Preparation method of bis (fluorosulfonyl) imide salt

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a preparation method of bis (fluorosulfonyl) imide salt. The preparation method of the bis (fluorosulfonyl) imide salt provided by the invention comprises the following steps: reacting hydrofluoric acid, alkali metal fluoride and bis (chlorosulfonyl) imide under a closed condition at the temperature of 100 DEG C or above, cooling to 10 DEG C or below after the reaction is completed, carrying out primary filtration to obtain a filter cake, heating to 100 DEG C or above, carrying out secondary filtration to obtain a filtrate, and drying to obtain the bis (fluorosulfonyl) imide salt. And removing impurities to obtain the bis (fluorosulfonyl) imide salt particles or a bis (fluorosulfonyl) imide salt solution. By controlling the reaction temperature and the temperature of two times of filtration after the reaction, the product and impurities are separated by utilizing the crystallization characteristics and solubility of the components in the reaction system at different temperatures, so that the high-purity bis (fluorosulfonyl) imide salt is prepared by a solvent-free one-pot method.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of secondary batteries, in particular to a preparation method of a double fluorosulfonylimide salt. BACKGROUND

[0002] With the development of the new energy industry, people's requirements for battery performance are gradually increasing, and it is imperative to develop lithium ion batteries with high energy density, high cycle performance, high safety and fast charging capacity. The battery that can be charged and discharged is widely used in many fields such as energy storage, electric vehicles and aerospace, because of its small size, high energy density, high safety and long service life, which makes it widely studied in the battery field in order to further improve its performance.

[0003] At present, the main steps of the industrial production method of double fluorosulfonylimide lithium (LiFSI) include: 1) first, double chlorosulfonylimide acid is synthesized by taking sulfonamide, dichlorosulfoxide, chlorosulfonic acid and other substances as raw materials; 2) double chlorosulfonylimide acid is reacted with fluorine-containing substances to synthesize double fluorosulfonylimide acid; 3) an alkali lithium salt (lithium carbonate, etc.) is added to react to obtain the corresponding double fluorosulfonylimide lithium salt, and finally the solid product is obtained by using crystallization purification and drying. In this production process, a large amount of toxic, corrosive and volatile raw materials and hazardous chemicals are involved, and the intermediate products are sensitive to water, air and temperature and are easy to decompose, the manufacturing technology barrier is high, and the industrialization process is not as expected.

[0004] Double fluorosulfonylimide potassium (KFSI) / sodium (NaFSI) is stable in air at room temperature, and can be prepared by anhydrous potassium / sodium salt to prepare double fluorosulfonylimide lithium, therefore, it has important social significance and economic value to develop a new process for directly reacting high-quality LiFSI by taking anhydrous KFSI / NaFSI as an intermediate. In addition, the prior art prepares high-purity double fluorosulfonylimide lithium by one-pot method, which avoids the problem that the intermediate product is easily affected. For example, a Chinese patent application with the application publication number CN112174101A published on January 5, 2021 discloses a preparation method of high-purity double fluorosulfonylimide lithium, which specifically mixes hydrogen fluoride, lithium fluoride and double chlorosulfonylimide at low temperature to generate crude double fluorosulfonylimide lithium, then dissolves the crude double fluorosulfonylimide lithium in a non-polar solvent, and obtains high-purity double fluorosulfonylimide lithium after heating and crystallization, which only needs to go through two steps of synthesis and impurity removal to prepare high-purity double fluorosulfonylimide lithium, and the process flow is short and the process is green and environmentally friendly.

[0005] However, the above one-pot method prepares double fluorosulfonylimide lithium, and a solvent is introduced, which causes the solvent to remain in the double fluorosulfonylimide lithium product, and there is a risk of reducing the electrochemical performance of the battery and a safety hazard. SUMMARY

[0006] The present invention provides a method for preparing a bisfluorosulfonyl imide salt, which solves the problem in the prior art that a solvent needs to be introduced when preparing the bisfluorosulfonyl imide salt, resulting in the easy generation of solvent residues in the product.

[0007] In order to solve the above technical problems, the technical solution of the preparation method of the bisfluorosulfonyl imide salt of the present invention is: A method for preparing a bisfluorosulfonyl imide salt comprises the following steps: reacting hydrofluoric acid, an alkali metal fluoride and bischlorosulfonyl imide under sealed conditions at a temperature above 100°C; cooling the mixture to below 10°C after the reaction is completed; filtering the mixture once to obtain a filter cake; heating the mixture to above 100°C; filtering the mixture twice to obtain a filtrate; and removing impurities to obtain bisfluorosulfonyl imide salt particles or a bisfluorosulfonyl imide salt solution.

