Aqueous composition of ionic liquid

Abstract

The invention relates to a composition comprising from 1 to 90% by weight of water, and comprising an ionic liquid comprising: an anion of formula (II): (II) in which R1 and R2 independently represent a fluorine atom or a perfluorinated group, and at least one onium cation, the composition having a total alkali and alkaline earth ion content less than or equal to 1000 ppm by weight. No figure.

Description

Title of the invention: Aqueous composition of ionic liquid Scope of the invention

[0001] The present invention relates to an aqueous composition of an ionic liquid comprising a bis(fluorosulfonyl)imide (FSI) anion, also known as a bis(fluorosulfonyl)imide, or a derivative thereof, and an onium cation, and having a low content of alkali and alkaline earth ions. This aqueous composition can be used as an intermediate composition for obtaining a high-purity ionic liquid. Technical background

[0002] Lithium (Li) batteries, such as lithium-ion batteries, are commonly used in electric vehicles and mobile and portable devices.

[0003] A lithium-ion battery or a lithium-sulfur battery comprises at least one negative electrode (anode), one positive electrode (cathode), an electrolyte, and preferably a separator. The electrolyte generally consists of a lithium salt dissolved in a solvent, which is usually a mixture of organic solvents, in order to achieve a good compromise between the viscosity and the dielectric constant of the electrolyte.

[0004] Additives can be added to improve the stability of electrolyte salts or passivation layers. Indeed, the passivation layers formed during the first charge-discharge cycles of a battery are crucial for battery lifespan. Examples of passivation layers include aluminum passivation, which is generally the current collector used at the cathode, and the solid-electrolyte interface (SEI), which is the inorganic and polymeric layer that forms at the anode / electrolyte and cathode / electrolyte interfaces. The stability of these interfaces is a key factor in improving battery lifespan.

[0005] Another major challenge is improving the overall safety of batteries, particularly for electric vehicle applications. Indeed, the flammability of the solvents used in electrolytes is a problem. Various solutions exist to avoid electrolyte flammability, such as the use of fluorinated solvents or ionic liquids.

[0006] The use of fluorinated solvents has the drawback of reducing the ionic conductivity of the electrolyte. Ionic liquids do not have this drawback; however, the use of significant quantities of ionic liquid is necessary to render the electrolyte non-flammable. Under these conditions, it is essential to use Ionic liquids exhibiting good electrochemical stability to obtain batteries with a sufficient lifespan.

[0007] In addition to the application of lithium batteries, ionic liquids can also be used in other applications. For example, document WO 2016 / 049391 describes ionic liquids, in particular for the treatment and cleaning of surfaces.

[0008] Documents EP 2162942, EP 2549577, WO 2018 / 172696, WO 2019 / 113406, US 10,446,875, EP 3503268 and the article by G. Girard et al. in Phys. Chem. Chem. Phys. 2015, 17, 8706-8713 describe various ionic liquids containing an anion such as FSI and their use in batteries.

[0009] It is known to manufacture an ionic liquid containing the FSI anion from potassium bis(fluorosulfonyl)imidide (KFSI), as taught in documents WO 99 / 40025, US 2009 / 0270286, WO 2018 / 172696 and US 2021 / 0194059.

[0010] Document WO 2020 / 241161 describes an electrolyte containing a sulfonylimide compound and an amidosulfuric acid compound.

[0011] Document WO 2019 / 229359 describes a process for manufacturing salts such as lithium bis(fluorosulfonyl)imide (LiFSI) from bis(fluorosulfonyl)imide (HFSI).

[0012] Document EP 3954651 describes an aqueous composition of LiFSI.

[0013] There is a need to supply ionic liquids that can be produced by relatively inexpensive methods and offer high performance, particularly when used as battery electrolytes. Summary of the invention

[0014] The invention relates primarily to a composition comprising from 1 to 90% by weight of water, and comprising an ionic liquid comprising: • an anion of formula (II):

[0015] [Chem.l] OO 1 II - Il 2 R—S—N—S—R OO (II)

[0016] wherein R1 and R2 independently represent a fluorine atom or a perfluorinated group, • and at least one onium cation,

[0017] the composition having a total content of alkali and alkaline earth ions less than or equal to 1000 ppm by weight.

[0018] In embodiments, the anion of formula (II) is the bis(fluorosulfonyl)imide anion or the bis(trifluoromethylsulfonyl)imide anion.

[0019] In embodiments, the onium cation is a quaternary ammonium ion, a pyridinium ion, an imidazolium ion, an oxazolidinium ion, a piperidinium ion, a phosphonium ion, a pyrrolidinium ion, a sulfonium ion and / or an oxonium ion.

[0020] In embodiments, the total content of alkali and alkaline earth ions is less than or equal to 100 ppm, preferably less than or equal to 20 ppm by weight.

[0021] In embodiments, the formula anion (II), the onium cation and water are present in the composition in a total quantity greater than or equal to 95% by weight, preferably greater than or equal to 98% by weight, preferably even greater than or equal to 99% by weight relative to the total weight of the composition.

[0022] In embodiments, the composition comprises from 5 to 50% by weight, preferably from 10 to 40% by weight of water.

[0023] The invention also relates to a method for preparing a composition as described above, comprising preparing the ionic liquid and then adding water to the ionic liquid.

[0024] The invention also relates to a method for preparing a composition as described above, comprising the preparation of the ionic liquid in the presence of water.

[0025] In embodiments of these processes, the preparation of the ionic liquid comprises the following steps: • supply of the compound of formula (I):

[0026] [Chem.2] OO 1 II II 2 R—S—NH—S—R II OO (I)

[0027] wherein R1 and R2 independently represent a fluorine atom or a perfluorinated group, • reaction of the compound of formula (I) with an onium cation precursor.

[0028] In some embodiments, the onium cation precursor is an onium cation halide, preferably an onium cation chloride or bromide.

[0029] In some embodiments, the preparation of the ionic liquid is carried out: • without organic solvents; and / or • with a compound molar ratio of formula (I) / onium cation precursor of 0.9 to 1.1, preferably of 1 to 1.05, preferably still of 1 to 1.01; and / or • at a temperature of 10 to 100°C, preferably 20 to 30°C.

[0030] In some embodiments, the process comprises the following step: • synthesis of the compound of formula (I), preferably by fluorination of a chlorinated compound and optionally by distillation.

[0031] The invention also relates to a method for preparing a purified ionic liquid comprising supplying the composition as described above, and removing at least some of the water from the composition.

[0032] In embodiments, at least 80% by weight, preferably at least 90% by weight, and even more preferably at least 99% by weight of the water is eliminated.

[0033] The invention also relates to a purified ionic liquid prepared by this process.

[0034] The invention also relates to an electrochemical cell comprising an electrode negative, a positive electrode and an electrolyte, wherein the electrolyte comprises the purified ionic liquid as described above; the negative electrode preferably comprising graphite.

[0035] The invention also relates to a battery comprising at least this electrochemical cell.

[0036] The invention also relates to a capacitor comprising a casing, at least one pair of positive and negative electrodes separated by a separator, and an electrolyte in the casing, in which the electrolyte comprises the purified ionic liquid as described above.

[0037] The present invention addresses the need expressed above. More particularly, it provides an intermediate aqueous composition for obtaining a purified ionic liquid with high performance, especially when used as a battery electrolyte, with simple and inexpensive recovery and / or purification steps.

[0038] The use of the intermediate aqueous composition of the invention makes it possible in particular to reduce the content of ionic impurities in the purified ionic liquid, preferably by removal of the aqueous phase, including decantation or any other form of separation.

