Electrolyte composition for lithium-ion electrochemical element

Abstract

An electrochemical lithium-ion element comprising: a) at least one positive electrode comprising a first positive active material which is a lithia phosphate of at least one transition metal operating at an average potential greater than or equal to 3.6 V vs. Li+ / Li; b) at least one negative electrode comprising a negative active material; c) an electrolyte comprising: - one or more solvents, one of which is methyl propionate (MP), - one or more diluents selected from a fluorinated alkyl ether, fluorobenzene, and a mixture thereof, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing 50 to 80% of the total volume of said one or more solvents and said one or more diluents, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a negative electrode passivation additive selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC), and a mixture thereof. Abbreviated figure: Figure 1

Description

Title of the invention: Electrolyte composition for lithium-ion electrochemical element. Technical field

[0001] The present exposition belongs to the technical field of electrolyte compositions for lithium-ion type electrochemical elements. Background

[0002] Lithium-ion electrochemical elements are known in the prior art. They are commonly used in many fields such as automotive, telecommunications, electronic devices, and aerospace. Their operating principle is based on the reversible exchange of lithium ions between the active material of a positive electrode (cathode), most often a lithium oxide of a transition metal or a lithium phosphate of a transition metal, and the active material of a negative electrode (anode), for example, graphite. The negative and positive electrodes are separated by a separator. The assembly formed by the negative electrode, the positive electrode, and the separator constitutes an electrochemical beam.The electrochemical beam is impregnated with an organic electrolyte, often liquid, generally composed of a mixture of cyclic or linear alkyl carbonates in which a lithium salt is dissolved, for example lithium hexafluorophosphate LiPF6.

[0003] Lithium-ion electrochemical elements undergo a more rapid loss of capacity when exposed to temperatures above room temperature (20-25°C). One of the causes of this capacity loss is the presence of secondary reactions at the interfaces between the positive electrode(s) and the electrolyte, and between the negative electrode(s) and the electrolyte. The formation of passivation layers on the electrode surface, called SEI (Solid Electrolyte Interphase) at the negative electrode and CEI (Cathode Electrolyte Interphase) at the positive electrode, limits these secondary reactions and thus limits the capacity loss during cycling. These passivation layers form spontaneously when the positive and negative electrodes come into contact with the electrolyte. They are mainly composed of the electrolyte's redox products.Their composition, and therefore their stability over time, depends both on the nature of the materials of the positive and negative electrodes and on the composition of the electrolyte.

[0004] We therefore sought to improve the cycling lifetime of an electrochemical element by modifying the composition of the electrolyte in order to create more stable and less soluble passivation layers over time.

[0005] Document WO 2024 / 011322 describes a lithium-ion electrochemical element comprising: - a linear ester and / or a cyclic ester as solvent(s), - a diluent, and - an alkali metal salt. Summary

[0006] An electrolyte composition has been discovered that improves the cycling life of a lithium-ion cell. The electrolyte composition according to the invention comprises: - one or more solvents, one of which is methyl propionate (MP), - one or more diluents chosen from a fluorinated alkyl ether, fluorobenzene and a mixture thereof, the volume proportion of fluorinated alkyl ether and / or fluorobenzene (FB) representing 50 to 80% of the total volume of said one or more solvents and said one or more diluents, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a negative electrode passivation additive selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof.

[0007] The association of methyl propionate, fluorinated alkyl ether and / or fluorobenzene, lithium bis(fluorosulfonyl)imidide and the passivation additive allows an improvement in the cycling life of the element compared with an electrochemical element containing a conventional electrolyte consisting of a mixture of one or more cyclic alkyl carbonate(s) with one or more linear alkyl carbonate(s) in which LiPF6 is dissolved.

[0008] It has been observed that the electrolyte according to the invention can be used in a lithium-ion element comprising a positive electrode based on a lithium phosphate of at least one transition metal operating at an average potential greater than or equal to 3.6 V vs. Li7Li. The electrolyte exhibits satisfactory oxidation resistance, even under the high potential conditions imposed by the nature of the active material of the positive electrode.

[0009] The invention therefore relates to a lithium-ion electrochemical element comprising: a) at least one positive electrode comprising a first positive active material which is a lithia phosphate of at least one transition metal operating at an average potential greater than or equal to 3.6 V vs. Li+ / Li; b) at least one negative electrode comprising a negative active material; c) the electrolyte as described above.

[0010] According to one embodiment, lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI) is the only salt of the electrolyte.

[0011] According to one embodiment, the electrolyte consists of: - a solvent which is methyl propionate and in one or more diluents chosen from a fluorinated alkyl ether, fluorobenzene and a mixture of these, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing 50 to 80% of the total volume of methyl propionate and fluorinated alkyl ether and / or fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a negative electrode passivation additive selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof.

[0012] According to one embodiment, the fluorinated alkyl ether is the 1,1,2,2-tetrafluoroethyl and 2,2,3,3-tetrafluoropropyl ether.

