Reactive distillation process for preparing fluorosulfonylimide salts

Abstract

The present invention relates to a method for preparing a fluorosulfonylimide salt, more particularly to a method for preparing lithium bis(fluorosulfonyl)imide (LiFSI).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED PATENT APPLICATIONS This invention claims priority to European Patent Application No. 21315147.5, filed in Europe on August 27, 2021, and European Patent Application No. 21201565.5, filed in Europe on October 8, 2021, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a method for preparing a fluorosulfonylimide salt, more particularly, to a method for preparing lithium bis(fluorosulfonyl)imide (LiFSI). [Background technology]

[0003] Fluorosulfonylimide salts are useful compounds in a wide range of fields, and are used as electrolytes, as additives added to electrolytes in fuel cells, as selective electron-withdrawing materials, and the like (see, for example, JP-A-08-511274, the published Japanese translation of the PCT). Alkali metal salts of fluorosulfonylimides and various onium salts of fluorosulfonylimides can be obtained by a cation exchange reaction using an alkali metal compound or an onium compound. Ammonium fluorosulfonylimide salts are useful as intermediates for the production of alkali metal fluorosulfonylimide salts and onium fluorosulfonylimide salts other than ammonium salts.

[0004] Various methods have been proposed for the synthesis of fluorosulfonylimide ammonium salts.

[0005] For example, Zeitschrift fur Chemie (1987-27(6), pages 227-228) discloses a method for synthesizing di(fluorosulfonyl)imide ammonium salt from di(fluorosulfonyl)imide and ammonia.

[0006] JP 2010-168308 A (Nippon Shokubai Co., Ltd.) discloses a method for synthesizing bis[di(fluorosulfonyl)imide]onium salt by reacting di(chlorosulfonyl)imide with an onium compound to obtain a chlorosulfonylimide onium salt, and then reacting this onium salt with a fluoride containing at least one element selected from the group consisting of elements in groups 11 to 15 and in the 4th to 6th periods (excluding arsenic and antimony). Examples of fluorides used in the manufacturing method described in JP 2010-168308 A include zinc fluoride (ZnF2), copper fluoride (CuF2), and bismuth fluoride (BiF2). All of these compounds are solid substances at room temperature.

[0007] Furthermore, John K. Ruff and Max Lustig, Inorg. Synth., 11, 138-140 (1968) and Jean'ne M. Shreeve et al., Inorg. Chem., 1998, 37(24), 6295-6303 disclose a method for directly synthesizing di(fluorosulfonyl)imide from di(chlorosulfonyl)imide using arsenic trifluoride (AsF3) or antimony trifluoride (SbF3) as a fluorinating agent.

[0008] Chinese Patent No. 109734061 (HUNAN FUBANG NEW MAT CO., LTD.) discloses a method for preparing lithium difluorosulfonylimide, which includes the following steps: obtaining a difluorosulfonylimide; mixing and reacting difluorosulfonylimide with an alkaline lithium source in a non-aqueous solvent capable of forming an azeotrope with water, the non-aqueous solvent comprising one or more of pyridine and chloroethanol, and a crude product solution of lithium difluorosulfonylimide is obtained by filtration, the alkaline lithium source comprising one or more of LiOH, LiHCO3, and Li2CO3; A step of drying the crude product solution of lithium di(fluorosulfonyl)imide under reduced pressure in an environment with a degree of vacuum of 1000 to 100 Pa and a temperature of 30 to 80° C.; and If the product is in a paste form, the vacuum is reduced to less than 10-2 Pa to dry it, thereby obtaining a crude product of lithium difluorosulfonylimide.

[0009] LiFSI (lithium bis(fluorosulfonyl)imide) is known to be sensitive to water and can react to form unwanted species such as FSO3Li and / or FSO2NH2, which significantly degrade the quality and electrochemical properties of LiFSI products.

[0010] European Patent No. 3170789 (Nippon Soda Co., Ltd.) discloses a method for preparing fluorosulfonylimide salts. However, the fluorosulfonyl salts are not protected from water present in the reaction solution during the cation exchange reaction.

[0011] European Patent Specification No. 2662332 (Nippon Soda Co., Ltd.) discloses a method for producing a metal salt or onium salt of bis(fluorosulfonyl)imide, which comprises carrying out a cation exchange reaction on an ammonium salt of bis(fluorosulfonyl)imide under reduced pressure using at least one compound selected from the group consisting of metal hydroxides and onium hydroxides. In this reaction, ammonia is produced as a by-product of the cation exchange reaction, but this is removed by carrying out the reaction under reduced pressure.

