Method for producing all-solid electrolyte for secondary batteries

Abstract

The present invention relates to a method for preparing a solid electrolyte in the form of a film, comprising the steps of: providing a solution C comprising at least one fluoropolymer A1, at least one organic solvent A2, at least one alkali metal salt B1 and at least one plasticizer B2; depositing said solution C on a support D to form a film; and drying the film thus obtained; wherein said at least one organic solvent A2 has a donor number greater than 4 kcal / mol and a saturated vapor pressure at 20° C. of less than 24 kPa, and said at least one plasticizer B2 comprises at least one ionic liquid.

Description

[Technical Field]

[0001] The present invention relates generally to the field of electrical energy storage in all-solid-state batteries, particularly secondary batteries of the Li-ion type. More specifically, the present invention relates to a solid electrolyte and a method for producing a film therefrom. The film is intended for use as an all-solid-state battery separator or electrolyte, particularly for Li-ion batteries. The present invention also relates to an all-solid-state battery comprising such a separator and / or such a non-porous film. [Background technology]

[0002] Secondary batteries, such as Li-ion batteries, comprise at least one negative electrode or anode bonded to a copper current collector, a positive electrode or cathode bonded to an aluminum current collector, a separator, and an electrolyte. The electrolyte consists of an alkali metal salt, typically a lithium salt, mixed with a solvent, typically a mixture of organic carbonates, selected to optimize ion transport and dissociation. A high dielectric constant facilitates ion dissociation and thus the number of ions available in a given volume, while a low viscosity facilitates ion diffusion, which, among other parameters, plays a key role in the charge / discharge rate of an electrochemical system. Secondary batteries, such as lithium-ion batteries, traditionally use liquid electrolytes composed of a solvent, an alkali metal salt, such as a lithium salt, and additives. While these electrolytes have good ionic conductivity, they are prone to leaking and catching fire if the battery is damaged.

[0003] The use of solid electrolytes makes it possible to overcome these difficulties. However, solid electrolytes generally have lower conductivity than liquid electrolytes. The difficulty with solid electrolytes is to combine high ionic conductivity, good electrochemical stability, and satisfactory thermal stability. Ionic conductivity must be comparable to that of liquid electrolytes. Electrochemical stability requires that the electrolyte be compatible with cathode materials capable of operating at high voltages (>4.5 V). Similarly, solid electrolytes must operate at temperatures up to at least 80°C.

[0004] Furthermore, the separator must have satisfactory mechanical strength. The latter must, in particular, prevent the formation of dendrites during charge-discharge cycling. In general, solid electrolytes must exhibit better safety, which cannot be achieved to the detriment of other performance qualities. Finally, from a packaging perspective, the solid electrolyte must be easy to handle (draw) and roll up.

[0005] Poly(vinylidene fluoride) (PVDF) and its derivatives are advantageous as the main constituent material of separators due to their electrochemical stability and high dielectric constant, which promotes ionic dissociation and therefore conductivity. The copolymer P(VDF-HFP) (a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP)) has been considered as a gelling membrane because it has lower crystallinity than PVDF. Therefore, the advantage of these P(VDF-HFP) copolymers is that they can achieve greater swelling and therefore promote conductivity.

[0006] However, solid or substantially solid electrolytes with a polymer matrix are generally complex to manufacture, requiring several steps: dissolution, addition of co-components, homogenization, deposition, and drying. For each of these steps, it is essential to control the homogeneity of the dried extract and slurry to achieve the best possible performance and ensure uniformity throughout the manufactured object.

[0007] WO2020 / 126750 describes a solid electrolyte composition containing a mixture of a fluoropolymer and an isocyanate compound to form a crosslinked network. The film is prepared in the presence of acetone. However, using the film in the presence of acetone results in an inconsistent film due to the low vapor pressure of acetone, which affects the ionic conductivity of the film and the final performance of the battery. Furthermore, the low vapor pressure leads to safety issues in the process.

[0008] Therefore, there is a need to develop new solid electrolytes that have a good compromise between ionic conductivity, electrochemical stability and thermal stability, and are suitable for simplified use to suit industrial applications. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2020 / 126750 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, it is an object of the present invention to remedy at least one of the drawbacks of the prior art, namely to prepare a uniform solid electrolyte membrane with good performance qualities. [Means for solving the problem]

[0011] According to a first aspect, the present invention provides a method for preparing a solid electrolyte in film form, comprising the steps of: providing a solution C comprising at least one fluoropolymer A1, at least one organic solvent A2, at least one alkali metal salt B1 and at least one plasticizer B2; - depositing said solution C on a support D to form a film; - drying the film thus obtained; Including, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol and a saturated vapor pressure at 20° C. of less than 24 kPa, and the at least one plasticizer B2 comprises at least one ionic liquid.

[0012] The use of organic solvent A2 as defined in this patent application allows the preparation of uniform films, which improves the ionic conductivity and final performance qualities of the battery.

[0013] According to a preferred embodiment, solution C is obtained according to the following steps: - preparing a solution A comprising said at least one fluoropolymer A1 and said at least one organic solvent A2; - preparation of a solution B comprising at least one alkali metal salt B1 and at least one plasticizer B2; - Mixing solution A and solution B to obtain solution C.

[0014] According to a preferred embodiment, said at least one organic solvent A2 has a flash point above -15°C.

[0015] According to a preferred embodiment, said at least one organic solvent A2 has a saturated vapor pressure of more than 7 Pa at 20° C. This allows the solvent to evaporate more easily and thus avoids excessive solvent contents in the film obtained by the method of the invention.

[0016] According to a preferred embodiment, the at least one organic solvent A2 has a mass content of water of less than 5000 ppm. Limiting the water content helps to prevent deterioration of certain components used in the process.

[0017] According to a preferred embodiment, said at least one fluoropolymer A1 comprises monomer units derived from vinylidene fluoride and, optionally, monomer units derived from a monomer selected from the group consisting of: vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X where X is SO2F, CO2H, CH2OH, CH2OCN, or CHOPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2 where n is 1, 2, 3, 4, or 5; products of the formula R 1 CH2OCF=CF2(in the formula, R 1 is hydrogen or F(CF2)m, where m is 1, 2, 3, or 4; 2 OCF=CH2(wherein, R 2 is F(CF2)p, where p is 1, 2, 3, or 4; perfluorobutylethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or mixtures thereof.

[0018] According to a preferred embodiment, said at least one fluoropolymer A1 is a homopolymer of vinylidene fluoride or a copolymer comprising monomer units deriving from vinylidene fluoride and from monomers selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or mixtures thereof.

[0019] According to a preferred embodiment, the at least one alkali metal salt B1 is selected from the group consisting of LiCF3SO3, LiPF6, LiClO4, LiBF4, LiB(C2O4), LiN(SO2F), LiN(SO2CF3), LiN(SO2C2F3), LiN(SO2C2F5), LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2C2F5), LiN(SO2CF3)(SO2C2F5), LiAsF6, LiBF2C2O4, LiNO3, LiPF3(CF2CF3), LiBETI, LiTDI, NaTDI, KTDI, NaC 104, KClO4, NaPF6, KPF6, NaBF4, KBF4, NaAsF6, KAsF6, NaCF3SO3, KCF3SO3, NaN(CF3SO2)2, KN(CF3SO2)2, NaN(SO2C2F5)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2C2F5), NaN(SO2CF3)(SO2C2F5), KN(SO2C2F5)2, KN(SO2F)(SO2CF3), KN(SO2F)(SO2C2F5), KN(SO2CF3)(SO2C2F5) or mixtures thereof.