[0008] The present invention improves the prior art and provides a method for preparing a bisfluorosulfonyl imide salt. The reaction equation of a one-pot reaction of a fluorination reaction and a salt-forming reaction is: Cl2HNO4S2+HF+MF→F2MNO4S2+2HCl↑, wherein M is potassium fluoride, sodium fluoride or lithium fluoride. The method is carried out under a relatively high temperature and sealed condition, and after the reaction is completed, the liquid hydrofluoric acid and the solid bisfluorosulfonyl imide salt are separated by cooling and filtering once. The bisfluorosulfonyl imide salt is then melted by heating, and the solid alkali metal fluoride and the molten bisfluorosulfonyl imide salt are separated by secondary filtration. No other solvent is introduced, and a molten bisfluorosulfonyl imide salt with high purity can be directly obtained. Solvent residue in the product can be avoided, and high-purity bisfluorosulfonyl imide salt can be prepared by the solvent-free one-pot method.

[0009] It is understood that when potassium bis(fluorosulfonylimide) is prepared, potassium fluoride is selected as the raw material; when sodium bis(fluorosulfonylimide) is prepared, sodium fluoride is selected as the raw material; and when lithium bis(fluorosulfonylimide) is prepared, lithium fluoride is selected as the raw material.

[0010] In order to further improve the purity of the bisfluorosulfonyl imide salt, preferably, the reaction is carried out at 100-160°C; the temperature after the cooling is -50-10°C; and the temperature after the heating is 100-160°C.

[0011] In order to further improve the purity of the bisfluorosulfonyl imide salt, preferably, when preparing potassium bisfluorosulfonyl imide, the reaction is carried out at 105-150°C, and the temperature after heating is 105-150°C; when preparing sodium bisfluorosulfonyl imide, the reaction is carried out at 120-150°C, and the temperature after heating is 120-150°C; when preparing lithium bisfluorosulfonyl imide, the reaction is carried out at 130-160°C, and the temperature after heating is 130-160°C.

[0012] To further improve the conversion rate of bisfluorosulfone imide, preferably, the molar ratio of bischlorosulfone imide, hydrofluoric acid, alkali metal fluoride is 1: (2.5-4): (1-2).

[0013] To further reduce the free acid in the bisfluorosulfone imide salt, preferably, the impurity removal includes nitrogen blowing and melt purification of the filtrate obtained by secondary filtration. It can be understood that the temperature of the filtrate obtained by secondary filtration is not changed, that is, the nitrogen blowing is carried out at a temperature of 100℃ or above. The acidity is reduced by a physical method, and no new impurities are introduced.

[0014] To further remove impurities, preferably, the melt purification is to cool the filtrate after nitrogen blowing to form a solid, then heat and melt the solid to remove impurities, and then melt the remaining solid to obtain a molten bisfluorosulfone imide salt. The purification is carried out by melt purification, and there is no loss of material, so the recycling yield is high.

[0015] To further remove water and acid, preferably, the bisfluorosulfone imide salt particles are obtained by spray drying the molten bisfluorosulfone imide salt. The granulation is carried out by the spray drying method, which is simple, efficient, and can further remove water and free acid from the product.

[0016] To further reduce the caking problem of the bisfluorosulfone imide salt in the downstream feeding and transportation process, preferably, the bisfluorosulfone imide salt solution is obtained by dissolving the molten bisfluorosulfone imide salt in a solvent at 5-15℃. The molten bisfluorosulfone imide salt is directly dissolved in a solvent to obtain a bisfluorosulfone imide salt solution, which is simple, efficient, and reduces production costs. The solvent is selected from electrolyte solvents, such as carbonic acid solvents, including dimethyl carbonate (DMC), diethyl carbonate (EDC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC).

[0017] To further facilitate observation of the reaction endpoint, preferably, the reaction is stopped when the pressure in the reaction system does not change within half an hour.

[0018] To further improve the utilization rate of raw materials, preferably, the filtrate obtained by primary filtration and the residue obtained by secondary filtration are returned to the reaction system for reaction. By recycling the raw materials, the production cost is reduced.

