Bis(fluorosulfonyl)imide salts and methods for preparing same

Abstract

The present invention relates to a bis(fluorosulfonyl)imide salt and a method for preparing the same. More specifically, the present invention provides a novel salt of bis(fluorosulfonyl)imide containing 0.01 ppm to 10,000 ppm of a halogenated alcohol. The present invention further relates to a method for producing the salt of bis(fluorosulfonyl)imide, which comprises crystallizing a raw salt of bis(fluorosulfonyl)imide in a crystallization solvent containing at least a halogenated alcohol. Uses of the salt of bis(fluorosulfonyl)imide are also disclosed.

Description

[Technical Field]

[0001] The present invention relates to bis(fluorosulfonyl)imide salts and methods for their preparation. More specifically, the present invention provides novel salts of bis(fluorosulfonyl)imides that have improved quality and can be obtained by a new, efficient, and cost-effective method. [Background technology]

[0002] Bis(fluorosulfonyl)imide (commonly represented by "FSIH") and its salts, particularly the lithium salt of bis(fluorosulfonyl)imide (commonly represented by "LiFSI"), are useful as intermediate or final compounds in various technical fields.

[0003] The preparation of bis(fluorosulfonyl)imides and lithium salts of bis(fluorosulfonyl)imides has been widely described in the literature. Among the various techniques described, the majority use fluorination reactions with either HF or metal fluorides such as KF, CsF, AsF3, SbF3, CuF2, ZnF2, SnF2, PbF2, BiF3, etc. Other techniques have been developed, for example, using chlorosulfonyl isocyanate in the presence of oleum and ammonium fluoride, or using urea and fluorosulfonic acid.

[0004] Bis(fluorosulfonyl)imides and their salts are particularly useful in battery electrolytes. For this type of use, the presence of impurities is a significant problem.

[0005] In order to reduce the contamination of metal impurities, the prior art document US Patent Application Publication No. 2013 / 0331609 discloses a chlorosulfonylimide compound of the formula NH4F(HF) P(wherein p is 0 to 10) with a fluorinating agent. The fluorosulfonylimide ammonium salt thus obtained can be subjected to a cation exchange reaction to produce another fluorosulfonylimide salt. This process is said to be industrially efficient and does not produce metal impurities.

[0006] Similarly, the prior art documents JP 2016-124735 A and JP 2016-145147 A disclose a method for producing a chlorosulfonylimide compound by the reaction of chlorosulfonylimide compounds with NHF(HF) P (wherein p is 0 to 10). The fluorosulfonylimide compound can be reacted with an alkali metal compound to produce an alkali metal salt of the fluorosulfonylimide.

[0007] Prior art document U.S. Patent Application Publication No. 2018 / 0370799 discloses a method for producing lithium bis(fluorosulfonyl)imide in high yield and purity, which includes reacting a bis(chlorosulfonyl)imide compound with a fluorinating agent, followed by immediate treatment with an alkaline reagent to produce ammonium bis(fluorosulfonyl)imide, and reacting the ammonium bis(fluorosulfonyl)imide with a lithium base.

[0008] Even though these documents claim that the product is obtained with high purity, there is still room for improvement. For example, U.S. Patent Application Publication No. 2018 / 0370799 even discloses that additional recrystallization of the concentrated, purified, and recrystallized lithium bis(fluorosulfonyl)imide product is necessary to remove insoluble components and finally obtain a lithium bis(fluorosulfonyl)imide product with the desired high purity of 99.9% or more.

[0009] In this regard, it is believed that an improved method for producing bis(fluorosulfonyl)imides and their salts, which is economically feasible on an industrial scale and provides high-purity products, is still desirable. In addition, one object of the present invention is to provide novel salts of bis(fluorosulfonyl)imides having improved quality and which can be obtained by a new, efficient, and cost-effective method. Summary of the Invention

[0010] One subject of the present invention is a salt of bis(fluorosulfonyl)imide containing 0.01 ppm to 10,000 ppm of a halogenated alcohol, preferably an onium salt of bis(fluorosulfonyl)imide, more preferably a quaternary ammonium salt of bis(fluorosulfonyl)imide, and even more preferably an ammonium bis(fluorosulfonyl)imide.

[0011] A further subject of the present invention is a method for preparing said salts of bis(fluorosulfonyl)imides, comprising the step of crystallizing the raw salt of bis(fluorosulfonyl)imides in a crystallization solvent comprising at least a halogenated alcohol.

[0012] A further subject of the present invention is the use of said salt of bis(fluorosulfonyl)imide as a starting material for preparing another salt of bis(fluorosulfonyl)imide. Additionally, the present invention claims a method for preparing an alkali salt of bis(fluorosulfonyl)imide, comprising the steps of preparing a crystallized salt of bis(fluorosulfonyl)imide as defined above and reacting said crystallized salt of bis(fluorosulfonyl)imide with an alkaline agent to obtain an alkali salt of bis(fluorosulfonyl)imide. [Brief explanation of the drawings]

[0013] [Figure 1]1 shows the cyclic voltammetry diagram obtained by cycling five times a solution of LiFSI at 30 wt. % in EMC obtained in Example 2. [Figure 2] 1 shows the cyclic voltammetry diagram obtained by cycling five times a solution of LiFSI at 30 wt. % in EMC obtained in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] In this disclosure, the expression "comprised of" should be understood to include both endpoints. Unless otherwise specified, 1 part per million means 1 part by weight per 1,000,000 parts by weight. It can be equivalently abbreviated as "ppm," "ppmw," or "mg / kg."

[0015] One subject of the present invention relates to salts of bis(fluorosulfonyl)imides, which have the formula (I): [(FSO2)2N - ] n M n+ (I) (In the formula, M n+ represents a cation, and n is an integer of 1 to 3 representing the valence of the cation M. Preferably, n is 1 or 2; more preferably, n is 1.

[0016] According to the first embodiment, M n+ represents an onium cation. n+ may be selected from the group consisting of quaternary ammonium, imidazolium, pyrazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, quaternary phosphonium, tertiary phosphine, sulfonium, guanidinium, isouronium and isothiouronium. More preferably, the onium cation M n+may be selected from the group consisting of quaternary ammonium compounds, in particular tetramethylammonium and ammonium cations (in such cases n=1 in formula (I)). Even more preferably, M n+ is the ammonium cation NH4 + As a result, the salt of a bis(fluorosulfonyl)imide according to the present invention is preferably an onium salt of a bis(fluorosulfonyl)imide, more preferably a quaternary ammonium salt of a bis(fluorosulfonyl)imide, even more preferably an ammonium bis(fluorosulfonyl)imide, which can be represented by the formula NHN(SOF) (which can be referred to as "NHFSI").

