Powder binder for preparing an electrode in a solvent-free process

Abstract

The present invention relates to an electrode binder comprising a polymer P1 and a polymer P2 forming an interpenetrating polymer network or a semi-interpenetrating polymer network.

Description

Title of the invention: Powder binder for preparing an electrode in a solvent-free 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 a dry-coated electrode for a Li-ion battery. 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 a lithium battery comprises an anode (on discharge), and a cathode (also on discharge) generally composed of a lithium insertion compound of metal oxide type, such as LiMn2O4, LiCoO2 or LiNiO2, between which is inserted an electrolyte which conducts the 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 so-called inactive components since they do not directly contribute to the 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 (high 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 involves preparing an ink by mixing an active material, a conductive filler, and a polymer binder in a solvent. This ink is then deposited onto a current collector, and the solvent is evaporated. A large portion of the energy consumed by this process comes from the solvent evaporation step. A strong trend in the field of lithium-ion batteries is to reduce manufacturing costs, which involves limiting the energy consumption costs associated with manufacturing.

[0007] Compared to the conventional wet suspension electrode manufacturing process, dry (solvent-free) manufacturing processes are simpler; these processes eliminate emissions of volatile organic compounds and offer the possibility of manufacturing electrodes with greater thicknesses (> 120 µm), resulting in a higher energy density of the final energy storage device. The change in production technology will have little impact on the active material of the electrodes; however, the polymer additives responsible for the mechanical integrity of the electrodes must be adapted to the new manufacturing conditions.

[0008] The adhesion of the coating to the current collector obtained with a solvent-free process is often lower than that obtained with a slurry process. To improve adhesion to the current collector, one solution is to use a current collector coated with a conductive coating that provides adhesion to the current collector and ensures electronic transfer between the current collector and the electrode coating. However, this solution is expensive and results in a significant additional cost.

[0009] Therefore, there is a need for a binder offering good electrochemical resistance and providing good adhesion to a metallic current collector via a solvent-free manufacturing process. Furthermore, it is essential that said binder have a high affinity with the other ingredients of the solvent-free formulation so that, during pressing, the binder provides intimate cohesion. Summary of the invention

[0010] According to a first aspect, the present invention relates to a binder in powder form comprising a polymer PI including monomeric units derived from a fluorinated monomer and a polymer P2 including at least one monomeric unit derived from a monomer M2 of formula R'R2C=C(R3)C(O)R in which the sub constituents R1, R2 and R3 are independently selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C18 alkyl optionally substituted by one or more -OH, CO2H, SO3H, PO3H or a five- or six-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; said polymer PI and said polymer P2 form an interpenetrating polymer network or a semi-interpenetrating polymer network; characterized in that said binder has a particle size distribution Dv50 less than or equal to 25 pm.

[0011] An interpenetrating polymer network is defined as a network in which the The polymers are at least partially intertwined at the molecular level but not covalently bonded to each other and can only be separated if chemical bonds are broken. A semi-interpenetrating polymer network comprises one or more polymer networks and one or more linear or branched polymers and is characterized by the molecular-level penetration of at least one of the networks by at least some of the linear or branched macromolecules. A mixture of two or more preformed polymer networks is not an interpenetrating polymer network or a semi-interpenetrating polymer network.

[0012] The present invention has one or more advantages. Among these, the present invention makes it possible to improve the cohesion of the electrode because no solvent is present during its manufacture, which will limit cracking phenomena, to improve adhesion to the metal substrate, i.e. the current collector, and to avoid the use of an expensive coated current collector, to limit the use of toxic organic solvents, or to increase productivity by eliminating the drying step after manufacture of the electrode.

[0013] According to a preferred embodiment, said binder has a particle size distribution Dv50 less than or equal to 10 pm.

[0014] According to a preferred embodiment, said binder has a particle size distribution Dv90 less than or equal to 100 pm, preferably less than or equal to 25 pm.

[0015] Said binder according to the present invention having the size distribution as described in this application makes it possible to improve the performance of the electrode containing it.

[0016] According to a preferred embodiment, said PI polymer is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units of a monomer Ml 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(CF 3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF 2 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 R2 OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

[0017] According to a preferred embodiment, the PI polymer is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer Ml selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or a mixture thereof.

[0018] According to a preferred embodiment, said PI polymer 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, or a mixture thereof.

[0019] According to a preferred embodiment, said monomer M2 has the formula R*R2C=C(R 3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of H and CrCi8 alkyl optionally substituted by one or more -OH, CO2H, SO3H, PO3H group(s).

