A preparation method of lithium bis(fluorosulfonyl)imide

Abstract

The invention discloses a method for preparing lithium bis(fluorosulfonyl)imide. The method for preparing lithium bis(fluorosulfonyl)imide of the invention comprises: step S1, mixing aminosulfonic acid, thionyl chloride and sulfur trioxide, and performing reduced pressure distillation to obtain bis(chlorosulfonyl)imide after the reaction; step S2, adding the bis(chlorosulfonyl)imide, antimony trifluoride and potassium carbonate to a polar solvent for reaction, and adjusting the pH value to neutral, performing solid-liquid separation, collecting the liquid phase, and obtaining a potassium bis(fluorosulfonyl)imide solution; step S3, adding a lithium perchlorate solution to the potassium bis(fluorosulfonyl)imide solution, performing solid-liquid separation, collecting the liquid phase, adding dichloromethane for recrystallization, and drying to obtain lithium bis(fluorosulfonyl)imide. The method for preparing lithium bis(fluorosulfonyl)imide of the invention has the advantages of high yield, low waste discharge, and meets the requirements for the development of the green chemical industry, and can be widely used in industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a method for preparing lithium bis(fluorosulfonyl)imide. Background Art

[0002] Lithium hexafluorophosphate is widely used as an electrolyte lithium salt in lithium-ion batteries. It has excellent ionic conductivity and electrochemical stability. However, lithium hexafluorophosphate has relatively poor thermal stability and easily decomposes in water to produce hydrofluoric acid. Lithium bis(fluorosulfonyl)imide (LiFSI) is a new type of electrolyte lithium salt with the molecular formula Li[N(SO2F)2]. It has excellent thermal stability and safety, and has good compatibility with electrodes. It is considered to be the most likely electrolyte lithium salt to replace lithium hexafluorophosphate.

[0003] In the related art, the mainstream preparation process of lithium bis(fluorosulfonyl)imide mainly uses aminosulfonic acid, thionyl chloride and chlorosulfonic acid as raw materials to first synthesize bis(chlorosulfonyl)imide, then mixes bis(chlorosulfonyl)imide with hydrogen fluoride to react to obtain bis(fluorosulfonyl)imide, and then reacts with lithium fluoride to obtain lithium bis(fluorosulfonyl)imide. The reaction formula is as follows:

[0004] NH2SO3H+2SOCl2+ClSO3H→(SO2Cl)2NH+2SO2↑+3HCl↑;

[0005] (SO2Cl)2NH+2HF→(SO2F)2NH+2HCl↑;

[0006] (SO2F)2NH+LiF=FSO2NLiSO2F+HF↑.

[0007] It can be seen that traditional lithium bis(fluorosulfonyl)imide will produce a large amount of hydrogen chloride waste gas during the preparation process, which is easy to pollute the environment and does not meet the development requirements of the green chemical industry.

[0008] Therefore, it is necessary to seek a preparation process for lithium bis(fluorosulfonyl)imide that meets the development requirements of the green chemical industry. Summary of the invention

[0009] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing lithium bis(fluorosulfonyl)imide, which has the advantages of high yield and low waste discharge, and meets the requirements for the development of the green chemical industry.

[0010] A method for preparing lithium bis(fluorosulfonyl)imide of the present invention comprises:

[0011] Step S1, mixing sulfamic acid, thionyl chloride and sulfur trioxide, and performing reduced pressure distillation after the reaction to obtain bischlorosulfonyl imide;

[0012] Step S2, adding the bis(chlorosulfonyl)imide, antimony trifluoride and potassium carbonate to a polar solvent for reaction, adjusting the pH value to neutral, separating the solid and the liquid, collecting the liquid phase, and obtaining a potassium bis(fluorosulfonyl)imide solution;

[0013] Step S3, adding lithium perchlorate solution to the potassium bis(fluorosulfonyl)imide solution, separating the solid and the liquid, collecting the liquid phase, adding dichloromethane for recrystallization, and drying to obtain lithium bis(fluorosulfonyl)imide.

[0014] The preparation method according to the embodiment of the present invention has at least the following beneficial effects:

[0015] (1) The present invention uses aminosulfonic acid, thionyl chloride and sulfur trioxide as initial raw materials to prepare bischlorosulfonyl imide. Compared with the traditional process using chlorosulfonic acid as the raw material, the process significantly reduces the emission of HCl waste gas by 1 / 3 and has a higher product recovery rate. The synthetic reaction route involved is:

[0016] NH2SO3H+2SOCl2+SO3→H[N(SO2Cl)2]+2SO2↑+2HCl↑.

