Lithium-ion battery separator

Abstract

The present invention relates to an electrochemical device comprising an electrolytic composition and a separator made of at least one fluorinated polymer resin characterized in that the ratio s*e / G is between 0.02 and 200.

Description

Title of the invention: Separator for lithium-ion battery Technical field of the invention

[0001] The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of the Li-ion type. More specifically, the invention relates to an electrochemical device comprising a separator. Technological background of the invention

[0002] The market for separators for electrochemical devices is dominated by the use of polyolefins (for example Celgard® or Hipore®) produced by extrusion and / or stretching via dry or wet processes. The separators must have low thicknesses, sufficient mechanical and temperature resistance, good electrochemical resistance to the voltages to which they are exposed, optimal affinity for the electrolyte and, more generally, excellent ionic conductivity.

[0003] Conventional electrolytes based on carbonated solvents are not stable at high potential. To improve the stability of high potential electrolytes, the carbonated solvents can be replaced by other solvents that are more stable in oxidation (ionic liquids, sulfones, nitriles), or the salt concentration can be increased to reduce the activity of the solvent. Both of these approaches tend to increase the viscosity of the electrolyte, which can cause wettability problems with polyolefin separators. WO2023 / 227846 discloses an electrochemical device comprising a separator and a viscous electrolytic composition. The separator consists of a polyethylene support coated with a polymer resin.There is still a need to develop new separators with improved properties, i.e. presenting a very good compromise between the wettability of the latter and its thermal stability making it possible to overcome the drawbacks mentioned above. Summary of the invention.

[0004] According to a first aspect, the present invention relates to an electrochemical device comprising an electrolytic composition and a separator characterized in that the ratio s*e / G is between 0.02 and 200; s being the value of the conductivity of the electrolytic composition in the separator measured at 25°C expressed in mS / cm, e being the thickness of the separator expressed in pm, and G expressed in s-1 being the air permeability of said separator measured by Gurley according to standard ISO 5636-5. The present invention provides a separator having both good thermal stability and good wettability even in the presence of viscous electrolyte. Indeed, it has It has been surprisingly found that polyolefin separators tend to shrink at high temperatures, which can lead to a short circuit in the battery, especially as the cell size increases. It has also been shown that applying a polymer coating to the surface of the porous polyolefin membrane improves thermal stability and wettability, but wettability remains insufficient for certain viscous electrolytes. The use of a separator having the s*e / G ratio as provided in the present invention makes it possible to overcome the drawbacks observed under particular conditions of use of a battery, i.e. high voltage and viscous electrolytic composition.

[0005] According to a preferred embodiment, said electrolytic composition comprises at least one solvent and one lithium salt; said electrolytic composition having a viscosity greater than 2 cP measured at 20°C and with a shear of 20s-1.

[0006] According to a preferred embodiment, said electrolytic composition has a viscosity greater than 5 cP, preferably greater than 10 cP, in particular greater than 15 cP measured at 20°C and with a shear of 20 s1.

[0007] According to a preferred embodiment, the electrolytic composition comprises from 5 to 70% by weight of lithium salt and from 20 to 85% by weight of at least one organic solvent.

[0008] According to a preferred embodiment, said separator has a porosity of between 25% and 70% measured by mercury intrusion porosimetry according to ISO 15901-1:2016. A porosity in the specified range makes it possible to maintain good mechanical strength. Too high a porosity, above 70%, creates a risk of dendrite formation.

[0009] According to a preferred embodiment, said separator has a thickness of between 5 μm and 40 μm.

[0010] According to a preferred embodiment, said separator has a thermal shrinkage factor at 150°C less than 10% in absolute value measured according to the method described in the present application. It has been observed that the separators according to the present invention have a thermal shrinkage factor lower than polyolefin separators.

[0011] According to a preferred embodiment, said separator has a G / e ratio of between 0.1 and 15 s '.pm1; G expressed in s-1 being the air permeability of said separator measured by Gurley according to the ISO 5636-5 standard and e expressed in pm being the thickness of said separator. A value beyond 15 s '.pm 1 will imply poorer wettability of the separator.

[0012] According to a preferred embodiment, said separator comprises at least one polymer resin selected from the group consisting of polyaramid, polyester, polyaryletherketone, polysulfone, polyethersulfone, polyimide, polyacrylonitrile, polyetherimide, polycarbonate, polybenzimidazole, polyarylether, polyarylthioether, fluoropolymer, cellulose or a mixture thereof.

[0013] According to a preferred embodiment, said separator comprises at least one polymer resin comprising a fluorinated polymer PI comprising repeating units derived from vinylidene fluoride and optionally repeating units derived from hexafluoropropene.

[0014] According to a preferred embodiment, said separator comprises at least one cellulose-type polymer resin.

[0015] According to a preferred embodiment, said separator also comprises a polymer P2 comprising repeating units of formula R'R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C8 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its ring chain.

[0016] According to a preferred embodiment, said electrochemical device also comprises a positive electrode and a negative electrode; said separator disposed between said positive electrode and said negative electrode.

[0017] According to a preferred embodiment, said negative electrode comprises an active material selected from the group consisting of lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, silicone, a silicon alloy and Li4Ti50i2.

[0018] According to a preferred embodiment, said positive electrode comprises an active material selected from the group consisting of LiCoO2, Li(Ni, Co, AI)O2, Li(i+x)NiaMnbCoc (x represents a real number of 0 or more, a = 0.9, 0.8, 0.6, 0.5, or 1 / 3, b = 0.05, 0.1, 0.2, 0.3, or 1 / 3, c = 0.05, 0.1, 0.2, or 1 / 3), LiNiO2, LiMn2O4, LiCoMnO4, Li3NiMn3O3, Li3Fe2(PO4)3, Li3V2(PO4)3, a spinel Li Mn substituted by a different element having a composition represented by Lii+xMn2_x_yMy O4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between 0 and 2, lithium titanate LixTiOy - x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni or a mixture thereof.

[0019] According to a preferred embodiment, said electrochemical device is a lithium-ion battery having a charge cut-off voltage greater than or equal to 4.4 V.

[0020] According to another aspect, the present invention relates to a separator having a G / e ratio of between 0.1 and 15 s '.pm1; G in s 1 being the air permeability of said separator measured by Gurley according to the ISO 5636-5 standard and e being the thickness of said separator in pm; said separator comprising at least one polymer resin as defined in the present application. Detailed description of the invention

[0021] According to a first aspect, the present invention provides an electrochemical device comprising an electrolytic composition and a separator. These are described in more detail below. In the electrochemical device according to the invention, the ratio s*e / G is between 0.02 and 200.

[0022] s represents the value of the conductivity of the electrolytic composition in the separator measured at 25°C expressed in mS / cm according to the method detailed below, e represents the thickness of the separator expressed in pm. G expressed in s 1 represents the air permeability of said separator measured by Gurley according to standard ISO 5636-5.

[0023] Advantageously, said ratio s*e / G is between 0.02 and 175, preferably between 0.03 and 150, more preferably between 0.03 and 125, in particular between 0.03 and 100, more particularly between 0.03 and 75, preferably between 0.03 and 50, advantageously between 0.03 and 25, preferably between 0.03 and 10. As mentioned above, a separator having said ratio in the range described above presents a very good compromise between the different properties sought for a separator, i.e. mechanical strength and wettability. Electrolytic composition

[0024] According to the present invention, said electrochemical device comprises an electrolytic composition. The electrolytic composition impregnates the separator to allow the impregnation of lithium ions within the device. As mentioned above, the electrolytic composition comprises a solvent and a lithium salt. The solvent may be one of the solvents mentioned below or a mixture thereof. The solvent is preferably an organic solvent. According to a first embodiment, said solvent used in the electrolytic composition has a high polarity. The term polarity refers to the dipole moment at 25°C of the solvent used in the electrolytic composition. According to another embodiment, the electrolytic composition has a high viscosity. The viscosity is measured with a Brookfield metek DV2T viscometer at 20°C and a shear of 20 s1.

[0025] Preferably, said electrolytic composition has a viscosity greater than 2.0 cP measured according to the method described above. According to a preferred embodiment, said electrolytic composition may also have a viscosity greater than 3 cP, greater than 4 cP, greater than 5 cP, greater than 6 cP, greater than 7 cP, greater than 8 cP, greater than 9 cP, greater than 10 cP, greater than 11 cP, greater than 12 cP, greater than 13 cP, greater than 14 cP, greater than 15 cP, greater than 16 cP, greater than 17 cP, greater than 18 cP, greater than 19 cP, greater than 20 cP, greater than 21 cP, greater than 22 cP, greater than 23 cP, greater than 24 cP, greater than 25 cP, greater than 26 cP, greater than 27 cP, greater than 28 cP, greater than 29 cP or greater than 30 cP. According to a preferred embodiment, said electrolytic composition may also have a viscosity of between 2 cP and 600 cP, advantageously between 5 and 500 cP, preferably between 10 and 450 cP, more preferably between 15 and 400 cP, in particular between 20 and 350 cP, more particularly between 25 and 300 cP, preferably between 25 and 250 cP, advantageously preferably between 30 and 200 cP.

[0026] The lithium salt may be present in the electrolytic composition at very variable concentrations. A high concentration of lithium salt will promote a high viscosity of the electrolytic composition. For example, the lithium salt may be present in the electrolytic composition at a concentration of between 0.01 and 20 mol.L *, advantageously between 0.01 and 15 mol.L *, preferably between 0.01 and 10 mol.L *. A high concentration of lithium salt in said electrolytic composition will promote the performance of the electrochemical device in terms of capacity.

[0027] Preferably, said electrolytic composition has a viscosity of less than 1000 cP measured according to the method described above, advantageously less than 900 cP, preferably less than 800 cP, more preferably less than 700 cP, in particular less than 600 cP.

[0028] The solvents may be chosen from ethers; carbonic acid esters or organic carbonates; cyclic carbonates, carboxylic acid esters; lactones; phosphoric acid esters; nitriles; amides; lactams; nitro compounds; sulfones; sulfoxides; ionic liquids with FSI (bis(fluorosulfonyl)imide) anion with a cation of ammonium, imidazolium, pyrrolidinium, piperidinium, phosphonium, sulfonium or oxonium type; fluorinated solvents; organic phosphorus compounds such as phosphates or phosphites.

[0029] For example, said solvent may be of formula (la), (Ib), (le), (Id), (le), (If), (Ig), (Ih), (li), (Ij), (Ik), (II), (Im), (In), (lo), (Ip), (Iq), (Ir), (Is), (It), (lu), (Iv), (Iw), (Ix), (Ix'), (ly) or (Iz):

[0030] wherein R4, R5 and R18 are independently selected from the group consisting of C1-C10 alkyl, C2-C5 alkenyl, C1-C10 (per)fluoroalkyl and C6aryl;

[0031] R6, R7, R8, R9, R10, R11, R12, R13, R15 and R16 are independently selected each other from the group consisting of H, C1-C10 alkyl, C2-C5 alkenyl, C1-C10 (per)fluoroalkyl and C6aryl;

[0032] n is an integer from 1 to 10, preferably from 1 to 5;

[0033] X is O or SO2;

[0034] Y1 and Y2 are selected from O or CR6R7 with R6 and R7 as defined above provided that Yi and Y2 are not simultaneously O;

[0035] Y3 is SO2 or S=O;

[0036] R14 and R17 are independently selected from the group consisting of H, C1-C5 alkyl, C2-C5 alkenyl, and C6aryl.

[0037] In the present application, the alkyl and alkenyl substituents described in connection with the above solvent formulas are optionally substituted with one or more fluorine atoms, a C1-C5 alkoxy group, a C1-C10 (per)fluoroalkyl group, a phenyl group, a CN, OH, NO2 or SO2 functional group. In the present application, the C6aryl substituent described in connection with the above solvent formulas is optionally substituted with one or more fluorine atoms, a C1-C10 alkyl group, a C1-C5 alkoxy group or a C1-C10 (per)fluoroalkyl group.