[0020] According to a preferred embodiment, said polymer P2 comprising: - 50 to 100% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of Ci-Ci8 alkyl; - from 0 to 30% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of H and C1-C18 alkyl bearing one or more functional groups selected from the group consisting of CO2H, PO3H, SO3H; - 0 to 20% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of C1-C18 alkyl bearing one or more -OH functional groups.

[0021] According to another aspect, the present invention provides a powder electrode composition for preparing a dry-coated electrode comprising said binder according to the present invention, an active material, and optionally a conductive agent, an additive, or a mixture of both; characterized in that said composition has a packed density of at least 70% of the packed density of said active material measured according to ISO 1068:1975. Packed density is an increased apparent density obtained after mechanically compacting a container holding the powder sample. Packed density is obtained by mechanically compacting a graduated cylinder or a container holding the powder sample. Packed density is measured according to ISO 1068:1975.

[0022] According to a preferred embodiment, said composition has the following mass composition:

[0023] a. 50% to 99.9% active material, preferably 50% to 99%

[0024] b. 0.1% to 25% binder according to the present invention, preferably 0.5% to 25%,

[0025] c. 0% to 25% conducting agent, preferably 0.5% to 25%

[0026] 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;

[0027] the sum of all these percentages being 100%.

[0028] According to a preferred embodiment, said composition comprises a conductive agent being composed of one or more materials selected from the group consisting of carbon black, graphite, carbon fibers, carbon nanotubes, carbon nanofibers, metal powders such as SUS powder and aluminum powder, or mixtures thereof.

[0029] According to a preferred embodiment, in said electrode composition, 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 LiMn spinel substituted by an element different 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.

[0030] According to another embodiment, in said electrode composition, 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, silicone, a silicon alloy and Li4TiOi2.

[0031] According to another aspect, the present invention provides a dry coated electrode comprising a current collector and a layer consisting of the electrode composition according to the present invention, preferably said layer is in contact with the current collector. In a non-limiting manner, said current collector may be made of copper or aluminum.

[0032] According to another aspect, the present invention provides a method of preparing a dry coated electrode according to the preceding claim characterized in that it comprises the steps of:

[0033] - mixture of said active material in powder form, of said binder according to the present invention, and optionally of the conductive agent in powder form, of the additive in powder form or both to form said electrode composition according to the present invention;

[0034] - deposition of said electrode composition on said current collector to form an electrode, and

[0035] - optionally consolidation of said electrode by a thermo treatment mechanical.

[0036] According to another aspect, the present invention provides a Li-ion battery comprising a positive electrode, a negative electrode and a separator, at least one electrode being a dry-coated electrode according to the present invention. Detailed description of the invention

[0037] According to a first aspect of the present invention, a binder is provided. Said binder according to the present invention is in powder form. Said binder comprises a PI polymer and a P2 polymer as described in the present invention. Said PI polymer and said P2 polymer form an interpenetrating polymer network or a semi-interpenetrating polymer network as defined above.

[0038] According to a preferred embodiment, said binder has a particle size distribution Dv50 less than or equal to 25 µm. Dv50 is the particle size at the 50th Percentile (by volume) of the cumulative particle size distribution. This parameter can be determined by laser diffraction. This applies to all Dv50s described herein. This parameter is determined by laser diffraction. A Malvem INSITEC System particle size analyzer is used for the measurement. This is performed using a dry method by laser diffraction on a powder with a 100 mm focal length.The binder may have a particle size distribution Dv50 less than or equal to 24 pm, advantageously less than or equal to 23 pm, preferably less than or equal to 22 pm, more preferably less than or equal to 21 pm, in particular less than or equal to 20 pm, more particularly less than or equal to 19 pm, preferably less than or equal to 18 pm, advantageously less than or equal to 17 pm, preferably less than or equal to 16 pm, more preferably less than or equal to 15 pm, particularly less than or equal to 14 pm, and more particularly less than or equal to 13 pm. According to a particular embodiment, the binder has a particle size distribution Dv50 less than or equal to 12 pm, preferably less than or equal to 11 pm, in particular less than or equal to 10 pm.

