CATHODE COATING FOR ALL-SOLID NA-ION OR K-ION BATTERIES

Abstract

The present invention relates generally to the field of electrical energy storage in rechargeable Na-ion or K-ion secondary batteries. More specifically, the invention concerns a cathode coating for an all-solid-state Na-ion or K-ion battery. The invention also relates to a method for preparing said coating. The invention further relates to a cathode coated with this coating, to the method for manufacturing such a cathode, and to Na-ion or K-ion secondary batteries comprising such a cathode.

Description

Title of the invention: CATHODE COATING FOR ALL-SOLID NA-ION OR K-ION BATTERIES FIELD OF INVENTION

[0001] The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of the Na-ion or K-ion type. More specifically, the invention relates to a cathode coating for an all-solid-state Na-ion or K-ion battery. The invention also relates to a method for preparing said coating. The invention further relates to a cathode coated with this coating, to the method for manufacturing such a cathode, and to Na-ion or K-ion secondary batteries comprising such a cathode. TECHNICAL BACKGROUND

[0002] Demand for lithium-ion batteries has increased in recent years due to their application in a wide variety of electronic devices such as mobile phones and electric vehicles. However, lithium-based compounds are relatively expensive, and natural lithium sources are unevenly distributed and difficult to access, being located in only a small number of countries. Alternatives to lithium have been sought. To this end, sodium-ion batteries have been developed. Sodium is indeed very abundant and homogeneously distributed in the Earth's crust. It is advantageously non-toxic and more economical.

[0003] However, the redox potential of the Na+ / Na couple is -2.71 V relative to the standard hydrogen electrode (SHE) and is therefore higher than that of the Li+ / Li couple, whose potential is -3.05 V relative to the standard hydrogen electrode, for a molar mass three times greater. These characteristics make sodium-ion batteries less energy-dense. New active oxide-type cathode materials bridge this gap between these two technologies by increasing the voltage and specific capacity. Unfortunately, these new materials have the drawback of being basic and therefore poorly suited to the binders conventionally used in the solvent-based cathode manufacturing process for lithium batteries. For example, a sodium-ion battery comprising a cathode prepared from a cathode material, PVDF, and carbon black is known from US2024079577.

[0004] Existing sodium secondary batteries generally use liquid electrolytes containing an organic substance. These liquid electrolytes advantageously have high ionic conductivity, but require devices additional safety measures are required due to the risk of liquid leakage, fire, or high-temperature explosion.

[0005] In an attempt to solve the safety problems associated with liquid electrolytes, recently, all-solid batteries using solid electrolytes have been developed.

[0006] An all-solid-state battery generally comprises a positive electrode, a solid electrolyte, and a negative electrode. The positive electrode comprises a positive electrode active material and a solid electrolyte, and further comprises an electronically conductive material and a binder. Like the positive electrode, the negative electrode comprises a negative electrode active material and a solid electrolyte, and further comprises a conductive material and a binder.

[0007] However, there is currently no solid electrolyte that meets the specifications for widespread use of all-solid-state batteries. Indeed, for solid electrolytes, it is generally difficult to combine ionic conductivity, electrochemical stability, mechanical strength, and compatibility with anode or cathode materials.

[0008] There is still a need to develop a solution that makes a cathode compatible with a solid electrolyte in an all-solid Na-ion or K-ion battery.

[0009] The invention therefore aims to provide a coating applicable directly to a positive electrode of a Na-ion or K-ion battery, thus allowing physical separation between the solid electrolyte and the active electrode material and making it possible to use solid electrolytes which seemed unstable with respect to certain active materials.

[0010] The invention also aims to provide a method for manufacturing said cathode coating. Finally, the invention relates to a cathode having such a coating, and to the method for manufacturing such a cathode.

[0011] Finally, the invention aims to provide rechargeable Na-ion or K-ion secondary batteries comprising such a cathode. Summary of the invention

[0012] The technical solution proposed by the present invention is to provide a cathode coating which makes the cathode compatible with a solid electrolyte in an all-solid battery.

[0013] The invention relates primarily to a cathode coating comprising, preferably consisting of: a. at least one fluoropolymer PI (component A), b. at least one sodium or potassium salt (component B), and c. at least one conductivity additive (component C).

[0014] According to a preferred embodiment, said at least one PI fluorinated polymer comprising repeating units from a monomer Mla selected from the group consisting of vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, 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); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2 =CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE);trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof. ;

[0015] According to a preferred embodiment, said PI fluorinated polymer comprises repeating units from monomer Mla and repeating units from monomer Mlb or repeating units from monomer Mlc; said monomer Mla being vinylidene fluoride; said monomer Mlb selected from the group consisting of vinyl fluoride; trifluoroethylene (TrFE); 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); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2 =CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5;the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2 OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof; said monomer Mlc being selected; among the group consisting of formula R1R2C=C(R3)((X1)PC(O)R4) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and C1-C5 alkyl; R4 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR5 with R5 selected from the group consisting of H and CrCi8 alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H, -OC(O)R6, -C(O)O-R6 or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; R6 being selected from the group consisting of Ci-C6 alkyl or C6-Ci2 aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H group(s); p is 0 or 1; X1 is selected from the group consisting of -[-C(O)OC(R7)(R8)C(R9)(R10)-]wi- and a Ci-Cio alkyl hydrocarbon group optionally bearing one or more -OH, -CO2H or ester(s) group(s);with wl being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5; R7, R8, R9, R10 are independently of each other, independently for each unit wl, selected from the group consisting of H and Ci-C5 alkyl.

[0016] According to a preferred embodiment, said at least one PI polymer comprises monomeric units derived from a monomer Mla being vinylidene fluoride and monomeric units derived from a monomer Mlb selected from the group consisting of trifluoroethylene, 1,1-chlorofluoroethylene, chlorotrifluoroethylene, hexafluoropropene and tetrafluoroethylene, or a mixture thereof.

[0017] According to a preferred embodiment, said PI fluorinated polymer comprises monomeric units bearing at least one of the following functions: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, or phosphonic.

[0018] According to a preferred embodiment, said sodium or potassium salt is selected from the group consisting of NaCF3SO3, NaPF6, NaC1O4, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2CF2CF3)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2CF2CF3), NaN(SO2CF3)(SO2CF2CF3), NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaTDI, KCF3SO3, KPF6, KC1O4, KBF4, KB(C2O4)2, KN(SO2F)2, KN(SO2CF3)2, KN(SO2C2F3)2, KN(SO2CF2CF3)2, KN(SO2F)(SO2CF3), KN(SO2F)(SO2CF2CF3), KN(SO2CF3)(SO2CF2CF3), KAsF6, kbf2c2o4, KNO3, KPF3(CF2CF3)3 and KTDI or a mixture of these.

[0019] According to a preferred embodiment, component C is chosen from linear or cyclic ethers, esters, lactones, cyclic ketones, nitriles, carbonates and ionic liquids.

[0020] According to a preferred embodiment, said coating has a thickness ranging from 0.1 to 100 pm, preferably from 0.1 to 50 pm and more preferably from 0.1 to 35 pm.

[0021] According to a preferred embodiment, said coating has the following mass composition:

[0022] - Component A with a ratio between 20 and 80%,

[0023] - Component B with a ratio between 1 and 40%,

[0024] - Component C with a ratio between 2 and 50%,

[0025] preferably, the sum of these ratios being 100%.

[0026] The present invention also provides a method for manufacturing said cathode coating according to the present invention from an ink obtained by mixing all the constituents of the coating in a solvent.