[0039] Furthermore, the aqueous nature of the composition limits emissions of volatile organic compounds (VOCs) by avoiding the use of organic solvents. It also provides safety guarantees by allowing the absorption of heat, thus generating a lower temperature rise compared to a pure ionic liquid or a mixture of ionic liquid and organic solvent during preparation.

[0040] Advantageously, the ionic liquid of the invention is produced without proceeding with an ion exchange from a reagent such as KFSI or LiFSI, which is costly and liable to give rise to contamination by cations such as K+ or Li+.

[0041] Advantageously, the purified ionic liquid of the invention makes it possible to improve the quality of the SEI, in particular in a lithium-ion battery with a graphite-based anode.

[0042] Advantageously, the purified ionic liquid of the invention improves coulombic efficiency after the formation of the SEI and increases the lifespan of a battery (i.e., increases the number of cycles required to retain at least 80% of the battery's initial capacity). Similarly, the lifespan of any other electrochemical device (such as a capacitor) containing the ionic liquid can be increased.

[0043] Advantageously, a battery (or any other electrochemical device) incorporating the purified ionic liquid of the invention has increased safety (due to low flammability) and exhibits good performance even at high charge and discharge rates. Detailed description

[0044] The invention is now described in more detail and in a non-limiting manner in the following description.

[0045] Unless otherwise indicated, all percentages and proportions are mass percentages and proportions and all ratios between two quantities are mass ratios. Aqueous composition

[0046] The invention relates primarily to a composition comprising an ionic liquid and water.

[0047] The total water and ionic liquid content in the composition is preferably greater than or equal to 95%, or 98%, or 99%, or 99.5%, or 99.8%, by weight. In some embodiments, the total water and ionic liquid content is 95% to 99.99%, preferably 98% to 99.95%, and even more preferably 99% to 99.90%, by weight.

[0048] The water content in the composition is preferably from 1 to 90%, more preferably from 5 to 50% by weight, more preferably from 10 to 40% by weight. The water content in the composition may be from 1 to 10%, or from 10 to 20%, or from 20 to 30%, or from 30 to 40%, or from 40 to 50%, or from 50 to 60%, or from 60 to 70%, or from 70 to 80%, or from 80 to 90% by weight.

[0049] The composition has a total alkali and alkaline earth ion content that may be less than or equal to 1000 ppm, preferably less than or equal to 500 ppm, or 200 ppm, or 100 ppm, or 50 ppm, or 20 ppm, or 10 ppm, or 5 ppm by weight. In some embodiments, the composition is essentially devoid of alkali and alkaline earth ions, or these ions may be present in a quantity greater than or equal to 0.1 ppm by weight. In some embodiments, the total content of alkali and alkaline earth ions is from 0.1 to 1000 ppm, or from 0.2 to 200 ppm, or from 0.3 to 20 ppm, or from 0.4 to 10 ppm by weight.

[0050] Advantageously, the composition comprises Na+ ions in an amount less than or equal to 100 ppm, preferably less than or equal to 50 ppm, preferably less than or equal to 20 ppm, in some cases less than or equal to 10 ppm or 5 ppm by weight. The Na+ ions may be essentially absent or present in an amount greater than or equal to 0.1 ppm by weight. For example, the Na+ ions may be present in an amount of 0.1 to 100 ppm, or 0.1 to 50 ppm, or 0.1 to 20 ppm, or 0.1 to 10 ppm, or 0.1 to 5 ppm, by weight.

[0051] Advantageously, the composition comprises K+ ions in an amount less than or equal to 100 ppm, preferably less than or equal to 50 ppm, preferably less than or equal to 20 ppm, in some cases less than or equal to 10 ppm or 5 ppm by weight. The K+ ions may be essentially absent or present in an amount greater than or equal to 0.1 ppm by weight. For example, the K+ ions may be present in an amount of 0.1 to 100 ppm, or 0.2 to 50 ppm, or 0.3 to 20 ppm, or 0.4 to 10 ppm, or 0.5 to 5 ppm, by weight.

[0052] Advantageously, the composition comprises Li+ ions in an amount less than or equal to 100 ppm, preferably less than or equal to 50 ppm, preferably less than or equal to 20 ppm, in some cases less than or equal to 10 ppm or 5 ppm by weight. The Li+ ions may be essentially absent or present in an amount greater than or equal to 0.1 ppm by weight. For example, the Li+ ions may be present in an amount of 0.1 to 100 ppm, or 0.2 to 50 ppm, or 0.3 to 20 ppm, or 0.4 to 10 ppm, or 0.5 to 5 ppm, by weight.

[0053] In embodiments, the composition may include one or more other anions and / or one or more other cations.

[0054] The composition may, in addition to the pennant of formula (II), comprise at least one other anion selected from F, Cf, Br, I, NO3, M(R*)4, A(R')6, R2 O2, [R2ONZ'], [R2YOCZ2Z3], 4,5-dicyano-1,2,3-triazolate, 3,5-bis(RF)-1,2,4-triazolate, tricyanomethanide, pentacyanocyclopentadienide, pentakis(trifluoromethyl)cyclopentadienide, wherein: • M is B, Al, Ga or Bi; • A is P, As or Sb; • R1 is a halogen; • R2 represents H, F, an alkyl, alkenyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, dialkylamino, alkoxy or thioalkoxy group, each having from 1 to 18 carbon atoms and being unsubstituted or substituted by one or more oxa, thia, or aza substituents, and in which one or more hydrogen atoms are optionally replaced by a halogen in a proportion of 0 to 100%, and which may possibly be part of a polymer chain; • Y representing C, SO, S=NCN, S=C(CN)2, POR2, P(NCN)R2, P(C(CN)2)R2, an alkyl, alkenyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl group having from 1 to 18 carbon atoms and optionally substituted by one or more oxa, thia or aza substituents; a dialkylamino N(R*)2 group; • Z1 to Z3 independently represent R2, R2YO or CN, this grouping optionally being part of a polymer chain; • RF is a perfluorinated or partially fluorinated alkyl chain containing 1 to 8 carbon atoms, or a phenyl, substituted phenyl, pyridyl or substituted pyridyl group.

[0055] The composition may have a weight content of sulfamate ion (NH2SO3) less than or equal to 5000 ppm; less than or equal to 3000 ppm; less than or equal to 2000 ppm; less than or equal to 1000 ppm; less than or equal to 500 ppm; less than or equal to 300 ppm; less than or equal to 200 ppm; less than or equal to 100 ppm; less than or equal to 50 ppm; less than or equal to 20 ppm.

[0056] The composition may in particular include a sulfamate ion content of 0.1 to 5000 ppm, preferably of 0.5 to 3000 ppm, preferably still of 1 to 1000 ppm, preferably still of 10 to 300 ppm by weight.

[0057] The composition may in particular include a sulfamate ion content of 0.1 to 10 ppm; 10 to 50 ppm; 50 to 100 ppm; 100 to 200 ppm; 200 to 300 ppm; 300 to 500 ppm; 500 to 1000 ppm; 1000 to 2000 ppm; 2000 to 3000 ppm; 3000 to 5000 ppm.

[0058] The sulfamate ion content indicated above can allow optimal performance to be obtained, in particular when the purified ionic liquid obtained from the aqueous composition is used in a battery electrolyte.

