Ionic conductive membranes

Abstract

The invention pertains to a process for manufacturing a fluoropolymer hybrid organic / inorganic composite and films and membranes thereof and to uses of said fluoropolymer hybrid organic / inorganic composite and films and membranes thereof in various applications.

Description

Ionic conductive membranesCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to European patent application No.24315151.1 filed on April 11 , 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical Field

[0002] The invention pertains to a process for manufacturing a fluoropolymer hybrid organic / inorganic composite, films and membranes thereof and to uses of said fluoropolymer hybrid organic / inorganic composite, films and membranes thereof in various applications.Background Art

[0003] Organic-inorganic polymer hybrids wherein inorganic solids on a nano or molecular level are dispersed in organic polymers have raised a great deal of scientific, technological and industrial interests because of their unique properties.

[0004] To elaborate organic-inorganic polymer hybrid composites, a sol-gel process using metal alkoxides is the most useful and important approach.

[0005] By properly controlling the reaction conditions of hydrolysis and polycondensation of metal alkoxydes, in particular of alkoxysilanes (e.g. tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS)), in the presence of pre-formed organic polymers, it is possible to obtain hybrids with improved properties compared to the original compounds. The polymer can enhance the toughness and processability of otherwise brittle inorganic materials, wherein the inorganic network can enhance scratch resistance, mechanical properties and surface characteristics of said hybrids.

[0006] Hybrids made from sol-gel technique starting from fluoropolymers, in particular from vinylidene fluoride polymers are known in the art.

[0007] EP 3140338 discloses the manufacture of the fluoropolymer hybrid organic / inorganic composite in the presence of a liquid medium, to provide a self-standing fluoropolymer film stably comprising and retaining said liquid medium and having outstanding ionic conductivity. When the hybridorganic / inorganic composite is for use as polymer electrolyte separator in electrochemical and photo-electrochemical devices, it may be obtained by a process comprising hydrolysing and / or polycondensing a mixture comprising a fluoropolymer, a metal compound of formula X4-mAYm, an ionic liquid, a solvent for the fluoropolymer, and one electrolytic salt. The resulting liquid mixture is then processed into a film by a solvent casting procedure, and dried to obtain the film. Said film can be used as polymer membranes suitable for use in electrochemical devices such as secondary batteries.

[0008] Known in the art is the use of certain electrolyte additives such as tris(2, 2, 2-trifluoroethy I) phosphite for the stabilization of lithium-rich layered oxide cathode (Journal of Power Source 296 (2015) 413-425).Summary of invention

[0009] The Applicant has now surprisingly found that it is possible to manufacture fluoropolymer hybrid organic / inorganic composites advantageously endowed with outstanding properties, which are suitable for use in various applications.

[0010] In particular, the Applicant has found that films of the fluoropolymer hybrid organic / inorganic composite of the present invention successfully exhibitsincreased cyclability, while maintaining good mechanical properties and good ionic conductivity properties, to be suitably used as polymer electrolyte membranes in electrochemical devices.

[0011] One object of the present invention thus pertains to a process for manufacturing a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)], said process comprising reacting:- at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)], with- at least one metal compound [compound (M1 )] of formula (I): X4-mAYm (I)wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, and- optionally, at least one metal compound [compound (M2)] of formula (II): X’4-mA’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consisting of Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; in the presence of- a liquid medium [medium (L)];- at least one metal salt [salt (MS)];- at least one Lewis base additive [additive (A)];- a solvent (S).

[0012] Another object of the present invention pertains to the fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] obtainable by the process of the invention.

[0013] In another object, the present invention provides a fluoropolymer film comprising at least one fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] according to the present invention.

[0014] Thus, the invention further pertains to a process for the manufacture of a fluoropolymer film comprising at least one fluoropolymer hybrid organic / inorganic composite [polymer (F-h)], said process comprising: i) reacting:- at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)], with- at least one metal compound [compound (M1 )] of formula (I):X4-mAYm (I) wherein m is an integer from 1 to 3, A is a metal selected from the groupconsisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, and- optionally, at least one metal compound [compound (M2)] of formula (II): X’4-mA’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consisting of Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; in the presence of- a liquid medium [medium (L)];- at least one metal salt [salt (MS)];- at least one Lewis base additive [additive (A)];- a solvent (S) to provide a composition (C); ii) processing into a film the composition (C) provided in step i); and iii) drying the film provided in step ii).Description of embodiments

[0015] In the context of the present invention, the term “weight percent” (wt %) indicates the content of a specific component in a mixture, calculated as the ratio between the weight of the component and the total weight of the mixture. When referred to the recurring units derived from a certain monomer in a polymer / copolymer, weight percent (wt %) indicates the ratio between the weight of the recurring units of such monomer over the total weight of the polymer / copolymer. When referred to the total solid content of a liquid composition, weight percent (wt %) indicates the ratio between the weight of all non-volatile ingredients in the liquid.

[0016] For the purpose of the present invention, the term “film” is intended to denote a continuous, generally thin, sheet.

[0017] For the purpose of the present invention, the term “membrane” is intended to denote a discrete, generally thin, interface, which moderates permeation of chemical species in contact with it.

[0018] By the term "electrochemical device", it is hereby intended to denote an electrochemical cell / assembly comprising a positive electrode, a negative electrode and a liquid electrolyte, wherein a monolayer or multilayer separator is in contact to at least one surface of one of the said electrodes. Non-limitative examples of suitable electrochemical devices include, notably, secondary batteries, especially, alkaline or an alkaline- earth secondary batteries such as lithium ion batteries, lead-acid batteries, and capacitors, especially lithium ion-based capacitors and electric double layer capacitors (supercapacitors). Non-limitative examples of electrochemical cells include, notably, batteries, preferably secondary batteries, and electric double layer capacitors.

[0019] For the purpose of the present invention, by "secondary battery" it is intended to denote a rechargeable battery.

[0020] Non-limitative examples of suitable electrochemical devices include, notably, secondary batteries, especially, alkaline or an alkaline-earth secondary batteries such as Lithium ion batteries, and capacitors, especially Lithium ion capacitors.

[0021] The polymer (F)

[0022] The polymer (F) is typically obtainable by polymerization of at least one monomer (MF) and at least one monomer (OH).

[0023] The polymer (F) may further comprise recurring units derived from at least one hydrogenated monomer [monomer (H)] different from the monomer (OH).

[0024] Should the polymer (F) further comprise recurring units derived from at least one hydrogenated monomer [monomer (H)] different from the monomer (OH), it is typically obtainable by polymerization of at least one monomer (MF), at least one monomer (OH) and at least one monomer (H) different from said monomer (OH).

[0025] By the term “fluorinated monomer [monomer (MF)]” it is hereby intended to denote an ethylenically unsaturated monomer comprising at least one fluorine atom.

[0026] By the term “hydrogenated monomer [monomer (H)]” it is hereby intended to denote an ethylenically unsaturated monomer comprising at least one hydrogen atom and free from fluorine atoms.

