Electrode binder, electrode compound for lithium ion battery, and method for manufacturing solventless electrode

Abstract

The present invention relates to a binder for dry-coating electrodes of storage batteries, comprising a fluoropolymer A and an acrylic polymer B, characterized in that said binder is in powder form.

Description

[Technical Field]

[0001] The present invention relates generally to the field of electrical energy storage in lithium accumulators of the Li-ion type. More specifically, the present invention relates to a binder for dry-coating electrodes for Li-ion batteries. Another subject of the present invention is a method for producing electrodes by using said binder. The present invention also relates to lithium ion batteries manufactured by incorporating said electrodes. [Background technology]

[0002] A Li-ion or lithium battery element cell comprises an anode (for discharge) and a cathode (for discharge) generally made of a lithium insertion compound of the metal oxide type, such as LiMn2O4, LiCoO2 or LiNiO2, with an electrolyte that conducts lithium ions inserted between them.

[0003] Rechargeable or storage cells have advantages over primary (non-rechargeable) cells because the associated chemical reactions that occur at the battery's positive and negative electrodes are reversible. The electrodes of a storage cell can be regenerated multiple times by applying an electrical charge. Many advanced electrode systems have been developed for storing electrical charge. At the same time, significant effort has been put into developing electrolytes that can improve the capacity of electrochemical cells.

[0004] For these, electrodes generally comprise at least one current collector on which is deposited in the form of a film a composite consisting of a material, called the active material because it is electrochemically active towards lithium, a polymer acting as a binder, one or more electronically conductive additives, generally carbon black or acetylene black, and optionally a surfactant.

[0005] Binders are classified as inactive components because they do not directly contribute to the cell's capacity. However, their important role in electrode processing and their significant impact on the electrode's electrochemical performance have been widely documented. The main relevant physical and chemical properties of binders are thermal stability, chemical and electrochemical stability, tensile strength (strong adhesion and strong bonding), and flexibility. The main purpose of using binders is to form a stable network (bond) of the electrode's solid components, i.e., the active material and conductive agent. Furthermore, the binder must ensure intimate contact (adhesion) between the composite electrode and the current collector.

[0006] The current method for manufacturing electrodes for lithium-ion batteries, the "slurry" method, requires the use of a solvent. This method involves creating 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. Most of the energy consumed by this method comes from the solvent evaporation step. A major trend in the field of lithium-ion batteries is to reduce manufacturing costs, which includes limiting the costs associated with energy consumption for manufacturing.

[0007] Compared to the traditional wet suspension method for producing electrodes, the dry (solvent-free) manufacturing method is simpler. This method eliminates the emission of volatile organic compounds and allows for the production of electrodes with greater thickness (>120 μm), potentially resulting in higher energy density for the final energy storage device. Changes in manufacturing technology have little effect on the active material of the electrode. However, the polymer additives responsible for the electrode's mechanical integrity must be adapted to the new manufacturing conditions. US2019 / 0305316 discloses a dry-processed electrode film containing a particulate, non-fibrillating binder with specific particle sizes, and a method for obtaining a film flexible enough to be handled in roll-to-roll processing using a fibrillating binder. However, the fibrillating binder requires additional shearing in addition to dispersing the components, which consumes a large amount of energy and destroys the active material. Document US2020 / 0313193 also discloses dry-processed electrode films containing elastic polymer binders, which are self-supporting and contain at most an insufficient amount of polytetrafluoroethylene.Document US2020 / 0313193 primarily discloses polyethylene as the elastic polymer binder, which is not sufficiently electrochemically stable for use in both the cathode and the anode of a lithium-ion accumulator.

[0008] The adhesion of the coating to the current collector obtained using the solvent-free process is often inferior to that obtained using the slurry process. One solution to improve adhesion to the current collector involves using a conductive coating on the current collector, which contributes to adhesion to the current collector and ensures electron transfer between the current collector and the electrode coating. However, this solution is expensive and results in significant additional costs.

[0009] Therefore, there is a need for a binder that provides good electrochemical resistance and contributes to good adhesion to the metal current collector via a solventless manufacturing process. Furthermore, it is essential that the binder has a high affinity for the other components of the solventless formulation, as this binder contributes to intimate bonding during compaction. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] US Patent Application Publication No. 2019 / 0305316 [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0313193 Summary of the Invention

[0011] According to a first aspect, the invention relates to a binder for dry coating electrodes of storage batteries comprising a fluoropolymer A and an acrylic polymer B, characterized in that said binder is in the form of a powder.

[0012] The binder according to the present invention, which includes two types of polymers, i.e., a fluoropolymer and an acrylic polymer, can improve adhesion to the current collector. The use of a powdered binder makes it possible to eliminate the use of solvents from the stage of mixing the components to the stage of deposition and solidification on the current collector. Furthermore, the use of a powdered binder for electrode production can avoid relying on a grinding or dispersion stage after mixing with the active material and conductive agent.

[0013] According to a preferred embodiment, said binder has a particle size distribution with a D90 of less than or equal to 750 μm.

[0014] According to a preferred embodiment, said acrylic polymer B has a pH of 1.5 to 4.0, measured in water at ambient temperature.

[0015] According to a preferred embodiment, said acrylic polymer B comprises at least 20% by weight, based on the total weight of said acrylic polymer B, of monomer units containing a —CO 2 H functional group.

[0016] According to a preferred embodiment, the fluoropolymer A is 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), products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CHOCN or CHOPO3H, products of the formula CF2=CFOCF2CF2SO2F, products of the formula F(CF2) n CH2OCF=CF2, where n is 1, 2, 3, 4, or 5; 1 The product of CH2OCF=CF2, where R 1 is hydrogen or F(CF2) m and m has the value 1, 2, 3 or 4; 2 OCF=CH2 products, where R 2 is F(CF2) p and p is 1, 2, 3 or 4, and the copolymer contains at least a monomer unit obtained from a monomer selected from the group consisting of perfluorobutylethylene (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 fluoropolymer A is a polymer comprising monomer units derived from vinylidene fluoride and, optionally, 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), products of formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CHOCN or CHOPO3H, products of formula CF2=CFOCF2CF2SO2F, products of formula F(CF2) n CH2OCF=CF2, where n is 1, 2, 3, 4, or 5; 1 The product of CH2OCF=CF2, where R 1 is hydrogen or F(CF2) m and m has the value 1, 2, 3 or 4; 2 OCF=CH2 products, where R 2 is F(CF2) p and p is 1, 2, 3, or 4; and

[0018] According to a preferred embodiment, fluoropolymer A is a homopolymer of vinylidene fluoride or a copolymer comprising monomer units derived from vinylidene fluoride and monomer units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or mixtures thereof.

[0019] According to a preferred embodiment, the fluoropolymer A comprises monomer units having at least one of the functional groups selected from the group consisting of carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy, e.g., glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic, sulfuric, phosphoric and phosphonic.

[0020] According to a preferred embodiment, the acrylic polymer B has a glass transition temperature of less than or equal to 230°C.

