Acrylate polymers as additives in battery electrodes

Abstract

The present invention pertains to a binder for a secondary battery positive electrode, to a method of preparation of said electrode and to its use in a secondary battery. The invention also relates to the secondary batteries manufactured by incorporating said electrode.

Description

1 SSPI 2024 / 033ACRYLATE POLYMERS AS ADDITIVES IN BATTERY ELECTRODESCross reference to previous applications

[0001] This application claims priority to European application No. 24315592.6 filed on 19 December 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical Field

[0002] The present invention pertains to a binder for a secondary battery positive electrode, to a method of preparation of said electrode and to its use in a secondary battery.

[0003] The invention also relates to the secondary batteries manufactured by incorporating said electrode.Background Art

[0004] Electrochemical devices such as secondary batteries typically comprise a positive electrode, a negative electrode and an electrolyte.

[0005] The electrodes for secondary batteries are usually produced by mixing a binder with a powdery electrode active material.

[0006] It is known in the art that polyvinylidene fluoride (PVDF) is the preferred polymer to be used as binder for forming electrodes, in particular as binder in Nickel-rich, LFP and LMFP cathodes production. Considering specific current cell production processes (eg. winding or lamination after winding) with pressures and stresses reached by the components, the use of more flexible additives becomes a need or, at least, a point of attention in materials choice.

[0007] Electrodes flexibility is indeed of primary importance for battery makers because it allows to increase electrode density and / or loading without cracking during the standard cell production process i.e. avoiding fracture of electrode (of either the coating or the collector) during winding or during lamination after winding. Moreover, flexible electrodes allow reaching higher electrode density in the standard pressing conditions or same density with milder pressing conditions.2 SSPI 2024 / 033

[0008] When electrodes cannot stand bending, there is the risk of mechanical failure, cracking of the electrodes, eventual materials detachment from current collector and / or battery failure during cycling.

[0009] EP 2953193 discloses that flexibility performances of Nickel-rich cathodes using PVDF homopolymer binders are improved when a nitrile group- containing acrylic polymer is added.

[0010] JP2005-123047 discloses a sheet-like positive electrode binder based on polyvinylidene fluoride containing acrylonitrile-butadiene rubber, which provides improved flexibility to a lithium nickel oxide cathode.

[0011] The solutions currently available in this field rely on the use of PVDF homopolymers-based binders, which however suffer from poor adhesion to current collectors.

[0012] Modified polar PVDF polymers, such as those comprising recurring units derived from hydrophilic (meth)acrylic monomers (e.g. acrylic acid), are well known in the art. Such copolymers have been developed aiming at adding to the mechanical properties and chemical inertness of PVDF suitable adhesion towards metals, e.g. aluminium or copper.

[0013] However, when modified polar PVDF polymers are used in the preparation of a slurry for forming positive electrodes with certain active materials, an important drawback is that the slurry often undergoes to a rapid viscosity increase, leading to the formation of a gel, thus preventing their use as binder for cathodes.

[0014] A time dependency in the rheological properties of the composite electrode slurries is observed also in sodium-ion secondary batteries; in fact, gelation of the slurry can be initiated by basic molecules present on the material when exposed to air, with consequent dehydrofluorination with crosslinking of PVDF. Said gelation leads to inhomogeneous coatings being produced.

[0015] The need for more performing polymers, which guarantee in particular better flexibility and higher adhesion to current collectors, is still felt both in research and from industrial perspectives.

[0016] One way is to find a blend of polymers which therefore avoids the drawbacks of modified polar PVDF polymers in contact with certain active materials such as Nickel-rich active materials, but which at the same time guarantees3 SSPI 2024 / 033 the feasibility of electrodes through wet casting and high adhesions of the final product.Summary of invention

[0017] It is thus an object of the invention a positive electrode-forming composition (C) for use in the preparation of electrodes for electrochemical devices, said composition (C) comprising: a) at least one positive electrode active material (AM); b) one binder (B), wherein binder (B) comprises: bi) at least one vinylidene fluoride (VDF) copolymer [polymer (F)] that comprises, preferably consists of:(i) recurring units derived from VDF; and(ii) recurring units derived from at least one vinyl monomer (MA) of formulawherein:- Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group, and- Rx is a C1-C20 hydrocarbon moiety comprising at least one functional group selected from the group consisting of a hydroxyl, a carboxyl, an epoxide, an ester, a phosphate and an ether group, monomer (MA) is present in an amount of from 0.05 to 10.00 % by moles of with respect to the total moles of recurring units of polymer (F); and b2) at least one block copolymer [copolymer (BC)] comprising, preferably consisting of- at least one first block [block (a)] consisting of a sequence of recurring units, said sequence consisting of recurring units derived from at least one a,|3- ethylenically unsaturated carboxylic acid monomer [monomer (AA)]; and- at least one second block [block (b)] consisting of a sequence of recurring units, said sequence consisting of:(i) recurring units derived from at least one (meth)acrylic acid ester [monomer(l)] of formula CH2=C(R)-C(=O)-O-Rh wherein R means4 SSPI 2024 / 033 hydrogen or an alkyl group with 1 to 3 carbon atoms and Rh means a linear or branched alkyl residue with 1 to 30 carbon atoms, preferably with 1 to 15 carbons, more preferably with 1 to 5 carbons; and(ii) optionally, recurring units derived from at least one nitrile group- containing monomer [monomer(ll)]; c) at least one solvent (S); and d) optionally at least one electroconductivity-imparting additive.

[0018] In a second instance, the present invention pertains to the use of the electrode-forming composition (C) of the invention in a process for the manufacture of a positive electrode for electrochemical devices [electrode (E)], said process comprising:(i) providing a metal substrate having at least one surface;(ii) providing an electrode-forming composition (C) as defined above;(iii) applying the composition (C) onto the at least one surface of the metal substrate, thereby providing an assembly comprising a metal substrate coated with said composition (C) onto the at least one surface;(iv) drying the assembly provided in step (iii).

[0019] In a third instance, the present invention pertains to the positive electrode (E) obtainable by the process of the invention.

[0020] In a fourth instance, the present invention pertains to an electrochemical device comprising a positive electrode (E) of the present invention.Description of embodiments

[0021] The terms “(meth)acrylic” or “(meth)acrylate” are intended to cover both the acrylic / acrylate and methacrylic / methacrylate forms of the indicated material, e.g., a (meth)acrylate monomer.

