Preparation method of bis (fluorosulfonyl) imide salt

Abstract

The invention provides a preparation method of bis (fluorosulfonyl) imide salt, which comprises the following steps: (1) reacting bis (fluorosulfonyl) imide with an organic alkali compound of HF (hydrogen fluoride), and performing post-treatment to obtain an organic alkali compound of bis (fluorosulfonyl) imide; and (2) reacting the organic alkali compound of the bis (fluorosulfonyl) imide obtained in the step (1) with a metal source, and performing post-treatment to obtain the bis (fluorosulfonyl) imide salt, the organic alkali compound of HF comprises a complex formed by HF and an organic amine compound. According to the preparation method of the bis (fluorosulfonyl) imide salt provided by the invention, an organic alkali compound of HF is adopted as a reaction raw material, and the use of a high-toxicity HF raw material with a low boiling point is avoided, so that the intrinsic safety is improved; the bis (fluorosulfonyl) imide salt subjected to solid-liquid separation can be simply dried to obtain a high-purity solid product, so that the separation process is simplified.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical engineering and relates to a preparation method of bis(fluorosulfonyl)imide salt. Background Art

[0002] Bis(fluorosulfonyl)imide salt has excellent electrochemical stability, thermal stability and low-temperature performance, and is a key high-performance electrolyte material in new energy fields such as primary batteries, secondary batteries and supercapacitors. For example, potassium bis(fluorosulfonyl)imide is used as an additive for supercapacitors, and lithium bis(fluorosulfonyl)imide is used as an additive for lithium battery electrolytes.

[0003] Among bis(fluorosulfonyl)imide salts, lithium bis(fluorosulfonyl)imide (LiFSI) is currently the most widely used. The most common synthesis route at present is: reacting chlorosulfonic acid, sulfamic acid and thionyl chloride, or reacting chlorosulfonic acid and chlorosulfonyl isocyanate to obtain bis(chlorosulfonyl)imide; then reacting with a fluorination reagent to obtain bis(fluorosulfonyl)imide (HFSI) or a metal salt of bis(fluorosulfonyl)imide; and then continuing to react with a lithiating reagent (commonly lithium hydroxide, lithium carbonate, lithium fluoride, etc.) to prepare LiFSI. The LiFSI prepared by the above method has problems such as low purity, many impurities or a relatively cumbersome crystallization separation step, which increases the energy consumption.

[0004] CN114804043A discloses a process for preparing lithium bis(fluorosulfonyl)imide, which includes the following steps: Step 1: Sequentially add sulfamic acid, thionyl chloride and chlorosulfonic acid into a dry reaction vessel to obtain a mixed solution, heat the mixed solution to 100-120 °C for reaction, absorb the overflow gas with an alkali solution, perform vacuum distillation under reduced pressure after reacting for 30 h, and collect the fraction at 110-114 °C / 0.267 kPa to obtain a colorless liquid of bis(chlorosulfonyl)imide; Step 2: Add the bis(chlorosulfonyl)imide liquid obtained in Step 1 and antimony pentachloride into a tetrafluoride reaction vessel, heat up to 100-105 °C, slowly introduce hydrogen fluoride gas under stirring, cool down to room temperature after reacting for 18 h, and blow nitrogen for 15 h to obtain a crude product, and perform short-path distillation to obtain bis(fluorosulfonyl)imide; Step 3: Add dichloromethane and lithium hydroxide monohydrate into the product obtained in Step 2, cool down to 0-5 °C, stir for 2 h, then heat up to 20-25 °C, add thionyl chloride, stir for 15 h, and then add a crown ether solvent for pulping, filter, and dry to obtain a lithium bis(fluorosulfonyl)imide product. The disclosed sulfamic acid process route needs to add thionyl chloride to remove water in the LiFSI crude product and crystallize in a crown ether to obtain the product, and the crystallization step is relatively complex.