[0019] To further improve the purity of the bisfluorosulfone imide salt, preferably, the purity of the molten bisfluorosulfone imide salt is ≥99.95%. DETAILED DESCRIPTION

[0020] The technical concept of the preparation method of the bisfluorosulfone imide salt of the present application is as follows: The prior art still uses a good solvent to remove impurities when preparing bisfluorosulfonyl imide salts in a one-pot process, but this inevitably introduces solvent into the product, resulting in residual solvent in the product. The present invention, however, controls the reaction temperature and the temperature of the two filtrations after the reaction, utilizing the crystallization characteristics and solubility of each component in the reaction system at different temperatures to separate the product and impurities, thereby achieving a solvent-free one-pot process for preparing high-purity bisfluorosulfonyl imide salts. The bisfluorosulfonyl imide salts prepared by the preparation method of the present invention, particularly the bisfluorosulfonyl imide salt products, have excellent social and economic value and are suitable for industrial production and promotion and application. Compared to potassium bisfluorosulfonyl imide, sodium bisfluorosulfonyl imide has a higher liquefaction temperature and high energy consumption.

[0021] The preparation method of bisfluorosulfonyl imide salt provided by the present invention comprises the following steps: reacting bischlorosulfonyl imide, hydrofluoric acid and alkali metal fluoride in a molar ratio of 1:(2.5-4):(1-2) under closed conditions at a temperature of 100-160° C., stopping the reaction when the pressure in the reaction system does not change within half an hour, cooling to -50-10° C. after the reaction is completed, filtering once to obtain a filter cake, then heating to 100-160° C., filtering twice to obtain a filtrate, purging the filtrate obtained by the secondary filtration with nitrogen, melting and purifying, and nitrogen After purging, a crude bisfluorosulfonyl imide salt with an acidity of 10-50 ppm is obtained. The melt purification comprises cooling the crude bisfluorosulfonyl imide salt to form a solid, then heating it to remove impurities at a heating rate of 1-2°C / h. After removing the molten liquid, the remaining solid is melted to obtain a molten bisfluorosulfonyl imide salt, wherein the purity of the molten bisfluorosulfonyl imide salt is ≥99.95%. The molten bisfluorosulfonyl imide salt is spray-dried to obtain bisfluorosulfonyl imide salt particles. The molten bisfluorosulfonyl imide salt is dissolved in a solvent at 5-15°C to obtain a bisfluorosulfonyl imide salt solution. The filtrate obtained from the first filtration and the filter residue obtained from the second filtration are returned to the reaction system for reaction.

[0022] It can be understood that dissolving the molten bisfluorosulfonyl imide salt in the solvent at 5-15° C. means dissolving the molten bisfluorosulfonyl imide salt in the solvent at 5-15° C. The molten bisfluorosulfonyl imide salt is dissolved in the solvent by dropwise addition.

[0023] The technical solution of the present invention is further described with reference to the following examples. Unless otherwise specified, the chemical substances used in the following examples are all commercially available conventional products.

[0024] 1. Specific Examples of the Preparation Method of the Bisfluorosulfonyl Imide Salt of the Present Invention Example 1 The preparation method of potassium bis(fluorosulfonyl)imide particles of this embodiment is as follows: To a tetrafluoroethylene reaction kettle equipped with a thermometer, a pressure gauge and a stirrer, 60 g of liquid hydrofluoric acid (kept below 10° C.) and 70 g of potassium fluoride were added, and 214 g of bis(chlorosulfonyl)imide acid was added dropwise. After completion, the kettle was sealed and the temperature was raised to 105° C. for reaction. Within half an hour, when the pressure gauge did not change, the reaction was stopped and the temperature was lowered. When the temperature was lowered to 10° C., a filter was performed once to obtain a filter cake. The filter cake was heated and filtered twice when the temperature was raised to 105° C. to obtain a filtrate. The filtrate was purged with nitrogen until a crude product of potassium bis(chlorosulfonyl)imide with an acidity of 50 ppm was obtained, and melt purification was performed. The specific method of melt purification was as follows: the molten potassium bis(chlorosulfonyl)imide was cooled to 10° C. to form a solid, and then the temperature was 1° C. per hour. The temperature was raised, and the purity of the molten liquid was monitored in real time until the purity reached 99.94% or more. The unmelted solid was collected and melted to obtain molten potassium bisfluorosulfonyl imide with a purity of 99.95%. Finally, 158.34 g of potassium bisfluorosulfonyl imide particles were obtained by spraying. The primary yield was 72.2%, and the cycle yield was 97.65%. The cycle yield was calculated as follows: potassium bisfluorosulfonyl imide was prepared by the same method, and the molten potassium bisfluorosulfonyl imide with an acidity of 50 ppm obtained after nitrogen purge was mixed with the molten liquid collected during the previous batch of melt purification, and then melt purified to obtain a molten potassium bisfluorosulfonyl imide with a purity of 99.95%. The ratio of the mass of the molten potassium bisfluorosulfonyl imide to the theoretical product mass of this batch was the cycle yield.

