Preparation method for bis(fluorosulfonyl)imide alkali metal salt

Abstract

In order to solve the problem of safety risk and high residual potassium content in existing methods for preparing sodium fluorosulfonyl imide or lithium fluorosulfonyl imide from potassium fluorosulfonyl imide, the present invention provides a preparation method for a bis(fluorosulfonyl)imide alkali metal salt, comprising the following operation steps: providing an alcohol solution of an alkali metal salt XFSI; providing a cation exchange resin column, the cation exchange resin column being filled with a strongly acidic cation exchange resin, and the strongly acidic cation exchange resin adsorbing second alkali metal ions Z; and performing ion exchange: introducing the alcohol solution of the alkali metal salt XFSI into the cation exchange resin column for ion exchange, replacing first alkali metal ions X on the alkali metal salt XFSI with the second alkali metal ions Z to obtain an alcohol solution containing an alkali metal salt ZFSI, and purifying to obtain the alkali metal salt ZFSI. The preparation method provided by the present invention involves simple operations and has high safety, the purity of the obtained alkali metal salt ZFSI is high, and the purification difficulty is effectively reduced.

Description

A preparation method of bis(fluorosulfonyl)imide alkali metal salt Technical Field

[0001] The invention belongs to the technical field of electrolyte salt materials, and particularly relates to a method for preparing a bisfluorosulfonyl imide alkali metal salt. Background Art

[0002] With increasing attention paid to a green, low-carbon economy, secondary batteries are attracting significant attention. As one of the core materials in secondary batteries, electrolyte salts significantly impact their cycle life, high- and low-temperature performance, and safety. As a novel electrolyte salt, lithium bis(fluorosulfonyl)imide (LiFSI) not only offers higher conductivity, thermal stability (does not decompose below 200°C), and good hydrolytic stability compared to lithium hexafluorophosphate (LFP), but also has advantages such as suppressing battery flatulence (J. Power Sources, 2022, 535, 231481). Compared to electrolyte systems such as sodium perchlorate and sodium hexafluorophosphate, sodium-ion batteries (NaFSI) exhibit higher coulombic efficiency and improved cycling performance (Adv. Energy Mater., 2013, 3, 156-160).

[0003] Currently, there are several main methods for preparing LiFSI: one is the fluorination of bis(chlorosulfonyl)imide (HClSI) to obtain bis(fluorosulfonyl)imide (HFSI), which is then reacted with a lithium salt to obtain LiFSI (CN 104925765 A, CN 106044728 A); the other is the use of HClSI to react with lithium fluoride to prepare LiFSI (CN 113247871 A). The former requires the use of corrosive and toxic gas hydrogen fluoride (HF), and often removes water by adding dichlorothion, which leads to a high chloride ion content in the product and reduced product quality; the latter produces a large amount of HF, and the HF remaining in the product reduces the performance of LiFSI and increases the cost of tail gas treatment. US 8377406 uses HFSI to react with lithium carbonate to prepare LiFSI. When HFSI dissolves in water, the heat released will cause it to decompose. This patent prepares the HFSI aqueous solution at ultra-low temperature (-78°C), which increases energy consumption.

[0004] Currently, the main methods for preparing NaFSI are as follows: CN 114572945 A uses bis(fluorosulfonyl)imide (HFSI) to react with sodium salt to prepare NaFSI. The reaction needs to be carried out at a relatively low temperature and the moisture content in the reaction system needs to be controlled to prevent HFSI from decomposing.

[0005] In addition, in the solution state, alkali metal salts of bis(fluorosulfonyl)imide have stronger Coulombic interaction, and alkali metal ions with small ionic radius and high charge density are more likely to cause FSI. -Decomposition (Electrochimica Acta, 2019, 321, 134644). Compared with sodium bisfluorosulfonyl imide and lithium bisfluorosulfonyl imide, potassium bisfluorosulfonyl imide is more stable, has lower difficulty in preparation, and is easier to remove impurities and purify to obtain a high-purity product. Therefore, an existing preparation route is to prepare high-purity sodium fluorosulfonyl imide or lithium fluorosulfonyl imide by potassium fluorosulfonyl imide. For example, in the prior art, CN 101747242A is prepared by metathesis exchange reaction of potassium bisfluorosulfonyl imide (KFSI) with lithium tetrafluoroborate, lithium perchlorate, sodium perchlorate or sodium tetrafluoroborate in an organic solvent to obtain LiFSI or NaFSI, and the potassium ions remaining in the product are higher, and the lithium perchlorate, sodium perchlorate and the perchloric acid produced by their reaction are all explosive compounds, and there is a certain safety risk, which is not suitable for industrial production. If bis(chlorosulfonyl)imide is directly reacted with sodium fluoride to obtain NaFSI, a large amount of highly toxic and corrosive hydrogen fluoride gas will be produced.

