Compositions, separators for electrochemical devices, electrochemical devices, and secondary batteries

Abstract

To provide a composition for coating separators for electrochemical devices, which can improve the heat shrinkage resistance of the separators. [Solution] A composition for coating a separator for electrochemical devices is provided, which contains a copolymer containing fluoromonomer units and amide bond-containing monomer units.

Description

Technical Field

[0001] The present disclosure relates to a composition, a separator for an electrochemical device, an electrochemical device, and a secondary battery.

Background Art

[0002] Patent Document 1 describes a composite containing a fluorine-containing copolymer, an alkali metal salt, and an ionic liquid, wherein the fluorine-containing copolymer structural unit represented by the general formula (1): -〔CR 1 R 2 -CR 3 R 4 〕- (1) (where R 1 ~R 4 are each independently H, F, Cl, CF3, OR 10 (R 10 is an organic group having 1 to 8 carbon atoms). However, at least one of R 1 ~R 4 is F) and structural unit represented by the general formula (2): -〔CR 5 R 6 -CR 7 R 8 〕- (2) (wherein, R 5 ~R 8 are each independently H, F, an alkyl group having 1 to 3 carbon atoms, a functional group containing a heteroatom other than a fluorine atom, or a group containing the functional group. However, at least one of R 5 ~R 8 is a functional group containing a heteroatom other than a fluorine atom or a group containing the functional group.) and is a fluorine-containing copolymer, a composite characterized in that the volatile component is 0.1% by mass or less based on the whole composite is described.

[0003] Patent Document 2 describes a composition characterized by containing an inorganic filler, a copolymer of a fluoromonomer and a polymerizable vinyl compound having an amide bond, and a solvent.

[0004] Patent Document 3 describes an inorganic composite porous separator film comprising (a) a polyolefin-based separator film substrate and (b) an active layer coated with a mixture of inorganic particles and a binder polymer on one or more regions selected from the group consisting of the surface of the substrate and a part of the pores present on the substrate, wherein the active layer is characterized in that the inorganic particles are bound together by the binder polymer and a pore structure is formed by the gaps between the inorganic particles. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021 / 221113 [Patent Document 2] International Publication No. 2020 / 054210 [Patent Document 3] Special Publication No. 2008-524824 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of this disclosure is to provide a composition for coating separators for electrochemical devices that can improve the heat shrinkage resistance of the separators. [Means for solving the problem]

[0007] According to a first aspect of this disclosure, a composition for coating a separator for an electrochemical device is provided, comprising a copolymer containing fluoromonomer units and amide bond-containing monomer units. [Effects of the Invention]

[0008] According to this disclosure, a composition for coating separators for electrochemical devices can be provided that can improve the heat shrinkage resistance of the separators. [Modes for carrying out the invention]

[0009] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0010] The basic structure of a lithium-ion secondary battery consists of a non-aqueous electrolyte placed between the positive and negative electrodes, with a separator in between if necessary. The separator is interposed between the positive and negative electrodes to prevent contact between the active materials of both electrodes, and by allowing the electrolyte to flow through its pores, it forms a passage for ion conduction between the electrodes. Furthermore, the separator is required to have a function (shutdown function) to interrupt the current and prevent excessive current flow in the battery if an abnormal current flows due to a short circuit between the positive and negative electrodes. The separator shuts down by closing its microporous membrane when the normal operating temperature of the battery is exceeded.

[0011] Conventionally, porous membranes such as microporous polyolefin films made of polyethylene, polypropylene, etc., have been commonly used as separators. However, these polyolefin-based porous membranes have high thermal shrinkage properties, resulting in poor dimensional stability at high temperatures. If the pores in the separator become blocked due to abnormal heating of a lithium-ion secondary battery, and the internal temperature of the battery continues to rise, there is a risk that the separator will shrink and break, causing an internal short circuit and potentially leading to fire. To improve the safety of batteries under these high-temperature conditions, there is a need to improve the heat shrinkage resistance of separators.

[0012] Through diligent research by the present inventors, it was discovered that the heat shrinkage resistance of a separator can be improved by coating it with a composition containing a copolymer of a fluoromonomer and an amide bond-containing monomer.

[0013] In other words, the composition of the present disclosure is a composition for coating a separator for electrochemical devices, and contains a copolymer of a fluoromonomer and an amide bond-containing monomer, and by coating the separator with the composition of the present disclosure, the heat shrinkage resistance of the separator can be improved.

[0014] (copolymer) The compositions of this disclosure contain copolymers of a fluoromonomer and an amide bond-containing monomer.

[0015] As for fluoromonomers, (1) sp 2 Examples include (2) olefins having a fluorine atom bonded to a hybrid carbon atom, (3) monomers represented by the general formula: CH2=CX-COORf (wherein X is Cl, H, or an alkyl group, and Rf is a fluoroalkyl group), (4) monomers represented by the general formula: CH2=CH-Rf (wherein Rf is a fluoroalkyl group), and (5) monomers represented by the general formula: CH2=CH-ORf (wherein Rf is a fluoroalkyl group).

[0016] Examples of alkyl groups include alkyl groups having 1 to 3 carbon atoms, with methyl groups being preferred.

[0017] As the fluoroalkyl group, a linear or branched fluoroalkyl group having 1 to 12 carbon atoms is preferred.

[0018] As a fluoromonomer, fluorine atoms bonded to carbon atoms constituting the polymer main chain can be introduced into the copolymer, thereby further improving the heat shrinkage resistance of the separator when it is coated. Therefore, (1) is preferred, and vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, monofluoroethylene, trifluorostyrene, and the general formula: CX2=CXRf 1 (In the formula, X is independently H or F, and at least one of X is F, Rf) 1It is more preferable that is at least one selected from the group consisting of fluoromonomers (which are straight-chain or branched fluoroalkyl groups having 1 to 12 carbon atoms).

