Manufacturing process for bis(fluorosulfonyl)imide salts

Abstract

The present invention relates to a process for the preparation of salts of bis(fluorosulfonyl)imides, preferably lithium bis(fluorosulfonyl)imide (LiFSI).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to prior European Patent Application No. 22305321.6, filed March 18, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a process for the preparation of salts of bis(fluorosulfonyl)imides, preferably lithium bis(fluorosulfonyl)imide (LiFSI). [Background technology]

[0003] Bis(fluorosulfonyl)imides and their salts, particularly the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are compounds that are useful in a variety of technical fields, such as in battery electrolytes.

[0004] Several methods and processes for the preparation of alkali metal salts of bis(fluorosulfonyl)imides are currently under development and have been described in the literature and patent documents.

[0005] Among the various techniques described, most use a fluorination reaction using a fluorinating agent in a solvent. For example, US Patent Application Publication No. 2019 / 0292054 (Nippon Shokubai Co., Ltd.) discloses a method for producing an alkali metal salt of a bis(fluorosulfonyl)imide, which comprises reacting a bis(fluorosulfonyl)imide with an alkali metal compound in a reaction solution containing an organic solvent selected from carbonate solvents, cyclic ether solvents, linear ether solvents having two or more oxygen atoms in the molecule, cyclic ester solvents, sulfolane solvents, N,N-dimethylformamide, dimethylsulfoxide, and N-methyloxazolidinone.

[0006] European Patent No. 3825278 (Shanghai Rolechem Co., Ltd.) discloses bis(fluorosulfonyl)imides and M +n X n-- Disclosed is a method for preparing a bis(fluorosulfonyl)imide salt starting from (wherein M is selected from Li, Na, K, Rb and Cs; X is an anion containing at least one element of B, O, N, P and Si, and n is 2 or more), in which the two raw materials are mixed in a non-aqueous solvent, reacted and post-treated (e.g., filtered, concentrated in vacuum and recrystallized in an anti-solvent).

[0007] U.S. Pat. No. 10,505,228 (Synthio Chemicals, LLC.) discloses a method for removing water from a liquid solution comprising a non-aqueous solvent, a hygroscopic metal salt, and water. More specifically, the method includes mixing the following ingredients: (i) a liquid solution comprising an acidic form of a hygroscopic alkali metal salt and a first solvent, (ii) an alkali metal base, and (iii) an aprotic electrolyte solvent. The resulting mixture produces a vapor comprising water, the first solvent, or a combination thereof. The vapor is then removed from the mixture to reduce the amount of water and produce an aprotic electrolyte solution. The alkali metal base typically includes an alkali metal carbonate, an alkali metal hydroxide, an alkali metal bicarbonate, or a combination thereof. Exemplary lithium bases include lithium hydroxide, lithium carbonate, lithium bicarbonate, and combinations thereof. Example 3 of U.S. Pat. No. 10,505,228 discloses the reaction of HFSI with lithium carbonate in a large volume of water.

[0008] Under the process disclosed in this patent, neutralization and distillation or drying steps are disclosed as subsequent steps. As a result, the water content in the reaction medium throughout the process is relatively high and remains high at the end of the neutralization step, which may give rise to FSI side reactions. In addition, the entire process takes a long time. Summary of the Invention

[0009] The applicant was faced with the problem of developing a process for the preparation of solutions of high purity salts of bis(fluorosulfonyl)imides characterized by low water content.

[0010] The Applicant was also faced with the problem of developing a process in which the formation of FSI by-products could be limited or even avoided, such that high purity salts of bis(fluorosulfonyl)imides could be obtained and the need for post-purification steps limited.

[0011] Faced with the above technical problems, the Applicant has unexpectedly developed a process in which the concentration of water before and during the neutralization step is kept very low, which may limit the formation of undesirable FSI by-products.

[0012] The process developed by the applicant is also characterized by low energy consumption, making it suitable for industrial applications.

