Composition of a primary cathode layer

Abstract

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

Description

[0001] CATHODE PRIMER LAYER COMPOSITION

[0002] 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 usable for manufacturing cells for secondary batteries.

[0003] Cathode preparation compositions are known, which generally comprise carbon and a metal in the form of particles associated with a binder composition. Binder compositions allow the particles to be fixed on a metal substrate. The binding power is therefore decisive when manufacturing a cathode using these compositions.

[0004] Cathode manufacturing time and yield are also important factors. Improving the efficiency of the various reactions involved must therefore be sought.

[0005] As electrochemically inactive components during cathode operation, binder compounds do not directly contribute to the capacity of the battery cell including the cathode, but their influence on the overall electrochemical performance remains considerable. These binder compounds must contribute to the formation of stable networks of the active or conductive solid components present in the cathodes.

[0006] The binder compounds used during the preparation of a cathode should also improve thermal stability, chemical and electrochemical stability, tensile strength, in particular through good adhesion and cohesion, as well as a certain flexibility.

[0007] 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 especially the absence of solubility or low solubility, with the battery electrolyte is a crucial property.

[0008] Easy and homogeneous application of 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 efficient conductive layer. Surface leveling, restructuring and flow behavior of cathode preparation compositions must be well controlled. 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 active elements should 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] Document CN 115881966 discloses cathode preparation compositions combining two polymers modified by conductive chemical groups, in particular by polyaniline groups. Document EP 4095213 describes electrode binder compositions comprising copolymers of N-vinylpyrrolidone, methacrylonitrile, vinyl acetate or propenesulfonic acid. Document WO 2014024937 describes anode preparation compositions comprising low molecular weight fluorinated copolymers.

[0011] WO 2015008626 describes electrode binder compositions comprising a very high molecular weight copolymer essentially prepared from anionic monomers. US 20170018770 discloses a method for preparing a cathode using a binder composition that combines at least two polyacrylic acids of very different molecular weights.

[0012] In addition to cathode preparation compositions comprising a pVDF binder in NMP, KR 20190143256 discloses a silicon anode composition comprising two polyacrylic acid binders having different molecular weights. WO 24028544, published after the filing of this application, discloses anode preparation compositions that use an acrylic-acrylate copolymer for carbon dispersion.

[0013] The known compositions used in the preparation of cathode primer layers of the state of the art are not always satisfactory. There is therefore a need for compositions used in the preparation of cathode primer layers which make it possible to provide solutions to all or part of the problems of the compositions of the state of the art.

[0014] Thus, the invention provides an aqueous composition C for preparing a cathode primary layer comprising:

[0015] • at least one material E comprising carbon particles and

[0016] • 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:

[0017] - a PI polymer prepared by a polymerization reaction, in the presence of at least one initiator compound, only:

[0018] ■ from 30% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof;

[0019] ■ from 5% by weight to 30% by weight 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, 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

[0020] ■ from 5% by weight to 40% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a), (b) and (c); - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound, only:

[0021] ■ from 35% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; and

[0022] ■ from 10% by weight to 65% by weight 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, 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, relative to the amount in weight of compounds (a) and (b);

[0023] - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound, only:

[0024] ■ from 35% by weight to 95% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; and

[0025] ■ from 5% by weight to 65% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a) and (c);

[0026] - a single 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; combinations thereof.

[0027] According to the invention, the molecular weight or mass of the polymers PI and P2 is determined by Size Exclusion Chromatography (SEC). A sample of the polymer solution corresponding to 20 mg of dry matter is introduced into a 10 mL flask. Mobile phase, containing 0.04% dimethylformamide (DMF), is added to a total mass of 10 g. The composition of this mobile phase is as follows: NaHCOv 0.05 mol / L, NaNOv 0.1 mol / L, triethanolamine: 0.02 mol / L, NaNs 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.

[0028] 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. Preferably according to the invention, the compound (a) is independently chosen from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and combinations thereof, preferably the compound (a) is acrylic acid or methacrylic acid.

[0029] 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.

[0030] Also preferably according to the invention, compound (c) is independently selected from 2-acrylamido-2-methylpropane sulfonic acid and a salt of 2-acrylamido-2-methylpropane sulfonic acid.

[0031] Essentially, polymers P1 to P4 according to the invention are prepared using compounds (a), (b) or (c). 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).

[0032] Preferably, the polymer P is not crosslinked. Also preferably, the compound (b) is not acrylonitrile or acrylamide or it does not comprise fluorine; the polymer P is then not a fluorinated polymer. Also preferably according to the invention, the polymer P is a free polymer, it is not grafted, in particular it is not grafted to a fluorinated polymer. In addition, the polymer P according to the invention is not prepared in the presence of polyaniline; it does not comprise a conductive group, in particular a conductive group resulting from a reaction with polyaniline.

[0033] The amounts 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 using: from 50% 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 20% by weight of compound (c), relative to the amount by weight of compounds (a), (b) and (c).

