Method for preparing lithium salts of bis(fluorosulfonyl)imides in solid form

Abstract

The present disclosure relates to a method for preparing a solid form of the lithium salt of bis(fluorosulfonyl)imide (LiFSI), wherein the solid form of LiFSI salt is extracted from a solution comprising at least one solvent by supercritical anti-solvent extraction. The present invention also relates to the solid form of LiFSI obtained therefrom, as well as the use of such LiFSI in a battery electrolyte.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to earlier European Patent Application No. 22305585.6, filed April 21, 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 the lithium salt of bis(fluorosulfonyl)imide (LiFSI) in solid form. The present invention also relates to the solid form of LiFSI obtained therefrom, as well as the use of such LiFSI in battery electrolytes. [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] The preparation of LiFSI has been described in the literature. Among the various techniques described, most use a fluorination reaction with a fluorinating agent in a solvent.

[0005] In particular, WO 2017 / 090877 (in the name of CLS) describes a method for preparing LiFSI, which includes the steps of (1) reacting bis(chlorosulfonyl)imide with a fluorinating agent in a solvent, followed by treatment with an alkaline agent, thereby preparing ammonium bis(fluorosulfonyl)imide, and (2) reacting ammonium bis(fluorosulfonyl)imide with a lithium base. The solvent used in step (1) is selected from the group consisting of alkyl ketones, such as acetone, methyl ethyl ketone, and methyl isopropyl ketone; alcohols, such as methanol, absolute ethanol, 1-propanol, and isopropanol; alkyl nitriles, such as acetonitrile and propionitrile; and ethers, such as tetrahydrofuran and dialkoxyalkanes. The solvent is then removed by distillation and concentration under reduced pressure.

[0006] WO 2012 / 117961 (Nippon Soda Co., Ltd.) describes a method for preparing fluorosulfonylimide salts. According to Examples 1 and 2, ammonium di(fluorosulfonyl)imide is prepared from di(chlorosulfonyl)imide in acetonitrile. The solvent is then removed by vacuum distillation.

[0007] JP 2016-145147 A (in the name of Nippon Shokubai Co., Ltd.) relates to a method for providing a fluorosulfonylimide compound represented by formula (1), which comprises reacting a compound represented by formula (2) with 1 to 3 stoichiometric equivalents of a compound represented by composition formula (3) based on 1 mole of the compound, in the presence of a solvent in an amount 0 to 4 times the mass of the compound. [ka] In the formula, R 1 is C 1~6 is a fluoroalkyl group, R 6 is halogen or C 1~6 Fluoroalkyl group, Cat1 + and Cat2 + is a monovalent group, and p is an integer from 1 to 10.

[0008] JP 2014-201453 A (in the name of Nippon Shokubai Co., Ltd.) describes a method for producing an alkali metal salt of a fluorosulfonylimide, comprising the steps of synthesizing an alkali metal salt of a fluorosulfonylimide in the presence of a reaction solvent containing at least one solvent selected from the group consisting of carbonate-based solvents, aliphatic ether-based solvents, ester-based solvents, amide-based solvents, nitro-based solvents, sulfur-based solvents, and nitrile-based solvents, and then concentrating the alkali metal salt solution of a fluorosulfonylimide by distilling off the reaction solvent in the presence of the reaction solvent and at least one poor solvent for the alkali metal salt of a fluorosulfonylimide selected from the group consisting of aromatic hydrocarbon-based solvents, aliphatic hydrocarbon-based solvents, and aromatic ether-based solvents, and the concentration step comprises mixing the poor solvent with a reaction solution containing the reaction solvent and the alkali metal salt of a fluorosulfonylimide.

[0009] Supercritical fluid extraction has been used for recycling purposes. Among others, US Patent Application Publication No. 2003 / 0186110 (in the name of ECO BAT INDIANA LLC, ONTO TECH LLC), China Patent No. 105406146 (in the name of HARBIN INST TECHNOLOGY) and China Patent No. 110534835 (in the name of University of Changzhou) disclose a method for removing electrolyte from energy storage devices (e.g., lithium batteries) using supercritical fluids.