[0021] According to a preferred embodiment, the acrylic polymer B has a molecular weight of 3000 g.mol -1 It has a number average molar mass of at least 1.0.

[0022] According to a preferred embodiment, the acrylic polymer B comprises monomer units having a carboxylic acid or carboxylic anhydride functional group and monomer units having a carboxylic ester functional group.

[0023] According to a preferred embodiment, the acrylic polymer B has the formula R 1 R 2 C=C(R 3 )COH monomer units, where R 1 , R 2 and R 3 are independently selected from the group consisting of H and C1-C5 alkyl, and 4 R 5 C=C(R6 )C(O)R 7 wherein the substituent R 4 , R 5 and R 6 are each independently selected from the group consisting of H and C1-C5 alkyl; R 7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 and -OR', where R' is a C1-C2 optionally substituted with one or more -OH groups or a 5- or 6-membered heterocycle containing at least one nitrogen atom in its cyclic chain. 18 alkyl.

[0024] According to a preferred embodiment, the weight content of the acrylic polymer B relative to the fluoropolymer A is 1% to 70%.

[0025] According to another aspect, the present invention provides a method for the preparation of said binder according to the invention, comprising the following steps: - mixing said polymer A in latex form with said polymer B in aqueous solution form or in latex form, and drying the mixture obtained, preferably by atomization or coatomization, - optionally grinding the dry mixture obtained in the previous step The present invention is characterized by comprising:

[0026] According to another aspect, the present invention provides a dry-coated electrode comprising a binder according to the present invention, a dry active material, and optionally a conductive agent.

[0027] According to a preferred embodiment, the electrode has the following composition by weight: a. 50% to 99.9%, preferably 50% to 99%, of an active material; b. 25% to 0%, preferably 25% to 0.5%, of a conductive agent; c. 25% to 0.05%, preferably 25% to 0.5%, of the binder according to the present invention; d. 0% to 5% of at least one additive selected from the group consisting of plasticizers, ionic liquids, dispersants for conductive additives, and flow aids; and the sum of all these percentages is 100%.

[0028] According to a preferred embodiment, the conductive agent is composed of one or more materials selected from the group consisting of carbon black such as acetylene black or ketjen black, carbon nanotubes, carbon nanofibers or vapor-grown carbon fibers, and metal powders such as SUS powder and aluminum powder.

[0029] According to a preferred embodiment, in the case of the positive electrode, the active material is LiCoO2, Li(Ni, Co, Al)O2, Li (1+x) Ni a Mn b Co c (x is a real number greater than or equal to 0, 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, Li 1+x Mn 2-x-y M y Lithium titanate Li-Mn spinel substituted with different elements having a composition represented by the formula O4, where M represents at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, and x and y independently represent real numbers from 0 to 2. x TiO y , x and y independently represent real numbers from 0 to 2, and lithium metal phosphate having a composition represented by LiMPO4, where M represents Fe, Mn, Co, or Ni.

[0030] According to a preferred embodiment, in the case of the negative electrode, the active material is selected from the group consisting of lithium alloys, metal oxides, carbon materials such as graphite or hard carbon, silicon, alloys of silicon, and Li4TiO 12 is selected from the group consisting of:

[0031] According to another aspect, the present invention provides a method for producing a dry-coated electrode according to the present invention, which is carried out at a temperature T1 where Tm - 50°C < T1 < Tg + 50°C when Tg > Tm, or at a temperature T1 where Tg - 50°C < T1 < Tm + 50°C when Tm > Tg. Here, Tm is the melting point of the fluoropolymer A, and Tg is the glass transition temperature of the acrylic polymer B.

[0032] According to a preferred embodiment, the present invention provides a Li-ion battery comprising a positive electrode, a negative electrode, and a separator, wherein at least one of the electrodes is a dry-coated electrode according to the present invention.

Embodiments for Carrying Out the Invention

[0033] According to a first aspect, a binder for a dry-coated electrode of a storage battery is provided. Preferably, the binder contains a mixture of at least two polymers. Thus, the binder contains a fluoropolymer A and an acrylic polymer B.

[0034] Preferably, the binder is in the form of a powder. In particular, the powder has a particle size distribution with a D90 of 750 μm or less, advantageously 700 μm or less, preferably 650 μm or less, more preferentially 600 μm or less, particularly 550 μm or less, and more particularly 500 μm or less. Advantageously, the powder has a particle size distribution with a D90 of 450 μm or less, preferably 400 μm or less, more preferentially 350 μm or less, particularly 300 μm or less, more particularly 250 μm or less, advantageously 200 μm or less, advantageously and advantageously 150 μm or less, preferentially 100 μm or less, and particularly advantageously 50 μm or less. D90 is the size of the particles at the 90th percentile (by volume) of the cumulative particle size distribution. This parameter is determined by laser granulometry. A particle size analyzer of the Malvern Insitec system type is used for the measurement. The latter is performed in the dry route by laser diffraction on the powder with a focal length of 100 mm, which is the case for all D90s described herein.

[0035] According to a preferred embodiment, the weight content of acrylic polymer B relative to fluoropolymer A is between 1% and 70%, advantageously between 2% and 60%, preferably between 3% and 50%, more preferentially between 4% and 40%, in particular between 5% and 30%.

[0036] Fluoropolymer A According to a preferred embodiment, said fluoropolymer A contains in its chain a vinyl group that can open to polymerize and, directly attached to this vinyl group, at least one monomer chosen from compounds containing at least one fluorine atom, one fluoroalkyl group or one fluoroalkoxy group.

[0037] Preferably, the fluoropolymer A is 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), products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CHOCN or CHOPO3H, products of the formula CF2=CFOCF2CF2SO2F, products of the formula F(CF2) n CH2OCF=CF2, where n is 1, 2, 3, 4, or 5; 1 The product of CH2OCF=CF2, where R 1 is hydrogen or F(CF2) m and m has the value 1, 2, 3 or 4; 2 OCF=CH2 products, where R 2 is F(CF2) pThe polymer contains at least a monomer unit obtained from a monomer selected from the group consisting of perfluorobutylethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or a mixture thereof, where p is 1, 2, 3, or 4. Among the trifluoropropenes, mention may be made of 3,3,3-trifluoropropene. Among the tetrafluoropropenes, mention may be made of 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene. Among the pentafluoropropenes, mention may be made of 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene can mean either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. 1-chloro-1-fluoroethylene isomers are preferred. As chlorotrifluoropropene, 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene is preferred.

[0038] In particular, said fluoropolymer A comprises at least monomer units derived from vinylidene fluoride. Fluoropolymer A may be a homopolymer or a copolymer. The copolymer may also comprise non-fluorinated monomers.

[0039] According to one embodiment, fluoropolymer A is a vinylidene fluoride homopolymer.

[0040] According to an alternative embodiment, the fluoropolymer A is a polymer comprising units deriving from vinylidene fluoride, preferably chosen from polyvinylidene fluoride homopolymers and copolymers comprising vinylidene fluoride units and units deriving from at least one other comonomer copolymerizable with vinylidene fluoride.

