COMPOUND BASED ON (2-CYANOETHYL)PHOSPHONIUM SALT, ELECTROLYTE AND BATTERY COMPRISING SAME

Abstract

The present invention relates to a (2-cyanoethyl)phosphonium salt compound, an electrolyte composition based on the (2-cyanoethyl)phosphonium salt compound and the battery comprising it. More particularly, it relates to an improved electrolyte composition for a lithium-ion or sodium-ion battery leading to improved capacity and cyclability. This electrolyte composition comprises a lithium or sodium salt, an aprotic organic solvent, a (2-cyanoethyl)phosphonium salt compound.

Description

Title of the invention: COMPOUND BASED ON (2-CYANOETHYL)PHOSPHONIUM SALT, ELECTROLYTE AND BATTERY COMPRISING IT

[0001] The present invention relates to a (2-cyanoethyl)phosphonium salt compound, an electrolyte composition based on the (2-cyanoethyl)phosphonium salt compound and the battery comprising it. More particularly, it relates to an improved electrolyte composition for a lithium-ion or sodium-ion battery leading to improved capacity and cyclability. This electrolyte composition comprises a lithium or sodium salt, an aprotic organic solvent, a (2-cyanoethyl)phosphonium salt compound. Field of invention

[0002] An electrochemical battery is assembled from a cathode (positive electrode), an anode (negative electrode), a separator and an electrolyte. The operating principle is based on the reversible exchange of ions between the cathode and the anode. There is oxidation of the anode material and reduction of the electrolytic components and there is reduction of the cathode material and oxidation of the electrolytic components. Through these redox reactions, a battery is charged by converting electrical energy into chemical energy. The electrolyte plays an important role in transporting ions between the cathode and the anode. Different compounds are used in electrolytes.Some electrolyte compounds degrade and participate in the formation of solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) to improve the properties and therefore the performance of the electrochemical cell, including cyclability, coulombic efficiency and capacity.

[0003] Current electrolyte technology uses compounds that do not allow sufficient improvement in the capacity and lifetime of the electrochemical cell.

[0004] The state of the art describes various compounds such as vinylene carbonate (commonly called VC), fluoroethylene carbonate (commonly called FEC), 1,3,6-hexanetricarbonitrile, acetonitrile, siloxanes, sulfates, sulfites, phosphates etc. which do not allow excellent cyclability to be achieved, i.e. a long battery life and excellent capacity while maintaining good electrolyte conductivity. They are not thermally stable and do not allow them to be soluble in variable proportions in the electrolyte solvent to adapt to the choice of electrode materials.

[0005] “The Role of Electrolyte Additives on the Interfacial Chemistry and Thermal Reactivity of Si-Anode-Based Li-Ion Battery”, ACS Applied Energy Materials 2019 2 (9), 6513-6527, describes conventional compounds that, despite their beneficial characteristics, lead to persistent problems. For example, the presence of VC in the electrolyte can lead to excessively high cell impedance. In another example, the presence of FEC in the electrolyte can lead to significant gassing at elevated temperatures and thus a risk of thermal runaway.

[0006] “Classical solid electrolyte interphase additives, such as vinylene carbonate and fluoroethylene carbonate, have limited potential for simultaneously achieving a long lifespan and fast chargeability in high-energy-density lithium-ion batteries (LIBs).” Park et al. 2021, describes the development of new electrolyte compounds for high-energy-density Li-ion batteries. This reference describes the disadvantages of conventional electrolyte compounds such as vinylene carbonate and fluoroethylene carbonate, they do not allow to simultaneously achieve a sufficient lifespan (cyclability) and a sufficiently fast chargeability in high-energy-density lithium-ion batteries.

[0007] Document DE102008021271 describes an electrolyte comprising a salt of mono(2-cyanoethyl)phosphonium.

[0008] Document JP2018056013 also describes an electrolyte comprising a mono(2-cyanoethyl)phosphonium salt.

[0009] Compounds based on (2-cyanoethyl)phosphonium salt are of particular interest because they are stable up to a temperature of 250°C; these compounds make it possible to choose one or other of its members to adapt to the nature of the electrode as well as to modulate its solubility in the solvent of the electrolyte and not to be the cause of an increase in the internal resistance of the electrochemical cell during the SEI and / or CEI formation step. However, mono(2-cyanoethyl)phosphonium compounds have the disadvantage of having to be in higher concentration to achieve the same efficiency over time as bis(2-cyanoethyl)phosphonium compounds or tris(2-cyanoethyl)phosphonium compounds.Indeed, to achieve the same efficiency, it is appropriate to multiply the concentration of mono(2-cyanoethyl)phosphonium whereas when the phosphonium molecule carries two or three 2-cyanoethyl chains, there is only a need for a lower concentration of molecule. This is important to avoid too high viscosity and therefore avoid a decrease in the conductivity of the electrolyte. There is a need for a thermally stable electrolyte compound, soluble in variable proportions in the electrolyte solvent to meet the need for the choice of electrodes and maintain excellent capacity, excellent cyclability as well as good conductivity and good electrochemical stability of the . battery. Summary of the invention

[0010] The inventors of the present invention have developed a new electrolyte compound for lithium-ion and sodium-ion batteries providing these systems with good cyclability and good capacity.

[0011] According to a first aspect of the invention, the electrolyte solvent thus comprises a (2-cyanoethyl)phosphonium salt of formula (I)

[0012] [Chem.l] (I)

[0013] in which

[0014] X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methanides, borates, phosphates, sulfonimides or aluminates;

[0015] RI is independently selected from an unsubstituted -CH2-CH2-CN chain, by a C1-C20 alkyl, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinylbenzyl group; in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof;

[0016] R2 is independently selected from a C1-C20 alkyl group, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinylbenzyl group; wherein the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof.

[0017] According to a second aspect, the invention also relates to an electrolyte composition comprising a lithium or sodium salt, an aprotic organic solvent, a (2-cyanoethyl)phosphonium salt compound as represented by formula (I).

[0018] According to a third aspect, the invention relates to a battery comprising an anode, a cathode and an electrolyte composition based on (2-cyanoethyl)phosphonium salt compound as represented by formula (I). Advantages of the invention

[0019] The invention proposes a new family of electrolyte compounds for batteries based on phosphonium salt. This compound makes it possible to have an electrolyte which will be used in a battery having good cyclability and capacity. This leads to obtaining a high-performance and durable battery.

[0020] This new family of electrolyte compounds has several advantages.

[0021] First, this family of compounds combines the properties of the nitrile present at least twice within the molecule and that of the phosphorus atom which allows better transport of Li+ ions. The molar ratio of the compound as a function of the number of nitrile functions carried by the compound is also improved. Indeed, the more nitrile functions there are carried by the compound, the less it will be necessary to increase the mass of compound added; each compound has an optimum concentration for which the conductivity is maximum. The concentration will be lower and the conductivity will thus be improved.

[0022] The nitrile function adds specific polarity and reactivity. This also influences other physical properties such as dipole moment and dielectric constant. In addition, the nitrile function adds solvation properties to the phosphonium cations intra- and intermolecularly, which improves the mobility of Li+ ions.

[0023] Second, the (2-cyanoethyl)phosphonium salt is thermally stable up to 250 °C. This allows it on the one hand not to decompose into by-products which could be unfavorable to the good performance of the battery. On the other hand the nitrile chemical function allows it to participate in the formation of the SEI and CEI in a sacrificial manner to preserve the chemical properties of the other electrolyte compounds in order to obtain a stable and efficient SEI for the good performance of the battery. This compound makes it possible to be able to form an SEI at a temperature of 45 °C.

[0024] Thirdly, the compound is soluble in the solvent of the electrolyte in variable proportions to meet the need to adapt to the nature of the electrode materials. Indeed, this compound by its ionic nature is soluble in a proportion necessary for the type of electrode chosen.

[0025] This new family of compounds makes it possible to meet this need.

[0026] Fourthly, a large number of molecules are accessible by replacing the radicals RI and R2 which makes it possible to have the molecule most suited to the electrochemical system, in particular with regard to the choice of electrodes and to achieve a high voltage.

[0027] Fifth, the process for synthesizing this family of electrolyte compounds is industrializable.