[0010] Supercritical fluid extraction has also been described for the extraction of bis(fluorosulfonyl)imide (HFSI) from a reaction mixture containing an acid. In particular, WO 2021 / 082450 (in the name of GUANGZHOU LIWEN TECH CO LTD) discloses a method for purifying HFSI from a reaction mixture containing a strong acid (e.g., concentrated sulfuric acid, phosphoric acid) and an FSI salt (e.g., NaFSI, KFSI or LiFSI, among others) using supercritical extraction, particularly supercritical CO2 fluid. Chinese Patent No. 111517293 (in the name of SHANGHAI INST ORGANIC CHEMISTRY CAS) also describes the following steps: [ka] (wherein X is an alkali metal; R 1 and R 2 are independently F or all F-substituted C1-12 alkyl. This application describes a method for preparing HFSI using a supercritical fluid, comprising: Summary of the Invention

[0011] As described in the literature, the preparation of LIFSI by fluorination is carried out in a solvent, e.g. an organic solvent, to disperse the reactive species and allow them to react.

[0012] However, such solvents need to be removed after the reaction in order to obtain a product as pure as possible that is usable for battery applications.

[0013] The applicant has recognized that the preparation process of solid forms of LiFSI based on LiFSI in solution is complicated, since, inter alia, the amount of residual solvent must be as low as possible in order to be suitable for battery electrolytes.

[0014] The Applicant therefore faced the task of developing a new method for the production of LiFSI, making it possible to overcome the complexities of the methods known so far.

[0015] Unexpectedly, the applicant has developed a method for the preparation of LiFSI which is simple to implement in terms of equipment and reaction conditions, and which is very benign in terms of environmental protection.

[0016] The method of the invention also makes it possible to obtain LiFSI in solid form with very high yield and high purity, so that it can then be used in battery electrolyte solutions.

[0017] An advantageous method for the preparation of LiFSI in solid form according to the invention is based on extraction with a supercritical fluid, said supercritical fluid acting herein as an anti-solvent for LiFSI.

[0018] The object of the present invention therefore relates to a process for the preparation of LiFSI in solid form from a solution comprising at least one solvent and a LiFSI salt, such a process being based on the use of a supercritical fluid. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 depicts a schematic diagram of the laboratory setup used in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] In this application: - the expression "included in ..." is to be understood as including the limiting values; - any description, although provided 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.

[0021] The first object of the present invention is a process for the preparation of the lithium salt of bis(fluorosulfonyl)imide (LiFSI) in solid form, comprising: a) injecting a supercritical fluid into a container; b) optionally injecting a solvent S into said vessel; c) injecting a LiFSI solution containing LiFSI and at least one solvent S into the vessel; d) contacting a LiFSI solution with the at least one supercritical fluid and the solvent S in the vessel; e) recovering the LiFSI in solid form; The present invention relates to a method comprising the steps of:

[0022] The terms "injecting" or "injecting" or "injection" as used herein refer to the placement of fluids, solvents, and solutions described herein in a container (also called a receiver or device) where the various components involved in the method will be contacted for LiFSI precipitation. Within the context of the present invention, "injecting a fluid / solvent / solution into a container" can be equivalently replaced, among others, by "adding a fluid / solvent / solution to a container" or by "delivering a fluid / solvent / solution to a container".

[0023] The term "contacting" as used herein means that the solution is contacted with the supercritical fluid in a vessel under specified conditions of pressure and temperature for a time sufficient for the fluid to remove at least a portion of the solvent present in the LiFSI solution, preferably greater than 80.0%, greater than 90.0%, greater than 95.0%, greater than 99.0%, greater than 99.5% or even greater than 99.9% of the solvent. This time is sufficient to precipitate the LiFSI in the solution.

[0024] The term "recovering" as used herein means that LiFSI in solid form is removed or extracted from the vessel in which the method is carried out.

[0025] The term "supercritical fluid" as used herein means a gas in its critical state. Depending on the gas used in step a), a certain pressure and temperature may be used in the vessel in which the contact between the solution and the supercritical fluid takes place. More precisely, to be in the supercritical state, the gas used in step a) is kept above its critical temperature and critical pressure.

[0026] The term "vessel" as used herein means a vessel that is suitable for the process of the present invention, i.e. a vessel 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. As detailed below, the vessel used herein can be, inter alia, an extraction column (also referred to as a "column") or an autoclave.

[0027] According to the method of the present invention, a supercritical fluid is used to extract LiFSI salt from the solution, with several advantages. Supercritical fluids, such as sCO2, offer obvious advantages, being usually readily available, inexpensive, non-toxic, non-explosive and not an organic solvent. Furthermore, the method of the present invention works at moderate temperatures (below 100°C), which ensures gentle processing of the LiFSI product. The method of the present invention also allows easy separation of the solvent and the extract in solid form. The method of the present invention offers additional advantages, described below, such as the possibility of fine-tuning the size of the LiFSI obtained from the method of the present invention.

[0028] Preferably, the process according to the invention is carried out in a vessel at a pressure P of at least 73 bar (7.3 MPa).

