Method for fluorinating hydrogen BIS(chlorosulfonyl)imide in gas phase

Abstract

The present invention relates to a method for producing bis(fluorosulfonyl)imide, which is economically feasible at industrial scale and which provides a high-purity product.

Description

METHOD FOR FLUORINATING HYDROGEN BIS(CHLOROSULFONYL)IMIDE IN GAS PHASECross reference to related patent applications

[0001] This application claims priority filed on 2023-12-20 in EUROPE with Nr 23307283.4, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0002] The present invention relates to a method for producing bis(fuorosulfonyl)imide (HFSI), which is economically feasible at industrial scale and which provides a higlh-purity product.Background

[0003] Fluorosulfonylimide salts, in particular the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds for battery electrolytes. Different processes, reactants and intermediates leading to LiFSI have been described in the patent literature, notably patent CA 2 527 802 (Universite de Montreal) which lists several routes to prepare LiFSI, for example the process for preparing LiFSI in one step starting from bis(chlorosulfonyl)imide (HCSI) using anhydrous hydrogen fluoride (HF):

[0004] Known in the art are also two-steps processes to prepare LiFSI, such as a process that involves the fluorination of bis(chlorosulfonyl)imide (HCSI) into bis(fluorosulfonyl)imide (HFSI) using a fluorination agent, for example anhydrous hydrogen fluoride (HF), followed by the lithiation of HFSI into LiFSI using a lithiation agent. An example of such a process is disclosed in US9,725,318, wherein HCSI is reacted with anhydrous HF in the presence of a solvent. The reaction time for obtaining conversion to HFSI is 18 hours.

[0005] Another known two-step process for preparing LiFSI involves a first step of fluorination of bis(chlorosulfonyl)imide (HCSI) into ammonium bis(fluorosulfonyl)imide (NH4FSI) using NH4F(HF)Xas a fluorinating agent, followed by a second step of lithiation of NH4FSI, leading then to the LiFSI product. Such a process is described for example in WO 2017 / 090877 A1 (CLS) and EP 3 170 789 A1 (Nippon Soda).

[0006] Another known two-step process for preparing LiFSI involves the lithiation of HCSI in a first step using a lithiation agent in order to prepare LiCSI as an intermediate product, and then the fluorination of LiCSI into LiFSI using a fluorination agent.

[0007] For example, KR 20200049164 (in the name of CLS) relates to a LIFSI preparation method, comprising a step reacting HCSI with various lithiation reagents in an (S1 ) solvent to produce LiCSI and then reacting it with an anhydrous fluorination reagent directly without purification. A long list of possible solvents is given in the specification, while dimethyl carbonate is used in the examples.

[0008] US 2017 / 0183230 (in the name of SES HOLDINGS PTE LTD) discloses a process for converting HCSI to HFSI that comprises reacting liquid HCSI with anhydrous gaseous HF under conditions of temperature and pressure sufficient to produce gaseous HFSI. The yield of HFSI achieved by this process is about 80%, based on conversion of HCSI.

[0009] As can be read from the patent publications above-cited, the production of HFSI takes place in solvents or with HCSI in liquid phase, in order to disperse the reactive entities to allow them to react or to allow recovery of the unreacted species.

[0010] WO 2024 / 002897 (in the name of Specialty Operations France, Centre National de la Recherche Scientifique, Universite de Poitiers) discloses a method for producing HFSI, comprising the step of contacting gaseous HCSI with gaseous anhydrous HF. The method is said to be carried out in the presence of a carriergas, which is a chemically stable and dry gas with a moisture content not higher than 100 ppm and is preferably nitrogen. Hence, this document discloses the use of an inert carrier gas.

[0011] The Applicant perceived that there is still the need in the art for improving the manufacturing process of HFSI.

[0012] In particular, the Applicant is well aware that the processes disclosed in the prior art require long reaction time and achieve a low level of selectivity.Summary of the invention

[0013] With the aim of overcoming the above drawbacks, the Applicant faced the problem of providing a continuous production process for preparing bis(fluorosulfonyl)imide (HFSI), with low residence time and with a high level of selectivity.