[0017] In the present invention, sulfur dioxide and hydrogen chloride tail gas generated during the reaction are absorbed by a multi-stage absorption tower to obtain a by-product hydrochloric acid aqueous solution and sulfur dioxide gas, wherein the hydrochloric acid aqueous solution can be used for subsequent pH adjustment, and the sulfur dioxide can be recovered and applied to the thionyl chloride production process.

[0018] (2) In the process of preparing lithium bis(fluorosulfonyl)imide using bis(chlorosulfonyl)imide as raw material, the present invention generates Sb2O3 and KCl by adding antimony trifluoride and potassium carbonate. Since Sb2O3 and KCl are not easily soluble in organic solvents such as dimethyl carbonate and acetonitrile, they can be removed by a simple filtration method. This method not only effectively solves the technical problem of excessive HCl waste gas emissions caused by traditional hydrogen fluoride fluorination treatment, but also overcomes the operation and product purity problems caused by the easy sublimation of SbCl3. In addition, this process does not emit HCl and HF waste gas, which meets the requirements for the development of the green chemical industry. The synthetic reaction route involved in this process includes:

[0019] 6H[N(SO2Cl)2]+4SbF3+9K2CO3→6K[N(SO2F)2]+9CO2↑+2Sb2O3↓+12KCl↓+3H2O;

[0020] K[N(SO2F)2]+LiClO4→Li[N(SO2F)2]+KClO4↓.

[0021] (3) The method for preparing lithium bis(fluorosulfonyl)imide of the present invention is simple to operate, the product is easy to separate and purify, and has no environmental pollution, and is suitable for industrial mass production.

[0022] In some embodiments of the present invention, the molar ratio of aminosulfonic acid, thionyl chloride and sulfur trioxide is 1:0.8 to 1.5:1.

[0023] In some embodiments of the present invention, in step S1, the reaction temperature is 60 to 90°C;

[0024] Preferably, the reaction time is 6 to 12 hours;

[0025] Preferably, the reaction pressure is 0.1-0.5 MPa.

[0026] In some embodiments of the present invention, the temperature of the reduced pressure distillation is 110°C to 120°C;

[0027] Preferably, the pressure of the reduced pressure distillation is 1 to 5 mmHg.

[0028] In some embodiments of the present invention, in step S2, the polar solvent is at least one of dimethyl carbonate and acetonitrile.

[0029] In some embodiments of the present invention, the molar ratio of the bischlorosulfonyl imide, antimony trifluoride and potassium carbonate is 1:0.5 to 1:1.5 to 2.5.

[0030] In some embodiments of the present invention, in step S2, the reaction is carried out under inert gas conditions.

[0031] In some embodiments of the present invention, in step S2, a molecular sieve is added during the reaction to absorb water in order to improve the yield.

[0032] In some embodiments of the present invention, the reagent used to adjust the pH value is hydrochloric acid.

[0033] In some embodiments of the present invention, the solid-liquid separation method is vacuum filtration.

[0034] In some embodiments of the present invention, the lithium perchlorate solution is a dimethyl carbonate solution containing lithium perchlorate or an acetonitrile solution containing lithium perchlorate;

[0035] Preferably, the molar mass of the lithium perchlorate is 1.5 to 2.5.

[0036] In some embodiments of the present invention, the drying is vacuum drying; preferably, the drying temperature is 45-65°C.

[0037] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0039] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0040] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0041] Example 1

[0042] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0043] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 119 g (1 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0044] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112° C. / 2 mmHg, and obtaining 105.86 g of bischlorosulfonyl imide;

[0045] Step S3, under nitrogen protection, 105.86 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of dimethyl carbonate were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves (for absorbing water) were added, and the mixture was reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0046] Step S4, at 25°C, slowly dropwise add a 2 mol / L lithium perchlorate solution in dimethyl carbonate to the potassium bisfluorosulfonyl imide solution obtained above, stir the reaction for 18 hours and then let it stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 87.67 lithium bisfluorosulfonyl imide, with a yield of 94.74%.