[0019] As for the fluoromonomer, it is more preferable to select at least one from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and 2,3,3,3-tetrafluoropropene, and tetrafluoroethylene is particularly preferred, because when the separator is coated with it, the heat shrinkage resistance of the separator can be further improved.

[0020] Amid bond-containing monomers contain an amide bond and a polymerizable vinyl group. The amide bond refers to the bond between a carbonyl group and a nitrogen atom. Examples of polymerizable vinyl groups include vinyl groups, allyl groups, vinyl ether groups, vinyl ester groups, and acrylic groups.

[0021] Examples of monomers containing amide bonds include N-vinyllactam compounds such as N-vinyl-β-propiolactam, N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, and N-vinyl-heptractam; acyclic N-vinylamide compounds such as N-vinylformamide and N-methyl-N-vinylacetamide; acyclic N-allylamide compounds such as N-allyl-N-methylformamide and allylurea; N-allyllactam compounds such as 1-(2-propenyl)-2-pyrrolidone; and acrylamide compounds such as (meth)acrylamide, N,N-dimethylacrylamide, and N-isopropylacrylamide.

[0022] As monomers containing amide bonds, [ka] (In the formula, R 11 and R 12 These are compounds represented independently by H or an alkyl group having 1 to 10 carbon atoms. [ka] (In the formula, R 11 and R 12 This also includes compounds that are independently represented by H or an alkyl group having 1 to 10 carbon atoms.

[0023] As amide bond-containing monomers, monomers having a lactam ring are preferred. The lactam ring is not particularly limited as long as it is a ring formed by an amide bond and a carbon atom, and may be monocyclic or polycyclic, but monocyclic is preferred. The lactam ring may also have any substituents. Examples of lactam rings include α-lactam rings, β-lactam rings, γ-lactam rings, δ-lactam rings, ε-caprolactam rings, and ω-heptalactam.

[0024] A amide bond-containing monomer can have a structure in which the remaining atomic group, after removing one or more hydrogen atoms bonded to the carbon or nitrogen atom forming the lactam ring, is directly or indirectly bonded to a polymerizable vinyl group. For example, an amide bond-containing monomer can have a structure in which the remaining atomic group, after removing one hydrogen atom bonded to the carbon or nitrogen atom forming the lactam ring, is bonded to a vinyl group or an allyl group.

[0025] As the amide bond-containing monomer, at least one selected from the group consisting of N-vinyl-β-propiolactam, N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-ε-caprolactam, and N-vinyl-heptractam is preferred, at least one selected from the group consisting of N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, and N-vinyl-ε-caprolactam is more preferred, and N-vinyl-2-pyrrolidone is even more preferred.

[0026] The copolymer may contain other monomer units in addition to fluoromonomer units and amide bond-containing monomer units. The other monomers are not particularly limited as long as they are copolymerizable with fluoromonomers and amide bond-containing monomers. Examples of other monomer units include vinyl ester monomer units, vinyl ether monomer units, (meth)acrylic monomer units having polyethylene glycol as a side chain, vinyl monomer units having polyethylene glycol as a side chain, (meth)acrylic monomer units having long-chain hydrocarbon groups, and vinyl monomer units having long-chain hydrocarbon groups.

[0027] Preferably, the content of fluoromonomer units in the copolymer is 75 to 7 mol% relative to the total monomer units, and the content of amide bond-containing monomer units in the copolymer is 25 to 93 mol% relative to the total monomer units.

[0028] The content of fluoromonomer units in the copolymer is more preferably 60 mol% or less, even more preferably 55 mol% or less, particularly preferably 50 mol% or less, most preferably 45 mol% or less, more preferably 15 mol% or more, even more preferably 20 mol% or more, particularly preferably 35 mol% or more, and most preferably 40 mol% or more.

[0029] The content of amide bond-containing monomer units in the copolymer is more preferably 40 mol% or more, even more preferably 45 mol% or more, particularly preferably 50 mol% or more, most preferably 55 mol% or more, more preferably 85 mol% or less, even more preferably 80 mol% or less, particularly preferably 65 mol% or less, and most preferably 60 mol% or less.

[0030] The content of other monomer units in the copolymer is preferably 50 mol% or less, more preferably 35 mol% or less, even more preferably 25 mol% or less, still more preferably 15 mol% or less, particularly preferably 5 mol% or less, and preferably 0 mol% or more.

[0031] Furthermore, the copolymer may be a copolymer that contains substantially only fluoromonomer units and amide bond-containing monomer units.

[0032] The composition of the copolymer is, for example, 1 H-NMR and 19 It can be measured by F-NMR.

[0033] The weight-average molecular weight (in polystyrene equivalent) of the copolymer is preferably 10,000 to 500,000, more preferably 15,000 or more, even more preferably 20,000 or more, particularly preferably 30,000 or more, and more preferably 400,000 or less. The weight-average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as the solvent.

[0034] (Method of manufacturing copolymers) Copolymers can be suitably produced by a manufacturing method in which fluoromonomers, amide bond-containing monomers, and, if necessary, other monomers are polymerized in a reactor.

[0035] Polymerization methods such as suspension polymerization, emulsion polymerization, and solution polymerization can be employed.

[0036] Furthermore, since copolymers with high molecular weights can be produced, polymerization methods using fluorine-containing solvents are preferred among various polymerization methods. Copolymers can be suitably produced, for example, by a production method in which at least a fluoromonomer and an amide bond-containing monomer are polymerized in a fluorine-containing solvent to obtain a copolymer.

