Composition for the preparation of a cathode priming coat

Abstract

The invention relates to a composition for preparing a cathode priming coat, comprising a polyacrylic binder that has a low molecular weight, and carbon particles. The invention also relates to the use of said composition for preparing a cathode as well as to the cathode that can be used for manufacturing cells for a rechargeable battery.

Description

[0001] COMPOSITION FOR PREPARING A PRIMER LAYER OF

[0002] CATHODE

[0003] The invention relates to a composition for preparing a cathode primer layer 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 usable for manufacturing cells for secondary batteries.

[0004] 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.

[0005] Cathode manufacturing time and yield are also important factors. Improving the efficiency of the various reactions involved must therefore be sought.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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 efficient conductive layer. The surface leveling, restructuring and flow behavior of the cathode preparation compositions must be well controlled.

[0010] 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.

[0011] 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.

[0012] CN 106876716 describes the preparation of a cathode by applying a carbon layer using a composition comprising a binder polymer in an organic solvent such as N-methyl-pyrrolidone. CN 115911388 and KR 20110111236 describe methods for preparing a cathode coating using carbon fixed using a binder crosslinked in an acidic medium or using a crosslinking agent containing an oxazoline group. CN 115881966 describes a conductive adhesive formulation composed of polymer compositions grafted using conductive monomers.

[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 T for preparing a cathode primary layer comprising:

[0015] • at least one binding agent R comprising at least one water-soluble polymer P, with a 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 initiator compound, of at least one compound (a) 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 methacrylic acid salt, and combinations thereof,

[0016] • at least one material E comprising carbon particles.

[0017] Thus, the invention provides a composition for preparing a cathode primary layer. Preferably, the primary layer obtained according to the invention does not comprise silicon or a metallic electroactive compound.

[0018] The polymer P used 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.

[0019] Preferably according to the invention, compound (a) is 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. 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).

[0020] Preferably according to the invention, compound (b) is chosen from: a compound (b1) chosen from 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 methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, more preferably, methylacrylate, ethylacrylate, butylacrylate; a compound (b2) chosen from acrylonitrile, acrylamide, N-methylolacrylamide, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate and combinations thereof, preferably acrylonitrile; a compound (b3) selected from maleic acid, maleic anhydride, itaconic acid, crotonic acid and combinations thereof;a compound (b4) chosen from hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam 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 hydroxyethylacrylate, phosphated hydroxyethylmethacrylate, phosphated hydroxypropylacrylate, phosphated hydroxypropylmethacrylate, phosphated hydroxybutylmethacrylate; a crosslinking compound (b6).;

[0021] According to the invention, the polymer P can be prepared solely by a polymerization reaction of the monomer (a) and optionally of at least one compound (b) chosen from compounds (b1) to (b6).

[0022] Preferably according to the invention, the polymer P is not crosslinked, in particular by means of calcium acetate, calcium hydroxide, calcium bicarbonate or calcium oxalate or by means of a compound comprising an oxazoline group. 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 or it is not grafted to a polyaniline, a polypyrrole, a polythiophene, a polyparaphenylene or to a polyphenylacetylene.

[0023] According to the invention, the PI polymer is not a conductive polymer.

[0024] The amounts of monomers present in the polymer P can vary relatively significantly. Preferably for the composition T according to the invention, the 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). Also preferably, the polymer P can be prepared by a polymerization reaction 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). The polymer P can also be prepared by a polymerization reaction of 55% by weight to 70% by weight of compound (a) and of 30% by weight to 45% by weight of compound (b).

[0025] Essentially according to the invention, the polymer P has a molecular mass Mw, measured by CES, of less than 100,000 g / mol, preferably strictly less than 100,000 g / mol. Preferably, the polymer P has a molecular mass Mw, measured by CES, of less than 80,000 g / mol or less than 50,000 g / mol.

[0026] Also preferably according to the invention, the polymer P has a molecular mass Mw, measured by CES, 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. 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. Much more preferably, it ranges from 8,500 g / mol to 25,000 g / mol or from 8,500 g / mol to 20,000 g / mol or from 9,000 g / mol to 25,000 g / mol or from 9,000 g / mol to 20,000 g / mol.

[0027] According to the invention, the molecular weight or mass of the polymer P is determined by Size Exclusion Chromatography (SEC). A sample of the polymer solution corresponding to 90 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: NaHCOs: 0.05 mol / L, NaNOs: 0.1 mol / L, triethanolamine: 0.02 mol / L, NaNs 0.03% by mass. The CES line consists of a Waters 510 isocratic pump with a flow rate set at 0.8 mL / min, a Waters 717+ autosampler, an oven containing a 6 cm long, 40 mm inner diameter Waters Guard Column Ultrahydrogel precolumn, followed by a 30 cm long, 7.8 mm inner 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 is heated to 45°C. The CES device is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standards Service with a peak molecular weight between 1000 g / mol and 1.10. 6 g / mol and a polydispersity index between 1.4 and 1.7. The calibration curve is linear and takes into account the correction obtained using the flow marker: dimethylformamide (DMF). The acquisition and processing of the chromatogram are carried out using the software “PSS WinGPC Scientific” v 4.02. The chromatogram obtained is integrated into the area corresponding to molecular weights greater than 250 g / mol.

