A method for preparing lithium bisfluorosulfonimide

Abstract

In order to overcome the problems of insufficient yield and more impurities in the existing preparation method of potassium bisfluorosulfonimide into lithium bisfluorosulfonimide, the application provides a preparation method of lithium bisfluorosulfonimide, characterized by comprising the following operation steps: providing a cation exchange resin column, the cation exchange resin column is filled with strong acid cation exchange resin, and the strong acid cation exchange resin is adsorbed with lithium ions; ion exchange: the aqueous solution of alkali metal salt XFSI is introduced into the cation exchange resin column for ion exchange, and the aqueous solution containing lithium bisfluorosulfonimide is obtained; distillation and concentration are carried out to obtain lithium bisfluorosulfonimide water concentrate; the lithium bisfluorosulfonimide water concentrate is mixed with a good solvent, and distillation is carried out; a poor solvent is added, and the lithium bisfluorosulfonimide solid is precipitated by cooling. The preparation method of lithium bisfluorosulfonimide provided by the application is simple and safe, and the obtained lithium bisfluorosulfonimide has high purity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolyte salt materials, and particularly relates to a preparation method of lithium bisfluorosulfonylimide. BACKGROUND

[0002] With the increasing attention of people to green low-carbon economy, secondary batteries are paid more and more attention. As one of the core materials of secondary batteries, electrolyte salt has an important influence on the cycle life, high and low temperature performance and safety performance of the battery. As a new type of electrolyte salt, compared with lithium hexafluorophosphate (poor thermal stability and easy to hydrolyze), lithium bisfluorosulfonylimide (LiFSI) not only has high electrical conductivity, thermal stability (not decomposed below 200 DEG C) and good hydrolysis stability, but also has the advantages of inhibiting battery gas expansion (J. Power Sources, 2022, 535, 231481).

[0003] At present, the preparation methods of LiFSI mainly include the following: one is to obtain bisfluorosulfonylimide (HFSI) by fluorination of bischlorosulfonylimide (HClSI), and then react with lithium salt to obtain LiFSI (CN 104925765 A, CN 106044728 A); the other is to use HClSI and lithium fluoride to prepare LiFSI (CN 113247871 A). The former needs to use the corrosive and toxic gas hydrogen fluoride (HF), and water is usually removed by adding thionyl chloride, which can lead to high chlorine ion content in the product and reduce the quality of the product; the latter will produce a large amount of HF, and the residual HF in the product will reduce the performance of LiFSI, and increase the cost of tail gas treatment. US8377406 uses HFSI and lithium carbonate to prepare LiFSI, and the heat release of HFSI dissolved in water will cause its decomposition, and the patent prepares HFSI aqueous solution at ultra-low temperature (-78 DEG C), which increases the energy consumption.

[0004] In addition, in the alkali metal salt of bisfluorosulfonylimide, due to the stronger coulomb effect, the alkali metal ion with small ionic radius and high charge density is more likely to cause FSI -Electrochimica Acta, 2019, 321, 134644). Compared with lithium bisfluorosulfonylimide, sodium bisfluorosulfonylimide and potassium bisfluorosulfonylimide are more stable, relatively low in preparation difficulty, and easier to obtain high-purity products by impurity removal. Therefore, one of the existing preparation routes is to prepare high-purity sodium bisfluorosulfonylimide or lithium bisfluorosulfonylimide from potassium bisfluorosulfonylimide. For example, CN 101747242 A in the prior art prepares lithium bisfluorosulfonylimide (LiFSI) by double fluorosulfonylimide potassium (KFSI) and lithium tetrafluoroborate, lithium perchlorate in an organic solvent to carry out metathesis exchange reaction, but the product prepared by this method has high residual potassium ion, low yield of lithium bisfluorosulfonylimide, and many impurities, and the lithium perchlorate used and the perchloric acid generated in the reaction are explosive compounds, which has certain safety risk and is not suitable for industrial production. SUMMARY

[0005] In view of the problems of insufficient yield and many impurities in the existing method for preparing lithium bisfluorosulfonylimide from potassium bisfluorosulfonylimide, the application provides a preparation method of lithium bisfluorosulfonylimide.

