Method for producing lithium bis(fluorosulfonyl)imide

Abstract

The present invention relates to the field of organic chemistry, and in particular to a method for producing lithium bis(fluorosulfonyl)imide by reacting bis(fluorosulfonyl)imide with lithium carbonate in a mixed organic solvent, followed by post-treatment to obtain lithium bis(fluorosulfonyl)imide. The synthetic route of the present invention limits the reaction to the lithium bicarbonate stage, resulting in very little water in the reaction system and making it very easy to recover the lithium bicarbonate produced. Furthermore, the process of the present invention is simple, and can produce lithium bis(fluorosulfonyl)imide in high yield and with high quality.

Description

Technical Field

[0001] The present invention relates to the field of organic chemistry, and particularly to a method for producing lithium bis(fluorosulfonyl)imide.

Background Art

[0002] Lithium-ion batteries are important secondary batteries because they have characteristics such as high operating voltage, small volume, light weight, high energy, no memory effect, no pollution, low self-discharge, and long cycle life, and have already been widely applied to various aspects of modern production and life. Lithium bis(fluorosulfonyl)imide (LiFSI) has better conductivity, higher electrochemical and thermal stability, and hydrolysis resistance compared to the conventional electrolyte salt LiPF6. When LiFSI is added, the charge-discharge cycle number of the battery can be significantly improved, and by stabilizing electrode materials with very strong activity such as high-nickel cathodes and high-voltage cathodes, the life of the battery can be extended while improving the flame-retardant performance of the electrolyte and enhancing safety.

[0003] Most of the synthesis methods of LiFSI first synthesize bis(chlorosulfonyl)imide (HClSI), and then react it with MFn (M is an element of Groups 11-15, Periods 4-6), produce a salt intermediate of bis(fluorosulfonyl)imide of the corresponding metal or organic base, and further carry out a cation exchange reaction with LiOH, Li2CO3 to obtain LiFSI (Patent Documents 1, Patent Document 2, Patent Document 3, Patent Document 4). The disadvantages of these methods are that after the exchange reaction reaches equilibrium, it is difficult to proceed sufficiently, and it is difficult to obtain a high-quality product by sufficiently separating the unreacted intermediate MSFI (M is a metal cation or an organic base cation) from LiSFI.

[0004] LiFSI is produced by metal exchange of purified potassium bis(fluorosulfonyl)imide (KFSI) with lithium salts such as LiClO4, LiBF4, lithium bis(oxalate) borate, and LiPF6. However, the potassium ion content in the product is often high, which affects its practical applications. In particular, both LiClO4 and the resulting KClO4 pose a certain degree of explosion risk (Non-Patent Documents 1, 2, 5, 6, 7, 8, 9, and 10).

[0005] Patent document 11 discloses a method for producing LiFSI by directly reacting bis(fluorosulfonyl)imide (HFSI) with lithium carbonate in an aqueous solution. However, this method also has obvious problems; when HFSI dissolves in water, it releases a great deal of heat, leading to the decomposition of HFSI. The patent solves the technical problem of the great heat release when HFSI dissolves in water by preparing an aqueous solution of HFSI at an ultra-low temperature (-78°C), but such a method increases energy consumption significantly. More importantly, because LiFSI has very good water solubility, the extraction efficiency is very low, making it unsuitable for industrial production.

[0006] Furthermore, Patent Document 12 describes a method of producing LiFSI in an organic solvent using bis(fluorosulfonyl)imide (HFSI) and lithium carbonate. This manufacturing process generates water, and since the product LiFSI is easily hydrolyzed in water, it is removed with SOCl2. However, this simultaneously generates acidic waste gases such as SO2 and HCl, resulting in high treatment costs for waste gas, wastewater, and solid waste. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent Application Publication No. 2013 / 0331609 [Patent Document 2] U.S. Patent Application Publication No. 2012 / 0041233 [Patent Document 3] European Patent Application Publication No. 2415757 [Patent Document 4] U.S. Patent Application Publication No. 2011 / 0034716 [Patent Document 5] Chinese Patent Application Publication No. 101747242 Specification [Patent Document 6] Chinese Patent Application Publication No. 101747243 Specification [Patent Document 7] Chinese Patent Application Publication No. 101654229 Specification [Patent Document 8] Chinese Patent Application Publication No. 105523970 Specification [Patent Document 9] Chinese Patent Application Publication No. 103910346 [Patent Document 10] Chinese Patent Application Publication No. 104495767 Specification [Patent Document 11] U.S. Patent No. 8377406 [Patent Document 12] Chinese Patent No. 104925765 Specification [Non-patent literature]

