Process for preparing solutions of bis(fluorosulfonyl)imide salts

Abstract

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

Description

Cross-reference to related patent applications

[0001] This application claims priority to European Patent Application No. 22306895.8 (Nr. 22306895.8), filed December 15, 2022, the entire contents of which are incorporated herein by reference for all purposes. [Technical Field]

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

[0003] Bis(fluorosulfonyl)imide (FSI) and its salts, particularly the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds in a variety of technical fields, including for the preparation of battery electrolytes.

[0004] Several methods for preparing FSI and its salts have been described in the art. Among the various techniques described, most of the preparation methods involve a fluorination reaction in which a fluorinating agent is reacted with a suitable compound in a solvent.

[0005] Much effort has been made in the art to improve the processes for producing FSI salts and their intermediate compounds, particularly with respect to the purity and yield of the intermediates and final compounds, as well as reducing the cost of the overall production process. Additionally, FSI salts are known to be sensitive to water and can react to form unwanted species that significantly degrade the quality and electrochemical properties of the FSI product.

[0006] For example, US Patent Application Publication No. 2019 / 0292053 (Arkema France) discloses a method for drying and purifying lithium bis(fluorosulfonyl)imide salt in solution in an organic solvent S1, the method comprising the steps of: a) adding deionized water to dissolve and extract lithium bis(fluorosulfonyl)imide salt [LiFSI] to form an aqueous solution of said salt; b) extracting LiFSI from said aqueous solution using an organic solvent S2; c) concentrating LiFSI by evaporating said organic solvent S2 and water in a short-path thin-film evaporator; and d) optionally crystallizing LiFSI. Summary of the Invention

[0007] Applicant has recognized that, despite all attempts in the art, there remains a need for a method for producing a solution containing a bis(fluorosulfonyl)imide salt (salt-FSI) that is efficient and can be easily scaled up from laboratory scale to pilot scale and industrial scale.

[0008] The Applicant also recognized that the FSI salt is highly sensitive to water, and therefore faced the challenge of developing a method that avoids contacting the raw salt-FSI salt with large amounts of water.

[0009] More specifically, the applicant faced the problem of providing a process that makes it possible to produce solutions of bis(fluorosulfonyl)imide salts (salt-FSI) without their degradation and with high recovery yields, even when applied on an industrial scale.

[0010] Surprisingly, the applicant has developed a new method for producing salt-FSI that meets the above criteria and needs and can be easily scaled up from laboratory scale to industrial plants.

[0011] The advantage of the process of the invention is that it results in solutions of salts of bis(fluorosulfonyl)imides which are characterized by very high purity and low water content, and in which no decomposition of the starting materials occurs.

[0012] Another advantage of the process of the present invention is that the organic solvent and water obtained as waste can be further recycled. DETAILED DESCRIPTION OF THE INVENTION

[0013] In this application: - Numerical ranges are inclusive unless otherwise stated. - 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, it is to be understood that in the relevant embodiments expressly contemplated herein, the element or component can also be any one of the individually enumerated elements or components, or can be selected from a group consisting of any two or more of the explicitly enumerated elements, and that components can be omitted from such lists; - The term "ppm" (or "parts per million") refers to weight fraction relative to the total weight of the composition, unless otherwise specified.

[0014] The present invention relates to a method for preparing a composition comprising a salt of a bis(fluorosulfonyl)imide (salt-FSI), said composition being in the form of a solution, said method comprising: (I) - a salt of bis(fluorosulfonyl)imide [Salt-FSI] in at least a first concentration (Salt-FSI 1), - providing a composition (composition (COMP)) comprising at least one solvent (solvent (S)), said solvent (S) comprising water in an amount of at least 1% by weight based on the total weight of said solvent (S); (II) filling the composition (COMP) into a first container; (III) charging at least one organic solvent [solvent (S1)] into said first container; (IV) subjecting said composition (COMP) and said solvent (S1) to a first distillation; (V) recovering the composition [composition (COMP-F)] in the form of a solution, the solution comprising: - at least one salt-FSI in a second concentration (salt-FSI 2), said second concentration (salt-FSI 2) being higher than said first concentration (salt-FSI 1) in the composition (COMP); and - an amount of water less than the amount of water in the composition (COMP); at least one solvent [solvent (S1)] comprising the aforementioned solvent (S1) in an amount of at least 95% by weight, based on the total weight of the composition (COMP-F); * and recovering the composition [composition (COMP-F)] in the form of a solution, the composition comprising:

[0015] Preferably, the salt-FSI is a salt of bis(fluorosulfonyl)imide with one of lithium, sodium, potassium, zinc, or magnesium, with lithium, sodium, and potassium being more preferred.