[0005] Therefore, developing a green, environmentally friendly and efficient preparation method of bis(fluorosulfonyl)imide salt is one of the important research directions in this field. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of bis(fluorosulfonyl)imide salt. The preparation method of the present invention is green, environmentally friendly, efficient, and the obtained bis(fluorosulfonyl)imide salt has high purity.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of bis(fluorosulfonyl)imide salt, and the preparation method includes:

[0009] (1) React bis(chlorosulfonyl)imide with an organic base compound of HF (hydrogen fluoride), and perform post-treatment to obtain an organic base compound of bis(fluorosulfonyl)imide;

[0010] (2) React the organic base compound of bis(fluorosulfonyl)imide obtained in step (1) with a metal source, and perform post-treatment to obtain the bis(fluorosulfonyl)imide salt; the metal source includes any one or a combination of at least two of alkali metal salts, alkali metal hydroxides, alkaline earth metal salts, or alkaline earth metal hydroxides;

[0011] The organic base compound of HF includes a complex formed by HF and an organic amine compound.

[0012] In the preparation method of bis(fluorosulfonyl)imide salt provided by the present invention, the reaction raw material adopts an organic base compound of HF, avoiding the use of highly toxic HF raw materials with low boiling points, thereby improving the inherent safety; the bis(fluorosulfonyl)imide salt after solid-liquid separation can obtain a high-purity solid product after simple drying, simplifying the separation process.

[0013] The preparation method of bis(fluorosulfonyl)imide salt provided by the present invention has the advantages of mild reaction conditions, high yield, low cost, weak equipment corrosion, less production of three wastes, environmental friendliness, etc., is green, environmentally friendly and efficient, and the obtained bis(fluorosulfonyl)imide salt has high purity.

[0014] Preferably, in the complex, the molar ratio of HF to the organic amine compound is (0.8 - 1.2):1, such as 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, etc.

[0015] Preferably, the organic amine compound includes any one or a combination of at least two of triethylamine (Et3N), pyridine, trimethylamine (Me3N), diethylamine, dimethylamine, 1-methylpyrrolidine, diisopropylamine, piperidine, dimethylisopropylamine, 1-methylpiperidine, diisopropylethylamine, or 2-methylpyridine, and preferably triethylamine and / or pyridine.

[0016] Preferably, the molar ratio of the bis(chlorosulfonyl)imide to the organic base compound of HF in step (1) is 1:(0.5 - 3), such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc., and preferably 1:(0.95 - 1.2).

[0017] Preferably, the temperature of the reaction in step (1) is 60 - 140 °C, such as 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, etc., preferably 80 - 120 °C, and more preferably 90 - 105 °C.

[0018] Preferably, the reaction in step (1) is carried out under normal pressure and stirring conditions.

[0019] Preferably, the post-treatment in step (1) includes filtration.

[0020] Preferably, step (1) specifically includes the following steps:

[0021] Simultaneously add dropwise the bis(chlorosulfonyl)imide and the organic base compound of HF to the reaction kettle. After the addition is completed, keep the temperature for reaction, filter to remove the solid therein, take the filtrate to obtain the organic base compound of bis(fluorosulfonyl)imide, and the solid is washed to obtain the organic base compound of HCl.

[0022] Preferably, the time for the dropwise addition is 0.5 - 1.5 h, such as 0.5 h, 1 h, 1.5 h, etc.

[0023] Preferably, the time for the temperature-keeping reaction is 5 - 10 h, such as 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc.

[0024] Preferably, the cation of the metal source includes any one of lithium, sodium, potassium, calcium, magnesium or zinc, and the corresponding anion is an inorganic anion or an organic anion.

[0025] Preferably, the inorganic anion includes any one of hydroxide, carbonate, bicarbonate, phosphate, dihydrogen phosphate, sulfate or halogen (such as fluorine, chlorine, bromine, iodine) ions.

[0026] Preferably, the organic anion includes any one of oxalate, acetate or formate.

[0027] Preferably, the metal source includes any one or a combination of at least two of lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium fluoride, sodium fluoride or potassium fluoride, and preferably any one or a combination of at least two of lithium fluoride, sodium fluoride or potassium fluoride.