[0038] Said solvent may also be a crown ether such as, for example, but not limited to, 18-crown-6 ether, 15-crown-5 ether, 12-crown-4 ether, dibenzo-18-crown-6 ether, dibenzo-24-crown-8 ether, dicyclohexano-18-crown-6 ether, dibenzo-12-crown-4 ether.

[0039] More preferably, said solvent is of formula (la), (Ib), (le), (Id), (le), (If), (Ig), (Ih), (li), (Ij), (Ik), (II), (Im), (In), (lo), (Ip), (Iq), (Ir), (Is), (It), (lu), (Iv), (Iw), (Ix), (Ix'), (ly) or (Iz) in which

[0040] R4, R5 and R18 are selected independently of each other from the group consisting of C1-C5 alkyl, C2-C3 alkenyl, C1-C5 (per)fluoroalkyl and C6aryl;

[0041] R6, R7, R8, R9, R10, R11, R12, R13, R15 and R16 are independently selected each other from the group consisting of H, C1-C5 alkyl, C2-C3 alkenyl, C1-C5 (per)fluoroalkyl and C6aryl;

[0042] n is an integer from 1 to 10, preferably from 1 to 5;

[0043] X is O or SO2;

[0044] Y1 and Y2 are selected from O or CR6R7 with R6 and R7 as defined above provided that Yi and Y2 are not simultaneously O;

[0045] Y3 is SO2 or S=O;

[0046] R14 and R17 are independently selected from the group consisting of H, C1-C5 alkyl, C2-C3 alkenyl, and C6aryl. In particular, said solvent is of formula (la), (Ib), (le), (Id), (le), (If), (Ig), (Ih), (li), (Ij), (Ik), (II), (Im), (In), (lo), (Ip), (Iq), (Ir), (Is), (It), (lu), (Iv), (Iw), (Ix), (Ix') or (ly) in which

[0048] R4, R5 and R18 are selected independently of each other from the group consisting of CrC3 alkyl, C2-C3 alkenyl, Ci-C3 perfluoroalkyl and C6aryl;

[0049] R6, R7, R8, R9, R10, R11, R12, R13, R15, R16, are independently selected each other from the group consisting of H, C1-C3 alkyl, C2-C3 alkenyl, C1-C3 (per)fluoroalkyl and C6aryl;

[0050] n is an integer from 1 to 10, preferably from 1 to 5;

[0051] X is O or SO2;

[0052] Y1 and Y2 are selected from O or CR6R7 with R6 and R7 as defined above provided that Yi and Y2 are not simultaneously O;

[0053] Y3 is SO2 or S=O;

[0054] R14 and R17 are independently selected from the group consisting of H, CrC3 alkyl, C2-C3 alkenyl, and C6aryl.

[0055] More particularly, said solvent may be of formula (Ia) in which R4 and R5 are independently of each other selected from the group consisting of ch3, ch2f, chf2, c2h5, ch2ch2f, ch2chf2, ch2cf3, ch2ch2ch3, ch2ch2ch2f, CH2CHFCH3, CH2CH2CF3, CH2CF2CHF2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h 5, CH(CH3)2, CH3CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CF2CF2CF2CF3 and CH(CH3)2; preferably R4 is CH3, C6H5, or CH2CH3 and R5 is selected from the group consisting of CH3, CH2F, CHF2, C2H5, CH2CH2F, CH2CHF2, CH2CF3, CH2CH 2CH3, ch2ch2ch2f, ch2chfch3, ch2ch2cf3, ch2cf2chf2, cf3, cf2cf3, cf2cf2 CF3, CH(CF3)2, C6H5, CF2CF2CF2CF3 and CH(CH3)2.

[0056] More particularly, said solvent may be of formula (Ib) in which R6, R7, R8 and R9 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3ch2ch2ch2, (ch3)2chch2, ch3ch 2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; preferably R6, R7 and R8 are H, CH3, C6H5, or CH2CH3 and R9 is selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2.

[0057] More particularly, said solvent may be of formula (Ic) in which R6 and R7 are independently of each other selected from the group consisting of H, F, ch3, ch2f, chf2, ch2ch2f, ch2chf2, ch2cf3, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3ch2ch2ch2, (ch3)2chch2, ch3ch2 CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; preferably R6 is H, CH3, C6H5, or CH2CH3 and R7 is selected from the group consisting of H, F, CH3, CH2F, chf2, ch2ch2f, ch2chf2, ch2cf3, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf 2 CF3, C6H5, CH2CH3 and CH=CH2.

[0058] More particularly, said solvent may be of formula (Id) in which R4 and R5 are independently of each other selected from the group consisting of CH3, CH2CH3, CH2F, CHF2, CH2CH2F, CH2CF3, CH2OCH3, CH(CH3)CH2OCH3, CH(CH3)2, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3 CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CHFCH3 and CH2CH2CH3; preferably R4 is selected from the group consisting of CH2CH2 F, CH3, C6H5, or CH2CH3 and R5 is selected from the group consisting of CH3, CH2 CH3, CH2F, CHF2, CH2CH2F, CH2CF3, CH2OCH3, CH(CH3)CH2OCH3, CH(CH3)2, cf3, CF2CF3, CF2CF2CF3, CH(CF3)2, cf2cf2cf2cf3, chfch3 and ch2ch2ch3.

[0059] More particularly, said solvent may be of formula (Ic) in which R6, R7, R8, R9, R10 and R11 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH(CH3)2, ch3ch2ch2ch 2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and ch=ch2; preferably R6, R7 and R8 are H, CH3, C6H5, or CH2CH3 and R9, R10 and R11 are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2.

[0060] More particularly, said solvent may be of formula (If) in which R6, R7, R8, R9, R10, R11, R12 and R13 are independently of one another selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2 CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH3CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; preferably R 6, R8, R10 and R12 are H, CH3, C6H5, or CH2CH3 and R7, R9, R11 and R13 are independently selected from the group consisting of H, F, CH3, CH2F, chf2, ch2ch2f, ch2chf2, ch2cf3, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf2 CF3, C6H5, CH2CH3 and CH=CH2.

[0061] More particularly, said solvent may be of formula (Ig) in which R6, R7, R8, R9, R10 and R11 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2 CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH(CH3)2, CH3CH2CH2CH2, (CH3)2CHCH 2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 is H, CH3, C6H5, CH2CH3 and CH=CH2; preferably R6, R7 and R8 are H, CH3, C6H5, or CH2CH3 and R9, R10 and R11 are selected independently of each other from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2 CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2; and R14 is H, CH3, C6H 5, or CH2CH3 and CH=CH2.

[0062] More particularly, said solvent may be of formula (Ih) in which R7, R8, R9 and R11 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH(CH3)2, CH3CH2CH2CH2, (CH3)2CHCH2, ch3ch2 CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 is H, CH3, C6H5, or CH2 CH3and CH=CH2; preferably R7 and R8 are H, CH3, C6H5, or CH2CH3 and R9 and R11 are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3) 2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2; and R14 is H, CH3, C6H5, or CH2CH3 and CH=CH2.

[0063] More particularly, said solvent may be of formula (li) in which R6, R7, R8, R9, R10, R11, R12 and R13 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2 CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH(CH3)2, CH3CH2CH2CH2, (CH3) 2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 is H, CH3, C6H5, or CH2CH3and CH=CH2; preferably R6, R8, R10 and R12 are H, CH3, C6H5, or CH2CH3 and R, R, R and R are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2; and R14 is H, CH3, C6H5, or CH2CH3 and CH=CH2.

[0064] More particularly, said solvent may be of formula (Ij) in which R6, R7, R8 and R9 are independently of one another selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3ch2ch2ch2, (ch3)2chch2, ch3ch 2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; preferably R6, R7 and R8 are H, CH3, C6H5, or CH2CH3 and R9 is selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2.

[0065] More particularly, said solvent may be of formula (Ik) in which R6, R7, R8, R9, R10, R11, R12, R13, R15 and R16 are independently of one another selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH(CH3)2, ch3ch2ch2 CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2,CH2CH3 and ch=ch2; preferably R6, R7, R8, R9 and R10 are H, CH3, C6H5, or CH2CH3 and R11, R12, R13, R15 and R16 are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2.

[0066] More particularly, said solvent may be of formula (II) in which R6, R7, R8, R9, R10, R11, R12, R13, R15 and R16 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH(CH3)2, ch3ch2ch2 CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and ch=ch2; R14 is H, CH3, C6H5, or CH2CH3and CH=CH2; preferably R6, R7, R8, R9 and R10 are H, CH3, C6H5, or CH2CH3 and R11, R12, R13, R15 and R16 are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, cf2cf2cf2cf3, c6h5, ch2 CH3 and CH=CH2; and R14 is H, CH3, C6H5, or CH2CH3 and CH=CH2.

[0067] More particularly, said solvent may be of formula (Im) in which R4 and R5 are independently of each other selected from the group consisting of CH3, CH2CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CH2OCH3, CH(CH3)CH2 OCH3, CH(CH3)2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, cf2cf2cf2cf3, c6h5, ch3ch 2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CHFCH3 and CH2CH2CH3; preferably R4 is selected from the group consisting of CH3, CH2CH3, CH2F, CHF2, CH2CH 2F, CH2CHF2, CH2CF3, CH2OCH3, CH(CH3)CH2OCH3, CH(CH3)2, cf3, cf2cf3, cf2 CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CHFCH3 and CH2CH2CH3and R5 is selected from the group consisting of CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CH2OCH3, CH(CH3)CH2OCH3, CH(CH3)2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h5, cf2cf2cf2 CF3 and CHFCH3;R6, R7, R8 and R9 are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2. ;

[0068] More particularly, said solvent may be of formula (In) in which R4 and R5 are independently of each other selected from the group consisting of CH3, CH2CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH(CH3)2, cf3ch2, cf3, cf2cf3, CF2CF2CF3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH3CH2CH2CH2, (CH3)2CHCH2, ch3ch 2CH(CH3), CHFCH3 and CH2CH2CH3; preferably R4 is selected from the group consisting of CH3, CH2CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH(CH3)2, CF3CH2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CHFCH3 and CH2CH2CH3; and R5 is selected from the group consisting of CH2F, CHF2, CH2CH2F, CH2CHF2, CF3CH2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, C6H5, CF2CF2CF2CF3 and CHFCH3.

[0069] More particularly, said solvent may be of formula (10) in which R4 is selected from the group consisting of CH3, CH2CH3, CH3OCH2CH2, CH3CH2CH2, CH(CH3)2, CH3CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), c6h5, cf3-c6h4, ch2f, CHF2, CH2CH2F, CH2CHF2, CH(CH3)2, CF3CH2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, CHFCH3 and CH2CH2CH3.

[0070] More particularly, said solvent may be of formula (Ip) in which R6 and R7 are independently of one another selected from the group consisting of H, F, ch3, ch2f, chf2, ch2ch2f, ch2chf2, ch2cf3, cf3, cf2cf3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3, CH3CH2CH2, CH(CH3)2, CH3CH2CH2CH2, (CH3)2 CHCH2, CH3CH2CH(CH3) and CH=CH2; preferably R6 and R7 are independently selected from the group consisting of H, F, CH3, CH2CF3, CF3, CF2 CF3, CF2CF2CF3, CH(CF3)2, C6H5, CH2CH3, CH3CH2CH2, CH(CH3)2, and CH=CH2; and n is an integer from 1 to 10, preferably from 1 to 5.

[0071] More particularly, said solvent may be of formula (Iq) in which R6, R7, R8, R9, R10, R11, R12 and R13 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2 CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3, CH3CH2CH2, CH(CH3) 2, CH3CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3) and CH=CH2; and X is O or SO 2 ; preferably R6, R7, R8, R9, R10, R11, R12 and R13 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h5, ch2ch3, ch3ch2ch2, CH(CH3)2 and CH=CH2; and X is O or SO2.

[0072] More particularly, said solvent may be of formula (Ir) in which R6 is selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF 2, ch2cf3, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3 CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 and R17 are selected independently of each other from the group consisting of H, CH3, C6H5, CH2CH3 and CH=CH2; preferably R6 is H, F, CH3, CH2 F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h5, CH(CH3)2, CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH; and R14 and R17 are independently selected from the group consisting of H, CH3, C6H5, or CH2 CH3 and CH=CH2.