[0029] Preferably, the process according to the invention is carried out in a vessel at a temperature T between 30°C and 90°C.

[0030] The temperature T inside the container may vary between 37°C and 75°C, for example between 38°C and 70°C or between 40°C and 65°C.

[0031] The pressure P in the vessel may be at least 80 bar (8.0 MPa), at least 100 bar (10.0 MPa), at least 130 bar (13.0 MPa) or at least 150 bar (15.0 MPa). Very high pressures can also be used in the method of the invention, for example the pressure P in the vessel may be up to 200 bar (20.0 MPa) or 300 bar (30.0 MPa). The pressure in the vessel will usually be less than 500 bar (50.0 MPa), for example less than 450 bar (45.0 MPa), less than 400 bar (40.0 MPa) or even less than 350 bar (35.0 MPa).

[0032] Preferably, the at least one supercritical fluid, the solvent S and the LiFSI solution are injected into the vessel through injectors or inlet valves attached to the vessel, each of which may be injected into the vessel through the same injector or inlet valve or through different ones.

[0033] Each of the at least one supercritical fluid, solvent S, and LiFSI solution are independently injected into the vessel after the vessel is heated and / or pressurized.

[0034] When step b) is performed, preferably steps a) and b) are performed simultaneously. The injection of the supercritical fluid and the solvent S according to this embodiment can be performed through the same inlet valve or injector (a coaxial nozzle can for example be used) or they can be performed through different inlet valves or injectors (two or more).

[0035] Alternatively, step b) is started after step a). The injection of supercritical fluid according to step a) can be continued, preferably when solvent S starts to be injected into the vessel at the beginning of step b). Alternatively, the injection of supercritical fluid according to step a) can be temporarily stopped and resumed after a period of time. As disclosed above, the injection of supercritical fluid and solvent S according to these embodiments can be done through the same inlet valve or injector, or they can be done through different inlet valves or injectors (two or more).

[0036] The supercritical fluid and the solvent S are combined if both steps a) and b) are carried out.

[0037] The solvent S of step b) and the solvent S of the LiFSI solution of step c) can be the same as each other or different. Preferably, the solvent S of step b) is the same as the solvent S of the LiFSI solution of step c).

[0038] According to step c), a LiFSI solution comprising LiFSI and solvent S is injected into the container. The LiFSI solution involved in the method of the invention may be obtained directly from a LiFSI preparation process (for example as described in the experimental part of the present invention) or it may be a commercial product.

[0039] Under step c) of the present invention, the LiFSI solution is injected into a vessel containing at least one supercritical fluid.

[0040] Under step c), the LiFSI solution can be injected into the container by any suitable means, such as a nozzle or an injector. According to a preferred embodiment, a capillary pipe can be used to inject said LiFSI solution. Other means for injecting said LiFSI solution can be used, such as an automatic nozzle.

[0041] According to a preferred embodiment, the method of the present invention comprises steps a) and c). In other words, step b) is not performed. Under this embodiment, the LiFSI solution is injected into a vessel containing a supercritical fluid. Such injection is performed at a high flow rate for a short period of time, which facilitates mixing with the supercritical fluid in the vessel.

[0042] Alternatively, the method of the present invention comprises steps a), optionally steps b) and c), where steps a), c) and optional step b) are carried out simultaneously. Under this embodiment, the LiFSI solution is injected into the vessel simultaneously with the supercritical fluid and optionally with the solvent S. For example, and particularly preferably on an industrial scale, a coaxial nozzle is used for the simultaneous introduction of the supercritical fluid and the LiFSI solution into the vessel.

[0043] Additionally or alternatively, the method of the present invention comprises: step c), step a) and optionally step b). Under this embodiment, the LiFSI solution is injected into the vessel before any one of the supercritical fluid and optionally solvent S. Preferably, the LiFSI solution is first introduced into the vessel, then the vessel is heated and placed under pressure, and then said supercritical fluid and optionally solvent S are injected.

[0044] Preferably, step a) is carried out by injecting the supercritical fluid at the bottom of the container. Advantageously, this makes it possible to improve the mixing of the LiFSI solution with the supercritical fluid.

[0045] According to an embodiment, if step b) is performed, step b) is stopped when step c) begins. In other words, the supply of solvent S to the vessel is replaced by the supply of LiFSI solution. For example, the inlet valve or injector for injecting solvent S into the vessel may be closed while the inlet valve or injector for injecting LiFSI solution into the vessel is open. Alternatively, the same inlet valve or injector is used for the supply of solvent S and LiFSI solution; in other words, the supply of LiFSI solution is introduced into the vessel through the same inlet valve or injector than solvent S.