[0027] The term “at least one fluorinated monomer” is understood to mean that the polymer (F) may comprise recurring units derived from one or more than one fluorinated monomers. In the rest of the text, the expression “fluorinated monomers” is understood, for the purposes of the present invention, both in the plural and the singular, that is to say that they denote both one or more than one fluorinated monomers as defined above.

[0028] The term “at least one hydrogenated monomer” is understood to mean that the polymer (F) may comprise recurring units derived from one or more than one hydrogenated monomers. In the rest of the text, the expression “hydrogenated monomers” is understood, for the purposes of the present invention, both in the plural and the singular, that is to say that they denote both one or more than one hydrogenated monomers as defined above.

[0029] The polymer (F) comprises preferably at least 0.01 % by moles, more preferably at least 0.05% by moles, even more preferably at least 0.1 % by moles of recurring units derived from at least one monomer (OH) as defined above.

[0030] The polymer (F) comprises preferably at most 20% by moles, more preferably at most 15% by moles, even more preferably at most 10% by moles, most preferably at most 3% by moles of recurring units derived from at least one monomer (OH) as defined above.

[0031] Determination of average mole percentage of monomer (OH) recurring units in polymer (F) can be performed by any suitable method. Mention can be notably made of acid-base titration methods, well suited e.g. for the determination of the acrylic acid content, of NMR methods, adequate for the quantification of monomers (OH) comprising aliphatic hydrogen atoms in side chains, of weight balance based on total fed monomer (OH) and unreacted residual monomer (OH) during polymer (F) manufacture.

[0032] The monomer (OH) is typically selected from the group consisting of (meth)acrylic monomers of formula (III) and vinylether monomers of formula (IV):(Ill)(IV)wherein each of Ri , R2 and R3, equal to or different from each other, is independently a hydrogen atom or a C1-C3 hydrocarbon group, and Rx is a C1-C5 hydrocarbon moiety comprising at least one hydroxyl group.

[0033] The monomer (OH) is preferably of formula (III) as defined above.

[0034] The monomer (OH) is more preferably of formula (lll-A):wherein R’1, R’2 and R’3 are hydrogen atoms and R’x is a C1-C5 hydrocarbon moiety comprising at least one hydroxyl group.

[0035] Non limitative examples of monomers (OH) include, notably, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate.

[0036] The monomer (OH) is even more preferably selected from the followings: - hydroxyethyl acrylate (HEA) of formula:- 2-hydroxypropyl acrylate (HPA) of either of formulae:- and mixtures thereof.

[0037] The polymer (F) may be amorphous or semi-crystalline.

[0038] The term “amorphous” is hereby intended to denote a polymer (F) having a heat of fusion of less than 5 J / g, preferably of less than 3 J / g, more preferably of less than 2 J / g, as measured according to ASTM D-3418-08.

[0039] The term “semi-crystalline” is hereby intended to denote a polymer (F) having a heat of fusion of from 10 to 90 J / g, preferably of from 30 to 60 J / g, more preferably of from 35 to 55 J / g, as measured according to ASTM D3418-08.

[0040] The polymer (F) is preferably semi-crystalline.

[0041] Non limitative examples of suitable monomers (F) include, notably, the followings:- C2-C8 perfluoroolefins, such as tetrafluoroethylene and hexafluoropropylene;- C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride, vinyl fluoride, 1 ,2-difluoroethylene and trifluoroethylene;- perfluoroalkylethylenes of formula CH2=CH-Rro wherein Rro is a Ci-Ce perfluoroalkyl;- chloro- and / or bromo- and / or iodo-C2-Ce fluoroolefins, such as chlorotrifluoroethylene;- (per)fluoroalkylvinylethers of formula CF2=CFORfi wherein Rn is a Ci-Ce fluoro- or perfluoroalkyl, e.g. CF3, C2F5, C3F7 ;- CF2=CFOXO (per)fluoro-oxyalkylvinylethers wherein Xo is a C1-C12 alkyl group, a C1-C12 oxyalkyl group or a C1-C12 (per)fluorooxyalkyl group having one or more ether groups, such as perfluoro-2-propoxy-propyl group;- (per)fluoroalkylvinylethers of formula CF2=CFOCF2ORf2 wherein Rf2 is a Ci-Ce fluoro- or perfluoroalkyl group, e.g. CF3, C2F5, C3F7 or a Ci-Ce(per)fluorooxyalkyl group having one or more ether groups, such as -C2F5- O-CF3;- functional (per)fluoro-oxyalkylvinylethers of formula CF2=CFOYo wherein Yo is a C1-C12 alkyl group or (per)fluoroalkyl group, a C1-C12 oxyalkyl group or a C1-C12 (per)fluorooxyalkyl group having one or more ether groups and Yo comprising a carboxylic or sulfonic acid group, in its acid, acid halide or salt form;- fluorodioxoles, preferably perfluorodioxoles.

[0042] Non limitative examples of suitable monomers (H) include, notably, ethylene, propylene and isobutylene, and styrene monomers such as styrene and p-methylstyrene.

[0043] The polymer (F) comprises preferably more than 25% by moles, preferably more than 30% by moles of recurring units derived from at least one monomer (MF).

[0044] The polymer (F) comprises preferably more than 1 % by moles, preferably more than 5% by moles, more preferably more than 10% by moles of recurring units derived from at least one monomer (H) different from the monomer (OH).

[0045] The monomer (MF) can further comprise one or more other halogen atoms (Cl, Br, I). Should the fluorinated monomer be free of hydrogen atoms, it is designated as per(halo)fluoromonomer.

[0046] Should the monomer (MF) comprise at least one hydrogen atom, it is designated as hydrogen-containing fluorinated monomer.

[0047] Should the monomer (MF) be a hydrogen-containing fluorinated monomer, such as for instance vinylidene fluoride, trifluoroethylene, vinyl fluoride, the polymer (F) is either a polymer comprising recurring units derived from said hydrogen-containing fluorinated monomer and at least one monomer (OH) as defined above, or it is a polymer comprising recurring units derived from said hydrogen-containing fluorinated monomer, at least one monomer (OH) as defined above and at least one other monomer.

[0048] Should the monomer (MF) be a per(halo)fluoromonomer, such as for instance tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, perfluoroalkylvinylethers, the polymer (F) is a polymer comprising recurring units derived from said per(halo)fluoromonomer, at least one monomer(OH) as defined above and at least one monomer (H) different from the monomer (OH).

[0049] Preferred polymers (F) are those comprising one or more backbone chains, said backbone chains comprising recurring units derived from at least one monomer (MF) selected from the group consisting of vinylidene fluoride (VDF), tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE).

