COMPOSITION OF A PRIMARY CATHODE LAYER

Abstract

The invention relates to a primary cathode layer preparation composition comprising a low 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: COMPOSITION OF A PRIMARY CATHODE LAYER

[0001] The invention relates to a primary cathode layer preparation composition comprising a low 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 being usable for manufacturing secondary battery cells.

[0002] Cathode preparation compositions are known which generally comprise carbon and a metal in the form of particles associated with a binding agent. The binding agents allow the particles to be fixed to a metallic substrate. The binding strength is therefore crucial when manufacturing a cathode using these compositions.

[0003] The manufacturing time and yield of the cathodes are also important factors. Therefore, improving the efficiency of the various reactions involved should be sought.

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

[0005] The binding compounds used in 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 degree of 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 and 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.

[0007] 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 electrode surface, resulting in a homogeneous and particularly efficient conductive layer. Surface leveling, restructuring, and the The flow behavior 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, and separation of ingredients must therefore be limited or avoided.

[0009] Generally, improving the adhesion of the active elements should always be a priority during cathode preparation. Therefore, the adhesion of the various layers of ingredients deposited on the metallic substrate must be enhanced. In particular, when a primary layer containing carbon is deposited on the metallic substrate, improving its adhesion is essential. Because they are in direct contact with the metallic substrate of the cathode and with the binding composition of the electroactive compound, the properties of the primary layer compositions are especially important.

[0010] The known compositions used in the preparation of the primary cathode layer in the prior art are not always satisfactory. Therefore, there is a need for compositions used in the preparation of the primary cathode layer that provide solutions to all or some of the problems with prior art compositions.

[0011] Thus, the invention provides an aqueous composition T for preparing a primary cathode layer comprising:

[0012] * at least one binding agent R comprising at least one water-soluble polymer P, of molecular mass Mw, measured by CES, ranging from 2,000 g / mol to less than 100,000 g / mol, prepared by a polymerization reaction, in the presence of at least one initiating compound, of at least one compound (a) 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,

[0013] * at least one material E comprising carbon particles.

[0014] The polymer P implemented according to the invention is a water-soluble polymer. Preferably according to the invention, the polymer P is water-soluble at a pH greater than 4.

[0015] Preferably according to the invention, compound (a) is selected from acrylic acid, methacrylic acid, a salt of acrylic acid, a salt of methacrylic acid and their combinations, preferably compound (a) is acrylic acid or methacrylic acid.

[0016] The polymer P according to the invention may be a homopolymer of compound (a). The polymer P may also be a copolymer of compounds (a) or a copolymer of at least one compound (a) and at least one other compound (b).

[0017] Preferably according to the invention, compound (b) is selected from: - a compound (bl) selected from the Ci-Ci2 esters of methacrylic acid, the C1-C12 esters of acrylic acid and their combinations, preferably the CrC8 esters of methacrylic acid, the CrC8 esters of acrylic acid and their combinations, preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, more preferably methyl acrylate, ethyl acrylate, butyl acrylate; - a compound (b2) selected from acrylonitrile, acrylamide, N-methylolacrylamide, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate and their combinations, preferably acrylonitrile; - a compound (b3) chosen from maleic acid, maleic anhydride, itaconic acid, crotonic acid and their combinations; - a compound (b4) selected from hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactame methacrylate, polycaprolactame acrylate, styrene, more preferably styrene; - a compound (b5) 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, phosphated hydroxyethyl acrylate, phosphated hydroxyethyl methacrylate, phosphated hydroxypropyl acrylate, phosphated hydroxypropyl methacrylate, phosphated hydroxybutyl methacrylate; - a crosslinking compound (b6).

[0018] Preferably according to the invention, polymer P is not crosslinked. Also preferably, compound (b) is not acrylonitrile or acrylamide, or it does not contain 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.

[0019] The quantities of monomers present in polymer P can vary relatively significantly. Preferably for composition T according to the invention, polymer P is prepared by a polymerization reaction of 55% by weight at 100% by weight of compound (a) and from 0% by weight to 45% by weight of compound (b). Preferably, polymer P can also be prepared by a polymerization reaction of 55% by weight to 90% by weight of compound (a) and 10% by weight to 45% by weight of compound (b), or of 55% by weight to 80% by weight of compound (a) and 20% by weight to 45% by weight of compound (b). Polymer P can also be prepared by a polymerization reaction of 55% by weight to 70% by weight of compound (a) and 30% by weight to 45% by weight of compound (b).