[0046] As explained, during the method of the present invention, the LiFSI solution is contacted with at least one supercritical fluid.

[0047] Preferably, the LiFSI solution is contacted with one fluid in a supercritical state.

[0048] Preferably, the LiFSI solution is contacted with two or more fluids in the supercritical state. The two or more fluids may be mixed or contacted sequentially with the LiFSI solution. As an example, the LiFSI solution may be contacted with a mixture of at least two supercritical fluids.

[0049] Additionally, in accordance with the present invention, at least one other component, also referred to herein as a modifier, may be mixed with the supercritical fluid.

[0050] Preferably, the at least one other component is selected from polar solvents having a solubility in the supercritical fluid of less than 10% by weight, based on the total weight of the supercritical fluid and the other components.

[0051] More preferably, when used, the at least one other component is in an amount in the range of 0.1 to 10.0 wt. %, such as 0.5 to 8.0 wt. % or 1.0 to 6.0 wt. %, based on the total weight of the supercritical fluid plus other components.

[0052] Preferably, said at least one other component is selected from polar solvents, more preferably in the group comprising alcohol, toluene, dimethylsulfoxide (DMSO), acetonitrile, etc. According to a preferred embodiment, said polar solvent is an alcohol. Even more preferably, said alcohol is ethanol.

[0053] Preferably, the supercritical fluid used in step a) comprises supercritical carbon dioxide (sCO2), which is a fluid state of carbon dioxide maintained above its critical temperature (31.0°C) and critical pressure (7.3773 MPa).

[0054] Advantageously, the supercritical fluid used in step a) consists essentially in sCO2 or it consists in sCO2.

[0055] According to one embodiment, the sCO2 is mixed with up to 10% ethanol by weight, for example, 0.1-8% ethanol by weight, the weight percentage being based on the total weight of the supercritical fluid and ethanol.

[0056] The weight ratio of the supercritical fluid to the LiFSI solution used in the method of the present invention may vary from 1 / 1 to 4000 / 1. For example, the weight ratio of the supercritical fluid / LiFSI solution preferably varies from 10 / 1 to 3500 / 1.

[0057] It will be clear to the skilled person that the parameters of the process according to the invention can be appropriately selected and optimized, for example, based on the starting materials (in particular the purity of the product) and on the scale at which the process is performed, for example, on an industrial scale or on a laboratory scale.

[0058] Preferably, when the method of the invention is carried out on a laboratory scale, the mass ratio between the supercritical fluid and the solution containing LiFSI is: - 21 to 1500, if the injection of the solution containing LiFSI is continuous; or - 350-3100 if the injection of the solution containing LiFSI is discontinuous or batchwise It is.

[0059] Preferably, when the method of the invention is carried out on an industrial scale, the mass ratio between the supercritical fluid and the solution containing LiFSI is less than 300 when the injection of the solution containing LiFSI is continuous.

[0060] Good results have been obtained on a laboratory scale by injecting the supercritical fluid, preferably comprising or consisting of sCO2, into the vessel at a flow rate of 5-50 g / min, preferably 10-40 g / min, for example about 30±5 g / min, as demonstrated in the experimental section below.

[0061] Good results have been obtained on a laboratory scale by injecting sCO2 into the vessel under step a) at a flow rate of 5-50 g / min, preferably about 30±5 g / min.

[0062] Good results have been obtained on a laboratory scale by injecting said at least one solvent S into the vessel under step b) at a flow rate of less than 1 mL / min, or less than 0.5 mL / min, preferably less than 0.1 mL / min.

[0063] The solution containing LiFSI comprises one solvent S or a mixture of two or more solvents S, for example two or three solvents S.

[0064] Preferably, the solvent S is selected from the group comprising, more preferably consisting of, 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, nitrobenzene, trifluoroethanol and mixtures thereof.

[0065] 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. The most preferred solvent is ethyl methyl carbonate.

[0066] In some embodiments, the LiFSI solution comprises 5-70% LiFSI by weight, based on the total weight of the solution.

[0067] The LiFSI solution preferably contains 10-60% by weight LiFSI, for example 15-50%, 20-40% by weight or 25-35% by weight LiFSI. For example, the solution contains 30±2% by weight LiFSI.

[0068] Good results have been obtained on a laboratory scale by injecting the LiFSI solution into the vessel under step c) at a flow rate of less than 3 mL / min, less than 2.5 mL / min, preferably 2 mL / min or less.

