Electrode binder, electrode formulation for Li-ion batteries and electrode manufacturing process

Abstract

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

Description

Title of the invention: Electrode binder, electrode formulation for Li-ion batteries and electrode manufacturing process. Technical field

[0001] The present invention relates generally to the field of electrical energy storage in lithium-ion 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. Technological background of the invention

[0002] An elementary cell of a Li-ion storage battery or lithium battery comprises an anode (at discharge), and a cathode (also at discharge) generally composed of a metal oxide type lithium insertion compound, such as LiMn2O4, LiCoO2 or LiNiO2, between which is inserted an electrolyte which conducts lithium ions.

[0003] 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. The electrodes of secondary cells can be regenerated several times by applying an electrical charge. Many advanced electrode systems have been developed to store an electrical charge. In parallel, considerable effort has been devoted to the development of electrolytes capable of improving the capabilities of electrochemical cells.

[0004] For their part, the electrodes generally include 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 with respect 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.

[0005] Binders are classified among the components called inactive components since they do not directly contribute to the cell's 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, and tensile strength (strong adhesion and cohesion). and flexibility. The main objective of using a binder is to form stable networks of the solid components of the electrodes, i.e., the active materials and conductive agents (cohesion). In addition, the binder must ensure close contact between the composite electrode and the current collector (adhesion).

[0006] The current manufacturing process for lithium-ion battery electrodes, the "slurry" process, uses a solvent. This process consists of preparing an ink by mixing an active material, a conductive charge, and a polymer binder in a solvent. This ink is then deposited onto a current collector, and the solvent is evaporated.

[0007] Dry (solvent-free) manufacturing processes are also known. These processes eliminate the emission of volatile organic compounds and offer the possibility of manufacturing electrodes with greater thicknesses (> 120 pm), resulting in a higher energy density of the final energy storage device. US Patent 2019 / 0305316 discloses dry-process electrode films comprising a microparticulate, non-fibrillable binder having certain particle sizes and a process for obtaining a film flexible enough to be handled for roll-to-roll processing using fibrillable binders. However, fibrillable binders require additional shearing beyond component dispersion. This consumes a significant amount of energy and is destructive to the active materials.It is also known from US patent 2020 / 0313193 that dry-process electrode films include an elastic polymeric binder in which the dry electrode film is self-supporting and comprises at most a non-substantial amount of polytetrafluoroethylene. US patent 2020 / 0313193 primarily discloses polyethylene, as an elastic polymeric binder, which is not sufficiently electrochemically stable for use in both a cathode and anode of secondary lithium-ion batteries.

[0008] There is a need for a binder offering good electrochemical resistance, providing good adhesion to a metallic current collector via a solvent-free manufacturing process, and improving the electrode's conductivity. Furthermore, it is important that this binder have a high affinity with the other ingredients of the solvent-free formulation so that, during pressing, it provides intimate cohesion. Summary of the invention

[0009] According to a first aspect, the present invention relates to a 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) CO2 Li+ and said acrylic polymer B has a lithiation level of at least 30%

[0010] The binder according to the present invention comprises two types of polymers, i.e., a fluorinated polymer and an acrylic-based polymer possessing CO2 Li+ functional groups while having a high lithiation level. This binder improves adhesion to the current collector and the conductivity of the electrode containing the binder. The binder can be used in the preparation of an electrode via a slurry process or a solvent-free process.

[0011] According to a preferred embodiment, said acrylic polymer B has a pH between 2.0 and 10.0 measured at room temperature.

[0012] According to a preferred embodiment, said acrylic polymer B also comprises at least 5% by moles of monomeric units containing a functional group -CO2H or carboxylic acid anhydride.

[0013] According to a preferred embodiment, the fluorinated polymer A contains at least monomeric units 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 R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4;the product of formula R2OCF=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.

[0014] According to a preferred embodiment, said fluorinated polymer 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=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropcnc and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.

[0015] According to a preferred embodiment, the fluorinated polymer 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.

[0016] According to a preferred embodiment, said fluorinated polymer A comprises monomeric units bearing 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.