[0025] Example 2 The preparation method of potassium bis(fluorosulfonyl)imide particles of this embodiment is as follows: 80g hydrofluoric acid and 116g Potassium monofluoride are added in the tetrafluoro reactor with thermometer, pressure gauge and stirring, 214g bis(chlorosulfonyl)imide acid is added drip, airtight is carried out after completion, react when being warming up to 120 ℃, in half an hour, when pressure gauge did not change, stopped reaction, cools the temperature, when being cooled to-20 ℃, once filters, obtain filter cake, filter cake is heated up, carry out secondary filtration when being warming up to 150 ℃, obtain filtrate, filtrate is carried out nitrogen purging, obtain the bis(fluorosulfonyl)imide) potassium crude product that acidity is 10ppm, carry out melt purification, obtain the bis(fluorosulfonyl)imide) potassium of the melting that purity is 99.99%, finally spray and obtain 155.93g bis(fluorosulfonyl)imide) potassium granules, primary yield is 71.2%, and circulation yield is 97.22%.

[0026] Example 3 The preparation method of potassium bis(fluorosulfonyl)imide particles of this embodiment is as follows: Into a four-fluoride reaction kettle with thermometer, pressure gauge and stirring, 75 g of hydrofluoric acid and 75.4 g of potassium fluoride were added, and 214 g of bischlorosulfonyl imide acid was added dropwise. After completion, it was sealed, heated to 110°C, and reacted. Within half an hour, when the pressure gauge did not change, the reaction was stopped, and the temperature was lowered to -50°C. Once filtered, the filter cake was warmed to 120°C and filtered again. The filtrate was nitrogen purged to obtain a crude bisfluorosulfonyl imide potassium with an acidity of 30 ppm. After melting purification, a melted bisfluorosulfonyl imide potassium with a purity of 99.97% was obtained. Finally, 155.05 g of bisfluorosulfonyl imide potassium particles were obtained by spraying, with a one-time yield of 70.7% and a cycle yield of 97.31%.

[0027] Example 4 The preparation method of the bisfluorosulfonyl imide potassium particles of this example is as follows: Into a four-fluoride reaction kettle with thermometer, pressure gauge and stirring, 75 g of hydrofluoric acid and 75.4 g of potassium fluoride were added, and 214 g of bischlorosulfonyl imide acid was added dropwise. After completion, it was sealed, heated to 110°C, and reacted. Within half an hour, when the pressure gauge did not change, the reaction was stopped, and the temperature was lowered to -50°C. Once filtered, the filter cake was warmed to 120°C and filtered again. The filtrate was nitrogen purged to obtain a crude bisfluorosulfonyl imide potassium with an acidity of 30 ppm. After melting purification, a melted bisfluorosulfonyl imide potassium with a purity of 99.97% was obtained. Finally, 155.05 g of bisfluorosulfonyl imide potassium particles were obtained by spraying, with a one-time yield of 70.7% and a cycle yield of 97.31%.

[0028] Example 5 The preparation method of the bisfluorosulfonyl imide potassium particles of this example is as follows: Into a four-fluoride reaction kettle with thermometer, pressure gauge and stirring, 75 g of hydrofluoric acid and 75.4 g of potassium fluoride were added, and 214 g of bischlorosulfonyl imide acid was added dropwise. After completion, it was sealed, heated to 110°C, and reacted. Within half an hour, when the pressure gauge did not change, the reaction was stopped, and the temperature was lowered to -50°C. Once filtered, the filter cake was warmed to 120°C and filtered again. The filtrate was nitrogen purged to obtain a crude bisfluorosulfonyl imide potassium with an acidity of 30 ppm. After melting purification, a melted bisfluorosulfonyl imide potassium with a purity of 99.97% was obtained. Finally, 155.05 g of bisfluorosulfonyl imide potassium particles were obtained by spraying, with a one-time yield of 70.7% and a cycle yield of 97.31%.

