A method for preparing lithium bisfluorosulfonimide

Abstract

The present application relates to a kind of preparation method of lithium bisfluorosulfonylimide, belong to lithium ion battery additive technical field.The preparation method of lithium bisfluorosulfonylimide of the present application, lithium bisfluorosulfonylimide and lithiating agent are reacted in nonpolar organic solvent, water is not introduced in the reaction process, and lithium bisfluorosulfonylimide generated in the reaction is precipitated in solid form, lithium bisfluorosulfonylimide crude product can be separated by solid-liquid separation, with the advantages of simple operation, mild reaction condition, little three wastes, environmental friendly, and it is beneficial to improve the yield of product.Lithium bisfluorosulfonylimide crude product is washed, and drying can remove the carboxylic acid generated in the reaction, and improve the purity of product.In addition, the free acid, fluoride ion, chloride ion and other impurities in the lithium bisfluorosulfonylimide prepared by the present application can be controlled at a low level.Because water is not introduced in the reaction process, the water content of the prepared lithium bisfluorosulfonylimide is low.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of lithium bisfluorosulfonylimide, and belongs to the technical field of lithium ion battery additives. BACKGROUND

[0002] An electrolyte solution is an important component of a lithium ion battery. Optimization and improvement of an electrolyte system can improve the composition of an SEI film on an electrode surface and the performance of a battery, thereby improving the reversible capacity of the battery, the cycle life of the battery, and the charge-discharge performance of an electrode. Lithium bisfluorosulfonylimide has suitable electrical conductivity and thermal stability, and can be used in an electrolyte of a rechargeable lithium battery to improve the comprehensive performance of the lithium ion battery. Therefore, lithium bisfluorosulfonylimide is a key high-performance electrolyte material in new energy devices and has high application value.

[0003] At present, lithium bisfluorosulfonylimide is mainly prepared by a lithiation reaction. For example, Chinese Patent Document CN114180542A discloses a preparation method of lithium bisfluorosulfonylimide, which comprises the following steps: 1) reacting aminodisulfonyl chloride with hydrogen fluoride to obtain bisfluorosulfonylimide; and 2) reacting the bisfluorosulfonylimide with lithium carbonate to obtain lithium bisfluorosulfonylimide. Chinese Patent Document CN102917979A discloses an alkali metal salt of fluorosulfonylimide and a preparation method thereof. In the patent, when lithium bisfluorosulfonylimide is prepared, an ammonium bisfluorosulfonylimide butyl acetate solution is reacted with a lithium hydroxide aqueous solution to obtain a butyl acetate solution of LIFSI, then the solution is concentrated, and finally, a poor solvent, toluene, is added to produce a precipitate. After filtration and drying, LIFSI is obtained. In the preparation of lithium bisfluorosulfonylimide, a large amount of LIFSI is decomposed, the purity and yield of the product are low, and the residual solvent butyl acetate is difficult to remove, which affects the quality of the product. The raw materials butyl acetate and toluene are difficult to separate in the later stage, resulting in a large amount of raw materials and waste, which is not conducive to industrial production. Chinese Patent Document CN107055493A discloses a preparation method of lithium bisfluorosulfonylimide, which comprises the following steps: (1) fluorination reaction: bischlorosulfonylimide is reacted with hydrogen fluoride in the presence of a catalyst to synthesize an intermediate, bisfluorosulfonylimide; and (2) reacting the bisfluorosulfonylimide obtained in step (1) with lithium carboxylate to obtain lithium bisfluorosulfonylimide. The preparation method has low cost, few by-products, and simple post-treatment, and can ensure the quality and purity of the product, especially the control of metal ions. However, the yield of lithium bisfluorosulfonylimide prepared by the method is low. SUMMARY

[0004] The application aims to provide a preparation method of lithium bisfluorosulfonylimide with high yield, high purity, and low metal ion content.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the preparation method of lithium bisfluorosulfonylimide is as follows:

[0006] A method for preparing lithium bis(fluorosulfonyl)imide includes the following steps: reacting bis(fluorosulfonyl)imide and a lithifying agent in a non-polar organic solvent, separating the solid and liquid phases to obtain crude lithium bis(fluorosulfonyl)imide, washing and removing impurities from the crude lithium bis(fluorosulfonyl)imide, and drying to obtain the final product; wherein the non-polar organic solvent is a poor solvent for lithium bis(fluorosulfonyl)imide; wherein the lithifying agent is selected from one or any combination of lithium oleate, lithium linoleate, lithium linolenic acid, lithium laurate, and lithium palmitate; and wherein the washing agent used for removing impurities is a poor organic solvent for lithium bis(fluorosulfonyl)imide, and the poor organic solvent is a non-polar solvent.