[0059] Advantageously, the composition comprises F ions in an amount less than or equal to 500 ppm, preferably less than or equal to 200 ppm, preferably less than or equal to 100 ppm, in some cases less than or equal to 50 ppm or 20 ppm by weight. The F ions may be essentially absent or present in an amount greater than or equal to 0.1 ppm, 1 ppm, 2 ppm, 5 ppm, or 10 ppm by weight. For example, the F ions may be present in an amount of 0.1 to 500 ppm, or 1 to 200 ppm, or 2 to 100 ppm, or 5 to 50 ppm, or 10 to 20 ppm, by weight.

[0060] Advantageously, the composition comprises Cl ions in an amount less than or equal to 500 ppm, preferably less than or equal to 200 ppm, preferably less than or equal to 100 ppm, in some cases less than or equal to 50 ppm or 20 ppm by weight. Cf ions may be essentially absent or present in an amount greater than or equal to 0.1 ppm, 1 ppm, 2 ppm, 5 ppm, or 10 ppm by weight. For example, Cf ions may be present in an amount of 0.1 to 500 ppm, or 1 to 200 ppm, or 2 to 100 ppm, or 5 to 50 ppm, or 10 to 20 ppm, by weight.

[0061] Advantageously, the composition comprises SO42 ions in an amount less than or equal to 500 ppm, preferably less than or equal to 200 ppm, preferably less than or equal to 100 ppm, in some cases less than or equal to 50 ppm or 20 ppm by weight. The SO42 ions may be essentially absent or present in an amount greater than or equal to 0.1 ppm, 1 ppm, 2 ppm, 5 ppm, or 10 ppm by weight. For example, the SO42 ions may be present in an amount of 0.1 to 500 ppm, or 1 to 200 ppm, or 2 to 100 ppm, or 5 to 50 ppm, or 10 to 20 ppm, by weight.

[0062] The ion content, and in particular the alkali or alkaline earth ion content, in the composition can be analyzed by ion chromatography and / or by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-AES) and / or by X-ray fluorescence spectrometry (XRF). Ionic liquid

[0063] The ionic liquid contained in the aqueous composition comprises at least one anion of formula (II):

[0064] [Chem.3] OO 1 II - Il 2 R—S—N—S—R OO (II)

[0065] and at least one onium cation.

[0066] Ionic liquids are salts having a melting point below 100 °C and preferably below ambient temperature (i.e., a temperature ranging from 15 to 35 °C). Thus, an "ionic liquid" is understood to mean a salt, that is, an ionic compound comprising at least one anion and one cation, present in liquid form at a temperature of 100 °C. An ionic liquid comprises only ionic species (cations and anions), with the exception of the presence of possible non-ionic impurities. Thus, in the sense of the present invention, an ionic liquid comprises at least 90% by weight, preferably at least 95% by weight, preferably still at least 98% by weight, preferably still at least 99% by weight, even more preferably at least 99.5% by weight, even more preferably greater than or equal to 99.9% by weight, of ionic species.

[0067] In formula (II), R1 and R2 independently represent a fluorine atom or a perfluorinated group, which preferably comprises from 1 to 8 carbon atoms, more preferably from 1 to 3 carbon atoms, and which more preferably is the trifluoromethyl group.

[0068] In some embodiments, several anions of formula (II) may be present, but preferably only one anion of formula (II) is present. Preferably, the anion of formula (II) is the bis(fluorosulfonyl)imide or bis(fluorosulfonyl)imidide anion, also called the FSI anion; and / or the bis(trifluoromethylsulfonyl)imide or bis(trifluoromethylsulfonyl)imide anion, also called TFSI. Even more preferably, it is the FSI anion.

[0069] The ionic liquid according to the invention comprises an onium cation. In some embodiments, several onium cations may be present, but preferably, only one onium cation is present.

[0070] In the whole of what follows, it is understood that the reference to the anion of formula (II) in the singular, respectively to the onium cation in the singular, may be a reference to a plurality of anions of formula (II), respectively of onium cations.

[0071] Preferably, the onium cation is chosen from the group consisting of quaternary ammonium ions, pyridinium ions, imidazolium ions, oxazolidinium ions, piperidinium ions, phosphonium ions, pyrrolidinium ions, sulfonium ions, oxonium ions and mixtures thereof.

[0072] Advantageously, the quaternary ammonium ion is an ion of formula NR / , in which each R independently represents a hydrogen atom or an alkyl chain of 1 to 14 carbon atoms optionally comprising one or more heteroatoms such as heteroatoms N, O, S and / or Si.

[0073] The term "pyridinium ion" means the ion with the molecular formula C5H5NH+ and the structural formula:

[0074] [Chem.4] H

[0075] as well as its derivatives, that is to say the ions in which this formula is modified in that one or more hydrogen atoms are substituted by a group, preferably an alkyl chain optionally comprising one or more heteroatoms such as N, O, S and / or Si heteroatoms, preferably still comprising from 1 to 14 carbon atoms.

[0076] The term "imidazolium ion" means the ion with the molecular formula C3H5N2+ and the structural formula:

[0077] [Chem.5]

[0078] as well as its derivatives, that is to say the ions in which this formula is modified in that one or more hydrogen atoms are substituted by a group, preferably an alkyl chain optionally comprising one or more heteroatoms such as N, O, S and / or Si heteroatoms, preferably still comprising from 1 to 14 carbon atoms.

[0079] The term "oxazolidinium ion" means the ion with the molecular formula C3H8NO+ and the structural formula:

[0080] [Chem.6] H2

[0081] as well as its derivatives, that is to say the ions in which this formula is modified in that one or more hydrogen atoms are substituted by a group, preferably an alkyl chain optionally comprising one or more heteroatoms such as N, O, S and / or Si heteroatoms, preferably still comprising from 1 to 14 carbon atoms.

[0082] The term “piperidinium ion” means the ion with the molecular formula C5Hi2N+ and the structural formula:

[0083] [Chem.7] H2

[0084] as well as its derivatives, that is to say the ions in which this formula is modified in that one or more hydrogen atoms are substituted by a group, preferably an alkyl chain optionally comprising one or more heteroatoms such as N, O, S and / or Si heteroatoms, preferably still comprising from 1 to 14 carbon atoms.

[0085] By "phosphonium ion" is meant the ion of formula PR4+, in which each R independently represents a hydrogen atom or an alkyl chain, preferably of 1 to 14 carbon atoms, optionally comprising one or more heteroatoms such as heteroatoms N, O, S and / or Si.

[0086] By "pyrrolidinium ion", we mean the ion with the molecular formula C4HiON+ and the structural formula:

[0087] [Chem. 8] H2

[0088] as well as its derivatives, that is to say the ions in which this formula is modified in that one or more hydrogen atoms are substituted by a group, preferably an alkyl chain optionally comprising one or more heteroatoms such as N, O, S and / or Si heteroatoms, preferably still comprising from 1 to 14 carbon atoms.

[0089] By "sulfonium ion" is meant the ion of formula SR3+, in which each R independently represents a hydrogen atom or an alkyl chain, preferably of 1 to 14 carbon atoms, optionally comprising one or more heteroatoms such as heteroatoms N, O, S and / or Si.

[0090] By "oxonium ion" is meant the ion of formula OR3+, in which each R independently represents a hydrogen atom or an alkyl chain, preferably of 1 to 14 carbon atoms, optionally comprising one or more heteroatoms such as heteroatoms N, O, S and / or Si.