[0028] 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.

[0029] 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.

[0030] 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 combinations thereof, much more preferably LiOH or Zn(OH)2 or ZnO.

[0031] According to the invention, the polymer P is prepared by a polymerization reaction at a temperature above 50°C, preferably at a temperature ranging from 60°C to 95°C or ranging from 65°C to 90°C, in particular at a temperature ranging from 70°C to 85°C. Preferably, the initiator compound is chosen from peroxides, hydroperoxides, persulfates and combinations thereof. More preferably according to the invention, the initiator compound is chosen from hydrogen peroxide, tert-butyl hydroperoxide, 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 combinations thereof. According to the invention, the initiator compound may also be an organic compound, preferably an organic initiator compound chosen from compounds with an azo group, preferably chosen from 4,4'-azobis(4-cyanovaleric) acid (CAS No. 2638-94-0), 2,2'-azobis(2-methylpropionamidine) dihydrochloride (CAS No. 2997-92-4), azo-bis-isobutyronitrile (AZDN or AIBN) and combinations thereof.

[0032] Within the composition T according to the invention, the ingredients may be present in amounts which may 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, relative to the total amount by dry weight of binding agent R and material E.

[0033] 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 chosen from ethanol, isopropanol and their combinations. Also preferentially 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.

[0034] Preferably according to the invention, the composition T comprises water, alone or combined with at least one polar solvent, for example a solvent chosen from ethanol, isopropanol and their combinations. More preferably according to the invention, the composition T does not comprise a polar solvent or does not comprise a solvent chosen from ethanol, isopropanol and their combinations, in particular not isopropanol.

[0035] Essentially according to the invention, in addition to the polymer P, the composition T 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.

[0036] The implementation of the 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 metal substrate comprising at least one metal chosen from aluminum, nickel, preferably aluminum; drying then optionally calendering the metal substrate carrying the primary 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; drying then calendering the metal substrate carrying the primary layer and the electroactive coating. 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.

[0037] 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 LiFePO (LFP), Li(Ni,Mn,Co)O2 (NMC) and their combinations.

[0038] Preferably according to the invention, the binder compound of the electroactive compound is polyvinylidene fluoride (PVDF). Preferably according to the invention, the binder compound of the electroactive compound is not a (meth)acrylic polymer.

[0039] 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.

[0040] 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.

[0041] The invention also provides a cathode comprising at least one metal substrate covered with at least one primary layer comprising a binding agent R and at least one material E according to the invention, preferably obtained according to the preparation method according to the invention.

[0042] The invention also provides a cathode manufactured according to the preparation method according to the invention.

[0043] The polymer P of the binding agent R of the composition T 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.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 T 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.

[0044] 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.

[0045] 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 metal cathode substrate, as well as cathodes, which are also advantageous, particular or preferred.

[0046] The various aspects of the invention may be illustrated by examples.

[0047] EXAMPLES

[0048] Preparation and characterization of polymers P and agents R according to the invention:

[0049] PI polymer and RI agent

[0050] In a 1 L reactor equipped with mechanical stirring, oil bath heating and peristaltic pumps, the following are weighed: 200 g of isopropanol and 1.7 g of 2,2'-azobis-(2-methylpropionitrile) (AZDN). The mixture is then heated to reflux at approximately 80°C and the following are added over 120 min, using peristaltic pumps: 200 g of acrylic acid and 81 g of butyl acrylate. Then, reflux heating is continued for 60 min. The isopropanol is then distilled and gradually replaced by water during the distillation. The whole is then cooled and then diluted in order to obtain the agent RI according to the invention whose dry matter content is 40% by weight, the pH is 2.3 and which comprises the polymer PI whose molecular mass Mw, measured by CES, is 9,000 g / mol. Polymer P2 and agent R2

[0051] In a 1 L reactor equipped with mechanical stirring, oil bath heating and peristaltic pumps, the following are weighed: 200 g of isopropanol and 1.7 g of AZDN. The mixture is then heated to reflux at approximately 80°C and the following are added over 120 min, using peristaltic pumps: 200 g of acrylic acid and 80 g of ethyl acrylate. Then, reflux heating is continued for 60 min. The isopropanol is then distilled and gradually replaced by water during the distillation. The mixture is then cooled and diluted to obtain the agent R2 according to the invention, the dry matter content of which is 40% by weight, the pH is 2.2 and which comprises the polymer P2, the molecular mass Mw of which, measured by CES, is 9,500 g / mol.