[0028] Preferably, the molar ratio of the organic base compound of bis(fluorosulfonyl)imide to the metal source in step (2) is 1:(1 - 3), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc., and preferably 1:(1.05 - 1.2).

[0029] Preferably, the temperature of the reaction in step (2) is 0 - 50 °C, such as 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, etc., and preferably 10 - 30 °C.

[0030] Preferably, the reaction in step (2) is carried out under normal pressure and stirring conditions.

[0031] Preferably, the solvent for the reaction in step (2) includes any one or a combination of at least two of acetonitrile, diethyl ether, or methyl tert-butyl ether, and preferably acetonitrile.

[0032] Preferably, the post-treatment in step (2) includes filtration, flash evaporation, addition of an inert solvent, crystallization, and purification.

[0033] Preferably, the inert solvent includes any one or a combination of at least two of toluene, dichloroethane, dichloromethane, or tetrachloroethane, and preferably toluene.

[0034] Preferably, step (2) specifically includes the following steps:

[0035] Use the solvent and the metal source to line the bottom of the reaction kettle, add the organic base compound of bis(fluorosulfonyl)imide dropwise to the reaction kettle under stirring conditions, keep the temperature for reaction after the addition is completed, filter, flash evaporate, then add an inert solvent, crystallize and purify to obtain the bis(fluorosulfonyl)imide salt.

[0036] Preferably, the dropping time is 0.5 - 1.5 h, such as 0.5 h, 1 h, 1.5 h, etc.

[0037] Preferably, the time for the heat preservation reaction is 1 - 3 h, such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.

[0038] As a preferred technical solution of the present invention, the preparation method of the bis(fluorosulfonyl)imide salt includes:

[0039] (1) At 60 - 140 °C, simultaneously add the organic base compounds of dichlorosulfonylimide and HF dropwise to the reaction kettle, and complete the addition within 0.5 - 1.5 h. After the addition is completed, continue to keep the temperature for reaction for 5 - 10 h, then filter to remove the solid therein, take the filtrate to obtain the organic base compound of bis(fluorosulfonyl)imide;

[0040] Among them, the molar ratio of dichlorosulfonylimide to the organic base compound of HF is 1:(0.5 - 3);

[0041] (2) Use a solvent and a metal source to line the bottom of a reaction kettle. Under stirring conditions at 0 - 50 °C, add an organic base compound of bis(fluorosulfonyl)imide dropwise to the reaction kettle, and complete the dropwise addition within 0.5 - 1.5 h. After the dropwise addition, continue the heat preservation reaction for 1 - 3 h, filter, flash distill, then add an inert solvent, crystallize and refine to obtain the bis(fluorosulfonyl)imide salt;

[0042] Among them, the molar ratio of the organic base compound of bis(fluorosulfonyl)imide to the metal source is 1:(1 - 3).

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) For the preparation method of the bis(fluorosulfonyl)imide salt provided by the present invention, the reaction raw material uses an organic base compound of HF, avoiding the use of highly toxic HF raw materials with low boiling points, thus improving the inherent safety; the bis(fluorosulfonyl)imide salt after solid-liquid separation can obtain a high-purity solid product through simple drying, simplifying the separation process.

[0045] (2) The preparation method of the bis(fluorosulfonyl)imide salt provided by the present invention has the advantages of mild reaction conditions, high yield (85.5% - 93.4%), low cost, weak equipment corrosion, less production of three wastes, environmental friendliness, etc., is green, environmentally friendly and efficient, and the obtained bis(fluorosulfonyl)imide salt has high purity (99.95% - 99.99%). Specific Embodiments

[0046] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0047] Example 1

[0048] In this example, a preparation method of a bis(fluorosulfonyl)imide salt is provided, and the preparation method includes:

[0049] (1) Weigh 214.5 g of dichlorosulfonylimide, and then weigh 121.3 g of a complex of hydrogen fluoride and triethylamine (HF-Et3N, the molar ratio of HF to Et3N is 1:1). Preheat the reaction kettle to 95 °C, and add dichlorosulfonylimide and HF-Et3N dropwise to the reaction kettle at the same time. Control the dropping rates of the two streams of materials to complete the dropwise addition within 1 h, and continue the heat preservation reaction for 6 h. After the reaction is completed, cool down to 25 °C and then filter. Take the filtrate to obtain triethylamine bis(fluorosulfonyl)imide salt. The reaction yield is 98.2%, and the purity is 99.5%.