[0091] Preferred onium cations are: EMIM (l-ethyl-3-methylimidazolium), BMIM (l-butyl-3-methylimidazolium), PYR14 (1-butyl-l-methylpyrrolidinium), PYR13 (l-propyl-3-methylpyrrolidinium), PIP14 (1-butyl-l-methylpiperidinium), PIP13 (1-methyl-l-propylpiperidinium), P1444 (methyl(tri-n-butyl)phosphonium), P1222 (methyl(tri-n-ethyl)phosphonium).

[0092] Thus, among the preferred ionic liquids, we can mention EMIM-FSI (1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide), BMIM-TFSI (1-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-1-propylpiperidinium bis(fluorosulfonyl)imide), P1444-FSI (methyl(tri-n-butyl)phosphonium bis(fluorosulfonyl)imide) and P1222-FSI (methyl(tri-n-ethyl l)phosphonium bis (fluorosulfonyl)imide). General scheme for preparing the ionic liquid

[0093] The ionic liquid can be prepared by a process comprising the following steps: • optionally, synthesis of the compound of formula (I):

[0094] [Chem.9] OO 1 II H 2 R—S—NH—S— R OO (I) • reaction of the compound of formula (I) with an onium cation precursor to obtain a reaction mixture comprising the compound of formula (II); • Optionally, purification of the reaction mixture.

[0095] In formula (I), R1 and R2 have the same meaning as in formula (II).

[0096] In particular, when R1 = R2 = F, the compound of formula (I) is the bis(fluorosulfonyl)imide or HFSI (which allows obtaining an ionic liquid including the FSI anion).

[0097] In particular, when R1 = R2 = CF3, the compound of formula (I) is bis(trifluoromethylsulfonyl)imide (which makes it possible to obtain an ionic liquid comprising the TFSI anion). Synthesis of the compound with formula (I)

[0098] The compound of formula (I) can be synthesized, in particular, by fluorinating a chlorinated compound. The chlorinated compound has the same structure as the compound of formula (I), except that R1 and R2 independently represent a halogen atom (F or Cl) or a perhalogenated group, which preferably comprises from 1 to 8 carbon atoms, more preferably from 1 to 3 carbon atoms, and which is preferably the trihalomethyl group, provided that the chlorinated compound comprises at least one chlorine atom. Preferably, the chlorinated compound has formula (I), R1 and R2 independently represent a chlorine atom or a perchlorinated group, which preferably comprises from 1 to 8 carbon atoms. preferably still of 1 to 3 carbon atoms, and which preferably is the trichloromethyl group.

[0099] In particular, the chlorinated compound can be (bis(chlorosulfonyl)imide), which allows the HFSI to be obtained.

[0100] In particular, the chlorinated compound can be (bis(trichloromethylsulfonyl)imide), which allows the bis(trifluoromethylsulfonyl)imide to be obtained.

[0101] Fluoridation is carried out by contacting the chlorinated compound with a fluorinating agent, which is preferably selected from the group consisting of HF (preferably anhydrous HF), KF, AsF3, BiF3, ZnF2, SnF2, PbF2, CuF2, and mixtures thereof, the fluorinating agent preferably being HF, and even more preferably anhydrous HF. By "anhydrous HF" is meant HF containing less than 500 ppm of water, preferably less than 300 ppm of water, and more preferably less than 200 ppm of water.

[0102] Fluorination is preferably carried out in at least one organic solvent SOL. The organic solvent SOI preferably has a donor number between 1 and 70 and advantageously between 5 and 65. The donor number of a solvent represents the value -AH, where AH is the enthalpy of the interaction between the solvent and antimony pentachloride (according to the method described in Journal of Solution Chemistry, vol. 13, no. 9, 1984). Examples of organic solvents SOI include esters, nitriles, dinitriles, ethers, diethers, amines, phosphines, and mixtures thereof.

[0103] Preferably, the organic solvent SOI is selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate, acetonitrile, propionitrile, isobutyronitrile, glutaronitrile, dioxane, tetrahydrofuran, triethylamine, tripropylamine, diethylisopropylamine, pyridine, trimethylphosphine, triethylphosphine, diethylisopropylphosphine, and mixtures thereof. In particular, the organic solvent SOI is dioxane.

[0104] Fluorination can be carried out at a temperature between 0°C and the boiling point of the organic solvent SOI (or the mixture of organic solvents SOI). Preferably, step b) is carried out at a temperature between 5°C and the boiling point of the organic solvent SOI (or the mixture of organic solvents SOI), preferably between 20°C and the boiling point of the organic solvent SOI (or the mixture of organic solvents SOI).

[0105] Fluoridation, preferably with anhydrous hydrofluoric acid, can be carried out at a pressure between 0 and 16 bar abs.

[0106] Fluorination is preferably carried out by dissolving the chlorinated compound in the organic solvent SOI, or the mixture of organic solvents SOI, before the reaction with the fluorinating agent (preferably anhydrous HF).

[0107] The mass ratio between the chlorinated compound and the organic solvent SOI, or the mixture of organic solvents SOI, is preferably between 0.001 and 10, and advantageously between 0.005 and 5.

[0108] According to one embodiment, anhydrous HF is introduced into the reaction medium, preferably in gaseous form.

[0109] The molar ratio between the fluorinating agent, preferably anhydrous HF, and the chlorinated compound is preferably between 1 and 10, and advantageously between 1 and 5.

[0110] The reaction with the fluorinating agent, preferably anhydrous HF, can be carried out in a closed environment or in an open environment, preferably in an open environment with in particular the release of HCl in gaseous form.

[0111] The fluorination reaction typically leads to the formation of HCl, the majority of which can be degassed from the reaction medium (as can excess HF if the fluorinating agent is HF), for example by stripping with a neutral gas (such as nitrogen, helium or argon).

[0112] However, residual HF and / or HCl may be dissolved in the reaction medium. In the case of HCl, the quantities are very small because at the working pressures and temperatures, HCl is mainly in gaseous form.

[0113] The product obtained at the end of the fluorination reaction can be stored in a container resistant to HF.

[0114] The product obtained at the end of the fluorination reaction may include HF (in particular unreacted HF), the chlorinated compound, the solvent SOI (such as, for example, dioxane), and possibly HCl, and / or possibly heavy compounds.

[0115] After the reaction, the compound of formula (I) can be purified, in particular by one or more distillation steps.

[0116] According to one embodiment, the distillation step allows the formation and recovery of: • a first stream Fl comprising HF, possibly the organic solvent SOI and / or possibly HCl, preferably at the top of the distillation column, said stream Fl being gaseous or liquid; • a second stream F2 comprising the compound of formula (I), and possibly heavy compounds, preferably at the bottom of the distillation column, said stream F2 being preferably liquid.

[0117] When the F2 stream contains heavy compounds, it can be subjected to an additional distillation step in a second distillation column, to form and recover: • a stream F2-1 comprising the compound of formula (I) free from heavy compounds, preferably at the top of the distillation column, said stream F2-1 being preferably liquid, • a F2-2 stream comprising the heavy compounds and the compound of formula (I), preferably at the bottom of the distillation column, said F2-2 stream containing less than 10% by weight of the compound of formula (I) contained in the composition obtained in step b), preferably less than 7% by weight, and preferably less than 5% by weight, said F2-2 stream being preferably liquid.

[0118] By "heavy compounds" we mean organic compounds having a boiling point higher than that of the compound of formula (I). They may result from cleavage reactions of the chlorinated compound leading for example to compounds such as FSO2NH2, and / or from solvent degradation reactions leading to the formation of oligomers.

