Lithium battery electrode binders

Abstract

The present invention pertains to vinylidene fluoride polymers use as binder for electrodes in Li-ion batteries.

Description

Lithium battery electrode bindersCross reference to previous applications

[0001] This application claims priority to European application No. 23188496.6filed on 28 July 2023, 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 lithium batteries are usually produced by mixing a binder with an electronic conductive agent and an electrochemically active powdery material.

[0006] Fluororesins such as vinylidene fluoride-based polymers have been used as binders for forming positive electrodes. In particular, polyvinylidene fluoride (PVDF) provides a good electrochemical stability and high adhesion to the electrode materials. PVDF is therefore a preferred binder material for electrode slurries.

[0007] 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.

[0008] CN110183562 discloses the preparation of a high molecular weight PVDF by using di-isopropyl peroxydicarbonate as initiator. The resulting PVDF is characterized by a high crystallinity, which makes the electrode slurry compositions comprising the same useless for preparing electrodes. The high crystallinity PVDF is thus blended with certain VDF-based copolymers to obtain a polymer mixture suitable for use as electrode binder.

[0009] 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 mechanicalproperties and chemical inertness of PVDF suitable adhesion towards metals, e.g. aluminum or copper.

[0010] However, modified polar PVDF polymers when used in the preparation of a slurry for forming positive electrodes with certain active materials can lead to processability issues. In particular, when olivine type active materials as LiFePO4 (LFP) and LiMnFePO4 (LMFP) are used, 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 LFP and / or LMFP cathodes.

[0011] The need for more performing polymers, which guarantee in particular better mechanical performance and higher adhesion to current collectors, is still felt both in research and from industrial perspectives.

[0012] One way is to find a blend of polymers which therefore avoids the drawbacks of PVDF homopolymer and of modified polar PVDF polymers in contact with certain active materials such as LFP and / or LMFP, but which at the same time guarantees the feasibility of electrodes through wet casting and high adhesions of the final product.

[0013] In the technical field of batteries, notably of lithium batteries, the problem of providing electrode binders characterized by very good adhesion that at the same time do not impact negatively on the fabrication process of the electrodes, such as by an increase of the slurry viscosity to produce the same, is felt.Summary of invention

[0014] It has been found that certain blends of vinylidene fluoride polymers are endowed with very good adhesion to metal substrates and can be used in the preparation of electrode-forming compositions having improved slurry viscosity at low shear rates.

[0015] It is thus an object of the invention a polymer composition (P) comprising: a) at least one VDF-based polymer [polymer (F)] having intrinsic viscosity, measured in dimethylformamide at 25 °C, in the range of from 0.25 l / g to 0.60 l / g, more preferably from 0.27 l / g to 0.50 l / g where the polymer (F) is characterized by containing end groups of formula (I): -(Ra)x-O-CO-O-CH2-CH3(I) wherein Rais a C1-C5 linear or branched hydrocarbon group and x is an integer selected from 1 and zero and the end-groups of formula (I) are present in an amount of at least 0.2 / 10000 VDF units, preferably at least 1.0 / 10000 VDF units, and of at most 10 / 10000 VDF units;b) at least one VDF-based polymer [polymer (A)], different from polymer (F), said polymer (A) having intrinsic viscosity, measured in dimethylformamide at 25 °C, lower than 0.25 l / g, said polymer (A) characterized by consisting of:(i) recurring units derived from vinylidene fluoride (VDF) monomer; and(ii) recurring units derived from at least one hydrophilic 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 and an ether group, wherein the at least one monomer (MA) is present in an amount of from 0.05 to 10 % by moles of with respect to the total moles of recurring units of polymer (A).

[0016] A second object of the present invention pertains to an electrode-forming composition (C) comprising: a) at least one electrode active material (AM); b) at least one polymer composition (P) as above defined; c) at least one solvent (S), and d) optionally, at least one conductive agent.

[0017] In another object, the present invention pertains to the use of the electrode-forming composition (C) in a process for the manufacture of an electrode [electrode (E)], said process comprising:(I) providing a metal substrate having at least one surface;(II) providing an electrode-forming composition (C) as above defined;(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);(V) submitting the dried assembly obtained in step (IV) to a compression step to obtain the electrode (E) of the invention.

[0018] In a further object, the present invention pertains to the electrode (E) obtainable by the process of the invention.

[0019] In still a further object, the present invention pertains to an electrochemical device comprising at least one electrode (E) of the present invention.Detailed description

[0020] By the term “VDF-based polymer” it is intended to denote a VDF homopolymer (PVDF) and VDF-based copolymers including recurring units derived from VDF and recurring units derived from at least one fluorinated comonomer (CF), different from VDF.

[0021] The VDF-based polymer (F) of the present invention does not include any hydrogenated monomer bearing polar groups.

[0022] By the term “recurring unit derived from vinylidene fluoride” (also generally indicated as vinylidene difluoride 1 ,1 -difluoroethylene, VDF), it is intended to denote a recurring unit of formula CF2=CH2.

[0023] 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-Rfo, wherein Rm is a Ci-Ce perfluoroalkyl group;(d) chloro- and / or bromo- and / or iodo-C2-Ce fluoroolefins such as chlorotrifluoroethylene (CTFE).(e) perfluoro(alkyl)vinyl ethers, such as perfluoro(methyl)vinyl ether (PMVE), perfluoro(ethyl) vinyl ether (PEVE) and perfluoro(propyl)vinyl ether (PPVE);(f) perfluoro(1 ,3-dioxole); perfluoro(2,2-dimethyl-1 ,3-dioxole) (PDD).