[0007] The method for preparing lithium difluorosulfonylimide of the present invention involves reacting difluorosulfonylimide and a lithiumizing agent in a nonpolar organic solvent without introducing water. The resulting lithium difluorosulfonylimide precipitates as a solid, and the crude lithium difluorosulfonylimide can be separated by solid-liquid separation. This method has the advantages of simple operation, mild reaction conditions, low waste generation, and environmental friendliness, and also helps to improve product yield. Washing and drying the crude lithium difluorosulfonylimide removes the carboxylic acid generated in the reaction, improving product purity. Furthermore, the free acid, fluoride ions, chloride ions, and other impurities in the lithium difluorosulfonylimide prepared by the present invention can be controlled at low levels. Because no water is introduced during the reaction, the prepared lithium difluorosulfonylimide has a low water content; the water in the product mainly comes from the water in the solvent.

[0008] Preferably, the nonpolar organic solvent and the undesirable organic solvent are each independently selected from one or any combination of aromatic solvents, aliphatic hydrocarbon solvents, and halogenated hydrocarbon solvents. Preferably, the aromatic solvent is selected from one or any combination of benzene, toluene, and xylene. Preferably, the aliphatic hydrocarbon solvent is a C5-C8 aliphatic hydrocarbon. Preferably, the aliphatic hydrocarbon solvent is selected from one or any combination of pentane, hexane, cyclohexane, heptane, and octane. Preferably, the halogenated hydrocarbon solvent is selected from one or any combination of chlorobenzene, dichloromethane, trichloromethane, carbon tetrachloride, dichloroethane, trichloroethane, tetrachloroethane, dichloropropane, trichloropropane, tetrachloropropane, and tetrachloroethane. To reduce toxicity and improve safety, preferably, the nonpolar organic solvent is dichloromethane and / or dichloroethane.

[0009] To avoid introducing moisture into the reaction system and reduce the moisture content in the prepared lithium bis(fluorosulfonyl)imide, preferably, the water content of the nonpolar organic solvent is less than 50 ppm.

[0010] To avoid introducing moisture into the reaction system and reduce the moisture content in the prepared lithium bis(fluorosulfonyl)imide, preferably, the water content of the undesirable organic solvent is less than 50 ppm.

[0011] Preferably, the molar ratio of the bisfluorosulfone imide and the lithiating agent is 1: (0.95-1). Using bisfluorosulfone imide in equivalent or slightly excess amount can ensure complete reaction of the lithiating agent, and since the lithiating agent cannot be removed by washing, by making the lithiating agent react completely, the introduction of lithiating agent impurities can be avoided, and the product purity can be improved.

[0012] Preferably, the mass ratio of the non-polar organic solvent and the bisfluorosulfone imide is (6-20): 1. Further preferably, the mass ratio of the non-polar organic solvent and the bisfluorosulfone imide is (6-10): 1. Too much non-polar organic solvent will cause the reaction liquid to be too dilute, the reaction speed to be slow or even the reaction to be incomplete; too little non-polar organic solvent will cause the reaction liquid to be too thick, and uneven stirring will occur. This reaction is an exothermic reaction, and too thick reaction liquid will cause local high temperature, which can cause the bisfluorosulfone imide lithium to deteriorate, and the later solid-liquid separation will not be easy to perform.

[0013] Preferably, the reaction temperature is -5-50℃. Further preferably, the reaction temperature is 25-50℃. Too low reaction temperature will cause long reaction time; too high reaction temperature will cause the reaction to be too violent, the temperature to rise too fast, which is not easy to control, and even the bisfluorosulfone imide lithium can be decomposed (bisfluorosulfone imide lithium is a heat-sensitive substance).

[0014] The solid-liquid separation can be performed by centrifugation or filtration. In order to reduce the cost, preferably, the solid-liquid separation is filtration.

[0015] Preferably, the solid-liquid separation is performed at 25-50℃. The by-product carboxylic acid generated by the reaction of bisfluorosulfone imide and the lithiating agent has a melting point below 50℃, and the solubility of bisfluorosulfone imide lithium in the non-polar organic solvent is relatively large when the solid-liquid separation is performed above 50℃, which will cause part of the bisfluorosulfone imide lithium to enter the filtrate, resulting in reduced yield; when the solid-liquid separation is performed below 25℃, the solubility of the by-product carboxylic acid in the non-polar organic solvent is relatively low, which will cause part of the by-product carboxylic acid to remain in the bisfluorosulfone imide lithium crude product, affecting the product purity.

[0016] In order to ensure that the carboxylic acid generated by the reaction can be washed out completely, preferably, the washing and impurity removal is performed at 25-50℃. The carboxylic acid (oleic acid, linoleic acid, linolenic acid, lauric acid, and palmitic acid) generated by the reaction of bisfluorosulfone imide and the lithiating agent can be washed out by non-polar solvents (poor organic solvents) having a higher melting point than these carboxylic acids, and bisfluorosulfone imide lithium is insoluble in the above non-polar solvents (poor organic solvents), which can better separate the carboxylic acid and bisfluorosulfone imide lithium.

