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 in particular to a method for preparing lithium bis(fluorosulfonyl)imide. [Background technology]

[0002] Lithium-ion batteries are important secondary batteries due to their high operating voltage, small volume, light weight, high energy, no memory effect, no pollution, low self-discharge, and long cycle life. They are widely used in various aspects of modern production and daily life. Compared to the conventional electrolyte salt LiPF6, lithium bis(fluorosulfonyl)imide (LiFSI) has better electrical conductivity, higher electrochemical and thermal stability, and hydrolysis resistance. The addition of LiFSI significantly increases the charge / discharge cycles of batteries and stabilizes highly active electrode materials such as high-nickel cathodes and high-voltage cathodes, thereby extending battery life and improving the flame retardancy of the electrolyte, thereby enhancing safety.

[0003] Most methods for synthesizing LiFSI involve first synthesizing bis(chlorosulfonyl)imide (HClSI) and then reacting it with MFn (where M is a group 11 to 15 element, period 4 to 6) to produce the corresponding metal or organic base bis(fluorosulfonyl)imide salt intermediate, which then undergoes a cation exchange reaction with LiOH or Li2CO3 to obtain LiFSI (Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4).The disadvantages of these methods are that the exchange reaction does not proceed sufficiently after reaching equilibrium, and it is difficult to sufficiently separate the unreacted intermediate MSFI (where M is a metal cation or an organic base cation) from LiFSI to obtain a high-quality product.

[0004] Purified potassium bis(fluorosulfonyl)imide (KFSI) is metal-exchanged with lithium salts such as LiClO4, LiBF4, lithium bis(oxalato)borate, and LiPF6 to produce LiFSI, but the potassium ion content in the product is often high, which affects its practical application. In particular, both LiClO4 and the resulting KClO4 pose some degree of explosion risk (Non-Patent Document 1, Non-Patent Document 2, Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, Patent Document 9, Patent Document 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 still has obvious problems. HFSI dissolves in water, releasing heat violently, leading to decomposition of HFSI. This patent solves the technical problem of HFSI dissolving in water by preparing an HFSI aqueous solution at an ultra-low temperature (-78°C), but this method consumes a large amount of energy. More importantly, LiFSI has excellent water solubility, resulting in very low extraction efficiency and making it unsuitable for industrial production.

[0006] In addition, in Patent Document 12, bis(fluorosulfonyl)imide (HFSI) and lithium carbonate were used to produce it in an organic solvent. Water was produced in the production process, and the product LiFSI was easily hydrolyzed in water, so it was removed with SOCl2, but at the same time acidic waste gases such as SO2 and HCl were produced, resulting in high costs for treating the waste gas, wastewater, and solid waste. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2013 / 0331609 [Patent Document 2] US Patent Application Publication No. 2012 / 0041233 [Patent Document 3] European Patent Application Publication No. 2415757 [Patent Document 4] US Patent Application Publication No. 2011 / 0034716 [Patent Document 5] Chinese Patent Application Publication No. 101747242 [Patent Document 6] Chinese Patent Application Publication No. 101747243 [Patent Document 7] Chinese Patent Application Publication No. 101654229 [Patent Document 8] Chinese Patent Application Publication No. 105523970 [Patent Document 9] Chinese Patent Application Publication No. 103910346 [Patent Document 10] Chinese Patent Application Publication No. 104495767 [Patent Document 11] U.S. Patent No. 8,377,406 [Patent Document 12] Chinese Patent No. 104925765 [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. Summary of the Invention [Problem to be solved by the invention]

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

[0010] In view of the above-mentioned problems of the existing techniques, an object of the present invention is to provide a method for producing lithium bis(fluorosulfonyl)imide, which is a simple process and capable of producing lithium bis(fluorosulfonyl)imide with high yield and high quality.