[0024] In one preferred embodiment, polymer (F) is semi-crystalline and comprises from 0.1 to 20.0% by moles, preferably from 0.3 to 10.0% by moles, more preferably from 0.5 to 5.0% by moles of recurring units derived from said at least one fluorinated comonomer (CF).

[0025] The polymer (F) can be an elastomer or a semi-crystalline polymer, preferably being a semi-crystalline polymer.

[0026] As used herein, the term “semi-crystalline” means a fluoropolymer that has, besides the glass transition temperature Tg, at least one crystalline melting point on DSC analysis. For the purposes of the present invention a semi-crystallinefluoropolymer is hereby intended to denote a fluoropolymer having a heat of fusion of from 10 to 90 J / g, preferably of from 30 to 80 J / g, more preferably of from 35 to 75 J / g, as measured according to ASTM D3418-08.

[0027] To the purpose of the invention, the term "elastomer" is intended to designate a true elastomer or a polymer resin serving as a base constituent for obtaining a true elastomer.

[0028] True elastomers are defined by the ASTM, Special Technical Bulletin, No. 184 standard as materials capable of being stretched, at room temperature, to twice their intrinsic length and which, once they have been released after holding them under tension for 5 minutes, return to within 10 % of their initial length in the same time.

[0029] The polymer (F) of the present invention usually has a melting temperature (Tm) comprised in the range from 100 to 200°C.

[0030] The polymer (F) of the present invention possesses a quasi-linear structure, with a very low amount of branching, which results in the insoluble fraction due to long branched chains being substantially negligible.

[0031] The polymer (F) of the present invention has in fact preferably a low fraction of insoluble components in standard polar aprotic solvents for VDF polymers, such as NMP. More preferably, solutions of polymer (F) in said standard polar aprotic solvents remain homogeneous and stable for several weeks, with substantially no insoluble residue.

[0032] Thanks to the low amount of insoluble components, the GPC and NMR analyses of polymer (F) are not affected, and there are no problems of reliability and reproducibility.

[0033] The melting temperature may be determined from a DSC curve obtained by differential scanning calorimetry (hereinafter, also referred to as DSC). In the case where the DSC curve shows a plurality of melting peaks (endothermic peaks), the melting temperature (Tm) is determined on the basis of the peak having the largest peak area.

[0034] It is understood that chain ends different from those above defined, defects or other impurity-type moieties might be comprised in the polymer (F) without these impairing its properties.

[0035] According to certain embodiments of the present invention, the polymer (F) is characterized by containing end groups of formula (I) as above defined, wherein x is zero.

[0036] According to other embodiments of the present invention, the polymer (F) is characterized by containing end groups of formula (I) as above defined, wherein xis 1 , and Rais a C2-C3 linear or branched alkyl radical, preferably C3 linear or branched alkyl radicals.

[0037] According to other embodiments of the present invention, the polymer (F) is characterized by containing end groups of formula (I) as above defined, wherein x is zero and containing end groups of formula (I) wherein x is 1 , and Rais a C2-C3 linear or branched alkyl radical, preferably C3linear or branched alkyl radicals.

[0038] Polymer (F) may be obtained by a process that comprises:- polymerizing the vinylidene fluoride (VDF) and optionally comonomer (CF), in an aqueous medium in the presence of a radical initiator system that introduces in the polymer chain end groups of formula (I).- maintaining the pressure in said reactor vessel exceeding the critical pressure of the vinylidene fluoride.

[0039] Suitable radical initiator systems include radical initiators such as di(ethyl) peroxydicarbonate and hydro-ethyl peroxydicarbonate.

[0040] The amount of radical initiator required for a polymerization is related to its activity and the temperature used for the polymerization. The total amount of radical initiator used is generally between 100 to 30000 ppm by weight on the total monomers weight used.

[0041] The radical initiator may be added in pure form, in solution, in suspension, or in emulsion, depending upon the initiator chosen.

[0042] The radical initiator systems may include a chain transfer agent (CTA).

[0043] Suitable CTA for the polymerization process for preparing the polymer (F) according to the present invention are those known in the art and are typically selected from the group consisting of short hydrocarbon chains like ethane and propane, esters such as ethyl acetate or diethyl maleate, diethylcarbonate and dimethylcarbonate. When an organic peroxide is used as the initiator, it could act also as effective CTA during the course of free radical polymerization.

[0044] When used, the CTA may be added all at once at the beginning of the reaction, or it may be added in portions, or continuously throughout the course of the reaction. The amount of CTA and its mode of addition depend on the desired properties of polymer (F) to be obtained.

[0045] Preferred CTA for use in the process of the present invention are ethyl acetate and diethylcarbonate.

[0046] In the process for preparing the polymer (F), 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.

[0047] Preferably, the process of the invention is carried out at a temperature superior to the critical temperature of the VDF monomer, i.e. of at least 31°C.

[0048] The polymer (F) is typically provided in form of powder according to the process described above.

[0049] Polymer (F) in the form of powder may be optionally further extruded to provide polymer (F) in the form of pellets.

[0050] The polymer (A) comprises recurring units derived from vinylidene fluoride (VDF) and recurring units derived from at least one hydrophilic 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 and an ether group, wherein the at least one monomer (MA) is present in an amount of from 0.05 to 10 % by moles of with respect to the total moles of recurring units of polymer (F).

[0051] The term "hydrophilic vinyl monomer" as employed herein may comprise recurring units derived from one or more than one hydrophilic vinyl monomer (MA) as above described. In the rest of the text, the expressions "hydrophilic 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 hydrophilic vinyl monomer (MA).

