Powder composition based on at least one fluoropolymer and at least one hydrophilic polymer for separator coating - Patent Application 20070122997

Abstract

The present invention relates to a polymer P1 comprising monomer units derived from vinylidene fluoride and optionally a comonomer M1 compatible with vinylidene fluoride, and a polymer of formula R 1 R 2 C=C(R 3 )C(O)R monomers M2, in which the substituent R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR', R' is H and a C1-C5 alkyl optionally substituted with one or more -OH groups or a 5- or 6-membered heterocycle containing at least one nitrogen atom in its cyclic chain. 18 and a polymer P2 comprising monomer units derived from a monomer M2 selected from the group consisting of alkyl, wherein the composition has a crystallization temperature Tc<-3.7496x+130, where x is the content by weight of comonomer M1 relative to the total weight of polymer P1, and wherein the composition is in powder form.

Description

[Technical Field]

[0001] The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of the Li-ion type. More specifically, the present invention relates to a composition that can be used as a separator coating. [Background technology]

[0002] Lithium-ion batteries also include a separator disposed between the cathode and anode. The separator must have a low thickness, sufficient mechanical strength and temperature resistance, good electrochemical resistance to the voltages to which the separator is exposed, optimal affinity for the electrolyte, and more generally, enable excellent ionic conductivity. Polyvinylidene fluoride (PVDF) and its derivatives are advantageous as polyolefin separator coatings due to their electrochemical stability and their high dielectric constant, which promotes ionic dissociation and therefore electrical conductivity. U.S. Patent Application Publication No. 2015 / 0155539 discloses a separator based on a PVDF copolymer grafted with side chains containing hydrophilic units.

[0003] There remains a need to develop new coatings for separators that are easy to use and have a good compromise between dry adhesion, wet adhesion, ionic conductivity, and thermal stability.

[0004] SUMMARY OF THE INVENTION Accordingly, the present invention aims to overcome at least one of the drawbacks of the prior art. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2015 / 0155539 Summary of the Invention [Means for solving the problem]

[0006] According to a first aspect, the present invention provides a polymer P1 comprising monomer units derived from vinylidene fluoride and optionally from a vinylidene fluoride-compatible comonomer M1, and a copolymer of formula R 1 R 2 C=C(R 3 )C(O)R monomers M2, in which the substituent R 1 , R 2 and R 3 are each independently selected from the group consisting of H and C1-C5 alkyl, R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR', R' is H and a C1-C5 alkyl optionally substituted with one or more -OH groups or a 5- or 6-membered heterocycle containing at least one nitrogen atom in its ring chain. 18 and a polymer P2 comprising monomer units derived from a monomer M2 selected from the group consisting of alkyl, wherein the composition has a crystallization temperature Tc<-3.7496x+130, where x is the mass content of comonomer M1 based on the total weight of the polymer P1, and the composition is in the form of a powder. The crystallization temperature Tc is determined according to standard ASTM D3418.

[0007] The present invention provides compositions that, when used in the implementation of separator compositions, have a good compromise between different properties, such as adhesion, electrical conductivity, and thermal stability. In particular, the production of compositions whose crystallization temperatures comply with the above equation allows the desired properties to be achieved. In some cases, the compositions may not have a crystallization temperature that can be measured by DSC according to standard ASTM D3418, but these compositions are included in the compositions according to the present invention because their crystallization temperature is considered to be zero. This type of composition can be obtained with a high mass content of the comonomer M1 in the polymer P1, for example, a mass content of more than 20 wt. % based on the total weight of the polymer P1.

[0008] According to a preferred embodiment, the particles of said composition have an average diameter of between 1 and 100 μm, preferably between 5 and 75 μm and more preferentially between 5 and 50 μm.

[0009] According to a preferred embodiment, the mass ratio P1 / P2 ranges from 95 / 5 to 5 / 95, advantageously from 95 / 5 to 25 / 75, preferably from 95 / 5 to 40 / 60, in particular from 95 / 5 to 50 / 50.

[0010] According to a preferred embodiment, said polymer P1 is selected from the group consisting of vinylidene fluoride homopolymers and copolymers based on vinylidene fluoride and on at least one comonomer M1 compatible with vinylidene fluoride.

[0011] According to a preferred embodiment, said at least one comonomer M1 compatible with vinylidene fluoride is selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ethers, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, chlorotrifluoropropene and ethylene or mixtures thereof.

[0012] According to a preferred embodiment, the polymer P1 comprises monomer units having at least one functional group selected from the group consisting of carboxylic acids, carboxylic anhydrides, carboxylic esters, epoxy groups, amide groups, hydroxyl groups, carbonyl groups, mercapto groups, sulfide groups, oxazoline groups, phenol groups, ester groups, ether groups, siloxane groups, sulfonic groups, sulfuric groups, phosphoric groups or phosphonic groups, preferably monomer units having at least one functional group selected from the group consisting of carboxylic acids, carboxylic anhydrides, carboxylic esters, hydroxyl groups, carbonyl groups and mercapto groups.