[0017] According to the second embodiment, M n+ represents an alkali metal cation. The alkali metal cation may be selected from the group consisting of lithium, sodium and potassium cations, and preferably M n+ is a lithium cation. The salt of bis(fluorosulfonyl)imide according to the present invention is preferably lithium bis(fluorosulfonyl)imide, which can be represented by the formula LiN(SOF) (referred to as "LiFSI").

[0018] The salts of bis(fluorosulfonyl)imides according to the invention are characterized by the fact that they contain certain traces of halogenated alcohols.

[0019] The halogenated alcohol may be a fluorinated alcohol, a chlorinated alcohol or a brominated alcohol. The halogenated alcohol is preferably a fluorinated alcohol.

[0020] In this context, the expression "fluorinated alcohol" refers to an organic fluorine compound containing at least one alcohol functional group with at least one C—F bond. The fluorinated alcohol may be a partially fluorinated alcohol or a perfluorinated alcohol. It preferably contains 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.

[0021] According to a preferred embodiment, the fluorinated alcohol according to the invention has the formula R f -OH(in the formula, R f is a fluorinated moiety selected from the group consisting of fluorinated alkyl, fluorinated heteroalkyl, and fluorinated aryl. f teeth, - may be a C1-C4 fluorinated alkyl, more preferably it is CH2F, CHF2, CF3, CF3CH2, HCF2CH2, CF3CF2, CF3CH2CH2, CF3CF2CH2, CF3CF2CF2, (CF3)2CH, (CF3)2CF, CF3CF2CF2CF2, (CF3)3C; or - may be a fluorinated aryl, such as a partially or fully fluorinated phenyl, more preferably R f is C6F5.

[0022] Highly preferably, the fluorinated alcohol according to the present invention may be selected from the group consisting of nonafluoro-tert-butanol ((CF3)3COH), hexafluoroisopropanol ((CF3)2CHOH), pentafluorophenol, difluoroethanol (HCF2CH2OH) and trifluoroethanol (CF3CH2OH); more preferably, the fluorinated alcohol is difluoroethanol and trifluoroethanol; even more preferably, the fluorinated alcohol is trifluoroethanol.

[0023] According to the present invention, the salt of bis(fluorosulfonyl)imide is characterized by the fact that it contains 0.01 ppm to 10000 ppm, preferably 0.1 ppm to 5000 ppm, more preferably 0.1 ppm to 1000 ppm, more preferably 0.5 ppm to 500 ppm, and even more preferably 1 ppm to 100 ppm of said halogenated alcohol.

[0024] The content of halogenated alcohols can be measured by gas chromatography (GC), or HPLC, or mass spectrometry. Typically, headspace gas chromatography for solid compounds can be used.

[0025] Except for the halogenated alcohol, the salts of bis(fluorosulfonyl)imides according to the invention advantageously exhibit very high purity, preferably greater than 90%, more preferably greater than 95%, and even more preferably between 99% and 100% (by mass percent).

[0026] Preferably, it has a content of the following anions: chloride anions (Cl) less than 10000 ppm, preferably less than 5000 ppm, more preferably less than 1000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm; - ) content; and / or - less than 10000 ppm, preferably less than 5000 ppm, more preferably less than 1000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm fluoride anions (F - ) content; and / or - less than 30,000 ppm, preferably less than 10,000 ppm, more preferably less than 5,000 ppm of sulfate anions (SO 2- ) content can be shown.

[0027] It should be understood that these anions are separate entities from the salt of bis(fluorosulfonyl)imide itself. In particular, the fluoride content does not include the fluorine content in the molecular structure of the salt of bis(fluorosulfonyl)imide.

[0028] Preferably, it has the following metal element contents: an iron (Fe) content of less than 1000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a chromium (Cr) content of less than 1000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a nickel (Ni) content of less than 1000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a zinc (Zn) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a copper (Cu) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or - a bismuth (Bi) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm can be shown.

[0029] In addition, if the salt of bis(fluorosulfonyl)imide is not sodium bis(fluorosulfonyl)imide, it is - sodium (Na) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm can be shown.

[0030] In addition, if the salt of bis(fluorosulfonyl)imide is not potassium bis(fluorosulfonyl)imide, it is - a potassium (K) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm can be shown.

[0031] The water content of the bis(fluorosulfonyl)imide salt according to the present invention is preferably less than 10,000 ppm, more preferably less than 1,000 ppm. Nevertheless, a higher water content may be acceptable depending on the end use of the bis(fluorosulfonyl)imide salt.

[0032] Due to their very high purity, the salts of bis(fluorosulfonyl)imides can be advantageously used as starting materials or intermediate compounds for the preparation of other bis(fluorosulfonyl)imide salts used in electrolyte compositions for batteries or in electrolyte compositions for batteries.

[0033] The salts of bis(fluorosulfonyl)imides according to the present invention may be in the form of solid crystallized compounds, preferably dry solid crystallized compounds, having a purity of greater than 99.9%.

[0034] A further subject of the present invention is a method for preparing a salt of a bis(fluorosulfonyl)imide as defined above, said method comprising the step of crystallizing a raw salt of the bis(fluorosulfonyl)imide in a crystallization solvent containing at least a halogenated alcohol.

[0035] According to a preferred embodiment, the crystallization process according to the present invention is a recrystallization process comprising the steps of first providing a solid raw salt of bis(fluorosulfonyl)imide, then dissolving said solid raw salt of bis(fluorosulfonyl)imide in said crystallization solvent; crystallizing the salt of bis(fluorosulfonyl)imide; and finally recovering the recrystallized salt of bis(fluorosulfonyl)imide.

[0036] The solid raw salt of the bis(fluorosulfonyl)imide can be purchased as such or can be pre-prepared by any method disclosed in the prior art.

[0037] The solid raw salt of bis(fluorosulfonyl)imide can be dissolved in a crystallization solvent containing at least a halogenated alcohol. The halogenated alcohol can be selected as disclosed herein above. Therefore, the halogenated alcohol can be very preferably selected from the group consisting of nonafluoro-tert-butanol ((CF3)3COH), hexafluoroisopropanol ((CF3)2CHOH), pentafluorophenol, difluoroethanol (HCF2CH2OH) and trifluoroethanol (CF3CH2OH), more preferably, the fluorinated alcohol is difluoroethanol or trifluoroethanol, and even more preferably, the fluorinated alcohol is trifluoroethanol.