[0052] More preferably, the hydrophilic vinyl monomer (MA) preferably complies with formula (II):wherein each of R1 and R2 have the meanings as above defined, R3 is hydrogen, and ROH is a hydrogen or a C1-C5 hydrocarbon moiety comprising at least one hydroxyl group and / or at least a carboxylic group; more preferably, each of R1 , R2, R3 are hydrogen, while ROH has the same meaning as above detailed.

[0053] Non limitative examples of hydrophilic vinylmonomers (MA) are notably carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; hydroxyethylhexyl(meth)acrylates, - 2-carboxyethyl (meth) acrylate, -3-butenoic acid,- (meth) acryloyloxyethyl succinic acid,- (meth) acryloyloxypropyl succinic acid,- 3-(allyloxy)propanoic acid, or hydroxyl group-containing vinyl monomers such as - hydroxyethyl(meth)acrylate (HEA),- 2-hydroxypropyl acrylate (HPA),- hydroxyethylhexyl(meth)acrylate.

[0054] With the term “hydroxyl group-containing vinyl monomer” it is intended to define a monomer having at least one hydroxyl group directly linked to an alkylic carbon is present.

[0055] The monomer (MA) is more preferably selected among:- hydroxyethylacrylate (HEA) of formula:- 2-hydroxypropyl acrylate (HPA) of either of formulae:- 2-carboxyethyl (meth) acrylate (CEA),- (meth) acryloyloxyethyl succinic acid (AES),- (meth) acryloyloxypropyl succinic acid (APS), and mixtures thereof.

[0056] Most preferably, the monomer (MA) is AA, HEA, CEA or AES.

[0057] Polymer (A) may still comprise other moieties such as defects, end-groups and the like, which do not affect nor impair its physico-chemical properties.

[0058] Polymer (A) is semi-crystalline. The term semi-crystalline is intended to denote a polymer (A) which possesses a detectable melting point. It is generally understood that a semi-crystalline polymer (A) 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.

[0059] Polymer (A) is preferably a linear copolymer, that is to say, it is composed of macromolecules made of substantially linear sequences of recurring units from VDF monomer and (MA) monomer; polymer (A) is thus distinguishable from grafted and / or comb-like polymers.

[0060] Polymer (A) comprises at least 0.05 % by moles, more preferably at least 0.1 % by moles, even more preferably at least 0.2 % by moles of recurring units derived from said hydrophilic vinyl monomer (MA).

[0061] Polymer (A) comprises preferably at most 2 % by moles, more preferably at most 1.8 % by moles, of recurring units derived from said hydrophilic vinyl monomer (MA).

[0062] In a preferred embodiment of the invention, in polymer (A) the recurring units derived from hydrophilic vinyl monomer (MA) of formula (I) are comprised in an amount of from 0.2 to 1.5 % by moles with respect to the total moles of recurring units of polymer (A).

[0063] The polymer (A) has an intrinsic viscosity, measured in dimethylformamide at 25 °C, of at most 0.25 l / g, preferably in the range of 0.01 - 0.20 l / g, more preferably comprised in the range of 0.03 - 0.16 l / g.

[0064] The polymer (A) more preferably comprises 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), and- from 0.2% to 1.5% by moles, of a hydrophilic vinyl monomer (MA) of formula (I).

[0065] The polymer (A) may be obtained by polymerization of a VDF monomer, at least one monomer (MA), 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).

[0066] The procedure for preparing the polymer (A) in suspension comprises polymerizing in an aqueous medium in the presence of a radical initiator the vinylidene fluoride (VDF) monomer, monomer (MA), 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.

[0067] 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.

[0068] The expressions "continuous feeding", “adding continuously” or "continuously feeding" means that slow, small, incremental additions of the aqueous solution of hydrophilic vinyl monomer (MA) take place until polymerization has concluded.

[0069] The polymer (A) 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.

[0070] The polymer (A) is typically provided in form of powder according to the process described above.

[0071] Polymer (A) in the form of powder may be optionally further extruded to provide polymer (A) in the form of pellets.

[0072] Polymer (F) and polymer (A) can be mixed to prepare the polymer composition (P) according to any known method in the art.

[0073] In an embodiment of the invention, polymer (F) and polymer (A) both in the form of powder are mixed to provide a powdery dry mixture of polymer composition (P).

[0074] Alternatively, polymer (F) and polymer (A) can be dissolved or dispersed in a proper solvent, mixed and the resulting solution or dispersion dried to obtain the polymer composition (P) in solid form.

[0075] In an alternative embodiment, the polymer composition (P), may be pressed, compacted and then granulated to obtain the polymer composition (P) is in the form of pellets, flakes or dices.

[0076] The polymer composition (P) preferably comprises at least 20% by weight of at least one polymer (F), based on the total weight of the composition (P). Preferably, the amount of polymer (F) in composition (P) is of at least 50% by weigh, more preferably it is at least 80% by weight, still more preferably it is at least 90% by weight based on the total weight of the composition (P).

[0077] The polymer composition (P) preferably comprises at most 80% by weight of at least one polymer (A), based on the total weight of the composition (P). Preferably, the amount of polymer (A) in composition (P) is of at most 50% by weigh, still more preferably it is at most 20% by weight, still more preferably it is at most 10% by weight based on the total weight of the composition (P).

[0078] In a preferred embodiment, the polymer composition (P) comprises 50% by weight of at least one polymer (F) and 50% by weight of at least one polymer (A).

[0079] In another preferred embodiment, the polymer composition (P) comprises 90% by weight of at least one polymer (F) and 10% by weight of at least one polymer (A), based on the total weight of the composition (P).

[0080] In another preferred embodiment, the polymer composition (P) comprises 95% by weight of at least one polymer (F) and 5% by weight of at least one polymer (A), based on the total weight of the composition (P).