[0022] As used herein, the term “binder” refers to a material that is generally capable of mechanically and / or chemically bonding one or more materials together.

[0023] The electrode active material (AM) of the positive electrode is preferably a compound capable of intercalating lithium ions or sodium ions.5 SSPI 2024 / 033

[0024] The conventional active materials (AM) at the positive electrode of sodium- ion batteries are generally selected from Na-based layered transition-metal oxides, Prussian blue analogs and polyanion-type materials.

[0025] In some embodiments the active materials are Na-based layered transitionmetal oxides classified as O3-, P2-, and P3-types depending on the stacking sequence of oxygen layers. These layers are stacked on top of each other and separated by alkali metal atoms, the exact positions of the alkali metals depending on whether the overall structure of the metal oxide is octahedral (O) or it is determined by which of the prisms (P) is represented. P2-type structures generally respond to the general formula NaxMC wherein M stands for a transition metal ion such as Co, Mn and x is 2 / 3.

[0026] In some embodiments the active materials are Prussian blue analogs (PBA) of general formula AxP[R(CN)6]i-yay.mH2O with A and alkali metal ion, P a N-coordinated transition metal ion, R a C-coordinated transition metal ion, a being a [R(CN)e] vacancy, with 0 < x < 2 and 0 < y < 1 such as Nao.si Fe[Fe(CN)6]o.79ao.2i , NaFe2(CN)e, Na1.63Fei.89(CN)6, Nai.72MnFe(CN)e, Nai.76Nio.i2Mno.88[Fe(CN)6]o.98, Na2NixCoi-xFe(CN)e with 0 < x < 1 e.g. Na2CoFe(CN)e.

[0027] In some other embodiments the active materials are polyanion-type materials of general formula NaxMy(XO4)n (where X = S, P, Si, As, Mo and W and M is transition metal), which possess a series of tetrahedron anion units (XO4)n- and their derivatives (Xm03m+i)n’. Among them, phosphates NaMPCM such as NaFePCM, NaojFePCM or NaMnPCM; natrium (sodium) superionic conductor of NASICON-type structures of general formula NaxM2(XO4)3 (where 1 < x < 4 andM = V, Fe, Ni, Mn, Ti, Cr, Zr...; X = P, S, Si, Se, Mo ... ) -with single transition metal type such as Na3V2(PO4)3 (NVP), Na3Cr2(PO4)3, Na3Fe2(PO4)3; - with binary transition metal type such as Na2VTi(PO4)3, Na3FeV(PO4)3, Na4MnV(PO4)3, Na3MnZr(PO4)3, Na3MnTi(PO4)3, Na4Fe3(PO4)2(P2O7) (NFPP); pyrophosphates Na2FeP2O7, Na2MnP2O7, Na2CoP2O7, Na4- xFe2+x / 2(P2O7)2 with 2 / 3 < x < 7 / 8 e.g. Na3.i2Fe2.44(P2O7)2 or Na3.32Fe2.34(P2O7)2, Na2(VO)P2O7, Na7V3(P2O7)4; fluorophosphates NaVPO4F, Na2CoPO4F, Na2FePO4F, Na2MnPO4F, Na3(VOi-xPO4)2Fi+2x (with 0 < x < 1 ) e.g. Na3(VOPO4)2F or Na3V2(PO4)2F3 (NVPF); fluoro sulfates6 SSPI 2024 / 033 such as NaMSCUF (with M = Fe, Co, Ni); mixed phosphates / pyrophosphates of general formula Na4M3(PO4)2(P2O?) (with M representing transition metals) such as Na4Mn3(PO4)2(P2O?),Na4Co3(PO4)2(P2O7), Na4Ni3(PO4)2(P2O7), Na4Fe3(PO4)2(P2O7) (NFPP), Na7V4(P2O7)4(PO4); sulfates such as Na2Fe2(SO4)3, Na2+2xFe2-x(SO4)3, Na2+2xCo2-x(SO4)3, Na2+2xMn2-x(SO4)3 (where 0 < x < 1 ) ; silicates of general formula Na2MSiO4 (with M = Mn, Fe, Co and Ni).

[0028] In some preferred embodiments the active materials are fluorophosphates preferably selected from the list consisting of NaVPCMF, Na2CoPO4F, Na2FePO4F, Na2MnPO4F, Na3(VOi-xPO4)2Fi+2x (with 0 < x < 1 ) e.g. Na3(VOPO4)2F or Na3V2(PO4)2F3 (NVPF).

[0001] The conventional active materials (AM) at the positive electrode of lithium- ion batteries may comprise a composite metal chalcogenide of formula LiMQ2, wherein M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V and Q is a chalcogen such as O or S. Among these, it is preferred to use a lithium-based composite metal oxide of formula LiMO2, wherein M is the same as defined above. Preferred examples thereof may include LiCoC , LiNiC , LiNixCoi-xO2 (0 < x < 1 ), LiNixMnyCo7-x- yO2(NMC), LiNixCoyAIzCh with x + y + z = 1 (NCA), Ni-Mn-Co-AI (NMCA) and spinel-structured LiMn2O4.

[0029] According to another preferred embodiment, the at least one positive electrode active material (AM) is selected from lithium-containing complex metal oxides of general formula (II)LiNixM1yM2zQ2(II) wherein M1and M2are the same or different from each other and are transition metals selected from Co, Fe, Mn, Cr and V, 0.5 < x < 1 , wherein y+z = 1 -x, and Q is the same as defined above.

[0030] As an alternative, still, the electrode active material may comprise a lithiated or partially lithiated transition metal oxyanion-based electro-active material of formula MiM2(JO4)fEi-f, wherein Mi is lithium, which may be partially substituted by another alkali metal representing less than 20% of the Mi metals, M2 is a transition metal at the oxidation level of +2 selected from Fe,7 SSPI 2024 / 033Mn, Ni or mixtures thereof, which may be partially substituted by one or more additional metals at oxidation levels between +1 and +5 and representing less than 35% of the M2 metals, including 0, JO4 is any oxyanion wherein J is either P, S, V, Si, Nb, Mo or a combination thereof, E is a fluoride, hydroxide or chloride anion, f is the molar fraction of the JO4 oxyanion, generally comprised between 0.75 and 1.

[0031] The MiM2(JO4)fEi-f electro-active material as defined above is preferably phosphate-based and may have an ordered or modified olivine structure.

