Process for the preparation of alkali salts of bis(fluorosulfonyl)imides

Abstract

The present invention relates to a process for the preparation of bis(fluorosulfonyl)imide salt (MFSI), which comprises at least a step of reacting ammonium salt of bis(fluorosulfonyl)imide (NHFSI) with fluorine-containing alkoxide. The present invention also relates to a process for the preparation of fluorine-containing alkoxide.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED PATENT APPLICATIONS This application claims priority to European Patent Application No. 21306857.0, filed December 20, 2021, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a process for producing bis(fluorosulfonyl)imide salts (MFSI), which comprises at least a step of reacting ammonium salts of bis(fluorosulfonyl)imides (NHFSI) with fluorine-containing alkoxides. The present invention also relates to a process for preparing such fluorine-containing alkoxides. [Background technology]

[0003] Bis(fluorosulfonyl)imides and their salts, especially the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds in various technical fields. Bis(fluorosulfonyl)imides and their salts are particularly useful in battery electrolytes. For use in batteries, it is very important to limit the presence of impurities.

[0004] The preparation of bis(fluorosulfonyl)imides and their salts has been described in the literature. Among the various techniques described, the majority use a fluorination reaction with a fluorinating agent in a solvent. The subsequent step is usually a cation exchange reaction, or more precisely, a lithiation step if LiFSI is to be prepared.

[0005] In particular, WO 2017 / 090877 (CLS) describes a method for preparing lithium bis(fluorosulfonyl)imide, which comprises the steps of (1) reacting bis(chlorosulfonyl)imide with a fluorinating agent in a solvent, followed by treatment with an alkaline agent, thereby producing ammonium bis(fluorosulfonyl)imide, and (2) reacting ammonium bis(fluorosulfonyl)imide with a lithium base. The lithiation is carried out in butyl acetate as a solvent, with lithium hydroxide hydrate (LiOH·H2O) as the lithium base. After completion of the reaction, the aqueous layer is separated, and lithium bis(fluorosulfonyl)imide is produced by concentration, recrystallization, and separation steps. This protocol for removing water suffers from low productivity due to its time consuming nature, and requires fresh solvent.

[0006] WO 2020 / 099527 (Solvay SA) discloses a method for producing an alkali salt of bis(fluorosulfonyl)imide, comprising the steps of a) reacting bis(chlorosulfonyl)imide or a salt thereof with ammonium fluoride to produce an ammonium salt of bis(fluorosulfonyl)imide, b) crystallizing and isolating the ammonium salt of bis(fluorosulfonyl)imide by adding at least one precipitating solvent, and c) reacting the crystallized ammonium salt of bis(fluorosulfonyl)imide with an alkali salt to obtain an alkali salt of bis(fluorosulfonyl)imide. In Example 3, the alkali salt is an aqueous solution of LiOH·H2O. No disclosure of fluorine-containing hydroxides is made in this document. Summary of the Invention

[0007] The object of the present invention is to provide a process for the preparation of an MFSI salt, where M represents a metal and the MFSI salt is preferably LiFSI, which takes less time and does not require additional solvents.

[0008] It is also an object of the present invention to provide a process for producing MFSI salts which does not generate water as the process proceeds.

[0009] Advantageously, the process of the invention comprises a compound of the formula RO - M + or its solvate form [RO - M +

[0033] [nROH], where R is a moiety containing a fluorine atom.

[0010] The present invention relates to a compound of formula (I): [F-SO2-N - -SO2-F]M + (I) (wherein M is selected from the group consisting of Li, Na, K, Rb, Cs and Fr). The present invention is directed to a process for producing bis(fluorosulfonyl)imide salts (MFSIs).

[0011] This process effectively replaces the conventional alkalizing agents used to prepare the alkali salts of bis(fluorosulfonyl)imides, represented by the formula RO - M + or a solvate form thereof [RO - M + [nROH] is based on the use of

[0012] The use of such fluorine-containing alkoxides advantageously makes it possible to avoid the production of water in the reaction medium after the reaction and, consequently, to avoid additional, time-consuming steps for removing such water.

[0013] The present invention is also directed to a process for the preparation of the fluorine-containing alkoxides used in the above processes, and to the fluorine-containing alkoxides thus obtained.

[0014] The present invention is also directed to the use of such fluorine-containing alkoxides for preparing bis(fluorosulfonyl)imide salts (MFSIs). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The first aspect of the present invention relates to a compound of formula (I): [F-SO2-N - -SO2-F]M + (I) (wherein M is selected from the group consisting of Li, Na, K, Rb, Cs and Fr). A process for producing a bis(fluorosulfonyl)imide salt (MFSI) of The process comprises reacting a compound of formula (II): [F-SO2-N - -SO2-F]NH4 + (II) The ammonium salt of bis(fluorosulfonyl)imide [NHFSI salt] of the formula (III): RO - M + (III) with a fluorine-containing alkoxide of Where: R is C1~C 20 Fluoroalkyl, C1-C 20 Fluoroalkenyl and C1-C 20 fluoroalkynyl; M is selected from the group consisting of Li, Na, K, Rb, Cs and Fr; The NH4FSI salt is optionally - 50 to 99.9% by weight of NH4FSI salt; - 0.1 to 50% by weight of at least one solvent S2 selected from the group consisting of cyclic and acyclic ethers, in the form of a solvate comprising Regarding the process.

