A method for synthesizing and purifying lithium bisfluorosulfonimide

Abstract

The present application relates to a kind of synthesis and purification method of lithium bisfluorosulfonylimide;The reaction temperature of the present application is lower, belongs to low energy consumption process, and process is simple, and less waste;Lithium bisfluorosulfonylimide prepared in the present application contains dicarboxylic acid / titanium complex, heptanal, weakly basic anion exchange resin, to absorb trace amount of chloride ion in lithium salt.The weakly basic anion exchange resin of the present application first absorbs chloride ion in solution by its weakly basic group, which is an ion exchange process, wherein the weakly basic group on the resin exchanges with chloride ion;Dicarboxylic acid / titanium complex and heptanal play a synergistic role in this process, dicarboxylic acid / titanium complex forms complex with chloride ion, thereby reducing its concentration in solution, so that it is more easily absorbed by resin;Aldehyde group is further promoted by competing with chloride ion to be absorbed on the resin, the adsorption of chloride ion.

Description

Technical Field

[0001] This invention relates to the field of environmental protection, and in particular to a method for the synthesis and purification of lithium bis(fluorosulfonyl)imide. Background Technology

[0002] Lithium-ion batteries possess numerous advantages, including high operating voltage, high energy density, long cycle life, and rapid charge / discharge capabilities. They are widely used in mobile phones, laptops, and small power tools, and are rapidly expanding into new energy electric vehicles and large-scale energy storage power stations. Current lithium-ion batteries typically use lithium hexafluorophosphate (LiPF6) as the electrolyte. However, LiPF6 is highly sensitive to moisture, and its preparation and usage conditions are quite demanding, requiring a completely moisture-free environment, which leads to a series of problems.

[0003] Chinese Patent CN117699748A discloses a method for preparing high-purity lithium difluorosulfonylimide, belonging to the fields of chemical synthesis and lithium battery technology. Dichlorosulfonylimide is prepared by heating and stirring under reflux with aminosulfonic acid, sulfonium chloride, and chlorosulfonic acid. The dichlorosulfonylimide is then fluorinated and concentrated in a good solvent. After concentration to a certain level, a poor solvent is added for crystallization. The crystals are filtered to obtain crude difluorosulfonylimide. The crude product is then lithiated with alkaline lithium to form a salt, followed by slurrying with dichloromethane solvent. After filtration and drying, lithium difluorosulfonylimide is obtained.

[0004] Chinese Patent CN117446762A discloses a method for preparing lithium bisfluorosulfonylimide, aiming to provide a method for preparing lithium bisfluorosulfonylimide by replacing the ammonium salt of bisfluorosulfonylimide with an easily separable N-alkylbisfluorosulfonylimide and reacting it with lithium salt. The preparation steps are short, the entire separation and purification process is simple and easy to implement, and the material hazard level is relatively low. The technical solution is: N-alkylbisfluorosulfonylimide and basic lithium salt are used as raw materials and reacted in organic solvent A at room temperature; it relates to the field of new energy technology.

[0005] Chinese Patent CN117105187A discloses a method for preparing high-purity, low-water lithium difluorosulfonylimide. The method includes: S1, dissolving crude lithium difluorosulfonylimide in an organic solvent to obtain solution A; S2, adding a dehydrating agent to solution A to obtain solution B; S3, adding activated carbon to solution B, stirring, filtering, concentrating the filtrate, crystallizing, and drying to obtain a high-purity, low-water lithium difluorosulfonylimide product; or the method is as follows: S1, dissolving crude lithium difluorosulfonylimide in an organic solvent to obtain solution C; S2, adding activated carbon powder to solution C, stirring, filtering, pumping the filtrate into a lithium molecular sieve column, filtering the received solution a second time, concentrating the filtrate, adding anhydrous dichloromethane to crystallize, and drying to obtain a high-purity, low-water lithium difluorosulfonylimide product.