[0006] The technical scheme adopted by the application to solve the above technical problems is as follows:

[0007] The application provides a preparation method of lithium bisfluorosulfonylimide, characterized by comprising the following operation steps:

[0008] A cation exchange resin column is provided, the cation exchange resin column is filled with strong acid type cation exchange resin, and the strong acid type cation exchange resin adsorbs lithium ions;

[0009] Ion exchange: an aqueous solution of alkali metal salt XFSI is provided, wherein X represents sodium ions and / or potassium ions, the aqueous solution of alkali metal salt XFSI is introduced into the cation exchange resin column for ion exchange, the X ions on the alkali metal salt XFSI are replaced by lithium ions, and an aqueous solution containing lithium bisfluorosulfonylimide is obtained;

[0010] The aqueous solution containing lithium bisfluorosulfonylimide is concentrated by distillation to obtain lithium bisfluorosulfonylimide aqueous concentrate;

[0011] The lithium bisfluorosulfonylimide aqueous concentrate is mixed with a benign solvent, and distillation is carried out until the water content is less than 50000 ppm;

[0012] An undesirable solvent is added, and the lithium bisfluorosulfonylimide is precipitated by cooling;

[0013] The solubility of lithium bisfluorosulfonylimide in the undesirable solvent is less than the solubility of lithium bisfluorosulfonylimide in the benign solvent.

[0014] Optionally, the mass concentration of the aqueous solution of the alkali metal salt XFSI is 1% to 50%.

[0015] Optionally, the cation exchange resin column is prepared by the following preparation method:

[0016] After the strong acid type cation exchange resin is packed, the cation exchange resin column is eluted with water, an acid solution, water, a lithium hydroxide or alkali salt solution, and water in sequence.

[0017] Optionally, when the cation exchange resin is eluted with water, the elution is ended when the conductivity of the effluent is <200 μS / cm;

[0018] When the cation exchange resin is eluted with an acid solution, the elution is ended when the metal cation in the effluent is <100 ppm;

[0019] When the cation exchange resin is eluted with a lithium hydroxide or alkali salt solution, the elution is ended when the pH of the effluent is >8.

[0020] Optionally, the acid solution comprises one or more of hydrochloric acid and sulfuric acid, and the acid concentration of the acid solution is 1% to 50%;

[0021] The lithium hydroxide or alkali salt solution is selected from one or more of LiOH, Li2CO3, LiHCO3, and LiOH solution, wherein n is 1 or 2; the mass concentration of the lithium hydroxide or alkali salt in the lithium hydroxide or alkali salt solution is 0.1% to 50%. n H 2n+1 OLi solution, wherein n is 1 or 2; the mass concentration of the lithium hydroxide or alkali salt in the lithium hydroxide or alkali salt solution is 0.1% to 50%.

[0022] Optionally, when the lithium ion in the effluent is <1000 ppm in the ion exchange operation, the cation exchange resin column is subjected to a regeneration operation, and the regeneration operation of the cation exchange resin column is the same as the preparation method of the cation exchange resin column.

[0023] Optionally, the operation of “adding a good solvent to the concentrated aqueous solution of lithium bisfluorosulfonylimide, performing distillation, distilling until the water content is <50000 ppm, adding a poor solvent, and precipitating lithium bisfluorosulfonylimide solid by cooling” comprises the following operations:

[0024] adding a benign solvent into the lithium bisfluorosulfonimide water concentrated solution, the benign solvent is selected from organic solvents capable of forming azeotropes with water, distillation is performed, the solution concentration is controlled to be 30%-40% during the distillation process, the water content in the solution is tested, if the water content in the solution is >50000 ppm, the distillation is continuously performed to remove water until the water content in the solution is <50000 ppm by continuously adding the benign solvent, the solution is filtered, and then the distillation is continuously performed until the mass concentration of the lithium bisfluorosulfonimide is 60%-80%;

[0025] adding a poor solvent, the addition amount of the poor solvent is greater than 20% of the total mass of the system, and the lithium bisfluorosulfonimide is precipitated by being cooled by more than 5℃, the obtained lithium bisfluorosulfonimide solid is filtered, washed and dried to obtain the lithium bisfluorosulfonimide.

[0026] Optionally, the mass concentration of the lithium bisfluorosulfonimide water concentrated solution is 30%-85%;

[0027] The distillation is performed by reduced pressure distillation, the temperature is 5℃-80℃, and the pressure is 0-30 KPa;

[0028] The drying process is controlled to have a temperature of 10℃-100℃.

[0029] Optionally, the boiling point of the poor solvent is more than 20℃ lower than the boiling point of the benign solvent.

[0030] Optionally, the benign solvent is selected from solvents capable of forming azeotropes with water, and the benign solvent includes one or more of pyridine, alcohol, ether, ester, nitrile and hydrocarbon;

[0031] The poor solvent includes one or more of benzene, toluene, xylene, chlorobenzene, n-hexane, cyclohexane, heptane, octane, dichloromethane, dichloroethane, trichloroethane, tetrachloroethane or ether solvent.