[0013] According to a preferred embodiment, the polymer P2 is selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxy acrylate. The copolymer contains monomer units derived from a monomer selected from the group consisting of ethyl, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureido methacrylate, and mixtures thereof.

[0014] According to a preferred embodiment, the crystallization temperature of said composition is Tc<-3.7496x+128, where x is the mass content of comonomer M1 based on the total weight of said polymer P1.

[0015] According to another aspect, the present invention provides a separator for an electrochemical device selected from the group: Li-ion, capacitor, electric double layer capacitor, and fuel cell membrane electrode assembly (MEA), said separator comprising a porous support and the composition according to the present invention.

[0016] According to a preferred embodiment, the composition has a mass ratio P1 / P2 ranging from 95 / 5 to 5 / 95.

[0017] According to another aspect, the present invention provides a Li-ion secondary battery comprising an anode, a cathode, and a separator, the separator being according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] composition According to a first aspect of the present invention, there is provided a composition comprising a polymer P1 and a polymer P2. The polymer P1 is a fluoropolymer, i.e., a polymer comprising monomer units containing at least one fluorine atom. The polymer P2 is a polymer comprising monomer units containing at least one hydrophilic group. The polymers P1 and P2 may be in crosslinked or non-crosslinked form and may be linear or branched.

[0019] According to a preferred embodiment, the composition comprising said polymers P1 and P2 and having a crystallization temperature as defined in the present invention makes it possible to achieve a good compromise of the targeted properties as a function of the application in which the composition is to be used. Thus, as demonstrated in this patent application, when the composition is used in a separator, it makes it possible to achieve a good compromise between dry adhesion and solvent resistance.

[0020] Advantageously, the above target properties are obtained when the crystallization temperature of the composition is Tc<-3.7496x+128, where x is the comonomer M1 mass content based on the total weight of the polymer P1. Preferably, the crystallization temperature of the composition is Tc<-3.7496x+126, where x is the comonomer M1 mass content based on the total weight of the polymer P1. More preferably, the crystallization temperature of the composition is Tc<-3.7496x+124, where x is the comonomer M1 mass content based on the total weight of the polymer P1. In particular, the crystallization temperature of the composition is Tc<-3.7496x+122, where x is the comonomer M1 mass content based on the total weight of the polymer P1. More specifically, the crystallization temperature of the composition is Tc<-3.7496x+120, where x is the comonomer M1 mass content based on the total weight of the polymer P1. In a preferred manner, the crystallization temperature of the composition is Tc<-3.7496x+118, where x is the mass content of the comonomer M1 based on the total weight of the polymer P1. In an advantageously preferred manner, the crystallization temperature of the composition is Tc<-3.7496x+116, where x is the mass content of the comonomer M1 based on the total weight of the polymer P1. In a preferentially preferred manner, the crystallization temperature of the composition is Tc<-3.7496x+115, where x is the mass content of the comonomer M1 based on the total weight of the polymer P1.

[0021] Preferably, in the composition, the weight ratio of polymer P1 to polymer P2 ranges from 95 / 5 to 5 / 95, advantageously from 95 / 5 to 25 / 75, preferably from 95 / 5 to 40 / 60, more preferentially from 95 / 5 to 50 / 50, in particular from 95 / 5 to 60 / 40, more preferably from 90 / 10 to 65 / 35.

[0022] Unless otherwise stated, the contents given are expressed on a weight basis. All ranges given are inclusive of the limits unless otherwise indicated.

[0023] i) Polymer P1 Preferably, said polymer P1 is based on vinylidene fluoride monomer (CF2=CH2 or VDF), i.e. comprises monomer units derived from vinylidene fluoride. Said polymer P1 may also be designated by the abbreviation PVDF.

[0024] According to one embodiment, the polymer P1 is a vinylidene fluoride homopolymer, in which case x is equal to 0 and the crystallization temperature of said composition is below 130°C.

[0025] According to another embodiment, the polymer P1 is a copolymer of vinylidene fluoride with at least one comonomer M1 that is compatible with vinylidene fluoride, which comonomer M1 may be halogenated (fluorinated, chlorinated or brominated) or non-halogenated. Examples of suitable fluorinated comonomers M1 are vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trifluoropropene and in particular 3,3,3-trifluoropropene, tetrafluoropropene and in particular 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene and in particular 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene, perfluoroalkyl vinyl ethers and in particular those of the general formula Rf-O-CF=CF2, where Rf is an alkyl group, preferably a C1-C4 alkyl group (preferred examples are perfluoropropyl vinyl ether and perfluoromethyl vinyl ether).

[0026] The fluorinated comonomer may contain chlorine or bromine atoms. The fluorinated comonomer may be selected from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Chlorofluoroethylene may represent either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0027] The VDF copolymer may also contain non-halogenated monomers such as ethylene and / or acrylic or methacrylic comonomers.