[0069] Under step c), the LiFSI solution can be provided sequentially, either semi-continuously or continuously. In other words, the LiFSI solution is continuously injected into the container, or the LiFSI solution is semi-continuously injected into the container. For example, the LiFSI solution can be injected into the container for a certain time, such as 30 to 120 seconds, preferably about 60 seconds, and then the injection is stopped for another period of time, which can be equal to, shorter than, or longer than the injection time. The LiFSI solution to be converted into a solid form can be injected into the container five times, four times, three times, two times, or all at once.

[0070] A particular advantage of the process of the present invention is the short contact time under step d).Equally advantageously, the contact time under step d) can be appropriately selected, for example, based on the starting material and the desired yield.

[0071] Preferably, the contact time under step d) varies from a few seconds, for example from 5 seconds to 24 hours, more preferably from 1 minute to 12 hours, for example from 5 minutes to 10 hours or from 10 minutes to 5 hours.

[0072] When step d) is completed, LiFSI in solid form is recovered under step e).

[0073] Preferably, the solid form of LiFSI recovered under step e) is in the form of a powder.

[0074] Preferably, step e) is carried out by continuously or semi-continuously removing solid LiFSI from the vessel.

[0075] According to a particular embodiment of step e), the solid LiFSI is recovered and separated from the supercritical fluid. The pressure is released and the supercritical fluid becomes a gas. Such gas is preferably recycled, as described in more detail below.

[0076] While the reaction conditions are controlled, at least a portion of the LiFSI in the LiFSI solution injected in step c) may not precipitate, and thus a portion of the LiFSI solution remains in the vessel in admixture with the supercritical fluid. It will be understood by those skilled in the art that the LiFSI solution remaining in the vessel has a lower concentration of LiFSI than the LiFSI solution provided in step c).

[0077] According to this embodiment, the mixture comprising the supercritical fluid, at least a portion of the LiFSI solution, and optionally the solvent S, is reinjected into the vessel as such.

[0078] Alternatively, the mixture comprising the supercritical fluid, at least a portion of the LiFSI solution and optionally the solvent S is injected into a second vessel, where the pressure is released, thus obtaining a gas that can be further recycled to the process, a solution of LiFSI and at least one solvent S that can be further reused in the process of the invention.

[0079] The process of the present invention can be carried out batchwise, continuously or semi-continuously. Preferably, it is carried out continuously or semi-continuously.

[0080] The method of the present invention may further comprise additional steps.

[0081] For example, the method of the invention may comprise, after step d), a step d') consisting in injecting at least one supercritical fluid into the container. This additional step has the advantage of completely drying the LiFSI in solid form before it is recovered under step e).

[0082] Preferably, said step d') is carried out at a pressure of at least 73 bar and at a temperature between 10° C. and 90° C. After step d'), the vessel can then be depressurized and the solid LiFSI product can be recovered under step e).

[0083] The process of the invention may also comprise, after step d), step d') or step e), at least one step consisting in recycling the solvent S and / or in recycling the supercritical fluid.

[0084] The method of the present invention preferably includes recycling of the solvent S and recycling of the supercritical fluid.

[0085] Preferably, the supercritical fluid may be reinjected into the process of the invention either as such or after an additional purification step.

[0086] Preferably, the recycled solvent S can be reused in a different process, for example an upstream process for preparing a LiFSI salt.

[0087] Recycling of the solvent S and the supercritical fluid can be accomplished in several ways.

[0088] According to a first embodiment, the supercritical fluid may be recycled continuously throughout the process using a supercritical fluid pipe under reduced pressure.

[0089] According to a second embodiment, the solvent S may be recovered as a liquid phase by releasing the pressure in the vessel and then recompressing the gas, for example with a compressor, in order to recycle it as a supercritical fluid which can be rejected by the vessel.

[0090] The method of the present invention comprises the steps of: - Gas tanks and supercritical gas generators; - optionally a solvent S tank; - LiFSI solution tank; - a container capable of withstanding a pressure P of at least 50 bar (5.0 MPa) and a temperature T of above 10°C; - a device for mixing the supercritical fluid with the LiFSI solution, for example a spray nozzle; - at least two injectors attached to the vessel; - Solvent trap; - optionally with a separator; - optionally with a filtering device The method may be implemented in a facility including:

[0091] The vessel may preferably be made of sapphire, SS316L, glass or graphite filled PTFE.

[0092] The vessel can be, inter alia, a column or an autoclave.

[0093] The equipment may include a separator. Different separators may be used in the method of the invention. In some embodiments, the separation of liquid and gas / fluid may be performed by traditional filtration (also called "dead-end filtration") or cross filtration (also called tangential filtration), as disclosed, for example, in US Patent Application Publication No. 2007 / 0021570 (in the name of Solvay SA.). Alternatively, cyclonic separators may be used, for example those that function as liquid / solid or gas / solid separators. Cyclonic separators are advantageous because they allow the recovery of solids that may clog the filter medium. There are several hybrid devices based on this principle. Among others, US Patent No. 7,410,620 (in the name of North Carolina State University) may be mentioned.

