Composition, separator for electrochemical device, electrochemical device, and secondary battery

Abstract

Provided is a composition for coating a separator for an electrochemical device, said composition containing a copolymer that contains fluoromonomer units and amide-bond-containing monomer units.

Description

Composition, separator for electrochemical device, electrochemical device and secondary battery

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

[0002] Patent Document 1 discloses a composite containing a fluorine-containing copolymer, an alkali metal salt, and an ionic liquid, wherein the fluorine-containing copolymer contains a structural unit represented by general formula (1): -[CR １ R ２ One CR ３ R ４ ]-(1) (In the formula, R １ ~R ４ are each independently H, F, Cl, CF ３ , OR １０ (R １０ is an organic group having 1 to 8 carbon atoms. １ ~R ４ at least one of which is F) and a structural unit represented by 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 above functional group. ５ ~R ８ at least one of which is a functional group containing a heteroatom other than a fluorine atom or a group containing such a functional group, and a volatile component content of the entire composite is 0.1 mass % or less.

[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 organic / inorganic composite porous separator membrane comprising (a) a polyolefin-based separator membrane substrate, and (b) an active layer formed by applying a mixture of inorganic particles and a binder polymer to one or more regions selected from the group consisting of the surface of the substrate and a portion of pores present in 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.

[0005] International Publication No. 2021 / 221113 International Publication No. 2020 / 054210 Special Publication No. 2008-524824

[0006] An object of the present disclosure is to provide a composition for coating a separator for an electrochemical device, which can improve the heat shrinkage resistance of the separator.

[0007] According to a first aspect of the present disclosure, there is provided a composition for coating a separator for an electrochemical device, which comprises a copolymer containing a fluoromonomer unit and an amide bond-containing monomer unit.

[0008] According to the present disclosure, it is possible to provide a composition for coating a separator for an electrochemical device, which can improve the heat shrinkage resistance of the separator.

[0009] Specific embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments.

[0010] The basic structure of a lithium-ion secondary battery is a nonaqueous electrolyte placed between a positive electrode and a negative electrode, optionally with a separator interposed between them. The separator is interposed between the positive and negative electrodes to prevent contact between the active materials of both electrodes, and also forms a path for ionic conduction between the electrodes by allowing the electrolyte to flow through its pores. The separator is also required to have a current-blocking function (shutdown function) to prevent excessive current flow in the battery due to an abnormal current flow caused by a short circuit between the positive and negative electrodes, etc. The separator shuts down the battery by blocking the microporous membrane when the temperature exceeds the normal battery operating temperature.

[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 a problem of poor dimensional stability at high temperatures due to their high heat shrinkage. If the internal temperature of a lithium-ion secondary battery continues to rise even after the pores in the separator are blocked due to abnormal heating, the separator may undergo thermal shrinkage and break, leading to internal short circuits and the risk of fire. To improve the safety of batteries at such high temperatures, there is a need to improve the heat shrinkage resistance of separators.

[0012] As a result of extensive research, the present inventors have found that the heat shrinkage resistance of a separator can be improved by coating the separator with a composition containing a copolymer of a fluoromonomer and an amide bond-containing monomer.

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

[0014] (Copolymer) The composition of the present disclosure contains a copolymer of a fluoromonomer and an amide bond-containing monomer.

[0015] The fluoromonomers include (1) sp２ (2) an olefin having a fluorine atom bonded to a hybridized carbon atom, ２ ═CX-COORf (wherein X is Cl, H or an alkyl group, and Rf is a fluoroalkyl group), (3) a monomer represented by the general formula: CH ２ (4) a monomer represented by the general formula: CH ２ Examples thereof include a monomer represented by the formula: ═CH—ORf (wherein Rf is a fluoroalkyl group).

[0016] The alkyl group may be an alkyl group having 1 to 3 carbon atoms, and a methyl group is preferred.

[0017] The fluoroalkyl group is preferably a straight-chain or branched fluoroalkyl group having 1 to 12 carbon atoms.