[0014] Further, the Applicant addressed environmental aspects of routes to HFSI, providing a process which would not need the use of hazardous liquid solvents, which would minimise the amount of solid / salt wastes, and which would provide for opportunities of valorization of side products.

[0015] The method for manufacturing HFSI according to the present invention is characterised by a high conversion yield and by a high level of selectivity, providing HFSI particularly suited for many applications, notably as an intermediate to prepare LiFSI used in battery applications.

[0016] Advantageously, the fluorination reaction of the present invention is carried out such that HCSI reacts when it is fully in the gas phase.

[0017] In other words, the method of the present invention is a solvent-free method, which means that no liquid solvent, such as liquid organic solvent, is added to the reaction mixture during the method of the present invention. This is advantageous because first, the step for removing the solvent is avoided, thus reducing the complexity of the industrial process, as well as its overall cost; secondly, the preliminary step of treating the solvent to decrease its moisture content is also avoided.

[0018] In addition, the side-reactions between HCSI and / or HFSI and the organic solvent(s) are avoided, increasing the overall yield and avoiding the occurrence of undesired species.Detailed description

[0019] Thus, in a first aspect, the present application relates to a method for manufacturing bis(fluorosulfonyl)imide (HFSI), said method comprising: step (I) of contacting gaseous bis(chlorosulfonyl)imide (HCSI) with anhydrous hydrogen fluoride (aHF), thus obtaining HFSI; wherein said method is carried out in the absence of liquid solvent(s) and wherein said step (I) is performed in the presence of a carrier gas selected in the group comprising, preferably consisting of: air; carbon dioxide (CO2); halogenated acid(s); chlorocarbon(s); fluorocarbon(s); chloro-fluorocarbon(s); and mixtures thereof.

[0020] Advantageously, HFSI is obtained at the end of such step (I) in the gas phase.

[0021] As used in the present description and in the following claims, the expression “in the absence of liquid solvent(s)” is intended to indicate that no liquid organic solvent is added to the reactor or reaction environment.

[0022] As used in the present description and in the following claims, the expression “carrier gas” is intended to indicate any chemically stable and dry gas, with a moisture content not higher than 100 ppm.

[0023] Preferably, said halogenated acid(s) is selected from HCI and HF. According to a preferred embodiment, said halogenated acid is HF.

[0024] Preferably, said chlorocarbon(s) is selected from CCk, CHCI3, CH2CI2, CH3CI, C2H4CI2.

[0025] Preferably, said fluorocarbon(s) is selected from C3H3F5, C2HF5, CeFu, CF4, C2H2F2 , CH3F, CHF2, C2F6, C2F4, C2H3F, CH2F2, C2H3F3,

[0026] Preferably, said chloro-fluorocarbon(s) is selected from CHFCI2, CHF2CI, CCI3F, C2HF3CI2, C2F3CI3, C2F4CI2, CCIF3.

[0027] Preferably, the carrier gas has a boiling point lower than 100°C, more preferably lower than 60°C and even more preferably lower than 20°C.

[0028] Preferably, the carrier gas has a molecular weight lower than 200 Dalton, more preferably lower than 100 Dalton.

[0029] Preferably, said carrier gas is selected from: HCI, HF, CH2CI2, CH3CI, C2H4CI2, CF4, C2H2F2, CH3F CHF2, C2F6, C2F4, C2H3F, CH2F2, C2H3F3, CCIF3, and mixtures thereof.

[0030] It is preferred that the carrier gas does not form an azeotrope with either HFSI or with aHF, so that the reuse and recycling of such materials is simplified.

[0031] It is also preferred that the carrier gas does not form an azeotrope with HCI, so that its processability as well as its disposal is simplified.