[0017] According to a preferred embodiment, the acrylic polymer B has a number molar mass greater than or equal to 3000 g.mol-1.

[0018] According to a preferred embodiment, the acrylic polymer B comprises monomeric units containing one or more CO2 Li+ functional group(s), monomeric units bearing one or more carboxylic acid or carboxylic acid anhydride functional group(s), and monomeric units bearing one or more carboxylic acid ester functional group(s).

[0019] According to a preferred embodiment, the acrylic polymer B comprises monomeric units MO derived from a monomer of formula R1R2C=C(R3)((X1)n-CO2 Li+) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and Ci-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being Ci-C5 alkyl, monomeric units Ml derived from a monomer of formula R'R2C=C(R3) ((X2)n-CO2H) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and Ci-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being Ci-C5 alkyl, ; X1 and X2 being independently of each other a C1-C10 alkyl hydrocarbon group optionally bearing one or more hydroxyl group(s); n is 0 or 1; and monomeric units M2 derived from a monomer of formula R4R5C=C(R6)C(O)R7 in which the substituents R4, R5 and R6 are independently 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; and R7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of C1-C18 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its cyclic chain.

[0020] According to a preferred embodiment, said acrylic polymer B in water solution has a pH between 2.0 and 10.0 measured at room temperature.

[0021] According to a preferred embodiment, the mass ratio of acrylic polymer B relative to fluorinated polymer A is from 1 to 70%.

[0022] According to a preferred embodiment, said acrylic polymer B also comprises a divalent cation.

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

[0024] According to a preferred embodiment, the electrode has the following mass composition:

[0025] a. 50% to 99.9% active material, preferably 50% to 99%

[0026] b. 25% to 0% of conducting agent, preferably 25% to 0.5%,

[0027] c. 25% to 0.05% binder according to the present invention, preferably 25% to 0.5%,

[0028] d. 0% to 5% of at least one additive chosen from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and an auxiliary flow agent;

[0029] the sum of all these percentages being 100%.

[0030] According to a preferred embodiment, said conducting agents being composed of one or more materials from among carbon blacks, such as acetylene black, Ketjen black; carbon fibers, such as a carbon nanotube, a carbon nanofiber, a carbon fiber by vapor phase growth; metal powders such as a SUS powder, and an aluminum powder.

[0031] According to a preferred embodiment, for a positive electrode, said active material is chosen 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 LiMn spinel substituted by a different element having a composition represented by Lil+xMn2-x-yMyO4, M representing at least one metal chosen 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 metal and lithium phosphate having a composition represented by LiMP04, M representing Fe, Mn, Co, or Ni.

[0032] According to a preferred embodiment, for a negative electrode, said active material is chosen 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 Li4TiO12.

[0033] According to another aspect, the present invention provides a method for preparing a dry-coated electrode comprising:

[0034] - the mixture in powder form of said binder according to the present invention, of a active material and optionally a conducting agent;

[0035] - the deposition of the mixture obtained in the previous step onto a current collector for obtain an electrode;

[0036] - 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.

[0037] According to another aspect, the present invention provides a method for preparing an electrode by solvent extraction comprising the steps of:

[0038] - mixing in the presence of a solvent of said binder according to the present invention, of a active material and optionally a conducting agent;

[0039] - deposition of the mixture obtained in the previous step onto a current collector for obtain an electrode;

[0040] - drying of said electrode.

[0041] 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. Detailed description of the invention

[0042] 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 fluorinated polymer A and an acrylic polymer B.

[0043] Preferably, said binder is in powder form. Using the binder in powder form allows for solvent-free processing from the mixing phase of the components to the deposition phases on the current collector and consolidation. Furthermore, using a binder in powder form for manufacturing the electrode eliminates the need for grinding steps. or dispersion after mixing with the active materials and conducting agents. In particular, said powder has a particle size distribution with a D90 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, particularly 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 Malvern INSITEC System particle size analyzer 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 having 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 preferred less than or equal to 150 pm, preferably preferred less than or equal to 100 pm, particularly preferred less than or equal to 50 pm.