[0050] The polymer (F) is more preferably selected from the group consisting of:- polymers (F-1 ) comprising recurring units derived from vinylidene fluoride (VDF), at least one monomer (OH) as defined above and, optionally, at least one monomer (MF) different from VDF, and- polymers (F-2) comprising recurring units derived from at least one per(halo)fluoromonomer selected from tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE), at least one monomer (H) selected from ethylene, propylene and isobutylene, and at least one monomer (OH) as defined above, optionally comprising one or more additional monomers, typically in amounts of from 0.01 % to 30% by moles, based on the total amount of TFE and / or CTFE and said monomer (H).

[0051] The polymer (F-1 ) preferably comprises:(a) at least 60% by moles, preferably at least 75% by moles, more preferably at least 85% by moles of vinylidene fluoride (VDF);(b) optionally, from 0.1% to 15% by moles, preferably from 0.1 % to 12% by moles, more preferably from 0.1 % to 10% by moles of at least one monomer (MF) selected from vinyl fluoride (VFi), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE); and(c) from 0.01 % to 20% by moles, preferably from 0.05% to 18% by moles, more preferably from 0.1 % to 10% by moles of at least one monomer (OH) of formula (III) as defined above.

[0052] In polymers (F-2) as defined above, the molar ratio per(halo)fluoromonomer(s) / monomer(s) (H) is typically of from 30:70 to 70:30. In polymers (F-2) as defined above, the monomer (H) is preferably ethylene, optionally in combination with other monomers (H).

[0053] Polymers (F-2) wherein the per(halo)fluoromonomer is predominantly chlorotrifluoroethylene (CTFE) will be identified herein below as ECTFE copolymers; polymers (F-2) wherein the per(halo)fluoromonomer is predominantly tetrafluoroethylene (TFE) will be identified herein below as ETFE copolymers.

[0054] The polymer (F-2) preferably comprises:(a’) from 35% to 65% by moles, preferably from 45% to 55% by moles, more preferably from 48% to 52% by moles of at least one per(halo)fluoromonomer selected from the group consisting of chlorotrifluoroethylene (CTFE) and tetrafluoroethylene (TFE);(b’) from 35% to 65% by moles, preferably from 45% to 55% by moles, more preferably from 48% to 52% by moles of ethylene; and(c’) from 0.01 % to 20% by moles, preferably from 0.05% to 18% by moles, more preferably from 0.1 % to 10% by moles of at least one monomer (OH) of formula (III) as defined above.

[0055] Among polymers (F-2), ECTFE polymers are preferred.

[0056] The polymer (F) is even more preferably selected from polymers (F-1 ) as defined above.

[0057] The polymer (F) is typically obtainable by emulsion polymerization or suspension polymerization, according to methods known to the person skilled in the art.

[0058] The compound (M1)

[0059] In the at least one metal compound (M1 ) of formula (I)X4-mAYm (I) wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, the selection of the hydrolysable group Y is not particularly limited, provided that it enables under appropriate conditions the formation of a - O-A= bond.

[0060] The hydrolysable group Y is typically selected from the group consisting of halogen atoms, preferably being a chlorine atom, hydrocarboxy groups, acyloxy groups and hydroxyl groups.

[0061] The compound (M1 ) is preferably of formula (l-A):RA4-mA(0RB)m (l-A) wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, RA, equal to or different from each other and at each occurrence, is a C1-C12 hydrocarbon group comprising at least one - N=C=O functional group and RB, equal to or different from each other and at each occurrence, is a C1-C5 linear or branched alkyl group, preferably RBbeing a methyl or ethyl group.

[0062] The compound (M1 ) is preferably of formula (l-B): O=C=N-RA’-A-(ORB’)3(l-B) wherein A is a metal selected from the group consisting of Si, Ti and Zr, RA’, equal to or different from each other and at each occurrence, is a linear or branched C1-C12 hydrocarbon group and RB, equal to or different from each other and at each occurrence, is a C1-C5 linear or branched alkyl group, preferably RBbeing a methyl or ethyl group.

[0063] Non-limitative examples of suitable compounds (M1 ) include the followings: trimethoxysilyl methyl isocyanate, triethoxysilyl methyl isocyanate, trimethoxysilyl ethyl isocyanate, triethoxysilyl ethyl isocyanate, trimethoxysilyl propyl isocyanate, triethoxysilyl propyl isocyanate, trimethoxysilyl butyl isocyanate, triethoxysilyl butyl isocyanate, trimethoxysilyl pentyl isocyanate, triethoxysilyl pentyl isocyanate, trimethoxysilyl hexyl isocyanate and triethoxysilyl hexyl isocyanate.

[0064] The liquid medium (L)

[0065] For the purpose of the present invention, by the term “liquid medium” it is hereby intended to denote a composition comprising one or more substances, which is suitable for solubilising the metal salt (MS).

[0066] The amount of the medium (L) in the composition (C) is typically at least 40% by weight, preferably at least 50% by weight, more preferably at least 60% by weight, based on the total weight of said medium (L) and the polymer (F).

[0067] Very good results have been obtained using a composition (C) comprising at least 50% by weight, preferably at least 70% by weight of the medium (L), based on the total weight of said medium (L) and the polymer (F).

[0068] The medium (L) preferably comprises at least one organic carbonate and / or at least one ionic liquid, triethyl phosphate (TEP), or sulfolane.

[0069] Non-limitative examples of suitable organic carbonates include, notably, ethylene carbonate, propylene carbonate, mixtures of ethylene carbonate and propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate and mixtures thereof.

[0070] In the present invention, a liquid medium (L) differs from a solvent (S).

[0071] For the purpose of the present invention, the term ’’ionic liquid” is intended to denote a compound formed by the combination of a positively charged cation and a negatively charged anion in the liquid state at temperatures below 100°C under atmospheric pressure.

[0072] The ionic liquid typically contains:- a positively charged cation selected from the group consisting of imidazolium, pyridinium, pyrrolidinium, piperidinium and ammonium ions optionally containing one or more C1-C30 alkyl groups, and- a negatively charged anion selected from the group consisting of halides, perfluorinated anions and borates.

[0073] The metal salt (MS)

[0074] The metal salt is typically selected from the group consisting of Mel, Me(PF6)n, Me(BF4)n, Me(CIO4)n, Me(bis(oxalato)borate)n("Me(BOB)n"), MeCF3SO3, Me[N(CF3SO2)2]n, Me[N(C2F5SO2)2]n, Me[N(CF3SO2)(RFSO2)]n with RF being C2F5, C4F9, CF3OCF2CF2, Me(AsFe)n, Me[C(CF3SO2)3]n, Me2Sn, MeTDI (2-trifluoromethyl-4,5-dicyanoimidazole), wherein Me is a metal, preferably a transition metal, an alkaline metal or an alkaline-earth metal, more preferably Me being Li, Na, Mg, K, Cs, and n is the valence of said metal, typically n being 1 or 2.