[0029] Example 6 The preparation method of the bisfluorosulfonyl imide potassium particles of this example is as follows: Into a four-fluoride reaction kettle with thermometer, pressure gauge and stirring, 60 g of hydrofluoric acid and 64 g of potassium fluoride were added, and 214 g of bischlorosulfonyl imide acid was added dropwise. After completion, it was sealed, heated to 130°C, and reacted. Within half an hour, when the pressure gauge did not change, the reaction was stopped, and the temperature was lowered to -5°C. Once filtered, the filter cake was heated to 130°C, and twice filtered. The filtrate was nitrogen purged to obtain a crude bisfluorosulfonyl imide potassium with an acidity of 30 ppm. After melting purification, a melted bisfluorosulfonyl imide potassium with a purity of 99.97% was obtained. Finally, 159.8 g of bisfluorosulfonyl imide potassium particles were obtained by spraying, with a one-time yield of 72.9% and a cycle yield of 97.41%.

[0030] Example 7 The preparation method of the bisfluorosulfonyl imide sodium particles of this example is as follows: Into a four-fluoride reaction kettle with thermometer, pressure gauge and stirring, 60 g of hydrofluoric acid and 64 g of potassium fluoride were added, and 214 g of bischlorosulfonyl imide acid was added dropwise. After completion, it was sealed, heated to 130°C, and reacted. Within half an hour, when the pressure gauge did not change, the reaction was stopped, and the temperature was lowered to -5°C. Once filtered, the filter cake was heated to 130°C, and twice filtered. The filtrate was nitrogen purged to obtain a crude bisfluorosulfonyl imide potassium with an acidity of 30 ppm. After melting purification, a melted bisfluorosulfonyl imide potassium with a purity of 99.97% was obtained. Finally, 159.8 g of bisfluorosulfonyl imide potassium particles were obtained by spraying, with a one-time yield of 72.9% and a cycle yield of 97.41%.

[0031] Example 8 The preparation method of the bisfluorosulfonyl imide sodium particles of this example is as follows: Into a four-fluoride reaction kettle with thermometer, pressure gauge and stirring, 60 g of hydrofluoric acid and 64 g of potassium fluoride were added, and 214 g of bischlorosulfonyl imide acid was added dropwise. After completion, it was sealed, heated to 130°C, and reacted. Within half an hour, when the pressure gauge did not change, the reaction was stopped, and the temperature was lowered to -5°C. Once filtered, the filter cake was heated to 130°C, and twice filtered. The filtrate was nitrogen purged to obtain a crude bisfluorosulfonyl imide potassium with an acidity of 30 ppm. After melting purification, a melted bisfluorosulfonyl imide potassium with a purity of 99.97% was obtained. Finally, 159.8 g of bisfluorosulfonyl imide potassium particles were obtained by spraying, with a one-time yield of 72.9% and a cycle yield of 97.41%.

[0032] Example 9 The preparation method of the bisfluorosulfonyl imide sodium particles of this example is as follows: 70g hydrofluoric acid and 60g sodium fluoride are added in the tetrafluoro reactor with thermometer, pressure gauge and stirring, 214g bis(chlorosulfonyl)imide acid is added dripped, airtight is carried out after completion, react when being warming up to 130 ℃, in half an hour, when pressure gauge did not change, stopped reaction, cools the temperature, when being cooled to 10 ℃, once filters, obtain filter cake, filter cake is heated, carry out secondary filtration when being warming up to 130 ℃, obtain filtrate, filtrate is carried out nitrogen purging, obtain the bis(fluorosulfonyl)imide) crude product that acidity is 18ppm, carry out melt purification, obtain the bis(fluorosulfonyl)imide) sodium of the melting that purity is 99.98%, finally spray and obtain 150.7g bis(fluorosulfonyl)imide) sodium particles, primary yield is 74.2%, and circulation yield is 97.96%.

[0033] Example 10 The preparation method of lithium bis(fluorosulfonyl)imide particles of this embodiment is as follows: 80g hydrofluoric acid and 26.4g lithium fluoride were added to a tetrafluoroethylene reactor with a thermometer, a pressure gauge and stirring, 214g of bis(chlorosulfonyl)imide acid was added dropwise, and the mixture was sealed after completion. The mixture was reacted when heated to 130°C. Within half an hour, when the pressure gauge did not change, the reaction was stopped and the temperature was lowered. When the temperature was lowered to 10°C, a filter was once filtered to obtain a filter cake. The filter cake was heated and a secondary filtration was performed when the temperature was raised to 130°C to obtain a filtrate. The filtrate was purged with nitrogen to obtain a crude bis(fluorosulfonyl)imide) lithium product having an acidity of 20ppm. The product was melt-purified to obtain a bis(fluorosulfonyl)imide) lithium product having a melting temperature of 99.96%. The product was then sprayed to obtain 139.5g of bis(fluorosulfonyl)imide) lithium particles. The primary yield was 74.6%, and the cycle yield was 98.21%.

