Binder for an electrode, electrode formulation for a li-ion battery, and method for manufacturing an electrode

Abstract

The present invention relates to a binder for an electrode of a secondary battery, comprising a fluorinated polymer A and an acrylic polymer B, characterized in that said acrylic polymer B comprises monomer units containing one or more functional group(s) CO2 -Li+ and said acrylic polymer B has a lithiation rate of at least 30%.

Description

[0001] Electrode binder, electrode formulation for Li-ion battery and electrode manufacturing method

[0002] Technical field

[0003] The present invention relates generally to the field of electrical energy storage in Li-ion type lithium storage batteries. More specifically, the invention relates to a binder for an electrode. Another subject of the invention is a method for preparing an electrode using said binder. The invention also relates to lithium-ion batteries manufactured by incorporating said electrode.

[0004] Technological background of the invention

[0005] An elementary cell of a Li-ion storage battery or a lithium battery comprises an anode (on discharge), and a cathode (also on discharge) generally composed of a lithium insertion compound of the metal oxide type, such as LiM^C, LiCoCh or LiNiÜ2, between which is inserted an electrolyte which conducts the lithium ions.

[0006] Rechargeable or secondary cells are more advantageous than primary (non-rechargeable) cells because the associated chemical reactions that take place at the positive and negative electrodes of the battery are reversible. Secondary cell electrodes can be regenerated multiple times by applying an electrical charge. Many advanced electrode systems have been developed to store an electrical charge. In parallel, much effort has been devoted to developing electrolytes capable of improving the capabilities of electrochemical cells.

[0007] For their part, the electrodes generally comprise at least one current collector on which is deposited, in the form of a film, a composite material consisting of a material called active material because it has electrochemical activity compared to lithium, a polymer which acts as a binder, plus one or more electronically conductive additives which are generally carbon black or acetylene black, and possibly a surfactant.

[0008] Binders are classified as inactive components since they do not directly contribute to cell capacity. However, their key role in electrode processing and their considerable influence on the electrochemical performance of electrodes have been widely described. 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 objective of using a binder is to form stable networks of the solid electrode components, i.e., active materials and conductive agents (cohesion). In addition, the binder must ensure close contact of the composite electrode to the current collector (adhesion).

[0009] The current manufacturing process for lithium-ion battery electrodes, the "slurry" process, uses a solvent. This process involves preparing an ink by mixing an active material, a conductive filler, and a polymer binder in a solvent. This ink is then deposited on a current collector, and the solvent is evaporated.

[0010] Dry (solvent-free) manufacturing processes are also known. These processes eliminate volatile organic compound emissions and offer the possibility of manufacturing electrodes with greater thicknesses (> 120 μm), with a higher energy density of the final energy storage device. US 2019 / 0305316 discloses dry-processed electrode films comprising a microparticulate non-fibrillable binder having certain particle sizes and a method of obtaining a film flexible enough to be handled for roll-to-roll processing using fibrillable binders. However, fibrillable binders require additional shear in addition to the dispersion of the components. This is energy-intensive and destructive to the active materials.Also known from US 2020 / 0313193 are dry-processed electrode films comprising an elastic polymeric binder wherein the dry electrode film is self-supporting and comprises at most an insubstantial amount of polytetrafluoroethylene. US 2020 / 0313193 primarily discloses polyethylene, as the elastic polymeric binder, which is not electrochemically stable enough for use in both a cathode and an anode of lithium ion secondary batteries.

[0011] There is a need for a binder that offers good electrochemical resistance, provides good adhesion to the metal current collector via a solvent-free manufacturing process and improves the conductivity of the electrode. It is also important that the binder has a high affinity with the other ingredients of the solvent-free formulation so that during pressing this binder provides intimate cohesion.

[0012] Summary of the invention

[0013] According to a first aspect, the present invention relates to a binder comprising a fluoropolymer

[0014] A and an acrylic polymer B, characterized in that said acrylic polymer B comprises monomeric units containing one or more CC Li* functional group(s) and said acrylic polymer B has a lithiation rate of at least 30%.

[0015] The binder according to the present invention comprises two types of polymers, i.e. a fluoropolymer and an acrylic-based polymer having CC Li* functional groups while having a high lithiation rate. Said binder makes it possible to improve the adhesion to the current collector and the conductivity of the electrode containing the binder. Said binder can be used in the preparation of an electrode via a slurry or solvent-free process.

[0016] According to a preferred embodiment, said acrylic polymer B has a pH between 2.0 and 10.0 measured at room temperature.

[0017] According to a preferred embodiment, said acrylic polymer B also comprises at least 5 mol% of monomeric units containing a functional group -CO2H or carboxylic acid anhydride.

[0018] According to a preferred embodiment, the fluoropolymer A contains at least monomeric units derived from a monomer selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SC>2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R 1 CH2OCF=CF2 in which R 1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R 2OCF=CH2 in which R 2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

[0019] According to a preferred embodiment, said fluoropolymer A comprises monomeric units derived from vinylidene fluoride and optionally monomeric units of a monomer selected from the group consisting of vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2in which n is 1, 2, 3, 4 or 5; the product of formula R 1 CH2OCF=CF2in which R 1is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R 2 OCF=CH2in which R 2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.

[0020] According to a preferred embodiment, the fluoropolymer A is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or a mixture thereof.

[0021] According to a preferred embodiment, said fluoropolymer A comprises monomer units carrying at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic.

[0022] According to a preferred embodiment, the acrylic polymer B has a number-average molar mass greater than or equal to 3000 g.mol-1.

[0023] According to a preferred embodiment, the acrylic polymer B comprises monomeric units containing one or more CO2Li functional group(s). +, monomeric units carrying one or more carboxylic acid or carboxylic acid anhydride functional group(s) and monomeric units carrying one or more carboxylic acid ester functional group(s).

