High performance hybrid polyacrylonitrile composites membranes

Abstract

The present invention pertains to a process for the manufacture of a hybrid organic / inorganic composite, to a polymer electrolyte membrane based on said hybrid and to uses of said electrolyte membrane in various applications, particularly in electrochemical applications.

Description

1 SSPI 2024 / 028High Performance Hybrid Polyacrylonitrile Composites MembranesCross-reference to related applications

[0001] This application claims priority to European application No. 24315486.1 filed on October 18, 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical Field

[0002] The present invention pertains to a process for the manufacture of a hybrid organic / inorganic composite, to a polymer electrolyte membrane based on said hybrid and to uses of said electrolyte membrane in various applications, particularly in electrochemical 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 organic polymer can enhance the toughness and processability of otherwise brittle inorganic materials, whereas the inorganic network formed by alkoxysilanes can enhance scratch resistance, mechanical properties and surface characteristics of said hybrids.

[0006] Polyacrylonitrile (PAN) has different advantages that makes this polymer suitable for the manufacturing of polymer electrolyte membranes, such as good fire resistance (Akashi et al., Electrochimica Acta, Vol. 43, Nos10-11, p1193-1197, 1998) and also good electrochemical stability at high voltages (A. Nagai, Chapter 6 “Lithium Ion Batteries, Sciences et Technologies”, 2009- Springer).

[0007] It was unexpectedly demonstrated by the present inventors that a wide range of hybrid organic / inorganic composites based on PAN can be suitably2 SSPI 2024 / 028 prepared by a process according to the present invention, which makes use of certain versatile metal compounds as grafting agents, with the further advantage of obtaining composites having improved mechanical properties and flexibility.Summary of invention

[0008] It is thus an object of the present invention a process for manufacturing a polyacrylonitrile (PAN) hybrid organic / inorganic composite [polymer (P-h)], said process comprising the following steps:(i) providing a composition [composition (C1)] containing a liquid medium [medium (L)] and at least one PAN-based polymer [polymer (P)], wherein said polymer (P) comprises:- recurring units derived from acrylonitrile (AN), and recurring units derived from at least one hydrogenated vinyl monomer[monomer (HM)] of formula (III):wherein:- Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a C1-C3 hydrocarbon group and Rx, and Rx is a C1-C20 hydrocarbon moiety comprising at least one functional group [group (FX)] selected from the group consisting of: hydroxyl group, amine, carboxylic acid group, thiol group and anhydride;(ii) contacting composition (C1) provided in step (i) with at least a first 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, each occurrence of Y is a hydrolysable group and each occurrence of X is a hydrocarbon group, wherein at least one X is a hydrocarbon group that comprises at least one functional group (FY) selected from epoxy and isocyanate functional groups, thereby providing a composition [composition (C2)];(iii) optionally, contacting composition (C2) with at least a second metal compound [compound (M2)] of formula (II), different from the compound (M1):3 SSPI 2024 / 028X’4-mA’Y’m' (II) wherein m’ is an integer from 1 to 4, A’ is a metal selected from the group consisting of Si, Ti and Zr, each occurrence of Y’ is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group and each occurrence of X’ is a hydrocarbon group.

[0009] A second object of the present invention pertains to the PAN hybrid organic / inorganic composite [polymer (P-h)] obtainable by the process of the invention.

[0010] In another object, the present invention provides a film comprising at least one PAN hybrid organic / inorganic composite [polymer (P-h)] according to the present invention.

[0011] Thus, the invention further pertains to a process for the manufacture of a film comprising at least one PAN hybrid organic / inorganic composite [polymer (P-h)].Description of embodiments

[0012] For the purpose of the present invention, the term “film” is intended to denote a continuous, generally thin, sheet.

[0013] The polymer (P)

[0014] The polymer (P) is typically obtainable by polymerization of acrylonitrile (AN) with at least one hydrogenated vinyl monomer (HM).

[0015] By the term “hydrogenated vinyl monomer [monomer (HM)]” it is hereby intended to denote an ethylenically unsaturated monomer comprising at least one hydrogen atom.

[0016] The term “at least one hydrogenated vinyl monomer” is understood to mean that the polymer (P) may comprise recurring units derived from one or more than one hydrogenated vinyl monomers. In the rest of the text, the expression “hydrogenated vinyl 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 vinyl monomers as defined below.