[0020] Essentially, according to the invention, the polymer P has a molecular mass Mw of less than 100,000 g / mol, preferably strictly less than 100,000 g / mol. Preferably, the polymer P has a molecular mass Mw of less than 80,000 g / mol or less than 50,000 g / mol.

[0021] Also preferably according to the invention, the polymer P has a molecular mass Mw ranging from 2,000 g / mol to 80,000 g / mol or from 2,000 g / mol to 50,000 g / mol. More preferably, the molecular mass Mw of the polymer P ranges from 2,000 g / mol to 40,000 g / mol or from 2,000 g / mol to 30,000 g / mol. Even more preferably, it ranges from 2,000 g / mol to 25,000 g / mol or from 2,000 g / mol to 20,000 g / mol or from 5,000 g / mol to 25,000 g / mol or from 5,000 g / mol to 20,000 g / mol.

[0022] According to the invention, the molecular weight or mass of polymer P is determined by Size Exclusion Chromatography (SEC). A test portion of the polymer solution corresponding to 90 mg of dry matter is introduced into a 10 mL bottle. 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 wt%. The CES chain consists of a Waters 510 type isocratic pump, with a flow rate set at 0.8 mL / min, a Waters 717+ sample changer, a furnace containing a 6 cm long and 40 mm internal diameter Waters Guard Column Ultrahydrogel pre-column, followed by a 30 cm long and 7.8 mm internal diameter Waters Ultrahydrogel linear column.Detection is performed using a Waters RI 410 differential refractometer. The oven is heated to 60°C and the refractometer to 45°C. The CES device is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standards Service, with peak molecular weights ranging from 1000 g / mol to 1.106 g / mol and polymolecularity indices from 1.4 to 1.7. The calibration curve is linear and incorporates the correction obtained using the flow marker dimethylformamide (DMF). Chromatogram acquisition and processing are performed using the "PSS WinGPC Scientific" software. v 4.02. The chromatogram obtained is integrated into the area corresponding to molecular weights greater than 250 g / mol.

[0023] 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.

[0024] Also, and more preferably according to the invention, polymer P is a copolymer whose Tg is greater than 50°C, preferably greater than 100°C. The Flory-Fox equation allows the glass transition temperature of a copolymer to be calculated from the parameters of the monomers used in its preparation.

[0025] The polymer P implemented according to the invention can be used in its acidic 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 using at least one compound selected from LiOH, NaOH, KOH, Zn(OH)2, Mg(OH)2, Ca(OH)2, ZnO, MgO, CaO, ammonium derivatives, ammonia, ammonia, amino bases, for example triethanolamine, aminomethylpropanol or 2-amino-2-methylpropanol (AMP) and their combinations, much more preferably LiOH or Zn(OH)2 or ZnO.

[0026] Within the composition T according to the invention, the ingredients may be present in quantities that can vary quite widely. Preferably according to the invention, the composition T according to the invention comprises, by dry weight, - from 0.5% to 70% of binding agent R, - from 30% to 99.5% of material E.

[0027] in relation to the total quantity by dry weight of binding agent R and material E.

[0028] Advantageously according to the invention, the binding agent R 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 selected from ethanol, isopropanol, and combinations thereof. Also preferably according to the invention, the binding agent R comprises: - from 5% by weight to 60% by weight of polymer P and - from 40% by weight to 95% by weight of liquid support, more preferably - from 10% by weight to 40% by weight of polymer P and - from 60% by weight to 90% by weight of liquid support.

[0029] Essentially, according to the invention, in addition to the polymer P, the composition T according to the invention comprises a material E which includes carbon particles. Preferably, according to the invention, the material E is selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, hardened carbon, and combinations thereof.