[0038] According to one embodiment, the crystallization solvent contains one halogenated alcohol or a mixture of two or more halogenated alcohols. According to another embodiment, the crystallization solvent contains a mixture of at least one halogenated alcohol and another alcohol that is not a halogenated alcohol. For example, the other solvent may be selected from the group consisting of carbonates such as ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC); esters such as ethyl acetate, butyl acetate, and ethyl propionate; halocarbons such as dichloromethane (DCM) and 1,2-dichloroethane; aromatic compounds such as benzene and toluene; hydrocarbons such as pentane, hexane, and heptane; and nitrile compounds such as valeronitrile and acetonitrile. Examples of crystallization solvent mixtures include TFE / EMC, TFE / EMC / DCM, TFE / DCM, TFE / butyl acetate / DCM, and TFE / butyl acetate. The content of the halogenated alcohol in the crystallization solvent may be between 1% and 95%, more preferably between 50% and 90%. Optionally, water may also be added to the crystallization solvent, with a content that may be between 0.01% and 20%, preferably between 0.1% and 10%, more preferably between 1% and 5%, based on the total weight of the crystallization solvent.

[0039] Optimal dissolution can be carried out by means well known to those skilled in the art, typically in batch, semi-batch or continuous mode, using suitable stirring means. Dissolution can be carried out at temperatures comprised between 25° C. and 70° C., preferably between 40° C. and 70° C., even more preferably between 50° C. and 60° C. Preferably, dissolution is carried out at atmospheric pressure, although working below or above atmospheric pressure, for example between 800 mbar and 1.2 bar, is not excluded.

[0040] After dissolution, crystallization of the salt of bis(fluorosulfonyl)imide can be induced by means well known to those skilled in the art in batch, semi-batch, or continuous modes. The design of the crystallization apparatus can be determined by those skilled in the art. The means for inducing crystallization can be a temperature reduction at a fixed pressure, a temperature reduction combined with a pressure reduction, or distillation of at least a portion of the crystallization solvent. In addition, seeding can be performed.

[0041] The separation of the crystallized salt of bis(fluorosulfonyl)imide can be carried out by any typical separation means known to those skilled in the art, such as filtration. Filtration can be carried out by any means known to those skilled in the art at atmospheric pressure, under pressure, or under vacuum. The mesh size of the filtration medium can preferably be 2 micrometers or less, more preferably 0.45 micrometers or less, and even more preferably 0.22 micrometers or less. The separated product can be washed one or more times with a suitable solvent.

[0042] Finally, the crystallized solid salt of bis(fluorosulfonyl)imide is preferably dried to obtain a pure, dry product. The drying step can be carried out by any means known to those skilled in the art, typically under reduced pressure and / or by heating and / or using an inert gas stream, typically a nitrogen stream.

[0043] The process according to the present invention advantageously provides a dry, solid, crystallized salt of the bis(fluorosulfonyl)imide according to the present invention, exhibiting very high purity. As explained above, due to its very high purity, the salt of the bis(fluorosulfonyl)imide can be advantageously used as a starting material or intermediate compound for the preparation of other bis(fluorosulfonyl)imide salts used in electrolyte compositions for batteries or in electrolyte compositions for batteries.

[0044]

[0023] Herein, one embodiment is described in which the salt of bis(fluorosulfonyl)imide is an onium salt of bis(fluorosulfonyl)imide. According to said embodiment, the raw solid onium salt of bis(fluorosulfonyl)imide can be prepared by the following process: - reacting a bis(chlorosulfonyl)imide or a salt thereof with an onium fluoride to produce an onium salt of a bis(fluorosulfonyl)imide; - precipitating and isolating the onium salt of bis(fluorosulfonyl)imide; It can be produced according to

[0045] According to certain embodiments, where the salt of bis(fluorosulfonyl)imide is a quaternary ammonium salt of bis(fluorosulfonyl)imide (such as ammonium bis(fluorosulfonyl)imide or tetramethylammonium bis(fluorosulfonyl)imide), the crude solid quaternary ammonium salt of bis(fluorosulfonyl)imide can be prepared by the following process: - reacting bis(chlorosulfonyl)imide or a salt thereof with a quaternary ammonium fluoride to produce a quaternary ammonium salt of bis(fluorosulfonyl)imide; - precipitating and isolating the quaternary ammonium salt of bis(fluorosulfonyl)imide; It can be produced according to

[0046] According to one particular embodiment, where the salt of bis(fluorosulfonyl)imide is ammonium bis(fluorosulfonyl)imide, the raw solid ammonium bis(fluorosulfonyl)imide can be prepared by the following process: - reacting bis(chlorosulfonyl)imide or a salt thereof with ammonium fluoride to produce the ammonium salt of bis(fluorosulfonyl)imide; - precipitating and isolating the ammonium salt of bis(fluorosulfonyl)imide; It can be produced according to

[0047] Bis(chlorosulfonyl)imide or its salt is used as the starting material. It has the formula: (Cl-SO2-N - -SO2-Cl)X + (wherein X represents one of the group consisting of H, Li, Na, K, Cs and NH4). It can be represented by:

[0048] According to a preferred embodiment, the starting material is a bis(chlorosulfonyl)imide of formula (Cl-SO)-NH (commonly represented by CSIH). CSIH is commercially available or can be prepared by known methods, for example, - reacting chlorosulfonyl isocyanate ClSO2NCO with chlorosulfonic acid ClSO2OH; - reacting cyanogen chloride CNCl with sulfuric anhydride SO3 and chlorosulfonic acid ClSO2OH; - Reacting sulfamic acid NH2SO2OH with thionyl chloride SOCl2 and chlorosulfonic acid ClSO2OH Manufactured by.

[0049] According to this embodiment, the fluorinating agent may be an onium fluoride, more particularly a quaternary ammonium fluoride, such as ammonium fluoride or tetramethylammonium fluoride. Within the present invention, the expression "onium fluoride" also includes HF adducts of onium fluorides. According to one particular embodiment, the fluorinating agent is ammonium fluoride NHF. Within the present invention, the expression "ammonium fluoride" therefore includes HF adducts of ammonium fluoride, such as NHF(HF). n (wherein n is 1 to 10, preferably 1 to 4), more preferably NH4F·HF or NH4F(HF)2. The fluorinating agent is commercially available or can be prepared by known methods.