[0020] According to a preferred embodiment, the at least one plasticizer B2 is selected from the group consisting of tetrafluoroborate (BF4-), bis(oxalato)borate BOB-, hexafluorophosphate (PF6-), hexafluoroarsenate (AsF6-), triflate or trifluoromethylsulfonate (CF3SO3-), bis(fluorosulfonyl)imide (FSI-), bis(trifluoromethanesulfonyl)imide (TFSI-), nitrate (NO3-), 4,5-dicyano-2-(trifluoromethyl)imidazole (TDI-), acrylate or methacrylate; and anions selected from the group consisting of ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolium, or the at least one plasticizer B2 is a mixture of at least one ionic liquid with at least one solvent S1 having a boiling point above 100°C and selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, trans-4,5-difluoro-1,3-dioxolan-2-one, ethylene carbonate, propylene carbonate, (2-cyanoethyl)triethoxysilane, 3-methoxypropionitrile, sulfolane and polyethylene glycol dimethyl ether.

[0021] According to a preferred embodiment, the film has a porosity of less than 10%.

[0022] According to a preferred embodiment, the film has a thickness variation of less than 20% over its entire length.

[0023] According to another aspect, the present invention provides a composition for preparing a solid electrolyte comprising at least one fluoropolymer A1, at least one organic solvent A2, at least one alkali metal salt B1, and at least one plasticizer B2 comprising at least one ionic liquid, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure at 20°C between 7 Pa and 24 kPa, a flash point greater than -15°C, and a water content by mass of less than 5000 ppm.

[0024] According to a preferred embodiment, the at least one fluoropolymer A1 is as defined in the present patent application, the at least one alkali metal salt B1 is as defined in the present patent application, and the at least one plasticizer B2 is as defined in the present patent application.

[0025] According to another aspect, the present invention provides a film comprising 15% to 70% by weight of at least one fluoropolymer A1, 10% to 80% by weight of a plasticizer B2 comprising at least one ionic liquid, 2% to 30% by weight of an alkali metal salt B1, and 1 ppb to 5000 ppm of water.

[0026] According to a preferred embodiment, said film also comprises between 1 ppb and 15% of said at least one organic solvent A2 as defined in the present patent application.

[0027] According to a preferred embodiment, the film consists of 15% to 70% by weight of at least one fluoropolymer A1, 10% to 80% by weight of a plasticizer B2 comprising at least one ionic liquid, 2% to 30% by weight of an alkali metal salt B1, 1 ppb to 15% of said at least one organic solvent A2, and 1 ppb to 5000 ppm of water, the sum of the components being equal to 100.

[0028] According to a preferred embodiment, said film has an ionic conductivity at 25° C. of 0.01 to 5 mS / cm, preferably 0.05 to 5 mS / cm, advantageously 0.5 to 5 mS / cm, measured by electrochemical impedance spectroscopy.

[0029] According to a preferred embodiment, said film is obtainable by the method according to the invention.

[0030] According to a preferred embodiment, the film has a thickness variation of less than 20% over its entire length.

[0031] According to a preferred embodiment, the film has a porosity of less than 10%.

[0032] According to another aspect, the present invention provides a separator for a Li-ion rechargeable battery comprising a film according to the present invention.

[0033] According to another aspect, the present invention provides an electrochemical device selected from the group consisting of a battery, a capacitor, an electrochemical double layer electric capacitor, and a membrane electrode assembly (MEA) for a fuel cell or an electrochromic device, comprising a film according to the present invention.

[0034] According to another aspect, the present invention provides an all-solid-state battery comprising an anode, a cathode, and a separator, wherein the separator comprises a film according to the present invention.

[0035] According to another aspect, the present invention provides an all-solid-state battery comprising an anode, a cathode and a separator, wherein the anode and / or the cathode comprises a film according to the present invention. [Brief explanation of the drawings]

[0036] [Figure 1] 1 represents the change in film mass as a function of coating length. [Figure 2] 1 depicts the change in film thickness as a function of coating length. DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention will now be explained in more detail, in a non-limiting manner, in the following description.

[0038] According to a first aspect of the present invention, there is provided a method for preparing a solid electrolyte in the form of a film. The method comprises the step of providing a solution C containing at least one fluoropolymer A1, at least one organic solvent A2, at least one alkali metal salt B1, and at least one plasticizer B2. Preferably, the at least one plasticizer B2 comprises at least one ionic liquid. The solution C is deposited on a support D to form a film. Preferably, the method also comprises the step of drying the film to remove the at least one organic solvent A2 used during preparation.

[0039] Preferably, therefore, the method according to the invention comprises: - providing a solution C comprising said at least one fluoropolymer A1, said at least one organic solvent A2, said at least one alkali metal salt B1, and said at least one plasticizer B2; - depositing said solution C on a support D to form a film; - drying the film thus obtained; Includes.

[0040] Preferably, solution C is obtained by mixing two different solutions A and B. Solution A comprises said at least one fluoropolymer A1 and said at least one organic solvent A2. Solution B comprises said at least one alkali metal salt B1 and said at least one plasticizer B2. Solution B may also comprise an organic solvent. The latter may be said organic solvent A2 or any other organic solvent capable of dissolving said alkali metal salt B1 and / or said plasticizer B2. Solutions A and B are then mixed to obtain solution C.

[0041] According to a preferred embodiment, the step of preparing solution A is carried out at a temperature between 15°C and 90°C, preferably between 15°C and 60°C.

[0042] According to a preferred embodiment, the step of preparing solution B is carried out at a temperature between 15°C and 90°C, preferably between 15°C and 60°C.

[0043] According to a preferred embodiment, the step of depositing said solution C on the support D is carried out at a temperature between 15°C and 100°C, preferably between 15°C and 90°C.

[0044] The film drying step can be carried out at temperatures between 20° C. and 120° C., preferably between 20° C. and 90° C., in particular between 40° C. and 80° C. This step is generally carried out under extraction.

[0045] Fluoropolymer A1 The fluoropolymer A1 comprises a monomer unit containing at least one fluorine atom. According to a preferred embodiment, the fluoropolymer A1 comprises at least one monomer selected from compounds containing a vinyl group in its chain that can be opened to polymerize, and that contains at least one fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group directly bonded to the vinyl group.

[0046] Preferably, the fluoropolymer A1 contains at least one monomer unit derived from a monomer selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PVBE), ) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X where X is SO2F, CO2H, CH2OH, CH2OCN, or CHOPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2 where n is 1, 2, 3, 4, or 5; 1 CH2OCF=CF2(in the formula, R 1 is hydrogen or F(CF2)m, where m is 1, 2, 3, or 4; 2 OCF=CH2(wherein, R 2 is F(CF2)p, where p is 1, 2, 3, or 4; perfluorobutylethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or mixtures thereof.

