Liquid bis(fluorosulfonyl)imide metal salt and preparation method therefor

Abstract

Provided are a liquid bis(fluorosulfonyl)imide metal salt and a preparation method therefor. The preparation method comprises the following steps: reacting a bis(fluorosulfonyl)imide with a fluorinated metal compound, so as to obtain a molten reaction solution; devolatilizing the reaction solution until the EP1 acidity in terms of HF is less than or equal to 0.5 ppm, so as to obtain a bis(fluorosulfonyl)imide compound; and dissolving same in a solvent, and then performing a resin-based deacidification treatment, so as to obtain a liquid bis(fluorosulfonyl)imide metal salt, wherein the heating temperature in the devolatilization treatment is lower than 140°C.

Description

A bis(fluorosulfonyl)imide metal liquid salt and its preparation method

[0001] Priority information

[0002] This application claims priority and benefits to patent application No. 202411729291.8, filed with the China National Intellectual Property Administration on November 28, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to a method for preparing a bis(fluorosulfonyl)imide metal compound, and more particularly to a bis(fluorosulfonyl)imide metal liquid salt and its preparation method, belonging to the field of new energy materials technology. Background Technology

[0004] With increasing attention paid to the green and low-carbon economy, metal compound batteries (such as lithium batteries and sodium batteries) have attracted much attention due to their advantages such as high operating voltage, high energy density, long lifespan, and no memory effect, and are widely used in new energy vehicles, digital products, energy storage instruments, and other fields. A battery consists of four main components: the positive electrode, the negative electrode, the separator, and the electrolyte. Among these, the electrolyte has a significant impact on the battery's cycle life, high and low temperature performance, and safety performance.

[0005] Metal hexafluorophosphate compounds (such as LiPF6 and NaPF6) are currently widely used liquid salt electrolytes, but they still have a number of drawbacks, such as poor thermal stability, poor stability to water, and the release of HF upon decomposition. Difluorosulfonyl imide metal compounds (such as LiFSI and NaFSI) are novel fluorine-containing metal salts that can serve as the next generation of main components for electrolytes. Compared to metal hexafluorophosphate compounds, difluorosulfonyl imide metal compounds have higher decomposition temperatures, higher water stability, and superior electrical conductivity and isoelectric properties.

[0006] Currently, bisfluorosulfonylimide metal compounds are prepared by reacting bisfluorosulfonylimide or its derivatives with alkali metal salts. After preparation, it is necessary to remove residual acid or high-boiling-point liquid impurities such as water byproducts. However, conventional impurity removal methods are costly and time-consuming, limiting the large-scale production of bisfluorosulfonylimide metal compounds.

[0007] Therefore, how to improve preparation efficiency and reduce costs while ensuring the high purity of bis(fluorosulfonyl)imide metal compounds is a problem that urgently needs to be solved by those skilled in the art.

[0008] Application content

[0009] This application provides a method for preparing bis(fluorosulfonyl)imide metal liquid salt, which can produce bis(fluorosulfonyl)imide metal liquid salt with high purity, and has the advantages of high production efficiency and low cost.

[0010] This application provides a bis(fluorosulfonyl)imide metal liquid salt, which exhibits high purity.

[0011] This application provides a method for preparing a bis(fluorosulfonyl)imide metal liquid salt, comprising the following steps:

[0012] A molten reaction solution is obtained by reacting bis(fluorosulfonyl)imide with a fluorinated metal compound. The reaction solution is then subjected to devolatilization treatment until the acidity of EP1 (first equivalence point) based on HF is ≤0.5ppm to obtain a bis(fluorosulfonyl)imide metal compound. This compound is then dissolved in a solvent and subjected to resin deacidification treatment to obtain a bis(fluorosulfonyl)imide metal liquid salt.

[0013] The heating temperature of the devolatilization treatment is below 140°C.

[0014] This application also provides a bis(fluorosulfonyl)imide metal liquid salt, wherein the bis(fluorosulfonyl)imide metal liquid salt is prepared by the preparation method of the bis(fluorosulfonyl)imide metal compound as described above;

[0015] The impurities in the bis(fluorosulfonyl)imide metal liquid salt, by mass percentage, include:

[0016] Aminosulfonate ≤100ppm, fluorosulfonate ≤300ppm, fluorosulfonamide ≤10ppm.

[0017] The method for preparing bis(fluorosulfonyl)imide metal liquid salt in this application combines devolatilization and resin deacidification. First, high temperature and negative pressure are used to efficiently and rapidly remove most of the acidic substances from the molten reaction solution, resulting in an EP1 acidity of ≤0.5 ppm (HF). Then, resin is used to quickly remove the remaining acidic substances. This method not only produces high-purity bis(fluorosulfonyl)imide metal liquid salt with short post-processing time, but also allows a batch of resin to be used multiple times, reducing costs and avoiding the cumbersome operation of frequent resin replacement. Furthermore, after the bis(fluorosulfonyl)imide metal compound is dissolved, the subsequent resin deacidification process yields the liquid salt. This reduces the need for powdering after cooling and solidification, simplifying the production process, shortening production time, and reducing costs. Moreover, the liquid salt can be directly used in the electrolyte, reducing the need for electrolyte salt dissolution during electrolyte preparation.

[0018] The bis(fluorosulfonyl)imide metal liquid salt provided in this application has high purity, which is beneficial for the widespread application of bis(fluorosulfonyl)imide metal liquid salt in the battery field. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] This application provides a method for preparing a bis(fluorosulfonyl)imide metal liquid salt, comprising the following steps:

[0021] A molten reaction solution was obtained by reacting bis(fluorosulfonyl)imide with a fluorinated metal compound. The reaction solution was then subjected to a devolatilization treatment until the EP1 acidity (based on HF) was ≤0.5 ppm to obtain a bis(fluorosulfonyl)imide metal compound. This compound was then dissolved in a solvent and subjected to a resin deacidification treatment to obtain a bis(fluorosulfonyl)imide metal liquid salt.

[0022] The heating temperature for the devolatilization treatment is below 140℃.

[0023] Specifically, bis(fluorosulfonyl)imide is mixed with a fluorinated metal compound and reacted at a certain temperature. After the reaction is completed, a reaction solution containing the bis(fluorosulfonyl)imide metal compound is obtained. This reaction solution containing the bis(fluorosulfonyl)imide metal compound is in a molten state. Then, by controlling parameters such as temperature (below 140°C) and vacuum degree, the reaction solution is subjected to a devolatilization treatment to quickly remove most of the low-boiling-point impurities (such as HF and bis(fluorosulfonyl)imide). The EP1 acidity of the reaction solution, calculated as HF, is monitored until it is no higher than 0.5 ppm to obtain the bis(fluorosulfonyl)imide metal compound. Subsequently, the bis(fluorosulfonyl)imide metal compound is dissolved in a solvent to obtain a bis(fluorosulfonyl)imide metal compound solution. The bis(fluorosulfonyl)imide metal compound solution is then subjected to resin deacidification treatment to obtain a bis(fluorosulfonyl)imide metal liquid salt.