[0011] To achieve the above and other related objects, the present invention provides 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, wherein the polarity of each solvent in the mixed organic solvent is different; The reaction scheme provides a method for preparing lithium bis(fluorosulfonyl)imide, which is as follows: [ka]

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

[0013] In some possible embodiments, the molar ratio of the lithium carbonate to the 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 the bis(fluorosulfonyl)imide may be 0.1:1 to 20:1.

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

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

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

[0018] The main beneficial effects of the present method for producing lithium bis(fluorosulfonyl)imide include the following: 1) Lithium bis(fluorosulfonyl)imide and lithium hydrogen carbonate are produced by reacting bis(fluorosulfonyl)imide with lithium carbonate in a mixed organic solvent. This reaction produces almost no water, and post-treatment is simple. The resulting lithium bis(fluorosulfonyl)imide is of high quality and in high yield. 2) The lithium bicarbonate produced in the reaction can be recovered and reused through a simple process. DETAILED DESCRIPTION OF THE INVENTION

[0019] The inventors of this application have conducted research and found that when bis(fluorosulfonyl)imide and lithium carbonate are reacted in a mixed organic solvent, the reaction progress can be controlled so that only lithium bicarbonate remains, and almost no water is produced. This has enabled them to optimize the production process and obtain lithium bis(fluorosulfonyl)imide in high yield and high quality. Furthermore, lithium bicarbonate is easily recovered, providing a clean and environmentally friendly process route. Based on this, the present invention has been completed.

[0020] The present invention relates to a method for producing lithium bis(fluorosulfonyl)imide by reacting bis(fluorosulfonyl)imide (HFSI) with lithium carbonate (LiCO) in a mixed organic solvent, followed by post-treatment, and the polarity of each solvent in the mixed organic solvent is different. The reaction scheme provides a method for preparing lithium bis(fluorosulfonyl)imide (LiFSI): [ka]

[0021] Using the above synthetic route, the reaction system contains very little water, and the resulting lithium bicarbonate is very easy to recover. The progress of the reaction can be controlled by selecting an appropriate reaction system. In some embodiments of the present invention, the mixed organic solvent is a combination of solvents A and B, where solvents A and B have different polarities. Although LiFSI has good solubility in some highly polar solvents, experimental results have shown that using a highly polar solvent alone makes it difficult for the reaction to remain at the LiHCO3 stage. LiHCO3 continues to react with HFSI to form LiFSI, simultaneously producing carbon dioxide and water. However, the inventors have found through research that the reaction between LiFSI and lithium bicarbonate remains at the LiHCO3 stage when organic solvents with different polarities are mixed as reaction solvents. Of course, the inventors also attempted to use a low-polarity solvent alone, but because LiFSI has poor solubility in low-polarity solvents, LiHCO3 and LiFSI precipitated together as solids, making further separation and purification impossible.

[0022] Specifically, solvent A is generally a polar solvent, for example, a solvent containing a polar group such as a hydroxyl group or a carboxyl group, 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, and ketone solvents, where the C chain in the carbonate ester solvent, carboxylic acid ester solvent, ether solvent, or ketone solvent is selected based on the solubility of the reactant or product. Preferably, the polar organic solvent 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, propionic acid, 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, and t-butyl isobutanoate.

[0023] Solvent B is generally at least one selected from alkanes, cycloalkanes, substituted alkanes (particularly halogen-substituted alkanes), aromatic hydrocarbons, or substituted aromatic hydrocarbons (particularly 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. Alternatively, 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. When considering process economics and product yield and quality, 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 the bis(fluorosulfonyl)imide is 0.1:1 to 20:1, and a reasonable mass ratio of the mixed solvent to the bis(fluorosulfonyl)imide is used in consideration of the reaction process, reaction efficiency, post-treatment 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 optionally 0.5:1 to 0.8:1, 0.8:1 to 3:1, 3:1 to 8:1, or 8:1 to 10:1. Experiments have demonstrated that maintaining a predetermined mass ratio of solvent B to bis(fluorosulfonyl)imide can keep the reaction process 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, optionally 0.5:1 to 1:1, 1:1 to 5:1, or 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 being 1:4 to 1:7. Experiments have demonstrated that maintaining a predetermined mass ratio of solvent A to bis(fluorosulfonyl)imide can ensure good solubility of lithium bis(fluorosulfonyl)imide.