[0047] In particular, said fluoropolymer A1 comprises at least monomer units derived from vinylidene fluoride. The fluoropolymer A1 may be a homopolymer or a copolymer. The copolymer may also comprise non-fluorinated monomers.

[0048] According to one embodiment, the fluoropolymer A1 is a vinylidene fluoride homopolymer.

[0049] According to an alternative embodiment, the fluoropolymer A1 is a copolymer comprising monomer units originating from vinylidene fluoride and from at least one other comonomer copolymerizable with vinylidene fluoride. The comonomer compatible with vinylidene fluoride can be halogenated (fluorinated, chlorinated or brominated) or non-halogenated.

[0050] Thus, the fluoropolymer A1 comprises monomer units derived from vinylidene fluoride and monomer units derived from a monomer selected from the group consisting of vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PVBE), and the like. perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); monomers of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CH2OCN, or CHOPO3H; monomers of the formula CF2=CFOCF2CF2SO2F; monomers of the formula F(CF2)nCH2OCF=CF2, where n is 1, 2, 3, 4, or 5; 1 CH2OCF=CF2(in the formula, R 1 is hydrogen or F(CF2)m, where m is 1, 2, 3 or 4; 2 OCF=CH2(wherein, R 2Monomers of F(CF2)p, where p is 1, 2, 3, or 4; perfluorobutylethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or mixtures thereof. Among the trifluoropropenes, mention may be made of 3,3,3-trifluoropropene. Among the tetrafluoropropenes, mention may be made of 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene. Among the pentafluoropropenes, mention may be made of 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene may represent either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. The chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0051] Preferably, fluoropolymer A1 is a copolymer comprising monomer units derived from vinylidene fluoride and monomer units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene and hexafluoropropylene or mixtures thereof. In fluoropolymer A1, the mass content of vinylidene fluoride units is at least 50%, preferably at least 60%, more preferably more than 70%, advantageously more than 80%.

[0052] In particular, the fluoropolymer A1 is a copolymer comprising monomer units originating from vinylidene fluoride and monomer units originating from hexafluoropropylene, preferably with a mass content of monomer units originating from vinylidene fluoride of at least 50%, preferably at least 60%, more preferably more than 70% and advantageously more than 80%.

[0053] More specifically, fluoropolymer A1 is a copolymer comprising monomer units originating from vinylidene fluoride and monomer units originating from hexafluoropropylene, the mass content of vinylidene fluoride units being greater than 65% and the mass content of hexafluoropropylene units being less than 35%.

[0054] According to one embodiment, the fluoropolymer A1 consists of a mixture of vinylidene fluoride homopolymer (PVDF) and at least one VDF copolymer, the mass content of PVDF homopolymer ranging from 0.1% to 20% based on the weight of said mixture.

[0055] According to one embodiment, said fluoropolymer A1 consists of a mixture of PVDF homopolymer and P(VDF-HFP) copolymer.

[0056] According to one embodiment, said fluoropolymer A1 consists of a mixture of two VDF copolymers of different structure.

[0057] According to a particular embodiment, the fluoropolymer A1 is fully or partially functionalized, which helps to improve its adhesion to metals. Thus, said fluoropolymer A1 may comprise monomer units having at least one functional group selected from the group consisting of carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy such as glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfone, sulfate, phosphate and phosphonate, preferably at least one carboxylic acid or hydroxyl functional group.

[0058] The functional groups are introduced by chemical reaction capable of grafting or copolymerizing a monomer unit having a fluorine atom with a monomer having at least one of said functional groups and a vinyl functional group capable of copolymerizing with the fluoromonomer, according to techniques well known to those skilled in the art.

[0059] According to one embodiment, the functional group comprises a carboxylic acid functional group, which is a (meth)acrylic acid type group selected from acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate and acryloyloxypropyl succinate.

[0060] According to one embodiment, the unit carrying the carboxylic acid function further comprises a heteroatom selected from oxygen, sulfur, nitrogen and phosphorus.

[0061] According to one embodiment, the functionality is introduced via a transfer agent used during the synthesis process. The transfer agent is a polymer having a molar mass of 20,000 g / mol or less and carrying functional groups selected from the following group: carboxylic acid, carboxylic anhydride, carboxylic ester, epoxy (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfone, sulfate, phosphate, or phosphonate. Acrylic acid oligomers are an example of this type of transfer agent. According to a preferred embodiment, the transfer agent is an acrylic acid oligomer having a molar mass of 20,000 g / mol or less.

[0062] The content of functional groups in PVDF is at least 0.01 mol %, preferably at least 0.1 mol %, and is not more than 15 mol %, preferably not more than 10 mol %.

[0063] Preferably, the PVDF is of high molecular weight. As used herein, the term "high molecular weight" refers to a PVDF that is resistant to 232°C and 100 s -1 "PVDF" refers to a PVDF having a melt viscosity of greater than 100 Pa.s, preferably greater than 500 Pa.s, and more preferably greater than 1000 Pa.s, as measured by the ASTM D-3835 method.

[0064] The PVDF homopolymers and VDF copolymers used in the present invention can be obtained by known polymerization methods such as emulsion polymerization or suspension polymerization.

[0065] According to one embodiment, they are prepared by an emulsion polymerization process in the absence of fluorosurfactants.

[0066] Polymerization of PVDF generally results in a latex having a solids content of 10% to 60% by weight, preferably 10% to 50%, and a weight-average particle size of less than 1 micrometer, preferably less than 1000 nm, preferably less than 800 nm, and more preferably less than 600 nm. The weight-average particle size is generally at least 20 nm, preferably at least 50 nm, and advantageously the average size is in the range of 100 to 400 nm. The polymer particles can form aggregates, the weight-average size of which is 1 to 30 micrometers, preferably 2 to 10 micrometers. The aggregates can break down into discrete particles during formation and application to a substrate.

[0067] According to a particular embodiment, the PVDF homopolymer and VDF copolymer are composed of bio-based VDF. The term "bio-based" means "originating from biomass." This makes it possible to improve the ecological footprint of the polymer. Bio-based VDF is produced according to the standard NF EN 16640. 14 It can be characterized by a content of renewable carbon, i.e. of natural origin derived from biological material or biomass, of at least 1 atomic % determined by the C content. The term "renewable carbon" indicates that the carbon is of natural origin and derived from biological material (or derived from biomass), as shown below. According to certain embodiments, the biocarbon content of the VDF is greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than 33%, preferably greater than 50%, preferably greater than 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, advantageously equal to 100%.

[0068] Organic solvent A2 The organic solvent A2 serves to dissolve the fluoropolymer A1. Therefore, the organic solvent A2 has a donor number of more than 4 kcal / mol. Preferably, the organic solvent has a donor number of more than 5 kcal / mol. The donor number or donor index of the solvent represents the value -ΔH, where ΔH is the enthalpy of interaction between the solvent and antimony pentachloride (according to the method described in Journal of Solution Chemistry, Vol. 13, No. 9, 1984).