[0037] Examples of fluorine-containing solvents include hydrochlorofluoroalkanes such as CH3CClF2, CH3CCl2F, CF3CF2CCl2H, and CF2ClCF2CFHCl; chlorofluoroalkanes such as CF2ClCFClCF2CF3 and CF3CFClCFClCF3; perfluorocyclobutanes such as CF3CF2CF2CF3, CF3CF2CF2CF2CF3, and CF3CF2CF2CF2CF2CF3; CF2HCF2CF2CF2H, CF3CFHCF2CF2CF3, CF3CF2CF2CF2CF2H, CF3CFHCFHCF2CF3, CF2HCF2CF2CF2CF2H, CF2HCFHCF2CF2CF3, and CF3CF Examples include hydrofluorocarbons such as 2CF2CF2CF2CF2H, CF3CH(CF3)CF3CF2CF3, CF3CF(CF3)CFHCF2CF3, CF3CF(CF3)CFHCFHCF3, CF3CH(CF3)CFHCF2CF3, CF2HCF2CF2CF2CF2CF2H, CF3CF2CF2CF2CH2CH3, and CF3CH2CF2CH3; (perfluoroalkyl)alkyl ethers such as F(CF2)4OCH3, F(CF2)4OC2H5, (CF3)2CFOCH3, and F(CF2)3OCH3; and hydrofluoroalkyl ethers such as CF3CH2OCF2CHF2, CHF2CF2CH2OCF2CHF2, and CF3CF2CH2OCF2CHF2.

[0038] As the fluorine-containing solvent, at least one selected from the group consisting of hydrofluorocarbons, (perfluoroalkyl)alkyl ethers, and hydrofluoroalkyl ethers is preferred, and hydrofluoroalkyl ethers are more preferred, because it is possible to produce copolymers with even higher molecular weights.

[0039] As the fluorine-containing solvent, at least one selected from the group consisting of CF3CH2CF2CH3, CF3CH2OCF2CHF2, CHF2CF2CH2OCF2CHF2, and CF3CF2CH2OCF2CHF2 is preferred, with CF3CH2OCF2CHF2 being more preferred.

[0040] In the polymerization described above, polymerization initiators, surfactants, and chain transfer agents can be used, and conventionally known ones can be used for each of these.

[0041] Radical polymerization initiators can be used as polymerization initiators. For example, Dialkyl peroxycarbonates such as dinormal propyl peroxydicarbonate, diisopropyl peroxydicarbonate, and disec-butyl peroxydicarbonate; Peroxy esters such as t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-hexyl peroxy 2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, and t-amyl peroxypivalate; Dialkyl peroxides such as di-t-butyl peroxide; Di[fluoro(or fluorochloro)acyl]peroxides; These are some typical examples.

[0042] Examples of di[fluoro(or fluorochloro)acyl]peroxides include diacylperoxides represented as [(RfCOO)-]2 (where Rf is a perfluoroalkyl group, an ω-hydroperfluoroalkyl group, or a fluorochloroalkyl group).

[0043] Examples of di[fluoro(or fluorochloro)acyl]peroxides include di(ω-hydro-dodecafluoroheptanoyl)peroxide, di(ω-hydro-tetradecafluorooctanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, di(perfluorobutyryl)peroxide, di(perfluoropareryl)peroxide, di(perfluorohexanoyl)peroxide, di(perfluoroheptanoyl)peroxide, di(perfluorooctanoyl)peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, di(ω-chloro-decafluorohexanoyl)peroxide, Examples include di(ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, and di(undecachlorotriacontafluorodocosanoyl) peroxide.

[0044] By polymerizing in the presence of a chain transfer agent, the solution viscosity, weight-average molecular weight, and other properties of the resulting copolymer can be appropriately adjusted. Examples of chain transfer agents include hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetic acid esters such as ethyl acetate and butyl acetate; alcohols such as methanol and ethanol; mercaptans such as methyl mercaptan; and halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride.

[0045] The polymerization temperature is not particularly limited, but from the viewpoint of polymerization rate and the cost required for temperature control, it is preferably 0 to 95°C, and more preferably 15 to 95°C.

[0046] The polymerization pressure is not particularly limited, but from the viewpoint of polymerization rate and reactor pressure resistance, it is preferably 0.3 to 1.5 MPaG, more preferably 0.4 MPaG or higher, and more preferably 1.0 MPaG or lower.

[0047] If the copolymer is obtained as a slurry after polymerization is complete, the copolymer can be recovered by removing the slurry from the reactor, washing it, and drying it.

[0048] (Inorganic filler) The compositions of the present disclosure preferably further contain an inorganic filler. The inclusion of an inorganic filler in the compositions of the present disclosure can further improve the heat shrinkage resistance of the separator.

[0049] As the inorganic filler, an inorganic filler containing at least one element selected from the group consisting of Mg, Al, Si, Ti, Zr, and Ba is preferred.

[0050] As the inorganic filler, at least one selected from the group consisting of metal oxide particles and metal hydroxide particles is preferred. More preferably, as the inorganic filler, metal oxide particles containing at least one element selected from the group consisting of Mg, Al, Si, Ti, Zr, and Ba are preferred.

[0051] As the metal oxide particles, at least one selected from the group consisting of magnesium oxide, silicon oxide, aluminum oxide, barium oxide, zirconium oxide, and titanium oxide is preferred.

[0052] As the metal hydroxide particles, at least one selected from the group consisting of magnesium hydroxide, aluminum hydroxide, and zirconium hydroxide is preferred.

[0053] Among the inorganic fillers, at least one selected from the group consisting of magnesium oxide, silicon oxide, aluminum oxide, and zirconium oxide is preferred, and at least one selected from the group consisting of magnesium oxide and aluminum oxide is more preferred.

[0054] The average particle size of the inorganic filler is preferably 25 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less, particularly preferably 1 μm or less, and preferably 0.02 μm or more. The average particle size of the inorganic filler is a value obtained by measuring with a transmission electron microscope, a laser particle size distribution analyzer, or the like.

[0055] In the compositions of this disclosure, the content ratio of copolymer to inorganic filler [(copolymer) / (inorganic filler)] is preferably 0.1 / 99.9 to 49.9 / 50.1 by mass ratio, more preferably 1 / 99 or more, even more preferably 5 / 95 or more, particularly preferably 10 / 90 or more, more preferably 45 / 55 or less, and even more preferably 40 / 60 or less.

[0056] (solvent) The compositions of this disclosure preferably further contain a solvent.