[0013] According to one embodiment, the electrolyte consists of: i) methyl propionate and 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether, ii) lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), and iii) vinylene carbonate.

[0014] According to one embodiment, the electrolyte consists of: i) methyl propionate and fluorobenzene, ii) lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), and iii) vinylene carbonate.

[0015] According to one embodiment, in the electrolyte, the volume proportion of fluorinated alkyl ether ranges from 65 to 75% of the total volume of said one or more solvents and said one or more diluents.

[0016] According to one embodiment, in the electrolyte, the volume proportion of fluorobenzene ranges from 65 to 75% of the total volume of said one or more solvents and said one or more diluents.

[0017] According to one embodiment, in the electrolyte, the mass of the passivation additive represents 1 to 4% of the total mass of said one or more solvents, said one or more diluents and lithium bis(fluorosulfonyl)imidide Li(FSO2)2N.

[0018] According to one embodiment, the concentration of lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI) ranges from 0.8 to 1.5 mol.L*.

[0019] According to one embodiment, the first positive active material is chosen from: i) a lithium manganese and iron phosphate of formula: LixMni _ y _ zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S, Hf, Bi, Se et des mélanges de ceux-ci ; ii) a lithium vanadium fluorophosphate of formula Lii+XVPO4F (LVPF) where 0 <x<0,15, ou l’un de ses dérivés de formule Lii+xVi _ yMyPO4Fz (LVMPF) où0<x<0,15, 0<y<0,5, 0,8<z<l,2 et M est choisi dans le groupe consistant en Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni, Zr et des mélanges de ceux-ci, ou un mélange de plusieurs composés des groupes i) et ii).

[0020] According to one embodiment, the first positive active ingredient is mixed with a second positive active ingredient selected from: iii) a lithium oxide of nickel, manganese and cobalt of formula Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x<l,l ; 0<y<l, 1 ; 0<z<l,l ; 0<t<l, 1 ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; (iv) a lithium oxide of nickel, cobalt and aluminium of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x<l,l ; 0<y<l,l ; 0<z<l,l ; 0<t<l,l ; M étant choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; v) a compound of formula Lii+xMi_xO2_yFy with cubic crystal structure where 0 <x<0,5 et 0<y<l et M représente un élément choisi dans le groupe constitué de Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd et Sm et des mélanges de ceux-ci ; vi) a lithium nickel manganese oxide (NMX) of formula Lia(Nii_x_y_zMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x<l ; 0<y<0,02 ; 0<z<l ; et M étant choisi dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci ; vii) un oxyde lithié de nickel et de manganèse de formule Liw(NixMnyCozMt)O2 où 1,1<w<1,6 ; 0<x<l ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t<l ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; viii) a lithium oxide of nickel, manganese, cobalt and aluminium (NMCA) of formula Liw(NixCoyAlzMntMs)O2 where 0.9 <w<l,l ; 0<x<l,l ; 0<y< 1,1 ; 0<z<l,l ; 0 <t< 1,1 ; 0<s<l,l, M étant au moins un élément choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr et La . ix) un oxyde lithié de manganèse de formule LixMn2_y_zM'yM"zO4.ô where M' and M" are chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 ; 0<z<0,2 ; 0<ô<l, ou un mélange de plusieurs composés des groupes iii) à ix).

[0021] According to one embodiment, the first positive active material represents from 30 to 99% of the total mass of positive active materials, and the second positive active material represents from 1 to 70% of the total mass of positive active materials.

[0022] According to one embodiment, the first positive active substance is a compound of group i) and the second positive active substance is a compound of group iii).

[0023] According to one embodiment, the negative active material is selected from carbon, preferably graphite, silicon, a carbon-silicon composite Si-C, silicon oxides SiOx with 0 <x<2 et un mélange de ceux-ci.

[0024] Finally, the invention relates to the use of an electrolyte consisting of: - a solvent which is methyl propionate and in one or more diluents chosen from a fluorinated alkyl ether, fluorobenzene and a mixture of these, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing 50 to 80% of the total volume of methyl propionate and fluorinated alkyl ether and / or fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a passivation additive for a negative electrode of a lithium-ion electrochemical element, the passivation additive being selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof, in a lithium-ion electrochemical element to improve its cycling life. Brief description of the figures

[0025] [Fig. 1] represents the percentage of capacity discharged by elements A and B, expressed in relation to their initial capacity during a cycle conducted at a temperature of 30°C and including charges and discharges at the C / 2 regime.

[0026] [Fig. 2] represents the percentage of capacity discharged by elements C, D, and E, expressed relative to their initial capacity during a cycle conducted at a temperature of 30°C and comprising charges and discharges at a rate of C / 2. Detailed description of embodiments Electrolyte:

[0027] The electrolyte contains methyl propionate MP, which is a linear ester. The low viscosity of methyl propionate allows for good performance of the element at low temperatures. Methyl propionate can be combined with one or more solvents. These can be chosen from: - saturated cyclic alkyl carbonates other than ethylene monofluorocarbonate (FEC), - unsaturated cyclic alkyl carbonates other than vinylene carbonate (VC), - saturated or unsaturated linear alkyl carbonates, - linear esters other than methyl propionate, - cyclic esters, - linear ethers other than fluorinated alkyl ethers, and - cyclic ethers.

