrode active
material is preferably from 0.3 to 10 m.sup.2/g. If the specific
surface area exceeds 10 m.sup.2/g, decomposed amount of the
electrolyte solution may increase thereby increasing the initial
irreversible capacity.
[0115] Note that the specific surface area of the electrode active
material can be determined by nitrogen adsorption method.
[0116] However, the positive electrode active material and the
negative electrode active material constituting the non-aqueous
electrolyte secondary battery of the present invention are not
particularly limited to these, and can be appropriately selected
depending on the type of the secondary battery.
[0117] In the present invention, the electrode mixture layer may
further contain a conductivity promoter as necessary. This
conductivity promoter is added for the purpose of enhancing the
conductivity of the electrode mixture layer in the case where an
active material having small electrical conductivity such as
LiCoO.sub.2 is used. As the conductivity promoter, carbonaceous
materials such as carbon black and graphite fine powders or fibers,
and metal fine powders or fibers such as nickel and aluminum are
used.
[0118] The binding agent used in the non-aqueous electrolyte
secondary battery of the present invention serves a function of
binding the electrode active material and the conductivity promoter
described above.
[0119] Here, although the binding agent is not particularly
limited, binding agents used widely in conventionally known
lithium-ion secondary battery can be suitably used. As the binding
agent, fluorine-containing resins such as polytetrafluoroethylene,
polyvinylidene fluoride, and fluororubber, mixtures of
styrene-butadiene rubber and carboxymethyl cellulose, thermoplastic
resins such as polypropylene and polyethylene, and the like can be
used. Furthermore, a vinylidene fluoride copolymer can be used as
the fluorine-containing resin. As the vinylidene fluoride
copolymer, vinylidene fluoride-monomethylester maleate copolymer,
or a vinylidene fluoride copolymer obtained by copolymerizing the
vinylidene fluoride and a compound represented by formula (1), and
the like can be used.
[0120] The positive electrode current collector and the negative
electrode current collector are not particularly limited as long as
the positive electrode current collector and the negative electrode
current collector have suitable electrical conductivity so that the
electricity can be supplied to the outside of the secondary
battery, and do not inhibit the electrode reaction of the secondary
battery.
[0121] Examples of these current collectors used in the present
invention include current collectors that are generally used as
current collectors for non-aqueous electrolyte secondary batteries
such as lithium-ion secondary batteries. Examples of the material
for such current collectors include iron, stainless steel, steel,
copper, aluminum, nickel, titanium, and the like. Current
collectors in which these metals are made into foil, a net, or the
like form are suitably used.
[0122] For cases where the lithium-ion secondary battery is a
non-aqueous electrolyte secondary battery, the positive electrode
current collector is preferably a positive electrode current
collector formed from aluminum or alloys of aluminum, and of these,
a positive electrode current collector formed from aluminum foil is
preferable. On the other hand, the negative electrode current
collector is preferably a negative electrode current collector
formed from copper, and of these, a negative electrode current
collector formed from copper foil is preferable. The current
collectors constituting the electrodes are not limited to these,
and can be appropriately selected depending on the types of the
secondary battery. The thickness of the current collector is
typically from 5 to 100 .mu.m.
[0123] Although the method of producing an electrode formed from a
current collector and an electrode mixture layer that can be used
in the present invention is not particularly limited, the electrode
can be obtained by applying the electrode mixture containing each
component constituting the electrode mixture layer onto the current
collector and drying.
[0124] When preparing the electrode mixture, the order of
compounding is not particularly limited as long as the electrode
active material, the binding agent, and the conductivity promoter
which is added as necessary, and the non-aqueous solvent are mixed
into a uniform slurry.
[0125] As the non-aqueous solvent that is used to disperse these
electrode active material, conductivity promoter, and binding
agent, for example, N-methyl-2-pyrrolidone and the like can be
used.
[0126] Although the electrode used in the present invention is
produced by applying the electrode mixture onto the current
collector and drying, the application of the electrode mixture is
performed on at least one side of the current collector, and
preferably performed on both sides. The method of applying the
electrode mixture is not particularly limited, and examples of the
method include methods of applying the electrode mixture using a
bar coater, die coater, or comma coater, and the like.