[0057] Examples of solvents include water; nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and dimethylformamide; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran, dioxane, ethyl cellosolve, methyl cellosolve, diglyme, and triglime; aromatic hydrocarbon solvents such as xylene, toluene, and solvent naphtha; aliphatic hydrocarbon solvents such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, and mineral spirits; and mixed solvents thereof.

[0058] Furthermore, at least one solvent selected from the group consisting of esters (1) represented by general formula (1) and ketones (2) represented by general formula (2) may also be used.

[0059] General formula (1): [ka] (In the formula, R 1 and R 2 These are independently H, C1~C 10 A linear or branched aliphatic group, or C6~C 10 It is the aromatic group of [the compound].

[0060] General formula (2): [ka] (In the formula, R 3 and R 4 These are independently H, C1~C 10 A linear or branched aliphatic group, or C6~C 10 It is the aromatic group of [the compound].

[0061] R in general formula (1) 1 and R 2 These are independently H, C1~C 10 A linear or branched aliphatic group, or C6~C 10 It is an aromatic group.

[0062] R 1 The number of carbon atoms in the aliphatic group is 1 to 10, preferably 2 or more, more preferably 3 or more, preferably 7 or less, and more preferably 5 or less. 1 An alkyl group is preferred as the aliphatic group. The alkyl group may be linear or branched.

[0063] R 1The aromatic group has 6 to 10 carbon atoms. The hydrogen atoms bonded to the carbon atoms of the aromatic ring of the aromatic group may or may not be substituted. Examples of substituents include alkyl groups such as methyl groups, and halo groups such as chlorine atoms. 1 The aromatic group is preferably a phenyl group or a benzyl group.

[0064] R 1 For example, C1~C 10 Linear or branched aliphatic groups are preferred, C1-C 10 Linear or branched alkyl groups or C2-C 10 Linear or branched alkenyl groups are more preferred, with methyl, ethyl, propyl, vinyl, isopropenyl, butyl, or pentyl groups being preferred, and propyl, butyl, or pentyl groups being more preferred. These groups may be linear or branched, but linear is preferred.

[0065] R 2 The number of carbon atoms in the aliphatic group is 1 to 10, preferably 3 or more, more preferably 4 or more, preferably 8 or less, and more preferably 6 or less. 2 An alkyl group is preferred as the aliphatic group. The alkyl group may be linear or branched.

[0066] R 2 The aromatic group has 6 to 10 carbon atoms. The hydrogen atoms bonded to the carbon atoms of the aromatic ring of the aromatic group may or may not be substituted. Examples of substituents include alkyl groups such as methyl groups, and halo groups such as chlorine atoms. 2 The aromatic group is preferably a phenyl group or a benzyl group.

[0067] R 2 For example, C1~C 10 Linear or branched aliphatic groups are preferred, C1-C 10Linear or branched alkyl groups are more preferred, with methyl, ethyl, propyl, butyl, pentyl, or hexyl groups being preferred, and butyl, pentyl, or hexyl groups being more preferred. These groups may be linear or branched, but linear is preferred.

[0068] The ester (1) represented by general formula (1) is preferably at least one selected from the group consisting of ethyl acetate, ethyl butyrate, butyl methacrylate, propyl propionate, ethyl butyrate, butyl butyrate, butyl pentanoate, butyl hexanoate, pentyl butyrate, pentyl pentanoate, pentyl hexanoate, hexyl butyrate, hexyl pentanoate, and hexyl hexanoate, with butyl butyrate being more preferred.

[0069] R in general formula (2) 3 and R 4 These are independently H, C1~C 10 A linear or branched aliphatic group, or C6~C 10 It is an aromatic group.

[0070] R 3 and R 4 The number of carbon atoms in the aliphatic group is 1 to 10, preferably 3 or less, and more preferably 2 or less. 3 An alkyl group is preferred as the aliphatic group. The alkyl group may be linear or branched.

[0071] R 3 and R 4 The aromatic group has 6 to 10 carbon atoms. The hydrogen atoms bonded to the carbon atoms of the aromatic ring of the aromatic group may or may not be substituted. Examples of substituents include alkyl groups such as methyl groups, and halo groups such as chlorine atoms. 3 and R 4 The aromatic group is preferably a phenyl group or a benzyl group.

[0072] R 3 and R 4For example, C1~C 10 Linear or branched aliphatic groups are preferred, C1-C 10 Linear or branched alkyl groups are more preferred, with methyl, ethyl, propyl, butyl, pentyl, or hexyl groups being preferred, and methyl or ethyl groups being more preferred. These groups may be linear or branched, but linear is preferred.

[0073] The ketone (2) represented by general formula (2) is preferably at least one selected from the group consisting of acetone and methyl ethyl ketone.

[0074] Water can also be used as a solvent. For example, when a copolymer is produced by a manufacturing method in which monomers are emulsion polymerized in water, a polymerization composition containing the copolymer and water is usually obtained, so the water contained in the polymerization composition can be used as the solvent for the composition of this disclosure.

[0075] The compositions of this disclosure preferably contain at least one selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, acetone, and methyl ethyl ketone, and more preferably contain N-methyl-2-pyrrolidone, in order to have excellent stability and coating properties.

[0076] When the composition of this disclosure contains a copolymer and a solvent, the copolymer content is preferably 0.1 to 20% by mass, more preferably 1% by mass or more, even more preferably 3% by mass or more, particularly preferably 10% by mass or more, most preferably 13% by mass or more, and more preferably 16% by mass or less, based on the mass of the composition.

[0077] (Other ingredients) The compositions of this disclosure may also contain organic fillers. Preferred organic fillers are non-conductive crosslinked polymers, with crosslinked polystyrene, crosslinked polymethacrylate, and crosslinked acrylate being more preferred.

[0078] The compositions of this disclosure may also contain other polymers such as polyacrylate, polymethacrylate, polyacrylonitrile, polyamide-imide, acrylic rubber, carboxyalkylcellulose, alkylcellulose, and hydroxyalkylcellulose.