[0073] More particularly, said solvent may be of formula (Is) in which R8, R9, R10, R11, R12 and R13 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2 CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH3CH2CH2CH2, (CH3)2CHCH2, ch3ch2 CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; preferably R8, R10 and R12 are H, CH3, C6H5, or CH2CH3 and R9, R11 and R13 are independently selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2 CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2; and Y1 and Y2 are selected from O or CR6R7 provided that Yi and Y2 are not simultaneously O with R6 and R7 independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2 cf3, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf2cf3, c6h5, ch3ch2ch2ch2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; preferably H, CH3, C6H5, or CH2CH3.

[0074] More particularly, said solvent may be of formula (It) in which R6, R7, R8 and R9 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2 cf3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3ch2ch2ch2, (CH3)2CHCH2 , CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 and R17 are independently of each other selected from the group consisting of H, CH3, C6H5, or CH2CH3and CH=CH2; preferably R6 and R8 are independently of each other H, CH3, C6H5, or CH2CH3 and R7, R9 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2 CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2; and R14 and R17 are independently of each other selected from the group consisting of H, CH3, C6H5, or CH2CH3 and CH=CH2.

[0075] More particularly, said solvent may be of formula (lu) in which R6, R7, R8, R9, R10 and R11 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2 CF2CF3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3ch2ch2ch2, (CH3)2CHCH 2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 and R17 are independently of each other selected from the group consisting of H, CH3, C6H5, or CH2CH3and CH=CH2; preferably R6, R8 and R10 are independently of each other H, CH3, C6H5, or CH2CH3 and R7, R9, R11 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2 CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3 and CH=CH2; and R14 and R17 are independently selected from the group consisting of H, CH3, C6H5, or CH2CH3and CH=CH2.

[0076] More particularly, said solvent may be of formula (Iv) in which R6, R7, R8, R9, R10 and R11 are independently of each other selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2 CF2CF3, CH(CF3)2, CF2CF2CF2CF3, C6H5, CH2CH3, CH3CH2CH2, CH(CH3)2, ch3ch 2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3) and CH=CH2; preferably R6, R7, R8 and R9 are independently selected from the group consisting of H, F, CH3, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h5, ch2ch3, ch3ch2ch2, CH(CH3)2, and CH=CH2; and n is an integer from 1 to 10, preferably from 1 to 5.

[0077] More particularly, said solvent may be of formula (Iw) in which R6 is selected from the group consisting of H, F, CH3, CH2F, CHF2, CH2CH2F, CH2CHF 2, ch2cf3, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, cf2cf2cf2cf3, c6h5, CH(CH3)2, ch3 CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH2; R14 and R17 are selected independently of each other from the group consisting of H, CH3, C6H5, CH2CH3 and CH=CH2; preferably R6 is H, F, CH3, CH2 F, CHF2, CH2CH2F, CH2CHF2, CH2CF3, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h5, CH(CH3)2, CH3CH2CH2, CH(CH3)2, CH2CH3 and CH=CH; and R14 and R17 are independently selected from the group consisting of H, CH3, C6H5, or CH2 CH3 and CH=CH2.

[0078] More particularly, said solvent may be of formula (Ix) or (Ix') in which R4, R5 and R18 are independently of each other selected from the group consisting of CH3, CH2F, CHF2, C2H5, CH2CH2F, CH2CHF2, CH2CF3, CH2CH2CH3, CH2CH2CH2F, ch2chfch3, ch2ch2cf3, ch2cf2chf2, cf3, cf2cf3, cf2cf2cf3, CH(CF3)2, C6H5, CH(CH3)2, CH3CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), cf2 CF2CF2CF3 andCH(CH3)2.

[0079] More particularly, said solvent may be of formula (ly) in which R4 and R5 are independently of each other selected from the group consisting of ch3, ch2f, chf2, c2h5, ch2ch2f, ch2chf2, ch2cf3, ch2ch2ch3, ch2ch2ch2f, CH2CHFCH3, CH2CH2CF3, CH2CF2CHF2, CF3, CF2CF3, CF2CF2CF3, CH(CF3)2, c6h 5, CH(CH3)2, CH3CH2CH2CH2, (CH3)2CHCH2, CH3CH2CH(CH3), CF2CF2CF2CF3 and CH(CH3)2; Y3 is SO2 or S=O.

[0080] More particularly, said solvent may be of formula (Iz) in which R4 is selected from the group consisting of CH3, CH2F, CHF2, C2H5, CH2CH2F, CH2CHF 2, CH2CF3, ch2ch2ch3, ch2ch2ch2f, ch2chfch3, ch2ch2cf3, ch2cf2chf2, cf3 , cf2cf3, cf2cf2cf3, CH(CF3)2, c6h5, CH(CH3)2, ch3ch2ch2ch2, (CH3)2CHCH2, CH3CH2CH(CH3), CF2CF2CF2CF3 and CH(CH3)2.

[0081] In a non-limiting manner, said solvent is for example selected from the group consisting of propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, gamma-butyrolactone, 3-fluoro-gamma-butyrolactone, delta-valerolactone, gamma-valerolactone, epsilon-caprolactone, gamma-caprolactone, butyrolactam, valerolactam, N-methyl-butyrolactam, N-methyl-valerolactam, fluoroethylene carbonate, fluoropropylene carbonate, monofluoromethyl methyl carbonate, methyl 2,2,2-trifluoroethyl carbonate, trifluoroethyl ethyl carbonate, bis(2,2,2-trifluoroethyl carbonate), propyl 2,2,2-trifluoroethyl carbonate, methylnonafluorobutyl ether, hexafluoroisopropyl methyl ether, bis(2,2,2-trifluoroethyl)ether, methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, methyl isopropyl carbonate, ethyl isopropyl carbonate, propyl ethyl carbonate, methyl propyl carbonate, 1-fluoropropyl methyl carbonate,2-fluoropropyl methyl carbonate, 1,1,1-trifluoropropyl methyl carbonate, 1,1,1,2,2-pentafluoropropyl methyl carbonate, 1,1,2,2-tetrafluoropropyl methyl carbonate, 1,1,1-trifluoroethyl methyl carbonate, 1,1-difluoroethyl methyl carbonate, 1-fluoroethyl methyl carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl fluoromethyl carbonate, 1-fluoroethyl ethyl carbonate, 1,1-difluoroethyl ethyl carbonate, 1,1,1-trifluoroethyl ethyl carbonate, vinyl ethylene carbonate, vinylene carbonate, ethyl ethanoate, ethyl 1-fluoroethanoate, ethyl 1,1-difluoroethanoate, 1-fluoroethyl ethanoate, methyl, 1-methoxy isopropyl ethanoate, 1-fluoroethyl propanoate, ethyl 2-fluoropropanoate, methyl butanoate, ethyl butanoate, methyl methoxyethanoate, N-methyl-2-oxazolidinone, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran,triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane, 1,3-dioxolane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate, methyl phenyl carbonate, ethylene 2,3-dimethylcarbonate, vinylene carbonate, ethylene 2-vinylcarbonate, methyl benzoate, ethyl benzoate, 5-valerolactone, trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, triethyl phosphate, acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutyronitrile, N-methylformamide, N-ethylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidinone, N-methylpyrrolidone, N-vinylpyrrolidone, dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, , dimethyl sulfoxide, methyl ethyl sulfoxide, diethyl sulfoxide, benzonitrile, tolunitrile, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetraliydro-2( 1 ,H)-pyrimidinone, 3-methyl-2-oxazolidinone, nitromethane, nitroethane, nitropropane, nitrobutane, tris(2,2,2-trifluoroethyl) phosphite, tris(2,2,2-trifluoroethyl) phosphate. These solvents can be used individually or in combination.

[0082] Alternatively, said solvent may be an ionic liquid. Preferably, the ionic liquid is of formula (Cation)FSI or (cation)TFSI where FSI is bis(fluorosulfonyl)imide and TFSI is bis(trifluoromethanesulfonyl)imide. Preferably, the cation is of the ammonium, imidazolium, pyrrolidinium, piperidinium, phosphonium, sulfonium, oxonium type. In a non-limiting manner, mention may be made of (l-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide), (l-Butyl-3-methylimidazolium bis(fluorosulfonyl)imide), (1-Butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide), (l-Propyl-3-methylpyrrolidinium bis(fluorosulfonyl)imide), (1 -butyl-1 -methylpiperidinium bis(fluorosulfonyl)imide), ( 1 -methyl-1 -propylpiperidinium bis(fluorosulfonyl)imide), (Methyl(tri-n-butyl)phosphonium bis(fluorosulfonyl)imide), (Methyl(tri-n-ethyl)phosphoium bis(fluorosulfoyl)imide), ( 1 -Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), (l-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide),( 1 -Butyl-1 -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide), ( 1 -Propyl-3-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide), (1-butyl-1 -methylpiperidinium bis(trifluoromethanesulfonyl)imide), ( 1 -methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide), (Methyl(tri-n-butyl)phosphonium bis(trifluoromethanesulfonyl)imide), (Methyl(tri-n-ethyl)phosphoium bis(trifluoromethanesulfonyl)imide). ,

[0083] Alternatively, said solvent used in the present electrolytic composition has a dipole moment greater than 2 Debye at 25°C. Preferably, said solvent has a dipole moment greater than 2.5 Debye, preferably greater than 3.0 Debye, more preferably greater than 3.5 Debye, in particular greater than 4.0 Debye at 25°C.For example, but not limited to, said solvent may be selected from the group consisting of propylene carbonate, 1-fluoroethyl methyl carbonate, 1-fluoroethyl ethyl carbonate, 1,1-difluoroethyl methyl carbonate, 1,1-difluoroethyl ethyl carbonate, 1,1,1-trifluoroethyl methyl carbonate, 1,1,1-trifluoroethyl ethyl carbonate, perfluoroethyl methyl carbonate, perfluoroethyl ethyl carbonate, propyl methyl carbonate, propyl ethyl carbonate, dimethoxymethane, ethylene carbonate, isopropyl methyl carbonate, isopropyl ethyl carbonate, fluoroethylene carbonate, vinylidene carbonate, butylene carbonate, vinyl ethylene carbonate, fluoropropylene carbonate, fluoro-gamma-butyrolactone, delta-valerolactone, gamma-butyrolactone, fluoropropyl methyl carbonate, . 2-fluoropropyl methyl carbonate, 1,1,1-trifluoropropyl methyl carbonate, 1,1,2,2-tetrafluoropropyl methyl carbonate, 1,1,1,2,2-pentafluoropropyl methyl carbonate, fluoropropyl ethyl carbonate, 2-fluoropropyl ethyl carbonate, 1,1,1-trifluoropropyl ethyl carbonate, 1,1,2,2-tetrafluoropropyl ethyl carbonate, 1,1,1,2,2-pentafluoropropyl ethyl carbonate, nitromethane, 18-crown-6 ether, 15-crown-5 ether, 12-crown-4 ether, dibenzo-18-crown-6 ether, dibenzo-24-crown-8 ether, dicyclohexano-18-crown-6 ether, dibenzo-12-crown-4 ether, nitromethane, nitroethane, nitropropane, nitrobutane, trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, triethyl phosphate, acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutyronitrile, N-methylformamide, N-ethylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidinone, N-methylpyrrolidone,N-vinylpyrrolidone, dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, dimethyl sulfoxide, methyl ethyl sulfoxide, diethyl sulfoxide, benzonitrile, tolunitrile, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone. ,