[0016] The terms "injecting" or "inject" or "injection" as used herein means that a composition described herein is placed into a suitable container (also called a receiver or apparatus) for carrying out a subsequent distillation step. In the context of the present invention, "injecting a composition into a container" is equivalent to "adding a composition to a container" or "feeding a composition into a container."

[0017] As used herein, the term "recovering" means that the composition (COMP-F) is removed, extracted, or removed from a container in which a previous step is carried out.

[0018] The term "vessel" as used herein means a vessel that is highly suitable for the process of the present invention, i.e., a vessel that is adapted to withstand the pressures and temperatures used in the process of the present invention and the potentially corrosive nature of the reactants and products involved in the process.

[0019] The process of the present invention can be operated in a batch, semi-continuous or continuous mode.

[0020] The configuration of the apparatus for carrying out the method of the present invention is not limited.

[0021] Preferably, for carrying out the process of the present invention, such a vessel is preferably a vessel such as a distillation column or a boiler equipped with a distillation column.

[0022] According to a preferred embodiment, in step (I), the composition (COMP) comprises at least a first concentration (salt-FSI1) of salt-FSI and at least a solvent (S) comprising water in an amount of 100% by weight based on the weight of the solvent (S). According to this embodiment, the solvent (S) consists of water. Also according to this embodiment, the solvent (S) does not comprise an organic solvent.

[0023] Preferably, the composition (COMP) contains the salt-FSI at a concentration of about 0.1 to about 35% by weight, more preferably about 0.5 to 30% by weight, and even more preferably 1 to 20% by weight, based on the total weight of the composition (COMP).

[0024] Alternatively, the solvent (S) comprises water in an amount of at least 5.0, 7.0, 12.0, 17.0, 22.0, 27.0, 32.0, 37.0, 42.0, 47.0, 52.0, 57.0, 62.0, 67.0, 72.0, 77.0, 82.0, 87.0, 92.0, 97.0, 98.0, or 99.9% by weight based on the weight of the solvent (S).

[0025] For example, the amount of water is about 65.0 to about 99.9% by weight, more preferably about 70.0 to about 99.5% by weight, and even more preferably 80.0 to 99.0% by weight, based on the total weight of the solvent (S).

[0026] When the amount of water in the composition (COMP) is different from 100% by weight based on the total weight of the solvent (S), the solvent (S) comprises at least one organic solvent. For example, the at least one organic solvent is at least one solvent that is miscible with water. For example, the organic solvent is selected from alcohols.

[0027] The method for producing the composition (COMP) is not limited.

[0028] Composition (COMP) can be prepared according to any method known in the art.For example, a predetermined amount of salt-FSI in solid form is dissolved in a suitable solvent (S) as defined above.Preferably, the solvent is the solvent (S) as defined above, and more preferably, the solvent (S) is water.

[0029] Preferably, step (II) is carried out by pump or gravity.

[0030] In step (II), the composition (COMP) is filled into the container by a suitable tool, preferably a nozzle or an injector.

[0031] In step (II), the composition (COMP) can be charged sequentially either semi-continuously or continuously.

[0032] Preferably, the composition (COMP) is continuously filled into said first container.

[0033] Alternatively, the composition (COMP) may be semi-continuously filled into the container, for example, the composition (COMP) may be filled into the container for a certain period of time, such as 30 to 120 seconds, preferably about 60 seconds, and then the filling is stopped for another period of time that may be equal to, shorter or longer than the filling time.

[0034] Preferably, in step (III), the at least one solvent (S1) is selected from the group consisting of optionally fluorinated carbonate solvents such as ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, lactones such as γ-butyrolactone, γ-valerolactone, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3 -dioxolane, optionally fluorinated esters such as methyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl acetate, n-butyl acetate, n-propyl propionate, 2,2-difluoroethyl acetate, and polar aprotic solvents such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, nitromethane, and nitrobenzene.

[0035] More preferably, said solvent (S1) is selected from the optionally fluorinated carbonate solvents and esters, as listed above.

[0036] Even more preferred solvents (S1) are selected from dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl acetate and n-butyl acetate.

[0037] According to a more preferred embodiment, said solvent (S1) is chosen from ethyl methyl carbonate (EMC), dimethyl carbonate and n-butyl acetate.