[0017] In order to ensure the washing effect and avoid the loss of lithium bisfluorosulfonylimide, improve the purity and yield of lithium bisfluorosulfonylimide, preferably, the mass of the washing agent used in the washing and impurity removal is 2-10 times the mass of lithium bisfluorosulfonylimide. From the comprehensive consideration of energy consumption, smooth filtration operation and the like, preferably, the mass of the washing agent used in the washing and impurity removal is 3-5 times the mass of lithium bisfluorosulfonylimide.

[0018] Preferably, the method for washing and removing impurities comprises the following steps: repeatedly performing beating-up, solid-liquid separation and elution on the lithium bisfluorosulfonylimide crude product for two or more times in sequence.

[0019] Preferably, the temperature used in the drying is -20-10 ℃. Further preferably, the temperature used in the drying is -10-5 ℃. For example, the temperature used in the drying is -10-0 ℃. If the temperature used in the drying is too high, lithium bisfluorosulfonylimide will deteriorate. If the temperature used in the drying is too low, the drying time will be too long, and lithium bisfluorosulfonylimide will also deteriorate.

[0020] In order to sufficiently remove the residual solvent, preferably, the drying is performed under negative pressure.

[0021] In order to avoid introducing water into the reaction system through the lithiating agent, and thus causing the water content in the prepared lithium bisfluorosulfonylimide to be too high, preferably, the water content of the lithiating agent is less than 50 ppm.

[0022] Since the lithiating agent used in the present application is insoluble in the reaction system, in order to ensure that lithium bisfluorosulfonylimide and the lithiating agent are in sufficient contact for reaction, preferably, the particle size of the lithiating agent is less than 60 μm.

[0023] Preferably, the lithiating agent is prepared by a method comprising the following steps: mixing and reacting an organic acid and a lithium-containing compound in water, performing first solid-liquid separation, then concentrating and crystallizing the liquid obtained by the first solid-liquid separation, and performing second solid-liquid separation to obtain the lithiating agent; the organic acid is selected from one or any combination of oleic acid, linoleic acid, linolenic acid, lauric acid and palmitic acid; the lithium-containing compound is lithium carbonate and / or lithium hydroxide.

[0024] From the economic and environmental protection point of view, preferably, the organic acid is oleic acid and / or lauric acid.

[0025] Preferably, the ratio of the molar mass of the carboxyl group in the organic acid to the molar mass of lithium in the lithium-containing compound is 1:(0.9-1). Ensuring that the organic acid is slightly excessive can avoid the introduction of excessive lithium carbonate or lithium hydroxide into the subsequent reaction system, causing the water content of the synthesis liquid to be too high.

[0026] Preferably, the mass of water used for preparing the lithiating agent is 8-20 times the mass of the organic acid. Too much water used for preparing the lithiating agent will result in a too dilute reaction solution, affecting the determination of the reaction end point (the end point is determined by pH or acidity), and also result in a too long time for later concentration. Too little water used for preparing the lithiating agent will result in a too viscous material, which is not easy to handle and control the reaction.

[0027] Preferably, the mass of water in the concentrated solution obtained by concentration is 3-10 times the mass of the organic acid. Too much water in the concentrated solution will result in a too viscous material, which is not easy to transfer the material. Too little water in the concentrated solution will result in a low yield of the prepared lithiating agent.

[0028] Further preferably, the mass of water used for preparing the lithiating agent is 8-12 times the mass of the organic acid.

[0029] Further preferably, the mass of water in the concentrated solution obtained by concentration is 3-5 times the mass of the organic acid. DETAILED DESCRIPTION

[0030] The technical solutions of the present application are further described below in combination with specific examples.

[0031] The purity of oleic acid, lithium carbonate, lauric acid, linoleic acid, linolenic acid, palmitic acid, lithium hydroxide and bisfluorosulfonylimide used in the examples and comparative examples of the present application is 99.9%, and the content of metal ions is less than 2 ppm, and the content of chloride ions in bisfluorosulfonylimide is less than 20 ppm.

[0032] The purity of acetic acid, propionic acid and benzoic acid used in the comparative examples of the present application is 99.95%, and the content of metal ions is less than 2 ppm.

[0033] The water content of dichloromethane, dichloroethane, benzene, toluene, dimethylbenzene, pentane, hexane, cyclohexane, heptane, octane, chlorobenzene, trichloromethane, carbon tetrachloride, trichloroethane, tetrachloroethane, dichloropropane, trichloropropane, tetrachloropropane and tetrachloroethane used in the examples and comparative examples of the present application is less than 50 ppm.