[0013] Thus, in a first embodiment, the present invention relates to a method for the preparation of a solution comprising at least one organic aprotic solvent and at least one bis(fluorosulfonyl)imide [solution (S1)].

[0014] The method of the invention according to the invention advantageously provides a solution (S1) in a solvent suitable for non-aqueous electrolyte formulations, the handling of which is much easier than in solid form. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In this application: - the expression "included in ..." is to be understood as including the 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 the relevant 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.

[0016] In a first embodiment, the present invention provides a process for the preparation of a cyclohexane-cyclohexane derivative comprising at least one organic aprotic solvent and a cyclohexane-cyclohexane derivative of the following formula (I): [ka] (In the formula, M n+ represents a metal cation, n is an integer from 1 to 4. A method for producing a solution [solution (S1)] containing at least one bis(fluorosulfonyl)imide salt represented by the following formula: The method comprises the steps of: (A) contacting hydrogen bis(fluorosulfonyl)imide (HFSI), at least one aprotic organic solvent [solvent (S)], and at least one alkali metal compound [compound (AM)] to provide a reaction mixture [mixture (M1)]; (B) removing any water present in said mixture (M1), thus obtaining said solution (S1); Including, Here, the method relates to steps (A) and (B) being carried out simultaneously.

[0017] Preferably, the metal cation M n+is more preferably an alkali metal cation selected from Na, Li, K, Rb, and Cs. Of these, Li, Na, and K are more preferred.

[0018] Preferably, said compound (AM) is selected from the group comprising, more preferably consisting of, LiOH, NaOH, KOH, RbOH, CsOH, LiOH·H2O, NaOH·H2O, KOH·H2O, RbOH·H2O, CsOH·H2O, Li2CO3, Na2CO3, K2CO3, Rb2CO3, Cs2CO3, LiHCO3, NaHCO3, KHCO3, RbHCO3 and CsHCO3. More preferably, said compound (AM) is selected from the group consisting of LiOH·H2O, NaOH·H2O, KOH·H2O, RbOH·H2O, CsOH·H2O, Li2CO3, Na2CO3, K2CO3, Rb2CO3 and CsHCO3. Even more preferably, said compound (AM) is selected from the group consisting of LiOH·H2O and Li2CO3.

[0019] Preferably, the amount of the compound (AM) is about 1.0 mol to about 10 mol, more preferably 1.0 mol to 5.0 mol, even more preferably 1.0 mol to 2.0 mol, and even more preferably 1.0 mol to 1.5 mol, per 1.0 mol of HFSI.

[0020] Preferably, the solvent (S) is selected from the group comprising 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 preferably, the solvent (S) is selected from ethylene carbonate, propylene carbonate, butylene carbonate, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl acetate and n-butyl acetate, and even more preferred solvents include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl acetate and n-butyl acetate. Even more preferably, the solvent (S) is selected from ethyl methyl carbonate and n-butyl acetate.

[0021] According to a preferred embodiment, said solvent (S) has a water content of less than or equal to 500 ppm, preferably less than or equal to 250 ppm, more preferably less than or equal to 100 ppm, even more preferably less than or equal to 50 ppm.

[0022] Advantageously, steps (A) and (B) are carried out at the same temperature.

[0023] Preferably, steps (A) and (B) can be carried out at a temperature of -10°C to 40°C, 25°C, more preferably -5°C to 30°C.

[0024] Advantageously, steps (A) and (B) are carried out at the same temperature.

[0025] Preferably, steps (A) and (B) are carried out at a pressure between 1 mbar and 1 bar, more preferably between 5 mbar and 50 mbar, even more preferably between 10 and 20 mbar.

[0026] The reaction times required for steps (A) and (B) are not limited and depend on the reaction scale and process conditions. Those skilled in the art will understand how to set the reaction times based on the applied process conditions.

[0027] Preferably, the reaction time for both steps (A) and (B) is from about 10 minutes to 48 hours.