[0119] According to one embodiment, the distillation step allows the formation and recovery of: • a first stream F' 1 comprising HF, possibly the organic solvent SOI and / or possibly HCl, preferably at the top of the distillation column, said stream F' 1 being gaseous or liquid; • a second stream F'2 comprising the compound of formula (I), preferably recovered by lateral withdrawal, said stream F'2 being preferably liquid; • a third stream F'3 comprising heavy compounds and the compound of formula (I), preferably at the bottom of the distillation column, said stream F'3 containing less than 10% by weight of the compound of formula (II) contained in the composition obtained in step b), preferably less than 7% by weight, and preferably less than 5% by weight, said stream F'3 being preferably liquid.

[0120] To perform the lateral drawing-off, the distillation column may contain at least one tray.

[0121] The distillation step can be carried out at a pressure ranging from 0 to 5 bar abs, preferably from 0 to 3 bar abs, preferably from 0 to 2 bar abs, and advantageously from 0 to 1 bar abs.

[0122] The distillation step can be carried out in any conventional apparatus. This may be a distillation apparatus comprising a distillation column, a boiler, and a condenser. The distillation column may include at least one packing, such as, for example, a bulk packing and / or a structured packing, and / or trays, such as, for example, perforated trays, trays with fixed flaps, trays with movable flaps, cap trays, or combinations thereof.

[0123] Following purification, the compound of formula (I) can be recovered with high purity. The use of a compound of formula (I) of high purity advantageously allows the preparation of a high-purity ionic liquid, avoiding complex subsequent purification steps.

[0124] The collected product (and / or used for the reaction with the onium cation precursor) thus preferably comprises at least 95% by weight of compound of formula (I), preferably still at least 98% by weight, at least 99% by weight, at least 99.5% by weight or even at least 99.8% by weight of compound of formula (I).

[0125] The collected product (and / or the product used for the reaction with the onium cation precursor) preferably has a sulfamic acid content of 5000 ppm or less, preferably 4000 ppm or less, 3000 ppm or less, 2500 ppm or less, or even 2000 ppm or less, by weight. In some cases, the sulfamic acid may be essentially absent, or present at a concentration of at least 1 ppm by weight. The sulfamic acid content may, in particular, be from 1 to 5000 ppm, from 10 to 4000 ppm, from 100 to 3000 ppm, or from 500 to 2500 ppm by weight. It can be, for example, 1 to 10 ppm, 10 to 50 ppm, 50 to 100 ppm, 100 to 200 ppm, 200 to 500 ppm, 500 to 1000 ppm, 1000 to 2000 ppm, 2000 to 3000 ppm, 3000 to 4000 ppm, or 4000 to 5000 ppm by weight. The sulfamic acid content can be determined by ion chromatography (expressed as NH2SO3).

[0126] For ion chromatography measurements, the THERMO brand "ICS 5000" instrument can be used. It has two analytical channels, one of which is dedicated to anion analysis and consists of: • an ultra-pure water supply (18.2 Mohm) via a double piston pump; • an automatic eluent generator (EGC); • a valve with injection loop (volume = 25 microlitres); • a pre-column (AG19, T=35°C) and a separation column (AS 19, T=20°C); • a suppressor (AERS 62 mA); • a conductivity meter for detecting peaks.

[0127] The eluent used may be a KOH solution at a concentration of 25 mmol / L and may have a flow rate of 1 mL / min.

[0128] Reaction of the compound of formula (I) with the onium cation precursor and obtaining the aqueous composition

[0129] By "onium cation precursor" is meant any compound capable of reacting with the compound of formula (I) to give the anion of formula (II) associated with the onium cation.

[0130] In particular, the onium cation precursor may be an onium cation halide, i.e. the compound AX, in which A represents a halogen atom and X+ represents the onium cation. Preferably, the precursor is a chloride or a bromide (A is Cl or Br).

[0131] In this case, the reaction with the compound of formula (I) produces, in addition to the ionic liquid composed of the anion of formula (II) and the onium cation, a co-product of formula HA (preferably HCl or HBr).

[0132] The reaction is preferably carried out in the absence (or essentially in the absence) of an organic solvent and optionally in the presence of water. The mass ratio of water to the onium cation precursor can be, for example, from 0.02 to 6, preferably from 0.5 to 5, preferably from 1 to 4, and preferably again from 1.5 to 3.

[0133] Water may in particular be present in the reaction medium in an amount of 1% to 90%, preferably 2% to 80%, preferably still 5% to 70%, or 10% to 60%, by weight, relative to the total weight of the precursor of the onium cation and the compound of formula (I).

[0134] The molar ratio of the compound of formula (I) in the presence of the onium cation precursor is preferably from 0.9 to 1.1, more preferably from 1 to 1.05, more preferably from 1 to 1.01.

[0135] The temperature of the reaction medium is preferably from 10 to 100°C, more preferably from 20 to 30°C.

[0136] In some embodiments, the onium cation precursor is poured molten onto the compound of formula (I) and maintained at a desired temperature.

[0137] In other embodiments, the compound of formula (I) is added molten to the onium cation precursor rendered in liquid form by the addition of water.

[0138] The progress of the reaction can be monitored by the release of co-product, in particular of formula HA.

[0139] The ionic liquid is thus obtained with a high yield, preferably greater than or equal to 70%.

[0140] When water is present during the reaction, an aqueous composition such as described above can be directly obtained at the end of the reaction.

[0141] Alternatively, an aqueous composition such as described above can be obtained by preparing the ionic liquid in the absence of water, and subsequently adding water.

[0142] Alternatively, an aqueous composition such as described above can be obtained by preparing the ionic liquid in the presence of water, and subsequently adding an additional quantity of water.

[0143] The water present or added in any of these embodiments may be in the form of an aqueous solution (water containing one or more dissolved species), or preferably in the form of demineralized water.

[0144] After the reaction, the reaction medium containing the ionic liquid can be purified, for example, by washing, decantation (or any other aqueous phase separation), and drying, at atmospheric pressure or preferably under vacuum. A decolorization step may also be included, for example, by contact with activated carbon. However, in preferred embodiments, no decolorization step is included.

[0145] When decolorization is carried out, it can be achieved by contacting the ionic liquid with activated carbon, with a mass ratio of activated carbon to ionic liquid advantageously of 0.05 to 0.5, preferably 0.1 to 0.5. The activated carbon may, for example, have a specific surface area greater than 300 m² / g, or even greater than 1000 m² / g, measured by the BET method by nitrogen adsorption. The duration of contact may be, in particular, from 1 to 72 h, preferably from 5 to 48 h. The temperature during contact may range from 10°C up to the boiling point of any solvent that may be present with the ionic liquid; or it may be a temperature higher than the melting point of the ionic liquid in the absence of solvent.After the decolorization step, the activated carbon can be separated from the decolorized ionic liquid, for example by filtration, for example using a polytetrafluoroethylene or poly(vinylidene fluoride) membrane or a cellulose membrane, or a filter medium (silica, alumina, diatomaceous earth).

[0146] The washing can be aqueous, that is to say, a step involving contacting the ionic liquid with water. Thus, the addition of water to obtain a composition such as that described above can be carried out during a washing step.

[0147] The ionic liquid undergoing the aqueous wash(s) may be pre-dissolved in a polar organic solvent insoluble in water. Preferably, the polar organic solvent insoluble in water is chosen from the group consisting of butyl acetate, ethyl acetate, tert-butyl acetate, butyronitrile, isobutyronitrile, glutaronitrile, diethyl ether, cyclopentyl methyl ether, tetrahydrofuran, methylisobutyl ketone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbon, and propylene carbonate.

[0148] Preferably, however, no organic solvent is used at this stage.