[0028] The polymer P1 preferably contains at least 50 mol % of vinylidene fluoride, advantageously at least 60 mol % of vinylidene fluoride, preferably at least 70 mol % of vinylidene fluoride. The comonomer M1 may be present in a content of from 1% to 50% by weight, advantageously from 2% to 30% by weight, relative to the weight of said polymer P1.

[0029] According to one embodiment, polymer P1 is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)) with a weight percentage of hexafluoropropylene monomer units of 2% to 30% by weight, advantageously 2% to 25% by weight, preferably 2% to 20% by weight, preferably 4% to 15% by weight, relative to the weight of said polymer P1. According to another embodiment, polymer P1 is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)) with a weight percentage of hexafluoropropylene monomer units of 20% to 30% by weight, advantageously 20% to 25% by weight, relative to the weight of said polymer P1.

[0030] According to one embodiment, the polymer P1 is a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE).

[0031] According to one embodiment, the polymer P1 is a copolymer of vinylidene fluoride and chlorotrifluoroethylene (CTFE).

[0032] According to one embodiment, polymer P1 is a VDF-TFE-HFP terpolymer. According to one embodiment, polymer P1 is a VDF-TrFE-TFE terpolymer (TrFE is trifluoroethylene). In these terpolymers, the VDF mass content is at least 10% and the comonomers are present in variable proportions.

[0033] According to one embodiment, polymer P1 comprises monomer units having at least one of the following functional groups: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfate, phosphate, or phosphonic acid. The functional groups are introduced by techniques well known to those skilled in the art, such as grafting or copolymerization of vinylidene fluoride (VDF) monomers with monomers having at least one of the functional groups and a vinyl function capable of copolymerizing with VDF monomers, or by adsorption of a functionalized polymer into polymer P1. Preferably, the monomer units are derived from a polymer containing the monomer units and having a molar mass of less than 100,000 g / mol, preferably less than 50,000 g / mol, in particular less than 20,000 g / mol. The latter can be grafted onto said polymer P1 or can be adsorbed by said polymer P1.

[0034] According to one embodiment, the functional groups have carboxylic acid functions, which are (meth)acrylic acid type groups selected from acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxyethylhexyl (meth)acrylate. Thus, said polymer P1 may comprise monomer units derived from monomers selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxyethylhexyl methacrylate.

[0035] According to one embodiment, the units bearing a carboxylic acid functionality also contain heteroatoms selected from oxygen, sulfur, nitrogen and phosphorus.

[0036] According to one embodiment, the functionality is introduced via a transfer agent used during the synthesis process. Preferably, the transfer agent has a molar mass of 20,000 g / mol or less and is a polymer containing functional groups selected from carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfate, phosphate, and phosphonic acid groups, preferably carboxylic acid, carboxylic anhydride, and carboxylic ester. An example of this type of transfer agent is an oligomer of acrylic acid. The transfer agent can be grafted onto the polymer P1 or adsorbed by the polymer P1.

[0037] The polymer P1 may contain end groups formed from the transfer agent. In particular, the transfer agent is a polymer having a molar mass of 20,000 g / mol or less and having a functional group selected from the group consisting of carboxylic acids or carboxylic acid esters. The molar mass of the transfer agent can be determined by GPC analysis performed on a Waters 2695e instrument coupled to a Wyatt NEON refractometer equipped with two PL Gel mixed C columns and a guard column (7.8 mm x 30 cm, 5 μm internal diameter) under the following conditions: temperature: 35°C; flow rate: 1.0 mL / min; injection volume: 100 μL; concentration: 1 mg / mL in THF (HPLC grade); calibration using 12 samples of poly(methyl methacrylate) ranging from 535 to 2,210,000 g / mol.

[0038] The functional group content of said polymer P1 is at least 0.01 mol %, preferably at least 0.1 mol %, and not more than 15 mol %, preferably not more than 10 mol %.

[0039] The polymer P1 preferably has a high molecular weight. As used herein, the term "high molecular weight" refers to a polymer that has been subjected to a tensile test at 232°C and 100 seconds according to the ASTM D-3835 method. -1 is understood to mean a polymer P1 having a melt viscosity, measured at 100 Pa.s, preferably at 500 Pa.s and more preferably at 1000 Pa.s.