[0012] European Patent No. 2977349 (Nippon Soda Co., Ltd.) discloses a method for preparing disulfonamine alkali metal salts, which comprises the following steps: A step of preparing an alkali metal salt of a disulfonylamine by subjecting the disulfonylamine onium salt to a cation exchange reaction in an organic solvent; and A step of filtering the organic solvent solution containing the disulfonylamine alkali metal salt through a filter having a particle retention size of 0.1 to 10 μm to obtain a filtrate.

[0013] According to the example, ammonium di(fluorosulfonyl)amine is first reacted with lithium hydroxide monohydrate under reflux in a suitable organic solvent, then the organic and aqueous phases are separated, and the organic phase is further treated under reduced pressure to remove water from the solution. This is followed by filtration, followed by distillation of the solvent. Thus, according to such description, the removal of water is not carried out simultaneously with the cation exchange reaction.

[0014] WO 2021 / 074142 (Solvay SA) discloses a method for producing a salt of bis(fluorosulfonyl)imide, comprising a step of crystallizing a raw salt of bis(sulfonylimide) in a crystallization solvent containing at least a halogenated alcohol. In Example 3, this document discloses a method comprising dissolving 33 g of NH4FSI crystals in 300 g of ethyl methyl carbonate and then adding 76 g of a 23 wt% LiOH·H2O aqueous solution. The organic phase was then recovered and concentrated by rotary evaporator at 20 ° C under reduced pressure (3 mbar). Thus, according to such a description, the removal of water proceeds after the cation exchange reaction. Summary of the Invention

[0015] The object of the present invention is to provide an efficient method for preparing fluorosulfonylimide salts, which suppresses salt decomposition and deterioration of electrochemical properties. Specifically, the object of the present invention is to provide an efficient method for preparing lithium bis(fluorosulfonyl)imide (LiFSI), which suppresses salt decomposition and deterioration of electrochemical properties.

[0016] It has now been found that these and other objects can be achieved by the method according to the present invention.

[0017] The present invention relates to a compound represented by the following formula (I): [ka] (In the formula, M n+represents a metal cation or an onium cation, the onium cation is not an ammonium cation, and n corresponds to the valence of the metal cation or the onium cation and is an integer of 1 to 4. A method for preparing a fluorosulfonylimide salt represented by ii) reacting ammonium bis(fluorosulfonyl)imide (NHFSI), preferably in the form of a solvate with at least one solvent S2, in at least one solvent S3 with a compound (C) selected from the group consisting of metal compounds, onium compounds, and organic amine compounds; and iii) removing at least a portion of the water present in the reaction solution from the reaction solution; wherein steps ii) and iii) are carried out simultaneously.

[0018] The present invention is based on the recognition that the moisture-induced decomposition of fluorosulfonylimide salt and the moisture-induced deterioration of electrochemical properties of fluorosulfonylimide salt can be effectively suppressed by removing the water present in the reaction solution from the reaction solution.Furthermore, the yield of the synthesis process of fluorosulfonylimide salt can be increased by removing the water present in the reaction solution from the reaction solution. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 shows a scheme of the process disclosed in the Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] According to the present invention, the term "about" means ±10%, preferably ±5%, more preferably ±2%, and even more preferably ±1% of the specified numerical value.

[0021] The present invention relates to a compound represented by the following formula (I): [ka] (In the formula, Mn+ represents a metal cation or an onium cation, and the onium cation is an ammonium cation (NH + ), and n corresponds to the valence of the metal cation or onium cation and is an integer from 1 to 4. A method for preparing a fluorosulfonylimide salt represented by ii) reacting ammonium bis(fluorosulfonyl)imide (NHFSI), preferably in the form of a solvate with at least one solvent S2, in at least one solvent S3 with a compound (C) selected from the group consisting of metal compounds, onium compounds, and organic amine compounds; and iii) removing at least a portion of the water present in the reaction solution from the reaction solution; wherein steps ii) and iii) are carried out simultaneously.

[0022] There is no particular limitation on the metal cation, but an alkali metal cation is preferred. Examples of the alkali metal cation include a lithium cation, a sodium cation, a potassium cation, a rubidium cation, and a cesium cation. Among these, a lithium cation, a sodium cation, or a potassium cation is preferred, and a lithium cation is most preferred.

