Electrode binders containing poly(vinylidene fluoride) and hydrophilic polymers

Abstract

The present invention relates to a polymer P1 comprising repeating units derived from vinylidene fluoride and a polymer of formula R 1 R 2 C=C(R 3 )C(O)R(I)(wherein, R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, and R is -NHC(CH3)2CH2C(O)CH3, -NR'R" or -OR' (where R' and R" are C1-C alkyl groups optionally substituted with H and one or more hydroxyl, thiol or amino functional groups or a 5-6 membered heterocycle containing at least one nitrogen atom in the ring). 18 and a hydrophilic polymer P2 comprising repeat units derived from at least one monomer M1 of the formula (I) (independently selected from the group consisting of alkyl groups), wherein the weight-average molecular weight of the hydrophilic polymer P2 is greater than 30,000 g / mol, advantageously greater than 50,000 g / mol, preferably greater than 65,000 g / mol, more preferably greater than 80,000 g / mol.

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 precisely, the invention relates to a binder for electrodes comprising a mixture of at least two polymers, at least one of which is a fluoropolymer. [Background technology]

[0002] Lithium batteries, including lithium metal batteries, lithium ion batteries, lithium polymer batteries, and lithium ion polymer batteries, are finding increasing use due to their higher voltage and energy density than those of conventional batteries (such as Ni-MH batteries).

[0003] The basic cell of a Li-ion or lithium battery comprises an anode (when discharged) and a cathode (also when discharged), usually made from a lithium insertion compound of the metal oxide type, such as LiMn2O4, LiCoO2 or LiNiO2, between which an electrolyte that conducts lithium ions is inserted.

[0004] Rechargeable or secondary batteries have advantages over primary (non-rechargeable) batteries because the associated chemical reactions that occur at the battery's positive and negative electrodes are reversible. The electrodes of secondary batteries can be regenerated several times by applying an electrical charge. Many advanced electrode systems have been developed to store electrical charge. At the same time, much effort has been put into developing electrolytes that can improve the performance of electrochemical cells.

[0005] An electrode generally comprises at least one current collector on which is coated in the form of a film a composite material consisting of a so-called active material, since it is electrochemically active towards lithium, a polymer acting as a binder, one or more electronically conductive additives, generally carbon black or acetylene black, and optionally a surfactant.

[0006] Binders are considered inactive components because they do not directly contribute to battery capacity. However, their important role in electrode processing and their significant impact on the electrode's electrochemical performance have been widely documented. The main relevant physical and chemical properties of binders are thermal stability, chemical and electrochemical stability, tensile strength (strong adhesion and cohesion), and flexibility. The main purpose of using binders is to form a stable network (cohesion) of the electrode's solid components, i.e., the active material and conductive agent. The binder also needs to ensure adhesion (adhesion) between the composite electrode and the current collector.

[0007] Poly(vinylidene fluoride) (PVDF) is used as a binder in lithium-ion batteries due to its excellent electrochemical stability, good binding capacity, and high adhesion to electrode materials and current collectors. In the wet slurry process for preparing electrodes, the active material and binder are dispersed in a liquid solution, typically based on an organic solvent or water. The dispersion is cast onto a current collector and then dried in a high-temperature oven to produce an electrode. Unfortunately, the excellent properties offered by fluoropolymers such as PVDF can also limit the applications in which they can be used. For example, it is difficult to adhere fluoropolymers to other materials. Therefore, organic solvents and other organic additives are commonly used in coating formulations to provide good adhesion (irreversible adhesion) between PVDF-based polymers, porous separators or electrodes, and optional powder particles. Alternatively, fluoropolymer binders can have functional groups that favor the adhesive behavior of the polymer. For example, US2020 / 0407543 discloses a polymer binder composition comprising two or more different phases, the phases including a highly crystalline fluoropolymer phase and an adhesive fluoropolymer phase, the adhesive fluoropolymer having functional groups.

[0008] Binder compositions containing a mixture of vinylidene fluoride polymer and acrylic polymer have also been disclosed in the art. For example, US 2013 / 252077 describes an electrode for a lithium-ion battery operating with a non-aqueous electrolyte. The electrode comprises an active material and a binder containing a vinylidene fluoride polymer and an acrylic polymer. EP 2953193 describes a binder for a lithium-ion battery comprising a fluoropolymer and an acrylic polymer containing nitrile groups. WO 97 / 27260 describes an electrode comprising a current collector made of a metal coated with a layer containing an active material and a binder. The binder comprises three components: a vinylidene fluoride polymer, a metal, and at least two of an acrylic or methacrylic polymer containing functional groups capable of binding to a vinylidene fluoride copolymer. EP 3796430 discloses an electrode mixture comprising a binder composition containing a vinylidene fluoride copolymer and an acrylic polymer having a low weight-average molecular weight. However, the adhesive strength of the binder composition is still not satisfactory and can still be improved. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2020 / 0407543 [Patent Document 2] US Patent Application Publication No. 2013 / 252077 [Patent Document 3] European Patent Application Publication No. 2953193 [Patent Document 4] International Publication No. 97 / 27260 [Patent Document 5] European Patent Application Publication No. 3796430 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, there remains a need to develop new binder and electrode compositions for Li-ion batteries that have improved adhesion while maintaining slurry stability, especially with active materials having high nickel content or based on lithium metal phosphate. [Means for solving the problem]