[0081] In another preferred embodiment, the polymer composition (P) comprises 98% by weight of at least one polymer (F) and 2% by weight of at least one polymer (A), based on the total weight of the composition (P).

[0082] The Applicant has surprisingly found that, when the polymer composition (P) comprises the polymer (F) in the amount as above specified, the viscosity of the slurry comprising said composition (P) is substantially unchanged in comparison with a slurry comprising a polymer (F) alone; meanwhile, it is possible to obtain homogeneous slurry compositions with no gelation evidence in all the preparation steps.

[0083] A second object of the present invention pertains to an electrode-forming composition (C) comprising: a) at least one electrode active material (AM); b) at least one polymer composition (P) as above defined; c) at least one solvent (S), and d) optionally, at least one conductive agent.

[0084] For the purpose of the present invention, the term “electro-active material (AM)” is intended to denote a compound that is able to incorporate or insert into its structure and substantially release therefrom alkaline or alkaline-earth metal ions during the charging phase and the discharging phase of an electrochemical device. The compound (AM) is preferably able to incorporate or insert and release lithium ions.

[0085] The nature of the compound (AM) in composition (C) depends on whether said composition is used in the manufacture of a positive electrode [electrode (Ep)] or a negative electrode [electrode (En)].

[0086] In the case of forming a positive electrode (Ep) for a secondary battery, the compound (AM) is preferably a compound capable of intercalating lithium ions or sodium ions.

[0087] 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.

[0088] In some embodiments the active materials are Na-based layered transition-metal oxides classified as O3-, P2-, and P3-types depending on the stacking sequence of oxygen layers. P2-type structures generally respond to the general formula NaxMC>2 wherein M stands for a transition metal ion such as Co, Mn and x is 2 / 3.

[0089] In some embodiments the active materials are Prussian blue analogs (PBA) of general formula AxP[R(CN)e]i-ymH20, with A being and alkali metal ion, P being a N-coordinated transition metal ion, R being a C-coordinated transition metal ion, y being a [R(CN)e] vacancy, with 0 < x < 2 and 0 < y < 1 , such as Nao.8iFe[Fe(CN)6]o.79, NaFe2(CN)e, Nai.63Fei.89(CN)e, Nai.72MnFe(CN)e, Nai.76Nio.i2Mno.88[Fe(CN)6]o.98, Na2NixCoi.xFe(CN)6 with 0 < x < 1 e.g. Na2CoFe(CN)6.

[0090] In some other embodiments the active materials are polyanion-type materials of general formula NaxMy(XC>4)n (where X = S, P, Si, As, Mo and W, and M is transition metal), which possess a series of tetrahedron anion units (XC>4)n' and their derivatives (XmO3m+i)n'. Among them, phosphates NaMPC>4 such as NaFePCU, NaojFePCU or NaMnPOt; natrium (sodium) superionic conductor of NASICON- type structures of general formula NaxM2(XC>4)3 (where 1 < x < 4, M = 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(PC>4)3; - with binary transition metal type such as Na2VTi(PC>4)3, Na3FeV(PC>4)3, Na4MnV(PO4)3, Na3MnZr(PC>4)3, Na3MnTi(PC>4)3, Na4Fe3(PO4)2(P2O7) (NFPP); pyrophosphates Na2FeP2C>7, Na2MnP2C>7, Na2CoP2C>7, Na4-xFe2+x / 2(P2O7)2with 2 / 3 < x < 7 / 8 e.g. Na3.i2Fe2.44(P2O7)2or Na3.32Fe2 34(P2O7)2, Na2(VO)P2O7, NayV3(P2O7)4; fluorophosphates NaVPO4F, Na2CoPC>4F, Na2FePC>4F, Na2MnPC>4F, Na3(VOi. XPO4)2FI+2X(with 0 < x < 1) e.g. Na3(VOPO4)2F or Na3V2(PO4)2F3(NVPF); fluoro sulfates such as NaMSOiF (with M = Fe, Co, Ni); mixed phosphates / pyrophosphates of general formula Na4M3(PO4)2(P2C>7) (with M representing transition metals) such as Na4Mn3(PO4)2(P2C>7), Na4Co3(PO4)2(P2C>7), 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 Na2MSiC>4 (with M = Mn, Fe, Co and Ni).

[0091] In some preferred embodiments the active materials are fluorophosphates preferably selected from the list consisting of NaVPOiF, Na2CoPC>4F, Na2FePC>4F, Na2MnPC>4F, Na3(VOi-xPO4)2Fi+2x(with 0 < x < 1) e.g. Na3(VOPO4)2F or Na3V2(PO4)2F3(NVPF).

[0092] 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, Al 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 LiCoO2, LiNiO2, LiNixCoi-xO2(0 < x < 1), LiNixMnyCo7.x.yO2(NMC), LiNixCoyAlzO2with x + y + z = 1 (NCA), Ni-Mn-Co-AI (NMCA) and spinel-structured LiMn2C>4.

[0093] 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(JC>4)fEi-f, wherein Mi is lithium, which may be partially substituted by another alkali metal representing less than 20% of the Mi metals, M2is a transition metal at the oxidation level of +2 selected from Fe, Mn, 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 M2metals, 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.

[0094] The MiM2(JO4)fEi.felectro-active material as defined above is preferably phosphate-based and may have an ordered or modified olivine structure.

[0095] 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 PO4 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 at least one selected from the group consisting of Mn, Fe, Co, Ni, Co 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 <xz <1.5.

[0096] The A component is preferably Fe, Mn, and Ni, and particularly preferably Fe or Mn.

[0097] The D component is preferably Mg or Ca.