[0028] Advantageously, the solution (S1) obtained at the end of step (B) contains between 5 and 70% by weight of said salt of formula (I), based on the total weight of the solution.

[0029] More preferably, said solution (S1) comprises 10 to 60% by weight, for example 15 to 50% by weight, 20 to 40% by weight or 25 to 25% by weight of said salt of formula (I).

[0030] Advantageously, said step (B) is carried out by means of a molecular sieve or by distillation. More preferably, said distillation is carried out under reduced pressure or azeotropic distillation. Even more preferably, the azeotropic distillation is carried out under reduced pressure.

[0031] Step (B) can be carried out such that only water is removed or water and part of said solvent (S) are removed simultaneously as a mixture [mixture (M2)].

[0032] The mixture (M2) may comprise water and the solvent (S) as separate phases or as a homogeneous phase.

[0033] Preferably, said mixture (M2) is an azeotropic mixture and said step (B) is carried out by azeotropic distillation.

[0034] According to a preferred embodiment, the method according to the invention comprises the steps of: Step (Ai) providing at least one aprotic organic solvent [solvent (S)] and at least one alkali metal compound [compound (AM)]; step (A-ii) removing any water by azeotropic distillation; Step (A-iii) adding hydrogen bis(fluorosulfonyl)imide [HFSI] to provide the mixture (M1); Step (B) removing any water present in said mixture (M1) to provide said solution (S1). Includes; Here, steps (A-iii) and (B) are carried out simultaneously.

[0035] Optionally, said step (B) can be followed by at least one step (C) of removing any impurities and / or compounds (AM) from the solution (S1).

[0036] Such optional step (C) may be carried out by any method known in the art, such as by filtration.

[0037] Optionally, said step (B) can be followed by a step (D) of adding an additional amount of said solvent (S).

[0038] Advantageously, said portion of said solvent (S) is recovered from said mixture (M2) and, for example, reused in the process of the invention, so that the overall consumption of solvent is reduced.

[0039] Thus, according to this embodiment, the process of the invention comprises, after step (B), a step (E) of recovering at least a portion of the solvent (S) from mixture (M2), advantageously followed by a step (F) of providing the solvent (S) to mixture (M1).

[0040] Preferably, step (E) and optionally step (F) are performed simultaneously. In addition, step (E) and optional step (F) are performed simultaneously with steps (A) and (B).

[0041] Said step (E) can be carried out by methods known in the art, for example by drying. More preferably, said drying is carried out by molecular sieves or, if an azeotrope is provided, by pressure swing distillation.

[0042] The order in which optional steps (C), (D), (E) and / or (F) are performed after step (B) is not limited.

[0043] The reaction vessel is preferably made of a resin, more preferably a fluororesin or a polyethylene resin.

[0044] The process of the present invention may be carried out in a batch mode or in a continuous or semi-continuous mode.

[0045] According to a preferred embodiment, the present invention provides a solution comprising at least one organic aprotic solvent and lithium bis(fluorosulfonyl)imide (LiFSI) [Solution (S1 ∧ )], the method comprising: (A ∧ ) contacting HFSI with at least one aprotic organic solvent [solvent (S)] and at least one lithium compound [compound (AM-L)] to provide a reaction mixture; (B ∧ ) The solution (S1 ∧ removing any water present in the reaction mixture to provide Including, wherein steps (A) and (B) are performed simultaneously.

[0046] Preferably, said compound (AM-L) is selected from the group comprising, more preferably consisting of, LiOH, LiOH·H2O, Li2CO3, LiHCO3. More preferably, said compound (AM-L) is selected from the group consisting of LiOH·H2O and Li2CO3.

[0047] All process conditions described above with respect to step (A) and / or step (B) may also be used in step (A) and / or step (B), respectively. ∧ ) and / or step (B ∧ ) is fully applicable.

[0048] Advantageously, the solution (S1) and the solution (S1 ∧ ) contains less than 100 ppm water, preferably less than 50 ppm water, and more preferably less than 20 ppm water, as measured by Karl Fischer analysis.