[0006] Summary of the Invention

[0007] In view of the problems of safety risks and high residual potassium content in the existing method of preparing sodium fluorosulfonylimide or lithium fluorosulfonylimide from potassium fluorosulfonylimide, the present invention provides a method for preparing alkali metal salt of bisfluorosulfonylimide.

[0008] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0009] The present invention provides a method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, comprising the following steps:

[0010] An alcohol solution of an alkali metal salt XFSI is provided, wherein X represents a first alkali metal ion and FSI represents a bis(fluorosulfonyl)imide anion;

[0011] A cation exchange resin column is provided, wherein the cation exchange resin column is filled with a strong acid cation exchange resin, and the strong acid cation exchange resin adsorbs a second alkali metal ion Z, wherein the ionic radius of the second alkali metal ion Z is smaller than the ionic radius of the first alkali metal ion X;

[0012] Ion exchange: The alcohol solution of the alkali metal salt XFSI is passed through a cation exchange resin column for ion exchange, and the first alkali metal ion X on the alkali metal salt XFSI is replaced by the second alkali metal ion Z to obtain an alcohol solution containing the alkali metal salt ZFSI, which is then purified to obtain the alkali metal salt ZFSI.

[0013] Optionally, the second alkali metal ion Z is selected from sodium or lithium; and the first alkali metal ion X is selected from potassium or sodium.

[0014] Optionally, in the alcohol solution of the alkali metal salt XFSI, the alcohol includes one or more of methanol, ethanol and isopropanol.

[0015] Optionally, the mass concentration of the alkali metal salt XFSI is 1% to 30%, and the water content is 5% or less.

[0016] Optionally, the cation exchange resin column is prepared by the following preparation method:

[0017] After the strongly acidic cation exchange resin is loaded into the column, the cation exchange resin column is eluted with water, acid solution, water, hydroxide or alkaline salt solution of the second alkali metal ion Z, water and alcohol solvent in sequence.

[0018] Optionally, when water is used to elute the cation exchange resin, the effluent conductivity < 200 μS / cm is used as the end mark of the eluent;

[0019] When using acid solution to elute cation exchange resin, the cation content of the effluent is less than 100ppm as the end of elution;

[0020] When the cation exchange resin is eluted with a hydroxide or alkaline salt solution of the second alkali metal ion Z, the pH of the effluent > 8 is used as the end mark of elution;

[0021] When using alcohol solvents to elute cation exchange resins, the elution is completed when the water content in the effluent is less than 80,000 ppm.

[0022] Optionally, 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%;

[0023] Optionally, the hydroxide or alkaline salt solution of the second alkali metal ion Z is selected from ZOH, Z2CO3, ZHCO3, C n H 2n+1 One or more of the OZ solutions, wherein n is 1 or 2, and the mass concentration of the hydroxide or alkaline salt in the hydroxide or alkaline salt solution is 0.1% to 50%;

[0024] The alcohol solvent includes one or more of methanol, ethanol and isopropanol.

[0025] Optionally, when the second alkali metal ion Z in the effluent is less than 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.

[0026] Optionally, the alcohol solution containing the alkali metal salt ZFSI is concentrated under reduced pressure, filtered, and dried to obtain the alkali metal salt ZFSI, wherein the temperature for the reduced pressure concentration is 5° C. to 80° C.

[0027] Optionally, the strongly acidic cation exchange resin is selected from sulfonic acid cation exchange resin.

[0028] According to the method for preparing an alkali metal salt of a bisfluorosulfonyl imide provided by the present invention, compared to the existing method through chemical reaction, this preparation method uses a cation exchange resin column adsorbed with a second alkali metal ion Z to treat an alcoholic solution of an alkali metal salt XFSI, thereby preparing an alcoholic solution of the alkali metal salt ZFSI by ion exchange. This method is simple to operate, has low preparation environmental requirements, and the cation exchange resin and solvent can be recycled and reused, which is highly safe. The obtained alcoholic solution of the alkali metal salt ZFSI has high purity and is easy to perform subsequent purification operations, which is conducive to obtaining a high-purity alkali metal salt ZFSI. At the same time, the inventors found through experiments that, compared with other organic solvents, using alcoholic solvents as carriers for the alkali metal salt XFSI is beneficial for reducing the content of X ions and the water content in the obtained alkali metal salt ZFSI, thereby improving the purity of the alkali metal salt ZFSI. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] The present invention provides a method for preparing an alkali metal salt of bis(fluorosulfonyl)imide, comprising the following steps:

[0031] An alcohol solution of an alkali metal salt XFSI is provided, wherein X represents a first alkali metal ion and FSI represents a bis(fluorosulfonyl)imide anion;

[0032] A cation exchange resin column is provided, wherein the cation exchange resin column is filled with a strong acid cation exchange resin, and the strong acid cation exchange resin adsorbs a second alkali metal ion Z, wherein the ionic radius of the second alkali metal ion Z is smaller than the ionic radius of the first alkali metal ion X;

[0033] Ion exchange: The alcohol solution of the alkali metal salt XFSI is passed through a cation exchange resin column for ion exchange, and the first alkali metal ion X on the alkali metal salt XFSI is replaced by the second alkali metal ion Z to obtain an alcohol solution containing the alkali metal salt ZFSI, which is then purified to obtain the alkali metal salt ZFSI.

[0034] Compared to existing chemical reaction methods, this preparation method uses a cation exchange resin column adsorbed with a second alkali metal ion Z to treat an alcoholic solution of an alkali metal salt XFSI. This ion exchange method prepares an alcoholic solution of the alkali metal salt ZFSI. This method is simple to operate, has low environmental requirements for preparation, and the cation exchange resin and solvent are recyclable, making it highly safe. The resulting alcoholic solution of the alkali metal salt ZFSI is of high purity, making subsequent purification operations easier and facilitating the production of a high-purity alkali metal salt ZFSI. Furthermore, the inventors have discovered through experiments that, compared to other organic solvents, using alcoholic solvents as carriers for the alkali metal salt XFSI reduces the X ion content in the resulting alkali metal salt ZFSI and increases its purity.

[0035] In some embodiments, the second alkali metal ion Z is selected from sodium or lithium; the first alkali metal ion X is selected from potassium or sodium.

[0036] Specifically, when the second alkali metal ion Z is selected from lithium, the first alkali metal ion X is selected from potassium or sodium;

[0037] When the second alkali metal ion Z is selected from sodium, the first alkali metal ion X is selected from potassium.

[0038] Using KFSI as the initial raw material for the reaction has the advantages of high raw material purity and few impurities, which is beneficial to reducing impurities in the finally prepared alkali metal salt ZFSI.

[0039] In some embodiments, in the alcohol solution of the alkali metal salt XFSI, the alcohol comprises one or more of methanol, ethanol, and isopropanol.

[0040] In some embodiments, the alcohol solution of the alkali metal salt XFSI has a mass concentration of the alkali metal salt XFSI of 1% to 30% and a water content of 5% or less.

[0041] Specifically, the mass concentration of the alkali metal salt XFSI can be 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% or 30%.

[0042] In a preferred embodiment, the mass concentration of the alkali metal salt XFSI in the alcohol solution of the alkali metal salt XFSI is 5-25%.

[0043] In a preferred embodiment, the alcohol solution of the alkali metal salt XFSI has a water content of 3% or less.

[0044] The moisture in the alcoholic solution of the alkali metal salt XFSI mainly comes from the moisture carried by the solvent alcohol. Since the finally prepared alkali metal salt ZFSI is used in the electrolyte of the battery, the introduced moisture will cause the electrolyte salt to deteriorate during the battery cycle and affect the cycle performance. Therefore, the moisture in the alcoholic solution of the alkali metal salt XFSI should be controlled at a low level to avoid excessive moisture that is difficult to completely remove in the subsequent purification operation.

[0045] In some embodiments, the cation exchange resin column is prepared by the following preparation method:

[0046] After the strongly acidic cation exchange resin is loaded into the column, the cation exchange resin column is eluted with water, acid solution, water, hydroxide or alkaline salt solution of the second alkali metal ion Z, water and alcohol solvent in sequence.