[0030] The implementation of composition T 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 of at least one aqueous composition T according to the invention, on a metallic substrate comprising at least one metal chosen from aluminium, nickel, preferably aluminium; - the drying and then the possible calendering of the metallic substrate carrying the primary layer; - the application of an electro-active composition comprising at least one electro-active compound, at least one binding compound for the electro-active compound and at least one organic solvent; - the drying and then the calendering of the metallic substrate carrying the primary layer and the electro-active coating.

[0031] 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.

[0032] Also preferably according to the invention, the electro-active compound comprises at least one metal selected from lithium, iron, nickel, manganese, cobalt and their combinations.

[0033] Also preferably according to the invention, the electro-active compound is in the form of a metallic salt, preferably a polymetallic salt, more preferably the electro-active compound is chosen from LiFePO4 (LFP), Li(Ni,Mn,Co)O2 (NMC) and their combinations.

[0034] Preferably according to the invention, the binding compound of the electroactive compound is polyvinylidene fluoride (PVDF). Preferably according to the invention, the binding compound of the electroactive compound is not a (meth)acrylic polymer.

[0035] Preferably according to the invention, the organic solvent is a polar aprotic solvent, preferably selected from pyrrolidone, N-methylpyrrolidone (NMP), alkyl carbonates and their combinations.

[0036] Preferably according to the invention, the electro-active composition comprises carbon, preferably selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, tempered carbon and combinations thereof.

[0037] The invention also provides a cathode comprising at least one metallic substrate covered with at least one primary layer comprising a binding agent R and at least one material E, preferably obtained according to the preparation method according to the invention.

[0038] The invention also provides a cathode manufactured according to the manufacturing method according to the invention.

[0039] The polymer P of the binding agent R of composition T according to the invention possesses particularly advantageous properties for the preparation of a primary cathode layer and thus for obtaining a cathode. The polymer P used according to the invention notably improves adhesion to the metallic substrate of the cathode. In particular, the polymer P used according to the invention improves adhesion to the metallic substrate when 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.

[0040] Thus, the invention provides a method for improving the adhesion of an electroactive composition to a metallic cathode substrate comprising at least one metal selected from aluminum and nickel, and comprising at least one electroactive compound, at least one binding compound for the electroactive compound, and at least one organic solvent. Preferably, this method for improving adhesion to a metallic cathode substrate comprises: - the preliminary application directly onto the metallic substrate, followed by drying and possible calendering, of at least one aqueous composition T for primer preparation according to the invention, then - the application of the electro-active composition, - the drying and then the calendering of the metallic substrate carrying the primary layer and the electro-active coating.

[0041] The polymer P implemented according to the invention improves subsequent adhesion to the binding compound of the electroactive compound. It acts as an adhesion promoter between the metallic substrate and this binding compound of the electroactive compound. It also helps to adhere the carbon particles of material E to the metallic substrate.

[0042] The advantageous, particular or preferred characteristics of the composition T according to the invention define methods of preparing a cathode according to the invention, methods of improving adhesion to a metallic substrate of cathode, as well as cathodes, which are also advantageous, particular or preferred.

[0043] The various aspects of the invention can be illustrated by examples.

[0044] Preparation and characterization of polymers P and agents R according to the invention: Polymer PI and agent RI

[0045] In a 1 L reactor equipped with mechanical stirring, an oil bath heater, and peristaltic pumps, 200 g of isopropanol and 1.7 g of 2,2'-azobis-(2-methylpropionitrile) (AZDN) are weighed out. The mixture is then heated under reflux at approximately 80°C, and over 120 min, 200 g of acrylic acid and 81 g of butyl acrylate are added using the peristaltic pumps. Heating under reflux is then continued for 60 min. The isopropanol is then distilled, and it is gradually replaced by water during the distillation process. The mixture is then cooled and diluted to obtain the RI agent according to the invention, which has a dry matter content of 40% by weight, a pH of 2.3 and comprises the PI polymer, whose molecular mass Mw measured by CES is 9,000 g / mol. P2 polymer and R2 agent