[0006] The above-mentioned patents and existing technologies, the preparation technology of lithium bis(fluorosulfonyl)imide, will generate a large amount of corrosive gas HF, and the product contains HF, LiF and LiFSI at the same time, which are not easy to separate. The residual HF in the electrolyte will have an adverse effect on the lithium battery. Summary of the Invention

[0007] To address the above problems, this invention provides a method for the synthesis and purification of lithium bis(fluorosulfonyl)imide, the steps of which are as follows:

[0008] S1: Add 150-200 parts by weight of dichlorosulfonamide and 40-50 parts by weight of pyridine to the fluorination reactor. Control the temperature of the fluorination reactor at 0-5℃, start stirring, and slowly add 80-100 parts by weight of pyridine hydrofluoric acid salt to the fluorination reactor. At this time, maintain the temperature inside the reactor at 20-25℃. After the reaction is completed, filter. Add 200-300 parts by weight of deionized water to the filtrate, let it stand to separate into layers, and the lower layer is the dichlorosulfonamide pyridine salt.

[0009] S2: Add 70-90 parts of water and 10-20 parts of lithium hydroxide monohydrate to the fluorination reactor, stir, and slowly add 80-100 parts of bis(fluorosulfonyl)imide pyridine salt. At this time, maintain the temperature inside the reactor at 30-35℃. After the reaction is completed, add 5-10 parts of dechlorination adsorption resin, stir for 30-60 minutes, filter, and distill the filtrate to remove pyridine, and obtain crude bis(fluorosulfonyl)imide lithium.

[0010] The reaction time of S1 is 1-3 hours.

[0011] The reaction time of S2 is 10-15 hours.

[0012] The purification method of lithium bis(fluorosulfonyl)imide:

[0013] H1: Dissolve 30-50 parts of crude lithium difluorosulfonylimide in 100-200 parts of solvent by stirring, filter, cool, and crystallize.

[0014] H2: Add 80-100 parts of dichloroethane to the crystallized lithium bisfluorosulfonylimide, filter, take the filter cake, dry it, and obtain high-purity lithium bisfluorosulfonylimide.

[0015] The solvent is one or more of 18-crown-6, 15-crown-6, acetonitrile, diethyl ether, ethylene glycol dimethyl ether, isopropyl ether, and methyl ethyl carbonate.

[0016] The crystallization time is 20-30 hours.

[0017] The drying temperature is 50-70℃ and the time is 20-25h.

[0018] The preparation method of the dechlorination adsorption resin is as follows:

[0019] By weight, 100-150 parts of weakly basic acrylic anion exchange resin are placed in 500-1000 parts of toluene, followed by 0.05-0.5 parts of ethylene oxide dicarboxylic acid / titanium complex, 0.5-2.5 parts of 2,3-epoxyheptanal, and 3-6 parts of 1,8-bis(dimethylaminonaphthalene). The mixture is stirred at 50-60℃ for 40-100 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin.

[0020] The preparation method of the ethylene oxide dicarboxylic acid / titanium complex is as follows:

[0021] Weigh 20-40 parts of 2,3-ethylene oxide dicarboxylic acid, 34-68 parts of n-butyl titanate, 2-4 parts of methanol, and 200-300 parts of cyclohexane and place them in a sealed reactor. Stir at 30-40℃ for 30-60 min, and remove cyclohexane by distillation to obtain the ethylene oxide dicarboxylic acid / titanium complex.

[0022] The weakly basic acrylic anion exchange resin is a commercially available product, such as AmberliteIRA-68, AP49, and D315 macroporous weakly basic acrylic anion exchange resin.

[0023] Reaction mechanism

[0024] The weakly basic acrylic anion exchange resin is a macroporous methyl acrylate copolymer crosslinked polymer. It is a polyamine-based weakly basic anion exchange resin obtained through the aminolysis of polyethylenepolyamine. It undergoes an amino-epoxy reaction with an ethylene oxide dicarboxylic acid / titanium complex, followed by an amino-epoxy reaction with 2,3-epoxyheptanal. 1,8-bis(dimethylaminonaphthalene) is used as an organic base catalyst. The mixture is stirred at 50-60℃ for 40-100 minutes, filtered, and dried to obtain a weakly basic anion exchange resin containing the dicarboxylic acid / titanium complex and heptanal, which can adsorb trace amounts of chloride ions from lithium salts.