[0034] Example 1

[0035] The method for preparing bisfluorosulfonylimide lithium of the present example specifically comprises the following steps:

[0036] (1) in a three-necked flask, 2260 g of water and 282.5 g of oleic acid were added, then the temperature of the materials in the three-necked flask was controlled at 10℃, 33.3 g of lithium carbonate was added into the three-necked flask in batches (the mass of lithium carbonate in each batch was the same, and the interval between the addition of adjacent two batches was 10 min), and the reaction was carried out, after the addition was completed, the reaction was continued for 2 h, and the reaction of lithium carbonate was basically completed at 2 h by testing the pH of the system after the reaction. Then the reaction system was filtered, and the obtained liquid was concentrated to crystallize (the mass of water in the concentrated liquid obtained by concentration was 10 times the mass of oleic acid), then filtered again, and the filter cake obtained by filtering again was dried at 120℃ until the moisture content was 45 ppm, and finally the dried solid was crushed to a particle size of 50 μm, and the obtained solid powder was lithium oleate with a mass of 176.5 g;

[0037] (2) under the protection of nitrogen, lithium oleate 137.0 g (0.475 mol) was added into a three-necked flask with stirring and condensing device, then dichloromethane 1776 g was added into the three-necked flask, and stirring was started, then the temperature of the materials in the three-necked flask was controlled at 25℃, and bisfluorosulfonyl imide 90.5 g (0.5 mol) was added dropwise into the three-necked flask, and the dropwise addition was completed after 0.5 h, the reaction process was detected by nuclear magnetic resonance, and when the hydrogen spectrum test ratio of dichloromethane and bisfluorosulfonyl imide was unchanged, the reaction was complete, and the reaction was stopped; then the filtration was carried out under the protection of nitrogen and heat preservation, the filter cake was slurried and rinsed twice with 25℃ dichloromethane with a mass of 280.5 g (the filter cake was first slurried with 25℃ dichloromethane with a mass of 187 g, then filtered, and then rinsed with 25℃ dichloromethane with a mass of 93.5 g, then the filter cake was slurried with 25℃ dichloromethane with a mass of 187 g, then filtered, and then rinsed with 25℃ dichloromethane with a mass of 93.5 g), and then the solid after rinsing was dried under negative pressure at -10℃, and lithium bisfluorosulfonyl imide product 87.81 g was obtained, with a yield of 98.85%.

[0038] Example 2

[0039] The preparation method of lithium bisfluorosulfonyl imide of the embodiment specifically comprises the following steps:

[0040] (1) in a three-necked flask, 4006 g of water and 200.3 g of lauric acid were added, then the temperature of the material in the three-necked flask was controlled at 10℃, 33.3 g of lithium carbonate was added into the three-necked flask in batches (the mass of lithium carbonate added in each batch was the same, and the interval between the addition of adjacent two batches was 10 min), and the reaction was carried out, after the addition was completed, the reaction was continued for 2 h, and the reaction of lithium carbonate was basically completed at 2 h by testing the pH of the system after the reaction. Then the reaction system was filtered, and the filtered liquid was concentrated to crystallize (the mass of water in the concentrated liquid obtained by concentration was 3 times the mass of lauric acid), then it was filtered again, and the filter cake obtained by filtering again was dried at 120℃ until the moisture content was 48 ppm, and finally the dried solid was crushed to a particle size of 45 μm, and the obtained solid powder was lithium laurate with a mass of 111.4 g;

[0041] (2) under the protection of nitrogen, 98.0 g of lithium laurate (0.475 mol) was added into a three-necked flask with stirring and condensing device, then 561 g of dichloromethane was added into the three-necked flask, and stirring was started, then the temperature of the material in the three-necked flask was controlled at 50℃, and 90.5 g of bisfluorosulfonyl imide (0.5 mol) was added dropwise into the three-necked flask, and the dropwise addition was completed after 0.5 h, the reaction process was detected by nuclear magnetic resonance, and when the hydrogen spectrum test ratio of dichloromethane and bisfluorosulfonyl imide was unchanged, the reaction was complete, and the reaction was stopped; then the filtration was carried out under the protection of nitrogen and heat preservation, the filter cake was slurried and rinsed twice with 280.5 g of 50℃ dichloromethane (the filter cake was first slurried with 187 g of 50℃ dichloromethane, then filtered, and then rinsed with 93.5 g of 50℃ dichloromethane, then the filter cake was slurried with 187 g of 50℃ dichloromethane, then filtered, and then rinsed with 93.5 g of 50℃ dichloromethane), and then the rinsed solid was dried under negative pressure at -10℃, and 86.86 g of lithium bisfluorosulfonyl imide product was obtained, with a yield of 97.78%.