[0024] According to a preferred embodiment, the acrylic polymer B comprises monomeric units MO derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 1 ) n -CO2Li + ) in which the substituents R 1 , R 2 and R 3 are independently of each other selected from the group consisting of H, CO2H and C1-C5alkyl optionally substituted by a CO2H or CO2R' group with R' being C1-C5alkyl, monomeric units M1 derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 2 ) n -CO2H) in which the substituents R 1 , R 2 and R 3are independently of each other selected from the group consisting of H, CO2H and C1-C5alkyl optionally substituted by a CO2H or CO2R' group with R' being C1-C5alkyl, ; X 1 and X 2 being independently of each other a Ci-Cio alkyl hydrocarbon group optionally carrying one or more hydroxyl group(s); n is 0 or 1; and monomeric units M2 derived from a monomer of formula R 4 R 5 C=C(R 6 )HORN 7 in which the substituents R 4 , R 5 and R 6 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted with a CO2H or CO2R' group with R' being C1-C5 alkyl; and R 7is selected from the group consisting of - NHC(CH3)2CH2C(O)CH3 OR -OR' with R' selected from the group consisting of Ci-Cis alkyl optionally substituted with one or more -OH group(s) or a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain.

[0025] According to a preferred embodiment, said acrylic polymer B in solution in water has a pH between 2.0 and 10.0 measured at room temperature.

[0026] According to a preferred embodiment, the mass rate of acrylic polymer B relative to the fluorinated polymer A is from 1 to 70%.

[0027] According to a preferred embodiment, said acrylic polymer B also comprises a divalent cation.

[0028] According to another aspect, the present invention provides an electrode comprising the binder according to the present invention, an active material and optionally a conductive agent.

[0029] According to a preferred embodiment, the electrode has the following mass composition: a. 50% to 99.9% of active material, preferably 50% to 99%, b. 25% to 0% of conductive agent, preferably 25% to 0.5%, c. 25% to 0.05% of binder according to the present invention, preferably 25% to 0.5%, d. 0% to 5% of at least one additive selected from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and a flow aid; the sum of all these percentages being 100%.

[0030] According to a preferred embodiment, said conductive agents are composed of one or more materials among carbon blacks, such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor-grown carbon fiber; metal powders such as SUS powder, and aluminum powder.

[0031] According to a preferred embodiment, for a positive electrode, said active material is selected from the group consisting of: LiCoO2, Li(Ni, Co, AI)O2, Li(l+ x), NiaMnbCoc (x represents a real number of 0 or more, a = 0.8, 0.6, 0.5, or 1 / 3, b = 0.1, 0.2, 0.3, or 1 / 3, c = 0.1, 0.2, or 1 / 3), LÎNÎ02, LiMn2O4, LiCoMnO4, Li3NiMn3O3, Li3Fe2(PO4)3, Li3V2(PO4)3, a Li Mn spinel substituted by a different element having a composition represented by Lil+xMn2-x- yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between 0 and 2, lithium titanate LixTiOy

[0032] - x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LÎMPO4, M representing Fe, Mn, Co, or Ni.

[0033] According to a preferred embodiment, for a negative electrode, said active material is selected from the group consisting of a lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy and Li4Ti5O12.

[0034] According to another aspect, the present invention provides a method for preparing a dry coated electrode comprising:

[0035] - the mixture in powder form of said binder according to the present invention, of an active material and optionally of a conductive agent;

[0036] - depositing the mixture obtained in the previous step on a current collector to obtain an electrode;

[0037] - consolidation of said electrode by a thermomechanical treatment step carried out at a temperature Tl between Tf - 50°C < Tl < Tg + 50°C when Tg > Tf or at a temperature Tl between Tg - 50°C < Tl < Tf + 50°C when Tf > Tg with Tf being the melting temperature of the fluorinated polymer A and Tg being the glass transition temperature of the acrylic polymer B.

[0038] According to another aspect, the present invention provides a method for preparing an electrode by solvent-based route comprising the steps of:

[0039] - mixing in the presence of a solvent of said binder according to the present invention, an active material and optionally a conductive agent;

[0040] - depositing the mixture obtained in the previous step on a current collector to obtain an electrode;

[0041] - drying of said electrode.

[0042] According to a preferred embodiment, the present invention provides a Li-ion battery comprising a positive electrode, a negative electrode and a separator, at least one electrode being an electrode according to the present invention.

[0043] Detailed Description of the Invention According to a first aspect, an electrode binder is provided. Preferably, said binder comprises a mixture of at least two polymers. Thus, said binder comprises a fluoropolymer A and an acrylic polymer B.

[0044] Preferably, said binder is in the form of a powder. The use of the binder in powder form allows solvent-free processing from the phase of mixing the constituents to the phases of deposition on the current collector and consolidation. In addition, the use of a binder in powder form for the manufacture of the electrode makes it possible to avoid having to resort to grinding or dispersion steps after mixing with the active materials and the conductive agents. In particular, said powder has a particle size distribution with a D90 of less than or equal to 750 pm, advantageously less than or equal to 700 pm, preferably less than or equal to 650 pm, more preferably less than or equal to 600 pm, in particular less than or equal to 550 pm, more particularly less than or equal to 500 pm. The D90 is the particle size at the 90th percentile (by volume) of the cumulative particle size distribution.This parameter is determined by laser granulometry. A particle size analyzer of the Malvern INSITEC System type is used for the measurement. This is carried out in a dry process by laser diffraction on a powder with a focal length of 100 mm. Advantageously, said powder has a particle size distribution with a D90 less than or equal to 450 pm, preferably less than or equal to 400 pm, more preferably less than or equal to 350 pm, in particular less than or equal to 300 pm, more particularly less than or equal to 250 pm, preferably less than or equal to 200 pm, advantageously less than or equal to 150 pm, preferably less than or equal to 100 pm, particularly preferably less than or equal to 50 pm.

[0045] According to a preferred embodiment, said fluoropolymer A contains in its chain at least one monomer chosen from compounds containing a vinyl group capable of opening to polymerize and which contains, directly attached to this vinyl group, at least one fluorine atom, a fluoroalkyl group or a fluoroalkoxy group.