[0027] According to a preferred embodiment, said solvent is selected from the group consisting of acetone, acetyl triethyl citrate, γ-butyrolactone, cyclohexanone, cyclopentanone, dibutyl phthalate, dibutyl sebacate, diethyl carbonate, diethyl phthalate, dihydrolevoglucosenone, dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 3-Heptanone, hexamethyl phosphoramide, 3-hexanone, methyl ethyl ketone, N-methyl-2-pyrrolidinone, 3-octanone, 3-pentanone, propylene carbonate, tetrahydrofuran, tetramethylurea, triacetin, triethyl citrate, triethyl phosphate, trimethyl phosphate, N,N' tetrabutylsuccindiamide and their mixtures.

[0028] The present invention also provides a cathode for an all-solid sodium-ion or potassium-ion battery, said cathode consisting of an active material, a binder and a conductive material, and having a coating layer according to the present invention.

[0029] According to a preferred embodiment, said active material is selected from the group consisting of at least one active material of formula NaxMyO2 or of formula KxMyO2; M comprising at least one metal or a mixture of metals; x is between 0 and 1; y is between 0 and 1.

[0030] According to a preferred embodiment, said conductive material is selected from carbon blacks, graphites, natural or synthetic, carbon fibers, carbon nanotubes, metal fibers and powders, and conductive metal oxides.

[0031] According to a preferred embodiment, said binder is a polymer selected from polyolefins, fluorinated polymers, fluorinated polymers having acid functions, polyacrylic acids, polyacrylonitril, polymers of the type cellulose, polyphenylsulfone, polyethersulfone, a phenolic resin, a vinyl ester resin, an epoxy resin, or a liquid-crystal polymer.

[0032] According to a preferred embodiment, said cathode has a porosity of less than 10%, preferably less than 5%.

[0033] The present invention also provides a method for manufacturing a positive electrode for a Na-ion or K-ion battery, said method comprising the steps of:

[0034] - provide a cathode,

[0035] - deposit on said cathode a coating layer according to the present invention.

[0036] The present invention also provides an all-solid Na-ion or K-ion secondary battery comprising an anode, a cathode according to the present invention and an all-solid electrolyte.

[0037] The present invention overcomes the drawbacks of the prior art. It provides an ionically conductive coating having a homogeneous distribution of its dielectric constant.

[0038] In the context of the invention, the coating allows the use of positive electrodes without solid electrolytes mixed with the active material of the cathode. Indeed, the coating can be applied directly to a conventional positive electrode having a porosity between 15 and 45% before or after calendering. This coating thus provides a physical separation between the solid electrolyte and the active material, thereby allowing the use of solid electrolytes that previously appeared unstable with respect to certain active materials. Thus, the present invention provides a positive electrode comprising a first layer consisting of a conventional positive electrode and a second layer consisting of a cathode coating according to the present invention.

[0039] The invention provides a coating exhibiting a very good compromise between ionic conductivity, electrochemical stability, high-temperature stability, and mechanical strength.

[0040] DESCRIPTION OF EMBODIMENT METHODS OF THE INVENTION

[0041] The invention is now described in more detail and in a non-limiting manner in the following description.

[0042] According to a first aspect, the invention relates to a cathode coating comprising, preferably consisting of: a. at least one fluoropolymer PI (component A), b. at least one sodium or potassium salt (component B), and c. at least one conductivity additive (component C).

[0043] According to various embodiments, said coating comprises the following characteristics, possibly combined. The contents indicated are expressed by weight, unless otherwise stated. Component A

[0044] Said fluorinated polymer PI comprises in its chain at least monomeric units derived from a fluorinated monomer Mla selected from compounds containing a vinyl group capable of opening to polymerize and which contains, directly attached to this vinyl group, at least one fluorine atom, a fluoroalkyl group or a fluoroalkoxy group. Preferably, said fluorinated polymer PI is semi-crystalline.

[0045] Preferably, said fluorinated polymer PI comprises monomeric units derived from a monomer Mla selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); 1,2-difluoroethylene; hexafluoropropylene (HFP); trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, 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); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2 X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and 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 a mixture thereof. Examples of trifluoropropene include 3,3,3-trifluoropropene. Examples of tetrafluoropropene include 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene. Examples of pentafluoropropene include 1,1,3,3,3-pentafluoropropene and 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene can refer to either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0046] In particular, said PI fluorinated polymer comprises at least monomeric units derived from a monomer Mla, namely vinylidene fluoride. The PI fluorinated polymer may be a homopolymer or a copolymer of vinylidene fluoride.

[0047] According to a particular embodiment, the PI fluorinated polymer is a vinylidene fluoride homopolymer.

[0048] According to another particular embodiment, the fluorinated polymer PI is a polymer comprising monomeric units derived from a monomer Mla, being vinylidene fluoride, and monomeric units derived from a fluorinated monomer Mlb copolymerizable with vinylidene fluoride, or monomeric units derived of a non-fluorinated monomer Mlc or a mixture of the two. In said fluorinated polymer PI, the mass percentage of monomeric units Mla is at least 50%, preferably at least 60%, more preferably greater than 70%, and advantageously greater than 80%. Preferably, when the fluorinated monomer Mla is vinylidene fluoride, the mass percentage of vinylidene fluoride monomeric units in said fluorinated polymer PI is at least 50%, preferably at least 60%, more preferably greater than 70%, and advantageously greater than 80%.

[0049] According to one embodiment, said fluorinated polymer PI comprises monomeric units derived from a monomer Mla being vinylidene fluoride and monomeric units derived from a fluorinated monomer Mlb selected from the group consisting of vinyl fluoride, 1,2-difluoroethylene, hexafluoropropylene (HFP), trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(l,3-dioxole); perfluoro(2,2-dimethyl-l,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF 3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4;the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. Preferably, the fluoropolymer PI comprises monomeric units derived from a monomer Mla being vinylidene fluoride and monomeric units derived from a fluoro monomer Mlb selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene; perfluoro(alkyl vinyl)ethers such as perfluoro(methyl vinyl)ether, perfluoro(ethyl vinyl)ether or perfluoro(propyl vinyl)ether; perfluoro(l,3-dioxole); perfluoro(2,2-dimethyl-l,3-dioxole); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H;the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R'CH2OCF=CF2 in which R' is hydrogen or F(CF2)z and z is 1, 2, 3 or 4; the product of formula R”OCF=CH2 in which R” is F(CF2)z and z is 1, 2, 3 or 4; trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene; Chlorofluoroethylene, chlorotrifluoropropene, or 2-trifluoromethyl-3,3,3-trifluoro-1-propene, or a mixture thereof. In particular, the fluorinated polymer PI comprises monomeric units derived from a monomer Mla, being vinylidene fluoride, and monomeric units derived from a fluorinated monomer Mlb selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, chlorofluoroethylene, and hexafluoropropylene, or a mixture thereof. Said polymer PI may, in particular, be a copolymer of vinylidene fluoride and hexafluoropropene. Preferably, said monomeric units derived from a fluorinated monomer Mlb may be present in a mass content of 1 to 40% based on the total weight of the polymer PI, advantageously from 3 to 35%, preferably from 3 to 30%, and more preferably from 3 to 25%.