[0084] Among the solvents cited in the present application, sulfones, sulfoxides, nitriles, ionic liquids, fluorinated ethers, organic phosphorus compounds such as phosphates or phosphites, and fluorinated carbonates are preferred. The nitriles may be chosen from acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, sebaconitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutyronitrile, benzonitrile and tolunitrile. The sulfones may be chosen from dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane and sulfolene. The sulfoxides may be chosen from dimethyl sulfoxide, methyl ethyl sulfoxide and diethyl sulfoxide.The ionic liquids can be chosen from EMIM-FSI (l-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide), BMIM-FSI (l-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), PYR14-FSI (1-Butyl-l-methylpyrrolidinium bis(fluorosulfonyl)imide), PYR13-FSI (l-Propyl-3-methylpyrrolidinium bis(fluorosulfonyl)imide), PIP14-FSI (1-butyl-l-methylpiperidinium bis(fluorosulfonyl)imide), PIP13-FSI (1-methyl-l-propylpiperidinium bis(fluorosulfonyl)imide), P1444-FSI (Methyl(tri-n-butyl)phosphonium bis(fluorosulfonyl)imide), P1222-FSI (Methyl(tri-n-ethyl)phosphoium bis(fluorosulfoyl)imide). The fluorinated solvents may be chosen from fluorinated ethers, fluorinated esters, fluorinated orthoformates, fluorinated carbonates, fluorinated phosphates, fluorinated phosphites or fluorinated sulfates. Non-exhaustive examples include 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, . 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, hexafluoroisopropyl-methyl ether, 1,1,3,3,3-pentafluoro-2-trifluoromethylpropyl-methyl ether, 1,1,2,3,3,3-hexafluoropropyl-methyl ether, 1,1,2,3,3,3-hexafluoropropyl-ethyl ether, 1,1,1,3,3,3-hexafluoro-2-(2,2,2-trifluoroethoxy)propane, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2,-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methoxynonafluorobutane, ethoxynonafluorobutane, 1,2-(1,1,2,2-Tetrafluoroethoxy)-ethane, 2,2,3,3-tetrafluoro-1,4-dimethoxybutane, 2-(2-ethoxyethyl)-1,1,1,-trifluoroethane, 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1-difluoroethane, 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane, 1,1,1-trifluoro-2-(2-(2-trifluoroethoxy)ethoxy)ethane, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, 2,2-difluoroethyl propionate, 3,3-difluoropropyl acetate, 3,3-difluoropropyl propionate, ethyl 4,4-difluorobutanoate, difluoroethyl formate,trifluoroethyl formate, 2,2,2-trifluoroethyl orthoformate, 4-fluoro-1,3-dioxolan-2-one (F1EC), 4,5-difluoro-1,3-dioxolan-2-one (F2EC), ethyl-(1-fluoroethyl)carbonate (F1DEC), 1-fluoroethyl (2,2,2-trifluoroethyl)carbonate (F4DEC), bis(2,2,2-trifluoroethyl)carbonate (BFEC), 2,2,2-trifluoroethyl-methyl carbonate (F3EMC), trifluoropropylene carbonate, monofluoro dimethyl carbonate, methyl 2,2,2-trifluoroethyl carbonate, 2,2-difluoroethyl-methyl carbonate, trifluoroethyl-ethyl carbonate, methyl-hexafluoro-i-propyl carbonate, ethyl hexafluoro-i-propyl carbonate, bis(trifluoroethyl)carbonate, propyl-trifluoroethyl carbonate, fluorotoluene and 1,4-dimethoxytetrafluorotoluene. Among ionic liquids, the pyrrolidinium, piperidinium and phosphonium families are preferred. Among organic phosphorus compounds such as phosphates or phosphites, tris(2,2,2-trifluoroethyl) phosphite and tris(2,2,2-trifluoroethyl) phosphate are preferred. Sulphones, and in particular sulfolane, are more preferred. The organic solvent content in the electrolytic composition according to the invention is preferably between 30 and 85% by weight relative to the total weight of the electrolytic composition, preferably between 40 and 85% by weight, more preferably between 50 and 80% by weight, even more preferably between 60 and 75% by weight, relative to the total weight of the electrolytic composition.

[0085] As mentioned above, said electrolytic composition also comprises a lithium salt. For example, the lithium salt may be LiPF6, LiF, FSO3Li, LiOSO2 CF3, LiN(SO2CF3)2, LiN(SO2F)2, LiBF4, LiC104, lithium 2-trifluoromethyl-4,5-dicyanoimidazolate, lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiB(C2O4)2), lithium difluoro(oxalato)borate (LiF2B(C2O4)2) or LiNO3 or a mixture thereof. In particular, said lithium salt comprises lithium bis(fluorosulfonyl)imide (LiFSI - LiN(SO2F)2). The electrolytic composition may have a lithium salt content of 5 to 70% by weight relative to the total weight of the electrolytic composition. The lithium salt content in said composition may be determined by NMR. This content may be 10 to 60% by weight, preferably 15 to 50% by weight, more preferably 20 to 40% by weight, relative to the total weight of the electrolytic composition. The electrolytic composition according to the invention is preferably non-aqueous or essentially non-aqueous. In the context of the present invention, the term "essentially non-aqueous" means a water content in the electrolytic composition of less than or equal to 50 ppm of water, preferably less than or equal to 20 ppm of water. The electrolytic composition preferably has an organic solvent content of 20 to 85% by weight relative to the total weight of the electrolytic composition.

[0086] The electrolytic composition according to the invention may optionally comprise one or more additives. Said additives may in particular be chosen from lithium salts other than LiFSI, organic compounds comprising silicon, organic compounds comprising boron, organic compounds comprising phosphorus, phosphazenes, anhydrides and compounds comprising aluminium.

[0087] Additional lithium salts other than LiFSI may be selected from LiPF6 (lithium hexafluorophosphate), LiTDI (lithium 2-trifluoromethyl-4,5-dicyanoimidazolate), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiB(C2O4)2), lithium difluoro(oxalato)borate (LiF2B(C2O4)2), lithium tetrafluorate (LiBF4), lithium nitrate (LiNO3), lithium perchlorate (LiClO4), lithium fluoride (LiF) and lithium fluorosulfonate (FSO3Li). The organic compounds comprising silicon may in particular be chosen from diphenylsilanediol, dimethoxyphenylsilane, tetrakis(trimethylsilyl)silane, trimethylsilyl acetate, trimethylsilyl trifluoroacetate, trimethylsilyl trifluoromethanesulfonate, bistrimethylsilyl sulfate and tert-butyl-dimethylsilyl trifluoromethanesulfonate.The organic compounds comprising phosphorus may in particular be chosen from tris(trimethylsylilyl)phosphate, tris(hexafluoroisopropyl)phosphate, ethyl polyphosphate, bis(2,2,2)trifluoroethyl phosphonate, trimethyl phosphite and tris(trimethylsylilyl)phosphite (TMSPi). The organic compounds comprising sulfur may in particular be chosen from propane sultone (PS), prop-1-ene-1,3-sultone (PES), methylene methane disulfonate (MMDS), ethylene sulfite, ethylene sulfate, 1,4-butanesultone and methyl methanesulfonate. The organic compounds comprising . boron may in particular be chosen from trimethyl borate, triethyl borate, triisopropyl borate; tributyl borate, tris-2,2,2-trifluoroethyl borate, tris-trimethylsilyl borate, tris(pentafluorophenyl)borane, trimethoxyboroxine, triisopropylboroxine and triphenylboroxine. The anhydrides may be chosen from maleic anhydride, succinic anhydride, glutaric anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride. The phosphazene compounds may in particular be chosen from ethoxy-(pentafluoro)-cyclotriphosphazene, hexafluorocyclotriphosphazene, pentafluoro(phenoxy)cyclotriphosphazene. The compounds comprising aluminum, preferably in the form of a salt,may be chosen from aluminum tris-bis(fluorosulfonyl)imide (A1(FSI)3=A1[(N(SO2F)2]3), aluminum tris-bis(trifluoromethanesulfonyl)imide (A1(TFSI)3=A1[(N(SO2CF3)2]3), aluminum acetate, aluminum acetylacetonate, aluminum carbonate, aluminum nitrate, aluminum chlorate, aluminum alkyls such as triethylaluminum and aluminum alcoholates such as aluminum triethylate, preferably A1(FSI)3. The additive content in the electrolyte composition may be from 0 to 10% by weight, preferably from 0 to 5% by weight, relative to the total weight of the electrolyte composition. Preferably, the electrolyte composition of the invention comprises aluminum salts dissolved so as to have a concentration by weight aluminum in the electrolyte composition between 0.5 and 10000 ppm, preferably between 0.5 and 9000 ppm, preferably between 0.5 and 8000 ppm, preferably between 0.5 and 7000 ppm, preferably between 0.5 and 6000 ppm,preferably between 0.5 and 5000 ppm, preferably between 0.5 and 4000 ppm, preferably between 0.5 and 3000 ppm, preferably between 0.5 and 2000 ppm, preferably between 0.5 and 1000 ppm, preferably between 0.5 and 900 ppm, preferably between 0.5 and 800 ppm, preferably between 0.5 and 700 ppm, preferably between 0.5 and 600 ppm, preferably between 0.5 and 500 ppm, preferably between 0.5 and 400 ppm, preferably between 0.5 and 300 ppm, preferably between 0.5 and 200 ppm, preferably between 0.5 and 100 ppm, preferably between 0.5 and 90 ppm, preferably between 0.5 and 80 ppm, preferably between 0.5 and 70 ppm, preferably between 0.5 and 60 ppm, preferably between 0.5 and 50 ppm, preferably between 0.5 and 40 ppm, preferably between 0.5 and 30 ppm, preferably between 0.5 and 20 ppm, preferably between 0,5 and 10 ppm. The aluminum content in the electrolytic composition can be determined by any method known to those skilled in the art and in particular by ICP-MS (inductively coupled plasma mass spectrometry), ICP-AES (inductively coupled plasma optical emission spectrometry, by induction) or X-ray fluorescence spectrometry, preferably by ICP-MS.

[0088] In a particular embodiment, which can be combined with the preferences and other embodiments of the invention, the electrolytic composition according to the invention has a pH greater than or equal to 3.5, measured at a temperature of 25°C after dilution at a mass ratio of 1:1 in distilled water having a pH of 6.5. The pH may be greater than or equal to 4, and preferably from 4 to 8. Said pH may be from 3.5 to 4; or from 4 to 4.5; or from 4.5 to 5; or from 5 to 5.5; or from 5.5 to 6; or from 6 to 6.5; or from 6.5 to 7; or from 7 to 7.5; or from 7.5 to 8; or from 8 to 8.5; or from 8.5 to 9; or from 9 to 9.5; or from 9.5 to 10; or from 10 to 10.5; or from 10.5 to 11; or from 11 to 11.5; or from 11.5 to 12; or from 12 to 12.5; or from 12.5 to 13; or from 13 to 13.5; or from 13.5; or from 13.5 to 14. The pH can be measured by any method known to those skilled in the art.For example, pH can be measured using a glass electrode, whose potential can vary depending on the concentration of hydrogen ions according to the Nernst equation. This potential can be measured relative to a reference electrode using a high-impedance potentiometer, commonly known as a pH meter. For example, the pHM210 model from Radiometer can be used as a pH meter. The pH meter can be pre-calibrated using three buffer solutions (for example, at pH=4.0, 7.0 and 10.0). The aqueous solution can be stirred during the pH measurement. The pH measurement is preferably carried out within one hour of dilution in distilled water. The fact that the aqueous solution (prepared by dissolving lithium bis(fluorosulfonyl)imide salt in distilled water) has a pH greater than or equal to 3.5 advantageously allows the stability of the electrolyte of high salt concentration to be maintained at high voltage (greater than 4.5 V).The electrolytic composition may be prepared by mixing the lithium salt, the organic solvent(s), and optionally one or more additives. Preferably, the desired quantity of lithium salts is dissolved in the organic solvent(s), then any additives are added. Separator

[0089] Said separator comprises at least one polymer resin. Said separator may also comprise inorganic particles. Said separator is preferably in the form of a layer consisting of said at least one polymer resin and optionally said inorganic particles. Alternatively, said inorganic particles may be deposited on a layer consisting of said at least one polymer resin.

