Anode coating composition

Abstract

The present invention relates to an anode coating composition comprising a polymer and an alkali metal salt having a mass ratio of 0.1 or more.

Description

[0001] Title: Coating anode

[0002] technical field

[0003] The present invention relates to an electrode coating composition. In particular, the present invention relates to a coating composition for protecting an anode, preferably a metallic anode of secondary batteries, as well as its production method.

[0004] Technological background of the invention

[0005] With the development of mobile electronic devices such as mobile phones and laptops, the demand for rechargeable secondary batteries as a power source for these devices is increasing significantly. The use of secondary batteries as a power source for hybrid electric vehicles (HEVs) and electric vehicles (EVs) is becoming increasingly common. Demand is growing for lithium secondary batteries with high energy density, high discharge voltage, and high efficiency. Current lithium-ion secondary batteries contain a liquid electrolyte made from products that are generally flammable. Future generations of batteries under development aim to preferentially use solid or near-solid electrolytes, which notably allows the use of lithium metal in the negative electrode. The use of lithium metal results in increased energy density.

[0006] In general, secondary lithium-ion batteries include carbon-based materials such as graphite, lithium metal, silicon, metals such as tin or their oxide, alloys including them as the active negative electrode material.

[0007] Until recently, the development of high energy density batteries using lithium as the negative electrode has generated considerable interest.

[0008] For example, compared to other electrochemical systems with a lithium-inserted carbon negative electrode and a nickel or cadmium electrode, which increase the weight and volume of the negative electrode, lithium metal offers the advantages of low weight and high capacity. It is attracting considerable attention as the active material for the negative electrode of electrochemical batteries. A lithium metal negative electrode, or a negative electrode composed primarily of lithium metal, allows for the construction of a battery that is lighter and has a higher energy density than conventional batteries. Consequently, the use of lithium electrodes has increased. However, the use of batteries combining solid electrolytes and a lithium metal electrode has drawbacks. Lithium metal is highly reactive and difficult to handle.The interface formed between the anode and the solid electrolyte can be resistive depending on the electrolytes used, which limits battery performance. Lithium dendrites can also form during charge / discharge cycles, leading to a short circuit in the battery when the dendrite passes through the separator and reaches the cathode. To mitigate these problems, the transfer of lithium ions between the solid electrolyte and the lithium metal anode must be facilitated (implying low interface resistance), or the flow of lithium ions near the anode must be as homogeneous as possible.

[0009] Summary of the invention

[0010] According to a first aspect, the present invention relates to a coating composition for a negative electrode comprising at least one PI polymer and at least one alkali metal salt SI, characterized in that the mass ratio Sl / Pl is greater than 1; said mass ratio Sl / Pl corresponding to the ratio between the mass of said at least one alkali metal salt SI and the mass of said at least one PI polymer in said composition; said at least one PI polymer comprising monomeric units derived from a monomer Mla, being vinylidene fluoride, and monomeric units derived from a monomer Mla' selected from the group consisting of trifluoroethylene, 1,1-chlorofluoroethylene, chlorotrifluoroethylene, and tetrafluoroethylene, or a mixture thereof. Said PI polymer may therefore contain one or more Mla' monomers as defined above.

[0011] The applicant has, surprisingly, found that the coating composition as described in the present invention makes it possible to limit the formation of dendrites while maintaining a low interface resistance.

[0012] According to a preferred embodiment, said at least one PI polymer comprises: 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.

[0013] According to a preferred embodiment, said at least one PI polymer comprises monomeric units derived from a non-fluorinated monomer Mla" of formula R a R b C=C(Rc )HORN d in which the R substituents a , R b and R c are independently selected from the group consisting of H and Ci-C5 alkyl; R d is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR d 'with R d 'selected from the group consisting of H and Ci-Ci8alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R group(s) d ", -C(O)OR d "or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; R d " being selected from the group consisting of Ci-C6alkyl or C6-Ci2aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2 group(s).