[0028] In summary, by selecting the appropriate ratio of the mixed solvent and the ratio of the reactants, the reaction process can be maintained at the lithium bicarbonate stage. Since water is not produced in this synthetic route, there is no need to remove water during the reaction process using a desiccant. This not only simplifies the process but also improves the yield and quality of lithium bis(fluorosulfonyl)imide.

[0029] In some embodiments of the present invention, the reaction temperature is −70°C to 50°C, and optionally −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, HFSI dissipates heat vigorously during dissolution in water, and the presence of a small amount of water in the reaction solvent or synthetic route is inevitable. Therefore, maintaining a certain low temperature can improve the yield and quality of HFSI. Of course, since little water is produced in the synthetic route of the present invention, the temperature can be controlled to −30°C to 0°C. It is necessary to maintain the initial temperature of the reaction system, which is −70°C to −10°C, and optionally −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 mentioned above, in order to avoid the intense heat generated during the dissolution of HFSI, the preferred process is to dropwise add bis(fluorosulfonyl)imide to the mixed organic solvent system of lithium carbonate, and adjust the dropwise addition rate appropriately according to the needs of the reaction system.

[0031] In some embodiments of the present invention, the reaction time for 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 crystallization.

[0033] Specifically, the reaction solution after the reaction is filtered. The filtration is performed using 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 completed, the filtrate is concentrated under normal pressure and / or reduced pressure. After concentration is complete, a poor solvent is added to precipitate crystals. The poor solvent is selected from organic solvents, preferably alkanes, cycloalkanes, halogenated alkanes, aromatic hydrocarbons, and halogenated aromatic hydrocarbons. Specifically, the poor solvent is selected 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, solid-liquid separation and drying are performed to obtain lithium bis(fluorosulfonyl)imide.

[0034] In some embodiments of the present invention, a small amount of water may be present in the reaction solvent during the reaction, or moisture may be introduced due to air humidity. Therefore, since trace amounts of water are produced during the reaction, a step (3) is further included between steps (1) and (2): adding a desiccant to the filtrate from step (1) to dry it, and then performing step (2) after the drying is complete. The desiccant is at least one selected from metallic lithium, butyllithium, lithium hydride (LiH), calcium hydride (CaH), lithium sulfate (LiSO), lithium bis(fluorosulfonyl)imide (LiFSI), thionyl chloride, phosgene, diphosgene, triphosgene, oxalyl chloride, and silicon tetrachloride (SiCl). After the drying is complete, the reaction solution is further filtered using suction filtration and / or pressure filtration. The filtrate obtained by this filtration is then subjected to concentration and crystallization in step (2). The use of a desiccant maintains the moisture content of the filtrate at 50 ppm or less, ensuring the yield and quality of LiFSI. Here, the drying agent is determined depending on the moisture content of the filtrate, and the mass ratio of bis(fluorosulfonyl)imide is generally 0.001 to 0.1:1.

[0035] The cake obtained in step (1) is dried to obtain lithium carbonate, which can be recovered and reused. Specifically, the reaction scheme in which LiHCO3 is thermally dehydrated to produce Li2CO3 is as follows: [ka]

[0036] Specifically, the cake from step (1) is subjected to gradient temperature drying to obtain lithium carbonate. The drying temperature is 60-120°C. More specifically, the first gradient drying (60-80°C) is performed at 60°C for 5-8 hours, the second gradient drying (80-110°C) is performed for 1-3 hours, and the third gradient drying (110-120°C) is performed for 2-5 hours. The LOD (loss on dry weight) is set to <0.1%. Here, gradient temperature increases the CO2 release rate more steadily; if the temperature is increased to the maximum temperature in one go, a large amount of CO2 will be released, posing a risk of material erupting due to overpressure.