[0050] (2) Add 400 g of acetonitrile and 28.6 g of lithium fluoride into the reaction kettle. While stirring, cool down the temperature to 15 °C. Weigh 282.6 g of triethylamine bis(fluorosulfonyl)imide salt obtained in step (1) and add it dropwise to the reaction kettle under stirring within 1 h. After the addition, continue to keep the temperature at 15 °C for 2 h for reaction, and filter to remove the unreacted lithium fluoride. Under reduced pressure at 25 °C, distill off 300 g of the solvent acetonitrile. Slowly add 200 g of toluene to the system and keep the temperature at 25 °C for crystallization to obtain lithium bis(fluorosulfonyl)imide. The total reaction yield is 92.5%, the product purity is 99.99%, and the acidity is 17 ppm (calculated as HF);

[0051] Among them, the yields and purities in step (1) and step (2) are obtained by ion chromatography detection, and the acidity in step (2) is obtained by acid-base titration detection. The detection methods used in other examples and comparative examples of the present invention are the same as those in Example 1 and will not be elaborated one by one.

[0052] Example 2

[0053] In this example, a preparation method of bis(fluorosulfonyl)imide salt is provided. The preparation method includes:

[0054] (1) Weigh 214.3 g of dichlorosulfonylimide, and then weigh 99.4 g of the complex of hydrogen fluoride and pyridine (HF-Pyridine, the molar ratio of HF to Pyridine is 1:1). Preheat the reaction kettle to 100 °C, and simultaneously add dichlorosulfonylimide and HF-Pyridine dropwise to the reaction kettle. Control the dropping rates of the two materials to be added dropwise within 1 h. After the addition, continue to keep the temperature for 7 h for reaction. After the reaction is completed, cool down to 25 °C and then filter. Take the filtrate to obtain pyridinium bis(fluorosulfonyl)imide. The reaction yield is 97.5% and the purity is 99.4%.

[0055] (2) Add 400 g of acetonitrile and 28.4 g of lithium fluoride into the reaction kettle. While stirring, keep the temperature at 20 °C. Weigh 260.4 g of pyridinium bis(fluorosulfonyl)imide obtained in step (1) and add it dropwise to the reaction kettle under stirring within 1 h. After the addition, continue to keep the temperature at 20 °C for 2 h for reaction, and filter to remove the unreacted lithium fluoride. Under reduced pressure at 25 °C, distill off 300 g of the solvent acetonitrile. Slowly add 200 g of toluene to the system and keep the temperature at 25 °C for crystallization to obtain lithium bis(fluorosulfonyl)imide. The total reaction yield is 90.3%, the product purity is 99.99%, and the acidity is 21 ppm (calculated as HF).

[0056] Example 3

[0057] In this example, a preparation method of bis(fluorosulfonyl)imide salt is provided. The preparation method includes:

[0058] Add 400 g of acetonitrile and 46.3 g of sodium fluoride into the reaction kettle. While stirring, cool down the temperature to 15°C. Weigh 282.8 g of the triethylamine salt of bis(fluorosulfonyl)imide obtained in step (1) of Example 1 and add it dropwise to the reaction kettle under stirring within 1 h. After the addition is completed, continue to keep the temperature at 15°C for heat preservation reaction for 2 h, and filter to remove the unreacted sodium fluoride. Under reduced pressure at 25°C, distill off 300 g of the solvent acetonitrile. Slowly add 200 g of toluene to the system and keep the temperature at 25°C for crystallization to obtain sodium bis(fluorosulfonyl)imide. The total reaction yield is 93.4%, the product purity is 99.99%, and the acidity is 19 ppm (calculated as HF).