[0098] Examples of the compound having an olivine structure include lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP) and lithium manganese phosphate.

[0099] 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.

[0100] 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.

[0101] The active Material (AM) is present in composition (C) in an amount of 70% by mass or more, with respect to 100% by mass of the entire composition (C).

[0102] More preferably, it is 90% by mass or more, and most preferably, the positive electrode active material (AM) is composed only of a compound having an olivine structure.

[0103] In the positive electrode composition of the present invention, the olivine type active material has preferably a surface area (BET) of at least 4 m2 / g, preferably between 6 and 20 m2 / g.

[0104] The average particle size of the positive electrode active material can be measured by a particle size distribution meter for dynamic light scattering.

[0105] By using a positive electrode active material containing a compound having an olivine structure having an average particle size of 3 pm or less, the electrical characteristics such as the output characteristics when the positive electrode composition for a secondary battery is used as the positive electrode of the battery are excellent. In the case of forming a negative composite electrode (En) for a Lithium-ion secondary battery, the compound (AM) may preferably comprise a carbon-based material and / or a silicon-based material.

[0106] In some embodiments of the present invention, the active material (AM) is a single material selected from the active materials as above defined.

[0107] In certain other embodiments, two or more active materials (AM) as above defined are blended and used in composition (C).

[0108] In one preferred embodiment, the active material (AM) is a combination of LFP or LMFP with NMC.

[0109] In some embodiments, the carbon-based material may be, for example, graphite, such as natural or artificial graphite, graphene, or carbon black.

[0110] These materials may be used alone or as a mixture of two or more thereof.

[0111] The carbon-based material is preferably graphite.

[0112] The silicon-based compound may be one or more selected from the group consisting of chlorosilane, alkoxysilane, aminosilane, fluoroalkylsilane, silicon, silicon chloride, silicon carbide and silicon oxide. More particularly, the silicon-based compound may be silicon oxide or silicon carbide.

[0113] When present in compound (AM), the at least one silicon-based compound is comprised in the compound (AM) in an amount ranging from 1 to 30 % by weight, preferably from 5 to 20 % by weight with respect to the total weight of the compound (AM).

[0114] The solvent (S) may preferably be an organic polar one, examples of which may include: N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, and trimethyl phosphate. These solvents may be used singly or in mixture of two or more species.

[0115] An optional conductive agent may be added in order to improve the conductivity of a resulting electrode.

[0116] Examples thereof may include carbonaceous materials, such as carbon black, acetylene black, graphite fine powder, carbon nanotubes, graphene, or fiber, or fine powder or fibers of metals such as nickel or aluminum. Carbon black is available, for example, under the brand names, Super P® or Ketjenblack®.

[0117] When present, the conductive agent is different from the carbon-based material described above.

[0118] The electrode-forming composition (C) can be prepared by any known method in the art.

[0119] A suitable method comprises:- dissolving polymer (F) with a solvent (S),- dissolving polymer (A) with a solvent (S),- adding at least one electrode active material (AM) and optional additives such as an electroconductivity-imparting additive and / or a viscosity modifying agent.

[0120] Alternatively, the electrode-forming composition can be prepared by adding to a dispersion of the at least one electrode active material (AM) and optional additives in solvent (S), the polymer composition (P) in the powdery form.

[0121] The total solid content (TSC) of the composition (C) of the present invention is typically comprised between 40 and 90 % by weight, preferably from 50 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 (A), the electrode active material and any solid, non-volatile additional additive.

[0122] When the solution of polymer (F) is combined with polymer (A), 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) and polymer (A) is employed. The amount of solvent used mayrange 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 (A), the active electrode material, the optional conductive material, and the other solid additives have been added.

[0123] In another object, the present invention pertains to the use of the electrode-forming composition (C) for the manufacture of an electrode (E), said process comprising:(I) providing a metal substrate having at least one surface;(II) providing an electrode-forming composition (C) as above defined;(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);(V) submitting the dried assembly obtained in step (IV) to a compression step to obtain the electrode (E) of the invention.

[0124] In a further object, the present invention pertains to the electrode (E) obtainable by the process of the invention.

[0125] The Applicant has surprisingly found that the electrode (E) of the present invention shows outstanding adhesion of the binder to current collector.

[0126] The electrode (E) of the invention is thus particularly suitable for use in electrochemical devices, in particular in secondary batteries.

[0127] For the purpose of the present invention, the term “secondary battery” is intended to denote a rechargeable battery.

[0128] The secondary battery of the invention is preferably an alkaline or an alkaline-earth metal secondary battery.

[0129] The secondary battery of the invention is more preferably a Lithium-ion secondary battery.

[0130] In still a further object, the present invention pertains to an electrochemical device comprising at least one electrode (E) of the present invention.

[0131] The electrochemical device according to the present invention, being preferably a secondary battery, comprises:- a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode (E) of the present invention.

[0132] In one preferred embodiment of the present invention it is provided an electrochemical device is a secondary battery comprising:- a positive electrode and a negative electrode,wherein the negative electrode is the electrode (E) according to the present invention.

[0133] An electrochemical device according to the present invention can be prepared by standard methods known to a person skilled in the art.

[0134] 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.

[0135] EXPERIMENTAL PART

[0136] Raw materials

[0137] LFP: LFP active material commercially available from Dynanonic Co. Ltd. DY-3, having d50 = 0.6-1.8 pm.

[0138] Carbon nanotubes: Orgacyl NMP0402 4% thin multiwall carbon nanotube (MWCNT) in N-Methyl-2-pyrrolidone (NMP) solvent.