[0046] Preferably, said fluoropolymer A contains at least monomeric units derived from a monomer selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R 1 CH2OCF=CF2 in which R 1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R 2 OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.

[0047] In particular, said fluorinated polymer A comprises at least monomeric units derived from vinylidene fluoride. The fluorinated polymer A may be a homopolymer or a copolymer. The copolymer may also comprise non-fluorinated monomers.

[0048] According to one embodiment, the fluoropolymer A is a vinylidene fluoride homopolymer.

[0049] According to an alternative embodiment, the fluorinated polymer A is a polymer comprising units derived from vinylidene fluoride, and is preferably chosen from polyvinylidene fluoride homopolymer and copolymers comprising vinylidene fluoride units and units derived from at least one other comonomer copolymerizable with vinylidene fluoride.

[0050] Thus, said fluoropolymer A comprises monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SC>2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R 1 CH2OCF=CF2 in which R 1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R 2OCF=CH2 in which R 2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

[0051] According to a preferred embodiment, the fluoropolymer A is a copolymer comprising vinylidene fluoride (VDF) units and units derived from one or more monomers selected from the group consisting of vinyl fluoride; trifluoroethylene; chlorotrifluoroethylene; 1,2-difluoroethylene, tetrafluoroethylene; hexafluoropropylene; perfluoro(alkyl vinyl)ethers such as perfluoro(methyl vinyl)ether, perfluoro(ethyl vinyl)ether or perfluoro(propyl vinyl)ether; perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPC>3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2in which n is 1, 2, 3, 4 or 5; the product of formula R'CH2OCF=CF2in which R' is hydrogen or F(CF2)z and z is 1, 2, 3 or 4; the product of formula R"OCF=CH2in which R" is F(CF2)z and z is 1, 2, 3 or 4; perfluorobutylethylene;3,3,3-trifluoropropene or 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.;

[0052] Preferably, the fluoropolymer A is a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene and hexafluoropropylene or a mixture thereof. In the fluoropolymer A, the mass content of the vinylidene fluoride units is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%.

[0053] According to a particular embodiment, the fluoropolymer A is functionalized in whole or in part, which allows it to improve adhesion to metal. Thus, said fluoropolymer A may comprise monomer units carrying at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic; preferably at least one carboxylic acid or hydroxyl function.

[0054] The function is introduced by a chemical reaction which may be grafting, or a copolymerization of the fluorinated monomer with a monomer carrying at least one of said functional groups and a vinyl function capable of copolymerizing with the fluorinated monomer, according to techniques well known to those skilled in the art.

[0055] According to one embodiment, the functional group carries a carboxylic acid function which is a (meth)acrylic acid type group chosen from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.

[0056] According to one embodiment, the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus. According to one embodiment, the functionality is introduced via the transfer agent used during the synthesis process. The transfer agent is a polymer with a molar mass less than or equal to 20,000 g / mol and carrying functional groups chosen from the groups: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic. An example of a transfer agent of this type is acrylic acid oligomers. According to a preferred embodiment, the transfer agent is an acrylic acid oligomer with a molar mass less than or equal to 20,000 g / mol.The molar mass of the transfer agent is determined according to the method described below for acrylic polymer B.

[0057] The content of functional groups in PVDF is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

[0058] The PVDF preferably has a high molecular weight. By high molecular weight, as used herein, is meant a PVDF having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to ASTM method D-3835 measured at 232°C and 100 sec-1.

[0059] The PVDF homopolymers and VDF copolymers used in the invention can be obtained by known polymerization methods such as emulsion or suspension polymerization.

[0060] According to one embodiment, they are prepared by an emulsion polymerization process in the absence of fluorinated surfactant.

[0061] Polymerization of PVDF results in a latex generally having a solids content of 10 to 60% by weight, preferably 10 to 50%, and having 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 may form agglomerates having a weight average size of 1 to 30 micrometers, and preferably 2 to 10 micrometers. The agglomerates may break into discrete particles during formulation and application to a substrate.

[0062] In some embodiments, the PVDF homopolymer and VDF copolymers are composed of bio-based VDF. The term "bio-based" means "derived from biomass." This improves the ecological footprint of the polymer. The bio-based VDF may be characterized by a renewable carbon content, i.e., carbon of natural origin and originating from a biomaterial or biomass, of at least 1 atomic % as determined by the 14C content according to standard NF EN 16640. The term "renewable carbon" indicates that the carbon is of natural origin and originates from a biomaterial (or biomass), as indicated below.According to certain embodiments, the bio-carbon content of the VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than or equal to 33%, preferably greater than 50%, preferably greater than or equal to 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, advantageously equal to 100%.

[0063] As mentioned above, said binder also comprises an acrylic polymer B.

[0064] Said acrylic polymer B comprises monomeric units containing one or more C02-Li functional group(s) + . Preferably, said acrylic polymer B has a lithiation rate of at least 30%. The lithiation rate corresponds to the ratio between the number of moles of -C02-Li groups + and the number of moles of carboxylic groups and -C02-Li groups+ in said acrylic polymer B. The number of moles of carboxylic groups can be determined by standard analysis techniques (for example NMR). The number of moles of -CO2 LC groups is deduced from the number of moles of carboxylic groups before and after the lithiation step (having a yield of 100%). In particular, said acrylic polymer has a lithiation rate of at least 35%, advantageously at least 40%, preferably at least 45%, more preferably at least 50%, in particular at least 55%. Said acrylic polymer B having a lithiation rate as expressed here makes it possible to improve the conductivity of an electrode containing said binder.

[0065] Preferably, said acrylic polymer B in solution in water has a pH of between 2.0 and 10.0, advantageously between 2.5 and 9.0, preferably between 3.0 and 8.0 measured at room temperature.