[0059] Example 4

[0060] In this example, a preparation method of a bis(fluorosulfonyl)imide salt is provided, and the preparation method includes:

[0061] Add 400 g of acetonitrile and 63.8 g of potassium fluoride into the reaction kettle. While stirring, keep the temperature at 20°C. Weigh 260.6 g of the pyridine salt of bis(fluorosulfonyl)imide obtained in step (1) of Example 2 and add it dropwise to the reaction kettle under stirring within 1 h. After the addition is completed, continue to keep the temperature at 20°C for heat preservation reaction for 2 h, and filter to remove the unreacted potassium fluoride. Under reduced pressure at 25°C, distill off 300 g of the solvent acetonitrile. Slowly add 200 g of toluene to the system and keep the temperature at 25°C for crystallization to obtain potassium bis(fluorosulfonyl)imide. The total reaction yield is 89.7%, the product purity is 99.99%, and the acidity is 24 ppm (calculated as HF).

[0062] Example 5

[0063] In this example, a preparation method of a bis(fluorosulfonyl)imide salt is provided, and the preparation method includes:

[0064] (1) Weigh 214.5 g of dichlorosulfonylimide, and then weigh 60.8 g of the complex of hydrogen fluoride and triethylamine (HF-Et3N, the molar ratio of HF to Et3N is 1:1). Preheat the reaction kettle to 60°C, and simultaneously add dichlorosulfonylimide and HF-Et3N dropwise to the reaction kettle. Control the dropping rate of the two streams of materials to be completed within 1 h, and continue the heat preservation reaction for 10 h. After the reaction is completed, cool down to 25°C and then filter. Take the filtrate to obtain the triethylamine salt of bis(fluorosulfonyl)imide. The reaction yield is 73.3% and the purity is 99.4%.

[0065] (2) Add 400 g of acetonitrile and 28.6 g of lithium fluoride into the reaction kettle. While stirring, cool down the temperature to 0 °C. Weigh 282.6 g of triethylamine bis(fluorosulfonyl)imide obtained in step (1) and add it dropwise into the reaction kettle under stirring within 1 h. After the dropping is completed, continue to keep the temperature at 0 °C for heat preservation reaction for 3 h, and filter to remove the unreacted lithium fluoride. Under reduced pressure distillate 300 g of the solvent acetonitrile at 25 °C, slowly add 200 g of toluene into the system and keep the temperature at 25 °C for crystallization to obtain lithium bis(fluorosulfonyl)imide. The total reaction yield is 87.6%, the product purity is 99.98%, and the acidity is 15 ppm (calculated as HF).

[0066] Example 6

[0067] In this example, a preparation method of bis(fluorosulfonyl)imide salt is provided, and the preparation method includes:

[0068] (1) Weigh 214.5 g of dichlorosulfonylimide, and then weigh 362.4 g of the complex of hydrogen fluoride and triethylamine (HF-Et3N, the molar ratio of HF to Et3N is 1:1). Preheat the reaction kettle to 140 °C, and simultaneously add dichlorosulfonylimide and HF-Et3N dropwise into the reaction kettle. Control the dropping rates of the two streams of materials to be added dropwise within 1 h, and continue to keep the temperature for heat preservation reaction for 5 h. After the reaction is completed, cool down to 25 °C and then filter. Take the filtrate to obtain triethylamine bis(fluorosulfonyl)imide. The reaction yield is 91.4% and the purity is 99.2%.

[0069] (2) Add 400 g of acetonitrile and 28.6 g of lithium fluoride into the reaction kettle. While stirring, keep the temperature at 50 °C. Weigh 282.6 g of triethylamine bis(fluorosulfonyl)imide obtained in step (1) and add it dropwise into the reaction kettle under stirring within 1 h. After the dropping is completed, continue to keep the temperature at 50 °C for heat preservation reaction for 1 h, and filter to remove the unreacted lithium fluoride. Under reduced pressure distillate 300 g of the solvent acetonitrile at 25 °C, slowly add 200 g of toluene into the system and keep the temperature at 25 °C for crystallization to obtain lithium bis(fluorosulfonyl)imide. The total reaction yield is 85.5%, the product purity is 99.95%, and the acidity is 21 ppm (calculated as HF).

