A preparation method of bis(fluorosulfonyl)imide salt

Abstract

The present invention belongs to the technical field of lithium-ion battery materials and discloses a method for preparing a bisfluorosulfonyl imide salt. The preparation method comprises the following steps: adding phosgene, diphosgene, or triphosgene to a reactor with sulfamic acid and chlorosulfonic acid, mixing, and then heating to react to obtain a mixture; subjecting the obtained mixture to vacuum distillation to obtain a bischlorosulfonyl imide; adding the obtained bischlorosulfonyl imide to a reactor, adding anhydrous HF under stirring conditions, and reacting to obtain a bisfluorosulfonyl imide; and subjecting the obtained bisfluorosulfonyl imide to a reaction mixture with an alkali metal source under moisture-isolating conditions. The product is separated and purified to obtain a bisfluorosulfonyl imide salt. The method of the present invention uses phosgene, diphosgene, or triphosgene instead of the commonly used thionyl chloride to prepare HCSI, and obtains the bisfluorosulfonyl imide salt through fluorination and salt formation, thereby improving the safety of the preparation process and reducing the production of toxic byproducts. It also significantly reduces production costs and is more suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery materials, and in particular relates to a method for preparing a bisfluorosulfonyl imide salt. Background Art

[0002] Bischlorosulfonyl imide ((SO2Cl)2NH, HCSI) and bisfluorosulfonyl imide ((SO2F)2NH, HFSI) are important intermediates in the synthesis of lithium bisfluorosulfonyl imide (LiN(SO2F)2, LiFSI), a lithium salt additive for lithium-ion batteries. LiFSI has better thermal stability and electrical conductivity than LiPF6, making it a superior lithium salt for electrolytes. Currently used primarily as an electrolyte additive, it is expected to replace LiPF6. Furthermore, with the advancement of battery technology, other alkali metal bisfluorosulfonyl imide salts also have broad application prospects.

[0003] The main preparation methods for bis(fluorosulfonyl)imide salts are as follows: R. Appel et al., 1962, 95, 1753; M. Berane et al., Z. Anorg. Allg. Chem., 2005, 631, 55; US Pat. No. 4,315,935; CN102,786,452, etc. disclose the synthesis of HCSI from chlorosulfonic acid, thionyl chloride, and aminosulfonic acid, followed by fluorination with a fluorinating agent to produce HFSI, which is then reacted with a lithium compound to prepare LiFSI. This method utilizes readily available raw materials and is relatively low in cost, but it produces a high amount of harmful acidic gases, and the raw material thionyl chloride is highly hazardous, water-sensitive, and easily decomposes. US8337797, US9156692, US5916475, and Inorg.Synth.11,138-143 (1968) disclose methods for preparing HFSI by heating a mixture of urea (CO(NH2)2) and fluorosulfonic acid (FSO3H). The generated HFSI and excess FSO3H can be recovered by vacuum distillation. US8337797 discloses the use of a polytetrafluoroethylene (PTFE) reactor and a reaction temperature of 120-130°C, resulting in a urea-based yield of approximately 40% for the HFSI product. The FSO3H used in this method is expensive, requiring high equipment requirements, resulting in very high costs. Furthermore, the method has a low yield, and the boiling points of FSO3H and HFSI are very close, making separation difficult.

[0004] Patent CN109786248A discloses a method for preparing an organic base salt of HFSI using sulfuryl fluoride, ammonium fluoride, and triethylamine in an organic solvent, followed by reaction with a strong acid and distillation to obtain HFSI. While this method can increase the yield to 90%, the use of an organic base can result in a high level of impurities and difficult-to-handle byproducts.

[0005] Patent CN106044728A discloses a method for preparing bischlorosulfonyl imide by reacting chlorosulfonyl isocyanate with chlorosulfonic acid, followed by fluorination and salt formation to prepare LiFSI. This method avoids the use of aminosulfonic acid, and the homogeneous reaction is easier to control. However, the raw material chlorosulfonyl isocyanate is expensive and difficult to supply, which greatly limits its industrial application.