[0039] According to a preferred embodiment, said binder has a particle size distribution Dv90 less than or equal to 100 pm. Dv90 is the particle size at the 90th percentile (by volume) of the cumulative particle size distribution. This parameter can be determined by laser diffraction. This applies to all Dv90 values ​​described herein. This parameter is determined by laser diffraction. A Malvem INSITEC System particle size analyzer is used for the measurement. This measurement is performed using a dry method by laser diffraction on a powder with a focal length of 100 mm.The said binder may have a particle size distribution Dv50 less than or equal to 90 pm, advantageously less than or equal to 80 pm, preferably less than or equal to 70 pm, more preferably less than or equal to 60 pm, in particular less than or equal to 50 pm, more particularly less than or equal to 40 pm, preferably less than 30 pm, advantageously preferably less than or equal to 25 pm.

[0040] PI Polymer

[0041] Said PI polymer comprises monomeric units derived from a fluorinated monomer. Said fluorinated monomer is a vinyl compound comprising at least one fluorine atom.

[0042] Preferably, said PI polymer 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 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); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.Among the trifluoropropenes, we can mention 3,3,3-trifluoropropene. Among the tetrafluoropropenes, we can mention 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene. Among the pentafluoropropenes, we can mention 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene can refer to either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0043] In particular, said PI polymer comprises at least monomeric units derived from vinylidene fluoride. The PI polymer may be a homopolymer or a copolymer. The copolymer may also comprise non-fluorinated monomers.

[0044] According to one embodiment, the PI polymer is a vinylidene fluoride homopolymer.

[0045] According to an alternative embodiment, the PI polymer is a polymer comprising motifs derived from vinylidene fluoride, and preferably is chosen from homopolymer poly-vinylidene fluoride and copolymers comprising motifs of vinylidene fluoride and motifs derived from at least one other comonomer copolymerizable with vinylidene fluoride.

[0046] Thus, said polymer PI 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(CF 3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

[0047] According to a preferred embodiment, the PI polymer 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;trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene or 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof. ;

[0048] Preferably, the PI polymer 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 PI polymer, 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%.

[0049] According to a particular embodiment, the PI polymer is functionalized in whole or in part, which allows it to improve adhesion to metal. Thus, said PI polymer 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.

[0050] 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.

[0051] 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, methyl acrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.

[0052] According to one embodiment, the units bearing the carboxylic acid function further comprise a heteroatom selected from oxygen, sulfur, nitrogen and phosphorus.

[0053] 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: 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 groups. An example of such a transfer agent 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.Alternatively, the functional group may be introduced by an oligomeric or polymeric compound comprising said functional group and mixed with the polymer PL. The oligomeric or polymeric compound may be impregnated in or mixed with the polymer PI or intimately mixed therewith. In this case, the functional group may be derived from a (meth)acrylic acid compound selected from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate. For example, the functional group may be an oligomer or a polymer comprising monomeric units derived from a monomer selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.According to one embodiment, the oligomer or polymer has a weight-average molecular mass less than or equal to 100,000 g / mol, advantageously less than 80,000 g / mol, preferably less than 60,000 g / mol, more preferably less than 40,000 g / mol, and in particular less than 20,000 g / mol. The weight-average molecular mass is determined by GPC using a Waters apparatus. 2695e coupled with a Wyatt NEON refractometer equipped with two PL Gel mixed C columns and a guard column (7.8 mm LD x 30 cm, 5 pm) under the following conditions: Temperature: 35°C; flow rate: 1.0 mL / min; injection volume: 100 pL. Samples were prepared at a concentration of 1 mg / ml in THF. Twelve poly(methyl methacrylate) samples with a molecular mass ranging from 535 to 2,210,000 g / mol were used as calibration standards.

[0054] The content of functional groups in the PVDF is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

[0055] The homopolymer PVDFs and VDF copolymers used in the invention can be obtained by known polymerization methods such as emulsion or suspension polymerization.

[0056] According to one embodiment, they are prepared by an emulsion polymerization process in the absence of fluorinated surfactant.

[0057] Polymerization of PVDF results in a latex generally having a solids content of 10 to 60% by weight, preferably 10 to 50%.

[0058] 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%.

[0059] Said PI polymer may have a melting temperature of between 80°C and 180°C measured according to ASTM D3418, preferably from 100°C to 170°C.

[0060] Polymer P2

[0061] As mentioned above, said polymer P2 comprising at least one monomeric motif derived from a monomer M2 of formula R1R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C18 alkyl optionally substituted by one or more -OH, CO2H, SO3H, PO3H group(s) or a five or six-membered heterocycle comprising at least one nitrogen atom in its cyclic chain.