[0018] As the fluoromonomer, (1) is preferred because it allows fluorine atoms bonded to carbon atoms constituting the polymer main chain to be introduced into the copolymer, thereby further improving the heat shrinkage resistance of the separator when coated with the copolymer, and vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, monofluoroethylene, trifluorostyrene, and fluoromonomers represented by the general formula: CX ２ = CXRf １ (Wherein, X is independently H or F, at least one of X is F, Rf １ is more preferably at least one selected from the group consisting of fluoromonomers represented by the formula (I) and (II),

[0019] The fluoromonomer is more preferably at least one selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and 2,3,3,3-tetrafluoropropene, since this can further improve the heat shrinkage resistance of the separator when coated with the fluoromonomer, and tetrafluoroethylene is particularly preferred.

[0020] The amide bond-containing monomer contains an amide bond and a polymerizable vinyl group. The amide bond is a bond between a carbonyl group and a nitrogen atom. Examples of the polymerizable vinyl group include vinyl, allyl, vinyl ether, vinyl ester, and acrylic groups.

[0021] Examples of the amide bond-containing monomer include N-vinyl lactam compounds such as N-vinyl-β-propiolactam, N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, and N-vinyl-heptolactam; acyclic N-vinyl amide compounds such as N-vinyl formamide and N-methyl-N-vinyl acetamide; acyclic N-allyl amide compounds such as N-allyl-N-methyl formamide and allyl urea; N-allyl lactam compounds such as 1-(2-propenyl)-2-pyrrolidone; and acrylamide compounds such as (meth)acrylamide, N,N-dimethylacrylamide, and N-isopropylacrylamide.

[0022] The amide bond-containing monomer also includes (In the formula, R １１ and R １２ are independently H or an alkyl group having 1 to 10 carbon atoms, (In the formula, R １１ and R １２ are independently H or an alkyl group having 1 to 10 carbon atoms.

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

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

[0025] Among these, the amide bond-containing monomer is preferably 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-heptolactam, more preferably at least one selected from the group consisting of N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, and N-vinyl-ε-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

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

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

[0028] The content of the fluoromonomer unit in the copolymer is more preferably 60 mol% or less, even more preferably 55 mol% or less, particularly preferably 50 mol% or less, and 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 the amide bond-containing monomer unit in the copolymer is more preferably 40 mol% or more, even more preferably 45 mol% or more, particularly preferably 50 mol% or more, and most preferably 55 mol% or more, and 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] The copolymer may also be a copolymer containing 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 (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 a solvent.

[0034] (Method for Producing Copolymer) The copolymer can be suitably produced by a production method in which a fluoromonomer, an amide bond-containing monomer, and, if necessary, other monomers are polymerized in a reactor.

[0035] As the polymerization method, methods such as suspension polymerization, emulsion polymerization, and solution polymerization can be used.

[0036] Among various polymerization methods, a polymerization method using a fluorine-containing solvent is preferred because it allows the production of a copolymer having a high molecular weight. The copolymer 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 the copolymer.

[0037] Examples of fluorine-containing solvents include CH ３ CClF ２ , C.H. ３ CCl ２ F, CF ３ CF ２ CCl ２ H, C.F. ２ ClCF ２ Hydrochlorofluoroalkanes such as CFHCl; CF ２ ClCFClCF ２ CF ３ , C.F. ３ CFClCFClCF ３ chlorofluoroalkanes such as perfluorocyclobutane, CF ３ CF ２ CF ２ CF ３ , C.F. ３ CF ２ CF ２ CF ２ CF ３ , C.F. ３ CF ２ CF ２ CF ２ CF ２ CF ３ perfluoroalkanes such as CF ２ HCF ２ CF ２ CF ２ H, C.F. ３ CFHCF ２ CF ２ CF３ , CF ３ CF ２ CF ２ CF ２ CF ２ H, CF ３ CF ２ CFHCF ２ CF ３ , CF ３ CFHCFHCF ２ CF ３ , CF ２ HCF ２ CF ２ CF ２ CF ２ H, CF ２ HCFHCF ２ CF ２ CF ３ , CF ３ CF ２ CF ２ CF ２ CF ２ CF ２ H, CF ３ CH(CF ３ )CF ３ CF ２ CF ３ , CF ３ CF(CF ３ )CFHCF ２ CF ３ , CF ３ CF(CF ３ )CFHCFHCF ３ , CF ３ CH(CF ３ )CFHCF ２ CF ３ , CF ２ HCF ２ CF ２ CF ２ CF ２ CF ２ H, CF ３ CF ２ CF ２ CF ２ CH ２ CH ３ , CF ３ CH ２ CF ２ CH ３ and other hydrofluorocarbons such as; F(CF[[ID=I20]] ２ ) ４OCH ３ , F(CF ２ ) ４ O.C. ２ H ５ , (CF ３ ) ２ CFOCH ３ , F(CF ２ ) ３ OCH ３ (Perfluoroalkyl) alkyl ethers such as CF ３ CH ２ OCF ２ CHF ２ , CHF ２ CF ２ CH ２ OCF ２ CHF ２ , C.F. ３ CF ２ CH ２ OCF ２ CHF ２ and the like hydrofluoroalkyl ethers.