[0032] It will be understood that the formation of azeotrope with any of HFSI and aHF depends on the pressure at which step (I) is performed. Accordingly, if the formation of an azeotrope is not desired, the carrier gas to be used in step (I) can be properly selected based on the pressure at which said step (I) is performed.

[0033] According to an embodiment, in step (I) gaseous HCSI is reacted with aHF in the gas phase.

[0034] According to another embodiment, in step (I) gaseous HCSI is reacted with aHF that is partially vaporised. Partially vaporised means that aHF is partially liquid and partially in the gas phase.

[0035] According to another embodiment, in step (I) gaseous HCSI is reacted with aHF in the liquid phase.

[0036] Anhydrous HF (aHF) means that the HF has a content of moisture below 200 ppm, preferably below 100 ppm, more preferably below 50 ppm, and even more preferably below 20 ppm as determined by Karl-Fisher titration. More preferably and advantageously, aHF has a content of moisture below 10 ppm and more preferably below 5 ppm.

[0037] HCSI in the gas phase can be obtained from solid HCSI or molten HCSI.

[0038] When solid HCSI is used, before step (I), a step (0-a) of providing solid HCSI and a step (0-b) of melting said solid HCSI to a temperature above its melting temperature (TrriHcsi) to obtain HCSI in a molten state (also called liquid state) is performed.

[0039] Preferably, step (0-b) is performed at a temperature (Ta) suitable for melting HCSI and maintaining HCSI in the molten state, while its thermal degradation is minimised.

[0040] Preferably, step (0-b) is conducted at a temperature (Ta) equal to or above the melting point of HCSI (Trnncsi). In this case, Ta > Tmncsi. For example, Ta may be equal to or above the melting point of HCSI (Tmncsi) plus 5°C. In this case, Ta > Tmncsi + 5. As another example, Ta may be equal to or above the melting point of HCSI (Tmncsi) plus 10°C. In this case, Ta > Tmncsi + 10.

[0041] It will be understood that the melting point of HCSI is influenced by the presence and amounts of impurities.

[0042] Preferably, the temperature (Ta) at which step (0-b) is conducted is equal to or higher than 30°C, for example equal to or higher than 37°C, for example equal to or higher than 38°C, equal to or higher than 40°C, equal to or higher than 45°C or even equal to or higher than 50°C. Temperature Ta is preferably lower than 150°C, more preferably equal or lower than 100°C. In any case, the temperature (Ta) at which step (0-b) is conducted is below the degradation temperature of HCSI.

[0043] When molten HCSI is used, gaseous HCSI is preferably obtained by heating molten HCSI at a temperature at which HCSI is stable and saturates the carrier gas with HCSI vapours, and / or by vaporising molten HCSI at reduced pressure.

[0044] Preferably, the heating of molten HCSI is performed at a temperature from about 35°C, more preferably from about 50°C, even more preferably from about 100C°.

[0045] Preferably, the heating of molten HCSI is performed at a temperature up to 200°C, more preferably up to 180°C and even more preferably up to 160°C.

[0046] According to a preferred embodiment, the method according to the present invention comprises before step (I), a step (0-b*) of providing molten HCSI and a step (0-c) of heating the HCSI provided in step (0-b*) to obtain gaseous HCSI, wherein said step (0-b*) is performed in the presence of at least one carrier gas as defined above.

[0047] According to this embodiment, the partial pressure of HCSI is reduced, and the vaporisation is more effective.

[0048] Said step (0-b*) can correspond to step (0-b) above mentioned.

[0049] Such step (0-c) can be performed under whichever pressure, including pressure beyond atmospheric pressure; about atmospheric pressure; or reduced pressure.

[0050] The gaseous HCSI obtained at the end of step (0-c) is then contacted with the aHF in step (I) of the method of the present invention.

[0051] Solid or molten HCSI is commercially available on the market or may be produced by any known method, for example:- by reacting chlorosulfonyl isocyanate (CISO2NCO) with chlorosulfonic acid (CISO2OH) (CSI route);- by reacting cyanogen chloride (CNCI) with sulfuric anhydride (SO3), and with chlorosulfonic acid (CISO2OH); or- by reacting sulfamic acid (NH2SO2OH) with thionyl chloride (SOCI2) and with chlorosulfonic acid (CISO2OH) (SFA route).