[0014] According to a preferred embodiment, said PI polymer is selected from the group consisting of 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 and a terpolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene.

[0015] According to a preferred embodiment, said alkali metal salt SI is selected from the group consisting of LiCF3SO3, LiPF6, LiClO4, LiBF4, LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F3)2, LiN(SO2CF2CF3)2, LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2CF2CF3), LiN(SO2CF3)(SO2CF2CF3), LiAsF6, LiBF2C2O4, LiNO3, LiPF3(CF2CF3)3, LiTDI, NaCF3SO3, NaPF6, NaClO4, 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), NaAsFe, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaTDI, KCF3SO3, KPF6, KCIO4, 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 thereof.

[0016] According to a preferred embodiment, said composition comprises at least one plasticizer selected from the group consisting of vinylidene carbonate, fluoroethylene carbonate, 4-fluoro-l,3-dioxolan-2-one, trans-4,5-difluoro-l,3-dioxolan-2-one, ethylene carbonate, propylene carbonate, (2-cyanoethyl)triethoxysilane, 3-methoxypropionitrile, sulfolane, triethylphosphate, γ-butyrolactone, 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) or ionic liquids.

[0017] According to a preferred embodiment, the mass ratio Sl / Pl is greater than or equal to 1.10, preferably greater than or equal to 1.25, in particular greater than or equal to 1.40.

[0018] According to another aspect, the present invention relates to a negative electrode comprising an electrochemically active material, optionally deposited on a current collector, said electrochemically active material being coated with said coating composition according to the present invention.

[0019] According to a preferred embodiment, said electrochemically active material is selected from the group consisting of lithium alloy, lithium metal, sodium alloy, potassium alloy, sodium metal, potassium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy, graphite / silicon composite and Li4Ti5O 12 .

[0020] According to another aspect, the present invention relates to a negative electrode comprising a current collector coated with said coating composition according to the present invention.

[0021] According to a preferred embodiment, said coating composition has a thickness of less than 10 pm.

[0022] According to another aspect, the present invention relates to a method for preparing an electrode according to the present invention comprising the steps of: a) Preparing a composition comprising said at least one polymer PI, said at least one alkali metal salt SI and a solvent; b) Depositing the composition prepared in step a) onto a current collector or onto an electrochemically active material to form an electrode; c) Consolidating said electrode formed in step b) by heat treatment.

[0023] According to another aspect, the present invention relates to a battery comprising a negative electrode according to the present invention.

[0024] According to a preferred embodiment, said battery is a secondary lithium-ion, sodium-ion or potassium-ion battery.

[0025] According to a preferred embodiment, said battery is an all-solid-state battery.

[0026] Brief description of the figures

[0027] Figure 1 shows the total strength of systems obtained with coating compositions according to the invention or in the absence thereof. Detailed description of the invention

[0028] As mentioned above, the applicant has found a new electrode coating composition, in particular for the anode, which, in addition to limiting dendrite formation, maintains low resistance at the interface between the anode and the electrolyte, the latter preferably being solid.

[0029] According to a first aspect of the present invention, a coating composition for a negative electrode is provided. This coating composition comprises a PI polymer and an alkali metal salt (SI). Preferably, the mass ratio Sl / Pl is greater than or equal to 0.1. In this application, the mass ratio Sl / Pl is defined as the ratio of the mass of at least one alkali metal salt (SI) to the mass of at least one PI polymer in the composition.

[0030] The said mass ratio Sl / Pl may be greater than or equal to 0.15, advantageously greater than or equal to 0.20, preferably greater than or equal to 0.25, more preferably greater than or equal to 0.30, in particular greater than or equal to 0.35, more particularly greater than or equal to 0.40, preferably greater than or equal to 0.45, advantageously preferred greater than or equal to 0.50, preferably preferred greater than or equal to 0.55, more preferably preferred greater than or equal to 0.60.