[0017] The at least one hydrogenated vinyl monomer (HM) is a compound of formula (HI):wherein:4 SSPI 2024 / 028Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a C1-C3 hydrocarbon group and Rx, andRx is a C1-C20 hydrocarbon moiety comprising at least one functional group [group (FX)] selected from the group consisting of: hydroxyl group, amine, carboxylic acid group, thiol group and anhydride. Rxmay further contain other functional groups different from group (FX) and may include heteroatoms.

[0018] The polymer (P) typically comprises from 0.02 % by moles to 20.0 % by moles of recurring units derived from the at least one monomer (HM), the aforementioned percentages by moles being referred to the total moles of recurring units of polymer (P).

[0019] Non limitative examples of monomers (HM) include, notably, methacrylic acid (MAA), itaconic acid (ITA), hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate, acrylic acid (AA).

[0020] When the functional group (FX) in monomer (HM) is an amine, it may be suitably selected from primary and secondary amines. Said amines may be both aliphatic and aromatic amines.

[0021] Determination of average mole percentage of monomer (HM) recurring units in polymer (P) can be performed by any suitable method, used alone or in combination. Mention can be notably made of acid-base titration methods, well suited e.g. for the determination of the carboxylic groups content, of FT-IR methods, of NMR methods, adequate for the quantification of monomers (HM) comprising aliphatic hydrogen atoms in side chains, of weight balance based on total fed monomer (HM) and unreacted residual monomer (HM) during polymer (P) manufacture.

[0022] The polymer (P) is preferably semi-crystalline. The term “semi-crystalline” is hereby intended to denote a polymer that is partially crystalline (organized in definite and regular order) and partially amorphous (random).

[0023] The molecular weight of the polymer (P) suitable for use according to the described process may be within the range of 50 to 3000 kg / mole, typically 90 to 500 kg / mole, more typically 115 to 200 kg / mole.

[0024] The polymer (P) preferably comprises, more preferably consists of:(a) at least 80% by moles, preferably at least 85% by moles, more preferably at least 95% by moles of acrylonitrile (AN); and(b) from 0.01% to 20% by moles, preferably from 0.05% to 5% by moles, more preferably from 0.1% to 2% by moles of at least one monomer (HM)5 SSPI 2024 / 028 of formula (III) as defined above, the aforementioned percentages by moles being referred to the total moles of recurring units of polymer (P).

[0025] The polymer (P) is typically obtainable by emulsion polymerization, suspension polymerization or solution polymerization, according to methods known to the person skilled in the art.

[0026] The average particle size (D50) of the polymer (P) powder is conveniently lower than 1000 microns, most preferably lower than 500 microns, even more preferably lower than 150 microns. The particle size (D50) of the polymer (P) powder is suitably higher than 1 micron, preferably higher than 5 microns, more preferably higher than 10 microns.

[0027] The particle size analysis of the powder can be carried out using laser diffraction according to the ISO 13320 norm. D50 designates the particle diameter where half the population lies below this value and half lies above.

[0028] The liquid medium (L)

[0029] For the purpose of the present invention, by the term “liquid medium [medium (L)]” it is hereby intended to denote a composition comprising one or more organic substances in the liquid state at 20°C under atmospheric pressure.

[0030] According to some embodiments of the present invention, said medium (L) is preferably selected from organic carbonates.

[0031] According to a first embodiment of the invention, said medium (L) comprises at least one organic carbonate as the only medium (L).

[0032] Non-limiting examples of suitable organic carbonates include, notably, ethylene carbonate, propylene carbonate, mixtures of ethylene carbonate and propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl-methyl carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate and mixtures thereof.

[0033] The medium (L) in composition (C1) may further comprise at least one metal salt (MS). By the term “metal salt (MS)”, it is hereby intended to denote a metal salt comprising electrically conductive ions.

[0034] The metal salt (MS)

[0035] A variety of metal salts may be employed as metal salts (MS). Metal salts which are stable and soluble in the chosen liquid medium (L) are generally used.

[0036] Non-limitative examples of suitable metal salts (MS) include, notably, 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)]nwith RF being C2Fs, C4Fg, CF3OCF2CF2, Me(AsFe)n, Me[C(CF3SO2)3]n, Me2Sn,6 SSPI 2024 / 028 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.