[0025] Technical effect

[0026] The present invention provides a method for the synthesis and purification of lithium bis(fluorosulfonyl)imide. Compared with the prior art, the present invention has the following significant advantages:

[0027] 1. The reaction temperature of this invention is relatively low, which is a low-energy-consumption process. The process is also simple and produces little waste.

[0028] 2. The lithium difluorosulfonylimide prepared by this invention contains a dicarboxylic acid / titanium complex, heptanal, and a weakly basic anion exchange resin, which is used to adsorb trace amounts of chloride ions in lithium salts.

[0029] 3. The weakly basic anion exchange resin of the present invention first adsorbs chloride ions in the solution through its weakly basic groups. This is an ion exchange process in which the weakly basic groups on the resin exchange with chloride ions. The dicarboxylic acid / titanium complex and heptanal play a synergistic role in this process. The dicarboxylic acid / titanium complex forms a complex with chloride ions, thereby reducing their concentration in the solution and making them easier for the resin to adsorb. The aldehyde group further promotes the adsorption of chloride ions by competing with chloride ions for adsorption on the resin. Attached Figure Description

[0030] Figure 1 FT-IR image of the product prepared in Example 2. Located at 3450 and 1634 cm⁻¹. -1 The peaks at 1385 and 575 cm are attributed to water. -1 The peaks at 1222, 1185, and 1114 cm⁻¹ are attributed to the asymmetric tensile and bending vibrations of -SO₂. -1 The peak at 851 cm⁻¹ is attributed to the symmetric tensile vibration of -SO₂. -1 The peak at 775 cm⁻¹ is attributed to the SNS asymmetric tensile vibration. -1 The peak at that point is attributed to the tensile vibration of SF. Detailed Implementation

[0031] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0032] The testing shall be conducted in accordance with Q / DFD0019-2017.

[0033] Example 1

[0034] A method for the synthesis and purification of lithium difluorosulfonylimide, comprising the following steps:

[0035] S1: Add 150g of dichlorosulfonyl imide and 40g of pyridine to the fluorination reactor. Control the temperature of the fluorination reactor at 0℃ and start stirring. Slowly add 80g of pyridine hydrofluoric acid salt to the fluorination reactor while maintaining the temperature inside the reactor at 20℃. After the reaction is complete, filter the solution. Add 200g of deionized water to the filtrate and let it stand to separate into layers. The lower layer is the dichlorosulfonyl imide pyridine salt.

[0036] S2: Add 70g of water and 10g of lithium hydroxide monohydrate to the fluorination reactor, stir, and slowly add 80g of bis(fluorosulfonyl)imide pyridine salt. At this time, maintain the temperature inside the reactor at 30℃. After the reaction is completed, add 5g of dechlorination adsorption resin, stir for 30 minutes, filter, and distill the filtrate to remove pyridine, and obtain crude bis(fluorosulfonyl)imide lithium.

[0037] The reaction time of S1 is 1 hour.

[0038] The reaction time of S2 is 10 hours.

[0039] The purification method of lithium bis(fluorosulfonyl)imide:

[0040] H1: Dissolve 30g of crude lithium difluorosulfonylimide in 100g of solvent by stirring, filter, cool, and crystallize.

[0041] H2: Add 80g of dichloroethane to the crystallized lithium bisfluorosulfonylimide, filter, take the filter cake, dry it, and obtain high-purity lithium bisfluorosulfonylimide.

[0042] The solvent is 18-crown-6.

[0043] The crystallization time is 20 hours.

[0044] The drying temperature is 50℃ and the time is 20 hours.

[0045] The preparation method of the dechlorination adsorption resin is as follows:

[0046] 100g of weakly basic acrylic anion exchange resin was placed in 500g of toluene, and then 0.05g of ethylene oxide dicarboxylic acid / titanium complex, 0.5g of 2,3-epoxyheptanal, and 3g of 1,8-bis(dimethylaminonaphthalene) were added. The mixture was stirred at 50℃ for 40 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin.

[0047] The preparation method of the ethylene oxide dicarboxylic acid / titanium complex is as follows:

[0048] Weigh 20g of 2,3-ethylene oxide dicarboxylic acid, 34g of tetrabutyl titanate, 2g of methanol, and 200g of cyclohexane and place them in a sealed reaction vessel. Stir at 30°C for 30 minutes and remove cyclohexane by distillation to obtain the ethylene oxide dicarboxylic acid / titanium complex.