[0046] In a 1 L reactor equipped with mechanical stirring, an oil bath heater, and peristaltic pumps, 200 g of isopropanol and 1.7 g of AZDN are weighed out. The mixture is then heated under reflux at approximately 80°C, and over 120 min, 200 g of acrylic acid and 80 g of ethyl acrylate are added using the peristaltic pumps. Heating under reflux is then continued for 60 min. The isopropanol is then distilled, and it is gradually replaced by water during the distillation. The mixture is then cooled and diluted to obtain agent R2 according to the invention, which has a dry matter content of 40% by weight, a pH of 2.2, and comprises polymer P2, whose molecular weight Mw, measured by CES, is 9,500 g / mol. P3 polymer and R3 agent

[0047] In a 1 L reactor equipped with mechanical stirring, an oil bath heater, and peristaltic pumps, 200 g of isopropanol and 1.9 g of AZDN are weighed out. The mixture is then heated under reflux at approximately 80°C, and over 120 min, 200 g of acrylic acid and 83 g of methyl methacrylate are added using the peristaltic pumps. Heating under reflux is then continued for 60 min. The isopropanol is then distilled, and it is gradually replaced by water during the distillation. The mixture is then cooled and diluted to obtain agent R3 according to the invention, which has a dry matter content of 40% by weight, a pH of 2.5, and comprises polymer P3, whose molecular weight Mw, measured by CES, is 8000 g / mol. P4 polymer and R4 agent

[0048] In a 1 L reactor equipped with mechanical stirring, oil bath heating and peristaltic pumps, the following are weighed: 209.7 g of water, 0.08 g of sulfate of iron heptahydrate and 0.011 g of copper sulfate pentahydrate are added. The mixture is then heated to 95°C and, over 120 minutes using peristaltic pumps, the following are added: 302.5 g of acrylic acid and 13 g of water, 25.6 g of sodium hypophosphite monohydrate dissolved in 29 g of water, and 20.46 g of 130V hydrogen peroxide diluted in 25 g of water. Heating is then continued under reflux for 60 minutes. The mixture is then cooled and diluted to obtain agent R4 according to the invention, which has a dry matter content of 40% by weight, a pH of 2.1, and comprises polymer P4, whose molecular weight Mw, measured by CES, is 4400 g / mol. P5 polymer and R5 agent

[0049] In a 1 L reactor equipped with mechanical stirring, an oil bath heater, and peristaltic pumps, the following are weighed out: 121 g of water, 121 g of isopropanol, 0.06 g of iron(II) sulfate heptahydrate, and 11 g of hydrazine hydrate at a concentration of 35% in water. The mixture is then heated under reflux to approximately 80°C, and over 120 min, the following are added using the peristaltic pumps:

[0050] - in a first test tube, 174 g of acrylic acid, 35 g of methacrylate methyl, 110g of ethylene glycol phosphate and 80g of water,

[0051] - in a second test tube, 20 g of 130V hydrogen peroxide and 100 g of water. Then, one continues heating under reflux for 60 min.

[0052] The isopropanol is then distilled and gradually replaced by water during the distillation. The mixture is then cooled and diluted to obtain agent R5 according to the invention, which has a dry matter content of 40% by weight, a pH of 2.0, and comprises polymer P5, whose molecular mass Mw, measured by CES, is 15,000 g / mol.

[0053] Preparation of aqueous compositions T2 to T5 for the preparation of the primary cathode layer according to the invention

[0054] 150 g of deionized water is weighed with 25 g of RI agent according to the invention 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) is added while stirring is maintained for 1.25 h at 1500 rpm to obtain a composition whose homogeneity and absence of aggregates are checked using a North gauge.

[0055] Similarly, primary cathode layer compositions T2 to T5 are prepared by replacing agent RI respectively with agents R2 to R5.

[0056] Preparation and characterization of cathodes according to the invention

[0057] On a sheet of aluminum degreased with acetone, 12 µm of cathode primary layer preparation composition Tl according to the invention is applied using a coater equipped with a threaded rod (RK Control Coater), at an application speed of 10 mm / s. It is then dried at 150°C in an oven for 5 min. The primary layer obtained by means of the applied and then dried composition Tl has a mass, measured by means of a precision balance, of 0.2 mg for an aluminum disc of 12 mm in diameter and 10 pm + / -1 pm in thickness.

[0058] In a similar way, primary cathode layers are prepared using compositions T2 to T5.