[0032] Compared with the existing method of preparing lithium bisfluorosulfonimide by chemically reacting potassium bisfluorosulfonimide, the preparation method provided by the present application uses a cation exchange resin column with lithium ions to treat an aqueous solution of potassium bisfluorosulfonimide and / or sodium bisfluorosulfonimide, and lithium bisfluorosulfonimide aqueous solution is prepared by ion exchange, which is simple to operate, has low requirements for the preparation environment, and is safe and has high purity.

[0033] In the presence of water, lithium bisfluorosulfonimide is easy to decompose, especially in the later stage of distillation, when the concentration of lithium bisfluorosulfonimide in the solution is large, which can easily lead to a decrease in yield and purity; at the same time, as a battery-grade lithium bisfluorosulfonimide, the water content thereof also needs to be at a low level, and water can react to form HF and other adverse products in the battery cycle process. Therefore, in the present preparation method, after the water in the lithium bisfluorosulfonimide water concentrate is distilled, the water content can be effectively removed by adding a benign solvent for distillation, while avoiding the decomposition of lithium bisfluorosulfonimide. Further, in order to avoid the decomposition of lithium bisfluorosulfonimide in the later stage of distillation, a poor solvent is further added to the benign solvent to reduce the solubility of lithium bisfluorosulfonimide, and the temperature is lowered for treatment, so that lithium bisfluorosulfonimide is precipitated from the system of the benign solvent and the poor solvent, thereby avoiding the generation of by-products to the greatest extent, improving the yield and purity of lithium bisfluorosulfonimide, and reducing the water content of lithium bisfluorosulfonimide. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0035] The present application provides a preparation method of lithium bisfluorosulfonimide, characterized in that the following operation steps are included:

[0036] A cation exchange resin column is provided, the cation exchange resin column is filled with a strong acid type cation exchange resin, and the strong acid type cation exchange resin adsorbs lithium ions;

[0037] Ion exchange: a water solution of an alkali metal salt XFSI is provided, wherein X represents sodium ions and / or potassium ions, the water solution of the alkali metal salt XFSI is introduced into the cation exchange resin column for ion exchange, the X ions on the alkali metal salt XFSI are replaced by lithium ions, and a water solution containing lithium bisfluorosulfonimide is obtained;

[0038] The water solution containing lithium bisfluorosulfonimide is distilled and concentrated to obtain a lithium bisfluorosulfonimide water concentrate;

[0039] A benign solvent is added to the lithium bisfluorosulfonimide water concentrate for mixing, and distillation is performed, and the distillation is performed until the water content is less than 50000 ppm;

[0040] A poor solvent is added, and the temperature is lowered to precipitate lithium bisfluorosulfonimide solid;

[0041] The solubility of lithium bisfluorosulfonimide in the poor solvent is less than the solubility of lithium bisfluorosulfonimide in the benign solvent.

[0042] Compared with the existing method of preparing lithium bisfluorosulfonimide by chemically reacting potassium bisfluorosulfonimide, the preparation method provided by the application uses a cation exchange resin column with lithium ions to treat an aqueous solution of potassium and / or sodium bisfluorosulfonimide, and prepares an aqueous solution of lithium bisfluorosulfonimide in an ion exchange manner, which is simple to operate, has low requirements for the preparation environment, and is safe and highly reproducible.

[0043] Meanwhile, lithium bisfluorosulfonimide is prone to decomposition in the presence of water, especially when the concentration of lithium bisfluorosulfonimide in the solution is high in the later stage of distillation, which can lead to a decrease in yield and purity. Meanwhile, as a battery-grade lithium bisfluorosulfonimide, the water content thereof needs to be low, and water can react to form HF and other adverse products in the battery cycle process. Therefore, in the preparation method, the water in the lithium bisfluorosulfonimide water concentrate obtained by distillation is removed by adding a benign solvent for distillation, which can effectively remove water and avoid the decomposition of lithium bisfluorosulfonimide. Further, to avoid the decomposition of lithium bisfluorosulfonimide in the later stage of distillation, an adverse solvent is further added to the benign solvent to reduce the solubility of lithium bisfluorosulfonimide, and the temperature is lowered for treatment, so that lithium bisfluorosulfonimide is precipitated from the system of the benign solvent and the adverse solvent, the generation of by-products is avoided to the greatest extent, the yield and purity of lithium bisfluorosulfonimide are improved, and the water content of lithium bisfluorosulfonimide is reduced.

[0044] In some embodiments, the aqueous solution of the alkali metal salt XFSI has a mass concentration of 1% to 50%.

[0045] Specifically, the aqueous solution of the alkali metal salt XFSI can have a mass concentration of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 27%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 37%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 47%, 49%, or 50%.

[0046] In preferred embodiments, the aqueous solution of the alkali metal salt XFSI has a mass concentration of 5% to 25%.