[0052] Preferably, HCSI in the gas phase is obtained in step (0-c) under reduced pressure, in conditions to reduce the partial pressure of HCSI, such as by heating into a suitable reactor, optionally thermostated and in the presence of at least one a carrier gas as defined above.

[0053] Said reactor can be selected with appropriate choice of constituent material for being corrosion resistant and compatible with the involved chemicals, which are particularly aggressive because of their acid character.

[0054] Loading molten HCSI into the reactor can be carried out by liquid-transfer methods, such as pumping or via temperature-controlled pipelines (with set-up to maintain HCSI in liquid state), or by cannulation.

[0055] The expression “cannulation” is not particularly limited and is intended to encompass means which will operate the inert-gas assisted transfer of HCSI into a reactor. Cannulation can be performed in the presence of an inert gas. Such inert gas can be selected from argon, nitrogen or those listed above.

[0056] Preferably, such step of loading is performed under inert atmosphere, in order to avoid any contact with the moisture of air.

[0057] Step (I) of the method of the present invention is performed by loading HCSI in the gas phase into a reactor suitable for contacting with aHF.

[0058] HCSI in the gas phase may be loaded into the reactor as it is.

[0059] According to this embodiment, the carrier gas as defined above can be introduced together with the aHF or separately.

[0060] Preferably, step (I) is performed by first loading into a suitable reactor a first mixture [mixture (M1 )] comprising gaseous HCSI and at least one carrier gas, as defined above.

[0061] Preferably, said mixture (M1 ) is obtained by bubbling at least one carrier gas into the molten HCSI.

[0062] Alternatively, said mixture (M1 ) can be obtained by sweeping with a carrier gas the head space over liquid HCSI. In such a case, the partial pressure of HCSI vapours will be below the vapour pressure of HCSI at the temperature of the mixture (M1 ): in other terms, HCSI in the said mixture will be at a temperature above its boiling point (Tbncsi) in the conditions of pressure in mixture (M1 ).

[0063] Step (I) can be performed by loading gaseous HCSI or mixture (M1) either progressively or at once.

[0064] It is understood that the gaseous HCSI and mixture (M1 ) might comprise impurities generated during heating steps (0-b) or (0-b*) or (I), or impurities already present in the solid or molten HCSI used as starting material, without these impairing its properties.

[0065] Preferably, the gaseous HCSI has a purity of at least 95%, preferably of at least 98%, more preferably of at least 99.5%.

[0066] Preferably, the aHF can be introduced into the reactor by injection.

[0067] Under step (I) of the method of the invention, aHF can be introduced into the reactor: before gaseous HCSI or mixture (M1 ) is loaded, or as the loading of gaseous HCSI or mixture (M1 ) proceeds, or after the loading of gaseous HCSI or mixture (M1 ) is finished.

[0068] Gaseous aHF is preferably provided to the reactor at atmospheric pressure. Gaseous aHF is preferably provided to the reactor at a temperature ranging from 19.5°C to 200°C, preferably at a temperature from 19.5°C to 150°C.

[0069] Liquid aHF is preferably provided to the reactor at a pressure above atm pressure. The pressure as well as the temperature for performing this step of providing liquid aHF are not limited.

[0070] The step of introducing aHF can be carried out continuously or semi- continuously.

[0071] Typically, aHF is continuously added or added in a controlled manner throughout the reaction time at a substantially constant rate.

[0072] Anhydrous HF can be provided to the reactor as it is.

[0073] Alternatively, aHF can be diluted with a carrier gas, and provided to the reactor in the gas phase in admixture with the carrier gas [mixture (M2)].

[0074] The carrier gas for use in the preparation of said mixture (M2) can be selected from nitrogen, argon or from the carrier gases defined above.