[0011] According to a first aspect, the invention provides a polymer P1 comprising repeating units derived from vinylidene fluoride and a compound of formula R 1 R 2 C=C(R 3 )C(O)R(I)(wherein, R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, and R is -NHC(CH3)2CH2C(O)CH3, -NR'R" or -OR' (where R' and R" are C1-C alkyl groups optionally substituted with H and one or more hydroxyl, thiol or amino functional groups or a 5-6 membered heterocycle containing at least one nitrogen atom in the ring). 18 and a hydrophilic polymer P2 comprising at least repeating units derived from at least one monomer M1 of the formula (I), wherein M1 is selected from the group consisting of alkyl groups, and M2 is independently selected from the group consisting of alkyl groups, wherein M2 is independently selected from the group consisting of alkyl groups, and M2 is independently selected from the group consisting of alkyl groups, wherein M2 is independently selected from the group consisting of alkyl groups, and M2 is independently selected from the group consisting of alkyl groups, wherein M2 is independently selected from the group consisting of alkyl groups, and M2 is independently selected from the group consisting of alkyl groups, wherein M2 is independently selected from the group consisting of alkyl groups, and M2 is independently selected from the group consisting of alkyl groups,

[0012] The present invention provides binders with improved adhesion to electrodes while also maintaining slurry stability when used in electrode coating formulations. Surprisingly, the applicant has found that the molecular weight of the hydrophilic polymer (designated P2 in this application) strongly influences the adhesive properties of the binder.

[0013] According to a preferred embodiment, said polymer P1 and said polymer P2 form an interpenetrating polymer network. Surprisingly, the Applicant has observed that the adhesive properties of the binder are further improved when an interpenetrating polymer network is present.

[0014] According to a preferred embodiment, the interpenetrating polymer network is formed by the reaction of a polymer of formula R 1 R 2 C=C(R 3 )C(O)R(I) by polymerizing at least one of said monomers (M1).

[0015] According to a preferred embodiment, said polymer P1 is selected from the group consisting of polyvinylidene fluoride homopolymers and copolymers based on polyvinylidene fluoride containing at least one comonomer compatible with vinylidene fluoride.

[0016] According to a preferred embodiment, the comonomer 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.

[0017] According to one embodiment, said polymer P1 comprises monomer units having at least one of the following functional groups: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy group, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid or phosphonic acid.

[0018] According to a preferred embodiment, the hydrophilic polymer P2 is selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, ethyl methacrylate, 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, ethyl methacrylate, propyl methacrylate, n- The copolymer contains at least repeating units derived from at least one monomer M1 selected from the group consisting of butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, and combinations thereof.

[0019] According to a preferred embodiment, the mass ratio P1 / P2 varies from 99 / 1 to 5 / 95.

[0020] According to a preferred embodiment, the polymer P1 is cured at 232°C and 100s according to the ASTM D-3835 method. -1 The composition has a melt viscosity, measured at 100 Pa.s, greater than 100 Pa.s, preferably greater than 500 Pa.s, and more preferably greater than 1000 Pa.s.

[0021] According to a second aspect, the present invention provides a process for producing a binder composition comprising the steps of: a) providing an aqueous solution comprising a polymer P1 comprising repeating units derived from vinylidene fluoride; b) Formula R as defined herein 1 R 2 C=C(R 3)C(O)R(I) and optionally one or more monomers from which the repeating units of the hydrophilic polymer P2 are derived, c) adding an initiator to initiate the polymerization of said monomer M1 and optionally one or more monomers from which the repeating units of the hydrophilic polymer P2 are derived to produce a binder composition according to the invention.

[0022] According to a preferred embodiment, step b) is carried out in the absence of a chain transfer agent or in the presence of less than 1.2 wt. %, preferably less than 1.0 wt. %, of a chain transfer agent, based on the total weight of all monomers added in step b).

[0023] According to a third aspect, the present invention provides an electrode composition comprising the binder composition according to the present invention, a conductive agent, and an active material.

[0024] According to a preferred embodiment, the conductive agent comprises one or more materials selected from carbon black, carbon nanotubes, carbon fibers or metal powders.

[0025] According to a preferred embodiment, the active material is selected from the group consisting of lithium salts of transition metal oxides, sulfides, phosphates and hydroxides, and preferably the active material is lithium metal phosphate having a composition represented by LiMPO4 (wherein M represents Fe, Mn, Co or Ni), LiCoO2, LiNi x Co 1-x O2, LiMn2O2, LiNiO2, LiNi x Co y Mn z O m , LiNi x Co y Al z O m and LiNi x Mn y Al z O m where x+y+z=1 and m is an integer representing the number of oxygen atoms in the oxide providing the electron balance molecule, and in particular, the active material is selected from the group consisting of LiFePO4 and LiNix Co y Mn z O m where x is 0.6 or greater, y is 0.2 or less, z is 0.2 or greater, x+y+z=1, and m is an integer representing the number of oxygen atoms in the oxide that provides the electron-balanced molecule.

[0026] According to a fourth aspect, the present invention provides a positive electrode comprising a current collector and an electrode composition according to the present invention disposed on at least one surface of the current collector.

[0027] According to a fifth aspect, the present invention provides a Li-ion secondary battery comprising a negative electrode, a positive electrode according to the present invention, and a separator between the negative electrode and the positive electrode.

[0028] According to a sixth aspect, the present invention provides an electrochemical device comprising a negative electrode, a positive electrode according to the present invention, and an electrolyte comprising lithium. DETAILED DESCRIPTION OF THE INVENTION

[0029] The invention will now be explained in more detail, in a non-limiting manner, in the following description. According to various embodiments, the binder comprises the following characteristics, where appropriate in combination: The indicated contents are expressed by weight unless otherwise indicated. For all ranges indicated, the limits are included unless otherwise indicated.