[0041] Thus, the fluoropolymer A may comprise monomer units derived from vinylidene fluoride and 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), products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CHOCN or CHOPO3H, products of the formula CF2=CFOCF2CF2SO2F, products of the formula F(CF2) n CH2OCF=CF2, where n is 1, 2, 3, 4, or 5; 1 The product of CH2OCF=CF2, where R 1 is hydrogen or F(CF2) m and m has the value 1, 2, 3 or 4; 2 OCF=CH2 products, where R 2 is F(CF2) p and p is 1, 2, 3, or 4; and

[0042] According to a preferred embodiment, the fluoropolymer A is a polymer comprising units of vinylidene fluoride (VDF) and 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), products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CHOCN or CHOPO3H, products of the formula CF2=CFOCF2CF2SO2F, products of the formula F(CF2) n Products of formula CH2OCF=CF2, where n is 1, 2, 3, 4, or 5; products of formula R'CH2OCF=CF2, where R' is hydrogen or F(CF2) z and z is a value of 1, 2, 3 or 4. z and z is 1, 2, 3 or 4, and units derived from one or more monomers selected from the group consisting of trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or mixtures thereof.

[0043] Preferably, fluoropolymer A is a copolymer comprising monomer units derived from vinylidene fluoride and monomer units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, and hexafluoropropylene or mixtures thereof. In fluoropolymer A, the weight content of vinylidene fluoride units is at least 50%, preferably at least 60%, more preferably more than 70%, advantageously more than 80%.

[0044] According to a particular embodiment, the fluoropolymer A is fully or partially functionalized, making it possible to improve adhesion to metals. Thus, said fluoropolymer A comprises monomer units having at least one functional group selected from the group consisting of carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy, e.g., glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid and phosphonic acid, preferably at least one carboxylic acid or hydroxyl functional group.

[0045] The functional groups are introduced by chemical reaction, which may be grafting or copolymerization, of a fluorinated monomer with a monomer having at least one of said functional groups and a vinyl functional group capable of copolymerizing with the fluorinated monomer, according to techniques well known to those skilled in the art.

[0046] According to one embodiment, the functional group comprises a carboxylic acid functional group, which is a (meth)acrylic acid type group selected from acrylic acid, methacrylic acid, methylacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate and acryloyloxypropyl succinate.

[0047] According to one embodiment, the unit having a carboxylic acid functionality further comprises a heteroatom selected from oxygen, sulfur, nitrogen and phosphorus.

[0048] According to one embodiment, the functionality is introduced via a transfer agent used during the synthesis process. The transfer agent is a polymer having a molar mass of 20,000 g / mol or less and having functional groups selected from the following group: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, or phosphonic acid. Acrylic acid oligomers are an example of this type of transfer agent. According to a preferred embodiment, the transfer agent is an acrylic acid oligomer having a molar mass of 20,000 g / mol or less. The molar mass of the transfer agent is determined according to the method described below for acrylic polymer B.

[0049] The content of functional groups in PVDF is 0.01 mol % or more, preferably 0.1 mol % or more, and 15 mol % or less, preferably 10 mol % or less.

[0050] Preferably, the PVDF is of high molecular weight. As used herein, the term "high molecular weight" refers to PVDF that is viscoelastically bonded to a polymeric polymer at 232°C and 100 seconds by ASTM D-3835. -1 is understood to mean PVDF having a melt viscosity, measured at 100 Pa.s, preferably more than 500 Pa.s and more preferably more than 1000 Pa.s.

[0051] The PVDF homopolymers and VDF copolymers used in the present invention can be obtained by known polymerization methods such as emulsion or suspension polymerization.

[0052] According to one embodiment, they are made by an emulsion polymerization process in the absence of fluorinated surfactants.

[0053] Polymerization of PVDF generally results in a latex having a solids content of 10% to 60% by weight, preferably 10% to 50%, and a weight-average particle size of less than 1 micrometer, preferably less than 1000 nm, preferably less than 800 nm, and more preferably less than 600 nm. The weight-average particle size is generally at least 20 nm, preferably at least 50 nm, and advantageously the average size is in the range of 100 to 400 nm. The polymer particles can form agglomerates, the weight-average size of which is 1 to 30 micrometers, preferably 2 to 10 micrometers. The agglomerates can break down into discrete particles during formulation and application to a substrate.

[0054] According to a particular embodiment, the PVDF homopolymer and VDF copolymer are composed of bio-based VDF. The term "bio-based" means "originating from biomass". This makes it possible to improve the ecological footprint of the polymer. Bio-based VDF is, according to the standard NF EN 16640: 14 It can be characterized by a content of at least 1 atomic % renewable carbon, i.e. naturally occurring carbon derived from biological materials or biomass, as determined by the C content. The term "renewable carbon" indicates that the carbon is of natural origin and derived from biological materials (or biomass), as shown below. According to certain embodiments, the biocarbon content of the VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than 33%, preferably greater than 50%, preferably greater than 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, and advantageously equal to 100%.

[0055] Acrylic Polymer B As mentioned above, the binder also includes an acrylic polymer B.

[0056] Preferably, said acrylic polymer B has a pH, measured in water at ambient temperature, of between 1.5 and 4.0, advantageously between 1.6 and 3.9, preferably between 1.7 and 3.8, more preferentially between 1.8 and 3.7, in particular between 1.9 and 3.6, and more particularly between 2.0 and 3.5.

[0057] Preferably, said acrylic polymer B comprises at least 20% by weight, based on the total weight of said acrylic polymer B, of monomer units containing a —CO 2 H functional group.

[0058] Preferably, said acrylic polymer B has a glass transition temperature of less than or equal to 230° C. Advantageously, said acrylic polymer B has a glass transition temperature of less than or equal to 220° C., preferably less than 200° C., more preferentially less than 180° C., in particular less than 160° C. and more particularly less than or equal to 150° C.

[0059] According to a preferred embodiment, the acrylic polymer B has a molecular weight of 3000 g.mol -1 More than 10,000 g.mol -1 or more, preferably 50,000 g.mol -1 More preferably, 100,000 g.mol -1 Above 150,000 g.mol -1The polymer has a number-average molar mass of 0.05 mol / l or more. The molecular weight or molar mass is determined by size exclusion chromatography (SEC). A test sample of the polymer solution corresponding to 90 mg of dry substance is introduced into a 10 ml flask. A mobile phase supplemented with 0.04% dimethylformamide (DMF) is added to a total weight of 10 g. The composition of this mobile phase is as follows: NaHCO3: 0.05 mol / l, NaNO3: 0.1 mol / l, triethanolamine: 0.02 mol / l, NaN3: 0.03 wt%. The SEC line consists of a Waters 510 type isocratic pump with a flow rate adjusted to 0.8 ml / min, a Waters 717+ autosampler, an oven containing a Waters Ultrahydrogel guard column type precolumn with a length of 6 cm and an internal diameter of 40 mm, followed by a Waters Ultrahydrogel type linear column with a length of 30 cm and an internal diameter of 7.8 mm. Detection is provided by a Waters 410 RI type differential refractometer. The oven is set to 60°C and the refractometer is set to 45°C. The SEC instrument is set to 1000 g / mol ~ 1.10 6 Calibration is performed with a series of sodium polyacrylate standards supplied by Polymer Standards Service, with peak-top molecular weights in g / mol and polydispersity indices ranging from 1.4 to 1.7. The calibration curve is linear and takes into account the correction obtained with the flow marker dimethylformamide (DMF).