[0127] Furthermore, the drying that is performed after application
is typically performed at a temperature of 50 to 150.degree. C. for
1 to 300 minutes. Although pressure at the drying is not
particularly limited, the drying is typically performed under
atmospheric pressure or reduced pressure. Note that heat treatment
can be further performed after the drying. Furthermore, instead of
the heat treatment or after the heat treatment, pressing treatment
can be further performed. When pressing treatment is performed, the
pressing treatment is typically performed at 1 to 200 MPa-G.
Performing the pressing treatment is preferable since the electrode
density can be enhanced.
[0128] (Separator)
[0129] When the substrate on which the resin composition is applied
is a separator, the separator is not particularly limited.
[0130] The separator used in the present invention is a separator
that constitutes a non-aqueous electrolyte secondary battery and
that serves a function of electrically insulating a positive
electrode and a negative electrode and holding the electrolyte
solution. The separator used in the present invention is not
particularly limited, and examples of the separator include
polyolefin-based polymers such as polyethylene and polypropylene,
polyester-based polymers such as polyethylene terephthalate,
aromatic polyamide-based polymers, polyimide-based polymer such as
polyether imide, polyether sulfone, polysulfone, polyether ketone,
polystyrene, polyethylene oxide, polycarbonate, polyvinyl chloride,
polyacrylonitrile, polymethyl methacrylate, ceramics, and the like,
and a monolayer and multilayer porous film, nonwoven fabric, or the
like that is formed from the mixture thereof, and the like. In
particular, a porous film of polyolefin-based polymer
(polyethylene, polypropylene) is preferably used. Examples of the
polyolefin-based polymer porous film include monolayer
polypropylene separators, monolayer polyethylene separators, and
trilayer polypropylene/polyethylene/polypropylene separators that
are commercially available as Celgard (registered trademark) from
Polypore International, Inc., and the like.
[0131] Note that, in order to secure the insulation between the
positive electrode structure and the negative electrode structure,
the separator is preferably larger than the positive electrode
structure and the negative electrode structure.
[0132] [Non-Aqueous Electrolyte Secondary Battery]
[0133] Hereinafter, the non-aqueous electrolyte secondary battery
having the filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention will be
described in detail.
[0134] The filler-containing resin film for a non-aqueous
electrolyte secondary battery of the present invention is
positioned in between an electrode and a separator.
[0135] A cross sectional schematic diagram of a non-aqueous
electrolyte secondary battery having a filler-containing resin film
for a non-aqueous electrolyte secondary battery (hereinafter, also
referred to as "separator auxiliary layer") of the present
invention is illustrated in FIG. 1.
[0136] In the non-aqueous electrolyte secondary battery containing
the separator auxiliary layer, the separator auxiliary layer is
arranged in between the positive electrode 11 and the separator 13,
in between the negative electrode 12 and the separator 13, or both
in between the positive electrode 11 and the separator 13 and in
between the negative electrode 12 and the separator 13. Note that,
in FIG. 1, the separator auxiliary layer arranged in between the
positive electrode 11 and the separator 13 is indicated as "14a",
and the separator auxiliary layer arranged in between the negative
electrode 12 and the separator 13 is indicated as "14b". Note that,
in FIG. 1, the separator auxiliary layers are arranged in between
the positive electrode 11 and the separator 13 as well as in
between the negative electrode 12 and the separator 13; however, it
is sufficient for an actual non-aqueous electrolyte secondary
battery to have a separator auxiliary layer arranged on at least
one side thereof. Note that at least one layer selected from a
porous layer formed from a vinylidene fluoride-based polymer, an
electrolyte layer or adhesive layer having a vinylidene
fluoride-based polymer or an acrylonitrile-based polymer as a
matrix polymer may be further contained at an arbitrary position
that is in between the positive electrode 11 and the separator
auxiliary layer 14a, in between the separator auxiliary layer 14a
and the separator 13, in between the negative electrode 12 and the
separator auxiliary layer 14b, or in between the separator
auxiliary layer 14b and the separator 13 in a range that does not
inhibit the ionic conductivity of the non-aqueous electrolyte
secondary battery.