[0016] The fluorine-containing alkoxides of formula (III) may advantageously be in the form of solvates as follows: [RO - M + ][nROH] (III*) n is an integer from 1 to 10, Each of M and R has the same meaning as described above.

[0017] The fluorine-containing alkoxide of formula (III) or (III*) is advantageously used to alkalize the NH4FSI salt. In other words, the fluorine-containing alkoxide of formula (III) or (III*) can transfer its alkali metal "M" to the NH4FSI salt.

[0018] The fluorine-containing alkoxide (III) or (III*) may be provided in the processes described herein in a solid state, a liquid state, or in an organic solution.

[0019] The fluorine-containing alkoxide of formula (III) or (III*) is represented by the formula RO - M + (Wherein, R is C1 to C 20 Fluoroalkyl, C1-C 20 Fluoroalkenyl and C1-C 20 Preferably, R is a fluoroalkyl group, in other words selected from the group consisting of fluoroalkyl, fluoroalkenyl and fluoroalkynyl groups having 1 to 20 carbon atoms. Preferably, the number of carbon atoms in the R group is 1 to 12, more preferably 1 to 8 or 1 to 6, even more preferably 1 to 3, this number being equal to 2 in a particular embodiment. Preferably, R is a fluoroalkyl group.

[0020] In some embodiments, R is of the formula R F -L(where R F is a monovalent group selected from the group consisting of C1-C3 perfluoroalkyl, C1-C3 perfluoroalkenyl, and C1-C3 perfluoroalkynyl, L is a divalent group selected from the group consisting of C1-C3 alkylene, C1-C3 alkenylene, and C1-C3 alkynylene; preferably R F is a C1-C2 perfluoroalkyl group, L is a C1-C2 alkylene group; more preferably R Fis CF3 and L is CH2), in other words the alcohol of formula (I) is 2,2,2-trifluoroethanol (TFE). The fluorine-containing alkoxide of the above formula (III) or (III*) can be prepared by the process described in detail below.

[0021] The NHFSI (II) involved in the process of the present invention may be in the form of a substantially pure salt, or it may be in the form of a solvate, as described below. It may be prepared by any method known to those skilled in the art. It may be prepared by fluorinating bis(chlorosulfonyl)imide (HCSI), or a salt thereof, with a fluorinating agent, such as ammonium fluoride.

[0022] In some embodiments, the NH4FSI salt is - 50 to 98% by weight of NH4FSI salt; - 2 to 50% by weight of at least one solvent S2 selected from the group consisting of cyclic and acyclic ethers,

[0033] A solvate [NH4FSI solvate], optionally in crystalline form.

[0023] Preferably, the NH4FSI solvate contains 51 to 98% by weight, more preferably 55 to 95% by weight, or 78 to 83% by weight, of the NH4FSI salt.

[0024] Preferably, the NH4FSI solvate comprises 2-49% by weight, more preferably 5-45% by weight or 17-22% by weight of at least one solvent S2.

[0025] The at least one solvent S2 is preferably selected from the group consisting of diethyl ether, diisopropyl ether, methyl t-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane, and mixtures thereof; more preferably from the list consisting of diethyl ether, diisopropyl ether, methyl t-butyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, and mixtures thereof; even more preferably 1,3-dioxane or 1,4-dioxane.

[0026] In some embodiments, the process for producing an MFSI salt according to the present invention comprises the following steps: i1) providing a crude salt of NH4FSI; i2) dissolving the crude salt of NH4FSI in at least one solvent S1; i3) crystallizing the crude salt of NH4FSI with at least one solvent S2; i4) separating the NH4FSI salt from at least a portion of the solvents S1 and S2, preferably by filtration; The method includes the preliminary step i) of preparing the NH4FSI solvate by

[0027] The crude salt of NH4FSI may contain 80 to 97% by weight, preferably 85 to 95% by weight, and more preferably 90 to 95% by weight of the salt of NH4FSI.

[0028] Solvent S1 is preferably selected from the group consisting of acetonitrile, valeronitrile, adiponitrile, benzonitrile, methanol, ethanol, 1-propanol, 2-propanol, 2,2,2-trifluoroethanol, n-butyl acetate, isopropyl acetate, and mixtures thereof; preferably 2,2,2-trifluoroethanol.