[0024] The fluorinated metal compound of this application can be selected according to the target bis(fluorosulfonyl)imide metal compound. For example, lithium fluoride can be selected to prepare lithium bis(fluorosulfonyl)imide, and sodium fluoride can be selected to prepare sodium bis(fluorosulfonyl)imide.

[0025] The main purpose of the reaction between bis(fluorosulfonyl)imide and fluorinated metal compounds is to generate bis(fluorosulfonyl)imide metal compounds. As for the reaction temperature and time, they can be determined according to the selection and ratio of raw materials, as long as the final reaction solution is in a molten state.

[0026] Before starting the devolatilization process, this application does not perform any temperature treatment on the reaction solution, but maintains the reaction temperature, so that the bis(fluorosulfonyl)imide metal compound reaction solution can be directly devolatilized in a molten state.

[0027] For the devolatilization treatment of the reaction solution, as long as impurities in the reaction solution (such as unreacted bis(fluorosulfonyl)imide and byproduct HF) can be removed as much as possible in a short time and the EP1 acidity of the bis(fluorosulfonyl)imide metal compound (calculated as HF) after devolatilization is guaranteed to be ≤0.5 ppm, those skilled in the art can determine the relevant parameters (such as vacuum degree) for the devolatilization treatment. The devolatilization treatment temperature in this application is below 140°C. If the heating temperature of the devolatilization treatment is too high, it will cause the bis(fluorosulfonyl)imide metal compound to undergo a condensation reaction, producing byproducts such as fluorosulfonic acid metal compounds, resulting in an abnormal increase in fluorosulfonate ions.

[0028] This application does not limit the specific choice of solvent; it can be selected according to actual needs.

[0029] This application does not limit the mass ratio of the bis(fluorosulfonyl)imide metal compound to the solvent, as long as the bis(fluorosulfonyl)imide metal compound can be dissolved.

[0030] This application does not limit the dissolution temperature of the bis(fluorosulfonyl)imide metal compound in the solvent, and the temperature can be selected according to actual needs.

[0031] This application does not limit the specific choice of resin; it can be selected according to actual needs.

[0032] The resin deacidification process described in this application can remove acidic substances from the bis(fluorosulfonyl)imide metal compound to obtain high-purity bis(fluorosulfonyl)imide metal liquid salt.

[0033] The preparation method of this application does not generate water, which not only avoids the waste of energy and time required for subsequent water removal, but also allows for efficient and rapid removal of impurities by performing devolatilization on the reaction solution while maintaining the reaction temperature, reducing the EP1 acidity of the reaction solution (calculated as HF) to ≤0.5 ppm. By combining immediate devolatilization while maintaining the reaction temperature with controlling the devolatilization concentration to an EP1 acidity of ≤0.5 ppm (calculated as HF), the devolatilization time is shortened, avoiding the need to spend a significant amount of time removing residual trace amounts of acid. Furthermore, because the acidity is controlled within a specific range, the deacidification effect of the resin is improved, achieving high purity of the bis(fluorosulfonyl)imide metal liquid salt. In addition, since the content of acidic substances in the bis(fluorosulfonyl)imide metal compound is low after devolatilization, the effective resin usage for each deacidification cycle is reduced, lowering costs and allowing the resin installed once to be used multiple times, avoiding the cumbersome operation caused by frequent resin replacement. Furthermore, dissolving the difluorosulfonamide metal compound obtained after devolatilization and then performing resin deacidification treatment can not only improve the resin deacidification effect, but also reduce the powdering process required after cooling and solidification, thereby simplifying the production process, shortening the production time, and reducing costs.

[0034] This application does not limit the source and purity of bis(fluorosulfonyl)imide; it can be purchased directly or prepared.

[0035] This application does not limit the source and purity of the fluorinated metal compound, which can be selected according to actual needs.

[0036] Generally, through the post-processing technology of this application, the bisfluorosulfonamide metal compound has high purity and low impurity content. Specifically, according to mass percentage, the impurities in the bisfluorosulfonamide metal compound include: aminosulfonate ≤350ppm, fluorosulfonate ≤1000ppm, fluorosulfonamide ≤50ppm, and chloride ion ≤20ppm.

[0037] The mass percentage of impurities in the bis(fluorosulfonyl)imide and bis(fluorosulfonyl)imide metal compounds of this application can be obtained by ion chromatography and nuclear magnetic fluorine spectroscopy.

[0038] The EP1 acidity of the bis(fluorosulfonyl)imide metal compound of this application can be obtained by triethylamine potentiometric titration.

[0039] In one specific embodiment, the vacuum degree of the devolatilization treatment is 1-0.1 kPa, for example, 1 kPa, 0.9 kPa, 0.8 kPa, 0.7 kPa, 0.6 kPa, 0.5 kPa, 0.4 kPa, 0.3 kPa, 0.2 kPa or 0.1 kPa; the heating temperature is not lower than 60°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C or 139°C; and the treatment time is 10-20 h, for example, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h. When the vacuum degree, heating temperature, and processing time of the devolatilization process are within the above-mentioned range, the devolatilization process can more quickly remove impurities from the reaction solution, and the separation effect between impurities and bis(fluorosulfonyl)imide metal compounds is good, avoiding the simultaneous removal of bis(fluorosulfonyl)imide metal compounds. This achieves the preparation of high-purity bis(fluorosulfonyl)imide metal compounds and high production efficiency. Furthermore, due to the appropriate selection of the temperature and vacuum degree of the devolatilization process, it has the advantage of low equipment requirements. In one specific embodiment, the heating temperature is 100-135℃, for example, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, or 135℃.

[0040] In one specific embodiment, the molten reaction liquid is prepared by reacting bis(fluorosulfonyl)imide and a fluorinated metal compound under solvent-free conditions. Specifically, in the reaction of bis(fluorosulfonyl)imide and the fluorinated metal compound of this application, no other reaction solvent is added. The bis(fluorosulfonyl)imide serves as both a reactant and a solvent environment for the reaction, allowing the bis(fluorosulfonyl)imide and the metal compound to react fully to generate a bis(fluorosulfonyl)imide metal compound. Reacting the bis(fluorosulfonyl)imide and the fluorinated metal compound under solvent-free conditions reduces impurities introduced during the addition of reactants and minimizes the impact of impurities caused by residual reactants, thereby further improving the purity of the bis(fluorosulfonyl)imide metal liquid salt. Simultaneously, it reduces the types of reactants used and lowers costs.