[0050] According to a preferred embodiment, the onium fluoride (more particularly a quaternary ammonium fluoride, even more particularly ammonium fluoride) is anhydrous. The water content may preferably be less than 5000 ppm, more preferably less than 1000 ppm, and even more preferably less than 500 ppm.

[0051] The amount of onium fluoride (more particularly quaternary ammonium fluoride, even more particularly ammonium fluoride) used is preferably comprised between 1 and 10 equivalents, more preferably between 1 and 7 equivalents, and even more preferably between 2 and 5 equivalents per mole of bis(chlorosulfonyl)imide or a salt thereof.

[0052] The reaction may be preferably carried out in an organic solvent, which may be an aprotic organic solvent, preferably cyclic and acyclic carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, cyclic and acyclic esters, such as gamma-butyrolactone, gamma-valerolactone, methyl formate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, isopropyl acetate, propyl propionate, butyl acetate, cyclic and acyclic ethers, such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, amide compounds, such as N,N-dimethylformamide, N-methyloxazolidinone, sulfoxide and sulfone compounds, such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, cyano-, nitro-, chloro- or alkyl-substituted alkanes or aromatic hydrocarbons, such as acetonitrile, valeronitrile, adiponitrile, benzonitrile, nitromethane, nitrobenzene may be selected from:

[0053] According to a preferred embodiment, the organic solvent is selected from the group consisting of ethyl acetate, isopropyl acetate, butyl acetate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, valeronitrile and acetonitrile.

[0054] According to a preferred embodiment, the organic solvent is anhydrous. The water content may preferably be less than 5000 ppm, more preferably less than 1000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, and even more preferably less than 50 ppm.

[0055] The reaction can be carried out at temperatures between 0° C. and 200° C., preferably between 30° C. and 100° C. Preferably, the reaction is carried out at atmospheric pressure, although working below or above atmospheric pressure, for example between 800 mbar and 1.2 bar, is not excluded.

[0056] The reaction can be carried out in a batch, semi-batch or continuous manner. According to a preferred embodiment, the onium fluoride (which can be more particularly a quaternary ammonium fluoride, even more particularly ammonium fluoride) is first added to an organic solvent. Then, bis(chlorosulfonyl)imide or its salt can be added to the reaction medium.

[0057] By reacting bis(chlorosulfonyl)imide or a salt thereof with an onium fluoride (more particularly a quaternary ammonium fluoride, even more particularly ammonium fluoride) according to the present invention, an onium salt of bis(fluorosulfonyl)imide (more particularly a quaternary ammonium salt of bis(fluorosulfonyl)imide, even more particularly an ammonium salt of bis(fluorosulfonyl)imide) can be obtained.

[0058] After reacting the bis(chlorosulfonyl)imide or its salt with the onium fluoride (or more particularly a quaternary ammonium fluoride, even more particularly ammonium fluoride), but before precipitating and isolating the onium salt of the bis(fluorosulfonyl)imide (or more particularly a quaternary ammonium salt of the bis(fluorosulfonyl)imide, even more particularly an ammonium salt of the bis(fluorosulfonyl)imide), the method according to this embodiment may include a step comprising adding a basic compound to the reaction medium. The basic compound may be a solid, a pure liquid, an aqueous or organic solution, or a gas. The basic compound may be selected from the group consisting of gaseous ammonia, aqueous ammonia, amines, alkali or alkaline earth metal hydroxides, carbonates, phosphates, silicates, borates, formates, acetates, stearates, palmitates, propionates, or oxalates. Among amines, aliphatic amines (ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, 2-ethylhexylamine, trimethylamine, triethylamine, tripropylamine, and tributylamine, etc.), alkylenediamines (ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, etc.), alkanolamines (monoethanolamine, diethanolamine, triethanolamine, mono ... Any type of amine may be advantageously used, including isopropanolamine, diisopropanolamine, and triisopropanolamine, alicyclic amines (such as cyclohexylamine and dicyclohexylamine), aromatic amines (such as benzylamine and metaxylenediamine), ethylene oxide adducts of these amines, formamidines, guanidines, amidines, and heterocyclic amines (such as diazabicycloundecene, diazabicyclononene, piperidine, morpholine, piperazine, pyrimidine, pyrrole, imidazole, imidazoline, triazole, thiazole, pyridine, and indole). The basic compound is preferably gaseous ammonia or aqueous ammonia.

[0059] The amount of the basic compound added is preferably 0.1 to 10 equivalents, preferably 0.5 to 5 equivalents, more preferably 0.5 to 3 equivalents, based on the initial amount of bis(chlorosulfonyl)imide or a salt thereof loaded in the first reaction step.

[0060] During the addition of the basic compound, the temperature is preferably maintained between 0° C. and 100° C., more preferably between 15° C. and 90° C. Advantageously, this step of adding the basic compound can be carried out at the same temperature as the preceding reaction step.

[0061] Optionally, the process according to the invention may comprise one or several intermediate separation steps after the reaction and before the addition of the basic compound or after the addition of the basic compound and before the precipitation and separation of the onium salt of the bis(fluorosulfonyl)imide (or more particularly the quaternary ammonium salt of the bis(fluorosulfonyl)imide, even more particularly the ammonium salt of the bis(fluorosulfonyl)imide), or both. This intermediate separation step may be carried out by any typical separation means known to those skilled in the art, such as filtration (e.g., under pressure or vacuum) or decantation.