[0090] According to a preferred embodiment, said separator has a porosity greater than 25%, advantageously greater than 26%, preferably greater than 27%, preferably greater than 28%, more preferably greater than 29%, in in particular greater than 30%, more particularly greater than 31%, preferably greater than 32%, advantageously more preferably greater than 33%, preferably more preferably greater than 34%, more preferably more preferably greater than 35%, particularly more preferably greater than 36%, more particularly more preferably greater than 37%, more particularly more preferably greater than 38%, more particularly more preferably greater than 39% measured by mercury intrusion porosimetry according to ISO 15901-1:2016.According to a preferred embodiment, said separator has a porosity of less than 70%, advantageously less than 69%, preferably less than 68%, preferably less than 67%, more preferably less than 66%, in particular less than 65%, more particularly less than 64%, preferably less than 63%, advantageously less than 62%, preferably less than 61%, more preferably less than 60% measured by mercury intrusion porosimetry according to standard ISO 15901-1:2016. According to a preferred embodiment, said separator has a porosity of between 25% and 70%, preferably between 30% and 65%, in particular between 35% and 65%, more particularly between 40% and 60% measured by mercury intrusion porosimetry according to standard ISO 15901-1:2016.

[0091] According to a preferred embodiment, said separator preferably has a thickness of between 5 μm and 40 μm. Advantageously, said separator may have a thickness of between 6 μm and 38 μm, preferably between 7 μm and 36 μm, more preferably between 8 μm and 34 μm, in particular between 9 μm and 32 μm, more particularly between 10 μm and 30 μm. According to a preferred embodiment, said separator may have a thickness of between 10 μm and 28 μm, advantageously between 10 μm and 26 μm, preferably between 10 μm and 24 μm, in particular between 10 μm and 22 μm, more particularly between 10 μm and 20 μm. Alternatively, said separator may have a thickness between 40 pm and 150 pm or between 40 pm and 130 pm or between 50 and 100 pm.

[0092] As mentioned above, said separator according to the invention has very good thermal stability characterized by a low thermal shrinkage factor at 150°C. Advantageously, said separator has a thermal shrinkage factor at 150°C of less than 10% in absolute value measured according to the method described in the present application. Preferably, said separator has a thermal shrinkage factor at 150°C of less than 9%, more preferably less than 8%, in particular less than 7%, more particularly less than 6%, preferably less than 5%, advantageously less than 4%, preferably less than 5%, preferably ... less than 3% in absolute value measured according to the method described in this application.

[0093] Said separator has a G / e ratio of between 0.1 and 15 s '.pm1; G being the air permeability of said separator measured by Gurley according to ISO 5636-5 and e being the thickness of said separator. Advantageously, the G / e ratio is between 0.1 and 14 s '.pm1 or between 0.1 and 13 s '.pm 1 or between 0.1 and 12 s *.pm1 or between 0.1 and 11 s *.pm1 or between 0.1 and 10 s *.pm1 or between 0.1 and 9 s *.pm1 or between 0.1 and 8 s *.pm1 or between 0.1 and 7 s *.pm1 or between 0.1 and 6 s *.pm1 or between 0.1 and 5 s '.pm '.

[0094] Said at least one polymer resin may be selected from the polymer resins described below alone or in combination. Said at least one polymer resin may be selected from the group consisting of polyaramid, polyester, polyaryletherketone, polysulfone, polyethersulfone, polyetherimide, polyimide, polyacrylonitrile, polycarbonate, polybenzimidazole, polyarylether, polyarylthioether, fluoropolymer, cellulose or a mixture thereof. In particular, said at least one polymer resin may be selected from the group consisting of polyaramid, polyester, polyaryletherketone, polysulfone, polyethersulfone, polyetherimide, polyimide, polyacrylonitrile, fluoropolymer, cellulose or a mixture thereof. More particularly, said at least one polymer resin contained in said separator may be polyaramid, polyester, polyaryletherketone, polyetherimide, polyimide, fluoropolymer, cellulose or a mixture thereof.

[0095] According to a preferred embodiment, said at least one polymer resin comprises a fluoropolymer PI comprising in its chain at least one fluoromonomer Mla chosen 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. Said fluoropolymer PI may carry polar groups. These polar groups may be present in said fluoropolymer PI via a monomer carrying said polar groups. Alternatively, said polar groups may be grafted onto a fluoropolymer to give said fluoropolymer PI according to known techniques.Preferably, the polar groups are introduced into said fluorinated polymer PI via a monomer carrying said polar groups, for example via the Mlc monomers as described below in the present application.

[0096] Preferably, said fluoropolymer PI comprises repeating units derived from a monomer Mla selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2 H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2 SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. Among the trifluoropropenes, mention may be made of 3,3,3-trifluoropropcnc. Examples of tetrafluoropropenes include 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene. Examples of pentafluoropropene include 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene may be either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0097] In particular, said fluoropolymer PI comprises at least repeating units derived from a monomer Mla being vinylidene fluoride. The fluoropolymer PI may be a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride. Thus, the fluoropolymer PI may comprise repeating units derived from a monomer Mla being vinylidene fluoride and repeating units derived from a fluorinated monomer Mlb and / or repeating units derived from a monomer Mlc. In said fluoropolymer PI, the mass content of repeating units Mla is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%.

[0098] Said fluorinated monomer Mlb is different from monomer Mla. Preferably, said fluorinated monomer Mlb is selected from the group consisting of vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF 3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF 2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutyl ene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. Preferably, the fluoropolymer PI comprises repeating units derived from a monomer Mla being vinylidene fluoride and repeating units derived from a fluorinated monomer Mlb selected from the group consisting of vinyl fluoride; trifluoroethylene; chlorotrifluoroethylene; 1,2-difluoroethylene, tetrafluoroethylene; hexafluoropropylene; perfluoro(alkyl vinyl)ethers such as perfluoro(methyl vinyl)ether,perfluoro(ethyl vinyl)ether or perfluoro(propyl vinyl)ether; perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2=CFOCF 2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R'CH2OCF=CF2 in which R' is hydrogen or F(CF2 )z and z is 1, 2, 3 or 4; the product of formula R”OCF=CH2 in which R” is F(CF2 )z and z is 1, 2, 3 or 4; trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene or 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. In particular,the fluoropolymer PI comprises repeating units derived from a monomer Mla being vinylidene fluoride and repeating units derived from a fluoromonomer Mlb selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene and hexafluoropropylene or a mixture thereof. Preferably, when it contains them, said fluoropolymer PI comprises from 1% to 40%, preferably from 1% to 30%, in particular from 2% to 20% by weight of repeating units derived from said monomer Mlb based on the total weight of said polymer. Said fluorinated polymer PI may be, for example, a copolymer of vinylidene fluoride and hexafluoropropene, 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 or a , terpolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene. Said fluoropolymer PI may be a copolymer of vinylidene fluoride and hexafluoropropene in which the mass content of hexafluoropropene is from 1% to 40%, preferably from 1% to 30%, in particular from 2% to 20% based on the total weight of the fluoropolymer PI. Said fluoropolymer PI may be a poly(vinylidene fluoride-trifluoroethylene and / or tetrafluoroethylene), preferably a poly(vinylidene fluoride-co-trifluoroethylene).These fluoropolymers preferably have a molar content of vinylidene fluoride units of 25 to 95%, preferably 55 to 80%, for example 25 to 35%, or 35 to 45%, or 45 to 55%, or 55 to 65%, or 65 to 80%, or 80 to 95%; and / or a molar content of trifluoroethylene and / or tetrafluoroethylene units of 5 to 75%, preferably 20 to 45%, for example 5 to 10%, or 10 to 20%, or 20 to 30%, or 30 to 45%, or 45 to 55%, or 55 to 65%, or 65 to 75%. Said fluoropolymer PI may be a poly(vinylidene fluoride-trifluoroethylene and / or tetrafluoroethylene-chlorofluoroethylene and / or chlorotrifluoroethylene), preferably a poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorofluoroethylene) or a poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene).These fluoropolymers preferably have a molar content of vinylidene fluoride units of 25 to 80%, preferably 35 to 70%, for example 25 to 35%, or 35 to 45%, or 45 to 55%, or 55 to 70%, or 70 to 80%; and / or a molar content of trifluoroethylene and / or tetrafluoroethylene units of between 3 and 60%, preferably 14 to 40%, for example 3 to 5%, 5 to 10%, 10 to 14%, 14 to 20%, or 20 to 30%, or 30 to 40%, or 40 to 50%, or 50 to 60%; and / or a molar content of chlorofluoroethylene and / or chlorotrifluoroethylene units of 2 to 20%, preferably 3 to 15%, preferably 4 to 12%, for example 2 to 3%, or 3 to 4%, or 4 to 5%, or 5 to 6%, or 6 to 7%, or 7 to 8%, or 8 to 9%, or 9 to 10%, or 10 to 12%, or 12 to 15%, or 15 to 18%, or 18 to 20%.

[0099] Said monomer Mlc may be of formula RaRbC=C(Rc)((X3)pC(O)Rd) in which the substituents Ra, Rb and Rc are independently of each other selected from the group consisting of H, CO2H and Ci-C5 alkyl; Rd is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -ORd' with Rd' selected from the group consisting of H and CrCi8 alkyl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd”, -C(O)O-Rd ” or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its ring chain; Rd” being selected from the group consisting of C1-C6 alkyl or C6-C12 aryl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H; p” is 0 or 1; X3 is selected from the group consisting of -[-C(O)OC(R26 )(R27 )C(R28 )(R29 )-]W2- and a C1-C10 alkyl hydrocarbon group optionally carrying one or more -OH, -CO 2H or ester group(s); with w2 being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular beyond 5;R ,R ,R ,R are independently of each other, independently for each unit w2, selected from the group consisting of H and C1-C5 alkyl. Said heterocycle may be saturated or 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, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone ring. Said heterocycle may be substituted by one or more C1-C5 alkyl groups.As mentioned above, the C1-C18 alkyl 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.

[0100] Advantageously, said monomer Mlc may be of formula RaRbC=C(Rc)((X3)P”C(O)Rd) in which the substituents Ra, Rb and Rc are independently of one another selected from the group consisting of H, CO2H and C1-C5 alkyl; Rd is -ORd' with Rd' selected from the group consisting of H and C1-C8 alkyl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd”, -C(O)O-Rd” or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its ring chain; Rd” being selected from the group consisting of C1-C6 alkyl or C6-C12 aryl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H; p” is 0 or 1; X3 is selected from the group consisting of -[-C(O)OC(R26 )(R27 )C(R28 )(R29 )-] w2- and a Ci-Cio alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s);with w2 being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5; R26, R27, R28, R29 are independently of each other, independently for each unit w2, selected from the group consisting of H and C1-C5 alkyl.;

[0101] Preferably, said monomer Mlc may be of formula RaRbC=C(Rc)((X3)p C(O)R d) in which the substituents Ra, Rb and Rc are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl; Rd is -ORd' with Rd' selected from the group consisting of H and C1-C15 alkyl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd ”, -C(O)O-Rd”; Rd” being selected from the group consisting of C1-C5 alkyl or C6-C10 aryl optionally substituted by one or more -OH, -CO2H, -SO3H, -PO3H groups; p” is 0 or 1; X3 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]W2- and a C1-C10 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester groups; with w2 being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, 26' 27' 28' 29' in particular beyond5;R ,R ,R ,R are independently of each other, independently for each unit w2, selected from the group consisting of H and Ci-C5 alkyl.