[0037] Preferred metal salts (MS) are selected from the followings: Lil, LiPF6, LiBF4, LiCIO4, lithium bis(oxalato) borate ("LiBOB"), LiCF3SO3, LiN(CF3SO2)2(“LiTFSI”), LiN(C2F5SO2)2, M[N(CF3SO2)(RFSO2)]nwith RF being C2F5, C4F9, CF3OCF2CF2, LiAsFe, LiC(CF3SO2)3, Li2Snand combinations thereof.

[0038] The medium (L) in composition (C1) may further comprise one or more additives.

[0039] Should one or more additives be present in the liquid medium, non-limitative examples of suitable additives include, notably, those which are soluble in the liquid medium.

[0040] The concentration of polymer (P) in the medium (L) of composition (C1) is advantageously lower than 40%, more preferably lower than 20% by weight.

[0041] The compound (M1)

[0042] 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, each occurrence of Y is a hydrolysable group and each occurrence of X is a hydrocarbon group comprising at least one functional group (FY) selected from epoxy and isocyanate functional groups.

[0043] The functional group (FY) is preferably an epoxy functional group.

[0044] A is preferably Si.

[0045] 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.

[0046] The hydrolysable group Y is typically selected from the group consisting of alkoxy groups, halogen atoms, preferably being a chlorine atom, hydrocarboxy groups, acyloxy groups and hydroxyl groups.

[0047] The hydrolysable group Y is preferably an alkoxy group.

[0048] According to one embodiment of the invention, the functional group (FY) is an isocyanate -N=C=O functional group.

[0049] The compound (M1) is preferably of formula (l-A):RA4.mA(ORB)m(l-A) wherein m is an integer from 1 to 3, A is a metal selected from the group7 SSPI 2024 / 028 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.

[0050] The compound (M1) is more preferably a compound 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.

[0051] 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.

[0052] According to another embodiment of the invention, the functional group (FY) is an epoxy functional group.

[0053] Examples of compounds (M1) including an epoxy functional group are, notably, [3-(2,3-epoxypropoxy)propyl]triethoxysilane, 2-(3,4- epoxycyclohexylethyltrimethoxysilane) of formula:glycidoxypropylmethyldiethoxysilane of formula:glycidoxypropyltrimethoxysilane of formula:

[0054] The compound (M2)

[0055] Compound (M2) is a compound of formula (II):X’4-mA’Y’m' (II)8 SSPI 2024 / 028 wherein m’ is an integer from 1 to 4, A’ is a metal selected from the group consisting of Si, Ti and Zr, each occurrence of Y’ is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group and each occurrence of X’ is a hydrocarbon group.

[0056] Preferably, X’ in metal compound (M2) is selected from C1-C18 hydrocarbon groups, optionally comprising one or more functional groups. More preferably, X’ in metal compound (M2) is a C1-C12 hydrocarbon group, optionally comprising one or more functional groups.

[0057] The selection of the hydrolysable group Y’ of the metal compound of formula (I) is not particularly limited, provided that it enables in appropriate conditions the formation of a -O-A = bond; said hydrolysable group can be notably a an alkoxy group, an acyloxy group, a hydroxyl group, a halogen atom (especially a chlorine atom), or a hydrocarboxy group.

[0058] Examples of functional metal compound (M2) 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:CH, H2NC2H4NHC3H6S Ii(OCH3)2aminoethylaminpropyltrimethoxysilane of formula:H2NC2H4NHC3H6Si(OCH3)39 SSPI 2024 / 0283-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.

[0059] Examples of non-functional metal compound (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.10 SSPI 2024 / 028

[0060] Compound (M2) may suitably be added to the reaction mixture obtained in step (ii) in the form of solid compound or, alternatively, in an admixture with an aqueous medium (A), possibly including an acid catalyst as defined below.

[0061] By the term “aqueous medium”, it is hereby intended to denote a liquid medium comprising water that is in the liquid state at 20°C under atmospheric pressure.

[0062] The aqueous medium (A) more preferably consists of water and one or more alcohols. The alcohol included in medium (A) is preferably ethanol.

[0063] Composition (C1) may further comprise at least one solvent (S).

[0064] Within the present invention, solvent (S) is intended to denote a solvent suitable for dissolving polymer (P) as defined above. To this aim, solvent (S) is typically selected from the group consisting of: N-methyl-2-pyrrolidone (NMP),N,N-dimethylformamide, N,N-dimethylacetamide and dimethylsulfoxide. These solvents may be used singly or in a mixture of two or more species.