[0062] The next step according to this embodiment involves precipitating and separating the onium salt of bis(fluorosulfonyl)imide (or more particularly the quaternary ammonium salt of bis(fluorosulfonyl)imide, even more particularly the ammonium salt of bis(fluorosulfonyl)imide). The precipitation of the onium salt of bis(fluorosulfonyl)imide (or particularly the quaternary ammonium salt of bis(fluorosulfonyl)imide, even more particularly the ammonium salt of bis(fluorosulfonyl)imide) can be obtained by different means that can be selected by a person skilled in the art. In particular, the means for precipitation of the onium salt of bis(fluorosulfonyl)imide (or more particularly the quaternary ammonium salt of bis(fluorosulfonyl)imide, even more particularly the ammonium salt of bis(fluorosulfonyl)imide) is - removing at least a portion of the solvent by distillation; - reducing the temperature of the reaction medium; - adding a precipitation solvent; and - any combination thereof You can choose from:

[0063] The removal of at least a portion of the solvent causes an increase in the concentration of the onium salt of the bis(fluorosulfonyl)imide (or more particularly the quaternary ammonium salt of the bis(fluorosulfonyl)imide, even more particularly the ammonium salt of the bis(fluorosulfonyl)imide) in the reaction medium. According to one embodiment, the concentration step may involve distillation of the solvent at a temperature comprised between 0°C and 120°C, preferably between 5°C and 80°C, more preferably between 10°C and 70°C. The pressure may vary, depending on the nature of the solvent, typically between atmospheric pressure and 10°C. -2 The pressure may be adjusted to between 1 mbar and 500 mbar, preferably between 5 mbar and 100 mbar. The distillation may be carried out by any typical means known to those skilled in the art in a continuous process or in a discontinuous / batch manner, for example in a continuous batch solvent evaporation, batch distillation, short-path continuous flow distillation or thin film evaporator.

[0064] Precipitation of the onium salt of a bis(fluorosulfonyl)imide (or more particularly a quaternary ammonium salt of a bis(fluorosulfonyl)imide, even more particularly an ammonium salt of a bis(fluorosulfonyl)imide) can also be obtained by lowering the temperature of the reaction mixture containing the salt, which can optionally be concentrated beforehand. The temperature of the reaction mixture containing the salt can be lowered to a value below the dissolution temperature of the salt. Preferably, the temperature is lowered to a value between the boiling point of the solvent and -20°C, more preferably between 70°C and -10°C, and even more preferably between 30°C and 0°C. During the temperature reduction, the pressure can preferably be kept constant. However, simultaneous pressure reduction is not excluded, which can cause evaporation of part of the organic solvent of the reaction mixture. The pressure can be between atmospheric pressure and 10°C. -2 The pressure can be reduced to a value comprised between 1 mbar and 500 mbar, preferably between 5 mbar and 100 mbar.

[0065] Alternatively or additionally, at least one precipitation solvent may be added to the reaction mixture containing the salt. The precipitation solvent may be preferably selected from among organic solvents that are highly soluble in the organic solvent of the reaction mixture and are poor solvents for the onium salt of bis(fluorosulfonyl)imide (or more particularly, the quaternary ammonium salt of bis(fluorosulfonyl)imide, even more particularly, the ammonium salt of bis(fluorosulfonyl)imide). The precipitation solvent may be selected from the group consisting of halogenated solvents such as dichloromethane, dichloroethane, chloroform, and carbon tetrachloride; substituted aromatic hydrocarbon solvents such as chlorobenzene and toluene; and alkane solvents such as hexane and heptane. The precipitation solvent may preferably be selected from dichloromethane and dichloroethane. The volume ratio between the precipitation solvent and the organic solvent of the reaction mixture may be comprised between 0.1 and 50, preferably between 0.2 and 20, more preferably between 0.5 and 15, and even more preferably between 1 and 10.

[0066] Separation of the precipitated onium salt of bis(fluorosulfonyl)imide (particularly the quaternary ammonium salt of bis(fluorosulfonyl)imide, and even more particularly the ammonium salt of bis(fluorosulfonyl)imide) can be carried out by any typical separation means known to those skilled in the art, such as filtration. Filtration can be carried out by any means known to those skilled in the art at atmospheric pressure, under pressure, or under vacuum. The mesh size of the filtration medium can preferably be 2 micrometers or less, more preferably 0.45 micrometers or less, and even more preferably 0.22 micrometers or less. The separated product can be washed once or several times with an appropriate solvent.

[0067] Finally, the separated solid onium salt of bis(fluorosulfonyl)imide (or particularly the separated quaternary ammonium salt of bis(fluorosulfonyl)imide or more particularly the separated ammonium salt of bis(fluorosulfonyl)imide) is preferably dried to obtain a pure, dry product. The drying step can be carried out by any means known to those skilled in the art, typically under reduced pressure and / or by heating and / or using a stream of inert gas, typically a stream of nitrogen.

[0068] According to one particular embodiment, the salts of bis(fluorosulfonyl)imides according to the invention can be used as starting compounds for the preparation of other bis(fluorosulfonyl)imide salts. Thus, one subject of the present invention comprises a method for producing an alkali salt of bis(fluorosulfonyl)imide, comprising the steps of producing a crystallized salt of bis(fluorosulfonyl)imide by the method disclosed above, and reacting the crystallized salt of bis(fluorosulfonyl)imide with an alkaline agent to obtain an alkali salt of bis(fluorosulfonyl)imide.

[0069] The alkali salt of bis(fluorosulfonyl)imide can be selected from the group consisting of lithium salt, sodium salt and potassium salt. Preferably, the alkali salt is a lithium salt, and the alkali salt of bis(fluorosulfonyl)imide obtained by the method according to the present invention is the lithium salt of bis(fluorosulfonyl)imide Li + (FSO2)2N - (LiFSI).

[0070] The crystallized salt of bis(fluorosulfonyl)imide can be used as such or solubilized in a solvent, depending on the nature of the alkali salt. According to a preferred embodiment, the crystallized salt of bis(fluorosulfonyl)imide is solubilized in an organic solvent, hereinafter referred to as "alkalinizing solvent". The alkalinizing solvent is an aprotic organic solvent, preferably cyclic and acyclic carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, cyclic and acyclic esters, such as gamma-butyrolactone, gamma-valerolactone, methyl formate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, isopropyl acetate, propyl propionate, butyl acetate, cyclic and acyclic ethers, such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, amide compounds, such as N,N-dimethylformamide, N-methyloxazolidinone, sulfoxide and sulfone compounds, such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, cyano-, nitro-, chloro- or alkyl-substituted alkanes or aromatic hydrocarbons, such as acetonitrile, valeronitrile, adiponitrile, benzonitrile, nitromethane, nitrobenzene may be selected from:

[0071] According to a preferred embodiment, the alkalinizing solvent is selected from the group consisting of ethyl acetate, isopropyl acetate, butyl acetate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, valeronitrile and acetonitrile.

[0072] The alkali salt may be selected from the group consisting of lithium salts, sodium salts, and potassium salts. Preferably, the alkali salt is a lithium salt, and the alkali salt of bis(fluorosulfonyl)imide obtained by the method according to the present invention is a lithium salt of bis(fluorosulfonyl)imide.