[0040] According to one embodiment, the polymer P1 having functional groups can undergo crosslinking by self-condensation of the functional groups or by reaction with known low molecular weight crosslinkers such as catalysts and / or crosslinkers, such as melamine resins, epoxy resins, di- or higher polyisocyanates, polyaziridines, polycarbodiimides, polyoxazolines, dialdehydes such as glyoxal, acetoacetates, malonates, acetals, thiols and di- and trifunctional acrylates, cycloaliphatic epoxy molecules, organosilanes such as epoxysilanes and aminosilanes, carbamates, diamines and triamines, inorganic chelating agents such as certain zinc and zirconium salts, titaniums, glycolils and other aminoplasts. In some cases, functional groups from other polymerization components, such as surfactants, initiators or seed particles, can participate in the crosslinking reaction. When two or more functional groups are involved in the crosslinking process, pairs of complementary reactive groups are, for example, hydroxyl-isocyanate, acid-epoxy, amine-epoxy, hydroxyl-melamine, acetoacetate-acid. The acrylate and / or methacrylate monomers that do not contain functional groups capable of participating in a crosslinking reaction after polymerization should preferably represent 70% or more by weight of the total mixture of monomers, more preferably more than 90% by weight. According to one embodiment, the polymer P1 comprises a crosslinker selected from the group consisting of isocyanates, diamines, adipic acid, dihydrazides, and combinations thereof.

[0041] According to one embodiment, the PVDF homopolymer and VDF copolymer are composed of bio-based VDF. The term "bio-based" means "derived from biomass." This allows for an improved ecological footprint of the separator. Bio-based VDF is produced in accordance with the standard NF EN 16640. 14It may be characterized by a content of renewable carbon, i.e. of naturally occurring carbon derived from biological materials or biomass, of at least 1 at% as determined by the C content. The term "renewable carbon" indicates that the carbon is of natural origin and derived from biological materials (or biomass), as indicated below. According to an embodiment, the biocarbon content of the VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than 33%, preferably greater than 50%, preferably greater than 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, and advantageously equal to 100%.

[0042] The P1 homopolymers and VDF copolymers used in the present invention can be obtained by known polymerization methods such as emulsion or suspension polymerization.

[0043] According to one embodiment, the P1 homopolymer and VDF copolymer used in the present invention are prepared by an emulsion polymerization process in the absence of fluorinated surfactants.

[0044] Polymerization of vinylidene fluoride preferably results in a latex having a solids content of generally 10% to 60% by weight, preferably 10% to 50%, and a weight-average particle size of less than 1 micrometer, preferably less than 1000 nm, preferably less than 800 nm, and more preferably less than 600 nm. The weight-average particle size is generally at least 20 nm, preferably at least 50 nm, and advantageously the average size is in the range of 100 to 400 nm. The polymer particles can form agglomerates, the weight-average size of which is 1 to 30 micrometers, preferably 2 to 20 micrometers. The agglomerates can be broken down into discrete particles during formulation and application to a substrate.

[0045] ii) Polymer P2 As mentioned above, the polymer P2 has the formula R 1 R 2 C=C(R 3)C(O)R monomers M2, in which the substituent R 1 , R 2 and R 3 are each independently selected from the group consisting of H and C1-C5 alkyl, R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR', R' is H and a C1-C5 alkyl optionally substituted with one or more -OH groups or a 5- or 10-membered heterocycle containing at least one nitrogen atom in its ring chain. 18 The heterocycle may comprise a monomer unit resulting from a monomer M2 selected from the group consisting of alkyl. The heterocycle may be saturated, unsaturated, or aromatic. The heterocycle may be monocyclic or bicyclic. The heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone ring. The heterocycle may be substituted with one or more C1-C5 alkyl groups. As described above, the C1-C5 alkyl groups may be substituted with one or more C1-C5 alkyl groups. 18 The alkyl is optionally substituted with said heterocycle. The latter may be linked to the alkyl chain via a nitrogen atom or any other atom forming the heterocycle. Preferably, the heterocycle is 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone or 4-imidazolidinone.

[0046] Preferably, the polymer P2 has the formula R 1 R 2 C=C(R 3 )C(O)R alkyl (meth)acrylate monomers M2, wherein the substituent R 1 , R 2 and R 3 are each independently selected from the group consisting of H and C1-C5 alkyl, R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR', R' is a C1-C5 alkyl optionally substituted with one or more -OH groups or a 5- or 10-membered heterocycle containing at least one nitrogen atom in its ring chain. 18The polymer P2 comprises monomer units resulting from an alkyl (meth)acrylate monomer M2 selected from the group consisting of alkyl (meth)acrylates of formula R 1 R 2 C=C(R 3 )C(O)R alkyl (meth)acrylate monomers M2, wherein the substituent R 1 , R 2 and R 3 are each independently selected from the group consisting of H and C1-C5 alkyl, R is -OR', R' is H and C1-C5 alkyl optionally substituted with one or more -OH groups; 18 The heterocycle comprises monomer units derived from an alkyl (meth)acrylate monomer M2 selected from the group consisting of alkyl. Preferably, the heterocycle is as defined above, in particular, the heterocycle is 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone or 4-imidazolidinone. The term "alkyl (meth)acrylate" refers to alkyl acrylate and alkyl methacrylate.

[0047] According to a preferred embodiment, the substituent R' is selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxyethyl, hydroxybutyl, hydroxypropyl and ethyl substituted with a ureido, hydroxyethyl, hydroxypropyl or hydroxybutyl group.