[0030] According to a first aspect of the present invention, a binder composition for a positive electrode is provided. According to a preferred embodiment, the binder composition comprises a polymer P1 and a hydrophilic polymer P2 as defined herein. This material is used as a polymer binder or adhesive component on the positive electrode. Surprisingly, it has been found that a binder composition comprising particles of a fluoropolymer P1 and a hydrophilic polymer P2 provides a better compromise of properties compared to known compositions consisting of fluoropolymers.

[0031] The polymer P1 comprises repeating units derived from vinylidene fluoride (CH2=CF2). In a preferred embodiment, the polymer P1 is selected from the group consisting of polyvinylidene fluoride homopolymers and polyvinylidene fluoride-based copolymers containing at least one comonomer compatible with vinylidene fluoride. The comonomer compatible with vinylidene fluoride may be halogenated (fluorinated, chlorinated or brominated) or non-halogenated.

[0032] The comonomer may be selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, chlorotrifluoropropene and ethylene, or mixtures thereof.

[0033] Examples of trifluoropropenes include, in particular, 3,3,3-trifluoropropene. Tetrafluoropropenes can be, for example, 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene. Pentafluoropropenes can be, for example, 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Perfluoroalkyl vinyl ethers are, for example, 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). Chlorofluoroethylene can represent either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. 1-Chloro-1-fluoroethylene isomers are preferred. Chlorotrifluoropropenes are preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0034] Said polymer P1 may also comprise non-halogenated monomers such as ethylene and / or acrylic or methacrylic acid comonomers.

[0035] Said polymer P1 may contain at least 50 mol% vinylidene fluoride, advantageously at least 60 mol% vinylidene fluoride, preferably at least 70 mol% vinylidene fluoride, more preferably at least 80 mol% vinylidene fluoride and in particular at least 90 mol% vinylidene fluoride.

[0036] In one embodiment, said polymer P1 may comprise monomer units having at least one of the following functional groups: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy group (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid or phosphonic acid. The functional groups are introduced by chemical reaction, which may be grafting or copolymerization, according to techniques well known to those skilled in the art, of a fluoromonomer with a monomer having at least one of said functional groups and a vinyl function capable of copolymerizing with the fluoromonomer.

[0037] According to one embodiment, said polymer P1 may comprise repeating units having a carboxylic acid function, which is a (meth)acrylic acid type group selected from acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxyethylhexyl (meth)acrylate.

[0038] According to one embodiment, the units having a carboxylic acid functionality may further comprise heteroatoms selected from oxygen, sulfur, nitrogen and phosphorus.

[0039] According to one embodiment, the functional groups are introduced by a transfer agent used during the synthesis process. The transfer agent is a polymer with a molar mass of 20,000 g / mol or less and has functional groups selected from the following group: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy group (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, or phosphonic acid. An example of this type of transfer agent is an oligomer of acrylic acid. According to a preferred embodiment, the transfer agent is an oligomer of acrylic acid with a molar mass of 20,000 g / mol or less.

[0040] The content of functional groups in polymer P1 is at least 0.01 mol %, preferably at least 0.1 mol %, and at most 15 mol %, preferably at most 10 mol %.

[0041] In a particular embodiment, the polymer P1 is a homopolymer of vinylidene fluoride or the polymer P1 comprises repeating units derived from vinylidene fluoride and repeating units with a carboxylic acid function, which is a (meth)acrylic acid type group selected from acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxyethylhexyl (meth)acrylate.

[0042] The polymer P1 preferably has a high molecular weight. As used herein, the term "high molecular weight" refers to a polymer that is polymerized at 232°C and 100°C 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 greater than 500 Pa.s and more preferably greater than 1000 Pa.s.

[0043] The polymers P1 used in the present invention can be obtained by known polymerization methods, such as emulsion or suspension polymerization. According to one embodiment, they are prepared by an emulsion polymerization process in the absence of fluorinated surfactants.

[0044] Polymerization of polymer P1 generally results in a latex having a solids content of 10% to 60% by weight, preferably 10% to 50% by weight, and a volume 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 volume 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 volume average size of which is 1 to 30 micrometers, preferably 2 to 10 micrometers. The volume average particle size of the latex particles is measured using a Nicomp CW380 Particle Size Analyzer (light scattering). The agglomerates can break down into individual particles during formulation and application to a substrate.

[0045] According to some embodiments, the polymer P1 (homopolymer or copolymer) is composed of biobased vinylidene fluoride. The term "biobased" means "obtained from biomass." This allows improving the ecological footprint of the membrane. Biobased vinylidene fluoride is produced in accordance with the standard NF EN 16640. 14 It can be characterized by a content of at least 1 atomic % renewable carbon, i.e., carbon of natural origin and derived from biological materials or biomass, 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 shown below. According to some embodiments, the biocarbon content of the VDF is 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%.

[0046] As mentioned above, the binder composition comprises a hydrophilic polymer P2, which has the formula R 1 R 2 C=C(R 3 )C(O)R(I), wherein R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, and R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3, -NR'R" or -OR', where R' and R" are C1-C5 alkyl groups optionally substituted with H and one or more hydroxyl, thiol or amino functional groups or 5- to 6-membered heterocycles containing at least one nitrogen atom in the ring. 18 alkyl groups.

[0047] In a preferred embodiment, the monomer M1 has the formula R 1 R 2 C=C(R 3 )C(O)R(I), wherein R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, and R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3, -NR'R" or -OR', where R' and R" are C1-C alkyl optionally substituted with H and one or more hydroxyl, thiol or amino functional groups or 5- to 6-membered heterocycles containing at least a nitrogen atom in the ring. 15 alkyl.