[0028] Methyl propionate can be associated with one or more cyclic alkyl carbonates, saturated or unsaturated and / or with one or more linear alkyl carbonates, saturated or unsaturated.

[0029] Among the saturated cyclic alkyl carbonates, ethylene carbonate EC, propylene carbonate PC, butylene carbonate BC and mixtures thereof may be mentioned.

[0030] Examples of saturated linear alkyl carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dipropyl carbonate (DPC), and mixtures thereof. Preferred saturated linear alkyl carbonates are DMC and DEC.

[0031] Preferably, the electrolyte does not contain saturated or unsaturated cyclic alkyl carbonate, nor saturated or unsaturated linear alkyl carbonate.

[0032] Methyl propionate can be associated with one or more linear esters and / or one or more cyclic esters. The term "linear ester" refers to a compound of general formula RC(=O)OR' in which the R and R' groups each independently designate an alkyl group, the compound not comprising an oxygen atom between the alkyl group R and the carbonyl function -C(=O). Examples of linear esters other than methyl propionate include methyl acetate, ethyl acetate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and mixtures thereof.

[0033] Preferably, the electrolyte does not contain any esters other than methyl propionate.

[0034] Methyl propionate may be associated with one or more linear ethers other than fluorinated alkyl ethers and / or may be associated with one or more cyclic ethers. Examples of linear ethers include dimethoxyethane, ethyl propyl ether, dimethyl ether (DME), diethyl ether (DEE), and mixtures thereof. Examples of cyclic ethers include tetrahydrofuran (THF) and 1,3-dioxolane.

[0035] Preferably, the electrolyte does not contain any ether(s) other than fluorinated alkyl ether(s).

[0036] The electrolyte contains one or more diluents, one of them being a fluorinated alkyl ether or fluorobenzene or a mixture of at least one fluorinated alkyl ether and fluorobenzene, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing from 50 to 80% of the total volume of said one or more solvents and one or more diluents. Unlike a solvent, as defined in the present invention, a diluent is a molecule that cannot dissolve the lithium salt into an anion and a cation, and therefore does not create a solvation sphere around the anion and cation that would result from the dissolution of the salt if such dissolution were to occur. The use of fluorinated alkyl ether is advantageous because it minimizes the viscosity of the electrolyte.The fluorinated alkyl ether may be selected from the group consisting of 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl ether and 2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, difluoromethyl ether and 2,2,3,3-tetrafluoropropyl ether, 2,2,3,3-tetrafluoropropyl ether and 1,1,2,3,3,3-hexafluoropropyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl ether and 1,1,2,2-tetrafluoroethyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, and mixtures of These. Preferably, they are 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl (TTE) ether.

[0037] Preferably, the electrolyte does not contain any ether other than 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl (TTE).

[0038] Preferably, the electrolyte does not contain any other diluent than fluorinated alkyl ether(s) or fluorobenzene.

[0039] The volume proportion of methyl propionate may range from 20 to 50%, or from 25 to 40%, or from 30 to 35%, or from 20 to 30%, expressed as a percentage of the total volume of said one or more solvents and said one or more diluents. A preferred range is from 25 to 35%.

[0040] The volume proportion of fluorinated alkyl ether and / or fluorobenzene may range from 50 to 80%, or from 60 to 75%, or from 65 to 70%, or from 70 to 80%, expressed as a percentage of the total volume of said solvent(s) and said diluent(s). A preferred range is from 65 to 75%. When fluorinated alkyl ether and fluorobenzene are used together, the sum of the mass volume proportions of fluorinated alkyl ether and fluorobenzene falls within these ranges.

[0041] The electrolyte contains a negative electrode passivation additive selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC), and a mixture thereof. The mass percentage of VC or FEC may range from 0.5 to 5%, or from 1 to 4%, or from 2 to 3%, expressed as a percentage of the total mass of the mixture of said solvent(s), said diluent(s), and the lithium salt(s). If VC and FEC are used together, the sum of the mass percentages of VC and FEC falls within these ranges.

[0042] Preferably, the electrolyte does not contain any other negative electrode passivation additives than VC and / or FEC.

[0043] Preferably, the electrolyte composition does not contain any solvent other than methyl propionate or any diluent other than 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl (TTE).

[0044] Preferably, the electrolyte composition does not contain any solvent other than methyl propionate or any diluent other than fluorobenzene.

[0045] The electrolyte composition contains one or more lithium salts, one of which is lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI). The combined use of a passivation additive with LiFSI results in the formation of a thin and stable passivation layer, thereby improving the cycling lifespan of the element.