[0102] More preferably, said monomer Mlc may be of formula RaRbC=C(Rc) ((XOp CIOjR'1) in which the substituents Ra, Rb and Rc are independently of each other selected from the group consisting of H, CO2H and CrC3 alkyl; Rd is -ORd' with Rd' selected from the group consisting of H and C1-C10 alkyl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd”, -C(O)O-Rd”; Rd” being selected from the group consisting of C1-C5 alkyl or C6 aryl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H; p” is 0 or 1; X3 is selected from the group consisting of -[-C(O)OC(R26 )(R27 )C(R28 )(R29 )-]w2- and a C1-C5 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with w2 being an integer greater than 5;R ,R ,R ,R are independently of each other, independently for each w2 unit, selected from the group consisting of H and C 1-C 3 alkyl. ;

[0103] In particular, said monomer Mlcmay be of formula RaRbC=C(Rc)(C(O)Rd) in which the substituents Ra, Rb and Rc are independently of each other selected from the group consisting of H, CO2H and C1-C3 alkyl; Rd is -ORd' with Rd' selected from the group consisting of H and C1-C10 alkyl optionally substituted by one or more groups -OH, -CO2H, -SO3H, -PO3H, -OC(O)Rd”, -C(O)O-Rd”; Rd” being selected from the group consisting of C1-C5 alkyl or C6 aryl optionally substituted by one or more groups -OH, -CO2H, -SO3 H, -PO3H.

[0104] Said monomer Mlc may also be of formula ReRfC=C(Rs)(OC(O)Rh); RRj C=CRkC(O)OC(O)CR=CRmRn; R°RpC=CRq(CN); RrRsC=CRt(C(O)NRuRv);

[0105] in which

[0106] Rh is CrC5 alkyl;

[0107] Re, Rf, Rs, Rh, R\ Rj, Rk, R1, R”, Rn, R°, RP, R\ Rr, Rs, R', Ru, Rv are independently of each other selected from the group consisting of H and C1-C5 alkyl, preferably selected from the group consisting of H and CH3.

[0108] Said monomer Mlc may also be of formula

[0109] wherein R", Rab, Rac, Rad, Rae, Raf, Rag, Rah, R”, Raj, R"k, Ral are independently of each other selected from the group consisting of H and Cr C5 alkyl, preferably selected from the group consisting of H and CH3.

[0110] According to a particularly preferred embodiment, said monomer Mlc may be acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, methyl acrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate,n-octyl methacrylate, ureido methacrylate, maleic anhydride, vinyl acetate, acrylamide, acrylonitrile, methacrylic anhydride of formula CH2=C(CH3)C(O)OC(O)C(CH 3)=CH2, monomers of formula CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH 2CH2-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. Of these, said Mlc monomer 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 fluoropolymer PI may comprise one or more repeating units derived from said Mlc monomer as defined herein. Preferably, when containing, said fluoropolymer PI comprises from 0.01% to 10%, preferably from 0.05% to 5%, in particular 0,1% to 5% by weight of repeating units derived from said monomer Mlc based on the total weight of said fluoropolymer PI.,

[0111] Preferably, the melt viscosity of said fluoropolymer PI is greater than or equal to 5 kP at 230°C and at a shear rate of 100 s-1 measured according to standard ASTM D3835. Advantageously, the melt viscosity of said fluoropolymer PI is greater than or equal to 8 kP, preferably greater than or equal to 10 kP, more preferably greater than or equal to 13 kP, in particular greater than or equal to 15 kP at 230°C and at a shear rate of 100 s-1 measured according to standard ASTM D3835.

[0112] Said at least one polymer resin may be a polyaramid. A polyaramid comprises repeating units comprising one or more amide functional groups adjacent to an aromatic ring. A polyaramid may therefore comprise repeating units of formula -[-C(O)-NH-A'-NH-C(O)-A2-]- in which A1 and A2 are independently of each other selected from the group consisting of C6-Ci8 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, C1-C10 carboxy, C2-Ci5 ester. Preferably, a polyaramid comprises repeating units of formula -[-C(O)-NH-A'-NH-C(O)-A2-]- wherein A1 and A2 are independently of each other selected from the group consisting of C6-C18 aryl. In particular, A1 and A2 = phenyl; more particularly, A1 and A2 are linked to their adjacent groups (C(O) or NH) in the meta or para position.

[0113] In the present application, the term halogen refers to F, Cl, Br or I; the term Cr Cio alkoxy refers to a group -OR with R being C1-C10 alkyl; the term C2-Ci5 ether refers to a hydrocarbon radical (alkyl or aryl) of 2 to 15 carbon atoms and containing an ether function -O-; the term C1-C10 carboxy refers to a hydrocarbon radical (alkyl or aryl) of 1 to 10 carbon atoms and containing a function -C(O)-; the term C1-C10 ester refers to a hydrocarbon radical (alkyl or aryl) of 1 to 10 carbon atoms and containing a function -C(O)O-. The term alkyl includes linear and branched alkyls. The term aryl includes hydrocarbons comprising from 6 to 18 carbon atoms and comprising at least one monocyclic (phenyl, tolyl, benzyl, xylyl, etc.) or polycyclic (bis-phenyl, anthracyl, naphthyl, etc.) aromatic ring.

[0114] Said at least one polymer resin may be a polyester. A polyester comprises repeating units comprising one or more functional group(s) -C(O)-O. The polyester may comprise repeating units of formula [-A'-C(O)-O-], [-A*-C(O)-O-A2-], [-OC(O)-A*-C(O)-O-] or [-OC(O)-A'-C(O)-O-A2-] in which A1 and A2 are independently of each other selected from the group consisting of C1-C10 alkyl and C6-C18 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, C1-C10 carboxy, C1-C10 ester. For example, the polyester may comprise repeating units of formula [-OC(O)-A*-C(O)-O-A2-] with A1 being C6-C18 aryl, preferably phenyl, and A 2 being C1-C10 alkyl, preferably C1-C5 alkyl. Particular examples are polyethylene terephthalate, polyethylene butylene terephthalate, polyethylene trimethylene terephthalate, polyethylene naphthalate.

[0115] Said at least one polymer resin may be a polyaryletherketone. A polyaryletherketone comprises repeating units comprising ether and ketone functional groups. The polyaryletherketone may comprise repeating units of formula [-OA'-O-A2-C(O)-A3-], [-OA'-C(O)-A2-], [-O-A'-C(O)-A2-C(O)-A3-], [-O-A'-O-A2-C(O)-A3-C(O)-A4-] or [-O-A1-C(O)-A2-O-A3-C(O)-A4-C(O)-A5-] wherein A1, A2, A3, A4 and A5 are independently of each other selected from the group consisting of C1-C10 alkyl and C6-C18 aryl optionally substituted with one or more groups selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, Ci-Ci0 carboxy, CrCio ester. Preferably, in the above formulas, A1, A2, A3, A4 and A5 are a phenyl substituent.Particular examples are polyetheretherketone (PEEK or polyphenylene etherketone), polyetherketone (PEK), polyetheretherketoneketone (PEEKK), polyetherketoneketone (PEKK), polyetherketoneetherketoneketone (PEKEKK).

[0116] Said at least one polymer resin may be a polysulfone. A polysulfone comprises repeating units comprising one or more sulfone functional group(s) SO2. Preferably, the polysulfone may comprise repeating units [-A'-SO2-] with A1 being selected from the group consisting of C1-C10 alkyl and C6-C18 aryl optionally substituted with one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, C1-C10 carboxy, C1-C10 ester; preferably A1 is C6-Ci8 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-Ci0 alkoxy, C2-Ci5 ether, C1-Ci0 carboxy, C1-Ci0 ester; in particular A1 is phenyl. A particular example is polyphenylene sulfone.

[0117] Said at least one polymer resin may be a polyethersulfone. A polyethersulfone comprises repeating units comprising ether and sulfone functional groups. A polyethersulfone may comprise repeating units of formula [-A'-O-A2-SO2-] or [-A'-SO2-A2-O-A3-O-] wherein A1 and A2 are independently of each other selected from the group consisting of C1-C10 alkyl and C6-C18 aryl optionally substituted with one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, C1-C10 carboxy, C1-C10 ester. Preferably, A1 and A2 are independently selected from the group consisting of C6-C18 aryl optionally substituted with one or more groups selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, CrC10 carboxy, CrC10 ester. Particular examples are polyethersulfones of formula [-A'-O-A2-SO2-] with A1 and A2 being phenyl or of formula [-A'-SO2-A2-O-A3-O-] with A1 and A2 being phenyl and A3 being C6H4-C(CH3)2-C6H4.

[0118] Said at least one polymer resin may be a polyetherimide. A polyetherimide comprises repeating units comprising one or more ether and imide functional groups. An example of a polyetherimide is poly(bisphenol A-co-4-nitrophthalic anhydride-co-1,3-phenylenediamine).

[0119] Said at least one polymer resin may be a polyimide. A polyimide comprises repeating units comprising one or more imide functional groups -C(O)-N(R)-C(O)-. The imide group may be linear or cyclic. A polyimide may comprise repeating units of formula A1 or A2 as described below.

[0120] in which

[0121] ni is an integer from 0 to 5; n2 is an integer from 0 to 5; RI and R2 are independently of each other selected from the group consisting of C1-C10 alkyl, C2-C15 ether, and C6-C18 aryl optionally substituted with one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C10 ether, C1-C10 carboxy, C1-C10 ester.

[0122] Said at least one polymer resin may be a polyacrylonitrile. A polyacrylonitrile comprises repeating units of formula [-CR'R2CR3(CN)-] in which R1, R2 and R3 are independently of each other selected from the group consisting of H, C1-C10 alkyl and C6-C18 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3 H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-C15 ether, C1-C10 carboxy, C1-C10 ester. Preferably a polyacrylonitrile comprises at least 50% by weight of repeating units of formula [-CR'R2CR3(CN)-] as defined above.

[0123] Said at least one polymer resin may be a polycarbonate. A polycarbonate comprises repeating units comprising one or more carbonate functional groups -OC(O)-O-. A polycarbonate may comprise repeating units of formula [-A'-OC(O)-O-] in which A1 is C6-Ci8 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-Ci5 ether, C1-C10 carboxy, C1-C10 ester; in particular A1 may be C6H4-C(CH3)2-C6H4.

[0124] Said at least one polymer resin may be a polybenzimidazole. A polybenzimidazole comprises repeating units comprising one or more benzimidazole groups. A particular example may be poly[2,2'-(m-phenylene)-5,5'-bisbenzimidazole].

[0125] Said at least one polymer resin may be polyarylether comprising repeating units of formula [-A'-O-] in which A1 is C6-Ci8 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-Ci5 ether, C1-C10 carboxy, C1-Cio ester; in particular A1 is phenyl, tolyl or xylyl. A particular example is poly[oxy-(2,6-dimethyl-1,4-phenylene)].

[0126] Said at least one polymer resin may be polyarylthioether comprising repeating units of formula [-A'-S-] in which A1 is C6-Ci8 aryl optionally substituted by one or more group(s) selected from the group consisting of halogen, SO3H, CO2H, OH, PO3H, C1-C10 alkoxy, C2-Ci5 ether, C1-C10 carboxy, C1-C10 ester; in particular A1 is phenyl, tolyl or xylyl.

[0127] Said at least one polymer resin may be of cellulose type, that is to say that it comprises repeating units of formula

[0128] wherein R is independently for each substituent -OR selected from the group consisting of H, C1-C10 alkyl optionally substituted with a group OH; n is an integer between 10 and 100000.

[0129] Preferably, said at least one polymer resin comprises repeating units of formula

[0130] wherein R is independently for each substituent -OR selected from the group consisting of H, C1-C5 alkyl optionally substituted with an OH group; n is an integer between 10 and 50000.

[0131] Said separator may also comprise, in addition to said at least one polymer resin detailed above, a polymer P2 comprising repeating units derived from a monomer M2 of formula (I), (II), (III), (IV), (V), (VI), (VII) or a mixture thereof.