[0137] Note that the non-aqueous electrolyte secondary battery
having a separator auxiliary layer 14a arranged in between the
positive electrode 11 and the separator 13 is preferable from the
perspective of enhancing the oxidation resistance.
[0138] Note that the method for producing the non-aqueous
electrolyte secondary battery can be a method that is the same as
conventional methods except for using the separator provided with
the separator auxiliary layer or the electrode provided with the
separator auxiliary layer.
[0139] Furthermore, the non-aqueous electrolyte secondary battery
can have a publicly known battery structure such as a coin-type
battery, button-type battery, cylinder-type battery, or square-type
battery structure.
[0140] Note that, in FIG. 1, the positive electrode mixture layer
constituting the positive electrode 11 is indicated as "111", the
positive electrode current collector is indicated as "112", the
negative electrode mixture layer constituting the negative
electrode 12 is indicated as "121", and the negative electrode
current collector is indicated as "122".
[0141] Furthermore, examples of the members that constitute the
non-aqueous electrolyte secondary battery other than the
electrodes, the separator, and the separator auxiliary layer
include a non-aqueous electrolyte solution, a cylindrical case,
laminated pouch, and the like.
[0142] The non-aqueous electrolyte solution is a solution formed by
dissolving an electrolyte in a non-aqueous solvent.
[0143] Examples of the non-aqueous solvent include aprotic organic
solvents that can transport cations and anions constituting the
electrolyte, and that does not substantially impair the function of
the secondary battery. Examples of such a non-aqueous solvent
include organic solvents that are generally used in a non-aqueous
electrolyte solution for lithium-ion secondary batteries, and for
example, carbonates, halogenated hydrocarbons, ethers, ketones,
nitriles, lactones, esters, oxolane compounds, and the like can be
used. Of these, propylene carbonate, ethylene carbonate, dimethyl
carbonate, diethyl carbonate, ethylmethyl carbonate,
1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
.gamma.-butyrolactone, methyl propionate, ethyl propionate, and the
like are preferable. These non-aqueous solvent may be used alone or
in a combination of two or more types thereof.
[0144] Furthermore, the types of the electrolyte is not
particularly limited as long as the electrolyte is an electrolyte
in which the constituent cations and anions can be transported by
the non-aqueous solvent, and that does not substantially impair the
function of the secondary battery. Here, examples of the
electrolyte that can be used for cases where the non-aqueous
electrolyte secondary battery is a lithium-ion secondary battery
include lithium salts of a fluoro complex anion such as LiPF.sub.6,
LiAsF.sub.6, and LiBF.sub.4; inorganic lithium salts such as
LiClO.sub.4, LiCl, and LiBr; and lithium salts of sulfonic acid
such as LiCH.sub.3SO.sub.3 and LiCF.sub.3SO.sub.3; and organic
lithium salts such as Li(CF.sub.3OSO.sub.2).sub.2N,
Li(CF.sub.3OSO.sub.2).sub.3C, Li(CF.sub.3SO.sub.2).sub.2N, and
Li(CF.sub.3SO.sub.2).sub.3C. These electrolytes may be used alone
or in a combination of two or more types thereof.
EXAMPLES
[0145] Next, the present invention will be further described in
detail using examples; however, the present invention is not
limited by these examples.
Production Example 1
(Production of Vinylidene Fluoride-Acryloyloxyethyl Succinate
Copolymer)
[0146] In an autoclave with a capacity of 2 L, 925 g of ion
exchanged water, 0.65 g of Metolose SM-100 (manufactured by
Shin-Etsu Chemical Co., Ltd.) as a cellulose-based suspending
agent, 0.22 g of acryloyloxyethyl succinate, 4.3 g of 50 wt. %
diisopropyl peroxydicarbonate-CFC 225cb solution, and 421 g of
vinylidene fluoride were charged, and the temperature was raised to
26.degree. C. in 1 hour.
[0147] Thereafter, the temperature was kept at 26.degree. C., and
30 g/L of acryloyloxyethyl succinate aqueous solution was gradually
added at a rate of 0.19 g/min. Total of 2.92 g of acryloyloxyethyl
succinate was added including the initially added amount.