[0073] Examples of alkaline agents include alkali hydroxides, alkali hydroxide hydrates, alkali carbonates, alkali hydrogen carbonates, alkali chlorides, alkali fluorides, alkoxide compounds, alkyl alkali compounds, alkali acetates, and alkali oxalates. Preferably, alkali hydroxides or alkali hydroxide hydrates are used. When the alkaline agent is a lithium salt, the lithium salt may be lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH·H2O), lithium carbonate (Li2CO3), or lithium hydrogen carbonate (Li2CO3). iThe lithium hydroxide may be selected from the group consisting of HCO3, lithium chloride LiCl, lithium fluoride LiF, alkoxide compounds such as CHOLi and EtOLi, alkyllithium compounds such as EtLi, BuLi and t-BuLi, lithium acetate CHCOOLi, and lithium oxalate LiCO4. Preferably, lithium hydroxide LiOH or lithium hydroxide hydrate LiOH·HO may be used.

[0074] The alkaline agent may be added as a solid, a pure liquid, or an aqueous or organic solution.

[0075] The amount of alkaline agent used is preferably comprised between 0.5 and 5 moles, more preferably between 0.9 and 2 moles, and even more preferably between 1 and 1.5 moles per mole of the onium salt of bis(fluorosulfonyl)imide (or in particular the quaternary ammonium salt of bis(fluorosulfonyl)imide, and even more particularly the ammonium salt of bis(fluorosulfonyl)imide).

[0076] The reaction may be carried out at temperatures between 0° C. and 50° C., more preferably between 15° C. and 35° C., even more preferably at about room temperature. Preferably, the reaction is carried out at atmospheric pressure, although it is not excluded to work below or above atmospheric pressure, for example between 5 mbar and 1.5 bar, preferably between 5 mbar and 100 mbar.

[0077] Further processing can be carried out to recover a highly pure alkali salt of the bis(fluorosulfonyl)imide. The reaction medium can be a biphasic (aqueous / organic) solution, especially when the alkaline agent is an aqueous solution. In this case, the method can include a phase separation step, during which the aqueous phase is removed and the alkali salt of the bis(fluorosulfonyl)imide is recovered in the organic phase. Additional steps can include filtration, concentration, extraction, recrystallization, chromatographic purification, drying, and / or formulation.

[0078] Advantageously, the alkali salts of bis(fluorosulfonyl)imides obtained by the process according to the invention have a very high purity: they may exhibit a purity of more than 90%, preferably more than 95%, more preferably between 99% and 100% of the salt.

[0079] Preferably, it has a content of the following anions: chloride ions (Cl) less than 10000 ppm, preferably less than 5000 ppm, more preferably less than 1000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm; - ) content; and / or - fluoride ions (F) of less than 10000 ppm, preferably less than 5000 ppm, more preferably less than 1000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm - ) content; and / or - less than 30,000 ppm, preferably less than 10,000 ppm, more preferably less than 5,000 ppm of sulfate ions (SO 2- ) content can be shown.

[0080] Preferably, it has the following metal element contents: an iron (Fe) content of less than 1000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a chromium (Cr) content of less than 1000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a nickel (Ni) content of less than 1000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a zinc (Zn) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a copper (Cu) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or - a bismuth (Bi) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm can be shown.

[0081] In addition, if the alkali salt of bis(fluorosulfonyl)imide is not sodium bis(fluorosulfonyl)imide, it is - sodium (Na) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm can be shown.

[0082] In addition, if the alkali salt of bis(fluorosulfonyl)imide is not potassium bis(fluorosulfonyl)imide, it is - a potassium (K) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm can be shown.

[0083] Due to its very high purity, the alkali salts of bis(fluorosulfonyl)imides, preferably lithium bis(fluorosulfonyl)imide, obtained by the process according to the invention can be advantageously used in electrolyte compositions for batteries.

[0084] Contrary to prior art methods, the method for producing alkali salts of bis(fluorosulfonyl)imides according to the present invention starts from a salt of bis(fluorosulfonyl)imide, preferably an onium salt of bis(fluorosulfonyl)imide, more preferably a quaternary ammonium salt of bis(fluorosulfonyl)imide, and even more preferably an ammonium salt of bis(fluorosulfonyl)imide, crystallized in a halogenated alcohol. Without being bound by any theory, the inventors believe that this method is advantageous for obtaining a final product of very high purity without the need for demanding final purification steps. As a result, the process according to the present invention is more efficient and less expensive overall, while the final product is of the highest quality.

[0085] Generally speaking, all raw materials used in the method according to the present invention, including solvents, reagents, etc., may preferably exhibit very high purity standards. Preferably, their content of metal components such as Na, K, Ca, Mg, Fe, Cu, Cr, Ni, Zn, etc. is less than 10 ppm, more preferably less than 2 ppm.

[0086] In addition, some or all of the steps of the process according to the invention are advantageously carried out in equipment that can withstand the corrosion of the reaction medium. For this purpose, corrosion-resistant materials are selected for the parts that come into contact with the reaction medium, such as alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon, and tungsten sold under the Hastelloy® brand, or alloys of nickel, chromium, iron, and manganese with added copper and / or molybdenum sold under the names Inconel® or Monel™, more particularly Hastelloy C276 or Inconel 600, 625, or 718 alloys. Austenitic steels, more particularly stainless steels such as 304, 304L, 316, or 316L stainless steels, can also be selected. Steels with a nickel content of up to 22% by weight, preferably between 6% and 20%, and more preferably between 8% and 14%, are used. 304 and 304L steels have nickel contents ranging from 8% to 12%, while 316 and 316L steels have nickel contents ranging from 10% to 14%. More particularly, 316L steel is selected. Equipment made of or coated with polymeric compounds resistant to corrosion by the reaction medium can also be used. Materials such as PTFE (polytetrafluoroethylene or Teflon) or PFA (perfluoroalkyl resin) can be mentioned in particular. Glass equipment can also be used. The use of equivalent materials would not be outside the scope of the present invention. Other materials that may be suitable for contact with the reaction medium include graphite derivatives. The material for filtration must be compatible with the medium used. Fluorinated polymers (PTFE, PFA), loaded fluorinated polymers (Viton™), as well as polyester (PET), polyurethane, polypropylene, polyethylene, cotton, and other compatible materials can be used. Materials that can be used for the filtration membrane include cellulose, PE / PP, polyurethane, and fluorinated materials such as PTFE and PFA.

[0087] If the disclosure of any patent, patent application, or publication incorporated herein by reference contradicts the statement of this application to the extent that it may render a term unclear, the statement shall control.