[0069] According to a preferred embodiment, said organic solvent A2 has a donor number of more than 6 kcal / mol, advantageously more than 7 kcal / mol, preferably more than 8 kcal / mol, more preferentially more than 9 kcal / mol and in particular more than 10 kcal / mol.

[0070] According to a preferred embodiment, said organic solvent A2 has a donor number of less than 30 kcal / mol, advantageously less than 29 kcal / mol, preferably less than 28 kcal / mol, more preferentially less than 27 kcal / mol, in particular less than 26 kcal / mol, more particularly less than 25 kcal / mol, in a preferred manner less than 24 kcal / mol, in an advantageous preferred manner less than 23 kcal / mol, in a preferentially preferred manner less than 22 kcal / mol, in a more preferentially preferred manner less than 21 kcal / mol and in a particularly preferred manner less than 20 kcal / mol.

[0071] Thus, according to a preferred embodiment, said organic solvent A2 has a donor number of more than 6 kcal / mol, advantageously more than 7 kcal / mol, preferably more than 8 kcal / mol, more preferentially more than 9 kcal / mol, in particular more than 10 kcal / mol, and a donor number of less than 30 kcal / mol, advantageously less than 29 kcal / mol, preferably less than 28 kcal / mol, more preferentially less than 27 kcal / mol, in particular less than 26 kcal / mol, more particularly less than 25 kcal / mol, in a preferred manner less than 24 kcal / mol, in an advantageous preferred manner less than 23 kcal / mol, in a preferentially preferred manner less than 22 kcal / mol, in a more preferentially preferred manner less than 21 kcal / mol, in a particularly preferred manner less than 20 kcal / mol.

[0072] According to a particular embodiment, said organic solvent A2 has a donor number between 5 and 30 kcal / mol, advantageously between 5 and 25 kcal / mol and preferably between 10 and 20 kcal / mol.

[0073] The use of specific A2 organic solvents or A2 organic solvent mixtures is preferred in order to also allow the preparation of uniform films, i.e., uniform thickness over the entire length of the coating. The use of organic solvents with saturated vapor pressures as described in the various embodiments below allows for an improvement in the quality of the films produced.

[0074] Said organic solvent A2 has a saturated vapor pressure of less than 24 kPa at 20° C. According to a preferred embodiment, said organic solvent A2 has a saturated vapor pressure of less than 23 kPa at 20° C., advantageously less than 22 kPa, preferably less than 21 kPa, more preferentially less than 20 kPa, in particular less than 18 kPa at 20° C., more particularly less than 16 kPa at 20° C., preferably less than 14 kPa at 20° C., advantageously preferably less than 12 kPa at 20° C.

[0075] According to a preferred embodiment, said organic solvent A2 has a saturated vapor pressure at 20° C. of more than 7 Pa, advantageously more than 8 Pa, preferably more than 9 Pa, more preferentially more than 10 Pa, in particular more than 25 Pa at 20° C., more particularly more than 50 Pa, preferably more than 100 Pa, advantageously preferably more than 500 Pa. This helps to prevent the residual solvent content in the film produced from being too high.

[0076] Thus, said organic solvent A2 has a saturated vapor pressure of less than 24 kPa at 20° C. According to a preferred embodiment, said organic solvent A2 has a saturated vapor pressure of less than 23 kPa at 20° C., advantageously less than 22 kPa, preferably less than 21 kPa, more preferentially less than 20 kPa, in particular less than 18 kPa at 20° C., more particularly less than 16 kPa at 20° C., preferably less than 14 kPa at 20° C., advantageously less than 12 kPa at 20° C., and said organic solvent A2 has a saturated vapor pressure of more than 7 Pa at 20° C., advantageously more than 8 Pa, preferably more than 9 Pa, more preferentially more than 10 Pa, in particular more than 25 Pa at 20° C., more particularly more than 50 Pa, preferably more than 100 Pa, advantageously preferably more than 500 Pa.

[0077] According to a preferred embodiment, the at least one organic solvent A2 has a flash point above -15°C, advantageously above -14°C, preferably above -13°C, in particular above -12°C. Preferably, the at least one organic solvent A2 has a flash point below 90°C, advantageously below 85°C, preferably below 80°C, in particular below 75°C. Thus, the at least one organic solvent A2 may have a flash point above -15°C, advantageously above -14°C, preferably above -13°C, in particular above -12°C, and a flash point below 90°C, advantageously below 85°C, preferably below 80°C, in particular below 75°C. The flash point corresponds to the lowest temperature at which a combustible substance releases enough vapor with the ambient air to form a gas mixture that ignites under the influence of an exothermic energy source, but not enough for combustion to continue. The flash point defined herein is the flash point measured in a closed cup.

[0078] According to a particular embodiment, the at least one organic solvent A2 is - a donor number of more than 6 kcal / mol, advantageously more than 7 kcal / mol, preferably more than 8 kcal / mol, more preferentially more than 9 kcal / mol, in particular more than 10 kcal / mol; and a donor number of less than 30 kcal / mol, advantageously less than 29 kcal / mol, preferably less than 28 kcal / mol, more preferentially less than 27 kcal / mol, in particular less than 26 kcal / mol, more particularly less than 25 kcal / mol, preferably less than 24 kcal / mol, advantageously preferably less than 23 kcal / mol, preferentially preferably less than 22 kcal / mol, more preferentially less than 21 kcal / mol, particularly preferably less than 20 kcal / mol; a saturated vapor pressure at -20°C of less than 23 kPa, advantageously less than 22 kPa, preferably less than 21 kPa, more preferentially less than 20 kPa, in particular less than 18 kPa at 20°C, more particularly less than 16 kPa at 20°C, preferably less than 14 kPa at 20°C, advantageously preferably less than 12 kPa at 20°C; and a saturated vapor pressure at 20°C of more than 7 Pa, advantageously more than 8 Pa, preferably more than 9 Pa, more preferentially more than 10 Pa, in particular more than 25 Pa at 20°C, more particularly more than 50 Pa, preferably more than 100 Pa, advantageously preferably more than 500 Pa; a flash point above -15°C, advantageously above -14°C, preferably above -13°C, in particular above -12°C; and a flash point below 90°C, advantageously below 85°C, preferably below 80°C, in particular below 75°C; It has.

[0079] Furthermore, the at least one organic solvent A2 preferably has a mass water content of less than 5000 ppm, advantageously less than 4000 ppm, preferably less than 3000 ppm, more preferentially less than 2000 ppm, in particular less than 1000 ppm, more particularly less than 500 ppm, preferably less than 100 ppm, advantageously preferably less than 50 ppm, preferentially preferably less than 10 ppm. Preferably, the at least one organic solvent A2 has a mass water content of more than 1 ppb, more preferentially more than 10 ppb, in particular more than 100 ppb. The low water content in the solvent prevents deterioration of other components present.

[0080] The organic solvent A2 may be selected in particular from esters, carbonates, nitriles or dinitriles, ethers or diethers, or ketones, which have the donor numbers provided in the present patent application, the saturated vapor pressures described in the present patent application, and preferably the flash points described in the present patent application, and combinations thereof can be used as organic solvents.