[0032] More preferably, the electrode active material has formula Li3-xM’yM”2- y(JO4)3 wherein 0<x<3, 0<y<2, M’ and M” are the same or different metals, at least one of which being a transition metal, JO4 is preferably PCM which may be partially substituted with another oxyanion, wherein J is either S, V, Si, Nb, Mo or a combination thereof. Still more preferably, the electrode active material (AM) is a phosphate-based electro-active material of formula LixAyDzPO4, wherein A is selected from the group consisting of Mn, Fe, Co, Ni and Cu; D is selected from the group consisting of Mg, Ca, Sr, Ba; x, y and z are numbers that satisfy the following relationships: 0 <x <2, 0 <y <1.5, 0z <1.5.

[0033] The A component is preferably Fe, Mn, and Ni, and particularly preferably Fe.

[0034] The D component is preferably Mg or Ca.

[0035] Preferred examples of the phosphate-based electro-active material of formula LixAyDzPCM, as defined above, having an olivine structure, include lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP) and lithium manganese phosphate.

[0036] Further, as the positive electrode active material (AM), it is possible to use a material whose surface is partially or wholly covered with carbon in order to supplement the conductivity.

[0037] The amount of carbon coated is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 5 parts by weight or less, based on 100 parts by weight of the positive electrode active material.8 SSPI 2024 / 033

[0038] Composition (C) of the invention further comprises a binder (B) that comprises: bi) at least one vinylidene fluoride (VDF) copolymer [polymer (F)], as above defined, and b2) at least one block copolymer [copolymer (BC)] as above defined.

[0039] The polymer (F) comprises, preferably consists of, recurring units derived from vinylidene fluoride (VDF) and recurring units derived from at least one vinyl monomer (MA) of formula (I):wherein:- R1 , R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group, and- Rx is a C1-C20 hydrocarbon moiety comprising at least one functional group selected from a hydroxyl, a carboxyl, an epoxide, an ester, a phosphate and an ether group, said monomer (MA) being present in an amount of from 0.05 to 10.00% by moles of with respect to the total moles of recurring units of polymer (F).

[0040] The term "vinyl monomer" as employed herein may comprise one or more than one vinyl monomer (MA) as above described. In the rest of the text, the expressions "vinyl monomer (MA)" is to be intended, both in the plural and the singular, that is to say that they denote both one or more than one vinyl monomer (MA).

[0041] More preferably, the vinyl monomer (MA) complies with formula (III):wherein each of Ri and R2 have the meanings as above defined, R3 is hydrogen or ROH, and ROH is a hydrogen or a C1-C5 hydrocarbon moiety comprising at least one hydroxyl group and / or at least a carboxylic group;9 SSPI 2024 / 033 more preferably, each of Ri , R2, R3 are hydrogen, while ROH has the same meaning as above detailed.

[0042] Non limitative examples of vinyl monomers (MA) are notably acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; hydroxyethylhexyl(meth)acrylates.

[0043] The monomer (MA) is more preferably selected among:- hydroxyethylacrylate (HEA) of formula:- 2-hydroxypropyl acrylate (HPA) of either of formulae:- and mixtures thereof.

[0044] Most preferably, the monomer (MA) is AA and / or HEA.

[0045] Polymer (F) may still comprise other moieties such as defects, end-groups and the like, which do not affect nor impair its physico-chemical properties.

[0046] Polymer (F) is semi-crystalline. The term semi-crystalline is intended to denote a polymer (F) which possesses a detectable melting point. It is generally understood that a semi-crystalline polymer (F) possesses a heat of fusion determined according to ASTM D 3418 of advantageously at least 0.4 J / g, preferably of at least 0.5 J / g, more preferably of at least 1 J / g.

[0047] Polymer (F) is preferably a linear copolymer, that is to say, it is composed of macromolecules made of substantially linear sequences of recurring units10 SSPI 2024 / 033 from VDF monomer and (MA) monomer; polymer (F) is thus distinguishable from grafted and / or comb-like polymers.

[0048] Polymer (F) comprises at least 0.05 % by moles, more preferably at least 0.10 % by moles, even more preferably at least 0.20 % by moles of recurring units derived from said vinyl monomer (MA).

[0049] Polymer (F) comprises preferably at most 2.00 % by moles, more preferably at most 1.80% by moles, even more preferably at most 1.50% by moles of recurring units derived from said vinyl monomer (MA).

[0050] In a preferred embodiment of the invention, in polymer (F) the recurring units derived from vinyl monomer (MA) of formula (I) are comprised in an amount of from 0.20 to 1 .00 % by moles with respect to the total moles of recurring units of polymer (F).

[0051] The polymer (F) has advantageously an intrinsic viscosity, measured in dimethylformamide at 25 °C, of above 0.15 l / g and at most 0.60 l / g, preferably in the range of 0.20 - 0.50 l / g, more preferably comprised in the range of 0.25 - 0.40 l / g.

[0052] The polymer (F) may further comprise recurring units derived from one or more fluorinated comonomers (CF) different from VDF.

[0053] By the term “fluorinated comonomer (CF)”, it is hereby intended to denote an ethylenically unsaturated comonomer comprising at least one fluorine atoms.

[0054] Non-limitative examples of suitable fluorinated comonomers (CF) include, notably, the followings:(a) C2-C8 fluoro- and / or perfluoroolefins such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), pentafluoropropylene and hexafluoroisobutylene;(b) C2-C8 hydrogenated monofluoroolefins, such as vinyl fluoride; 1 ,2- difluoroethylene and trifluoroethylene;(c) perfluoroalkylethylenes of formula CH2=CH-Rro, wherein Rro is a C1- Ce perfluoroalkyl group;(d) chloro- and / or bromo- and / or iodo-C2-Ce fluoroolefins such as chlorotrifluoroethylene (CTFE).

[0055] In one embodiment of the invention, polymer (F) comprises from 0.10 to 10.00% by moles, preferably from 0.30 to 5.00% by moles, more preferably11 SSPI 2024 / 033 from 0.50 to 3.00% by moles of recurring units derived from said fluorinated comonomer (CF).

[0056] The polymer (F) more preferably comprises, still more preferably consists of, recurring units derived from:- at least 70% by moles, preferably at least 75% by moles, more preferably at least 85% by moles of vinylidene fluoride (VDF),- from 0.20% to 1 .00% by moles, of a vinyl monomer (MA) of formula (I);- optionally from 0.50 to 3.00% by moles of recurring units derived from at least one fluorinated comonomer (CF).