[0028] The battery has a high capacity and a long cyclability due to the nature of this molecule, namely the presence of the phosphorus atom and the presence of at least two - 2-cyanoethyl chains, this molecule being in monomeric or dimeric form. The dimer being a homodimer, the nature of the chemical substitution remaining the same, the monomer and the dimer will have similar chemical properties.

[0029] Bis(2-cyanoethyl)phosphonium and tris(2-cyanoethyl)phosphonium compounds are preferred compounds. Detailed description of the invention

[0030] A first subject of the invention relates to an electrolyte compound based on (2-cyanoethyl)phosphonium salt for a high capacity and long cyclability battery as represented by formula (I)

[0031] [Chem.l] CH (I)

[0032] in which

[0033] X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methanides, borates, phosphates, sulfonimides or aluminates;

[0034] RI is independently selected from the group consisting of an unsubstituted -CH2-CH2 -CN chain, a C1-C20 alkyl, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinyl-benzyl group; in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a fluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof.

[0035] R2 is independently selected from the group consisting of a C1-C20 alkyl group, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinylbenzyl group; in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a group thioether or their combinations.

[0036] The hydrogen atoms can therefore be partially substituted as long as the molecule is stable.

[0037] The term "alkyl" means a saturated, linear or branched aliphatic radical having the indicated number of carbon atoms. The alkyl moiety may be straight or branched chain.

[0038] The term "alkenyl" denotes an alkyl group, as defined above, comprising at least one C=C double bond.

[0039] The term "alkynyl" denotes an alkyl group, as defined above, comprising at least one C=C triple bond.

[0040] The term "cycloalkyl" refers to a set of saturated or partially unsaturated, monocyclic, bicyclic, bridged polycyclic or spiro rings. Monocyclic rings include, for example, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl rings.

[0041] In a particularly preferred embodiment, the (2-cyanoethyl)phosphonium salt comprises three 2-cyanoethyl chains and corresponds to formula (II) in which

[0042] X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methanides, borates, phosphates, sulfonimides or aluminates;

[0043] RI is independently selected from C1-C20 alkyl, C3-C6 cycloalkyl, C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl group; wherein the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl group, perfluorinated alkyl group, silyl group, siloxy group, sulfoxide group, nitrile group, thioether group or combinations thereof.

[0044] R2 is independently selected from a C1-C20 alkyl group, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinylbenzyl group; wherein the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof.

[0045] In a more particularly preferred embodiment, RI is a C1-C10 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a nitrile group, a sulfoxide group, a thioether group or combinations thereof;

[0046] Even more preferably, R1 is selected from a methyl or a C1-C4 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a nitrile group, a sulfoxide group, a thioether group or combinations thereof; and R2 is a C1-C10 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof;and more preferably R2 is a C1-C4 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a nitrile group, a sulfoxide group, a thioether group or combinations thereof and most preferably among a methyl, an ethyl, a propyl, an iso-butyl, an n-butyl, or an allyl. ;

[0047] In a preferred embodiment, bis(oxalato)borate, di-fluorobis(oxalato)borate, acetate., N-ethyl-N-methyl-functionalized sulfonimide, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, (methanesulfonyl)(trifluoromethanesulfonyl)imide, (difluoromethanesulfonyl)(fluoromethanesulfonyl)imide, (methanesulfonyl)(fluoromethanesulfonyl)imide.

[0048] In an even more preferred embodiment, X- is selected from FSI or TFSI.

[0049] The preferred embodiments as to the choice of the anion X set out above can be combined with the preferred embodiments as to the choice of the groups RI and R2 set out previously.

[0050] In a preferred embodiment, the (2-cyanoethyl)phosphonium salt comprises three 2-cyanoethyl chains and corresponds to formula (II)

[0051] [Chem.2] (II)

[0052] in which

[0053] X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methanides, borates, phosphates, sulfonimides or aluminates;

[0054] R2 is independently selected from C1-C20 alkyl, C3-C6 cycloalkyl, C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl; wherein the hydrogen atoms may be substituted with fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, nitrile, thioether or combinations thereof.

[0055] In a preferred embodiment, R2 is C1-C10 alkyl in which the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl group, perfluorinated alkyl group, silyl group, siloxy, sulfoxide group, nitrile group, thioether group or combinations thereof; more preferably R2 is selected from C1-C4 alkyl in which the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl group, perfluorinated alkyl group, silyl group, siloxy group, sulfoxide group, nitrile group, thioether group or combinations thereof; most preferably R2 is chosen from methyl, ethyl, propyl, isobutyl, n-butyl or allyl.

[0056] In a preferred embodiment, bis(oxalato)borate, di-fluorobis(oxalato)borate, acetate. iV-ethyl-iV-methyl-functionalized sulfonimide, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, (methanesulfonyl)(trifluoromethanesulfonyl)imide, (difluoromethanesulfonyl)(fluoromethanesulfonyl)imide, (methanesulfonyl)(fluoromethanesulfonyl)imide.

[0057] In an even more preferred embodiment, X- is selected from FSI or TFSI.

[0058] The preferred embodiments as to the choice of the anion X set out above can be combined with the preferred embodiments as to the choice of the groups RI and R2 set out previously.

[0059] In a particular embodiment the (2-cyanoethyl)phosphonium salt is in the form of a phosphonium salt dimer as represented by formula (III),

[0060] [Chem.3] CN CN (III)

[0061] in which

[0062] Z is chosen from C1-C20 alkyl diradicals of the -(CH2)n- type which may comprise one or more ethers or which may comprise one or more chains of the -CH2-Y-CH2- type with Y=S or SO or SO2; preferably the alkyl diradical is an ethyl, propyl, butyl or pentyl diradical.

[0063] X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methanides, borates, phosphates, sulfonimides or aluminates;

[0064] R2 is independently selected from the group consisting of an unsubstituted -CH2-CH2-CN chain, a C1-C20 alkyl, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinylbenzyl group, a vinylbenzyl group; wherein the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof.

[0065] In a more particularly preferred embodiment, R2 is a C1-C10 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a thioether group or combinations thereof.

[0066] Even more preferably, R2 is chosen from a methyl or a C1-C4 alkyl in which the hydrogen atoms can be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a thioether group or combinations thereof.

[0067] In a preferred embodiment, X- is selected from bis(fluorosulfonyl)imide (FSI), bis(trifluoromethanesulfonyl)imide (TFSI), tetrafluoroborate, hexafluoro-phosphate, dicyanamide, triflate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, fluoro-sulfonyl(trifluoromethanesulfonyl)imide, bis(oxalato)borate, di-fluorobis(oxalato)borate, acetate. Y-cthyl-Y-mcthyl-functionalizcd sulfonimide, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, (methanesulfonyl)(trifluoromethanesulfonyl)imide, (difluoromethanesulfonyl)(fluoromethanesulfonyl)imide, (methanesulfonyl)(fluoromethanesulfonyl)imide.

[0068] In an even more preferred embodiment, X- is selected from FSI or TFSI.

[0069] The preferred embodiments as to the choice of the anion X set out above can be combined with the preferred embodiments as to the choice of the R2 groups set out previously.

[0070] A second subject of the invention is an electrolyte composition comprising a lithium or sodium salt, an aprotic organic solvent and a (2-cyanoethyl)phosphonium salt compound as described above.

[0071] According to a preferred embodiment, the aprotic organic solvent is chosen from an ionic liquid, a carbonate, a glyme, an alkyl-sulfonamide or a mixture thereof.

[0072] In a preferred embodiment, the solvent is an ionic liquid.

[0073] As used herein, "ionic liquid" means a molten salt at a temperature below 100°C.

[0074] When the solvent is an ionic liquid, it comprises (i) a cation selected from an imidazolium, or a pyrrolidinium, a morpholinium, a pyridinium, a piperidinium, a phosphonium, an ammonium and (ii) an anion selected from hexafluorophosphate (PF6-), tetrafluoroborate (BF4-), bis(trifluoromethanesulfonyl)imide (TFSI), bis(fluorosulfonyl)imide (FSI), dicyanamide (DCA), 4,5-dicyano-2-(trifluoromethyl)imidazolide (TDI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (DFTFSI), bis(oxalato)borate (BOB), difluoro(oxalato)borate (DFOB).