[0062] Said heterocycle may be saturated or unsaturated or aromatic. Said heterocycle may be monocyclic or bicyclic. Said heterocycle may be a pyrrole, pyr-rolidine, 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-C8 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, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.

[0063] Preferably, said polymer P2 comprises monomeric motifs derived from a monomer M2 of formula R'R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2 C(O)CH3 or -OR' with R' selected from the group consisting of Ci-Ci8 alkyl optionally substituted by one or more -OH, CO2H, SO3H, PO3H group(s), a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain. Preferably, the heterocycle is as defined above; in particular, the heterocycle is 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone. The term "alkyl (meth)acrylate" encompasses both alkyl acrylates and alkyl methacrylates.

[0064] Preferably, said monomer M2 is of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of H and CrCi8 alkyl optionally substituted by one or more -OH, CO2H, SO3H, PO3H group(s).

[0065] According to a preferred embodiment, the substituent R' is selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxybutyl, hydroxypropyl, ethyl substituted by a ureido, hydroxyethyl, hydroxypropyl, hydroxybutyl group.

[0066] In particular, said polymer P2 comprises monomeric motifs derived from a monomer M2 of formula R'R2C=C(R3)C(O)R in which the substituents R1 and R2 are H; R3 is H or CH3; R is -OR' with R' selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, hydroxypropyl, hydroxy butyl, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.

[0067] Thus, the monomer M2 can be methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, methyl acrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, methacrylate amyl, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureido methacrylate.Among these, alkyl acrylates with an alkyl group having from 1 to 8 carbon atoms are preferred, and alkyl acrylates with an alkyl group having from 1 to 5 carbon atoms are even more preferable. These compounds can be used alone or in mixtures of two or more. Thus, the polymer P2 can be a homopolymer of a monomer M2 as defined above or a copolymer resulting from a mixture of one or more monomers M2 as defined above.

[0068] The P2 polymer may also comprise monomeric units derived from:

[0069] - (A) an alkenyl compound containing a functional group, and

[0070] - (B) an alkenyl compound without a functional group.

[0071] The alkenyl compound (A) containing a functional group includes, for example, α,[3-unsaturated] carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, crotonic acid, itaconic acid and the like; vinyl ester compounds such as vinyl acetate, vinyl neodecanoate and the like; amide compounds such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, diacetone acrylamide and the like; acrylic acid esters such as 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, fluoroalkyl acrylate and the like;methacrylic acid esters such as dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate and the like; maleic anhydride, and alkenyl glycidyl ether compounds such as allyl glycidyl ether and the like. Among these, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, acrylamide; Diacetone, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and allyl glycidyl ether. These compounds can be used alone or in mixtures of two or more.

[0072] The functional group-free alkenyl compound (B) includes, for example, conjugated dienes such as 1,3-butadiene, isoprene and the like; divinyl hydrocarbon compounds such as divinyl benzene and the like; and alkenyl cyanides such as acrylonitrile, methacrylonitrile and the like. Among these, preferred are 1,3-butadiene, and acrylonitrile. These compounds may be used alone or as a mixture of two or more.

[0073] It is preferable that the functional alkenyl compound (A) is used in a proportion of less than 50% by weight relative to the weight of the monomer mixture and that the functional group-free alkenyl compound (B) is used in a proportion of less than 30% by weight relative to the weight of the monomer mixture.

[0074] According to a particular embodiment, said polymer P2 comprises: - from 50 to 100% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of Ci-Ci8 alkyl; - from 0 to 30% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of H and C1-C18 alkyl bearing one or more functional groups selected from the group consisting of CO2H, PO3H, SO3H; - 0 to 20% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of C1-C18 alkyl bearing one or more -OH functional groups.

[0075] Preferably, said polymer P2 comprises: - 50 to 100% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of Ci-Cio alkyl; - from 0 to 30% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of H and C1-C10 alkyl carrying one or more functional groups selected from the group consisting of CO2H, PO3H, SO3H; - from 0 to 20% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and Ci-C5 alkyl; R' selected from the group consisting of Ci-Cio alkyl carrying one or more -OH functional groups.

[0076] In particular, said polymer P2 comprises: - 50 to 100% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C3 alkyl; R' selected from the group consisting of Ci-Cio alkyl; - from 0 to 30% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and Ci-C3 alkyl; R' selected from the group consisting of H and Ci-Cio alkyl carrying one or more functional groups selected from the group consisting of CO2H, PO3H, SO3H; - 0 to 20% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and CrC3 alkyl; R' selected from the group consisting of Ci-Cio alkyl bearing one or more -OH functional groups.