[0057] The polymer (F) may be obtained by polymerization of a VDF monomer, at least one monomer (MA) and optionally at least one comonomer (CF), either in suspension in organic medium, according to the procedures described, for example, in WO 2008 / 129041 , or in aqueous emulsion, typically carried out as described in the art (see e.g. US 4,016,345, US 4,725,644 and US 6,479,591).

[0058] The procedure for preparing the polymer (F) in suspension comprises polymerizing in an aqueous medium in the presence of a radical initiator the vinylidene fluoride (VDF) monomer, monomer (MA) and optionally comonomer (CF), in a reaction vessel, said process comprising- continuously feeding an aqueous solution comprising monomer (MA); and- maintaining the pressure in said reactor vessel exceeding the critical pressure of the vinylidene fluoride.

[0059] During the whole suspension polymerization run, pressure is maintained above critical pressure of vinylidene fluoride. Generally, the pressure is maintained at a value of more than 50 bars, preferably of more than 75 bars, even more preferably of more than 100 bars.

[0060] The expressions "continuous feeding", “adding continuously” or "continuously feeding" means that slow, small, incremental additions the aqueous solution of vinyl monomer (MA) take place until polymerization has concluded.

[0061] The polymer (F) thus obtained has a high uniformity of monomer (MA) distribution in the polymer backbone, which advantageously maximizes the effects of the modifying monomer (MA) on both adhesiveness and / or hydrophilic behaviour of the resulting copolymer.12 SSPI 2024 / 033

[0062] In addition, the Applicant has surprisingly found that the presence of the monomer (MA) uniformly distributed in the polymer (F) has the effect of improving the thermal stability of VDF copolymers, which otherwise is unsatisfactorily low, in particular lower than that of VDF homopolymers.

[0063] The amount of polymer (F) in composition (C) is suitably in the range of from 0.50 to 5.00 % by weight.

[0064] The term “block copolymer” refers to a polymer comprising two or more chemically distinct regions or segments (referred to as “blocks”) joined in a linear manner, that is, a polymer comprising chemically differentiated units that are joined (covalently bonded) end-to-end with respect to polymerized functionality, rather than in pendent or grafted fashion. Block copolymers comprise sequences (“blocks”) of the same sequence, covalently bound to sequences of unlike type. The blocks can be connected in a variety of ways, such as a-b in diblock and a-b-a or b-a-b triblock structures, where a represents one block and b represents a different block. In a multiblock copolymer, a and b can be connected in a number of different ways and be repeated multiply.

[0065] The at least one a,|3-ethylenically unsaturated carboxylic acid monomer (AA) is preferably a compound of formula (IV):wherein Ra, Rband Rc, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group.

[0066] More preferably, the at least one monomer (AA) is a compound of formula (IV) as above defined, that is selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, crotonic, methyl (meth)acrylic acid, ethyl (meth)acrylic acid, propyl (meth)acrylic acid, isopropyl (meth)acrylic acid, n-butyl (meth)acrylic acid, 2-ethylhexyl (meth)acrylic acid, n-hexyl (meth)acrylic acid and n-octyl (meth)acrylic acid.13 SSPI 2024 / 033

[0067] The at least one first block [block (a)] may further include, besides the at least one monomer (AA), at least an additional comonomer. The additional comonomer can be for example selected from monomers (I) as below defined.

[0068] Preferably, said block (a) consists of a sequence of recurring units derived from acrylic acid (AA).

[0069] According to a preferred embodiment of the invention, the monomer (I) is selected from the group consisting of: esters or anhydrides of acrylic, methacrylic, citraconic, maleic, fumaric, itaconic or crotonic, ethacrylic, methyl (meth)acrylic, ethyl (meth)acrylic, propyl (meth)acrylic, isopropyl (meth)acrylic, n-butyl (meth)acrylic, 2-ethylhexyl (meth)acrylic, n-hexyl (meth)acrylic, n-octyl (meth)acrylic groups; hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate; Sipomer® I3.CEA (sold by Syensqo), Sipomer® WAM (sold by Syensqo), Sipomer® WAM II (sold by Syensqo) and other urido-containing monomers; - allyl glycidyl ether (AGE), ethylene glycol alkyl ether acrylates such as di(ethylene glycol) ethyl ether acrylate (DEGEEA); glycidyl methacrylate; glycerol methacrylate; (meth) acryloyloxyalkyl succinic acid, such as (meth) acryloyloxyethyl succinic acid and (meth) acryloyloxypropyl succinic acid.

[0070] More preferably, monomer (I) is selected from methyl methacrylic acid ester (MMA) and n-butyl acrylic acid ester (BA).

[0071] The nitrile group-containing monomer (II) is preferably selected from acrylonitrile (AN) and methacrylonitrile.

[0072] The content of nitrile group-containing monomer (II) units in block (b) is preferably lower than 15.00 % by moles.

[0073] Preferably, the weight ratio between said block(s) (a) and said block(s) (b) in said copolymer (BC) is comprised between 1 :1 and 1 :5.

[0074] Advantageously, said copolymer (BC) comprises alternately arranged blocks (a) and block(s) (b). In other words, copolymer (BC) according to the present invention does not comprise randomly distributed blocks (a) and / or (b).

[0075] According to an embodiment, one block (a) is interposed between two blocks (b), i.e. co-polymer (BC) complies with the following formula: b-a-b.14 SSPI 2024 / 033

[0076] According to another embodiment, one block (b) is interposed between two blocks (a), i.e. co-polymer (BC) complies with the following formula: a-b-a.

[0077] The amount of monomer (I) in block (b) of copolymer (BC) is preferably comprised between 80 to 90% by moles.

[0078] The amount of monomer (II) in block (b) of copolymer (BC) is preferably comprised between 10 to 20% by moles.

[0079] Preferably, said block (b) consists of a sequence of recurring units derived from n-butyl methacrylic acid ester (MBA) or n-butyl acrylic acid ester (BA) and recurring units derived from methyl methacrylic acid ester (MMA).

[0080] In one preferred embodiment of the present invention, block copolymer (BC) is a copolymer comprising a block (a) consisting of a sequence of recurring units derived from acrylic acid (AA) and a block (b) consisting of a sequence of recurring units derived from n-butyl (meth)acrylic acid ester (BA) and recurring units derived from acrylonitrile (AN).