[0038] The fluorine-containing solvent is preferably at least one selected from the group consisting of hydrofluorocarbons, (perfluoroalkyl) alkyl ethers, and hydrofluoroalkyl ethers, and more preferably hydrofluoroalkyl ethers, because it allows the production of a copolymer having a higher molecular weight.

[0039] Among the fluorine-containing solvents, CF ３ CH ２ CF ２ CH ３ , C.F. ３ CH ２ OCF ２ CHF ２ , CHF ２ CF ２ CH ２ OCF ２ CHF ２ and C.F. ３ CF ２ CH ２ OCF ２ CHF ２ At least one selected from the group consisting of CF ３ CH ２ OCF２ CHF ２ is more preferred.

[0040] In the above polymerization, a polymerization initiator, a surfactant and a chain transfer agent can be used, and conventionally known ones can be used for each of them.

[0041] The polymerization initiator may be a radical polymerization initiator. Representative examples of the polymerization initiator include dialkyl peroxycarbonates such as di-normal propyl peroxydicarbonate, diisopropyl peroxydicarbonate, and di-sec-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; and di[fluoro(or fluorochloro)acyl]peroxides.

[0042] Di[fluoro(or fluorochloro)acyl]peroxides include [(RfCOO)-] ２ (Rf is a perfluoroalkyl group, a 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(perfluoroparyl)peroxide, di(perfluorohexanoyl)peroxide, di(perfluoroheptanoyl)peroxide, di(perfluorooctanoyl)peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, and di(ω-chloro-decafluorohexanoyl)peroxide. Examples of the peroxide include di(ω-chlorotetradecafluorooctanoyl) peroxide, ω-hydrododecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl peroxide, ω-chlorohexafluorobutyryl-ω-chlorodecafluorohexanoyl peroxide, ω-hydrododecafluoroheptanoylperfluorobutyryl peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, and di(undecachlorotriacontafluorodocosanoyl) peroxide.

[0044] Polymerization in the presence of a chain transfer agent allows the solution viscosity, weight average molecular weight, etc. of the resulting copolymer to 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; acetates 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 is preferably 0 to 95°C, more preferably 15 to 95°C, from the viewpoint of the polymerization rate and the cost required for temperature control.

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

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

[0048] (Inorganic Filler) The composition of the present disclosure preferably further contains an inorganic filler. By containing an inorganic filler in the composition of the present disclosure, the heat shrinkage resistance of the separator can be further improved.

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

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

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

[0052] The metal hydroxide particles are preferably at least one selected from the group consisting of magnesium hydroxide, aluminum hydroxide, and zirconium hydroxide.

[0053] Of these, the inorganic filler is preferably at least one selected from the group consisting of magnesium oxide, silicon oxide, aluminum oxide, and zirconium oxide, and more preferably at least one selected from the group consisting of magnesium oxide and aluminum oxide.

[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 measurement using a transmission electron microscope, a laser particle size distribution analyzer, or the like.

[0055] In the composition of the present disclosure, the content ratio of the copolymer to the inorganic filler [(copolymer) / (inorganic filler)], in mass ratio, is preferably 0.1 / 99.9 to 49.9 / 50.1, 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 composition of the present disclosure preferably further contains a solvent.

[0057] Examples of the solvent 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 triglyme; 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] As the solvent, at least one selected from the group consisting of esters (1) represented by general formula (1) and ketones (2) represented by general formula (2) can also be used.