[0050] Said PI polymer may also comprise monomeric units derived from a monomer Mla selected from the group consisting of vinylidene fluoride (VDF); trifluoroethylene (TrFE); chlorotrifluoroethylene (CTFE), chlorofluoroethylene (CFE), 1,2-difluoroethylene, and tetrafluoroethylene (TFE). Preferably, said fluorinated PI polymer comprises monomeric units derived from a monomer Mla being vinylidene fluoride and monomeric units derived from a fluorinated monomer Mlb selected from the group consisting of trifluoroethylene, 1,1-chlorofluoroethylene, chlorotrifluoroethylene, hexafluoropropene, and tetrafluoroethylene, or a mixture thereof.Said at least one PI polymer may comprise monomeric units derived from vinylidene fluoride, trifluoroethylene and optionally from 1,1-chlorofluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene or hexafluoropropene or a mixture thereof; or monomeric units derived from vinylidene fluoride, tetrafluoroethylene and optionally from 1,1-chlorofluoroethylene, trifluoroethylene, chlorotrifluoroethylene or hexafluoropropene or a mixture thereof.The said PI polymer may in particular be a copolymer of vinylidene fluoride and trifluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and chlorotrifluoroethylene, a terpolymer of vinylidene fluoride, chlorotrifluoroethylene and tetrafluoroethylene, a terpolymer of vinylidene fluoride, chlorotrifluoroethylene and trifluoroethylene, a terpolymer of vinylidene fluoride, trifluoroethylene and hexafluoropropene, a terpolymer of vinylidene fluoride, tetrafluoroethylene and 1,1-chlorofluoroethylene, a terpolymer of vinylidene fluoride, trifluoroethylene and 1,1-chlorofluoroethylene or a terpolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene. In the PI polymer, the molar content of vinylidene fluoride can be at least 10 mol%, advantageously at least 20 mol%, preferably at least 30 mol%. %, more preferably at least 40 mol%, in particular at least 50 mol%, more particularly at least 55 mol%. Preferably, the molar content of vinylidene fluoride may be between 55 and 99 mol%, advantageously between 55 and 95 mol%, preferably between 60 and 95 mol%, in particular between 65 and 95 mol%. In the PI polymer, the molar content of trifluoroethylene may be at least 1 mol%, advantageously at least 5 mol%, preferably at least 7 mol%, more preferably at least 10 mol%, in particular at least 12 mol%, more particularly at least 15 mol%. Preferably, the molar content of trifluoroethylene can be between 15 and 50%, advantageously between 17 and 45 mol%, preferably between 20 and 40 mol%, in particular between 20 and 35 mol%, more particularly between 20 and 30 mol%.In the PI polymer, the molar content of chlorotrifluoroethylene may be at least 0.5 mol%, advantageously at least 1 mol%, preferably at least 2 mol%, more preferably at least 3 mol%, in particular at least 4 mol%, more particularly at least 5 mol%. Preferably, the molar content of chlorotrifluoroethylene may be between 1 and 20%, advantageously between 2 and 17 mol%, preferably between 3 and 15 mol%, in particular between 4 and 15 mol%, more particularly between 5 and 12 mol%. In the PI polymer, the molar content of tetrafluoroethylene may be at least 1 mol%, advantageously at least 5 mol%, preferably at least 7 mol%, more preferably at least 10 mol%, in particular at least 15 mol%, more particularly at least 20 mol%.Preferably, the molar content of tetrafluoroethylene may be between 1 and 60%, advantageously between 2 and 55 mol%, preferably between 5 and 50 mol%, in particular between 7 and 45 mol%, more particularly between 10 and 40 mol%.

[0051] In the PI polymer, the molar content of chlorofluoroethylene may be at least 0.5 mol%, advantageously at least 1 mol%, preferably at least 2 mol%, more preferably at least 3 mol%, in particular at least 4 mol%, more particularly at least 5 mol%. Preferably, the molar content of chlorofluoroethylene may be between 1 and 20%, advantageously between 2 and 17 mol%, preferably between 3 and 15 mol%, in particular between 4 and 15 mol%, more particularly between 5 and 12 mol%. In a copolymer of vinylidene fluoride and trifluoroethylene, the molar content of vinylidene fluoride may be between 60 and 99 mol%, advantageously between 65 and 95 mol%, preferably between 65 and 90 mol%, more preferably between 70 and 85 mol%; and the molar content of trifluoroethylene may be between 1 and 40 mol%, advantageously between 5 and 35 mol%, preferably between 10 and 35 mol%, more preferably between 15 and 30 mol%.In a copolymer of vinylidene fluoride and tetrafluoroethylene, the molar content of vinylidene fluoride may be between 40 and 99 mol%, advantageously between 45 and 95 mol%, preferably between 50 and 90 mol%, plus. preferably between 55 and 85 mol%; and the molar content of tetrafluoroethylene may be between 1 and 60 mol%, advantageously between 5 and 55 mol%, preferably between 10 and 50 mol%, more preferably between 15 and 45 mol%. In a copolymer of vinylidene fluoride and chlorotrifluoroethylene, the molar content of vinylidene fluoride may be between 60 and 99 mol%, advantageously between 65 and 98 mol%, preferably between 65 and 97 mol%, more preferably between 70 and 96 mol%, in particular between 75 and 95 mol%; and the molar content of trifluoroethylene can be between 1 and 40 mol%, advantageously between 2 and 35 mol%, preferably between 3 and 35 mol%, more preferably between 4 and 30 mol%, in particular between 5 and 25 mol%.In a terpolymer of vinylidene fluoride, chlorotrifluoroethylene and tetrafluoroethylene, the molar content of vinylidene fluoride may be between 20 and 98 mol%, advantageously between 35 and 90 mol%, preferably between 50 and 90 mol%; and the molar content of tetrafluoroethylene may be between 1 and 50 mol%, advantageously between 5 and 50 mol%, preferably between 5 and 40 mol%; and the molar content of chlorotrifluoroethylene may be between 1 and 30 mol%, advantageously between 1 and 15 mol%, preferably between 1 and 12 mol%.In a terpolymer of vinylidene fluoride, chlorotrifluoroethylene and trifluoroethylene, the molar content of vinylidene fluoride may be between 20 and 98 mol%, advantageously between 35 and 90 mol%, preferably between 50 and 90 mol%; and the molar content of trifluoroethylene may be between 1 and 50 mol%, advantageously between 5 and 50 mol%, preferably between 5 and 40 mol%; and the molar content of chlorotrifluoroethylene may be between 1 and 30 mol%, advantageously between 1 and 15 mol%, preferably between 1 and 12 mol%.In a terpolymer of vinylidene fluoride, trifluoroethylene and hexafluoropropene, the molar content of vinylidene fluoride may be between 20 and 98 mol%, advantageously between 35 and 90 mol%, preferably between 50 and 90 mol%; and the molar content of trifluoroethylene may be between 1 and 50 mol%, advantageously between 5 and 50 mol%, preferably between 5 and 40 mol%; and the molar content of hexafluoropropene may be between 1 and 30 mol%, advantageously between 1 and 15 mol%, preferably between 1 and 12 mol%.In a terpolymer of vinylidene fluoride, tetrafluoroethylene, and 1,1-chlorofluoroethylene, the molar content of vinylidene fluoride may be from 20 to 98 mol%, advantageously from 35 to 90 mol%, preferably from 50 to 90 mol%; and the molar content of tetrafluoroethylene may be from 1 to 50 mol%, advantageously from 5 to 50 mol%, preferably from 5 to 40 mol%; and the molar content of 1,1-difluoroethylene may be from 1 to 30 mol%, advantageously from 1 to 15 mol%, preferably from 1 to 12 mol%. In a terpolymer of vinylidene fluoride, trifluoroethylene, and 1,1- chlorofluoroethylene, the molar content of vinylidene fluoride may be between 20 and 98 mol%, advantageously between 35 and 90 mol%, preferably between 50 and 90 mol%; and the molar content of trifluoroethylene may be between 1 and 50 mol%, advantageously between 5 and 50 mol%, preferably between 5 and 40 mol%; and the molar content of 1,1-difluoroethylene may be between 1 and 30 mol%, advantageously between 1 and 15 mol%, preferably between 1 and 12 mol%.In a terpolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene, the molar content of vinylidene fluoride may be between 20 and 98 mol%, advantageously between 35 and 90 mol%, preferably between 50 and 90 mol%; and the molar content of tetrafluoroethylene may be between 1 and 50 mol%, advantageously between 5 and 50 mol%, preferably between 5 and 40 mol%; and the molar content of hexafluoropropene may be between 1 and 30 mol%, advantageously between 1 and 15 mol%, preferably between 1 and 12 mol%.