[0023] Ammonium cation (NH4 +Examples of onium cations that are not aryl include phosphonium cations, oxonium cations, sulfonium cations, fluoronium cations, chloronium cations, bromonium cations, iodonium cations, selenonium cations, telluronium cations, arsonium cations, stibonium cations, bismuthonium cations; iminium cations, diazenium cations, nitronium cations, diazonium cations, nitrosonium cations, hydrazonium cations, diazenium dications, diazonium dications, imidazolium cations, pyridinium cations, quaternary ammonium cations, tertiary ammonium cations, secondary ammonium cations, primary ammonium cations, piperidinium cations, pyrrolidinium cations, morpholinium cations, pyrazolium cations, guanidinium cations, isouronium cations, and isothiuronium cations.

[0024] The onium cation is preferably an onium cation having an organic group, that is, an organic onium cation. Examples of the organic group include saturated and unsaturated hydrocarbon groups. The saturated or unsaturated hydrocarbon group may be linear, branched, or cyclic. The number of carbon atoms constituting the saturated or unsaturated hydrocarbon group is preferably 1 to 18, more preferably 1 to 8. The atom or atomic group constituting the organic group is preferably a hydrogen atom, a fluorine atom, an amino group, an imino group, an amide group, an ether group, a hydroxyl group, an ester group, a carboxyl group, a carbamoyl group, a cyano group, a sulfone group, a sulfide group, a nitrogen atom, an oxygen atom, or a sulfur atom, more preferably a hydrogen atom, a fluorine atom, an ether group, a hydroxyl group, a cyano group, or a sulfone group. The organic group may have only one of these atoms or atomic groups, or may have two or more of these atoms or atomic groups. When two or more organic groups are bonded, the bond may be formed between the main structures of the organic groups, between the main structure of the organic group and the above-mentioned atomic group, or between the above-mentioned atomic groups themselves.

[0025] Examples of onium cations having an organic group include imidazolium cations, such as 1,3-dimethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-decyl-3-methylimidazolium cation, 1-tetra ... ladecyl-3-methylimidazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-allyl-3-ethylimidazolium cation, 1-allyl-3-butylimidazolium cation, 1,3-diallylimidazolium cation, 1-ethyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1-hexyl-2,3-methylimidazolium cation, and 1-hexadecyl-2,3-methylimidazolium cation; Pyridinium cations, such as the 1-ethylpyridinium cation, the 1-butylpyridinium cation, the 1-hexylpyridinium cation, the 1-octylpyridinium cation, the 1-ethyl-3-methylpyridinium cation, the 1-ethyl-3-hydroxymethylpyridinium cation, the 1-butyl-3-methylpyridinium cation, the 1-butyl-4-methylpyridinium cation, the 1-octyl-4-methylpyridinium cation, the 1-butyl-3,4-dimethylpyridinium cation, and the 1-butyl-3,5-dimethylpyridinium cation; Quaternary ammonium cations, such as tetramethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetrabutylammonium cation, tetraheptylammonium cation, tetrahexylammonium cation, tetraoctylammonium cation, triethylmethylammonium cation, propyltrimethylammonium cation, diethyl-2-methoxyethylmethylammonium cation, methyltrioctylammonium cation, cyclohexyltrimethylammonium cation, 2-hydroxyethyltrimethylammonium cation, trimethylphenylammonium cation, benzyltrimethylammonium cation, benzyltributylammonium cation, benzyltriethylammonium cation, dimethyldistearylammonium cation, diallyldimethylammonium cation, 2-methoxyethoxymethyltrimethylammonium cation, and tetrakis(pentafluoroethyl)ammonium cation; Tertiary ammonium cations, such as trimethylammonium cation, triethylammonium cation, tributylammonium cation, diethylmethylammonium cation, dimethylethylammonium cation, dibutylmethylammonium cation, and 4-aza-1-azoniabicyclo[2.2.2]octane cation; Secondary ammonium cations, such as the dimethylammonium cation, the diethylammonium cation, and the dibutylammonium cation; Primary ammonium cations, such as methylammonium cation, ethylammonium cation, butylammonium cation, hexylammonium cation, and octylammonium cation; organic ammonium cations, such as N-methoxytrimethylammonium cation, N-ethoxytrimethylammonium cation, and N-propoxytrimethylammonium cation; piperidinium cations, such as the 1-propyl-1-methylpiperidinium cation and the 1-(2-methoxyethyl)-1-methylpiperidinium cation; Pyrrolidinium cations, such as the 1-propyl-1-methylpyrrolidinium cation, the 1-butyl-1-methylpyrrolidinium cation, the 1-hexyl-1-methylpyrrolidinium cation, and the 1-octyl-1-methylpyrrolidinium cation; morpholinium cations, such as the 4-propyl-4-methylmorpholinium cation and the 4-(2-methoxyethyl)-4-methylmorpholinium cation; Pyrazolium cations, such as the 2-ethyl-1,3,5-trimethylpyrazolium cation, the 2-propyl-1,3,5-trimethylpyrazolium cation, the 2-butyl-1,3,5-trimethylpyrazolium cation, and the 2-hexyl-1,3,5-trimethylpyrazolium cation; Guanidinium cations, such as the guanidinium cation and the 2-ethyl-1,1,3,3-tetramethylguanidinium cation; Sulfonium cations, such as the trimethylsulfonium cation; Phosphonium cations, such as the trihexyltetradecylphosphonium cation; Isouronium cations, such as the 2-ethyl-1,1,3,3-tetramethylisouronium cation; and isothiouronium cations, such as the 2-ethyl-1,1,3,3-tetramethylisothiouronium cation; Examples include:

[0026] Among these, the onium cation preferably does not contain a metal element that deteriorates the electrolyte properties, etc. Specifically, the onium cation is, for example, a 1,3-dimethylimidazolium cation, a 1-ethyl-3-methylimidazolium cation, a 1-butyl-3-methylimidazolium cation, a 1-hexyl-3-methylimidazolium cation, a 1-octyl-3-methylimidazolium cation, a 1-allyl-3-ethylimidazolium cation, a 1-allyl-3-butylimidazolium cation, a 1,3-diallylimidazolium cation, a 1-ethyl-2,3-dimethylimidazolium cation, or a 1-butyl-2,3-dimethylimidazolium cation. and the 1-hexyl-2,3-dimethylimidazolium cation; and organic ammonium cations such as the propyltrimethylammonium cation, the diethyl-2-methoxyethylmethylammonium cation, the methyltrioctylammonium cation, the cyclohexyltrimethylammonium cation, the 2-hydroxyethyltrimethylammonium cation, the trimethylammonium cation, the triethylammonium cation, the tributylammonium cation, and the 4-aza-1-azoniabicyclo[2.2.2]octane cation.

[0027] According to the present invention, the fluorosulfonylimide salt represented by the following formula (I) is most preferably LiFSI.

[0028] According to the present invention, the method for preparing a compound according to formula (I) comprises step ii) of reacting NHFSI (ammonium bis(fluorosulfonyl)imide) in a solvent with a compound (C) selected from the group consisting of metal compounds, onium compounds, and organic amine compounds. Hereinafter, this reaction is also referred to as cation exchange reaction.

[0029] According to a preferred embodiment, the NH4FSI salt is a solvate, preferably in crystalline form.

[0030] Preferably, the solvate is 50-99% by weight of NH4FSI salt, and 1-50% by weight of solvent S2, Includes.

[0031] Preferably, said solvent S2 is selected from the group consisting of cyclic and acyclic ethers.

[0032] Preferably, the NH4FSI solvate contains 51 to 98% by weight, more preferably 55 to 95% by weight, or 78 to 83% by weight, of the NH4FSI salt.

[0033] Preferably, the NH4FSI solvate contains 2-49% by weight, more preferably 5-45% by weight or 17-22% by weight of the solvent S2 as defined above.

[0034] If NH4FSI is in the form of a solvate as defined above, the method comprises, prior to step ii), a step i) of preparing a NH4FSI solvate comprising the steps of: i1) preparing a crude salt of NH4FSI; i2) dissolving the crude salt of NH4FSI in at least one solvent S1; i3) crystallizing the crude salt of NH4FSI from at least one solvent S2; and i4) Separating the NH4FSI salt from at least a portion of the solvents S1 and S2, preferably by filtration.

[0035] The crude salt of NH4FSI preferably contains 80 to 97% by weight, preferably 85 to 95% by weight, more preferably 90 to 95% by weight of the salt of NH4FSI.

[0036] Solvent S1 is preferably selected from the group consisting of acetonitrile, valeronitrile, adiponitrile, benzonitrile, methanol, ethanol, 1-propanol, 2-propanol, 2,2,2-trifluoroethanol, n-butyl acetate, isopropyl acetate, and mixtures thereof; preferably 2,2,2-trifluoroethanol.

[0037] Solvent S2 is preferably selected from the group consisting of diethyl ether, diisopropyl ether, methyl t-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane, and mixtures thereof. More preferably, solvent S2 is selected from the group consisting of diethyl ether, diisopropyl ether, methyl t-butyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, and mixtures thereof. Even more preferably, solvent S2 is 1,3-dioxane or 1,4-dioxane.