[0094] For example, the frit filter can be made of stainless steel. Preferably, the frit filter has at least one of the following characteristics: a pore size of 1-6 μm, preferably 2-4 μm; a diameter of 1-20 mm, preferably 5-15 mm, more preferably about 10 mm; and / or a thickness of 0.1-5 mm, preferably 0.7-3.5 mm, more preferably 1.5-2.5 mm.

[0095] If the device comprises a filter, or several filters, the filters may in particular be located at the bottom or at the top of the vessel.

[0096] In an exemplary embodiment of the present invention, the method for preparing a solid form of LiFSI salt can be carried out on a laboratory scale, a*) injecting sCO2 into a container at a flow rate comprised between 5 and 50 g / min, preferably about 30±5 g / min, the container being at a pressure P of at least 73 bar and at a temperature comprised between 10 and 90° C., preferably at a pressure P of 200±10 bar and at a temperature of 40±5° C.; b*) injecting solvent S into the vessel at a flow rate of less than 1 mL / min, preferably less than 0.1 mL / min; c*) stopping the injection of solvent S according to step b) and injecting LiFSI solution into the container at a flow rate of less than 3 mL / min, preferably less than 2 mL / min, wherein the LiFSI solution is injected into the container discontinuously, for example less than 5 times over the entire process; d*) contacting the LiFSI solution with a supercritical fluid and a solvent S in a vessel for a period of time between 5 minutes and 24 hours, preferably less than 5 hours; e*) recovering LiFSI in solid form; Includes.

[0097] A second object of the invention relates to the lithium salt of bis(fluorosulfonyl)imide (LiFSI) in solid form which can be obtained by the process of the invention.

[0098] Advantageously, such LiFSI salt in solid form is characterized in that it contains less than 100 ppm of water, as measured according to the KF method (oven).

[0099] Preferably, the amount of water is less than 50 ppm, less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm or even less than 5 ppm, as measured according to the KF method (oven).

[0100] Such LiFSI salts in solid form are also characterized in that the amount of solvent S in the salt is less than 50 ppm as measured by Li NMR. The amount of solvent S in LiFSI in solid form, e.g., powder form, is preferably less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm, or even less than 5 ppm.

[0101] Preferably, the LiFSI salt in solid form is characterized in that it contains at least one other substance, which is preferably: - Fluoride (F) in an amount preferably less than 100 ppm as measured by ion chromatography (IC) - ); and / or - Chloride (Cl) preferably in an amount of less than 100 ppm as measured by IC - ); and / or - Sulfates (SO4) preferably in an amount less than 1,000 ppm as measured by IC 2- ); and / or - Sulfamate (NH2SO3 - ); and / or - Fluorosulfonates (FSO3 - ) It is.

[0102] Advantageously, the amounts of such other substances in the solid form of the LiFSI salt recovered from the process of the invention are preferably as follows: - Fluoride (F) in an amount 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 (SO42- ) different acidic substances; - Sulfate (SO4) in an amount up to 100 ppm, e.g. less than 50 ppm, less than 30 ppm, less than 10 ppm, less than 5 ppm 2- ) different acidic substances and The amount is measured by ion chromatography (IC).

[0103] Preferably, sulfate (SO4 2- ) The acidic substance is different from NH2SO3 - and / or FSO3 - is selected from.

[0104] Preferably, (SO 2- ) the acidic substance is present in the amount of: - 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 (FSO3 - ) is located.

[0105] The LiFSI of the present invention also preferably has the following contents of chemicals: - an iron (Fe) content of less than 1,000 ppm, preferably less than 500 ppm, more preferably less than 100 ppm; - a chromium (Cr) content of less than 1,000 ppm, preferably less than 500 ppm, more preferably less than 100 ppm; - a nickel (Ni) content of less than 1,000 ppm, preferably less than 500 ppm, more preferably less than 100 ppm; - a zinc (Zn) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; - a copper (Cu) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; - a bismuth (Bi) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm or even less than 100 ppm sodium (Na + ) content; and / or - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm or even less than 100 ppm of potassium (K + ) content At least one of the following is shown.

[0106] Indeed, it is an object of the present invention to provide LiFSI salts that have very low amounts of impurities, preferably exhibiting a purity of greater than 99.50%, greater than 99.60%, greater than 99.70%, greater than 99.80%, greater than 99.90% and even greater than 99.95% as measured by Li-NMR.