[0048] In particular, said polymer P2 has the formula R 1 R 2 C=C(R 3 )C(O)R alkyl (meth)acrylate monomers M2, wherein the substituent R 1 and R 2 is H and R 3is H or CH3, R is -OR', and R' comprises a monomer unit derived from an alkyl (meth)acrylate monomer M2 selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone, and 4-imidazolidinone.

[0049] Thus, the alkyl (meth)acrylate may be methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ureido methacrylate, or a mixture thereof. Among these, alkyl acrylates in which the alkyl group contains 1 to 8 carbon atoms are preferred, and alkyl acrylates in which the alkyl group contains 1 to 5 carbon atoms are more preferred. These compounds may be used alone or in mixtures of two or more. Thus, the polymer P2 may be a homopolymer of the monomer M2 defined above or a copolymer derived from a mixture of one or more monomers M2 defined above.

[0050] As used herein, the term "acrylate" includes acrylates and methacrylates.

[0051] The optional ethylenically unsaturated compounds copolymerizable with the alkyl acrylate and alkyl methacrylate are: (A) an alkenyl compound containing a functional group, and -(B) Alkenyl compounds without functional groups Includes:

[0052] Examples of the alkenyl compound (A) containing a functional group include α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, crotonic acid, and itaconic acid; vinyl ester compounds such as vinyl acetate and vinyl neodecanoate; and alkynyl compounds such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, and diacetoneacrylamide. These include amide compounds; acrylic acid esters such as 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, and fluoroalkyl acrylate; and methacrylic acid esters such as dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, and ethylene glycol dimethacrylate; and alkenyl glycidyl ether compounds such as maleic anhydride and allyl glycidyl ether. Among these, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and allyl glycidyl ether are preferred. These compounds may be used alone or in combination.

[0053] Examples of the non-functional alkenyl compound (B) include conjugated dienes such as 1,3-butadiene and isoprene; divinyl hydrocarbon compounds such as divinylbenzene; and alkenyl cyanides such as acrylonitrile and methacrylonitrile. Among these, preferred compounds are 1,3-butadiene and acrylonitrile. These compounds may be used alone or as a mixture of two or more.

[0054] The functional alkenyl compound (A) is preferably used in a proportion of less than 50% by weight, based on the weight of the monomer mixture, and the non-functional alkenyl compound (B) is preferably used in a proportion of less than 30% by weight, based on the weight of the monomer mixture.

[0055] Methods for preparing compositions The composition according to the present invention comprises: a) providing a reactor containing said polymer P1 comprising monomer units derived from vinylidene fluoride; b) Formula R as defined in this patent application 1 R 2 C=C(R 3 ) adding at least one monomer M2 of C(O)R to the reactor and contacting the polymer P1 with the at least one monomer M2 for at least 5 minutes; c) carrying out the polymerization of said at least one monomer M2 to form a composition comprising said polymer P1 and polymer P2 as defined in the present application; d) drying and optionally grinding the composition obtained in step c) to prepare the composition according to the invention. It can be prepared via a method comprising:

[0056] The polymer P1 is preferably in the form of a latex.

[0057] During step b), a compound of formula R as defined in the present patent application is 1 R 2 C=C(R 3 At least one monomer M2 of the formula R(O)R is added to the reactor. 1 R 2 C=C(R 3If the polymer P2 contains different monomer units of the formula (C(O)R), then preferably all of the constituent monomers of polymer P2 are added during step b). The addition of all of the at least one constituent monomer M2 of polymer P2 in step b) allows for improved intimacy of the mixture between polymer P1 and all of the constituent monomer units of polymer P2. Preferably, the at least one monomer M2 is selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxybutyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ureido methacrylate, and combinations thereof. Step b) may optionally also comprise the addition of alkenyl compounds (A) and / or (B) as described above for polymer P2.

[0058] During step b), the polymer P1 and the at least one monomer M2 are contacted for a time long enough to allow the monomer M2 to penetrate the particles of the polymer P1 before their polymerization. This contact time is at least 5 minutes, preferably 10 minutes, in particular at least 15 minutes, more particularly at least 20 minutes. Preferably, the monomer M2 is added before the initiator. This allows the preferred compositions of the present invention to be obtained.

[0059] The method also includes step c) during which the at least one monomer M2 is polymerized. Step c) is preferably carried out in the presence of water. Step c) of polymerizing the at least one monomer M2 is carried out in the presence of an initiator. The initiator may be a persulfate type initiator such as sodium persulfate, potassium persulfate, barium persulfate, or ammonium persulfate; an alkali metal bisulfite; a peroxide such as benzoyl peroxide or dicumyl peroxide; a hydroperoxide such as methyl hydroperoxide or tert-butyl hydroperoxide; an acyloin such as benzoin; a peracetate such as methyl peracetate or tert-butyl peracetate; a perbenzoate such as tert-butyl perbenzoate; a peroxalate such as dimethyl peroxalate or di(tert-butyl) peroxalate; or an azo compound initiator such as azobisisobutyronitrile or dimethyl azobisisobutyrate. The initiator is preferably added in a content of 0.005% to 1% by weight, based on the weight of said at least one monomer M2 and, if present, optionally said alkenyl compounds (A) and (B).