[0031] Preferably, said mass ratio Sl / Pl may be greater than or equal to 0.64, advantageously greater than or equal to 0.68, preferably greater than or equal to 0.70, more preferably greater than or equal to 0.74, in particular greater than or equal to 0.78, more particularly greater than or equal to 0.80, preferably greater than or equal to 0.84, advantageously preferred greater than or equal to 0.88, preferentially preferred greater than or equal to 0.90, more preferably preferred greater than or equal to 0.94, particularly preferred greater than or equal to 0.98, more particularly preferred greater than or equal to 1.0.

[0032] In particular, the said mass ratio Sl / Pl may be greater than or equal to 1.02, advantageously greater than or equal to 1.04, preferably greater than or equal to 1.06, more preferably greater than or equal to 1.08, in particular greater than or equal to 1.10, more particularly greater than or equal to 1.12, preferably greater than or equal to 1.14, advantageously greater than or equal to 1.16, preferentially greater than or equal to 1.18, more preferably greater than or equal to 1.20, particularly greater than or equal to 1.24, more particularly greater than or equal to 1.26. When the mass ratio Sl / Pl is greater than or equal to 1.0, it has been observed that the interface resistance decreases to a more acceptable level.

[0033] More specifically, the mass ratio Sl / Pl may be greater than or equal to 1.28, advantageously greater than or equal to 1.30, preferably greater than or equal to 1.32, more preferably greater than or equal to 1.34, particularly greater than or equal to 1.36, more particularly greater than or equal to 1.38, preferably greater than or equal to 1.40, advantageously greater than or equal to 1.42, preferably greater than or equal to 1.44, and more preferably greater than or equal to 1.45. It has been observed that the interface resistance decreases sharply with increasing mass ratio Sl / Pl. Compared to an uncoated anode, an anode containing the coating composition according to the present invention exhibits low interface resistance as the mass ratio Sl / Pl increases, as demonstrated in the examples.

[0034] PI Polymer

[0035] According to a preferred embodiment, 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.

[0036] Preferably, said PI fluorinated polymer comprises monomeric units derived from a monomer Mla selected from the group consisting of vinylidene fluoride (VDF), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, 1,1-chlorofluoroethylene (CFE) and tetrafluoroethylene (TFE).

[0037] 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 copolymer of vinylidene fluoride.

[0038] Preferably, 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 Mla' copolymerizable with vinylidene fluoride, or monomeric units derived from a non-fluorinated monomer Mla' or a mixture of the two.

[0039] According to one embodiment, said PI fluorinated polymer comprises monomeric units derived from a monomer Mla being vinylidene fluoride and monomeric units derived from a fluorinated monomer Mla' selected from the group consisting of trifluoroethylene, 1,1-chlorofluoroethylene, chlorotrifluoroethylene, hexafluoropropene and tetrafluoroethylene 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 and a terpolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene.

[0040] In the PI polymer according to the present invention, the molar content of vinylidene fluoride may 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 90 mol%, in particular between 60 and 90 mol%.

[0041] In the PI polymer according to the present invention, the molar content of trifluoroethylene can 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%.

[0042] In the PI polymer according to the present invention, 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%.

[0043] In the PI polymer according to the present invention, 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%.

[0044] In the PI polymer according to the present invention, the molar content of 1,1-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 1,1-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%.

[0045] 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 68 and 85 mol%, particularly between 70 and 82 mol%, and more particularly between 73 and 82 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 32 mol%, particularly between 18 and 30 mol%, and more particularly between 18 and 27 mol%. In the most preferred proportions, the copolymer possesses ferroelectric and ferroelectric relaxor properties.

[0046] 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%, more 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%.

[0047] 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 may 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%.

[0048] 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%.