[0060] Preferably, the acrylic polymer B contains a monomer unit having a carboxylic acid or carboxylic anhydride functional group and, optionally, a monomer unit having a carboxylic acid ester functional group. By using the acrylic polymer B according to the present invention having such a functional group, adhesion to the current collector can be improved.

[0061] According to a preferred embodiment, the acrylic polymer B comprises:

[0062] -Formula R 1 R 2 C=C(R 3)COH monomer units M1, wherein the substituent R 1 , R 2 and R 3 are selected independently from the group consisting of H and C1-C5 alkyl, preferably H and C1-C3 alkyl, in particular H or CH3, and optionally, a compound of formula R 4 R 5 C=C(R 6 )C(O)R 7 where the substituent R 4 , R 5 and R 6 are each independently selected from the group consisting of H and C1-C5 alkyl; R 7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 and -OR', where R' is a C1-C2 optionally substituted with one or more -OH groups or a 5- or 6-membered heterocycle containing at least one nitrogen atom in its cyclic chain. 18 The monomeric unit M2 is selected from the group consisting of alkyl.

[0063] The combined presence of carboxylic acid and carboxylic acid ester functional groups not only improves adhesion to the current collector, but also makes it possible to obtain polymer particles that are deformable and compatible with fluoropolymer A.

[0064] The heterocycle may be saturated, unsaturated, or aromatic. The heterocycle may be monocyclic or bicyclic. The heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone ring. The heterocycle may be substituted with one or more C1-C5 alkyl groups. As described above, the C1-C5 alkyl groups may be substituted with one or more C1-C5 alkyl groups. 18The alkyl is optionally substituted with said heterocycle. The latter can be linked to the alkyl chain via a nitrogen atom or any other atom forming the heterocycle. Preferably, the heterocycle is 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone or 4-imidazolidinone.

[0065] Preferably, the acrylic polymer B is of formula R 4 R 5 C=C(R 6 )C(O)R 7 Based on alkyl acrylate monomer M2 of the formula 4 , R 5 and R 6 are each independently selected from the group consisting of H and C1-C5 alkyl; R 7 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 and -OR', where R' is a C1-C2 optionally substituted with one or more -OH groups or a 5- or 10-membered heterocycle containing at least one nitrogen atom in its cyclic chain. 18 Preferably, the heterocycle is as defined above, in particular the heterocycle is 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone or 4-imidazolidinone. In this patent application, the term "alkyl" includes straight-chain and branched alkyl.

[0066] 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 with a ureido group, and hydroxyethyl.

[0067] In particular, the acrylic polymer B is of the formula R 4 R 5 C=C(R 6 )C(O)R 7 wherein the substituent R 4 and R 5 is H and R6 is H or CH3, and R 7 is —OR′, and 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, hydroxypropyl, hydroxybutyl, 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone, 4-imidazolidinone, ethyl substituted with a ureido group, and hydroxyethyl.

[0068] Thus, the acrylic polymer B comprises monomer 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, methacrylic acid, methyl methacrylate, or ureido methacrylate. The term "acrylate" in this example includes acrylate and methacrylate.

[0069] In particular, the acrylic polymer B is of the formula R 1 R 2 C=C(R 3 )COH monomer units M1, wherein the substituent R 1 and R 2 is H and R 3 is H or CH3.

[0070] Optionally, the acrylic polymer B is a polymer of formula R 1 R 2 C=C(R 3 )COH monomer and formula R 4 R 5 C=C(R 6 )C(O)R 7Advantageously, the resulting monomeric unit M3 is of the formula (R 8 )(R 9 )C=C(R 10 )(R 11 -R 12 ), (R 8 )(R 9 )C=C(R 10 )(P(O)(OR 13 )(OR 14 )), (R 8 )(R 9 )C=C(R 10 )(C(O)NH(R 17 -R 18 )) or (R 8 )(R 9 )C=C(R 10 )(C(O)N(R 15 -R 16 )(R 17 -R 18 )) monomers, wherein the substituent R 8 , R 9 and R 10 are each independently selected from the group consisting of H and C1-C5 alkyl; R 11 , R 15 and R 17 are independent of each other, C1-C 18 Alkyl, C6-C 18 Aryl, C4-C 18 Cycloalkyl, C1-C 18 Fluoroalkyl, C6-C 18 Fluoroaryl, C4-C 18 R is selected from the group consisting of fluorocycloalkyl, propylene glycol oligomer, ethylene glycol oligomer, hexafluoropropylene oxide oligomer, and tetrafluoroethylene oxide oligomer; 12 , R 16 and R 18 are, independently of each other, CO2H, COOM, OH, CONH2, CON(R 19 )2, SO3H, and SO3M, and R 19 is C1-C5 alkyl and M is NH4+ , N.R. 19 4 + , Na + or K + and R 13 and R 14 are, independently of each other, H, C1-C 18 Alkyl, C6-C 18 Aryl, C4-C 18 Cycloalkyl, C1-C 18 Fluoroalkyl, C6-C 18 Fluoroaryl, C4-C 18 Fluorocycloalkyl, propylene glycol oligomer, ethylene glycol oligomer, hexafluoropropylene oxide oligomer, tetrafluoroethylene oxide oligomer, alkali cation, NH4 + and NR 19 4 + is.

[0071] Preferably, the monomer unit M3 is selected from the group consisting of fumaric acid, crotonic acid, itaconic acid, vinyl acetate, vinyl neodecanoate, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, diacetoneacrylamide, 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n The copolymer can be obtained from a monomer selected from the group consisting of 1,3-butadiene, 2-dodecyl acrylate, fluoroalkyl acrylate, dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, maleic anhydride, alkenyl glycidyl ether compounds, such as allyl glycidyl ether, 1,3-butadiene, isoprene, divinylbenzene, acrylonitrile, and methacrylonitrile. Among these, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, acrylamido-2-methylpropanesulfonic 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 combination.

[0072] According to a preferred embodiment, the acrylic polymer B comprises at least 30% by weight, advantageously at least 40% by weight, preferably at least 50% by weight of monomer units M1, based on the weight of the acrylic polymer B. According to another embodiment, the acrylic polymer B comprises at least 90% by weight, advantageously at least 95% by weight, preferably at least 99% by weight, in particular 100% by weight of monomer units M1, based on the weight of the acrylic polymer B.

[0073] According to a preferred embodiment, said acrylic polymer B comprises at least 1% by weight, advantageously at least 5% by weight, preferably at least 10% by weight, more preferentially at least 20% by weight, in particular at least 30% by weight and more particularly at least 40% by weight of monomer units M2, based on the weight of said acrylic polymer B. According to an alternative embodiment, the acrylic polymer B cannot comprise any monomer units M2.