[0081] In another preferred embodiment of the present invention, block copolymer (BC) is a copolymer comprising a block (a) consisting of a sequence of recurring units derived from acrylic acid (AA) and a block (b) consisting of a sequence of recurring units derived from methyl methacrylic acid ester (MMA) and recurring units derived from acrylonitrile (AN).

[0082] In a further preferred embodiment of the present invention, block copolymer (BC) is a copolymer comprising a block (a) consisting of a sequence of recurring units derived from acrylic acid (AA) and a block (b) consisting of a sequence of recurring units derived from n-butyl (meth)acrylic acid ester (BA), recurring units derived from methyl methacrylic acid ester (MMA) and recurring units derived from acrylonitrile (AN).

[0083] When monomer (I) in block (b) of copolymer (BC) is n-butyl acrylic acid ester (BA), it is preferably present in an amount comprised between 60.00 to 90.00% by moles.

[0084] When monomer (I) in block (b) of copolymer (BC) is methyl methacrylic acid ester (MMA), it is preferably present in an amount comprised between 10.00 to 20.00% by moles.

[0085] When monomer (II) in block (b) of copolymer (BC) is acrylonitrile (AN), it is preferably present in an amount comprised between 10.00 to 20.00% by moles.15 SSPI 2024 / 033

[0086] In a particularly preferred embodiment, block (b) of copolymer (BC) comprises recurring units derived from methyl methacrylic acid ester (MMA) in an amount of from 10.00 to 20.00 % by moles, n-butyl acrylic acid ester (BA) in an amount of from 60.00 to 90.00 % by moles and acrylonitrile (AN) in an amount of from 10.00 to 20.00 % by moles.

[0087] In a more preferred embodiment, block (b) of copolymer (BC) comprises recurring units derived from methyl methacrylic acid ester (MMA) in an amount of 10.00 % by moles, n-butyl acrylic acid ester (BA) in an amount of 80.00 % by moles and acrylonitrile (AN) in an amount of 10.00 % by moles.

[0088] The weight average molecular weight MW of the polymer (CB) is generally between 3 000 and 300 000, preferably between 3 500 and 16 000.

[0089] Copolymers (BC) according to the present invention comprising said block (a) and said block (b) can be advantageously synthetized in an emulsion polymerization process or in a solution polymerization process.

[0090] The amount of copolymer (BC) in composition (C) is suitably in the range of from 2 to 40% by weight, preferably from 15 to 30 % by weight, more preferably in an amount of 20 % by weight.

[0091] The choice of the solvent (S) is not particularly limited, provided that it is suitable for dissolving polymer (F) and dispersing / dissolving polymer (BC).

[0092] Solvent (S) is typically selected from the group consisting of:- alcohols such as methyl alcohol, ethyl alcohol and diacetone alcohol,- ketones such as acetone, methylethylketone, methylisobutyl ketone, diisobutylketone, cyclohexanone and isophorone,- linear or cyclic esters such as isopropyl acetate, n-butyl acetate, methyl acetoacetate, dimethyl phthalate and y-butyrolactone,- linear or cyclic amides such as N,N-diethylacetamide, N,N- dimethylacetamide, dimethylformamide and N-methyl-2-pyrrolidone, and- dimethyl sulfoxide.

[0093] The electrode-forming compositions of the present invention may further include one or more optional electroconductivity-imparting additives in order to improve the conductivity of an electrode made from the composition of the present invention. Electroconductivity-imparting additives for batteries are known in the art.16 SSPI 2024 / 033

[0094] Examples thereof may include: carbonaceous materials, such as carbon black, graphite fine powder carbon nanotubes, graphene, or fiber, or fine powder or fibers of metals such as nickel or aluminum. The optional conductive agents are preferably carbon black or carbon nanotubes.

[0095] The amount of optional conductive agent is preferably from 0 to 30 % by weight with respect to the total solids in the electrode forming composition. In particular, for positive electrode forming compositions the optional conductive agent is typically from 0 % by weight to 10 % by weight, more preferably from 0 % by weight to 5 % by weight of the total amount of the solids within the composition (C).

[0096] Composition (C) may further comprise at least one wetting agent and / or at least one surfactant and one or more than one additional additives.

[0097] Composition (C) may further comprise at least one non-electroactive inorganic filler material.

[0098] By the term "non-electroactive inorganic filler material", it is hereby intended to denote an electrically non-conducting inorganic filler material, which is suitable for the manufacture of an electrically insulating separator for electrochemical cells.

[0099] The non-electroactive inorganic filler material in the electrode forming compositions according to the invention typically has an electrical resistivity (p) of at least 0.1 x 1010 ohm cm, preferably of at least 0.1 x 1012 ohm cm, as measured at 20°C according to ASTM D 257.

[0100] Non-limitative examples of suitable non-electroactive inorganic filler materials include, notably, natural and synthetic silicas, zeolites, aluminas, titanias, metal carbonates, zirconias, silicon phosphates and silicates and the like.

[0101] Binder (B) for use in the composition (C) according to the present invention can be prepared by any known method in the art.

[0102] A suitable method comprises:- dissolving polymer (F) with a solvent (S),- dissolving or dispersing polymer (BC) with a solvent (S),- mixing the solution of polymer (F) in solvent (S) with the solution or dispersion of polymer (BC) in solvent (S) to provide a binder mixture (B).

[0103] Alternatively, the method can comprise:17 SSPI 2024 / 033- dissolving or dispersing both polymer (F) and polymer (BC) together with a solvent (S), and- mixing to provide a binder mixture (B).

[0104] The weight ratio of polymer (F) to polymer (BC) in binder (B) is conveniently in the range of from 95:5 to 70:30. In a preferred embodiment of the invention, the weight ratio of polymer (F) to polymer (BC) in binder (B) is 80:20.

[0105] The electrode-forming composition (C) may be obtained by adding and dispersing a powdery electrode active material, and optional additives, such as an electroconductivity-imparting additive and / or a viscosity modifying agent, into the thus-obtained binder mixture (B), to obtain a homogeneous slurry.

[0106] The solution of polymer (F) in solvent (S) is notably comprising the polymer (F) in an amount of from 5 to 20 % by weight, preferably about 7 to 10 % by weight.