[0049] In a terpolymer of vinylidene fluoride, chlorotrifluoroethylene, and trifluoroethylene, 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 trifluoroethylene may be from 1 to 50 mol%, advantageously from 5 to 50 mol%, preferably from 5 to 40 mol%; and the molar content of chlorotrifluoroethylene may be from 1 to 30 mol%, advantageously from 2 to 15 mol%, preferably from 4 to 12 mol%. In the most preferred proportions, the copolymer possesses ferroelectric and ferroelectric-relaxant properties.

[0050] 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%.

[0051] In a terpolymer of vinylidene fluoride, tetrafluoroethylene 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 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 1,1-chlorofluoroethylene may be between 1 and 30 mol%, advantageously between 1 and 15 mol%, preferably between 1 and 12 mol%.

[0052] In a terpolymer of vinylidene fluoride, trifluoroethylene, 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 trifluoroethylene 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-chlorofluoroethylene may be from 1 to 30 mol%, advantageously from 2 to 15 mol%, preferably from 4 to 12 mol%. In the most preferred proportions, the copolymer possesses ferroelectric and ferroelectric relaxor properties.

[0053] 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%.

[0054] The said PI polymer may optionally comprise monomeric units derived from a non-fluorinated monomer Mla" of formula R a R b C=C(R c )HORN d in which the R substituents a , R b and R c are independently selected from the group consisting of H and Ci-C5 alkyl; R dis selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR d 'with R d 'selected from the group consisting of H and Ci-Ci8alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R group(s) d ", -C(O)OR d "or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; R d"being selected from the group consisting of Ci-C6alkyl or C6-Ci2aryl optionally substituted by one or more -OH, -CO2H, -SO3H, or -PO3H2 groups. Said heterocycle may be saturated, unsaturated, or aromatic. Said heterocycle may be monocyclic or bicyclic. Said heterocycle 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. Said heterocycle may be substituted by one or more Ci-C5alkyl groups. As mentioned above, the Ci-Ci8alkyl is optionally substituted by said heterocycle. The latter 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 Mla" can be of formula R. a R b C=C(R c )HORN d in which the R substituents a , R b and R c are independently selected from the group consisting of H and Ci-C5 alkyl; R d is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR d 'with R d 'selected from the group consisting of H and Ci-Ci8alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R group(s) d ", -C(O)OR d "or a heterocycle with five or ten links comprising at least one nitrogen atom in its cyclic chain; R d"being selected from the group consisting of Ci-C6alkyl or C6-Ci2aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2 group(s). Preferably, the heterocycle is as defined above, in particular the heterocycle is 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. Preferably, the substituent R d ' 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 with a ureido group. In particular, said monomer Mla" has the formula R a R b C=C(R c )HORN d in which the R substituents a and R b are H; R c is H or CH3; R d is -OR d 'with R d' 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 Mla" 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, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylate n-butyl, 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 of 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 Mla" with an alkyl group having from 1 to 8 carbon atoms is preferred, and an alkyl group having from 1 to 5 carbon atoms is more preferable. Said fluorinated polymer PI may comprise one or more monomeric units derived from said monomer Mla" as defined herein. In polymer P1A, said monomeric units derived from said monomer Mla" as defined herein may be present in a molar content of 0.05 to 10%.preferably from 0.1 to 5% by moles.

[0055] 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 ASTM D-3835 method measured at 232°C and 100 sec-1.

[0056] 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 a suspension polymerization process. In this type of suspension process, a dispersant is used. The dispersant can be polyvinyl alcohol (PVA) or a compound comprising a cellulose motif such as methylcellulose, hydroxypropylmethylcellulose, or carboxymethylcellulose. The average particle size is between 1 µm and 500 µm, preferably between 10 µm and 500 µm. The average particle size is determined by laser diffraction. A Malvern INSITEC System particle size analyzer is used for the measurement. This measurement is performed in a dry process by laser diffraction on a powder with a focal length of 100 mm.