[0048] In a preferred embodiment, the monomer M1 has the formula R 1 R 2 C=C(R 3 )C(O)R(I), wherein R 1 , R 2 and R 3are independently selected from the group consisting of H and C1-C5 alkyl, and R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3, -NR'R" or -OR', where R' and R" are C1-C alkyl optionally substituted with H and one or more hydroxyl, thiol or amino functional groups or 5- to 6-membered heterocycles containing at least a nitrogen atom in the ring. 10 alkyl.

[0049] In a preferred embodiment, the monomer M1 has the formula R 1 R 2 C=C(R 3 )C(O)R(I), wherein R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, and R is selected from the group consisting of -OR', where R' is H and C1-C5 alkyl optionally substituted with one or more -OH functional groups. 10 alkyl.

[0050] In a preferred embodiment, the monomer M1 has the formula R 1 R 2 C=C(R 3 )C(O)R(I), wherein R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C3 alkyl, and R is selected from the group consisting of -OR', where R' is H and C1-C3 alkyl optionally substituted with one or more -OH functional groups. 10 alkyl.

[0051] In a more preferred embodiment, the monomer M1 has the formula R 1 R 2 C=C(R 3 )C(O)R(I), wherein R 1 , R 2 and R 3are independently selected from the group consisting of H and C1-C3 alkyl, and R is selected from the group consisting of -OR', where R' is selected from the group consisting of H and C1-C5 alkyl optionally substituted with one or more -OH functional groups.

[0052] In a preferred embodiment, the hydrophilic polymer P2 is selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, 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, ethyl methacrylate, propyl methacrylate, n-butyl acrylate, ... The monomer M1 contains at least a repeating unit derived from at least one monomer M1 selected from the group consisting of butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, and combinations thereof. Among these, alkyl acrylates having an alkyl group with 1 to 8 carbon atoms are preferred, and alkyl acrylates having an alkyl group with 1 to 5 carbon atoms are more preferred. These may be used alone or in a mixture of two or more.In a more preferred embodiment, the hydrophilic polymer P2 comprises at least repeating units derived from at least one monomer M1 selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, amyl acrylate, isoamyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, and combinations thereof, in particular acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, ethyl methacrylate, propyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, and combinations thereof.

[0053] In a preferred embodiment, said hydrophilic polymer P2 has a weight-average molecular weight Mw greater than 30 000 g / mol, advantageously greater than 40 000 g / mol, preferably greater than 50 000 g / mol, more preferably greater than 65 000 g / mol, in particular greater than 80 000 g / mol and more particularly greater than 100 000 g / mol.

[0054] The hydrophilic polymer P2 may contain a repeating unit derived from a monomer M2 copolymerizable with the monomer M1. - (A) an alkenyl compound containing a functional group, or (B) may be an alkenyl compound without a functional group, or a mixture thereof.

[0055] 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; amide compounds such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, diacetoneacrylamide, acrylates ... Examples of suitable acrylic acid esters include 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, fluoroalkyl acrylates, methacrylic acid esters include dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, maleic anhydride, and alkenyl glycidyl ethers include allyl glycidyl ether compounds. Among these, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolacrylamide, diacetone acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and allyl glycidyl ether are preferred. These may be used alone or in combination.

[0056] Examples of the alkenyl compound (B) having no functional group 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, 1,3-butadiene and acrylonitrile are preferred. These may be used alone or as a mixture of two or more.

[0057] It is preferred that the functional alkenyl compound (A) is used in an amount of less than 50% by weight based on the weight of the monomer mixture, and the alkenyl compound (B) having no functional group is used in an amount of less than 30% by weight based on the weight of the monomer mixture.

[0058] According to a preferred embodiment, the binder composition is provided in a non-crosslinked form. In an alternative embodiment, the binder composition described herein can undergo crosslinking by self-condensation of its functional groups or by reaction with a catalyst and / or crosslinking agent, such as melamine resins, epoxy resins, and the like, as well as known low molecular weight crosslinking agents, such as diisocyanates or higher polyisocyanates, polyaziridines, polycarbodiimides, polyoxazolines, dialdehydes, such as glyoxal, acetoacetates, malonates, acetals, di- and trifunctional acrylates and thiols, cycloaliphatic epoxy molecules, organic silanes such as epoxysilanes and aminosilanes, carbamates, diamines and triamines, inorganic chelating agents such as certain zinc and zirconium salts, titanium, glycolyl, and other aminoplasts. In certain cases, functional groups from other polymerization components, such as surfactants, initiators, seed particles, etc., can participate in the crosslinking reaction. When two or more functional groups are involved in the crosslinking process, the complementary reactive group pairs are, for example, hydroxyl-isocyanate, acid-epoxy, amine-epoxy, hydroxyl-melamine, acetoacetate-acid. The monomer that does not contain a functional group capable of entering into a crosslinking reaction after polymerization should preferably represent 70% by weight or more of the total monomer mixture, more preferably more than 90% by weight. According to one embodiment, the binder composition comprises a crosslinker selected from the group consisting of isocyanates, diamines, adipic acid, dihydrazides, and combinations thereof.

[0059] In the binder composition, the P1 / P2 weight ratio can vary from 99 / 1 to 5 / 95, preferably from 95 / 5 to 50 / 50, advantageously from 95 / 5 to 60 / 40.