[0066] Preferably, said acrylic polymer B comprises at least 5%, advantageously at least 10%, preferably at least 15%, in particular at least 20% by mole of monomeric units containing a functional group -CO2H or carboxylic acid anhydride. The presence of carboxylic groups or carboxylic acid anhydride also improves adhesion to the current collector.

[0067] According to a preferred embodiment, the acrylic polymer B has a number-average molar mass greater than or equal to 3000 g.mol-1, advantageously greater than or equal to 10000 g.mol-1, preferably greater than or equal to 50000 g.mol-1, more preferably greater than or equal to 100000 g.mol-1, in particular greater than or equal to 150000 g.mol-1. The molecular or molar mass is determined by Size Exclusion Chromatography (SEC). A test portion of the polymer solution corresponding to 90 mg of dry matter is introduced into a 10 mL flask. Mobile phase, supplemented with 0.04% dimethylformamide (DMF), is added up to a total mass of 10 g. The composition of this mobile phase is as follows: NaHCOs: 0.05 mol / L, NaNOs: 0.1 mol / L, triethanolamine: 0.02 mol / L, NaNs 0.03% by mass.The CES system consists of a Waters 510 isocratic pump with a flow rate set at 0.8 mL / min, a Waters 717+ autosampler, an oven containing a 6 cm long, 40 mm inner diameter Waters Guard Column Ultrahydrogel precolumn, followed by a 30 cm long, 7.8 mm inner diameter Waters Ultrahydrogel linear column. Detection is performed using a Waters RI 410 differential refractometer. The oven is heated to 60°C and the refractometer is heated to 45°C. The CES system is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standards Service with a peak molecular weight between 1000 g / mol and 1.10. 6 g / mol and a polydispersity index between 1.4 and 1.7. The calibration curve is linear and takes into account the correction obtained using the flow marker: dimethylformamide (DMF).

[0068] Preferably, the acrylic polymer B comprises monomeric units containing one or more CO2 LC functional group(s), monomeric units carrying one or more carboxylic acid or carboxylic acid anhydride functional group(s) and monomeric units carrying one or more carboxylic acid ester functional group(s).

[0069] The use of an acrylic polymer B with this type of functional group according to the present invention makes it possible to improve the adhesion to the current collector on which said binder according to the present invention is deposited and the conductivity of the electrode containing a binder according to the present invention.

[0070] According to a preferred embodiment, the acrylic polymer B comprises: monomeric units MO derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 1 ) n -CO2 _ Li +) in which the substituents R 1 , R 2 and R 3 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being C1-C5 alkyl, monomeric units Ml derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 2 ) n -CO2H) in which the substituents R 1 , R 2 and R 3 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being C1-C5 alkyl, ; X 1 and X 2 being independently of each other a C1-C10 alkyl hydrocarbon group optionally carrying one or more hydroxyl group(s); n is 0 or 1; and optionally monomeric units M2 derived from a monomer of formula R 4 R 5 C=C(R6 )HORN 7 in which the substituents R 4 , R 5 and R 6 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted with a CO2H or CO2R' group with R' being C1-C5 alkyl; and R 7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of Ci-Cis alkyl optionally substituted with one or more -OH groups or a five or six-membered heterocycle comprising at least one nitrogen atom in its ring chain.

[0071] The combined presence of lithium carboxylate, carboxylic acid and carboxylic acid ester functions makes it possible to improve adhesion to the current collector and the conductivity performance of the electrode, but also to obtain deformable polymer particles compatible with fluorinated polymer A.

[0072] In particular, the monomeric units MO are derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 1 )n-CO2-Li + ) in which the substituents R 1 and R 2 are independently of each other H or CO2H; and R 3 is H, CH2CO2H or CH3; X 1 is a C1-C5 alkyl hydrocarbon group optionally carrying one or more hydroxyl groups; n is 0 or 1. More particularly, the monomeric units MO are derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 1 ) n -CO2 _ Li + ) in which the substituents R 1 and R 2 are independently of each other H or CO2H; and R 3 is H, CH2CO2H or CH3; X 1is a C1-C3 alkyl hydrocarbon group optionally carrying one or more hydroxyl groups; n is 0 or 1. Preferably, the monomeric units MO are derived from a monomer of formula R 1 R 2 C=C(R 3 )(CO2-Li + ) in which the substituents R 1 and R 2 are independently of each other H or CO2H; and R 3 is H, CH2CO2H or CH3. In particular, the monomeric units Ml are derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 2 ) n -CO2H) in which the substituents R 1 and R 2 are independently of each other H or CO2H; and R 3 is H, CH2CO2H or CH3; X 2 is a C1-C5 alkyl hydrocarbon group optionally carrying one or more hydroxyl groups; n is 0 or 1. More particularly, the monomeric units Ml are derived from a monomer of formula R 1 R 2C=C(R 3 )((X 2 ) n -CO2H) in which the substituents R 1 and R 2 are independently of each other H or CO2H; and R 3 is H, CH2CO2H or CH3; X 2 is a C1-C3 alkyl hydrocarbon group optionally carrying one or more hydroxyl groups; n is 0 or 1. Preferably, the monomeric units Ml are derived from a monomer of formula R 1 R 2 C=C(R 3 )(CO2H) in which the substituents R 1 and R 2 are independently of each other H or CO2H; and R 3 is H, CH2CO2H or CH3. According to a preferred embodiment, said acrylic polymer B comprises at least 5%, advantageously at least 10%, preferably at least 15%, in particular at least 20%, more particularly at least 30%, preferably at least 40%, particularly preferably at least 50% by mole of monomeric units Ml.