[0057] According to another preferred embodiment, the fluorinated polymer P1A is prepared by an emulsion polymerization process in the presence of a non-fluorinated surfactant. Thus, the fluorinated polymer P1A 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.The fluorinated polymer P1A 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. The agglomerates may break down into discrete particles during formulation and application to a substrate.

[0058] In 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 some 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%.

[0059] Alkaline metal salt SI

[0060] When in a pre-delivery mode, metal alcalin SI is selected from a group consisting of LiCF3SO3, LiPF6, LiCIO4, LiBF4, LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F3)2, LiN(SO2CF2CF3)2, LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2CF2CF3), LiN(SO2CF3)(SO2CF2CF3), LiAsFg, LiBF2C2O4, LiNO3, LiPF3(CF2CF3)3, LiTDI, NaCF3SO3, NaPF6, NaCIO4, Na BF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2CF2CF3)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2CF2CF3), NaN(SO2CF3)(SO2CF2CF3), NaAsFe, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaTDI, KCF3SO3, KPF6, KCIO4, 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), KAsFe, KBF2C2O4, KNO3, KPF3(CF2CF3)3 KTDI or a phone number.

[0061] Preferably, said alkali metal salt SI is selected from the group consisting of LiCF3SO3, LiPF6, LiCIO4, LiBF4, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2CF2CF3)2, LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2CF2CF3), LiN(SO2CF3)(SO2CF2CF3), LiNO3, LiTDI, NaCF3SO3, NaPF6, NaCIO4, NaBF4, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2CF2CF3)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2CF2CF3), NaN(SO2CF3)(SO2CF2CF3), NaNO3, NaTDI, KCF3SO3, KPF6, KCIO4, KBF4, KN(SO2F)2, KN(SO2CF3)2, KN(SO2CF2CF3)2, KN(SO2F)(SO2CF3), KN(SO2F)(SO2CF2CF3), KN(SO2CF3)(SO2CF2CF3), KNO3, and KTDI or a mixture thereof.

[0062] In particular, said alkali metal salt SI is selected from the group consisting of LiCF3SO3, LiPF6, LiClO4, LiBF4, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2CF2CF3)2, LiNO3, LiTDI, NaCF3SO3, NaPF6, NaClO4, NaBF4, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2CF2CF3)2, NaNO3, NaTDI, KCF3SO3, KPF6, KClO4, KBF4, KN(SO2F)2, KN(SO2CF3)2, KN(SO2CF2CF3)2, KNO3, and KTDI or a mixture thereof.

[0063] Plasticizer

[0064] As mentioned above, the said composition may include at least one plasticizer. The said plasticizer may be selected from the group consisting of vinylidene carbonate, fluoroethylene carbonate (FEC), 4-fluoro-l,3-dioxolan-2-one, trans-4,5-difluoro-l,3-dioxolan-2-one, ethylene carbonate (EC), propylene carbonate, (2-cyanoethyl)triethoxysilane, 3-methoxypropionitrile, sulfolane, triethyl phosphate, γ-butyrolactone, 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), or ionic liquids.

[0065] An ionic liquid is a salt that is liquid at room temperature, meaning it has a melting point below 100°C under atmospheric pressure. It is formed by the association of an organic cation and an anion whose ionic interactions are weak enough not to form a solid. Examples of cations found in ionic liquids include ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolinium, phosphonium, guanidinium, piperidinium, thiazolium, triazolium, oxazolium, pyrazolium, and mixtures thereof. In one embodiment, this cation may include an alkyl group (Ci-C). 30 , such as 1-butyl-l-methylpyrrolidinium, l-ethyl-3-methylimidazolium, N-methyl-N-propylpyrrolydinium or N-methyl-N-butylpiperidinium.