[0034] Also preferably for composition C according to the invention, polymer P2 is prepared using: from 65% by weight to 90% by weight of compound (a) and from 10% by weight to 35% by weight of compound (b), relative to the quantity by weight of compounds (a) and (b).

[0035] Also preferably for composition C according to the invention, polymer P3 is prepared using: from 65% by weight to 95% by weight of compound (a) and from 5% by weight to 35% by weight of compound (c), relative to the quantity by weight of compounds (a) and (c).

[0036] 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.

[0037] 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. Also preferably, the molecular mass Mw of the polymer P, measured by CES, may be less than 4,000,000 g / mol, more preferably less than 3,500,000 g / mol.

[0038] 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.

[0039] 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. 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-methyl-propanol (AMP) and their combinations, much more preferably NaOH, Ca(OH)2, CaO.

[0040] 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.

[0041] 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.

[0042] 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 respective combinations or associations with an ion chosen from Fe 11 , Fe 111 , Cu 1 , Cu 11and their combinations. According to the invention, the Fe ions 11 , Fe 111 , Cu 1 , Cu 11can be implemented using 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, copper sulfate pentahydrate, copper hydroxide, copper halide. 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 (EbPC '), in particular a compound chosen from sodium hypophosphite (EhPC Na), potassium hypophosphite (H2PO2K), calcium hypophosphite ([EEPCh^Ca).

[0043] 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.

[0044] Preferably according to the invention, the binding agent Q comprises a single polymer P.

[0045] 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.

[0046] 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.

[0047] 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 material E relative to the total amount by dry weight of binding agent Q and material E.

[0048] 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. 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 polymer PI prepared by a polymerization reaction, in the presence of at least one initiator compound, only:

[0049] ■ from 30% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof;

[0050] ■ from 5% by weight to 30% by weight 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, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam acrylate and combinations thereof; and

[0051] ■ from 5% by weight to 40% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a), (b) and (c);

[0052] - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound, only:

[0053] ■ from 35% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof;and ■ from 10% by weight to 65% by weight 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, ureidomethacrylate, maleic acid, maleic anhydride, itaconic acid, crotonic acid, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, hydroxybutylacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam acrylate and combinations thereof, relative to the amount by weight of compounds (a) and (b);

[0054] - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound, only:

[0055] ■ from 35% by weight to 95% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; and

[0056] ■ from 5% by weight to 65% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a) and (c);

[0057] - a single 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; combinations thereof.

[0058] 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. 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 combinations thereof.

[0059] The implementation 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 primer layer of at least one composition C defined according to the invention; the drying and then the optional calendering of the metal substrate carrying the primer layer, then the application 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, the drying and then the calendering of the metal substrate carrying the primer layer and the electroactive coating.

[0060] 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.

[0061] Also preferably according to the invention, the electroactive compound comprises at least one metal chosen from lithium, iron, nickel, manganese, cobalt and their combinations. 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 LiFePCU (LFP), Li(Ni,Mn,Co)O2 (NMC) and their combinations.

[0062] 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-di oxole) (PDD), perfluorobutyl ethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluorop. Preferably according to the invention, the binding compound of the electroactive compound is not a (meth)acrylic polymer.

[0063] Preferably according to the invention, the organic solvent is an aprotic polar solvent, preferably chosen from pyrrolidone, N-methyl-pyrrolidone (NMP), alkyl carbonates and combinations thereof.

[0064] 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.

[0065] 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 obtained according to the preparation method according to the invention.

[0066] The invention also provides a cathode manufactured according to the manufacturing method according to the invention.

[0067] 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.

[0068] 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 to the metal substrate then the drying and optional calendering, of at least one aqueous composition C for preparing a primer layer according to the invention, then the application of the electroactive composition, the drying and then the calendering of the metal substrate carrying the primer layer and the electroactive coating.

[0069] The polymer P used according to the invention makes it possible to improve subsequent adhesion with the binder compound of the electroactive compound. It acts as an adhesion promoter between the metal substrate and this binder compound of the electroactive compound. It also helps to make the carbon particles of material E adhere to the metal substrate.

[0070] 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.

[0071] The various aspects of the invention may be illustrated by examples.

[0072] EXAMPLES

[0073] Preparation and characterization of polymers P and agents O according to the invention

[0074] PI A polymer and Q1 agent

[0075] In a 1 L glass reactor equipped with mechanical stirring and oil bath heating, 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 sodium salt (AMPS) are introduced. The whole is then heated to approximately 70°C.

[0076] 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 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.

[0077] After cooling to room temperature, agent Q1 is obtained comprising the polymer PI A at 10% by weight of dry extract and whose pH is 2.1. The molecular mass Mw of the polymer PI A measured by CES is 533,000 g / mol and its Ip is 44.

[0078] PIB polymer and agent 02

[0079] In a 1 L glass reactor equipped with mechanical stirring and oil bath heating, 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 sodium salt (AMPS) are introduced. The whole is then heated to approximately 70°C.

[0080] 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 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.

[0081] 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.

[0082] Polymer P4A and agent Q3

[0083] 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 mixture is then heated to approximately 70°C.

