Method for producing lithium fluorosulfonylimide salt

Abstract

The present invention relates to a method for producing a lithium salt of a bis(fluorosulfonyl)imide.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to earlier European Patent Application No. 22305260.6, filed March 7, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a method for producing a lithium salt of a bis(fluorosulfonyl)imide. [Background technology]

[0003] Fluorosulfonylimide salts, especially the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds for battery electrolytes. Various processes, reactants and intermediates leading to LiFSI are described in the patent literature, notably in Canadian Patent 2 527 802 (Universite de Montreal), which describes several routes for preparing LiFSI, such as the process for preparing LiFSI in one step starting from bis(chlorosulfonyl)imide (HCSI) using anhydrous hydrogen fluoride (HF): [ka] The following are listed.

[0004] One alternative known process for preparing LiFSI is a two-step process that involves fluorination of bis(chlorosulfonyl)imide (HCSI) to bis(fluorosulfonyl)imide (HFSI) using a fluorinating agent, such as anhydrous hydrogen fluoride (HF), followed by fluorination of HFSI to LiFSI using a lithiation agent.

[0005] Another known two-step process for preparing LiFSI uses NHF(HF) as the fluorinating agent. xThe process comprises a first step of fluorination of bis(chlorosulfonyl)imide (HCSI) to ammonium bis(fluorosulfonyl)imide (NHFSI) using 1,4-dichlorophenylsulfonyl, followed by a second step of lithiation of NHFFSI, which then leads to the LiFSI product. Such processes are described, for example, in WO 2017 / 090877 A1 (CLS) and EP 3 170 789 A1 (Nippon Soda Co., Ltd.).

[0006] Another known two-step process for preparing LiFSI involves the lithiation of HCSI in the first step using a lithiation agent to prepare LiCSI as an intermediate product, and then the fluorination of LiCSI to LiFSI using a fluorination agent. For example, Korean Patent No. 20200049164 (CLS) describes a method for preparing LIFSI, which includes the steps of reacting HCSI with various lithiation agents in a (SI) solvent to produce LiCSI, and then reacting it directly with anhydrous fluorination agents without purification. A long list of possible solvents is given in the specification, but dimethyl carbonate is used in the examples.

[0007] As can be seen from the above patent documents, the preparation of bis(fluorosulfonyl)imides, their salts and intermediate products is carried out in a solvent, e.g. an organic solvent, to disperse the reactive entities and to allow them to react. Summary of the Invention

[0008] Applicants have recognized that there remains a need in the art for improved processes for the manufacture of LiFSI and of the intermediate compounds for its manufacture.

[0009] In particular, the applicant is aware that the organic solvents used in the processes disclosed in the prior art usually must be treated to remove residual amounts of water and / or may need to be removed after the reaction. This step to remove the solvent increases the complexity of the industrial process as well as its overall cost.

[0010] With the aim of overcoming the above mentioned drawbacks, the Applicant faced the task of providing a simpler manufacturing process for preparing LiCSI products, which in particular does not require the use of solvents.

[0011] In a first aspect, the present invention provides a method for preparing a lithium salt of a bis(fluorosulfonyl)imide (LiFSI), comprising the steps of: (a) providing a lithium salt of bis(chlorosulfonyl)imide (LiCSI) having a solvent content of less than 1000 ppm, preferably less than 500 ppm, and more preferably less than 100 ppm, as measured by gas chromatography or headspace gas chromatography; (b) contacting the LiCSI of step (a) with at least one fluorinating agent to produce LiFSI; The present invention relates to a method comprising the steps of:

[0012] In a second aspect, the present invention relates to lithium bis(fluorosulfonyl)imide (LiFSI) obtainable by the process of the invention.