[0046] Imidide salts can be associated with LiFSI. Examples include lithium bis(trifluoromethane esulfonyl)imidide LiN(CF3SO2)2 (LiTFSI) and lithium bisperfluoroethylsulfonylimidide LiN(C2F5SO2)2 (LiBETI).

[0047] Other lithium salts besides imidides may also be present. They may be selected from lithium hexafluorophosphate LiPF6, lithium perchlorate LiC104, lithium tetrafluoroborate LiBF4, lithium hexafluoroarsenate LiAsF6, lithium hexafluoroantimonate LiSbF6, lithium trifluoromethanesulfonate LiCF3SO3, lithium trifluoromethanesulfonemethide LiC(CF3SO2)3 (LiTFSM), lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LIDFOB), lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3 (LiFAP) and mixtures thereof.

[0048] The percentage of lithium ions from LiFSI can represent 50 to 100%, 60 to 90%, or 70 to 80% of the total number of lithium ions in the electrolyte. In a preferred embodiment, the only salt in the electrolyte is lithium bis(fluorosulfonyl)imidide, Li(FSO2)2N (LiFSI). In a preferred embodiment, the electrolyte does not contain LiPF6.

[0049] The total concentration of lithium salts generally ranges from 0.5 to 3 mol.L 1 or from 0.8 to 2 mol.L 1 or from 1 to 1.5 mol.L *. Preferred electrolyte compositions:

[0050] A preferred electrolyte composition consists of: - methyl propionate in volume proportions of 25-45% / 25-40% / 25-35%, - one or more fluorinated alkyl ethers and / or fluorobenzene in volume proportions of 55-75% / 60-75% / 65-75%, the volume proportions being expressed in relation to the total volume of methyl propionate and said one or more fluorinated alkyl ethers and / or fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - 1 to 4% by mass of a negative electrode passivation additive chosen from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture of these, the mass percentage of passivation additive being expressed in relation to the total mass of methyl propionate, said one or more fluorinated alkyl ethers and / or fluorobenzene and lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI).

[0051] A preferred electrolyte composition consists of: - methyl propionate in volume proportions of 25-45% / 25-40% / 25-35%, - 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether (TTE) in volume proportions of 55-75% / 60-75% / 65-75%, the proportions being expressed relative to the total volume of methyl propionate and 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether (TTE), - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - 1 to 4% by mass of a negative electrode passivation additive chosen from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof, the mass percentage being expressed relative to the total mass of methyl propionate, 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether (TTE) and lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI).

[0052] A preferred electrolyte composition consists of: - methyl propionate in a volume proportion of 25-35%, - of 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether (TTE) in a volume proportion of 65-75%, the volume proportions being expressed in relation to the total volume of methyl propionate and 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether (TTE), - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - 1 to 4% by mass of vinylene carbonate (VC), the mass percentage being expressed in relation to the total mass of methyl propionate, 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl ether (TTE) and lithium bis(fluorosulfonyl)i midide Li(FSO2)2N (LiFSI).

[0053] A preferred electrolyte composition consists of: - methyl propionate in volume proportions of 25-45% / 25-40% / 25-35%, - fluorobenzene in volume proportions of 55-75% / 60-75% / 65-75%, the proportions being expressed relative to the total volume of methyl propionate and fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - 1 to 4% by mass of a negative electrode passivation additive chosen from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof, the mass percentage being expressed relative to the total mass of methyl propionate, fluorobenzene and lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI).

[0054] A preferred electrolyte composition consists of: - methyl propionate in a volume proportion of 25-35%, - fluorobenzene in a volume proportion of 65-75%, the volume proportions being expressed relative to the total volume of methyl propionate and fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - 1 to 4% by mass of vinylene carbonate (VC), the mass percentage being expressed in relation to the total mass of methyl propionate, fluorobenzene and lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI). Positive active material and positive electrode:

[0055] The positive electrode comprises a first positive active material which is a lithium phosphate of at least one transition metal operating at an average potential greater than or equal to 3.6 V vs. Li7Li. The lithium phosphate of at least one transition metal may be selected from compounds of the following groups: i) a lithium manganese and iron phosphate of formula: LixMni_yzFeyMzPO4(LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S, Hf, Bi, Se et des mélanges de ceux-ci. In one embodiment, 0.7 <l-y-z<0,9 ou 0,75<l-y-z<0,9 ; In one embodiment, 0.15 <y<0,25 ; Typical formulas of lithium manganese and iron phosphate are LiMnoj8Feoj2P04, LiMno>7Feoj3P04, LiMn2 / 3Fei / 3P04 and LiMnosFeosPCL. ii) a lithium vanadium fluorophosphate of formula Lil+xVPO4F (LVPF) where 0 <x<0,15, ou l’un de ses dérivés formule lil+xvl-ymypo4fz (lvmpf) où 0<x<0,15, 0<y<0,5, 0,8<z<l,2 et m est choisi dans le groupe consistant en ti, al, y, cr, cu, mg, mn, fe, co, ni, zr des mélanges ceux-ci, un mélange plusieurs composés groupes i) à ii).