[0038] Preferably, step (III) is carried out by pump or gravity.

[0039] Preferably, the aforementioned step (III) is carried out by sequentially charging the solvent (S1) semi-continuously or continuously.

[0040] Preferably, steps (II) and (III) are carried out simultaneously.

[0041] Alternatively, step (III) is initiated after step (II) or when step (II) is completed or stopped.

[0042] Preferably, step (IV) is carried out via a distillation column.

[0043] According to one embodiment, step (IV) is initiated after each of steps (II) and (III) has been completed or stopped.

[0044] Alternatively, step (IV) is initiated while step (II) and / or step (III) are in progress.

[0045] Preferably, step (IV) is carried out at a pressure of less than 50 mbar abs (0.005 MPa), more preferably less than 40 mbar abs (0.004 MPa). According to a preferred embodiment, step (IV) is carried out at a pressure of 25 to 40 mbar abs (0.0025 to 0.004 MPa).

[0046] Preferably, step (IV) is carried out at a temperature below 50°C, more preferably below 40°C. According to a preferred embodiment, step (IV) is carried out at a temperature between 20 and 35°C.

[0047] The method of the present invention optionally comprises, after step (IV) and before step (V), step (IV-a) of filling the composition obtained in step (IV) into a second container.

[0048] Optionally, the process according to the invention comprises, after step (IV) or after step (IV-a), a step (IV-b) of charging at least one second organic solvent [solvent (2)] into said first vessel or said second vessel, and a step (IV-c) of carrying out a second distillation.

[0049] In step (IV-b), the aforementioned solvent (S2) is the same as or different from the aforementioned solvent (S1).

[0050] Preferably, solvent (S2) is selected from the group comprising the list of solvents disclosed above for solvent (S1).

[0051] According to a preferred embodiment, said solvent (S2) is the same as solvent (S1).

[0052] Preferably, step (VI-c) is carried out at a pressure lower than that applied in step (IV). Preferably, step (IV-c) is carried out at a pressure of less than 35 mbar abs (0.0035 MPa), even more preferably less than 25 mbar abs (0.0025 MPa).

[0053] Preferably, step (IV-c) is carried out at a temperature below 50° C., more preferably below 40° C. According to a preferred embodiment, step (IV) is carried out at a temperature between 20 and 35° C.

[0054] According to a preferred embodiment, the composition (COMP-F) in step (V) comprises at least one salt-FSI in a second concentration (Salt-FSI2), the second concentration (Salt-FSI2) being higher than the first concentration (Salt-FSI1) in the composition (COMP), water in an amount of less than 30,000 ppm based on the weight of the salt-FSI, and a solvent (S * ) containing solvent (S1) in an amount of more than 97.0 wt. % based on the total weight of * ) and

[0055] Preferably, the aforementioned composition (COMP-F) contains the salt-FSI in an amount of about 0.2 to about 70 wt %, more preferably about 1.0 to 60 wt %, and even more preferably 2 to 40 wt %, based on the total weight of the composition (COMP-F).

[0056] Preferably, said composition (COMP-F) comprises water in an amount of less than 10,000 ppm, preferably less than 1,000 ppm, more preferably less than 500 ppm, and even more preferably less than 100 ppm, based on the total weight of said salt-FSI.

[0057] According to a more preferred embodiment, said composition (COMP-F) comprises water in an amount of less than 80 ppm, more preferably less than 50 ppm, even more preferably less than 20 ppm, based on the total weight of said salt-FSI.

[0058] Preferably, the solvent (S * ) comprises solvent (S1), optionally in a mixture with solvent (S2), in an amount of more than 98.0% by weight, more preferably more than 99.0% by weight, even more preferably more than 99.5% by weight.

[0059] More preferably, the solvent (S * ) optionally in a mixture with solvent (S2) * ), and more preferably, the solvent (S1) is present in an amount of 99.7% by weight, based on the total weight of the solvent (S1). * ) consists of a solvent (S1).

[0060] Preferably, the composition (COMP-F) comprises at least one other substance.

[0061] The at least one other substance is preferably - fluoride (F) in an amount preferably less than 100 ppm, as measured by ion chromatography (IC) - ), and / or -chloride (Cl) in an amount preferably less than 100 ppm as measured by IC - ), and / or - Sulfate (SO4) in an amount preferably less than 1000 ppm as measured by IC 2- ), and / or - Sulfamate (NH2SO3 - ), and / or - Fluorosulfonates (FS03), preferably in an amount of less than 1000 ppm, as measured, for example, by ion chromatography (IC) - ) is selected from The amount is based on the weight of the salt-FSI.