[0047] In some embodiments, the cation exchange resin column is prepared by the following preparation method:

[0048] After the strong acid type cation exchange resin is packed, the cation exchange resin column is eluted with water, acid solution, water, lithium hydroxide or basic salt solution of lithium and water in sequence.

[0049] During the above operation, the first water elution is used to remove soluble impurities in the strong acid type cation exchange resin; the acid solution elution is used to elute the impurity ions adsorbed in the strong acid type cation exchange resin, at this time, H + ions in the acid solution will embed into the strong acid type cation exchange resin to replace other impurity ions such as Ca 2+ ions, Mg 2+ ions, Na + ions, K + ions, so as to restore the ion exchange capacity of the strong acid type cation exchange resin; the second water elution is used to remove the residual acid in the strong acid type cation exchange resin; the lithium hydroxide or basic salt solution of lithium elution is used to replace H + ions in the strong acid type cation exchange resin with lithium ions, so as to form the strong acid type cation exchange resin adsorbing lithium ions, which is used for ion exchange with potassium bisfluorosulfonylimide or sodium bisfluorosulfonylimide; the third water elution is used to remove the residual base in the strong acid type cation exchange resin.

[0050] In some embodiments, when the cation exchange resin is eluted with water, the elution is ended when the effluent conductivity is <200 μS / cm.

[0051] In preferred embodiments, when the cation exchange resin is eluted with water, the elution is ended when the effluent conductivity is <100 μS / cm.

[0052] In more preferred embodiments, when the cation exchange resin is eluted with water, the elution is ended when the effluent conductivity is <50 μS / cm.

[0053] In some embodiments, when the cation exchange resin is eluted with acid solution, the elution is ended when the cation in the effluent is <100 ppm.

[0054] In preferred embodiments, when the cation exchange resin is eluted with acid solution, the elution is ended when the metal cation in the effluent is <50 ppm.

[0055] In some embodiments, when the cation exchange resin is eluted with lithium hydroxide or basic salt solution of lithium, the elution is ended when the pH of the effluent is >8.

[0056] In some embodiments, the acid solution comprises one or more of hydrochloric acid and sulfuric acid, and the acid concentration of the acid solution is 1% to 50%.

[0057] In some embodiments, when the acid solution is hydrochloric acid, the acid concentration of the acid solution is 1% to 30%.

[0058] In some embodiments, when the acid solution is sulfuric acid, the acid concentration of the acid solution is 1% to 50%.

[0059] In some embodiments, when the acid solution is hydrochloric acid, the second water rinse operation is performed to make the effluent conductivity <200 μS / cm, and Cl - <5 ppm as the end of rinse mark, preferably Cl - <2 ppm.

[0060] In some embodiments, when the acid solution is sulfuric acid, the second water rinse operation is performed to make the effluent conductivity <200 μS / cm, and SO4 2- <5 ppm as the end of rinse mark, preferably SO4 2- <2 ppm.

[0061] In some embodiments, the lithium hydroxide or basic salt solution is selected from one or more of LiOH, Li2CO3, LiHCO3, C n H 2n+1 OLi solution, wherein n is 1 or 2; and the mass concentration of the lithium hydroxide or basic salt in the lithium hydroxide or basic salt solution is 0.1% to 50%.

[0062] In preferred embodiments, when the lithium hydroxide or basic salt in the lithium hydroxide or basic salt solution is lithium hydroxide, the mass concentration of the lithium hydroxide in the lithium hydroxide solution is 0.1% to 11%, and more preferably, the mass concentration of the lithium hydroxide in the lithium hydroxide solution is 3% to 10%.

[0063] In some embodiments, when the lithium ion in the effluent is <1000 ppm in the ion exchange operation, the cation exchange resin column is subjected to a regeneration operation, and the regeneration operation of the cation exchange resin column is the same as the preparation method of the cation exchange resin column.

[0064] The potassium ion or sodium ion adsorbed in the cation exchange resin column is eluted by the acid solution rinse operation, and the lithium ion loading capacity of the strong acid type cation exchange resin is restored by the lithium hydroxide or basic salt solution rinse operation, so as to ensure the regeneration and reuse of the cation exchange resin column.

[0065] In preferred embodiments, the lithium ion in the effluent is <500 ppm, and the cation exchange resin column is subjected to a regeneration operation.

[0066] In more preferred embodiments, the cation exchange resin column is regenerated when the effluent has less than 200 ppm lithium ions.

[0067] In some embodiments, the ion exchange operation is complete when the effluent has less than 6 ppm potassium ions or sodium ions.

[0068] In preferred embodiments, the ion exchange operation is complete when the effluent has less than 3 ppm potassium ions or sodium ions.

[0069] In more preferred embodiments, the ion exchange operation is complete when the effluent has less than 1 ppm potassium ions or sodium ions.