[0084] 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 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.

[0085] 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.

[0086] Preparation of aqueous compositions C for preparing a cathode primary layer according to the invention

[0087] 91 g of deionized water are weighed with 100 g of agent Q1 and then mixed under 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 1500 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.

[0088] Similarly, cathode primer layer compositions C2 and C3 are prepared from agents Q2 and Q3.

[0089] Preparation and characterization of cathodes according to the invention

[0090] On an aluminum foil degreased with acetone, 6 μm of cathode primer layer preparation composition Cl according to the invention are applied using 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 using the applied and then dried composition Cl has a mass, measured using a precision balance, of 0.2 mg for an aluminum disc 12 mm in diameter and 10 μm + / - 1 μm thick.

[0091] In a similar manner, cathode primer layers are prepared using compositions C2 and C3.

[0092] The adhesion of the primer layer obtained using compositions C1 to C3 according to the invention to the cathode aluminum substrate is evaluated using a peel-off 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.

[0093] 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.

[0094] On a cathode primer 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.

[0095] A standardized adhesive tape (“Intertape” 51596 CIC8091013) is manually applied to the secondary cathode layer. The adhesive tape is then peeled off and the adhesion is visually assessed.

[0096] 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:

[0097] 1: aluminum foil visible on the majority of the surface of the adhesive strip,

[0098] 2: aluminum foil visible on part of the surface of the adhesive strip,

[0099] 3: non-visible aluminum foil on the surface of the adhesive tape,

[0100] 4: primary layer mostly intact,

[0101] 5: primary layer completely intact.

[0102] 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.

[0103] The Q binding agents comprising the P polymers 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 PVDF secondary 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

CLAIMS 1. 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, only: ■ from 30% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; ■ from 5% by weight to 30% by weight 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, 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 ■ from 5% by weight to 40% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a), (b) and (c); - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound, only: ■ from 35% by weight to 90% by weight 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 ■ from 10% by weight to 65% by weight 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, 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, relative to the amount in weight of compounds (a) and (b); - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound, only: ■ from 35% by weight to 95% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; and ■ from 5% by weight to 65% by weight 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 and combinations thereof, relative to the quantity by weight of compounds (a) and (c); - a single 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; combinations thereof.

2. 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: the compound (a) is independently chosen from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and combinations thereof, preferably the compound (a) is acrylic acid or methacrylic acid;or 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, preferably C1-Cs esters of methacrylic acid, C1-Cs esters of acrylic acid and combinations thereof, preferably styrene, t-Bu-acrylamide, methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, methylacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, more preferably, methylmethacrylate, methylacrylate, ethyl acrylate, butyl acrylate; or compound (c) is independently selected from 2-acrylamido-2-methylpropane sulfonic acid and a salt of 2-acrylamido-2-methylpropane sulfonic acid; or the polymer P4 is prepared using a single compound (a) or using two different compounds (a).; 3. Composition C according to one of claims 1 or 2 for which: the polymer PI is prepared by means of: • from 50% 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 20% 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 65% by weight to 90% by weight of compound (a) and • from 10% by weight to 35% 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 65% by weight to 95% by weight of compound (a) and • from 5% by weight to 35% 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, isopropanol 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 their combinations.

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 PI polymer prepared by a polymerization reaction, in the presence of at least one initiator compound, only: ■ from 30% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; ■ from 5% by weight to 30% by weight 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, 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 ■ from 5% by weight to 40% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a), (b) and (c); - a polymer P2 prepared by a polymerization reaction, in the presence of at least one initiator compound, only: ■ from 35% by weight to 90% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a methacrylic acid salt, an acid oligomer salt acrylic, a salt of oligomer of methacrylic acid and combinations thereof; and ■ from 10% by weight to 65% by weight 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, 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, relative to the amount in weight of compounds (a) and (b); - a polymer P3 prepared by a polymerization reaction, in the presence of at least one initiator compound, only: ■ from 35% by weight to 95% by weight of at least one compound (a) independently selected from acrylic acid, methacrylic acid, an oligomer of acrylic acid, an oligomer of methacrylic acid, an acrylic acid salt, a salt of methacrylic acid, an oligomer salt of acrylic acid, a salt of oligomer of methacrylic acid and combinations thereof; and ■ from 5% by weight to 65% by weight 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 and combinations thereof, relative to the amount by weight of compounds (a) and (c); - a single 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 acid salt acrylic, a salt of methacrylic acid, an oligomeric salt of acrylic acid, an oligomeric salt of methacrylic acid and combinations thereof; 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 wherein: 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 metallic salt, preferably a polymetallic salt, preferably the electroactive compound is chosen from LiFePC (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 selected 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 (PP VE), perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), perfluorobutyl ethylene (PFBE), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluorop, or the organic solvent is an aprotic polar solvent, preferably selected 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 1 E 13. Method for improving the adhesion on 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, comprising: the prior application directly to the metal substrate then the drying and optional 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 electroactive composition, the drying then the calendering of the metal substrate carrying the primer layer and the electroactive coating.

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