[0049] A further object of the invention relates to a solution (S1) as defined above, said solution containing at least one salt of formula (I), at least one solvent (S) as defined above and less than 100 ppm of water as measured by Karl Fischer analysis.

[0050] According to a preferred embodiment, the at least one salt of formula (I) is the lithium salt of bis(fluorosulfonyl)imide (LiFSI).

[0051] A further object of the present invention is to provide a method for producing a solution as defined above (S1 ∧ ), said solution containing at least one salt of formula (I), at least one solvent (S) as defined above, and less than 100 ppm of water as measured by Karl Fischer analysis (S1 ∧ ) regarding.

[0052] Advantageously, in solution (S1) or in solution (S1 ∧ The LiFSI salt in - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 1,000 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, more preferably less than 2 ppm chloride (Cl - ) content; and / or - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 1,000 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 (F - ) content; and / or - Less than 30,000 ppm, preferably less than 10,000 ppm, more preferably less than 5,000 ppm, more preferably less than 2 ppm sulfate (SO4 2- ) content; and / or an iron (Fe) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm, more preferably less than 1 ppm; and / or - a chromium (Cr) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm, more preferably less than 1 ppm; and / or a nickel (Ni) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm, more preferably less than 1 ppm; and / or - a zinc (Zn) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm, more preferably less than 1 ppm; and / or a copper (Cu) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm, more preferably less than 1 ppm; and / or - a bismuth (Bi) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm, more preferably less than 1 ppm; and / or - a sodium (Na+) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm, more preferably less than 1 ppm; and / or - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm, more preferably less than 1 ppm potassium (K + ) content At least one of the following is shown.

[0053] A further object of the present invention is to provide a method for the preparation of a non-aqueous battery electrolyte solution comprising the steps of: ∧ ) is used.

[0054] Alternatively, if required by the end use or other circumstances, said solution (S1) or (S1 ∧ ) can be appropriately treated to obtain solid LiFSI.

[0055] Preferably, said treatment is carried out by known methods such as concentration, precipitation, washing and drying.

[0056] To the extent that the disclosures of any patents, patent applications, and publications incorporated herein by reference conflict with the statements in this application to the extent that any term may be unclear, the statements in this application shall control.

[0057] The present disclosure will now be described in more detail with reference to the following examples, the purpose of which is merely illustrative and is not intended to limit the scope of the present disclosure.

[0058] Experimental section Example 1 - Preparation of LiFSI solution A three-neck PTFE round-bottom flask equipped with mechanical stirring, a thermostatic bath, a temperature probe, a liquid inlet, a packed PTFE column, a condenser and a vacuum pump was placed inside a glove bag and supplied with a flow of dry nitrogen.

[0059] The flask is charged with ethyl methyl carbonate (EMC) and LiOH·H2O (LiOH:HFSI 1.2:1 mol). The condenser temperature setpoint is set to 0° C. and the reaction medium to 10° C. The pressure is then gradually reduced until distillation is observed.

[0060] HFSI is then added to the reaction medium over 1 h. If the distillation ceases, the pressure is reduced to maintain the distillate flow. The LiFSI concentration in the mixture at the end of the 1 h addition is in the range of 20-40 wt%.

[0061] The setup was then placed at atmospheric pressure and the crude material was filtered on a 0.22 micron PTFE membrane to obtain a filtrate of EMC containing LiFSI, which was then subjected to the following technique: - Anionic impurities, especially from FSI hydrolysis (especially NH2FSO3 - , FSO3 - , SO4 2- , F - ) by ion chromatography; - To evaluate the formation of alcohols (especially ethanol and methanol) from EMC hydrolysis 1 H-NMR and gas chromatography; - Karl Fischer method for quantifying water concentration Analyze by:

Claims

1. at least one organic aprotic solvent and a compound represented by the following formula (I): 【Chemistry 1】 (In the formula, M ｎ＋ represents a metal cation, n is an integer from 1 to 4. A method for producing a solution [solution (S1)] containing at least one bis(fluorosulfonyl)imide salt represented by the following formula: The method comprises the steps of: (A) contacting HFSI with at least one aprotic organic solvent [solvent (S)] and at least one alkali metal compound [compound (AM)] to provide a reaction mixture; (B) removing any water present in the reaction mixture by means of a molecular sieve or by distillation, thus providing the solution (S1), wherein steps (A) and (B) are performed simultaneously.