[0029] In some preferred embodiments, step i4) comprises reacting a NH4FSI salt with - more than 99.9% by weight of solvent S1; and - 50-99% by weight of at least one solvent S2 The objective of the present invention is to separate the

[0030] The reaction between the NH4FSI salt and the fluorine-containing alkoxide of formula (III) or (III*) can be carried out in one or more solvents. However, the reaction can be solventless.

[0031] The fluorine-containing alkoxides of formula (III) or (III*) may be provided in such a state that they are already dissolved in a solvent. In this case, the addition of a solvent is possible but not necessary. This additional solvent may be the same as or different from the solvent used in step i).

[0032] The fluorine-containing alkoxide of formula (III) or (III*) may be provided in a substantially dry solid state or may be dissolved in a solvent prior to use in the process of the invention.

[0033] In some embodiments, a solvent is used (added) to carry out the reaction between NHFSI and the fluorine-containing alkoxide (III) or (III*). It is preferable to select the same solvent as that used to prepare the alkoxide (III) or (III*). Alternatively, a different solvent can be used.

[0034] The solvent is advantageously of formula ROH, where R is a C1-C 20 Fluoroalkyl, C1-C 20 Fluoroalkenyl and C1-C 20R is preferably selected from the group consisting of fluoroalkyl, fluoroalkenyl and fluoroalkynyl groups having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 3 carbon atoms. R has 2 carbon atoms in a particular embodiment. Preferably, R is a fluoroalkyl group. According to one embodiment, R is of the formula R F -L(where R F is a monovalent group selected from the group consisting of C1-C3 perfluoroalkyl, C1-C3 perfluoroalkenyl, and C1-C3 perfluoroalkynyl, L is a divalent group selected from the group consisting of C1-C3 alkylene, C1-C3 alkenylene, and C1-C3 alkynylene; preferably R F is a C1-C2 perfluoroalkyl group, L is a C1-C2 alkylene group; more preferably R F is CF3 and L is CH2): In other words, the alcohol of formula (I) used in the process for the preparation of the salt of bis(fluorosulfonyl)imide is 2,2,2-trifluoroethanol.

[0035] Such a solvent may preferably be selected among solvents S1 or S2.

[0036] The reactants, optionally the solvent, may be contacted in any order. In particular, the solvent may be added before, after or simultaneously with the reactants. NHFFSI (II) may, for example, be dissolved in a solvent before adding the alkoxide (III) or (III*). The molar ratio solvent / NHFSI may range from 1 to 10, in particular from 1 to 5, more in particular from 1 to 2.

[0037] In some embodiments, the process of the present invention may be a solvent-free process. In other words, no solvent / diluent is added to the reaction mixture during the reaction, or a very small amount of solvent / diluent is added. The process may be carried out with molten NHFFSI salt in the absence of a solvent or in the presence of less than 5% by weight of a solvent based on the total weight of the reaction mixture involved in the process. According to these embodiments, the process is carried out in the melt in the absence of a solvent and a diluent. More precisely, the molten NHFFSI (II) serves to disperse the reactants, allowing them to contact and react with each other.

[0038] When the process of the present invention is solvent-free, the addition of alkoxide (III) or (III*) in molten NHFSI salt can be carried out in sequence, incrementally or continuously. For example, batch reactors, extruders and mixer-kneaders can be used in the present invention. Acid corrosion-resistant materials (e.g. PTFE, PFA, etc.) can be coated (in other words lined) in the selected reactor. Industrial melt mixers or melt blenders can be mentioned.

[0039] The process of the invention is preferably carried out under an inert atmosphere to avoid contamination with moisture. The process of the invention may be carried out, for example, under nitrogen or argon.

[0040] The molar ratio alkoxide (III) or (III*) / NH4FSI salt may range from 1 to 10, in particular from 1 to 5, more in particular from 1 to 2.

[0041] The process of the present invention may be carried out at a temperature below 100° C., for example from 0° C. to 50° C., more preferably from 15° C. to 35° C., even more preferably at about room temperature.

[0042] Preferably, the process according to the invention is carried out under atmospheric pressure, although it is not excluded to work below or above atmospheric pressure, for example from 5 mbar to 1.5 bar, preferably from 5 mbar to 100 mbar.

[0043] The reaction time of the process of the present invention can be freely selected depending, for example, on the reactor used, the reaction temperature involved and the amount of reactants. The reaction time is preferably 1 to 12 hours, particularly preferably 1.5 to 10 hours or 2 to 9 hours.

[0044] The MFSI salt is obtained in the reaction medium at the end of the reaction between the NH4FSI salt and the fluorine-containing alkoxide (III) or (III*).

[0045] Further steps may be carried out to purify / isolate the MFSI salt.

[0046] According to one particular embodiment, the process of the invention comprises at least one further step of concentrating the MFSI salts, preferably carried out under reduced pressure.