[0077] More specifically, said polymer P2 comprises: - 50 to 99% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and CrC3 alkyl; R' selected from the group consisting of CrC10 alkyl; - from 0.5 to 30% by weight of monomeric units from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and Ci-C3 alkyl; R' selected from the group consisting of H and Ci-Cio alkyl bearing one or more functional groups selected from the group consisting of CO2H, PO3H, SO3H; - from 0.5 to 20% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and Ci-C3 alkyl; R' selected from the group consisting of Ci-Cio alkyl carrying one or more -OH functional groups. Binder preparation process

[0078] Said binder can be prepared by a process comprising the steps of:

[0079] a) Supply of a reactor containing said PI polymer comprising monomeric motifs derived from a fluorinated monomer,

[0080] b) Addition of at least one monomer M2 of formula R'R2C=C(R3)C(O)R as defined in the present application in said reactor and bringing said polymer PI into contact with said at least one monomer M2;

[0081] c) Implementation of the polymerization of said at least one monomer M2;

[0082] d) Drying and optionally grinding the product obtained in step c) to prepare said binder according to the present invention.

[0083] In step a), said PI polymer is preferably in the form of a latex.

[0084] During step b), at least one monomer M2 of formula R'R2C=C(R3)C(O)R as defined in the present application is added to said reactor. During step b), preferably all of the monomers constituting the polymer P2 are added, if the latter contains different monomeric units of formula R'R2 C=C(R3)C(O)R. The addition of all of said at least one monomer M2 constituting the polymer P2 in step b) makes it possible to improve the intimacy of the mixture between the polymer PI and all of the monomeric units constituting the polymer P2.

[0085] In step b), the polymer PI and said at least one monomer M2 are brought into contact for a sufficiently long period to allow said monomer M2 to impregnate the particles of the polymer PI before the polymerization of the latter is carried out. This contact period may be at least 5 minutes, preferably 10 minutes, and in particular at least 15 minutes. The longer the contact period between the monomer M2 and the polymer PI, the more intimate the mixing between the polymer PI and the polymer P2 (after polymerization of the monomer M2).

[0086] The process also includes a step c) in which said at least one monomer M2 is polymerized. Step c) is preferably carried out in the presence of water. The polymerization step c) of said at least one monomer M2 is carried out in the presence of an initiator. Said initiator may be a persulfate-type initiator such as sodium persulfate, potassium persulfate, barium persulfate, or ammonium persulfate; alkali metal bisulfites; peroxides such as benzoyl peroxide or dicumyl peroxide; hydroperoxides such as that methyl hydroperoxide or tert-butyl hydroperoxide; acyloins such as benzoin; peracetates such as methyl peracetate, tert-butyl peracetate; perbenzoates such as tert-butyl perbenzoate; peroxalates such as dimethyl peroxalate or di(tert-butyl) peroxalate; azo compounds such as azo-bisisobutyronitrile or dimethyl azo-bisisobutyrate. The initiator is preferably added in a content of 0.005 to 1% by weight based on the weight of said at least one monomer M2 and optionally of said alkenyl compounds (A) and (B) if present.

[0087] Optionally, step c) is carried out in the presence of a chain transfer agent. The chain transfer agent may be an oxygenated compound such as an alcohol, carbonate, ketone, ester, or ether; a halocarbon or hydrohalocarbon compound such as chlorocarbons, hydrochlorocarbons, chlorofluorocarbons, or hydrochlorofluorocarbons; ethane; or propane. Alternatively, the chain transfer agent may be a polymer with a molar mass less than or equal to 20,000 g / mol and bearing functional groups selected from the following: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, or phosphonic groups. An example of such a transfer agent is acrylic acid oligomers.Preferably, if present, the chain transfer agent is added at a level of 0.05 to 5% by weight based on the weight of said at least one monomer M2 and optionally of said alkenyl compounds (A) and (B) if present.

[0088] Other compounds may also be in the implementation of said composition according to the present process as mentioned in the protocol described in WO 2007 / 018783.

[0089] Step c) can be carried out at a temperature of 20°C to 160°C. Step c) can be carried out at a pressure of 280 to 20000 kPa.

[0090] Preferably steps b) and c) are carried out under agitation.