[0066] According to one embodiment, the anions associated with them are chosen from: imides, in particular bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide; borates; phosphates; phosphinates and phosphonates, in particular alkyl-phosphonates; 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), trifluoromethanesulfonate; and sulfates, in particular hydrogen sulfate; an acrylate or a methacrylate.In a preferred embodiment, the anions of the ionic liquid 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), 4,5-dicyano-2-(trifluoromethyl)imidazole (TDI), an acrylate, or a methacrylate. In a particular embodiment, said anion of the ionic liquid is selected from TDI', FSE, TFSI', PF6', BF4, NO3', BOB', CH2=CHCOO'. In one embodiment, said anion of the ionic liquid is FSI'.

[0067] According to one embodiment, said plasticizer B2 is a mixture of at least one ionic liquid and at least one SI solvent with a boiling point above 100°C, preferably above 110°C, more preferably above 125°C, in particular above 150°C, more particularly above 160°C.

[0068] Plasticizers enable improved properties of conductivity, electrochemical stability, thermal stability, electrode compatibility, and capacitance retention compared to conventional liquid electrolytes.

[0069] Examples of plasticizer B2 according to the invention are the following mixtures:

[0070] - l-ethyl-3-methylimidazolium-FSI and EC,

[0071] - l-ethyl-3-methylimidazolium-FSI and tetraethylene glycol dimethyl ether,

[0072] - l-ethyl-3-methylimidazolium-FSI and EC and FEC,

[0073] 1-butyl-l-methylpyrrolidinium-FSI and tetraethylene glycol dimethyl ether,- 1-butyl-l-methylpyrrolidinium-FSI and EC and FEC,

[0074] - N-propyl-N-methylpyrrolidinium and tetraethylene glycol dimethyl ether - l-ethyl-3-methyl imidazolium-TFSI and FEC,

[0075] - l-ethyl-3-methylimidazolium-FSI,

[0076] - 1-butyl-l-methylpyrrolidinium-FSI.

[0077] Negative electrode

[0078] The negative electrode may include a current collector or electrochemically active material optionally deposited on the current collector. The coating composition according to the present invention may be deposited on the current collector or on the electrochemically active material.

[0079] The electrochemically active material is selected from the group consisting of lithium alloy, lithium metal, sodium alloy, potassium alloy, sodium metal, potassium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy, graphite / silicon composite and Li4Ti50i2. Preferably, the electrochemically active material is selected from the group consisting of lithium alloy or lithium metal, sodium alloy, potassium alloy, sodium metal and potassium metal.

[0080] Preferably, when the electrochemically active material is a lithium alloy or lithium metal, said alkali metal salt SI contained in said coating composition comprises at least one of the lithium salts selected from the group consisting of LiPF6, LiBF4, LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiNO3 and LiTDI.

[0081] Preferably, when the electrochemically active material is a sodium alloy or sodium metal, said alkali metal salt SI contained in said coating composition comprises at least one of the sodium salts selected from the group consisting of NaPF6, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaNO3 and NaTDI.

[0082] Preferably, when the electrochemically active material is a potassium alloy or potassium metal, said alkali metal salt SI contained in said coating composition comprises at least one of the potassium salts selected from the group consisting of KPF6, KBF4, KB(C2O4)2, KN(SO2F)2, KN(SO2CF3)2, KNO3 and KTDI.

[0083] The current collector can be made of copper, optionally coated with carbon.

[0084] According to one embodiment, when said coating composition is deposited on the current collector or on the electrochemically active material, it has a thickness of less than 10 µm. Advantageously, the thickness of said coating composition is less than 8 µm, preferably less than 6 µm, more preferably less than 4 µm, in particular less than 2 µm, and more particularly less than 1 µm. A thinner coating allows for better conduction of lithium, sodium, or potassium ions. Preparation process

[0085] In another aspect, the present invention provides a method for preparing a negative electrode according to the present invention. This method comprises the steps of: a) Preparing a composition comprising said PI polymer, said alkali metal salt SI, and a solvent; b) Depositing the composition prepared in step a) onto a current collector or onto a layer containing an electrochemically active material to form an electrode; c) Consolidating said electrode formed in step b) by heat treatment.