[0052] Said fluorinated polymer PI may comprise, in addition to monomeric units derived from the monomer Mla as defined above, in particular when Mla is vinylidene fluoride, monomeric units derived from a non-fluorinated monomer Mlc of formula RaRbC=C(Rc)C(O)Rd in which the substituents Ra, Rb and Rc are independently selected from each other from the group consisting of H and Ci-C5 alkyl; Rd is selected from the group consisting of -NHC(CH3)2CH2 C(O)CH3 or -ORd' with Rd' selected from the group consisting of H and CrCi8 alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd”, -C(O)O-Rd” or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; Rd” being selected from the group consisting of Ci-C6 alkyl or C6-Ci2 aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H groups.The heterocycle may be saturated, unsaturated, or aromatic. It may be monocyclic or bicyclic. It may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone ring. The heterocycle may be substituted by one or more C1-C5 alkyl groups. As mentioned above, the alkyl Ci-Ci8 group is optionally substituted by the heterocycle. The heterocycle may be linked to the alkyl chain by the nitrogen atom or any other atom forming the heterocycle. Preferably the heterocycle is 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.The said monomer Mlc can be of formula RaRbC=C(Rc)C(O)Rd in which the substituents Ra, Rb and Rc are independently selected from the group consisting of H. and C1-C5 alkyl; Rd is selected from the group consisting of -NHC(CH3)2CH2 C(O)CH3 or -ORd' with Rd' selected from the group consisting of H and Ci-Ci8 alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd”, -C(O)O-Rd” group(s) or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; Rd” being selected from the group consisting of Ci-C6 alkyl or C6-Ci2 aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H groups. Preferably, the heterocycle is as defined above, in particular the heterocycle is 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. Preferably, the substituent Rd' is selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxyethyl, hydroxybutyl, hydroxypropyl,ethyl substituted by a ureido group. In particular, said monomer Mlc is of formula RaRbC=C(Rc)C(O)Rd in which the substituents Ra and Rb are H; Rc is H or CH3; Rd is -ORd' with Rd' selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, hydroxypropyl, hydroxybutyl, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. More specifically, said monomer Mlc may be acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate,hydroxybutyl acrylate, methyl acrylic acid (or methacrylic acid), methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureido methacrylate, monomers with the formula CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH(CH3)CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-C6H4CO2H), CH2=CH(CO2CH2CH2CH2CH(CO2H)CH2CH2CO2H); and mixtures thereof. Among these, said monomer Mlc with an alkyl group having from 1 to 8 carbon atoms is preferred,and an alkyl group having 1 to 5 carbon atoms is preferable. Said fluorinated polymer PI may comprise one or more monomeric units derived from said monomer Mlc as defined herein. In , the PI polymer, said monomeric units derived from said monomer Mlc as defined herein may be present in a molar content of 0.05 to 10%, preferably 0.1 to 5% by moles.

[0053] According to another embodiment, said fluorinated polymer PI comprises monomeric units derived from a monomer Mla being vinylidene fluoride, monomeric units derived from a fluorinated monomer Mlb, monomeric units derived from a non-fluorinated monomer Mlc of formula RaRbC=C(Rb)C(O)Rd; said monomers Mlb and Mlc being as defined above.For example, said fluorinated polymer PI comprises monomeric units derived from a monomer Mla being vinylidene fluoride, monomeric units derived from a fluorinated monomer Mlb being hexafluoropropene, and monomeric units derived from a non-fluorinated monomer Mlc selected from the group consisting of acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methyl acrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, the monomers of formula CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-CH2CH2CO2H), CH2 =CH(CO2CH(CH3)CH2-OC(O)-CH2CH2CO2H),CH2=CH(CO2CH2CH2-OC(O)-C6 H4CO2H), CH2=CH(CO2CH2CH2CH2CH(CO2H)CH2CH2CO2H); and mixtures thereof.

[0054] In said fluorinated polymer PI, the mass percentage of monomeric units Mla is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%. Preferably, when the fluorinated monomer Mla is vinylidene fluoride, the mass percentage of vinylidene fluoride monomeric units in said fluorinated polymer PI is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%.

[0055] According to a particular embodiment, the fluorinated PI polymer can be functionalized in whole or in part, which allows it to improve adhesion to metal. Thus, said fluorinated PI polymer can comprise monomeric units bearing at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic; preferably at least one carboxylic acid or hydroxyl function.

[0056] The function is introduced by a chemical reaction which may be grafting, or a copolymerization of the fluorinated monomer with a monomer (for example the Mlc monomer) bearing at least one of said functional groups and a vinyl function capable of copolymerizing with the fluorinated monomer, according to techniques well known to those skilled in the art.

[0057] According to one embodiment, the functional group carries a carboxylic acid function which is a (meth)acrylic acid type group selected from acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.

[0058] According to one embodiment, the units bearing the carboxylic acid function further comprise a heteroatom selected from oxygen, sulfur, nitrogen and phosphorus.

[0059] In one embodiment, the functionality is introduced via the transfer agent used in the synthesis process. The transfer agent is a polymer with a molecular mass less than or equal to 20,000 g / mol and bearing functional groups selected from the following: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, and phosphonic groups. An example of such a transfer agent is acrylic acid oligomers. In a preferred embodiment, the transfer agent is an acrylic acid oligomer with a molecular mass less than or equal to 20,000 g / mol. Alternatively, the functional group may be introduced by an oligomeric or polymeric compound comprising said functional group and mixed with the fluorinated polymer PI.The oligomeric or polymeric compound may be impregnated in, mixed with, or intimately blended with the fluorinated polymer PI. In this case, the functional group may be derived from a (meth)acrylic acid compound selected from acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate, and acryloyloxy propylsuccinate. For example, the functional group may be an oligomer or a polymer comprising monomeric units derived from a monomer selected from the group consisting of acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate, and acryloyloxy propylsuccinate.According to one embodiment, said oligomer or polymer has an average molecular mass by weight less than or equal to 100,000 g / mol, advantageously less than 80,000 g / mol, preferably less than 60,000 g / mol, more preferably less than 40,000 g / mol, in particular less than . at 20,000 g / mol. The weight-average molecular weight is determined by GPC using a Waters 2695e instrument coupled to a Wyatt NEON refractometer equipped with two PL Gel mixed C columns and a guard column (7.8 mm ID x 30 cm, 5 µm) under the following conditions: Temperature: 35°C; flow rate: 0 mL / min; injection volume: 100 pL. Samples are prepared at a concentration of 1 mg / mL in THF. Twelve poly(methyl methacrylate) samples with a molecular weight ranging from 535 to 2,210,000 g / mol are used as calibration standards. This oligomer or polymer is preferably added during the production process of the fluorinated polymer PI. The functional group content of PVDF is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

[0060] Said PI fluorinated polymer preferably has a high molecular weight. By high molecular weight, as used here, is meant a PI fluorinated polymer having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to the ASTM D-3835 method measured at 232°C and 100 sec-1.

[0061] The fluorinated PI polymer used in the invention can be obtained by known polymerization methods such as emulsion or suspension polymerization. In a preferred embodiment, the fluorinated PI polymer is prepared by an emulsion polymerization process in the presence of a non-fluorinated surfactant. Thus, the fluorinated PI polymer may comprise between 10 ppm and 2 wt% of a non-fluorinated surfactant comprising polyethylene glycol or polypropylene glycol units. Preferably, the non-fluorinated surfactant has an HLB value of 1 to 20, in particular an HLB value of 1 to 5 or 10 to 15. In particular, the non-fluorinated surfactant comprises at least one polyethylene glycol segment and at least one polypropylene glycol segment, and has an HLB value of 1 to 5 and a weight-average molecular weight of 5000 to 10000 g.mol-1.Alternatively, said surfactant comprises at least one segment of polyethylene glycol and at least one segment of polypropylene glycol, and has an HLB value of 10 to 15 and a weight-average molecular weight of 500 to 2500 g·mol⁻¹. Said fluoropolymer PI may be in the form of a latex, generally having a solids content of 10 to 60% by weight, preferably 10 to 50%, and having 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 may form agglomerates with a weight-average size of 1 to . 30 micrometers, and preferably 2 to 10 micrometers. Agglomerates can break down into discrete particles during formulation and application to a substrate.