[0047] This step can be carried out by reducing the temperature, by reducing the pressure or by both. The temperature can in particular be reduced to a temperature in the range of -10°C to 10°C, preferably -5°C to 5°C, preferably about 0°C.

[0048] The pressure can be adjusted depending on the nature of the chemical species present in the reaction medium at the end of the reaction; it can be, in particular, between 10 -2 The pressure can be adjusted to a value between 1 mbar and atmospheric pressure, preferably between 1 mbar and 500 mbar, preferably between 5 mbar and 100 mbar, more preferably between 10 and 30 mbar.

[0049] The operation can be repeated one or several times to further purify the salt. Fresh solvent is added to the concentrated reaction medium containing the salt before a subsequent concentration operation.

[0050] A mixture of purified alkali salts of bis(fluorosulfonyl)imides in said solvent can thereby be obtained.

[0051] Further processing may be carried out to recover the highly pure alkali salt of the bis(fluorosulfonyl)imide. Additional steps may include filtration, extraction, recrystallization, chromatographic purification, drying, and / or formulation.

[0052] All raw materials used in the processes described herein, such as solvents and reagents, preferably exhibit very high purity standards: preferably, their content of metal components such as Na, K, Ca, Mg, Fe, Cu, Cr, Ni, Zn is less than 10 ppm, more preferably less than 2 ppm.

[0053] In addition, some or all of the steps of the process according to the invention are advantageously carried out in equipment that can withstand corrosion. For this purpose, the materials intended to come into contact with the reaction medium are selected from corrosion-resistant materials, such as alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon and tungsten sold under the Hastelloy® brand, or alloys of nickel, chromium, iron and manganese with the addition of copper and / or molybdenum sold under the names Inconel® or Monel®, more particularly Hastelloy C276 or Inconel 600, 625 or 718 alloys. Stainless steels may also be selected, such as austenitic steels, more particularly 304, 304L, 316 or 316L stainless steels. Steels are used that have a nickel content of at most 22% by weight, preferably between 6% and 20%, more preferentially between 8% and 14%. 304 and 304L steels have a nickel content that varies between 8% and 12%, while 316 and 316L steels have a nickel content that varies between 10% and 14%. More particularly, 316L steel is chosen. Equipment made of or coated with polymeric compounds that are resistant to corrosion by the reaction medium may also be used. In particular, materials such as PTFE (polytetrafluoroethylene or Teflon) or PFA (perfluoroalkyl resins) may be mentioned. Glass equipment may also be used. It would not be outside the scope of the invention to use comparable materials. Other materials that may be suitable for contacting the reaction medium may also include graphite derivatives. The material for the filtration must be compatible with the medium used. Fluorinated polymers (PTFE, PFA), loaded fluorinated polymers (Viton™), as well as polyester (PET), polyurethane, polypropylene, polyethylene, cotton, and other compatible materials may be used.

[0054] A second aspect of the present invention relates to the metal salts of bis(fluorosulfonyl)imides (MFSIs) obtainable by the process of the present invention.

[0055] The MFSI salts advantageously have the following characteristics: - 19 a purity of at least 98% by weight, for example 99% to 100% by weight or 99.50 to 100% by weight, as measured by F NMR; a solvent content of less than 20% by weight, less than 10% by weight, less than 1% by weight, preferably between 0% and 1% by weight, as measured by GC (or alternatively headspace GC); - a water content of less than 500 ppm, less than 100 ppm, less than 50 ppm or even less than 20 ppm, as measured, for example, by Karl Fischer water titration, performed in a glove box At least one (preferably all) of the above is shown.

[0056] The MFSI salts of the invention advantageously have the following characteristics: - a chloride (Cl-) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, or more preferably less than 2 ppm; - a fluoride (F-) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 40 ppm, more preferably less than 30 ppm, more preferably less than 20 ppm; and - less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, or more preferably less than 2 ppm sulfate (SO 2- ) content At least one (preferably all) of the above is shown.

[0057] The fluoride and chloride content can be measured, for example, by argentometric titration using an ion selective electrode (or ISE). The sulfate content can alternatively be measured by ion chromatography or by turbidimetry.

[0058] Preferably, the MFSI salt of the present invention has the following contents of metal elements: - an iron (Fe) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a chromium (Cr) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a nickel (Ni) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a zinc (Zn) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a copper (Cu) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a copper (Cu) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a manganese (Mg) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a sodium (Na) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - a potassium (K) content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm; - Pb content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm At least one (preferably all) of the above is shown.

[0059] The elemental impurity content can be measured, for example, by ICP-AES (inductively coupled plasma); more specifically, the Na content can be measured by AAS (atomic absorption spectroscopy).