[0091] The polymerization product obtained in step c) is dried in step d). The step of Drying 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, for example using 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 further grinding to obtain the desired particle size distribution.

[0092] Electrode composition, electrode and preparation process

[0093] According to another aspect of the present invention, an electrode composition is provided. Said electrode composition is in powder form. The electrode composition is used for the preparation of a dry coated electrode. Said electrode composition comprises said binder according to the present invention, an active material and optionally a conductive agent, an additive or a mixture of both; characterized in that said composition has a tapped density of at least 70% of the tapped density of said active material measured according to ISO 1068:1975.

[0094] In a preferred embodiment, the dry-coated electrode has the following mass composition:

[0095] a. 50% to 99.9% active material, preferably 50% to 99%

[0096] b. 0.1% to 25% binder according to the present invention, preferably 0.5% to 25%,

[0097] c. 0% to 25% conducting agent, preferably 0.5% to 25%

[0098] 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;

[0099] the sum of all these percentages being 100%.

[0100] In a particular embodiment, the dry-coated electrode has the following mass composition:

[0101] a. 65% to 99.9% active material, preferably 70% to 99%

[0102] b. 0.1% to 25% binder according to the present invention, preferably 0.5% to 25%,

[0103] c. 0% to 10% conducting agent, preferably 0.5% to 5%,

[0104] 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;

[0105] the sum of all these percentages being 100%.

[0106] The conductive agents in the dry-coated electrode are composed of one or more materials that can improve conductivity. According to a preferred embodiment, said electrode composition comprises a conductive agent. This may be selected from the group consisting of carbon black, graphite, carbon fibers, carbon nanotubes, carbon nanofibers, metal powders such as SUS powder and aluminum powder, or mixtures thereof. The carbon black may be, for example, acetylene black or Ketjen black.

[0107] Active materials are materials that are capable of storing and releasing lithium ions.

[0108] 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, silicone, an alloy of silicon and Li4TiOi2. The shape of the active material of the negative electrode is not particularly limited but is preferably particulate.

[0109] 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 Lii+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.

[0110] 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 the coating material include LiNbO3, Li4Ti5O2, and Li3PO4.

[0111] The shape of the active material of the positive electrode is not particularly limited but is preferably particulate.

[0112] According to a preferred embodiment of the present invention, a dry-coated electrode is provided. Said electrode comprises a current collector and a layer consisting of the electrode composition according to the present invention, preferably said layer being in contact with the current collector.

[0113] According to another aspect of the present invention, a method for preparing the dry-coated electrode is provided. This method for preparing the dry-coated electrode comprises the following steps:

[0114] - mixture of the active material in powder form, said binder according to the present invention, and optionally of the conductive agent in powder form of the additive in powder form or of both to form said electrode composition according to the present invention;

[0115] - deposition of said electrode composition on said current collector to form an electrode, and

[0116] - optionally consolidation of said electrode by a thermo treatment mechanical.

[0117] Said dry-coated electrode is thus prepared according to a “solvent-free” process, i.e. one which does not require a step of evaporation of residual solvent after the deposition step because all the constituents are mixed in the dry state, in powder form, and the The deposit is also made without solvent.

[0118] A thermomechanical treatment refers to the application of mechanical pressure to the electrode at a given temperature. Such a thermomechanical treatment can be carried out, for example, by a calendering machine having rollers that can be heated or a plate press that can also be heated.

[0119] As solvent-free mixing processes of the different constituents of the electrode composition 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.

[0120] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free spraying process, by depositing the electrode composition 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.

[0121] According to one embodiment, the consolidation of the electrode after a deposition process on the metallic substrate by solvent-free spraying (pneumatic spraying, electrostatic spraying, fluidized bed immersion, sputtering, electrostatic screen printing, deposition with rotary brushes, deposition with rotary addition rollers) is carried out by a calendering process. This process consists of applying pressure to the electrode using two rollers, which may be heated. The consolidation step is optional. Its implementation depends on the technique used to deposit the constituents onto the electrode. Thus, when the deposition step has been carried out by calendering, this consolidation step is optional because calendering allows for the simultaneous deposition and consolidation of the electrode.

[0122] 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 manufacturing a self-supporting film from the premixed formulation using a thermomechanical process such as extrusion, calendering, or thermocompression. In the second step, the self-supporting film is laminated onto the metallic substrate by a process combining temperature and pressure, such as calendering or thermocompression.