[0044] According to a preferred embodiment, said fluorinated polymer A contains in its chain at least one monomer selected 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.

[0045] Preferably, said fluorinated polymer A contains at least monomeric units 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 R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4;the product of formula R2OCF=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.

[0046] 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 include non-fluorinated monomers.

[0047] According to one embodiment, the fluorinated polymer A is a vinylidene fluoride homopolymer.

[0048] According to an alternative embodiment, the fluorinated polymer A is a polymer comprising motifs derived from vinylidene fluoride, and preferably is chosen from homopolymer polyvinylidene fluoride and copolymers comprising motifs of vinylidene fluoride and motifs derived from at least one other comonomer copolymerizable with vinylidene fluoride.

[0049] Thus, said fluorinated polymer 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=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4;the product of formula R2OCF=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.

[0050] According to a preferred embodiment, the fluorinated polymer A is a copolymer comprising vinylidene fluoride (VDF) units and units 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 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'CH2OCF=CF2 in which R' is hydrogen or F(CF2)z and z is 1, 2, 3 or 4; the product of formula R”OCF=CH2 in which R” is F(CF2)z and z is 1, 2, 3 or 4; perfluorobutylethylene; 3,3,3-trifluoropropcnc or 2-trinuoromcthyl-3,3,3-trifluoro-1-propene or a mixture thereof.

[0051] Preferably, the fluorinated polymer 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 fluorinated polymer A, the mass percentage of vinylidene fluoride units is at least 50%, preferably at least 60%, more preferably greater than 70%, and advantageously greater than 80%.

[0052] According to a particular embodiment, the fluorinated polymer A is functionalized in whole or in part, which allows it to improve adhesion to metal. Thus, said fluorinated polymer A may comprise monomeric units bearing 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.

[0053] The function is introduced by a chemical reaction which may be grafting, or a copolymerization of the fluorinated monomer with a monomer bearing 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.

[0054] According to one embodiment, the functional group carries a carboxylic acid function which is a (meth)acrylic acid type group selected from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.

[0055] According to one embodiment, the units bearing the carboxylic acid function further comprise a heteroatom selected from oxygen, sulfur, nitrogen and phosphorus.

[0056] 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 bearing functional groups selected from the following 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, and phosphonic. An example of such a transfer agent is acrylic acid oligomers. According to one embodiment The preferred transfer agent is an acrylic acid oligomer with a molar mass less than or equal to 20000 g / mol.

[0057] The functional group content of 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 here, is meant a PVDF having a molten viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to the ASTM D-3835 method measured at 232°C and 100 sec-1.

[0059] The homopolymer PVDFs 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] The 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 can form agglomerates with a weight-average size of 1 to 30 micrometers, and preferably 2 to 10 micrometers. The agglomerates can break down into discrete particles during formulation and application to a substrate.

[0062] According to certain embodiments, homopolymer PVDF and VDF copolymers are composed of bio-based VDF. The term "bio-based" means "derived from biomass." This improves the polymer's environmental footprint. Bio-based VDF can be characterized by a renewable carbon content, i.e., carbon of natural origin from a biomaterial or biomass, of at least 1 atomic percent 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 comes from a biomaterial (or biomass), as described below.According to certain embodiments, the bio-carbon content of 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 CO2 Li+ functional group(s). Preferably, said acrylic polymer B has a lithiation level of at least 30%. The lithiation level corresponds to the ratio between the number of moles of -CO2 Li+ groups and the number of moles of carboxylic groups and -CO2 Li+ groups in said acrylic polymer B. In particular, said acrylic polymer has a lithiation level of at least 35%, advantageously at least 40%, preferably at least 50%. Said acrylic polymer B having a lithiation level such as expressed herein makes it possible to improve the conductivity of an electrode containing said binder.

[0065] Preferably, said acrylic polymer B in water solution has a pH 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 -CO2H functional group 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 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.