[0075] The metal salt is preferably selected from the group consisting of Lil, LiPFe, LiBF4, LiCIC , lithium bis(oxalato)borate ("LiBOB"), LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, M[N(CF3SO2)(RFSO2)]n with RFbeing C2F5, C4F9, CF3OCF2CF2, LiAsFe, LiC(CF3SO2)3, Li2Sn, lithium 2-trifluoromethyl- 4,5-dicyanoimidazole (LiTDI) and combinations thereof.

[0076] The concentration of the metal salt in the medium (L) is advantageously at least 0.01 M, preferably at least 0.025 M, more preferably at least 0.05 M.

[0077] The concentration of the metal salt in the medium (L) is advantageously at most 1 .3 M, preferably at most 0.9 M, more preferably at most 0.8 M.

[0078] The Lewis base additive (A)

[0079] The Lewis base additive additive (A) is preferably selected from the group consisting of tris(2, 2, 2-trif luoroethy l)phosph ite (TTFP), hexamethyldisilazane, heptamethyldisilazane, 1 -(trim ethy Isi ly l)im idazole, trimethylamine, tris(trimethylsilyl)phosphite, diethyl phenylphosphonite, triethly Iphosphite, hexamethyl-phosphoramide, 1 -methyl-2-pyrrolidinone, tris(trimethylsilyl)phosphate, tri(phenyl phosphite), trimethyl phosphite, tris(pentafluorophenyl) borane, triphenyl phosphine oxide, hexamethylphosphoramide, hexakis(2,2,2-trifluoroethoxy) cyclotriphosphazene (HFEPN), tris(pentafluorophenyl)borane (TPFPB), tris(trimethylsilyl)borate (TMSB) and triphenylborane (TPB).

[0080] The compound (M2)

[0081] In the at least one metal compound [compound (M2)] of formula (II): X’4-m A’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consisting of Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; the selection of the hydrolysable group Y’ is not particularly limited, provided that it enables under appropriate conditions the formation of a -O-A= bond.

[0082] The hydrolysable group Y’ is typically selected from the group consisting of halogen atoms, preferably being a chlorine atom, hydrocarboxy groups, acyloxy groups and hydroxyl groups.

[0083] In case the compound (M2) of formula (II) as defined above comprises at least one functional group different from the -N=C=O functional group on group X’, it will be designated as functional compound (M2); in case none of groups X’ comprise a functional group different from the -N=C=O functional group, the compound (M2) of formula (II) as defined above will be designated as non-functional compound (M2).

[0084] Mixtures of one or more functional compounds (M2) and one or more nonfunctional compounds (M2) may be used in the process of the invention.

[0085] Functional compounds (M2) can advantageously further modify the chemistry and the properties of the polymer (F-g) over native polymer (F) and native inorganic phase.

[0086] The compound (M2) is preferably of formula (ll-A): RC4-m’A(0RD)m’ (ll-A) wherein m’ is an integer from 1 to 4, and, according to certain embodiments, from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Rcand RD, equal to or different from each other and at each occurrence, are independently selected from C1-C18 hydrocarbon groups, wherein Rcoptionally comprises at least one functional group different from the -N=C=O functional group.

[0087] Non limitative examples of functional groups different from the -N=C=O functional group include, notably, epoxy group, carboxylic acid group (in its acid, ester, amide, anhydride, salt or halide form), sulphonic group (in its acid, ester, salt or halide form), hydroxyl group, phosphoric acid group (in its acid, ester, salt, or halide form), thiol group, amine group, quaternary ammonium group, ethylenically unsaturated group (like vinyl group), cyano group, urea group, organo-silane group, aromatic group.

[0088] Should the compound (M2) be a functional compound (M2), it is more preferably of formula (ll-B): RC4-m”A(0RD)m” (ll-B) wherein m” is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Rc, equal to or different from each other and at each occurrence, is a C1-C12 hydrocarbon group comprising at least one functional group different from the -N=C=O functional group and RD, equal to or different from each other and at each occurrence, is a C1-C5 linear or branched alkyl group, preferably RD’ being a methyl or ethyl group.

[0089] Examples of functional metal compound of formula (I) are notably vinyltriethoxysilane, vinyltrimethoxysilane, vinyltrismethoxyethoxysilane of formula CH2=CHSi(OC2H4OCH3)3, 2-(3,4- epoxycyclohexylethyltrimethoxysilane) of formula:glycidoxypropylmethyldiethoxysilane of formula:glycidoxypropyltrimethoxysilane of formula:methacryloxypropyltrimethoxysilane of formula:aminoethylaminpropylmethyldimethoxysilane of formula:am inoethylam inpropyltrimethoxysilane of formula:H2NC2H4NHC3H65i(OCH3)33-aminopropyltriethoxysilane, 3-phenylaminopropyltrimethoxysilane, 3- chloroisobutyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3- mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, n-(3- acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, (3- acryloxypropyl)dimethylmethoxysilane, (3- acryloxypropyl)methyldichlorosilane, (3- acryloxypropyl)methyldimethoxysilane, 3-(n- allylamino)propyltrimethoxysilane, 2-(4- chlorosulfonylphenyl)ethyltrimethoxysilane, 2-(4- chlorosulphonylphenyl)ethyl trichlorosilane, carboxyethylsilanetriol, and its sodium salts, triethoxysilylpropylmaleamic acid of formula:3-(trihydroxysilyl)-1 -propane-sulphonic acid of formula HOSO2- CH2CH2CH2-Si(OH)3, N-(trimethoxysilylpropyl)ethylene-diamine triacetic acid, and its sodium salts, 3-(triethoxysilyl)propylsuccinic anhydride of formula:acetamidopropyltrimethoxysilane of formula H3C-C(O)NH-CH2CH2CH2- Si(OCH3)3, alkanolamine titanates of formula Ti(A)x(OR)y, wherein A is an amine-substitued alkoxy group, e.g. OCH2CH2NH2, R is an alkyl group, and x and y are integers such that x+y = 4.

[0090] Examples of non-functional compounds (M2) are notably trimethoxysilane, triethoxysilane, tetramethoxysilane, tetraethoxysilane (TEOS), tetramethyltitanate, tetraethyltitanate, tetra-n-propyltitanate, tetraisopropyltitanate, tetra-n-butyltitanate, tetra-isobutyl titanate, tetra-tert- butyl titanate, tetra-n-pentyltitanate, tetra-n-hexyltitanate, tetraisooctyltitanate, tetra-n-lauryl titanate, tetraethylzirconate, tetra-n- propylzirconate, tetraisopropylzirconate, tetra-n-butyl zirconate, tetra-sec- butyl zirconate, tetra-tert-butyl zirconate, tetra-n-pentyl zirconate, tetra-tert- pentyl zirconate, tetra-tert-hexyl zirconate, tetra-n-heptyl zirconate, tetra-n- octyl zirconate, tetra-n-stearyl zirconate.

[0091] The solvent (S)

[0092] The choice of the solvent (S) is not particularly limited provided that it is suitable for solubilising the polymer (F).