[0008] [Non-Patent Document 1] Electrochimical Acta, 2012, 66, PP. 320-324. [Non-Patent Document 2] Polyhedron, 2006, 25, PP. 1292-1298. [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the main objective of the present invention is to provide a novel method for producing lithium bis(fluorosulfonyl)imide that is simple, clean, and improves the yield and quality of lithium bis(fluorosulfonyl)imide. [Means for solving the problem]

[0010] In view of the problems of the existing technology as described above, an object of the present invention is to provide a method for producing lithium bis(fluorosulfonyl)imide, which has a simple process method and can produce lithium bis(fluorosulfonyl)imide with high yield and high quality.

[0011] To achieve the above object and other related objects, the present invention reacts bis(fluorosulfonyl)imide with lithium carbonate in a mixed organic solvent, and performs post-treatment to obtain lithium bis(fluorosulfonyl)imide, and the polarities of each individual solvent in the mixed organic solvent are different. The reaction scheme provides a method for producing lithium bis(fluorosulfonyl)imide as follows.

Chemical formula

[0012] In some possible embodiments, the mixed organic solvent is a combination of solvent A and solvent B, where the polarities of solvent A and solvent B may be different.

[0013] In some possible embodiments, the molar ratio of the lithium carbonate to bis(fluorosulfonyl)imide may be 0.5:1 to 20:1.

[0014] In some possible embodiments, the mass ratio of the mixed organic solvent to bis(fluorosulfonyl)imide may be 0.1:1 to 20:1.

[0015] In some possible embodiments, the reaction temperature of the reaction may be -70°C to 50°C.

[0016] In some possible embodiments, the specific process of the reaction may be to drop bis(fluorosulfonyl)imide into the mixed organic solvent system of lithium carbonate.

[0017] In some feasible embodiments, the post-treatment may include: (1) filtering the reaction system after the reaction to obtain a filtrate; (2) adding a drying agent to the filtrate and drying it; and (3) obtaining lithium bis(fluorosulfonyl)imide after drying by filtration, concentration and crystal precipitation.

[0018] The main beneficial effects of the present invention's method for producing lithium bis(fluorosulfonyl)imide are as follows: 1) By reacting bis(fluorosulfonyl)imide and lithium carbonate in a mixed organic solvent, lithium bis(fluorosulfonyl)imide and lithium bicarbonate are produced, with almost no water being generated, making post-treatment easy, and resulting in a high yield and high quality of lithium bis(fluorosulfonyl)imide. 2) The lithium bicarbonate produced in the reaction can be recovered and reused through a simple process. [Modes for carrying out the invention]

[0019] The inventors of this invention, through research, discovered that when bis(fluorosulfonyl)imide and lithium carbonate are reacted in a mixed organic solvent, the reaction is controlled to remain in lithium bicarbonate, and very little water is produced. This allowed for the optimization of the manufacturing process, enabling the production of lithium bis(fluorosulfonyl)imide in high yield and high quality. Furthermore, since lithium bicarbonate is easily recovered, a clean and environmentally friendly process pathway is provided. Based on this, the present invention was completed.

[0020] The present invention involves reacting bis(fluorosulfonyl)imide (HFSI) and lithium carbonate (Li2CO3) in a mixed organic solvent, followed by post-treatment to obtain lithium bis(fluorosulfonyl)imide, wherein the polarity of each individual solvent in the mixed organic solvent is different. The reaction scheme is as follows, and this provides a method for producing lithium bis(fluorosulfonyl)imide (LiFSI). [ka]

[0021] Using the above synthesis route, the reaction system contains very little water, and the resulting lithium bicarbonate is very easy to recover. By selecting an appropriate reaction system, the progress of the above reaction can be controlled. In some embodiments of the present invention, the mixed organic solvent is a combination of solvent A and solvent B, where solvents A and B have different polarities. LiFSI has good solubility in some highly polar solvents, but when a highly polar solvent is used alone, it is difficult for the reaction to remain at the LiHCO3 stage. Experiments have shown that LiHCO3 continues to react with HFSI to form LiFSI, simultaneously producing carbon dioxide and water. However, the inventors have found that when organic solvents with different polarities are mixed as the reaction solvent, the reaction between LiFSI and lithium bicarbonate tends to remain at the LiHCO3 stage. Of course, the inventors also tried using only low-polarity solvents, but because LiFSI has poor solubility in low-polarity solvents, LiHCO3 and LiFSI precipitate together as a solid, and further separation and purification were not possible.