[0059] The adhesion of the primary layer obtained using compositions T1 to T5 according to the invention to the aluminum cathode substrate is evaluated by a peel test. A standardized adhesive strip (Intertape 51596 CIC8091013) is manually applied to the primary cathode layer. The adhesive strip is then removed, and the adhesion of the primary layer to the aluminum is visually assessed.

[0060] The compatibility of the primary 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 N-methylpyrrolidone (NMP) solvent medium.

[0061] On a primary cathode layer obtained according to the method described above, a layer of PVDF bonding agent is applied using a solution with a 5% concentration of PVDF in NMP, then applied in a layer of 9 pm and then dried at 150°C in an oven for 5 min.

[0062] A standard adhesive strip (Intertape 51596 CIC8091013) is manually applied to the secondary cathode layer. The adhesive strip is then peeled off and the adhesion is visually assessed.

[0063] The results obtained for the adhesion of the primary layer and for its compatibility with the secondary PVDF layer are presented in Table 1 according to the scale: - 1: aluminum foil visible over the majority of the surface of the strip adhesive, - 2: Aluminum foil visible on part of the surface of the strip adhesive, - 3: Aluminum foil not visible on the surface of the adhesive strip, - 4: primary layer mostly intact, - 5: primary layer completely intact.

[0064] Evaluations 1 and 2 are not acceptable for the use of the cathode in a secondary battery. Evaluations 3 to 5 are acceptable for the use of the cathode in a secondary battery. The results are presented in Table 1.

[0065] [Tables 1] Composition T according to the invention Adhesion Compatibility T1 5 5 T2 3 4 T3 4 5 T4 4 4 T5 5 5

[0066] The R-linking agents comprising the polymers according to the invention make it possible, on the one hand, to create high-quality primary adhesion layers that very effectively retain the conductive carbon on the surface of the aluminum foil. They also act as bonding agents compatible with the PVDF secondary bonding agent, which is the polymeric constituent of the LFP layer, thereby increasing the adhesion of the LFP layer to the primary adhesion layer of the cathode.

Claims

Demands

1. Aqueous composition T of cathode primary layer preparation comprising: * at least one binder R comprising at least one water-soluble, non-grafted, non-crosslinked polymer P of molecular weight Mw, measured by CES, from 5,000 g / mol to less than 100,000 g / mol, prepared by a polymerization reaction, in the presence of at least one initiator compound, of at least one compound (a) 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, * at least one material E comprising carbon particles.

2. Composition T according to claim 1 wherein compound (a) is 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.

3. Composition T according to any one of claims 1 or 2 wherein polymer P is water-soluble at a pH greater than 4 or wherein polymer P is a homopolymer of compound (a) or polymer P is a copolymer of compounds (a) or polymer P is a copolymer of at least one compound (a) and at least one other compound (b), preferably compound (b) selected from: - compound (bl) selected from Ci-Ci2 esters of methacrylic acid, CrCi2 esters of acrylic acid and combinations thereof, preferably Ci-C8 esters of methacrylic acid, CrC8 esters of acrylic acid and combinations thereof, preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, more preferably methyl acrylate, ethyl acrylate, butyl acrylate;- a compound (b2) selected from acrylonitrile, acrylamide, N-methylolacrylamide, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate and their combinations, preferably acrylonitrile; - a compound (b3) selected from maleic acid, maleic anhydride, itaconic acid, crotonic acid and their combinations; - a compound (b4) selected from hydroxyethylacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, styrene, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactame methacrylate, lactame acrylate, polycaprolactame methacrylate, polycaprolactame acrylate, more preferably styrene; - a compound (b5) 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, phosphated hydroxyethyl acrylate, phosphated hydroxyethyl methacrylate, phosphated hydroxypropyl acrylate, phosphated hydroxypropyl methacrylate, phosphated hydroxybutyl methacrylate; - a crosslinking compound (b6).

4. Composition T according to any one of claims 1 to 3 wherein polymer P is prepared by a polymerization reaction - of 55% by weight to 100% by weight of compound (a) and - of 0% by weight to 45% by weight of compound (b); or - of 55% by weight to 90% by weight of compound (a) and - of 10% by weight to 45% by weight of compound (b); or - of 55% by weight to 80% by weight of compound (a) and - of 20% by weight to 45% by weight of compound (b) or - of 55% by weight to 70% by weight of compound (a) and - of 30% by weight to 45% by weight of compound (b).