[0107] A third object of the present invention is a powder comprising the lithium salt of bis(fluorosulfonyl)imide (LiFSI) and at least one other substance, said at least one other substance being - preferably less than 50 ppm of solvent S, as measured by Li NMR; and / or - water, preferably in an amount of less than 50 ppm, as determined by KF analysis by the oven method; and / or - Fluoride (F) preferably in an amount less than 25 ppm - ); and / or - Chloride (Cl) preferably in an amount less than 8 ppm - ); and / or - Sulfates (SO4) preferably in amounts less than 20 ppm 2- ); and / or - Sulfates (SO4) preferably in amounts less than 1 ppm 2- ) different acidic substances The present invention relates to a powder having a formula:

[0108] Preferably, the acidic substance is NH2SO 3- and / or FSO3 - is selected from.

[0109] A fourth object of the present invention relates to the use of the solid form of the lithium salt of bis(fluorosulfonyl)imide (LiFSI) according to the invention in a battery electrolyte solution.

[0110] A fifth object of the present invention is the use of supercritical anti-solvent extraction to prepare a solid form of the lithium salt of bis(fluorosulfonyl)imide (LiFSI) from a solution comprising LiFSI and at least one solvent.

[0111] 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, this statement shall control.

[0112] The present invention 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 disclosure. EXAMPLES

[0113] Example 1 - Preparation of LiFSI solution The method for preparing the LiFSI solution is as follows:

[0114] The process was carried out in a 1 L reactor under N2 equipped with stirring means, a double jacket for heat regulation, a condenser, pressure regulation means and means for adding liquids or gases. At room temperature, 577.18 g of ethyl methyl carbonate (EMC) were introduced in which 145.77 g of anhydrous NH4F was suspended. 190.52 g of bis(chlorosulfonyl)imide of formula (Cl-SO2)2-NH (HCSI) were gradually added over 1 hour and the mixture was heated to below 75 °C during 18-20 hours with stirring. The mixture was cooled to room temperature and 0.945 g of 25% NH4OH(aq) (aqueous ammonia) was added. The mixture obtained was stirred at room temperature for 2 hours and then filtered.

[0115] The product was then concentrated to 866.18 g, and 247.5 g of the concentrated solution was transferred to a glass reactor. 371.3 g of dichloromethane was added slowly over 1 hour. The precipitated NH4FSI was filtered, washed with dichloromethane, and dried in a vacuum oven to give 144.5 g of NH4FSI as a white solid.

[0116] 110.12 g of crystallized NHFSI was dissolved in 902.7 g of EMC. 23.37 g of a 25 wt% aqueous solution of LiOH·H2O was added. The resulting biphasic mixture was stirred at room temperature for 1 h and then decanted. The organic phase was collected and cooled under reduced pressure (10 -1 The mixture was placed in a thin film evaporator at 60° C. under 10 bar.

[0117] A 30 wt % LiFSI solution in EMC was obtained.

[0118] Example 2 - Preparation of LiFSI in powder form starting from the LiFSI solution of Example 1 Using the equipment configuration in FIG. 1 and detailed operating conditions summarized in Table 1, the experiment was carried out in the following procedure.

[0119] To provide supercritical CO2 (sCO2), the autoclave was filled with CO2 at the desired pressure (pressure = 80-200 bar) and temperature (temperature = 35-50 °C). sCO2 was continuously flowed at a rate of 15-30 g / min (sCO2 flow rate = 15-30 g / min) throughout the experiment.

[0120] Pure EMC was then introduced (EMC flow rate = 0–0.7 mL / min) and mixed with sCO2 to achieve steady state at the desired sCO2 / EMC mass ratio.

[0121] The EMC supply was replaced with the LiFSI solution (LiFSI solution flow rate = 0-2 mL / min) of Example 1. The injection of the LiFSI solution was performed either continuously or discontinuously for 30-120 seconds per injection.

[0122] Injection of pure CO2 was performed to completely dry the powder. After depressurizing the autoclave, the powder was collected by filtration.

[0123] [Table 1]

[0124] result: Experiment 10 resulted in 50% LiFSI salt (white and dry) which was obtained under the following conditions: 3 discontinuous LiFSI solution injections (30 s / injection), pressure=200 bar, temperature=40° C., CO2 flow rate=30 g / min, EMC flow rate=0 mL / min, LiFSI solution flow rate=2 mL / min, CO2 / LiFSI solution mass ratio=30.