[0041] In one specific embodiment, the reaction temperature of bis(fluorosulfonyl)imide and the fluorinated metal compound is 130-140°C, and the reaction time is 4-8 hours. For example, the reaction temperature is 130°C, 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C, 139°C, or 140°C, and the reaction time is 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours. When the reaction temperature and reaction time are within the above ranges, the bis(fluorosulfonyl)imide and the fluorinated metal compound can react fully, which is beneficial to the subsequent devolatilization treatment and resin deacidification, allowing impurities to be quickly removed from the reaction solution, thereby achieving the preparation of high-purity bis(fluorosulfonyl)imide metal liquid salt.

[0042] In one specific embodiment, the molar ratio of bis(fluorosulfonyl)imide to the fluorinated metal compound is 1:(0.95-1.05), for example, a molar ratio of 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04 or 1:1.05. When the molar ratio of bis(fluorosulfonyl)imide to the fluorinated metal compound is within the above range, bis(fluorosulfonyl)imide and the fluorinated metal compound can react to form bis(fluorosulfonyl)imide metal compound, reducing the residue of unreacted bis(fluorosulfonyl)imide or fluorinated metal compound in the system after the reaction. This is beneficial for subsequent devolatilization and resin deacidification treatments, and avoids the situation where the amount of fluorinated metal compound added is too large, which would prevent the first filtration treatment from completely removing the fluorinated metal compound. It also avoids the situation where the fluorinated metal compound residue leads to an excessively high fluoride ion content, thereby helping to improve the purity of the bis(fluorosulfonyl)imide metal liquid salt and reduce the fluoride ion content, while avoiding the waste of raw materials and saving costs.

[0043] In one specific embodiment, the dissolution of the bis(fluorosulfonyl)imide metal compound in the solvent is carried out while it is in a molten state. When the bis(fluorosulfonyl)imide metal compound is dissolved in the solvent while remaining in a molten state, the powdering process required after the bis(fluorosulfonyl)imide metal compound cools and solidifies can be reduced, thereby simplifying the production process, shortening production time, and lowering costs.

[0044] In one specific embodiment, the temperature of the obtained bis(fluorosulfonyl)imide metal compound is maintained while it is mixed into a solvent, so that the bis(fluorosulfonyl)imide metal compound remains in a molten state during the aforementioned dissolution in the solvent. Specifically, the temperature of the bis(fluorosulfonyl)imide metal compound obtained from the devolatilization process is maintained so that the bis(fluorosulfonyl)imide metal compound is in a molten state, and then it is mixed into a solvent, maintaining the molten state while dissolving in the solvent to obtain a bis(fluorosulfonyl)imide metal compound solution. In this way, the bis(fluorosulfonyl)imide metal compound is kept in a molten state, which facilitates rapid dissolution in the solvent and avoids the bis(fluorosulfonyl)imide metal compound from condensing into lumps after cooling, making it difficult to dissolve in the solvent. This reduces the need for powder production, shortens production time, and lowers time costs.

[0045] In one specific embodiment, the solvent is an electrolyte solvent, which includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and ethylene carbonate; the mass ratio of the bis(fluorosulfonyl)imide metal compound to the electrolyte solvent is (59:141)-(61:139). When the above-mentioned solvent is selected as the electrolyte solvent, the bis(fluorosulfonyl)imide metal compound can dissolve in the electrolyte solvent to form a bis(fluorosulfonyl)imide metal compound solution, and the impurities in the bis(fluorosulfonyl)imide metal compound do not react with the electrolyte solvent, thus avoiding the occurrence of by-products. When the mass ratio of the bis(fluorosulfonyl)imide metal compound to the electrolyte solvent is within the above-mentioned range, the impurity content in the bis(fluorosulfonyl)imide metal compound solution is within a suitable range, which is beneficial to the subsequent resin deacidification treatment. The resin has better adsorption capacity for impurities, thereby improving the deacidification effect of the resin deacidification treatment and further improving the purity of the bis(fluorosulfonyl)imide metal liquid salt.

[0046] In one specific embodiment, the resin includes one of poly(4-vinylpyridine) resin, poly(N,N-dimethyl-p-styrene) resin, and poly(N,N-diethyl-p-styrene) resin; the A / B ratio is 1-5%, where A is the mass of the resin and B is the mass of the bis(fluorosulfonyl)imide metal compound. When the above-mentioned resin is selected, the resin can adsorb impurities in the bis(fluorosulfonyl)imide metal compound solution more quickly and efficiently, improving the deacidification effect of the resin deacidification treatment and increasing the purity of the bis(fluorosulfonyl)imide metal liquid salt. When the mass of the resin and the mass of the bis(fluorosulfonyl)imide metal compound are within the above-mentioned range, it is beneficial for the resin to quickly adsorb impurities in the bis(fluorosulfonyl)imide metal compound, avoiding the problem of poor deacidification effect caused by excessive adsorption of impurities by the resin, thereby improving the effect of resin deacidification treatment, increasing the purity of the bis(fluorosulfonyl)imide metal liquid salt, and reducing production costs.

[0047] In one specific embodiment, the turbidity of the reaction solution is ≤100; or, the EP1 acidity of the reaction solution, expressed as HF, is ≤100 ppm. When the molar ratio of bis(fluorosulfonyl)imide to the fluorinated metal compound is less than 1, the reaction solution contains unreacted fluorinated metal compound, which is a solid, and the turbidity of the reaction solution is tested. When the molar ratio of bis(fluorosulfonyl)imide to the fluorinated metal compound is greater than 1, the reaction solution contains unreacted bis(fluorosulfonyl)imide, and the acidity of the reaction solution is tested. When the turbidity or acidity of the reaction solution is within the above range, the bis(fluorosulfonyl)imide reacts completely with the fluorinated metal compound, allowing for subsequent devolatilization treatment. Furthermore, the low turbidity or acidity of the reaction solution reduces the difficulty of subsequent devolatilization and resin deacidification treatments, and significantly improves the purity of the bis(fluorosulfonyl)imide metal liquid salt.