[0062] Preferably, the amount of said at least one other substance in the composition (COMP-F) is preferably as follows: - Fluoride (F) in an amount of up to 50 ppm, e.g., less than 40 ppm, less than 30 ppm, less than 25 ppm - ), Chloride (Cl) in an amount of up to 50 ppm, for example less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm or even less than 8 ppm - ), -Sulfates (SO4 2- ) different salts, The amount is determined, for example, by ion chromatography (IC) and is based on the weight of the salt-FSI.

[0063] Preferably, sulfate (SO4 2- ) The aforementioned salts, which are different from NH2SO3 - and / or FSO3 - is selected from.

[0064] Preferably, sulfate (SO4 2- ) the aforementioned salts different from the following amounts: - Less than 50 ppm, e.g., less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm, or even less than 5 ppm of sulfamate (NH2SO3 - ), and / or - Less than 50 ppm, e.g., less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm, or even less than 5 ppm of fluorosulfonates (FS03 - ), The amount is based on the weight of the salt-FSI.

[0065] The method of the present invention may further comprise a step (Va) of filtering the composition (COMP-F) after step (V). Such a filtering step can be carried out according to methods known in the art. If required by circumstances, a filtering step can also be carried out after step (IV) and before step (V), or during the course of step (V).

[0066] Alternatively or additionally, the method of the present invention may further comprise a step (VI) of concentrating the composition (COMP-F). Such a concentration step may be carried out according to methods known in the art.

[0067] To the extent that the disclosure of any patents, patent applications, and publications incorporated herein by reference conflicts with the statements of this application to the extent that a term may be unclear, the statements of this application shall control.

[0068] The present invention will now be described in more detail with reference to the following examples, the purpose of which is illustrative only and is not intended to limit the scope of the present disclosure. [Example]

[0069] Example 1 High-purity lithium bis(fluorosulfonyl)imide salt (10.0 g) was dissolved in distilled water (90.3 g) and placed in a 2.5 L PFA-coated vessel equipped with a mechanically stirred, four-blade PTFE shaft, a 30 cm Raschig-garnished distillation column, a glass distillation head, and a Bertrand separator, connected to a cold trap and a vacuum pump. Ethyl methyl carbonate (EMC) (902.4 g) was added to the vessel. The mixture was stirred at 300 rpm, and distillation was initiated.

[0070] The first azeotropic distillation step was performed at 30-35 mbar abs (0.0030-0.0035 MPa) and 25-30 °C (boiler temperature) to allow distillation of the biphasic mixture. A sample of the resulting LiFSI solution (sample 1: 538.3 g) was analyzed by Karl Fischer titration (KF) and ion chromatography (IC).

[0071] Fresh EMC was added (670 g) and a second azeotropic distillation step was performed at 8-20 mbar abs (0.0008-0.0020 MPa) and 29-31 °C (boiler temperature) to obtain the final LiFSI solution in EMC. This composition (Sample 2) was analyzed by KF, NMR, and IC.

[0072] KF analysis Sample 1: 2.3 wt% LiFSI in EMC with a moisture content of approximately 13900 ppm relative to the weight percent of LiFSI.

[0073] Sample 2: 45 wt% LiFSI in EMC with a moisture content of less than 2500 ppm based on the weight percent of LiFSI.

[0074] IC analysis showed that no chemical degradation occurred during the process.

[0075] All the above results showed that the method according to the invention allows the preparation of solutions of salts of FSI in organic solvents, while the water and solvent removed by distillation can be recycled in the same or a different process.

Claims

1. 1. A method for preparing a composition comprising a salt of a bis(fluorosulfonyl)imide (salt-FSI), wherein the composition is in the form of a solution, the method comprising: (I) - at least a first concentration (Salt-FSI 1) of a salt of bis(fluorosulfonyl)imide [Salt-FSI], at least one solvent [solvent (S)], said solvent (S) comprising water in an amount of at least 1% by weight based on the total weight of said solvent (S); providing a composition [composition (COMP)] comprising: (II) filling the composition (COMP) into a first container; (III) charging at least one organic solvent [solvent (S1)] into said first container; (IV) subjecting said composition (COMP) and said solvent (S1) to a first distillation; (V) recovering the composition [composition (COMP-F)] in the form of a solution, the solution comprising: - said at least one salt-FSI in a second concentration (Salt-FSI 2), said second concentration (Salt-FSI 2) being higher than said first concentration (Salt-FSI 1) in composition (COMP); and - an amount of water less than the amount of water in the composition (COMP), at least one solvent [solvent (S*)] comprising said solvent (S1) in an amount of at least 95% by weight, based on the total weight of the composition (COMP-F); recovering the composition [composition (COMP-F)] in the form of a solution, A method comprising:

2. 2. The method of claim 1, wherein the salt-FSI is a salt of bis(fluorosulfonyl)imide and one of lithium, sodium, potassium, zinc, or magnesium.