[0123] According to one embodiment, after the powder mixing step, the electrode is Manufactured using a solvent-free process and a calendering method, this electrode allows for the film formation and transfer of the coating onto the current collector in a single step, eliminating the need for a separate self-supporting film. To achieve this, the calender employs several rollers (at least three). The powder obtained after the mixing stage is fed between the first two rollers, which are typically heated and operate at different speeds to shear the powder. The coating, which adheres to the fastest roller, is then directly laminated onto the current collector by a third roller. The resulting electrode can be further calendered to adjust its porosity or thickness if necessary.

[0124] The mass ratio of conducting agents to active material is preferably 0 to 10%, more preferably 0 to 7%.

[0125] The mass ratio of binder to active material is preferably from 0.1 to 10%, more preferably from 0.5 to 7%.

[0126] According to one embodiment, the electrode components are all mixed at once according to conventional processes, leading to an electrode composition.

[0127] According to one embodiment, the electrode components are sequentially mixed using conventional methods, resulting in an electrode composition. In another embodiment, said electrode composition 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.

[0128] The preferred thickness of an electrode is from 0.1 pm to 1000 pm, preferably from 0.1 pm to 300 pm.

[0129] 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 a dry-coated electrode according to the present invention. Examples

[0130] The following examples illustrate the present invention without limiting it. Anode preparation

[0131] A Pla polymer is used which is a copolymer of vinylidene fluoride and hexafluoropropylene with a melting temperature of 145°C measured for a hexafluoropropylene content of 5% by weight. A Pib polymer is also used which is a copolymer of vinylidene fluoride and hexafluoropropylene with a melting temperature of 145°C for a hexafluoropropylene content of 6% by weight. The melting temperature was measured according to ASTM D3418. The active ingredient The material used is C-NERGY Actilion GHDR 15-4 graphite, marketed by the company IMERYS.

[0132] The binders used for preparing the electrode are prepared according to the process detailed in this application. The binders have the following composition, shown in Table 1:

[0133] [Tables 1] Polymer PI Mass Ratio P1 / P2 Polymer P2 Methyl Methacrylate (%wt) Methacrylic Acid (%wt) Binder 1 Pla 90 / 10 90 10 Binder 2 Pla 80 / 20 90 10 Binder 3 Pib 90 / 10 90 10

[0134] Said binders according to the present invention have a particle size distribution Dv50 less than or equal to 25pm determined by laser granulometry. Electrode preparation

[0135] Graphite lithium-ion battery anodes were produced using a solvent-free process, the electrostatic spraying process.

[0136] The anodes are composed of X% by weight of polymer binder according to the invention and (100-X)% by weight of graphite. Each electrode is prepared according to the following protocol: - Mixture of components:

[0137] The graphite and binder powder are weighed and introduced into a 250ml metal pot. The graphite / binder formulation is mixed for 1 minute thirty using a Minimix type vibrating mixer marketed by the company MERRIS. The formulation containing the binder according to the present invention has a packed density of at least 70% of the packed density of said active material (here graphite) measured according to the ISO 1068:1975 standard. - Deposition of the formulation onto the current collector

[0138] Once mixed, the powder formulation is deposited onto an 18 µm thick copper current collector. The deposition is carried out by electrostatic spraying using the Optiselect Pro gun controlled by an Optiflex Pro control unit, a system marketed by GEMA. The deposited quantity is between 10 and 15 mg / cm² over a 10 x 5 cm² area. - Electrode consolidation

[0139] Once the deposition step is completed, the electrode is consolidated using a table calender (model CA3 / 200-SP marketed by SUMET GmbH). The speed of the The roller speed is fixed at 0.1 m / min. The compression force is controlled to apply a force per unit length of 44 N / mm with a maximum calendering consolidation temperature of 150°C.

[0140] Table 2 summarizes the compositions of the anodes prepared with a weight of approximately 12 mg / cm2.

[0141] [Tables2] Composition of the electrodes Graphite Binder 1 Binder 2 Binder 3 Pla Example 1 95 5 Example 2 95 5 Example 3 95 5 Example 4 97 3 Comparative example 95 5

[0142] Composition in % mass Measuring membership

[0143] The adhesion between the coating and the copper foil is evaluated by measuring the peel force at 180° using a dynamometer. To do this, a 25 mm wide strip of electrode material is cut. This strip is then bonded to a rigid aluminum plate using double-sided adhesive, with the adhesive applied to the graphite / binder coating side. The peel test is performed using an MTS System Synergie 200H dynamometer, with the rigid aluminum plate held in one jaw and the flexible aluminum foil on which the coating was applied held in the other. In this configuration, the peel angle is 180°. The jaw movement speed is set at 100 mm / min. Table 3 summarizes the electrode peel force values.