[0060] In a preferred embodiment, the binder composition has a viscosity of 3.36 s on a Brookfield DVII viscometer equipped with an SC24-25 spindle at 25°C. -1 Advantageously, the binder composition has a solution viscosity of less than 15,000 cP (9 wt. % in NMP) measured at 25°C. Advantageously, the binder composition has a viscosity of 3.36 s on a Brookfield DVII viscometer equipped with an SC24-25 spindle at 25°C. -1 % solution viscosity in NMP of less than 14,000 cP, preferably less than 13,000 cP, more preferably less than 12,000 cP, especially less than 11,000 cP, as measured by HPLC.

[0061] In a particular embodiment, the binder of the present invention consists of said polymer P1 and said polymer P2 as defined herein.

[0062] In a preferred embodiment, the binder composition of the present invention exhibits an interpenetrating polymer network (IPN) type morphology, in which the chains of polymer P1 and hydrophilic polymer P2 are intertwined. An interpenetrating polymer network (IPN) is a polymer containing two or more networks that are at least partially entangled on a molecular scale, but are not covalently bonded to each other and cannot be separated unless the chemical bonds are broken. The term interpenetrating polymer network (IPN) type morphology can also refer to a polymer containing one or more polymer networks and one or more linear or branched polymers, characterized by the molecular-scale penetration of at least one network by at least some linear or branched macromolecules. A mixture of two or more preformed polymer networks is not an IPN. In particular, the binder composition of the present invention exhibits a sequential interpenetrating polymer network. The latter is an interpenetrating polymer network prepared by a process in which a network of a first component is formed after a network of a second component is formed. Binder compositions according to the present invention exhibiting this morphology have been observed to have improved adhesive properties compared to corresponding dry blends.

[0063] The interpenetrating polymer network is formed by the reaction of the polymer P1 with the formula R1 R 2 C=C(R 3 )C(O)R(I) and optionally a monomer M2 as defined above.

[0064] In another embodiment, the binder composition is a dry blend of polymer P1 and hydrophilic polymer P2 as defined herein.

[0065] In a second aspect of the present invention, a process for making a binder composition is provided.

[0066] In a preferred embodiment, the process comprises the following steps: a) providing an aqueous solution comprising a polymer P1 comprising repeating units derived from vinylidene fluoride; b) Formula R as defined herein 1 R 2 C=C(R 3 )C(O)R(I) and optionally one or more monomers from which the repeating units of the hydrophilic polymer P2 are derived, c) adding an initiator to initiate the polymerization of said monomer M1 and, optionally, one or more monomers from which the repeating units of the hydrophilic polymer P2 are derived, to produce a binder composition according to the invention. This process is particularly suitable for preparing binder compositions according to the invention that exhibit an interpenetrating polymer network (IPN) type morphology.

[0067] In a preferred embodiment, said step b) of the process is carried out in the absence of a chain transfer agent or in the presence of less than 1.2 wt. %, preferably less than 1.0 wt. %, of a chain transfer agent based on the total weight of all monomers added in step b).

[0068] Chain transfer agents are added to polymerizations to control the molecular weight of the product. They can be added in a single step at the beginning of the reaction, or incrementally or continuously throughout the reaction. The amount and mode of chain transfer agent addition depend on the activity of the specific chain transfer agent used and the desired molecular weight of the polymer product. Oxygenated compounds such as alcohols, carbonates, ketones, esters, and ethers can serve as chain transfer agents. Examples of oxygenated compounds useful as chain transfer agents include isopropyl alcohol, as described in U.S. Patent No. 4,360,652. Other classes of compounds that can act as chain transfer agents in the polymerization of halogen-containing monomers include, for example, halocarbons and hydrohalocarbons, such as chlorocarbons, or mercaptans, such as n-dodecyl mercaptan or isooctyl 3-mercaptopropionate. Alkanes such as ethane and propane can also function as chain transfer agents. Chain transfer agents can be added in steps b) and / or c) of the process.

[0069] The term initiator refers to a chemical substance capable of providing a source of free radicals, either spontaneously or induced by exposure to heat or light. Examples of suitable initiators include peroxides, peroxydicarbonates, and azo compounds. "Initiator" also includes redox systems useful for providing a source of free radicals. The term "radical" and the expression "free radical" refer to a chemical species containing at least one unpaired electron. The radical initiator is added to the reaction mixture in an amount sufficient to initiate and maintain the polymerization reaction at the desired reaction rate. The order of addition can vary depending on the desired process and latex emulsion characteristics. The radical initiator may include a persulfate salt, such as sodium persulfate, potassium persulfate, or ammonium persulfate. The amount of persulfate added to the reaction mixture (based on the total weight of the monomers added to the reaction mixture) can be, for example, from about 0.002 to about 1.0 weight percent. The radical initiator may include organic peroxides, such as alkyl, dialkyl, or diacyl peroxides, peroxydicarbonates, and peroxyesters, or mixtures thereof. A preferred alkyl peroxide is tert-butyl hydroperoxide. A preferred dialkyl peroxide is di-tert-butyl peroxide (DTBP). The organic peroxide may be added to the reaction mixture in an amount of about 0.01 to about 5 weight percent based on total monomers, preferably about 0.05 to about 2.5 weight percent based on total monomers. Preferred peroxydicarbonate initiators are di-n-propyl peroxydicarbonate and diisopropyl peroxydicarbonate, which may be added to the reaction mixture in an amount of about 0.5 to about 2.5 weight percent based on total monomers. Peroxyester initiators include tert-amyl peroxypivalate, tert-butyl peroxypivalate, and succinic acid peroxide. The radical initiator may include an azo initiator such as 2,2'-azobis(2-methylpropionamidine) dihydrochloride. The radical initiator may also include a redox system. By "redox system" is meant a system comprising an oxidizing agent, a reducing agent, and optionally a promoter as an electron transfer medium.Oxidizing agents include, for example, peroxides such as persulfates and hydrogen peroxide, hydroperoxides such as tert-butyl hydroperoxide and cumene hydroperoxide, and metal oxide salts such as ferric sulfate. Reducing agents include, for example, sodium formaldehyde sulfoxylate, sodium and potassium sulfite, ascorbic acid, bisulfite, metabisulfite, and reducing metal salts. Accelerators are components of redox systems that can react with both the oxidizing agent and the reducing agent in different oxidation states, thereby accelerating the overall reaction. Accelerators include, for example, transition metal salts such as ferrous sulfate. In redox systems, the oxidizing agent and reducing agent may be utilized in amounts of about 0.01 to about 0.5 weight percent based on total monomers. Optional accelerators may be utilized in amounts of about 0.005 to about 0.025 weight percent based on total monomers. The redox system is described in GS Misra and UDN Bajpai, Prog. Polym. Sci., 1982, 8(1-2), pp. 61-131.