[0022] Specifically, solvent A is generally a polar solvent, for example, a solvent containing polar groups such as hydroxyl groups or carboxyl groups, and preferably solvent A is a polar aprotic solvent. More preferably, solvent A is at least one selected from carbonate ester solvents, carboxylic acid ester solvents, ether solvents, or ketone solvents, where the C chain in the carbonate ester solvent, carboxylic acid ester solvent, ether solvent, or ketone solvent is selected based on its solubility in the reactants or products. Preferably, polar organic solvents include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethyl formate, n-propyl formate, isopropyl formate, n-butyl formate, isobutyl formate, t-butyl formate, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, and propionic acid It is at least one selected from n-butyl, isobutyl propionate, t-butyl propionate, methyl n-butanoate, ethyl n-butanoate, n-propyl n-butanoate, isopropyl n-butanoate, n-butyl n-butanoate, isobutyl n-butanoate, t-butyl n-butanoate, methyl isobutanoate, ethyl isobutanoate, n-propyl isobutanoate, isopropyl isobutanoate, n-butyl isobutanoate, isobutyl isobutanoate, or t-butyl isobutanoate.

[0023] Solvent B is generally at least one selected from alkanes, cycloalkanes, substituted alkanes (especially halogen-substituted alkanes), aromatic hydrocarbons, or substituted aromatic hydrocarbons (especially halogen-substituted aromatic hydrocarbons). More preferably, solvent B is at least one selected from pentane, hexane, heptane, cyclohexane, methylcyclohexane, dichloromethane (DCM), chloroform, carbon tetrachloride, dichloroethane (DCE), trichloroethane, tetrachloroethane, benzene, toluene, xylene, ethylbenzene, propylbenzene, isopropylbenzene, chlorobenzene, or dichlorobenzene.

[0024] In some embodiments of the present invention, the molar ratio of lithium carbonate to bis(fluorosulfonyl)imide is 0.5:1 to 20:1. Selectively, the molar ratio of lithium carbonate to bis(fluorosulfonyl)imide is 0.5:1 to 1:1, 1:1 to 2:1, 2:1 to 8:1, 8:1 to 10:1, 8:1 to 10:1, or 15:1 to 20:1, and when considering the economics of the process and the yield and quality of the product, the molar ratio of lithium carbonate to bis(fluorosulfonyl)imide is preferably 3:1 to 8:1, more preferably 3:1 to 5:1.

[0025] In some embodiments of the present invention, the mass ratio of the mixed solvent to bis(fluorosulfonyl)imide is 0.1:1 to 20:1, and a reasonable mass ratio of the mixed solvent to bis(fluorosulfonyl)imide is used considering the reaction process, reaction efficiency, workup efficiency, or product yield and quality.

[0026] Specifically, the mass ratio of solvent B to bis(fluorosulfonyl)imide is 0.5:1 to 10:1, and selectively, 0.5:1 to 0.8:1, 0.8:1 to 3:1, 3:1 to 8:1, and 8:1 to 10:1. Experiments have shown that maintaining a predetermined mass ratio of solvent B to bis(fluorosulfonyl)imide allows the reaction process to remain at the lithium bicarbonate stage.

[0027] More specifically, the mass ratio of solvent A to bis(fluorosulfonyl)imide is 0.1:1 to 10:1, selectively 0.5:1 to 1:1, 1:1 to 5:1, and 5:1 to 10:1. Preferably, the mass ratio of solvent A to bis(fluorosulfonyl)imide is 2:1 to 4:1, and the mass ratio of solvent A to solvent B is 1:3 to 1:10, with a preferred mass ratio of 1:4 to 1:7. Experiments have shown that maintaining a predetermined mass ratio of solvent A to bis(fluorosulfonyl)imide ensures good solubility of lithium bis(fluorosulfonyl)imide.