[0088] The present invention will now be further described in examples that are given by way of illustration and are not intended to limit the scope of the specification or claims in any way. [Example]

[0089] Example 1: Synthesis of NH4FSI This process was carried out in a 500 mL Hastelloy reactor equipped with a stirring means, a double jacket for heat regulation, a condenser, a pressure regulator, and a means for adding liquid or gas under N2. 200 g of ethyl methyl carbonate was introduced at room temperature, and 36 g of anhydrous NHF was suspended therein. 50 g of molten CSIH was gradually added over 1 hour, and the mixture was heated at 65°C under stirring for 15 hours. It was cooled to room temperature, and 12 g of NH3 (aqueous) (aqueous ammonia) was added. The resulting mixture was stirred at room temperature for 1 hour and then filtered. The filtrate was concentrated to dryness under reduced pressure to give 40 g of NHFSI as a white solid.

[0090] Example 2: Synthesis of LiFSI - Comparative Example 40 g of solid NHFSI obtained according to Example 1 was solubilized in 400 g of ethyl methyl carbonate. 9.2 g of a 25 wt % aqueous solution of LiOH·H2O was added. The resulting two-phase mixture was stirred at room temperature for 1 hour and then decanted. The organic phase was recovered and concentrated by rotary evaporation at 20 °C under reduced pressure (5 mbar). A 30 wt % concentrated solution of LiFSI in ethyl methyl carbonate was obtained.

[0091] FIG. 1 shows the cyclic voltammetry diagram obtained by cycling five times the solution of LiFSI at 30 wt. % in EMC obtained in Example 2.

[0092] Cyclic voltammetry (CV) was performed using a three-electrode cell and VSP (BioLogic); CV tests were performed at 1 mV.s. -1 At a scan rate of Li / Li + The voltage was measured from 0 to 3.0 V vs. CV. The first CV cycle started from OCV with a reduction scan. A total of five CV cycles were recorded.

[0093] Example 3: Synthesis of LiFSI according to the present invention 40 g of solid NH4FSI obtained according to Example 1 was dissolved in 60 g of TFE at 60° C. for 1 hour, and then the resulting solution was cooled to 0° C. for 3 hours. The crystallized NH4FSI was filtered off, washed with cold TFE, and dried under vacuum to obtain 33 g of NH4FSI crystals.

[0094] 33 g of NHFSI crystals were solubilized in 300 g of ethyl methyl carbonate. 7.6 g of a 25 wt % aqueous solution of LiOH·H2O was added. The resulting two-phase mixture was stirred at room temperature for 1 h and then decanted. The organic phase was collected and concentrated by rotary evaporation at 20 °C under reduced pressure (5 mbar). A 30 wt % LiFSI solution in ethyl methyl carbonate was obtained.

[0095] 2 shows the cyclic voltammetry diagram obtained by cycling five times the solution of 30 wt % LiFSI in EMC obtained in Example 3. The conditions of the CV test were the same as those in Example 2.

[0096] By comparing Figures 1 and 2, the current range recorded for the composition of Example 3 (according to the invention) (approximately 7 mA / cm 2 ) was in the current range recorded with the composition of Example 2 (comparative) (about 4 mA / cm 2) is significantly greater than that of Example 2 (Comparative). Furthermore, while the current remains rather stable from the first to the fifth cycle for the composition of Example 3 (Inventive), the cycling curve changes for the composition of Example 2 (Comparative). In addition, it can be seen that the current shows some shoulder after 0.5 V on the cyclic voltammetry diagram of Figure 1 (Comparative), while this shoulder is absent in the diagram of Figure 2 (Inventive).

[0097] These data indicate that salts of bis(fluorosulfonyl)imides according to the present invention are more suitable for use in electrolyte compositions for batteries than the comparative salts.

[0098] Example 4: Synthesis of NH4FSI This process was carried out in a 500 mL Hastelloy reactor equipped with a stirring means, a double jacket for heat regulation, a condenser, a pressure regulator means, and a means for adding liquid or gas under N2. At room temperature, 200 g of butyl acetate was introduced and 44 g of anhydrous NHF was suspended. 60 g of molten CSIH was gradually added over 1 hour, and the mixture was heated at 65°C under stirring for 15 hours. It was cooled to room temperature, and 15 g of NH3 (aqueous) (aqueous ammonia) was added. The resulting mixture was stirred at room temperature for 1 hour and then filtered. The filtrate was concentrated to dryness under reduced pressure to give 45 g of NHFSI as a white solid.

[0099] Example 5: Synthesis of LiFSI according to the present invention 45 g of solid NH4FSI obtained according to Example 4 was dissolved in 60 g of TFE at 60° C. for 1 hour, and then the resulting solution was cooled to 0° C. for 3 hours. The crystallized NH4FSI was filtered off, washed with cold TFE, and dried under vacuum to obtain 37 g of NH4FSI crystals.

[0100] 37 g of NHFSI crystals were solubilized in 300 g of ethyl methyl carbonate. 8.5 g of a 25 wt % aqueous solution of LiOH·H2O was added. The resulting two-phase mixture was stirred at room temperature for 1 h and then decanted. The organic phase was collected and concentrated by rotary evaporation at 20 °C under reduced pressure (5 mbar). A 30 wt % LiFSI solution in ethyl methyl carbonate was obtained.

[0101] Example 6: Synthesis of Neat N(CH3)4FSI This process was carried out in a 500 mL Hastelloy reactor equipped with a stirring means, a double jacket for heat regulation, a condenser, a pressure regulator, and a means for adding liquid or gas under N2. 300 g of butyl acetate was introduced at room temperature, and 110 g of anhydrous N(CH3)4F was suspended therein. 60 g of molten CSIH was gradually added over 1 hour, and the mixture was heated at 65°C under stirring for 15 hours. It was cooled to room temperature, and 15 g of NH3 (aq) (aqueous ammonia) was added. The resulting mixture was stirred at room temperature for 1 hour and then filtered. The filtrate was concentrated to dryness under reduced pressure to give 42 g of N(CH3)4FSI as a white solid.

[0102] Example 7: Preparation of N(CH3)4FSI according to the present invention 42 g of solid N(CH)FSI obtained according to Example 6 was dissolved in 160 g of hexafluoroisopropanol (HFIP) at 58° C. for 1 hour and cooled to −15° C. for 3 hours. The crystallized N(CH)FSI was filtered off, washed with cold HFIP, and dried under vacuum to obtain 33 g of N(CH)FSI crystals.