3. 3. The method according to claim 1 or 2, wherein in step (I), the composition (COMP) comprises salt-FSI at least in a first concentration (salt-FSI 1) and at least a solvent (S) comprising water in an amount of 100% by weight, based on the weight of the solvent (S).

4. The method of claim 3 , wherein the solvent (S) does not comprise an organic solvent.

5. 5. The method according to any one of claims 1 to 4, wherein the composition (COMP) comprises the salt-FSI in an amount of about 0.1 to about 35 wt. %, more preferably about 0.5 to 30 wt. %, even more preferably 1 to 20 wt. %, based on the total weight of the composition (COMP).

6. The at least one solvent (S1) may be any of the following: optionally fluorinated carbonate solvents, such as ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate; lactones, such as γ-butyrolactone, γ-valerolactone; ethers, such as dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxolane; methyl phosphates, such as methyl phosphates; 6. The process according to any one of claims 1 to 5, wherein the solvent is selected from the group comprising optionally fluorinated esters such as methyl acetate, ethyl acetate, methyl propionate, isopropyl acetate, n-butyl acetate, n-propyl propionate, 2,2-difluoroethyl acetate, sulfolane, 3-methylsulfolane, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, nitromethane and nitrobenzene.

7. The method according to any one of claims 1 to 6, wherein steps (II) and (III) are carried out simultaneously.

8. Step (IV) is via a distillation column, and / or at a pressure below -50 mbar abs (0.005 MPa), and / or The method of any one of claims 1 to 7, carried out at a temperature below -50°C.

9. The method according to any one of claims 1 to 8, comprising, after step (IV) and before step (V), step (IV-a) of filling the composition obtained in step (IV) into a second container.

10. After step (IV) or after step (IV-a), the following step: Step (IV-b) of charging at least one second organic solvent [solvent (2)] into the first container or the second container; and (IV-c) performing a second distillation.

11. The solvent (S2) may be any of fluorinated carbonate solvents such as ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone and γ-valerolactone; ethers such as dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, and 4-methyl-1,3-dioxolane; 2. The process according to claim 1, wherein the solvent is selected from the group comprising optionally fluorinated esters such as methyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl acetate, n-butyl acetate, n-propyl propionate, 2,2-difluoroethyl acetate, sulfolane, 3-methylsulfolane, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, nitromethane and nitrobenzene.

12. solvent (S2) is the same as solvent (S1), and / or 12. The method according to claim 10 or 11, wherein step (VI-c) is carried out at a pressure lower than the pressure applied in step (IV).

13. The composition (COMP-F) is - said at least one salt-FSI in a second concentration (Salt-FSI 2), said second concentration (Salt-FSI 2) being higher than said first concentration (Salt-FSI 1) in composition (COMP); and water in an amount of less than 30,000 ppm based on the weight of said salt-FSI; - a solvent (S*) comprising solvent (S1) in an amount of more than 97.0 wt.-%, based on the total weight of solvent (S*).

14. The composition (COMP-F) further comprises: one or both of said solvents (S1) and (S2), preferably in an amount of less than 100 ppm based on the total weight of the composition (COMP-F), and / or preferably - fluoride (F) in an amount preferably less than 100 ppm, as measured by ion chromatography (IC) － ), and / or - Chloride (Cl) in an amount preferably less than 100 ppm as measured by IC － ), and / or - Sulfates (SO 4 ) in an amount preferably less than 1000 ppm as measured by IC ４ ２－ ), and / or - Sulfamate (NH ２ SO ３ － ), and / or - Fluorosulfonates (FSO ) in an amount preferably less than 1000 ppm, as determined, for example, by ion chromatography (IC). ３ － ) and at least one other substance selected from The method according to any one of claims 1 to 13, wherein the amount is based on the weight of the salt-FSI.

15. After step (V), - a step (Va) of filtering the composition (COMP-F), and / or The method according to any one of claims 1 to 14, comprising a step (VI) of concentrating the composition (COMP-F).

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