[0081] As non-limiting examples, organic solvents A2 according to the invention may be N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, 2-butanone, 1,2-dimethoxyethane, 1,3-dioxolane, 2,3-butanedione, 2-methylpentan-3-one, 2-methyltetrahydrofuran, 2-pentanone, methyl cyanide, 3,3-dimethyl-2-butanone, 3-methyl-2-butanone, 3-pentanone, butyl acetate, cyclohexanone, cyclopentanone, 4-methylpentan-2-one, dibutyl ether, 1,4-dioxane, dipropyl ether, ethyl acetate, ethyl butanoate or methylpropanoate. Mention may in particular be made of 2-butanone, 1,2-dimethoxyethane, 1,3-dioxolane, 2,3-butanedione, 2-methylpentan-3-one, 2-methyltetrahydrofuran, 2-pentanone, methyl cyanide, 3,3-dimethyl-2-butanone, 3-methyl-2-butanone, 3-pentanone, butyl acetate, cyclohexanone, cyclopentanone, 4-methylpentan-2-one, dibutyl ether, 1,4-dioxane, dipropyl ether, ethyl acetate, ethyl butanoate or methyl propanoate, or mixtures thereof.

[0082] Alkali metal salts B1 The alkali metal salts include LiCF3SO3, LiPF6, LiClO4, LiBF4, LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F3)2, LiN(SO2C2F5)2, LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2C2F5), LiN(SO2CF3)(SO2C2F5), LiAsF6, LiBF2C2O4, LiNO3, LiPF3(CF2CF3)3, LiBETI, LiTDI, NaTDI, KTDI, NaClO4, KClO4, N aPF6, KPF6, NaBF4, KBF4, NaAsF6, KAsF6, NaCF3SO3, KCF3SO3, NaN(CF3SO2)2, KN(CF3SO2)2, NaN(SO2C2F5)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2C2F5), NaN(SO2CF3)(SO2C2F5), KN(SO2C2F5)2, KN(SO2F)(SO2CF3), KN(SO2F)(SO2C2F5), KN(SO2CF3)(SO2C2F5) or mixtures thereof. Preferably, the alkali metal salt is selected from the group consisting of LiCF3SO3, LiPF6, LiClO4, LiBF4, LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F3)2, LiN(SO2C2F5)2, LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2C2F5), LiN(SO2CF3)(SO2C2F5), LiAsF6, LiBF2C2O4, LiNO3, LiPF3(CF2CF3)3, LiBETI, LiTDI, or mixtures thereof.

[0083] Plasticizer B2 According to a preferred embodiment, said plasticizer B2 comprises at least one ionic liquid.

[0084] Ionic liquids are salts that are liquid at ambient temperature, i.e., have a melting point below 100°C at atmospheric pressure. They are formed by the combination of organic cations and anions, whose ionic interactions are weak enough not to form a solid.

[0085] Examples of organic cations that may be mentioned include: ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolinium, phosphonium, guanidinium, piperidinium, thiazolium, triazolium, oxazolium, pyrazolium and mixtures thereof. According to one embodiment, the cation is C1-C 30 It may contain an alkyl group, for example, 1-butyl-1-methylpyrrolidinium, 1-ethyl-3-methylimidazolium, N-methyl-N-propylpyrrolidinium, or N-methyl-N-butylpiperidinium.

[0086] According to one embodiment, the anion associated therewith is selected from imides, particularly bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide; borates; phosphates; phosphinates and phosphonates, particularly alkylphosphonates; amides, particularly dicyanamide; aluminates, particularly tetrachloroaluminate; halides (such as bromide, chloride or iodide anions); cyanates; acetates (CHCOO-), particularly trifluoroacetate; sulfonates, particularly methanesulfonate (CHSO-) or trifluoromethanesulfonate; and sulfates, particularly hydrogen sulfate; acrylates or methacrylates.

[0087] According to one embodiment, the anion is selected from tetrafluoroborate (BF4-), bis(oxalato)borate (BOB-), hexafluorophosphate (PF6-), hexafluoroarsenate (AsF6-), triflate or trifluoromethylsulfonate (CF3SO3-), bis(fluorosulfonyl)imide (FSI-), bis(trifluoromethanesulfonyl)imide (TFSI-), nitrate (NO3-) and 4,5-dicyano-2-(trifluoromethyl)imidazole (TDI-), acrylate or methacrylate.

[0088] According to one embodiment, the anion of the ionic liquid is selected from TDI-, FSI-, TFSI-, PF6-, BF4-, NO3-, BOB- and CH2=CHCOO-. According to one embodiment, the anion of the ionic liquid is FSI-.

[0089] According to one embodiment, said plasticizer B2 is a mixture of at least two ionic liquids selected from those mentioned above.

[0090] According to one embodiment, said plasticizer B2 is a mixture of at least one ionic liquid and at least one solvent S1 having a boiling point above 100° C., preferably above 110° C., more preferentially above 125° C., in particular above 150° C. and more particularly above 160° C. According to one embodiment, said solvent S1 is -Vinylene carbonate (VC) (CAS: 872-36-6) - Fluoroethylene carbonate or 4-fluoro-1,3-dioxolan-2-one (FEC or F1EC) (CAS: 114435-02-8), -trans-4,5-difluoro-1,3-dioxolan-2-one (F2EC) (CAS: 171730-81-7), - ethylene carbonate (EC) (CAS: 96-49-1), - propylene carbonate (PC) (CAS: 108-32-7), -(2-cyanoethyl)triethoxysilane (CAS: 919-31-3), -3-Methoxypropionitrile (CAS: 110-67-8), - sulfolane (CAS: 126-33-0), - triethyl phosphate (TEP) (CAS: 78-40-0), -b-Butyrolactone (CAS: 96-48-0), ethers, such as polyethylene glycol dimethyl ethers, in particular diethylene glycol dimethyl ether (EG2DME), triethylene glycol dimethyl ether (EG3DME) and tetraethylene glycol dimethyl ether (EG4DME) is selected from.

[0091] The plasticizer makes it possible to obtain improved properties in terms of conductivity, electrochemical stability, thermal stability, compatibility with electrodes, and capacity retention compared to conventional liquid electrolytes.

[0092] Examples of plasticizers B2 according to the invention are the following mixtures: -1-ethyl-3-methylimidazolium FSI and EC, -1-ethyl-3-methylimidazolium FSI and tetraethylene glycol dimethyl ether, -1-ethyl-3-methylimidazolium FSI and EC and FEC, -1-butyl-1-methylpyrrolidinium FSI and tetraethylene glycol dimethyl ether, -1-butyl-1-methylpyrrolidinium FSI and EC and FEC, -N-propyl-N-methylpyrrolidinium and tetraethylene glycol dimethyl ether, -1-ethyl-3-methylimidazolium TFSI and FEC, -1-ethyl-3-methylimidazolium FSI, -1-Butyl-1-methylpyrrolidinium FSI.