[0006] Patent CN115028146A discloses a method for preparing sodium bis(fluorosulfonyl)imide, using aminosulfonic acid, fluorosulfonic acid, and carbonyl fluoride gas in a one-step reaction to produce the bis(fluorosulfonyl)imide. However, this method also suffers from the difficulties in obtaining the raw materials fluorosulfonic acid and carbonyl fluoride, as well as their high cost. In particular, the lack of large-scale production capacity for fluorosulfonic acid in China significantly limits its industrial application. Summary of the Invention

[0007] In response to the shortcomings and deficiencies of the above-mentioned prior art, the present invention aims to provide a method for preparing a bis(fluorosulfonyl)imide salt. This method utilizes phosgene (phosgene), diphosgene (trichloromethyl chloroformate), or triphosgene (bis(trichloromethyl)carbonate) instead of the commonly used thionyl chloride to prepare HCSI. Fluorination and salt formation yield the bis(fluorosulfonyl)imide salt, improving the safety of the preparation process and reducing the production of toxic byproducts. This method also significantly reduces production costs and is more suitable for industrial production.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a bisfluorosulfonyl imide salt comprises the following steps:

[0010] (1) adding sulfamic acid and chlorosulfonic acid to a reactor, mixing, heating to 50-60° C., introducing phosgene, stopping the introduction when the solid sulfamic acid is completely dissolved and the reaction liquid is clear, heating to 70-130° C., maintaining the temperature for reaction, and exhausting the gas to obtain a mixture; or, adding sulfamic acid and chlorosulfonic acid to a reactor, adding diphosgene or triphosgene, mixing, heating to 70-120° C., maintaining the temperature for reaction, and obtaining a mixture; and subjecting the obtained mixture to vacuum distillation to obtain bischlorosulfonyl imide;

[0011] (2) adding the bischlorosulfonyl imide obtained in step (1) into a reactor, adding anhydrous HF under stirring conditions and mixing to obtain bisfluorosulfonyl imide;

[0012] (3) Under moisture-proof conditions, the bis(fluorosulfonyl)imide obtained in step (2) is mixed with an alkali metal source for reaction, and the product is separated and purified to obtain a bis(fluorosulfonyl)imide salt.

[0013] Furthermore, in step (1), the molar ratio of the reaction of sulfamic acid, chlorosulfonic acid and phosgene is preferably (1-1.1):1:(2-3); the molar ratio of the reaction of sulfamic acid, chlorosulfonic acid and diphosgene is preferably (1-1.1):1:(1-1.2); and the molar ratio of the reaction of sulfamic acid, chlorosulfonic acid and triphosgene is preferably (1-1.1):1:(0.67-1).

[0014] Furthermore, the time for introducing phosgene in step (1) is preferably 0.5 to 4 hours.

[0015] Furthermore, the insulation reaction time in step (1) is preferably 3 to 6 hours.

[0016] Furthermore, the molar ratio of the reaction of bischlorosulfonyl imide and HF in step (2) is preferably 1:(1-2).

[0017] Furthermore, the temperature of the mixing reaction in step (2) is preferably 10 to 120° C., and the time of the mixing reaction is preferably 4 to 8 hours.

[0018] Furthermore, the bisfluorosulfonyl imide obtained in step (2) is further purified by distillation or rectification.

[0019] Furthermore, the alkali metal source in step (3) includes but is not limited to alkali metal elements, halogenated salts, acid salts, hydroxides, etc.

[0020] Furthermore, the molar ratio of the bis(fluorosulfonyl)imide to the alkali metal source in step (3) is preferably 1:(1-1.3).

[0021] Furthermore, the temperature of the mixing reaction in step (3) is preferably 20 to 150°C.

[0022] Furthermore, the mixed reaction of the bisfluorosulfonyl imide and the alkali metal source in step (3) is carried out under the conditions of an organic good solvent, and the organic good solvent is selected from acetonitrile, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, methyl acetate, propyl acetate, isopropyl acetate, butyl acetate, ethylene glycol dimethyl ether, ethylene glycol diisoethyl ether, diethylene glycol dimethyl ether, acetone, tetrahydrofuran, methyltetrahydrofuran, ethyl ether, propyl ether, butyl ether, anisole, diphenyl ether, 1,4-dioxane, etc., or a mixed solvent of two or more.

[0023] Furthermore, the separation and purification step in step (3) includes filtration, concentration, addition of a poor solvent for crystallization or washing, solid-liquid separation and drying; the poor solvent is selected from one or more of toluene, xylene, chlorobenzene, dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dichloromethane, trichloromethane, tetrachloromethane, dichloroethane, trichloroethane, tetrachloroethane, etc.