[0068] Preferably, the acrylic polymer B comprises monomeric units containing one or more CO2 Li+ functional group(s), monomeric units bearing one or more carboxylic acid or carboxylic acid anhydride functional group(s), and monomeric units bearing 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 on 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 R1R2C=C(R3)((X1)n-CO2 Li+) in which the substituents R1, R2 and R3 are independently 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 R1R2C=C(R3)((X2)n-CO2H) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and a C1-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being a C1-C5 alkyl; X1 and X2 being independently a C1-C10 alkyl hydrocarbon group optionally bearing one or more hydroxyl group(s); n is 0 or 1; and - optionally monomeric units M2 from a monomer of formula R4R5C=C(R6)C(O)R7 in which the substituents R4, R5 and R6 are independently 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; and R7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of CrCi8 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its cyclic 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, the conductivity performance of the electrode, and also to obtain deformable polymer particles compatible with the fluorinated polymer A.

[0072] In particular, the monomeric units M0 are derived from a monomer of formula R1R2C=C(R3)((X1)n-CO2 Li+) in which the substituents R1 and R2 are independently of each other H or CO2H; and R3 is H, CH2CO2H or CH3; X1 is a C1-C5 alkyl hydrocarbon group optionally bearing one or more hydroxyl groups; n is 0 or 1. More particularly, the monomeric units M0 are derived from a monomer of formula R1R2C=C(R3)((X1)n-CO2 Li+) in which the substituents R1 and R2 are independently of each other H or CO2H; and R3 is H, CH2CO2H or CH3; X1 is a CrC3 alkyl hydrocarbon group optionally bearing one or more hydroxyl groups; n is 0 or 1. Preferably, the monomeric units M 0 are derived from a monomer of formula R'R2C=C(R3)(CO2 Li+) in which the substituents R1 and R2 are independently of each other H or CO2H; and R3 is H, CH2CO2H or CH3.

[0073] In particular, the monomeric units M1 are derived from a monomer of formula R1R2C=C(R3)((X2)n-CO2H) in which the substituents R1 and R2 are independently of each other H or CO2H; and R3 is H, CH2CO2H or CH3; X2 is a C1-C5 alkyl hydrocarbon group optionally bearing one or more hydroxyl groups; n is 0 or 1. More specifically, the monomeric units M1 are derived from a monomer of formula R'R2C=C(R3)((X2)n-CO2H) in which the substituents R1 and R2 are independently of each other H or CO2H; and R3 is H, CH2CO2H or CH3; X2 is a CrC3 alkyl hydrocarbon group optionally bearing one or more hydroxyl groups; n is 0 or 1. Preferably, the monomeric units Ml are derived from a monomer of formula R'R2C=C(R3)(CO2H) in which the substituents R1 and R2 are independently of each other H or CO2H; and R3 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%, particularly at least 20%, more particularly at least 30%, preferably at least 40%, particularly preferably at least 50% in moles of monomeric units Ml.

[0074] Preferably, said acrylic polymer B comprises monomeric units M2 of formula R4R5C=C(R6)C(O)R7 in which the substituents R4, R5, and R6 are independently selected from the group consisting of H, CO2H, and Ci-C5 alkyls optionally substituted with a CO2H or CO2R' group, with R' being C1-C5 alkyl; R7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR', with R' selected from the group consisting of C1-C18 alkyls optionally substituted with one or more -OH groups; and a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain. Said heterocycle may be saturated, unsaturated, or aromatic. Said heterocycle may be monocyclic or bicyclic.The heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone ring. The heterocycle may be substituted by one or more C1-C5 alkyl groups. As mentioned above, the alkyl CrCi8 group is optionally substituted by the heterocycle. The heterocycle may be linked to the alkyl chain by the nitrogen atom or any other atom forming the heterocycle. Preferably, the heterocycle is 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone. In this 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, hydroxyethyl group. In particular, said acrylic polymer B comprises monomeric units M 2 of formula R4R5C=C(R6)C(O)R7 in which the substituents R4 and R5 are H; R6 is H or CH3; R7 is -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 by a ureido, hydroxyethyl group.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" here includes acrylates and methacrylates.

[0075] 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% in moles of monomeric units M 2.