[0042] Example 3

[0043] The preparation method of lithium bisfluorosulfonyl imide of the embodiment specifically comprises the following steps:

[0044] (1) in a three-necked flask, 2260 g of water and 282.5 g of oleic acid were added, then the temperature of the material in the three-necked flask was controlled at 20℃, 21.5 g of lithium hydroxide was added into the three-necked flask in batches (7 batches in total, the mass of lithium hydroxide added in each batch was the same, and the interval between the addition of adjacent two batches was 10 min), and the reaction was carried out, after the addition was completed, the reaction was continued for 2 h, and the reaction was determined by testing the pH of the system after the reaction. When the lithium carbonate is substantially completely reacted after 2 h, the reaction system is filtered, the obtained liquid is concentrated and crystallized (the mass of water in the concentrated solution obtained by concentration is 5 times the mass of oleic acid), then filtered again, and the filter cake obtained by filtering again is dried at 130℃ until the moisture content is 30 ppm, and finally the dried solid is crushed to a particle size of 40 μm, and the obtained solid powder is lithium oleate, with a mass of 177.1 g;

[0045] (2) under a nitrogen atmosphere, lithium oleate 133.3 g (0.475 mol) was added into a dry three-necked flask with stirring and condensing device, then dichloroethane 900 g was added into the three-necked flask, and stirring was started, then the temperature of the material in the three-necked flask was controlled at 30℃, and bisfluorosulfonyl imide 90.5 g (0.5 mol) was added dropwise into the three-necked flask, and the dropwise addition was completed after 0.5 h, the reaction progress was detected by nuclear magnetic resonance, and when the hydrogen spectrum test ratio of dichloroethane and bisfluorosulfonyl imide was unchanged, the reaction was complete, and the reaction was stopped; then filtration was carried out under nitrogen protection and heat preservation, the filter cake was slurried and rinsed twice with 280.5 g of 30℃ dichloroethane (the filter cake was first slurried with 187 g of 30℃ dichloroethane, filtered, then rinsed with 93.5 g of 30℃ dichloroethane, then slurried with 187 g of 30℃ dichloroethane, filtered, and then rinsed with 93.5 g of 30℃ dichloroethane), and then the rinsed solid was dried under negative pressure at 0℃, to obtain 87.6 g of lithium bisfluorosulfonyl imide product, with a yield of 98.62%.

[0046] Example 4

[0047] The preparation method of lithium bisfluorosulfonyl imide of the present embodiment specifically comprises the following steps:

[0048] (1) In a three-necked flask, 2003 g of water and 200.3 g of lauric acid were added, and then the temperature of the material in the three-necked flask was controlled at 20°C, and then 39.9 g of lithium hydroxide was added in batches (7 batches in total, the mass of lithium hydroxide added in each batch was the same, and the interval between the addition of adjacent two batches was 10 min), and the reaction was carried out, after the addition was completed, the reaction was continued for 2 h, and the reaction was determined by testing the pH of the system after the reaction, and it was determined that the lithium carbonate was substantially completely reacted after 2 h, then the reaction system was filtered, and the filtered liquid was concentrated to crystallize (the mass of water in the concentrated liquid obtained by concentration was 4 times the mass of lauric acid), then the filtered again, and the filter cake obtained by filtering again was dried at 130°C until the moisture content was 41 ppm, and finally the dried solid was crushed to a particle size of 47 μm, and the obtained solid powder was lithium laurate, with a mass of 112.2 g;

[0049] (2) Under a nitrogen atmosphere, lithium laurate 98.0 g (0.475 mol) was added to a dry three-necked flask with stirring and condensing device, then dichloroethane 561 g was added to the three-necked flask, and stirring was started, then the temperature of the material in the three-necked flask was controlled at 50°C, and bisfluorosulfonyl imide 90.5 g (0.5 mol) was added dropwise to the three-necked flask, and the addition was completed after 0.5 h, and the reaction progress was detected by nuclear magnetic resonance, and when the hydrogen spectrum test ratio of dichloroethane and bisfluorosulfonyl imide was unchanged, the reaction was complete, and the reaction was stopped; then filtering was carried out under nitrogen protection and heat preservation, the filter cake was slurried and rinsed twice with 50°C dichloroethane with a mass of 280.5 g (the filter cake was first slurried with 50°C dichloroethane with a mass of 187 g, then filtered, then rinsed with 50°C dichloroethane with a mass of 93.5 g, then slurried with 50°C dichloroethane with a mass of 187 g, then filtered, and then rinsed with 50°C dichloroethane with a mass of 93.5 g), and then the rinsed solid was dried under negative pressure at 0°C, to obtain lithium bisfluorosulfonyl imide product 86.92 g, with a yield of 97.85%.

[0050] Example 5

[0051] The preparation method of lithium bisfluorosulfonyl imide of the embodiment specifically comprises the following steps:

[0052] (1) This step is the same as step (1) in Example 4;

[0053] (2) Under the protection of nitrogen, 98.0 g of lithium laurate (0.475 mol) was added into a dry three-neck flask with stirring and condensing device, then 561 g of dichloroethane was added into the flask, and stirring was started. Then the temperature of the material in the flask was controlled at -5°C, and 90.5 g of bisfluorosulfonyl imide (0.5 mol) was added dropwise into the flask. The reaction was completed after 0.5 h, as indicated by the fact that the hydrogen spectrum test ratio of dichloroethane to bisfluorosulfonyl imide remained unchanged. The reaction was stopped. Then the filtration was carried out under the protection of nitrogen and heat preservation. The filter cake was slurried and rinsed twice with 280.5 g of 50°C dichloroethane (the filter cake was first slurried with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane, and then the filter cake was slurried again with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane). Then the rinsed solid was dried under negative pressure at -15°C to obtain 86.54 g of lithium bisfluorosulfonyl imide product, with a yield of 97.43%.