[0070] The process can also be carried out in the presence of surfactants, particularly non-fluorinated surfactants. Among non-fluorinated surfactants, non-ionic emulsifiers, such as, in particular, alkoxylated alcohols, for example, ethoxylated alcohols, propoxylated alcohols, mixed ethoxylated / propoxylated alcohols, anionic surfactants, in particular, fatty acid salts, alkyl sulfonates (e.g., sodium dodecyl sulfate), alkylaryl sulfonates, arylalkyl sulfonates, etc., and organically modified siloxanes, such as polyethers, siloxanes modified with a side chain having a primary hydroxyl group or a double bond, can be mentioned.

[0071] The binder composition obtained by this process is preferably in the form of a latex, which is defined as a colloidal dispersion of a polymer dispersed in a continuous (generally aqueous) phase. The product of the polymerization is preferably a latex, which can be used in this form, usually after filtering off the solid by-products of the polymerization process. When used in the form of a latex, the latex can be stabilized by adding a surfactant. This surfactant can be the same as or different from the surfactant present during polymerization (if appropriate). The surfactant added later can be, for example, an ionic or nonionic surfactant.

[0072] Alternatively, the binder composition may be recovered as a powder for redisbursement in water or an organic solvent, and thus the process may further comprise the step of drying the binder composition obtained in step c) of the process.

[0073] Therefore, the binder composition of the present invention is preferably a latex or a powder.

[0074] The binder composition according to the present invention is part of an electrode composition, particularly a positive electrode composition.

[0075] In another aspect of the present invention, there is provided an electrode composition, particularly a positive electrode composition, comprising the binder composition according to the present invention, a conductive agent, and an active material.

[0076] The conductive agent is preferably selected from the group consisting of carbon black, such as acetylene black, ketjen black, carbon nanotubes, carbon fibers, such as carbon nanofibers, vapor-grown carbon fibers, metal powders, such as SUS powder and aluminum powder, or mixtures thereof.

[0077] The active material is preferably selected from the group consisting of lithium salts of transition metal oxides, sulfides, phosphates and hydroxides. Preferably, the active material is a lithium metal phosphate having a composition represented by LiMPO4 (where M represents Fe, Mn, Co or Ni), LiCoO2, LiNi x Co 1-x O2, LiMn2O2, LiNiO2, LiNi x Co y Mn z O m , LiNi x Co y Al z O m and LiNi x Mn y Al z O m where x+y+z=1 and m is an integer representing the number of oxygen atoms in the oxide that provides the electron-balanced molecule.

[0078] More preferably, the active material is LiFePO4 and LiNi x Co y Mn z O m wherein x is 0.6 or greater, y is 0.2 or less, z is 0.2 or greater, and x+y+z=1, and m is an integer representing the number of oxygen atoms in the oxide to provide an electron-balanced molecule.

[0079] In particular, the active material is LiFePO4 and LiNi x Co y Mn z O m wherein x is 0.8 or greater, y is 0.1 or less, z is 0.1 or greater, and x+y+z=1, and m is an integer representing the number of oxygen atoms in the oxide to provide an electron-balanced molecule.

[0080] The electrode composition may further include a solvent, such as water or an organic solvent.

[0081] The organic solvent is preferably selected from the group consisting of n-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), triethyl phosphite (TEP), acetone, cyclopentanone, tetrahydrofuran, methyl ethyl ketone (MEK), methyl isobutyl ketone (MiBK), ethyl acetate (EA), butyl acetate (BA), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone and N-butylpyrrolidone, and combinations thereof.

[0082] The electrode composition is typically prepared by mixing the components: the binder composition, the active material, the conductive agent, and optionally, the solvent. When mixed in the presence of an organic solvent, the binder is preferably in powder form.

[0083] In another aspect of the present invention, a positive electrode is provided, the positive electrode comprising a current collector and the electrode composition according to the present invention disposed on at least one surface of the current collector. Once the electrode composition is disposed on at least one surface of the current collector, the electrode is dried to remove any organic solvent or water.

[0084] According to a preferred embodiment, after evaporation of the organic solvent or water, the electrode composition cast onto the current collector has the following mass composition: a. 80% to 99.9%, preferably 80% to 99%, of an active material; b. 0.05% to 10%, preferably 10% to 0.5%, of a conductive agent; c. 0.05% to 10%, preferably 10% to 0.5%, of the binder composition of the present invention, the sum of all these percentages being 100%.

[0085] The present invention also provides a Li-ion secondary battery, which includes a negative electrode, a positive electrode according to the present invention, and a separator between the negative electrode and the positive electrode.