[0056] Transition metal phosphates of formula LiMPO4 in which M designates one or more transition metals and in which Fe or Ni or Co is the major element, do not exhibit an average potential greater than or equal to 3.6 V vs. Li7Li.

[0057] The lithium phosphate of at least one transition metal can be coated with a layer of carbon and / or carbon nanotubes, in particular to increase its electronic conductivity and / or its ionic diffusivity.

[0058] The first positive active ingredient may be associated with a second positive active ingredient which is a lamellar lithia oxide of at least one transition metal which may be selected from: iii) a lithium oxide of nickel, manganese and cobalt of formula Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x<l,l 0<y<l, 1 0<z<l,l 0<t<l, m étant choisi dans le groupe constitué de al, b, mg, si, ca, ti, v, cr, fe, cu, zn, y, zr, nb, w, mo, s, sr, ce, ta, ga, nd, pr, la et des mélanges ceux-ci (iv) a lithium oxide of nickel, cobalt and aluminium of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x<l,l 0<y<l,l 0<z<l,l 0<t<l,l m étant choisi dans le groupe constitué de b, mg, si, ca, ti, v, cr, mn, fe, cu, zn, y, zr, nb, w, mo, s, sr, ce, ta, ga, nd, pr, la et des mélanges ceux-ci v) a compound of formula Lii+xMi.xO2_yFy with cubic crystal structure where 0 <x<0,5 et 0<y<l m représente un élément choisi dans le groupe constitué de na, k, mg, ca, b, sc, ti, v, cr, mn, fe, co, ni, cu, zn, al, y, zr, nb, mo, ru, ag, sn, sb, ta, w, bi, la, pr, eu, nd sm des mélanges ceux-ci ; vi) a lithium nickel manganese oxide (NMX) of formula Lia(Nii_x y zMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 0<x<l 0<y<0,02 0<z<l et m étant choisi dans le groupe consistant en al, b, mg, si, ca, ti, v, cr, fe, cu, zn, y, zr, nb, w, mo, s, sr, ce, ga, ta, nd, pr, la des mélanges de ceux-ci vii) a lithium oxide of nickel and manganese of formula Liw(NixMnyCozMt)O2 where 1.1 <w<1,6 ; 0<x<l 0,50<y<0,80 0<z<0,02 0<t<l m étant choisi dans le groupe constitué de al, b, mg, si, ca, ti, v, cr, fe, cu, zn, y, zr, nb, w, mo, s, sr, ce, ta, ga, nd, pr, la et des mélanges ceux-ci viii) a lithium oxide of nickel, manganese, cobalt and aluminium (NMCA) of formula Liw(NixCoyAlzMntMs)O2 where 0.9 <w<l,l ; 0<x<l,l 0<y< 1,1 0<z<l,l 0<t< 0<s<l,l, m étant au moins un élément choisi dans le groupe constitué de b, mg, si, ca, ti, v, cr, fe, cu, zn, y, zr, nb, w, mo, sr, ce, ga, ta, nd, pr et la, avec plus particulièrement 0,83 < x. ix) a lithium manganese oxide of formula LixMn2.y.zM'yM"zO4.ô where M' and M" are chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 0<z<0,2 0<ô<l, ou un mélange de plusieurs composés des groupes iii) à ix).

[0059] The composition of positive active matter may comprise a first active matter consisting of one or more of the compounds of groups i) to ii) and a second active matter consisting of one or more of the compounds of groups iii) to ix).

[0060] The composition of the positive active ingredient may include: - from 30 to 99% or from 40 to 99% or 50 to 99% or from 65 to 95% or from 75 to 90% by mass of the first active ingredient, - from 1 to 70% or from 1 to 60% or from 1 to 50% or from 5 to 35% or from 10 to 25% by mass of the second active ingredient, the percentages are expressed in relation to the total mass of the first positive active substance and the second positive active substance.

[0061] According to one embodiment, one or more of the compounds of group i) (LMFP) is or are associated with one or more compounds of group iii) (NMC).

[0062] According to one embodiment, the positive active material composition comprises: - 30 to 99% or 50 to 99% or 65 to 95% or 75 to 90% or 75 to 85% by mass of an LMFP type compound, - 1 to 70% or 1 to 50% or 5 to 35% or 10 to 25% or 15 to 25% by mass of an NMC type compound, the percentages being expressed in relation to the total mass of the LMFP type compound and the NMC type compound.

[0063] The positive electrode includes a current collector, at least one of whose faces is coated with a layer of a composition of positive active materials, which includes one or more active materials and optionally one or more binders and one or more electronically conductive materials.

[0064] The positive current collector is a current-conducting support that can take the form of a grid, foam, or metal strip. The metal strip can be solid or perforated. It can be made of aluminum or an alloy consisting mainly of aluminum, optionally coated with a conductive material, such as carbon. It can be made of steel or stainless steel. Its thickness can be in the range of 6 to 30 µm, 5 to 20 µm, or 10 to 15 µm, preferably 10 to 15 µm.