[0073] Preferably, said acrylic polymer B comprises monomeric units M2 of formula R 4 R 5 C=C(R 6 )HORN 7 in which the substituents R 4 , R 5 and R 6 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted with a CO2H or CO2R' group with R' being C1-C5 alkyl; R 7is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of Ci-Cis alkyl optionally substituted with one or more -OH group(s) a five- or ten-membered heterocycle comprising at least one nitrogen atom in its ring chain. Said heterocycle may be saturated or unsaturated or aromatic. Said heterocycle may be monocyclic or bicyclic. Said heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone ring. Said heterocycle may be substituted by one or more C1-C5 alkyl groups. As mentioned above, the C1-C5 alkyl is optionally substituted by said heterocycle.The latter may be linked to the alkyl chain by the nitrogen atom or any other atoms forming the heterocycle. Preferably the heterocycle is 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. In the present application, the term alkyl includes linear and branched alkyls. According to a preferred embodiment, the substituent R' is selected from the group consisting of methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxybutyl, hydroxypropyl, ethyl substituted by a ureido group, hydroxyethyl. In particular, said acrylic polymer B comprises monomeric units M2 of formula R. 4 R 5 C=C(R 6 )HORN 7 in which the substituents R 4 and R 5 are H; R 6 is H or CH3; R 7is -OR' with R' selected from the group consisting of methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxypropyl, hydroxybutyl, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4- imidazolidinone ethyl substituted with a ureido group, hydroxyethyl. Thus, said acrylic polymer B comprises monomeric units M2 derived from 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, methyl acrylic acid, methyl methacrylate or ureido methacrylate. The term "acrylate" herein includes acrylates and methacrylates.

[0074] According to a preferred embodiment, said acrylic polymer B comprises at least 1%, advantageously at least 5%, preferably at least 10%, in particular at least 25%, more particularly at least 20% by mole of monomeric units M2.

[0075] Optionally, the acrylic polymer B may also comprise monomeric units M3 derived from an unsaturated monomer copolymerizable with the monomers of formula R 1 R 2 C=C(R 3 )((X 2 ) n -CO2H), R 1 R 2 C=C(R 3 )((X 1 ) n -CO2 _ Li + ) and monomers of formula R 4 R 5 C=C(R 6 )HORN 7 as defined above. Advantageously, the resulting monomeric units M3 may be derived from a monomer of formula (R 8 )(R 9 )C=C(R 10 )(R 1:L -R 12 ), (R 8 )(R 9 )C=C(R 10)(P(O)(OR 13 )(GOLD 14 )), (R 8 )(R 9 )C=C(R 10 )(C(O)NH(R 17 -R 18 )) OR

[0076] (R 8 )(R 9 )C=C(R 10 )(C(O)N(R 15 -R 16 )(R 17 -R 18 )) in which the substituents R 8 , R 9 and R 10 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R 11 , R 15 and R 17 are independently of each other selected from the group consisting of C1-C18 alkyl, C8-C18 aryl, C4-C18 cycloalkyl, C1-C18 fluoroalkyl, C8-C18 fluoroaryl, C4-C18 fluorocycloalkyl, propylene glycol oligomers, ethylene glycol oligomers, hexafluoropropylene oxide oligomers and tetrafluoroethylene oxide oligomers; R 12 , R 16 and R 18are independently of each other selected from the group consisting of CO2H, COOM, OH, CONH2, CON(R 19 )2, SO3H, SO3M with R 19 being C1-C5 alkyl, M is NH4 + , NR 19 4 + , N / A + or K + ; R 13 and R 14 are independently of each other selected from the group consisting of H, C1-C18 alkyl, C1-C18 aryl, C4-C48 cycloalkyl, C1-C48 fluoroalkyl, C1-C48 fluoroaryl, C4-C18 fluorocycloalkyl, propylene glycol oligomers, ethylene glycol oligomers, hexafluoropropylene oxide oligomers, tetrafluoroethylene oxide oligomers, an alkali cation, NH4 + and NR 19 4 +. Preferably, the monomeric units M3 may be derived from a monomer selected from the group consisting of fumaric acid, crotonic acid, itaconic acid, vinyl acetate, vinyl neodecanoate, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, diacetone acrylamide, 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, fluoroalkyl acrylate, dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, maleic anhydride, and alkenyl glycidyl ether compounds such as, for example, allyl glycidyl ether, 1,3-butadiene, isoprene, divinyl benzene, acrylonitrile, methacrylonitrile. Of these, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, acrylamido-2-methylpropane sulfonic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and allyl glycidyl ether, 1,3-butadiene and acrylonitrile are preferred. These compounds may be used alone or as a mixture of two or more. Preferably, the acrylic polymer B comprises less than 30%, advantageously less than 20% by mole of monomeric units M3.,

[0077] The acrylic polymer B used in the invention can be obtained by polymerization of the monomers according to known polymerization methods such as emulsion or suspension polymerization. The acrylic polymer B thus obtained is then brought into contact with a solution or dispersion of lithium hydroxide in order to obtain the monomers comprising -CO2LL groups. The concentration of LiOH is adapted to the desired content of -CChLi groups.

[0078] According to a preferred embodiment, said acrylic polymer B also comprises a divalent cation. Said divalent cation may be Ca 2+ , Mg 2+ , Ba 2+ , Cu 2+ or Zn 2+ or a mixture thereof. Preferably, said divalent cation may be Ca 2+ or Zn 2+or a mixture thereof. Said divalent cation is preferably linked to a carboxylate group CCh- of said acrylic polymer B. Said divalent cation may be added in the form of a solution or dispersion of hydroxide of said cation. This is added to the acrylic polymer B simultaneously or not with the solution or dispersion of LiOH mentioned above. In this case, the lithiation rate corresponds to the ratio between (the number of moles of -C02-Li groups + and [COz RX 2 *) and (the number of moles of carboxylic groups, of -C02-Li groups + and [CC kX 2 * in said acrylic polymer B); X being the divalent cation. The presence of this divalent cation makes it possible to improve the efficiency of the battery comprising said acrylic polymer B. The molar ratio between the divalent cation and the lithium is from 0.01 to 1, preferably from 0.05 to 0.5.

[0079] According to a preferred embodiment, the mass content of acrylic polymer B relative to the fluorinated polymer A is from 1 to 70%, advantageously from 2 to 60%, preferably from 3 to 50%, more preferably from 4 to 40%, in particular from 5 to 30%.