[0038] Preferably, step i4) comprises reacting NH4FSI salt with more than 99.9% by weight of solvent S1; and · 50-99 wt% of solvent S2; It consists of separating it from

[0039] According to the present invention, the cation exchange reaction is preferably carried out by mixing NHFSI with a compound selected from the group consisting of a metal compound, an onium compound, and an organic amine compound in the presence of a solvent, the compound being preferably a metal compound, more preferably an alkali metal compound, even more preferably a lithium compound, even more preferably LiOHxH2O or Li2CO3, and most preferably LiOHxH2O.

[0040] The metal compound used in the cation exchange reaction is not particularly limited as long as it undergoes a cation exchange reaction with NH4FSI.

[0041] Preferably, the metal compound is an alkali metal sulfide. More preferably, the metal compound is an alkali metal compound selected from the group consisting of LiOH, NaOH, KOH, RbOH, CsOH, LiOHxH2O, NaOHxH2O, KOHxH2O, RbOHxH2O, CsOHxH2O, Li2CO3, Na2CO3, K2CO3, Rb2CO3, Cs2CO3, LiHCO3, NaHCO3, KHCO3, RbHCO3, and CsHCO3, even more preferably, the metal compound is an alkali metal compound selected from the group consisting of LiOHxH2O, NaOHxH2O, KOHxH2O, RbOHxH2O, CsOHxH2O, Li2CO3, Na2CO3, K2CO3, Rb2CO3, and CsHCO3, even more preferably, the metal compound is an alkali metal compound selected from the group consisting of LiOHxH2O and Li2CO3, and most preferably, the metal compound is LiOHxH2O.

[0042] When an alkali metal compound is used, the amount of the alkali metal compound used is preferably about 1 mol to about 10 mol, more preferably about 1 mol to about 5 mol, even more preferably about 1 mol to about 2 mol, still more preferably about 1 mol to about 1.5 mol, and most preferably about 1.1 mol, per mol of NHFSI.

[0043] Examples of onium compounds used in cation exchange reaction include nitrogen-based onium compounds, such as imidazolium compounds, pyrazolium compounds, pyridinium compounds, pyrrolidinium compounds, piperidinium compounds, morpholinium compounds, and quaternary ammonium compounds, phosphorus-based onium compounds, such as quaternary phosphonium compounds and tertiary phosphine compounds, sulfur-based onium compounds, such as sulfonium compounds, and guanidinium compounds, isouronium compounds, and isothiouronium compounds.Among these compounds, organic onium compounds are preferred.Furthermore, onium compounds are preferably free of metal elements that reduce electrolyte properties.

[0044] Preferably, the onium compound is a hydroxide-based compound.

[0045] Specific examples of the imidazolium compound include hydroxides such as 1,3-dimethylimidazolium hydroxide, 1-ethyl-3-methylimidazolium hydroxide, 1-butyl-3-methylimidazolium hydroxide, 1-hexyl-3-methylimidazolium hydroxide, 1-octyl-3-methylimidazolium hydroxide, 1-allyl-3-ethylimidazolium hydroxide, 1-allyl-3-butylimidazolium hydroxide, 1,3-diallylimidazolium hydroxide, 1-ethyl-2,3-dimethylimidazolium hydroxide, 1-butyl-2,3-dimethylimidazolium hydroxide, and 1-hexyl-2,3-dimethylimidazolium hydroxide.

[0046] Specific examples of pyrazolium compounds include hydroxides such as 2-ethyl-1,3,5-trimethylpyrazolium hydroxide, 2-propyl-1,3,5-trimethylpyrazolium hydroxide, 2-butyl-1,3,5-trimethylpyrazolium hydroxide, and 2-hexyl-1,3,5-trimethylpyrazolium hydroxide.

[0047] Specific examples of morpholinium compounds include 4-propyl-4-methylmorpholinium hydroxide and 4-(2-methoxyethyl)-4-methylmorpholinium hydroxide.

[0048] Specific examples of quaternary ammonium compounds include hydroxides such as propyltrimethylammonium hydroxide, diethyl-2-methoxyethylmethylammonium hydroxide, methyltrioctylammonium hydroxide, cyclohexyltrimethylammonium hydroxide, and 2-hydroxyethyltrimethylammonium hydroxide.

[0049] Specific examples of guanidinium compounds include guanidinium hydroxide and 2-ethyl-1,1,3,3-tetramethylguanidinium hydroxide.