[0060] In some embodiments, the MFSI salt of the present invention is the lithium salt of bis(fluorosulfonyl)imide, Li + (FSO2)2N - (LiFSI). The lithium salt of bis(fluorosulfonyl)imide has the following impurity profile: - 19 A purity of at least 99.90% by weight, ranging from 99.90% by weight to 100% by weight, as measured by F NMR; and - Water content less than 50 ppm as measured by Karl Fischer water titration It can be characterized as:

[0061] A third aspect of the present invention relates to a compound of formula (III) or (III*): RO - M + (III) [RO - M + ][nROH] (III*) (In the formula, Each R is C1~C 20 Fluoroalkyl, C1-C 20 Fluoroalkenyl and C1-C 20 fluoroalkynyl; M is an alkali metal, preferably selected from the group consisting of Li, Na, K, Rb, Cs and Fr, n is an integer ranging from 1 to 10. of a fluorine-containing alkoxide, Formula (I): [F-SO2-N - -SO2-F]M + (I) for producing metal salts of bis(fluorosulfonyl)imides (MFSI).

[0062] The fluorine-containing alkoxide (III) or (III*) used in the process of the present invention for producing the metal salt of MFSI is selected from the group consisting of C1-C 20 Fluoroalkyl, C1-C 20 Fluoroalkenyl and C1-C 20 It contains an R moiety selected from the group consisting of fluoroalkynyl, i.e. fluoroalkyl, fluoroalkenyl and fluoroalkynyl having 1 to 20 carbon atoms. Preferably, the number of carbon atoms in the R group ranges from 1 to 12, more preferably 1 to 8 or 1 to 6, even more preferably 1 to 3, with this number being equal to 2 in certain embodiments. Preferably, R is a fluoroalkyl.

[0063] In some embodiments, R is of the formula R F -L(where R F is a monovalent group selected from the group consisting of C1-C3 perfluoroalkyl, C1-C3 perfluoroalkenyl, and C1-C3 perfluoroalkynyl, L is a divalent group selected from the group consisting of C1-C3 alkylene, C1-C3 alkenylene, and C1-C3 alkynylene; preferably R F is a C1-C2 perfluoroalkyl group, L is a C1-C2 alkylene group; more preferably R F is CF3 and L is CH2), in other words the alcohol of formula (I) is 2,2,2-trifluoroethanol (TFE).

[0064] A fourth aspect of the present invention is a process for the preparation of fluorine-containing alkoxides of formula (III) or (III*) used in the process of the present invention, comprising the formula (IV): ROH (IV) with an alcohol of formula (V) MOH (V) or a hydrate thereof, where R and M are as defined above. Regarding the process.

[0065] Preferably, M represents an alkali metal selected from the group consisting of Li, Na, K, Rb, Cs and Fr.

[0066] "Hydrate" is intended to indicate any compound of formula (V) containing water, usually, but not necessarily, in the form of HO molecules, with the content of water determined by weight.

[0067] Preferably, the metal M is selected from the group consisting of Li, Na, K and Cs; more preferably, M is Li.

[0068] The metal hydroxide of formula (V) is preferably lithium hydroxide. In particular, in one embodiment, the metal hydroxide of formula (V) used in the process for producing the fluorine-containing alkoxide used in the process of the present invention is LiOH·H2O.

[0069] The fluorine-containing alkoxide (III) of the present invention can be in the form of a solvate as represented by the above formula (III*), i.e., a crystalline solid containing molecules of a solvent within the crystalline mass. The crystalline solvate can be preferably formed in a crystallization process with the aid of a solvent.

[0070] The alcohol of formula (IV) and the metal hydroxide of formula (V) or its hydrate can be contacted in various ways. They are preferably contacted under an inert atmosphere, typically nitrogen or argon atmosphere. The molar ratio alcohol / metal hydroxide is preferably in the range of 1 to 30, preferably 1 to 20, more preferably 2 to 10, even more preferably 3 to 6. It is advantageous to solubilize the metal hydroxide (V) in the alcohol (IV) because, in addition to its role as a reactant, the alcohol acts as a solvent. The metal hydroxide (V) is preferably in high concentration in the alcohol (IV). To facilitate the dissolution of the metal hydroxide (V) in the alcohol (IV), the reaction medium can be stirred for a sufficient period, which can be at least 30 minutes, for example 30 minutes to 6 hours, in particular 30 minutes to 3 hours, for example about 1 hour. The reaction can be carried out at a temperature in the range of at least 5°C, for example 5 to 200°C, preferably 10 to 100°C, more preferably 15 to 50°C, even more preferably 15 to 30°C. The reaction can be carried out at ambient temperature, which is preferably economically advantageous. Preferably, the reaction is carried out under atmospheric pressure, but it is not excluded to work below or above atmospheric pressure, for example from 5 mbar to 1.5 bar, preferably from 5 mbar to 100 mbar.

[0071] The fluorine-containing alkoxide (III) or (III*) described herein, as obtained from the process described above, can be used as such in the process for producing the bis(fluorosulfonyl)imide salt (MFSI) described above. The fluorine-containing alkoxide described herein can also be provided in a solid and / or purified form to facilitate its storage and implementation into the process.