[0139] Determination of intrinsic viscosity of polymer (F)

[0140] Intrinsic viscosity (q) [dl / g] was measured using the following equation on the basis of dropping time, at 25°C, of a solution obtained by dissolving the polymer (F) in N,N-dimethylformamide at a concentration of about 0.2 g / dl using a Ubbelhode viscosimeter:where c is polymer concentration [g / dl], r|ris the relative viscosity, i.e. the ratio between the dropping time of sample solution and the dropping time of solvent, r|spis the specific viscosity, i.e. qr-1 , and F is an experimental factor, which for polymer (F) and for polymer (A) corresponds to 3.

[0141] DSC analysis

[0142] DSC analyses were carried out according to ASTM D 3418 standard; the melting point (Tf2) was determined at a heating rate of 10°C / min.

[0143] Determination of the end-groups and of the amount of monomer Acrylic Acid (AA) in the polymer (F) by NMR

[0144] The content of end groups was calculated by applying the following formula:[EG] = (IEG / IVDF) X 10000 wherein:- [EG] is the content of the generic end-groups expressed as moles per 10000 VDF units,- IEG is the intensity, normalized to one hydrogen, of the integral of the end-group [EG]- IVDF is the intensity, normalized to one hydrogen, of the integrals of normal and reverse VDF recurring units.

[0145] The amount of end groups of the polymers (F-1 ; A-1 ; A-2) arising from the Ethyl chloroformate initiator precursor used in the polymerization process, was determined by1H-NMR, measuring the intensity of the H atoms of the CH2group (in bold in following formula) with respect to the total intensity of CH2moieties of the polymer (F) backbone VDF monomer units:CH3-CH2-OZCOZO-CH2-CF2-

[0146] About 20 mg of polymer were dissolved in 0.7 ml of hexadeuteroacetone. The1H -NMR spectrum, recorded at 60°C, revealed the aforementioned CH2at 4.47 ppm whereas CH2signals from VDF recurring normal and reverse units resonated as broad peaks centered at 2.93 and 2.36 ppm respectively.

[0147] The amount of end groups of the polymers (F) arising from diethylcarbonate used in the polymerization process, was determined by1H-NMR, measuring the intensity of the H atoms of the CH2groups for linear chain end and CH groups for branched one (in bold in following formulas) with respect to the total intensity of CH2moieties of the polymer (F) backbone VDF monomer units:CH3-CH2-O-CO-O-CH2-CH2-VDF- and CH3-CH2-O-CO-O-CH-(CH3)-VDF

[0148] About 20 mg of polymer were dissolved in 0.7 ml of hexadeuteroacetone. The1H- NMR spectrum, recorded at 60°C, revealed the aforementioned CH2at 4.05 ppm and CH at 5.10 ppm whereas CH2signals from VDF recurring normal and reverse units resonated as broad peaks centered at 2.93 and 2.36 ppm respectively.

[0149] The amount of end groups of the polymers (F) arising from the initiator t- amylperpivalate used in the polymerization process, was determined by1H-NMR, measuring the intensity of the H atoms of the (CH3)3groups (in bold in following formula) with respect to the total intensity of CH2moieties of the polymer (F) backbone VDF monomer units:(CH3)3-C-VDF

[0150] About 20 mg of polymer were dissolved in 0.7 ml of hexadeuteroacetone. The1H- NMR spectrum, recorded at 60°C, revealed the aforementioned (CH3)3at 1.08 ppm whereas CH2signals from VDF recurring normal and reverse units resonated as broad peaks centered at 2.93 and 2.36 ppm respectively.

[0151] Alternated AA contents in the polymer (F) were determined by19F-NMR spectroscopy. Signals related to CF2moieties of VDF units (in bold in the following formula) adjacent to isolated hydrogenated comonomers have been found to resonate at about 94 ppm in the19F-NMR:CH3CF2CH2CH(COOH)-CH2CF2-

[0152] Similar NMR methods were applied to the determination of -CF2H and -CF2CH3end groups, as known to people skilled in the art.

[0153] Example 1 : Preparation of Polymer F-1

[0154] In a 80 I reactor equipped with an impeller running at a speed of 250 rpm were introduced in sequence: 48.15 Kg of demineralized water, and 120.40 g of trisodium phosphate dodeca hydrate, and then 0.27 g of PEO (Alkox® -E45 from Alroko) and 0.33 g of hydroxypropyl methylcellulose (Methocel®-K100 from DuPont Nutrition Biosciences SAS) per kg of total monomers. The oxygen present in the reactor was removed with a sequence of vacuum and purge of nitrogen at a fixed temperature of 14°C. This sequence was repeated 3 times.

[0155] Then, 114.59 g of hydrogen peroxide solution (from Brenntag), 34.38 g of ethyl chloroformate (from Framochem) and 355.93 g of diethylcarbonate were introduced in the reactor.

[0156] After 15 minutes with the stirring speed of 300 rpm, 26.96 Kg of VDF were introduced in the reactor. The reactor was then gradually heated until the set-point temperature of 35°C was reached.

[0157] The pressure was kept constantly equal to 120 bars during the whole polymerization run by VDF. A total of 13.48 Kg of VDF was charged. Then the temperature was brought to 40°C and then, after a total of 314 minutes, the reaction was stopped by degassing the suspension until reaching atmospheric pressure.

[0158] The polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C overnight. 31 .46 Kg of dry powder were collected.

[0159] A polymer having an intrinsic viscosity of 0.31 l / g in DMF at 25°C and a T2f of 171.0°C was obtained.

[0160] The polymer contained 0.4 / 10000 VDF units derived from ethyl chloroformate initiator precursor and 2.4 / 10000 VDF units derived from diethylcarbonate.