[0013] In a third aspect, the present invention relates to the use of lithium bis(fluorosulfonyl)imide (LiFSI), as described above, in an electrolyte for a battery, particularly a non-aqueous electrolyte, which can then be used in the manufacture of a battery or battery cell by disposing it between a cathode and an anode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In this application: - the expression "of" is to be understood as including limiting values; - any description, even if made in relation to a particular embodiment, is applicable to and interchangeable with other embodiments of the invention; - when an element or component is said to be included in and / or selected from a list of enumerated elements or components, in related embodiments expressly contemplated herein, the element or component can also be any one of the individual enumerated elements or components, or can also be selected from a group consisting of any two or more of the explicitly enumerated elements or components; it is to be understood that any element or component enumerated in a list of elements or components may be omitted from such list; - any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited range, as well as the endpoints of the range, and equivalents thereof; - the term "solvent" is intended to mean a compound that exhibits the following three cumulative properties: 1 / is present throughout the reaction and is optionally added during the process; 2 / does not change during the process, in other words is non-reactive towards the reactants involved; and 3 / must be removed at the end of the process if the reaction product must be in its pure form. For clarity, the molten HCSI used in the process of the present invention does not fall within this definition and is not intended as a "solvent" or "diluent" as mentioned above. Solvents typically used in such processes are well known and have been extensively described in the literature. Such solvents may be aprotic, e.g. polar aprotic solvents, 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, dimethylsulfoxide, and cyano-, nitro-, chloro- or alkyl-substituted alkanes or aromatic hydrocarbons, such as acetonitrile, valeronitrile, adiponitrile, benzonitrile, nitromethane, nitrobenzene may be selected from the group consisting of:

[0015] Under step (a), the LiCSI having a solvent content of less than 100 ppm is preferably subjected to the following steps: (A) providing bis(chlorosulfonyl)imide (HCSI); (B) melting the HCSI obtained in step (a) to obtain a molten HCSI; (C) treating the molten HCSI obtained in step (b) with a compound of formula (I): (I)M + B - (In the formula, M is selected from Na, Li, K, Ce, Rb and Fr; B is Cl, F; carbonate (CO3 2- );Sulfate (SO4 2- ); carboxylate; silicate, preferably metasilicate; borate, preferably tetraborate; and mixtures thereof. and reacting the compound to produce a salt of bis(chlorosulfonyl)imide. Includes; wherein steps (B) and (C) are carried out in the absence of a solvent. It is produced by the method [Method (MI)].

[0016] The salt of bis(chlorosulfonyl)imide obtained by said method (MI) is characterized by an undetectable amount of solvent, which makes it suitable for many applications, especially as an intermediate for the preparation of LiFSI used in battery applications.

[0017] Advantageously, the method (MI) is carried out in molten HCSI, which serves to disperse the compound of formula (I) in the absence of solvents and diluents. In other words, the method of the present invention is a solvent-free method, meaning that no solvents and / or diluents are added to the reaction mixture during the reaction. This is advantageous because, firstly, the step of removing the solvent is avoided, thus reducing the complexity of the industrial process as well as its overall cost, and secondly, the preliminary step of treating the solvent to reduce its water content is also avoided.

[0018] In the context of the present invention, the starting HCSI as provided in step (A) of method (MI) can be prepared by known methods, for example: - by reacting chlorosulfonyl isocyanate (ClSO2NCO) with chlorosulfonic acid (ClSO2OH); - by reacting cyanogen chloride (CNCl) with sulfur trioxide (SO3) and with chlorosulfonic acid (ClSO2OH); or - By reacting sulfamic acid (NH2SO2OH) with thionyl chloride (SOCl2) and with chlorosulfonic acid (ClSO2OH), It can be manufactured.

[0019] According to the method of the present invention, in step (B), a quantity of HCSI is in a molten state (also called liquid state) and is heated to its melting temperature (Tm HCSI ) is heated above

[0020] Preferably, step (B) is carried out at a temperature (Tb) suitable to melt the HCSI and to maintain it in the molten state while avoiding its decomposition.

[0021] Step (B) is the melting temperature (Tm) of HCSI (Tm HCSI In this case, Tb ≧ Tm HCSI For example, Tb is the melting point Tm of HCSI (Tm HCSI ) plus 5°C or more. In this case, Tb ≥ Tm HCSI As another example, Tb is the melting point Tm of HCSI (Tm HCSI ) plus 10°C or more. In this case, Tb ≥ Tm HCSI It's +10.

[0022] One of skill in the art will appreciate that the Tm of HCSI is affected by the presence and amount of impurities.

[0023] Preferably, the temperature (Tb) at which step (B) is carried out is at least 30° C., such as at least 37° C., such as at least 38° C., at least 40° C., at least 45° C. or even at least 50° C. In any case, the temperature (Tb) at which step (B) is carried out is below the decomposition temperature of the HCSI.

[0024] Preferably, under step (C), said compound of formula (I) is added either gradually or all at once.

[0025] Alternatively, the molten HCSI is added, either gradually or all at once, to said compound of formula (I) previously loaded into the reactor.