[0107] The solution or dispersion of polymer (BC) in solvent (S) is notably comprising the polymer (BC) in an amount of from 0.1 to 15% by weight in 100 parts by weight of such a solvent.

[0108] The total solid content (TSC) of the composition (C) of the present invention is typically comprised between 50 and 85 % by weight, preferably from 60 and 80 % by weight, over the total weight of the composition (C). The total solid content of the composition (C) is understood to be cumulative of all non-volatile ingredients thereof, notably including polymer (F), polymer (BC), the electrode active material and any solid, non-volatile additional additive.

[0109] When the solution of polymer (F) is combined with polymer (BC), with an electrode active material and with the optional conductive material and other additives to prepare composition (C), an amount of solvent sufficient to create a stable solution of polymer (F) is employed. The amount of solvent used may range from the minimum amount needed to create a stable solution of polymer (F) to an amount needed to achieve a desired total solid content in an electrode mixture after the polymer (BC), the active electrode material, the optional conductive material, and the other solid additives have been added.18 SSPI 2024 / 033

[0110] The presence of polymer (BC) in the composition (C) makes it possible to obtain high quality homogenous slurry compositions with neither gelation evidence nor inhomogeneity in all the preparation steps. Said composition is suitable for use in the preparation of electrodes.

[0111] The most relevant aspect detected with the addition of polymer (BC) to the composition (C) is a huge flexibility enhancement of the electrodes obtained therefrom, wherein flexibility is evaluated as cracking diameter of the electrodes, as detailed in the experimental part.

[0112] The lower the cracking diameter, the more flexible is the electrode: it is strictly dependent on binder / additive type.

[0113] Applicative flexibility performances are therefore enhanced by the use of the polymer (BC) as additive to the VDF polymer (F), not affecting or even improving other parameters such as adhesion to current collector.

[0114] This effect of flexibility improvement is particularly evident when polymer (BC) is a copolymer derived from the polymerization of methyl methacrylic acid ester (MMA), n-butyl acrylic acid ester (BA) and acrylonitrile (AN), with an AN content lower than 20 % by moles in copolymer (BC).

[0115] Another advantage of the composition (C) of the present invention is that it is possible to provide an electrode which comprises a relatively low content by weight of binder and to make it possible to increase the content of active material in the positive electrode, in order to maximise the capacity of the battery.

[0116] The electrode-forming composition (C) of the invention can be used in a process for the manufacture of a positive electrode [electrode (E)], said process comprising:(i) providing a metal substrate having at least one surface;(ii) providing an electrode-forming composition [composition (C)] as above defined;(iii) applying the composition (C) onto the at least one surface of the metal substrate, thereby providing an assembly comprising a metal substrate coated with said composition (C) onto the at least one surface;(iv) drying the assembly provided in step (iii).

[0117] The metal substrate is generally a foil, mesh or net made from a metal, such as from aluminium, nickel, titanium, and alloys thereof.19 SSPI 2024 / 033

[0118] In step (iii) of the process of the invention, the electrode forming composition (C) is applied onto at least one surface of the metal substrate typically by any suitable procedures such as casting, printing and roll coating.

[0119] Optionally, step (iii) may be repeated, typically one or more times, by applying the electrode forming composition (C) provided in step (ii) onto the assembly provided in step (iv).

[0120] In step (iv) of the process of the invention, drying may be performed either under atmospheric pressure or under vacuum. Alternatively, drying may be performed under modified atmosphere, e.g. under an inert gas, typically exempt notably from moisture (water vapour content of less than 0.001 % v / v).

[0121] The drying temperature will be selected so as to effect removal by evaporation of the aqueous medium from the electrode (E) of the invention.

[0122] The dried assembly obtained in step (iv) may further be submitted to a compression step such as a calendaring process, to achieve the target porosity and density of the electrode (E) of the invention.

[0123] Preferably, the dried assembly obtained at step (iv) is submitted to a calendaring process.

[0124] When the at least one positive electrode active material (AM) in composition (C) is a composite metal chalcogenide such as NMC, the preferred target density for electrode (E) is comprised between 3 and 4 g / cc, more preferably is comprised between 3.4 and 3.5 g / cc.

[0125] When least one positive electrode active material (AM) in composition (C) is a phosphate-based electro-active material having an olivine structure, the preferred target density for electrode (E) is comprised between 2 and 3 g / cc, more preferably at least 2.1 g / cc.

[0126] The density of electrode (E) is calculated as the sum of the product of the densities of the components of the electrode multiplied by their mass ratio in the electrode formulation.

[0127] In a further aspect, the present invention pertains to the positive electrode [electrode (E)] obtainable by the process of the invention.

[0128] Therefore the present invention relates to a positive electrode (E) comprising:- a metal substrate having at least one surface, and20 SSPI 2024 / 033- directly adhered onto at least one surface of said metal substrate, at least one layer consisting of a composition [composition (C’)] comprising: a) at least one positive electrode active material (AM); b) a binder composition [binder (B’)] comprising: b’) at least one polymer (F) as above defined, b”) at least one copolymer (BC) as above defined; c) optionally, at least one electroconductivity-imparting additive.

[0129] The composition (C’) directly adhered onto at least one surface of said metal substrate corresponds to the electrode forming composition (C) of the invention wherein the solvent has been at least partially removed during the manufacturing process of the electrode, for example in step (iv) (drying) and / or in the further compression step.

[0130] Therefore all the preferred embodiments described in relation to the electrode forming compositions (C) of the invention are also applicable to the composition (C’) directly adhered onto at least one surface of said metal substrate, in electrodes of the invention, except for the aqueous medium removed during the manufacturing process.

[0131] The preferred positive electrode (E) comprises:- a metal substrate having at least one surface, and- directly adhered onto at least one surface of said metal substrate, at least one layer consisting of: j) at least one positive electrode active material (AM) in an amount from 90.0 to 99.0 % by weight; jj) the binder (B’) in an amount from 0.5 to 10.0 % by weight, preferably from 1 .0 to 5.0 % by weight; and jjj) an electroconductivity-imparting additive in an amount from 0.5 to 5.0 % by weight, wherein the above mentioned % by weight are in respect to the total weight of j)+jj)+jjj).

[0132] Preferably, the positive electrode (E) comprises of at least 95.0% by weight of active material (AM).