[0037] Although the present invention will be described below with reference to specific examples, those skilled in the art will readily appreciate other advantages and effects of the present invention from the disclosure herein. The present invention may be implemented or applied in other different specific embodiments, and the details herein may be modified or changed in various ways based on different perspectives and applications without departing from the spirit of the present invention.

[0038] When a range of values ​​is given in an example, unless otherwise specified in the present invention, it is possible to select any value between the endpoints of each range. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art. Apart from the specific methods, equipment, and materials used in the examples, a person skilled in the art can realize the present invention using any method, equipment, and material in the existing art that is similar or equivalent to the method, equipment, and material described in the examples of the present invention, based on their understanding of the existing technology and the description of the present invention. [Example]

[0039] Example 1 A 5000 mL glass reaction bottle was charged with 2250 g of DCE and 450 g of methyl formate, and stirring was initiated. 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, 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 a cake of 737 g. 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, after which it was filtered. The solvent was removed from the filtrate under reduced pressure, and 1086 g of DCE was added. The mixture was stirred at room temperature for 1 hour, filtered, and the cake was dried to obtain 445.3 g of purified LiFSI, with a yield of 95.3%. The quality of the LiFSI refined product was evaluated and found to have an acid value (calculated using 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 of 23 ppm. The product met the parameters specified in the industry standard YS / T 1302-2019.

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

[0041] Example 2 A 5000 mL glass reaction bottle was charged with 2250 g of DCM and 450 g of methyl formate and stirred. 630 g of Li2CO3 and 110 g of fresh Li2CO3 were added. The reaction mixture was cooled to -25°C, and then 452.5 g of HFSI was added dropwise to the reaction mixture while maintaining the temperature at -30±5°C. After the addition, 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 a cake of 776 g. 0.5 g of CaH2 was added to the filtrate and stirred for 2 hours until the water content in the reaction mixture was <50 ppm, after which it was filtered. The filtrate was stripped of solvent under reduced pressure, and 1086 g of DCE was added. The mixture was stirred at room temperature for 1 hour, filtered, and the cake was dried to obtain 447.0 g of purified LiFSI, a yield of 95.7%. The quality of the LiFSI refined product was evaluated and found to have an acid value (calculated using 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 of 27 ppm. The product met the parameters specified in the industry standard YS / T 1302-2019.

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

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

[0044] Example 4 A 1000 mL glass reaction bottle was charged with 540 g of DCE and 90 g of dimethyl carbonate, and stirring was initiated. 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, 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 a cake of 147 g. 2.5 g of SOCl2 was added to the filtrate and stirred for 2 hours until the water content in the reaction system was <50 ppm. The reaction solution 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). After stirring for 2 hours, the mixture was filtered. The filtrate was stripped of solvent under reduced pressure, and 216g of DCE was added. The mixture was stirred at room temperature for 1 hour, then filtered. The cake was dried to obtain 90.3g of purified LiFSI. The yield was 96.6%, with an acid value (calculated using HF) of 9ppm, chloride ions 8ppm, fluoride ions 3ppm, sulfate ions <1ppm, sodium 3ppm, potassium 1ppm, and water 13ppm. The product met the specifications specified in the industry standard YS / T 1302-2019.

[0045] Example 5 A 1000 mL glass reaction bottle was charged with 540 g of DCE and 90 g of butyl acetate, and stirring was initiated. 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 yield 614 g of filtrate with a water content of 604 ppm and 142 g of cake. 9.5 g of Li2SO4 was added to the filtrate, and the mixture was stirred for 2 hours until the water content in the reaction system was less than 50 ppm, after which it was filtered. The filtrate was stripped of solvent under reduced pressure, and 216g of DCE was added. The mixture was stirred at room temperature for 1 hour, then filtered. The cake was dried to obtain 88.4g of purified LiFSI. The yield was 94.5%, with an acid value (calculated using HF) of 22ppm, chloride ions 3ppm, fluoride ions 3ppm, sulfate ions <1ppm, sodium 4ppm, potassium 2ppm, and water 25ppm. The product met the specifications specified in the industry standard YS / T 1302-2019.