[0079] (Separator for electrochemical devices) By using the composition of this disclosure, a separator for electrochemical devices can be manufactured. The separator for electrochemical devices of this disclosure comprises a substrate and a coating layer formed from the above composition.

[0080] The substrate and the coating layer may be directly bonded or bonded via another layer, but it is preferable that the coating layer be formed directly on the substrate. The coating layer may be provided on only one side of the substrate or on both sides. Furthermore, the coating layer may be provided so as to cover the entire substrate on which the coating layer is provided, or so as to cover only a part of it.

[0081] The weight of the coating layer, when formed on only one side of the substrate, should be 0.5 to 50.0 g / m², from the viewpoint of heat shrinkage resistance, adhesion to electrodes, and ionic conductivity. 2 A range of this magnitude is preferred. When forming coating layers on both sides of the substrate, the weight of the coating layer is preferably 1.0 g / m². 2 The above is preferable, and more preferably 3.0 g / m 2 The above is preferable, and preferably 25.0 g / m² 2 The following, and more preferably 20.0 g / m² 2 The following applies:

[0082] The thickness of the coating layer on each side is preferably 1 to 5 μm. When the thickness of the coating layer is within this range, film break strength and insulation properties can be ensured, and the curling of the substrate is less likely to become excessive.

[0083] As the substrate, a porous substrate having voids or cavities inside is preferred. Examples of porous substrates include microporous membranes, porous sheets made of fibrous materials such as nonwoven fabrics or paper-like sheets, or composite coating layers in which one or more other porous layers are laminated onto these microporous membranes or porous sheets. A microporous membrane refers to a membrane having a large number of fine pores inside, in which these fine pores are interconnected, allowing gas or liquid to pass from one side to the other.

[0084] The materials constituting the base material can be either electrically insulating organic or inorganic materials. In particular, from the viewpoint of providing the base material with a shutdown function, it is preferable to use an organic material as the constituent material of the base material, more preferably a thermoplastic resin, and even more preferably at least one selected from the group consisting of polyethylene, polypropylene, polyimide, polyamide, polyamideimide, polyethylene terephthalate, polyester, and polyacetal.

[0085] The shutdown function refers to a function that prevents thermal runaway of the battery by blocking ion movement when the battery temperature rises, by melting the thermoplastic resin and blocking the pores in the substrate. Suitable thermoplastic resins have a melting point of less than 200°C, and polyolefins are particularly preferred.

[0086] A polyolefin microporous membrane is preferred as the substrate using polyolefin. As the polyolefin microporous membrane, a conventional polyolefin microporous membrane used in separators for non-aqueous secondary batteries, possessing sufficient mechanical properties and ion permeability, can be used. Furthermore, from the viewpoint of having the aforementioned shutdown function, the polyolefin microporous membrane preferably contains polyethylene.

[0087] Polyolefins with a weight-average molecular weight of 100,000 to 5,000,000 are preferable. If the weight-average molecular weight is less than 100,000, it may be difficult to ensure sufficient mechanical properties. If it is greater than 5,000,000, the shutdown characteristics may deteriorate or molding may become difficult.

[0088] Such polyolefin microporous membranes can be manufactured by, for example, the following methods: (i) extruding molten polyolefin resin from a T-die to form a sheet, (ii) subjecting the sheet to a crystallization treatment, (iii) stretching the sheet, and (iv) heat-treating the sheet in sequence to form a microporous membrane. Another method involves (i) melting polyolefin resin together with a plasticizer such as liquid paraffin, extruding it from a T-die, and cooling it to form a sheet, (ii) stretching the sheet, (iii) extracting the plasticizer from the sheet, and (iv) heat-treating the sheet in sequence to form a microporous membrane.

[0089] As porous sheets made of fibrous materials, porous sheets can be made of fibrous materials made of polyester such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, heat-resistant polymers such as aromatic polyamides and polyimides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides, or mixtures thereof.

[0090] The base material may be a composite base material in which a functional layer is further laminated. A composite base material is preferable in that it allows for the addition of further functionality by the functional layer. As for the functional layer, for example, from the viewpoint of providing heat resistance, a porous layer made of a heat-resistant resin or a porous layer made of a heat-resistant resin and an inorganic filler can be used. Examples of heat-resistant resins include one or more heat-resistant polymers selected from aromatic polyamides, polyimides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides. Suitable inorganic fillers include metal oxides such as alumina and metal hydroxides such as magnesium hydroxide. As for composite formation methods, there are methods such as coating a porous sheet with a functional layer, joining with an adhesive, and heat-pressing.

[0091] As a base material, a porous base material consisting of at least one selected from the group consisting of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, polyester, and polyacetal is preferred among those mentioned above.

[0092] The film thickness of the substrate is preferably in the range of 5 to 50 μm from the viewpoint of obtaining good mechanical properties and internal resistance. The upper limit of the above film thickness is more preferably 40 μm, and even more preferably 30 μm. The lower limit of the above film thickness is more preferably 10 μm.

[0093] The Gurley value of the substrate is preferably 500 sec / 100cc Air or less, and more preferably 300 sec / 100cc Air or less. Furthermore, a Gurley value of 50 sec / 100cc Air or more is also preferred. The Gurley value is obtained by measurement using a Gurley densometer in accordance with JIS P 8117.

[0094] The porosity of the substrate is preferably 30-70%, and more preferably 35-60%. The porosity is calculated using the following formula. Porosity = (1 - sample mass (g) / (sample density (g / cm³)) 3 ) × sample volume (cm³) 3 ))) × 100 Sample volume (cm³) 3 The dimensions are calculated as 10cm x 10cm x thickness (cm).

