CATHODE PRIMARY LAYER COMPOSITION

Abstract

The invention relates to a primary cathode layer preparation composition comprising a very high molecular weight polyacrylic binding agent and carbon particles. The invention also relates to the use of this composition for preparing a cathode, as well as the cathode itself, which can be used for manufacturing secondary battery cells.

Description

Title of the invention: CATHODE PRIMER COMPOSITION

[0001] The invention relates to a composition for preparing a cathode primer layer comprising a very high molecular weight polyacrylic binding agent and carbon particles. The invention also relates to the use of this composition for preparing a cathode as well as the cathode which can be used for manufacturing cells for secondary batteries.

[0002] Cathode preparation compositions are known which generally comprise carbon and a metal in the form of particles associated with a binder composition. The binder compositions make it possible to fix the particles on a metal substrate. The binding power is therefore decisive when manufacturing a cathode using these compositions.

[0003] The time and efficiency of manufacturing the cathodes are also important factors. Improving the efficiency of the various reactions implemented must therefore be sought.

[0004] As electrochemically inactive components during cathode operation, binder compounds do not directly contribute to the capacity of the battery cell comprising the cathode but their influence remains considerable on the overall electrochemical performance. These binder compounds must contribute to forming stable networks of the active or conductive solid components present in the cathodes.

[0005] The binder compounds used during the preparation of a cathode should also make it possible to improve thermal stability, chemical and electrochemical stability, tensile strength, in particular through good adhesion and good cohesion, as well as through a certain flexibility.

[0006] Furthermore, the compatibility of the various ingredients of the cathode preparation compositions and the battery is also an important factor to consider when preparing these compositions as well as when preparing the cathodes using these compositions. In particular, compatibility, and in particular the absence of solubility or low solubility, with the battery electrolyte is a crucial property.

[0007] Easy and homogeneous application of the cathode preparation compositions is sought in order to obtain a homogeneous layer and to limit or avoid defects on the surface of the electrode, in order to achieve a homogeneous and particularly effective conductive layer. Surface leveling, restructuring and behavior flow characteristics of cathode preparation compositions must be well controlled.

[0008] Cathode preparation compositions must also be stable and homogeneous during their preparation, storage or application. Sedimentation, formation of agglomerates or aggregates, separation of ingredients must therefore be limited or avoided.

[0009] Generally, improving the adhesion of the active elements must always be sought during cathode preparation. The adhesion of the different layers of ingredients deposited on the metal substrate must therefore be improved. In particular, when a primer layer comprising carbon is deposited on the metal substrate, improving its adhesion is essential. Because they are in direct contact with the metal substrate of the cathode and with the binder composition of the electroactive compound, the properties of the primer layer compositions are particularly important.

[0010] The known compositions used during the preparation of the cathode primer layer of the state of the art are not always satisfactory. There is therefore a need to have compositions used during the preparation of the cathode primer layer which make it possible to provide solutions to all or part of the problems of the compositions of the state of the art.

[0011] Thus, the invention provides an aqueous composition C for preparing a cathode primary layer comprising: * at least one material E comprising carbon particles and * at least one binding agent Q comprising at least one water-soluble polymer P with a molecular mass Mw, measured by CES, greater than 300,000 g / mol, and chosen from: - a PI polymer prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; ** of at least one compound (b) independently selected from styrene, C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, alkyla-crylamides, N-methylolacrylamide, acrylonitrile, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, me polycaprolactam acrylate, polycaprolactam acrylate and combinations thereof; and ** of at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof, and ** of at least one compound (b) independently selected from styrene, C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, alkyl acrylamides, N-methylolacrylamide, acrylonitrile, vinyl lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam acrylate and combinations thereof; - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P4 prepared by a polymerization reaction, in the presence of at least one initiator compound, of at least one compound (a) independently chosen from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a methacrylic acid salt, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; - their combinations.