[0080] According to another aspect, the present invention provides a method for preparing said binder according to the present invention. According to a preferred embodiment, said method comprises a step of:

[0081] Mixture of said fluoropolymer A in latex form and said acrylic polymer B in the form of an aqueous solution or latex, and

[0082] Optionally, drying of the mixture obtained in the previous step, preferably by atomization or co-atomization,

[0083] Optionally, grinding of the dried mixture obtained in the previous step.

[0084] The drying step may be carried out by atomization or co-atomization, preferably at a temperature of 100°C to 220°C. The powder may also be obtained by grinding techniques, such as cryo-grinding, where the mixture is brought to a temperature below room temperature, for example by means of liquid nitrogen, before grinding. At the end of the powder manufacturing step, i.e. after the drying step, the particle size may be adjusted and optimized by selection or screening processes and / or by grinding. The drying and grinding steps are carried out when said binder is put into the form of a powder.

[0085] Alternatively, said fluoropolymer A and said acrylic polymer B may be mixed in the presence of an organic solvent or a mixture of water and organic solvent.

[0086] According to another aspect, the present invention provides an electrode. The electrode comprises said binder according to the present invention, a conductive agent and an active material.

[0087] In a preferred embodiment, the electrode has the following mass composition: a. 50% to 99.9% of active material, preferably 50% to 99%, b. 25% to 0% of conductive agent, preferably 25% to 0.5%, c. 25% to 0.05% of said binder according to the invention, preferably 25% to 0.5%, d. 0% to 5% of at least one additive selected from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and a flow aid; the sum of all these percentages being 100%.

[0088] The conductive agents in the electrode are composed of one or more materials that can improve conductivity. Some examples include carbon blacks such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor-grown carbon fiber; metal powders such as SUS powder, and aluminum powder.

[0089] Active materials are materials that are capable of storing and releasing lithium ions.

[0090] In a preferred embodiment, said electrode is a negative electrode. In particular, for a negative electrode, said active material is selected from the group consisting of a lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy, and Li4Ti50i2. The shape of the negative electrode active material is not particularly limited but is preferably particulate.

[0091] In another preferred embodiment, said electrode is a positive electrode. Preferably, for a positive electrode, said active material is selected from the group consisting of LiCoCh, Li(Ni, Co, AI)C>2, Li(1+ x), NiaMnbCoc (x represents a real number of 0 or more, a = 0.8, 0.6, 0.5, or 1 / 3, b = 0.1, 0.2, 0.3, or 1 / 3, c = 0.1, 0.2, or 1 / 3), LiNiO2, LiMn2O4, LiCoMnC , LisNiMnsOs, LÎ3Fe2(PO4)3, LÎ3V2(PO4)3, a Li Mn spinel substituted by a different element having a composition represented by Lil+xMn2-x-yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between between 0 and 2, lithium titanate LixTiOy - x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LÎMPO4, M representing Fe, Mn, Co, or Ni.

[0092] In addition, the surface of each of the materials described above can be coated. The coating material is not particularly limited as long as it has lithium ion conductivity and contains a material capable of being maintained as a coating layer on the surface of the active material. Examples of the coating material include LiNbCh, Li4Ti50i2, and LisPC. The shape of the positive electrode active material is not particularly limited but is preferably particulate.

[0093] According to another aspect of the present invention, a method of preparing the dry coated electrode is provided.

[0094] Said method of preparing the dry coated electrode comprises the following steps:

[0095] - mixing the active material, said binder according to the present invention in powder form as described above, and the conductive agent using a process which provides an electrode formulation applicable to a metal substrate by a “solvent-free” process;

[0096] - depositing said electrode formulation on a substrate by a solvent-free process to obtain a Li-ion battery electrode, and

[0097] - consolidation of said electrode by a thermomechanical treatment step carried out at a temperature Tl between Tf - 50°C < Tl < Tg + 50°C when Tg > Tf or at a temperature Tl between Tg - 50°C < Tl < Tf + 50°C when Tf > Tg with Tf being the melting temperature of the fluorinated polymer A and Tg being the glass transition temperature of the acrylic polymer B.

[0098] The glass transition temperatures given here are calculated using the Fox equation. The Fox equation is an equation used to predict the glass transition temperature of random copolymers: 1 / Tg,copo = i coi / Tg,i ; Tg,copo is the glass transition temperature of the copolymer; Tg,i are those of the homopolymers i corresponding to each comonomer, coi are the mass fractions of the monomers i composing this copolymer. The mass fractions are expressed without units. The glass transition temperatures are expressed in degrees Kelvin. The temperature is then converted to degrees Celsius.

[0099] A “solventless” process is one that does not require a residual solvent evaporation step after the deposition step.

[0100] Thermomechanical processing can be carried out, for example, by a calendering machine with rollers that can be heated or a plate press that can also be heated.

[0101] Solvent-free mixing processes for the various constituents of the electrode formulation before the deposition phase on the collector include, but are not limited to: stirring mixing, air jet mixing, high shear mixing, V-mixer mixing, screw mass mixer mixing, double cone mixing, drum mixing, conical mixing, double Z-arm mixing, fluidized bed mixing, planetary mixer mixing, mechanical melting mixing, extrusion mixing, calendering mixing, grinding mixing.

[0102] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free spraying process, by depositing the formulation on the metal substrate, by a pneumatic spraying process, by electrostatic spraying, by dipping in a fluidized powder bed, by spraying, by electrostatic screen printing, by deposition with rotating brushes, by deposition with rotating addition rollers, by calendering.

[0103] According to one embodiment, the consolidation of the electrode after a deposition process on the metal substrate by solvent-free spraying (pneumatic spraying process, by electrostatic spraying, by dipping in a fluidized powder bed, by sprinkling, by electrostatic screen printing, by deposition with rotating brushes, by deposition with rotating addition rollers) is carried out by a calendering process. This process consists of applying pressure to the electrode using two optionally heated rollers.