[0034] Example 11 The preparation method of lithium bis(fluorosulfonyl)imide particles of this embodiment is as follows: 50g hydrofluoric acid and 48g lithium fluoride were added to a tetrafluoroethylene reactor with a thermometer, a pressure gauge and stirring, 214g of bis(chlorosulfonyl)imide acid was added dropwise, and the mixture was sealed after completion. The mixture was reacted when heated to 160°C. Within half an hour, when the pressure gauge did not change, the reaction was stopped and the temperature was lowered. When the temperature was lowered to -5°C, a filter was once filtered to obtain a filter cake. The filter cake was heated and a secondary filtration was performed when the temperature was raised to 160°C to obtain a filtrate. The filtrate was purged with nitrogen to obtain a crude bis(fluorosulfonyl)imide) lithium product having an acidity of 26ppm. The product was melt-purified to obtain a bis(fluorosulfonyl)imide) lithium product having a melting temperature of 99.98%. The product was then sprayed to obtain 140.4g of bis(fluorosulfonyl)imide) lithium particles. The primary yield was 75.1%, and the cycle yield was 98.49%.

[0035] Example 12 The preparation method of lithium bis(fluorosulfonyl)imide particles of this embodiment is as follows: 70g hydrofluoric acid and 40g lithium fluoride were added to a tetrafluoroethylene reactor with a thermometer, a pressure gauge and stirring, 214g of bis(chlorosulfonyl)imide acid was added dropwise, and the mixture was sealed after completion. The mixture was reacted when heated to 140°C. Within half an hour, when the pressure gauge did not change, the reaction was stopped and the temperature was lowered. When the temperature was lowered to 0°C, a filter was once filtered to obtain a filter cake. The filter cake was heated and a secondary filtration was performed when the temperature was raised to 140°C to obtain a filtrate. The filtrate was purged with nitrogen to obtain a crude bis(fluorosulfonyl)imide) lithium product having an acidity of 23ppm. The bis(fluorosulfonyl)imide) lithium product was melt-purified to obtain a 99.97% molten bis(fluorosulfonyl)imide lithium product. The 140.1g bis(fluorosulfonyl)imide) lithium particles were finally sprayed. The primary yield was 74.9%, and the cycle yield was 98.11%.

[0036] The impurity component test results of the molten bisfluorosulfonyl imide salts prepared in Examples 1 to 12 are shown in Table 1. It should be noted that the free acid was measured in the crude bisfluorosulfonyl imide salt obtained after nitrogen purging, and the other impurity components were measured in the molten bisfluorosulfonyl imide salt obtained after melt purification.