[0070] In some embodiments, the ion exchange operation can be performed by passing the aqueous alkali metal salt XFSI solution through the cation exchange resin column once, or by passing the aqueous alkali metal salt XFSI solution through the cation exchange resin column multiple times, or by connecting multiple cation exchange resin columns in series to perform multiple ion exchange operations on the aqueous alkali metal salt XFSI solution, when the effluent after the aqueous alkali metal salt XFSI solution is passed through the cation exchange resin column once does not meet the criteria for completing the ion exchange operation (less than 6 ppm potassium ions or sodium ions).

[0071] In some embodiments, the operation of "adding a benign solvent to the aqueous lithium bisfluorosulfonylimide concentrate, mixing, distilling, distilling until the water content is less than 50000 ppm, adding a poor solvent, and cooling to precipitate lithium bisfluorosulfonylimide" includes the following operations:

[0072] In some embodiments, the operation of "adding a benign solvent to the aqueous lithium bisfluorosulfonylimide concentrate, mixing, distilling, distilling until the water content is less than 50000 ppm, adding a poor solvent, and cooling to precipitate lithium bisfluorosulfonylimide" includes the following operations:

[0073] In some embodiments, the operation of "adding a benign solvent to the aqueous lithium bisfluorosulfonylimide concentrate, mixing, distilling, distilling until the water content is less than 50000 ppm, adding a poor solvent, and cooling to precipitate lithium bisfluorosulfonylimide" includes the following operations:

[0074] In some embodiments, the temperature is reduced by 10-40°C.

[0075] The azeotrope is removed by distillation, so that the water content in the solution continues to decrease. By controlling the distillation conditions, water can be removed without decomposing the product, avoiding decomposition of the generated lithium bisfluorosulfonylimide during the drying process.

[0076] In preferred embodiments, the benign solvent is selected from organic solvents that can form an azeotrope with water but are immiscible with water, facilitating the removal of water in the form of an azeotrope during distillation. During distillation, the azeotrope formed by water and the benign solvent is separated from the system, and after condensation, the benign solvent can be separated by layering due to the immiscibility of water and the benign solvent. The benign solvent is then returned to the distillation system, ensuring its recycling and continuous reduction of water content in the distillation system.

[0077] In preferred embodiments, the water content in the test solution is < 25000 ppm, and the distillation is continued until the mass concentration of lithium bisfluorosulfonylimide is 60%-80%.

[0078] In more preferred embodiments, the water content in the test solution is < 15000 ppm, and the distillation is continued until the mass concentration of lithium bisfluorosulfonylimide is 60%-80%.

[0079] In some embodiments, the mass concentration of the lithium bisfluorosulfonylimide water concentrate is 30%-85%.

[0080] In preferred embodiments, the mass concentration of the lithium bisfluorosulfonylimide water concentrate is 50%-75%.

[0081] In some embodiments, the distillation is carried out under reduced pressure, with a temperature of 5°C-80°C and a pressure of 0-30 KPa.

[0082] In preferred embodiments, the reduced pressure distillation temperature is 30°C-70°C.

[0083] Reduced pressure distillation can effectively reduce the distillation temperature, avoiding decomposition of lithium bisfluorosulfonylimide at high temperatures or side reactions with water.

[0084] In some embodiments, the drying process control temperature is 10°C-100°C.

[0085] In preferred embodiments, the boiling point of the poor solvent is more than 20°C lower than that of the benign solvent.

[0086] By selecting a poor solvent with a lower boiling point, it is easier to remove the poor solvent during the subsequent drying process, avoiding the impact of residual poor solvent on product purity, and facilitating the separation and recycling of benign and poor solvents in the filtrate after filtration.

[0087] In some embodiments, the benign solvent is selected from solvents capable of forming azeotropes with water, the benign solvent including one or more of pyridine, alcohols, ethers, esters, nitriles, hydrocarbons.

[0088] In preferred embodiments, the benign solvent is selected from organic solvents containing at least one functional group including ester groups, cyano groups, ether linkages.

[0089] In more preferred embodiments, the benign solvent is selected from carbonate solvents.

[0090] In some embodiments, the poor solvent includes one or more of benzene, toluene, xylene, chlorobenzene, n-hexane, cyclohexane, heptane, octane, dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, or ether solvents.

[0091] In preferred embodiments, the poor solvent is added in an amount of 35% to 60% of the total mass of the system.

[0092] The application is further illustrated by the following examples.