[0059] General formula (1): (In the formula, R １ and R ２ are independently H, C １ ~C １０ or a linear or branched aliphatic group of ６ ~C １０ is an aromatic group of the formula

[0060] General formula (2): (In the formula, R ３ and R ４ are independently H, C １ ~C １０ or a linear or branched aliphatic group of ６ ~C １０ is an aromatic group of the formula

[0061] R in general formula (1) １ and R ２ are independently H, C １ ~C １０ or a linear or branched aliphatic group of ６ ~C １０ is an aromatic group of the formula:

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

[0063] R １ 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 be substituted or unsubstituted. Examples of the substituent 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 As for C １ ~C １０ A linear or branched aliphatic group represented by the formula C is preferred.１ ~C １０ or a linear or branched alkyl group of C ２ ~C １０ More preferred are linear or branched alkenyl groups, and more preferred are methyl, ethyl, propyl, vinyl, isopropenyl, butyl or pentyl groups, and more preferred are propyl, butyl or pentyl groups. These groups may be linear or branched, but are preferably linear.

[0065] R ２ The carbon number of the aliphatic group of R is 1 to 10, preferably 3 or more, more preferably 4 or more, and preferably 8 or less, more preferably 6 or less. ２ The aliphatic group is preferably an alkyl group, and 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 be substituted or unsubstituted. Examples of the substituent 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 As for C １ ~C １０ A linear or branched aliphatic group represented by the formula C is preferred. １ ~C １０ More preferred are linear or branched alkyl groups such as those listed above, and more preferred are methyl, ethyl, propyl, butyl, pentyl or hexyl groups, and more preferred are butyl, pentyl or hexyl groups. These groups may be linear or branched, but are preferably linear.

[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, and more preferably butyl butyrate.

[0069] R in general formula (2) ３ and R ４ are independently H, C １ ~C １０ or a linear or branched aliphatic group of ６ ~C １０ is an aromatic group of the formula:

[0070] R ３ and R ４ The aliphatic group has 1 to 10 carbon atoms, preferably 3 or less, and more preferably 2 or less. ３ The aliphatic group is preferably an alkyl group, and 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 be substituted or unsubstituted. Examples of the substituent 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 ４ As for C １ ~C １０ A linear or branched aliphatic group represented by the formula C is preferred. １ ~C １０More preferred are linear or branched alkyl groups such as those listed above, with methyl, ethyl, propyl, butyl, pentyl, and hexyl being preferred, and methyl and ethyl being more preferred. These groups may be linear or branched, but are preferably linear.

[0073] The ketone (2) represented by the 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 the solvent. For example, when a copolymer is produced by a production method of emulsion polymerizing a monomer in water, a polymer composition containing the copolymer and water is usually obtained, and therefore, the water contained in the polymer composition can be used as the solvent for the composition of the present disclosure.

[0075] In particular, the composition of the present disclosure preferably contains 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 contains N-methyl-2-pyrrolidone, in terms of excellent composition stability and coatability.

[0076] When the composition of the present disclosure contains a copolymer and a solvent, the content of the copolymer 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, relative to the mass of the composition.

[0077] (Other Components) The composition of the present disclosure may also contain an organic filler. As the organic filler, a non-conductive crosslinked polymer is preferred, and a crosslinked polystyrene, a crosslinked polymethacrylate, or a crosslinked acrylate is more preferred.

[0078] The compositions of the present disclosure may also contain other polymers such as polyacrylates, polymethacrylates, polyacrylonitriles, polyamideimides, acrylic rubbers, carboxyalkyl celluloses, alkyl celluloses, hydroxyalkyl celluloses, and the like.

[0079] (Separator for electrochemical device) A separator for electrochemical device of the present disclosure can be produced using the composition of the present disclosure. The separator for electrochemical device of the present disclosure includes a substrate and a coating layer formed from the composition.

[0080] The substrate and the coating layer may be bonded directly or via another layer, but it is preferable that the coating layer is 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 portion of the substrate.

[0081] When the coating layer is formed on only one side of the substrate, the weight of the coating layer is set to 0.5 to 50.0 g / m from the viewpoints of heat shrinkage resistance, adhesion to the electrode, and ion conductivity. ２ When a coating layer is formed on both sides of the substrate, the weight of the coating layer is preferably 1.0 g / m ２ More preferably, it is 3.0 g / m or more. ２ or more, and preferably 25.0 g / m ２ More preferably, it is 20.0 g / m or less. ２ The following is the result.