[0065] The process

[0066] In a first phase of the process for manufacturing a polyacrylonitrile (PAN) hybrid organic / inorganic composite [polymer (P-h)], polymer (P) is reacted with compound (M1) and, optionally, with compound (M2).

[0067] The concentration of polymer (P) dispersed in the medium (L) in composition (C1) is advantageously lower than 50%, more preferably lower than 25% by weight.

[0068] The concentration of polymer (P) dispersed in the medium (L) in composition (C1) is advantageously higher than 3%, more preferably higher than 5% by weight.

[0069] The amount of metal salt (MS) in the liquid medium (L) is preferably lower than 1M, more preferably lower than 0.5M. The amount of metal salt (MS) in the liquid medium (L) is preferably higher than 0.05M, more preferably higher thanO.1M.

[0070] In step (ii) of the process for manufacturing polymer (P-h), at least a fraction of the functional groups of the monomer (FX) of polymer (P) reacts with at least a fraction of functional groups (FY) of compound (M1) thereby providing a composition [composition (C2)] comprising at least one grafted PAN [polymer (P-j)] bearing -AYmpendant groups, residual polymer (P) and liquid medium (L).

[0071] The polymer (P) and the metal compound (M1) are reacted at temperatures typically comprised between 20°C and 250°C.11 SSPI 2024 / 028

[0072] The skilled in the art will properly select the temperature depending on the boiling point of the medium (L), the equipment and the technique used for the reactions in the process.

[0073] Under step (ii) of the process of the invention, the composition (C1) advantageously further comprises at least one catalyst.

[0074] In one preferred embodiment, the group (FX) of polymer (P) is a hydroxyl group and the group (FY) of compound (M1) is an isocyanate group. In this embodiment, the catalyst for the grafting reaction of polymer (F) with metal compound (M1) is preferably selected from dibutyltin dilaurate (DBTDL) and Manganese(lll) acetylacetonate (Mn(acac)3).

[0075] In another embodiment of the invention, the group (FX) of polymer (P) is a carboxylic group, and the group (FY) of compound (M1) is an epoxy group. In this embodiment, the catalyst for the grafting reaction of polymer (F) with metal compound (M1) is preferably selected from the group consisting of organic aluminum compounds such as aluminum trifluoromethanesulfonate.

[0076] The molar amount of compound (M1) in composition (C2) suitably corresponds to the molar amount of monomer (HM) of polymer (P).

[0077] Under step (ii) of the process of the invention, the catalyst is typically added to the composition (C1) in an amount comprised between 0.1% and 50% by moles, preferably between 0.3% and 20% by moles, more preferably between 0.5% and 10% by moles, based on the total amount by moles of compound (M1).

[0078] In one embodiment of the present invention, the process also comprises a step (iii) of contacting the composition (C2) as above defined with at least a second metal compound [compound (M2)] of formula (II), different from the compound (M1): X’4-mA’Y’m' (II).

[0079] The molar amount of compound (M2) is in general comprised between 1 and 90% referred to the total molar content of compound (M1) and polymer (P).

[0080] Step (iii) may be carried out in the same equipment used for step (ii), at the same conditions of temperature and concentration.

[0081] All the details described above for the process conditions of step (ii) can be applied here for defining step (iii).

[0082] In step (iii), at least a fraction of compound (M2) reacts with at least a fraction of the -AYmpendant groups of polymer (F-j), thereby providing a composition [composition (C3)] comprising at least one grafted [polymer (F-g)] bearing - A’Y’m pendant groups.12 SSPI 2024 / 028

[0083] Compound (M2) may further react with residual fraction of the group (FX) of monomer (HM) of polymer (P).

[0084] The possible reactivity of compound (M2) with any residual fraction of the group (FX) of monomer (HM) of polymer (P) depends on the reaction conditions and the liquid medium used in the previous steps.

[0085] In one preferred embodiment, the group (FX) of polymer (P) is a hydroxyl group, preferably hydroxyethylacrylate, the group (FY) of compound (M1) is an isocyanate group and compound (M2) is 3-(triethoxysilyl) propyl isocyanate (TSPI). In this embodiment, the catalyst for the grafting reaction of polymer (F) with metal compound (M1) is preferably selected from dibutyltin dilaurate (DBTDL) and manganese(lll) acetylacetonate (Mn(acac)3).