[0093] Non-limitative examples of suitable solvents (S) include, notably, the followings:- aliphatic, cycloaliphatic or aromatic ether oxides, more particularly, diethyl oxide, dipropyl oxide, diisopropyl oxide, dibutyl oxide, methyltertiobutylether, dipentyl oxide, diisopentyl oxide, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether benzyl oxide; dioxane, tetrahydrofuran,- glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycolmono-n-butyl ether,- glycol ether esters such as ethylene glycol methyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate,- alcohols such as methyl alcohol, ethyl alcohol, diacetone alcohol,- ketones such as acetone, methylethylketone, methylisobutyl ketone, diisobutylketone, cyclohexanone, isophorone, and- linear or cyclic esters such as isopropyl acetate, n-butyl acetate, methyl acetoacetate, dimethyl phthalate, g-butyrolactone;- linear or cyclic amides such as N,N-diethylacetamide, N,N- dimethylacetamide, N,N-dimethylformamide and N-methyl-2-pyrrolidone; and- dimethyl sulfoxide.

[0094] The process

[0095] In a first phase (a) of the process for manufacturing polymer (F-h), at least a fraction of the hydroxyl groups of the monomer (OH) of polymer (F) reacts with at least a fraction of compound (M1 ) and, optionally, at least a fraction of compound (M2) thereby providing a composition [composition (C1 )] comprising at least one grafted fluoropolymer [polymer (F-g)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer [monomer (HH)], said monomer (HH) comprising at least one pendant side chain comprising an end group of formula -O-C(O)-NH-Z-AYmX3-m (M1 -g), wherein m, Y, A, X have the same meaning as defined above and Z is a hydrocarbon group, optionally comprising at least one -N=C=O functional group, and, optionally, at least one pendant side chain comprising an end group of formula -0-A’Y’m -iX’4-m’ (M2-g), wherein m’, Y’, A’, X’ have the same meaning as defined above.

[0096] The skilled in the art will properly select the temperature in the phase (a) of the process, depending on the boiling point of the medium (L) and of solvent (S).

[0097] Under phase (a) of the process of the invention, advantageously at least one condensation catalyst is further added to the mixer-reactor where the process of the invention takes place.

[0098] The condensation catalyst is typically added in an amount comprised between 0.1 % and 50% by moles, preferably between 1 % and 25% by moles, more preferably between 5% and 15% by moles, based on the total amount by moles of compound (M1 ) and, optionally, compound (M2).

[0099] The condensation catalyst is preferably selected from the group consisting of organic tin compounds and manganese compounds, such as manganese (III) acetylacetonate (Mn(Acac)s).

[0100] Non-limitative examples of organic tin compounds suitable as condensation catalysts in the process of the invention include, notably, dibutyltin dilaurate, dibutyltin oxide, tributyltin oxide, dioctyltin oxide, methyltin mercaptide, tributyltin chloride and tributyltin fluoride.

[0101] In a second phase (b) of the process for the manufacture of polymer (F-h), the end groups of formula -O-C(O)-NH-Z-AYmX3-m (M1 -g) and, optionally, the end groups of formula -0-A’Y’m -iX’4-m’ (M2-g) of the polymer (F-g) undergo hydrolysing and / or condensing thereby providing a composition [composition (C)] comprising at least one fluoropolymer hybrid organic / inorganic composite [polymer (F-h)], a liquid medium (L), a metal salt (MS) and a solvent (S).

[0102] The hydrolysis and / or condensation under phase (b) is usually carried out at room temperature or upon heating at a temperature lower than 150°C. The temperature will be selected having regards to the boiling point of the medium (L) and of solvent (S). Temperatures between 50°C and 120°C will be preferred.

[0103] It is understood that, while the hydrolysis and / or condensation reaction may be initiated during phase (a) of the process of the invention, said reaction may be continued during phase (b) of the process of the invention.

[0104] As this will be recognized by the skilled in the art, the hydrolysis and / or condensation usually generates low molecular weight side products, which can be notably water or alcohols, as a function of the nature of the compound (M1 ) and, optionally, of the compound (M2).

[0105] An acid catalyst is typically added to the composition of any one of phases (a) or (b) of the process of the invention.

[0106] The selection of the acid catalyst is not particularly limited. The acid catalyst is typically selected from the group consisting of organic and inorganic acids.

[0107] The acid catalyst is typically added in an amount comprised between 0.5% and 10% by weight, preferably between 1 % and 5% by weight, based on the total weight of the composition.

[0108] The acid catalyst is preferably selected from the group consisting of organic acids.

[0109] Very good results have been obtained with formic acid.

[0110] The ingredients to be reacted are preferably fed into the mixer-reactor in sequence, so that the phases of the process of the invention occur in due time.

[0111] Preferably, the ingredients are added into the mixer-reactor in the following order of addition:- polymer (F);- solvent (S)- condensation catalyst;- compound (M1 );- liquid medium (L), containing the metal salt (MS) and the additive (A);- acid catalyst;- optionally compound (M2).

[0112] The skilled person will adapt the preferred addition time of the sequence of ingredients to the temperature in the mixer-reactor.

[0113] Usually, the ingredients are mixed for about 1 to 10 hours to obtain a solution and completing the reaction.

[0114] Polymer (F), the compound (M1 ) of formula (I) and, optionally, the compound (M2) of formula (II) are reacted at temperatures typically comprised between 50°C and 150°C. Temperatures between 50°C and 100°C will be preferred.

[0115] The reaction mixture typically comprises at least one compound (M1 ) of formula (I) in an amount comprised between 0.1 % and 95% by weight, preferably between 0.5% and 50% by weight, more preferably between1 % and 25% by weight, based on the total weight of the polymer (F), the compound (M1 ) and, optionally, the compound (M2).

[0116] The reaction mixture may further comprise at least one inorganic filler [filler (I)].

[0117] The choice of the filler (I) is not particularly limited.

[0118] The filler (I) is typically provided in the form of solid particles.

[0119] The filler (I) particles generally have an average particle size of from 0.001 pm to 200 pm, preferably of from 0.01 pm to 50 pm, more preferably of from 0.03 pm to 10 pm.

[0120] The reaction mixture typically comprises at least one filler (I) different from the either the compound (M1 ) or the compound (M2) in an amount of from 60% to 95% by weight, more preferably of from 65% to 90% by weight, with respect to the total weight of the polymer (F) and the filler (I).

[0121] Among fillers (I) suitable for being used in the process of the invention, mention can be made of inorganic oxides, including mixed oxides, metal sulphates, metal carbonates, metal sulphides and the like.

[0122] A class of compounds which gave particularly good results within the context of the present invention are notably silicates, aluminium-silicates and magnesium silicates, all optionally containing additional metals such as sodium, potassium, iron or lithium.

[0123] These silicates, aluminium-silicates and magnesium silicates, all optionally containing additional metals such as sodium, potassium, iron or lithium, can be notably smectic clays, possibly of natural origin, such as notably montmorillonites, sauconite, vermiculite, hectorite, saponite, nontronite. As an alternative, silicates, aluminium-silicates and magnesium silicates, all optionally containing additional metals such as sodium, potassium, iron or lithium, can be selected among synthetic clays, like notably fluorohectorite, hectorite, laponite.