[0052] Polymer P 3 and agent R3

[0053] In a 1 L reactor equipped with mechanical stirring, oil bath heating and peristaltic pumps, the following are weighed: 200 g of isopropanol and 1.9 g of AZDN. The mixture is then refluxed to approximately 80°C and the following are added over 120 min, using peristaltic pumps: 200 g of acrylic acid and 83 g of methyl methacrylate. Then, reflux heating is continued for 60 min. The isopropanol is then distilled and gradually replaced by water during the distillation. The mixture is then cooled and diluted to obtain the agent R3 according to the invention, the dry matter content of which is 40% by weight, the pH of 2.5 and which comprises the polymer P3, the molecular mass Mw of which, measured by CES, is 8,000 g / mol.

[0054] Polymer P4 and agent R4

[0055] 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 iron sulfate heptahydrate and 0.011 g of copper sulfate pentahydrate. The mixture is then heated to 95°C and the following are added over 120 min, using peristaltic pumps: 302.5 g of acrylic acid, 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. Then, reflux heating is continued for 60 min. The whole is then cooled and diluted in order to obtain the agent R4 according to the invention whose dry matter content is 40% by weight, the pH of 2.1 and which comprises the polymer P4 whose molecular mass Mw, measured by CES, is 4,400 g / mol.

[0056] Polymer P5 and agent R5

[0057] In a 1 L reactor equipped with mechanical stirring, oil bath heating and peristaltic pumps, the following are weighed: 121 g of water, 121 g of isopropanol, 0.06 g of iron sulfate heptahydrate and 11 g of hydrazine hydrate at 35% concentration in water. The whole is then heated to reflux at approximately 80°C and the following are added over 120 min, using peristaltic pumps: in a first test tube, 174 g of acrylic acid, 35 g of methyl methacrylate, 110 g of ethylene glycol phosphate and 80 g of water, in a second test tube, 20 g of hydrogen peroxide at 130V and 100 g of water.

[0058] Then, reflux heating is continued for 60 min.

[0059] The isopropanol is then distilled and gradually replaced by water during the distillation. The whole is then cooled and diluted to obtain the agent R5 according to the invention, the dry matter content of which is 40% by weight, the pH of 2.0 and which comprises the polymer P5, the molecular mass Mw of which, measured by CES, is 15,000 g / mol.

[0060] Preparation of aqueous compositions T1 to T5 for preparing a cathode primary layer according to the invention

[0061] 150 g of deionized water are weighed with 25 g of RI agent according to the invention and then mixed with stirring using a dispersion device (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 stirring for 1.25 h at 1,500 rpm to obtain a composition whose homogeneity and absence of aggregate are controlled using a North gauge.

[0062] Similarly, cathode primer layer compositions T2 to T5 are prepared by replacing agent RI with agents R2 to R5 respectively.

[0063] Preparation and characterization of cathodes according to the invention

[0064] On an aluminum foil degreased with acetone, 12 μm of cathode primer layer preparation composition Tl 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 min. The primer layer obtained using the applied and then dried composition Tl 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.

[0065] In a similar manner, cathode primer layers are prepared using compositions T2 to T5.

[0066] The adhesion of the primer layer obtained using compositions T1 to T5 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.

[0067] The compatibility of the primer layer prepared according to the invention with a secondary layer of binding agent is evaluated for a polyvinylidene fluoride binding agent (PVDF, Kynar HSV900 Arkema) applied in an N-methylpyrrolidone (NMP) solvent medium.

[0068] 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 min.

[0069] 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.

[0070] 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:

[0071] 1: aluminum foil visible on the majority of the surface of the adhesive strip,

[0072] 2: aluminum foil visible on part of the surface of the adhesive strip,

[0073] 3: non-visible aluminum foil on the surface of the adhesive tape,

[0074] 4: primary layer mostly intact,

[0075] 5: primary layer completely intact.

[0076] 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.