[0050] A specific example of an isouronium compound is 2-ethyl-1,1,3,3-tetramethylisouronium hydroxide.

[0051] A specific example of an isothiouronium compound is 2-ethyl-1,1,3,3-tetramethylisothiouronium hydroxide.

[0052] When an onium compound is used, the amount of the onium compound used is about 1 mol to about 10 mol, more preferably about 1 mol to about 5 mol, even more preferably about 1 mol to about 2 mol, still more preferably about 1 mol to about 1.5 mol, and most preferably about 1.1 mol, per mol of NHFSI.

[0053] Examples of organic amine compounds used in the cation exchange reaction include tertiary amines such as trimethylamine, triethylamine, and tributylamine, cyclic amines such as 1,4-diazabicyclo[2.2.2]octane, tertiary amine salts such as trimethylamine hydrochloride, triethylamine hydrochloride, tributylamine hydrochloride, 1,4-diazabicyclo[2.2.2]octane hydrochloride, trimethylamine hydrobromide, triethylamine hydrobromide, and tributylamine hydrobromide, and cyclic amine salts such as 1,4-diazabicyclo[2.2.2]octane hydrobromide.

[0054] Among these, tertiary amines and cyclic amines are preferred.

[0055] When an organic amine compound is used, the amount of the organic amine compound used is about 1 mol to about 10 mol, more preferably about 1 mol to about 5 mol, even more preferably about 1 mol to about 2 mol, still more preferably about 1 mol to about 1.5 mol, and most preferably about 1.1 mol, per mol of NH4FSI.

[0056] Preferably, the metal compound is LiOHxH2O or Li2CO3 and the amount of metal compound used is about 1.1 moles per mole of NH4FSI, more preferably the metal compound is LiOHxH2O and the amount of metal compound used is about 1.1 moles per mole of NH4FSI.

[0057] The temperature during the cation exchange reaction is not particularly limited, but the reaction temperature in step ii) is preferably about 0°C to about 100°C, more preferably about 5°C to about 70°C, even more preferably about 10°C to about 50°C, and most preferably about 15°C.

[0058] The reaction pressure during the cation exchange reaction is not particularly limited, but the reaction pressure in step ii) is preferably from atmospheric pressure to about 0.01 mbar, more preferably from about 800 mbar to about 0.1 mbar, even more preferably from about 600 mbar to about 1 mbar, even more preferably from about 400 mbar to about 10 mbar, even more preferably from about 200 mbar to about 15 mbar, and most preferably about 30 mbar.

[0059] There is no particular limitation on the organic solvent S3 used in the cation exchange reaction. Examples of preferred solvents include aprotic solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxolane, methyl formate, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, 3-methylsulfolane, dimethylsulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, ethyl acetate, isopropyl acetate, n-butyl acetate, nitromethane, and nitrobenzene. More preferred solvents include ethylene carbonate, propylene carbonate, butylene carbonate, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl acetate, and n-butyl acetate, even more preferred solvents include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl acetate, and n-butyl acetate, even more preferred solvents include ethyl methyl carbonate and n-butyl acetate, and the most preferred solvent is ethyl methyl carbonate.

[0060] The reaction time required for the cation exchange reaction varies depending on the reaction scale, but is preferably about 1 hour to about 48 hours, more preferably about 1.5 hours to about 24 hours, even more preferably about 1.5 hours to about 12 hours, even more preferably about 2 hours to about 10 hours, and most preferably about 3 hours to about 6 hours.

[0061] Preferably, the compound in step ii) is added to ammonium bis(fluorosulfonyl)imide (NHFSI) over a time range of about 0.5 hours to about 10 hours, more preferably about 1 hour to about 8 hours, even more preferably about 1 hour to about 6 hours, even more preferably about 1.5 hours to about 5 hours, and most preferably about 2 hours to about 4 hours.

[0062] The reaction vessel may be made of a resin such as a fluororesin or a polyethylene resin, and is preferably made of a fluororesin.

[0063] The process according to the invention comprises a step iii) of removing at least a portion of the water present in the reaction solution from the reaction solution.

[0064] At least a portion of the solvent S2 present in the NH4FSI solvate may also be removed from the reaction solution during step iii).

[0065] Preferably, step iii) consists of removing by distillation, preferably by azeotropic distillation: - at least a portion of the water from the reaction solution present in the reaction solution, preferably more than 99.0% by weight of water, and - at least a portion of the solvent S2 present in the NH4FSI solvate, preferably more than 99.0% by weight of the solvent S2 present in the NH4FSI solvate.