[0133] When the at least one positive electrode active material (AM) in composition (C) is a composite metal chalcogenide such as NMC, the preferred21 SSPI 2024 / 033 electrode loading is comprised between 9 and 60 mg / cm2, more preferably is comprised between 25 and 35 mg / cm2.

[0134] When least one positive electrode active material (AM) in composition (C) is a phosphate-based electro-active material having an olivine structure, the preferred electrode loading is comprised between 10 and 30 mg / cm2.

[0135] The term “electrode loading,” or “loading,” as used herein, generally refers to the amount of electrode active material placed into an electrochemical cell at assembly.

[0136] The positive electrode (E) of the invention is particularly suitable for use in electrochemical devices.

[0137] Non-limitative examples of suitable electrochemical devices include, notably, secondary batteries, especially, alkaline or an alkaline- earth secondary batteries such as lithium-ion batteries, solid state batteries, lithium-metal batteries, lead-acid batteries, and capacitors, especially lithium ion-based capacitors and electric double layer capacitors (supercapacitors).

[0138] The secondary battery of the invention is more preferably a sodium-ion or a lithium-ion secondary battery.

[0139] An electrochemical device according to the present invention can be prepared by standard methods known to a person skilled in the art.

[0140] The invention will be now described with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.Experimental section

[0141] Raw materials

[0142] CNT: Carbon nanotubes, commercially available from Advanced Nano Products.

[0143] AM: NMC 811 active material commercially available from Cosmo.

[0144] Polymer (F-1 ): VDF-AA (0.8% by moles) polymer having an intrinsic viscosity of 0.36 l / g in DMF at 25°C.

[0145] Preparation of Polymer (A-1)

[0146] The synthesis of Polymer A-1 is done in two steps: First Step - Synthesis of Poly Acrylic acid block PAA.22 SSPI 2024 / 033In a 2L double-jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and nitrogen inlet, 4.26 g of Rhodixan A1 , 6.13 g of acrylic acid and 720 g of NMP were introduced. The mixture was deoxygenated with nitrogen for 30 minutes and then heated to 70 °C. When the temperature in the reactor reached 70 °C, a solution of AMBN (0.04 g of AMBN in 8.21 g in NMP) was added shot wise. This moment is considered as to. At t = to + 5 minutes, 185,19 g of acrylic acid were introduced into the reactor for 240 minutes and 76.4 g of AMBN at 0.5 wt% in NMP were introduced for 300 minutes. The reacting mixture was kept at 70 °C for 90 minutes after the end of the introduction of AMBN solution. The solution was then cooled down to room temperature in 60 minutes. The final product was a yellowish solution (Solid content = 19.5 %, Mn = 6000 g / mol, B = 1.7)Second Step - Synthesis of Poly Acrylic acid-b-Poly(Butyl Acrylate-co- Methyl Methacrylate-co-Acrylonitrile) PAA-b-P(BA-co-MMA-co-ACN).In a 2L double-jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and nitrogen inlet, 224 g of the PAA solution prepared in the first step, and 94 g of NMP were introduced. The mixture was deoxygenated with nitrogen for 30 minutes. Then 22.22 g of a mixture containing 86.92 wt% of butyl acrylate, 8.57 wt% of methyl methacrylate and 4.51 wt% of acrylonitrile was introduced in the reactor. The mixture was then heated to 70 °C in one hour. When the temperature in the reactor reached 70 °C, a solution of AMBN (1 .21 g of AMBN in 1 .91 g in NMP) was added shot wise. This moment is considered as to. At t = to, 154.23 g of the same mixture based on BA, MMA and ACN were introduced in 6 hours. At to + 6 hours, the reacting mixture was kept at 70 °C for 4 hours and then cooled down at room temperature in hour. The final product was a yellowish solution (Solid content = 45.05 %, Mn = 12000 g / mol, D =2.1 ).

[0147] Slurry and Electrode Preparation

[0148] A binder comprising 80% by weight of polymer (F-1 ) and 20% by weight of polymer (A-1 ) was prepared in NMP.23 SSPI 2024 / 033

[0149] Once a homogeneous solution was obtained, carbonaceous material (CNT in this specific example) and active materials were added and homogeneously dispersed. The mixing phase follows.

[0150] Slurry composition (C-1 ) comprising 1.1 / 0.9 / 98 (binder / CNT / AM) of the above described binders and active material was prepared. TSC=72%.

[0151] Afterwards, the homogenized slurry was casted an inert support and dried in two steps (overall 50’, with a first step “dynamic vacuum” and the last one in “static vacuum”) at 90°C.

[0152] Positive Electrodes Flexibility Evaluation

[0153] Flexibility of the electrodes obtained as above detailed was measured by a U-bending test, using the coating cracking diameter as parameter to assess and determine flexibility. Double-sided electrodes are cut in stripes (2x10 cm) and fixed at the two ends between two horizontal parallel plates of a dynamometer, placed at a distance of 20 mm, having a bended shape. During the test, the plates are approached one to the other with the automated crossbeam movement with a speed of 10 mm / min. The diameter of the bended electrode is progressively reduced, till a cracking in the electrode coating is observed.

[0154] Lower the cracking diameter, more flexible are the electrodes and therefore more prone to bare the stresses during winding or lamination after winding. Higher flexibility implies also the possibility to reach higher electrode density in the standard pressing conditions or same density with milder pressing conditions.

[0155] The results are reported in Table 1.

[0156] Positive Electrode Adhesion Evaluation

[0157] A positive electrode prepared as above detailed was cut in stripes (10 cm long and 2.5 cm wide) and applied onto rigid aluminium foils having thickness of 2 mm, using a biadhesive tape of dimensions 2.5 x 8 cm, with the coated side of the electrode facing the aluminium plate. A portion of the electrode was kept from adhering to the tape, thus leaving one end of each stripe not in contact with the biadhesive tape, allowing for its pulling from the foil.

[0158] Each specimen was pulled from the foil at an angle of 180° by a dynamometer that allowed the measurement of the force needed to peel off24 SSPI 2024 / 033 the sample from the biadhesive tape. Peeling speed is 300 mm / min, with T=25°C. The results are summarized in Table 1.Table 1‘Normalized vs polymer (F-1 ) alone

[0159] It has been demonstrated that the electrodes of the invention have an improved flexibility in comparison with standard electrodes of the prior art comprising polymer (F) only, while keeping at the same time the same good adhesion to metal foil.