[0028] In summary, by selecting the appropriate ratio of the mixed solvent and the ratio of reactants, the reaction process can be maintained at the lithium bicarbonate stage. Since no water is produced in this synthesis pathway, there is no need to remove water during the reaction process with a drying agent, which is not only simpler but also advantageous for improving the yield and quality of lithium bis(fluorosulfonyl)imide.

[0029] In some embodiments of the present invention, the reaction temperature of the reaction is -70°C to 50°C, and selectively, -70°C to -50°C, -50°C to -30°C, -30°C to -15°C, -15°C to 0°C, 0°C to 20°C, or 20°C to 50°C. Specifically, since HFSI releases heat vigorously during the process of dissolving in water, and the presence of small amounts of water in the reaction solvent or synthesis route is unavoidable, maintaining a predetermined low temperature can improve the yield and quality of HFSI. Of course, in the synthesis route of this application, almost no water is produced, so the temperature may be controlled to -30°C to 0°C. It is also necessary to maintain the initial temperature of the reaction system, which is -70°C to -10°C, and selectively, -70°C to -50°C, -50°C to -20°C, or -20°C to -10°C.

[0030] In some embodiments of the present invention, as described above, a preferred process is to add bis(fluorosulfonyl)imide dropwise to a lithium carbonate mixed organic solvent system in order to avoid the intense heat dissipation during the dissolution of HFSI, and to adjust the dropping rate appropriately according to the requirements of the reaction system.

[0031] In some embodiments of the present invention, the reaction time of the reaction is 1 to 5 hours, and the reaction time can be determined by detecting the degree of consumption of the reactants using conventional detection means, and is generally maintained at 2.5 to 3.5 hours.

[0032] In some embodiments of the present invention, the post-treatment includes step (1): filtering the reaction system after the reaction to obtain a filtrate and a cake; and step (2): obtaining lithium bis(fluorosulfonyl)imide by filtration, concentration and crystal precipitation.

[0033] Specifically, the reaction solution after the reaction is filtered, and the filtration is carried out by conventional filtration methods, such as suction filtration or pressure filtration. The filtered filtrate is concentrated and crystallized to obtain lithium bis(fluorosulfonyl)imide. Specifically, after filtration is complete, the filtrate is concentrated under atmospheric pressure and / or reduced pressure, and after concentration is complete, a poor solvent is added to precipitate crystals. The poor solvent is selected from organic solvents, preferably from alkanes, cycloalkanes, halogenated alkanes, aromatic hydrocarbons, and halogenated aromatic hydrocarbons, and specifically from pentane, hexane, heptane, cyclohexane, methylcyclohexane, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, tetrachloroethane, benzene, toluene, xylene, ethylbenzene, propylbenzene, isopropylbenzene, chlorobenzene, and dichlorobenzene. After crystallization is complete, further solid-liquid separation and drying are performed to obtain lithium bis(fluorosulfonyl)imide.

[0034] In some embodiments of the present invention, since a small amount of water may be present in the reaction solvent during the reaction process, or moisture may be introduced due to the humidity of the air, and a trace amount of water is produced by the reaction, a further step (3) is included between step (1) and step (2): adding a desiccant to the filtrate from step (1) and drying it, and then performing step (2) after drying is complete. Here, the desiccant is at least one selected from metallic lithium, butyllithium, lithium hydride (LiH), calcium hydride (CaH2), lithium sulfate (Li2SO4), lithium bis(fluorosulfonyl)imide (LiFSI), thionyl chloride, phosgene, diphosgene, triphosgene, oxalyl chloride, or silicon tetrachloride (SiCl4). After drying is complete, the reaction solution is further filtered, using suction filtration and / or pressure filtration, and the filtrate obtained by this filtration is further concentrated and crystallized in step (2). The desiccant is used to maintain the moisture content in the filtrate at 50 ppm or less to ensure the yield and quality of LiFSI. Here, the desiccant is determined by the moisture content of the filtrate, and generally, the mass ratio of bis(fluorosulfonyl)imide is 0.001 to 0.1:1.