[0070] Comparative Example 1

[0071] In this comparative example, a preparation method of bis(fluorosulfonyl)imide salt is provided, and the preparation method includes:

[0072] (1) Weigh 214.5 g of bis(chlorosulfonyl)imide, and then weigh 161.4 g of triethylamine hydrofluoride (HF-Et3N, with a molar ratio of HF to Et3N of 3:1). Preheat the reaction kettle to 95 °C, and simultaneously add bis(chlorosulfonyl)imide and HF-Et3N dropwise to the reaction kettle. Control the dropping rate of the two materials to be completed within 1 h, and continue the heat preservation reaction for 6 h. After the reaction is completed, cool down to 25 °C and then filter. Take the filtrate to obtain triethylamine bis(fluorosulfonyl)imide salt, with a reaction yield of 56.6% and a purity of 99.4%.

[0073] (2) Add 400 g of acetonitrile and 28.6 g of lithium fluoride to the reaction kettle, cool down to 15 °C with stirring. Weigh 282.6 g of the triethylamine bis(fluorosulfonyl)imide salt obtained in step (1) and add it dropwise to the reaction kettle under stirring within 1 h. After the dropping is completed, continue the heat preservation reaction at 15 °C for 2 h, and filter to remove the unreacted lithium fluoride. Under reduced pressure at 25 °C, distill off 300 g of the solvent acetonitrile. Slowly add 200 g of toluene to the system and keep the temperature at 25 °C for crystallization to obtain lithium bis(fluorosulfonyl)imide. The total reaction yield is 92.2%, the product purity is 99.98%, and the acidity is 18 ppm (calculated as HF).

[0074] It can be seen that, compared with Example 1, when using the method provided in Comparative Example 1 to prepare bis(fluorosulfonyl)imide salt, there is a relatively large difference in the reaction yield obtained in step (1). This is because when the molar ratio of hydrogen fluoride to triethylamine in triethylamine hydrofluoride is 1:1, its fluorination effect is the best. Similarly, for pyridine hydrofluoride, when the molar ratio of hydrogen fluoride to pyridine is greater than 1:1, the yield of the fluorination step (i.e., step (1)) also decreases significantly compared with Example 2.

[0075] In summary, when using the preparation method of bis(fluorosulfonyl)imide salt provided by the present invention, the reaction raw materials adopt organic base compounds of HF, avoiding the use of highly toxic HF raw materials with low boiling points, thereby improving the intrinsic safety; after solid-liquid separation, the bis(fluorosulfonyl)imide salt can obtain a high-purity solid product through simple drying, simplifying the separation process. And when using the preparation method provided by the present invention, the yield of the fluorination step is relatively high (73.3% - 98.2%).

[0076] The applicant declares that the present invention uses the above embodiments to illustrate the preparation method of the bis(fluorosulfonyl)imide salt of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a bis(fluorosulfonyl)imide salt, characterized in that, The preparation method includes the following steps: (1) Reacting dichlorosulfonylimide with an organic base compound of HF, and performing post-treatment to obtain an organic base compound of bis(fluorosulfonyl)imide; (2) Reacting the organic base compound of bis(fluorosulfonyl)imide obtained in step (1) with a metal source, and performing post-treatment to obtain the bis(fluorosulfonyl)imide salt; the metal source includes any one or a combination of at least two of alkali metal salts, alkali metal hydroxides, alkaline earth metal salts or alkaline earth metal hydroxides; The organic base compound of HF includes a complex formed by HF and an organic amine compound.

2. The preparation method according to claim 1, characterized in that, The organic amine compound includes any one or a combination of at least two of triethylamine, pyridine, trimethylamine, diethylamine, dimethylamine, 1-methylpyrrolidine, diisopropylamine, piperidine, dimethylisopropylamine, 1-methylpiperidine, diisopropylethylamine or 2-methylpyridine, preferably triethylamine and / or pyridine; Preferably, the molar ratio of the dichlorosulfonylimide to the organic base compound of HF in step (1) is 1:(0.5 - 3), preferably 1:(0.95 - 1.2).