[0124] The filler (I) may be also selected from ion-conducting inorganic filler materials.

[0125] For the purpose of the present invention, by the term “ion-conducting” it is hereby intended to denote a material allowing electrolyte ions to flow there through.

[0126] Non-lim itative examples of suitable ion-conducting inorganic filler materials include, notably, lithium ceramics such as LiTaOs-SrTiOs, LiTi2(PO4)3-Li2O and Li4SiO4-Li3PO4.

[0127] Also, fillers (I) having on their surface reactive groups towards the compound (M1 ) can be used in the process of the invention.

[0128] Among surface reactive groups, mention is notably made of hydroxyl groups.

[0129] Without being bound by this theory, the Applicant believes that reaction between at least a fraction of the hydrolysable group(s) Y of the compound (M1 ) with at least a fraction of said surface reactive groups of the filler (I) can occur simultaneously with the reaction of at least a fraction of the hydrolysable group(s) Y of the compound (M1 ) with at least a fraction of the hydroxyl groups of the polymer (F) so that, in subsequent hydrolysis and / or condensation, chemical bonding between the polymer (F) and the filler (I) is likely achieved through the inorganic domains derived from the compound (M1 ).

[0130] The filler (I) is preferably selected among inorganic oxides.

[0131] Non-limitative examples of suitable inorganic oxides include, notably, SiC>2, TiO2, ZnO, AI2O3.

[0132] The polymer (F-h) may be suitably processed in the form of a film.

[0133] In another object, the present invention provides a fluoropolymer film comprising at least one fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] according to the present invention.

[0134] The process for the manufacture of a fluoropolymer film comprising at least one fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] comprises a step (i) or providing a composition (C) by: i) reacting:- at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)], with- at least one metal compound [compound (M1 )] of formula (I): X4-mAYm (I)wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, and- optionally, at least one metal compound [compound (M2)] of formula (II): X’4-mA’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consisting of Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; in the presence of- a liquid medium [medium (L)];- at least one metal salt [salt (MS)];- at least one Lewis base additive [additive (A)];- a solvent (S); ii) processing into a film the composition (C) provided in step i); and iii) drying the film provided in step ii).

[0135] Under step (ii) of the process of the invention, the composition (C) is applied onto the surface of an inert substrate typically by any suitable procedures such as casting, printing and roll coating.

[0136] Under step (iii) 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).

[0137] The drying temperature will be selected so as to effect removal by evaporation of the solvent (S).

[0138] The film or the polymer (F-h) provided in step iii) of the process of the invention may be further submitted to a post-treatment step, preferably may be further submitted to compression, typically at a temperature comprised between 50 and 300°C, depending on the melting point and vapor tension of polymer (F).

[0139] The film of a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] obtained by the process of the present invention is particularlysuitable for use as polymer electrolyte membrane in secondary batteries that comprise gelled electrodes.

[0140] In a further aspect, thus, the present invention provides a polymer electrolyte membrane comprising a film of a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] obtainable by the process defined above.

[0141] The Applicant has found that when the film of polymer (F-h) is obtained by the process of the present invention where a Lewis base additive [additive (A)] is added to the reaction mixture, said film is endowed with improved stability.

[0142] Further, when the film of polymer (F-h) is used for the manufacture of a polymer electrolyte membrane for use in secondary batteries, the cycling, especially at high C rates, of said battery is substantially improved.

[0143] In one aspect, the present invention provides an electrochemical device being a secondary battery comprising:- a polymer electrolyte membrane comprising a film polymer (F-h) obtained by the process of the present invention, and- a positive electrode and a negative electrode, wherein the positive and negative electrodes are gelled electrodes.

[0144] For the purpose of the present invention, the term “gelled electrode” is intended to denote an electrode comprising a current collector, and adhered to said current collector at least a binder composition comprising:- at least one polymer (F) as above defined,- at least one electro-active compound (EA),- a liquid medium (L) as above defined,- optionally, at least one metal salt (MS) as above defined,- optionally, at least one conductive compound, and- optionally, one or more additives.

[0145] Gelled electrodes can be prepared according to the prior art, for examples as described in EP3140876, EP3329529, EP3963650 and EP4008031.

[0146] For the purpose of the present invention, the term “electro-active compound” 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 dischargingphase of an electrochemical device. The electrode active material is preferably able to incorporate or insert and release lithium ions.

[0147] The nature of the electrode active material (AM) depends on whether said composition is used in the manufacture of a negative electrode or a positive electrode.

[0148] The binder composition in at least one of the gelled electrodes may comprise a Lewis base additive (A) as above defined.

[0149] When at least one of the gelled electrodes comprising additive (A) is placed in a secondary battery that includes the polymer electrolyte membrane comprising the film of polymer (F-h) of the present invention, said additive (A) can migrate from any of a positive electrode and a negative electrode towards the polymer electrolyte membrane; then, the additive (A) and can be distributed homogeneously throughout the cell, thus improving the stability of the membrane and the operation of the secondary battery itself.

[0150] In one embodiment, therefore, the present invention provides a secondary battery comprising: i) - a polymer electrolyte membrane comprising a film of a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)], obtained by a process comprising reacting:- at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)], with- at least one metal compound [compound (M1 )] of formula (I): X4-mAYm (I) wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, and- optionally, at least one metal compound [compound (M2)] of formula (II): X’4-mA’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consistingof Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; in the presence of- a liquid medium [medium (L)];- at least one metal salt [salt (MS)];- at least one Lewis base additive [additive (A)];- a solvent (S); ii) processing into a film the composition (C) provided in step i); and drying the film provided in step ii); and- a positive electrode and a negative electrode, wherein both the positive and negative electrodes are gelled electrodes comprising a current collector, and adhered to said current collector at least a binder composition comprising:- at least one polymer (F) as above defined,- at least one electro-active compound (EA),- a liquid medium (L) as above defined,- optionally, at least one metal salt (MS) as above defined,- optionally, at least one conductive compound,- optionally, one or more additives, and- a Lewis base additive (A) as above defined.

[0151] The film of polymer (F-h) obtained by the process of the present invention is advantageously endowed with outstanding crosslinking density properties and thus successfully exhibits outstanding mechanical properties to be suitably used as a free-standing polymer electrolyte membrane.

[0152] Determination of the crosslinking density of the film of polymer (F-h) of the present invention can be performed by any suitable method. A specimen of the film of polymer (F-h) is typically swollen in a suitable solvent at a specific temperature and either the change in mass or the change in volume is measured.

[0153] It has been surprisingly found that the free-standing film of polymer (F-h) obtained by the process of the present invention can stably comprise andretain high fractions of electrolytes while maintaining outstanding mechanical properties and excellent ionic conductivity properties.