[0086] In another aspect of the present invention, there is provided an electrochemical device comprising a negative electrode, a positive electrode according to the present invention, and an electrolyte comprising lithium. [Example]

[0087] The following examples illustrate, but do not limit, the scope of the present invention.

[0088] <Preparation of Binder Compositions (Binders 1 to 4 Exhibiting IPN Morphology)> Polyvinylidene fluoride latex was used as a seed to synthesize a binder composition in which PVDF and a hydrophilic polymer form an interpenetrating network. 1000 g of PVDF latex and 500 g of deionized water were added to a 2-liter reactor. 32 g of an acrylic monomer mixture (corresponding to the repeating units of hydrophilic polymer P2), 3.2 g of a 10.0 wt. % VAZO-67 solution in tripropylene glycol methyl ether, and an optional chain transfer agent (e.g., isooctyl 3-mercaptopropionate) were added to the reactor. The reactor temperature was increased between 50°C and 100°C. 11.0 g of 3.5% tert-butyl hydroperoxide was fed to the reactor. The mixture was stirred and cooled to room temperature. The binder composition was discharged from the reactor. The product could be spray-dried to a powder or used as a latex. All examples were prepared according to the procedure described above. The amounts of PVDF latex, hydrophilic monomer, and chain transfer agent used in each example are listed in Table 1 below.

[0089] <Preparation of Binder Composition (Binder 5 - Dry Blend)> A binder composition based on a dry blend of PVDF and a hydrophilic polymer was also prepared by dry mixing the PVDF used as the seed to prepare Binder 2 with the hydrophilic polymer P2 obtained according to the same procedure detailed above, except that no PVDF seed was used.

[0090] Measurement of Mw of hydrophilic polymer P2 The weight average molecular weight of the hydrophilic polymer P2 was determined by preparing the hydrophilic polymer according to the same procedure detailed above, except that no polyvinylidene fluoride seeds were used, and recovering and analyzing the hydrophilic polymer so obtained. The GPC analysis was carried out on a Waters 2695e coupled to a Wyatt NEON Refractometer equipped with two PL gel mixed C columns and a guard column (7.8 mm i.d. x 30 cm, 5 μm) under the following conditions: - Temperature: 35℃, - Flow rate: 1.0mL / min, - Injection volume: 100μl.

[0091] Samples were provided as solids and made up at 1 mg / mL in THF (HPLC grade). Twelve poly(methyl methacrylate) standards ranging in Mp from 535 to 2,210,000 g / mol were used for calibration. Calibration data were fit to a cubic polynomial equation with an R of at least 0.999.

[0092] [Table 1]

[0093] <Preparation of electrode composition> <NMC as an active material> The cathode electrode composition was prepared by wet mixing. A binder solution was prepared by dissolving the binder composition in NMP (4.66 g of a 9% NMP solution). The active material (carbon black - 0.42 g) was added, mixed, and then diluted with NMP. The wet-mix formulation was prepared using a Thinky ARE-310 mixer. The carbon black was added to a Thinky cup, followed by the binder composition in NMP solution. The mixture was mixed at 2000 RPM. The active material (NMC811 - 27.16 g) was added along with NMP. The total amount of NMP was (3.36 mL). The resulting electrode composition was cast onto aluminum foil using a doctor blade. The electrode was dried in an oven at 120 °C to evaporate the NMP. The electrode was calendered and then tested for physical properties. Adhesion was measured using a 180 °C peel test according to ASTM D903. The results are reported in Table 2.

[0094] [Table 2]

[0095] As clearly demonstrated by the results detailed in Table 2, the binder composition according to the present invention provides improved properties compared to a binder composition consisting solely of PVDF (Binder 6). Peel adhesion is further improved when the binder composition exhibits an IPN morphology compared to a dry blend.

[0096] <LiFePO4 as an active material> <Peel adhesion strength> Peel adhesion was also evaluated for electrode compositions containing LiFePO4 as the active material instead of NMC811. For all formulations, electrode compositions were prepared using Lenergy N2 lithium iron phosphate (LiFePO4 or LFP) as the cathode active material and carbon black (Super P C65) as the conductive agent. The weight ratio of active material / conductive agent / binder was 94 / 3 / 3. All procedures were performed in a dry room environment (temperature = 20 °C, dew point = -50 to -60 °C). Electrodes were fabricated by casting the electrode composition onto aluminum foil using an adjustable 150 mm wide film applicator (doctor blade, Elcometer 3580 / 5). All electrodes were dried in a convection oven at 120 °C for at least 30 minutes, and each electrode was sliced ​​into three 1-inch wide strips for peel adhesion measurements. Each electrode strip was calendered at 0.1 MPa using a HSTK-1515H Roll Press to obtain a density of 10.5–11.5 mg / cm 2 Mass loading of 2 to 2.1 g / cm 3 An electrode density of 1000 μm was achieved. For peel evaluation of each formulation, three electrode strips cut from the same electrode sheet were conditioned in a dry room for three days, and then the 180° peel adhesion was measured using an Instron 3340 load frame equipped with a 10 N load cell (method based on ASTM D903). The values ​​were averaged to determine the peel adhesion of each binder sample.

[0097] The results are detailed in Table 3 below.

[0098] [Table 3]

[0099] As clearly demonstrated by the results in Table 3, electrode compositions prepared with binders according to the present invention have improved peel adhesion compared to PVDF alone.