[0054] Example 6

[0055] The method for preparing lithium bisfluorosulfonyl imide in this example specifically includes the following steps:

[0056] (1) This step is the same as step (1) in Example 4.

[0057] (2) Under the protection of nitrogen, 98.0 g of lithium laurate (0.475 mol) was added into a dry three-neck flask with stirring and condensing device, then 561 g of dichloroethane was added into the flask, and stirring was started. Then the temperature of the material in the flask was controlled at -5°C, and 90.5 g of bisfluorosulfonyl imide (0.5 mol) was added dropwise into the flask. The reaction was completed after 0.5 h, as indicated by the fact that the hydrogen spectrum test ratio of dichloroethane to bisfluorosulfonyl imide remained unchanged. The reaction was stopped. Then the filtration was carried out under the protection of nitrogen and heat preservation. The filter cake was slurried and rinsed twice with 280.5 g of 50°C dichloroethane (the filter cake was first slurried with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane, and then the filter cake was slurried again with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane). Then the rinsed solid was dried under negative pressure at -15°C to obtain 86.54 g of lithium bisfluorosulfonyl imide product, with a yield of 97.43%.

[0058] In other embodiments, lithium bisfluorosulfonimide is prepared according to the method of Example 1, except that the oleic acid in step (1) is replaced by linoleic acid, linolenic acid, or palmitic acid to prepare lithium linoleate, lithium linolenate, or lithium palmitate, respectively, and then lithium bisfluorosulfonimide is prepared according to step (2) of Example 1. The yield, purity, and impurity ion types and contents of the lithium bisfluorosulfonimide prepared in this way are close to the corresponding indicators of the lithium bisfluorosulfonimide prepared in Example 1.

[0059] In other embodiments, lithium bisfluorosulfonimide is prepared according to the method of Example 1, except that the dichloromethane used in step (2) is replaced by benzene, toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, chlorobenzene, trichloromethane, carbon tetrachloride, trichloroethane, tetrachloroethane, dichloropropane, trichloropropane, tetrachloropropane, or tetrachloroethane. The yield, purity, and impurity ion types and contents of the lithium bisfluorosulfonimide prepared in this way are consistent with the corresponding indicators of the lithium bisfluorosulfonimide prepared in Example 1.

[0060] Comparative Example 1

[0061] The method for preparing lithium bisfluorosulfonimide in this comparative example specifically includes the following steps:

[0062] (1) 1608 g of water and 180 g of acetic acid were added to a three-necked flask, and the temperature of the contents of the three-necked flask was controlled at 20°C. Then 72 g of lithium hydroxide was added to the three-necked flask in 8 batches (the mass of lithium hydroxide added in each batch was the same, and the time interval between the addition of adjacent batches was 10 min), and the reaction was continued for 2 h after the addition was completed. After the reaction was completed, the system after the reaction was filtered, and the liquid obtained by the filtration was concentrated to induce crystallization (the mass of water in the concentrated liquid obtained by the concentration was 5 times the mass of acetic acid). The resulting filter cake was then dried at 130°C until the water content was 41 ppm, and finally the dried solid was pulverized to a particle size of 45 μm. The resulting solid powder was lithium acetate, and the mass was 122.61 g.

[0063] (2) under nitrogen atmosphere, add lithium acetate 31.34 g (0.475 mol) into a dry three-neck flask with stirring and condensing device, then add dichloroethane 561 g into the three-neck flask, start stirring, then control the temperature of the material in the three-neck flask at -5 ℃, and drop bisfluorosulfonyl imide 90.5 g (0.5 mol) into the three-neck flask, drop for 0.5 h, detect the reaction progress by nuclear magnetic resonance, when the hydrogen spectrum test ratio of dichloroethane and bisfluorosulfonyl imide is unchanged, the reaction is complete, stop the reaction; then filter under nitrogen protection and heat preservation, the filter cake is slurried and rinsed twice with 280.5 g of 50 ℃ dichloroethane (the filter cake is first slurried with 187 g of 50 ℃ dichloroethane, filtered, then rinsed with 93.5 g of 50 ℃ dichloroethane, then slurried with 187 g of 50 ℃ dichloroethane, filtered, and then rinsed with 93.5 g of 50 ℃ dichloroethane), then dry the rinsed solid at -15 ℃ under negative pressure to obtain lithium bisfluorosulfonyl imide product 86.03 g, with a yield of 96.85%.