[0154] The Applicant has found that the film of polymer (F-h) obtained by the process of the present invention has a similar or even improved performance in terms of cyclability when used as polymer membrane electrolyte in secondary batteries.

[0155] Moreover, the film of polymer (F-h) obtained by the process of the invention has the further advantage of having improved homogeneity and discolouration.

[0156] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0157] The invention will be now described in more detail with reference to the following examples whose purpose is merely illustrative and not limitative of the scope of the invention.

[0158] Raw materials

[0159] Polymer F-A: VDF / HEA (0.4% by moles) / HFP (2.5% by moles) copolymer having an intrinsic viscosity of 0.11 l / g in DMF at 25°C.

[0160] Tetraethylorthosilicate (TEOS) commercially available as liquid from Aldrich Chemistry purity >99%.

[0161] Polymer 1 : VDF-AA (0.9% by moles)-HFP (2.4% by mole) polymer having an intrinsic viscosity of 0.30 l / g in DMF at 25°C.

[0162] LiPFe: Lithium hexafluorophosphate (Battery Grade) commercially available from Fluorochem.

[0163] NMC: LiNio.6Mno.2Coo.2O2, commercially available from Umicore.

[0164] Liquid medium (L-1 ): a mixture of ethylene carbonate (EC, anhydrous, 99%, commercially available from Sigma Aldrich / Merck) and propylene carbonate (PC, anhydrous, 99.7%, commercially available from Sigma Aldrich / Merck) (1 / 1 by volume) in which LiPFe (1 mol / L) and vinylene carbonate (VC) (2% by weight, commercially available from Sigma Aldrich / Merck) were dissolved.

[0165] Graphite: 75% SMG N-HE1 (Hitachi Chemical Co., Ltd.) / 25% TIMREX® SFG 6.

[0166] Additive (A-1 ): Tris(2,2,2-trifluoroethyl) phosphite

[0167] DBTDL: dibutyl tin dilaurate, commercially available from Sigma Aldrich.

[0168] Mn(acac)3: Manganese(lll) acetylacetonate, commercially available from Sigma Aldrich.

[0169] TSPI: 3-(triethoxysilyl) propyl isocyanate, commercially available from Sigma Aldrich.

[0170] Determination of intrinsic viscosity of polymer (F)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], qris the relative viscosity, i.e. the ratio between the dropping time of sample solution and the dropping time of solvent, qspis the specific viscosity, i.e. qr-1, and T is an experimental factor, which for polymer (F) corresponds to 3.

[0171] Dissolution test

[0172] A sample of about 5-10 mg of film was placed in about 10 mL of N,N- dimethylformamide (DMF) for 60 minutes at room temperature. As it is well known, DMF is a very good solvent for polymers (F). The more crosslinking density of the film, the more swelling and less dissolution of the film in DMF is attainable. On the contrary, a poor crosslinked film will lead to a mostly dissolution of the film in DMF.

[0173] Example 1 : manufacture of a film according to the invention

[0174] The polymer (F-A) (10 g) was dissolved in 68.13 g of acetone at 60°C thereby providing a solution containing 12.8% by weight of said polymer. The solution was homogeneous and transparent after homogenization. DBTDL (0.052 g) was then added. The solution was homogenized at 60°C. TSPI (0.21 g) was added thereto. The quantity of DBTDL was calculated to be 10% by moles vs. TSPI. TSPI itself was calculated to be 0.55% by mole vs. the polymer (F-A). The solution was kept at 60°C for about 90 min so as to let isocyanate functional groups of TSPI to react with the hydroxyl groups of the polymer (F-A)In the next step, a mixture of the Liquid Medium (L-1 ) comprising 5 wt% additive (A-1 ), relative to the total weight of Liquid Medium (L-1 ), was added to the solution so obtained.The weight ratio [muvi I (rriLM + m polymer (F-AJ)] was 80%.After homogenization at 60°C, formic acid was added.TEOS was then added thereto. The quantity of TEOS was calculated from the weight ratio (msio2 / m polymer (F-AJ) assuming total conversion of TEOS into SiO2. This ratio was 10%.The quantity of formic acid was calculated from the following equation: nformic acid I HTEOS=2.7.All the ingredients were fed to the solution mixture so obtained under Argon atmosphere. The solution mixture was spread with a constant thickness onto a PET substrate using a roll-to roll coating machine (reverse comma bar coater) in a dry room (dew point: - 20°C). The thickness was controlled by the distance between the knife (comma bar) and the steel roll (applicator roll) and the distance between the two rolls (applicator and transfer (also named rubber roll)).The solvent was quickly evaporated from the solution mixture in the machine oven and the membrane was obtained. After a few hours, the membrane was detached from the PET substrate. The membrane so obtained had a constant thickness of 60 pm.

[0175] The membrane was not dissolved in DMF according to the test described above.

[0176] Example 2- Comparative

[0177] Example 1 was repeated in absence of any additive (A).

[0178] General procedure for the manufacture of electrodes

[0179] A solution of polymer 1 in acetone was prepared at room temperature in dry room (about 40 min for dissolution).

[0180] Negative electrode: Graphite was added to the solution so obtained in a weight ratio of 95 / 5 (graphite / polymer 1 ).

[0181] Positive electrode: A composition comprising a blend of 50% by weight of C-NERGY® SUPER C65 carbon black and 50% by weight of VGCF® carbon fiber (CF) was added. After 15 min of dispersion, NMC was addedto the solution so obtained in a weight ratio of 96 / 4 ((C65+CF+NMC) / polymer 1 ).

[0182] Composition of the positive electrode: NMC 93 wt %, C65 2 w%, VGCF 1 wt % and Polymer 1 4 wt %.

[0183] In the last step, a mixture of ethylene carbonate (EC) and propylene carbonate (PC) (1 / 1 by volume) in which LiPFe (1 mol / l) and vinylene carbonate (VC) (2% by weight) were dissolved was added to the solutions so obtained (anode and cathode).

[0184] The weight ratio [rriEs / (rriEs + mPoiymeri)] x 100 was 75.2% for the cathode and 80% for the anode. After mixing, if needed, additional acetone can be added to the mixture to adjust the viscosity.

[0185] Casting procedure

[0186] The negative electrode and positive electrode solution mixtures were spread or casted with a constant thickness onto a metal collector using a roll-to-roll coating machine reverse comma bar coater in a dry room (dew point: -20). The thickness was controlled by the distance between the knife (comma bar) and the steel roll (applicator roll) and the distance between the two rolls (applicator and transfer (also named rubber roll)).

[0187] The thickness of the wet layer of the anode so obtained was about 130 pm. The thickness of the wet layer of the cathode so obtained was about 155 pm.The viscosity of the mixture was tuned by adding acetone. The solvent was then evaporated from said mixture in the machine oven thereby providing the electrode.