[0047] Example 2

[0048] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0049] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 107.1 g (0.9 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0050] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112°C / 2 mmHg, and obtaining 103.49 g of bischlorosulfonyl imide;

[0051] Step S3, under nitrogen protection, 103.49 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of dimethyl carbonate were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves were added, and the mixture was reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0052] Step S4, at 25°C, slowly dropwise add a 2 mol / L lithium perchlorate solution in dimethyl carbonate to the potassium bisfluorosulfonyl imide solution obtained above, stir the reaction for 18 hours and then let it stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 86.5 lithium bisfluorosulfonyl imide, with a yield of 93.48%.

[0053] Example 3

[0054] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0055] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 148.75 g (1.25 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0056] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112°C / 2 mmHg, and obtaining 104.34 g of bischlorosulfonyl imide;

[0057] Step S3, under nitrogen protection, 104.34 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of dimethyl carbonate were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves were added, reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0058] Step S4, at 25°C, slowly dropwise add a 2 mol / L lithium perchlorate solution in dimethyl carbonate to the potassium bisfluorosulfonyl imide solution obtained above, stir the reaction for 18 hours and then let it stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 87.20 lithium bisfluorosulfonyl imide, with a yield of 94.24%.

[0059] Example 4

[0060] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0061] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 119 g (1 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0062] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112°C / 2 mmHg, and obtaining 105.74 g of bischlorosulfonyl imide;

[0063] Step S3, under nitrogen protection, 105.74 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of dimethyl carbonate were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves were added, reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0064] Step S4, at 25°C, slowly dropwise add a 1.8 mol / L dimethyl carbonate solution containing lithium perchlorate to the above-obtained potassium bisfluorosulfonyl imide solution, stir the reaction for 18 hours and then let it stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, and then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 85.63 lithium bisfluorosulfonyl imide, with a yield of 92.54%.

[0065] Example 5

[0066] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0067] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 119 g (1 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0068] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112°C / 2 mmHg, and obtaining 105.65 g of bischlorosulfonyl imide;

[0069] Step S3, under nitrogen protection, 105.65 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of dimethyl carbonate were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves were added, and the mixture was reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0070] Step S4, at 25°C, slowly dropwise add a 2.5 mol / L dimethyl carbonate solution containing lithium perchlorate into the above-obtained potassium bisfluorosulfonyl imide solution, stir the reaction for 18 hours and then let it stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, and then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 86.45 lithium bisfluorosulfonyl imide, with a yield of 93.43%.

[0071] Example 6

[0072] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0073] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 119 g (1 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0074] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112°C / 2 mmHg, and obtaining 105.79 g of bischlorosulfonyl imide;

[0075] Step S3, under nitrogen protection, 105.79 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of acetonitrile were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves were added, reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0076] Step S4, at 25°C, slowly dropwise add 2 mol / L lithium perchlorate in acetonitrile solution to the potassium bisfluorosulfonyl imide solution obtained above, stir the reaction for 18 hours and then stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 86.47 lithium bisfluorosulfonyl imide, with a yield of 93.45%.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0079] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid, 119 g (1 mol) of thionyl chloride and 58.28 g (0.5 mol) of chlorosulfonic acid to a reaction kettle, and incubating at 120° C. for 24 h to obtain a bischlorosulfonyl imide solution;

[0080] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112° C. / 2 mmHg, and obtaining 92.62 g of bischlorosulfonyl imide;

[0081] Step S3, under nitrogen protection, 92.62 g of the above-mentioned bis(chlorosulfonyl)imide, 89 g of anhydrous antimony trifluoride and 300 mL of dimethyl carbonate were mixed, stirred until most of the solid was dissolved, and then 138 g of anhydrous potassium carbonate and an appropriate amount of molecular sieves were added, reacted for 12 h under stirring conditions, the pH was adjusted to neutral, and the precipitate was removed by filtration under reduced pressure to obtain a potassium bis(fluorosulfonyl)imide solution;

[0082] Step S4, at 25°C, slowly dropwise add a 2 mol / L lithium perchlorate solution in dimethyl carbonate to the potassium bisfluorosulfonyl imide solution obtained above, stir the reaction for 18 hours and then let it stand overnight, remove the insoluble potassium perchlorate by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2 and vacuum dry to obtain 74.61 lithium bisfluorosulfonyl imide, with a yield of 80.63%.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing lithium bis(fluorosulfonyl)imide, which specifically comprises the following steps:

[0085] Step S1, adding 48.55 g (0.5 mol) of aminosulfonic acid and 119 g (1 mol) of thionyl chloride to a reactor, stirring at 65° C. and 0.2 MPa until the aminosulfonic acid is dissolved, then adding 40 g of sulfur trioxide, reacting at 85° C. and 0.4 MPa for 6 h to obtain a bischlorosulfonyl imide solution;