[0072] In some embodiments, the process for the preparation of the fluorine-containing alkoxide (III) or (III*) further comprises a step of concentration of the fluorine-containing alkoxide (III) or (III*), for example by evaporating a portion of the alcohol of formula (IV). This concentration can be carried out by heating the reaction mixture and / or by reducing the pressure. According to one embodiment, the concentration step can consist in distillation of the alcohol of formula (I) at a temperature comprised between 0° C. and 120° C., preferably between 5° C. and 80° C., more preferably between 10° C. and 70° C. The pressure can be typically between atmospheric pressure and 10° C., depending on the nature of the alcohol of formula (I). -2 The pressure may be adjusted between 1 mbar and 500 mbar, preferably between 5 mbar and 100 mbar. The distillation may be carried out by any typical means known to the skilled person in a continuous process or in a discontinuous / batch manner, such as continuous batch solvent evaporation, batch distillation, short path continuous flow distillation, or thin film evaporator.

[0073] In some embodiments, the process for the preparation of fluorine-containing alkoxides (III) or (III*) comprises further steps of crystallization and separation. Crystallization can be carried out by any suitable method available to the skilled person, such as evaporation of the remaining alcohol (IV), addition of an additional solvent different from the alcohol (IV), also called anti-solvent or drawn out, solvent layering or sublimation. In a preferred embodiment, crystallization is carried out by lowering the temperature of the reaction mixture to a temperature at which crystals (i.e. a crystalline solid) form. In other words, the temperature can be lowered to a value below the temperature of solubility of the alkoxides (III) or (III*). Preferably, the temperature of the reaction mixture is lowered to a value comprised between the boiling point of the alcohol of formula (IV) and -20°C, more preferably between 70°C and -10°C, even more preferably between 30°C and 0°C. During the reduction of the temperature, the pressure is preferably kept constant. However, a simultaneous reduction of the pressure is not excluded. It may cause evaporation of part of the alcohol of formula (IV) from the reaction medium. The pressure can be lowered to a value comprised between 10°C and -20°C. -2 The reduced temperature may be maintained for a time in the range of from 1 to 20 hours, in particular from 2 to 15 hours, more in particular from 3 to 10 hours.

[0074] The separation of the fluorine-containing alkoxide (III) or (III*) can be carried out by any typical separation method available to those skilled in the art, for example, by filtration. The filtration can be carried out at atmospheric pressure, under pressure or under vacuum. The mesh size of the filtration medium can be 2 μm or less, more preferably 0.45 μm or less, even more preferably 0.22 μm or less. The separated product can be washed once or several times with a suitable solvent, such as any solvent in which the fluorine-containing alkoxide (III) or (III*) is insoluble and the alcohol of formula (IV) is at least partially soluble. In addition, the selected solvent should be easily separated from the alcohol of formula (IV) by any means known to those skilled in the art, such as distillation or phase separation. The selected solvent should preferably form an azeotrope with the alcohol of formula (IV).

[0075] The crystallization and separation steps may be carried out once or may be repeated two or more times if necessary to improve the purity of the separated fluorine-containing alkoxide (III) or (III*). When repeating this procedure, the alkoxide (III) or (III*) may be solubilized in fresh alcohol of formula (IV), preferably identical to that used in the initial production. The same conditions as those described above (molar ratio alcohol / alkali hydroxide, time, temperature, pressure, etc.) may be applied.

[0076] In some embodiments, the process for the preparation of fluorine-containing alkoxides (III) or (III*) comprises a further step consisting in drying the alkoxides (III) or (III*) after the crystallization and separation steps described above. A substantially dry solid product can be obtained from such an additional step, taking all the advantages of obtaining a product that is easier to store and to use in reactions for preparing salts of bis(fluorosulfonyl)imides, in particular those according to the invention. Drying can be carried out by any method available to the skilled person, typically under reduced pressure and / or by heating and / or using an inert gas stream, typically a nitrogen or argon stream.

[0077] According to a preferred embodiment, the drying of the alkoxide (III) or (III*) is carried out under reduced pressure. The pressure is in particular between 10 -2 mbar to atmospheric pressure (1013.25 mbar), preferably 10 -1 The pressure may be reduced to a value comprised between 5 and 50°C, preferably between 1 and 100 mbar, and more preferably between 1 and 10 mbar. The temperature may be comprised between 5 and 50°C, and preferably between 10 and 30°C. Advantageously, the drying of the alkalizing agent may be carried out at room temperature. The drying time may range from 1 to 20 hours, and preferably from 1 to 10 hours.

[0078] The fluorine-containing alkoxide (III) or (III*) is obtained at the end of the process described above.