[0093] According to one embodiment, in a mixture of at least one ionic liquid and solvent S1, the mass ratio between ionic liquid and solvent forming said plasticizer B2 ranges from 10:0.1 to 0.1:10.

[0094] Support D The film prepared from solution C is deposited on a support D. According to a preferred embodiment, support D is removed after the film drying step to obtain a self-supporting film. In this case, support D can be, by way of non-limiting example, polyethylene terephthalate, polypropylene, aluminum or aluminum coated with a polymer layer.

[0095] According to an alternative embodiment, the support D is a fiber reinforcement. This allows the film prepared from solution C to be held in place. Generally, if the support is a fiber reinforcement, it is not removed. The fiber reinforcement consists of any material (porous membrane, woven or nonwoven) that allows improved mechanical properties. It may be, but is not limited to, a polypropylene nonwoven, a polyethylene terephthalate nonwoven, a polyvinylidene fluoride nonwoven, or a polypropylene microporous membrane.

[0096] composition According to another aspect, the present invention provides a composition for preparing a solid electrolyte, the composition corresponding to the solution C used in the above method. Preferably, the composition comprises the at least one fluoropolymer A1, the at least one organic solvent A2, the at least one alkali metal salt B1, and the at least one plasticizer B2, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure of 7 Pa to 24 kPa at 20°C, and a flash point preferably greater than -15°C, and a mass content of water less than 5000 ppm based on the total weight of the composition.

[0097] Advantageously, the composition comprises, based on the total weight of the composition, 0.75% to 18% by weight of the at least one fluoropolymer A1, 75% to 95% by weight of the at least one organic solvent A2, 0.1% to 7.5% by weight of the at least one alkali metal salt B1, and 0.5% to 20% by weight of the at least one plasticizer B2, and a mass content of water of less than 5000 ppm, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure at 20°C of 7 Pa to 24 kPa, and preferably a flash point greater than -15°C.

[0098] Preferably, the composition comprises, based on the total weight of the composition, 0.75 wt % to 18 wt % of the at least one fluoropolymer A1, 75 wt % to 95 wt % of the at least one organic solvent A2, 0.1 wt % to 7.5 wt % of the at least one alkali metal salt B1, and 0.5 wt % to 20 wt % of the at least one plasticizer B2, and a mass content of water greater than 1 ppb to less than 5000 ppm, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure at 20°C of 7 Pa to 24 kPa, and preferably a flash point greater than -15°C.

[0099] In particular, the composition comprises, based on the total weight of the composition, 2.25% to 18% by weight of the at least one fluoropolymer A1, 75% to 85% by weight of the at least one organic solvent A2, 0.3% to 7.5% by weight of the at least one alkali metal salt B1, and 1.5% to 20% by weight of the at least one plasticizer B2, and a mass content of water of less than 5000 ppm, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure at 20°C of 7 Pa to 24 kPa, and preferably a flash point greater than -15°C.

[0100] More specifically, the composition comprises, based on the total weight of the composition, 2.25 wt % to 18 wt % of the at least one fluoropolymer A1, 75 wt % to 85 wt % of the at least one organic solvent A2, 0.3 wt % to 7.5 wt % of the at least one alkali metal salt B1, and 1.5 wt % to 20 wt % of the at least one plasticizer B2, and a mass content of water greater than 1 ppb to less than 5000 ppm, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure at 20°C of 7 Pa to 24 kPa, and preferably a flash point greater than -15°C.

[0101] The organic solvent A2 can be as described above. The fluoropolymer A1 can be as described above. The alkali metal salt B1 can be as described above. The plasticizer B2 can be as described above.

[0102] Furthermore, the composition may have a water content by mass of less than 5000 ppm, advantageously less than 4000 ppm, preferably less than 3000 ppm, more preferentially less than 2000 ppm, in particular less than 1000 ppm, more particularly less than 500 ppm, preferably less than 100 ppm, advantageously preferably less than 50 ppm, preferentially preferably less than 10 ppm, based on the total weight of the composition. Preferably, the composition may have a water content by mass of more than 1 ppb, more preferentially more than 10 ppb, preferably more than 100 ppb, in particular more than 1 ppm, based on the total weight of the composition.

[0103] According to a preferred embodiment, the composition is heated at room temperature for 10 seconds. -1 It has a solution viscosity of 100 to 50,000 cP.

[0104] film According to another aspect, the present invention provides a film, preferably a non-porous film, i.e. a film having a porosity of less than 10%, more preferentially less than 5%, in particular less than 1%. The porosity of the film is obtained according to the following calculation, as described in the publication by M. Cai, Nature Communications, 10, 2019, 4597:

[0105]

number

[0106]

number

[0107] According to a preferred embodiment, the film comprises, based on the total weight of the film, 15% to 70% by weight of the at least one fluoropolymer A1, 10% to 80% by weight of the plasticizer B2, 2% to 30% by weight of the alkali metal salt B1, and 1 ppb to 5000 ppm of water. The contents expressed herein relate to the film without taking into account the support D, i.e. after its removal. Preferably, the film also comprises 1 ppb to 15% of the at least one organic solvent A2. The film may comprise 20% to 70% of the at least one fluoropolymer A1, advantageously 25% to 70% of the at least one fluoropolymer A1, preferably 30% to 70% of the at least one fluoropolymer A1.

[0108] Thus, preferably, the film consists of 15% to 70% by weight of the at least one fluoropolymer A1, 10% to 80% by weight of the plasticizer B2, 2% to 30% by weight of the alkali metal salt B1, 1 ppb to 15% of the at least one organic solvent A2, and 1 ppb to 5000 ppm of water, based on the total weight of the film, the sum of the components being equal to 100. More preferentially, the film consists of 20% to 70% by weight of the at least one fluoropolymer A1, 10% to 80% by weight of the plasticizer B2, 2% to 30% by weight of the alkali metal salt B1, 1 ppb to 15% of the at least one organic solvent A2, and 1 ppb to 5000 ppm of water, based on the total weight of the film, the sum of the components being equal to 100.

[0109] According to a preferred embodiment, the content of organic solvent A2 as defined in the present patent application in the film is between 1 ppb and 10%, more preferentially between 1 ppb and 5%, in particular between 1 ppb and 1%, and more particularly between 1 ppb and 5000 ppm. More preferentially, the content of organic solvent A2 as defined in the present patent application in the film is between 10 ppb and 15%, advantageously between 10 ppb and 10%, preferably between 10 ppb and 5%, more preferentially between 10 ppb and 1%, and in particular between 10 ppb and 5000 ppm. In particular, the content of organic solvent A2 as defined in the present patent application in the film is between 100 ppb and 15%, advantageously between 100 ppb and 10%, preferably between 100 ppb and 5%, more preferentially between 100 ppb and 1% and in particular between 100 ppb and 5000 ppm.

[0110] Furthermore, in this film, the water content by mass is less than 5000 ppm, advantageously less than 4000 ppm, preferably less than 3000 ppm, more preferentially less than 2000 ppm, in particular less than 1000 ppm, more particularly less than 500 ppm, preferably less than 100 ppm, advantageously preferably less than 50 ppm, preferentially preferably less than 10 ppm, and the water content by mass is greater than 1 ppb, more preferentially greater than 10 ppb, in particular greater than 100 ppb, more particularly greater than 1 ppm.