[0060] Optionally, step c) is carried out in the presence of a chain transfer agent. The chain transfer agent may be an oxygen-containing compound such as an alcohol, carbonate, ketone, ester, or ether; a halocarbon or hydrohalocarbon compound such as a chlorocarbon, hydrochlorocarbon, chlorofluorocarbon, or hydrochlorofluorocarbon; or ethane or propane. Alternatively, the chain transfer agent may be a polymer having a molar mass of 20,000 g / mol or less and having functional groups selected from the following groups: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, and phosphonic acid groups. An example of this type of transfer agent is an oligomer of acrylic acid. Preferably, when a chain transfer agent is present, it is added in a content of 0.05% to 5% by weight, based on the weight of the at least one monomer M2 and, if present, the optional alkenyl compounds (A) and (B).

[0061] Other compounds may also be present in the practice of the composition according to the present methods, as referenced in the protocols described in WO 2007 / 018783.

[0062] Step c) may be carried out at a temperature of 20° C. to 160° C. Step c) may be carried out at a pressure of 280 to 20,000 kPa.

[0063] Preferably, steps b) and c) are carried out with stirring.

[0064] The composition obtained in step c) is preferably in the form of a latex, i.e., a dispersion in an aqueous medium. Thus, the composition is an aqueous dispersion obtained by emulsion polymerization in an aqueous medium of 5 to 100 parts by weight, preferably 5 to 95 parts by weight, of a monomer mixture containing at least one monomer M2 selected from the group consisting of alkyl acrylates, alkyl methacrylates, whose alkyl groups contain 1 to 18 carbon atoms, and optionally, ethylenically unsaturated compounds copolymerizable with the alkyl acrylates and alkyl methacrylates, in the presence of 100 parts by weight of particles of polymer P1 as defined above. The particles of polymer P1 function as seeds for the polymerization of monomer M2. As long as they are dispersed in the aqueous medium in the form of particles, the particles of polymer P1 can be added to the polymerization system in an optional state. Since polymer P1 is generally produced in the form of an aqueous dispersion, it is advantageous to use the aqueous dispersion as produced as seed particles.

[0065] The polymerization product obtained in step c) is dried in step d). The drying step can be carried out by spraying or co-spraying, preferably at temperatures between 100°C and 220°C. Powders can also be obtained by grinding techniques such as cryomilling, in which the mixture is brought to a temperature below ambient temperature, for example using liquid nitrogen, before grinding. At the end of the powder-producing step, i.e., after the drying step, the particle size can be adjusted and optimized by a selection or sieving process and / or by grinding. In the composition obtained in step d), the particles have an average diameter of 1 to 100 μm, preferably 5 to 75 μm, and more preferentially 5 to 50 μm. The average particle diameter is determined by laser particle size analysis using a Malvern INSITEC System analyzer. The measurement is carried out by laser diffraction on the powder at a focal length of 100 mm. In the composition, the P1 and P2 polymer chains are entangled to form an interpenetrating polymer network (IPN) as defined by IUPAC, which is different from a preformed mixture of polymers. Preferably, the P1 and P2 polymer chains are entangled to form a continuous interpenetrating polymer network as defined by IUPAC.

[0066] Separator The composition according to the present invention can be used as one of the materials for preparing separators in electrochemical devices. In this application, the mass ratio P1 / P2 is preferably in the range of 95 / 5 to 5 / 95, in particular 95 / 5 to 40 / 60, more preferably 90 / 10 to 50 / 50. Preferably, polymer P1 is a copolymer of vinylidene fluoride and at least one comonomer compatible with vinylidene fluoride, as described above. In particular, polymer P1 may be a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), or a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE), or a copolymer of vinylidene fluoride and chlorotrifluoroethylene (CTFE), or a VDF-TFE-HFP terpolymer as defined above, with a weight percentage of hexafluoropropylene monomer units of 2% to 30% by weight, advantageously 2% to 25% by weight, and preferably 2% to 20% by weight, relative to the weight of polymer P1. Furthermore, polymer P1 may comprise monomer units selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxyethylhexyl methacrylate.