[0035] The cake produced in step (1) is dried to obtain lithium carbonate, which can be recovered and used. Specifically, the reaction scheme for the thermal dehydration of LiHCO3 to produce Li2CO3 is as follows. [ka]

[0036] Specifically, in process (1), the cake is dried using a gradient heating method to obtain lithium carbonate. The drying temperature is 60-120°C, more specifically, a first gradient drying method (60-80°C) is performed at 60°C for 5-8 hours, a second gradient drying method (80-110°C) for 1-3 hours, and a third gradient drying method (110-120°C) for 2-5 hours. The standard is LOD < 0.1% (LOD is the dry weight loss). Here, gradient heating makes the release of CO2 more stable, as heating to the maximum temperature in one go would release a large amount of CO2, leading to a risk of material ejection due to excessive pressure.

[0037] The embodiments of the present invention will be described below with specific examples, but those skilled in the art will readily understand other advantages and effects of the present invention from the disclosure herein. Furthermore, the present invention can be implemented or applied by other different specific embodiments, and the details herein can be modified or altered in various ways based on different perspectives and applications, without violating the spirit of the invention.

[0038] Where numerical ranges are given in the examples, of course, unless otherwise specified in the present invention, any value at both endpoints of each numerical range and any value between the endpoints is selectable. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. Except for the specific methods, equipment, and materials used in the examples, those skilled in the art can implement the present invention using any existing methods, equipment, and materials that are similar or equivalent to the methods, equipment, and materials used in the examples of the present invention, based on their familiarity with the existing art and the description of the present invention. [Examples]

[0039] Example 1 2250 g of DCE and 450 g of methyl formate were placed in a 5000 mL glass reaction bottle, and stirring was started. 740 g of Li2CO3 was added, and the reaction system was cooled to -30 ± 5 °C. While maintaining this temperature, 452.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 3018 g of filtrate, with a water content of 552 ppm and 737 g of cake. 0.5 g of LiH was added to the filtrate, and the mixture was stirred for 2 hours until the water content in the reaction system was <50 ppm, and then filtered. The solvent was removed from the filtrate under reduced pressure, 1086 g of DCE was added, and the mixture was stirred at room temperature for 1 hour, then filtered. The cake was dried to obtain 445.3 g of purified LiFSI, with a yield of 95.3%. Quality evaluation of the LiFSI purified product revealed an acid value (calculated in HF) of 12 ppm, chloride ions of 2 ppm, fluoride ions of 8 ppm, sulfate ions of <1 ppm, sodium of 3 ppm, potassium of 1 ppm, and moisture content of 23 ppm. The product met the standards specified in industry standard YS / T 1302-2019.

[0040] The cake obtained from the first filtration weighed 737g. It was dried at 60°C for 7 hours, 100°C for 2 hours, and 120°C for 3 hours until the LOD < 0.1%, and 638g of lithium bicarbonate was recovered with a dry weight of 98.7%.

[0041] Example 2 2250 g of DCM and 450 g of methyl formate were placed in a 5000 mL glass reaction bottle, and stirring was started. 630 g of Li2CO3 and 110 g of fresh Li2CO3 were added, and the reaction system was cooled to -25°C. Then, while maintaining a temperature of -30 ± 5°C, 452.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 3036 g of filtrate, with a water content of 498 ppm and 776 g of cake. 0.5 g of CaH2 was added to the filtrate, and the mixture was stirred for 2 hours until the water content in the reaction system was <50 ppm, and then filtered. The solvent was removed from the filtrate under reduced pressure, 1086 g of DCE was added, and the mixture was stirred at room temperature for 1 hour, then filtered. The cake was dried to obtain 447.0 g of purified LiFSI, with a yield of 95.7%. Quality evaluation of the LiFSI purified product revealed an acid value (calculated in HF) of 15 ppm, chloride ions of 3 ppm, fluoride ions of 7 ppm, sulfate ions of <1 ppm, sodium of 3 ppm, potassium of 1 ppm, and moisture content of 27 ppm. The product met the standards specified in industry standard YS / T 1302-2019.

[0042] The cake obtained after the first filtration weighed 776g. It was dried at 60°C for 7 hours, 100°C for 2 hours, and 120°C for 3 hours until the LOD < 0.1%, and 640g of lithium bicarbonate was recovered with a dry weight of 98.5%.