[0037] Table 1 Impurity components of bis(fluorosulfonyl)imide salts prepared in Examples 1 to 12 Free acid (ppm) purity(%) Moisture (ppm) DMC insoluble matter (ppm) Chloride ion (ppm) Sulfate ion (ppm) Cations (ppm) Example 1 50 99.95 35 5 1.6 1.7 ≤2 Example 2 10 99.99 20 2 0.9 1.2 ≤2 Example 3 30 99.97 26 3 1.3 1.3 ≤2 Example 4 50 99.95 26 4 1.5 1.2 ≤2 Example 5 10 99.98 15 1 1.1 0.8 ≤2 Example 6 30 99.97 19 2 1.4 1.0 ≤2 Example 7 12 99.99 12 2 1.2 0.7 ≤2 Example 8 22 99.96 19 2 1.5 1.0 ≤2 Example 9 18 99.98 15 2 1.4 0.9 ≤2 Example 10 20 99.96 16 2 1.6 0.9 ≤2 Example 11 26 99.98 13 3 1.1 0.7 ≤2 Example 12 23 99.97 12 2 1.2 0.7 ≤2 Example 13 The preparation method of the potassium bis(fluorosulfonylimide) solution of this embodiment is basically the same as that of Example 1, except that: after obtaining molten potassium bis(fluorosulfonylimide) with a purity of 99.95%, the potassium bis(fluorosulfonylimide) is dissolved in a solvent at 5-15° C. to obtain the potassium bis(fluorosulfonylimide) solution. The specific preparation method is as follows: Add 60g of liquid hydrofluoric acid (maintained below 10°C) and 70g of potassium fluoride to a tetrafluoroethylene reactor equipped with a thermometer, a pressure gauge and a stirrer, and dropwise add 214g of bischlorosulfonyl imide acid. After completion, seal the reactor and heat it to 105°C for reaction. If the pressure gauge does not change within half an hour, stop the reaction and cool it down. When the temperature drops to 10°C, filter it once to obtain a filter cake. Heat the filter cake and filter it twice when the temperature rises to 105°C to obtain a filtrate. Purge the filtrate with nitrogen until an acidity of 5 is obtained. The crude potassium bisfluorosulfonyl imide with a concentration of 0 ppm was melt-purified. The specific method of melt purification was as follows: the molten potassium bisfluorosulfonyl imide was cooled to 10°C to form a solid, and then heated at a rate of 1°C per hour, and the purity of the molten liquid was monitored in real time until the purity reached 99.94% or more. The unmelted solid was collected and melted to obtain molten potassium bisfluorosulfonyl imide with a purity of 99.95%. Finally, the dissolution temperature was controlled at 5-15°C, and the molten potassium bisfluorosulfonyl imide was dissolved in 369.4 g of ethyl methyl carbonate (EMC) by dropwise addition to alleviate the exothermic phenomenon during dissolution, to obtain 527.8 g of a potassium bisfluorosulfonyl imide solution with a mass fraction of 30±0.5%.

[0038] Example 14 The preparation method of the potassium bis(fluorosulfonyl)imide solution in this example is basically the same as that in Example 2, except that: after obtaining molten potassium bis(fluorosulfonyl)imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the potassium bis(fluorosulfonyl)imide is dissolved in 363.8 g of EMC to obtain 519.7 g of potassium bis(fluorosulfonyl)imide solution with a mass fraction of 30±0.5%.

[0039] Example 15 The preparation method of the potassium bis(fluorosulfonyl)imide solution in this example is basically the same as that in Example 3, except that: after obtaining molten potassium bis(fluorosulfonyl)imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the potassium bis(fluorosulfonyl)imide is dissolved in 361.7 g of EMC to obtain 516.8 g of potassium bis(fluorosulfonyl)imide solution with a mass fraction of 30±0.5%.

[0040] Example 16 The preparation method of the potassium bis(fluorosulfonylimide) solution in this example is basically the same as that in Example 4, except that: after obtaining molten potassium bis(fluorosulfonylimide) with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the potassium bis(fluorosulfonylimide) is dissolved in 373.5 g of EMC to obtain 533.6 g of potassium bis(fluorosulfonylimide) solution with a mass fraction of 30±0.5%.

[0041] Example 17 The preparation method of the potassium bis(fluorosulfonylimide) solution in this example is basically the same as that in Example 5, except that: after obtaining molten potassium bis(fluorosulfonylimide) with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the potassium bis(fluorosulfonylimide) is dissolved in 372.4 g of EMC to obtain 532 g of a potassium bis(fluorosulfonylimide) solution with a mass fraction of 30±0.5%.

[0042] Example 18 The preparation method of the potassium bis(fluorosulfonyl)imide solution in this example is basically the same as that in Example 6, except that: after obtaining molten potassium bis(fluorosulfonyl)imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the potassium bis(fluorosulfonyl)imide is dissolved in 372.8 g of EMC to obtain 532.6 g of potassium bis(fluorosulfonyl)imide solution with a mass fraction of 30±0.5%.

[0043] Example 19 The preparation method of the sodium bisfluorosulfonyl imide solution in this example is basically the same as that in Example 7, except that: after obtaining molten sodium bisfluorosulfonyl imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15°C, and the sodium bisfluorosulfonyl imide is dissolved in 353.5g of EMC to obtain 505g of sodium bisfluorosulfonyl imide solution with a mass fraction of 30±0.5%.

[0044] Example 20 The preparation method of the sodium bisfluorosulfonyl imide solution in this example is basically the same as that in Example 8, except that: after obtaining molten sodium bisfluorosulfonyl imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15°C, and the sodium bisfluorosulfonyl imide is dissolved in 349.3g of EMC to obtain 499g of sodium bisfluorosulfonyl imide solution with a mass fraction of 30±0.5%.