[0064] Comparative Example 2

[0065] (1) add 1776 g of water and 222 g of propionic acid into a three-neck flask, then control the temperature of the material in the three-neck flask at 20 ℃, then add 72 g of lithium hydroxide (the lithium hydroxide is added in 8 batches, and the mass of lithium hydroxide added in each batch is the same, and the time interval between adjacent two batches is 10 min) into the three-neck flask for reaction, after the addition is completed, continue to react for 2 h, after the reaction is completed, filter the reaction system, then concentrate the obtained liquid to crystallize (the mass of water in the concentrated liquid obtained by concentration is 5 times the mass of propionic acid), then filter again, then dry the filter cake obtained by re-filtering at 130 ℃ until the water content is 44 ppm, and finally crush the dried solid to a particle size of 47 μm, to obtain lithium propionate with a mass of 147.02 g;

[0066] (2) under nitrogen atmosphere, add 38.0 g of lithium propionate (0.475 mol) into a dry three-neck flask with stirring and condensing device, then add 561 g of dichloroethane into the three-neck flask, start stirring, then control the temperature of the material in the three-neck flask at -5°C, and then drop 90.5 g of bisfluorosulfonyl imide (0.5 mol) into the three-neck flask, drop for 0.5 h, and then stop the reaction when the hydrogen spectrum test ratio of dichloroethane and bisfluorosulfonyl imide is unchanged, indicating that the reaction is complete; then filter under nitrogen protection and heat preservation, and then use 280.5 g of 50°C dichloroethane to pulp and rinse the filter cake twice (first use 187 g of 50°C dichloroethane to pulp the filter cake, filter, then use 93.5 g of 50°C dichloroethane to rinse, then use 187 g of 50°C dichloroethane to pulp the filter cake, filter, then use 93.5 g of 50°C dichloroethane to rinse), and then dry the rinsed solid at -15°C under negative pressure to obtain 86.16 g of lithium bisfluorosulfonyl imide product, with a yield of 97.0%.

[0067] Comparative Example 3

[0068] (1) add 1960 g of water and 245 g of benzoic acid into a three-neck flask, then control the temperature of the material in the three-neck flask at 20°C, then add 48 g of lithium hydroxide (divided into 6 batches, the mass of lithium hydroxide added in each batch is the same, and the time interval between adjacent two batches is 10 min) into the three-neck flask for reaction, continue to react for 2 h after the addition is completed, then filter the reaction system, then concentrate and crystallize the liquid obtained by filtering (the mass of water in the concentrated liquid obtained by concentrating is 5 times the mass of benzoic acid), then filter again, then dry the filter cake obtained by filtering again at 130°C until the water content is 40 ppm, and finally crush the dried solid to a particle size of 40 μm to obtain lithium benzoate with a mass of 158.77 g;

[0069] (2) under nitrogen atmosphere, lithium benzoate 60.8 g (0.475 mol) was added into a dry three-necked flask with stirring and condensing device, then dichloroethane 561 g was added into the flask, stirring was started, then the temperature of the material in the flask was controlled at -5°C, and difluorosulfurylimide 90.5 g (0.5 mol) was added dropwise into the flask, the reaction process was detected by nuclear magnetic resonance, when the hydrogen spectrum test ratio of dichloroethane to difluorosulfurylimide was unchanged, the reaction was complete, and the reaction was stopped; then filtration was carried out under nitrogen protection and heat preservation, the filter cake was slurried and rinsed twice with 280.5 g of 50°C dichloroethane (the filter cake was first slurried with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane, then the filter cake was slurried again with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane), then the rinsed solid was dried under negative pressure at -15°C, to obtain 88.53 g of crude lithium difluorosulfurylimide, then recrystallization was carried out at room temperature using a mixed solvent of DMC and DCM in a volume ratio of 1:20, filtration and drying were carried out, to obtain 67.28 g of lithium difluorosulfurylimide product, with a yield of 75.74%.

[0070] Comparative Example 4

[0071] under nitrogen atmosphere, lithium carbonate 17.55 g (0.2375 mol) was added into a dry three-necked flask with stirring and condensing device, then dichloroethane 561 g was added into the flask, stirring was started, then the temperature of the material in the flask was controlled at -5°C, and difluorosulfurylimide 90.5 g (0.5 mol) was added dropwise into the flask, the reaction process was detected by nuclear magnetic resonance, when the hydrogen spectrum test ratio of dichloroethane to difluorosulfurylimide was unchanged, the reaction was complete, and the reaction was stopped; then filtration was carried out under nitrogen protection and heat preservation, the filter cake was slurried and rinsed twice with 280.5 g of 50°C dichloroethane (the filter cake was first slurried with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane, then the filter cake was slurried again with 187 g of 50°C dichloroethane, then filtered, and then rinsed with 93.5 g of 50°C dichloroethane), then the rinsed solid was dried under negative pressure at -15°C, to obtain 88.01 g of crude lithium difluorosulfurylimide, with a yield of 99.08%.