[0043] Example 3 540 g of DCE and 90 g of methyl ethyl carbonate were placed in a 1000 mL glass reaction bottle, and stirring was started. 148 g of Li2CO3 was added, and the reaction system was cooled to -25°C. Then, while maintaining a temperature of -30 ± 5°C, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 614 g of filtrate, with a water content of 604 ppm and 142 g of cake. 2.5 g of SOCl2 was added to the filtrate, and the mixture was stirred for 2 hours until the water content in the reaction system was <50 ppm. The solvent was removed from the reaction mixture under reduced pressure, 216 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. After filtration, the cake was dried to obtain 89.6 g of purified LiFSI, with a yield of 95.8%. Quality evaluation of the LiFSI purified product revealed an acid value (calculated in HF) of 35 ppm, chloride ions of 32 ppm, fluoride ions of 5 ppm, sulfate ions of <1 ppm, sodium of 2 ppm, potassium of 2 ppm, and moisture content of 18 ppm. The product met the indicators specified in industry standard YS / T 1302-2019.

[0044] Example 4 540 g of DCE and 90 g of dimethyl carbonate were placed in a 1000 mL glass reaction bottle, and stirring was started. 148 g of Li2CO3 was added, and the reaction system was cooled to -25°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 609 g of filtrate, with a water content of 583 ppm and 147 g of cake. 2.5 g of SOCl2 was added to the filtrate, and the mixture was stirred for 2 hours until the water content in the reaction system was <50 ppm. The reaction mixture was degassed under reduced pressure for 1 hour, and then 0.1 g of LiH was added to the reaction system (to adjust the acid value and chloride ions), and after stirring for 2 hours, the mixture was filtered. The filtrate was desoldered under reduced pressure, 216 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. After filtration, the cake was dried to obtain 90.3 g of purified LiFSI with a yield of 96.6%. The acid value (calculated in HF) was 9 ppm, chloride ions 8 ppm, fluoride ions 3 ppm, sulfate ions <1 ppm, sodium 3 ppm, potassium 1 ppm, and moisture 13 ppm. The product met the indicators specified in industry standard YS / T 1302-2019.

[0045] Example 5 540 g of DCE and 90 g of butyl acetate were placed in a 1000 mL glass reaction bottle, and stirring was started. 148 g of Li2CO3 was added, and the reaction system was cooled to -25°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 614 g of filtrate, with a moisture content of 604 ppm and a cake of 142 g. 9.5 g of Li2SO4 was added to the filtrate, and the mixture was stirred for 2 hours until the moisture content in the reaction system was <50 ppm, and then filtered. The filtrate was desoldered under reduced pressure, 216 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. After filtration, the cake was dried to obtain 88.4 g of purified LiFSI with a yield of 94.5%. The acid value (calculated in HF) was 22 ppm, chloride ions 3 ppm, fluoride ions 3 ppm, sulfate ions <1 ppm, sodium 4 ppm, potassium 2 ppm, and moisture 25 ppm. The product met the indicators specified in industry standard YS / T 1302-2019.

[0046] Example 6 540 g of DCE and 90 g of dimethyl carbonate were placed in a 1000 mL glass reaction bottle, and stirring was started. 300 g of Li2CO3 was added, and the reaction system was cooled to -25°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 662 g of filtrate, with a water content of 152 ppm, and 327 g of cake. The solvent was removed from the filtrate under reduced pressure, 216 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. After filtering, the cake was dried to obtain 82.5 g of purified LiFSI, with a yield of 88.3%. The quality of the purified LiFSI was evaluated, and the acid value (calculated using HF) was 12 ppm, chloride ions 1 ppm, fluoride ions 9 ppm, sulfate ions 5 ppm, sodium 4 ppm, potassium 1 ppm, and water content 47 ppm. The product met the standards specified in industry standard YS / T 1302-2019.

[0047] Example 7 225 g of DCE and 45 g of methyl acetate were placed in a 500 mL glass reaction bottle, and stirring was started. 111 g of Li2CO3 was added, and the reaction system was cooled to -25°C. While maintaining this temperature, 45.3 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 296 g of filtrate, with a water content of 257 ppm and 118 g of cake. 90 g of commercially available LiFSI (water content ≤ 20 ppm) was added to the filtrate, and the mixture was stirred for 1 hour. The solvent was removed under reduced pressure, 330 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. The cake was dried to obtain 133.9 g of purified LiFSI, with a conversion yield of 94.0%. The acid value (calculated using HF) was 8 ppm, chloride ions 2 ppm, fluoride ions 11 ppm, sulfate ions 3 ppm, sodium 2 ppm, potassium 1 ppm, and water content 35 ppm. In this example, LiFSI was added to allow the product dissolved in the solvent to crystallize. The product met the criteria specified in industry standard YS / T 1302-2019.