[0082] The thickness of the coating layer per side is preferably 1 to 5 μm. When the thickness of the coating layer is within this range, the film rupture strength and insulating properties can be ensured, and the substrate is less likely to curl significantly.

[0083] The substrate is preferably a porous substrate having pores or gaps therein. Examples of the porous substrate include a microporous membrane, a porous sheet made of a fibrous material such as a nonwoven fabric or a paper-like sheet, or a composite coating layer in which one or more other porous layers are laminated on the microporous membrane or porous sheet. The microporous membrane refers to a membrane having a large number of micropores therein, a structure in which the micropores are connected, and which allows gas or liquid to pass from one surface to the other surface.

[0084] The material constituting the substrate may be either an organic material or an inorganic material having electrical insulation properties. In particular, from the viewpoint of imparting a shutdown function to the substrate, it is preferable to use an organic material as the material constituting the substrate, 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 the function of preventing thermal runaway of the battery by blocking the movement of ions by dissolving the thermoplastic resin and blocking the pores of the substrate when the battery temperature rises. As the thermoplastic resin, a thermoplastic resin with a melting point of less than 200°C is suitable, and polyolefin is particularly preferred.

[0086] A polyolefin microporous membrane is suitable as a polyolefin substrate. As the polyolefin microporous membrane, a polyolefin microporous membrane having sufficient mechanical properties and ion permeability and used in conventional separators for nonaqueous secondary batteries can be used. Furthermore, the polyolefin microporous membrane preferably contains polyethylene in order to provide the shutdown function described above.

[0087] The weight-average molecular weight of the polyolefin is preferably 100,000 to 5,000,000. 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 be poor and molding may be difficult.

[0088] Such a polyolefin microporous membrane can be produced, for example, by the following method. That is, a method of forming a microporous membrane by sequentially performing the steps of (i) extruding a molten polyolefin resin through a T-die to form a sheet, (ii) crystallizing the sheet, (iii) stretching the sheet, and (iv) heat-treating the sheet. Another example is a method of forming a microporous membrane by sequentially performing the steps of (i) melting a polyolefin resin together with a plasticizer such as liquid paraffin, extruding it through 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.

[0089] Examples of porous sheets made of fibrous materials include fibrous materials made of polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, aromatic polyamides and polyimides, heat-resistant polymers such as polyethersulfone, polysulfone, polyetherketone, and polyetherimide, and porous sheets made of mixtures of these fibrous materials.

[0090] The substrate may be a composite substrate further laminated with a functional layer. Composite substrates are preferred because the functional layer allows for the addition of additional functions. For example, from the viewpoint of imparting heat resistance, the functional layer may be a porous layer made of a heat-resistant resin or a porous layer made of a heat-resistant resin and an inorganic filler. Examples of heat-resistant resins include one or more heat-resistant polymers selected from aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyetherketone, and polyetherimide. Examples of inorganic fillers that can be suitably used include metal oxides such as alumina and metal hydroxides such as magnesium hydroxide. Examples of composite methods include coating a porous sheet with a functional layer, bonding with an adhesive, and thermocompression bonding.

[0091] Among the above-mentioned substrates, a porous substrate made of at least one material selected from the group consisting of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, polyester, and polyacetal is preferred.

[0092] The 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 thickness is more preferably 40 μm, and even more preferably 30 μm. The lower limit of the thickness is more preferably 10 μm.

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

[0094] The porosity of the substrate is preferably 30 to 70%, more preferably 35 to 60%. The porosity is a value calculated by the following formula: Porosity = (1 - sample mass (g) / (sample density (g / cm ３ ) × sample volume (cm ３ ))) × 100 Sample volume here (cm ３ ) is calculated as 10 cm x 10 cm x thickness (cm).