5. Composition T according to any one of claims 1 to 4 comprising, by dry weight, - from 0.5% to 70% of binder R, - from 30% to 99.5% of material E. relative to the total quantity by dry weight of binder R and material E.

6. Composition T according to any one of claims 1 to 5, wherein the polymer P has a molecular weight Mw, measured by CES, of 5,000 g / mol to 80,000 g / mol or of 5,000 g / mol to 50,000 g / mol, preferably of 5,000 g / mol to 40,000 g / mol or of 5,000 g / mol to 30 000 g / mol, more preferably from 5,000 g / mol to 25,000 g / mol or from 5,000 g / mol to 20,000 g / mol.

7. Composition T according to any one of claims 1 to 6 wherein 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 wherein the polymer P is a homopolymer whose Tg is greater than 0°C, preferably greater than 10°C; or wherein the polymer P is a copolymer whose Tg is greater than 50°C, preferably greater than 100°C.

8. Composition T according to any one of claims 1 to 7 wherein polymer P is totally or partially acidic or totally or partially non-neutralized, preferably polymer P is partially neutralized, preferably by means of at least one compound selected from LiOH, NaOH, KOH, Zn(OH)2, Mg(OH)2, Ca(OH)2, ZnO, MgO, CaO, ammonium derivatives, ammonia, ammonia, amino bases, for example triethanolamine, aminomethylpropanol or 2-amino-2-methylpropanol (AMP) and combinations thereof, more preferably LiOH or Zn(OH)2 or ZnO.

9. Composition T according to any one of claims 1 to 8 wherein the binding agent R comprises at least one polymer P and at least one liquid carrier, preferably water alone or combined with at least one polar solvent, for example a solvent selected from ethanol, isopropanol and combinations thereof; also preferably the binding agent R comprises: - from 5% by weight to 60% by weight of polymer P and - from 40% by weight to 95% by weight of liquid carrier, more preferably - from 10% by weight to 40% by weight of polymer P and - from 60% by weight to 90% by weight of liquid carrier.

10. Composition T according to any one of claims 1 to 9 wherein material E is selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, tempered carbon and combinations thereof.

11. Method of preparing a cathode comprising: - the application of at least one aqueous composition T according to one of claims 1 to 10, on a metallic substrate comprising at least one metal selected from aluminium, nickel, preferably aluminium; - drying and then possible calendering of the metallic substrate bearing the primary layer, then - application of an electro-active composition comprising at least one electro-active compound, at least one binding compound for the electro-active compound and at least one organic solvent, - drying and then calendering of the metallic substrate bearing the primary layer and the electro-active coating.

12. The method of claim 11, wherein: - the substrate is a purely metallic substrate or a composite substrate comprising at least one metal and at least one insulating support, - the electroactive compound comprises at least one metal selected from lithium, iron, nickel, manganese, cobalt, and combinations thereof, - the electroactive compound is in the form of a metallic salt, preferably a polymetallic salt, preferably selected from LiFePO4 (LFP), Li(Ni,Mn,Co)O2 (NMC), and combinations thereof, - the binding compound of the electroactive compound is polyvinylidene fluoride (PVDF), - the organic solvent is a polar aprotic solvent, preferably selected from pyrrolidone, N-methylpyrrolidone (NMP), alkyl carbonates, and combinations thereof, - the electroactive composition comprises carbon, preferably selected from carbon black, acetylene black, Ketjen black, carbon fibers, nanotubes, carbon, carbon nanofiber,hardened carbon and their combinations.

13. Cathode comprising at least one metallic substrate covered with at least one primary layer comprising a binding agent R and at least one material E defined according to any one of claims 1 to 10, preferably obtained according to the method according to any one of claims 11 or 12.

14. A method for improving adhesion to a metallic 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 for the electroactive compound, and at least one organic solvent, comprising: - the prior application directly onto the metallic substrate, followed by drying and optional calendering, of at least one composition aqueous T primer preparation according to one of the claims 1 to 10, then - the application of the electro-active composition, - the drying and then the calendering of the metallic substrate carrying the primary layer and the electro-active coating.