[0076] Optionally, the acrylic polymer B may also include monomeric units M3 derived from an unsaturated monomer copolymerizable with monomers of formula R1R2C=C(R1)OX2)1-CO2H), R'R^QR^^X'VCO, Li+) and monomers of formula R4R5C=C(R6)C(O)R7 as defined above. Advantageously, the resulting M3 monomeric units can be derived from a monomer of formula (R8)(R9)C=C(R10)(Rn-R12), (R8)(R9)C=C(R10)(P(O)(OR13)(OR14)), (R8)(R9)C=C(R10)(C(O)NH(R17-R18)) or (R8)(R9)C=C(R10)(C(O)N(R15-R16)(R17-R18)) in which the substituents R8, R9 and R10 are independently selected from the group consisting of H and Ci-C5 alkyl;R11, R15 and R17 are independently selected from each other from the group consisting of CrCi8 alkyl, C6-Ci8 aryl, C4-Ci8 cycloalkyl, Ci-Ci8 fluoroalkyl, C6-Ci8 fluoroaryl, C4-Ci8 fluorocycloalkyl, propylene glycol oligomers, ethylene glycol oligomers, hexafluoropropylene oxide oligomers and tetrafluoroethylene oxide oligomers; R12, R16 and R18 are independently selected from each other from the group consisting of CO2H, COOM, OH, CONH2, CON(R19)2, SO3H, SO3M with R19 being Ci-C5 alkyl, M is NH4+, NR194+, Na+ or K+; R13 and R14 are independently selected from each other from the group; consisting of H, CrCi8 alkyl, C6-Ci8 aryl, C4-Ci8 cycloalkyl, CrCi8 fluoroalkyl, C6-Ci8 fluoroaryl, C4-Ci8 fluorocycloalkyl, propylene glycol oligomers, ethylene glycol oligomers, hexafluoropropylene oxide oligomers, tetrafluoroethylene oxide oligomers, an alkali cation, NH4+ and NR194+-. Preferably, the M3 monomeric units 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, the 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. Among these, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, acrylamido-2-methylpropane sulfonic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, allyl glycidyl ether, 1,3-butadiene, and acrylonitrile are preferred. These compounds can be used alone or in mixtures of two or more. Preferably, the acrylic polymer B comprises less than 30%, advantageously less than 20% by moles, of monomeric M3 units.

[0077] The acrylic polymer B used in the invention can be obtained by polymerizing the monomers according to known polymerization methods such as emulsion or suspension polymerization. The acrylic polymer B thus obtained is then contacted with a solution or dispersion of lithium hydroxide to obtain monomers containing -CO2Li groups. The concentration of LiOH is adjusted to achieve the desired -CO2Li group content.

[0078] According to a preferred embodiment, said acrylic polymer B also comprises a divalent cation. Said divalent cation may be Ca2+, Mg2+, Ba2+, Cu2+, or Zn2+, or a mixture thereof. Preferably, said divalent cation may be Ca2+ or Zn2+, or a mixture thereof. Said divalent cation is preferably bonded to a CO2 carboxylate group of said acrylic polymer B. Said divalent cation may be added in the form of a solution or a hydroxide dispersion of said cation. This is added to the acrylic polymer B simultaneously or not with the solution or LiOH dispersion mentioned above. The presence of this divalent cation improves the efficiency of the battery comprising said acrylic polymer B. The molar ratio between the divalent cation and lithium is 0.01 to 1, preferably 0.05 to 0.5.

[0079] According to a preferred embodiment, the mass percentage of acrylic polymer B relative to 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] In another aspect, the present invention provides a method for preparing said binder according to the present invention. In a preferred embodiment, said method comprises a step of: - A mixture of said fluorinated polymer A in the form of latex and said acrylic polymer B in the form of an aqueous solution or latex, and - Optionally, drying of the mixture obtained in the previous step, preferably by spray drying or co-spray drying, - Optionally, grinding of the dried mixture obtained in the previous step.

[0081] The drying step can be carried out by spraying or co-spraying, preferably at a temperature of 100°C to 220°C. The powder can also be obtained by grinding techniques, such as cryo-milling, where the mixture is brought to a temperature below ambient 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 can 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 in powder form.