[0048] In one specific embodiment, the bis(fluorosulfonyl)imide comprises, by mass percentage: bis(fluorosulfonyl)imide 99.93-100%, aminosulfonate ≤200ppm, fluorosulfonate ≤300ppm, fluorosulfonamide ≤100ppm, chloride ion ≤50ppm, and fluoride ion ≤50ppm; in one specific embodiment, the fluorinated metal compound comprises one of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, and francium fluoride; in one specific embodiment, the fluorinated metal compound comprises, by mass percentage: fluorinated metal compound 99.84-100%, carbonate metal compound ≤1000ppm, and moisture ≤600ppm. When bis(fluorosulfonyl)imide and fluorinated metal compounds with the above-mentioned purity are used for the reaction, the bis(fluorosulfonyl)imide and fluorinated metal compounds have few impurities, avoiding the introduction of excessive impurities. This helps to achieve high purity of bis(fluorosulfonyl)imide metal liquid salt, and can reduce the devolatilization time, improve production efficiency, and save costs. At the same time, since chloride ions mainly come from bis(fluorosulfonyl)imide, reducing the chloride ion content in bis(fluorosulfonyl)imide helps to prepare bis(fluorosulfonyl)imide liquid salt with low chloride ion content.

[0049] This application can prepare corresponding bisfluorosulfonylimide metal liquid salts by selecting specific fluorinated metal compounds, such as lithium bisfluorosulfonylimide, sodium bisfluorosulfonylimide, potassium bisfluorosulfonylimide, rubidium bisfluorosulfonylimide, cesium bisfluorosulfonylimide, and francium bisfluorosulfonylimide.

[0050] In one specific embodiment, before the resin deacidification treatment, a first filtration treatment is performed on the bis(fluorosulfonyl)imide metal compound solution; in another specific embodiment, after the resin deacidification treatment, a second filtration treatment is performed on the deacidified solution system. The first filtration treatment of the bis(fluorosulfonyl)imide metal compound solution before the resin deacidification treatment removes insoluble substances from the solution, preventing damage to the resin caused by insoluble substances, which could lead to resin blockage or poor deacidification effect, thereby improving the purity of the bis(fluorosulfonyl)imide metal liquid salt. The second filtration treatment after the resin deacidification treatment removes insoluble substances not filtered out in the first filtration treatment, as well as any insoluble substances that may be generated after the resin deacidification treatment, further improving the purity of the bis(fluorosulfonyl)imide metal liquid salt.

[0051] This application does not limit the pore size of the filter membranes used in the first and second filtration processes, and they can be selected according to actual needs. For example, compared with the first filtration process, the second filtration process uses a filter membrane with a smaller pore size, which can better remove insoluble substances in the system and improve the purity of the bis(fluorosulfonyl)imide metal liquid salt to a greater extent.

[0052] This application also provides a bis(fluorosulfonyl)imide metal liquid salt, which is prepared by the above-described method. The impurities in the bis(fluorosulfonyl)imide metal liquid salt, by mass percentage, include: aminosulfonate ≤ 100 ppm, fluorosulfonate ≤ 300 ppm, and fluorosulfonamide ≤ 10 ppm. The bis(fluorosulfonyl)imide metal liquid salt provided in this application exhibits high purity, thus facilitating its widespread application in the battery field.

[0053] In one specific embodiment, the bis(fluorosulfonyl)imide metal liquid salt also includes chloride and fluoride ion impurities, wherein the mass percentage of chloride ions in the bis(fluorosulfonyl)imide metal liquid salt is not higher than 5 ppm, and the mass percentage of fluoride ions in the bis(fluorosulfonyl)imide metal liquid salt is not higher than 50 ppm. Exemplarily, during the preparation process, the preparation of a bis(fluorosulfonyl)imide metal liquid salt with fluoride ions not higher than 5 ppm and chloride ions not higher than 5 ppm can be achieved by controlling the molar ratio of bis(fluorosulfonyl)imide and the fluoride metal compound, as well as the purity of bis(fluorosulfonyl)imide and the fluoride metal compound.

[0054] The present application will be further described in detail below through specific embodiments.

[0055] Example 1

[0056] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0057] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0058] The impurities in bis(fluorosulfonyl)imide (Guangdong Wengjiang Chemical Reagent) by mass percentage include: aminosulfonate 180ppm, fluorosulfonate 150ppm, fluorosulfonamide 44ppm, chloride ion 37ppm, and fluoride ion 25ppm; the impurities in lithium fluoride by mass percentage include: lithium fluoride 99.84%, lithium carbonate 1000ppm, and moisture 600ppm.

[0059] 2. Lithium difluorosulfonylimide, kept at 120℃, is dissolved in methyl ethyl carbonate solvent. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 80ppm, fluorosulfonate 150ppm, fluorosulfonamide 8ppm, chloride ion 3ppm, and fluoride ion 35ppm.

[0060] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140.

[0061] A / B is 2%, where A is the mass of the resin and B is the mass of lithium bis(fluorosulfonyl)imide.

[0062] Example 2

[0063] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0064] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 67 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.8 kPa, a temperature of 120°C, and a time of 15 h to obtain lithium difluorosulfonyl imide, which had an EP1 acidity of 0.5 ppm, calculated as HF.

[0065] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 200 ppm, fluorosulfonate 180 ppm, fluorosulfonamide 50 ppm, chloride ion 460 ppm, and fluoride ion 390 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.88%, lithium carbonate 800 ppm, and moisture 400 ppm.

[0066] 2. Lithium difluorosulfonylimide, kept at 120°C, is dissolved in diethyl carbonate solvent. During the dissolution process, the temperature of the dissolution system is maintained at 20°C to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PED resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 100ppm, fluorosulfonate 250ppm, fluorosulfonamide 6ppm, chloride ion 4ppm, and fluoride ion 45ppm.

[0067] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0068] Example 3

[0069] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0070] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution was 100, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 1 kPa, a temperature of 130℃, and a time of 20 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0071] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 150 ppm, fluorosulfonate 280 ppm, fluorosulfonamide 48 ppm, chloride ion 320 ppm, and fluoride ion 480 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.89%, lithium carbonate 600 ppm, and moisture 500 ppm.

[0072] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to dimethyl carbonate solvent. During the dissolution process, the temperature of the dissolution system is maintained at 30℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 55ppm, fluorosulfonate 240ppm, fluorosulfonamide 10ppm, chloride ion 4ppm, and fluoride ion 32ppm.

[0073] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 59:141; the A / B ratio is 1%.

[0074] Example 4

[0075] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0076] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution reached 89, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.1 kPa, a temperature of 120℃, and a time of 10 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0077] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 56 ppm, fluorosulfonamide 22 ppm, chloride ion 5 ppm, and fluoride ion 12 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.928%, lithium carbonate 400 ppm, and moisture 320 ppm.

[0078] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 40℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEB resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 45ppm, fluorosulfonate 124ppm, fluorosulfonamide 7ppm, chloride ion 1ppm, and fluoride ion 22ppm.

[0079] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 5%.

[0080] Example 5

[0081] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0082] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 92 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0083] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0084] 2. Lithium difluorosulfonylimide, kept at 120°C, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10°C to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 65ppm, fluorosulfonate 124ppm, fluorosulfonamide 5ppm, chloride ion 3ppm, and fluoride ion 17ppm.