[0024] The reaction formula of the present invention is as follows:

[0025]

[0026]

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The preparation method of the present invention uses phosgene (phosgene), diphosgene (trichloromethyl chloroformate), or triphosgene (bis(trichloromethyl) carbonate) instead of the commonly used thionyl chloride to prepare HCSI. The bisfluorosulfonyl imide salt is obtained through fluorination and salt formation. Because the raw materials used, especially diphosgene and triphosgene, are more stable, the safety of the preparation process is improved and the production of toxic byproduct sulfur dioxide is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the F-NMR spectrum of the bis(fluorosulfonyl)imide obtained in Example 1;

[0030] Figure 2 This is the F-NMR spectrum of the lithium bis(fluorosulfonyl)imide product obtained in Example 1;

[0031] Figure 3 This is the F-NMR spectrum of the sodium bis(fluorosulfonyl)imide product obtained in Example 5. DETAILED DESCRIPTION

[0032] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0033] Example 1

[0034] (1) Preparation of bis(chlorosulfonyl)imide:

[0035] 50 g of aminosulfonic acid and 60 g of chlorosulfonic acid were added to a 500 mL reaction flask, mixed, and heated to 50-60°C. 101.9 g of phosgene was introduced over 2 h. After the reactants were clarified, the temperature was raised to 110°C and the reaction was continued for 5 h. The reaction was then distilled under reduced pressure to obtain a colorless, transparent liquid, i.e., 101.5 g of bischlorosulfonyl imide, with a yield of 92.1%.

[0036] (2) Preparation of bis(fluorosulfonyl)imide:

[0037] In a 500 mL tetrafluoroethylene reaction bottle, 100 g of the bis(chlorosulfonyl)imide obtained in step (1) was added, the temperature was raised to 100° C., and about 14 g of HF gas was slowly introduced under stirring. After reacting for 6 h, the temperature was lowered to room temperature and nitrogen was blown in for 2 h to obtain about 82 g of a crude product. After vacuum distillation, 74.35 g of a colorless liquid was obtained, with a yield of 87.9%. The F-NMR spectrum of the obtained bis(fluorosulfonyl)imide is shown below: Figure 1shown.

[0038] (3) Preparation of lithium bis(fluorosulfonyl)imide:

[0039] In a 500 mL tetrafluoroethylene reaction bottle, 12 g of lithium chloride and 150 g of acetonitrile were added to prepare a mixed solution, 50 g of the bis(fluorosulfonyl)imide prepared in step (2) was added dropwise, and the mixture was reacted at 25° C. for 2 h. After that, the unreacted lithium chloride was removed by filtration and concentrated to obtain a viscous liquid. Dichloromethane was added to precipitate crystals, which were filtered and the filter cake was dried under reduced pressure at 40° C. to obtain 49.7 g of lithium bis(fluorosulfonyl)imide product with a yield of 96.21%. The F-NMR spectrum of the obtained lithium bis(fluorosulfonyl)imide product is shown as follows: Figure 2 shown.

[0040] Example 2

[0041] (1) Preparation of bis(chlorosulfonyl)imide:

[0042] 55 g of aminosulfonic acid and 60 g of chlorosulfonic acid were added to a 500 mL reaction flask, mixed, and heated to 50-60°C. 152 g of phosgene was introduced over 2 h. After the reactants were clarified, the temperature was raised to 80°C and the reaction was continued for 6 h. The reaction was then distilled under reduced pressure to obtain a colorless, transparent liquid, i.e., 102.6 g of bischlorosulfonyl imide, with a yield of 93.1%.

[0043] (2) Preparation of bis(fluorosulfonyl)imide:

[0044] In a 500 mL tetrafluoroethylene reaction flask, 100 g of bischlorosulfonyl imide obtained in step (1) was added, the temperature was raised to 80° C., and about 10 g of HF gas was slowly introduced under stirring. After reacting for 8 h, the temperature was lowered to room temperature and nitrogen was blown for 2 h to obtain about 83 g of a crude product, which was then distilled under reduced pressure to obtain 73.52 g of a colorless liquid with a yield of 86.9%.