[0072] Comparative Example 5

[0073] The preparation method of lithium difluorosulfurylimide in the present comparative example specifically includes the following steps:

[0074] Under nitrogen atmosphere, lithium hydroxide 11.4 g (0.475 mol) was added into a dry three-necked flask with stirring and condensing device, then dichloroethane 561 g was added into the three-necked flask, stirring was started, then the temperature of the three-necked flask was controlled at -5 ℃, and difluorosulfurylimide 90.5 g (0.5 mol) was added dropwise into the three-necked flask, the dropwise addition was completed after 0.5 h, the reaction progress was detected by nuclear magnetic resonance, when the hydrogen spectrum test ratio of dichloroethane and difluorosulfurylimide was unchanged, the reaction was complete, and the reaction was stopped; then filtration was carried out under nitrogen protection and heat preservation, the filter cake was slurried and rinsed twice with 50 ℃ dichloroethane 280.5 g (the filter cake was first slurried with 50 ℃ dichloroethane 187 g, then filtered, and then rinsed with 50 ℃ dichloroethane 93.5 g, then the filter cake was slurried with 50 ℃ dichloroethane 187 g, then filtered, and then rinsed with 50 ℃ dichloroethane 93.5 g), and then the rinsed solid was dried under negative pressure at -15 ℃ to obtain crude lithium difluorosulfurylimide 88.03 g, with a yield of 99.10%.

[0075] Experimental Example

[0076] In order to evaluate different preparation methods of lithium difluorosulfurylimide, the purity, yield, and impurity types and contents of lithium difluorosulfurylimide prepared in Examples 1-6 and Comparative Examples 1-5 were respectively tested and analyzed, and the results are shown in Table 1.

[0077] Table 1 Purity, yield, and impurity types and contents of lithium difluorosulfurylimide prepared in Examples 1-6 and Comparative Examples 1-5

[0078]

[0079] Note: The free acid in Table 1 is calculated based on HF.

[0080] As can be seen from Table 1, the purity of lithium difluorosulfurylimide prepared in Examples 1-6 is not less than 99.90%, the water content is not higher than 15 ppm, and the contents of free acid, insoluble substance and other impurity ions are extremely low. The detection results show that the product prepared by the preparation method of lithium difluorosulfurylimide of the present application has high purity, meets the use requirements of lithium ion battery electrolyte salt, and is suitable for popularization and use.

Claims

1. A method for producing lithium bisfluorosulfonimide, characterized by, The method comprises the following steps: The difluorosulfurylimide and the lithiating agent are reacted in a non-polar organic solvent, solid-liquid separation is performed, and a crude difluorosulfurylimide lithium is obtained, then the crude difluorosulfurylimide lithium is washed to remove impurities, and drying is performed, and the difluorosulfurylimide lithium is obtained; the non-polar organic solvent is one or both of dichloromethane and dichloroethane; the lithiating agent is selected from one or any combination of lithium oleate, lithium linoleate, lithium linolenate, lithium laurate and lithium palmitate; the washing agent used for washing and removing impurities is one or both of dichloromethane and dichloroethane.

2. The method for producing lithium bisfluorosulfonimide according to any one of claims 1, wherein The mass ratio of the non-polar organic solvent to the difluorosulfurylimide is (6-20):

1.

3. The method of claim 1, wherein the lithium bisfluorosulfimide is prepared by the process comprising: reacting lithium fluoride with sulfur dioxide in the presence of a solvent to form lithium bisfluorosulfimide; and removing the solvent from the lithium bisfluorosulfimide. The particle size of the lithiating agent is less than 60 μm.

4. The process for producing lithium bisfluorosulfonimide according to any one of claims 1 to 3, characterized in that, The molar ratio of the difluorosulfurylimide to the lithiating agent is 1:(0.95-1).

5. The method of claim 1, wherein the lithium bisfluorosulfimide is prepared by the process comprising: reacting lithium fluoride with sulfur dioxide in the presence of a solvent to form lithium bisfluorosulfimide; and removing the solvent from the lithium bisfluorosulfimide. The reaction temperature is -5-50 ℃.

6. The method for preparing lithium bisfluorosulfonimide according to claim 1, wherein The solid-liquid separation is performed at 25-50 ℃, and the washing and removing impurities are performed at 25-50 ℃.

7. The method for preparing lithium bisfluorosulfonimide according to claim 1, wherein The lithiating agent is prepared by a method comprising the following steps: mixing and reacting an organic acid and a lithium-containing compound in water, performing first solid-liquid separation, then performing concentration and crystallization on the liquid obtained by the first solid-liquid separation, and performing second solid-liquid separation to obtain the lithiating agent; the organic acid is selected from one or any combination of oleic acid, linoleic acid, linolenic acid, lauric acid and palmitic acid; and the lithium-containing compound is lithium carbonate and / or lithium hydroxide.

8. The method for producing lithium bisfluorosulfonimide according to claim 7, wherein The molar ratio of the carboxyl in the organic acid to the lithium element in the lithium-containing compound is 1:(0.9-1). The molar ratio of the carboxyl in the organic acid to the lithium element in the lithium-containing compound is 1:(0.9-1).

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