[0148] Polymerization was stopped at the time when the addition of
acryloyloxyethyl succinate aqueous solution was completed, and the
polymerization was performed for total of 9.1 hours from the start
of the temperature increase. Note that the pressure at the initial
stage of the polymerization was 4.09 MPa-G, and the pressure at the
time of stopping the polymerization was 4.1 MPa-G. Furthermore, the
polymerization was performed while stirring at a rotational speed
of 600 rpm.
[0149] After stopping the polymerization, the polymer slurry was
heat treated at 95.degree. C. for 60 minutes. Thereafter, the
polymer slurry was dewatered, washed with water, and further dried
at 80.degree. C. for 20 hours to obtain polymer powder of
vinylidene fluoride-acryloyloxyethyl succinate copolymer.
[0150] A .sup.1H NMR spectrum of the polymer powder was recorded
under the following conditions.
[0151] Device: AVANCE AC 400FT NMR SPECTROMETER, manufactured by
Bruker
Measurement Conditions
Frequency: 400 MHz
[0152] Measurement solvent: DMSO-d.sub.6 Measurement temperature:
25.degree. C.
[0153] The .sup.1H NMR spectrum was analyzed to determine the
contents of structural units derived from vinylidene fluoride and
of structural units derived from acryloyloxyethyl succinate in the
polymer based on the integral intensities of the signal at 4.18 ppm
mainly assigned to acryloyloxyethyl succinate and of the signals at
2.23 ppm and 2.87 ppm mainly assigned to vinylidene fluoride.
[0154] In the obtained vinylidene fluoride copolymer, the content
of the structural units derived from vinylidene fluoride (VDF
content: mol %) was 99.53 mol %, and the AES content was 0.47 mol
%.
[0155] A .sup.19F NMR spectrum of the polymer powder was recorded
under the following conditions.
[0156] Device: AVANCE AC 400FT NMR SPECTROMETER, manufactured by
Bruker
Measurement Conditions
Frequency: 376 MHz
[0157] Measurement solvent: DMSO-d.sub.6 Measurement temperature:
25.degree. C.
[0158] The .sup.19F NMR spectrum was analyzed to determine the
content of polymer chains derived from acryloyloxyethyl succinate
in the polymer by dividing the intensity of peak(s) (an integral
value) at around -94 ppm assigned to the fluorine atoms present in
the vinylidene fluoride-derived structural units adjacent to the
acryloyloxyethyl succinate units by the intensity of all the peaks
assigned to the fluorine atoms in the spectrum. In the obtained
vinylidene fluoride copolymer, the content of the polymer chains
derived from acryloyloxyethyl succinate was 0.37 mol %.
[0159] The yield of the polymer was 33%, the inherent viscosity of
the obtained polymer was 2.30 dL/g, the randomness was 78%, and the
absorbance ratio (A.sub.R) was 0.93.
Production Example 2
(Production of Vinylidene Fluoride-Carboxyethyl Acrylate
Copolymer)
[0160] In an autoclave with a capacity of 2 L, 900 g of ion
exchanged water, 0.4 g of Metolose 90SH-100 (manufactured by
Shin-Etsu Chemical Co., Ltd.) as a cellulose-based suspending
agent, 0.2 g of carboxyethyl acrylate, 2.0 g of 50 wt. % t-butyl
peroxypivalate-CFC 225cb solution, and 396 g of vinylidene fluoride
were charged, and the temperature was raised to 50.degree. C. in 2
hours.
[0161] Thereafter, the temperature was kept at 50.degree. C., and
15 g/L of carboxyethyl acrylate aqueous solution was gradually
added at such a rate that the polymerization pressure became
constant. Total of 4.0 g of carboxyethyl acrylate was added
including the initially added amount.
[0162] Polymerization was stopped at the time when the addition of
carboxyethyl acrylate aqueous solution was completed, and the
polymerization was performed for total of 8.6 hours from the start
of the temperature increase. Note that the pressure at the initial
stage of the polymerization was 6.23 MPa-G, and the pressure at the
time of stopping the polymerization was 6.03 MPa-G. Furthermore,
the polymerization was performed while stirring at a rotational
speed of 600 rpm.