[0065] An ink is prepared by dispersing one or more positive active substances in a solvent or a mixture of several solvents. Optionally, a binder and an electronically conductive material are added to the dispersion. By varying the amount of solvent incorporated into the mixture, the viscosity of the ink can be varied before it is deposited on a face of the current collector. The ink-coated current collector is dried and then laminated to adjust its thickness. After evaporation of the solvent(s), a layer of a composition is obtained. of one or more active substances whose proportions of the various constituents are typically: - 80 to 98% or 90 to 95% by mass of one or more active ingredients, - 1 to 10% or 2 to 5% by mass of one or more binders, - from 0.1 to 10% or from 2 to 5% by mass of one or more electronically conductive materials.

[0066] The binder can be selected from poly(vinylidene fluoride) (PVDF) and its copolymers, polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl or butyl methacrylate), poly(vinyl chloride) (PVC), poly(vinyl formalin), polyester, sequenced polyetheramides, polymers of acrylic acid, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers, and cellulosic compounds such as carboxymethylcellulose (CMC). Elastomers usable as binders can be selected from styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), and hydrogenated butadiene-acrylonitrile (HNBR).Preferably, said at least one binder is an aqueous dispersible binder, such as polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile (HNBR) and polyvinyl alcohol (PVA).

[0067] The electronically conductive material is generally chosen from graphite, carbon black, acetylene black, soot, graphene, carbon fibers, carbon nanotubes or a mixture thereof. Negative active material and negative electrode:

[0068] The negative electrode may comprise an active material capable of inserting lithium into its structure. This may be graphite, coke, carbon black, and vitreous carbon. It may also be tin, silicon, carbon-silicon compounds such as Si-C composites, carbon-tin compounds, carbon-tin-silicon compounds, or silicon oxides (SiOx) with 0 <x<2. il peut aussi s’agir d’oxydes de titane, tels que li4ti50i2. de préférence, il s’agit graphite ou composite si-c.

[0069] Preferably, the negative active material is not lithium or a lithium-based alloy.

[0070] To obtain the negative active ingredient composition, an ink is prepared by dispersing one or more negative active ingredients, and optionally one or more binders and one or more electronically conductive compounds, in a solvent or a mixture of solvents. The solvent(s) may be organic or aqueous. Preferably, it is N-methylpyrrolidone.

[0071] The binder(s) may be chosen from the same list as that described in relation to the positive electrode, without necessarily being the same as those of the positive electrode. Similarly, the electronically conductive material(s) may be chosen from the same list as that described in relation to the positive electrode, without necessarily being the same as those of the positive electrode.

[0072] By varying the amount of solvent incorporated into the mixture, the viscosity of the ink can be varied before it is deposited on a face of a current collector. The negative current collector is a current-conducting support that can take the form of a grid, foam, or foil. The metal foil can be solid or perforated and can be made of copper or a copper-based alloy, or aluminum or an aluminum-based alloy, depending on the operating potential of the chosen negative active material with respect to the Li+ / Li couple. It is made of copper in the case of a graphite-based active material. The thickness of the current collector can range from 3 to 25 µm, or from 3 to 10 µm, preferably from 5 to 8 µm. The ink-coated current collector is dried and then laminated to adjust its thickness.After evaporation of the solvent(s), a layer is obtained with a composition of one or more active substances whose proportions of the various constituents are typically: . - 85 to 98% or 90 to 98% by mass of one or more negative active ingredients, - 1 to 10% or 1 to 5% by mass of one or more binders, - 0 to 5% by mass or 1 to 5% of one or more electronically conductive materials. Separator:

[0073] A separator is generally interposed between a negative electrode and a positive electrode to prevent potential short circuits. It prevents electrical contact between a negative electrode and a positive electrode but nevertheless allows the transport of ions between these two electrodes. The separator material can be selected from the following materials: a polyolefin, for example polypropylene and polyethylene, a polyester, glass fibers bonded together by a polymer, polyimide, polyamide, polyaramid, polyamideimide, and cellulose. The polyester can be selected from polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Advantageously, the polyester, polypropylene, or polyethylene contains or is coated with a material selected from the group consisting of a metal oxide, a carbide, a nitride, a boride, a silicide, and a sulfide. This material can be SiO2 or Al2O3.The separator can be coated with an organic coating, for example comprising an acrylate or PVDF or P(VdF-HFP). A preferred separator is made of polyethylene or is made of . from the association of three layers which are polypropylene PP / polyethylene PE / polypropylene PP.

[0074] A first preferred electrochemical element comprises: - at least one positive electrode comprising a mixture of an LMFP-type compound and an NMC-type compound, in the mass proportions described above, - at least one negative electrode comprising a mixture of graphite and a Si-C composite, - an electrolyte consisting of a solvent which is methyl propionate, a diluent which is 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl (TTE) in a volume proportion of 50 to 80% of the total volume of methyl propionate and TTE, LiFSI and vinylene carbonate, in the proportions or percentages as described above.