[0161] In addition, the presence of 3.0 / 10000 VDF units of -CF2H and 1.6 / 10000 VDF units of -CF2CH3 was determined.

[0162] Example 2: Preparation of Polymer A-1

[0163] In a 80 I reactor equipped with an impeller running at a speed of 250 rpm were introduced in sequence: 46.59 Kg of demineralized water, and then 0.79 g of hydroxypropyl methylcellulose (Methocel®^K100 from DuPont Nutrition Biosciences SAS) per Kg of monomers. The oxygen present in the reactor was removed with a sequence of vacuum and purge of nitrogen at a fixed temperature of 14°C. This sequence was repeated 3 times.

[0164] Then, 170.30 g of a solution of the initiator t-amylperpivalate (from United Initiators) in isododecane (75%) and 664.17 g of diethylcarbonate were introduced in the reactor. Immediately after, the stirring speed is brought to 300 rpm, then 10.80 g of acrylic acid (AA) were added to the reactor, followed by 25.27 Kg of VDF. The reactor was then gradually heated until the set-point temperature of 55°C was reached.

[0165] The pressure was kept constantly equal to 110 bars during the whole polymerization run by feeding an aqueous solution comprising 14.26 g of AA per liter of solution. A total of 17.77 Kg of the solution was loaded into the reactor. After a total of 438 minutes, the reaction was stopped by degassing the suspension until reaching atmospheric pressure.

[0166] The polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C overnight. 19.26 Kg of dry powder were collected.

[0167] A polymer comprising VDF-AA (0.9% by moles), having an intrinsic viscosity of 0.08 l / g in DMF at 25°C and a T2f of 168.7°C was obtained.

[0168] The polymer contained 5.0 / 10000 VDF units derived from Diethylcarbonate, 3.9 / 10000 VDF units derived from t-amylperpivalate.

[0169] In addition, the presence of 11.2 / 10000 VDF units of -CF2H and 3.8 / 10000 VDF units of -CF2CH3 was determined.

[0170] Example 3: Preparation of Polymer A-2

[0171] In a 4 I reactor equipped with an impeller running at a speed of 650 rpm were introduced in sequence: 2.53 Kg of demineralized water, 29.96 g of trisodium phosphate dodeca hydrate, and then 1 .48 g of polyvinyl alcohol (Alcotex TM 80 from Synthomer) per kg of total monomers. The oxygen present in the reactor was removed with a sequence of vacuum and purge of nitrogen at a fixed temperature of 14°C. This sequence was repeated 3 times.

[0172] Then, 27.01 g of hydrogen peroxide solution (from Brenntag), 25.66 g of Diethylcarbonate and 8.55 g of Ethyl chloroformate (from Framochem) were introduced in the reactor.

[0173] After 15 minutes with the stirring speed of 880 rpm, 0.70 g of acrylic acid (AA) were added to the reactor, followed by 1 .06 Kg of VDF. The reactor was then gradually heated until the set-point temperature of 40°C was reached.

[0174] The pressure was kept constantly equal to 120 bars during the whole polymerization run by feeding an aqueous solution comprising 16.97 g of AA per liter of solution. A total of 0.59 Kg of the solution was loaded into the reactor. Aftera total of 516 minutes, the reaction was stopped by degassing the suspension until reaching atmospheric pressure.

[0175] The polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C overnight. 0.71 Kg of dry powder were collected.

[0176] A polymer comprising VDF-AA (0.9% by moles), having an intrinsic viscosity of 0.10 l / g in DMF at 25°C and a T2f of 167.4°C was obtained

[0177] The polymer contained 6.1 / 10000 VDF units derived from ethyl chloroformate initiator precursor and 5.0 / 10000 VDF units derived from diethylcarbonate.

[0178] In addition, the presence of 2.5 / 10000 VDF units of -CF2CH3 was determined.

[0179] General Preparation of the Electrodes

[0180] Positive electrodes having final composition of 95.75% by weight of LFP, 3.5% by weight of polymer or polymer composition, 0.75% by weight of conductive additive were prepared as follows.

[0181] A first dispersion was prepared by pre-mixing for 10 minutes in a centrifugal mixer 34.3 g of an 8% by weight solution of the polymer or polymer composition in NMP, 75.07 g of LFP, 14.7 g of graphite fine powder carbon nanotubes pre-dispersed in NMP at 4% by weight and 15.93 g of NMP.

[0182] The mixture was then mixed using a high speed butterfly type impeller at 1500 rpm for 50 minutes. Additional 5.2 g of NMP were subsequently added to the dispersion, which was further mixed with a centrifugal mixer for 5 min. Positive electrodes were obtained by casting the as obtained compositions on 15 pm thick Al foil with doctor blade and drying the as coated layers in a vacuum oven at temperature of 90°C for about 50 minutes. The thickness of the dried coating layers was about 100 pm.

[0183] Slurry viscosity

[0184] The slurry viscosity of the compositions as above defined was measured with an AntonPaar Rheolab QC using a Concentric cylinder setup (Measuring Cup: C- CC27 / QC-LTD Bob: CC27 / P6) with peltier temperature control at 25°C. Steady state viscosities were measured from shear rate of 0.1 to 1000 1 / s.

[0185] Adhesion Measurement

[0186] Adhesion Peeling Force between Aluminium foil and the Electrodes was measured as follows:

[0187] 180° peeling tests were performed following the setup described in the standard ASTM D903 at a speed of 300 mm / min at 20°C in order to evaluate the adhesion of the dried coating layer as above defined to the Aluminium foil.