[0086] In another preferred embodiment of the invention, the group (FX) of polymer (P) is a carboxylic group, preferably acrylic acid, the group (FY) of compound (M1) is an epoxy group and compound (M2) is 3-(2,3- epoxypropoxy)propyl]triethoxysilane. In this embodiment, the catalyst for the grafting reaction of polymer (F) with metal compound (M1) is preferably selected from the group consisting of organic aluminum compounds such as aluminum trifluoromethanesulfonate.

[0087] In a second phase of the process for the manufacture of polymer (P-h), the end groups -AYmof polymer (P-j) and / or the end groups -A’Y’mof polymer (P- g) undergo hydrolysis and / or condensation thereby providing a composition [composition (C)] comprising at least one PAN hybrid organic / inorganic composite [polymer (P-h)], and a liquid medium (L) possibly comprising a metal salt (MS).

[0088] The hydrolysis and / or condensation under this second phase of the process 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). Temperatures between 50°C and 120°C will be preferred.

[0089] It is understood that, while the hydrolysis and / or condensation reaction may be initiated during the first phase of the process of the invention, said reaction may be continued during the second phase of the process of the invention.

[0090] As this will be recognized by the person 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).13 SSPI 2024 / 028

[0091] The process of the present invention is advantageously carried out in the absence of solvents, according to a continuous request from the industry to allow the production of batteries with a low carbon foot-print.

[0092] An acid catalyst is typically added to the composition of any one of the first or the second phases of the process of the invention.

[0093] 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.

[0094] The acid catalyst is typically added to the composition of any one of the steps of the process of the invention in an amount comprised between 0.01% and 100% by weight, preferably between 0.5% and 60% by weight, based on the total weight of compound (M2).

[0095] The acid catalyst is preferably selected from the group consisting of organic acids such as citric acid, acetic acid and formic acid.

[0096] Very good results have been obtained with formic acid and citric acid.

[0097] In one embodiment of the invention, step (ii) and step (iii) are carried out simultaneously.

[0098] By the term “carried out simultaneously” it is intended that metal compound (M1) and metal compound (M2) are added together to composition (C1).

[0099] Without being bound by this theory, the Applicant believes that in the reaction conditions the group (FX) of monomer (HM) of polymer (P) first reacts with metal compound (M1) thus providing at least one grafted PAN [polymer (P-j)] bearing -AYmpendant groups; then, at least a fraction of compound (M2) reacts with at least a fraction of the -AYmpendant groups of polymer (P-j), thereby providing a composition [composition (C3)] comprising at least one grafted [polymer (P-g)] bearing -A’Y’mpendant groups.

[0100] According to another embodiment of the invention, step (ii) and step (iii) are carried out sequentially.

[0101] According to said embodiment of the invention, polymer (P-j) can be isolated from composition (C2) after step (ii). In this embodiment, the [composition (C2)] comprising at least one grafted [polymer (P-j)] bearing -AYmpendant groups obtained at the end of step (ii) can be further submitted to step (iib):(lib) isolating the [polymer (P-j)] as solid by filtration of composition (C2), washing the solid with polar solvents and drying to recover dry polymer (P-j).

[0102] The polar solvent used in the washing is suitably selected from solvents that are not able to solubilize the polymer (P-j). The polar solvent may typically be selected from alcohols.14 SSPI 2024 / 028

[0103] Under step (iib) of the process of the invention, the polymer (P-j) after filtration and washing is dried at a temperature typically comprised between 25°C and 200°C.

[0104] Drying can be performed either under atmospheric pressure or under vacuum. Alternatively, drying can 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).

[0105] Polymer (P-j) formed during the process, being an intermediate in the process for preparing said polymer (P-h), is novel and represents a further aspect of the present invention.

[0106] The polymer (P-h) may be suitably processed in the form of a film.

[0107] In another object, thus, the present invention provides a fluoropolymer film comprising at least one PAN hybrid organic / inorganic composite [polymer (P- h)] according to the present invention.

[0108] The process for the manufacture of a film comprising at least one PAN hybrid organic / inorganic composite [polymer (P-h)] comprises: a step (a) or providing a composition (C) as above defined; a step (b) of processing into a film the composition (C) provided in step (a); and a step (c) of drying the film provided in step (b).