[0149] The aqueous wash(s) make it possible to reduce and eliminate impurities present in the ionic liquid, such as chloride ions, fluoride ions, sulfate ions, sulfamate ions and others.

[0150] During each aqueous wash, the mass ratio of the aqueous wash solution, preferably demineralized water, to the ionic liquid is preferably from 0.01 to 2, for example from 0.01 to 0.05, or from 0.05 to 0.1, or from 0.1 to 0.5, or from 0.5 to 1, or from 1 to 2, or from 2 to 5. A ratio of 0.1 to 0.5 may be preferred.

[0151] The duration of contact between the ionic liquid and the aqueous washing solution can vary from 1 second to 24 hours. In particular, it can be from 1 second to 1 minute, or from 1 minute to 10 minutes, or from 10 minutes to 30 minutes, or from 30 minutes to 1 hour, or from 1 hour to 2 hours, or from 2 hours to 3 hours, or from 3 hours to 4 hours, or from 4 hours to 5 hours, or from 5 hours to 6 hours, or from 6 hours to 12 hours, or from 12 hours to 24 hours. For the shortest contact times, a static mixer can be used.

[0152] The washing can be followed by decantation to separate the aqueous phase from the organic phase. The organic phase is enriched in ionic liquid and depleted in impurities (e.g., depleted in chloride, fluoride, sulfate, sulfamate ions, etc.), meaning that in the organic phase, the ratio of molar concentrations of ionic liquid to impurities (in particular chloride, fluoride, sulfate, and sulfamate ions) is greater than that of the initial ionic liquid. The aqueous phase is enriched in impurities (e.g., enriched in chloride, fluoride, sulfate, and sulfamate ions), meaning that in the aqueous phase, the ratio of molar concentrations of ionic liquid to impurities (in particular chloride, fluoride, sulfate, and sulfamate ions) is less than that of the initial ionic liquid. The aqueous phase can then be removed.

[0153] Several aqueous washes may be carried out, in particular from two to eleven aqueous washes (for example, two, or three, or four, or five, or ten washes). When several washes are carried out, each may independently be as described above. Preferably, the subsequent wash is carried out on the organic phase obtained, after decantation, at the end of the preceding wash.

[0154] At the end of this or these steps, the solvent of the organic phase, if present, can be removed, for example by evaporation of the solvent, preferably under reduced pressure.

[0155] The product obtained can be characterized by nuclear magnetic resonance, by Karl Fisher type analysis for its water content and by ion chromatography for its anion and cation content. Purified ionic liquid

[0156] The purified ionic liquid is defined as the ionic liquid obtained from the aqueous composition described above, by removing the water, and possibly any other complementary treatment step. Preferably, at least 90% by weight, and even more preferably at least 95% or 99% by weight, of the water is removed. This removal can be carried out by decantation and / or drying as described above.

[0157] Optional additional treatment steps may include one or more washing steps (for example by adding water), decantation and / or drying as described above.

[0158] The purified ionic liquid may have a total content of formula (II) anion and onium cation greater than or equal to 97% by weight, 98% by weight, preferably greater than or equal to 99% by weight, and preferably greater than or equal to 99.5% by weight relative to the total weight of the composition. The total content of formula (II) anion and onium cation may be less than or equal to 99.99% by weight, for example, less than or equal to 99.95% by weight or less than or equal to 99.90% by weight. The total content of formula (II) anion and onium cation may be from 97% to 99.99% by weight, preferably from 98% to 99.95% by weight, and preferably from 99% to 99.90% by weight.

[0159] The purified ionic liquid may have a total water content of 3% or less by weight, preferably 2% or less, or 1%, or 1000 ppm, or 500 ppm, or 200 ppm by weight. The purified ionic liquid may have a total water content of 0.1 ppm or more, preferably 1 ppm or more, or 5 ppm, or 10 ppm by weight. The purified ionic liquid may have a total water content of 0.1 ppm to 3%, preferably 1 ppm to 1000 ppm, or 5 ppm to 500 ppm, or 10 ppm to 200 ppm by weight.

[0160] The purified ionic liquid may contain alkali and alkaline-earth ions, and possibly other anions and / or cations, which may be in the ranges already set out above in relation to the aqueous composition.

[0161] When the purified ionic liquid is obtained directly by decantation and optionally drying from an aqueous composition according to the invention, a reduction in the ion content (other than the anion of formula (II) and the onium cation) can be obtained.

[0162] More specifically, the ratio of the total ion content (other than Fanion of formula (II) and the onium cation) in the aqueous composition to the total ion content (other than Fanion of formula (II) and the onium cation) in the purified ionic liquid may be greater than or equal to 1.5, preferably greater than or equal to 2, for example greater than or equal to 3 or 5. The ratio of the fluoride ion content in the aqueous composition to the fluoride ion content in the purified ionic liquid may be greater than or equal to 1.5, preferably greater than or equal to 2, for example greater than or equal to 3 or 5. The ratio of the chloride ion content in the aqueous composition to the chloride ion content in the purified ionic liquid may be greater than or equal to 1.5, preferably greater than or equal to 2, for example greater than or equal to 3 or 5.The ratio of the sulfate ion content in the aqueous composition to the sulfate ion content in the purified ionic liquid may be greater than or equal to 1.5, preferably greater than or equal to 2, for example greater than or equal to 3 or 5, or even 10. Electrochemical cell and battery

[0163] The invention also relates to an electrolyte comprising a purified ionic liquid as described above and at least one other component selected from metallic salts, polar polymers and / or aprotic solvents.

[0164] The metallic salt preferably comprises as a cation the hydrogen cation, the cation of an alkali metal, an alkaline earth metal, a transition metal or a rare earth, lithium being particularly preferred.

[0165] By way of non-limiting examples, the lithium salt (or lithium salts) may be selected from LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imidide), LiTDI (lithium 2-trifluoromethyl-4,5-dicyanoimidazolate), LiPOF2, LiB(C2O4)2, LiF2B(C2O4)2, LiBF4, LiNO3, LiC104.

[0166] The polar polymer preferably comprises monomeric units derived from ethylene oxide, propylene oxide, epichlorohydrin, epifluorohydrin, trifluoroepoxypropane, acrylonitrile, methacrylonitrile, esters and amides of acrylic and methacrylic acid, vinylidene fluoride, N-methylpyrrolidone, and / or polycation or polyanion-type electrolytes. When the present electrolytic composition comprises more than one polymer, at least one of them may be crosslinked.

[0167] The aprotic solvent(s) may be chosen from the following non-exhaustive list: ethers, esters, ketones, alcohols, nitriles, carbonates, amides, sulfonamides and their mixtures.

[0168] Among the ethers, one can cite linear or cyclic ethers, such as for example dimethoxyethane (DME), methyl ethers of oligoethylene glycols of 2 to 5 oxyethylene units, dioxolane, dioxane, dibutyl ether, tetrahydrofuran, and their mixtures.

[0169] Examples of esters include phosphoric acid esters and sulfite esters. Examples include methyl formate, methyl acetate, methyl propionate, ethyl acetate, butyl acetate, gamma butyrolactone, or mixtures thereof.

[0170] Among the ketones, cyclohexanone can be mentioned in particular.

[0171] Examples of alcohols include ethyl alcohol, alcohol isopropyl.