[0163] After stopping the polymerization, the polymer slurry was
heat treated at 95.degree. C. for 60 minutes. Thereafter, the
polymer slurry was dewatered, washed with water, and further dried
at 80.degree. C. for 20 hours to obtain polymer powder of
vinylidene fluoride-carboxyethyl acrylate copolymer.
[0164] A .sup.1H NMR spectrum of the polymer powder was recorded in
the same manner as in Production Example 1.
[0165] The .sup.1H NMR spectrum was analyzed to determine the
contents of structural units derived from vinylidene fluoride and
of structural units derived from carboxyethyl acrylate in the
polymer based on the integral intensities of the signal at 4.19 ppm
mainly assigned to carboxyethyl acrylate and of the signals at 2.24
ppm and 2.87 ppm mainly assigned to vinylidene fluoride.
[0166] In the obtained vinylidene fluoride copolymer, the content
of the structural units derived from vinylidene fluoride (VDF
content: mol %) was 98.95 mol %, and the content of the structural
units derived from carboxyethyl acrylate (CEA content: mol %) was
1.05 mol %.
[0167] A .sup.19F NMR spectrum of the polymer powder was recorded
in the same manner as in Production Example 1.
[0168] The .sup.19F NMR spectrum was analyzed to determine the
content of polymer chains derived from carboxyethyl acrylate in the
polymer by dividing the intensity of peak(s) (an integral value) at
around -94 ppm assigned to the fluorine atoms present in the
vinylidene fluoride-derived structural units adjacent to the
carboxyethyl acrylate units by the intensity of all the peaks
assigned to the fluorine atoms in the spectrum. In the obtained
vinylidene fluoride copolymer, the content of the polymer chains
derived from carboxyethyl acrylate was 0.71 mol %.
[0169] The yield of the polymer was 39%, the inherent viscosity of
the obtained polymer was 3.12 dL/g, the randomness was 68%, and the
absorbance ratio (A.sub.R) was 1.10.
Production Example 3
(Production of Vinylidene Fluoride Homopolymer)
[0170] In an autoclave with a capacity of 2 L, 1020 g of ion
exchanged water, 0.2 g of Metolose SM-100, 2.8 g of 50 wt. %
diisopropyl peroxydicarbonate-CFC 225cb solution, 400 g of
vinylidene fluoride, and 2.8 g of ethyl acetate were charged, and
the temperature was raised to 26.degree. C. in 1 hour.
[0171] Thereafter, the temperature was kept at 26.degree. C., and
the polymerization was performed for total of 15.3 hours from the
start of the temperature increase. Note that the pressure at the
initial stage of the polymerization was 4.12 MPa-G, and the
pressure at the time of stopping the polymerization was 1.62 MPa-G.
Furthermore, the polymerization was performed while stirring at a
rotational speed of 600 rpm.
[0172] After stopping the polymerization, the polymer slurry was
heat treated at 95.degree. C. for 60 minutes. Thereafter, the
polymer slurry was dewatered, washed with water, and further dried
at 80.degree. C. for 20 hours to obtain polymer powder of
vinylidene fluoride homopolymer.
[0173] The yield of the polymer was 87% and the inherent viscosity
of the obtained polymer was 2.14 dL/g.
Working Example 1
[0174] In 87.50 parts by mass of N-methyl-2-pyrrolidone, 1.25 parts
by mass of vinylidene fluoride-acryloyloxyethyl succinate copolymer
obtained in Production Example 1, and 11.25 parts by mass of high
purity alumina particles (AKP3000, manufactured by Sumitomo
Chemical Co., Ltd.; primary particle size: 0.5 .mu.m) were
dissolved and dispersed to obtain a coating liquid for a separator
(solid concentration: 12.5 wt. %).
[0175] The coating liquid was applied onto a separator (Celgard
2500, manufactured by Polypore International, Inc.; monolayer
polypropylene porous film; film thickness: 25 .mu.m; Gurley air
permeability: 200 [s/100 mL]) using a Meyer bar (wet 24
[g/m.sup.2]) and dried using a drier to obtain a separator on which
a filler-containing resin film was formed. The thickness of the
obtained filler-containing resin film part was approximately 2
.mu.m.