[0132] R1R2C=C(R3)((X2)PC(O)R4) (I)

[0133] R5R6C=C(R7)(OC(O)R8) (II)

[0134] R9R10C=CRnC(O)OC(O)CR12=CR13R14 (III)

[0135] R30R31C=CR32(CN) (VI)

[0136] R33R34C=CR35(C(O)NR36R37) (VII)

[0137] in which

[0138] R1, R2 and R3 are independently of each other selected from the group consisting of H, CO2H and C1-C5 alkyl;

[0139] R4 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 and -OR25 with R25 selected from the group consisting of H and CrCi8 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, SO3H, -OPO32, -C(O)OR25, -OC(O)R25, and a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain;

[0140] R25 is selected from the group consisting of C1-C5 alkyl and C6-C12 aryl substituted by one or more CO2H functional groups;

[0141] X2 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]wr and a C1-C10 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with wl being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5; R26, R27,

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150] R28, R29 are independently of each other, independently for each wl unit, selected from the group consisting of H and C1-C5 alkyl; p' is 0 or 1; R5, R6 and R7 are independently selected from the group consisting of H and C1-C5 alkyl; R8 is C1-C5 alkyl; R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R30 R31 R32 33 34 35 , R , R , R are independently of each other selected from the group consisting of H and C1-C5 alkyl, preferably selected from the group consisting of H and CH3; R36 and R37 are, independently of each other, selected from the group consisting of H and C1-C10 alkyl optionally substituted by one or more -OH, -CO2H, SO3H, -OPO32, -C(O)OR38, -OC(O)R38 groups; R38 is selected from the group consisting of C1-C5 alkyl and C6-C12 aryl substituted by one or more CO2H functional groups. Advantageously, said polymer P2 comprises repeating units derived from a monomer M2 of formula (I), (II), (III), (IV), (V) or a mixture thereof R1R2C=C(R3)((X2)PC(O)R4) (I) R5R6C=C(R7)(OC(O)R8) (II) R9R10C=CR11C(O)OC(O)CR12=CR13R14 (III)

[0151]

[0152]

[0153]

[0154]

[0155] R30R31C=CR32(CN) (VI) r 33 r 34 C=CR 35 (C(O)NR 36 R 37 ) (VII) in which R1, R2 and R3 are independently selected from the group consisting of H, CO2H and C1-C5 alkyl; R4 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 and -OR25 with R25 selected from the group consisting of H and C1-C15 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, SO3H, -OPO32, -C(O)OR25, -OC(O)R25, and a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain;

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166] R25 is selected from the group consisting of C1-C5 alkyl and C6-C12 aryl substituted with one or more CO2H functional groups; X2 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]wr and a C1-C10 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with wl being an integer from 1 to 10, 26 27 28 29 in particular beyond5;R ,R ,R ,R are independently of each other, independently for each wl unit, selected from the group consisting of H and Ci-C5 alkyl; p' is 0 or 1; R5, R6 and R7 are independently selected from the group consisting of H and C1-C3 alkyl; R8 is CrC3 alkyl; r9 r10 R11 r12 r13 r14 r15 r16 r17 r18 r19 r20 r21 r22 r23 r24 r30 r31 r32 , R , R , R are independently of each other selected from the group consisting of H and C 1-C 3 alkyl, preferably selected from the group consisting of H and CH 3 ; R36 and R37 are, independently of each other, selected from the group consisting of H and C1-C5 alkyl optionally substituted by one or more -OH, -CO2H, SO3H, -OPO32, -C(O)OR38, -OC(O)R38 groups; R38 is selected from the group consisting of C1-C3 alkyl and C6 aryl substituted by one or more CO2H functional groups. Preferably, said polymer P2 comprises repeating units derived from a monomer M2 of formula (I), (II), (III) (IV), (V), (VI), (VII) or a mixture thereof R1R2C=C(R3)((X2)PC(O)R4) (I) R5R6C=C(R7)(OC(O)R8) (II) R9R10C=CR11C(O)OC(O)CR12=CR13R14 (III)

[0167]

[0168]

[0169] R30R31C=CR32(CN) (VI) R33R34C=CR35(C(O)NR36R37) (VII) in which

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180] R1, R2 and R3 are independently selected from the group consisting of H, C02H and C1-C5 alkyl; R4 is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 and -OR25 with R25 selected from the group consisting of H and C1-C18 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, -SO3H, -OPO32, -C(O)OR25, -OC(O)R25, and a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain; R25 is selected from the group consisting of C1-C5 alkyl and C6-C12 aryl substituted with one or more CO2H functional groups; X2 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]wr and a C1-C10 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with wl being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5; R26, R27, R28, R29 are independently of each other, independently for each wl unit, selected from the group consisting of H and C1-C5 alkyl; p' is 0 or 1; R5, R6 and R7 are independently selected from the group consisting of H and C1-C5 alkyl; R8 is C1-C5 alkyl; R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R30 R31 R32 , R , R , R are independently of each other selected from the group consisting of H and C1-C5 alkyl, preferably selected from the group consisting of H and CH3; R36 and R37 are, independently of each other, selected from the group consisting of H and C1-C10 alkyl optionally substituted by one or more -OH, -CO2H, SO3H, -OPO32, -C(O)OR38, -OC(O)R38 groups; R38 is selected from the group consisting of C1-C5 alkyl and C6-C12 aryl substituted by one or more CO2H functional groups. More preferably, said polymer P2 is of formula (I), (III), or (IV) in which R1, R2 and R3 are independently of each other selected from the group consisting of H, CO2H and CrC3 alkyl; R4 is -OR25 with R25 selected from the group consisting of H and C1-C15 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, SO3H, -OPO32, -C(O)OR25, -OC(O)R25, and a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain;

[0181] R25 is selected from the group consisting of C1-C5 alkyl and C6-C12 aryl substituted by one or more CO2H functional groups;

[0182] X2 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]wr and a C1-C10 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with wl being an integer from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5; R26, R27, R28, R29 are independently of each other, independently for each wl unit, selected from the group consisting of H and C1-C5 alkyl;

[0183] p' is 0 or 1;

[0184] R9, R10, R11, R12, R13, R14, R15, R16 are independently of each other selected from the group consisting of H and C1-C5 alkyl, preferably selected from the group consisting of H and CH3.

[0185] In particular, said polymer P2 is of formula (I), (III) or (IV) in which R1, R2 and R3 are independently of each other selected from the group consisting of H, CO2H and C1-C3 alkyl;

[0186] R4 is -OR25 with R25 selected from the group consisting of H and C1-C10 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, SO3H, -OPO32, -C(O)OR25, -OC(O)R25, and a five or six membered heterocycle comprising at least one nitrogen atom in its ring chain;

[0187] R25 is selected from the group consisting of C1-C5 alkyl and C6 substituted aryl by one or more CO2H functional groups;

[0188] X2 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]wr and a C1-C5 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with wl being an integer from 1 to 5; R26, R27, R28, R29 are independently of each other, independently for each wl unit, selected from the group consisting of H and C1-C5 alkyl;

[0189] p' is 0 or 1;

[0190] R9, R10, R11, R12, R13, R14, R15, R16 are independently of each other selected from the group consisting of H and C1-C5 alkyl, preferably selected from the group consisting of H and CH3.

[0191] More particularly, said polymer P2 comprises repeating units derived from a monomer M2 of formula (I), (III) or (IV) in which

[0192] R1, R2 and R3 are independently of each other selected from the group consisting of H, CO2H and CrC3 alkyl;

[0193] R4 is -OR25 with R25 selected from the group consisting of H and C1-C10 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, SO3H, -OPO32, -C(O)OR25, -OC(O)R25;

[0194] R25 is selected from the group consisting of C1-C5 alkyl and C6 substituted aryl by one or more CO2H functional groups;

[0195] X2 is selected from the group consisting of -[-C(O)OC(R26)(R27)C(R28)(R29)-]wr and a C1-C5 alkyl hydrocarbon group optionally carrying one or more -OH, -CO2H or ester group(s); with wl being an integer from 1 to 5; R26, R27, R28, R29 are independently of each other, independently for each wl unit, selected from the group consisting of H and C1-C5 alkyl;

[0196] p' is 0 or 1;

[0197] R9, R10, R13, R14, R15, R16 are H; R11 and R12 are CH3.

[0198] Preferably, said polymer P2 comprises repeating units derived of a monomer M2 of formula (I) R'R2C=C(R3)(C(O)R4) (I), (III) as defined above or (IV) as defined above in which

[0199] R1, R2 and R3 are independently of each other selected from the group consisting of H, CO2H and C1-C3 alkyl;

[0200] R4 is -OR25 with R25 selected from the group consisting of H and C1-C5 alkyl optionally substituted with one or more group(s) selected from the group consisting of -OH, -CO2H, SO3H, -OPO32, -C(O)OR25, -OC(O)R25;

[0201] R25 is selected from the group consisting of CrC3 alkyl and C6 substituted aryl by one or more CO2H functional groups;

[0202] R9, R10, R13, R14, R15, R16 are H; R11 and R12 are CH3.

[0203] According to one embodiment, said polymer P2 is a homopolymer of said monomer M2 according to any one of formulas (I) to (VII) above. According to another embodiment, said polymer P2 is a copolymer of several monomers M2 according to any one of formulas (I) to (VII) above. By copolymer is meant repeating units derived from at least two monomers M2 according to any one of formulas (I) to (VII) above.

[0204] According to a preferred embodiment, said polymer P2 has a molar mass by weight of between 500 g / mol and 5,000,000 g / mol, advantageously between 1,000 g / mol and 4,000,000 g / mol, preferably between 2,000 g / mol and 3,000,000 g / mol, more preferably between 3,000 g / mol and 2,500,000 g / mol, in particular between 4,000 g / mol and 2,000,000 g / mol, more particularly between 5,000 g / mol and 1,500,000 g / mol, preferably between 10,000 g / mol and 1,000,000 g / mol. The molecular or molar mass is determined by Size Exclusion Chromatography (CES). A test sample of the polymer solution corresponding to 90 mg of dry matter is introduced into a 10 mL flask. Mobile phase is added, containing 0.04% dimethylformamide (DMF), up to a total mass of 10 g. The composition of this mobile phase is as follows: NaHCO3: 0.05 mol / L, NaNO3: 0.1 mol / L, triethanolamine: 0.02 mol / L, NaN3 0.03% by mass. The CES system consists of a Waters 510 isocratic pump with a flow rate set at 0.8 mL / min, a Waters 717+ autosampler, an oven containing a 6 cm long, 40 mm inner diameter Waters Guard Column Ultrahydrogel precolumn, followed by a 30 cm long, 7.8 mm inner diameter Waters Ultrahydrogel linear column. Detection is performed using a Waters RI 410 differential refractometer. The oven is heated to a temperature of 60°C and the refractometer is heated to a temperature of 45°C.The CES device is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standards Service with a peak molecular weight between 1000 g / mol and 1.106 g / mol and a polydispersity index between 1.4 and 1.7. The calibration curve is linear and takes into account the correction obtained using the flow marker: dimethylformamide (DMF).

[0205] Preferably, in said separator, said at least one polymer resin as described above is the main constituent. Thus, according to a preferred embodiment, said separator comprises at least 45% by weight of said at least one polymer resin according to the invention, advantageously at least 50% by weight, preferably at least 55% by weight, more preferably at least 60% by weight, in particular at least 65% by weight, more particularly at least 70% by weight based on the total weight of said separator. When said at least one polymer resin is as described above and is the main constituent of the separator, this makes it possible to obtain a higher s*e / G ratio compared to separators made of polyolefins. Better final properties are thus obtained.

[0206] The method for obtaining the separator is not particularly limiting. Generally, a separator can be prepared by a phase inversion or dry stretching process. A dry stretching process involves producing a dense film by coating a polymer dissolved in a solvent or by coating a molten polymer and then stretching it unilaterally. A phase inversion process involves coating a solution of a polymer dissolved in a solvent onto a glass substrate using a height-controlled doctor blade; the wet film is then transferred to a bath of water and isopropyl alcohol (70 / 30) and then to a water bath.

[0207] According to a particular embodiment, said separator also comprises inorganic particles chosen from the group consisting of: BaTiO3, Pb(Zr,Ti)O3, Pbj xLaxZryO3 (0<x<l, 0<y<l), PbMg3Nb2 / 3O3, PbTiO3, hafnie (HfO, HfO 2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, Y2O3, bohémite (y-AlO(OH)), A12O3, TiO2, SiC, ZrO2, silicate de bore, BaSO4, nano-argiles, ou leurs mélanges. Utilisation

[0208] The electrochemical device according to the present invention comprises a positive electrode, a negative electrode and said separator according to the present invention; the latter being arranged between said positive electrode and said negative electrode. By "negative electrode" is meant the electrode which acts as anode, when the cell delivers current (i.e. when it is in the process of discharging) and which acts as cathode when the cell is in the process of charging. The negative electrode typically comprises an electrochemically active material, possibly an electronically conductive material, and possibly a binder. By "positive electrode" is meant the electrode which acts as cathode, when the cell delivers current (i.e. when it is in the process of discharging) and which acts as an anode when the cell is in the process of charging.The positive electrode typically comprises an electrochemically active material, optionally an electronically conductive material, and optionally a binder. An "electrochemically active material" means a material capable of reversibly inserting ions. An "electronically conductive material" means a material capable of conducting electrons.