[0062] According to another preferred embodiment, said fluorinated PI polymer is prepared by a suspension polymerization process. Said fluorinated PI polymer may be in powder form. This powder is obtained from latex which is subjected, for example, to a drying step and optionally to granulation.

[0063] According to certain embodiments, the vinylidene fluoride contained in said PI fluorinated polymer is bio-based. The term "bio-based" means "derived from biomass." This improves the polymer's environmental footprint. Bio-based VDF can be characterized by a renewable carbon content, i.e., carbon of natural origin from a biomaterial or biomass, of at least 1 atomic percent as determined by the 14C content according to standard NF EN 16640. The term "renewable carbon" indicates that the carbon is of natural origin and comes from a biomaterial (or biomass), as described below.According to certain embodiments, the bio-carbon content of VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than or equal to 33%, preferably greater than 50%, preferably greater than or equal to 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%. Component B Said sodium or potassium salt is selected from the group consisting of NaCF3SO3, NaPF6, NaC104, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2CF2CF3)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2CF2CF3), NaN(SO2CF3)(SO2CF2CF3), NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaTDI, KCF3SO3, KPF6, KC1O4, KBF4, KB(C2O4)2, KN(SO2F)2, KN(SO2CF3)2, KN(SO2C2F3)2, KN(SO2CF2CF3)2, KN(SO2F)(SO2CF3), KN(SO2F)(SO2CF2CF3), KN(SO2CF3)(SO2CF2 CF3), KAsF6, KBF2C2O4, KNO3, KPF3(CF2CF3)3 and KTDI or a mixture thereof.

[0065] Preferably, said sodium or potassium salt is selected from the group consisting of: NaCF3SO3, NaPF6, NaC104, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2CF2CF3)2, NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaTDI, KCF3SO3, KPF6, KC1O4, KBF4, KB(C2O4)2, KN(SO2F)2, KN(SO2CF3)2, KN(SO2C2F3)2, KN(SO2CF2CF3)2, KAsF6, KBF2C2O4, KNO3, KPF3(CF2 CF3)3 and KTDI or a mixture of these. Component C

[0066] The conductivity additive may be an organic molecule or a mixture of organic molecules capable of swelling the fluorinated polymer without dissolving it and having a dielectric constant greater than 1. According to one embodiment, component C is selected from linear or cyclic ethers, esters, lactones, cyclic ketones, nitriles, carbonates and ionic liquids.

[0067] By way of non-limiting examples, among the ethers, one may mention linear or cyclic ethers, such as for example dimethoxyethane (DME), methyl ethers of oligoethylene glycols of 2 to 5 oxyethylene units (for example dimethyl ether of tetraethylene glycol), dioxolane, dioxane, dibutyl ether, tetrahydrofuran, and mixtures thereof.

[0068] Examples of esters include phosphoric acid esters and sulfite esters. Examples include methyl formate, methyl acetate, methyl propionate, ethyl acetate, butyl acetate, or mixtures thereof.

[0069] Among the lactones, gamma butyrolactone can be mentioned in particular.

[0070] Among the cyclic ketones, cyclohexanone can be mentioned in particular.

[0071] Examples of nitriles include acetonitrile, pyruvonitrile, propionitrile, methoxypropionitrile, dimethylaminopropionitrile, butyronitrile, isobutyronitrile, valeronitrile, pivalonitrile, isovaleronitrile, glutaronitrile, methoxyglutaronitrile, 2-methylglutaronitrile, 3-methylglutaronitrile, adiponitrile, malononitrile, and mixtures thereof.

[0072] Examples of carbonates include cyclic carbonates such as ethylene carbonate (EC) (CAS: 96-49-1), propylene carbonate (PC) (CAS: 108-32-7), butylene carbonate (BC) (CAS: 4437-85-8), dimethyl carbonate (DMC) (CAS: 616-38-6), diethyl carbonate (DEC) (CAS: 105-58-8), ethyl methyl carbonate (EMC) (CAS: 623-53-0), diphenyl carbonate (CAS 102-09-0), methyl phenyl carbonate (CAS: 13509-27-8), dipropyl carbonate (DPC) (CAS: 623-96-1), and methyl carbonate. propyl (MPC) (CAS: 1333-41-1), ethyl propyl carbonate (EPC), vinylene carbonate (VC) (CAS: 872-36-6), fluoroethylene carbonate (FEC) (CAS: 114435-02-8), trifluoropropylene carbonate (CAS: 167951-80-6) or mixtures thereof.

[0073] An ionic liquid is formed by the association of an organic cation and an anion. Examples of organic cations include: ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolinium, phosphonium, guanidinium, piperidinium, thiazolium, triazolium, oxazolium, pyrazolium, and mixtures thereof. In one embodiment, this cation may comprise a C1-C30 alkyl group, such as 1-butyl-1-methylpyrrolidinium, 1-ethyl-3-methylimidazolium, N-methyl-N-propylpyrrolidinium, or N-methyl-N-butylpiperidinium. Preferably, the associated anions are selected from: imides, in particular bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide; borates; phosphates; phosphinates and phosphonates, in particular alkylphosphonates; amides, in particular dicyanamide; aluminates, in particular tetrachloroaluminate; halides (such as bromide, chloride, iodide anions); cyanates; Acetates (CH3COO), in particular trifluoroacetate; sulfonates, in particular methanesulfonate (CH3SO3) and trifluoromethanesulfonate; and sulfates, in particular hydrogen sulfate. In one embodiment, the anions are 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). Preferably, said anion of the ionic liquid is selected from TDI, FSI, TFSI, PF6, BF4, NO3, and BOB. In particular, the anion in question in the ionic liquid is FSI. Among the ionic liquids, we can notably mention EMIM:FSi, PYR:FSI, EMIM:TFSI, PYR:TFSI, EMIM:BOB, PYR:BOB, EMIM:TDI, PYR:TDI, EMIM:BF4, PYR:BF4.

[0074] The mass composition of the cathode coating according to the invention is:

[0075] - Component A with a mass ratio between 20 and 80%;

[0076] - Component B with a mass ratio between 1 and 40%;

[0077] - Component C with a mass ratio between 2 and 50%;

[0078] preferably the sum of these ratios being 100%.

[0079] The invention also relates to a method of manufacturing the cathode coating described above from an ink obtained by mixing all the constituents of the coating in a solvent.

[0080] The inks used to make the coatings can be produced by any type of mixer known to those skilled in the art, such as a planetary mixer, centrifugal mixer, orbital mixer, stirrer shaft, or ultrathurax. The various constituents of the ink are not added in a specific order. The ink can be manufactured at various temperatures, ranging from ambient temperature up to the boiling point of the solvent used to manufacture the ink. The solvent used is preferably a polar solvent with a Hansen parameter greater than 2.By way of non-limiting example, we can mention in particular acetone, acetyl triethyl citrate (ATEC), y-butyrolactone (GBL), cyclohexanone (CHO), cyclopentanone (CPO), dibutyl phthalate (DBP), dibutyl sebacate (DBS), diethyl carbonate (DEC), diethyl phthalate (DEP), dihydrolvoglucosenone (Cyrene), dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 1,4-dioxane, 3-Heptanone, hexamethyl phosphoramide (HMPA), 3-hexanone, methyl ethyl ketone (MEK), N-methyl. -2-pyrrolidinone (NMP), 3-octanone, 3-pentanone, propylene carbonate (PC), tetrahydrofuran (THF), tetramethylurea (TMU), triacetin, triethyl citrate (TEC), triethyl phosphate (TEP), trimethyl phosphate (TMP), N,N' tetrabutylsuccindiamide (TBSA) or a mixture of two or more of the listed solvents.