[0075] In a preferred embodiment, the selected ionic liquids are of high quality [purity 99.9%; H2O < 5 ppm; halides < 1 ppm; lithium, sodium and potassium < 10 ppm; organic nitrogen compounds < 10 ppm; 20-10 Hazen color test].

[0076] In a preferred embodiment, the electrolyte composition comprises at least 30% ionic liquid, in particular at least 50% ionic liquid and preferably at least 70% ionic liquid.

[0077] A third object of the invention is a battery comprising a cathode, an anode, a separator and the electrolyte comprising a (2-cyanoethyl)phosphonium salt compound as described previously.

[0078] In a particular embodiment, the battery according to the invention can provide a energy density greater than 350 Wh / kg when the electrolyte is composed of ionic liquid and the (2-cyanoethyl)phosphonium salt compound. Indeed, the compound is compatible with the performances of ionic liquids such as non-flammability, high voltage and use with high temperatures.

[0079] The active material for the cathode is chosen from: has. For a Lithium-ion battery: a lithium intercalating compound, selected from lithium iron phosphate, (LiFePO4), lithium nickel manganese cobalt oxide, (LiNixMnyCozO2), doped lithium nickel manganese cobalt oxide, (LiNixMnyCozO2), lithium cobalt oxide (LiCoO2), doped lithium cobalt oxide, lithium nickel oxide (LiNiO2), doped lithium nickel oxide, lithium manganese oxide (LiMn2O4), doped lithium manganese oxide, NCA, lithium vanadium oxide, doped lithium vanadium oxide, lithium mixed metal oxides, Lithium Manganese Nickel Oxide (LMNO), lithium mixed transition metal oxides, lithium mixed transition metal oxides mixed transition doped (NCA, LMNX,), lithium vanadium phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium mixed metal phosphates, metal sulfides and their combinations. b. For a Sodium-ion battery: a metal oxide such as VO2, V2O5, H2V3O8, b- Mn02;

[0080] layered NaMOX such as Na0.71CoO2, Na0.7MnO2, b-NaMnO2, Nal.lV3O7.9, Na2RuO3, Na2 / 3[Nil / 3Mn2 / 3]O2, Na0.67Co0.5Mn0.502, Na0.66Li0.18Mn0.71Ni0.21Co0.0802+x; - 1D tunnel oxides such as Na0.44Mn02, Na0.66[Mn0.66Ti0.34]02, Na0.61[Mn0.27Fe0.34Ti0.39]02; - fluorides such as FeO0.7F1.3 and NaFeF3; - sulfates such as Na2Fe2(SO4)3 and Eldfellite NaFe(SO4)2; phosphates NaFePO4 and FePO4; Na3V2(PO4)3, Na3V2(PO4)3, Na3V2(PO4)3@C@rGO, Na3V2(PO4)3 / C, NaVOPO4; - pyrophosphates such as Na2CoP2O7, Na2FeP2O7 and Na3.12Fe2.44(P2O7)2;

[0081] fluorophosphates such as NaVPO4F, Na3V2(PO4)2F3, Na3V2O2(PO4)2F@RuO2, Na3(VOl-xPO4)2Fl+2x, Na3.5V2(PO4)2F3; - mixed phosphates such as Na7V4(P2O7)4(PO4), Na3MnPO4CO3; - hexacyanometalates such as MnHCMn PB As, Nal.32Mn[Fe(CN)6]0.83.3.5H2O, NaxCo[Fe(CN)6]0.90-2.9H20; - cathodes without critical metal such as Na2C6O6, Na6C6O6, SSDC, C6C14O2 / CMK, PTCDA-PI, poly(anthraquinonyl imide)s and functionalized graphite; - Prussian white analogues; - analogues of Prussian blue.

[0082] The active material for the anode is chosen from: a. For a Lithium-ion battery: - a lithium-containing titanium composite oxide (LTO); - mixture of niobium oxides (XNO) - metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe or alloys thereof; - graphite, graphene, including particles of natural graphite, artificial graphite, meso-carbon microbeads (MCMB) and carbon (including soft carbon, hard carbon, carbon nanofibers and carbon nanotubes); - silicon (Si), silicon / graphite composites, silicon-germanium (Ge) combinations, tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe) and cadmium (Cd); - alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al or Cd with other elements, said alloys or compounds being stoichiometric or non-stoichiometric; - oxides, carbides, nitrides, sulfides, phosphides, selenides and tellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti, Mn or Cd, and their mixtures or composites; - oxides (MeOx) of metals (Me); - composites of metals (Me) with carbon; - MXene materials, [MXC where X = 2,3,4). a. For a sodium-ion battery: oxide, sulfide, selenide, phosphide and MOF-based materials and carbon-based materials; carbon-based materials include expanded graphite, N-doped expanded graphite, carbon black, amorphous carbon, carbon microspheres, hard carbon, meso-strong soft carbon, carbon nanotubes, graphene nanosheets, nitrogen-doped CNTs, N-doped graphene foam, N-doped porous nanofibers, microporous carbon and cube-shaped porous carbon; oxides include MnO2 nanoflowers, NiO nanosheets, porous SnO, porous SnO2 nanotubes, porous 3D Fe3O4-C, porous CuO-RGO, ultrasmall nitrogen-doped MnO-CNTs, CuS microflowers, SnS2-RGO, Co3S4-PANI, ZnS-RGO, NiS-RGO, Co3S4-PANI, MoS2-C, nitrogen-doped WS2-conductive carbon nanosheets, Sb3Se3-RGO nanorods, MoSe2-carbon fiber, Sn4P3 multi-shell nanostructures, Sn4P3-C nanospheres, Se4P4, CoP nanoparticles, FeP nanorod arrays on carbon fabric, MoP-C, CUP2-C, hollow NiO / Ni graphene, nitrogen-doped yellow-shell structured CoSe / C; Na metal.

[0083] In a preferred embodiment, for Lithium-ion and Sodium-ion batteries, when the cathode is made of Lithium Manganese Nickel Oxide (LMNO) then the anode is made of graphite or Lithium Titanate (LTO); when the cathode is made of Nickel Manganese Cobalt 532 (NMC532) then the anode is made of graphite; when the cathode is made of Nickel Manganese Cobalt 622 (NMC622) then the anode is made of graphite; when the cathode is made of Nickel Manganese Cobalt 811 (NMC811) then the anode is made of graphite when the cathode is made of Lithium Iron Phosphate (LFP) then the anode is made of graphite; when the cathode is made of Lithium Iron Phosphate (LFP) then the anode is made of graphite.

[0084] The separators can be made up of:

[0085] - of a microporous polymer membrane which is a semi-crystalline polyolefin such as polyethylene (PE), polypropylene (PP), high density polyethylene (HDPE), PE-PP, PS-PP, polyethylene terephthalate-polypropylene blends (PET-PP), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN); polyoxymethylene, poly(4-methyl-l-pentene); nonwoven fabric mats such as cellulose, polyolefin, polyamide, polytetrafluoroethylene (PTFE), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), polyester. Other types of polymers are polyolefin-based materials and their blends such as polyethylene-polypropylene. Grafted polymers such as siloxane-grafted polyethylene separators, poly(methylmethacrylate)-grafted microporous separators. Polyvinylidene fluoride (PVDF) nanofiber webs. Polytriphenylamine (PTPAn)-modified separator. Polymer electrolytes such as ionic polymer electrolytes.

[0086] Examples of such ionic polymers are compounds formed from, for example, poly(diallyldimethylammonium) with an anion selected from hexafluorophosphate (PF6-), tetrafluoroborate (BF4-), bis(trifluoromethanesulfonyl)imide (TFSI), bis(fluorosulfonyl)imide (FSI), dicyanamide (DCA), 4,5-dicyano-2-(trifluoromethyl)imidazolide (TDI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI) and (difluoromethanesulfonyl) (trifluoromethanesulfonyl)imide (DFTFSI), bis(oxalato)borate (BOB), difluoro(oxalato)borate (DFOB).

[0087] - Of ionic liquid polymers with additionally ionic liquids (or without), elec polymer / copolymer electrolytes blended with polyethylene oxide (PEO), polyvinylpyrrolidone, polyethylene oxide, polyacrylonitrile, polyethylene glycols, glymes, fluorinated polymers to any other combination of polymer electrolytes and ionic liquids or to a combination of ionic liquids and ionic liquid polymer.