[0085] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0086] Example 6

[0087] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0088] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution (calculated as HF) was 78 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide with an acidity of 0.5 ppm (calculated as HF).

[0089] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.89%, lithium carbonate 600 ppm, and moisture 500 ppm.

[0090] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 88ppm, fluorosulfonate 145ppm, fluorosulfonamide 7ppm, chloride ion 3ppm, and fluoride ion 45ppm.

[0091] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0092] Example 7

[0093] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0094] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0095] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0096] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 55ppm, fluorosulfonate 188ppm, fluorosulfonamide 4ppm, chloride ion 2.5ppm, and fluoride ion 37ppm.

[0097] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 61:139; the A / B ratio is 2%.

[0098] Example 8

[0099] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0100] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0101] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0102] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 47ppm, fluorosulfonate 120ppm, fluorosulfonamide 4ppm, chloride ion 3.7ppm, and fluoride ion 37ppm.

[0103] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 4%.

[0104] Example 9

[0105] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0106] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution reached 89, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.1 kPa, a temperature of 120℃, and a time of 10 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0107] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 56 ppm, fluorosulfonamide 22 ppm, chloride ion 5 ppm, and fluoride ion 12 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.928%, lithium carbonate 400 ppm, and moisture 320 ppm.

[0108] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 40℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEB resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 67ppm, fluorosulfonate 141ppm, fluorosulfonamide 5ppm, chloride ion 3ppm, and fluoride ion 37ppm.

[0109] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 61:139; the A / B ratio is 5%.

[0110] Example 10

[0111] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0112] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution reached 89, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.1 kPa, a temperature of 120℃, and a time of 10 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0113] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 56 ppm, fluorosulfonamide 22 ppm, chloride ion 5 ppm, and fluoride ion 12 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.928%, lithium carbonate 400 ppm, and moisture 320 ppm.

[0114] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 40℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEB resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 67ppm, fluorosulfonate 130ppm, fluorosulfonamide 7ppm, chloride ion 2.4ppm, and fluoride ion 18ppm.

[0115] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 3%.

[0116] Example 11

[0117] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0118] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.1 at a reaction temperature of 130°C until the turbidity of the reaction solution reached 150, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.08 ppm.

[0119] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0120] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 24ppm, fluorosulfonate 147ppm, fluorosulfonamide 8ppm, chloride ion 3ppm, and fluoride ion 89ppm.

[0121] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0122] Example 12

[0123] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0124] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0125] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0126] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 97ppm, fluorosulfonate 280ppm, fluorosulfonamide 8ppm, chloride ion 4ppm, and fluoride ion 46ppm.

[0127] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 50:150; the A / B ratio is 2%.

[0128] Example 13

[0129] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0130] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0131] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0132] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 88ppm, fluorosulfonate 255ppm, fluorosulfonamide 9ppm, chloride ion 4.5ppm, and fluoride ion 47ppm.

[0133] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 0.5%.

[0134] Example 14

[0135] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0136] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution reached 89, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.1 kPa, a temperature of 120℃, and a time of 10 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0137] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 56 ppm, fluorosulfonamide 22 ppm, chloride ion 5 ppm, and fluoride ion 12 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.928%, lithium carbonate 400 ppm, and moisture 320 ppm.

[0138] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 40℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEB resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 91ppm, fluorosulfonate 289ppm, fluorosulfonamide 10ppm, chloride ion 3ppm, and fluoride ion 57ppm.

[0139] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 70:130; the A / B ratio is 5%.

[0140] Example 15

[0141] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0142] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution reached 89, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.1 kPa, a temperature of 120℃, and a time of 10 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0143] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 56 ppm, fluorosulfonamide 22 ppm, chloride ion 5 ppm, and fluoride ion 12 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.928%, lithium carbonate 400 ppm, and moisture 320 ppm.

[0144] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 40℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEB resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 88ppm, fluorosulfonate 213ppm, fluorosulfonamide 7ppm, chloride ion 2.5ppm, and fluoride ion 44ppm.

[0145] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 0.5%.

[0146] Example 16

[0147] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0148] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 74 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, which had an EP1 acidity of 0.3 ppm, calculated as HF.

[0149] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 220 ppm, fluorosulfonate 180 ppm, fluorosulfonamide 150 ppm, chloride ion 70 ppm, and fluoride ion 70 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0150] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 100ppm, fluorosulfonate 278ppm, fluorosulfonamide 8ppm, chloride ion 6ppm, and fluoride ion 45ppm.

[0151] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0152] Example 17

[0153] The preparation method of lithium bis(fluorosulfonyl)imide liquid salt provided in this embodiment includes the following steps:

[0154] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1.05 at a reaction temperature of 140℃ until the turbidity of the reaction solution reached 89, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.1 kPa, a temperature of 120℃, and a time of 10 h to obtain lithium difluorosulfonyl imide. The EP1 acidity of lithium difluorosulfonyl imide, calculated as HF, was 0.1 ppm.

[0155] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 56 ppm, fluorosulfonamide 22 ppm, chloride ion 5 ppm, and fluoride ion 12 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.8%, lithium carbonate 1200 ppm, and moisture 800 ppm.

[0156] 2. Lithium difluorosulfonylimide, maintained at 130℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 40℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEB resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 97ppm, fluorosulfonate 214ppm, fluorosulfonamide 10ppm, chloride ion 1.4ppm, and fluoride ion 18ppm.

[0157] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 5%.

[0158] Example 18

[0159] The preparation method of sodium difluorosulfonamide liquid salt provided in this embodiment includes the following steps:

[0160] 1. Difluorosulfonyl imide and sodium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 80 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain sodium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0161] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: 180 ppm aminosulfonate, 150 ppm fluorosulfonate, 44 ppm fluorosulfonamide, 37 ppm chloride ions, and 25 ppm fluoride ions; the sodium fluoride, by mass percentage, includes: 99.9% sodium fluoride, 600 ppm sodium carbonate, and 400 ppm moisture.

[0162] 2. Sodium difluorosulfonamide, kept at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a sodium difluorosulfonamide solution. The sodium difluorosulfonamide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain sodium difluorosulfonamide liquid salt. The impurities in the sodium difluorosulfonamide liquid salt, by mass percentage, include: aminosulfonate 60ppm, fluorosulfonate 122ppm, fluorosulfonamide 7ppm, chloride ion 3ppm, and fluoride ion 33ppm.

[0163] The mass ratio of sodium difluorosulfonamide to electrolyte solvent is 60:140; the ratio of A to B is 2%.