[0012] According to the invention, the molecular weight or mass of the polymers PI and P2 is determined by Size Exclusion Chromatography (SEC). A test sample of the polymer solution corresponding to 20 mg of dry matter is introduced into a 10 mL flask. Mobile phase, supplemented with 0.04% dimethylformamide (DMF), is added up to a total mass of 10 g. The composition of this mobile phase is as follows: NaHCO3: 0.05 mol / L, NaNO3: 0.1 mol / L, triethanolamine: 0.02 mol / L, NaN3 0.03% by mass. The CES chain consists of a “Waters” 510 isocratic pump, with a flow rate set at 1 mL / min, a “Waters” 717+ autosampler, an oven containing a “PSS Suprema” guard column of 5 cm length and 8 mm inner diameter, followed by a “PSS Suprema” 30,000 Å column of 30 cm length and 8 mm inner diameter.Detection is ensured by means of a differential refractometer type "RI Waters" 410. The oven is brought to the temperature of 60°C and the refractometer is brought to the temperature of 45°C. The CES device is calibrated with a series of sodium polyacrylate standards supplied by "Polymer Standards Service" with a molecular weight at the peak between 1,200 g / mol and 1,390,000 g / mol and a polydispersity index Ip between 1.09 and 2. The calibration curve is of the linear type and takes into account the correction obtained thanks to the flow marker: dimethylformamide (DMF). The acquisition and processing of the chromatogram are carried out using the software "ConSenxus hs NTeqGPC" V 5.1.5. The chromatogram obtained is integrated in the zone corresponding to molecular weights greater than 180 g / mol. .

[0013] Preferably according to the invention, the polymer P has a polymolecularity index Ip, measured by CES, greater than 10, preferably greater than 15 or greater than 20. More preferably, the polymolecularity index Ip of the polymer P, measured by CES, is greater than 25 or greater than 30 or greater than 40.

[0014] Preferably according to the invention, compound (a) is independently chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and combinations thereof, preferably compound (a) is acrylic acid or methacrylic acid.

[0015] Also preferably according to the invention, compound (b) is independently selected from styrene, t-Bu-acrylamide, C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid and combinations thereof. More preferably, compound (b) is selected from C1-C8 esters of methacrylic acid, C1-C8 esters of acrylic acid and combinations thereof, preferably styrene, t-Bu-acrylamide, methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, more preferably, methylmethacrylate, methylacrylate, ethylacrylate, butylacrylate.

[0016] Also preferably according to the invention, compound (c) is independently chosen from 2-acrylamido-2-methylpropane sulfonic acid and a salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0017] Essentially, polymers P1 to P4 according to the invention are prepared using compounds (a), (b) or (c). Preferably, polymers P1 to P4 according to the invention are prepared using only compounds (a), (b) or (c). Then, polymer P1 is prepared using only compounds (a), (b) and (c). Polymer P2 is prepared using only compounds (a) and (b). Polymer P3 is prepared using only compounds (a) and (c). Polymer P4 is prepared using a single compound (a) or using two different compounds (a).

[0018] Nevertheless, the polymer P according to the invention can also be prepared by a polymerization reaction which uses other monomers. Thus, the polymer P can also be prepared using at least one compound (d) chosen independently from phosphated hydroxyethylacrylate, phosphated hydroxyethylmethacrylate, phosphated hydroxypropylacrylate, phosphated hydroxypropylmethacrylate, phosphated hydroxybutylmethacrylate.

[0019] Polymer P may also be prepared by means of at least one crosslinking compound (e). However, preferably, polymer P is not crosslinked. Also preferably, compound (b) is not acrylonitrile or acrylamide or it does not comprise fluorine; polymer P is then not a fluorinated polymer. Also preferably according to the invention, polymer P is a free polymer, it is not grafted, in particular it is not grafted to a fluorinated polymer.

[0020] The quantities of monomer residues present in the polymer P can vary relatively significantly. Preferably for the composition C according to the invention, the polymer PI is prepared by means of: - from 30% by weight to 90% by weight of compound (a), - from 5% by weight to 30% by weight of compound (b) and - from 5% by weight to 40% by weight of compound (c), relative to the quantity by weight of compounds (a), (b) and (c).

[0021] Also preferably for composition C according to the invention, polymer P2 is prepared by means of: - from 35% by weight to 90% by weight of compound (a) and - from 10% by weight to 65% by weight of compound (b), relative to the quantity by weight of compounds (a) and (b).

[0022] Also preferably for composition C according to the invention, polymer P3 is prepared by means of: - from 35% by weight to 95% by weight of compound (a) and - from 5% by weight to 65% by weight of compound (c), relative to the amount by weight of compounds (a) and (c).