[0026] Those skilled in the art will appreciate that other ingredients or reactants, either in powder or liquid form, can be added to the reaction environment based on the needs or circumstances.

[0027] In some embodiments, the molar ratio of HCSI to compound of formula (I) ranges from 0.001:1 to 20:1, particularly from 0.1:1 to 10:1, more particularly from 0.5:1 to 5:1, and even more particularly is about 1:1.

[0028] Preferably, in said compound of formula (I), M is selected from Na, Li and K.

[0029] Even more preferably, M is Li. According to this embodiment, the compound of formula (I) will be referred to as "compound LiX".

[0030] According to this embodiment, the compound LiX used in the method of the present invention is a component that does not generate water or soluble species over the course of the reaction.

[0031] In some embodiments, the compound LiX is lithium chloride (LiCl), lithium fluoride (LiF), lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium carboxylate (Li n (RCO2) n ), Li2SiO3, Li2B4O7 and mixtures thereof.

[0032] Even more preferably, said compound LiX is anhydrous lithium chloride (LiCl) in solid form.

[0033] Depending on the circumstances, said steps (B) and (C) can be carried out at the same temperature or at different temperatures.

[0034] Those skilled in the art will understand that the choice of compound of formula (I) will affect the temperature at which step (C) is carried out. The detailed description of step (C) as provided later in this specification refers to the step in which in compound (I), M is Li, and therefore the salt as obtained at the end of step (C) is lithium bis(chlorosulfonyl)imide (LiCSI).

[0035] Preferably, step (C) is carried out at a temperature (Tc) at which LiCSI is in liquid form, which is below the melting temperature (Tm) of LiCSI (Tm LiCSI In this case, Tc ≥ Tm LiCSI For example, (Tc) is the melting point Tm of LiCSI (Tm LiCSI ) plus 5°C or more. In this case, Tc ≥ Tm LiCSI +5. As another example, Tc is the melting point Tm of LiCSI (Tm LiCSI ) plus 10°C or more. In this case, Tc ≥ Tm LiCSI It's +10.

[0036] Alternatively and more preferably, step (C) is carried out while the HCSI is in a molten state, i.e., Tc≧Tm HCSI and LiCSI is at least partially in solid form, i.e., Tc≦Tm LiCSI According to this embodiment, Tc is the melting point Tm of LiCSI (Tm LiCSI ) minus 5°C or less. In this case, Tc≦Tm LiCSI -5. As another example, Tc is the melting point Tm of LiCSI (Tm LiCSI ) minus 10 degrees Celsius or less. In this case, Tc ≦ Tm LiCSI In other words, according to these embodiments, the temperature Tc at which step (C) is performed is less than the melting point (Tm HCSI ) and the melting point of LiCSI (Tm LiCSI )

[0037] Preferably, the temperature (Tc) at which step (C) is carried out is 37° C. or higher, such as 50° C. or higher, 60° C. or higher, 80° C. or higher, or even 100° C. or higher. In some embodiments, the temperature (Tc) at which step (C) is carried out is 220° C. or lower, such as 218° C. or lower, 215° C. or lower, 212° C. or lower, or even 210° C. or higher.

[0038] Each of step (B) and / or step (C) may be carried out at atmospheric pressure or under reduced pressure, for example, each of step (B) and step (C) may be carried out under vacuum or at about 1 atmosphere, preferably 1 atmosphere.

[0039] In embodiments where the temperature (Tc) at which step (C) is carried out varies between the melting point of HCSI (Tm1) and the melting point of LiCSI (Tm2), the molar ratio of HCSI to compound LiX is preferably such that HCSI is the excess reactant, so that unconverted HCSI allows the final reaction medium to be processed for further LiCSI filtration, for example, the molar ratio of HCSI to compound LiX is 2:1.

[0040] In other embodiments where the temperature (Tc) at which step (C) is carried out is equal to or greater than the melting point (Tm2) of LiCSI, the molar ratio of HCSI to compound LiX is preferably such that compound LiX is an excess reactant, such that HCSI can be completely converted and compound LiX can be filtered to provide isolated LiCSI. For example, the molar ratio of HCSI to compound LiX is 1:1.05.

[0041] Preferably, when LiCl is used, hydrogen chloride (HCl) formed as a by-product during step (B) and / or step (C) is continuously removed from the reaction vessel throughout step (B) and / or step (C). For example, HCl removal is performed under vacuum or by stripping with an inert gas (such as nitrogen, helium or argon). The sparged HCl can be further recycled.