[0077] Table 1

[0078] The binding agents R comprising the 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 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

CLAIMS 1- Aqueous composition T for preparing a cathode primary layer comprising: • at least one binding agent R comprising at least one water-soluble polymer P, with a 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 initiator compound, of at least one compound (a) chosen 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 for which the compound (a) is chosen from acrylic acid, methacrylic acid, an acrylic acid salt, a methacrylic acid salt and their combinations, preferably the compound (a) is acrylic acid or methacrylic acid. 3- Composition T according to one of claims 1 or 2 in which the polymer P is water-soluble at a pH greater than 4 or in which the polymer P is a homopolymer of the compound (a) or the polymer P is a copolymer of compounds (a) or the polymer P is a copolymer of at least one compound (a) and at least one other compound (b), preferably a compound (b) chosen from: a compound (b1) chosen from C1-C12 esters of methacrylic acid, C1-C12 esters of acrylic acid and combinations thereof, preferably C1-C8 esters of methacrylic acid, C1-C8 esters of acrylic acid and combinations thereof, preferably methylmethacrylate, ethylmethacrylate, propylmethacrylate, butylmethacrylate, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, more preferably methylacrylate, ethylacrylate, butylacrylate;a compound (b2) chosen from acrylonitrile, acrylamide, N-methylolacrylamide, vinyl-lactam, N-vinylpyrrolidone, ureidomethacrylate and combinations thereof, preferably acrylonitrile; a compound (b3) chosen from maleic acid, maleic anhydride, itaconic acid, crotonic acid and combinations thereof; a compound (b4) chosen from hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylmethacrylate, styrene, caprolactone methacrylate, caprolactone acrylate, polycaprolactone methacrylate, polycaprolactone acrylate, lactam methacrylate, lactam acrylate, polycaprolactam methacrylate, polycaprolactam 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 hydroxyethylacrylate, phosphated hydroxyethylmethacrylate, phosphated hydroxypropylacrylate, phosphated hydroxypropylmethacrylate, phosphated hydroxybutylmethacrylate; a crosslinking compound (b6). 4- Composition T according to one of claims 1 to 3 for which the polymer P is prepared by a polymerization reaction: from 55% by weight to 100% by weight of compound (a) and from 0% by weight to 45% by weight of compound (b); or from 55% by weight to 90% by weight of compound (a) and from 10% by weight to 45% by weight of compound (b); or from 55% by weight to 80% by weight of compound (a) and from 20% by weight to 45% by weight of compound (b) or from 55% by weight to 70% by weight of compound (a) and from 30% by weight to 45% by weight of compound (b). 5- Composition T according to one of claims 1 to 4 comprising, by dry weight: from 0.5% to 70% of binding agent R, from 30% to 99.5% of material E, relative to the total quantity by dry weight of binding agent R and material E. 6- Composition T according to one of claims 1 to 5 for which the polymer P has a molecular mass Mw, measured by CES, ranging from 2,000 g / mol to 80,000 g / mol or 2,000 g / mol to 50,000 g / mol, preferably from 2,000 g / mol to 40,000 g / mol or from 2,000 g / mol to 30,000 g / mol, more preferably 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, much more preferably from 8,500 g / mol to 25,000 g / mol or from 8,500 g / mol to 20,000 g / mol or from 9,000 g / mol to 25,000 g / mol or from 9,000 g / mol to 20,000 g / mol g / mol. 7- Composition T according to one of claims 1 to 6 for which 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. 8- Composition T according to one of claims 1 to 7 for which 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 their combinations, more preferably LiOH or Zn(OH)2 or ZnO. 9- Composition T according to one of claims 1 to 8 for which 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 chosen from ethanol, isopropanol and their combinations; 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 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. 10- Composition T according to one of claims 1 to 9 in which the material E is chosen from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nano fiber, hardened carbon and their combinations. 11- Method for preparing a cathode comprising: the application of at least one aqueous composition T according to one of claims 1 to 10, on a metal substrate comprising at least one metal chosen from aluminum, nickel, preferably aluminum; drying then optionally calendering the metal substrate carrying the primary 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 then calendering the metal substrate carrying the primary layer and the electro-active coating. 12- Method according to claim 11 for which: 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 chosen from lithium, iron, nickel, manganese, cobalt and their combinations, the electroactive compound is in the form of a metallic salt, preferably a polymetallic salt, preferably the electroactive compound is chosen from LU -,:P() : (I..FP), Li(Ni,Mn,Co)O2 (NMC) and combinations thereof, the binder compound of the electroactive compound is polyvinylidene fluoride (PVDF), the organic solvent is an aprotic polar solvent, preferably selected from pyrrolidone, N-methyl-pyrrolidone (NMP), alkyl carbonates and combinations thereof the electroactive composition comprises carbon, preferably selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, carbon nanofiber, quenched carbon and combinations thereof. 13- Cathode comprising at least one metal substrate covered with at least one primary layer comprising a binding agent R and at least one material E defined according to one of claims 1 to 10, preferably obtained according to the method according to one of claims 11 or 12. 14- 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 the optional calendering, of at least one aqueous composition T for preparing a primer layer according to one of claims 1 to 10, then the application of the electroactive composition, the drying then the calendering of the metal substrate carrying the primer layer and the electroactive coating.

Images