[0164] Example 19

[0165] The preparation method of potassium difluorosulfonyl imide liquid salt provided in this embodiment includes the following steps:

[0166] 1. Difluorosulfonyl imide and potassium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130℃ until the EP1 acidity of the reaction solution (calculated as HF) was 80 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.5 kPa, a temperature of 120℃, and a time of 12 h to obtain potassium difluorosulfonyl imide.

[0167] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the potassium fluoride, by mass percentage, includes: potassium fluoride 99.9%, potassium carbonate 600 ppm, and moisture 400 ppm.

[0168] 2. Potassium difluorosulfonyl imide, kept at 120°C, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10°C to obtain a potassium difluorosulfonyl imide solution. The potassium difluorosulfonyl imide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain potassium difluorosulfonyl imide liquid salt. The impurities in the potassium difluorosulfonyl imide liquid salt, by mass percentage, include: aminosulfonate 88ppm, fluorosulfonate 247ppm, fluorosulfonamide 6ppm, chloride ion 4ppm, and fluoride ion 34ppm.

[0169] The mass ratio of potassium difluorosulfonamide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0170] Example 20

[0171] The preparation method of potassium difluorosulfonyl imide liquid salt provided in this embodiment includes the following steps:

[0172] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 135°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0173] The impurities in bis(fluorosulfonyl)imide (Guangdong Wengjiang Chemical Reagent) by mass percentage include: aminosulfonate 180ppm, fluorosulfonate 150ppm, fluorosulfonamide 44ppm, chloride ion 37ppm, and fluoride ion 25ppm; the impurities in lithium fluoride by mass percentage include: lithium fluoride 99.84%, lithium carbonate 1000ppm, and moisture 600ppm.

[0174] 2. Lithium difluorosulfonylimide, kept at 120℃, is dissolved in methyl ethyl carbonate solvent. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin, and finally a second filtration treatment to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 78ppm, fluorosulfonate 161ppm, fluorosulfonamide 7ppm, chloride ion 4ppm, and fluoride ion 44ppm.

[0175] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140.

[0176] A / B is 2%, where A is the mass of the resin and B is the mass of lithium bis(fluorosulfonyl)imide.

[0177] Example 21

[0178] The preparation method of potassium difluorosulfonyl imide liquid salt provided in this embodiment includes the following steps:

[0179] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 100°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0180] The impurities in bis(fluorosulfonyl)imide (Guangdong Wengjiang Chemical Reagent) by mass percentage include: aminosulfonate 180ppm, fluorosulfonate 150ppm, fluorosulfonamide 44ppm, chloride ion 37ppm, and fluoride ion 25ppm; the impurities in lithium fluoride by mass percentage include: lithium fluoride 99.84%, lithium carbonate 1000ppm, and moisture 600ppm.

[0181] 2. Lithium difluorosulfonylimide, kept at 120°C, is dissolved in methyl ethyl carbonate. The temperature of the dissolution system is maintained at 10°C during the dissolution process to obtain a lithium difluorosulfonylimide solution. This solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 89 ppm, fluorosulfonate 198 ppm, fluorosulfonamide 7 ppm, chloride ion 4 ppm, and fluoride ion 38 ppm.

[0182] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140.

[0183] A / B is 2%, where A is the mass of the resin and B is the mass of lithium bis(fluorosulfonyl)imide.

[0184] Example 22

[0185] The preparation method of potassium difluorosulfonyl imide liquid salt provided in this embodiment includes the following steps:

[0186] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.5 kPa, a temperature of 80°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0187] The impurities in bis(fluorosulfonyl)imide (Guangdong Wengjiang Chemical Reagent) by mass percentage include: aminosulfonate 180ppm, fluorosulfonate 150ppm, fluorosulfonamide 44ppm, chloride ion 37ppm, and fluoride ion 25ppm; the impurities in lithium fluoride by mass percentage include: lithium fluoride 99.84%, lithium carbonate 1000ppm, and moisture 600ppm.

[0188] 2. Lithium difluorosulfonylimide, kept at 120°C, is dissolved in methyl ethyl carbonate. The temperature of the dissolution system is maintained at 10°C during the dissolution process to obtain a lithium difluorosulfonylimide solution. This solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 88 ppm, fluorosulfonate 243 ppm, fluorosulfonamide 8 ppm, chloride ion 3 ppm, and fluoride ion 41 ppm.

[0189] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140.

[0190] A / B is 2%, where A is the mass of the resin and B is the mass of lithium bis(fluorosulfonyl)imide.

[0191] Example 23

[0192] The preparation method of potassium difluorosulfonyl imide liquid salt provided in this embodiment includes the following steps:

[0193] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 60°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0194] The impurities in bis(fluorosulfonyl)imide (Guangdong Wengjiang Chemical Reagent) by mass percentage include: aminosulfonate 180ppm, fluorosulfonate 150ppm, fluorosulfonamide 44ppm, chloride ion 37ppm, and fluoride ion 25ppm; the impurities in lithium fluoride by mass percentage include: lithium fluoride 99.84%, lithium carbonate 1000ppm, and moisture 600ppm.

[0195] 2. Lithium difluorosulfonylimide, kept at 120°C, is dissolved in methyl ethyl carbonate. The temperature of the dissolution system is maintained at 10°C during the dissolution process to obtain a lithium difluorosulfonylimide solution. This solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 90 ppm, fluorosulfonate 294 ppm, fluorosulfonamide 8 ppm, chloride ion 4 ppm, and fluoride ion 49 ppm.

[0196] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140.

[0197] A / B is 2%, where A is the mass of the resin and B is the mass of lithium bis(fluorosulfonyl)imide.

[0198] Comparative Example 1

[0199] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0200] 1. Reaction of bis(fluorosulfonyl)imide and lithium fluoride at a molar ratio of 1:1 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution (calculated as HF) is 92 ppm, yielding a molten reaction solution.

[0201] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0202] 2. The reaction solution is subjected to a first filtration treatment, then deacidified by PEP resin, and finally subjected to a second filtration treatment to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt include, by mass percentage: aminosulfonate 1450ppm, fluorosulfonate 3657ppm, fluorosulfonamide 77ppm, chloride ion 145ppm, and fluoride ion 889ppm.

[0203] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0204] During the resin deacidification process, the PEP resin needs to be replaced after one use due to the excessively high impurity content in the reaction solution.

[0205] Comparative Example 2

[0206] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0207] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:1 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 92 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 0.5 ppm, calculated as HF.

[0208] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0209] 2. Lithium difluorosulfonylimide, kept at 120°C, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10°C to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then filtered twice to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 148ppm, fluorosulfonate 347ppm, fluorosulfonamide 5ppm, chloride ion 3ppm, and fluoride ion 266ppm.

[0210] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140.