[0095] The average pore size of the substrate is preferably 0.01 to 0.5 μm, more preferably 0.1 to 0.3 μm. The average pore size is determined by applying the BET method to the gas adsorption method and calculating the specific surface area (m ２ / g) was measured, and the basis weight (g / m ２ ) to obtain the base material 1m ２ Calculate the pore surface area S per 1 m of the substrate from the porosity. ２ The pore volume V per sieve is calculated. The obtained value is used to calculate the average pore size (diameter) d using the following formula: d = 4 V / S

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

[0097] A separator for an electrochemical device can be produced by coating the composition on 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. For example, a method of applying the composition to the substrate and drying the coating film can be used. More specific examples of the coating method include roll-coating the composition onto the substrate, dipping the substrate in the composition, and applying the composition to the substrate and then immersing it in an appropriate coagulation liquid. Alternatively, a separator for an electrochemical device can be produced by preparing a film using the composition and laminating the resulting film onto the substrate by a method such as lamination. An example of a method of producing a film using the composition is to cast the composition onto a film having a smooth surface, such as a polyester film or an aluminum film, and then peeling 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 / 100 cc Air or less, more preferably 800 sec / 100 cc Air or less, and even more preferably 500 sec / 100 cc Air or less. The Gurley value is also preferably 50 sec / 100 cc Air or more. The Gurley value is a value obtained by measurement using a Gurley densometer in accordance with JIS P 8117.

[0100] The electrochemical device separator preferably has an increase in Gurley value of 500% or less, more preferably 400% or less, and even more preferably 250% or less. The increase in Gurley value is also preferably 103% or more. The increase in Gurley value can be calculated using the following formula: Gurley value increase rate (%) = (Gurley value of electrochemical device separator / Gurley value of substrate only) x 100

[0101] (Electrochemical Device) The separator for an electrochemical device of the present disclosure can be applied to an electrochemical device. The electrochemical device of the present disclosure includes the separator for an electrochemical device described above.

[0102] Examples of electrochemical devices include batteries such as secondary batteries and capacitors. The battery may be a primary battery, a storage battery (secondary battery), or a storage element. The battery may be a non-aqueous electrolyte battery. Non-aqueous electrolyte batteries include all batteries that include 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 the present disclosure can be used together with a positive electrode, a negative electrode, and a nonaqueous electrolyte to form a secondary battery. As the secondary battery, a lithium-ion secondary battery is particularly preferred. Below, we will explain typical configurations when the separator for electrochemical devices of the present disclosure is applied to a lithium-ion secondary battery, but the electrochemical device of the present disclosure is not limited to these configurations.

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

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

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

[0107] Any material can be used as the binder as long as it is safe against the solvent and electrolyte used in producing the electrodes. Examples of the binder 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 thickeners include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, 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 fibers.

[0110] Examples of the material for the positive electrode current collector include metals such as aluminum, titanium, and tantalum, and alloys thereof, with aluminum and its alloys being preferred.

[0111] The positive electrode may be manufactured by a conventional method, for example, by adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned positive electrode active material to form a slurry positive electrode mixture, which is then applied to a current collector, dried, and pressed to increase density.

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

[0113] Examples of the negative electrode material include carbonaceous materials capable of absorbing and desorbing lithium ions, such as pyrolysis products of organic substances under various pyrolysis conditions, artificial graphite, and natural graphite; metal oxide materials capable of absorbing and desorbing lithium ions, such as tin oxide and silicon oxide; lithium metal; various lithium alloys; etc. Two or more of these negative electrode materials may be mixed and used.

[0114] As the carbonaceous material capable of absorbing and releasing lithium ions, artificial graphite or purified natural graphite produced by high-temperature treatment of graphitizable pitch obtained from various raw materials, or graphite obtained by surface treatment of such graphite with pitch or other organic matter and then carbonizing it, are preferred.

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

[0116] Examples of materials for the negative electrode current collector include copper, nickel, stainless steel, etc. Among these, copper is preferred from the viewpoints of ease of processing into a thin film and cost.

[0117] The negative electrode may be produced by a conventional method, for example, by adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned negative electrode material to form a slurry, which is then applied to a current collector, dried, and pressed to increase density.

[0118] The non-aqueous electrolyte may be prepared by dissolving a known electrolyte salt in a known organic solvent for dissolving electrolyte salts.

[0119] The organic solvent for dissolving the electrolyte salt is not particularly limited, and 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 fluorine-based solvents such as fluoroethylene carbonate, fluoroethers, and fluorinated carbonates.

[0120] The electrolyte salt is LiClO ４ , LiAsF ６ , LiBF ４ , LiPF ６ , LiCl, LiBr, CH ３ SO ３ Li, CF ３ SO ３ Li, LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ ) ２ , cesium carbonate, etc.