[0049] The weakly basic acrylic anion exchange resin is the commercially available product AmberliteIRA-68 macroporous weakly basic acrylic anion exchange resin.

[0050] Example 2

[0051] A method for the synthesis and purification of lithium difluorosulfonylimide, comprising the following steps:

[0052] S1: Add 160g of dichlorosulfonamide and 43g of pyridine to the fluorination reactor. Control the temperature of the fluorination reactor at 0℃ and start stirring. Slowly add 85g of pyridine hydrofluoric acid salt to the fluorination reactor while maintaining the temperature inside the reactor at 22℃. After the reaction is complete, filter the solution. Add 240g of deionized water to the filtrate and let it stand to separate into layers. The lower layer is the dichlorosulfonamide pyridine salt.

[0053] S2: Add 75g of water and 13g of lithium hydroxide monohydrate to the fluorination reactor, stir, and slowly add 85g of bis(fluorosulfonyl)imide pyridine salt. At this time, maintain the temperature inside the reactor at 30℃. After the reaction is completed, add 6g of dechlorination adsorption resin, stir for 40 minutes, filter, and distill the filtrate to remove pyridine, and obtain crude bis(fluorosulfonyl)imide lithium.

[0054] The reaction time of S1 is 2 hours.

[0055] The reaction time of S2 is 12 hours.

[0056] The purification method of lithium bis(fluorosulfonyl)imide:

[0057] H1: Dissolve 35g of crude lithium difluorosulfonylimide in 140g of solvent by stirring, filter, cool, and crystallize.

[0058] H2: Add 85g of dichloroethane to the crystallized lithium bisfluorosulfonylimide, filter, take the filter cake, dry it, and obtain high-purity lithium bisfluorosulfonylimide.

[0059] The solvent is acetonitrile.

[0060] The crystallization time is 24 hours.

[0061] The drying temperature is 55℃ and the time is 22 hours.

[0062] The preparation method of the dechlorination adsorption resin is as follows:

[0063] 110g of weakly basic acrylic anion exchange resin was placed in 600g of toluene, and then 0.2g of ethylene oxide dicarboxylic acid / titanium complex, 1g of 2,3-epoxyheptanal, and 4g of 1,8-bis(dimethylaminonaphthalene) were added. The mixture was stirred at 55℃ for 50 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin.

[0064] The preparation method of the ethylene oxide dicarboxylic acid / titanium complex is as follows:

[0065] Weigh 25g of 2,3-ethylene oxide dicarboxylic acid, 46g of tetrabutyl titanate, 3g of methanol, and 240g of cyclohexane and place them in a sealed reaction vessel. Stir at 35°C for 40 minutes and remove cyclohexane by distillation to obtain the ethylene oxide dicarboxylic acid / titanium complex.

[0066] The weakly basic acrylic anion exchange resin is the commercially available AP49 macroporous weakly basic acrylic anion exchange resin.

[0067] Example 3

[0068] A method for the synthesis and purification of lithium difluorosulfonylimide, comprising the following steps:

[0069] S1: Add 190g of dichlorosulfonamide and 48g of pyridine to the fluorination reactor, control the temperature of the fluorination reactor at 5℃, start stirring, and slowly add 95g of pyridine hydrofluoric acid salt to the fluorination reactor while maintaining the temperature inside the reactor at 25℃. After the reaction is complete, filter; add 280g of deionized water to the filtrate, let it stand to separate into layers, and the lower layer is the dichlorosulfonamide pyridine salt.

[0070] S2: Add 85g of water and 18g of lithium hydroxide monohydrate to the fluorination reactor, stir, and slowly add 95g of bis(fluorosulfonyl)imide pyridine salt. At this time, maintain the temperature inside the reactor at 35℃. After the reaction is completed, add 8g of dechlorination adsorption resin, stir for 50 minutes, filter, and distill the filtrate to remove pyridine, and obtain crude bis(fluorosulfonyl)imide lithium.

[0071] The reaction time of S1 is 2 hours.

[0072] The reaction time of S2 is 14 hours.