[0125] The water content was measured according to KF analysis (oven method). Samples were prepared by a fully automatic oven sample processor (Metrohm); sample weight 0.1 g, carrier gas = N2, oven temperature = 160 °C. Titration was performed using a mixture of methanol and NHF (1:1 v / v). The polarization current for potentiometric measurement of the reaction end point was 10 μA, and the titration end point voltage was 50 mV.

[0126] The moisture content in the LiFSI product of Run 10 was below 50 ppm.

[0127] No major impurities were detected by ion chromatography (DIONEX ICS-3000). - F - <20 ppm - Cl - <5 ppm - SO4 2- <15 ppm - NH2SO 3- n / d (not detected) - FSO3 - n / d (not detected)

[0128] The purity of >99.9% was determined by Li-NMR.

Claims

1. A method for preparing lithium salts (LiFSI) of bis(fluorosulfonyl)imides in solid form, a) The process of injecting a supercritical fluid into a container; b) The step of optionally injecting solvent S into the container; c) A step of pouring a LiFSI solution containing LiFSI and at least one solvent S into the container; d) A step of bringing the LiFSI solution into contact with the at least one supercritical fluid and the solvent S in the container; e) A process for recovering LiFSI in solid form and Methods that include...

2. The method according to claim 1, wherein the at least one supercritical fluid in step a) is selected from one fluid in a supercritical state or a mixture of at least two fluids in a supercritical state.

3. - Step b) is not performed, and step c) begins after step a); or The method according to claim 1, wherein step b) is performed, and step c) begins after steps a) and b), and the solvent S injected in step b) is the same as the solvent S in the LiFSI solution injected in step c).

4. The method according to claim 1, wherein the solvent S is preferably 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, dimethyl sulfoxide, N,N-dimethylformamide, N-methyloxazolidinone, acetonitrile, valeronitrile, benzonitrile, ethyl acetate, isopropyl acetate, n-butyl acetate, nitromethane, nitrobenzene, trifluoroethanol, and mixtures thereof.

5. The method according to claim 1, wherein the LiFSI solution contains 5 to 70% by weight of LiFSI based on the total weight of the solution.

6. The method according to claim 1, wherein the method is carried out in a vessel with a pressure P of at least 73 bar and / or a temperature T of 30°C to 90°C.

7. The supercritical fluid contains CO2 and is optionally mixed with at least one polar solvent having a solubility in the supercritical fluid of less than 10% by weight, based on the total weight of the supercritical fluid and at least one polar solvent, to form CO2. ２ The method according to claim 1, including the method described in claim 1.

8. - The pressure P inside the container is within the range of 80 bar to 500 bar, and / or - The temperature inside the container is within the range of 35°C to 80°C. The method according to claim 7.

9. The method according to claim 1, wherein the method is carried out continuously or semi-continuously.

10. The method according to claim 1, further comprising at least one step of recycling the solvent S and / or recycling the supercritical fluid.

11. The method described above is - Gas tanks and supercritical gas generators; - Optionally, with solvent tank S; - LiFSI solution tank and; - A container capable of withstanding a pressure P of at least 50 bar and a temperature P of more than 10°C; - A device for mixing the supercritical fluid and the LiFSI solution; - With at least two injectors attached to the container; - With a solvent trap; - Selectively with a separator; - Optionally select a filtration device and The method according to claim 1, which is carried out within a facility including the following:

12. A lithium salt (LiFSI) of bis(fluorosulfonyl)imide in solid form, obtainable by the method of claim 1, characterized by containing less than 100 ppm of water and / or less than 50 ppm of solvent S, as measured according to the KF method (oven).

13. A powder comprising a lithium salt of bis(fluorosulfonyl)imide (LiFSI) and at least one other substance, wherein the at least one other substance is - A solvent S in an amount preferably less than 50 ppm, as measured by Li NMR; and / or - Water in an amount preferably less than 50 ppm, as measured by oven-based KF analysis; and / or - A quantity of fluoride (F) preferably less than 25 ppm, measured by ion chromatography (IC). － ); and / or - Chloride (Cl) in an amount preferably less than 8 ppm, as measured by IC. － ); and / or - A quantity of sulfate (SO4) measured by IC, preferably less than 20 ppm. ４ ２－ ); and / or - A quantity of sulfate (SO4) measured by IC, preferably less than 1 ppm. ４ ２－ ) Different acidic substances It is a powder.

14. Use of the lithium salt (LiFSI) of bis(fluorosulfonyl)imide described in claim 12 or the powder described in claim 13 in a battery electrolyte solution.

15. The use of supercritical poor solvent extraction to prepare LiFSI in solid form from a solution containing a lithium salt of bis(fluorosulfonyl)imide (LiFSI) and at least one solvent S.

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