2. Metal cation M ｎ＋ 2. The method of claim 1, wherein R is an alkali metal cation, preferably selected from Na, Li, K, Rb, and Cs.

3. Compound (AM) is LiOH, NaOH, KOH, RbOH, CsOH, LiOH·H ２ O, NaOH·H ２ O, KOH·H ２ O, RbOH·H ２ O, CsOH·H ２ O, Li ２ CO ３ , Na ２ CO ３ , K. ２ CO ３ , Rb ２ CO ３ , Cs ２ CO ３ , LiHCO ３ , NaHCO ３ , KHCO ３ , RbHCO ３ and CsHCO ３ 2. The method of claim 1, wherein the compound is selected from the group comprising, more preferably consisting of:

4. 2. The method according to claim 1, wherein the amount of compound (AM) is 1 mol to 10 mol, preferably 1 mol to 5 mol, per mol of HFSI.

5. 2. The method of claim 1, wherein the solvent (S) is selected from the group comprising 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-methyl sulfolane, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, ethyl acetate, isopropyl acetate, n-butyl acetate, nitromethane, and nitrobenzene.

6. Each of step (A) and step (B) comprises: at a temperature between -10°C and 40°C; and / or At a pressure of 1 mbar to 1 bar The method of claim 1 , wherein

7. 2. The method of claim 1, wherein the solution (S1) comprises 5 to 70% by weight of the salt of formula (I), based on the total weight of the solution.

8. In formula (I), Mn ＋ Li ＋ and n is 1; The at least one compound (AM) is LiOH, LiOH.H ２ O, Li ２ CO ３ , LiHCO ３ The method according to claim 1, wherein the lithium compound [compound (AM-L)] is preferably selected from the group comprising, more preferably consisting of:

9. 2. The method according to claim 1, wherein under step (B) water and at least a portion of the solvent (S) are simultaneously removed as a mixture [mixture (M2)].

10. 10. The method of claim 9, wherein the mixture (M2) is an azeotropic mixture and step (B) is carried out by azeotropic distillation.

11. 10. The method of claim 1, comprising: (A-i) providing at least one aprotic organic solvent [solvent (S)] and at least one alkali metal compound [compound (AM)]; (A-ii) removing any water by azeotropic distillation; (A-iii) adding hydrogen bis(fluorosulfonyl)imide [HFSI] to provide the mixture (M1); (B) removing any water present in said mixture (M1) to provide said solution (S1), wherein steps (A-iii) and (B) are performed simultaneously.

12. 10. The method of claim 1, wherein after step (B): At least one step (C) of removing any impurities and / or compounds (AM) from the solution (S1); and / or Step (D) of adding an additional amount of said solvent (S); and / or a step (E) of recovering at least a portion of the solvent (S) from the mixture (M2), optionally followed by a step (F) of feeding the recovered solvent (S) into the mixture (M1); A method comprising:

13. at least one organic aprotic solvent and a compound represented by the following formula (I): 【Chemistry 2】 (In the formula, M ｎ＋ represents a metal cation, n is an integer from 1 to 4. and at least one bis(fluorosulfonyl)imide salt represented by the formula: A solution (S1) containing less than 100 ppm water as determined by Karl Fischer analysis.

14. A solution (S1) according to claim 13, obtainable by a method according to any one of claims 1 to 11.

15. 14. Use of the solution (S1) according to claim 13 in a non-aqueous battery electrolyte.