[0079] A fifth aspect of the present invention relates to a compound of formula (III) or (III*): RO - M + (III) [RO - M + ][nROH] (III*) (In the formula, Each R is C1~C 20 Fluoroalkyl, C1-C 20 Fluoroalkenyl and C1-C 20 fluoroalkynyl; M represents a metal, preferably selected from Li, Na, K, Rb, Cs and Fr, n is an integer ranging from 1 to 10, preferably from 1 to 5, in particular from 1 to 3, and in particular it can be equal to 2) This relates to fluorine-containing alkoxides.

[0080] The fluorine-containing alkoxides represented by formula (III*) are in the form of solvates, i.e., crystalline solids that contain molecules of a solvent (stoichiometrically or non-stoichiometrically) within their crystalline mass, as characterized by fluorine nuclear magnetic resonance (NMR) analysis.

[0081] Preferably, in formula (III) or (III*), each R is selected from fluoroalkyl, fluoroalkenyl and fluoroalkynyl groups having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, especially 2 carbon atoms. Preferably, R is a fluoroalkyl group. According to one embodiment, R is a group of formula R F -L(where R F is a monovalent group selected from the group consisting of C1-C3 perfluoroalkyl, C1-C3 perfluoroalkenyl, and C1-C3 perfluoroalkynyl, L is a divalent group selected from the group consisting of C1-C3 alkylene, C1-C3 alkenylene, and C1-C3 alkynylene; preferably R F is C1~ C2 is a perfluoroalkyl group, and L is a C1-C2 alkylene group; more preferably R F is CF3 and L is CH2).

[0082] Preferably, in each of formulas (III) or (III*), M represents an alkali metal selected from the group consisting of Li, Na, K and Cs; more preferably M is Li.

[0083] According to one particular embodiment, in the compound of formula (III*), R is CF3-CH2, M is Li and n=2, in other words a solvate of lithium 2,2,2-trifluoroethoxide and 2,2,2-trifluoroethanol. Preferably, this compound is a crystalline solid.

[0084] Advantageously, the alkoxide (III) or (III*) obtained by the process described in the present invention is 19 It has a very high purity, in particular a purity of at least 98% by weight, such as 99% to 100% or 99.50% to 100% by weight, as measured by F NMR.

[0085] The MFSI salts, especially LiFSI, obtained by the process according to the invention can be advantageously used in electrolyte compositions for batteries.

[0086] 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 herein shall control.

[0087] The invention will now be further described in the examples, without any intention of limiting the invention. EXAMPLES

[0088] Example 1. Formula [CF3CH2O - Li + Synthesis of alkoxides of [2CF3CH2OH] Under nitrogen, 7.7 g (0.18 mol) LiOH monohydrate was mixed with 143 g (1.43 mol) 2,2,2-trifluoroethanol (TFE) and stirred at room temperature for 1 h. The mixture was cooled to T=5°C for 2 h. Some crystals were observed in the cloudy suspension. The crystals were isolated by filtration. The crystals were then dissolved in 145 g (1.45 mol) fresh TFE at room temperature for 1 h and cooled to T=5°C for 2 h. The solid was obtained by filtration. It was then dried under vacuum (P=5 mbar) at room temperature for 5 h. NMR analysis revealed the compound of formula [CF3CH2O - Li + This is consistent with a solvate of [2CF3CH2OH].

[0089] Example 2. Synthesis of the lithium salt of bis(fluorosulfonyl)imide using the solvate alkoxide of Example 1 Under a nitrogen atmosphere, a solution of 6.9 g (0.35 mmol) ammonium bis(fluorosulfonyl)imide (NH4FSI) was prepared in 60 g (0.60 mol) TFE. 10.6 g (0.035 mmol) of the solid alkoxide of Example 1 was then added to the vessel at room temperature under stirring over a period of 10 minutes, at which time the solid dissolved in the medium immediately upon addition. NaOH titration revealed that NH4 +It shows a conversion of ions of more than 90%. No water was produced. The medium was concentrated under reduced pressure (P=20 mbar, T=0° C.). Then 120 ml of TFE were added and the concentration was repeated twice under the same conditions. 13 g of a viscous transparent liquid was obtained. 19 F NMR is consistent with a mixture of LiFSI, NHFSI, and TFE. No other fluorinated species are detected. NaOH titration suggests high conversion to LiFSI.

Claims

1. Formula (I): [F-SO ２ -N － -SO ２ -F]M ＋ (I) (In the formula, M is selected from the group consisting of Li, Na, K, Rb, Cs and Fr. A method for preparing a bis(fluorosulfonyl)imide (MFSI) salt of the formula: The method comprises: - Formula (II): [F-SO ２ -N － -SO ２ -F]NH ４ ＋ (II) Ammonium salt of bis(fluorosulfonyl)imide (NH ４ FSI) with a compound represented by formula (III) or (III*): RO － M ＋ (III) [RO － M ＋ ][nROH] (III*) with a fluorine-containing alkoxide of where: ・Each R is C １ ~C ２０ Fluoroalkyl, C １ ~C ２０ Fluoroalkenyl and C １ ~C ２０ fluoroalkynyl; M is selected from the group consisting of Li, Na, K, Rb, Cs and Fr; n is an integer ranging from 1 to 10; ・NH ４ The FSI salt optionally comprises: - 50 to 99.9% by weight of NH ４ FSI salt, - 0.1 to 50% by weight of at least one solvent S preferably selected from the group consisting of cyclic and acyclic ethers ２ and in the form of a solvate comprising method.