[0075] A second preferred electrochemical element comprises: - at least one positive electrode comprising a mixture of an LMFP-type compound and an NMC-type compound, in the mass proportions described above, - at least one negative electrode whose active material is made of graphite, - an electrolyte consisting of a solvent which is methyl propionate, a diluent which is 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl (TTE) in a volume proportion of 50 to 80% of the total volume of methyl propionate and TTE, LiFSI and vinylene carbonate, in the proportions or percentages as described above.

[0076] A third preferred electrochemical element comprises: - at least one positive electrode comprising a mixture of an LMFP-type compound and an NMC-type compound, in the mass proportions described above, - at least one negative electrode whose active material is made of graphite, - an electrolyte consisting of a solvent which is methyl propionate, a diluent which is fluorobenzene in a volume proportion of 50 to 80% of the total volume of methyl propionate and fluorobenzene, LiFSI and vinylene carbonate, in the proportions or percentages as described above.

[0077] The electrochemical element is manufactured in a conventional manner. It can be in prismatic, cylindrical, pocket or button format. Examples

[0078] Electrochemical elements of pouch type A to E have been prepared. Their components are detailed in Table 1.

[0079] [Tables 1] A* BC* DE Positive active material LMFP (40% m) NMC (60% m) LMFP (40% m) NMC (60% m) LMFP (40% m) NMC (60% m) LMFP (40% m) NMC (60% m) LMFP (40% m) NMC (60% m) Negative active material Si-C (40% m) graphite (60% m) Si-C (40% m) graphite (60% m) Graphite 100% Graphite 10 0% Graphite 100% Solvent or diluent EC / EMC 30 / 70 (%vol) MP / TTE 30 / 70 (%vol) EC / EMC 30 / 70 (%vol) MP / TTE 30 / 70 (%vo D MP / FB 30 / 70 (%vol) Salt lithium LiPF6 1 mol.L 1 LiFSI 1 mol.L 1 LiPF6 1 mol.L 1 LiFSI 1 mol.L 1 LiFSI 1 mol.L 1 Additive VC3% VC3% VC3% VC3% VC3% * Example outside of invention

[0080] Elements A and C are comparative. Their electrolyte comprises a mixture of two solvents EC and EMC, but no diluent. Elements B, D, and E are according to the invention. Their electrolyte comprises a mixture of a solvent and a diluent, which is either 1,1,2,2-tetrafluoroethyl ether and 2,2,3,3-tetrafluoropropyl (TTE) ether, or fluorobenzene (FB).

[0081] Cells A to E underwent cycling at 30°C during which they were subjected to charging and discharging at a rate of C / 2, where C is the nominal capacity of the cell. The capacity discharged by each cell in each cycle was compared to its initial capacity. The change in the percentage of capacity discharged by cells A and B relative to their initial capacity is shown in [Fig. 1]. It can be noted that the capacity discharged by cell B is greater than that discharged by cell A over the entire duration of the cycle. This test highlights the effect of replacing the EC / EMC mixture with the MP / TTE mixture and replacing LiPF6 with LiFSI on increasing the cell's cycle life. Similarly, the change in the percentage of capacity discharged by cells C, D, and E relative to their initial capacity is shown in [Fig. 2].It can be noted that the discharged capacities of cells D and E are greater than that discharged by cell C over the entire cycling period. This test highlights the effect of replacing the EC / EMC mixture with the MP / TTE or MP / FB mixture and replacing LiPF6 with LiFSI on increasing the cell's cycling lifetime.

Claims

Demands

1. Lithium-ion electrochemical element comprising: a) at least one positive electrode comprising a first positive active material which is a lithium phosphate of at least one transition metal operating at an average potential greater than or equal to 3.6 V vs. Li7Li; b) at least one negative electrode comprising a negative active material; (c) an electrolyte comprising: - one or more solvents, one of which is methyl propionate (MP), - one or more diluents selected from a fluorinated alkyl ether, fluorobenzene and a mixture thereof, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing 50 to 80% of the total volume of said one or more solvents and said one or more diluents, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a negative electrode passivation additive selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof.

2. Lithium-ion electrochemical element according to claim 1, wherein lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI) is the only salt of the electrolyte.

3. Lithium-ion electrochemical element according to claim 1 or 2, wherein the electrolyte consists of: - a solvent which is methyl propionate and one or more diluents selected from a fluorinated alkyl ether, fluorobenzene and a mixture thereof, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing from 50 to 80% of the total volume of methyl propionate and fluorinated alkyl ether and / or fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a negative electrode passivation additive selected from ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof.

4. Lithium-ion electrochemical element according to any one of the preceding claims, wherein the fluorinated alkyl ether is the ether of 1,1,2,2-tetrafluoroethyl and 2,2,3,3-tetrafluoropropyl.

5. Lithium-ion electrochemical element according to claim 3 or 4, wherein the electrolyte consists of: i) methyl propionate and 1,1,2,2-tetrafluoroethyl and 2,2,3,3-tetrafluoropropyl ether, ii) lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), and iii) vinylene carbonate.