[0086] In step a), said solvent may be selected, by way of non-limiting example, from the group consisting of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, 2-butanone, 1,2-dimethoxyethane, 1,3-dioxolane, 2,3-butanedione, 2-methylpentan-3-one, 2-methyltetrahydrofuran, tetrahydrofuran, 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, dimethyl ether, 1,4-dioxane, dipropyl ether, ethyl acetate, ethyl butanoate or methyl propanoate, tetrahydrofuran, N-butyl-2-pyrrolidone or a mixture thereof;in particular 2-butanone, 1,2-dimethoxyethane, 1,3-dioxolane, 2,3-butanedione, 2-methylpentan-3-one, 2-methyltetrahydrofuran, tetrahydrofuran, 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 a mixture thereof. Among these, 1,2-dimethoxyethane, 1,3-dioxolane, 2-methyltetrahydrofuran, dibutyl ether, 1,4-dioxane, dipropyl ether, tetrahydrofuran are preferred.

[0087] Use

[0088] The negative electrode according to the present invention can be used in a secondary Li-ion, Na-ion, or K-ion battery. The battery also comprises a positive electrode and a separator disposed between the positive and negative electrodes.

[0089] Three polymers according to the invention were tested:

[0090] Polymer 1: Terpolymer containing 65.6 mol% vinylidene fluoride, 25.8 mol% trifluoroethylene and 8.6 mol% chlorotrifluoroethylene;

[0091] Polymer 2: Terpolymer containing 67.0 mol% vinylidene fluoride, 26.0 mol% trifluoroethylene and 7.0 mol% 1,1-chlorofluoroethylene;

[0092] Polymer 3: Copolymer containing 79.6 mol% vinylidene fluoride and 20.4 mol% trifluoroethylene. Example 1 - Preparation of a solid electrolyte membrane for a Li-ion battery separator

[0093] 0.500 g of P(VDF-HFP) (containing 11% HFP by weight) are dissolved in 3.28 g of acetone at room temperature. Separately, 0.041 g of LiFSI is dissolved in 0.477 g of EMIM-FSI. This latter solution is added to the P(VDF-HFP) solution and mixed. The resulting solution is then applied as a film using a squeegee and dried at 40°C for 1 h. A transparent, self-supporting film of 15 µm thickness is obtained.

[0094] Example 2 - Deposition of a coating on a lithium metal anode

[0095] 0.16 g of polymer 1 are dissolved in 3.5 g of DME at room temperature. Then, 0.24 g of LiFSI is added. The solution is then deposited as a film using a squeegee onto a lithium metal anode. The anode is then dried at 40°C for 1 hour. This results in a lithium anode with a coating thickness of less than 10 µm.

[0096] Example 3 - Interface resistance measurement

[0097] The interface resistance between the solid electrolyte membrane prepared in Example 1 and lithium metal anodes coated with different materials is evaluated. An anode A, consisting solely of lithium metal (reference), is prepared. Anodes B, C, and D, coated with LiFSI / Polymer 1 coatings having the following mass ratios Sl / Pl, respectively, are then prepared according to the procedure in Example 2. A solid electrolyte membrane is then placed between two anodes A in a button cell, and the total resistance of the system is measured by electrochemical impedance spectroscopy. The same procedure is repeated for anodes C and D, placing a solid electrolyte membrane between two anodes B (with the anode coating facing the solid electrolyte membrane).

[0098] Figure 1 compares the total strength of coated Li / membrane / coated Li systems for different types of Polymer 1 / LiFSI coatings. It can be seen that coatings with Sl / Pl mass ratios greater than 0.1 reduce the total system strength. Since the membrane is the same in all systems, this means that the interface strength has been reduced. This reduction is even greater with higher Sl / Pl mass ratios. Good results are also obtained with polymers 2 and 3.