[0144] [Tables3] Peel force (N / m) Example 1 300 Example 2 200 Example 3 280 Example 4 200 Comparative example <10

[0145] As can be seen, the binders according to the present invention make it possible to prepare anodes in which the adhesion between the binder and the current collector is greatly improved.

Claims

Claims

1. A binder in powder form comprising a polymer PI comprising monomeric units derived from a fluorinated monomer and a polymer P2 comprising at least one monomeric unit derived from a monomer M2 of formula R'R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C18 alkyl optionally substituted by one or more groups -OH, CO2H, SO3 H, PO3H or a five- or six-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; said polymer PI and said polymer P2 form an interpenetrating polymer network or a semi-interpenetrating polymer network; characterized in that said binder has a particle size distribution Dv50 less than or equal to 25 pm.

2. Binder according to the preceding claim characterized in that it has a particle size distribution Dv50 less than or equal to 10 pm.

3. Binder according to any one of the preceding claims, characterized in that it has a particle size distribution Dv90 less than or equal to 100 pm, preferably less than or equal to 25 pm.

4. Binder according to any one of the preceding claims characterized in that said polymer PI is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units of a monomer M1 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); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

5. Binder according to any one of the preceding claims, characterized in that the polymer PI is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1 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 PI polymer 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, or a mixture thereof.

7. Binder according to any one of the preceding claims, characterized in that said monomer M2 is of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of H and C1-C8 alkyl optionally substituted by one or more group(s) -OH, CO2H, SO3 H, PO3H.

8. Binder according to any one of the preceding claims, characterized in that said polymer P2 comprises: - from 50 to 100% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of C1-C18 alkyl; - from 0 to 30% by weight of monomeric units derived from at least a monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of H and C1-C8 alkyl carrying one or more functional groups selected from the group consisting of CO2H, PO3H, SO3 H; - from 0 to 20% by weight of monomeric units derived from at least one monomer of formula R1R2C=C(R3)C(O)OR' in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R' selected from the group consisting of C1-C18 alkyl carrying one or more -OH functional groups.

9. An electrode composition in powder form for preparing a dry coated electrode comprising said binder according to any one of the preceding claims, an active material and optionally a conductive agent, an additive or a mixture of both; characterized in that said composition has a tapped density of at least 70% of the tapped density of said active material measured according to ISO 1068:1975.

10. An electrode composition according to the preceding claim, having the following mass composition: a. 50% to 99.9% of active material, preferably 50% to 99%, b. 0.1% to 25% of binder according to any one of the preceding claims 1 to 8, preferably 0.5% to 25%, c. 0% to 25% of conductive agent, preferably 0.5% to 25%, d. 0% to 5% of at least one additive selected from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for a conductive additive, and a flow aid; the sum of all these percentages being 100%.

11. Electrode composition according to any one of the preceding claims 9 or 10 characterized in that it comprises a conductive agent being composed of one or more materials selected from the group consisting of carbon black, graphite, carbon fibers, carbon nanotubes, carbon nanofibers, metal powders- metals such as SUS powder and aluminum powder, or mixtures thereof.

12. An electrode composition according to any one of the preceding claims 9 to 11 wherein said active material is selected from the group consisting of: LiCoO2, Li(Ni, Co, AI)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 Li Mn 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 lithium metal phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni.

13. An electrode composition according to any one of preceding claims 9 to 12 wherein 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, silicone, a silicon alloy and Li4TiO|2.

14. A dry coated electrode comprising a current collector, preferably copper, and a layer consisting of the electrode composition according to any one of the preceding claims 9 to 13, preferably said layer is in contact with the current collector.

15. A method of preparing a dry-coated electrode according to the preceding claim, characterized in that it comprises the steps of: - mixing said active material in powder form, said binder according to any one of claims 1 to 8, and optionally the conductive agent in powder form, the additive in powder form or both to form said electrode composition according to any one of the preceding claims 9 to 13; - depositing said electrode composition on said current collector to form an electrode, and - Optionally, consolidating said electrode by thermomechanical treatment.

16. A Li-ion battery comprising a positive electrode, a negative electrode and a separator, at least one electrode being a dry-coated electrode according to claim 14.