[0066] Water present in the reaction solution may be formed as a by-product during the reaction or it may be introduced into the reaction solution by moist starting materials.

[0067] By removing at least a portion of the water present in the reaction solution from the reaction solution, two effects can be obtained. On the one hand, the decomposition of the water-sensitive fluorosulfonylimide salts according to formula (I) is suppressed, and as a result, the deterioration of the electrochemical properties of these salts is also suppressed. On the other hand, if water is formed as a by-product during the cation exchange reaction, as shown in the following reaction scheme, by removing water, the equilibrium can be adjusted to a state in which the cation exchange reaction is promoted. Thus, by removing at least a portion of the water present in the reaction solution from the reaction solution, the yield of the process according to the invention can be increased, and the quality of the fluorosulfonylimide salts and their electrochemical properties can also be improved. [ka]

[0068] At least a portion of the water present in the reaction solution, and preferably at least a portion of the solvent S2, can be removed from the reaction solution by any method known in the art, such as drying agents or distillation methods.

[0069] Preferably, at least a portion of the water present in the reaction solution, and preferably at least a portion of the solvent S2, is removed from the reaction solution by distillation, more preferably at least a portion of the water is removed by azeotropic distillation.

[0070] Preferably, at least a part of the water present in the reaction solution, and preferably at least a part of the solvent S2, is removed by azeotropic distillation, in step ii), the reaction temperature is about 10°C to about 50°C and the reaction pressure is about 200 mbar to about 50 mbar, more preferably, at least a part of the water present in the reaction solution is removed by azeotropic distillation, in step ii), the reaction temperature is about 15°C and the reaction pressure is about 100 mbar.

[0071] Preferably, the process according to the invention further comprises, after step iii), iv) further adding solvent S3 to the reaction solution; Further comprising: In this case, steps ii), iii) and iv) are carried out simultaneously.

[0072] If the reaction solution is depleted of solvent S3 by removal of at least a portion of the water present therein, then further solvent S3 is added to the reaction solution, for example by a solvent addition unit.

[0073] Preferably, in step iv), the solvent is added over time such that the molar concentration of the sulfonylimide salt in the reaction solution remains substantially constant, where "substantially constant" in this context means that the molar concentration of the sulfonylimide salt in the reaction solution does not change by more than about 0.2 mol / l, preferably about 0.1 mol / l.

[0074] Schematically, the main scheme of the process is shown in Figure 1. Step ii) can be carried out in a stirred reactor equipped with a distillation column using EMC (ethyl methyl carbonate) as solvent and LiOHxH2O as lithiated compound. Step iii) is carried out by azeotropic distillation. A vacuum pump may be used to carry out the azeotropic distillation. The wet solvent can be condensed and separated from the reaction solution in a condenser. Step iii) is carried out by an EMC addition unit, and the lithiated compound is added over time from a solid addition unit. EXAMPLES

[0075] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is obvious that appropriate modifications can be made while still remaining within the spirit of the present invention, and all such modifications are deemed to be included in the technical scope of the present invention.

[0076] A 500 ml stirred tank reactor equipped with a distillation column, a condenser, a powder addition unit and a solvent addition unit (see FIG. 1) was charged with 3.75 moles (390 g) of EMC and 0.250 moles (49.5 g) of bisammonium(fluorosulfonyl)imide (NH4FSI) and stirred at 15° C. 0.275 moles (11.5 g) of lithium hydroxide monohydrate (LiOHxH2O) was gradually added to the reaction solution over 3 hours via a solid addition unit (see FIG. 1). During the addition of LiOHxH2O, the reaction temperature was kept at 15° C., the reaction pressure was reduced to less than 30 mbar and EMC and water were removed by azeotropic distillation. The removed EMC and water were condensed at the top of the column and fresh EMC was added to the reactor to replace the removed wet EMC and to keep the molar concentration of fluorosulfonylimide salt constant (see FIG. 1). After 3 h of LiOHxH2O addition and an additional 1 h reaction time, the conversion of NH4FSI was complete and the yield of LiFSI was >95%.

Claims

1. A method for preparing a fluorosulfonylimide salt represented by the following formula (I): 【Chemical 1】 (wherein, M ｎ＋ represents a metal cation or an onium cation, the onium cation is not an ammonium cation, n corresponds to the valence of the metal cation or the onium cation, and is an integer of 1 to 4) comprising: ii) reacting ammonium bis(fluorosulfonyl)imide (NH₄FSI) with a compound (C) selected from the group consisting of a metal compound, an onium compound, and an organic amine compound in at least one solvent S ３ a step of reacting; and iii) removing at least a portion of the water present in the reaction solution from the reaction solution; wherein steps ii) and iii) are carried out simultaneously.