[0075] According to a preferred embodiment of the invention, step (I) is carried out in the presence of at least one carrier gas, which derives from mixture (M1 ) and / or from mixture (M2).

[0076] An additional gas (also referred to as “dilution gas”) can be directly fed into the reactor. Such dilution gas can be selected from nitrogen, argon or from the carrier gases listed above.

[0077] A purging gas can be optionally used to flush the reactor without any of the previously cited streams being introduced. It can be the same gas used in step (I) or a different gas.

[0078] The molar ratio between gaseous HCSI and aHF is preferably between 1 :1 to 1 :100, more preferably between 1 :1 to 1 :50 and even more preferably between 1 :1 and 1 :10. The preferred molar ratio can be selected considering for example the need for recycling excess of HF, and the kinetics / yield dependence upon the said HCSkHFSI ratios.

[0079] Similarly, the molar ratio between gaseous HCSI and the total amount of carrier gas in the reactor mixture may be preferably between 1 :1 .25 and 1 : 100, preferably between 1 :1.5 and 1 :75.

[0080] The reaction between HCSI and anhydrous HF in the gas phase generally takes place at temperature and at a pressure that are suitable for keeping all the reactants and carrier gas into the gas phase.

[0081] Typically, the reaction is carried out at a temperature of from 100 to 300 °C, more preferably from 160 to 220 °C, still more preferably from 160 to 180 °C.

[0082] Preferably, the residence time of the reactants in the closed reactor is between 1 millisecond to 3 hours.

[0083] The reaction conditions are maintained such that the HFSI produced is removed from the reaction mixture as a gas.

[0084] HFSI is typically obtained at the end of step (I) in admixture with at least one other gas, e.g. in admixture with unreacted HF, with the carrier gas, or with unreacted HCSI, etc. Such a mixture can be referred to as mixture (M3).

[0085] At the end of the reaction under step (I) or as step (I) proceeds, HFSI is separated from the other components of such a mixture (M3) by suitable methods. For example, HFSI can be separated by condensation. According to this embodiment, HFSI is obtained as a liquid.

[0086] Preferably, such a separation step is performed such that the other gaseous products, such as HCI and HF, remain in the gas phase.

[0087] According to certain embodiments, the excess gaseous products, such as unreacted HF and HCI can be separated by any method known in the art, such as distillation or stripping.

[0088] More preferably, HF is advantageously recovered for reuse in the method of the present invention.

[0089] The embodiments described allow direct conversion of HCSI to HFSI with anhydrous HF in a high-atom efficiency approach that enables continuous fluorination with good to excellent yield and reduced environmental impact (mostly valorizable gaseous effluents).

[0090] The method according to the present invention advantageously provides a high conversion of HCSI to HFSI, with yields above 90%, preferably above 95%, and more preferably above 99%.

[0091] HFSI isolated after the end of the reaction may include some impurities, such as fluorosulfuric acid. Such fluorosulfuric acid can be in an amount up to 10% by moles. In preferred embodiments of the present invention, the amount of impurities in HFSI is lower than 1 % by moles.

[0092] Furthermore, the method according to the present invention advantageously provides HFSI with a high level of conversion and selectivity, in a molar yield which may be as high as > 90%, and even higher than 99%, which makes it particularly suited for many applications, notably as an intermediate to prepare LiFSI used in battery applications.

[0093] A further advantage of the present invention is that the above mentioned high level of conversion and high level of selectivity are obtained without the need to add catalyst(s), thus reducing the operating costs and expenses of the process.

[0094] Advantageously, the method of the present invention is carried out in the absence of added catalyst, such as cobalt oxides, nickel oxides, molybdenum oxides and mixtures thereof, which can be supported or not supported for example on silica, alumina or active charcoal. This leads to a more sustainable and economically viable process.

[0095] Thus, more advantageously, the method of the present invention is carried out in the absence of any liquid organic solvent and in the absence of any catalyst.