3. The preparation method according to claim 1 or 2, characterized in that, The temperature of the reaction in step (1) is 60 - 140 °C, preferably 80 - 120 °C, more preferably 90 - 105 °C; Preferably, the post-treatment in step (1) includes filtration.

4. The preparation method according to any one of claims 1-3, characterized in that, Step (1) specifically includes the following steps: Simultaneously dropping dichlorosulfonylimide and the organic base compound of HF into a reaction kettle, keeping the temperature for reaction after the dropping is completed, filtering to remove the solid therein, and taking the filtrate to obtain the organic base compound of bis(fluorosulfonyl)imide.

5. The preparation method according to claim 4, wherein, The dropping time is 0.5 - 1.5 h; Preferably, the time for the heat preservation reaction is 5 - 10 h.

6. The preparation method according to any one of claims 1-5, characterized in that, The cation of the metal source includes any one of lithium, sodium, potassium, calcium, magnesium or zinc, and the corresponding anion is an inorganic anion or an organic anion; Preferably, the inorganic anion includes any one of hydroxide, carbonate, bicarbonate, phosphate, dihydrogen phosphate, sulfate or halide ion; Preferably, the organic anion includes any one of oxalate, acetate or formate; Preferably, the metal source includes any one or a combination of at least two of lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium fluoride, sodium fluoride or potassium fluoride, preferably any one or a combination of at least two of lithium fluoride, sodium fluoride or potassium fluoride.

7. The preparation method according to any one of claims 1-6, characterized in that, The molar ratio of the organic base compound of bis(fluorosulfonyl)imide to the metal source in step (2) is 1:(1 - 3), preferably 1:(1.05 - 1.2); Preferably, the temperature of the reaction in step (2) is 0 - 50 °C, preferably 10 - 30 °C; Preferably, the solvent for the reaction in step (2) includes any one or a combination of at least two of acetonitrile, ether or methyl tert-butyl ether, preferably acetonitrile; Preferably, the post-treatment in step (2) includes filtration, flash evaporation, adding an inert solvent, crystallization and purification; Preferably, the inert solvent includes any one or a combination of at least two of toluene, dichloroethane, dichloromethane or tetrachloroethane, preferably toluene.

8. The preparation method according to any one of claims 1-7, characterized in that, Step (2) specifically includes the following steps: Use a solvent and a metal source as the bottom layer in a reaction kettle. While stirring, add an organic base compound of bis(fluorosulfonyl)imide dropwise to the reaction kettle. After the addition is completed, keep the temperature for reaction, filter, flash distill, then add an inert solvent, crystallize and refine to obtain the bis(fluorosulfonyl)imide salt.

9. The preparation method according to claim 8, characterized in that, The dropping time is 0.5 - 1.5 h; Preferably, the time for keeping the temperature for reaction is 1 - 3 h.

10. A preparation method according to any one of claims 1-9, characterized in that, The preparation method includes: (1) At 60 - 140 °C, add an organic base compound of dichlorosulfonylimide and HF dropwise to the reaction kettle simultaneously, and complete the dropping within 0.5 - 1.5 h. After the addition is completed, continue to keep the temperature for reaction for 5 - 10 h, then filter to remove the solid therein, take the filtrate to obtain the organic base compound of bis(fluorosulfonyl)imide; Among them, the molar ratio of dichlorosulfonylimide to the organic base compound of HF is 1:(0.5 - 3); (2) Use a solvent and a metal source as the bottom layer in the reaction kettle. While stirring at 0 - 50 °C, add an organic base compound of bis(fluorosulfonyl)imide dropwise to the reaction kettle, and complete the dropping within 0.5 - 1.5 h. After the addition is completed, continue to keep the temperature for reaction for 1 - 3 h, filter, flash distill, then add an inert solvent, crystallize and refine to obtain the bis(fluorosulfonyl)imide salt; Among them, the molar ratio of the organic base compound of bis(fluorosulfonyl)imide to the metal source is 1:(1 - 3).