[0088] - Of polymerizable ionic liquid;

[0089] - Inorganic composite separator such as metal oxide powders (TiO2, ZrO2, LiA102, A12O3, MgO, CaCO3) in a polymer matrix (PVDF-HFP, PTFE), A1O(OH) / polyvinyl alcohol (PVA) on PET; ceramic separators such as alumina or ceramic particles blended with polymers or a combination of polymers and / or ionic liquids; surface-coated polymer such as a gel-like polymer film (PEO, PVDF-HFP) on microporous membranes; impregnation of a gel polymer electrolyte such as an ionic liquid-based electrolyte into microporous membranes; glass fibers; conductive glass separators. Separators may also include solid-state electrolytes such as solid ceramic electrolytes and solid polymer electrolytes.

[0090] In a preferred embodiment, the battery comprises an electrolyte composition comprising an ionic liquid solvent and the (2-cyanoethyl)phosphonium salt compound described in formulas (I), (II) or (III) as well as a cathode made of Lithium Manganese Nickel Oxide (LMNO) material.

[0091] In a particular embodiment, the battery comprises a cathode, an electrolyte as described previously and a separator.

[0092] In a particular embodiment, the battery comprises a separator and an electrolyte which are identical. This is the case in particular when the electrolyte is solid because it also plays the role of separator. BRIEF DESCRIPTION OF THE FIGURES

[0093] [Fig. 1] [Fig. 1]: Graph showing the charge / discharge profiles of the battery (LMNO / / Graphite) at charge and discharge rates of 0.1 C and the 10th, 100th, 250th and 450th cycles at 0.5 C from 2 V to 5 V versus Li+ / Li for the electrolyte 1 M LiFSI in PYR13FSI + 0.063 mol / kg of Tris(2-cyanoethyl)methylphosphonium bis(fluorosulfonyl)imide (P1(2CN)3FSI) at 20 °C.

[0094] [Fig.2] [Fig.2]: Graph showing the charge / discharge profiles of the battery (LMNO / / Graphite) at charge and discharge rates of 0.1 C and the 10th and 47th cycles at 0.5 C from 2 V to 5 V versus Li+ / Li for 1 M electrolyte LiFSI in PYR13FSI at 20°C.

[0095] [Fig.3] [Fig.3]: Graph showing discharge capacities and efficiencies Coulombic energy versus cycle number for whole cells (LMNO / / Graphite) with and without Tris(2-cyanoethyl)methylphosphonium bis(fluorosulfonyl)imide (P1(2CN)3FSI) compound at a charge and discharge rate of 0.5 C from 2 V to 5 V versus Li+ / Li at 20 °C.

[0096] [Fig.4] [Fig.4]: Graph showing the charge / discharge profiles of the battery (LMNO / / Graphite) at charge and discharge rates of 0.1 C and the 10th, 50th, 150th and 274th cycles at 0.5 C from 2 V to 5 V versus Li+ / Li for the IM LiFSI electrolyte in PYR13FSI + 0.063 mol / kg of Bis(2-cyanoethyl)butylmethylphosphonium bis(fluorosulfonyl)imide (P14(2CN)2FSI) at 20 °C.

[0097] [Fig.5] [Fig.5]: Graph showing the charge / discharge profiles of the battery (LMNO / / Graphite) at charge and discharge rates of 0.1 C and the 10th, 50th, 150th and 247th cycles at 0.5 C from 2 V to 5 V versus Li+ / Li for IM LiFSI electrolyte in PYR13FSI at 20 °C.

[0098] [Fig.6] [Fig.6]: Graph showing discharge capacities and cou efficiencies lombics as a function of cycle number for whole cells (LMNO / / Graphite) with and without ^is(2-cyanoethyl)butylmethylphos b>ïs(fluorosulfonyl)imide compound (P14(2CN)2FSI) at a charge and discharge rate of 0.5 C between 2V and 5V versus Li+ / Li at 20 °C.

[0099] [Fig.7] [Fig.7]: Graph showing the charge / discharge profiles of the battery (LMNO / / LTO) at charge and discharge rates of 0.05 C, 0.2 C and 0.5 C from 1.2 V to 3.5 V versus Lr7Li for the IM LiFSI electrolyte in PYR13FSI + 0.126 mol / kg Bis(2-cyanoethyl)propylmethylphosphonium bis(fluorosulfonyl)imide (P13(2CN)2FSI) at 20 °C.

[0100] [Fig.8][Fig.8]: Graph showing the charge / discharge profiles of the battery (LMNO / / LTO) at charge and discharge rates of 0.05 C, 0.2 C and 0.5 C from 1.2 V to 3.5 V versus Lr7Li for IM LiFSI electrolyte in PYR13FSI at 20 °C.

[0101] [Fig.9] [Fig.9]: Graph showing discharge capacities and cou efficiencies Lumbic as a function of cycle number for whole cells (LMNO / / LTO) with and without compound Bis(2-cyanoethyl)propylmethylphosphonium bis(fluorosulfonyl)imide (P13(2CN)2FSI) at different charge and discharge rates from 1.2 V to 3.5 V versus Lr7Li at 20 °C.

[0102] [Fig. 10][Fig. 10]: Graph showing discharge capacities and coulombic efficiencies as a function of cycle number for whole cells (NMC622 / / Gr) with and without P14(2CN)2FSI compound at different charge and discharge rates from 2 V to 4.2 V versus Li+ / Li at temperature ambient (TA).

[0103] [Fig. 1 l][Fig. 11]: Graph showing discharge capacities and coulombic efficiencies as a function of cycle number for whole cells (NMC622 / / Gr) with and without compound Bis(2-cyanoethyl)butylmethylphosphonium bis(fluorosulfonyl)imide (P14(2CN)2FSI) at long C / 2 cycling from 2 V to 4.2 V versus Li+ / Li at room temperature (RT).

[0104] [Fig. 12][Fig. 12]: Graph showing discharge capacities and coulombic efficiencies as a function of cycle number for whole cells (NMC532 / / Graphite) with and without bis(2-cyanoethyl)ethylmethylphosphonium bis(fluorosulfonyl)imide compound

[0105] (P12(2CN)2FSI) at different charge and discharge rates between 2.5 V to 4.2 V compared to Li+ / Li at 45°C. EXAMPLES

[0106] EXAMPLE 1: Preparation of electrolyte and button cells

[0107] In a glove box under an inert atmosphere (Argon) with water and O2 contents less than 1 ppm, the metal salt is dissolved in an aprotic organic solvent in a desired concentration. One or more compounds are then added and mixed to obtain a homogeneous electrolyte solution.

[0108] The complete button cells (CR2032) are assembled in a glove box under argon atmosphere with contents of less than 1 ppm in O2 and H2O. The electrodes used are commercial and they were purchased already coated on the current collectors (aluminum and copper). They have capacities between 1 and 4 mAh / cm2 and are cut into discs of 13 mm diameter.

[0109] The electrodes are separated by a 16 mm diameter separator having a thickness between 11 and 180 μm which can be made of different materials. The separator is then soaked in electrolyte. The button cells were then sealed by a button cell crimping instrument in order to obtain a battery before carrying out the electrochemical characterizations.

[0110] Electrochemical impedance spectroscopy (EIS) and galvanostatic cycling measurements were performed using a VMP3 potentiostat (BioLogic) and a multi-channel battery cycler (Arbin Inc). The impedance (EIS) measurements were performed on two-electrode cells at open-circuit bias by applying a 10 mV RMS sine wave at frequencies ranging from 1 MHz to 10 mHz.

[0111] Galvanostatic cycling is achieved by charging and discharging the cells at different constant currents at the maximum and minimum cut-off voltages specific to the different combinations of active materials.

[0112] The impedances and galvanostatic cycling were carried out in an enclosure climate maintaining a constant temperature of 20°C.

[0113] EXAMPLE 2: PREPARATION OF AN LMNO / / Graphite BATTERY WITH AND WITHOUT COMPOUND [P1(2CN)3FSI] and CHARGING AND DISCHARGING THE BATTERY

[0114] In a glove box under an inert atmosphere (Argon) with a water and O2 content of less than 1 ppm, the lithium salt LiFSI (0.936 g) is dissolved in the ionic liquid PYR13FSI (6.045 g) to obtain the desired concentration, the compound (2-cyanoethyl)phosphonium P1(2CN)3FSI (0.170 g) is then added and mixed to obtain a homogeneous electrolyte solution.