[0176] When the coating surface of the separator on which the
filler-containing resin film was formed was rubbed with a finger,
nothing was attached to the finger when the finger was visually
observed.
[0177] The Gurley air permeability of the separator on which the
filler-containing resin film was formed was measured using a Gurley
type densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in
accordance with JIS P 8117 and ISO 5636. The Gurley air
permeability of the separator was 240 s/100 mL.
Working Example 2
[0178] A separator on which the filler-containing resin film was
formed was obtained in the same manner as in Working Example 1
except for using the vinylidene fluoride-carboxyethyl acrylate
copolymer obtained in Production Example 2 in place of the
vinylidene fluoride-acryloyloxyethyl succinate copolymer used in
Working Example 1. The thickness of the obtained filler-containing
resin film part was approximately 2 .mu.m.
[0179] When the coating surface of the separator on which the
filler-containing resin film was formed was rubbed with a finger,
nothing was attached to the finger when the finger was visually
observed.
[0180] The Gurley air permeability of the separator on which the
filler-containing resin film was formed was measured using a Gurley
type densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in
accordance with JIS P 8117 and ISO 5636. The Gurley air
permeability of the separator was 258 s/100 mL.
Comparative Example 1
[0181] A separator on which the filler-containing resin film was
formed was obtained in the same manner as in Working Example 1
except for using the vinylidene fluoride homopolymer obtained in
Production Example 3 in place of the vinylidene
fluoride-acryloyloxyethyl succinate copolymer used in Working
Example 1. The thickness of the obtained filler-containing resin
film part was approximately 2 .mu.m.
[0182] When the coating surface of the separator on which the
filler-containing resin film was formed was rubbed with a finger,
white powder was attached to the finger.
[0183] The Gurley air permeability of the separator on which the
filler-containing resin film was formed was measured using a Gurley
type densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in
accordance with JIS P 8117 and ISO 5636. The Gurley air
permeability of the separator was 236 s/100 mL.
[0184] As a result of the working examples and comparative example,
all of the separators exhibited sufficient Gurley air permeability.
Furthermore, in the Working Examples 1 and 2, white powder (i.e.
alumina particles) was bound by vinylidene fluoride copolymer, and
filler-containing resin films in which peeling of alumina particles
(fillers) hardly occurs.
Working Example 3
[0185] In 82 parts by weight of N-methyl-2-pyrrolidone, 1.8 parts
by weight of vinylidene fluoride-acryloyloxyethyl succinate
copolymer obtained in Production Example 1, and 16.2 parts by
weight of high purity alumina particles (AKP3000, manufactured by
Sumitomo Chemical Co., Ltd.) were dissolved and dispersed to obtain
a coating liquid for a separator (solid concentration: 18 wt.
%).
[0186] Both sides of a separator (Hipore ND420, manufactured by
Asahi Kasei Corporation; film thickness: 20 .mu.m; Gurley air
permeability: 320 [s/100 mL]) was successively coated with the
coating liquid using a gravure coater (drier: 2 zones). The drying
temperatures in the drying furnaces were 80.degree. C. for both the
first zone and the second zone. The thickness of one side of the
obtained filler-containing resin film part was approximately 2
.mu.m.
[0187] When the coating surface of the separator on which the
filler-containing resin film was formed was rubbed with a finger,
nothing was attached to the finger when the finger was visually
observed.
[0188] The Gurley air permeability of the separator on which the
filler-containing resin film was formed was measured using a Gurley
type densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in
accordance with JIS P 8117 and ISO 5636. The Gurley air
permeability of the separator was 482 s/100 mL.
[0189] [Cycle Test of Non-Aqueous Electrolyte Secondary Battery
Using Filler-Containing Resin Film]
(Production of Positive Electrode)
[0190] An N-methyl-2-pyrrolidone solvent slurry (solid
concentration: 69 wt. %) was produced in the manner such that the
weight ratio of lithium cobaltate (Cellseed C5, manufactured by
Nippon Chemical Industrial Co., Ltd.) to a conductivity promoter
(Super P, manufactured by TIMCAL) to PVDF (KF#1100, manufactured by
Kureha Corporation) was 93:3:4. The slurry was coated on Al foil
(thickness: 15 .mu.m) using a 115 .mu.m spacer. Thereafter, the
coated foil was dried at 120.degree. C. for 3 hours, and pressed to
obtain a positive electrode in which the bulk density of the layer
obtained by coating and drying the slurry was 3.6 g/cm.sup.3, and
the basis weight was 150 g/m.sup.2.