[0096] If required, the HFSI obtained at the end of step (I) can be purified to produce a high-purity HFSI.

[0097] Such purification step is not limited and can be performed via techniques such as distillation or crystallisation.

[0098] All raw materials used in the method according to the invention, including reactants, may preferably show very high purity criteria. Preferably, their content of metal components such as Na, K, Ca, Mg, Fe, Cu, Cr, Ni, Zn, is below 10 ppm, more preferably below 5 ppm, or below 2 ppm.

[0099] The HFSI as obtained at the end of the process of the present invention can be advantageously used as such for other reactions.

[0100] HFSI obtained by the process of the present invention may also be salified by subjecting it to a cation exchange step in order to obtain alkali metal salts, alkaline-earth metal salts or a quaternary ammonium cation salt.

[0101] Consistently, the present invention further pertains to a method of making a salt of HFSI, wherein said salt is preferably selected from alkali metal salt, an alkaline-earth metal salt or a quaternary ammonium cation, said method comprising: step (I) of contacting gaseous bis(chlorosulfonyl)imide (HCSI) with anhydrous hydrogen fluoride (aHF), thus obtaining HFSI; optionally, step (II) of separating such HFSI; and step (III) of salifying the HFSI obtained at the end of step (I) or step (II), wherein said method is carried out in the absence of liquid solvent(s); said step (I) is performed in the presence of a carrier gas selected in the group comprising, preferably consisting of: air; carbon dioxide (CO2); halogenated acid(s); chlorocarbon(s); fluorocarbon(s); chloro-fluorocarbon(s); and mixtures thereof; and said step (III) is formed with a salt selected from lithium, sodium, potassium or ammonium.

[0102] According to a preferred embodiment, HFSI is salified with a lithium salt, a sodium salt or a potassium salt. Preferably, HFSI is salified with a lithium salt to provide direct lithiation of HFSI to lithium bis(fluorosulfonyl)imide (LiFSI), suitable for use in secondary batteries the person skilled in the art.

[0103] Advantageously, the lithium bis(fluorosulfonyl)imide (LiFSI) prepared according to the method of the present invention can be used in an electrolyte composition for an electrochemical cell.

[0104] In a further aspect, the present invention pertains to an electrolyte composition comprising the LiFSI as obtained with the method of the present invention.Advantageously, said electrolyte composition is a non-aqueous electrolyte composition.

[0105] Some of the steps or all steps of the method according to the invention are advantageously carried out in equipment capable of withstanding the corrosion of the reactants, reaction medium and products.

[0106] For this purpose, materials are selected for the part in contact with the reaction medium that are corrosion-resistant, such as the alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminium, carbon and tungsten, sold under the Hastelloy® brands or the alloys of nickel, chromium, iron and manganese to which copper and / or molybdenum are added, sold under the name Inconel® or Monel™, and more particularly the Hastelloy C276 or Inconel 600, 625 or 718 alloys. Use may also be made of equipment consisting of or coated with a polymeric compound resistant to the corrosion of the reaction medium. Mention may in particular be made of fluorinated polymers, such as PTFE (polytetrafluoroethylene or Teflon(R)), PFA (perfluoroalkyl resins), FEP (fluorinated ethylene propylene), PCTFE (polychlorotrifluoroethylene). Glass and glass-lined as well as enamel equipment may also be used. Furthermore, corrosion-resistant silicon carbide (or SiC) materials can be advantageously used. It will not be outside the scope of the invention to use an equivalent material (tungsten carbide, etc).

[0107] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

Claims

Claims1 . A method for manufacturing bis(fluorosulfonyl)imide (HFSI), said method comprising: step (I) of contacting gaseous bis(chlorosulfonyl)imide (HCSI) with anhydrous hydrogen fluoride (aHF), thus obtaining HFSI; wherein said method is carried out in the absence of liquid solvent(s) and wherein said step (I) is performed in the presence of a carrier gas selected in the group comprising, preferably consisting of: air; carbon dioxide (CO2); halogenated acid(s); chlorocarbon(s); fluorocarbon(s); chloro-fluorocarbon(s); and mixtures thereof.