[0115] The batteries were prepared according to the method described in Example 1. Table 1 below lists the different cathode / anode / electrolyte combinations tested in the battery.

[0116] [Tables 1] Positive Electrode - Capacity Negative Electrode - Capacity Electrolytes LMNO-l.lrnAh?W Graphite ~ 2.2 mAh / cm* IM LÎFSS in PYR13FSI + 0.063 moi / kg Pl(2CN)jFS! LMNO-1.1 mAh / cm2 Graphite - 2.2 mAh / cm* IM UFSi in PYR13FSÎ

[0117] Table 1: Combinations of LMNO cathode / Graphite anode / electrolyte tested in battery.

[0118] The batteries were tested in galvanostatic cycling from 2 to 5 V at different C rates: 0.1 C and 0.5 C in a climatic chamber at 20 °C.

[0119] [Fig. 1], in which the electrolyte contains the compound P1(2CN)3FSI, shows a discharge capacity loss of 7% between 0.1C and 0.5C respectively 114.54 mAh / g and 106.33 mAh / g. As the charge and discharge rate increases, the polarization between charge and discharge increases. For cycling at 0.5 C, the discharge capacity loss in 450 cycles is 18.5% (from 114.54 to 93.30 mAh / g).

[0120] [Fig.2], in which the electrolyte does not contain the compound P1(2CN)3FSI shows a loss of capacity in discharge of 38% between 0.1 C and 0.5 C respectively 118.54 mAh / g and 73.22 mAh / g. For charges and discharges at a rate of 0.5 C, the profiles differ slightly from those of 0.1 C. Indeed, the transition plateaus are less well defined, more particularly that of 4.56 V.

[0121] Comparing the charge / discharge profiles of the two systems, those containing the (2-cyanoethyl)phosphonium compound are more stable.

[0122] [Tables2] Electrolyte C-rate Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency IM LiFSI in PYR13FSI + 0.063 mol / kg Pl(2CNhFSI 0.50 (1st cycle) 106.52 106.23 99.72 IM LiFSi in PYR13FSI +0.063 mol / kg PlpCNJaFSI 0.5C (450^^= cycle) 93.43 93.39 99.86 1M LiFSI in PYR13FSI 0.50 (1st cycle) 76.53 75.80 99.04 IM LiFSI in PYR13FSI 0.5C cycle) 63.39 62.85 99.15

[0123] Table 2: Characteristics of batteries with an LMNO / / Graphite system at 0.5 C with and without (2-cyanoethyl)phosphonium compound.

[0124] Table 2 and [Fig.3] show the discharge capacity as a function of the number of cycles of the two systems, with and without (2-cyanoethyl)phosphonium salt compound, as well as their coulombic efficiencies.

[0125] Without the (2-cyanoethyl)phosphonium salt compound, the discharge capacity of the battery decreases from the first cycles for charge and discharge rates of 0.5 C unlike the system containing the (2-cyanoethyl)phosphonium compound for which the capacity remains stable longer, 12% capacity loss in 450 cycles (106.23mAh / g to 93.39mAh / g) at 100% DoD. The coulombic efficiency is also higher for the electrolyte containing the (2-cyanoethyl)phosphonium, it is close to 99.9% compared to 99.2% without it.

[0126] EXAMPLE 3: PREPARATION OF AN LMNO / / Graphite BATTERY WITH AND WITHOUT COMPOUND [P14(2CN)2FSI] and CHARGING AND DISCHARGING THE BATTERY

[0127] In a glove box under an inert atmosphere (Argon) with a water and O2 content of less than 1 ppm, the lithium salt LiFSI (0.936 g) is dissolved in the ionic liquid PYR13FSI (6.045 g) to obtain the desired concentration, a (2-cyanoethyl)phosphonium compound P14(2CN)2FSI (0.172 g) is then added and mixed to obtain a homogeneous electrolyte solution.

[0128] The batteries were prepared according to the method described in Example 1. Table 3 below lists the different cathode / anode / electrolyte combinations tested in the battery.

[0129] [Tables3] Positive Electrode - Capacity Negative Electrode - Capacity Electrolytes IMNO-LlmAh / cm2 Graphite -1.4 mAh / cm2 IM LIFSI in PYR13FSI + 0.0628 mol / kg P14(2CN)2FSI LMNO ~ l.lmAh / cm2 Graphite ~ 1.4 mAh / cm2 IM LiFSÏ in PYR13FSI

[0130] Table 3: Combinations of LMNO cathode / Graphite anode / electrolyte tested in battery.

[0131] The batteries were tested in galvanostatic cycling from 2 to 5 V at different C rates: 0.1 C and 0.5 C in a climatic chamber at 20 °C.

[0132] [Fig.4], in which the electrolyte contains the compound P14(2CN)2FSI, shows a discharge capacity loss of 7.5% between 0.1 C and 0.5 C respectively 124.08 mAh / g and 114.73 mAh / g. As the charge and discharge rates increase, the polarization between charge and discharge increases. For cycling at 0.5 C, the discharge capacity loss in 243 cycles is 4.5% (from 114.73 to 109.63mAh / g).

[0133] [Fig.5], in which the electrolyte does not contain the compound P14(2CN)2FSI, shows a loss of discharge capacity of 9% between 0.1 C and 0.5 C respectively 117.19 mAh / g and 107.02 mAh / g. At a charge and discharge rate of 0.2 C, the discharge capacity decreases by 13% between the 10th and 247th cycle in C / 2 from 107.02mAh / g to 93.39mAh / g.

[0134] The capacity loss is less significant for the system in which the electrolyte contains the compound P14(2CN)2FSI.

[0135] [Tables4] Electrolyte Grate (Number of cycles) Charge capacity (mAh / g) Discharge capacity (mAh / g) CM efficiency IM LiFSI in PYR13FS! + 0.063 mol / kg P14(2CN)2FSI 0.5 C {let cycle) 115.30 114.83 99.59 IM LIFSI in PYR13FS! + 0.063 mol / kg P14(2CN)2FSI 0.5 C j247^® CyC|e) 109.73 109.63 99.87 IM LÎFSÎ in PYR13FS! 0.5 C [1st cycle) 107.99 107.46 99.51 IM LÎFSÎ in PYR13FSI 0.5 C (247^ cycle) 93.64 93.33 99.67

[0136] Table 4: Characteristics of batteries with a LMNO / / Graphite system at 0.5 C with and without compound P14(2CN)2FSI.

[0137] Table 4 and [Fig.6] show the discharge capacity as a function of the number of cycles of the two systems, with and without (2-cyanoethyl)phosphonium salt compound

[0138] Without P14(2CN)2FSI compound, the discharge capacity of the first cycle at a charge and discharge rate of 0.5 C is lower than with the (2-cyanoethyl)phosphonium compound (respectively 107.99 mAh / g and 115.30 mAh / g). Concerning the cyclability, the capacity of the system containing the P14(2CN)2FSI compound is more stable during the cycles. Indeed, taking into account the first 247 cycles, the capacity loss for the system without P14(2CN)2FSI compound is 13.1% compared to 4.9% for the one containing the P14(2CN)2FSI compound. The coulombic efficiency is also higher for the electrolyte containing (2-cyanoethyl)phosphonium.

[0139] EXAMPLE 4: PREPARATION OF AN LMNO / / LTO BATTERY WITH AND WITHOUT COMPOUND [P13(2CN)2FSI] AND CHARGING AND DISCHARGING THE BATTERY

[0140] In a glove box under an inert atmosphere (Argon) with a water and O2 content of less than 1 ppm, the lithium salt LiFSI (0.936 g) is dissolved in the ionic liquid PYR13FSI (6.045 g) to obtain the desired concentration, a (2-cyanoethyl)phosphonium compound P13(2CN)2FSI (0.331 g) is then added and mixed to obtain a homogeneous electrolyte solution.

[0141] The batteries were prepared according to the method described in Example 1. Table 5 below lists the different cathode / anode / electrolyte combinations tested in the battery.