[0103] Example 8: Synthesis of NH4FSI This process was carried out in a 500 mL Hastelloy reactor equipped with stirring, a double jacket for heat regulation, a condenser, a pressure regulator, and a means for adding liquid or gas under N2. 200 g of dimethyl carbonate was introduced at room temperature, and 44 g of anhydrous NHF was suspended therein. 60 g of molten CSIH was gradually added over 1 hour, and the mixture was heated at 65°C under stirring for 15 hours. It was cooled to room temperature, and 15 g of NH3 (aqueous) (aqueous ammonia) was added. The resulting mixture was stirred at room temperature for 1 hour and then filtered. The filtrate was concentrated to dryness under reduced pressure to give 42 g of NHFSI as a white solid.

[0104] Example 9: Synthesis of KFSI according to the present invention 42 g of solid NH4FSI obtained according to Example 8 was dissolved in 60 g of TFE at 60° C. for 1 hour, and then the resulting solution was cooled to 0° C. for 3 hours. The crystallized NH4FSI was filtered off, washed with cold TFE, and dried under vacuum to obtain 35 g of NH4FSI crystals.

[0105] 35 g of NHFSI crystals were solubilized in 300 g of dimethyl carbonate. 8.0 g of a 25 wt % aqueous solution of LiOH·H2O was added. The resulting two-phase mixture was stirred at room temperature for 1 h and then decanted. The organic phase was collected and concentrated by rotary evaporation at 20 °C under reduced pressure (5 mbar). A 30 wt % LiFSI solution in dimethyl carbonate was obtained.

Claims

1. Formula (I): [(FSO ２ ) ２ N － ] ｎ M ｎ＋ (I) (In the formula, M ｎ＋ represents an ammonium cation or an alkali metal cation, and n is an integer from 1 to 3 representing the valence of the cation M, A salt of bis(fluorosulfonyl)imide containing 0.01 ppm to 10,000 ppm of a halogenated alcohol.

2. Formula (I): [(FSO ２ ) ２ N － ] ｎ M ｎ＋ (I) (In the formula, M ｎ＋ represents an ammonium cation, and n is an integer of 1 to 3 representing the valence of the cation M.

3. Formula (I): [(FSO ２ ) ２ N － ] ｎ M ｎ＋ (I) (In the formula, M ｎ＋ represents an alkali metal cation, and n is an integer from 1 to 3 representing the valence of the cation M.

2. The salt of bis(fluorosulfonyl)imide of claim 1, represented by:

4. The salt of bis(fluorosulfonyl)imide according to any one of claims 1 to 3, wherein the halogenated alcohol is a fluorinated alcohol.

5. The salt of bis(fluorosulfonyl)imide according to any one of claims 1 to 4, which exhibits a mass percent purity of more than 90%.

6. - Less than 10,000 ppm chloride ions (Cl － ) content; and / or - Less than 10,000 ppm of fluoride ions (F － ) content; and / or - Less than 30,000 ppm of sulfate ions (SO ４ ２－ ) content; and / or - an iron (Fe) content of less than 1000 ppm; and / or a chromium (Cr) content of less than 1000 ppm; and / or a nickel (Ni) content of less than 1000 ppm; and / or a zinc (Zn) content of less than 1000 ppm; and / or a copper (Cu) content of less than 1000 ppm; and / or a bismuth (Bi) content of less than 1000 ppm; and / or - a sodium (Na) content of less than 10,000 ppm; and / or - Potassium (K) content less than 10,000 ppm The salt of bis(fluorosulfonyl)imide according to any one of claims 1 to 5, wherein

7. The salt of bis(fluorosulfonyl)imide according to any one of claims 1 to 6, in the form of a solid crystalline compound having a purity of more than 99.9%.

8. A method for producing the salt of the bis(fluorosulfonyl)imide according to any one of claims 1 to 7, comprising the step of crystallizing a raw salt of the bis(fluorosulfonyl)imide in a crystallization solvent containing at least a halogenated alcohol.

9. The crystallization step comprises: providing a solid base salt of a bis(fluorosulfonyl)imide; - dissolving said solid raw salt of bis(fluorosulfonyl)imide in said crystallization solvent; - crystallizing the salt of bis(fluorosulfonyl)imide; - recovering the recrystallized salt of bis(fluorosulfonyl)imide; 9. The method of claim 8, wherein the recrystallization process comprises the steps of:

10. 10. The method of claim 8 or 9, wherein the halogenated alcohol is a fluorinated alcohol.

11. 11. The method of any one of claims 8 to 10, wherein the crystallization solvent comprises a mixture of at least one halogenated alcohol and another solvent that is not a halogenated alcohol.

12. 12. The method according to any one of claims 8 to 11, wherein the crystallization solvent contains water in a content that can be between 0.01% and 20% based on the total weight of the crystallization solvent.

13. The salt of bis(fluorosulfonyl)imide has the formula (I): [(FSO ２ ) ２ N － ] ｎ M ｎ＋ (I) (In the formula, M ｎ＋ represents an onium cation, and n is an integer of 1 to 3 representing the valence of the cation M. and the raw salt of bis(fluorosulfonyl)imide can be prepared by the following process: - reacting a bis(chlorosulfonyl)imide or a salt thereof with an onium fluoride to produce an onium salt of a bis(fluorosulfonyl)imide; - precipitating and isolating said onium salt of bis(fluorosulfonyl)imide; The method according to any one of claims 8 to 12, wherein the composition is produced according to the following formula:

14. The salt of bis(fluorosulfonyl)imide is ammonium bis(fluorosulfonyl)imide; and the raw solid ammonium bis(fluorosulfonyl)imide can be prepared by the following process: - reacting bis(chlorosulfonyl)imide or a salt thereof with ammonium fluoride to produce the ammonium salt of bis(fluorosulfonyl)imide; - precipitating and isolating said ammonium salt of bis(fluorosulfonyl)imide; The method according to any one of claims 8 to 13, wherein the composition is produced according to the following formula:

15. A method for producing an alkali salt of a bis(fluorosulfonyl)imide, the method comprising the steps of producing a crystallized salt of the bis(fluorosulfonyl)imide according to any one of claims 8 to 14, and reacting the crystallized salt of the bis(fluorosulfonyl)imide with an alkaline agent to obtain the alkali salt of the bis(fluorosulfonyl)imide.

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