[0067] The composition is preferably used in a separator coating. In addition to the composition, the separator coating may contain inorganic particles that form micropores (gaps between inorganic particles) in the coating. The addition of inorganic particles can contribute to heat resistance and improve wettability. According to one embodiment, the coating contains 50% to 99% by weight of inorganic particles based on the weight of the coating. These inorganic particles must be electrochemically stable (not subject to oxidation and / or reduction within the voltage range used). Furthermore, the powdered inorganic material preferably has high ionic conductivity. Low-density materials are preferred over higher-density materials because they can reduce the weight of the produced battery. The dielectric constant is preferably 5 or greater. According to one embodiment, the inorganic particles are selected from BaTiO3, Pb(Zr,Ti)O3, Pb 1-x Lax Zr y O3(0 <x<1,0<y<1)、PbMg3Nb 2 / 3 )3, PbTiO3, hafnia (HfO(HfO2)), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, YO3, boehmite (γ-AlO(OH)), Al2O3, TiO2, SiC, ZrO2, boron silicate, BaSO4, nanoclay or mixtures thereof. In this case, the ratio of the solids of polymers P1 and P2 to the inorganic particles is 0.5 to 40 parts by weight of the solids of polymers P1 and P2 per 60 to 99.5 parts by weight of the inorganic particles. Advantageously, the ratio of the solids of polymers P1 and P2 to the inorganic particles is 0.5 to 35 parts by weight per 65 to 99.5 parts by weight of the inorganic particles. Preferably, the solids ratio of polymers P1 and P2 to the inorganic particles is 0.5 to 30 per 70 to 99.5 parts by weight of the inorganic particles. The separator coating may optionally contain 0 to 15% by weight, preferably 0.1 to 10% by weight, based on the polymer, of an additive selected from thickeners, pH adjusters, anti-settling agents, surfactants, wetting agents, fillers, anti-foaming agents, and temporary or non-temporary adhesion promoters. The fillers listed here as additives are different from the inorganic particles listed above.

[0068] The separator according to the present invention comprises the above-described coating, optionally disposed on one or both surfaces of a porous support. In this case, the coating is used to coat the separator support in the form of a single layer or multiple layers on at least one surface. There are no particular limitations on the choice of support to be coated with the coating of the present invention, as long as the support is a porous substrate having pores. The support may comprise a single layer or several separate layers. If the support comprises several layers, the coating according to the present invention is disposed on the outer surface of the support, i.e., on the surface that first comes into contact with the electrolyte composition used in the battery. Advantageously, the coating is applied to the support by an aqueous route or a solvent route. The porous substrate may be in the form of a membrane or a fibrous fabric. If the porous substrate is fibrous, it may be a nonwoven web forming a porous web, such as a web obtained by direct spinning or by meltblowing (spunbond or meltblown type) or electrospinning. Examples of porous substrates useful as supports in the present invention include, but are not limited to, polyolefins, polyethylene terephthalate, polybutylene terephthalate, polyesters, polyacetals, polyamides, polycarbonates, polyimides, polyether ether ketones, polyether sulfones, poly(phenylene oxide), poly(phenylene sulfide), polyethylene naphthalate, or mixtures thereof. However, other heat-resistant engineering plastics may also be used, without particular limitation. Nonwoven materials made from natural or synthetic materials may also be used as separator substrates. The porous substrate generally has a thickness of 1 to 50 μm and is typically a membrane obtained by extrusion and pultrusion (wet or dry processes) or cast nonwoven fabrics. The porous substrate preferably has a porosity of 5% to 95%. The average pore size (diameter) is preferably 0.001 to 50 μm, more preferably 0.01 to 10 μm.

[0069] According to an alternative embodiment, the separator does not include a porous support. In this case, the separator consists of a coating comprising the above-described composition and placed directly on the cathode or anode of an electrochemical device. The absence of a porous support allows for reduced production costs and dimensions of the electrochemical device. In this case, the coating replaces the porous support. In this embodiment, the polymer resin preferably has a porosity of 5% to 95%. The average size of the pores in the polymer resin is preferably 0.001 to 50 μm, more preferably 0.01 to 10 μm.

[0070] According to another alternative embodiment, the separator does not include a porous support, and the separator is in the form of a gel. The separator is as described in this patent application. The separator is formed in the form of a gel by conventional techniques such as solvent casting or extrusion. The separator coating of the present invention has an excellent compromise of properties for separator coating applications: good dry and wet adhesion, good resistance to electrolyte solvent(s) characterized by good preserved integrity, and moderate swelling. [Example]

[0071] The crystallization temperature is measured by DSC during cooling according to the following program: Heats from 10°C to 200°C at 10°C / min. -Hold at 200℃ for 1 minute Cools from 200°C to -80°C at 5°C / min.

[0072] Preparation of the composition according to the present invention (Example 1) The polymer P1 used in Example 1 is a latex of P(VDF-HFP) copolymer. It is used as a seed for synthesizing the composition according to the present patent application via an emulsion polymerization process according to the protocol described in WO 2007 / 018783 A1, in the presence of a chain transfer agent of the acrylic acid oligomer type having a molar mass of less than 20,000 g / mol. The monomer M2 used to prepare the polymer P2 in Example 1 is a mixture of methyl (meth)acrylate, ethyl acrylate, and methacrylic acid in a mass ratio of 58 / 40 / 2. Before polymerization of the monomer M2, the monomer M2 is contacted with the polymer P1 for 25 minutes. The resulting composition is dried by co-spraying and milled to obtain particles with an average diameter of 10 to 25 μm, as determined by laser particle size analysis.