[0142] [Tables5] Positive Electrode - Capacity Negative Electrode - Capacity Electrolytes LMNO-1.1mAh / cm2 LT0-2mAh / cm2 IM MFSÎ in PYR13FSI + 0.126 mol / kg P13(2CN)2FSI LMNO - 1.1mAh / cm* LTO-2 mAh / cm2 IM UF$t in PYR13FS!

[0143] Table 5: LMNO cathode / LTO anode / electrolyte combinations tested in battery.

[0144] The batteries were tested in galvanostatic cycling from 1.2 to 3.5 V at different C rates: 0.05 C, 0.1 C, 0.14 C, 0.2 C, 0.33 C and 0.5 C in a climatic chamber at 20 °C.

[0145] [Fig.7], in which the electrolyte contains the compound P13(2CN)2FSI, shows a loss of capacity in discharge of 14% between 0.05 C and 0.5 C respectively 141.08 mAh / g and 121.44 mAh / g. As the charge and discharge speed increases, the polarization between charge and discharge increases.

[0146] [Fig.8], in which the electrolyte does not contain the compound P13(2CN)2FSI, shows a loss of capacity in discharge of 30% between 0.05 C and 0.5 C respectively 131.54 mAh / g and 91.22 mAh / g. From the rate 0.2 C, the charge / discharge profile differs by 0.05 C. Indeed, the disappearance of one of the transition plateaus is observed around 2.5 V, this may be due to an irreversible consumption of Li+ ions during the formation of passivation films on the surface of the electrodes. When there are no longer enough Li+ ions to participate in the Mn4+ / Mn3+ conversion process, the transition plateau disappears.

[0147] Comparing the charge / discharge profiles of the two systems, the one containing the (2-cyanoethyl)phosphonium compound in [Fig.7] is more stable because no transition plateau disappears during the cycles. This P13(2CN)2FSI compound plays a role in the formation of the passivation film and therefore reduces the irreversible consumption of Li+ ions during the cycles.

[0148] [Tableauxô] Electrotype C-rate Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency (%) IM LiFS! in PYR13FS! + 0.126 mol / kg P13(2CN)2FSI 0.05 C 146.18 141.08 96.47 IM LiFSi in PYR13FS! + 0.126 mol / kg P13(2CN)2FSI 0.5 C 122.76 121.44 98.96 IM LiFS! in PYR13FSI 0.05 C 138.15 131.54 95.22 IM LiFSi in PYR13FSI 0.5 C 92.45 91.22 98.72

[0149] Table 6: Characteristics of batteries with an LMNO / / LTO system at 0.05 C and 0.5 C with and without compound.

[0150] Table 6 and [Fig.9] show the discharge capacity of the two systems, with and without (2-cyanoethyl)phosphonium salt compound.

[0151] Without the P13(2CN)2FSI compound, the discharge capacity of the battery decreases from C / 10 unlike the system containing the (2-cyanoethyl)phosphonium compound for which the capacity remains stable for longer and higher for C rates up to 0.5 C. The coulombic efficiency is also higher with the formulation containing (2-cyanoethyl)phosphonium.

[0152] EXAMPLE 5: PREPARATION OF AN NMC622 / / Graphite BATTERY WITH AND WITHOUT COMPOUND [P14(2CN)2FSI] and CHARGING AND DISCHARGING THE BATTERY

[0153] In a glove box under an inert atmosphere (Argon) with a water and O2 content lower than Ippm, the lithium salt LiFSI (1.00g) is dissolved in the ionic liquid EMIMFSI (6.49g) in a desired concentration, a (2-cyanoethyl)phosphonium compound P14(2CN)2FSI (0.184g) is then added and mixed to obtain a homogeneous solution.

[0154] The batteries were prepared according to the method described in Example 1.

[0155] [Tables?] Positive Electrode / Capacity Negative Electrode / Capacity Electrolytes NMC622 -1.86 mAh / cm2 Graphite - 2.4 mAh / cm2 1.07M LiFSI in EMIMFSI + 0.0628 mci / kgP14(2CN)2FSI NMC622-1.86 mAh / cm2 Graphite - 2.4 mAh / cm2 1.07M LiFSI in EMIMFSI

[0156] Table 7: NMC622 cathode / electrolyte / Graphite anode combinations tested in battery.

[0157] The batteries were tested in galvanostatic cycling from 2 to 4.2V at different C rates: 0.05C, 0.1C, 0.14C, 0.2C, 0.33C and 0.5C at room temperature (RT).

[0158] [Tables8] Electrolyte C-rate (number of cycles) Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency (%) 1.07M LiFSI in EMIMFSI+ 0.063 mol / kg P14(2CN)2FSI 0.Q5C 2^ 156.69 153.54 97.98 1.07M LiFSI in EMIMFSI+ 0.063 mol / kg P14(2CNhFSI 0.5C (45th) 146.00 145.84 99.89 1.07M LiFSI in EMIMFSI +0.063 mol / kg P14(2CN)2FSI O.SC (265th) 127.35 126.74 99.52 1.07M LiFSI in EMIMFSI 0.05C (2nd) 151.41 144.47 95.41 1.07M LiFSI in EMIMFSI 0.5C {45«^) 113.66 113.29 99.67 1.07M LiFSI in EMIMFSI 0.5C (265th) 111.43 92.50 83.01

[0159] Table 8: Characteristics of batteries with an NMC622 / / Gr system at 0.05 C and 0.5 C with and without compound.

[0160] Table 8 and Figures 10 and 11 show the discharge capacity as a function of the number of cycles of the two systems, with and without compound. [Fig. 10] shows the first 60 cycles and [Fig. 11] shows the continuation of the cycles at C / 2 up to 250 cycles at room temperature.

[0161] Without the compound, the discharge capacity of the battery gradually decreases, unlike the system containing the (2-cyanoethyl)phosphonium compound, for which the capacity at different charging and discharging rates is better retained. [Fig. 10] shows that the effect is even more marked on the return to charging and discharging rates of 0.1 C, where the discharge capacity retention capacity is significantly lower without the (2-cyanoethyl)phosphonium than with it. The coulombic efficiency is also higher with the formulation containing the (2-cyanoethyl)phosphonium.

[0162] EXAMPLE 6: Comparative table showing the impact of the number of nitrile functions on the concentration required to achieve the effectiveness of the molecule.

[0163] [Tables9] Products Molar mass Number of nitrile functions Number of nitrile functions / Molar mass Pl[2CN)3FSi 388.351 3 1 / 129 P12(2CNhFSl 353.342 2 1 / 181 P13(2CN)2FSi 377.368 2 1 / 188 P14(2CN)2FSi 391.395 2 1 / 195

[0164] Table 9 Comparative table showing the ratio Molar mass of the molecule / Number of nitrile functions carried by the molecule.

[0165] For the same electrode system, when using P1(2CN)3FSI, 129g of molecule will be required whereas for P14(2CN)2FSI, 195g of molecule will be required for the same efficiency, which results in a higher concentration and therefore a reduction in conductivity.

[0166] [Tables 10] Products Capacity (mAh / g) 1st cycle C / 2 Capacity (mAh / g) 174th cycle C / 2 Capacity Retention (%) l~(cyanoethyl Ipl-methylpy rrol id iniu m P¥Rl(lCN)FSi 107.37 96.47 89.85 f2~cyanoethyl)tnmethylphasphoniijm bi&(fluorosulfonyi)im)de Pin(2CN)FSI 108.12 86.78 80.26 3ïs(2-cyanoethyl)butylmethylphosphoniLm 114.83 110.86 96.54 Tri$(2<yan©éthyl)iméthylpho$phç> ni.um bis(fiuür0$dfonyl)îmide P1(2Œ)3FSI 106.23 105 98.84

[0167] Table 10: At equivalent concentration of products (electrolyte compound), the capacity retentions with molecules containing two or three nitrile functions are greater than with molecules containing a single nitrile function.

[0168] Example 7: PREPARATION OF A NMC532 / / GRAPHITE BATTERY WITH AND WITHOUT COMPOUND [P12(2CN)2FSI] and CHARGING AND DISCHARGING THE BATTERY

[0169] In a glove box under an inert atmosphere (Argon) with a water and O2 content of less than 1 ppm, the lithium salt LiFSI (0.936 g) is dissolved in the ionic liquid PYR13FSI (6.045 g) to obtain the desired concentration, a (2-cyanoethyl)phosphonium compound P12(2CN)2FSI (0.320 g) is then added and mixed to obtain a homogeneous electrolyte solution.