[0188] General procedure for the manufacture of a Lithium-ion battery

[0189] A coin cell was prepared by placing the film prepared according to examples 1 and 2 above between the cathode (2.4 mAh / cm2) and the anode (2.8 mAh / cm2) prepared according to the general procedure as detailed above.

[0190] The coin cell was cycled between 2.8 V and 4.2 V.

[0191] After a step of 2 cycles at C / 20 - D / 20, the test protocol was carried out according to successive series of 5 cycles at C / 10 - D / 10, C / 5 - D / 5, C / 2 - D / 2, C / 2 - D, C / 2 - 2D.

[0192] The results are shown in Table 1 below.Table 1

[0193] As it can be seen the performance of the coin cell made including the films obtained by the process of the present invention is better than that of the coin cells including the films obtained in the absence of Additive (A), especially at high D rate, where the performance of the battery needs to be improved.

Claims

Claims1 . A process for manufacturing a film of a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)], said process comprising reacting:- at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)], with- at least one metal compound [compound (M1 )] of formula (I):X4-mAYm (I) wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, and- optionally, at least one metal compound [compound (M2)] of formula (II): X’4-mA’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consisting of Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; in the presence of- a liquid medium [medium (L)] comprising at least one organic carbonate and / or at least one ionic liquid, triethyl phosphate (TEP) or sulfolane;- at least one metal salt [salt (MS)] selected from the group consisting of Mel, Me(PF6)n, Me(BF4)n, Me(CI04)n, Me(bis(oxalato)borate)n("Me(BOB)n"), MeCF3SO3, Me[N(CF3SO2)2]n, Me[N(C2F5SO2)2]n, Me[N(CF3SO2)(RFSO2)]n with RF being C2F5, C4F9, CF3OCF2CF2, Me(AsFe)n, Me[C(CF3SO2)3]n, Me2Sn, MeTDI (2-trifluoromethyl-4,5- dicyanoimidazole), wherein Me is a metal, preferably a transition metal, an alkaline metal or an alkaline-earth metal, more preferably Me being Li, Na, K, Cs, and n is the valence of said metal, typically n being 1 or 2;- at least one Lewis base additive [additive (A)]; and- a solvent (S).

2. The process according to claim 1 , wherein the additive (A) is selected from the group consisting of tris(2, 2, 2-trifluoroethy l)phosph ite (TTFP), hexamethyldisilazane, heptamethyldisilazane, 1 -(trim ethy Isi ly l)im idazole, trimethylamine, tris(trimethylsilyl)phosphite, diethyl phenylphosphonite, triethly Iphosphite, hexamethyl-phosphoramide, 1 -methyl-2-pyrrolidinone, tris(trimethylsilyl)phosphate, tri(phenyl phosphite), trimethyl phosphite, tris(pentafluorophenyl) borane, triphenyl phosphine oxide, hexamethylphosphoramide, hexakis(2,2,2-trifluoroethoxy) cyclotriphosphazene (HFEPN), tris(pentafluorophenyl)borane (TPFPB), tris(trimethylsilyl)borate (TMSB) and triphenylborane (TPB).

3. The process according to claim 1 or 2, wherein the polymer (F) may further comprise recurring units derived from at least one hydrogenated monomer [monomer (H)] different from the monomer (OH).

4. The process according to any one of claims 1 to 3, wherein the monomer (OH) of the polymer (F) is selected from the group consisting of (meth)acrylic monomers of formula (III) and vinylether monomers of formula (IV):wherein each of Ri , R2 and R3, equal to or different from each other, is independently a hydrogen atom or a C1-C3 hydrocarbon group, and Rx is a C1- Cs hydrocarbon moiety comprising at least one hydroxyl group.

5. The process according to any one of claims 1 to 4, wherein the polymer (F) is selected from the group consisting of:- polymers (F-1 ) comprising recurring units derived from vinylidene fluoride (VDF), at least one monomer (OH) and, optionally, at least one monomer (MF) different from VDF, and- polymers (F-2) comprising recurring units derived from at least one per(halo)fluoromonomer selected from tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE), at least one monomer (H) selected from ethylene, propylene and isobutylene, and at least one monomer (OH),optionally comprising one or more additional monomers, typically in amounts of from 0.01 % to 30% by moles, based on the total amount of TFE and / or CTFE and said monomer (H).

6. The process according to claim 5, wherein the polymer (F-1 ) comprises:(a) at least 60% by moles, preferably at least 75% by moles, more preferably at least 85% by moles of vinylidene fluoride (VDF);(b) optionally, from 0.1 % to 15% by moles, preferably from 0.1 % to 12% by moles, more preferably from 0.1 % to 10% by moles of at least one monomer (MF) selected from vinyl fluoride (VFi), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE); and(c) from 0.01 % to 20% by moles, preferably from 0.05% to 18% by moles, more preferably from 0.1 % to 10% by moles of at least one monomer (OH) of formula (III) as defined in claim 4.

7. The process according to any one of claims 1 to 6, wherein the compound (M1 ) is of formula (l-A):RA4-mA(0RB)m (l-A) wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, RA, equal to or different from each other and at each occurrence, is a C1-C12 hydrocarbon group comprising at least one -N=C=O functional group and RB, equal to or different from each other and at each occurrence, is a C1-C5 linear or branched alkyl group, preferably RBbeing a methyl or ethyl group.

8. The process according to any one of claims 1 to 7, wherein reaction mixture further comprises at least one condensation catalyst.

9. The process according to any one of claims 1 to 8, wherein the reaction temperature is comprised between 20°C and 100°C.

10. A fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] obtainable by the process of anyone of claims 1 to 9.11 . A process for the manufacture of a fluoropolymer film comprising at least one fluoropolymer hybrid organic / inorganic composite [polymer (F-h)], said process comprising: i) reacting:- at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (MF)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)], with- at least one metal compound [compound (M1 )] of formula (I):X4-mAYm (I) wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one -N=C=O functional group, and- optionally, at least one metal compound [compound (M2)] of formula (II): X’4-mA’Y’m’ (II) wherein m’ is an integer from 1 to 4 and, according to certain embodiments, from 1 to 3, A’ is a metal selected from the group consisting of Si, Ti and Zr, Y’ is a hydrolysable group and X’ is a hydrocarbon group, optionally comprising at least one functional group different from the - N=C=O functional group; in the presence of- a liquid medium [medium (L)];- at least one metal salt [salt (MS)];- at least one Lewis base additive [additive (A)];- a solvent (S) to provide a composition (C); ii) processing into a film the composition (C) provided in step i); and iii) drying the film provided in step ii).

12. A film of a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] obtainable by the process according to claim 11 .

13. A polymer electrolyte membrane comprising a film of a fluoropolymer hybrid organic / inorganic composite [polymer (F-h)] according to claim 12.

14. An electrochemical device being a secondary battery comprising:- a polymer electrolyte membrane comprising a film polymer (F-h) obtained by the process according to claim 11 , and- a positive electrode and a negative electrode, wherein the positive and negative electrodes are gelled electrodes.

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