[0047] In the above operation process, the first water elution operation is used to remove soluble impurities in the strong acidic cation exchange resin; the acid solution elution operation is used to elute the impurity ions adsorbed in the strong acidic cation exchange resin. At this time, the H + Ions will be embedded in the strong acid cation exchange resin to replace other impurity ions, such as Ca 2+ ions, Mg 2+ ions, Na + ions, K + The position of the ions is restored to restore the ion exchange capacity of the strong acid cation exchange resin; the second water elution operation is used to remove the residual acid in the strong acid cation exchange resin; the elution operation of the hydroxide or alkaline salt solution of the second alkali metal ion Z is used to allow the second alkali metal ion Z to replace the H in the strong acid cation exchange resin. + ions, forming a strongly acidic cation exchange resin adsorbed with a second alkali metal ion Z for ion exchange with XFSI; a third water elution operation is used to remove the residual alkali in the strongly acidic cation exchange resin; finally, an alcohol solvent elution operation is performed to replace the water in the strongly acidic cation exchange resin, thereby obtaining a cation exchange resin column with an alcohol solvent as the exchange solvent system, thereby reducing the water introduced into the reaction system.

[0048] In some embodiments, when water is used to rinse the cation exchange resin, the elution end is marked by an effluent conductivity of <200 μS / cm.

[0049] In a preferred embodiment, when water is used to elute the cation exchange resin, the effluent conductivity <100 μS / cm is used as the end mark of the eluent.

[0050] In a more preferred embodiment, when water is used to elute the cation exchange resin, the elution end sign is when the conductivity of the effluent is less than 50 μS / cm.

[0051] In some embodiments, when the cation exchange resin is eluted with an acid solution, the cation content of the effluent is less than 100 ppm, which is used as the end mark of elution.

[0052] In a preferred embodiment, when the cation exchange resin is eluted with an acid solution, the cation content in the effluent is less than 50 ppm, which is used as the end mark of elution.

[0053] It should be noted that the "cation" here refers to cations other than hydrogen ions.

[0054] In some embodiments, when the cation exchange resin is eluted with a hydroxide or alkaline salt solution of the second alkali metal ion Z, the pH of the effluent > 8 is used as the end mark of elution;

[0055] In a preferred embodiment, when the cation exchange resin is eluted with the hydroxide or alkaline salt solution of the second alkali metal ion Z, the pH of the outflow is equal to that of the hydroxide or alkaline salt solution of the second alkali metal ion Z as the end of elution.

[0056] In some embodiments, when an alcohol solvent is used to elute the cation exchange resin, the elution is completed when the water content in the effluent is less than 80,000 ppm.

[0057] In a preferred embodiment, when an alcohol solvent is used to elute the cation exchange resin, the elution is completed when the water content in the effluent is less than 50,000 ppm.

[0058] In a more preferred embodiment, when an alcohol solvent is used to elute the cation exchange resin, the elution is completed when the water content in the effluent is less than 30,000 ppm.

[0059] In a more preferred embodiment, when an alcohol solvent is used to elute the cation exchange resin, the elution is completed when the water content in the effluent is less than 20,000 ppm.

[0060] In some embodiments, 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%.

[0061] In some embodiments, when the acid solution is hydrochloric acid, the acid concentration of the acid solution is 1% to 30%.

[0062] In some embodiments, when the acid solution is sulfuric acid, the acid concentration of the acid solution is 1% to 50%.

[0063] In some embodiments, when the acid solution is hydrochloric acid, the second water rinse operation is performed with the effluent conductivity <200 μS / cm and Cl - <5ppm is the end mark of elution, preferably Cl - <2ppm.

[0064] In some embodiments, when the acid solution is sulfuric acid, the second water rinse operation is performed with an effluent conductivity of <200 μS / cm and SO4 2- <5ppm is the end mark of elution, preferably SO4 2- <2ppm.

[0065] In some embodiments, the hydroxide or alkaline salt solution of the second alkali metal ion Z is selected from ZOH, Z2CO3, ZHCO3, C n H 2n+1 One or more of the OZ solutions, wherein n is 1 or 2; the mass concentration of the hydroxide or alkaline salt in the hydroxide or alkaline salt solution is 0.1% to 50%.

[0066] In a preferred embodiment, when the hydroxide or the hydroxide in the alkaline salt solution is lithium hydroxide, the mass concentration of lithium hydroxide in the lithium hydroxide solution is 0.1% to 11%, and more preferably, the mass concentration of lithium hydroxide in the lithium hydroxide solution is 3% to 10%.

[0067] In a preferred embodiment, when the hydroxide or the hydroxide in the alkaline salt solution is sodium hydroxide, the mass concentration of sodium hydroxide in the sodium hydroxide solution is 10% to 30%.

[0068] In some embodiments, the alcohol solvent includes one or more of methanol, ethanol, and isopropanol.

[0069] In some embodiments, when the second alkali metal ion Z in the effluent is less than 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.