[0023] Essentially according to the invention, the molecular mass Mw of the polymer P, measured by CES, is greater than 300,000 g / mol. Preferably according to the invention, the polymer P has a molecular mass Mw, measured by CES, ranging from 300,000 g / mol to 10,000,000 g / mol or from 350,000 g / mol to 10,000,000 g / mol. More preferably, the polymer P has a molecular mass Mw ranging from 300,000 g / mol to 8,000,000 g / mol or from 350,000 g / mol to 8,000,000 g / mol, more preferably from 300,000 g / mol to 5,000,000 g / mol or from 350,000 g / mol to 5,000,000 g / mol or from 300,000 g / mol to 2,000,000 g / mol or from 350,000 g / mol to 2,000,000 g / mol.

[0024] Also preferably, the molecular mass Mw of the polymer P, measured by CES, may be greater than 1,000,000 g / mol, more preferably strictly greater than 1,000,000 g / mol.

[0025] Also preferably according to the invention, the polymer P has a glass transition temperature Tg, calculated according to the Flory-Fox equation, ranging from -10°C to 230°C or from 20°C to 230°C. More preferably according to the invention, the polymer P is a homopolymer whose Tg is greater than 0°C, preferably greater than 10°C.

[0026] Also more preferably according to the invention, the polymer P is a copolymer whose Tg is greater than 50°C, preferably greater than 100°C. The Flory-Fox equation makes it possible to calculate the glass transition temperature of a copolymer from the parameters of the monomers used for its preparation.

[0027] The polymer P used according to the invention can be used in its acid form or in a form in which all or part of its carboxylic groups can be neutralized. Preferably according to the invention, the polymer P is therefore totally or partially acidic or totally or partially non-neutralized. More preferably, the polymer P is partially neutralized. According to the invention, the neutralization of the polymer P is preferably carried out by means of at least one compound chosen from LiOH, NaOH, KOH, Zn(OH)2, Mg(OH)2, Ca(OH)2, ZnO, MgO, CaO, ammonium derivatives, ammonia, aqueous ammonia, amine bases, for example triethanolamine, aminomethylpropanol or 2-amino-2-methylpropanol (AMP) and combinations thereof, much more preferably NaOH, Ca(OH)2, CaO.

[0028] The polymer P according to the invention is prepared by a polymerization reaction whose implementation conditions can vary. Preferably according to the invention, the polymer P is prepared by a polymerization reaction in a liquid medium whose initial monomer concentration ranges from 5% by weight to 20% by weight, preferably from 5% by weight to 15% by weight or from 8% by weight to 15% by weight, more preferably from 10% by weight to 12% by weight.

[0029] Preferably according to the invention, the polymerization reaction is carried out in water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, isopropanol and their combinations.

[0030] According to the invention, an initiator or radical-generating compound is present during the polymerization reaction. Preferably according to the invention, the radical-generating compound is chosen from 4,4'-azobis-4-cyanopentanoic acid (ACPA or 4,4'-azobis-(4-cyanovaleric) acid or AZDN or 2,2'-azobisisobutyronitrile), hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkali metal persulfate (in particular sodium persulfate, potassium persulfate), an azo compound and their combinations or their respective associations with an ion chosen from Fe11, Fe111, Cu1, Cu11 and their combinations.According to the invention, the ions Fe11, Fe111, Cu1, Cu11 can be implemented by means of at least one compound chosen from iron sulfate, hydrated iron sulfate, hemihydrated iron sulfate, heptahydrated iron sulfate, iron carbonate, hydrated iron carbonate, hemihydrated iron carbonate, iron chloride, copper carbonate, hydrated copper carbonate, hemihydrated copper carbonate, copper acetate, copper sulfate, pentahydrated copper sulfate, copper hydroxide, copper halide.

[0031] According to the invention, the polymerization reaction can be carried out in the presence of a compound comprising phosphorus in oxidation state I, in particular hypophosphorous acid (H3PO2) or a derivative of hypophosphorous acid (H3PO2), such as compounds comprising at least one hypophosphite ion (H2PO2), in particular a compound chosen from sodium hypophosphite (H2PO2Na), potassium hypophosphite (H2PO2K), calcium hypophosphite ([H2PO2]2Ca).

[0032] According to the invention, the polymerization reaction can also be carried out in the presence of a compound comprising phosphorus in oxidation state III, in particular phosphorous acid or a phosphorous acid derivative. According to the invention, the polymerization reaction can also be carried out in the presence of a compound comprising a bisulfite ion, preferably sodium bisulfite or potassium bisulfite.

[0033] Preferably according to the invention, the agent Q comprises a single polymer P.

[0034] Advantageously according to the invention, the binding agent Q comprises at least one polymer P and at least one liquid support, preferably water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, isopropanol and their combinations.