[0073] Preparation of latex mixture (Example 2 - comparative composition): Polymer P1 and polymer P2 are prepared independently of each other via emulsion polymerization process. In this example, polymer P2 is prepared in the absence of polymer P1 seeds. The two polymers in the form of latex are then mixed in a 70 / 30 ratio. The composition of polymer P1 and polymer P2 is the same as that of polymer P1 and polymer P2 in Example 1. The resulting composition is dried by co-spraying.

[0074] Comparative composition of Example 3 Example 3 is carried out using a composition consisting of the polymer P1 of Example 1 in the form of a latex.

[0075] Preparation of the Coating Composition The indicated powder (100 parts) is added to an aqueous solution (900 parts) of thickener (CMC250k-(4.5 parts)) and dispersant (BYK2055-(2 parts)), and then dispersed under high shear (Thinky mixer 2000 rpm / 5 min in the presence of zirconia beads) to obtain a dispersion of fine polymer particles in water. Then, only for compositions that do not already contain acrylic in the latex, other additives are added - wetting agent (BYK 349-(1.8 parts)), adhesion promoter (BYK LPC-22346, already supplied in a 50% solution (6 parts)), and then mixing is carried out under low shear (magnetic stirrer).

[0076] Coating Application: Each coating composition is applied to a porous separator (Celgard H2512) using a coater equipped with a spiral bar, depositing 6 μm (wet thickness) at a rate of approximately 25 mm / sec, and then allowed to dry at ambient temperature for 24 hours.

[0077] The results are shown in Table 1 below.

[0078] [Table 1]

[0079] The separator coating according to the present invention has an excellent compromise of properties for the intended application: good dry adhesion, good resistance to the electrolyte solvent(s) characterized by good preserved integrity. On the other hand, the comparative examples, which have crystallization temperatures higher than the value defined by the formula -3.7496x+130, exhibit at least one very unfavorable property.

Claims

1. A polymer P1 comprising monomer units derived from vinylidene fluoride and optionally a vinylidene fluoride compatible comonomer M1, and the formula R １ R ２ C═C(R ３ )C(O)R, wherein the substituents R １ , R ２ and R ３ are each independently selected from the group consisting of H and C １ -C ５ alkyl, and R is selected from the group consisting of -NHC(CH ３ ) ２ CH ２ C(O)CH ３ or -OR', where R' is selected from the group consisting of H and C １ -C １８ alkyl optionally substituted with one or more -OH groups or a 5- or 6-membered heterocyclic ring containing at least one nitrogen atom in its ring chain, a polymer P2 comprising monomer units derived from monomer M2, a composition comprising the polymer P2, wherein the crystallization temperature of the composition is Tc < -3.7496x + 130, where x is the mass content ratio of the comonomer M1 based on the total weight of the polymer P1, and the composition is in the form of a powder.

2. The composition according to claim 1, characterized in that the particles of the composition have an average diameter of 1 to 100 μm.

3. The composition according to claim 1, characterized in that the mass ratio P1 / P2 is in the range of 95 / 5 to 5 / 95.

4. The composition according to claim 1, characterized in that the polymer P1 is selected from the group consisting of vinylidene fluoride homopolymers and copolymers based on vinylidene fluoride and at least one comonomer M1 compatible with vinylidene fluoride.

5. The composition according to claim 4, characterized in that the at least one comonomer M1 compatible with vinylidene fluoride is selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, chlorotrifluoropropene, and ethylene or mixtures thereof.

6. The composition according to claim 1, characterized in that the polymer P1 comprises a monomer unit having at least one functional group selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid ester, epoxy group, amide group, hydroxyl group, carbonyl group, mercapto group, sulfide group, oxazoline group, phenol group, ester group, ether group, siloxane group, sulfonic acid group, sulfate group, phosphoric acid group, or phosphonic acid group.

7. The polymer P2 is methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid The composition according to claim 1, characterized by comprising monomer units derived from monomer M2 selected from the group consisting of methylacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureid methacrylate, and mixtures thereof.

8. The composition according to claim 1, characterized in that the crystallization temperature of the composition is Tc < -3.7496x + 128, where x is the mass content of comonomer M1 based on the total weight of the polymer P1.

9. A separator for an electrochemical apparatus selected from the following group: Li ions, capacitors, electric double-layer capacitors, and fuel cell membrane electrode assemblies (MEAs), wherein the separator comprises a porous support and the composition according to any one of claims 1 to 8.

10. The separator according to claim 9, characterized in that the composition has a mass ratio P1 / P2 in the range of 95 / 5 to 5 / 95.

11. A lithium-ion secondary battery comprising an anode, a cathode, and a separator, wherein the separator is as described in claim 9.