[0070] The first alkali metal ion X adsorbed in the cation exchange resin column is eluted by an acid solution elution operation, and then the second alkali metal ion Z is eluted by a hydroxide or alkaline salt solution elution operation to restore the loading amount of the second alkali metal ion Z in the strongly acidic cation exchange resin, thereby ensuring the regeneration and reuse of the cation exchange resin column.

[0071] In a preferred embodiment, when the second alkali metal ion Z in the effluent is less than 500 ppm, the cation exchange resin column is regenerated.

[0072] In a more preferred embodiment, when the second alkali metal ion Z in the effluent is less than 200 ppm, the cation exchange resin column is regenerated.

[0073] In some embodiments, during the ion exchange operation, the concentration of the first alkali metal ion X in the effluent is lower than 6 ppm, which is considered to be the sign of completion of the ion exchange operation.

[0074] In a preferred embodiment, during the ion exchange operation, the concentration of the first alkali metal ion X in the effluent is lower than 3 ppm, which is considered as a sign of completion of the ion exchange operation.

[0075] In a more preferred embodiment, during the ion exchange operation, the completion of the ion exchange operation is marked by the concentration of the first alkali metal ion X in the effluent being lower than 1 ppm.

[0076] In some embodiments, during the ion exchange operation, the alcoholic solution of the alkali metal salt XFSI can be passed through the cation exchange resin column once for ion exchange. When the effluent of the alcoholic solution of the alkali metal salt XFSI after passing through the cation exchange resin column once fails to reach the mark of completing the ion exchange operation (the concentration of the first alkali metal ion X is less than 6 ppm), the alcoholic solution of the alkali metal salt XFSI can be circulated through the cation exchange resin column multiple times for ion exchange, or multiple cation exchange resin columns can be connected in series to perform multiple ion exchange operations on the alcoholic solution of the alkali metal salt XFSI.

[0077] In some embodiments, the alcohol solution containing the alkali metal salt ZFSI is concentrated under reduced pressure, filtered, and dried to obtain the alkali metal salt ZFSI, wherein the temperature for the reduced pressure concentration is 5° C. to 80° C.

[0078] In a preferred embodiment, the temperature of the reduced pressure concentration is 50°C to 70°C.

[0079] During the reduced pressure concentration process, the evaporated alcohol solvent is condensed and recovered, and the recovered alcohol solvent is used for the preparation of the alcohol solution of the alkali metal salt XFSI or the elution in the regeneration process of the cation exchange resin column.

[0080] The reduced pressure operation is beneficial to lowering the required processing temperature and improving the concentration efficiency. If the reduced pressure concentration temperature is too low, it is not conducive to increasing the concentration speed. If the reduced pressure concentration temperature is too high, it is easy to cause the alkali metal salt ZFSI to decompose due to heat and produce impurities, affecting the purity of the alkali metal salt ZFSI.

[0081] In some embodiments, the strongly acidic cation exchange resin is selected from a sulfonic acid cation exchange resin. The present invention is further described below with reference to examples.

[0082] Preparation Example 1, Sodium Resin A: The preparation method is as follows:

[0083] Measure about 300mL of sulfonic acid type strong acid cation exchange resin and add it to 500mL chromatography column, add 250mL ultrapure water for elution, the conductivity of the effluent is 45μS / cm, then add 250mL of 16% hydrochloric acid solution, the K in the effluent is 45μS / cm. + =0ppm, Na + =0.98ppm, then add 1250mL ultrapure water to elute the resin column, the conductivity of the effluent is 175μS / cm, Cl - =1.39ppm; 1600mL of 10% Na2CO3 solution was added, the effluent pH = 12, 1750mL of ultrapure water was added to elute the resin column, the effluent conductivity was 160μS / cm, and finally 1000mL of anhydrous ethanol solution was added to elute the resin column, and the water content in the effluent was 32246ppm.

[0084] Preparation Example 2, Sodium Resin B: The preparation method is as follows:

[0085] Measure about 300mL of sulfonic acid type strong acid cation exchange resin and add it to 500mL chromatography column. Add 250mL ultrapure water for elution. The conductivity of the effluent is 42μS / cm. Then add 250mL of 8% sulfuric acid solution. The K in the effluent is 0.01μS / cm. + =0.68ppm, Na + =0.62ppm, then add 1750mL ultrapure water to elute the resin column, the conductivity of the effluent is 46μS / cm, SO4 2- = 0.33ppm; 1700mL 7.5% NaOH solution was added, the effluent pH = 14, 1750mL ultrapure water was added to elute the resin column, the effluent conductivity was 163μS / cm, and finally 1750mL anhydrous ethanol solution was added to elute the resin column, and the water content in the effluent was 18716ppm.