[0093] Preparation Example 1, Lithium Resin A: The preparation method is as follows:

[0094] About 300 mL of sulfonic acid type strong acid cation exchange resin was measured and added to a 500 mL chromatographic column, 250 mL of ultrapure water was added for washing, the conductivity of the effluent was 40 μS / cm, then 250 mL of 16% hydrochloric acid solution was added, K + = 0 ppm, Na + = 0 ppm, Li + = 0 ppm; then 1250 mL of ultrapure water was added to wash the resin column, the conductivity of the effluent was 150 μS / cm, Cl - = 1.42 ppm, 500 mL of 6% LiOH solution was added, the effluent pH was 14, and finally 2000 mL of ultrapure water was added to wash the resin column, the conductivity of the effluent was 173 μS / cm.

[0095] Preparation Example 2, Lithium Resin B: The preparation method is as follows:

[0096] About 300 mL of sulfonic acid type strong acid cation exchange resin was measured and added to a 500 mL chromatographic column, 250 mL of ultrapure water was added for washing, the conductivity of the effluent was 43 μS / cm; then 250 mL of 35% sulfuric acid solution was added, K + = 0 ppm, Na + = 0.33 ppm, Li += 0 ppm; then 1250 mL of ultrapure water was added to rinse the resin column, and the conductivity of the effluent was 195 μS / cm, SO4 2- = 0.17 ppm; then 900 mL of 1.2% Li2CO3 solution was added, and the pH of the effluent was 10.5; finally, 2000 mL of ultrapure water was added to rinse the resin column, and the conductivity of the effluent was 139 μS / cm.

[0097] Example 1

[0098] This example is used to illustrate the preparation method of the disclosed lithium bisfluorosulfonylimide, which comprises the following operations:

[0099] A 1456 g aqueous solution of KFSI with a concentration of 7.5% was prepared and added to the chromatographic column in which the lithium resin A was placed, and the flow rate of the effluent was controlled to be 40-90 mL / h, and a total of 1435 g (K + = 0.13 ppm) of the effluent was obtained. The effluent was added to a flask, and distilled under reduced pressure at 40°C until the volume was reduced to 122 g. Then, 305 g of dimethyl carbonate was added, and distilled under reduced pressure at 40-60°C until the volume was reduced to 283 g. The distillate was refluxed into the flask, and the above-mentioned distillation-reflux operation was repeated until the water content in the solution was 29333 ppm. After filtration, the solution was concentrated under reduced pressure at 40°C until the volume was reduced to 122 g. Then, 122 g of dichloromethane was added, and the temperature was lowered to 25°C under stirring until crystals were precipitated. The crystals were filtered, and the filtrate was rinsed with dichloromethane. After drying, 42.54 g of LiFSI product was obtained, with a water content of 95 ppm and a main content of 99.97%.

[0100] Example 2

[0101] This example is used to illustrate the preparation method of the disclosed lithium bisfluorosulfonylimide, which comprises the following steps:

[0102] A 778 g aqueous solution of NaFSI with a concentration of 10% was prepared and added to the chromatographic column in which the lithium resin A was placed, and the flow rate of the effluent was controlled to be 40-90 mL / h, and a total of 760 g (Na +=0.40 ppm). The effluent was added to a flask and concentrated under reduced pressure at 55°C to 95 g, ethyl methyl carbonate 190 g was added, concentrated under reduced pressure at 35-60°C to 207 g, the moisture content of the solution was 63210 ppm, then ethyl methyl carbonate was added in batches for several times, a total of 380 g, repeated concentration under reduced pressure at 35-60°C to 207 g, the moisture content of the solution was 13228 ppm, after filtration, concentrated under reduced pressure at 45°C to 83 g, dichloroethane 83 g was added, the temperature was lowered to 25°C under stirring, crystals were precipitated and then filtered, the filtrate was washed with dichloroethane, and after drying, LiFSI product 29.79 g was obtained, the moisture content was 108 ppm, and the main content was 99.92%.

[0103] Example 3

[0104] The present embodiment is used to illustrate the preparation method of the disclosed lithium bisfluorosulfonylimide, comprising the following steps:

[0105] A KFSI aqueous solution with a concentration of 12.5% and a volume of 643 g was prepared and added to a chromatographic column in which lithium resin B was placed, the flow rate of the effluent was controlled at 40-90 mL / h, and a total of 623 g of effluent was obtained (K + =0.33 ppm). The effluent was added to a flask and concentrated under reduced pressure at 60°C to 80 g, acetonitrile 190 g was added, concentrated under reduced pressure at 40-65°C to 126 g, the moisture content of the solution was 97574 ppm, then acetonitrile was added in batches for several times, a total of 770 g, repeated concentration under reduced pressure at 40-65°C to 126 g, the moisture content of the solution was 38721 ppm, after filtration, concentrated under reduced pressure at 50°C to 80 g, dichloromethane 80 g was added, the temperature was lowered to 25°C under stirring, crystals were precipitated and then filtered, the filtrate was washed with dichloromethane, and after drying, LiFSI product 27.38 g was obtained, the moisture content was 184 ppm, and the main content was 99.90%.