[0035] Also preferably according to the invention, the binding agent Q comprises: - from 5% by weight to 20% by weight of polymer P and from 95% by weight to 80% by weight of liquid support, also preferably: - from 10% by weight to 40% by weight of polymer P and from 60% by weight to 90% by weight of liquid support.

[0036] Within the composition C according to the invention, the ingredients may be present in amounts which may vary quite widely. Preferably according to the invention, the composition C according to the invention comprises, by dry weight: - from 0.5% to 70% of binding agent Q, - from 30% to 99.5% of material E; preferably: - from 0.5% to 60% of binding agent Q, - from 40% to 99.5% of E material relative to the total quantity by dry weight of binding agent Q and material E.

[0037] Essentially according to the invention, in addition to the polymer P, the composition C according to the invention comprises a material E which comprises carbon particles. Preferably according to the invention, the material E is chosen from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, hardened carbon and combinations thereof.

[0038] The invention also provides a method for preparing a water-soluble polymer P with a molecular mass Mw, measured by CES, greater than 300,000 g / mol, chosen from: - a PI polymer prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; ** of at least one compound (b) independently selected from styrene, C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, alkyla-crylamides, N-methylolacrylamide, acrylonitrile, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam acrylate and combinations thereof; and ** of at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound,: ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least one compound (b) independently selected from styrene, C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, alkyl acrylamides, N-methylolacrylamide, acrylonitrile, vinyl lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam acrylate and combinations thereof; - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound,: ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P4 and which is prepared by a polymerization reaction, in the presence of at least one initiator compound, of at least one compound (a) independently chosen from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a methacrylic acid salt, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof.

[0039] Preferably according to the invention, the method for preparing the polymer P according to the invention comprises a polymerization reaction which is carried out in a liquid medium whose initial monomer concentration ranges from 5% by weight to 20% by weight. Preferably, the initial monomer concentration ranges from 5% by weight to 15% by weight or from 8% by weight to 15% by weight, more preferably from 10% by weight to 12% by weight.

[0040] Also preferably, the polymerization reaction is carried out in water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, isopropanol and their combinations.

[0041] The use of composition C according to the invention is particularly advantageous for the manufacture of a cathode. Thus, the invention also provides a method for preparing a cathode comprising: - the application to a metal substrate comprising at least one metal chosen from aluminum, nickel and their combinations, of a primary layer of at least one composition C defined according to the invention; - drying and then possible calendering of the metal substrate bearing the primer layer, then - the application of an electro-active composition comprising at least one electro-active compound, at least one binding compound of the electro-active compound and at least one organic solvent, - drying and then calendering of the metal substrate bearing the primer layer and the electro-active coating.

[0042] Preferably according to the invention, the substrate is a purely metallic substrate or a composite substrate comprising at least one metal and at least one insulating support.

[0043] Also preferably according to the invention, the electroactive compound comprises at least one metal chosen from lithium, iron, nickel, manganese, cobalt and their combinations.

[0044] Also preferably according to the invention, the electroactive compound is in the form of a metal salt, preferably a polymetallic salt, more preferably the electroactive compound is chosen from LiFePO4 (LFP), Li(Ni,Mn,Co)O2 (NMC) and their combinations.

[0045] Preferably according to the invention, the binder compound of the electroactive compound is polyvinylidene fluoride (PVDF), preferably a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride with a monomer chosen from vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, 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), perfluorobutyl ethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropyl. Preferably according to the invention, the binding compound of the electroactive compound is not a (meth)acrylic polymer.

[0046] Preferably according to the invention, the organic solvent is a polar solvent. aprotic, preferably selected from pyrrolidone, N-methyl-pyrrolidone (NMP), alkyl carbonates and combinations thereof.

[0047] Preferably according to the invention, the electro-active composition comprises carbon, preferably chosen from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, hardened carbon and combinations thereof.

[0048] The invention also provides a cathode comprising at least one metal substrate covered with at least one primary layer comprising a binding agent Q and at least one material E, preferably obtained according to the preparation method according to the invention.

[0049] The invention also provides a cathode manufactured according to the manufacturing method according to the invention.

[0050] The polymer P of the binding agent Q of the composition C according to the invention has particularly advantageous properties for the preparation of a cathode primer layer and therefore for obtaining a cathode. The polymer P used according to the invention makes it possible in particular to improve the adhesion to the metal substrate of the cathode. In particular, the polymer P used according to the invention makes it possible to improve the adhesion to the metal substrate when it is used in combination with the binding compound of the electroactive compound. The compatibility of the polymer P used according to the invention and the binding compound of the electroactive compound is particularly advantageous during the preparation of a cathode.