[0082] Alternatively, said fluorinated polymer A and said acrylic polymer B can be mixed in the presence of an organic solvent or a water-organic solvent mixture.

[0083] 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.

[0084] In a preferred embodiment, the electrode has the following mass composition:

[0085] a. 50% to 99.9% active material, preferably 50% to 99%

[0086] b. 25% to 0% of conducting agent, preferably 25% to 0.5%,

[0087] c. 25% to 0.05% of said binder according to the invention, preferably 25% to 0.5%,

[0088] d. 0% to 5% of at least one additive chosen from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and an auxiliary flow agent;

[0089] the sum of all these percentages being 100%.

[0090] 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 a carbon nanotube, a carbon nanofiber, a carbon fiber by vapor phase growth; metal powders such as SUS powder, and aluminum powder.

[0091] Active materials are materials that are capable of storing and releasing lithium ions.

[0092] 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 Li4TiO12. The shape of the active material of the negative electrode is not particularly limited but is preferably particulate.

[0093] In another preferred embodiment, said electrode is a positive electrode. Preferably, for a positive electrode, said active material is chosen 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 LiMn spinel substituted by a different element having a composition represented by Ll+xMn2-x-yMyO4, M representing at least one metal chosen 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 metal and lithium phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni.

[0094] Furthermore, 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 coating materials include LiNbO3, Li4Ti5O2, and Li3PO4.

[0095] The shape of the active material of the positive electrode is not particularly limited but is preferably particulate.

[0096] According to another aspect of the present invention, a method for preparing the dry coated electrode is provided.

[0097] Said method for preparing the dry-coated electrode comprises the following steps:

[0098] - mixture of the active material, said binder according to the present invention in the form of powder as described above, and the conductive agent using a process that provides an electrode formulation applicable to a metallic substrate by a "solvent-free" process;

[0099] - deposition of said electrode formulation onto a substrate by a solvent-free process to obtain a Li-ion battery electrode, and

[0100] - 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.

[0101] A “solvent-free” process is a process that does not require a residual solvent evaporation step after the deposition step.

[0102] A thermomechanical treatment can be carried out for example by a calendering machine comprising rollers which can be heated or a plate press which can also be heated.

[0103] As solvent-free mixing processes of the different constituents of the electrode formulation before the deposition phase on the collector, the following may be mentioned without being exhaustive: mixing by agitation, mixing by air jet, high shear mixing, mixing by V mixer, mixing by screw mass mixer, mixing by double cone, mixing by drum, conical mixing, mixing by double Z arm, fluidized bed mixing, planetary mixer mixing, mechano-fusion mixing, mixing by extrusion, mixing by calendering, mixing by grinding.

[0104] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free spraying process, by depositing the formulation onto the metallic substrate, by a pneumatic spraying process, by electrostatic spraying, by dipping in a fluidized powder bed, by sprinkling, by electrostatic screen printing, by deposition with rotary brushes, by deposition with rotary adding rollers, by calendering.

[0105] According to one embodiment, the electrode is consolidated after a solvent-free spray deposition process on the metallic substrate (pneumatic spraying, electrostatic spraying, fluidized bed immersion, sprinkling, electrostatic screen printing, deposition with rotary brushes, deposition with rotary addition rollers) by a calendering process. This process consists of applying pressure to the electrode using two rollers, optionally heated.

[0106] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free, two-step process. The first step consists of in the manufacture of a self-supporting film from the premixed formulation using a thermomechanical process such as extrusion, calendering, or thermocompression. In a second step, the self-supporting film is laminated onto the metallic substrate by a process combining temperature and pressure, such as calendering or thermocompression.

[0107] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free process using a calendering process that allows the film formation and coating transfer to the current collector to be performed in a single step, i.e., without a separate step for manufacturing a self-supporting film. To achieve this, the calender used has several rollers (at least three). The powder obtained after the mixing step is introduced between the first two rollers, which are usually heated and have differential rotation speeds to shear the powder. The coating formed and remaining adhered to the fastest roller is then directly laminated onto the current collector with a third roller. The electrode thus obtained can be subsequently passed through another calender to adjust its porosity or thickness if necessary.