[0211] Comparative Example 3

[0212] The preparation method of lithium bis(fluorosulfonyl)imide provided in this comparative example includes the following steps:

[0213] 1. Under nitrogen protection, aminosulfonic acid, chlorosulfonic acid and thionyl chloride were added to the reaction vessel in a molar ratio of 1:1.3:2.3. After thorough stirring and uniform dispersion, the mixture was heated to 120℃ and reacted for 120 min. After the reaction was completed, the low-boiling-point compounds were removed by atmospheric distillation, and then vacuum distillation was performed to collect the fraction at 112-114℃ / 2 mm Hg. The fraction was condensed to obtain HClSI.

[0214] 2. HClSI was introduced into a reactor, and HF gas was introduced at 90°C to make the molar ratio of HF to HClSI 2.25:1. After reacting at 90°C for 8 hours, the temperature was lowered to room temperature. Nitrogen gas was introduced into the reactor for 3 hours to remove the mixed gas of HCl and HF, yielding bis(fluorosulfonyl)imide. Bis(fluorosulfonyl)imide and NaCl were mixed at a mass ratio of 100:3 and reacted at 70°C for 3 hours. Nitrogen gas was introduced into the reactor for 0.5 hours to remove the HCl gas. The obtained product was subjected to vacuum distillation at 0.05 MPa and 100°C for 2 hours, and the distillate was collected to obtain the HFSI.

[0215] 3. HFSI was added to a reaction vessel, and LiF was slowly added to the vessel under sealed conditions and stirring, so that the molar ratio of HFSI to LiF was 1.05:1; the reaction was carried out at 145℃ for 6 hours to obtain LiFSI; the crystalline LiFSI was dissolved in ethyl methyl carbonate (EMC) to obtain an EMC solution of LiFSI. Ion chromatography and nuclear magnetic resonance fluorine spectroscopy analysis revealed that the impurities in lithium difluorosulfonylimide, by mass percentage, included: aminosulfonate 4599 ppm, fluorosulfonate 22110 ppm, fluorosulfonamide 124 ppm, chloride ion 518 ppm, and fluoride ion 247 ppm.

[0216] Comparative Example 4

[0217] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0218] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 200 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 12 h to obtain lithium difluorosulfonyl imide, which had an EP1 acidity of 0.6 ppm, calculated as HF.

[0219] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0220] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 150ppm, fluorosulfonate 581ppm, fluorosulfonamide 8ppm, chloride ion 3.4ppm, and fluoride ion 267ppm.

[0221] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0222] Comparative Example 5

[0223] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0224] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 1.5 kPa, a temperature of 120°C, and a time of 10 h to obtain lithium difluorosulfonyl imide, which had an EP1 acidity of 34 ppm, calculated as HF.

[0225] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0226] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 214ppm, fluorosulfonate 547ppm, fluorosulfonamide 5ppm, chloride ion 3.8ppm, and fluoride ion 145ppm.

[0227] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0228] Comparative Example 6

[0229] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0230] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum of 0.5 kPa, a temperature of 120°C, and a time of 8 h to obtain lithium difluorosulfonyl imide, with an EP1 acidity of 8 ppm, calculated as HF.

[0231] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0232] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 314ppm, fluorosulfonate 648ppm, fluorosulfonamide 11ppm, chloride ion 4ppm, and fluoride ion 245ppm.

[0233] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0234] Comparative Example 7

[0235] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0236] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.1 kPa, a temperature of 140°C, and a time of 10 h to obtain lithium difluorosulfonyl imide, which had an EP1 acidity of 0.2 ppm, calculated as HF.

[0237] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0238] 2. Lithium difluorosulfonylimide, maintained at 120℃, is added to the solvent methyl ethyl carbonate. During the dissolution process, the solvent system temperature is maintained at 10℃ to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to a first filtration treatment, followed by resin deacidification treatment using PEP resin. Finally, a second filtration treatment is performed to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 78ppm, fluorosulfonate 1891ppm, fluorosulfonamide 7ppm, chloride ion 3.4ppm, and fluoride ion 36ppm.

[0239] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0240] Comparative Example 8

[0241] The preparation method of the lithium bis(fluorosulfonyl)imide liquid salt provided in this comparative example includes the following steps:

[0242] 1. Difluorosulfonyl imide and lithium fluoride were reacted at a molar ratio of 1:0.95 at a reaction temperature of 130°C until the EP1 acidity of the reaction solution, calculated as HF, was 88 ppm, resulting in a molten reaction solution. The reaction solution was then subjected to a devolatilization treatment at a vacuum degree of 0.1 kPa, a temperature of 145°C, and a time of 10 h to obtain lithium difluorosulfonyl imide, which had an EP1 acidity of 0.2 ppm, calculated as HF.

[0243] The impurities in bis(fluorosulfonyl)imide, by mass percentage, include: aminosulfonate 180 ppm, fluorosulfonate 150 ppm, fluorosulfonamide 44 ppm, chloride ion 37 ppm, and fluoride ion 25 ppm; the impurities in lithium fluoride, by mass percentage, include: lithium fluoride 99.84%, lithium carbonate 1000 ppm, and moisture 600 ppm.

[0244] 2. Lithium difluorosulfonylimide, kept at 120°C, is added to the solvent methyl ethyl carbonate. During the dissolution process, the temperature of the dissolution system is maintained at 10°C to obtain a lithium difluorosulfonylimide solution. The lithium difluorosulfonylimide solution is then subjected to resin deacidification treatment using PEP resin to obtain lithium difluorosulfonylimide liquid salt. The impurities in the lithium difluorosulfonylimide liquid salt, by mass percentage, include: aminosulfonate 78ppm, fluorosulfonate 1289ppm, fluorosulfonamide 6ppm, chloride ion 4ppm, and fluoride ion 49ppm.

[0245] The mass ratio of lithium bis(fluorosulfonyl)imide to electrolyte solvent is 60:140; the A / B ratio is 2%.

[0246] A comparison of Examples 1-4 and Example 11 shows that when the molar ratio of bis(fluorosulfonyl)imide to lithium fluoride is in the range of 1:(0.95-1.05), bis(fluorosulfonyl)imide and lithium fluoride can react fully, and the turbidity of the corresponding molten reaction solution is ≤100 or the acidity is ≤100ppm, thereby reducing the fluoride ion content in the lithium bis(fluorosulfonyl)imide liquid salt.

[0247] By comparing Examples 1, 7, and 12 with Examples 4, 9, and 14, it can be seen that when the mass ratio of lithium difluorosulfonylimide to electrolyte solvent is (59:141)-(61:139), the impurity content in lithium difluorosulfonylimide liquid salt can be controlled within a limited range.