Claims

Demands 1. Coating composition for a negative electrode comprising at least one PI polymer and at least one SI alkali metal salt characterized in that the mass ratio Sl / Pl is greater than 1; said mass ratio Sl / Pl corresponding to the ratio between the mass of said at least one SI alkali metal salt and the mass of said at least one PI polymer in said composition; said at least one PI polymer comprising monomeric units derived from a monomer Mla being vinylidene fluoride and monomeric units derived from a monomer Mla' selected from the group consisting of trifluoroethylene, 1,1-chlorofluoroethylene, chlorotrifluoroethylene and tetrafluoroethylene, or a mixture thereof.

2. Coating composition according to the preceding claim characterized in that said at least one PI polymer comprises 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.

3. Coating composition according to any one of the preceding claims, characterized in that said at least one PI polymer comprises monomeric units derived from a non-fluorinated monomer Mla" of formula R a R b C=C(R c )HORN d in which the R substituents a , R b and R care independently selected from the group consisting of H and Ci-C5 alkyl; R d is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR d 'with R d 'selected from the group consisting of H and Ci-Ci8alkyl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R group(s) d ", -C(O)OR d "or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain; R d " being selected from the group consisting of Ci-C6alkyl or C6-Ci2aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H2 group(s).

4. Coating composition according to any one of the preceding claims, characterized in that said PI polymer is selected from the group consisting of 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 and a terpolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene.

5. Coating composition according to any one of the preceding claims characterized in that said alkali metal salt SI is selected from the group consisting of LiCF3SO3, LiPF6, LiClIO4, LiBF4, LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F3)2, LiN(SO2CF2CF3)2, LiN(SO2F)(SO2CF3), LiN(SO2F)(SO2CF2CF3), LiN(SO2CF3)(SO2CF2CF3), LiAsF6, LiBF2C2O4, LiNO3, LiPF3(CF2CF3)3, LiTDI, NaCF3SO3, NaPF6, NaClIO4, 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, KCIO4, 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.

6. Coating composition according to any one of the preceding claims characterized in that it comprises at least one plasticizer selected from the group consisting of vinylidene carbonate, fluoroethylene carbonate, 4-fluoro-l,3-dioxolan-2-one, trans-4,5-difluoro-l,3-dioxolan-2-one, ethylene carbonate, propylene carbonate, (2-cyanoethyl)triethoxysilane, 3-methoxypropionitrile, sulfolane, triethylphosphate, γ-butyrolactone, 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) or ionic liquids.

7. Coating composition according to any one of the preceding claims characterized in that the mass ratio Sl / Pl is greater than or equal to 1.10, preferably greater than or equal to 1.25, in particular greater than or equal to 1.

40.

8. Negative electrode comprising an electrochemically active material, optionally deposited on a current collector, said electrochemically active material being coated with said coating composition according to any one of claims 1 to 7.

9. Negative electrode according to the preceding claim, characterized in that said electrochemically active material is selected from the group consisting of lithium alloy, lithium metal, sodium alloy, potassium alloy, sodium metal, potassium metal, an oxide metallic, a carbon material such as graphite or hard carbon, silicon, a silicon alloy, graphite / silicon composite and Li4Ti50i2.

10. Negative electrode comprising a current collector coated with said coating composition according to any one of claims 1 to 7.

11. Electrode according to any one of claims 8 to 10 characterized in that said coating composition has a thickness of less than 10 pm.

12. A method for preparing an electrode according to any one of claims 8 to 11 comprising the steps of: a) Preparing a composition comprising said at least one polymer PI, said at least one alkali metal salt SI and a solvent; b) Depositing the composition prepared in step a) onto a current collector or onto an electrochemically active material to form an electrode; c) Consolidating said electrode formed in step b) by heat treatment.

13. Battery comprising a negative electrode according to any one of claims 8 to 11.

14. Battery according to the preceding claim characterized in that it is a secondary lithium-ion, sodium-ion or potassium-ion battery.

15. Battery according to any one of claims 13 or 14 characterized in that it is an all-solid battery.

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