[0104] According to one embodiment, after the powder mixing step, the electrode is manufactured by a two-step solvent-free process. A first step consists of manufacturing a self-supporting film from the premixed formulation with a thermomechanical process such as extrusion, calendering or thermo-compression. In a second step, the self-supporting film is laminated onto the metal substrate by a process combining temperature and pressure such as calendering or thermo-compression.

[0105] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free process using a calendering process which makes it possible to carry out the film-forming step and transfer of the coating onto the current collector in a single step, i.e. without going through a step of manufacturing a self-supporting film. To do this, the calender used has several rollers (at least three). The powder obtained after the mixing step is introduced between the first two rollers, most often heated and having differential rotation speeds to shear the powder. The coating formed and remaining stuck on the fastest roller is then directly laminated onto the current collector with a third roller. The electrode thus obtained can be subsequently passed through a calender to adjust its porosity or thickness if necessary.

[0106] The mass ratio of conductive agents to active material is preferably 0 to 10%, more preferably 0 to 7%.

[0107] The mass ratio of binder to active material is preferably 0.1 to 10%, more preferably 0.5 to 7%. According to one embodiment, the electrode components are all mixed at once according to conventional methods, resulting in an electrode formulation.

[0108] In one embodiment, said electrode formulation is applied to a substrate by electrostatic screen printing. Some examples of substrate are current collectors such as metal foil and metal mesh, polymer films, or a solid electrolyte layer of a solid-state battery.

[0109] The preferred thickness of an electrode is 0.1 pm to 1000 pm, preferably 0.1 pm to 300 pm.

[0110] According to another aspect, the present invention provides a method of preparing an electrode by solvent-based route comprising the steps of:

[0111] - mixing in the presence of a solvent of said binder according to the present invention, an active material and optionally a conductive agent;

[0112] - depositing the mixture obtained in the previous step on a current collector to obtain an electrode;

[0113] - drying of said electrode.

[0114] In this method, said solvent may be water or an organic solvent or a mixture of both. Said organic solvent may be selected from the group consisting of n-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), triethylphosphite (TEP), acetone, cyclopentanone, tetrahydrofuran, methyl ethylketone (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), gamma-butyrolactone and N-butylpyrrolidone; and mixtures thereof.

[0115] According to another aspect of the present invention, a Li-ion battery is provided. Preferably, the Li-ion battery comprises a positive electrode, a negative electrode and a separator, at least one electrode being an electrode according to the present invention.

[0116] The following examples illustrate the present invention without limiting it.

[0117] pH measurement method

[0118] We use a Mettler Toledo SevenEasy brand pH meter or equivalent and an Electrode

[0119] In Lab Routine Pro. Before calibration, ensure the electrode is clean. If necessary, clean the electrode with warm soapy water. Ensure that the pH electrode is always kept filled with KCl filling solution. The device is calibrated with buffer solutions of pH 10, 7 and 4. To calibrate, dip the electrode in the pH 10 buffer solution and press Cal, once the pH has stabilized, repeat the operation with the pH 7 buffer then 4. Rinse with distilled water and dry the electrode between each buffer. The electrode is pre-prepared before measurement by soaking in a 0.1M HCl solution for one to two hours and then rinsed with deionized water. To measure the pH, dip the electrode in the product to be tested and shake for a few seconds. The measurement is allowed to stabilize for 15 minutes and the value displayed by the pH meter is read. The measurement is taken at room temperature.

[0120] Polymer B

[0121] In a 1000ml glass reactor equipped with mechanical stirring and oil bath heating, 416g of deionized water and 3.2g of 97% sodium dodecyl sulfate were weighed. In a first container equipped with a magnetic stirrer bar, 150g of deionized water, 1.06g of 97% sodium dodecyl sulfate, 0.7g of diallylphthalate, 163g of methyl methacrylate, 116g of methacrylic acid were weighed. This mixture was kept under constant stirring throughout the polymerization. In a second container, a solution consisting of 0.7g of ammonium persulfate, 10g of deionized water was prepared. In a third container, a solution consisting of 0.1 g of sodium metabisulfite and 10 g of deionized water was prepared. The reactor was heated to 76°C.The contents of the second and third containers were introduced into the latter, then the contents of the first container were introduced, still under stirring, using a peristaltic pump into the reactor over 120 min at 76°C. The dispersion was heated at 78°C for 60 min. A dispersion containing 28% dry matter was obtained. The particles have a median diameter measured by DDL of 100 nm. The pH of the aqueous dispersion is 3.1. To this solution, a dispersion of 20% lithium hydroxide in water was added so as to obtain a lithiation rate of 35%.

[0122] Polymer A

[0123] An aqueous dispersion of PVDF polymer is available in the form of a latex with a pH of 3.6, a dry extract of 24.1% and a particle size of 145nm. PVDF is a copolymer of vinylidene fluoride and hexafluoropropylene characterized by a melting temperature of 148°C measured by DSC (differential scanning calorimetry). The aqueous formulations are produced according to the following process:

[0124] Polymer A is weighed into a container and acrylic polymer B is introduced over 10 minutes while stirring using a mechanical stirrer. The stirring time after introduction of the acrylic polymer is 10 minutes.

[0125] Example 1

[0126] 70.11g of polymer A are weighed and 30.04g of polymer B are added. The aqueous formulation containing in dry ratio 70% by mass of PVDF and 30% of acrylic polymer is placed in a crystallizer and dried for 24 hours in an oven at 110°C. A homogeneous powder is obtained which is ground using an electric knife mill of the coffee grinder type in a first step, then cryogenically ground using a ball mill in a second step. The powder obtained is particularly homogeneous and can be very easily compressed in order to obtain polymeric layers on metal surfaces, using for example presses or calendering machines.This process therefore allows dry coating on aluminum-type supports, which makes it possible to produce cathodes without the presence of toxic solvents such as NMP, or even to avoid aqueous processes which require particularly expensive drying and complex formulations requiring difficult control of rheology. The same type of solvent-free process can be used for anode manufacturing.