[0095] The average pore size of the substrate is preferably 0.01 to 0.5 μm, and more preferably 0.1 to 0.3 μm. The average pore size is determined by applying the BET formula to the specific surface area (m²) of the substrate using the gas adsorption method. 2 Measure the basis weight (g / m²) of the substrate and measure the basis weight (g / m²). 2 ) multiply by the base material 1m 2 The surface area S of the voids per unit area is calculated. Separately, the porosity is used to calculate the surface area S of the substrate per 1 m². 2 The pore volume V per unit area is calculated. Using the obtained value, the average pore diameter d is calculated from the following formula. d = 4·V / S

[0096] When the Gurley value, porosity, and average pore diameter of the substrate are within the above range, a separator with excellent ion permeability can be obtained, resulting in a battery with good charge-discharge characteristics.

[0097] A separator for electrochemical devices can be manufactured by coating the above composition onto a substrate. The coating method is not particularly limited as long as it can cover the surface of the substrate with a coating layer formed from the composition, but for example, one method is to apply the above composition onto the substrate and dry the coating film. More specifically, as a coating method, one is to roll-coat the above composition onto the substrate, one is to dip the substrate into the above composition, and one is to coat the above composition onto the substrate and then immerse it in a suitable solidifying solution. Alternatively, a separator for electrochemical devices may be manufactured by making a film using the above composition and laminating the obtained film and the substrate by a method such as lamination. An example of a method for making a film using the above composition is to cast the above composition onto a film having a smooth surface, such as a polyester film or an aluminum film, and then peel it off.

[0098] The air permeability of the separator for electrochemical devices is preferably 1000 s / 100 mL or less, more preferably 800 s / 100 mL or less, even more preferably 500 s / 100 mL or less, and preferably 50 s / 100 mL or more. The air permeability can be measured using an air permeability tester.

[0099] The Gurley value of the separator for electrochemical devices is preferably 1000 sec / 100cc Air or less, more preferably 800 sec / 100cc Air or less, and even more preferably 500 sec / 100cc Air or less. The above Gurley value is also preferably 50 sec / 100cc Air or more. The Gurley value is obtained by measurement using a Gurley densometer in accordance with JIS P 8117.

[0100] For separators used in electrochemical devices, the increase in the Gurley value is preferably 500% or less, more preferably 400% or less, and even more preferably 250% or less. The increase in the Gurley value is also preferably 103% or more. The increase in the Gurley value can be calculated using the following formula. Gurley value increase rate (%) = (Gurley value of separator for electrochemical devices / Gurley value of substrate only) × 100

[0101] (Electrochemical devices) The separator for electrochemical devices of this disclosure is applicable to electrochemical devices. The electrochemical device of this disclosure comprises the above-described separator for electrochemical devices.

[0102] Examples of electrochemical devices include batteries such as secondary batteries and capacitors. Batteries may be primary batteries, storage batteries (secondary batteries), or energy storage elements. Batteries may also be non-aqueous electrolyte batteries. Non-aqueous electrolyte batteries include all batteries that have an electrolyte and a power generation element. Examples of non-aqueous electrolyte batteries include lithium-ion primary batteries, lithium-ion secondary batteries, nickel-metal hydride batteries, lithium-ion capacitors, and electric double-layer capacitors.

[0103] The separator for electrochemical devices of this disclosure can constitute a secondary battery together with a positive electrode, a negative electrode, and a non-aqueous electrolyte. Among secondary batteries, lithium-ion secondary batteries are particularly preferred. A typical configuration when the separator for electrochemical devices of this disclosure is applied to a lithium-ion secondary battery is described below, but the electrochemical devices of this disclosure are not limited to these configurations.

[0104] The positive electrode consists of a positive electrode mixture containing a positive electrode active material, which is the material for the positive electrode, and a current collector.

[0105] The positive electrode active material is not particularly limited as long as it is electrochemically capable of intercalating and releasing lithium ions. A material containing lithium and at least one transition metal is preferred, and examples include lithium transition metal composite oxides such as lithium-cobalt composite oxide, lithium-nickel composite oxide, and lithium-manganese composite oxide, as well as lithium-containing transition metal phosphate compounds.

[0106] The positive electrode mixture preferably further includes a binder, a thickener, and a conductive material.

[0107] As a binder, any material can be used as long as it is safe for the solvent and electrolyte used during electrode manufacturing. Examples include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer.

[0108] Examples of thickening agents include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, starch oxide, phosphated starch, and casein.

[0109] Examples of conductive materials for the positive electrode include carbon materials such as graphite, carbon black, carbon nanotubes, and carbon fiber.

[0110] Suitable materials for the positive electrode current collector include metals such as aluminum, titanium, or tantalum, or alloys thereof. Aluminum or its alloys are particularly preferred.

[0111] The positive electrode can be manufactured by conventional methods. For example, the positive electrode active material can be mixed with the aforementioned binder, thickener, conductive material, solvent, etc., to form a slurry-like positive electrode mixture, which can then be applied to a current collector, dried, and pressed to increase its density.

[0112] The negative electrode consists of a negative electrode mixture containing negative electrode material and a current collector.

[0113] Examples of negative electrode materials include carbonaceous materials capable of intercalating and releasing lithium ions, such as thermal decomposition products of organic materials under various thermal decomposition conditions, artificial graphite, and natural graphite; metal oxide materials capable of intercalating and releasing lithium ions, such as tin oxide and silicon oxide; lithium metal; and various lithium alloys. Two or more of these negative electrode materials may be used in combination.

[0114] Preferred carbonaceous materials capable of intercalating and releasing lithium ions include artificial graphite or refined natural graphite produced by high-temperature treatment of easily graphitizable pitch obtained from various raw materials, or graphite obtained by surface-treating these graphites with pitch or other organic materials and then carbonizing them.

[0115] The negative electrode mixture preferably further includes a binder, a thickener, and a conductive material. Examples of binders include those similar to those used for the positive electrode, as described above. Examples of thickeners include those similar to those used for the positive electrode, as described above. Examples of conductive materials for the negative electrode include metallic materials such as copper and nickel; and carbon materials such as graphite and carbon black.

[0116] Suitable materials for the negative electrode current collector include copper, nickel, and stainless steel. Among these, copper is preferred due to its ease of processing into thin films and its cost-effectiveness.