[0109] Under step (b) 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.

[0110] Under step (c) 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).

[0111] The film or the polymer (P-h) provided in step (c) 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 (P).

[0112] The film of a PAN hybrid organic / inorganic composite [polymer (P-h)] obtained by the process of the present invention is particularly suitable for use as polymer electrolyte membrane in secondary batteries that comprise gelled electrodes.15 SSPI 2024 / 028

[0113] In a further aspect, thus, the present invention provides a polymer electrolyte membrane comprising a film of a PAN hybrid organic / inorganic composite [polymer (P-h)] obtainable by the process defined above.

[0114] In still a further aspect, the present invention provides an electrochemical device comprising a polymer electrolyte membrane comprising a film polymer (P-h) obtained by the process of the present invention.

[0115] Non-limitative examples of suitable electrochemical devices include, notably, secondary batteries, especially, alkaline or an alkaline-earth secondary batteries such as Lithium ion batteries, capacitors, especially Lithium ion capacitors, supercapacitors and smart windows.

[0116] 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.

[0117] 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.Experimental section

[0118] Raw materials

[0119] Polymer (P-1): AN / ITA (0.4% by moles). Mw: 133000 g / mol from GPC, D50=27 microns.

[0120] Polymer (P-2): AN / MAA (1.4% by moles. Mw: 170000 g / mol from GPC, D50=37 microns.

[0121] Epoxy silane (EPP-1): [3-(2,3-epoxypropoxy)propyl]triethoxysilane.

[0122] Catalyst (ATS): Aluminum trifluoromethanesulfonate.

[0123] LiTFSI: bis(trifluoromethanesulfonyl)imide lithium salt.

[0124] Medium (L-1): ethylene carbonate (EC) / propylene carbonate (PC) (1 / 1 by weight).

[0125] Medium (L-2): solution of LiTFSI (0.4 mol / L) in ethylene carbonate (EC) / propylene carbonate (PC) (1 / 1 by weight).

[0126] CMC / SBR: mixture of styrene butadiene rubber and sodium carboxyl methyl cellulose

[0127] TEOS: tetraethoxysilane of formula Si(OC2Hs)4

[0128] Preparation of Polymer (P-1) and Polymer (P-2)

[0129] In the continuous polymerization process for producing Polymer (P-1) and Polymer (P-2) an aqueous suspension free radical method was employed.16 SSPI 2024 / 028The reaction took place in a one-gallon continuous stirred tank reactor. Each ingredient, including both monomers and initiator system, was fed independently and continuously via a peristaltic pump to the bottom of the reactor through a feed tube. Oxalic acid was used to control the pH of the solution.

[0130] The polymerization conditions for preparing polymer (P-1) are reported in table 1.Table 1

[0131] The polymerization conditions for preparing polymer (P-2) are reported in table 2.Table 2

[0132] The reactor was maintained at 55°C. As the polymer formed, it rose to the top and flowed out through an overflow slot before being collected in a separate vessel where the reaction is quenched to prevent further polymerization. The redox initiator system utilized included various ammonium and ferrous sulfates and sulfites. Acrylonitrile was the only component introduced in its pure form; all other components, including the comonomer, were dissolved in deionized17 SSPI 2024 / 028 water to ensure a steady supply via peristaltic pump. The comonomer content in the polymers was 0.4% by weight for ITA and 1.4% by weight for MAA. After reaching steady state, polymer was collected at approximately 0.4 kg / hr.

[0133] Example 1 - Manufacture of a polymer membrane with P-2 being conductive to ionic species in the molten state.

[0134] The following ingredients were fed into the reactor: Polymer (P-2) (5 g), Medium (L-1) (20 g), ATS (12 mg), EPP-1 (1.25 g), TEOS (17.25 g) and formic acid (10 g).

[0135] The reactor used is Novoclave by Buchiglasuster having the following characteristics:Novoclave by Buchiglasuster - Laboratory high pressure I high temperature reactor (HPHT). Reactor volume: 100 - 600 ml, Pressure: up to 1500 bar, Temperature: -20 °C to + 500°C. Electrical heating with built-in automated tap water cooling for fast and precise temperature control and programmable PID controller. The magnetic stirrer drive ensures efficient mixing and stirring of the process media as well as excellent heat transfer. Material: stainless steel.