[0248] By comparing Examples 1, 8, and 13 with Examples 4, 10, and 15, it can be seen that when the mass ratio of resin to bis(fluorosulfonyl)imide metal compound is in the range of 1-5%, the resin can fully adsorb impurities in bis(fluorosulfonyl)imide lithium liquid salt, thereby achieving high purity of bis(fluorosulfonyl)imide lithium liquid salt.

[0249] A comparison of Examples 1, 6, 16, and 17 shows that when the purity of bis(fluorosulfonyl)imide or lithium fluoride is higher, the impurity content in the prepared bis(fluorosulfonyl)imide lithium liquid salt is lower.

[0250] By comparing Examples 1, 20-23 and Comparative Examples 7 and 8, it can be seen that when the devolatilization temperature is higher than 140°C, lithium difluorosulfonylimide undergoes a condensation side reaction to generate lithium fluorosulfonate byproduct, resulting in an excessively high fluorosulfonate content in the lithium difluorosulfonylimide liquid salt.

[0251] As can be seen from Example 19, the preparation method of the bis(fluorosulfonyl)imide metal liquid salt of this application can also be applied to the preparation of bis(fluorosulfonyl)imide potassium liquid salt, which is beneficial to the preparation of various bis(fluorosulfonyl)imide metal liquid salts.

[0252] The comparison between Example 1 and Comparative Examples 1-3 shows that devolatilization treatment and resin deacidification treatment can effectively remove impurities such as aminosulfonate, fluorosulfonate, fluorosulfonamide, chloride ions and fluoride ions from lithium difluorosulfonamide liquid salt.

[0253] A comparison of Example 1 and Comparative Examples 4-6 shows that if most of the acidic substances in the reaction solution are not removed during the devolatilization process, resulting in an acidity higher than 0.5 ppm, the subsequent use of resin can still remove the acidic substances, but this leads to resin waste, requiring frequent resin replacement and increasing the preparation cost and time of the lithium bis(fluorosulfonyl)imide liquid salt. Therefore, first using devolatilization to quickly remove most of the acidic substances from the molten reaction solution, and then using resin to quickly remove the remaining acidic substances, simplifies the production process, shortens production time, and reduces production costs.

[0254] In summary, the preparation method of the bis(fluorosulfonyl)imide metal liquid salt of this application can produce bis(fluorosulfonyl)imide metal liquid salt with high purity by controlling the devolatilization treatment and resin deacidification treatment, and also takes into account the advantages of cost saving, simple process and convenient operation.

[0255] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a bis(fluorosulfonyl)imide metal liquid salt, wherein, Includes the following steps: A molten reaction solution is obtained by reacting bis(fluorosulfonyl)imide with a fluorinated metal compound. The reaction solution is then subjected to a devolatilization treatment until the EP1 acidity (calculated as HF) is ≤0.5ppm to obtain a bis(fluorosulfonyl)imide metal compound. This compound is then dissolved in a solvent and subjected to a resin deacidification treatment to obtain a bis(fluorosulfonyl)imide metal liquid salt. The heating temperature of the devolatilization treatment is below 140°C.

2. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to claim 1, wherein, The vacuum degree of the devolatilization treatment is 1-0.1 kPa, the heating temperature is not lower than 60℃, and the treatment time is 10-20 h.

3. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to claim 1 or 2, wherein, The heating temperature is 100-135℃.

4. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-3, wherein, The dissolution of the bis(fluorosulfonyl)imide metal compound in the solvent is carried out while it is in a molten state.

5. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to claim 4, wherein, Maintaining the temperature of the obtained bis(fluorosulfonyl)imide metal compound, it is mixed into a solvent to keep the bis(fluorosulfonyl)imide metal compound in the molten state for dissolution in the solvent.

6. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-5, wherein, The solvent is an electrolyte solvent, which includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and ethylene carbonate. The mass ratio of the bis(fluorosulfonyl)imide metal compound to the electrolyte solvent is (59:141)-(61:139).

7. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-6, wherein, The resin includes one of poly(4-vinylpyridine) resin, poly(N,N-dimethyl-p-styrene) resin, and poly(N,N-diethyl-p-styrene) resin; A / B is 1-5%, where A is the mass of the resin and B is the mass of the bis(fluorosulfonyl)imide metal compound.

8. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-7, wherein, The molten reaction solution is prepared by reacting bis(fluorosulfonyl)imide and a fluorinated metal compound under solvent-free conditions.

9. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to claim 8, wherein, The reaction temperature of the bis(fluorosulfonyl)imide and the fluorinated metal compound is 130-140℃, and the reaction time is 4-8h.

10. The method for preparing the bis(fluorosulfonyl)imide metal liquid salt according to claim 8, wherein, The molar ratio of the bis(fluorosulfonyl)imide to the fluorinated metal compound is 1:(0.95-1.05).

11. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-10, wherein, The turbidity of the reaction solution is ≤100.

12. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-11, wherein, The EP1 acidity of the reaction solution, calculated as HF, is ≤100ppm.

13. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-12, wherein, The difluorosulfonyl imide comprises, by mass percentage: Difluorosulfonamide 99.93-100%, aminosulfonate ≤200ppm, fluorosulfonate ≤300ppm, fluorosulfonamide ≤100ppm, chloride ion ≤50ppm, fluoride ion ≤50ppm.

14. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-13, wherein, The fluorinated metal compound includes one of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, and francium fluoride.

15. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-14, wherein, The fluorinated metal compounds, by mass percentage, include: Fluorinated metal compounds 99.84-100%, carbonated metal compounds ≤1000ppm, moisture ≤600ppm.

16. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to any one of claims 1-15, wherein, Prior to the resin deacidification treatment, the solution of the difluorosulfonyl imide metal compound is subjected to a first filtration treatment.

17. The method for preparing bis(fluorosulfonyl)imide metal liquid salt according to claim 16, wherein, Following the resin deacidification treatment, a second filtration treatment is also performed on the deacidified solution system.

18. A bis(fluorosulfonyl)imide metal liquid salt, wherein, The bis(fluorosulfonyl)imide metal liquid salt is prepared by the method for preparing the bis(fluorosulfonyl)imide metal compound according to any one of claims 1-17; The impurities in the bis(fluorosulfonyl)imide metal liquid salt, by mass percentage, include: Aminosulfonate ≤100ppm, fluorosulfonate ≤300ppm, fluorosulfonamide ≤10ppm.

19. The bis(fluorosulfonyl)imide metal liquid salt according to claim 18, wherein, The bis(fluorosulfonyl)imide metal liquid salt also includes chloride and fluoride ion impurities, wherein the mass percentage of chloride ions in the bis(fluorosulfonyl)imide metal liquid salt is not higher than 5 ppm, and the mass percentage of fluoride ions in the bis(fluorosulfonyl)imide metal liquid salt is not higher than 50 ppm.