Claims

Claims 1. Binder comprising a fluorinated polymer A and an acrylic polymer B, characterized in that said acrylic polymer B comprises monomeric units containing one or more functional group(s) C02-Li + and said acrylic polymer B has a lithiation rate of at least 30%.

2. Binder according to any one of the preceding claims, characterized in that said acrylic polymer B also comprises at least 5 mol% of monomeric units containing a functional group -CO2H or carboxylic acid anhydride.

3. Binder according to any one of the preceding claims, characterized in that the fluoropolymer A contains at least monomeric units derived from a monomer selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SC>2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R 1 CH2OCF=CF2 in which R 1 is hydrogen or F(CF2) mand m is 1, 2, 3 or 4; the product of formula R 2 OCF=CH2 in which R 2 is F(CF2) P and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.

4. Binder according to any one of the preceding claims, characterized in that said fluoropolymer A comprises monomeric units derived from vinylidene fluoride and optionally monomeric units of a monomer selected from the group consisting of vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SC>2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R 1 CH2OCF=CF2 in which R 1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R 2 OCF=CH2 in which R 2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.

5. Binder according to any one of the preceding claims, characterized in that the fluoropolymer A is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or a mixture thereof.

6. Binder according to any one of the preceding claims, characterized in that said fluoropolymer A comprises monomer units carrying at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic.

7. Binder according to any one of the preceding claims, characterized in that the acrylic polymer B has a number-average molar mass greater than or equal to 3000 g.mol-1.

8. Binder according to any one of the preceding claims, characterized in that the acrylic polymer B comprises monomeric units containing one or more functional group(s) C02-Li + , monomeric units carrying one or more carboxylic acid or carboxylic acid anhydride functional group(s) and monomeric units carrying one or more carboxylic acid ester functional group(s).

9. Binder according to any one of the preceding claims, characterized in that the acrylic polymer B comprises monomeric units MO derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 1 ) n -CO2 _ Li + ) in which the substituents R 1, R 2 and R 3 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being C1-C5 alkyl, monomeric units Ml derived from a monomer of formula R 1 R 2 C=C(R 3 )((X 2 ) n -CO2H) in which the substituents R 1 , R 2 and R 3 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being C1-C5 alkyl; X 1 and X 2 being independently of each other a C1-C10 alkyl hydrocarbon group optionally carrying one or more hydroxyl group(s); n is 0 or 1; and optionally monomeric units M2 derived from a monomer of formula R 4 R 5 C=C(R 6 )HORN 7in which the substituents R 4 , R 5 and R 6 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl optionally substituted with a CO2H or CO2R' group with R' being C1-C5 alkyl; and R 7 is selected from the group consisting of - NHC(CH3)2CH2C(O)CH3 OR -OR' with R' selected from the group consisting of Ci-Cis alkyl optionally substituted with one or more -OH group(s) or a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain.

10. Binder according to any one of the preceding claims, characterized in that said acrylic polymer B in solution in water has a pH of between 2.0 and 10.0 measured at room temperature.

11. Binder according to any one of the preceding claims, characterized in that the mass content of acrylic polymer B relative to the fluorinated polymer A is from 1 to 70%.

12. Binder according to any one of the preceding claims, characterized in that said acrylic polymer B also comprises a divalent cation. Tl 13. Electrode comprising said binder according to any one of claims 1 to 12, an active material and optionally a conductive agent.

14. Electrode according to the preceding claim having the following mass composition: a. 50% to 99.9% of active material, preferably 50% to 99%, b. 25% to 0% of conductive agent, preferably 25% to 0.5%, c. 25% to 0.05% of binder according to any one of the preceding claims 1 to 12, preferably 25% to 0.5%, d. 0% to 5% of at least one additive selected from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and a flow aid; the sum of all these percentages being 100%.

15. An electrode according to any one of claims 13 and 14, said conductive agents being composed of one or more materials among carbon blacks, such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor-grown carbon fiber; metal powders such as SUS powder, and aluminum powder.

16. An electrode according to any one of claims 13 to 15, wherein, for a positive electrode, said active material is selected from the group consisting of: LiCoO2, Li(Ni, Co, Al)O2, Li(l+ x), NiaMnbCoc (x represents a real number of 0 or more, a = 0.8, 0.6, 0.5, or 1 / 3, b = 0.1, 0.2, 0.3, or 1 / 3, c = 0.1, 0.2, or 1 / 3), LiNiO2, LiMn2O4, LiCoMnO4, Li3NiMn3O3, Li3Fe2(PO4)3, Li3V2(PO4)3, a spinel Li Mn substituted by a different element having a composition represented by Li11+xMn2-x-yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between 0 and 2, lithium titanate LixTiOy - x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by UMPO4, M representing Fe, Mn, Co, or Ni.

17. An electrode according to any one of claims 13 to 15, wherein, for a negative electrode, said active material is selected from the group consisting of a lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy and Li4Ti5O12.

18. A process for preparing a dry coated electrode comprising: - the mixture in powder form of said binder according to any one of claims 1 to 12, of an active material and optionally of a conductive agent; - depositing the mixture obtained in the previous step on a current collector to obtain an electrode; - consolidation of said electrode by a thermomechanical treatment step carried out at a temperature Tl between Tf - 50°C < Tl < Tg + 50°C when Tg > Tf or at a temperature Tl between Tg - 50°C < Tl < Tf + 50°C when Tf > Tg with Tf being the melting temperature of the fluoropolymer A and Tg being the glass transition temperature of the acrylic polymer B.

19. Process for the preparation of an electrode by solvent-based means comprising the steps of: - mixing in the presence of a solvent of said binder according to any one of claims 1 to 12, of an active material and optionally of a conductive agent; - depositing the mixture obtained in the previous step on a current collector to obtain an electrode; - drying of said electrode.

20. Li-ion battery comprising a positive electrode, a negative electrode and a separator, at least one electrode being an electrode according to any one of claims 13 to 17.

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