[0209] Preferably, said negative electrode comprises an active material selected from the group consisting of lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, silicone, a silicon alloy and LqTisOn. When the negative electrode comprises lithium, it may be in the form of a metallic lithium film or an alloy comprising lithium. Among the lithium-based alloys that may be used, mention may be made, for example, of lithium-aluminum alloys, lithium-silica alloys, lithium-tin alloys, Li-Zn, Li3Bi, Li3Cd and Li3SB. An example of a negative electrode may comprise a live lithium film prepared by rolling, between rollers, a lithium foil.

[0210] Preferably, said positive electrode comprises an active material selected from the group consisting of LiCoO2, Li(Ni, Co, AI)O2, Li(i+x)NiaMnbCoc (x represents a real number of 0 or more, a = 0.9, 0.8, 0.6, 0.5, or 1 / 3, b = 0.05, 0.1, 0.2, 0.3, or 1 / 3, c = 0.05, 0.1, 0.2, or 1 / 3), LiNiO2, LiMn2O4, LiCoMnO4, Li3NiMn 3O3, Li3Fe2(PO4)3, Li3V2(PO4)3, a spinel Li Mn substituted by a different element having a composition represented by Lii+xMn2 x yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y representing independently a real number between 0 and 2, lithium titanate LixTiOy - x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LiMP04, M representing Fe, Mn, Co, or Ni or a mixture thereof.

[0211] Each electrode may also comprise, in addition to the electrochemically active material, an electronically conductive material such as a carbon source, including, for example, carbon black, Ketjen® carbon, Shawinigan carbon, graphite, graphene, carbon nanotubes, carbon fibers (e.g., gas-formed carbon fibers or VGCF), non-powdery carbon obtained by carbonization of an organic precursor, or a combination of two or more thereof. Other additives may also be present in the positive electrode material, such as lithium salts or inorganic particles of the ceramic or glass type, or other compatible active materials (e.g., sulfur).

[0212] Each electrode may also comprise a binder. Non-limiting examples of binders include linear, branched and / or crosslinked polyether polymer binders (e.g., polymers based on poly(ethylene oxide) (PEO), or poly(propylene oxide) (PPO) or a mixture of both (or an EO / PO copolymer), and optionally including crosslinkable units), water-soluble binders (such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), HNBR (hydrogenated NBR), CHR (epichlorohydrin rubber), ACM (acrylate rubber)), or fluoropolymer binders (such as PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), and combinations thereof. Some binders, such as water-soluble ones, may also include an additive such as CMC (carboxymethylcellulose).

[0213] The metal supports of the electrodes serving as current collectors are generally made of aluminum for the cathode and copper for the anode. The metal supports may be surface-treated and have a conductive primer. The conductive primer may contain carbon materials, metallic materials, and polymer materials. The supports may also be carbon fiber woven or nonwoven.

[0214] Said electrochemical device may be a Li-ion battery, in particular a Li-ion battery of portable electronic devices, for example mobile phones or laptops, of electric vehicles, of renewable energy storage for example photovoltaic or wind energy.

[0215] Preferably, said electrochemical device is a Li-ion battery having a charge cut-off voltage greater than or equal to 4.4 V, more preferably greater than or equal to 4.5 V. Examples

[0216] Method for measuring conductivity

[0217] The ionic conductivity of the electrolyte in the separator is measured by electrochemical impedance spectroscopy in a CR2032 button cell. A separator cut to a diameter of 16 mm is soaked with 100 pL of electrolyte, then placed between two stainless steel shims of diameter 16 mm in a CR2032 button cell which is sealed. The button cell is connected to a potentiostat (Biology, VMP3) and placed in an oven at 25 ° C. The resistance of the separator soaked in electrolyte is measured by impedance (PEIS technique): A voltage sinusoid of amplitude 10 mV is applied around the open circuit potential, sweeping the frequencies from 200 kHz to 100 mHz. The resistance "R" of the electrolyte-soaked separator is extracted from the Nyquist diagram obtained, by reading on the abscissa axis the value of the intersection of this axis with the extrapolation of the straight line obtained at high frequency.The conductivity ° of the separator soaked in electrolyte is obtained from the formula: °[mS / cm] = (e*1000) / (S*R) with .

[0218] e [cm]: thickness of the separator

[0219] S [cm2]: surface area of ​​stainless steel shims R [Ohm]: Resistance of the electrolyte-soaked separator measured by impedance

[0220] Method of measuring the thermal shrinkage factor at 150°C

[0221] The sample was cut 100 mm in the MD direction and 100 mm in the TD direction. A rectangular mark of 59 mm (MD) x 44 mm (TD) was lightly stamped in the center. Then, this sample was allowed to stand for 1 hour in an oven at 150°C. During this time, the sample was sandwiched between two sheets of hard paper. After removing the sample from the oven and cooling it, the length (mm) of the rectangular mark in each direction was measured. The operation was repeated with 4 separate samples and the average value in each direction was taken as the length after heating. The thermal shrinkage factor in each direction was calculated by the following formula, with the highest value recorded as the thermal shrinkage factor.

[0222] Heat shrinkage factor (%) = [(initial length - length after heating) / initial length] x 100

[0223] Method for measuring the thickness of the separator

[0224] The thickness of the separator is measured using a thickness gauge (Mitutoyo, Digimatic ID-H comparator)

[0225] The performance of the separator is evaluated using an electrolytic composition consisting of 73.4% by weight sulfolane and 26.6% by weight of LiFSI i.e. a concentration of 2.5 mol / L. The composition has a viscosity of 88 cP measured at 20°C and with a shear of 20 s1.

[0226] Polymers P1 to P3, according to the invention, and polymers C1 and C2 (comparative examples) below were used to prepare separators. The ratios s*e / G and G / e are reported in Table 1 below.

[0227] PI Polymer: Homopolymer of poly(vinylidene fluoride) having a melt viscosity of 34 kP at 230°C and a shear rate of 100 s-1 measured according to ASTM D3835 and a melting point of 162°C.

[0228] Polymer P2: Homopolymer of poly(vinylidene fluoride) having a melt viscosity of 30.5 kP at 230°C and at a shear rate of 100 s-1 measured according to ASTM D3835 and a melting point of 165°C.

[0229] Polymer P3: Cellulose having a density of 0.4 g / cm3 and a porosity of 73%.

[0230] Polymer Cl: Polyethylene

[0231] Polymer C2: Polyethylene coated with a 3 μm thick layer composed of a copolymer of vinylidene fluoride and hexafluoropropene

[0232] [Tables 1] Ratio G / e (s '.pm ') Ratio s*e / G Thermal shrinkage factor at 150°C (%) Polymer PI (Inv.) 2.3 0.24 3.4 Polymer P2 (Inv.) 0.54 0.73 2.8 Polymer P3 (Inv.) 0.14 5.27 1 Polymer Cl (Com P-) 15.2 0.01 >50 Polymer C2 (Com P-) 18.4 0.00 1

[0233] The separators according to the present invention present the best compromise for use in high voltage electrochemical devices in the presence of a high viscosity electrolytic composition. The polyolefin separators (polymer Cl) have a low thermal stability represented here by the thermal shrinkage factor greater than 50% which can cause short circuits in a battery. The presence of a coating on the polyolefin separators (polymer P2) improves the thermal shrinkage factor but it has been surprisingly demonstrated that the wettability could be greatly improved by specifically selecting separators prepared from a polymer resin making it possible to obtain an s*e / G ratio greater than 0.02 in the presence of a viscous electrolytic composition, which is necessary for high voltage applications.

Claims

Claims

1. Electrochemical device comprising an electrolytic composition and a separator characterized in that the ratio s*e / G is between 0.02 and 200; s being the value of the conductivity of the electrolytic composition in the separator measured at 25°C expressed in mS / cm, e being the thickness of the separator expressed in pm, and G expressed in s 1 being the air permeability of said separator.

2. Electrochemical device according to the preceding claim characterized in that said electrolytic composition comprises at least one solvent and one lithium salt; said electrolytic composition having a viscosity greater than 2 cP measured at 20°C and with a shear of 20 s1.

3. Electrochemical device according to any one of the preceding claims characterized in that said electrolytic composition has a viscosity greater than 5 cP, preferably greater than 10 cP, in particular greater than 15 cP measured at 20°C and with a shear of 20 s1.

4. Electrochemical device according to any one of the preceding claims, characterized in that the electrolytic composition comprises from 5 to 70% by weight of lithium salt and from 20 to 85% by weight of at least one solvent.

5. Electrochemical device according to any one of the preceding claims, characterized in that said separator has a porosity of between 25% and 70% measured by mercury intrusion porosimetry according to standard ISO 15901-1:2016.

6. Electrochemical device according to any one of the preceding claims, characterized in that said separator has a thermal shrinkage factor at 150°C of less than 10% in absolute value.

7. Electrochemical device according to any one of the preceding claims, characterized in that said separator has a G / e ratio of between 0.1 and 15 s '.pm 1; G expressed in s-1 being the air permeability of said separator and e expressed in pm being the thickness of said separator.

8. Electrochemical device according to any one of the preceding claims characterized in that said separator comprises at least one polymer resin selected from the group consisting of polyaramid, polyester, polyaryletherketone, polysulfone, polyethersulfone, polyetherimide, polyimide, polyacrylonitrile, polycarbonate, polybenzimidazole, polyarylether, polyarylthioether, fluoropolymer, cellulose or a mixture thereof.

9. Electrochemical device according to any one of the preceding claims, characterized in that said separator comprises at least one polymer resin comprising a fluorinated polymer PI comprising repeating units derived from vinylidene fluoride and optionally repeating units derived from hexafluoropropene.

10. Electrochemical device according to any one of the preceding claims, characterized in that said separator comprises at least one cellulose-type polymer resin.

11. Electrochemical device according to any one of the preceding claims 8 to 10 characterized in that said separator also comprises a polymer P2 comprising repeating units of formula R'R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C5 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its ring chain.

12. Electrochemical device according to any one of the preceding claims characterized in that it also comprises a positive electrode and a negative electrode; said separator arranged between said positive electrode and said negative electrode.

13. Electrochemical device according to the preceding claim characterized in that said negative electrode comprises an active material selected from the group consisting of lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, silicone, a silicon alloy and Li4Ti50i2.

14. An electrochemical device according to any one of the preceding claims characterized in that said positive electrode comprises an active material selected from the group consisting of LiCoO2, Li(Ni, Co, AI)O2, Li(i+x)NiaMnbCoc (x represents a real number of 0 or more, a = 0.9, 0.8, 0.6, 0.5, or 1 / 3, b = 0.05, 0.1, 0.2, 0.3, or

15.

16. 1 / 3, c = 0.05, 0.1, 0.2, or 1 / 3), LiNiO2, LiMn2O4, LiCoMnO4, Li3 NiMn3O3, Li3Fe2(PO4)3, Li3V2(PO4)3, a Li Mn spinel substituted by a different element having a composition represented by Lil+xMn2-x-yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between 0 and 2, lithium titanate LixTiOy - x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni or a mixture thereof. Electrochemical device according to the preceding claim, characterized in that it is a lithium-ion battery having a charge cut-off voltage greater than or equal to 4.4 V. Separator having a G / e ratio of between 0.1 and 15 s '.pm 1; G in s 1 being the air permeability of said separator and e being the thickness of said separator in pm; said separator comprising at least one polymer resin as defined in any one of claims 8 to 11.