[0073] The purification method of lithium bis(fluorosulfonyl)imide:

[0074] H1: 45g of crude lithium difluorosulfonylimide was stirred and dissolved in 180g of solvent, filtered, cooled, and crystallized.

[0075] H2: Add 95g of dichloroethane to the crystallized lithium bisfluorosulfonylimide, filter, take the filter cake, dry it, and obtain high-purity lithium bisfluorosulfonylimide.

[0076] The solvent is ethylene glycol dimethyl ether.

[0077] The crystallization time is 28 hours.

[0078] The drying temperature is 65℃ and the time is 24 hours.

[0079] The preparation method of the dechlorination adsorption resin is as follows:

[0080] 140g of weakly basic acrylic anion exchange resin was placed in 800g of toluene, and then 0.4g of ethylene oxide dicarboxylic acid / titanium complex, 2g of 2,3-epoxyheptanal, and 5g of 1,8-bis(dimethylaminonaphthalene) were added. The mixture was stirred at 55℃ for 80 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin.

[0081] The preparation method of the ethylene oxide dicarboxylic acid / titanium complex is as follows:

[0082] Weigh 35g of 2,3-ethylene oxide dicarboxylic acid, 58g of tetrabutyl titanate, 3g of methanol, and 280g of cyclohexane and place them in a sealed reaction vessel. Stir at 35°C for 50 minutes and remove cyclohexane by distillation to obtain the ethylene oxide dicarboxylic acid / titanium complex.

[0083] The weakly basic acrylic anion exchange resin is the commercially available AP49 macroporous weakly basic acrylic anion exchange resin.

[0084] Example 4

[0085] A method for the synthesis and purification of lithium difluorosulfonylimide, comprising the following steps:

[0086] S1: Add 200g of dichlorosulfonyl imide and 50g of pyridine to the fluorination reactor, control the temperature of the fluorination reactor at 5℃, start stirring, slowly add 100g of pyridine hydrofluoric acid salt to the fluorination reactor, at this time maintain the temperature inside the reactor at 25℃, after the reaction is completed, filter; add 300g of deionized water to the filtrate, let it stand to separate into layers, the lower layer is dichlorosulfonyl imide pyridine salt;

[0087] S2: Add 90g of water and 20g of lithium hydroxide monohydrate to the fluorination reactor, stir, and slowly add 100g of bis(fluorosulfonyl)imide pyridine salt. At this time, maintain the temperature inside the reactor at 35℃. After the reaction is completed, add 10g of dechlorination adsorption resin, stir for 60 minutes, filter, and distill the filtrate to remove pyridine, and obtain crude bis(fluorosulfonyl)imide lithium.

[0088] The reaction time of S1 is 3 hours.

[0089] The reaction time of S2 is 15 hours.

[0090] The purification method of lithium bis(fluorosulfonyl)imide:

[0091] H1: Dissolve 50g of crude lithium difluorosulfonylimide in 200g of solvent by stirring, filter, cool, and crystallize.

[0092] H2: Add 100g of dichloroethane to the crystallized lithium bisfluorosulfonylimide, filter, take the filter cake, dry it, and obtain high-purity lithium bisfluorosulfonylimide.

[0093] The solvent is ethyl methyl carbonate.

[0094] The crystallization time is 30 hours.

[0095] The drying temperature is 70℃ and the time is 25 hours.

[0096] The preparation method of the dechlorination adsorption resin is as follows:

[0097] 150g of weakly basic acrylic anion exchange resin was placed in 1000g of toluene, and then 0.5g of ethylene oxide dicarboxylic acid / titanium complex, 2.5g of 2,3-epoxyheptanal, and 6g of 1,8-bis(dimethylaminonaphthalene) were added. The mixture was stirred at 60℃ for 100 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin.

[0098] The preparation method of the ethylene oxide dicarboxylic acid / titanium complex is as follows:

[0099] Weigh 40g of 2,3-ethylene oxide dicarboxylic acid, 68g of tetrabutyl titanate, 4g of methanol, and 300g of cyclohexane and place them in a sealed reaction vessel. Stir at 40°C for 60 minutes and remove cyclohexane by distillation to obtain the ethylene oxide dicarboxylic acid / titanium complex.