[0051] Thus, the invention provides a method for improving the adhesion to a metal cathode substrate comprising at least one metal chosen from aluminum and nickel, of an electroactive composition comprising at least one electroactive compound, at least one binding compound of the electroactive compound and at least one organic solvent. Preferably, this method for improving the adhesion to a metal cathode substrate comprises: - the prior application directly onto the metal substrate, then drying and possible calendering, of at least one aqueous composition C for preparing the primer layer according to the invention, then - the application of the electro-active composition, - drying and then calendering of the metal substrate bearing the primer layer and the electro-active coating.

[0052] The polymer P used according to the invention makes it possible to improve the subsequent adhesion with the binding compound of the electroactive compound. It acts as an adhesion promoter between the metal substrate and this binding compound of the electroactive compound. It also helps to make the carbon particles of the material E adhere to the metal substrate.

[0053] The advantageous, particular or preferred characteristics of composition C according to the invention define methods of preparing a cathode according to the invention, methods of improving adhesion to a metal cathode substrate, as well as cathodes, which are also advantageous, particular or preferred.

[0054] The various aspects of the invention can be illustrated by examples.

[0055] EXAMPLES

[0056] Preparation and characterization of polymers P and agents Q according to the invention

[0057] Polymer PI A and agent Q1

[0058] 805 g of deionized water, 15 g of ethyl acrylate, 60 g of acrylic acid and 50 g of a 50% aqueous solution of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) sodium salt are introduced into a 1 L glass reactor equipped with mechanical stirring and oil bath heating. The whole is then heated to approximately 70°C.

[0059] A solution of 0.35 g of ammonium persulfate and 10 g of deionized water is then added all at once. The mixture is heated to 85+ / -2°C for 1 hour, while maintaining stirring. Finally, a solution of 0.35 g of ammonium persulfate and 20 g of deionized water is added over 1 hour, while maintaining the temperature at 85°C.

[0060] After cooling to room temperature, agent Q1 is obtained comprising polymer P1A at 10% by weight of dry extract and whose pH is 2.1. The molecular mass Mw of polymer P1A measured by CES is 533,000 g / mol and its Ip is 44.

[0061] PIB polymer and Q2 agent

[0062] 805 g of deionized water, 15 g of ethyl acrylate, 60 g of acrylic acid and 50 g of a 50% aqueous solution of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) sodium salt are introduced into a 1 L glass reactor equipped with mechanical stirring and oil bath heating. The whole is then heated to approximately 70°C.

[0063] A solution of 0.25 g of ammonium persulfate and 10 g of deionized water is then added all at once. The mixture is heated to 85+ / -2°C for 1 hour, while maintaining stirring. Finally, a solution of 0.35 g of ammonium persulfate and 20 g of deionized water is added over 1 hour, while maintaining the temperature at 85°C.

[0064] After cooling to room temperature, agent Q2 is obtained comprising the PIB polymer at 10% by weight of dry extract and whose pH is 2.2. The molecular mass Mw of the PIB polymer measured by CES is 1,020,000 g / mol and its Ip is 49.

[0065] Polymer P4A and agent Q3

[0066] 805 g of deionized water and 100 g of acrylic acid are introduced into a 1 L glass reactor equipped with mechanical stirring and oil bath heating. The whole thing is then heated to around 70°C.

[0067] A solution of 0.45 g of ammonium persulfate and 10 g of deionized water is then added all at once. The mixture is heated to 85+ / -2°C for 1 hour, while maintaining stirring. Finally, a solution of 0.35 g of ammonium persulfate and 20 g of deionized water is added over 1 hour, while maintaining the temperature at 85°C.

[0068] After cooling to room temperature, agent Q3 is obtained comprising the polymer P4A at 10.6% by weight of dry extract and whose pH is 2.2. The molecular mass Mw of the polymer P4A measured by CES is 1,438,000 g / mol and its Ip is 86.

[0069] Preparation of aqueous compositions C for preparing a cathode primary layer according to the invention

[0070] 91 g of deionized water are weighed with 100 g of agent Q1 and then mixed with stirring using a dispersion apparatus (VMI) equipped with a toothed blade 6.5 cm in diameter. Then, 10 g of carbon black (“C-Nergy Super” C65 “Imerys”) are added while maintaining stirring for 1.25 hours at 1,500 rpm to obtain a composition whose homogeneity and absence of aggregate are controlled using a North gauge. Composition Cl is obtained from agent Q1 comprising the polymer PI A.