[0136] The reactor was brought to 110°C and kept at that temperature under agitation at 1000 rpm for 24 h. Then, the reactor was discharged and the product obtained was grinded and dried for 1h at 40°C.

[0137] The powder was compression molded using a Collin P 200 T press. The material was heated at 90°C and pressed at 0 bar for 3 minutes. Then the press was degassed and a pressure of 100 bar was set for 2 minutes, still with a temperature of at 90°C. The press was then cooled down and it was opened at about 30-40°C.

[0138] A film of about 100 microns was obtained.

[0139] Example 2 - Manufacture of an ionic polymer membrane with P-1 by processing in the molten state.

[0140] The following ingredients were fed into a reactor as defined in Example 1: Polymer (P-1) (3 g), Medium (L-2) (22 g), ATS (2 mg), EPP-1 (0.18 g), TEOS (17.25 g) and formic acid (10 g). The reactor was brought to 110°C and kept at that temperature under agitation at 1000 rpm for 24 h. Then, the reactor was discharged and the product obtained was grinded and dried for 1 h at 40°C. This material was fed in a15 ml twin screw compounder (DSM Xplore) (Miniextruder) and processed at 110°C at 100 rpm for 5 minutes to homogeneize the powder obtained from the reactor. The resulting extruded material was compression molded using a Collin P 200 T press. The material was heated at 90°C and pressed at 0 bar for 3 minutes. Then the press was18 SSPI 2024 / 028 degassed and a pressure of 100 bar was set for 2 minutes, still with a temperature of at 90°C. The press was then cooled down and it was opened at about 30-40°C.

[0141] A film of about 100 microns was obtained.

[0142] Example 3. Manufacture of a polymer membrane with P-2 being conductive to ionic species in the molten state (Polymer (P-2) 35% and medium (L-1) 65%).

[0143] The reaction was carried out in the Miniextruder described above.

[0144] The following ingredients were fed into a miniextruder as defined in Example 2 at 110°C and at 100 rpm: Polymer (P-2) (14 g), EL-1 (26 g), ATS (35 mg) and EPP-1 (3.5 g).

[0145] After 5 minutes, the extrudate from the miniextruder was collected and it was compression molded using a Collin P 200 T press. The material was heated at 90°C and pressed at 0 bar for 3 minutes. Then the press was degassed and a pressure of 100 bar was set for 2 minutes, still with a temperature of at 90°C. The press was then cooled down and it was opened at about 30-40°C.

[0146] A flexible film of about 100 microns was obtained.

[0147] Example 4 - Manufacture of an ionic polymer membrane with P-2 by processing in the molten state.

[0148] A film was obtained following the same procedure detailed in Example 2, but using polymer (P-1) instead of polymer (P-2).

[0149] A film of about 83 microns was obtained.

[0150] Determination of the crosslinking density of membranes

[0151] A sample of about 5-10 mg of each membrane obtained in examples 1-3 was placed in about 10 mL of N,N-dimethylformamide (DMF) for 60 minutes at room temperature.

[0152] DMF is a very good solvent for polymer (P). The more crosslinking density of the membrane, the more swelling and less dissolution of the membrane in DMF is attainable. On the contrary, a poor crosslinked membrane will lead to a mostly dissolution of the membrane in DMF.

[0153] No dissolution in DMF was obtained for any of the membranes of examples 1- 3.

[0154] Determination of the ionic conductivity of the polymer membrane.

[0155] The bulk resistance of the polymer membrane of example 2 was measured in EL- Cells, with stainless steel blocking electrodes. The VMP e3 potentiostat was used to perform the impedance spectroscopy.19 SSPI 2024 / 028

[0156] The ionic resistance was determined by performing linear fitting in the nyquist plot between 500,000 and 70 Hz.

[0157] The point of contact between the resulting line and the axis of the real impedance defined the bulk resistance value.

[0158] The ionic conductivity 6 was obtained using the following equation dwherein d is the thickness of the film, Rb the bulk resistance and S is the area of the stainless steel electrode.

[0159] The ionic conductivity obtained according to the above method was 1.1 mS / cm for the membrane of example 2 and 12 mS / cm for the membrane of example 4.