[0117] The negative electrode can be manufactured using conventional methods. For example, the negative electrode material may be mixed with the aforementioned binder, thickener, conductive material, solvent, etc., to form a slurry, which is then applied to a current collector, dried, and pressed to increase its density.

[0118] As the non-aqueous electrolyte, a known electrolyte salt dissolved in a known organic solvent for dissolving electrolyte salts may be used.

[0119] The organic solvent for dissolving the electrolyte salt is not particularly limited, but one or more of the following can be used: hydrocarbon solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and vinylene carbonate; and fluorinated solvents such as fluoroethylene carbonate, fluoroether, and fluorinated carbonate.

[0120] Examples of electrolyte salts include LiClO4, LiAsF6, LiBF4, LiPF6, LiCl, LiBr, CH3SO3Li, CF3SO3Li, LiN(SO2CF3)2, LiN(SO2C2F5)2, and cesium carbonate.

[0121] The concentration of the electrolyte salt is preferably 0.8 mol / liter or higher, and more preferably 1.0 mol / liter or higher. The upper limit depends on the organic solvent used to dissolve the electrolyte salt, but is usually 1.5 mol / liter.

[0122] The shape of a lithium-ion secondary battery can be arbitrary, and examples include cylindrical, prismatic, laminated, coin-type, and large-sized batteries. The shape and configuration of the positive electrode, negative electrode, and separator can be modified according to the shape of each battery.

[0123] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0124] <1> According to a first aspect of this disclosure, a composition for coating a separator for an electrochemical device is provided, comprising a copolymer containing fluoromonomer units and amide bond-containing monomer units. <2> A composition according to the first aspect is provided, wherein the fluoromonomer is at least one selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and 2,3,3,3-tetrafluoropropene. <3> According to a third aspect of this disclosure, compositions according to the first or second aspect are provided, wherein the amide bond-containing monomer has a lactam ring. <4> According to a fourth aspect of this disclosure, a composition according to any one of the first to third aspects is provided, wherein the amide bond-containing monomer is N-vinyl-2-pyrrolidone. <5> According to the fifth aspect of this disclosure, a composition according to any of the first to fourth aspects is provided, wherein the content of fluoromonomer units of the copolymer is 75 to 7 mol% relative to the total monomer units, and the content of amide bond-containing monomer units of the copolymer is 25 to 93 mol% relative to the total monomer units. <6> According to a sixth aspect of this disclosure, a composition according to any one of the first to fifth aspects is further provided, comprising an inorganic filler. <7> According to a seventh aspect of this disclosure, a composition according to any one of the first to sixth aspects is provided, further comprising an inorganic filler containing at least one element selected from the group consisting of Mg, Al, Si, Ti, Zr, and Ba. <8> According to the eighth aspect of this disclosure, a composition according to any of the first to seventh aspects is provided, further containing an inorganic filler, wherein the ratio of copolymer to inorganic filler (copolymer):(inorganic filler) is 0.1:99.9 to 49.9:50.1 by mass. <9> According to the ninth aspect of this disclosure, a composition according to any of the first to eighth aspects is further provided, comprising a solvent. <10> According to the tenth aspect of this disclosure, a separator for an electrochemical device is provided, comprising a substrate and a coating layer formed from a composition according to any of the first to ninth aspects. <11> According to the eleventh aspect of this disclosure, a separator for an electrochemical device according to the tenth aspect is provided, wherein the substrate is formed from an organic material. <12> According to the twelfth aspect of this disclosure, an electrochemical device is provided comprising a separator for an electrochemical device according to the tenth or eleventh aspect. <13> According to the thirteenth aspect of this disclosure, a secondary battery is provided comprising a separator for an electrochemical device according to the tenth or eleventh aspect. [Examples]

[0125] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0126] Each value in the examples was measured by the following method.

[0127] <Monomial composition of polymers> Using an NMR analyzer (Agilent Technologies, VNS400MHz), 1 H-NMR and 19 The monomer composition of the polymer was determined by 1F-NMR measurement in a deuterated chloroform solution.

[0128] <Weight average molecular weight> Measurements were taken using gel permeation chromatography (GPC). A Tosoh AS-8010, CO-8020, and column (three GMHHR-H columns connected in series) were used, along with a Shimadzu RID-10A. Dimethylformamide (DMF) was used as the solvent, flowing at a rate of 1.0 ml / min. The data (reference: polystyrene) was used for calculation.

[0129] <Air permeability> The air permeability was measured using an air permeability tester (manufactured by Kumagai Riki Kogyo Co., Ltd.). The air permeability (s / 100mL) was calculated by multiplying the time (s) required for the gas to pass through from 0mL to 25mL on the scale by four.

[0130] <Coating thickness> The thickness was measured using a high-precision thickness measuring instrument (HKT-1240). The film thickness of the substrate alone before coating and the film thickness of the coated separator were measured, and the difference between these values ​​was calculated as the coating thickness.

[0131] <Area maintenance rate> The separators prepared in each experimental example were placed in an oven and heated at 150°C for 30 minutes. The area of ​​the separators was measured before and after heating, and the area retention rate was calculated using the following formula. Separators with a high area retention rate have excellent heat shrinkage resistance. Area retention rate (%) = (Area of ​​separator after heating) / (Area of ​​separator before heating) × 100

[0132] <Synthesis Example 1> 245 g of HFE-347pc-f(CF3CH2OCF2CHF2), 9.7 g of N-vinyl-2-pyrrolidone, 35 g of tetrafluoroethylene, and 0.5 g of a 70 wt% t-butyl peroxypivalate hydrocarbon solution (hereinafter abbreviated as "perbutyl PV") as an initiator were charged into a 500 mL autoclave, and a polymerization reaction was carried out at 50°C. After the polymerization reaction reduced the pressure from 0.81 MPa to 0.71 MPa, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover the copolymer (polymer a). Polymer a had a tetrafluoroethylene-based polymerization unit / N-vinyl-2-pyrrolidone-based polymerization unit ratio of 38 / 62 (molar ratio) as measured by NMR, and a weight-average molecular weight of 320,000 as measured by GPC.