[0081] According to one embodiment, the porosity of the coated cathode according to the invention is less than 10%, preferably less than 5%.

[0082] The porosity of the coated electrode (ER) is obtained according to the following calculation described in the publication by M.CAI, Nature Communications, 10, 2019, 4597:

[0083] _ VES~VdenseEX P “ V FR

[0084] where VER represents the actual volume of the coated electrode and is calculated by multiplying the surface area of ​​the coated electrode by the thickness of the coated electrode. VdenSeER represents the volume occupied by each of the components without any porosity and is calculated according to the following formula:

[0085] y - y^ V denseER “d.

[0086] VdenSeER is the sum of the volume occupied by each constituent of the coated electrode.

[0087] The thickness of this coating can range from 0.1 to 100 pm, preferably from 0.1 to 50 pm and more preferably from 0.1 to 35 pm.

[0088] The invention also relates to a cathode for an all-solid sodium-ion or potassium-ion battery, said cathode comprising, preferably, at least one active material, a binder, and a conductive material, and having a coating layer according to the invention. Said cathode is deposited on a metallic support. Said cathode thus forms a first layer on said metallic support.

[0089] According to one embodiment, the active material at the positive electrode is chosen from the compounds described below.

[0090] For a cathode of a sodium-ion battery, said at least one active material may have the formula NaxMyO2; M comprising at least one metal or a mixture of metals; x is between 0 and 1; y is between 0 and 1. Advantageously, M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Ca, Li, Rb, Cs, Ce, Mo, Ba, Sc, B, and Hf. Preferably, M is selected from the group consisting of Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, and Hf. In particular, M is selected from the group consisting of Ni, Mn, Fe, Co, Cu, Zn, and Mg.

[0091] Thus, the active material used in a positive electrode of a sodium-ion battery is selected from the group consisting of: Na₂O₅, Ni₃O₇, Mn₃O₇, Mg₅O₈, Ti₂O₈O₂, Na₆O₇, Ni₃O₇, Mn₆O₇, Mg₃O₇, Ti₆O₆, Na₆O₇, Ni₃O₇, Mn₆O₇, Mg₃O₇, Na₆O₇, Cu₃O₇, Mn₆O₆, Na₆O₇, Cu₃O₇, Fe₁₂, Mn₂O₃, Na₆O₇ Cu0.22Fe0.30Mn0.4sO2, NaNii / 3Fei / 3Mni / 3O2, NaxMnO2, Nao.67Nii / 3Mn2 / 3O2, NaFe0.5Co0.5O2, NaxFei / 2Mni / 2O2, NaxCrO2, NaNio.25Feo.5MnO25O2, Na2Z3MgO.2sMnO72O2, Na0.4eCo0.5MnO2, Nao.67Nio.15Feo.2MnO65O2, NaxFeO2, NaFeo.3Nio.7O2, NaLio.O5(Nio.25Feo.25Mn0.5)O.9502, Na0.7Fe0.4Mn0.4Co0.2O2 Nao.97Feo.5MnO.5O2, Nao.7(Feo.5MnO.5)o.sCoo.2O2, NaxCoO2, NaxNiO2, Nai / 3Nii / 3Mn2 / 3O2, Nao.67Nio.2Mgo.1MnO.7O2, Na2 / 3Nii / 3_xZnxMn2 / 3O2, Na0.7Mn0.eNi 0.3CO0.1O2, Nao.7MnO.65Nio.15Feo.2O2, Nao.85Lio.17Nio.21MnO.64O2, NaxTiO2, NaNio.5TiO.5O2, NaxVO2, NaxV2O5, Nai+xV30s.The active material used in a positive electrode can also have the formula Nai+aNixMnyFezAmBnO2 in which -0.35 <a<0,20, 0,08<x<0,5, 0,05<y<0,48, 0,03<z<0,4, 0,03<m<0,24, 0,001<n<0,06, x+y+z+m+n=l ; avec A sélectionné parmi le groupe consistant en Ti, Zn, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P et Cu, ou un mélange de ceux-ci ; B sélectionné parmi le groupe consistant en Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P et Cu, ou un mélange de ceux-ci. Ladite au moins une matière active peut être de formule NaxMy(XOz)anH2O, où M représente un métal de transition tel que Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc ; et X est un élément non métallique comme P, S, Si, As, Mo, ou W.In the phosphate family, where X=P, examples include NaFePO4, Na3V2(PO4)3, NaMnPO4, NaCoPO4, NaTi2(PO4)3, Na2FeP2O7, Na2MnP2O7, Na2CoP2O7, Na7V3(P2O7)4, or a combination thereof. In the sulfate family, where X=S, examples include Na2Fe2(SO4)3, NaFe(SO4)2, or a combination thereof. In the silicate family, where X=Si, examples include Na2MnSiO4, Na2FeSiO4, or a combination thereof. In the molybdenate family, where X=Mo, examples include Fe2(MoO4)3, Ag2Mo2O7, or a combination thereof. The said at least one active substance may also be of the formula NaxMy(XOz)aYb.nH2O, where M represents a transition metal such as Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc, and X is a non-metallic element such as P, S, Si, As, Mo, or W, and Y is a halogen such as F, Cl or Br.In the fluorophosphate family, we can notably mention Na2FePO4F, Na3V2(PO4)3F3, Na3V2O2(PO4 )2F, Na2CoPO4F, Na2CoPO4F, Na2CoPO4F or a combination of these. The said at least one active material may also be of formula NaxM'[M2(CN)6]y where M1 is a transition metal such as Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc, and M2 is also a transition metal such as Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc. M1 may be identical or different from M2. Examples include Na2_xFe[Fe(CN)6], Na2 xMn[Mn(CN)6], Na2_xMn[Fe(CN)6], Na4 Fe(CN)6, NaxFe[Co(CN)6], Na2Zn3[Fe(CN)6]2 or a combination thereof.