2. Said NH ４ FSI is in the form of a solvate with at least one solvent S ２ The method according to claim 1, which is in the form of a solvate with a solvent S

3. The NH in the form of the solvate ４ FSI salt is - being in crystalline form and / or - 50 to 99% by weight of NH ４ FSI salt, and 1 to 50% by weight of at least one solvent S ２ comprising The method according to claim 2.

4. the solvent S ２ The method according to claim 2 or 3, wherein the [solvent S] is selected from the group consisting of cyclic ethers and acyclic ethers.

5. Before step ii), the following: i １ ) NH ４ Step of preparing a crude salt of NHFSI; i ２ )(ii) Dissolving the crude salt of NH ４ FSI in at least one solvent S １ ; i ３ (ii) crystallizing the crude salt of the NH ２ FSI with at least one solvent S; and ４ (iii) i ４ )(ii) separating the NH １ FSI salt from at least a part of the solvent S ２ and S ４ ; NH containing ４ The method according to claim 1, comprising step i) of preparing an FSI solvate.

6. In step ii), the compound (C) is a lithium compound (C*), preferably lithium hydroxide LiOH, lithium hydroxide hydrate LiOH.H ２ O, lithium carbonate Li ２ CO ３ , lithium hydrogen carbonate LiHCO ３ , lithium chloride LiCl, lithium fluoride LiF, an alkoxide compound, an alkyllithium compound, lithium acetate CH ３ COOLi, and lithium oxalate Li ２ C ２ O ４ The method according to claim 1, selected from the group consisting of.

7. The method according to claim 1, wherein in step iii), at least a portion of the water present in the reaction solution is removed from the reaction solution by distillation.

8. In step iii), the solvent S present in the NH ４ FSI solvate is removed from the reaction solution by distillation, the method according to claim 1. ２ ​

9. The method according to claim 1, wherein the reaction temperature in step iii) is from about 0 °C to about 100 °C.

10. The method according to claim 1, wherein in step iii), the reaction pressure is from atmospheric pressure to about 0.01 mbar.

11. the solvent S １ The method according to claim 1, wherein the solvent S is selected from the group consisting of acetonitrile, valeronitrile, adiponitrile, benzonitrile, methanol, ethanol, 1-propanol, 2-propanol, 2,2,2-trifluoroethanol, n-butyl acetate, isopropyl acetate, and mixtures thereof.

12. the solvent S ２ The method according to claim 1, wherein the solvent S is selected from the group consisting of diethyl ether, diisopropyl ether, methyl-t-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane, and mixtures thereof.

13. The solvent S ３ The method according to claim 1, wherein the solvent S is ethyl methyl carbonate (EMC) or n-butyl acetate.

14. The compound (C) of step ii) is added to the ammonium bis(fluorosulfonyl)imide (NH ４ FSI) over a time range of from about 0.5 hours to about 10 hours, the method according to claim 1.

15. A method according to claim 1, wherein in formula (I): [Chemical Formula 2] wherein M ｎ＋ represents Li+, and the method comprises the following steps: i) i １ )(NH ４ Step of preparing crude salt of NHFSI; i ２ )(ii) Dissolving the crude salt of the NH ４ FSI in at least one solvent S １ ; i ３ (ii) crystallizing the crude salt of NHFSI with at least one solvent S ２ by said NH ４ FSI; and i ４ Solvent S １ and S ２ Separating at least a part of the NH ４ FSI salt to obtain an NH ４ FSI solvate; by NH ４ Step of preparing an NHFSI solvate: ii) reacting the NH ４ FSI solvate from step i) with a lithium compound (C*) in at least one solvent; and ３ ​ iii) by azeotropic distillation, - removing from the reaction solution at least a portion of the water present in the reaction solution, preferably more than 99.0% by weight of said water, and - Said NH ４ The solvent S present in the FSI solvate ２ At least a portion, preferably more than 99.0% by weight of said solvent S ２ , ; comprising wherein steps ii) and iii) are carried out simultaneously. - Process i ４ ), the solvent S exceeding 99.9% by weight １ and 50 to 99% by weight of the solvent S ２ both from the NH ４ FSI salt is separated; - the method comprising step i ４ ) the NH ４ FSI solvate obtained in step i ５ ) of drying;

16. The method according to claim 15.

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