2. The method according to Claim 1 , wherein the HFSI obtained at the end of step (I) is in the gas phase.

3. The method according to Claim 1 or 2, wherein:- said halogenated acid(s) is selected from HCI and HF;- said chlorocarbon(s) is selected from CCI4, CHCI3, CH2CI2, CH3CI, C2H4CI2;- said fluorocarbon(s) is selected from C3H3F5, C2HF5, CeFu, CF4, C2H2F2 , CH3F, CHF2, C2F6, C2F4, C2H3F, CH2F2, C2H3F3;- said chloro-fluorocarbon(s) is selected from CHFCI2, CHF2CI, CCI3F, C2HF3CI2, C2F3CI3, C2F4CI2, CCIF3.

4. The method according to any one of the preceding Claims, wherein said carrier gas has a boiling point lower than 100°C and / or a molecular weight lower than 200 Dalton.

5. The method according to Claim 3 or 4, wherein said carrier gas is selected from: HCI, HF, CH2CI2, CH3CI, C2H4CI2, CF4, C2H2F2, CH3F CHF2, C2F6, C2F4, C2H3F, CH2F2, C2H3F3, CCIF3, and mixtures thereof.

6. The method according to any one of the preceding Claims, wherein aHF is in the gas phase, partially vaporised or in the liquid phase.

7. The method according to any one of the preceding Claims, wherein HCSI in the gas phase is obtained from solid HCSI or molten HCSI.

8. The method according to Claim 7, wherein HCSI in the gas phase is obtained from solid HCSI and the method comprises before step (I), a step (0-a) of providing solid HCSI and a step (0-b) of melting said solid HCSI to a temperature above its melting temperature (TrriHcsi) to obtain HCSI in a molten state.

9. The method according to Claim 7, wherein HCSI in the gas phase is obtained from molten HCSI and the method comprises before step (I), a step (0-b*) of providing molten HCSI and a step (0-c) of heating the HCSI provided in step (0-b*) to obtain gaseous HCSI, wherein said step (0-b*) is performed in the presence of at least one carrier gas as defined in Claim 1 and in Claims 3 to 5.

10. The method according to Claim 9, wherein said heating is performed at a temperature from 35°C and / or up to 200°C.11 . The method according to any one of the preceding Claims, wherein step (I) is performed by loading into a reactor a first mixture [mixture (M1 )] comprising gaseous HCSI and at least one carrier gas as defined in Claim 1 and in Claims 3 to 5.

12. The method according to Claim 11 , wherein aHF is contacted with HFSI or with mixture (M1 ) in the reactor and aHF is introduced into such reactor before gaseous HCSI or mixture (M1 ) is loaded, or as the loading of gaseous HCSI or mixture (M1 ) proceeds, or after the loading of gaseous HCSI or mixture (M1 ) isfinished.

13. The method according to any one of the preceding Claims, said method comprising at the end of step (I) or as step (I) proceeds, a step (II) of separating HFSI.

14. The method according to Claim 13, wherein said separation of HFSI is performed by condensation and HFSI is obtained in the liquid phase.

15. A method for manufacturing a salt of bis (fluorosulfonyl) imide, said method comprising: step (I) of contacting gaseous bis(chlorosulfonyl)imide (HCSI) with anhydrous hydrogen fluoride (aHF), thus obtaining HFSI; optionally, step (II) of separating such HFSI; and step (III) of salifying the HFSI obtained at the end of step (I) or step (II), wherein said method is carried out in the absence of liquid solvent(s); said step (I) is performed in the presence of a carrier gas selected in the group comprising, preferably consisting of: air; carbon dioxide (CO2); halogenated acid(s); chlorocarbon(s); fluorocarbon(s); chloro-fluorocarbon(s); and mixtures thereof; and said step (III) is formed with a salt selected from lithium, sodium, potassium or ammonium.

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