[0092] For a cathode of a potassium-ion battery, said at least one active material has the formula KxMyO2; M comprising at least one metal or a mixture of metals; x is between 0 and 1; y is between 0 and 1. Advantageously, M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Ca, Li, Rb, Cs, Ce, Mo, Ba, Sc, B, and Hf. Preferably, M is selected from the group consisting of Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, and Hf. In particular, M is selected from the group consisting of Ni, Mn, Fe, Co, Cu, Zn, and Mg. Thus, the active material used in a positive electrode of a potassium-ion battery is selected from the group consisting of: Ko.95Nio.3i7Mno.3i7Mgo.i5sTio.2osO2, Ko.677Nio.3ooMno.6ooMgo.o33Tio.o67O2, Kq.68Cuo.34Mno.eeO2, K7 / 9Cu2 / 9Fe1 / 9Mn2 / 3O2, K0.g0Cu0.22Fe0.30Mn0.43O2, KNii / 3Fe1 / 3Mn1 / 3O2, KxMnO2, K0.67Nii / 3Mn2 / 3O2, KFe0.5Co0.5O2, KxFei / 2Mni / 2O2, KxCrO2, KNio.25Feo.5MnO.25O2, K2z3MgO.23MnO.72O2, K0.4eCo0.5Mn0.5O2, Ko.67Nio.15Feo.2MnO.65O2, KxFeO2, KFeo.3Nio.7O2, KLio.o5(Nio.25Feo.25Mn0.5)o.9502, K0.7Fe0.4Mn0.4Co0.2O2, Ko.g7Feo.5MnO.5O2, Ko.7(Feo.5Mn o.5)o.sCoo.2O2, KxCoO2, KxNiO2, Ki / 3Nii / 3Mn2 / 3O2 Ko.67Nio.2Mgo.1Mno.7O2, Ko.85Lio.17Nio.21Mno.64O2, Ko.7Mno.65Nio.15Feo.2O2, Ko. KxMnO2, KNio.5Tio.5O2, KxVO2, KxV2O5, Ki+xV3O8, KxCo0j5Mn0j5O2.The active material used in a positive electrode can also have the formula Ki+aNixMnyFezAmB nO2 in which -0.35 <a<0,20, 0,08<x<0,5, 0,05<y<0,48, 0,03<z<0,4, 0,03<m<0,24, 0,001<n<0,06, x+y+z+m+n=l ; avec A sélectionné parmi le groupe consistant en Ti, Zn, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P et Cu, ou un mélange de ceux-ci ; B sélectionné parmi le groupe consistant en Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P et Cu, ou un mélange de ceux-ci. Ladite au moins une matière active peut être de formule KxMy(XOz)anH2 O, où M représente un métal de transition tel que Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc, et X est un élément non métallique comme P, S, Si, As, Mo, ou W.In the phosphate family, where X=P, examples include KFePO4, K3V2(PO4)3, KMnPO4, KCoPO4, KTi2(PO4)3, K2FeP2O7, K2MnP2O7, K2COP2O7, K7V3(P2O7)4, or combinations thereof. In the sulfate family, where X=S, examples include K2Fe2(SO4)3, KFe(SO4)2, or combinations thereof. In the silicate family, where X=Si, examples include K2MnSiO4, K2FeSiO4, or combinations thereof. In the molybdenate family, where X=Mo, examples include Fe2(MoO4)3, Ag2Mo2O7, or combinations thereof. The said at least one active material may also be of formula KxMy(XOz)aYb.nH2O, where M represents a transition metal such as Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc, and X is a non-metallic element such as . P, S, Si, As, Mo, or W, and Y is a halogen such as F, Cl, or Br. In the fluorophosphate family, we can notably mention K2FePO4F, K3V2(PO4)3F3, K3V2O2(PO4)2F, K2CoPO4F, K|.3VP04.xFo.7 or a combination of these. The said at least one active material may also be of formula KxM'[M2(CN)6]y where M1 is a transition metal such as Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc, and M2 is also a transition metal such as Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Mo, Sc. M1 may be identical or different from M2. Examples include K2xFe[Fe(CN)6], K2xMn[Mn(CN)6], K2xMn[Fe(CN)6], IQFeCCN) 6, KxFe[Co(CN)6], K2Zn3[Fe(CN)6]2, K2 xNi[Fe(CN)6]y, or a combination of these.

[0093] The electronically conductive material is preferably selected from carbon blacks, graphites (natural or synthetic), carbon fibers, carbon nanotubes, metal fibers and powders, and conductive metal oxides. Preferably, they are selected from carbon blacks, graphites (natural or synthetic), carbon fibers, and carbon nanotubes.

[0094] The binder used to manufacture the cathode is preferably a polymer chosen from among polyolefins (for example: polyethylene or polypropylene), fluorinated polymers (PVDF) which may have acid functions, polyacrylic acids (PAA), polyacrylonitril (PAN), cellulose-type polymers, polyphenylsulfone, polyethersulfone, a phenolic resin, a vinyl ester resin, an epoxy resin, or a liquid-crystal polymer.

[0095] At the cathode level, this coating is electrochemically stable up to 5V.

[0096] Preferably, said cathode forming said first layer comprises less than 3% by weight, advantageously less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.1% by weight, in particular is free of solid electrolyte on a basis of the total weight of said cathode; said solid electrolyte being preferably present in said coating layer according to the present invention.

[0097] The invention also relates to a method for manufacturing a positive electrode for a Na-ion or K-ion battery, said method comprising the following operations:

[0098] - provide a cathode,

[0099] - deposit on said cathode a coating layer according to the invention.

[0100] This coating can be produced by any deposition method known to those skilled in the art, such as solvent coating, dip-shrink methods, centrifugal coating, spray coating, or calendering. These techniques of Deposition can be carried out at different temperatures ranging from 5°C up to 180°C.

[0101] According to one embodiment, the coating can be applied directly to a conventional positive electrode having a porosity between 15 and 45% before or after calendering. This coating then allows for physical separation between the solid electrolyte and the active material, thus enabling the use of solid electrolytes that previously appeared unstable with respect to certain active materials.

[0102] According to one embodiment, the manufacturing process for a positive electrode of a Na-ion or K-ion battery comprises, upstream of the deposition of the coating according to the invention, the following steps:

[0103] - mixing of the active charge, the polymer binder and the conductive charge using of a process which makes it possible to obtain an electrode formulation applicable on a metallic support;

[0104] - deposition of said electrode formulation onto the metallic substrate,

[0105] - the consolidation of said electrode by a heat treatment (application of a temperature up to 50°C above the polymer melting temperature, without mechanical pressure), and / or thermo-mechanical treatment such as calendering.

[0106] The metal supports for the electrodes are generally made of aluminum for the cathode. The metal supports may be surface-treated and have a conductive primary layer 5 µm or thicker. The supports may also be woven or non-woven carbon fiber.

[0107] Thus the positive electrode comprises a metallic support on which is deposited a first layer comprising, preferably consisting of, an active material, a binder and a conductive material, and a second layer deposited on said first layer; said second layer consisting of said cathode coating according to the present invention.

[0108] Another object of the invention is an all-solid Na-ion or K-ion secondary battery comprising a negative electrode, a positive electrode and an all-solid electrolyte, wherein the cathode is as described above.

[0109] EXAMPLES

[0110] The following examples illustrate, in a non-limiting manner, the scope of the invention. Preparation of fluorinated polymer (PI) solution

[0111] 149.92 g of VDF-HFP copolymer with a mass percentage of HFP of 23% is dissolved in 857.53 g of acetone using a planetary mixer at 2000 rpm for six times 1 min to obtain complete dissolution.

[0112] Preparation of ink I for coating: Pl / NaFSI 80 / 20

[0113] 0.589 g of NaFSI (NaN(SO2F)2) is dissolved in 14.524 g of the polymer solution (PI). The solution is stirred using a magnetic stir bar at 21°C for 30 min.

[0114] Preparation of ink II for coating: Pl / NaFSI / Sl 60 / 20 / 20

[0115] 0.882 g of NaFSI is dissolved in 0.898 g of tetraethylene glycol dimethyl ether (Cas 143-24-8) using a magnetic stirrer for 10 min at 21°C. Then 17.652 g of a 15% PI solution in acetone is added.

[0116] Preparation of ink III for coating: Pl / NaFSI / Sl 60 / 20 / 20

[0117] 0.882 g of NaFSI is dissolved in 0.449 g of tetraethylene glycol dimethyl ether (Cas 143-24-8) and 0.449 g of 1-Butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (Cas 143-24-8) using a magnetic stirrer for 10 min at 21°C. Then 17.652 g of a 15% PF solution in acetone is added.

[0118] Preparation of ink IV for Pl / NaFSI / Sl 40 / 30 / 30 coating

[0119] 0.528 g of NaFSI is dissolved in 0.528 g of tetraethylene glycol dimethyl ether (Cas 143-24-8) using a magnetic stirrer for 10 min at 21°C. Then 4.675 g of a 15% PI solution in acetone is added.

[0120] Preparation of ink V for Pl / NaFSI / Sl 50 / 15 / 35 coating

[0121] 0.568 g of NaFSI is dissolved in 1.232 g of dimethyl tetraethylene glycol Sl(Cas 143-24-8) using a magnetic stirrer for 10 min at 21°C. Then 7.04 g of a 25% PI solution in acetone is added.