2. In the fluorine-containing alkoxide (III) or (III*), each R is independently a group of the formula R Ｆ -L (in the formula: -R Ｆ is C １ ~C ３ Perfluoroalkyl, C １ ~C ３ Perfluoroalkenyl and C １ ~C ３ perfluoroalkynyl; - L is C １ ~C ３ Alkylene, C １ ~C ３ Alkenylene and C １ ~C ３ alkynylene) The method of claim 1 according to

3. In the fluorine-containing alkoxide (III) or (III*), each R is independently a group of the formula R Ｆ -L (in the formula: -R Ｆ is C １ ~C ２ is a perfluoroalkyl group, - L is C １ ~C ２ alkylene) The method according to claim 2, wherein

4. In the fluorine-containing alkoxide (III), each R is independently a group of the formula R Ｆ -L (in the formula: -R Ｆ is CF ３ and - L is CH ２ is) The method according to claim 3, wherein

5. NH ４ FSI is reacted with a compound of formula (IIIa): [CF ３ CH ２ O － Li ＋ ][2CF ３ CH ２ OH] (IIIa) with a fluorine-containing alkoxide to obtain the lithium salt of bis(fluorosulfonyl)imide (LiFSI).

6. The reaction is carried out by reacting a compound of the formula ROH, where R is C １ ~C ２０ Fluoroalkyl, C １ ~C ２０ Fluoroalkenyl and C １ ~C ２０ 2. The process of claim 1, wherein the solvent is selected from the group consisting of fluoroalkynyl.

7. 10. The process of claim 1, wherein the reaction is carried out at a temperature of from 0 to 200°C.

8. 10. The process of claim 1, wherein the reaction is carried out at a pressure varying from 0.01 to 1 atmosphere.

9. NH ４ Before the step of reacting FSI with alkoxide (III) or (III*), NH ４ The method of claim 1 , comprising solubilizing the FSI in a solvent.

10. NH ４ 10. The method of claim 1, further comprising the step of concentrating MFSI under reduced pressure after reacting MFSI with alkoxide (III) or (III*).

11. NH ４ Before the step of reacting FSI (II) with alkoxide (III) or (III*), - ammonium salt of bis(chlorosulfonyl)imide (NH ４ CSI) with a fluorinating agent; or - bis(chlorosulfonyl)imide (HCSI) of the formula NH ４ F (HF) ｐ (wherein p is a number from 0 to 10) By NH ４ 2. The method of claim 1, comprising the step of preparing FSI(II).

12. An alkali metal salt of bis(fluorosulfonyl)imide (MFSI) obtainable by the process according to any one of claims 1 to 10.

13. Formula (III) or (III*): RO － M ＋ (III) [RO － M ＋ ][nROH] (III*) (In the formula, ・Each R is C １ ~C ２０ Fluoroalkyl, C １ ~C ２０ Fluoroalkenyl and C １ ~C ２０ fluoroalkynyl; M represents an alkali metal preferably selected from the group consisting of Li, Na, K, Rb, Cs and Fr, n is an integer ranging from 1 to 10. of fluorine-containing alkoxides, Formula (I): [F-SO ２ -N － -SO ２ -F]M ＋ (I) Use of the compound of formula (I) for producing an alkali metal salt of bis(fluorosulfonyl)imide (MFSI).

14. The fluorine-containing alkoxide of formula (III*) is a compound of formula (IIIa): [CF ３ CH ２ O － Li ＋ ][2CF ３ CH ２ OH] (IIIa) According to the formula (Ia): [F-SO ２ -N － -SO ２ -F]Li ＋ (Ia) 14. The use according to claim 13, wherein the lithium salt is according to

15. Formula (III) or (III*): RO － M ＋ (III) [RO － M ＋ ][nROH] (III*) (In the formula, ・Each R is C １ ~C ２０ Fluoroalkyl, C １ ~C ２０ Fluoroalkenyl and C １ ~C ２０ fluoroalkynyl; M represents an alkali metal preferably selected from the group consisting of Li, Na, K, Rb, Cs and Fr, n is an integer ranging from 1 to 10. A method for preparing a fluorine-containing alkoxide of the formula: The method comprises reacting a compound of formula (IV): ROH (IV) with an alcohol of formula (V) MOH (V) or a hydrate thereof, method.