Claims

25 SSPI 2024 / 033Claims1. A positive electrode-forming composition (C) for use in the preparation of electrodes for electrochemical devices, said composition (C) comprising: a) at least one positive electrode active material (AM); b) one binder (B), wherein binder (B) comprises: bi) at least one vinylidene fluoride (VDF) copolymer [polymer (F)] that comprises:(i) recurring units derived from VDF; and(ii) recurring units derived from at least one vinyl monomer (MA) of formula (I):wherein:- Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group, and- Rx is a C1-C20 hydrocarbon moiety comprising at least one functional group selected from a hydroxyl, a carboxyl, an epoxide, an ester, a phosphate and an ether group, wherein monomer (MA) is present in in an amount of from 0.05 to 10 % by moles of with respect to the total moles of recurring units of polymer (F); and b2) at least one block copolymer [copolymer (BC)] comprising:- at least one first block [block (a)] consisting of a sequence of recurring units, said sequence consisting of recurring units derived from at least one a,|3- ethylenically unsaturated carboxylic acid monomer [monomer (AA)]; and- at least one second block [block (b)] consisting of a sequence of recurring units, said sequence consisting of:(i) recurring units derived from at least one (meth)acrylic acid ester [monomer (I)] of formula CH2=C(R)-C(=O)-O-Rh wherein R means hydrogen or an alkyl group with 1 to 3 carbon atoms and Rh means a linear or branched alkyl residue with 1 to 30 carbon atoms,26 SSPI 2024 / 033 preferably with 1 to 15 carbons, more preferably with 1 to 5 carbons; and(ii) optionally, recurring units derived from at least one nitrile group- containing monomer [monomer (II)]; c) at least one solvent (S); and d) optionally at least one electroconductivity-imparting additive.

2. The composition (C) according to claim 1 , wherein the vinyl monomer (MA) is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; hydroxyethylhexyl(meth)acrylates.

3. The composition (C) according to any one of claim 1 or claim 2, wherein polymer (F) further comprises recurring units derived from one or more fluorinated comonomers (CF) different from VDF.

4. The composition (C) according to any one of the preceding claims, wherein least one a,|3-ethylenically unsaturated carboxylic acid monomer (AA) in block (a) of copolymer (BC) is a compound of formula (IV):wherein Ra, Rband Rc, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group.

5. The composition (C) according to claim 4, wherein monomer (AA) is selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, crotonic, methyl (meth)acrylic acid, ethyl (meth)acrylic acid, propyl (meth)acrylic acid, isopropyl (meth)acrylic acid, n-butyl (meth)acrylic acid, 2-ethylhexyl (meth)acrylic acid, n-hexyl (meth)acrylic acid and n-octyl (meth)acrylic acid.

6. The composition (C) according to any one of the preceding claims, wherein monomer (I) is selected from the group consisting of: esters or anhydrides of acrylic, methacrylic, citraconic, maleic, fumaric, itaconic or crotonic,27 SSPI 2024 / 033 ethacrylic, methyl (meth)acrylic, ethyl (meth)acrylic, propyl (meth)acrylic, isopropyl (meth)acrylic, n-butyl (meth)acrylic, 2-ethylhexyl (meth)acrylic, n- hexyl (meth)acrylic, n-octyl (meth)acrylic groups; hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate; Sipomer® I3.CEA (sold by Syensqo), Sipomer® WAM (sold by Syensqo), Sipomer® WAM II (sold by Syensqo) and other urido-containing monomers; - allyl glycidyl ether (AGE), ethylene glycol alkyl ether acrylates such as di(ethylene glycol) ethyl ether acrylate (DEGEEA); glycidyl methacrylate; glycerol methacrylate; (meth) acryloyloxyalkyl succinic acid, such as (meth) acryloyloxyethyl succinic acid and (meth) acryloyloxypropyl succinic acid; preferably, monomer (I) is selected from methyl methacrylic acid ester (MMA) and n-butyl (meth)acrylic acid ester (BA).

7. The composition (C) according to any one of the preceding claims, wherein monomer (II) is selected from acrylonitrile (AN) and methacrylonitrile.

8. The composition according to any one the preceding claims, wherein the active material (AM) is a compound capable of intercalating lithium ions or sodium ions.

9. The composition (C) according to any one of the preceding claims, wherein polymer (BC) is a copolymer comprising a block (a) consisting of a sequence of recurring units derived from acrylic acid (AA) and a block (b) consisting of a sequence of recurring units derived from n-butyl acrylic acid ester (BA) and recurring units derived from acrylonitrile (AN).

10. The composition (C) according to any one of the preceding claims, wherein polymer (BC) is a copolymer comprising a block (a) consisting of a sequence of recurring units derived from acrylic acid (AA) and a block (b) consisting of a sequence of recurring units derived from methyl methacrylic acid ester (MMA) and recurring units derived from acrylonitrile (AN).11 . The composition (C) according to any one of the preceding claims, wherein polymer (BC) is a copolymer comprising a block (a) consisting of a sequence of recurring units derived from acrylic acid (AA) and a block (b) consisting of a sequence of recurring units derived from n-butyl acrylic acid ester (BA), recurring units derived from methyl methacrylic acid ester (MMA) and recurring units derived from acrylonitrile (AN).28 SSPI 2024 / 03312. The composition (C) according to any one of the preceding claims, wherein block (b) of copolymer (BC) comprises recurring units derived from methyl methacrylic acid ester (MMA) in an amount of 10.0 % by moles, n-butyl acrylic acid ester (BA) in an amount of 80.0 % by moles and acrylonitrile (AN) in an amount of 10 % by moles.

13. The composition (C) according to any one of the preceding claims, wherein the weight ratio between said block (a) and said block (b) in said copolymer (BC) is comprised between 1 :1 and 1 :5.

14. A process for the manufacture of a positive electrode [electrode (E)], said process comprising:(i) providing a metal substrate having at least one surface;(ii) providing an electrode-forming composition [composition (C)] according to any one of claims 1 to 13;(iii) applying the composition (C) provided in step (ii) onto the at least one surface of the metal substrate provided in step (i), thereby providing an assembly comprising a metal substrate coated with said composition (C) onto the at least one surface;(iv) drying the assembly provided in step (iii).

15. A positive electrode (E) obtainable by the process according to claim 14.

16. An electrochemical device comprising the positive electrode (E) according to claim 15.

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