[0100] The weakly basic acrylic anion exchange resin is the commercially available product D315 macroporous weakly basic acrylic anion exchange resin.

[0101] Comparative Example 1

[0102] No dechlorination adsorption resin was added; otherwise, it was the same as in Example 1.

[0103] Comparative Example 2

[0104] Without the addition of ethylene oxide dicarboxylic acid / titanium complex, otherwise the same as in Example 1.

[0105] Comparative Example 3

[0106] Without adding 2,3-epoxyheptanal, otherwise the same as in Example 1.

[0107]

[0108] The data from the above examples and comparative examples demonstrate that the lithium bis(fluorosulfonyl)imide prepared by this invention has a high content and low content of impurities such as moisture, chloride, free acid, and insoluble matter.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for the synthesis and purification of lithium difluorosulfonylimide, comprising the following steps: S1: Add 150-200 parts by weight of dichlorosulfonamide and 40-50 parts by weight of pyridine to the fluorination reactor. Control the temperature of the fluorination reactor at 0-5℃, start stirring, and slowly add 80-100 parts by weight of pyridine hydrofluoric acid salt to the fluorination reactor. At this time, maintain the temperature inside the reactor at 20-25℃. After the reaction is completed, filter. Add 200-300 parts by weight of deionized water to the filtrate, let it stand to separate into layers, and the lower layer is the dichlorosulfonamide pyridine salt. S2: Add 70-90 parts of water and 10-20 parts of lithium hydroxide monohydrate to the fluorination reactor, stir, and slowly add 80-100 parts of bis(fluorosulfonyl)imide pyridine salt. At this time, maintain the temperature inside the reactor at 30-35℃. After the reaction is completed, add 5-10 parts of dechlorination adsorption resin, stir for 30-60 minutes, filter, and distill the filtrate to remove pyridine to obtain crude bis(fluorosulfonyl)imide lithium. The purification method of lithium bis(fluorosulfonyl)imide: H1: Dissolve 30-50 parts of crude lithium difluorosulfonylimide in 100-200 parts of solvent by stirring, filter, cool, and crystallize. H2: Add 80-100 parts of dichloroethane to the crystallized lithium difluorosulfonylimide, filter, take the filter cake, dry it, and obtain high-purity lithium difluorosulfonylimide; The preparation method of the dechlorination adsorption resin is as follows: 100-150 parts by weight of weakly basic acrylic anion exchange resin are placed in 500-1000 parts of toluene, and then 0.05-0.5 parts of ethylene oxide dicarboxylic acid / titanium complex, 0.5-2.5 parts of 2,3-epoxyheptanal, and 3-6 parts of 1,8-bis(dimethylaminonaphthalene) are added. The mixture is stirred at 50-60℃ for 40-100 minutes, filtered, washed, and dried to obtain the dechlorination adsorption resin. The preparation method of the ethylene oxide dicarboxylic acid / titanium complex is as follows: Weigh 20-40 parts of 2,3-ethylene oxide dicarboxylic acid, 34-68 parts of n-butyl titanate, 2-4 parts of methanol, and 200-300 parts of cyclohexane and place them in a closed reaction vessel. Stir at 30-40℃ for 30-60 min, and remove the cyclohexane by distillation to obtain the ethylene oxide dicarboxylic acid / titanium complex.

2. The method for synthesizing and purifying lithium bisfluorosulfonimide according to claim 1, characterized in that: The reaction time of S1 is 1-3 hours.

3. The method for synthesizing and purifying lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The reaction time of S2 is 10-15 hours.

4. The method for synthesizing and purifying lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The solvent for purifying the lithium bis(fluorosulfonyl)imide is one or more selected from 18-crown-6, 15-crown-6, acetonitrile, diethyl ether, ethylene glycol dimethyl ether, isopropyl ether, and methyl ethyl carbonate.

5. The method for synthesizing and purifying lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The purification and crystallization time of the lithium difluorosulfonylimide is 20-30 h.

6. The method for synthesizing and purifying lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The purification and drying of the lithium difluorosulfonylimide was carried out at a temperature of 50-70°C for 20-25 hours.

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