[0045] Example 21 The preparation method of the sodium bisfluorosulfonyl imide solution in this example is basically the same as that in Example 9, except that after obtaining molten sodium bisfluorosulfonyl imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the sodium bisfluorosulfonyl imide is dissolved in 351.6 g of EMC to obtain 502.3 g of sodium bisfluorosulfonyl imide solution with a mass fraction of 30±0.5%.

[0046] Example 22 The preparation method of the lithium bis(fluorosulfonyl)imide solution in this example is basically the same as that in Example 10, except that after obtaining molten lithium bis(fluorosulfonyl)imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the lithium bis(fluorosulfonyl)imide is dissolved in 325.5 g of EMC to obtain 465 g of a lithium bis(fluorosulfonyl)imide solution with a mass fraction of 30±0.5%.

[0047] Example 23 The preparation method of the lithium bis(fluorosulfonyl)imide solution in this example is basically the same as that in Example 11, except that after obtaining molten lithium bis(fluorosulfonyl)imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15° C., and the lithium bis(fluorosulfonyl)imide is dissolved in 327.6 g of EMC to obtain 468 g of a lithium bis(fluorosulfonyl)imide solution with a mass fraction of 30±0.5%.

[0048] Example 24 The preparation method of the lithium bis(fluorosulfonyl)imide solution in this embodiment is basically the same as that in Example 12, except that: after obtaining molten lithium bis(fluorosulfonyl)imide with a purity of 99.99%, the dissolution temperature is controlled at 5-15°C, and the lithium bis(fluorosulfonyl)imide is dissolved in 326.9g of EMC to obtain 467g of lithium bis(fluorosulfonyl)imide solution with a mass fraction of 30±0.5%.

[0049] The test results of impurity components in the bis(fluorosulfonyl)imide salt solutions prepared in Examples 13 to 24 are shown in Table 2.

[0050] Table 2 Impurity components of the bis(fluorosulfonyl)imide salt solutions prepared in Examples 13 to 24 Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be 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 following steps are involved: The hydrofluoric acid, alkali metal fluoride and bis(chlorosulfonyl)imide are reacted under sealed conditions at a temperature above 100°C. After the reaction is completed, the temperature is lowered to below 10°C, filtered once to obtain a filter cake, then the temperature is raised to above 100°C, filtered twice to obtain a filtrate, and then impurities are removed to obtain bis(fluorosulfonyl)imide salt particles or a bis(fluorosulfonyl)imide salt solution.

2. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The reaction is carried out at 100-160°C; the temperature after cooling is -50-10°C; and the temperature after heating is 100-160°C.

3. The method for preparing a bisfluorosulfonyl imide salt according to claim 2, wherein: When preparing potassium bisfluorosulfonylimide, the reaction is carried out at 105-150°C, and the temperature after heating is 105-150°C; when preparing sodium bisfluorosulfonylimide, the reaction is carried out at 120-150°C, and the temperature after heating is 120-150°C; when preparing lithium bisfluorosulfonylimide, the reaction is carried out at 130-160°C, and the temperature after heating is 130-160°C.

4. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The molar ratio of the bischlorosulfonyl imide, hydrofluoric acid and alkali metal fluoride is 1: (2.5-4): (1-2).

5. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The impurity removal includes nitrogen purging and melting purification of the filtrate obtained by the secondary filtration.

6. The method for preparing a bisfluorosulfonyl imide salt according to claim 5, wherein: The melt purification is to cool the filtrate after nitrogen purge to form a solid and then heat it up to melt and remove impurities. After removing the molten liquid, the remaining solid is melted to obtain a molten bis(fluorosulfonyl)imide salt.

7. The method for preparing a bisfluorosulfonyl imide salt according to claim 6, wherein: The bisfluorosulfonyl imide salt particles are obtained by spray-drying molten bisfluorosulfonyl imide salt.

8. The method for preparing a bisfluorosulfonyl imide salt according to claim 6, wherein: The bisfluorosulfonyl imide salt solution is obtained by dissolving molten bisfluorosulfonyl imide salt in a solvent at 5-15° C.

9. The method for preparing a bisfluorosulfonyl imide salt according to claim 1, wherein: The reaction was stopped when the pressure in the reaction system did not change within half an hour.

10. The method for preparing a bisfluorosulfonyl imide salt according to claim 6, wherein: The purity of the molten bis(fluorosulfonyl)imide salt is ≥99.95%.

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