[0074] According to a particular embodiment, the acrylic polymer B comprises less than 30% by weight, advantageously less than 20% by weight, preferably less than 10% by weight, in particular less than 5% by weight and more particularly less than 1% by weight of monomer units M3, based on the weight of said acrylic polymer B. According to an alternative embodiment, the acrylic polymer B cannot comprise any monomer units M3.

[0075] The acrylic polymer B used in the present invention can be obtained by polymerizing monomers by a known polymerization method such as emulsion polymerization or suspension polymerization.

[0076] According to another aspect, the present invention provides a method for preparing the binder according to the invention. According to a preferred embodiment, the method comprises the following steps:

[0077] - mixing said polymer A in latex form with said polymer B in aqueous solution form or in latex form, and drying the mixture obtained in the previous step, preferably by atomization or coatomization, Optionally, grinding the dry mixture obtained in the previous step.

[0078] The drying step can be carried out by atomization or coatomization, preferably at temperatures between 100°C and 220°C. Powders can also be obtained by comminution techniques such as cryogenic grinding, in which the mixture is brought to a temperature below ambient temperature, for example with liquid nitrogen, before grinding. At the end of the powder production step, i.e. after the drying step, the particle size can be adjusted and optimized by a selection or screening process and / or grinding.

[0079] Preferably, the binder has a pH, measured in water at ambient temperature, of between 1.5 and 4.0, advantageously between 1.6 and 3.9, preferably between 1.7 and 3.8, more preferentially between 1.8 and 3.7, in particular between 1.9 and 3.6, and more particularly between 2.0 and 3.5.

[0080] In another aspect, the present invention provides a dry-coated electrode, which comprises the binder according to the present invention, a conductive agent, and a dry active material.

[0081] According to a preferred embodiment, the dry coated electrode has the following composition by weight:

[0082] a. 50% to 99.9%, preferably 50% to 99%, of an active material; b. 25% to 0%, preferably 25% to 0.5%, of a conductive agent; c. 25% to 0.05%, preferably 25% to 0.5%, of said binder; d. 0% to 5% of at least one additive selected from the group consisting of plasticizers, ionic liquids, dispersants for conductive additives, and flow aids; All these percentages add up to 100%.

[0083] The conductive agent in the dry-coated electrode is composed of one or more materials capable of improving electrical conductivity. Some examples include carbon black, such as acetylene black or ketjen black; carbon fiber, such as carbon nanotubes, carbon nanofibers, or vapor-grown carbon fiber; or metal powder, such as SUS powder and aluminum powder.

[0084] The active material is a substance that can absorb and release lithium ions.

[0085] In a preferred embodiment, the electrode is a negative electrode. In particular, in the case of a negative electrode, the active material is a lithium alloy, a metal oxide, a carbon material such as graphite or hard carbon, silicon, an alloy of silicon, and Li4TiO 12 The form of the negative electrode active material is not particularly limited, but is preferably in the form of particles.

[0086] In another preferred embodiment, the electrode is a positive electrode. Preferably, in the case of a positive electrode, the active material is LiCoO2, Li(Ni, Co, Al)O2, Li (1+x) Ni a Mn b Co c (x is a real number greater than or equal to 0, 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, Li 1+x Mn 2-x-y M y Lithium titanate Li-Mn spinel substituted with different elements having a composition represented by the formula O4, where M represents at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, and x and y independently represent real numbers from 0 to 2. x TiO y , x and y independently represent real numbers from 0 to 2, and lithium metal phosphate having a composition represented by LiMPO4, where M represents Fe, Mn, Co, or Ni.

[0087] Furthermore, the surfaces of each of the above-described materials can be coated. The coating material is not particularly limited as long as it has conductivity with respect to lithium ions and can be maintained in the form of a coating layer on the surface of the active material. Examples of the coating material include LiNbO3, Li4Ti5O 12 and include Li3PO4.

[0088] The form of the positive electrode active material is not particularly limited, but it is preferably in the form of particles.

[0089] According to another aspect of the present invention, a method for manufacturing a dry-coated electrode is provided. The method includes a step of thermomechanical treatment performed at a temperature T1 where Tm - 50°C < T1 < Tg + 50°C when Tg > Tm, or at a temperature T1 where Tg - 50°C < T1 < Tm + 50°C when Tm > Tg, where Tm is the melting point of the fluoropolymer A and Tg is the glass transition temperature of the acrylic polymer B.

[0090] The method for manufacturing the dry-coated electrode includes the following steps.

[0091] - Using a method for providing an electrode composition that can be applied to a metal substrate by a "solvent-free" process, mixing an active material, the binder according to the present invention in powder form as described above, and a conductive agent. - Depositing the electrode composition on a substrate by a solvent-free process to obtain a Li-ion battery electrode, and - Solidifying the electrode by thermomechanical treatment performed at a temperature T1 where Tm - 50°C < T1 < Tg + 50°C when Tg > Tm, or at a temperature T1 where Tg - 50°C < T1 < Tm + 50°C when Tm > Tg, where Tm is the melting point of the fluoropolymer A and Tg is the glass transition temperature of the acrylic polymer B.

[0092] The "solvent-free" process is a method that does not require a step of evaporating residual solvents after the deposition step.

[0093] Thermomechanical treatment means adding heat together with mechanical pressure at a temperature T1 where Tm - 50°C < T1 < Tg + 50°C when Tg > Tm, or at a temperature T1 where Tg - 50°C < T1 < Tm + 50°C when Tm > Tg, where Tm is the melting point of the fluoropolymer A and Tg is the glass transition temperature of the acrylic polymer B. Such thermomechanical treatment can be carried out, for example, by a calendar processing apparatus equipped with rolls that can be heated, or by a plate compressor that can similarly heat a compressor.

[0094] As a method for solvent-free mixing of various components of the electrode formulation before the stage of deposition onto the current collector, although not exhaustive, mixing by stirring, mixing by air jet, high-shear mixing, mixing in a V-type mixer, mixing in a screw mixer, double-cone mixing, drum mixing, conical mixing, double-Z arm mixing, mixing in a fluidized bed, mixing in a planetary mixer, mixing by mechanofusion, mixing by extrusion, mixing by calendar processing, mixing by grinding can be mentioned.

[0095] According to one embodiment, after the powder mixing stage, the electrode is produced by a solvent-free spraying process, by deposition of the formulation onto a metal substrate, by an air pressure spraying process, by electrostatic spraying, by immersion in a fluidized powder bed, by spraying, by electrostatic screen printing, by deposition with a rotating brush, by deposition with a rotating metering roll, by calendar processing.

[0096] According to one embodiment, the curing of the electrode after the deposition step onto the metal substrate by solvent-free spraying (by an air pressure spraying process, by electrostatic spraying, by immersion in a fluidized powder bed, by spraying, by electrostatic screen printing, by deposition with a rotating brush, by deposition with a rotating metering roll) is carried out by a calendar processing step. This step consists of applying pressure to the electrode using two optionally heated rolls.