[0042] Preferably, the process according to the invention comprises, after step (C), a step (D) which comprises the separation of the salt of bis(chlorosulfonyl)amide (LiCSI) from the reaction mixture. When the process comprises step (D), the HCSI remaining after the reaction can be reused. The remaining HCSI is preferably in a molten state.

[0043] This separation step can be carried out by any separation means known to those skilled in the art. Separation can be carried out, for example, by filtration, for example under pressure or under vacuum, or by decantation. The mesh size of the filtration medium can be, for example, 2 μm or less, 0.45 μm or less, or 0.22 μm or less. The separated product can be washed once or several times with a suitable solvent, which can be determined by the skilled person, such as, for example, dichloromethane. Preferably, the solvent is then evaporated and the recovered HCSI can be recycled. The separation step can be carried out once or repeated two or more times if necessary.

[0044] Some or all of the steps of the method according to the invention are advantageously carried out in equipment capable of withstanding the corrosion of the reaction medium.

[0045] For this purpose, alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon and tungsten sold under the Hastelloy® brand or under the names Inconel® or Monel® are also available. TMMaterials that are corrosion resistant are selected for the parts that come into contact with the reaction medium, such as alloys of nickel, chromium, iron and manganese to which copper and / or molybdenum have been added, more particularly Hastelloy C276 or Inconel 600, 625 or 718 alloys, sold by AB 12000. Austenitic steels may also be selected, more particularly stainless steels, such as 304, 304L, 316 or 316L stainless steels. Steels are used that have a nickel content of at most 22% by weight, preferably between 6% and 20% by weight, more preferentially between 8% and 14% by weight. 304 and 304L steels have a nickel content that varies between 8% and 12% by weight, and 316 and 316L steels have a nickel content that varies between 10% and 14% by weight. More particularly, 316L steel is selected. Equipment made of or coated with polymeric compounds that are resistant to corrosion of the reaction medium may also be used. In particular, materials such as PTFE (polytetrafluoroethylene or Teflon) or PFA (perfluoroalkyl resins) may be mentioned. Glass and glass-lined as well as elastomer devices may also be used. It would not be outside the scope of the invention to use equivalent materials. The material for filtration must be compatible with the medium used. Fluorinated polymers (PTFE, PFA), loaded fluorinated polymers (Viton TM ), and other compatible materials may be used.

[0046] All raw materials used in the method according to the invention, including the reactants, may preferably exhibit very high purity, preferably with their content of metal components such as Na, K, Ca, Mg, Fe, Cu, Cr, Ni, Zn being less than 10 ppm, more preferably less than 5 ppm, or even less than 2 ppm.

[0047] Other methods known to those skilled in the art can be used to prepare salts of bis(chlorosulfonyl)imides having a solvent content of less than 1000 ppm.

[0048] Preferably, said LiCSI as obtained at the end of step (a) is in its molten state or crystallized.

[0049] The LiCSI can be dissolved in an organic solvent for further use.

[0050] The fluorinating agents used in step (b) of the process of the present invention can be in any form, such as in powder form, in liquid form or in gaseous form. Fluorinating agents are commercially available or they can be prepared by known methods.

[0051] In some embodiments, step (b) is carried out directly on LiCSI as obtained from step (a), eg, in molten or solid form, eg, without any further purification.

[0052] The fluorinating agent used in the process of the present invention can be anhydrous hydrogen fluoride (HF). Such anhydrous hydrogen fluoride preferably has a high purity, for example, greater than 99.95 mole %, with less than 1000 ppm HO, less than 10 ppm SO, less than 100 ppm HSO, less than 20 ppm HSiF and less than 25 ppm As.

[0053] When anhydrous hydrogen fluoride is used as the fluorinating agent in step b), it can be introduced in any form into the reaction mixture. It can be introduced as a liquid or it can be introduced as a gas into the reaction vessel. It can be introduced into the molten LiCSI or into the organic solvent dispersing the LiCSI obtained from step (a). It can be introduced in liquid form or in gas form. It can also be introduced as a gas into the gas phase of the reaction vessel. Anhydrous hydrogen fluoride can be dispersed in the reaction mixture by any means known to those skilled in the art.

[0054] For example, step (b) can be carried out by fluorinating LiCSI using HF gas in a fluidized bed.