[0172] Examples of nitriles include acetonitrile, pyruvonitrile, propionitrile, methoxypropionitrile, dimethylaminopropionitrile, butyronitrile, isobutyronitrile, valeronitrile, pivalonitrile, isovaleronitrile, glutaronitrile, methoxyglutaronitrile, 2-methylglutaronitrile, 3-methylglutaronitrile, adiponitrile, malononitrile, 1,2,6-tricyanohexane and mixtures thereof.

[0173] Examples of carbonates include cyclic carbonates such as ethylene carbonate (EC) (CAS: 96-49-1), propylene carbonate (PC) (CAS: 108-32-7), butylene carbonate (BC) (CAS: 4437-85-8), dimethyl carbonate (DMC) (CAS: 616-38-6), diethyl carbonate (DEC) (CAS: 105-58-8), ethyl methyl carbonate (EMC) (CAS: 623-53-0), diphenyl carbonate (CAS 102-09-0), methyl phenyl carbonate (CAS: 13509-27-8), dipropyl carbonate (DPC) (CAS: 623-96-1), and methyl carbonate. propyl (MPC) (CAS: 1333-41-1), ethyl propyl carbonate (EPC), vinylene carbonate (VC) (CAS: 872-36-6), fluoroethylene carbonate (FEC) (CAS: 114435-02-8), trifluoropropylene carbonate (CAS: 167951-80-6) or mixtures thereof.

[0174] Among the amides, dimethylformamide and N-methylpyrrolidinone may be mentioned.

[0175] More preferably, the aprotic solvent is chosen from EC, EMC, mixtures of EC and EMC, mixtures of EC and DMC, mixtures of EC and DEC, PC, mixtures of EC, DMC and EMC.

[0176] Preferably, the electrolyte comprises, or consists of, the purified ionic liquid as described above, one or more lithium salts (for example as cited above) dissolved in a solvent or a mixture of solvents (for example as cited above), optionally with one or more additives.

[0177] The additive(s) may be selected from the group consisting of fluoroethylene carbonate (FEC), vinylene carbonate, 4-vinyl-1,3-dioxolan-2-one, pyridazine, vinyl pyridazine, quinoline, vinyl quinoline, butadiene, sebaconitrile, alkyl disulfides, fluorotoluene, 1,4-dimethoxytetrafluorotoluene, t-butylphenol, di-t-butylphenol, tris(pentafluorophenyl)borane, oximes, aliphatic epoxides, halogenated biphenyls, methacrylic acids, allyl ethyl carbonate, vinyl acetate, divinyl adipate, propanesultone, acrylonitrile, 2-vinylpyridine, maleic anhydride, cinnamate methyl, phosphonates, silane compounds containing vinyl, and / or 2-cyanofuran.

[0178] Advantageously, the purified ionic liquid is present in the electrolyte in an amount of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 40 to 80% by weight, relative to the total weight of the electrolyte. In some embodiments, the electrolyte may comprise 10 to 20%, or 20 to 30%, or 30 to 40%, or 40 to 50%, or 50 to 60%, or 60 to 70%, or 70 to 80%, or 80 to 90% by weight, of purified ionic liquid (relative to the total weight of the electrolyte).

[0179] The invention also relates to an electrochemical cell comprising an electrolyte comprising a purified ionic liquid as described above. The cell electrochemical also includes a negative electrode (or anode) and a positive electrode (or cathode).

[0180] The electrochemical cell may also include a separator, in which the electrolyte is impregnated.

[0181] The electrolyte may be as described above.

[0182] By "negative electrode" is meant the electrode which acts as an anode when the cell is delivering current (i.e. when it is in the process of discharging) and which acts as a cathode when the cell is in the process of charging.

[0183] The negative electrode typically comprises an electrochemically active material, possibly an electronically conductive material, and possibly a binder.

[0184] By "positive electrode" is meant the electrode which acts as cathode when the cell is delivering 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.

[0185] The positive electrode typically comprises an electrochemically active material, possibly an electronically conductive material, and possibly a binder.

[0186] The term "electrochemically active material" means a material capable of reversibly inserting ions.

[0187] The term "electronic conductive material" means a material capable of conducting electrons.

[0188] The negative electrode of the electrochemical cell may include, in particular, as an electrochemically active material, graphite, lithium, a lithium alloy, a lithium titanate of the type Li4Ti50i2 or titanium oxide TiO2, silicon or a lithium and silicon alloy, a tin oxide, an intermetallic lithium compound, or a mixture thereof.

[0189] When the negative electrode includes lithium, it may be in the form of a metallic lithium film or a lithium alloy. Examples of lithium-based alloys that may be used include lithium-aluminum alloys, lithium-silica alloys, lithium-tin alloys, Li-Zn, Li3Bi, Li3Cd, and Li3SB. An example of a negative electrode may include a live lithium film prepared by rolling a lithium strip between rollers.

[0190] The negative electrode can simply consist of a current collector (for example made of copper); the lithium metal, which then constitutes the active material of the electrode, is deposited on the collector during charging.

[0191] The positive electrode comprises an electrochemically active oxide-type material. Preferably, it is a lithium iron phosphate (LixFePO4 with 0 <x<l), ou d’un oxyde composite lithium-nickel-manganèse-cobalt à haut taux de nickel (LiNixMny CozO2 avec x+y+z = 1, en abrégé NMC, avec x> y and x>z), or a composite oxide high nickel-cobalt-aluminium (LiNixCoyAlz- with x'+y'+z'=l, abbreviated NCA, with x'>y' and x'>z').

[0192] Particular examples of these oxides are NMC532 (LiNi,5MNi,3CoO,2O2), NMC622 (LiNi,6MNi2CoO2O2) and NMC811 (LiNi0.xMNi.|CoO.|C)2).

[0193] Mixtures of these oxides may be used. The oxide material described above may, where appropriate, be combined with another oxide such as, for example: manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium-manganese composite oxides (e.g., LixMn2O4 or LixMnO2), lithium-nickel composition oxides (e.g., LixNiO2), lithium-cobalt composite oxides (e.g., LixCoO2), lithium-nickel-cobalt composite oxides (e.g., LiNiyCoyO2), lithium and transition metal composite oxides, spinel-structured lithium-manganese-nickel composite oxides (e.g., LixMn2yNiyO4), vanadium oxides, NMC and NCA oxides that are not high in nickel, and mixtures thereof.

[0194] Preferably, the high nickel NMC or NCA oxide represents at least 50% by weight, preferably at least 75% by weight, preferably still at least 90% by weight, and preferably still substantially all of the oxide material present in the positive electrode as electrochemically active material.

[0195] Alternatively, or additionally, the positive electrode may comprise sulfur, Li2S, O2, and / or LiO2 as an electrochemically active material.

[0196] The material of each electrode may also include, 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-powdered carbon obtained by carbonization of an organic precursor, or a combination of two or more of these. 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).

[0197] The material of each electrode may also include 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 the two (or an EO / PO copolymer), and possibly 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 their combinations. Some binders, such as water-soluble ones, may also include an additive such as CMC (carboxymethylcellulose).

[0198] The separator may be a porous polymer film. By way of non-limiting example, the separator may consist of a porous polyolefin film such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / methacrylate copolymers, or multilayer structures of the above-mentioned polymers. Alternatively, the separator may be made of glass fibers.

[0199] The invention also relates to a battery comprising at least one, and preferably several, electrochemical cells as described above. The electrochemical cells can be assembled in series and / or in parallel in the battery. Other applications

[0200] The purified ionic liquid according to the invention can also be used in an electrolyte in an electrochromic light modulation system comprising at least one electrochromic material. In such a system, the electrochromic material is advantageously deposited on a layer of a visible-transparent semiconductor, preferably a tin oxide or indium oxide derivative, on a glass or polymer substrate. Examples of preferred electrochromic materials include molybdenum, tungsten, titanium, vanadium, niobium, cerium, and tin oxides, as well as mixtures thereof. The electrochromic material can optionally be dissolved in the electrolyte.