[0097] According to one embodiment, after the powder mixing step, the electrode is manufactured by a two-stage solventless process. The first stage consists of producing a free-standing film from the pre-mixed formulation by a thermomechanical process such as extrusion, calendering, or thermocompression. In the second stage, the free-standing film is laminated onto a metal substrate by a combined temperature and pressure process such as calendering or thermocompression.

[0098] According to one embodiment, after the powder mixing step, the electrode is produced by a solvent-free process using a calendering process, which allows the film formation and transfer of the coating onto the current collector to be carried out in a single step, i.e., without the production of a free-standing film. To achieve this, the calender used has several rolls (at least three). The powder obtained after the mixing step is generally heated and introduced between the first two rolls, which have different rotation speeds to shear the powder. The coating formed and remaining attached to the fastest roll is then directly laminated to the current collector with the third roll. The electrode thus obtained can then be passed through the calender again to adjust its porosity or thickness, if necessary.

[0099] The weight ratio of the conductive agent to the active material is preferably 0% to 10%, and more preferably 0% to 7%.

[0100] The weight ratio of the binder to the active material is preferably 0.1% to 10%, and more preferably 0.5% to 7%.

[0101] According to one embodiment, the electrode components are mixed all at once according to conventional methods to obtain the electrode formulation.

[0102] According to one embodiment, the electrode components are mixed sequentially according to conventional methods to obtain an electrode formulation. In one embodiment, the electrode formulation is applied to a substrate by electrostatic screen printing. Some examples of substrates are current collectors such as metal sheets or meshes, polymer films, or layers of solid electrolyte in solid-state batteries.

[0103] The preferred thickness of the electrode is 0.1 μm to 1000 μm, preferably 0.1 μm to 300 μm.

[0104] According to another aspect of the present invention, a lithium ion battery is provided. Preferably, the lithium ion battery includes a positive electrode, a negative electrode, and a separator, and at least one of the electrodes is a dry coating electrode according to the present invention.

Examples

[0105] The following examples illustrate the present invention without limiting the present invention.

[0106] <Method for Measuring pH> Use a pH meter of the Mettler Toledo SevenEasy brand or equivalent and an InLab Routine Pro electrode. Before calibration, check the cleanliness of the electrode. If necessary, wash the electrode with warm soap water. Make sure that the pH electrode is always filled with KCl filling solution. Calibrate the device with buffer solutions of pH 10, 7, and 4. To calibrate, immerse the electrode in the pH 10 buffer solution, support it on Cal, and when the pH stabilizes, repeat the operation with the pH 7 and then the pH 4 buffer solutions. Rinse the electrode with distilled water and dry it between each buffer solution. Prepare the electrode in advance by immersing it in a 0.1 M HCl solution for 1 to 2 hours before measurement and then rinsing it with deionized water. To measure the pH, immerse the electrode in the product in the test state and stir for a few seconds. Stabilize the measured value for 15 minutes and read the value displayed by the pH meter. The measurement is carried out at ambient temperature.

[0107] <Calculation of Glass Transition Temperature> The glass transition temperature shown here is calculated using Fox's equation. Fox's equation is an equation used to predict the glass transition temperature of a random copolymer.

[0108] 1 / Tg,copo≒Σi ωi / Tg,i In the formula, Tg,copo is the glass transition temperature of the copolymer, Tg,i is the glass transition temperature of the homopolymer i corresponding to each comonomer, ωi is the weight fraction of monomer i that constitutes this copolymer.

[0109] Weight fractions are expressed unitless. Glass transition temperatures are expressed in degrees Kelvin. Temperatures are then converted to degrees Celsius.

[0110] <Synthesis of Acrylic Polymer B> Several acrylic polymers B were prepared.

[0111] Polymer B-1 416 g of deionized water and 3.2 g of 97% sodium dodecyl sulfate were weighed into a 1000 ml glass reactor equipped with mechanical stirring and oil bath heating. In a first vessel equipped with magnetic bar stirring, 150 g of deionized water, 1.06 g of 97% sodium dodecyl sulfate, 0.7 g of diallyl phthalate, 163 g of ethyl acrylate, and 116 g of methacrylic acid were weighed. This mixture was continuously stirred throughout the polymerization process. A solution consisting of 0.7 g of ammonium persulfate and 10 g of deionized water was prepared in a second vessel. A solution consisting of 0.1 g of sodium metabisulfite and 10 g of deionized water was prepared in a third vessel. The reactor was heated to 76°C. The contents of the second and third vessels were introduced into the reactor, and then the contents of the first vessel were introduced into the reactor at 76°C in 120 minutes using a peristaltic pump, with constant stirring. The dispersion was heated to 78°C for 60 minutes. A dispersion containing 28% dry matter was obtained. The particles had a median diameter of 100 nm as measured by DLS. The pH of the aqueous dispersion was 3.1.

[0112] Polymer B-2 Polymer B-2 was prepared according to the method described in Patent WO2011 / 1611511A1. It consists of 57.7% ethyl acrylate, 40.9% methacrylic acid, 0.3% diallyl phthalate, and 1.1% AMPS. The resulting dispersion contained 25.8% dry matter. The particles have a median diameter of 187 nm as measured by DLS. The pH of the aqueous dispersion is 3.0.

[0113] Polymer B-3 Polymer B-3 is prepared according to the method described in patent WO2011 / 161508A1.

[0114] It consists of 67.2% ethyl acrylate, 32% acrylic acid, 0.25% diallyl phthalate, and 0.55% AMPS. The resulting dispersion contained 19.8% dry matter. The particles have a median diameter of 191 nm as measured by DLS. The pH of the aqueous dispersion is 2.1.

[0115] Polymer B-4 875 g of deionized water and 100 g of acrylic acid were weighed into a 1000 ml reactor equipped with oil-bath heating and mechanical stirring. The combined mixture was heated to 72°C with stirring. A solution consisting of 0.35 g of ammonium persulfate and 10 g of deionized water was added. The temperature was raised to 90°C in 15 minutes and then maintained at 90°C for 90 minutes. The final solution thus obtained was cooled, and 50% sodium hydroxide solution was added until a pH of 2.5 was obtained. Thus, an aqueous polyacrylic acid solution with a pH of 2.5 was obtained.

[0116] Polymer B-5 300 g of isopropyl alcohol and 2 g of AZDN were weighed into a 1000 ml reactor equipped with oil-bath heating and mechanical stirring. The combined mixture was brought to isopropanol reflux (approximately 81 °C). 200 g of acrylic acid and 80 g of butyl acrylate were weighed into a container. The monomer mixture was then added to the reactor over 130 minutes using a peristaltic pump, and the reactor was still heated to reflux the combined mixture. Reflux was maintained for 60 minutes. The isopropanol was then slowly replaced with deionized water during distillation, and the polymer had a number-average molar mass of approximately 7000 g / mol.