[0055] According to another embodiment, the fluorinating agent is (i) KF(HF) p(wherein p is 0 or 1); (ii) NaF(HF) p (wherein p is 0 or 1); (iii) X2F(HF) p (Wherein, X2 is an onium cation and p is 0 or 1); (iv) NH4F(HF) p (wherein p ranges from 0 to 10); (v) LiF; (vi) ZnF2, preferably selected from the group consisting of them.

[0056] According to a preferred embodiment, specific examples of fluorinating agents (iv) include NH4F, NH4F·HF, NH4F·2HF, NH4F·3HF, and NH4F·4HF.

[0057] A preferred fluorinating agent (iv) is NH4F.

[0058] In the present invention, the fluorinating agent used in step b) is preferably anhydrous. The water content can be preferably less than 100 ppm, less than 50 ppm, or even less than 10 ppm. Those skilled in the art can determine the most suitable method for measuring such water content. For example, such methods can include infrared techniques or Karl Fischer titration, if applicable.

[0059] In some embodiments, the stoichiometric amount (also called molar amount) of fluorinating agent to LiCSI is from 0.1:1 to 50:1, such as from 1:1 to 10:1, or from 2:1 to 8:1.

[0060] In some embodiments, the stoichiometric amount of the fluorinating agent is 2 or more equivalents per mole of LiCSI, for example, 2 to 100 equivalents per mole of LiCSI. Preferably, the stoichiometric amount of the fluorinating agent is 2 to 80 equivalents per mole of LiCSI, or 2 to 60 equivalents per mole of LiCSI. More preferably, the stoichiometric amount of the fluorinating agent is 2 to 50 equivalents per mole of LiCSI.

[0061] The processes described herein may be carried out in batch, semi-batch, or continuous mode.

[0062] Residual HF present in the final reaction crude product can be eliminated using any relevant method such as evaporation under vacuum or stripping with an inert gas or a combination thereof.

[0063] The LiFSI as obtained by the method of the invention advantageously has at least one of the following characteristics, preferably: - 19 a purity of at least 98% by weight, e.g., 99% to 100% by weight or 99.50 to 100% by weight, as measured by F NMR; - a solvent content of less than 20% by weight, less than 10% by weight, less than 1% by weight, preferably between 0% and 1% by weight, as measured by GC; - Moisture content of less than 500 ppm, less than 100 ppm, less than 50 ppm or even less than 20 ppm as measured by infrared method Show all.

[0064] The LiFSI of the present invention advantageously has the following characteristics: - less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, or more preferably less than 2 ppm chloride (Cl - ) content; - Fluoride (F) less than 100 ppm, preferably less than 50 ppm, more preferably less than 40 ppm, more preferably less than 30 ppm, more preferably less than 20 ppm - ) content; and - less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, or more preferably less than 2 ppm sulfate (SO 2- ) content At least one, preferably all of the following are shown:

[0065] Fluoride and chloride content can be measured by argonometric titration using an ion selective electrode (or ISE), and sulfate content can be measured by ion chromatography or turbidimetry.

[0066] Preferably, it has the following contents of metal elements: - an iron (Fe) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a chromium (Cr) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a nickel (Ni) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a zinc (Zn) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a copper (Cu) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a manganese (Mg) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a sodium (Na) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - a potassium (K) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm; - Pb content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, even more preferably less than 1 ppm At least one, preferably all, of the following may be exhibited.

[0067] The elemental impurity content may be measured by ICP-AES (inductively coupled plasma); more specifically, the Na content may be measured by AAS (atomic absorption spectroscopy).

[0068] Advantageously, the lithium bis(fluorosulfonyl)imide (LiFSI) prepared according to the method of the present invention can be used in electrolyte compositions for electrochemical cells.

[0069] In a further aspect, the present invention relates to an electrolyte composition comprising LiFSI as obtained by the process of the present invention. Advantageously, said electrolyte composition is a non-aqueous electrolyte composition.

[0070] To the extent that the disclosures of any patents, patent applications, and publications incorporated herein by reference conflict with the statements of this application to the extent that any term may be unclear, the statements of this application shall control.

Claims

1. 1. A method for preparing the lithium salt of bis(fluorosulfonyl)imide (LiFSI), comprising the steps of: (a) providing a lithium salt of bis(chlorosulfonyl)imide (LiCSI) having a solvent content of less than 1000 ppm as measured by gas chromatography or headspace gas chromatography; (b) contacting the LiCSI of step (a) with at least one fluorinating agent to produce LiFSI; A method comprising:

2. 10. The method of claim 1, wherein the LiCSI is in molten or solid form.