6. Lithium-ion electrochemical element according to claim 3, wherein the electrolyte consists of: i) methyl propionate and fluorobenzene, ii) lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), and iii) vinylene carbonate.

7. Lithium-ion electrochemical element according to any one of claims 1 to 5, wherein in the electrolyte the volume proportion of fluorinated alkyl ether ranges from 65 to 75% of the total volume of said one or more solvents and said one or more diluents.

8. Lithium-ion electrochemical element according to any one of claims 1 to 3 and 6, wherein in the electrolyte the volume proportion of fluorobenzene is from 65 to 75% of the total volume of said one or more solvents and of said one or more diluents.

9. Lithium-ion electrochemical element according to any one of the preceding claims, wherein in the electrolyte the mass of the passivation additive represents 1 to 4% of the total mass of said one or more solvents, said one or more diluents and lithium bis(fluorosulfonyl)imidide Li(FSO2)2N.

10. Lithium-ion electrochemical element according to any one of the preceding claims, wherein the concentration of lithium bis(fluorosulfonyl)imi Li(FSO2)2N (LiFSI) ranges from 0.8 to 1.5 mol.L*.

11. Lithium-ion electrochemical element according to any one of the preceding claims, wherein the first positive active material is selected from: i) a lithium manganese iron phosphate of formula: LixMni . y. zFeyMzPO4(LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al,

12. B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S, Hf, Bi, Se and mixtures thereof; ii) a lithium vanadium fluorophosphate of formula Lii+XVPO4F (LVPF) where 0 <x<0,15, ou l’un de ses dérivés de formule Lii+xVi _ yM yPO4Fz (LVMPF) où0<x<0,15, 0<y<0,5, 0,8<z<l,2 et M est choisi dans le groupe consistant en Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni, Zr et des mélanges de ceux-ci, ou a mixture of several compounds from groups i) and ii). Lithium-ion electrochemical element according to claim 11, wherein the first positive active material is mixed with a second positive active material selected from: iii) a lithium oxide of nickel, manganese and cobalt of formula Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x<l,l ; 0<y<l,l ; 0<z<l,l ; 0<t< 1,1 ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; (iv) a lithium oxide of nickel, cobalt and aluminium of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x<l,l ; 0<y< 1,1 ; 0<z<l,l ; 0<t< 1,1 ; M étant choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; v) a compound of formula Lii+xMi.xO2.yFy with cubic crystal structure where 0 <x<0,5 et 0<y<l et M représente un élément choisi dans le groupe constitué de Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd et Sm et des mélanges de ceux-ci ; vi) a lithium nickel manganese oxide (NMX) of formula Lia(Nii.xyzMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x<l ; 0<y<0,02 ; 0<z<l ; et M étant choisi dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci ; vii) a lithium oxide of nickel and manganese of formula Liw(NixMny CozMt)O2 where 1.1 <w<1,6 ; 0<x<l ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t<l ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; viii) a lithium oxide of nickel, manganese, cobalt and aluminium (NMCA) of formula Liw(NixCoyAlzMntMs)O2 where 0.9 <w<l,l ; 0<x<l,l ; 0<y<l, 1 ; 0<z<l,l ; 0<t<l,l ; 0<s<l,l, M étant au moins un élément choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr et La. ix) un oxyde lithié de manganèse de formule LixMn2-y-zM'yM"zO4 ô où M' et M" sont choisis dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb et Mo; M' et M" étant différents l’un de l’autre, et 1<x<1,4 ; 0<y<0,6 ; 0<z<0,2 ; 0<ô<l, ou un mélange de plusieurs composés des groupes iii) à ix).

13. Lithium-ion electrochemical element according to claim 12, wherein the first positive active material represents from 30 to 99% of the total mass of the positive active materials and the second positive active material represents from 1 to 70% of the total mass of the positive active materials.

14. Lithium-ion electrochemical element according to any one of claims 11 to 13, wherein the first positive active material is a compound of group i) and the second positive active material is a compound of group iii).

15. Lithium-ion electrochemical element according to any one of the preceding claims, wherein the negatively active material is selected from carbon, preferably graphite, silicon, a carbon-silicon composite Si-C, silicon oxides SiOx with 0 <x<2 et un mélange de ceux-ci.

16. Use of an electrolyte consisting of: - a solvent which is methyl propionate and one or more diluents selected from a fluorinated alkyl ether, fluorobenzene and a mixture thereof, the volume proportion of fluorinated alkyl ether and / or fluorobenzene representing 50 to 80% of the total volume of methyl propionate and fluorinated alkyl ether and / or fluorobenzene, - lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), - a passivation additive for a negative electrode of a lithium-ion electrochemical element, the passivation additive being selected including ethylene monofluorocarbonate (FEC), vinylene carbonate (VC) and a mixture thereof, in a lithium-ion electrochemical element to improve its cycling life.

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