[0160] Example 5 - Manufacture of a hybrid Lithium Ion Capacitor

[0161] A full coin cell (CR2032) was assembled, the cell comprising, in order:1. Bottom cap2. Graphite electrode (95% Graphite Actilion GHDR; 5% CMC / SBR in water prepared by roll to roll on copper (Mass Loading 3.7 mg cm-2) with a piece of Li metal to carry on graphite pre-lithiation. A drop of medium (L-2) was added to make sure apiece of lithium could entirely dissolve as sacrificial anode material to pre-intercalate graphite.3. Membrane of example 44. Activated carbon electrode (85% activated carbon; 10% Carbon Black; 5% CMC / SBR in water prepared by roll to roll on aluminium (Mass Loading 3.4 mg cm-2))5. Spacer (stainless steel)6. Spring (stainless steel)7. Top cap

[0162] The cell was galvanostatically cycled at 50 mA g-1and Specific Capacitance was evaluated. The voltage window was limited to 2.6 V to 3.8 V.

[0163] The results are shown in Table 3.20 SSPI 2024 / 028Table 3

[0164] The data show that the device properly worked and that the capacitance increased with time.

Claims

21 SSPI 2024 / 028Claims1. A process for manufacturing a polyacrylonitrile (PAN) hybrid organic / inorganic composite [polymer (P-h)], said process comprising the following steps:(i) providing a composition [composition (C1)] containing a liquid medium [medium (L)] and at least one PAN-based polymer [polymer (P)], wherein said medium (L) is a composition comprising one or more organic substances in the liquid state at 20°C under atmospheric pressure, wherein said polymer (P) comprises:• recurring units derived from acrylonitrile (AN), and• recurring units derived from at least one hydrogenated vinyl monomer [monomer (HM)] of formula (III):wherein:Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a C1-C3 hydrocarbon group and Rx, and Rx is a C1-C20 hydrocarbon moiety comprising at least one functional group [group (FX)] selected from the group consisting of: hydroxyl group, amine, carboxylic acid group, thiol group and anhydride;(ii) contacting composition (C1) provided in step (i) with at least a first 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, each occurrence of Y is a hydrolysable group and each occurrence of X is a hydrocarbon group, wherein at least one X comprises at least one functional group (FY) selected from epoxy and isocyanate functional group, more preferably epoxy functional group, thereby providing a composition [composition (C2)];(iii) optionally contacting composition (C2) with at least a second metal compound [compound (M2)] of formula (II), different from the compound (M1):X’4-m’A’Y’m’ (II) wherein m’ is an integer from 1 to 4, A’ is a metal selected from the group consisting of Si, Ti and Zr, each occurrence of Y’ is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group, and each occurrence of X’ is a hydrocarbon group.22 SSPI 2024 / 0282. The process according to claim 1 , wherein the polymer (P) preferably comprises, more preferably consists of:(a) at least 80% by moles, preferably at least 85% by moles, more preferably at least 95% by moles of acrylonitrile (AN); and(b) from 0.01% to 20% by moles, preferably from 0.05% to 5% by moles, more preferably from 0.1% to 2% by moles of at least one monomer (HM) of formula (III), the aforementioned percentages by moles being referred to the total moles of recurring units of polymer (P).

3. The process according to anyone of the preceding claims, wherein the medium (L) comprises organic carbonates and at least one metal salt (MS).

4. The process according to anyone of the preceding claims, wherein compound (M1) is a compound of formula (l-A):RA4.mA(ORB)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.

5. The process according to anyone of the preceding claims, wherein compound (M2) is selected from 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.

6. The process according to anyone of the preceding claims, wherein composition (C1) further comprises at least one catalyst.

7. A PAN hybrid organic / inorganic composite [polymer (P-h)] obtainable by the process according to anyone of claims 1 to 6.

8. A film comprising at least one PAN hybrid organic / inorganic composite [polymer (P-h)] according to claim 7.

9. A process for the manufacture of a film comprising at least one PAN hybrid organic / inorganic composite [polymer (P-h)] according to claim 1 , said process comprising:• a step (a) or providing a composition (C) comprising at least one [polymer (P-h)]23 SSPI 2024 / 028 and a liquid medium (L) optionally comprising a metal salt (MS);• a step (b) of processing into a film the composition (C) provided in step (a); and• a step (c) of drying the film provided in step (b).

10. A polymer electrolyte membrane comprising a film of a PAN hybrid organic / inorganic composite [polymer (P-h)] obtainable by the process according to claim 9.

11. An electrochemical device comprising a polymer electrolyte membrane according to claim 10.

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