[0117] Polymer B-6 463 g of deionized water and 0.68 g of copper sulfate pentahydrate were weighed into a 1000 ml reactor equipped with oil-bath heating and mechanical stirring. The combined mixture was brought to 96°C. 330 g of methacrylic acid and 63 g of deionized water were weighed into a first vessel. 20 g of 35% aqueous hydrogen peroxide solution and 54 g of deionized water were weighed into a second vessel. The contents of the two vessels were then added in 120 minutes using two peristaltic pumps. The pumps were rinsed with twice the amount of deionized water. The temperature was maintained at 96°C for 90 minutes. The combined mixture was cooled to ambient temperature. An aqueous solution with a pH of 2.5 was obtained. The resulting polymer had a number-average molar mass of 10,000 g / mol.

[0118] Polymer B-7 460 g of deionized water and 3.5 g of 97% sodium dodecyl sulfate were weighed into a 1000 ml glass reactor equipped with mechanical stirring and oil bath heating. 150 g of deionized water, 1.1 g of 97% sodium dodecyl sulfate, 200 g of ethyl acrylate, and 117 g of methacrylic acid were weighed into a first vessel equipped with magnetic bar stirring. This mixture was continuously stirred throughout the polymerization process. A solution consisting of 1 g of ammonium persulfate and 10 g of deionized water was prepared in a second vessel. A solution consisting of 0.1 g of sodium metabisulfite and 10 g of deionized water was prepared in a third vessel. The reactor was heated to 76°C. The contents of the second and third vessels were introduced into the reactor, and then the contents of the first vessel were introduced into the 76°C reactor using a peristaltic pump with stirring over 120 minutes. The pump was rinsed with deionized water. The temperature is maintained at 78°C for 60 minutes. The polymer is then cooled. A dispersion containing 30% dry matter is obtained. The particles have a median diameter of 95 nm, as determined by DLS. The pH of the aqueous dispersion is 2.8.

[0119] Polymer A An aqueous dispersion of PVDF polymer is available in the form of a latex with a solids content of 24.1% and a particle size of 145 nm, pH 3.6. PVDF is a copolymer of vinylidene fluoride and hexafluoropropylene, characterized by a melting point of 148°C as measured by DSC (differential scanning calorimetry).

[0120] An aqueous formulation is prepared according to the following method.

[0121] Polymer A is weighed into a container and stirred with a mechanical stirrer while acrylic polymer B is added over 10 minutes. The stirring time after adding the acrylic polymer is 10 minutes.

[0122] [Example 1] 73.31 g of polymer A are weighed out and 27.14 g of polymer B-1 are added. A stable aqueous dispersion is obtained with a solids content of 25% and a measured particle size of 128 nm, pH 2.9.

[0123] [Example 2] 66.22 g of Polymer A is weighed out and 34.55 g of Polymer B-2 is added.

[0124] A stable aqueous dispersion is obtained with a pH of 2.7 and a solids content of 23% with a measured particle size of 270 nm.

[0125] [Example 3] 70.8 g of Polymer A is weighed out and 29.24 g of Polymer B-3 is added.

[0126] A stable aqueous dispersion is obtained with a pH of 2.5, a solids content of 24% and a measured particle size of 174 nm.

[0127] [Example 4] 57.8 g of polymer A are weighed out and 59 g of polymer B-4 are added. A viscous aqueous dispersion of pH 2.7 is obtained with a solids content of 16% and a measured particle size of 150 nm.

[0128] [Example 5] 213.7 g of polymer A are weighed out and 48.7 g of polymer B-5 are added. An aqueous dispersion of pH 2.2 is obtained with a solids content of 24.6% and a measured particle size of 160 nm.

[0129] [Example 6] 195.5 g of polymer A are weighed out and 60.3 g of polymer B-6 are added. An aqueous dispersion of pH 2 is obtained with a solids content of 26.1% and a measured particle size of 155 nm.

[0130] [Example 7] 75.7 g of polymer A are weighed out and 25.5 g of polymer B-7 are poured on top. An aqueous dispersion of pH 3.3 is obtained with a solids content of 26.4% and a measured particle size of 135 nm.

[0131] Each aqueous formulation, containing 70% PVDF and 30% acrylic polymer by weight on a dry basis, was placed in a crystallizing dish and dried in an oven at 110°C for 24 hours. A homogeneous powder was obtained in each case, which was first ground using a coffee-type electric knife mill and then cryogenically ground using a ball mill. The resulting powder was particularly homogeneous, allowing it to be very easily compressed to obtain a polymer layer on the metal surface, for example, using a calendering machine or a press. This inventive method therefore allows dry coating to be performed on aluminum-type supports, thereby making it possible to produce cathodes without the presence of toxic solvents such as NMP, and in fact even avoiding water-containing processes that require particularly expensive drying operations and complex formulations that require difficult rheological control. A similar solvent-free process can be used for anode production.

[0132] <Preparation of electrodes> Graphite lithium-ion battery anodes were produced according to a solvent-free process. The graphite used was Actilion GHDR 15-4 graphite sold by Imerys. The anodes consisted of 95% by weight of graphite and 5% by weight of a polymer binder according to the invention. Each electrode was produced according to the following procedure: The graphite and polymer binder powders were weighed and introduced into a 250 ml metal pot. The graphite / binder mixture was mixed for 1 minute 30 seconds using a Minimix type vibratory mixer sold by Merris. Once mixed, the mixture in powder form was deposited by sprinkling on a copper current collector with a thickness of 18 μm. The deposition volume was 10 × 5 cm. 2 15-20 mg / cm over a surface area of 2Once the deposition step has been carried out, the electrode is solidified using a table calender (model CA3 / 200-SP sold by Sumet GmbH). The temperature of each roll is 110°C and the speed is 0.1 m / min. The compression force is controlled to apply a force per unit length of 44 N / mm. To prevent the electrode from sticking to the upper roll, heat-resistant silicone-treated paper is inserted between the coating and the upper roll.

[0133] [Example 8] (according to the present invention) Anode based on a mixture of graphite and Example 1

[0134] [Example 9] (according to the present invention) Anode based on a mixture of graphite and Example 2

[0135] [Example 10] (according to the present invention) Anode based on a mixture of graphite and Example 4

[0136] [Example 11] (according to the present invention) Anode based on a mixture of graphite and Example 7

[0137] [Example 12] (Comparative Example) Anode based on graphite and polymer A powder.

[0138] Adhesion evaluation: If the coating spontaneously peels off at the end of the solidification stage, adhesion is considered to be zero.

[0139] [Table 1]

[0140] All coatings of electrodes with the binder of the present invention show adhesion with cohesive failure during coating. The level of adhesion obtained is sufficient to allow handling of the electrodes. In contrast, coatings using pure PVDF binder do not show any adhesion. The coating spontaneously peels off from the copper after the calendering step.

Claims

1. A binder for dry-coating electrodes of a storage battery, comprising a fluoropolymer A and an acrylic polymer B, characterized in that said binder is in the form of a powder.

2. 2. The binder of claim 1, characterized in that it has a particle size distribution with a D90 of 750 μm or less.

3. The acrylic polymer B contains at least 20% by weight of —CO based on the total weight of the acrylic polymer B. ２ 3. A binder according to claim 1, characterized in that it comprises monomer units containing H-functional groups.