[0108] The mass ratio of conducting agents to active material is preferably 0 to 10%, more preferably 0 to 7%.

[0109] The mass ratio of binder to active material is preferably from 0.1 to 10%, more preferably from 0.5 to 7%.

[0110] According to one embodiment, the electrode components are all mixed at once according to conventional processes, leading to an electrode formulation.

[0111] In one embodiment, said electrode formulation is applied to a substrate by electrostatic screen printing. Some examples of substrates are current collectors such as a metal foil and metal mesh, polymer films, or a solid electrolyte layer of a solid-state battery.

[0112] The preferred thickness of an electrode is from 0.1 pm to 1000 pm, preferably from 0.1 pm to 300 pm.

[0113] According to another aspect, the present invention provides a solvent-based method for preparing an electrode comprising the steps of:

[0114] - mixing in the presence of a solvent of said binder according to the present invention, of a active material and optionally a conducting agent;

[0115] - deposition of the mixture obtained in the previous step onto a current collector for obtain an electrode;

[0116] - drying of said electrode.

[0117] In this process, 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), dimethyl sulfoxide (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.

[0118] 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. Examples

[0119] The following examples illustrate the present invention without limiting it. Method for measuring pH

[0120] A Mettler Toledo SevenEasy or equivalent pH meter and an Electrode In Lab Routine Pro are used. Before calibration, the electrode is checked for cleanliness. If necessary, clean the electrode with warm soapy water. The pH electrode is always kept filled with KC1 filling solution. The instrument is calibrated with pH 10, 7, and 4 buffer solutions. To calibrate, the electrode is immersed in the pH 10 buffer solution and the Cal button is pressed. Once the pH has stabilized, the procedure is repeated with the pH 7 buffer and then the pH 4 buffer. The electrode is rinsed with distilled water and dried between each buffer. The electrode is prepared beforehand by soaking it in a 0.1 M HCl solution for one to two hours and then rinsing it with deionized water. To measure pH, the electrode is dipped into the product as it is to be tested and shaken 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.

[0121] Polymer B

[0122] In a 1000 ml glass reactor equipped with mechanical stirring and an oil bath heater, 416 g of deionized water and 3.2 g of 97% sodium dodecyl sulfate were weighed out. In a first container equipped with a magnetic stir bar, 150 g of deionized water, 1.06 g of 97% sodium dodecyl sulfate, 0.7 g of diallyl phthalate, 163 g of methyl methacrylate, and 116 g of methacrylic acid were weighed out. This mixture was stirred constantly throughout the polymerization process. In a second container, a solution was prepared consisting of 0.7 g of ammonium persulfate and 10 g of deionized water. In a third container, a solution was prepared consisting of 0.1 g of sodium metabisulfite and 10 g of deionized water. The reactor was heated to 76°C. The contents of the second and third containers were introduced into the reactor, and then the contents of the first container were added. The dispersion was introduced, always under stirring using a peristaltic pump, into the reactor for 120 minutes at 76°C. It was then heated to 78°C for 60 minutes. A dispersion containing 28% dry matter was obtained. The particles had a median diameter of 100 nm, measured by the degree of freedom. The pH of the aqueous dispersion was 3.1. A 20% lithium hydroxide dispersion in water was added to this solution to achieve a lithiation level of 35%.

[0123] Polymer A

[0124] 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 particle sizes of 145 nm. PVDF is a copolymer of vinylidene fluoride and hexafluoropropylene characterized by a melting point of 148°C measured by DSC (differential scanning calorimetry).

[0125] Aqueous formulations are prepared according to the following process:

[0126] Polymer A is weighed into a container and, under agitation using a mechanical stirrer, acrylic polymer B is introduced in 10 min. The agitation time after introduction of the acrylic polymer is 10 min.