[0045] (3) Preparation of lithium bis(fluorosulfonyl)imide:

[0046] In a 500 mL tetrafluoroethylene reaction flask, 13 g of lithium chloride and 150 g of ethyl methyl carbonate were added to prepare a mixed solution, and 50 g of the bisfluorosulfonyl imide prepared in step (2) was added dropwise. After reacting at 50° C. for 2 h, the unreacted lithium chloride was removed by filtration and concentrated to obtain a viscous liquid. Dichloroethane was added to precipitate crystals, which were filtered and the filter cake was dried under reduced pressure at 40° C. to obtain 50.1 g of lithium bisfluorosulfonyl imide product with a yield of 97.0%.

[0047] Example 3

[0048] (1) Preparation of bis(chlorosulfonyl)imide:

[0049] 102 g of diphosgene, 50 g of aminosulfonic acid and 60 g of chlorosulfonic acid were added to a 500 mL reaction bottle, mixed, heated to 120° C. and reacted for 5 h. The mixture was distilled under reduced pressure to obtain a colorless transparent liquid, i.e., 95.22 g of bischlorosulfonyl imide, with a yield of 86.4%.

[0050] (2) Preparation of bis(fluorosulfonyl)imide:

[0051] In a 500 mL tetrafluoroethylene reaction flask, 90 g of the crude bischlorosulfonyl imide obtained in step (1) was added, the temperature was raised to 100° C., and about 12.6 g of HF gas was slowly introduced under stirring. After reacting for 6 h, the temperature was lowered to room temperature and nitrogen was blown in for 2 h to obtain about 75 g of the crude product. After vacuum distillation, 66.75 g of a colorless liquid was obtained, with a yield of 87.69%.

[0052] (3) Preparation of lithium bis(fluorosulfonyl)imide:

[0053] In a 500 mL tetrafluoroethylene reaction flask, 7.2 g of lithium fluoride and 150 g of ethyl methyl carbonate were added to prepare a mixed solution, 50 g of the bis(fluorosulfonyl)imide prepared in step (2) was added dropwise, and the mixture was reacted at 50° C. for 2 h. After filtration, unreacted lithium fluoride was removed and the mixture was concentrated to obtain a viscous liquid. Toluene was added to precipitate crystals, which were filtered and the filter cake was dried under reduced pressure at 50° C. to obtain 48.2 g of lithium bis(fluorosulfonyl)imide product with a yield of 93.3%.

[0054] Example 4

[0055] (1) Preparation of bis(chlorosulfonyl)imide:

[0056] 122 g of diphosgene, 55 g of aminosulfonic acid and 60 g of chlorosulfonic acid were added to a 500 mL reaction bottle, mixed, heated to 90° C. and reacted for 6 h. The mixture was distilled under reduced pressure to obtain a colorless transparent liquid, namely 96.40 g of bischlorosulfonyl imide, with a yield of 87.5%.

[0057] (2) Preparation of bis(fluorosulfonyl)imide:

[0058] In a 500 mL tetrafluoroethylene reaction flask, 90 g of the crude bischlorosulfonyl imide obtained in step (1) was added, the temperature was raised to 90° C., and about 15 g of HF gas was slowly introduced under stirring. After reacting for 6 h, the temperature was lowered to room temperature and nitrogen was blown in for 2 h to obtain about 78 g of the crude product. After vacuum distillation, 67.24 g of a colorless liquid was obtained, with a yield of 88.33%.

[0059] (3) Preparation of lithium bis(fluorosulfonyl)imide:

[0060] In a 500 mL tetrafluoroethylene reaction bottle, 9.3 g of lithium fluoride and 150 g of dimethyl carbonate were added to prepare a mixed solution, 50 g of the bis(fluorosulfonyl)imide prepared in step (2) was added dropwise, and the mixture was reacted at 80° C. for 1 h, and then the unreacted lithium fluoride was removed by filtration. The mixture was concentrated to obtain a viscous liquid, and xylene was added to precipitate crystals. The crystals were filtered, and the filter cake was dried under reduced pressure at 50° C. to obtain 48.5 g of lithium bis(fluorosulfonyl)imide product with a yield of 93.8%.