[0048] Example 8 300 g of DCE and 45 g of methyl acetate were placed in a 500 mL glass reaction bottle, and stirring was started. 111 g of Li2CO3 was added, and the reaction system was cooled to -25°C. While maintaining this temperature, 45.3 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, then filtered, and the filtrate had a water content of 317 ppm. 160 g of commercially available LiFSI (water content ≤ 20 ppm) was added to the filtrate, and after stirring for 1 hour, the solvent was removed under reduced pressure. 500 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. The cake was dried to obtain 204.4 g of purified LiFSI, with a conversion yield of 95.0%. The acid value (calculated using HF) was 11 ppm, chloride ions 3 ppm, fluoride ions 7 ppm, sulfate ions 5 ppm, sodium 2 ppm, potassium 2 ppm, and water content 26 ppm. The product met the standards specified in industry standard YS / T 1302-2019.

[0049] Comparative Example 1 540 g of DCE and 90 g of dimethyl carbonate were placed in a 1000 mL glass reaction bottle, and stirring was started. 148 g of Li2CO3 was added, and the reaction system was cooled to 0-5°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 674 g of filtrate, with a water content of 6600 ppm and 135 g of cake. The solvent was removed from the filtrate under reduced pressure, and 216 g of DCE was added and stirred at room temperature for 1 hour. The reaction system then separated into two layers: the upper layer was a clear liquid and the lower layer was a viscous solid, making filtration impossible.

[0050] Comparative Example 2 540 g of DCE and 90 g of dimethyl carbonate were placed in a 1000 mL glass reaction bottle, and stirring was started. 148 g of Li2CO3 was added, and the reaction system was cooled to -25°C. Then, while maintaining a temperature of -30 ± 5°C, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 600 g of filtrate, with a water content of 562 ppm and a cake of 143 g. The solvent was removed from the filtrate under reduced pressure, 216 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. After filtering, the cake was dried to obtain 87.2 g of purified LiFSI, with an acid value (calculated using HF) of 53 ppm, chloride ions of 2 ppm, fluoride ions of 38 ppm, sulfate ions of 61 ppm, sodium of 2 ppm, potassium of 1 ppm, and water content of 57 ppm. The product's moisture and sulfate ion levels were unacceptable, exceeding the standards specified in industry standard YS / T 1302-2019.

[0051] Comparative Example 3 450 g of dimethyl carbonate was placed in a 1000 mL glass reaction bottle, and stirring was started. 148 g of Li2CO3 was added, and the reaction system was cooled to -25°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise to the reaction system. After the addition was complete, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to obtain 528 g of filtrate, with a water content of 8210 ppm, and 139 g of cake. 34.4 g of SOCl2 was added to the filtrate, and the mixture was stirred for 12 hours until the water content in the reaction system was <50 ppm. The solvent was removed from the reaction mixture under reduced pressure, 216 g of DCE was added, and the mixture was stirred at room temperature for 1 hour. After filtration, the cake was dried to obtain 87.1 g of purified LiFSI, with a yield of 92.2%. Quality evaluation of the LiFSI purified product revealed an acid value (calculated in HF) of 174 ppm, chloride ions of 144 ppm, fluoride ions of 57 ppm, sulfate ions of 61 ppm, sodium of 2 ppm, potassium of 2 ppm, and moisture content of 24 ppm. This did not meet the standards specified in industry standard YS / T 1302-2019.

[0052] The above embodiments are for illustrative purposes only and should not be understood as limitations of the present invention. Furthermore, the various modifications and method variations in the inventions listed herein are readily conceivable to those skilled in the art, as long as they do not depart from the scope and spirit of the invention. While the present invention has been specifically described by combining many specific preferred embodiments, the present invention is, of course, not limited to these specific embodiments. In fact, inventions obtained by various modifications readily conceivable to those skilled in the art, as described above, all fall within the scope of the present invention.