[0122] Coating of a porous NaNi 0.4 Fe 0.2 Mn 0.4 O₂ cathode with ink I:

[0123] A cathode with the following formulation NaNi 0.4 Fe 0.2 Mn 0.4 O₂ / HSV 1810 / C65 97 / 1.5 / 1.5 is coated with ink B. The electrode before coating has an average porosity of 43% and a density of 2.22 g / cm³. The coating is applied by sizing. After drying at room temperature, the coating has a mass of 18.24 mg / cm², which allows the coating to completely fill the porosity of the electrode. The ionic conductivity of the electrode was measured by impedance spectroscopy at 0.056 mS / cm.

[0124] Coating of a porous NaNi 0.4 Fe 0.2 Mn 0.4 O 2 cathode with V ink

[0125] A NaNioj4Fe0j2Mnoj4O2 cathode with a thickness of 31 µm is coated with ink V is coated using a bar coater. The wet thickness deposited is 200 µm. The coating is dried using a heater at 35°C. The coated electrode is then calendered to achieve a total thickness of 51 µm. Power test#:

[0126] A power test was carried out to compare an electrode coated with V ink with a standard electrode.

[0127] Method: The method consists of charging a battery at a slow rate of C / 10 and discharging it at different rates and thus measuring the capacity that can be restored by the battery at different discharge rates.

[0128] System used:

[0129] Cathode: Coated or uncoated electrode

[0130] Electrolyte: IM NaPF6 in EC / EMC 3 / 7 by volume

[0131] Fiberglass separator

[0132] Anode: sodium metal

[0133] Table 1 shows the capacity restored during discharge by the two batteries for two different regimes.

[0134] [Tables 1] Technology Capacity at C / 5 Capacity at C Bare electrode 115 mAh / g 95 mAh / g Coated electrode 120 mAh / g 102 mAh / g

Claims

Demands

1. Cathode coating comprising, preferably consisting of: a. at least one PI fluorinated polymer (component A), b. at least one sodium or potassium salt (component B), and c. at least one conductivity additive (component C).

2. Coating according to the preceding claim characterized in that said at least one PI fluoropolymer comprising repeating units derived from a monomer Mla selected from the group consisting of vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(l,3-dioxole); perfluoro(2,2-dimethyl-l,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2 )nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2 )m and m is 1, 2, 3 or 4;the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof.;

3. A coating according to any one of the preceding claims, characterized in that said PI fluoropolymer comprises repeating units derived from monomer Mla and repeating units derived from monomer Mlb or repeating units derived from monomer Mlc; said monomer Mla being vinylidene fluoride; said monomer Mlb selected from the group consisting of vinyl fluoride; trifluoroethylene (TrFE); 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); the

4. perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2 =CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R'CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-l-propene or a mixture thereof;said monomer Mlc being selected from the group consisting of formula R1R2C=C(R3)((X1)PC(O)R4) in which the substituents R1, R2 and R3 are independently selected from the group consisting of H, CO2H and Ci-C5 alkyl; R4 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR5 with R5 selected from the group consisting of H and C1-C18 alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H, -OC(O)R6, -C(O)O-R6 or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; R6 being selected from the group consisting of Ci-C6 alkyl or C6-Ci2 aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H group(s); p is 0 or 1; X1 is selected from the group consisting of -[-C(O)OC(R7)(R8)C(R9)(R10)-]wr and a Ci-Cio alkyl hydrocarbon group optionally bearing one or more -OH, -CO2H or ester group(s);with wl being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5; R7, R8, R9, R10 are independently of each other, independently for each unit wl, selected from the group consisting of H and Ci-C5 alkyl. A coating according to any one of the preceding claims, characterized in that said at least one PI polymer comprises monomeric units derived from a monomer Mla, being vinylidene fluoride, and monomeric units derived from a monomer Mlb selected from the group consisting of trifluoroethylene, 1,1-chlorofluoroethylene, chlorotrifluoroethylene, hexafluoropropene and tetrafluoroethylene, or a mixture thereof.

5. Coating according to any one of the preceding claims characterized in that said PI fluorinated polymer comprises monomeric units bearing at least one of the following functions: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, or phosphonic.

6. Coating according to any one of the preceding claims characterized in that said sodium or potassium salt is selected from the group consisting of NaCF3SO3, NaPF6, NaC1O4, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2CF2CF3)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2CF2CF3), NaN(SO2CF3)(SO2CF2CF3), NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaTDI, KCF3SO3, KPF6, KC1O4, KBF4, KB(C2O4)2, KN(SO2F)2, KN(SO2CF3)2, KN(SO2C2F3)2, KN(SO2CF2CF3)2, KN(SO2F)(SO2CF3 ), KN(SO2F)(SO2CF2CF3), KN(SO2CF3)(SO2CF2CF3), KAsF6, kbf2c 2O4, KN03, KPF3(CF2CF3)3 and KTDI or a mixture of these.

7. Coating according to any one of the preceding claims, wherein component C is selected from linear or cyclic ethers, esters, lactones, cyclic ketones, nitriles, carbonates and ionic liquids.

8. Coating according to any one of the preceding claims, having a thickness from 0.1 to 100 pm, preferably from 0.1 to 50 pm and more preferably from 0.1 to 35 pm.

9. Coating according to any one of the preceding claims, having the following mass composition: - Component A with a ratio between 20 and 80%, - Component B with a ratio between 1 and 40%, - Component C with a ratio between 2 and 50%, preferably the sum of these ratios being 100%.

10. Method of manufacturing the cathode coating according to any one of the preceding claims from an ink obtained by mixing all the constituents of the coating in a solvent.

11. A process according to the preceding claim, wherein said solvent is selected from the group consisting of acetone, acetyl triethyl citrate, γ-butyrolactone, cyclohexanone, cyclopentanone, dibutyl phthalate, dibutyl sebacate, diethyl carbonate, diethyl phthalate, dihydrolevoglucosenone, dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 3-Heptanone, hexamethyl phosphoramide, 3-hexanone, methyl ethyl ketone, N-methyl-2-pyrrolidinone, 3-octanone, 3-pentanone, propylene carbonate, tetrahydrofuran, tetramethylurea, triacetin, triethyl citrate, triethyl phosphate, trimethyl phosphate, N,N' tetrabutylsuccindiamide and their mixtures.

12. Cathode for a solid sodium-ion or potassium-ion battery, said cathode consisting of at least one active material, a binder and a conductive material, and having a coating layer according to any one of the preceding claims 1 to 9.

13. Cathode according to the preceding claim, wherein said at least active material is selected from the group consisting of an active material of formula NaxMyO2 or of formula KxMyO2; M comprising at least one metal or mixture of metals; x is between 0 and 1; y is between 0 and 1.

14. Cathode according to any one of the preceding claims 12 or 13, wherein said conductive material is selected from carbon blacks, graphites, natural or synthetic, carbon fibers, carbon nanotubes, metal fibers and powders, and conductive metal oxides.

15. Cathode according to any one of the preceding claims 12 to 14, wherein said binder is a polymer selected from polyolefins, fluorinated polymers, fluorinated polymers having acid functions, polyacrylic acids, polyacrylonitril, cellulose-type polymers, polyphenylsulfone, polyethersulfone, a phenolic resin, a vinyl ester resin, an epoxy resin, or a liquid-crystal polymer.

16. Cathode according to any one of the preceding claims 12 to 15, having a porosity of less than 10%, preferably less than 5%.

17. A method for manufacturing a positive electrode for a Na-ion or K-ion battery, said method comprising the steps of: 31 - provide a cathode, - deposit on said cathode a coating layer according to any one of the preceding claims 1 to 9.

18. All-solid Na-ion or K-ion secondary battery comprising an anode, a cathode according to any one of the preceding claims 12 to 16 and an all-solid electrolyte.