[0061] Example 5

[0062] (1) Preparation of bis(chlorosulfonyl)imide:

[0063] 102g of triphosgene, 50g of aminosulfonic acid, and 60g of chlorosulfonic acid were added to a 500mL reaction flask, mixed, and heated to 80-85°C to completely melt the triphosgene. The mixture was allowed to react for 3 hours, then the temperature was raised to 120°C and maintained for 3 hours. Vacuum distillation afforded 96.37g of bis(chlorosulfonyl)imide, a colorless, transparent liquid with a yield of 87.44%.

[0064] (2) Preparation of bis(fluorosulfonyl)imide:

[0065] The steps are the same as those in Example 1, with a yield of 88.01%.

[0066] (3) Preparation of sodium bis(fluorosulfonyl)imide:

[0067] In a 500 mL tetrafluoroethylene reaction bottle, 12.18 g of sodium fluoride and 150 g of dimethyl carbonate were added to prepare a mixed solution, and 50 g of the bis(fluorosulfonyl)imide prepared in step (2) was added dropwise. After reacting at 50° C. for 2 h, the unreacted sodium fluoride was removed by filtration. The solution was concentrated under reduced pressure at 40° C. to obtain a solid crude product. Dichloromethane was added to wash the crude product, filtered, and the filter cake was dried under reduced pressure at 50° C. to obtain 54.07 g of sodium bis(fluorosulfonyl)imide product with a yield of 96.42%. The F-NMR spectrum of the obtained sodium bis(fluorosulfonyl)imide product is shown as follows: Figure 3 shown.

[0068] The above embodiments are preferred implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any other modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a bis(fluorosulfonyl)imide salt, characterized in that: The method comprises the following preparation steps: (1) Adding aminosulfonic acid and chlorosulfonic acid into a reactor, adding diphosgene or triphosgene, mixing, heating to 70-120°C and then reacting to obtain a mixture; subjecting the obtained mixture to vacuum distillation to obtain bischlorosulfonyl imide; (2) adding the bis(chlorosulfonyl)imide obtained in step (1) into a reactor, adding anhydrous HF under stirring conditions and mixing to obtain bis(fluorosulfonyl)imide; (3) mixing the bis(fluorosulfonyl)imide obtained in step (2) with an alkali metal source for reaction under moisture-proof conditions, and separating and purifying the product to obtain a bis(fluorosulfonyl)imide salt; In step (1), the molar ratio of aminosulfonic acid, chlorosulfonic acid and diphosgene in the reaction is (1-1.1):1:(1-1.2); the molar ratio of aminosulfonic acid, chlorosulfonic acid and triphosgene in the reaction is (1-1.1):1:(0.67-1).

2. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The insulation reaction time in step (1) is 3 to 6 hours.

3. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The molar ratio of the reaction of bischlorosulfonyl imide and HF in step (2) is 1:(1~2).

4. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The temperature of the mixed reaction in step (2) is 10-120° C., and the time of the mixed reaction is 4-8 h.

5. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The bis(fluorosulfonyl)imide obtained in step (2) is further purified by distillation or rectification.

6. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, characterized in that: The alkali metal source in step (3) includes a simple substance, a halide salt, an acid salt or a hydroxide of an alkali metal.

7. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, characterized in that: The molar ratio of the bis(fluorosulfonyl)imide to the alkali metal source in step (3) is 1:(1-1.3).

8. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, characterized in that: The temperature of the mixed reaction in step (3) is 20~150℃; the mixed reaction of the bisfluorosulfonyl imide and the alkali metal source is carried out under the condition of an organic good solvent, and the organic good solvent is selected from acetonitrile, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, methyl acetate, propyl acetate, isopropyl acetate, butyl acetate, ethylene glycol dimethyl ether, ethylene glycol diisoethyl ether, diethylene glycol dimethyl ether, acetone, tetrahydrofuran, methyltetrahydrofuran, ethyl ether, propyl ether, butyl ether, anisole, diphenyl ether, 1,4-dioxane, or a mixed solvent of two or more thereof.

9. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The separation and purification step in step (3) includes filtration, concentration, addition of a poor solvent for crystallization or washing, solid-liquid separation and drying; the poor solvent is selected from one or more of toluene, xylene, chlorobenzene, dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dichloromethane, trichloromethane, tetrachloromethane, dichloroethane, trichloroethane and tetrachloroethane.

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