[0133] <Synthesis Example 2> 245 g of HFE-347pc-f, 9.5 g of N-vinyl-2-pyrrolidone, 34 g of tetrafluoroethylene, and 1.0 g of perbutyl PV as an initiator were charged into a 500 mL autoclave, and the polymerization reaction was carried out at 50°C. After the polymerization reaction reduced the pressure from 0.77 MPa to 0.66 MPa, the monomers in the autoclave were purged, and the copolymer (polymer b) was recovered by drying the resulting polymer solution at 120°C. Polymer b had a molecular ratio of 38 / 62 (molar ratio) of polymerization units based on tetrafluoroethylene, as measured by NMR, and a weight-average molecular weight of 240,000, as measured by GPC.

[0134] <Synthesis Example 3> 245 g of HFE-347pc-f, 7.4 g of N-vinyl-2-pyrrolidone, 38 g of tetrafluoroethylene, and 0.5 g of perbutyl PV as an initiator were charged into a 500 mL autoclave, and the polymerization reaction was carried out at 50°C. After the polymerization reaction reduced the pressure from 0.83 MPa to 0.73 MPa, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover the copolymer (polymer c). Polymer c had a molecular ratio of 41 / 59 (molar ratio) of polymerization units based on tetrafluoroethylene to polymerization units based on N-vinyl-2-pyrrolidone, as measured by NMR, and a weight-average molecular weight of 320,000, as measured by GPC.

[0135] <Synthesis Example 4> 245 g of HFE-347pc-f, 7.4 g of N-vinyl-2-pyrrolidone, 38 g of tetrafluoroethylene, and 1.0 g of perbutyl PV as an initiator were charged into a 500 mL autoclave, and the polymerization reaction was carried out at 50°C. After the polymerization reaction reduced the pressure from 0.90 MPa to 0.79 MPa, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover the copolymer (polymer d). Polymer d had a molecular weight ratio of 41 / 59 (molar ratio) of polymerization units based on tetrafluoroethylene to polymerization units based on N-vinyl-2-pyrrolidone, as measured by NMR, and a weight-average molecular weight of 250,000, as measured by GPC.

[0136] The following copolymers were used in the examples and comparative examples. Polymer a (Composition ratio: tetrafluoroethylene / N-vinyl-2-pyrrolidone = 38 / 62, weight-average molecular weight: 320,000) Polymer b (Composition ratio: tetrafluoroethylene / N-vinyl-2-pyrrolidone = 38 / 62, weight-average molecular weight: 240,000) Polymer c (Composition ratio: tetrafluoroethylene / N-vinyl-2-pyrrolidone = 41 / 59, weight-average molecular weight: 320,000) Polymer d (Composition ratio: tetrafluoroethylene / N-vinyl-2-pyrrolidone = 41 / 59, weight-average molecular weight: 250,000) Polymer e (Composition ratio: tetrafluoroethylene / N-vinyl-2-pyrrolidone = 33 / 67, weight-average molecular weight: 97,000) Polymer f (Composition ratio: vinylidene fluoride / hexafluoropropylene = 93 / 7, weight-average molecular weight: 320,000)

[0137] Example 1 Polymer a, aluminum oxide (alumina) powder (average particle size 0.67 μm), and N-methylpyrrolidone (NMP) were blended in a container in the following proportions: 12.2 parts by mass, 18.7 parts by mass, and 69.1 parts by mass, respectively. Zirconia beads were added, the mixture was mixed using a bead mill, and then the zirconia beads were filtered to prepare a coating composition.

[0138] Furthermore, NMP / water was mixed in a 55 / 45 ratio to prepare a phase separation solution. The coating composition was applied to both sides of a polyethylene separator, and the coated separator was immersed in the phase separation solution for 3 minutes. Next, the separator was immersed in water for 3 minutes and dried in an 80°C oven for 30 minutes to produce a coated separator. The air permeability and surface retention rate of the produced separator were measured. The results are shown in Table 1.

[0139] Example 2 A separator was prepared in the same manner as in Example 1, except that polymer b, aluminum oxide (alumina) powder (average particle size 0.67 μm), and N-methylpyrrolidone (NMP) were blended into a container in the following proportions: 15.4 parts by mass, 23.1 parts by mass, and 61.5 parts by mass, respectively. The obtained separator was then evaluated. The results are shown in Table 1.

[0140] Examples 3 and 4 Separators were manufactured using polymers c and d individually, in the same manner as in Example 2, and the obtained separators were evaluated. The results are shown in Table 1.

[0141] Example 5 Polymer e, aluminum oxide (alumina) powder (average particle size 0.67 μm), and N-methylpyrrolidone (NMP) were blended in a container in the following proportions: 10.0 parts by mass, 15.0 parts by mass, and 75.0 parts by mass, respectively. After this, a separator was manufactured in the same manner as in Example 1, and the obtained separator was evaluated. The results are shown in Table 1.

[0142] Example 6 Polymer c, magnesium oxide powder (average particle size 0.54 μm), and N-methylpyrrolidone (NMP) were blended into a container in the following proportions: 10.0 parts by mass, 15.0 parts by mass, and 75.0 parts by mass, respectively. After this, a separator was manufactured in the same manner as in Example 1, and the obtained separator was evaluated. The results are shown in Table 1.

[0143] Comparative Example 1 A separator was prepared using polymer f in the same manner as in Example 5, and the obtained separator was evaluated. The results are shown in Table 1.

[0144] Comparative Example 2 A separator was prepared using polymer f in the same manner as in Example 6, and the obtained separator was evaluated. The results are shown in Table 1.

[0145] Comparative Example 3 A polyethylene separator (uncoated raw material) was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0146] [Table 1]

Claims

[Claim 1] A composition for coating separators for electrochemical devices, comprising a copolymer containing fluoromonomer units and amide bond-containing monomer units.

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