[0111] Advantageously, the film contains little or no solvent and has high ionic conductivity. Advantageously, the film is self-supporting, meaning that it can be handled without the aid of a support. Advantageously, the film is windable, meaning that it can be handled so that it can be wound onto a reel.

[0112] According to an alternative embodiment, when the film comprises a fiber reinforcement, the mass ratio between the film and the fiber reinforcement is between 1.5 and 9.

[0113] According to one embodiment, said film has a thickness of between 5 and 60 μm, preferably between 5 and 30 μm and more preferentially between 7 μm and 20 μm.

[0114] Advantageously, said film has a thickness variation of less than 20% over its entire length, preferably less than 15% over its entire length, in particular less than 10% over its entire length.

[0115] According to one embodiment, the film according to the invention has an ionic conductivity in the range of 0.01 to 5 mS / cm, preferably 0.05 to 5 mS / cm, advantageously 0.5 to 5 mS / cm at 25°C. The conductivity is measured by electrochemical impedance spectroscopy. According to one embodiment, the non-porous film is placed between two gold electrodes in a leak-proof conductive cell and under an inert atmosphere (CESH, Biologic), and electrochemical impedance spectroscopy is carried out between 1 Hz and 1 MHz at an amplitude of 10 mV. The resistance R of the film is then determined by linear regression of the curve -Im(Z)=f(Re(Z)). The conductivity σ is obtained by the following relationship:

[0116]

number

[0117] Advantageously, the films according to the invention have good electrochemical stability over a temperature range extending from -20°C to 80°C.

[0118] Advantageously, the film retains its properties up to 80°C and does not ignite below 130°C.

[0119] According to one embodiment, the film according to the invention has a mechanical strength characterized by a modulus of elasticity greater than 0.1 MPa, preferentially greater than 1 MPa, more preferentially greater than 10 MPa, measured by dynamic mechanical analysis at 1 Hz and 23°C.

[0120] Another subject of the invention is a separator for an all-solid-state battery, consisting entirely or partly of said film, in which case the presence of said lithium salt may be optional.

[0121] The present invention also relates to an electrochemical device selected from the following group, comprising the separator described above: a battery, a capacitor, an electrochemical double layer electric capacitor, and a membrane electrode assembly (MEA) for a fuel cell or an electrochromic device.

[0122] Another subject of the present invention is an all-solid-state battery, such as a Li-ion battery, or a Li-S or Li-air battery, comprising an anode, a cathode and a separator, said separator comprising a film such as defined above.

[0123] According to one embodiment, the battery includes a lithium metal anode.

[0124] The present invention also relates to an all-solid-state battery comprising such a film, preferably a non-porous film, according to the present invention. [Example]

[0125] The following examples illustrate the scope of the present invention in a non-limiting manner.

[0126] Measurement of polymer electrolyte film thickness Pellets with a diameter of 20 mm are cut from the polymer electrolyte film, and the mass and thickness of each pellet are measured. The mass of the pellets is measured using a Mettler Toledo XPE105 balance with a reading accuracy of 0.01 mg. The pellet thickness is measured using a Mitutoyo IDH0530 Digimatic Comparator with an accuracy of 0.5 μm. These pellets are collected every 10 cm along the length of the coating. The mass and thickness of these pellets are shown in Figure 1.

[0127] [Example 1] (Comparison): Film preparation in the presence of acetone 5.91 g of P(VDF-HFP) (poly(vinylidene fluoride)-co-hexafluoropropylene) was dissolved in 30 g of acetone (donor number = 17 kcal / mol; saturated vapor pressure = 24.7 kPa at 20 °C) in a Thinky ARE250 planetary mixer at room temperature. Separately, 0.47 g of LiFSI (lithium bis(fluorosulfonyl)amide) was dissolved in 5.48 g of EMIM-FSI (1-ethyl-3-methylimidazolium bis(fluorosulfonylimide)). The latter solution was added to the P(VDF-HFP) solution and then mixed. The final solution was coated onto a 13 μm-thick, 30 cm-wide aluminum strip at a coating speed of 0.5 m / min using a coating machine with a doctor blade set at 200 μm from the aluminum strip. The coating was dried in an oven at 25 °C for 2 hours to evaporate the acetone. This results in a polymer electrolyte film approximately 1.50 m long and 10 cm wide.

[0128] As can be seen from Figure 1, acetone is not a suitable solvent for the preparation of flexible electrolyte films, as the film thickness and mass are not uniform along the length of the coating, with approximately 40% variation in film thickness and mass between the start and end of coating (over a length of 1.50 m).

[0129] [Example 2] (Invention): Film production in the presence of 2-butanone 5.91 g of P(VDF-HFP) (poly(vinylidene fluoride)-co-hexafluoropropylene) was dissolved in 30 g of 2-butanone (donor number = 17.4 kcal / mol; saturated vapor pressure = 10.3 kPa at 20 °C) in a Thinky ARE250 planetary mixer at room temperature. Separately, 0.47 g of LiFSI (lithium bis(fluorosulfonyl)amide) was dissolved in 5.48 g of EMIM-FSI (1-ethyl-3-methylimidazolium bis(fluorosulfonylimide)). The latter solution was added to the P(VDF-HFP) solution and then mixed. The final solution was coated onto a 13 μm-thick, 30 cm-wide aluminum strip at a coating speed of 0.5 m / min using a coating machine with a doctor blade set at 200 μm from the aluminum strip. The coating was dried in an oven at 25 °C for 2 hours to evaporate the acetone. This results in a polymer electrolyte film approximately 1.50 m long and 10 cm wide.

[0130] 2-Butanone is a suitable solvent for preparing flexible electrolyte films because the film thickness and mass are relatively uniform along the coating length (approximately 10% variation as shown in Figures 1 and 2), unlike solvents such as acetone (approximately 50% variation along the coating length).

Claims

1. 1. A method for preparing a solid electrolyte in film form, comprising: providing a solution C comprising at least one fluoropolymer A1, at least one organic solvent A2, at least one alkali metal salt B1 and at least one plasticizer B2; - depositing said solution C on a support D to form a film; - drying the film thus obtained; Including, 10. The method of claim 9, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol and a saturated vapor pressure at 20° C. of less than 24 kPa, and the at least one plasticizer B2 comprises at least one ionic liquid.

2. 2. The method according to claim 1, wherein solution C is obtained according to the following steps: - preparing a solution A comprising said at least one fluoropolymer A1 and said at least one organic solvent A2; - preparing a solution B comprising said at least one alkali metal salt B1 and said at least one plasticizer B2; - Mixing solution A and solution B to obtain solution C.

3. 3. The method according to claim 1, wherein the at least one organic solvent A2 has a flash point above -15°C.

4. 4. The method according to claim 1, wherein the at least one organic solvent A2 has a saturated vapor pressure of more than 7 Pa at 20°C.

5. 5. The method according to claim 1, wherein the at least one organic solvent A2 has a mass content of water of less than 5000 ppm.