[0188] Example 4: Adhesion and slurry viscosity

[0189] Polymers and polymer compositions as defined in Table 1 have been used in the electrode compositions have been produced according to the procedure shown above. The values of slurry viscosity and adhesion are shown in Table 1.Table 1normalized vs F-1 alone

[0190] Example 5: Slurry gelation measurement

[0191] The slurry viscosity increment at fix frequency 10 rad / s / a.u. over time of the electrode compositions I, produced according to the procedure shown above, was measured with an AntonPaar MCR92 using smooth parallel plates setup with a diameter of 50 mm (Measuring Plate: PP50) with Peltier temperature control at 25°C. Frequency sweep test was performed in the range of 0.1 to 100 rad / s with constant strain (0.5%) at different times to evidence the trend of viscosity by time.

[0192] The values of the relative slurry viscosity increment over time are shown in Table 2.Table 2

[0193] The results in Table 1 and Table 2 show that the polymers compositions of the present invention are more performing and easier to be handled in the fabrication process of electrodes than the polymer (F-1) alone, thanks to a low slurry viscosity, good adhesion and good resistance to gelation. Surprisingly, the compositions comprising 2% of polymer (A) shows an even improved performance than the composition comprising polymer (A) in a 5% amount.

Claims

ClaimsClaim 1. A polymer composition (P) comprising: a) at least one VDF-based polymer [polymer (F)] having intrinsic viscosity, measured in dimethylformamide at 25 °C, in the range of from 0.25 l / g to 0.60 l / g, more preferably from 0.27 l / g to 0.50 l / g where the polymer (F) is characterized by containing end groups of formula (I): -(Ra)x-O-CO-O-CH2-CH3(I) wherein Rais a C1-C5 linear or branched hydrocarbon group and x is an integer selected from 1 and zero and the end-groups of formula (I) are present in an amount of at least 0.2 / 10000 VDF units, preferably at least 1.0 / 10000 VDF units, and of at most 10 / 10000 VDF units; b) at least one VDF-based polymer [polymer (A)], different from polymer (F), having intrinsic viscosity, measured in dimethylformamide at 25 °C, lower than 0.25 l / g, said polymer (A) characterized by consisting of:(i) recurring units derived from vinylidene fluoride (VDF) monomer; and(ii) recurring units derived from at least one hydrophilic vinyl monomer (MA) of formula (I):wherein:- R1, R2and 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 and an ether group, wherein the at least one monomer (MA) is present in an amount of from 0.05 to 10 % by moles of with respect to the total moles of recurring units of polymer (A).Claim 2. The composition (P) according to claim 1 , wherein polymer (F) is a VDF homopolymer.Claim 3. The composition (P) according to claim 1 , wherein polymer (F) is a VDF- based copolymer comprising including recurring units derived from VDF and recurring units derived from at least one fluorinated comonomer (CF), different from VDF.Claim 4. The composition (P) according to any one of claims 1 to 3, wherein the fluorinated comonomer (CF) is selected from the group consisting of:(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-Rfo, wherein Rf0is a Ci-Ce perfluoroalkyl group;(d) chloro- and / or bromo- and / or iodo-C2-Ce fluoroolefins such as chlorotrifluoroethylene (CTFE).(e) perfluoro(alkyl)vinyl ethers, such as perfluoro(methyl)vinyl ether (PMVE), perfluoro(ethyl) vinyl ether (PEVE) and perfluoro(propyl)vinyl ether (PPVE);(f) perfluoro(1 ,3-dioxole); perfluoro(2,2-dimethyl-1 ,3-dioxole) (PDD).Claim 5. The composition (P) according to any one of the preceding claims, wherein polymer (F) contains end groups of formula (I) wherein x is zero and / or end groups of formula (I) wherein x is 1 , and Rais a C2-C3 linear or branched alkyl radical.Claim 6. The composition (P) according to any one of the preceding claims, wherein the hydrophilic vinyl monomer (MA) is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylates, 2-carboxyethyl (meth) acrylate, 3-butenoic acid,- (meth) acryloyloxyethyl succinic acid, (meth) acryloyloxypropyl succinic acid, 3- (allyloxy)propanoic acid, hydroxyethyl(meth)acrylate (HEA),2-hydroxypropyl acrylate (HPA), hydroxyethylhexyl(meth)acrylate.Claim 7. The composition (P) according to any one of the preceding claims, which is in the form of powder.Claim 8. The composition (P) according to any one of the preceding claims, wherein the amount of polymer (F) is of at least 20% by weigh, preferably of at least 50% by weigh, more preferably it is of at least 80% by weight, still more preferably it is of at least 90% by weight, based on the total weight of the composition (P).Claim 9. The composition (P) according to claim 8, wherein composition (P) comprises 95% by weight of at least one polymer (F) and 5% by weight of at least one polymer (A), based on the total weight of the composition (P).Claim 10. The composition (P) according to claim 8, wherein composition (P) comprises 98% by weight of at least one polymer (F) and 2% by weight of at least one polymer (A), based on the total weight of the composition (P).Claim 11. An electrode-forming composition (C) comprising: a) at least one electrode active material (AM); b) at least one polymer composition (P) according to anyone of claims 1 to 10; c) at least one solvent (S), andd) optionally, at least one conductive agent.Claim 12. The electrode-forming composition (C) according to claim 11 , wherein the at least one electrode active material (AM) has an olivine structure.Claim 13. A process for the manufacture of an electrode [electrode (E)], said process comprising:(I) providing a metal substrate having at least one surface;(II) providing an electrode-forming composition (C) according to claim 11 or claim 12;(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);(V) submitting the dried assembly obtained in step (IV) to a compression step to obtain the electrode (E) of the invention.Claim 14. An electrode (E) obtainable by the process of claim 13.Claim 15. An electrochemical device comprising at least one electrode (E) according to claim 14.

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