[0170] The batteries were prepared according to the method described in Example 1. Table 11 below lists the different cathode / anode / electrolyte combinations tested in the battery.

[0171] [Tables] Positive Electrode - Negative Electrode Capacity Electrolytes NMC532- 1.5mAh / cm* Graphite IM LiFSI in PYR13FSI + 0.126 moi / kg P12(2CNhFSÎ NMC532-1.5mAh / cm* Graphite IM LiFSI in PYR13FSI

[0172] Table 11: NMC532 cathode / Graphite anode / electrolyte combinations tested in battery.

[0173] The batteries were tested in galvanostatic cycling from 2.5 to 4.2 V at different C rates: 0.05 C, 0.1 C, 0.14 C, 0.2 C, 0.33 C and 0.5 C in a climatic chamber at 45 °C.

[0174] [Tablesl2] Electrolyte C-rate (number of cycles) Charge capacity {mAh / cm*) Discharge capacity (mAh / cm*) Efficiency (%) IM UF51 in PYR13FSI + 0.126 mol / kg P12(2CN)2FSI 0.05 C (2nd) 1.52 1.50 98.26 IM LiFSI in PYR13FSÎ + 0.126 mol / kg P12{2CNhFSI 0.5 C (24tes) 1.37 1.37 99.93 IM LIFSI in PYR13FSÎ 0.05 C Pnd) 1.16 1.06 91.30 IM LIFSI in PYR13FSI 0.5 C (24*me) 0.89 0.89 99.28

[0175] Table 12: Characteristics of batteries with an NMC532 / / Graphite system at 0.05 C and 0.5 C with and without compound

[0176] Table 12 and [Fig. 12] show the discharge capacity as a function of number of cycles of the two systems, with and without (2-cyanoethyl)phosphonium salt compound at 45 °C.

[0177] [Fig. 12], in which the electrolyte contains the compound P12(2CN)2FSI, shows a discharge capacity loss of 8.6% between 0.05 C and 0.5 C respectively 1.5 mAh / cm2 and 1.37 mAh / cm2 against a discharge capacity loss of 16% for the electrolyte not containing the (2-cyanoethyl)phosphonium compound.

[0178] [Fig. 12] shows that the capacity at a rate of 0.05C for the electrolyte containing the compound P12(2CN)2FSI is greater than in the electrolyte not containing the compound, 1.50 mAh / cm2 against 1.06mAh / cm2.

[0179] Without the P12(2CN)2FSI compound, the discharge capacity of the battery is not stable from the first cycles unlike the system containing the (2-cyanoethyl)phosphonium compound for which the discharge capacity remains stable for longer and is higher for C rates up to 0.5 C. The coulombic efficiency is also higher with the formulation containing (2-cyanoethyl)phosphonium.

Claims

1. Claims An electrolyte composition comprising a lithium salt or a sodium salt, an aprotic organic solvent and an electrolyte compound, wherein said electrolyte compound comprises a (2-cyanoethyl)phosphonium salt as represented by formula (I): [Chem.l] (I) in which: X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methanides, borates, phosphates, sulfonimides or aluminates; RI is independently selected from an unsubstituted -CH2-CH2-CN chain, a C1-C20 alkyl, a C3-C6 cycloalkyl, a C2-C20 alkenyl, a C5-C8 cycloalkenyl, a C2-C20 alkynyl, a vinylbenzyl group; wherein the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof. R2 is independently selected from C1-C20 alkyl, C3-C6 cycloalkyl, C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl; wherein the hydrogen atoms may be substituted with fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, nitrile, thioether or combinations thereof.

1. Electrolyte composition according to claim 1 in which RI is chosen from unsubstituted -CH2-CH2-CN chain, a C1-C10 alkyl in which the hydrogen atoms can be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof; and R2 is a C1-C10 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a nitrile group, a thioether group or combinations thereof.

2. An electrolyte composition according to claim 2 wherein R1 is selected from methyl or C1-C4 alkyl in which the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, nitrile, thioether or combinations thereof; and wherein R2 is selected from methyl, ethyl, propyl, isobutyl, n-butyl or allyl.

3. Electrolyte composition according to claim 1 in which: X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methides, borates, phosphates, sulfonimides or aluminates; RI is independently selected from C1-C20 alkyl, C3-C6 cycloalkyl, C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl; wherein the hydrogen atoms may be substituted with fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, thioether or combinations thereof. R2 is independently selected from C1-C20 alkyl, C3-C6 cycloalkyl, C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl; wherein the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, thioether or combinations thereof.

1. An electrolyte composition according to claim 4 wherein R1 and R2 are independently selected from C1-C10 alkyl in which the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl group, perfluorinated alkyl group, silyl group, siloxy group, sulfoxide group, thioether group or combinations thereof.

2. An electrolyte composition according to claim 5 wherein R1 is selected from methyl or C1-C4 alkyl in which the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl group, perfluorinated alkyl group, silyl group, siloxy group, sulfoxide group, thioether group or combinations thereof; and R2 is selected from methyl, ethyl, propyl, isobutyl, n-butyl or allyl.

3. Electrolyte composition according to one of claims 1 to 6 in which the anion is chosen from bis(fluorosulfonyl)imide (FSI), bis(trifluoromethanesulfonyl)imide (TFSI), tetrafluoroborate, hexafluorophosphate, dicyanamide, triflate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, fluorosulfonyl(trifluoromethanesulfonyl)imide, bis(oxalato)borate, difluorobis(oxalato)borate, acetate., N-ethyl-N-methyl-functionalized sulfonimide, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, (methanesulfonyl)(trifluoromethanesulfonyl)imide, (difluoromethanesulfonyl)(fluoromethanesulfonyl)imide, (methanesulfonyl)(fluoromethanesulfonyl)imide.

4. Electrolyte composition according to claim 7 in which the anion X- is chosen from FSI or TFSI.

5. Electrolyte composition according to claim 1, the (2-cyanoethyl)phosphonium salt of which is represented by the formula (II): [Chem. 2] CH X (II) in which X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methides, borates, phosphates, sulfonimides or aluminates; and R2 is independently selected from C1-C20 alkyl, C3-C6 cycloalkyl, C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl; wherein the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, thioether or combinations thereof.

1. An electrolyte composition according to claim 9 wherein R2 is a C1-C10 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a thioether group or combinations thereof.

2. Electrolyte composition according to claim 10 in which R2 is chosen from a C1-C4 alkyl in which the hydrogen atoms can be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a thioether group or combinations thereof.

3. Electrolyte composition according to claim 11 in which R2 is selected from methyl, ethyl, propyl, isobutyl, n-butyl or allyl.

4. Electrolyte composition according to one of claims 9 to 12 in which Fanion is chosen from bis(fluorosulfonyl)imide (FSI), bis(trifluoromethanesulfonyl)imide (TFSI), tetrafluoroborate, hexafluorophosphate, dicyanamide, triflate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, fluoro-sulfonyl(trifluoromethanesulfonyl)imide, bis(oxalato)borate, difluorobis(oxalato)borate, acetate., N-ethyl-N-methyl-functionalized sulfonimide, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, (methanesulfonyl)(trifluoromethanesulfonyl)imide, (difluoromethanesulfonyl)(fluoromethanesulfonyl)imide, (methanesulfonyl)(fluoromethanesulfonyl)imide.

5. Electrolyte composition according to claim 13 in which the anion X- is chosen from FSI or TFSI.

6. An electrolyte composition according to claim 1 wherein the (2-cyanoethyl)phosphonium salt is in the form of a phosphonium salt dimer, said dimer being represented by formula (III) [Chem. 3] CN CN (HD in which Z is chosen from C1-C20 alkyl diradicals of the -(CH2)n- type which may comprise one or more ethers or which may comprise one or more chains of the -CH2-Y-CH2- type with Y=S or SO or SO2; preferably the alkyl diradical is an ethyl, propyl, butyl or pentyl diradical; X- is selected from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, amides, methides, borates, phosphates, sulfonimides or aluminates; R2 is independently selected from an unsubstituted -CH2-CH2-CN chain, by a C1-C20 alkyl, a C3-C6 cycloalkyl, a C2-C20 alkenyl, C5-C8 cycloalkenyl, C2-C20 alkynyl, vinylbenzyl; wherein the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl, perfluorinated alkyl, silyl, siloxy, sulfoxide, nitrile, thioether or combinations thereof; 1. An electrolyte composition according to claim 15 wherein R2 is a C1-C10 alkyl in which the hydrogen atoms may be substituted by a fluorine, a -CF3, an ether, an alkyl group, a perfluorinated alkyl group, a silyl group, a siloxy group, a sulfoxide group, a thioether group or combinations thereof.