3. 10. The method of claim 1, wherein the LiCSI has a solvent content of less than 500 ppm, preferably less than 100 ppm, as measured by gas chromatography or headspace gas chromatography.

4. The fluorinating agent may be prepared from anhydrous hydrogen fluoride (HF) or (i) KF(HF) ｐ (wherein p is 0 or 1); (ii) NaF(HF) ｐ (wherein p is 0 or 1); (iii) X ２ F (HF) ｐ (In the formula, X ２ is an onium cation, and p is 0 or 1; (iv) NH ４ F (HF) ｐ where p varies from 0 to 10; (v) LiF; (vi)ZnF ２ 4. The method of claim 3, wherein the compound is selected from the group comprising:

5. Step (a) comprises the steps of: (A) providing bis(chlorosulfonyl)imide (HCSI); (B) melting the bis(chlorosulfonyl)imide (HCSI) provided in step (A) to obtain molten bis(chlorosulfonyl)imide (HCSI); (C) treating the molten bis(chlorosulfonyl)imide (HCSI) obtained in step (B) with a compound of formula (I): (I)M ＋ B － (In the formula, M is selected from Na, Li, K, Ce, Rb and Fr; B is Cl, F; carbonate (CO ３ ２－ ); sulfate (SO ４ ２－ carboxylate; silicate, preferably metasilicate; borate, preferably tetraborate; and mixtures thereof) to react to produce a salt of bis(chlorosulfonyl)imide. Including; wherein steps (B) and (C) are carried out in the absence of a solvent. The method of claim 1.

6. Step (C) adding said compound of formula (I) to said molten bis(chlorosulfonyl)imide (HCSI) either gradually or all at once, or - loading the compound of formula (I) into a reactor and adding the molten bis(chlorosulfonyl)imide (HCSI) either gradually or all at once; The method of claim 5 , comprising:

7. 6. The method of claim 5, wherein in the compound of formula (I), M is selected from Na, Li and K and / or B is selected from Cl, F, carbonate and sulfate.

8. step (B) is carried out at a temperature of at least 30°C, preferably at least 38°C; and / or step (C) is carried out at a temperature of at least 37°C and at most 220°C; and / or the molar ratio of said HCSI to said compound of formula (I) ranges from 0.001:1 to 20:1, in particular from 0.1:1 to 10:1, more particularly from 0.5:1 to 5:1, The method of claim 5.

9. In the compound of formula (I), M is Li [compound LiX], and the salt of bis(chlorosulfonyl)imide is LiCSI: Step (C) is to determine the melting point (Tm １ ) and the melting point (Tm ２ ) and the molar ratio of HCSI to compound of formula (I) is preferably such that HCSI is an excess reactant, preferably the molar ratio of HCSI to compound LiX is 2:1; or step (C) is carried out at a temperature equal to or greater than the melting point (Tm2) of LiCSI, the molar ratio of HCSI to compound of formula (I) being such that the compound LiX is in excess of reactant, preferably the molar ratio of HCSI to compound LiX being 1:1.05; The method of claim 5.

10. The compound of formula (I) can be any of lithium chloride (LiCl), lithium fluoride (LiF), lithium carbonate (Li ２ CO ３ ), lithium sulfate (Li ２ SO ４ ), lithium carboxylate (Li ｎ (R.C.O. ２ ) ｎ ), Li ２ SiO ３ , Li ２ B ４ O ７ and mixtures thereof.

11. 6. The method of claim 5, wherein hydrogen chloride (HCl) formed as a by-product during step (b) and / or step (c) is continuously removed from the reaction vessel throughout step (b) and / or step (c).

12. 6. The method of claim 5, comprising, after step (C), a step (D) comprising separating the salt of the bis(chlorosulfonyl)amide from the reaction mixture.

13. Lithium bis(fluorosulfonyl)imide (LiFSI) obtainable by the method according to any one of claims 1 to 12.

14. Use of the lithium bis(fluorosulfonyl)imide (LiFSI) according to claim 13 in a non-aqueous electrolyte for a battery.

15. 14. An electrolyte composition comprising the lithium bis(fluorosulfonyl)imide (LiFSI) of claim 13.