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

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

[0048] Example 8 A 500 mL glass reaction bottle was charged with 300 g of DCE and 45 g of methyl acetate, and stirring was initiated. 111 g of Li2CO3 was added, and the reaction mixture was cooled to -25°C. While maintaining this temperature, 45.3 g of HFSI was added dropwise. After the addition, the mixture was stirred for 3 hours while maintaining the temperature. The mixture was then filtered, and the resulting 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 stirred at room temperature for 1 hour. The cake was dried to yield 204.4 g of purified LiFSI, with a 95.0% conversion yield, an acid value (calculated using HF) of 11 ppm, chloride ions 3 ppm, fluoride ions 7 ppm, sulfate ions 5 ppm, sodium 2 ppm, potassium 2 ppm, and water 26 ppm. The product met the specifications set out in industry standard YS / T 1302-2019.

[0049] Comparative Example 1 A 1000 mL glass reaction bottle was charged with 540 g of DCE and 90 g of dimethyl carbonate, and stirring was initiated. 148 g of Li2CO3 was added, and the reaction mixture was cooled to 0-5°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise. After the addition, the mixture was stirred for 3 hours while maintaining the temperature, and then filtered to yield 674 g of filtrate with a water content of 6600 ppm and a cake of 135 g. The solvent was removed from the filtrate under reduced pressure, and 216 g of DCE was added. After stirring at room temperature for 1 hour, the reaction mixture 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 A 1000 mL glass reaction bottle was charged with 540 g of DCE and 90 g of dimethyl carbonate, and stirring was initiated. 148 g of Li2CO3 was added, and the reaction mixture was cooled to -25°C. Then, while maintaining the temperature at -30±5°C, 90.5 g of HFSI was added dropwise. After the addition, the mixture was stirred for 3 hours while maintaining the temperature. The mixture was then filtered, yielding 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, and 216 g of DCE was added. The mixture was stirred at room temperature for 1 hour. The cake was then filtered and dried to yield 87.2 g of purified LiFSI. The acid value (calculated using HF) was 53 ppm, chloride ions 2 ppm, fluoride ions 38 ppm, sulfate ions 61 ppm, sodium 2 ppm, potassium 1 ppm, and water 57 ppm. The moisture and sulfate ions of the product failed, exceeding the indicators specified in the industry standard YS / T 1302-2019.

[0051] Comparative Example 3 A 1000 mL glass reaction bottle was charged with 450 g of dimethyl carbonate and stirred. 148 g of Li2CO3 was added, and the reaction mixture was cooled to -25°C. While maintaining this temperature, 90.5 g of HFSI was added dropwise. After the addition, the mixture was stirred for 3 hours while maintaining the temperature. The mixture was then filtered, yielding 528 g of filtrate with a water content of 8210 ppm and a cake of 139 g. 34.4 g of SOCl2 was added to the filtrate and stirred for 12 hours until the water content in the reaction mixture was <50 ppm. The solvent was removed from the reaction mixture under reduced pressure, and 216 g of DCE was added. The mixture was stirred at room temperature for 1 hour. The cake was then filtered and dried to yield 87.1 g of purified LiFSI, a 92.2% yield. The quality of the LiFSI refined product was evaluated and found to have an acid value (calculated using 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 of 24 ppm. These did not meet the criteria specified in the industry standard YS / T 1302-2019.

[0052] The above examples are intended to illustrate the embodiments disclosed in the present invention and are not to be construed as limiting the present invention. Furthermore, various modifications and variations of the methods of the invention described herein will be readily apparent to those skilled in the art without departing from the scope and spirit of the present invention. While the present invention has been specifically described by combining many specific preferred embodiments of the present invention, the present invention is not, of course, limited to these specific examples. Indeed, any inventions obtained by various modifications readily apparent to those skilled in the art as described above are all included within the scope of the present invention.