2. An electrolyte composition according to claim 16 wherein R2 is selected from methyl or C1-C4 alkyl in which the hydrogen atoms may be substituted by fluorine, -CF3, ether, alkyl group, perfluorinated alkyl group, silyl group, siloxy group, sulfoxide group, thioether group or combinations thereof; and R2 is selected from methyl, ethyl, propyl, isobutyl, n-butyl or allyl.

3. Electrolyte composition according to one of claims 15 to 17 in which Fanion is chosen from bis(fluorosulfonyl)imide (FSI), bis(trifluoromethanesulfonyl)imide (TFSI), tetrafluoroborate, hexafluorophosphate, dicyanamide, triflate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, fluoro-sulfonyl(trifluoromethanesulfonyl)imide, bis(oxalato)borate, difluorobis(oxalato)borate, acetate., N-ethyl-N-methyl-functionalized sulfonimide, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, (methanesulfonyl)(trifluoromethanesulfonyl)imide, (difluoromethanesulfonyl)(fluoromethanesulfonyl)imide, (methanesulfonyl)(fluoromethanesulfonyl)imide.

4. Electrolyte composition according to claim 18 in which Fanion X- is chosen from FSI or TFSI.

1. Electrolyte composition according to one of claims 1 to 19 wherein said aprotic organic solvent is selected from an ionic liquid, a carbonate, a glyme, an alkyl sulfonamide or a mixture thereof.

1. Electrolyte composition according to one of claims 1 to 20 in which the ionic liquid comprises (i) a cation chosen from an imidazolium, or based on pyrrolidinium, morpholinium, pyridinium, piperidinium, phosphonium, ammonium and (ii) an anion chosen from hexafluorophosphate (PF6), tetrafluoroborate (BF4), bis(trifluoromethanesulfonyl)imide (TFSI), bis(fluorosulfonyl)imide (FSI), dicyanamide (DCA), 4,5-dicyano-2-(trifluoromethyl)imidazolide (TDI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (DFTFSI), bis(oxalato)borate (BOB), difluoro(oxalato)borate (DFOB).

2. Electrolyte composition according to one of claims 1 to 21 comprising a lithium or sodium salt, an electrolyte compound as defined in one of claims 1, 4 or 9 and an ionic liquid.

3. Battery comprising a cathode, a separator and an electrolyte composition as described in one of claims 1 to 22.

4. Battery comprising a cathode, an anode, a separator and an electrolyte composition as defined in one of claims 1 to 22.

5. Battery according to one of claims 23 or 2 where the separator and the electrolyte are identical.

6. Battery according to one of claims 23 to 25 in which the cathode is chosen from a. For a Lithium battery: a lithium intercalating compound, chosen from lithium-iron phosphate (LiFePO4), lithium-nickel-manganese-cobalt oxide (LiNixMnyCozO2), doped lithium-nickel-manganese-cobalt oxide, (LiNixMnyCozO2), lithium cobalt oxide (LiCoO2), doped lithium cobalt oxide, lithium nickel oxide (LiNiO2), doped lithium nickel oxide, lithium manganese oxide (LiMn2O4), doped lithium manganese oxide, NCA, lithium vanadium oxide, doped lithium vanadium oxide, lithium mixed metal oxides, Lithium Manganese Nickel Oxide (LMNO), lithium mixed transition metal oxides, doped lithium mixed transition metal oxides (NCA, LMNX,), lithium vanadium phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium mixed metal phosphates, metal sulfides and combinations thereof. b. For a Sodium-ion battery: a metal oxide such as VO2, V2O5, H2V3O8, b- Mn02; layered NaMOX such as Na0.71CoO2, Na0.7MnO2, b-NaMnO2, Nal.lV3O7.9, Na2RuO3, Na2 / 3[Nil / 3Mn2 / 3]O2, Na0.67Co0.5Mn0.502, Na0.66Li0.18Mn0.71Ni0.21Co0.0802+x ; 1D tunnel oxides such as Na0.44Mn02,Na0.66[Mn0.66Ti0.34]02, Na0.61[Mn0.27Fe0.34Ti0.39]02; fluorides such as FeO0.7F1.3 and NaFeF3; sulfates such as Na2Fe2(SO4)3 and Eldfellite NaFe(SO4)2; NaFePO4 and FePO4 phosphates; Na3V2(PO4)3, Na3V2(PO4)3, Na3V2(PO4)3@C@rGO, Na3V2(PO4)3 / C, NaV0P04; pyrophosphates such as Na2CoP2O7, Na2FeP2O7 and Na3.12Fe2.44(P2O7)2; fluorophosphates such as NaVPO4F, Na3V2(PO4)2F3, Na3V2O2(PO4)2F @ Ru02, Na3(V01 -xPO4)2F 1 +2x, Na3.5V2(PO4)2F3; mixed phosphates such as Na7V4(P2O7)4(PO4), Na3MnPO4CO3; hexacyanometalates such as MnHCMn PB As, Nal.32Mn[Fe(CN)6]0.83.3.5H2O, NaxCo[Fe(CN)6]0.90-2.9H20; critical metal-free cathodes such as Na2C6O6, Na6C6O6, SSDC, C6C14O2 / CMK, PTCDA-PI, poly(anthraquinonyl imide)s and functionalized graphite; Prussian white analogues Prussian blue analogues 1. Battery according to one of claims 24 to 26 in which the anode is chosen from: a. For a Lithium-ion battery: a composite titanium oxide containing lithium; mixture of niobium oxides (XNO); metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe or alloys thereof; graphite, graphene, including natural graphite particles, artificial graphite particles, meso-carbon microbeads (MCMB) and carbon (including soft carbon, hard carbon, carbon nanofibers and carbon nanotubes; silicon (Si), silicon / graphite composites, silicon-germanium (Ge) combinations, tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe) and cadmium (Cd); alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al or Cd with other elements, said alloys or compounds being stoichiometric or non-stoichiometric; oxides, carbides, nitrides, sulfides, phosphides, selenides and tellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti, Mn or Cd, and their mixtures or composites; oxides (MeOx) of metals (Me); and composites of metals (Me) with carbon; MXene materials, [MXC where X = 2,3,4). a. For a sodium-ion battery: oxide, sulfide, selenide, phosphide and MOF-based materials and carbon-based materials; carbon-based materials include expanded graphite, N-doped expanded graphite, carbon black, amorphous carbon, carbon microspheres, hard carbon, meso-strong soft carbon, carbon nanotubes, graphene nanosheets, nitrogen-doped CNTs, N-doped graphene foam, N-doped porous nanofibers, microporous carbon and cube-shaped porous carbon; oxides include MnO2 nanoflowers, NiO nanosheets, porous SnO, porous SnO2 nanotubes, porous 3D Fe3O4-C, porous CuO-RGO, ultrasmall nitrogen-doped MnO-CNTs, CuS microflowers, SnS2-RGO, Co3S4-PANI, ZnS-RGO, NiS-RGO, Co3S4-PANI, MoS2-C, nitrogen-doped WS2-conductive carbon nanosheets, Sb3Se3-RGO nanorods, MoSe2-carbon fiber, multi-shell Sn4P3 nanostructures, Sn4P3-C, Se4P4 nanospheres, CoP nanoparticles, FeP nanorod arrays on carbon fabric, MoP-C, CUP2-C, graphene Hollow NiO / Ni, nitrogen-doped yellow-shell structured CoSe / C; Na metal.

1. Battery according to one of claims 24 to 27 in which when the cathode is made of LMNO then the anode is made of graphite or LTO; when the cathode is made of NMC532 then the anode is made of graphite; when the cathode is made of NMC622 then the anode is made of graphite; when the cathode is made of LFP then the anode is made of graphite; when the cathode is made of LFP then the anode is made of LTO.

Images