[0100] <Slurry stability> In addition, a Brookfield Cone Plate LVDV-III Ultra viscometer was used to record the viscosity while varying the shear rate from 0.1 to 20 s -1 The stability of the slurries was evaluated using a rotational method, varying the viscosity from 0d to 100d. The initial slurry viscosity was measured on the same day of compounding (0d viscosity). The slurries were mixed in the Thinky at 2000 rpm for 30 seconds and immediately sampled. The slurry samples were then placed in the same sealed Thinky jar in a dry room until it was time for the 3-day viscosity measurements. All viscosity measurements were performed inside a fume hood in a non-dry room laboratory. The results are detailed in Table 4 below.

[0101] [Table 4]

[0102] The binder composition according to the invention shows better stability over time compared to PVDF alone (Binder 6 - Comparative).

Claims

1. a polymer P1 containing repeating units derived from vinylidene fluoride and a polymer of formula R １ R ２ C=C(R ３ )C(O)R(I) (wherein, R １ , R ２ and R ３ is H and C １ ~C ５ alkyl, and R is independently selected from the group consisting of -NHC(CH ３ ) ２ CH ２ C(O)CH ３ , -NR'R" or -OR' (where R' and R" are optionally substituted with H and one or more hydroxyl, thiol or amino functional groups or a 5- to 6-membered heterocycle containing at least one nitrogen atom in the ring). １ ~C １８ and a hydrophilic polymer P2 containing at least a repeating unit derived from at least one monomer M1 selected from the group consisting of alkyl groups, A binder composition for a positive electrode, characterized in that the weight average molecular weight of said hydrophilic polymer P2 is greater than 30,000 g / mol, advantageously greater than 50,000 g / mol, preferably greater than 65,000 g / mol, more preferably greater than 80,000 g / mol.

2. 2. The binder composition of claim 1, wherein said polymer P1 and said hydrophilic polymer P2 form an interpenetrating polymer network.

3. The interpenetrating polymer network is formed by the reaction of a compound of formula R １ R ２ C=C(R ３ 3. The binder composition according to claim 2, obtained by polymerizing at least one monomer M1 of the formula:

4. 4. The binder composition according to claim 1, wherein the polymer P1 is selected from the group consisting of polyvinylidene fluoride homopolymers and copolymers based on polyvinylidene fluoride comprising at least one comonomer compatible with vinylidene fluoride.

5. 5. The binder composition of claim 4, wherein the comonomer 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. 6. A binder composition according to claim 1, wherein the polymer P1 comprises monomer units having at least one of the following functional groups: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy group, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid or phosphonic acid.

7. The hydrophilic polymer P2 is selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, 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, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate.

7. The binder composition according to claim 1, comprising at least a repeating unit derived from at least one monomer M1 selected from the group consisting of acrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, and combinations thereof.

8. Binder composition according to any one of claims 1 to 7, wherein the mass ratio P1 / P2 varies from 99 / 1 to 5 / 95.

9. The polymer P1 is subjected to ASTM D-3835 method at 232°C for 100 seconds. －１ 9. A binder composition according to any one of claims 1 to 8, having a melt viscosity, measured at 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s.

10. A process for producing a binder composition comprising the steps of: a) providing an aqueous solution comprising a polymer P1 comprising repeating units derived from vinylidene fluoride; b) Formula R as defined in any one of claims 1 to 9 １ R ２ C=C(R ３ ) adding at least one monomer M1 of C(O)R(I) and optionally one or more monomers from which the repeating units of the hydrophilic polymer P2 are derived, c) adding an initiator to initiate the polymerization of said monomer M1 and optionally one or more monomers from which the repeat units of the hydrophilic polymer P2 are derived to produce a binder composition according to any one of claims 1 to 9.

11. 11. The process of claim 10, wherein step b) is carried out in the absence of a chain transfer agent or in the presence of less than 1.2 wt. %, preferably less than 1.0 wt. %, of a chain transfer agent based on the total weight of all monomers added in step b).

12. An electrode composition comprising the binder composition according to any one of claims 1 to 9, a conductive agent, and an active material.

13. 13. The electrode composition of claim 12, wherein the conductive agent comprises one or more materials selected from carbon black, carbon nanotubes, carbon fibers, or metal powders.

14. The active material is selected from the group consisting of lithium salts of transition metal oxides, sulfides, phosphates, and hydroxides, and preferably the active material is LiMPO ４ Lithium metal phosphate having a composition represented by the formula: LiCoO (wherein M represents Fe, Mn, Co, or Ni). ２ , LiNi ｘ Co １－ｘ O ２ , LiMn ２ O ２ , LiNiO ２ , LiNi ｘ Co ｙ Mn ｚ O ｍ , LiNi ｘ Co ｙ Al ｚ O ｍ and LiNi ｘ Mn ｙ Al ｚ O ｍ where x+y+z=1 and m is an integer representing the number of oxygen atoms in the oxide providing the electron balance molecule, and in particular, the active material is selected from the group consisting of LiFePO ４ and LiNi ｘ Co ｙ Mn ｚ O ｍ 13. The electrode composition according to claim 11, wherein x is 0.6 or more, y is 0.2 or less, z is 0.2 or more, x+y+z=1, and m is an integer representing the number of oxygen atoms in the oxide that provides the electron-balancing molecule.

15. A positive electrode comprising a current collector and the electrode composition according to any one of claims 11 to 13 disposed on at least one surface of the current collector.

16. A lithium ion secondary battery comprising a negative electrode, the positive electrode according to claim 14, and a separator between the negative electrode and the positive electrode.

17. 15. An electrochemical device comprising a negative electrode, the positive electrode of claim 14, and an electrolyte comprising lithium.

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