Claims

1. bis(fluorosulfonyl)imide and lithium carbonate are reacted in a mixed organic solvent, followed by post-treatment to obtain lithium bis(fluorosulfonyl)imide, and the polarities of the individual solvents in the mixed organic solvent are different; The reaction scheme for preparing lithium bis(fluorosulfonyl)imide is as follows: 【Chemical 1】

2. [a1] The mixed organic solvent is a combination of solvent A and solvent B, wherein solvent A and solvent B have different polarities; [a2] the molar ratio of the lithium carbonate to the bis(fluorosulfonyl)imide is 0.5:1 to 20:1; [a3] the mass ratio of the mixed organic solvent to the bis(fluorosulfonyl)imide is 0.1:1 to 20:1; [a4] the reaction temperature of the reaction is −70° C. to 50° C.; [a5] the reaction time of the reaction is 1 to 5 hours; [a6] The specific process of the reaction is to dropwise add bis(fluorosulfonyl)imide to a mixed organic solvent system of lithium carbonate; [a7] the post-treatment comprises: 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 crystallization; 2. The method for producing lithium bis(fluorosulfonyl)imide according to claim 1, further comprising at least one of the following:

3. The manufacturing method further comprises: [a11] In the above a1, the A solvent is at least one selected from a carbonate ester solvent, a carboxylic acid ester solvent, an ether solvent, or a ketone solvent, and the B solvent is at least one selected from an alkane, a cycloalkane, a substituted alkane, an aromatic hydrocarbon, or a substituted aromatic hydrocarbon; [a12] In the above-mentioned a1, the mass ratio of the solvent A to the bis(fluorosulfonyl)imide is 0.1:1 to 10:1, preferably 0.5:1 to 8:1, and more preferably 0.8:1 to 3:1; [a13] In the above-mentioned a1, the mass ratio of the solvent B to the bis(fluorosulfonyl)imide is 0.5:1 to 10:1, preferably 1:1 to 5:1, and more preferably 2:1 to 4:1; 3. The method for producing lithium bis(fluorosulfonyl)imide according to claim 2, further comprising at least one of the following:

4. The solvent A may be 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 4. The method for producing lithium bis(fluorosulfonyl)imide according to claim 3, wherein the carboxylic acid is at least one selected from the group consisting of 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, and t-butyl isobutanoate.

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

6. The manufacturing method further comprises: [a21] In the a2, the molar ratio of the lithium carbonate to the bis(fluorosulfonyl)imide is 1:1 to 15:1, preferably 2:1 to 10:1; [a41] In the above-mentioned a4, the reaction temperature of the reaction is −50 to 20° C., preferably −30 to 0° C.; 3. The method for producing lithium bis(fluorosulfonyl)imide according to claim 2, further comprising at least one of the following:

7. 3. The method for producing lithium bis(fluorosulfonyl)imide according to claim 2, further comprising, after the step (1), a step (3): adding a desiccant to the filtrate from the step (1) to dry it, and then performing the step (2) after the drying is completed.

8. 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, and silicon tetrachloride; 8. The method for producing lithium bis(fluorosulfonyl)imide according to claim 7, wherein the mass ratio of the desiccant to the bis(fluorosulfonyl)imide is 0.001 to 0.1:

1.

9. 3. The method for producing lithium bis(fluorosulfonyl)imide according to claim 2, wherein the solvent used for the crystal precipitation is a poor solvent for the lithium bis(fluorosulfonyl)imide salt, and preferably the solvent used for the crystal precipitation is at least one selected from alkanes, cycloalkanes, substituted alkanes, aromatic hydrocarbons, and substituted aromatic hydrocarbons, and more preferably the solvent used for the crystal precipitation 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, and dichlorobenzene.

10. The method for producing lithium bis(fluorosulfonyl)imide according to claim 2, wherein the cake in the step (1) is dried to obtain lithium carbonate, preferably by drying the cake in the step (1) with a temperature ramp, and the drying temperature is 60 to 120°C.

Images