[0106] Example 4

[0107] The present embodiment is used to illustrate the preparation method of the disclosed lithium bisfluorosulfonylimide, comprising the following steps:

[0108] A KFSI aqueous solution with a concentration of 7.5% and a volume of 4576 g was prepared and added to a chromatographic column in which lithium resin A was placed, the flow rate of the effluent was controlled at 40-90 mL / h, and the Li +=82 ppm, lithium in the resin column was consumed; the resin column was regenerated by sequentially adding 1000 mL of ultrapure water, 5500 mL of a 16% hydrochloric acid solution, 2000 mL of ultrapure water, 1250 mL of a 6% LiOH solution, and 2250 mL of ultrapure water to the resin column for elution; the above effluent was added to the resin column, and 1560 g of a 7.5% KFSI aqueous solution was added again, with the effluent flow rate being controlled at 40-90 mL / h; when the Li + =142 ppm, the above resin column regeneration operation was performed again; all of the above effluent was added to the resin column, with the effluent flow rate being controlled at 40-90 mL / h, and 6063 g (K + =0.21 ppm) of effluent was obtained. The effluent was added to a flask, 0.6063 g of lithium carbonate was added, and after being uniformly mixed, the mixture was distilled at 60°C under reduced pressure, concentrated to 522 g, 1044 g of methyl ethyl carbonate was added, and distilled at 40-65°C under reduced pressure to concentrate to 979 g of solution, with the water content in the solution being 63004 ppm; then methyl ethyl carbonate was added in batches for multiple times, a total of 3654 g, and distilled at 50°C under reduced pressure to concentrate to 979 g of solution, with the water content in the solution being 8255 ppm; after filtration, the solution was concentrated at 40-65°C under reduced pressure to 522 g, 522 g of dichloromethane was added, the temperature was lowered to 25°C under stirring, crystals were precipitated and then filtered, the filtrate was eluted with dichloromethane, and after drying, 178.67 g of LiFSI product was obtained, with the water content being 64 ppm and the main content being 99.95%.

[0109] Example 5

[0110] This example is used to illustrate the preparation method of the lithium bisfluorosulfonylimide disclosed in the present application, which comprises the following steps:

[0111] A 778 g 10% NaFSI aqueous solution was prepared and added to a chromatographic column in which lithium resin A was placed, with the effluent flow rate being controlled at 40-90 mL / h, and a total of 760 g (Na + =0.40 ppm) of effluent was obtained. The effluent was added to a flask, distilled at 55°C under reduced pressure, concentrated to 95 g, 190 g of dimethyl carbonate was added, and distilled at 35-60°C under reduced pressure to concentrate to 207 g of solution, with the water content in the solution being 69210 ppm; then dimethyl carbonate was added in batches for multiple times, a total of 570 g, and distilled at 35-60°C under reduced pressure to concentrate to 207 g, with the water content in the solution being 10300 ppm; after filtration, the solution was concentrated at 45°C under reduced pressure to 83 g, 83 g of dichloroethane was added, the temperature was lowered to 25°C under stirring, crystals were precipitated and then filtered, the filtrate was eluted with dichloroethane, and after drying, 26.87 g of LiFSI product was obtained, with the water content being 82 ppm and the main content being 99.92%.

[0112] Comparative Example 1

[0113] This example is used to illustrate the preparation method of the disclosed lithium bisfluorosulfonylimide, comprising the following steps:

[0114] A KFSI aqueous solution with a concentration of 7.5% and a volume of 1456 g was prepared and added to a chromatographic column containing lithium resin A. The flow rate of the effluent was controlled at 40-90 mL / h, and a total of 1430 g of effluent (KFSI) was obtained. + =0.13 ppm). The effluent was added to a flask and dried under reduced pressure at 50°C to obtain 80.39 g of LiFSI product with a moisture content of 13828 ppm and a main content of 87.589%.

[0115] Comparative Example 2

[0116] This example is used to illustrate the preparation method of the disclosed lithium bisfluorosulfonylimide, comprising the following steps:

[0117] A KFSI aqueous solution with a concentration of 7.5% and a volume of 1456 g was prepared and added to a chromatographic column containing lithium resin A. The flow rate of the effluent was controlled at 40-90 mL / h, and a total of 1430 g of effluent (KFSI) was obtained. + =0.20 ppm). The effluent was added to a flask and distilled under reduced pressure at 40°C to concentrate to 122 g. Dimethyl carbonate 305 g was added, and distilled under reduced pressure at 40-60°C to concentrate to 283 g. The dimethyl carbonate component in the distillate was refluxed into the flask, and the above-mentioned distillation-reflux operation was repeated until the moisture content of the solution was 29555 ppm. After filtration, the product was dried under reduced pressure at 40°C to obtain 86.61 g of LiFSI product with a moisture content of 356 ppm and a main content of 99.12%.