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

[0122] The shape of the lithium ion secondary battery is arbitrary, and examples thereof include cylindrical, rectangular, laminated, coin, large, etc. The shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

[0123] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0124] <1> According to a first aspect of the present disclosure, there is provided a composition for coating a separator for an electrochemical device, the composition containing a copolymer containing a fluoromonomer unit and an amide bond-containing monomer unit. <2> According to a second aspect of the present disclosure, there is provided a composition according to the first aspect, in which 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 the present disclosure, there is provided a composition according to the first or second aspect, in which the amide bond-containing monomer has a lactam ring. <4> According to a fourth aspect of the present disclosure, there is provided a composition according to any of the first to third aspects, in which the amide bond-containing monomer is N-vinyl-2-pyrrolidone. <5> According to a fifth aspect of the present disclosure, there is provided a composition according to any one of the first to fourth aspects, wherein the content of fluoromonomer units in the copolymer is 75 to 7 mol % based on all monomer units, and the content of amide bond-containing monomer units in the copolymer is 25 to 93 mol % based on all monomer units. <6> According to a sixth aspect of the present disclosure, there is provided a composition according to any one of the first to fifth aspects, further comprising an inorganic filler. <7> According to a seventh aspect of the present disclosure, there is provided a composition according to any one of the first to sixth aspects, 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 an eighth aspect of the present disclosure, there is provided a composition according to any one of the first to seventh aspects, further comprising an inorganic filler, wherein the content ratio of the copolymer to the inorganic filler (copolymer):(inorganic filler) is 0.1:99.9 to 49.9:50.1 by mass. <9> According to a ninth aspect of the present disclosure, there is provided a composition according to any one of the first to eighth aspects, further containing a solvent. <10> According to a tenth aspect of the present disclosure, there is provided a separator for an electrochemical device, comprising a substrate and a coating layer formed from the composition according to any one of the first to ninth aspects.<11> According to an eleventh aspect of the present disclosure, there is provided a separator for an electrochemical device according to the tenth aspect, in which the substrate is formed from an organic material. <12> According to a twelfth aspect of the present disclosure, there is provided an electrochemical device comprising the separator for an electrochemical device according to the tenth or eleventh aspect. <13> According to a thirteenth aspect of the present disclosure, there is provided a secondary battery comprising the separator for an electrochemical device according to the tenth or eleventh aspect.

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

[0126] The values ​​in the examples were measured by the following methods.

[0127] <Monomer Composition of Polymer> Using an NMR analyzer (Agilent Technologies, VNS 400 MHz), １ H-NMR and １９ The monomer composition of the polymer was measured by F-NMR measurement in the state of a polymer solution in deuterated chloroform.

[0128] <Weight-average molecular weight> Measured by gel permeation chromatography (GPC). Calculations were made from data measured using Tosoh AS-8010, CO-8020, a column (three GMHHR-H columns connected in series), and Shimadzu RID-10A, using dimethylformamide (DMF) as a solvent at a flow rate of 1.0 ml / min (reference: polystyrene).

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

[0130] <Coating Film Thickness> 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 film thickness.

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

[0132] Synthesis Example 1 HFE-347pc-f(CF ３ CH ２ OCF ２ CHF ２ 245 g of tetrafluoroethylene, 9.7 g of N-vinyl-2-pyrrolidone, 35 g of tetrafluoroethylene, and 0.5 g of a 70 wt % hydrocarbon solution of t-butyl peroxypivalate (hereinafter abbreviated as "Perbutyl PV") as an initiator were charged, and a polymerization reaction was carried out at 50°C. When the pressure decreased from 0.81 MPa to 0.71 MPa due to the polymerization reaction, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover a copolymer (polymer a). Polymer a had a ratio of tetrafluoroethylene-based polymerization units / N-vinyl-2-pyrrolidone-based polymerization units of 38 / 62 (molar ratio) as measured by NMR measurement, and a weight average molecular weight of 320,000 as measured by GPC measurement.