[0071] Similarly, cathode primer layer compositions C2 and C3 are prepared from agents Q2 and Q3.

[0072] Preparation and characterization of cathodes according to the invention

[0073] On an aluminum sheet degreased with acetone, 6 μm of cathode primer layer preparation composition Cl according to the invention are applied by means of a coater equipped with a threaded rod ("RK Control Coater"), at an application speed of 10 mm / s. Then, it is dried at 150°C in an oven for 5 minutes. The primer layer obtained by means of the composition Cl applied and then dried, has a mass, measured by means of a precision balance, of 0.2 mg for an aluminum disc 12 mm in diameter and 10 μm + / - 1 μm thick.

[0074] Similarly, cathode primary layers are prepared using compositions C2 and C3.

[0075] The adhesion to the cathode aluminum substrate of the primer layer obtained using compositions C1 to C3 according to the invention is evaluated according to a peel test. A standardized adhesive tape (“Intertape” 51596 CIC8091013) is manually applied to the cathode primer layer. The adhesive tape is then peeled off and the adhesion of the primer layer to the aluminum is visually evaluated.

[0076] The compatibility of the primer layer prepared according to the invention with a secondary layer of binding agent is evaluated for a polyvinylidene fluoride (PVDF, “Kynar” HSV900 “Arkema”) binding agent applied in an N-methylpyrrolidone (NMP) solvent medium.

[0077] On a primary cathode layer obtained according to the method described above, a layer of PVDF binding agent is applied using a 5% concentration solution of PVDF in NMP and then applied in a 9 μm layer and then dried at 150°C in an oven for 5 minutes.

[0078] On the secondary cathode layer, a standardized adhesive tape (“Intertape” 51596 CIC8091013) is manually applied. Then, the adhesive tape is peeled off and the adhesion is visually assessed.

[0079] The results obtained for the adhesion of the primary layer and for its compatibility with the secondary layer of PVDF are presented in Table 1 according to the scale: - 1: aluminum foil visible on the majority of the surface of the adhesive strip, - 2: aluminum foil visible on a part of the surface of the adhesive strip, - 3: aluminum foil not visible on the surface of the adhesive strip, - 4: primary layer mostly intact, - 5: primary layer totally intact.

[0080] Ratings 1 and 2 are not acceptable for use of the cathode in a secondary battery. Ratings 3 to 5 are acceptable for use of the cathode in a secondary battery. The results are shown in Table 1.

[0081] [tab.l] Composition C according to the invention - Adhesion Compatibility Cl 5 4 C2 5. s C3 4 3

[0082] The binding agents Q comprising the polymers P according to the invention make it possible, on the one hand, to produce good quality primary adhesion layers which hold the conductive carbon very well on the surface of the aluminum foil. They also act as binding agents compatible with the secondary PVDF binding agent which is the polymeric constituent of the LFP layer, which makes it possible to increase the adhesion of the LFP layer to the primary adhesion layer of the cathode.

Claims

1. Claims Aqueous composition C for preparing a cathode primary layer comprising: * at least one material E comprising carbon particles and * at least one binding agent Q comprising at least one water-soluble polymer P with a molecular mass Mw, measured by CES, greater than 300,000 g / mol, and chosen from: - a PI polymer prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; ** of at least one compound (b) independently selected from styrene, CrCi2 esters of methacrylic acid, CrCi2 esters of acrylic acid, acrylamide, alkylacrylamides, N-methylolacrylamide, acrylonitrile, vinyl lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polyca-prolactam methacrylate, polycaprolactam acrylate and combinations thereof;and ** at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least compound (b) independently selected from styrene,

2. C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, alkylacrylamides, N-methylolacrylamide, acrylonitrile, vinyl lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polyca-prolactam methacrylate, polycaprolactam acrylate and combinations thereof; - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound, ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P4 prepared by a polymerization reaction, in the presence of at least one initiator compound, of at least one compound (a) independently chosen from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a methacrylic acid salt, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; - their combinations. Composition C according to claim 1 for which: - the polymer P has a polymolecularity index Ip, measured by CES, greater than 10, preferably greater than 15 or greater than 20, more preferably greater than 25 or greater than 30 or greater than 40; or for which: - compound (a) is independently selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and combinations thereof, preferably compound (a) is acrylic acid or methacrylic acid; or