[0118] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing lithium bis(fluorosulfonyl)imide, characterized in that, The following steps are included: A cation exchange resin column is provided, wherein the cation exchange resin column is filled with a strong acid type cation exchange resin, and the strong acid type cation exchange resin adsorbs lithium ions. The cation exchange resin column is prepared by the following method: After packing the strong acid cation exchange resin column, the cation exchange resin column is rinsed sequentially with water, acid solution, water, lithium hydroxide or alkaline salt solution and water. Ion exchange: An aqueous solution of an alkali metal salt XFSI is provided, wherein X represents sodium ions and / or potassium ions. The aqueous solution of the alkali metal salt XFSI is passed through a cation exchange resin column for ion exchange, and the X ions on the alkali metal salt XFSI are replaced with lithium ions to obtain an aqueous solution containing lithium bis(fluorosulfonyl)imide. When the lithium ion content of the effluent is <1000 ppm during the ion exchange operation, the cation exchange resin column is regenerated. The regeneration operation of the cation exchange resin column is the same as the preparation method of the cation exchange resin column. An aqueous solution containing lithium bis(fluorosulfonyl)imide was concentrated by distillation to obtain a concentrated aqueous solution of lithium bis(fluorosulfonyl)imide. Add a good solvent to the lithium difluorosulfonyl imide aqueous solution, mix, and distill until the water content is reduced. <50000ppm; Adding a poor solvent and cooling causes lithium difluorosulfonylimide solid to precipitate; Lithium difluorosulfonylimide has a lower solubility in the poor solvent than in the good solvent.

2. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that, The aqueous solution of the alkali metal salt XFSI has a mass concentration of 1% to 50%.

3. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that, When rinsing cation exchange resin with water, the end of rinsing is indicated when the conductivity of the effluent is <200 μS / cm. When rinsing cation exchange resin with acid solution, the end of rinsing is marked when the metal cations in the effluent are less than 100 ppm. When rinsing cation exchange resins with lithium hydroxide or alkaline salt solutions, the end of rinsing is indicated when the pH of the effluent is greater than 8.

4. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that, The acid solution includes one or more of hydrochloric acid and sulfuric acid, and the acid concentration of the acid solution is 1% to 50%. The lithium hydroxide or alkaline salt solution is selected from LiOH, Li₂CO₃, LiHCO₃, C. n H 2n+1 One or more of the OLi solutions, wherein n is 1 or 2; the mass concentration of the hydroxide or alkaline salt in the lithium hydroxide or alkaline salt solution is 0.1% to 50%.

5. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that, The process involves adding a good solvent to the lithium difluorosulfonyl imide concentrate, mixing, and then distilling until the water content reaches a certain level. "<50000 ppm; Adding a poor solvent and cooling to precipitate lithium bis(fluorosulfonyl)imide solid" includes the following operations: A good solvent, selected from organic solvents capable of forming azeotropes with water, is added to a concentrated aqueous solution of lithium difluorosulfonylimide. The solution is then distilled, with the concentration controlled at 30%–40%. The water content is tested; if the water content is >50,000 ppm, the good solvent is added again for further distillation to remove water until the water content is <50,000 ppm. The solution is then filtered and distilled further until the mass concentration of lithium difluorosulfonylimide is 60%–80%. Add a poor solvent, the amount of which is greater than 20% of the total mass of the system, and cool the system to a temperature of 5°C or higher to precipitate lithium bisfluorosulfonylimide solid. Filter, wash and dry the obtained lithium bisfluorosulfonylimide solid to obtain lithium bisfluorosulfonylimide.

6. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 5, characterized in that, The mass concentration of the lithium difluorosulfonylimide aqueous concentrate is 30%-85%; The distillation is carried out under reduced pressure, with a temperature of 5℃~80℃ and a pressure of 0~30 kPa. The drying process temperature is controlled between 10℃ and 100℃.

7. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1 or 5, characterized in that, The boiling point of the undesirable solvent is more than 20°C lower than that of the beneficial solvent.

8. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that, The benign solvent is selected from solvents capable of forming azeotropes with water, and the benign solvent includes one or more of pyridine, alcohols, ethers, esters, nitriles, and hydrocarbons; The undesirable solvents include one or more of the following: benzene, toluene, xylene, chlorobenzene, n-hexane, cyclohexane, heptane, octane, dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, or ether solvents.