[0127] Example 1

[0128] 70.11 g of polymer A is weighed out and 30.04 g of polymer B is added. The aqueous formulation, containing 70% PVDF and 30% acrylic polymer by dry weight, is placed in a crystallizing dish and dried for 24 hours in an oven at 110°C. A homogeneous powder is obtained, which is first ground using an electric knife mill of the coffee grinder type, and then cryogenically ground using a ball mill. The resulting powder is particularly homogeneous and can be easily compressed to obtain polymer coatings on metal surfaces, for example, using presses or calendering machines.This process allows for dry coating on aluminum substrates, enabling the production of cathodes without the use of toxic solvents such as NMP, and even eliminating the need for aqueous processes that require costly drying and complex formulations demanding precise rheological control. The same solvent-free process can be used for anode manufacturing.

Claims

Demands

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 CO2 Li+ functional group(s) and said acrylic polymer B has a lithiation rate of at least 30% and in that the acrylic polymer B comprises monomeric units containing one or more CO2 Li+ functional group(s), monomeric units bearing one or more carboxylic acid or carboxylic acid anhydride functional group(s) and monomeric units bearing one or more carboxylic acid ester functional group(s).

2. Binder according to the preceding claim characterized in that said acrylic polymer B also comprises at least 5 mole percent 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 fluorinated polymer A contains at least monomeric units 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 R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4;the product of formula R2OCF=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.;

4. Binder according to any one of the preceding claims characterized in that said fluorinated polymer 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=CF2 in which n is 1, 2, 3, 4 or 5;the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=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.;

5. Binder according to any one of the preceding claims characterized in that the fluorinated polymer 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 fluorinated polymer A comprises monomeric units bearing 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 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 MO derived from a monomer of formula R'R^^CR3)((X1)n-CO2 Li+) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and Ci-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being Ci-C5 alkyl, monomeric units Ml derived from a monomer of formula R'R2C=C(R3)((X2)n-CO2H) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and Ci-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being Ci-C5 alkyl; X1 and X2 being independently of each other a hydrocarbon group Ci-Cio alkyl optionally bearing one or more hydroxyl group(s); n is 0 or 1;and optionally monomeric units M2 derived from a monomer of formula R4R5C=C(R6)C(O)R7 in which the substituents R4, R5 and R6 are independently selected from the group consisting of H, CO2H and Ci-C5 alkyl optionally substituted by a CO2H or CO2R' group with R' being Ci-C5 alkyl; and R7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of Ci-Ci8 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its cyclic chain.;

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

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

11. Binder according to any one of the preceding claims characterized in that said acrylic polymer B also comprises a divalent cation.

12. Electrode comprising said binder according to any one of claims 1 to 11, a conductive agent and an active material.

13. Electrode according to the preceding claim having the following mass composition: a. 50% to 99% of active material, b. 25% to 0.5% of conductive agent, 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-aiding agent; the sum of all these percentages being 100%.

14. Electrode according to any one of claims 12 and 13, said conducting agent being composed of one or more materials from among carbon blacks, such as acetylene black, Ketjen black; carbon fibers, such as a carbon nanotube, a carbon nanofiber, a carbon fiber by vapor phase growth; metal powders such as a SUS powder, and an aluminum powder.

15. Electrode according to any one of claims 12 to 14, wherein, for a positive electrode, said active material is selected from the group consisting of: LiCoO2, Li(Ni, Co, Al)O2, Li(i+ 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 LiMn spinel substituted by a different element having a composition represented by Lii+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 metal and lithium phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni.

16. Electrode according to any one of claims 12 to 14, 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 Li4Ti50i2.

17. A method for preparing a dry-coated electrode comprising: - mixing said binder in powder form according to any one of claims 1 to 11, with an active material and optionally with a conductive agent; - depositing the mixture obtained in the previous step onto a current collector to obtain an electrode; - consolidating 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.

18. A process for preparing an electrode by solvent means comprising the steps of: - mixing in the presence of a solvent said binder according to any one of claims 1 to 11, an active material and optionally a conductive agent; - depositing the mixture obtained in the previous step onto a current collector to obtain an electrode; - drying said electrode.

19. 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 12 to 16.