3. - compound (b) is independently selected from styrene, t-Bu-acrylamide, C1-C12 methacrylic acid esters, C1-C12 acrylic acid esters and combinations thereof, preferably Cr-C8 methacrylic acid esters, Cr-C8 acrylic acid esters and combinations thereof, preferably styrene, t-Bu-acrylamide, methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, more preferably, methylmethacrylate, methylacrylate, ethylacrylate, butylacrylate; or - compound (c) is independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid; or - the polymer PI is prepared using only compound (a), compound (b) and compound (c); or - polymer P2 is prepared using only compound (a) and compound (b); or - polymer P3 is prepared using only compound (a) and compound (c); or - the polymer P4 is prepared using a single compound (a) or using two different compounds (a); or - polymer P is also prepared by means of: * at least one compound (d) independently selected from phosphated hydroxyethylacrylate, phosphated hydroxyethylmethacrylate, phosphated hydroxypropylacrylate, phosphated hydroxypropylmethacrylate, phosphated hydroxybutylmethacrylate; or * of at least one crosslinking compound (e). Composition C according to one of claims 1 or 2 for which: - the PI polymer is prepared by means of: * from 30% by weight to 90% by weight of compound (a), * from 5% by weight to 30% by weight of compound (b) and * from 5% by weight to 40% by weight of compound (c), relative to the quantity by weight of compounds (a), (b) and (c); or - the polymer P2 is prepared by means of: * from 35% by weight to 90% by weight of compound (a) and * from 10% by weight to 65% by weight of compound (b), relative to the quantity by weight of compounds (a) and (b); or - the polymer P3 is prepared by means of: * from 35% by weight to 95% by weight of compound (a) and * from 5% by weight to 65% by weight of compound (c), relative to the quantity by weight of compounds (a) and (c); or for which: - the polymer P has a molecular mass Mw, measured by CES, ranging from 300,000 g / mol to 10,000,000 g / mol or from 350,000 g / mol to 10,000,000 g / mol, preferably from 300,000 g / mol to 8,000,000 g / mol or from 350,000 g / mol to 8,000,000 g / mol, more preferably from 300,000 g / mol to 5,000,000 g / mol or from 350,000 g / mol to 5,000,000 g / mol or from 300,000 g / mol to 2,000,000 g / mol or from 350,000 g / mol to 2,000,000 g / mol; or - the polymer P has a glass transition temperature Tg, calculated according to the Flory-Fox equation, ranging from -10°C to 230°C or from 20°C to 230°C; or for which the polymer P is a homopolymer whose Tg is greater than 0°C, preferably greater than 10°C or for which the polymer P is a copolymer whose Tg is greater than 50°C, preferably greater than 100°C;or - the polymer P is totally or partially acidic or totally or partially non-neutralized, preferably the polymer P is partially neutralized, preferably by means of at least one compound chosen from LiOH, NaOH, KOH, Zn(OH)2, Mg(OH)2, Ca(OH)2, ZnO, MgO, CaO, ammonium derivatives, ammonia, aqueous ammonia, amine bases, for example triethanolamine, aminomethylpropanol or 2-amino-2-methyl-propanol (AMP) and combinations thereof, more preferably NaOH, Ca(OH)2, CaO.;

4. Composition C according to one of claims 1 to 3 for which: - the polymer P is prepared by a polymerization reaction in a liquid medium whose initial monomer concentration ranges from 5% by weight to 20% by weight, preferably from 5% by weight to 15% by weight or from 8% by weight to 15% by weight, more preferably from 10% by weight to 12% by weight; or for which: - the polymerization reaction is carried out in water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, isopropanol and their combinations.

5. Composition C according to one of claims 1 to 4 for which: - the binding agent Q comprises a single polymer P; or - the binding agent Q comprises at least one polymer P and at least one liquid support, preferably water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, iso- propanol and their combinations; or for which: - the binding agent Q comprises: * from 5% by weight to 20% by weight of polymer P and from 95% by weight to 80% by weight of liquid support, also preferably: * from 10% by weight to 40% by weight of polymer P and from 60% by weight to 90% by weight of liquid support.

6. Composition C according to one of claims 1 to 5 for which the material E is chosen from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, hardened carbon and combinations thereof.