[0201] The purified ionic liquid according to the invention can also be used as an electrolyte in an electrochemical capacitor. Such a capacitor may comprise a sealed casing, at least one pair of electrodes (positive and negative) separated by a separator, and the electrolyte within the casing. Reference is made to document FR 3094555 as an example of such an electrochemical capacitor.

[0202] The purified ionic liquid according to the invention can also be used in a composition as a reaction medium for chemical or electrochemical reactions, preferably for Diels-Alder, Friedel-Craft, mixed aldol condensation, condensation, polymerization, and nucleophilic and electrophilic substitution reactions. When the purified ionic liquid comprises a chiral onium cation, the purified ionic liquid can be used in a composition as a reaction medium for enantion-selective reactions.

[0203] The purified ionic liquid according to the invention can also be used for the treatment of a surface, for example for cleaning that surface. Examples

[0204] The following examples illustrate the invention without limiting it. Example 1

[0205] In a 250 mL reactor, 37.6 g of bis(fluorosulfonyl)imide (HFSI, 99.85% purity, containing 580 ppm sulfamic acid, 0.208 mol) are loaded. The reactor is fitted with a dropping funnel heated to 95°C containing 30.5 g of l-ethyl-3-methylimidazolium chloride (EMIM-Cl, 0.208 mol). Under stirring and at a temperature of 25°–30°C, the EMIM-Cl is added over a period of 1 hour. At the end of the addition, the mixture is allowed to react for 3 hours in the presence of a nitrogen diffuser. 61 g of demineralized water is added to obtain the composition of the invention, which then contains, by weight: • 49.76% of EMIM-FSI • 50.10% water • 145 ppm of F ions • 262 ppm of NH2SO3 ions • 599 ppm of Cl- ions • 456 ppm of SO42 ions • 1 ppm of Na+ • 0 ppm of K+ Example 2

[0206] 60.7 g of the aqueous phase of the composition in Example 1 is removed to obtain 60.6 g of a composition which contains, by weight: • 97.2% of EMIM-FSI • 2.74% water • 77 ppm of F ions • 431 ppm of NH2SO3 ions • 91 ppm of Cl- ions • 29 ppm of SO42 ions • 0 ppm of Na+ • 0 ppm of K+ Example 3

[0207] In a 250 mL reactor, 30.3 g of 1-ethyl-3-methylimidazolium chloride (EMIM-C1, 0.21 mol) and 60.63 g of demineralized water are loaded. The reactor is fitted with a dropping funnel containing 37.3 g of bis(fluorosulfonyl)imide (99.85% purity, containing 580 ppm sulfamic acid, 0.21 mol). Under stirring and at room temperature without temperature control, the HFSI is poured over a period for 75 minutes. The starting temperature is 26°C, and during the addition it rises to 30°C. One hour after the end of the addition, a nitrogen diffuser is placed in the reaction mixture and the reaction is allowed to continue for another 1 hour and 30 minutes. The resulting composition contains 57 g of a phase mainly composed of EMIM-FSI and 69.45 g of an aqueous phase. The aqueous phase is removed by decantation, and a composition is obtained which contains, by weight: • 97.40% of EMIM-FSI • 2.57% water • 22 ppm of F ions • 98 ppm of NH2SO3 ions • 87 ppm of Cl- ions • 45 ppm of SO42 ions • 0 ppm of Na+ • 0 ppm of K+

[0208] During this preparation, no measurable VOCs were emitted into the atmosphere. Example 4

[0209] The composition obtained in Example 3 is dried under 2 mbar at 50°C to obtain a high-purity EMIM-FSI containing only 150 ppm of water, with an overall yield of 75% compared to the starting HFSI. This EMIM-FSI is of a quality compatible with good application performance in Li-ion batteries.

Claims

Demands

1. Composition comprising from 1 to 90% by weight of water, and comprising an ionic liquid comprising: • an anion of formula (II): [Chem. 10] O 0 ,11 - H 2 R—S—N—S—R II II 0 0 (II) in which R1 and R2 independently represent a fluorine atom or a perfluorinated group, • and at least one onium cation, the composition having a total alkali and alkaline earth ion content less than or equal to 1000 ppm by weight.

2. Composition according to claim 1, wherein Fanion of formula (II) is Fanion bis(fluorosulfonyl)imide or Fanion bis(trifluoromethylsulfonyl)imide.

3. Composition according to claim 1 or 2, wherein the onium cation is a quaternary ammonium ion, a pyridinium ion, an imidazolium ion, an oxazolidinium ion, a piperidinium ion, a phosphonium ion, a pyrrolidinium ion, a sulfonium ion and / or an oxonium ion.

4. Composition according to claim 1 or 3, wherein the total content of alkali and alkaline earth ions is less than or equal to 100 ppm, preferably less than or equal to 20 ppm by weight.

5. Composition according to any one of claims 1 to 4, wherein Fanion of formula (II), the onium cation and water are present in the composition in a total amount greater than or equal to 95% by weight, preferably greater than or equal to 98% by weight, preferably still greater than or equal to 99% by weight relative to the total weight of the composition.

6. Composition according to any one of claims 1 to 5, comprising from 5 to 50% by weight, preferably from 10 to 40% by weight of water.

7. A method for preparing a composition according to any one of claims 1 to 6, comprising preparing the ionic liquid and then adding water to the ionic liquid.

8. A method for preparing a composition according to any one of claims 1 to 6, comprising preparing the ionic liquid in the presence of water.

9. A process according to claim 7 or 8, wherein the preparation of the ionic liquid comprises the following steps: • supplying the compound of formula (I): [Chem. 11] OO 1 II II 2 R—S—NH—S—R II II OO (I) in which R1 and R2 independently represent a fluorine atom or a perfluorinated group, • reacting the compound of formula (I) with an onium cation precursor.

10. A process according to claim 9, wherein the precursor of the onium cation is a halide of the onium cation, preferably a chloride or bromide of the onium cation.

11. A process according to any one of claims 9 or 10, wherein the preparation of the ionic liquid is carried out: • without organic solvent; and / or • with a compound molar ratio of formula (I) / onium cation precursor of 0.9 to 1.1, preferably of 1 to 1.05, more preferably of 1 to 1.01; and / or • at a temperature of 10 to 100°C, preferably of 20 to 30°C.

12. A process according to any one of claims 9 to 11, comprising the following step: • synthesis of the compound of formula (I), preferably by fluorination of a chlorinated compound and optionally by distillation.

13.

14.

15.

16.

17.

18. A process for preparing a purified ionic liquid comprising supplying the composition according to any one of claims 1 to 6, and removing at least some of the water from the composition. A method according to claim 13, wherein at least 80% by weight, preferably at least 90% by weight, and even more preferably at least 99% by weight of the water is removed. Purified ionic liquid prepared by the process of one of claims 13 or 14. Electrochemical cell comprising a negative electrode, a positive electrode and an electrolyte, wherein the electrolyte comprises the purified ionic liquid according to claim 15; the negative electrode preferably comprising graphite. Battery comprising at least one electrochemical cell according to claim 16. Capacitor comprising a casing, at least one pair of positive and negative electrodes separated by a separator, and an electrolyte in the casing, wherein the electrolyte comprises the purified ionic liquid according to claim 15.