6. 6. The method according to claim 1, wherein the at least one fluoropolymer A1 comprises monomer units derived from vinylidene fluoride and optionally monomer units derived from a monomer selected from the group consisting of: vinyl fluoride; trifluoroethylene (VF ３ ), chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ X (wherein X is SO ２ F, CO ２ H, CH ２ OH, CH ２ OCN or CH ２ OPO ３ H); the product of formula CF ２ = CFOCF ２ CF ２ SO ２ F product; ２ ) nCH ２ OCF = CF ２ wherein n is 1, 2, 3, 4 or 5; １ CH ２ OCF = CF ２ (In the formula, R １ is hydrogen or F(CF ２ ) m, where m has a value of 1, 2, 3 or 4; ２ OCF=CH ２ (In the formula, R ２ is F(CF ２ )p, where p is 1, 2, 3, or 4); perfluorobutylethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, and 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or mixtures thereof.

7. 7. The method according to any one of claims 1 to 6, characterized in that the at least one fluoropolymer A1 is a homopolymer of vinylidene fluoride or a copolymer comprising monomer units arising from vinylidene fluoride and from monomers selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or mixtures thereof.

8. The at least one alkali metal salt B1 is LiCF ３ SO ３ 4, LiPF ６ 6, LiClO ４ 4, LiBF ４ 4, LiB(C ２ 2O ４ 4), LiN(SO ２ 2F) ２ 2CF ３ 3), ２ 2C ２ F ３ 3), ２ 2C ２ F ５ 3), ２ 2F)(SO ２ 2CF ３ 3), LiN(SO ２ 2C ２ F ５ 3), LiN(SO ３ 2CF ２ 3)(SO ５ 2C ２ F ５ 3), LiAsF ６ 6, LiBF ２ 4C ２ 2O ４ 4), ３ LiBETI, LiTDI, NaTDI, KTDI, NaClO ４ 4, KClO ４ 4, NaPF ６ 6, KPF ６ 6, NaBF ４ 4, KBF ４ 4, NaAsF ６ 6, KAsF ６ 6, NaCF ３ 4SO ３ 4, KCF ３ 4, NaN(CF ３ 2SO ２ 3), KN(CF ３ SO ２ ) ２ , NaN(SO ２ C ２ F ５ ) ２ , NaN(SO ２ F) (SO ２ CF ３ ), NaN(SO ２ F) (SO ２ C ２ F ５ ), NaN(SO ２ CF ３ ) (SO ２ C ２ F ５ ), KN(SO ２ C ２ F ５ ) ２ , KN(SO ２ F) (SO ２ CF ３ ), KN(SO ２ F) (SO ２ C ２ F ５ ), KN(SO ２ CF ３ ) (SO ２ C ２ F ５ 8. The method according to claim 1, wherein the hydroxybenzoate is selected from the group consisting of hydroxybenzoates, ...

9. The at least one plasticizer B2 is selected from the group consisting of tetrafluoroborate (BF4-), bis(oxalato)borate BOB-, hexafluorophosphate (PF6-), hexafluoroarsenate (AsF6-), triflate or trifluoromethylsulfonate (CF3SO3-), bis(fluorosulfonyl)imide (FSI-), bis(trifluoromethanesulfonyl)imide (TFSI-), nitrate (NO3-), 4,5-dicyano-2-(trifluoromethyl)imidazole (TDI-), acrylate or methacrylate, and an anion selected from the group consisting of ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolinium, phosphonium, guanidinium, piperazine, methylcellulose ...

9. The method according to claim 1, wherein the at least one plasticizer B2 is an ionic liquid comprising a cation selected from the group consisting of thiazolium, triazolium, oxazolium, pyrazolium, and mixtures thereof, or the at least one plasticizer B2 is a mixture of at least one ionic liquid and at least one solvent S1 having a boiling point above 100°C selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, trans-4,5-difluoro-1,3-dioxolan-2-one, ethylene carbonate, propylene carbonate, (2-cyanoethyl)triethoxysilane, 3-methoxypropionitrile, sulfolane, and polyethylene glycol dimethyl ether.

10. 10. The method according to any one of claims 1 to 9, characterized in that the film has a porosity of less than 10%.

11. 11. The method of any one of claims 1 to 10, wherein the film has a thickness variation of less than 20% over its entire length.

12. 1. A composition for preparing a solid electrolyte comprising at least one fluoropolymer A1, at least one organic solvent A2, at least one alkali metal salt B1, and at least one plasticizer B2 comprising at least one ionic liquid, wherein the at least one organic solvent A2 has a donor number greater than 4 kcal / mol, a saturated vapor pressure at 20°C of 7 Pa to 24 kPa, a flash point greater than -15°C, and a mass content of water less than 5000 ppm.

13. 13. Composition according to claim 12, characterized in that said at least one fluoropolymer A1 is as defined in claim 6 or 7, said at least one alkali metal salt B1 is as defined in claim 8 and said at least one plasticizer B2 is as defined in claim 9.

14. A film comprising, based on the total weight of the film, 15% to 70% by weight of at least one fluoropolymer A1, 10% to 80% by weight of a plasticizer B2) comprising at least one ionic liquid, 2% to 30% by weight of an alkali metal salt B1, and 1 ppb to 5000 ppm of water.

15. 15. The film according to claim 14, characterized in that it comprises from 1 ppb to 15% of the at least one organic solvent A2 as defined in any one of claims 1 to 5.

16. 16. The film according to claim 14 or 15, characterized in that it consists of 15% to 70% by weight of at least one fluoropolymer A1, 10% to 80% by weight of a plasticizer B2 comprising at least one ionic liquid, 2% to 30% by weight of an alkali metal salt B1, 1 ppb to 15% of said at least one organic solvent A2, and 1 ppb to 5000 ppm of water, with the sum of each component being equal to 100, based on the total weight of the film.

17. 17. A film according to any one of claims 14 to 16, characterized in that it has an ionic conductivity at 25°C, measured by electrochemical impedance spectroscopy, of 0.01 to 5 mS / cm, preferably 0.05 to 5 mS / cm, advantageously 0.5 to 5 mS / cm.

18. 18. A film according to any one of claims 14 to 17, characterized in that it is obtainable by the method according to any one of claims 1 to 11.

19. 19. A film according to any one of claims 14 to 18, characterized in that it has a thickness variation of less than 20% over its entire length.

20. 20. A film according to any one of claims 14 to 19, characterized in that it has a porosity of less than 10%.

21. A separator for a lithium-ion rechargeable battery comprising the film of any one of claims 14 to 20.

22. 21. An electrochemical device selected from the group consisting of a battery, a capacitor, an electrochemical double layer electric capacitor, and a membrane electrode assembly (MEA) for a fuel cell or an electrochromic device, comprising the film of any one of claims 14 to 20.

23. 21. An all-solid-state battery comprising an anode, a cathode, and a separator, wherein the separator comprises the film of any one of claims 14 to 20.

24. 21. An all-solid-state battery comprising an anode, a cathode, and a separator, wherein the anode and / or the cathode comprises the film of any one of claims 14 to 20.

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