[0133] Synthesis Example 2 A 500 mL autoclave was charged with 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, and a polymerization reaction was carried out at 50°C. When the pressure decreased from 0.77 MPa to 0.66 MPa due to the polymerization reaction, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover a copolymer (polymer b). Polymer b had a ratio of polymerization units based on tetrafluoroethylene / polymerization units based on N-vinyl-2-pyrrolidone of 38 / 62 (molar ratio) as measured by NMR measurement, and a weight average molecular weight as measured by GPC measurement of 240,000.

[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 a polymerization reaction was carried out at 50°C. When the pressure was reduced from 0.83 MPa to 0.73 MPa due to the polymerization reaction, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover a copolymer (polymer c). Polymer c had a ratio of polymerization units based on tetrafluoroethylene / polymerization units based on N-vinyl-2-pyrrolidone of 41 / 59 (molar ratio) as measured by NMR measurement, and a weight average molecular weight as measured by GPC measurement of 320,000.

[0135] Synthesis Example 4 A 500 mL autoclave was charged with 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, and a polymerization reaction was carried out at 50°C. When the pressure was reduced from 0.90 MPa to 0.79 MPa due to the polymerization reaction, the monomers in the autoclave were purged, and the resulting polymer solution was dried at 120°C to recover a copolymer (polymer d). Polymer d had a ratio of polymerization units based on tetrafluoroethylene / polymerization units based on N-vinyl-2-pyrrolidone of 41 / 59 (molar ratio) as measured by NMR measurement, and a weight average molecular weight as measured by GPC measurement of 250,000.

[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 mixed in a container in proportions of 12.2 parts by mass, 18.7 parts by mass, and 69.1 parts by mass, respectively, and zirconia beads were added thereto. The mixture was mixed using a bead mill, and the zirconia beads were then filtered to prepare a coating composition.

[0138] Additionally, a 55 / 45 mixture of NMP and water was used to prepare a phase separation liquid. The coating composition was applied to both sides of a polyethylene separator, and the coated separator was immersed in the phase separation liquid for 3 minutes. The separator was then immersed in water for 3 minutes and dried in an oven at 80°C for 30 minutes to produce a coated separator. The air permeability and area retention of the produced separator were measured. The results are shown in Table 1.

[0139] Example 2 A separator was produced 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 mixed in a container in proportions of 15.4 parts by mass, 23.1 parts by mass, and 61.5 parts by mass, respectively, and the resulting separator was evaluated. The results are shown in Table 1.

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

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

[0142] Example 6 After polymer c, magnesium oxide powder (average particle size 0.54 μm), and N-methylpyrrolidone (NMP) were mixed in a container in proportions of 10.0 parts by mass, 15.0 parts by mass, and 75.0 parts by mass, respectively, a separator was produced 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 produced 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 produced 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 sheet) was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0146]

Claims

1. A composition for coating a separator for an electrochemical device, comprising a copolymer containing a fluoromonomer unit and an amide bond-containing monomer unit, wherein the content of the fluoromonomer unit in the copolymer is 75 to 7 mol % based on the total monomer units, and the content of the amide bond-containing monomer unit in the copolymer is 25 to 93 mol % based on the total monomer units.

2. 2. The composition according to claim 1, wherein the fluoromonomer is at least one member selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and 2,3,3,3-tetrafluoropropene.

3. The composition according to claim 1 or 2, wherein the amide bond-containing monomer has a lactam ring.

4. 3. The composition according to claim 1, wherein the amide bond-containing monomer is N-vinyl-2-pyrrolidone.

5. The composition according to claim 1 or 2, further comprising an inorganic filler.

6. 3. The composition according to claim 1, further comprising an inorganic filler containing at least one element selected from the group consisting of Mg, Al, Si, Ti, Zr and Ba.

7. The composition according to claim 1 or 2, further comprising an inorganic filler, and a content ratio of the copolymer to the inorganic filler (copolymer):(inorganic filler) is 0.1:99.9 to 49.9:50.1 in mass ratio.

8. The composition according to claim 1 or 2, further comprising a solvent.

9. A separator for an electrochemical device comprising a substrate and a coating layer formed from the composition according to claim 1 or 2.

10. The separator for electrochemical devices according to claim 9, wherein the substrate is made of an organic material.

11. An electrochemical device comprising the separator for electrochemical devices according to claim 9 .

12. A secondary battery comprising the separator for an electrochemical device according to claim 9.