[0191] (Production of Negative Electrode)
[0192] An aqueous solvent slurry (solid concentration: 53 wt. %)
was produced in the manner such that the weight ratio of BTR918
(modified natural graphite, manufactured by BTR) to a conductivity
promoter (Super P, manufactured by TIMCAL) to SBR
(styrene-butadiene rubber latex; BM-400, manufactured by Zeon
Corporation) to CMC (carboxymethyl cellulose; Cellogen 4H,
manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was 90:2:3:1. The
slurry was coated on Cu foil (thickness: 10 .mu.m) using a 90 .mu.m
spacer. Thereafter, the coated foil was dried at 120.degree. C. for
3 hours, and pressed to obtain a negative electrode in which the
bulk density of the layer obtained by coating and drying the slurry
was 1.5 g/cm.sup.3, and the basis weight was 56 g/m.sup.2.
[0193] (Production of Battery and Cycle Test)
[0194] A laminated cell was obtained by connecting the positive
electrode and the negative electrode via the separator on which the
filler-containing resin film was formed obtained in Working Example
3, impregnating the electrolyte solution (ethylene carbonate
(EC)/ethyl methyl carbonate (EMC)=3/7, LiPF.sub.6 1.2 M), and
sealing the assembly in an aluminum pouch using a vacuum sealer to
obtain a laminated cell.
[0195] Three cycles of charge-discharge cycles including constant
current constant voltage charging (charging conditions: 0.1 C and
4.2 V) and cut-off constant current discharging (discharging
conditions: 0.1 C and 3V) were performed, and then 30 cycles of
charge-discharge cycles including constant current constant voltage
charging (charging conditions: 1 C and 4.2 V) and cut-off constant
current discharging (discharging conditions: 1 C and 3 V) were
performed.
[0196] The results are shown in FIG. 2.
Comparative Example 2
[0197] A separator on which the filler-containing resin film was
formed was obtained in the same manner as in Working Example 3
except for using the vinylidene fluoride homopolymer obtained in
Production Example 3 in place of the vinylidene
fluoride-acryloyloxyethyl succinate copolymer.
[0198] When the coating surface of the separator on which the
filler-containing resin film was formed was rubbed with a finger,
white powder was attached to the finger.
[0199] [Measurement of Peel Strength of Filler-Containing Resin
Film]
[0200] Measurements of the peel strength of the filler-containing
resin film were performed for the separator on which the
filler-containing resin film obtained in Working Example 3 was
formed, and for the separator on which the filler-containing resin
film obtained in Comparative Example 2 was formed. The measurement
was performed by attaching an adhesive tape to the surface of the
filler-containing resin film, and pulling the adhesive tape at an
angle of 180.degree. using a TENSILON Universal Testing Instrument
(manufactured by A&D Company, Limited).
[0201] The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Working Example 3 23.3 gf/mm Comparative
Example 2 0.4 gf/mm
[0202] As a result of the working examples and comparative
examples, the filler-containing resin film of the invention of the
present application can be used as a separator auxiliary layer
constituting a non-aqueous electrolyte secondary battery since the
peeling off of alumina particles (fillers) hardly occurs, adhesion
to separators is excellent, and movement of ions are not
inhibited.
REFERENCE SIGNS LIST
[0203] 10 . . . Laminated structure of battery [0204] 11 . . .
Positive electrode [0205] 111 . . . Positive electrode mixture
layer [0206] 112 . . . Positive electrode current collector [0207]
12 . . . Negative electrode [0208] 121 . . . Negative electrode
mixture layer [0209] 122 . . . Negative electrode current collector
[0210] 13 . . . Separator [0211] 14a, 14b . . . Separator auxiliary
layer
* * * * *