7. Composition C according to one of claims 1 to 6 comprising, by dry weight: - from 0.5% to 70% of binding agent Q, - from 30% to 99.5% of material E; preferably: - from 0.5% to 60% of binding agent Q, - from 40% to 99.5% of material E; relative to the total quantity by dry weight of binding agent Q and material E.

8. Method for preparing a water-soluble polymer P with a molecular mass Mw, measured by CES, greater than 300,000 g / mol, chosen from: - a polymer PI prepared by a polymerization reaction, in the presence of at least one initiator compound,: ** of at least one compound (a) chosen independently from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a methacrylic acid salt, an oligomer salt of acrylic acid, a methacrylic acid oligomer salt and combinations thereof;** of at least one compound (b) independently selected from styrene, CrCi2 esters of methacrylic acid, CrCi2 esters of acrylic acid, acrylamide, alkylacrylamides, N-methylolacrylamide, acrylonitrile, vinyl lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polyca-methacrylate; prolactam, polycaprolactam acrylate and combinations thereof; and ** at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound,: ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least one compound (b) independently selected from styrene, C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid, acrylamide, alkylacrylamides, N-methylolacrylamide, acrylonitrile, vinyl lactam, N-vinylpyrrolidone, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam acrylate and combinations thereof; - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound,: ** of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an acrylic acid oligomer, a methacrylic acid oligomer, an acrylic acid salt, a methacrylic acid salt, an acrylic acid oligomer salt, a methacrylic acid oligomer salt and combinations thereof; and ** of at least one compound (c) independently selected from 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, ethoxymethacrylate sulfonic acid, sodium methallyl sulfonate, styrene sulfonate; - a polymer P4 prepared by a polymerization reaction, in the presence of at least one initiator compound, of at least one compound (a) chosen independently from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid, an oligomeric salt of acrylic acid, an oligomeric salt of methacrylic acid and combinations thereof.

9. Preparation method according to claim 8, in which: - the polymerization reaction is carried out in a liquid medium whose initial monomer concentration ranges from 5% by weight to 20% by weight, preferably from 5% by weight to 15% by weight or from 8% by weight to 15% by weight, more preferably from 10% by weight to 12% by weight; or for which: - the polymerization reaction is carried out in water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, isopropanol and their combinations.

10. Method for preparing a cathode comprising: - applying to a metal substrate comprising at least one metal chosen from aluminum, nickel and their combinations, a primary layer of at least one composition C defined according to one of claims 1 to 7; - drying then optionally calendering the metal substrate carrying the primary layer, then - applying an electroactive composition comprising at least one electroactive compound, at least one binding compound of the electroactive compound and at least one organic solvent, - drying then calendering the metal substrate carrying the primary layer and the electroactive coating.

11. Method according to claim 10 for which: - the substrate is a purely metallic substrate or a composite substrate comprising at least one metal and at least one insulating support, or - the electroactive compound comprises at least one metal chosen from lithium, iron, nickel, manganese, cobalt and combinations thereof, or - the electroactive compound is in the form of a metal salt, preferably a polymetallic salt, preferably the electroactive compound is chosen from LiFePO4 (LFP), Li(Ni,Mn,Co)O2 (NMC) and combinations thereof, or - the binder compound of the electroactive compound is polyvinylidene fluoride (PVDF), preferably a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride with a monomer chosen from vinyl fluoride, trifluoroethylene, chlorotri- fluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE), perfluoro(l,3-dioxole), perfluoro(2,2-dimethyl-l,3-dioxole) (PDD), perfluorobutyl ethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluorop, or - the organic solvent is an aprotic polar solvent, preferably chosen from pyrrolidone, N-methyl-pyrrolidone (NMP), alkyl carbonates and combinations thereof, or - the electroactive composition comprises carbon, preferably selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, hardened carbon and combinations thereof.

12. Cathode comprising at least one metal substrate covered with at least one primary layer comprising a binding agent Q and at least one material E obtained according to the method according to one of claims 10 or 11.

13. Method for improving the adhesion to a metal cathode substrate comprising at least one metal selected from aluminum and nickel, of an electroactive composition comprising at least one electroactive compound, at least one binding compound of the electroactive compound and at least one organic solvent, comprising: - the prior application directly onto the metal substrate, then the drying and possible calendering, of at least one aqueous composition C for preparing a primer layer according to one of claims 1 to 7, then - the application of the electro-active composition, - drying and then calendering of the metal substrate bearing the primer layer and the electro-active coating.