Claims

1. Lithium bis(fluorosulfonyl)imide is obtained by reacting bis(fluorosulfonyl)imide with lithium carbonate in a mixed organic solvent and post-treatment, wherein each individual solvent in the mixed organic solvent has a different polarity, and the mixed organic solvent is a combination of solvent A and solvent B, where solvent A and solvent B have different polarities, and solvent A is at least one selected from carbonate ester solvents, carboxylic acid ester solvents, ether solvents, or ketone solvents, and solvent B is at least one selected from alkanes, cycloalkanes, substituted alkanes, aromatic hydrocarbons, or substituted aromatic hydrocarbons. The reaction scheme is as follows, with an initial reaction temperature of -70°C to -10°C, and maintaining the above initial temperature, 【Chemistry 1】 The post-treatment includes step (1): filtering the reaction system after the reaction to obtain a filtrate and a cake; and step (2): obtaining lithium bis(fluorosulfonyl)imide by filtration, concentration and crystal precipitation. After step (1) above, step (3) further includes: adding a desiccant to the filtrate from step (1) and drying it, and after drying is complete, performing step (2) above. A method for producing lithium bis(fluorosulfonyl)imide, wherein the desiccant is at least one selected from metallic lithium, butyllithium, lithium hydride, calcium hydride, lithium sulfate, lithium bis(fluorosulfonyl)imide, thionyl chloride, phosgene, diphosgene, triphosgene, oxalyl chloride, or silicon tetrachloride.

2. [a2] The molar ratio of lithium carbonate to bis(fluorosulfonyl)imide is 0.5:1 to 20:

1. [a3] The mass ratio of the mixed organic solvent to bis(fluorosulfonyl)imide is 0.1:1 to 20:

1. [a4] The reaction temperature of the above reaction shall be between -70°C and 50°C. [a5] The reaction time of the above reaction is 1 to 5 hours. [a6] The specific process of the above reaction is to add bis(fluorosulfonyl)imide dropwise to a mixed organic solvent system of lithium carbonate. A method for producing lithium bis(fluorosulfonyl)imide according to claim 1, characterized by comprising at least one of the following.

3. The above manufacturing method further [a12] The mass ratio of solvent A to bis(fluorosulfonyl)imide is 0.1:1 to 10:

1. [a13] The mass ratio of solvent B to bis(fluorosulfonyl)imide is 0.5:1 to 10:

1. A method for producing lithium bis(fluorosulfonyl)imide according to claim 1, characterized by comprising at least one of the following.

4. The aforementioned solvent A is dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethyl formate, n-propyl formate, isopropyl formate, n-butyl formate, isobutyl formate, t-butyl formate, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, propionic acid A method for producing lithium bis(fluorosulfonyl)imide according to claim 3, characterized in that it is at least one selected from t-butyl, methyl n-butanoate, ethyl n-butanoate, n-propyl n-butanoate, isopropyl n-butanoate, n-butyl n-butanoate, isobutyl n-butanoate, t-butyl n-butanoate, methyl isobutanoate, ethyl isobutanoate, n-propyl isobutanoate, isopropyl isobutanoate, n-butyl isobutanoate, isobutyl isobutanoate, or t-butyl isobutanoate.

5. The method for producing lithium bis(fluorosulfonyl)imide according to claim 3, characterized in that the solvent B is at least one selected from pentane, hexane, heptane, cyclohexane, methylcyclohexane, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, tetrachloroethane, benzene, toluene, xylene, ethylbenzene, propylbenzene, isopropylbenzene, chlorobenzene, or dichlorobenzene.

6. The aforementioned manufacturing method further includes, [a21] In a2 above, the molar ratio of lithium carbonate to bis(fluorosulfonyl)imide is 1:1 to 15:

1. [a41] In a4 above, the reaction temperature of the reaction is -50 to 20°C. A method for producing lithium bis(fluorosulfonyl)imide according to claim 2, characterized by comprising at least one of the following.

7. The method for producing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that the mass ratio of the desiccant to the bis(fluorosulfonyl)imide is 0.001 to 0.1:

1.

8. The method for producing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that the solvent used for the crystal precipitation is a poor solvent for lithium bis(fluorosulfonyl)imide salt.

9. A method for producing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that the cake in step (1) is dried to obtain lithium carbonate.

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