[0086] Step S2, distilling the bischlorosulfonyl imide solution under reduced pressure, collecting the fraction at 112° C. / 2 mmHg, and obtaining 104.84 g of bischlorosulfonyl imide;

[0087] Step S3, under nitrogen protection, 104.84 g of the above-mentioned bis(chlorosulfonyl)imide and 0.085 g of antimony pentachloride were mixed, the temperature was raised to 90° C., 20 g of anhydrous hydrofluoric acid gas was slowly introduced under stirring, the temperature was lowered to 25° C. after reacting for 20 h, and 80 g of bis(fluorosulfonyl)imide acid was obtained by distillation;

[0088] Step S4, add 200 mL of dimethyl carbonate solution to the above-mentioned bisfluorosulfonyl imide acid, stir thoroughly, add 14 g of lithium fluoride, react for 12 h and then stand overnight, remove the remaining lithium fluoride by vacuum filtration to obtain a lithium bisfluorosulfonyl imide solution, and then concentrate the lithium bisfluorosulfonyl imide solution to about 60 mL, add an equal volume of CH2Cl2 for recrystallization, filter, wash with CH2Cl2, and vacuum dry to obtain 78.33 lithium bisfluorosulfonyl imide, with a yield of 84.64%.

[0089] Test example

[0090] The lithium bis(fluorosulfonyl)imide prepared in Examples 1 to 6 of the present invention and Comparative Examples 1 to 2 were tested, and the yield and the three waste contents were statistically analyzed.

[0091] The reaction yield is calculated based on the percentage of nitrogen, specifically by adding water to the sample to fully hydrolyze it, titrating it with sodium nitrite solution, and using starch potassium iodide as an indicator;

[0092] The test results are shown in Table 1.

[0093] Table 1: Test results

[0094]

[0095] It can be seen from Table 1 that the method of the present invention for preparing lithium bis(fluorosulfonyl)imide has the advantage of high yield, and during the preparation process, chloride ions are removed in the form of potassium chloride, which effectively reduces the emission of waste gases such as hydrogen chloride.

[0096] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing lithium bis(fluorosulfonyl)imide, characterized in that: include: Step S1, mixing sulfamic acid, thionyl chloride and sulfur trioxide, and performing reduced pressure distillation after the reaction to obtain bischlorosulfonyl imide, wherein the reaction temperature is 85° C., the time is 6-12 hours, and the pressure is 0.1-0.5 MPa. During the reduced pressure distillation, the temperature of the fraction of the bischlorosulfonyl imide collected is 112° C. and the pressure is 2 mmHg; Step S2, adding the bischlorosulfonyl imide, antimony trifluoride, potassium carbonate and molecular sieve into a polar solvent for reaction, adjusting the pH value to neutral, separating the solid and the liquid, collecting the liquid phase, and obtaining a potassium bischlorosulfonyl imide solution, wherein the mass ratio of the bischlorosulfonyl imide, antimony trifluoride and potassium carbonate is 103.49, 104.34, 105.65, 105.74, 105.79 or 105.86:89:138; Step S3, adding lithium perchlorate solution to the potassium bis(fluorosulfonyl)imide solution, separating the solid and the liquid, collecting the liquid phase, adding dichloromethane for recrystallization, and drying to obtain lithium bis(fluorosulfonyl)imide.

2. The method according to claim 1, characterized in that The temperature of the reduced pressure distillation is 110° C. to 120° C. and the pressure is 1 to 5 mmHg.

3. The method according to claim 1 or 2, characterized in that: In step S2, the polar solvent is at least one of dimethyl carbonate and acetonitrile.

4. The method according to claim 3, characterized in that In step S2, the reaction is carried out under inert gas conditions.

5. The method according to claim 3, characterized in that: The solid-liquid separation method is vacuum filtration.

6. The method according to claim 3, characterized in that The lithium perchlorate solution is a dimethyl carbonate solution containing lithium perchlorate or an acetonitrile solution containing lithium perchlorate.

7. The method according to claim 6, characterized in that The molar mass of the lithium perchlorate is 1.5-2.

5.

8. The method according to claim 4, characterized in that The drying is vacuum drying.

9. The method according to claim 8, characterized in that The drying temperature is 45-65°C.

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