4. Fluoropolymer A is vinyl fluoride, vinylidene fluoride (VDF), trifluoroethylene (VF ３ ), 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), perfluoro(2,2-dimethyl-1,3-dioxole) of the formula CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ X product, where X is SO ２ F, CO ２ H, CH ２ OH, CH ２ OCN or CH ２ OPO ３ H, of formula CF ２ = CFOCF ２ CF ２ SO ２ The product of F, formula F(CF ２ ) ｎ CH ２ OCF = CF ２ wherein n is 1, 2, 3, 4 or 5; １ CH ２ OCF = CF ２ wherein R １ is hydrogen or F(CF ２ ) ｍ and m has the value 1, 2, 3 or 4; ２ OCF=CH ２ wherein R ２ is F(CF ２ ) ｐ and p is 1, 2, 3 or 4, or a mixture thereof.

1. The binder according to claim 1, wherein p is 1, 2, 3 or 4, and the binder contains at least a monomer unit obtained from a monomer selected from the group consisting of perfluorobutylethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or a mixture thereof.

5. The fluoropolymer A is a copolymer of monomer units derived from vinylidene fluoride and, optionally, vinyl fluoride, trifluoroethylene (VF ３ ), 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), perfluoro(2,2-dimethyl-1,3-dioxole) of the formula CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ X product, where X is SO ２ F, CO ２ H, CH ２ OH, CH ２ OCN or CH ２ OPO ３ H, of formula CF ２ = CFOCF ２ CF ２ SO ２ The product of F, formula F(CF ２ ) ｎ CH ２ OCF = CF ２ wherein n is 1, 2, 3, 4 or 5; １ CH ２ OCF = CF ２ wherein R １ is hydrogen or F(CF ２ ) ｍ and m has the value 1, 2, 3 or 4; ２ OCF=CH ２ wherein R ２ is F(CF ２ ) ｐ and p is 1, 2, 3 or 4, and monomer units of a monomer selected from the group consisting of perfluorobutylethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or mixtures thereof.

6. 6. The binder according to claim 1, wherein fluoropolymer A is a homopolymer of vinylidene fluoride or a copolymer comprising monomer units derived from vinylidene fluoride and monomer units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, or a mixture thereof.

7. 7. A binder according to claim 1, characterized in that the fluoropolymer A comprises monomer units having at least one of the functional groups selected from the group consisting of carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy, e.g. glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid and phosphonic acid.

8. 8. The binder according to claim 1, wherein the acrylic polymer B has a glass transition temperature of 230° C. or less.

9. Acrylic polymer B is 3000 g.mol －１ 9. The binder according to claim 1, characterized in that it has a number-average molar mass equal to or greater than 1000 .mu.m.

10. 10. The binder according to claim 1, wherein the acrylic polymer B comprises a monomer unit having a carboxylic acid or carboxylic anhydride functional group and a monomer unit having a carboxylic ester functional group.

11. The acrylic polymer B is a compound represented by the formula R １ R ２ C=C(R ３ ) CO ２ H, where the substituent R １ , R ２ and R ３ are, independently of each other, H and C １ -C ５ alkyl, and of the formula R ４ R ５ C=C(R ６ ) C(O)R ７ wherein the substituent R ４ , R ５ and R ６ are, independently of each other, H and C １ -C ５ alkyl; R ７ Ha-NHC(CH ３ ) ２ CH ２ C(O)CH ３ and —OR′, where R′ is a C optionally substituted with one or more —OH groups or a 5- or 6-membered heterocycle containing at least one nitrogen atom in its cyclic chain. １ -C １８ 11. The binder according to claim 1, wherein the binder is selected from the group consisting of alkyl.

12. 12. A binder according to any one of claims 1 to 11, characterized in that the acrylic polymer B has a pH, measured in water at ambient temperature, of 1.5 to 4.

0.

13. 13. The binder according to claim 1, wherein the weight content of the acrylic polymer B relative to the fluoropolymer A is 1% to 70%.

14. A method for the preparation of a binder according to any one of claims 1 to 13, comprising the following steps: Mixing the polymer A in latex form with the polymer B in aqueous solution form or in latex form; and drying the resulting mixture, preferably by atomization or coatomization; Optionally, grinding the dry mixture obtained in the previous step. A method comprising:

15. A dry-coated electrode comprising the binder according to any one of claims 1 to 13, a dry active material, and optionally a conductive agent.

16. The following composition by weight: a. 50% to 99.9%, preferably 50% to 99%, of active material; b. 25% to 0%, preferably 25% to 0.5%, of a conductive agent; c. 25% to 0.05%, preferably 25% to 0.5%, of the binder according to any one of claims 1 to 13; d. 0% to 5% of at least one additive selected from the group consisting of plasticizers, ionic liquids, dispersants for conductive additives, and flow aids; 16. The dry-coated electrode of claim 15, wherein the sum of all these percentages is 100%.

17. 17. The dry-coated electrode according to claim 15, wherein the conductive agent is composed of one or more materials selected from the group consisting of carbon black such as acetylene black or ketjen black; carbon fiber such as carbon nanotube, carbon nanofiber, or vapor-grown carbon fiber; and metal powder such as SUS powder and aluminum powder.

18. In the case of a positive electrode, the active material is LiCoO ２ , Li(Ni, Co, Al)O ２ , Li （１＋ｘ） Ni ａ Mn ｂ Co ｃ (x is a real number equal to or greater than 0; 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), LiNiO ２ , LiMn ２ O ４ , LiCoMnO ４ , Li ３ NiMn ３ O ３ , Li ３ Fe ２ (P.O. ４ ) ３ , Li ３ V ２ (P.O. ４ ) ３ , Li １＋ｘ Mn ２－ｘ－ｙ M ｙ O ４ LiMn spinel substituted with different elements, having a composition represented by the formula: where M represents at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, and x and y independently represent real numbers from 0 to 2. ｘ TiO ｙ , x and y independently represent real numbers from 0 to 2, and LiMPO ４ 18. The dry-coated electrode according to claim 15, wherein M is selected from the group consisting of lithium metal phosphates having a composition represented by the formula:

19. In the case of a negative electrode, the active material is a lithium alloy, a metal oxide, a carbon material such as graphite or hard carbon, silicon, an alloy of silicon, and Li ４ TiO １２ The dry-coated electrode according to any one of claims 15 to 17, selected from the group consisting of:

20. 20. A method for producing a dry-coated electrode according to any one of claims 15 to 19, comprising a step of thermomechanical treatment carried out at a temperature T1 such that Tm-50°C<T1<Tg+50°C if Tg>Tm, or such that Tg-50°C<T1<Tm+50°C if Tm>Tg, wherein Tm is the melting point of fluoropolymer A and Tg is the glass transition temperature of acrylic polymer B.

21. A Li-ion battery comprising a positive electrode, a negative electrode, and a separator, wherein at least one of the electrodes is the dry-coated electrode according to any one of claims 15 to 19.

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