[0086] Example 1

[0087] This example is used to illustrate the preparation method of the alkali metal salt of bis(fluorosulfonyl)imide disclosed in the present invention, which includes the following operations:

[0088] Prepare 1792g of 7.5% KFSI ethanol solution (water = 18069ppm) and add it to the chromatography column filled with sodium resin B. Control the flow rate to 40-90mL / h to obtain a total of 1766g (K +=0.67ppm). The effluent was added to a flask and distilled under reduced pressure at 50°C for 40h to obtain 108.10g (0.5325mol) of a white powdery product with a yield of 86.77% (based on KFSI), a moisture content of 178ppm, and a main content of 99.98wt% NaFSI.

[0089] Example 2

[0090] This example is used to illustrate the preparation method of the bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, which comprises the following steps:

[0091] Prepare 789g of 10% KFSI ethanol solution (water = 15940ppm) and add it to the chromatography column containing sodium resin B. Control the flow rate to 40-90mL / h to obtain a total of 774g (K + =1.73ppm). The effluent was added to a flask and distilled under reduced pressure at 60°C for 13h to obtain 62.83g (0.3095mol) of a white powdery product with a yield of 85.92% (based on KFSI), a moisture content of 97ppm, and a main content of 99.98wt% NaFSI.

[0092] Example 3

[0093] This example is used to illustrate the preparation method of the bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, which comprises the following steps:

[0094] Prepare 631g of 12.5% ​​KFSI ethanol solution (water = 10043ppm) and add it to the chromatography column filled with sodium resin B. Control the flow rate to 40-90mL / h to obtain a total of 606g (K + =2.17ppm). The effluent was added to a flask and distilled under reduced pressure at 70°C for 10h to obtain 61.96g (0.3052mol) of a white powdery product with a yield of 84.74% (based on KFSI), a moisture content of 75ppm, and a main content of 99.97wt% NaFSI.

[0095] Example 4

[0096] This example is used to illustrate the preparation method of the bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, which comprises the following steps:

[0097] Prepare 3071g of 7.5% KFSI ethanol solution (water = 12069ppm) and add it to the chromatography column containing sodium resin A. Control the flow rate of the effluent to 40-90mL / h. The final Na +=415ppm, sodium in the resin column was consumed; 1000mL ultrapure water, 5500mL 16% hydrochloric acid solution, 2250mL ultrapure water, 1250mL 10% NaOH solution, 2250mL ultrapure water and 1250mL anhydrous ethanol were added to the resin column in sequence for elution to regenerate the resin column; the above effluent was added to the resin column, and 2560g of a 7.5% KFSI ethanol solution was added again, and the effluent flow rate was controlled to be 40-90mL / h; and then the resin column was regenerated again; all the above effluents were added to the resin column, and the effluent flow rate was controlled to be 40-90mL / h, to obtain a total of 5578g (K + =0.82ppm). The effluent was added to a flask and distilled under reduced pressure at 70°C for 80h to obtain 387.20g (1.9074mol) of a white powdery product with a moisture content of 92ppm and a yield of 98.91% (based on KFSI), with the main content being 99.97wt% NaFSI.

[0098] Preparation Example 3, Sodium Resin C: The preparation method includes most of the operations in Preparation Example 1, except that:

[0099] Ethyl methyl carbonate was used instead of anhydrous ethanol solution for the final elution operation.

[0100] Comparative Example 1

[0101] This comparative example is used to illustrate the preparation method of bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, and includes most of the operations in Example 1, except that:

[0102] The 7.5% KFSI ethyl methyl carbonate solution was used to replace the 7.5% KFSI ethanol solution, and the sodium resin C was used to replace the sodium resin B;

[0103] K in the effluent + =9442.33ppm;

[0104] 114.44 g of white powdery product was obtained. + The content is too high and the ion exchange is not complete. The product is a mixture of KFSI and NaFSI. The NaFSI content is 27.57wt% calculated by ion detection, the yield is 25.32% (based on KFSI), and the moisture content is 192ppm.

[0105] Preparation Example 4, Sodium Resin D: The preparation method includes most of the operations in Preparation Example 1, except that:

[0106] Acetonitrile was used instead of anhydrous ethanol solution for the final elution operation.

[0107] Comparative Example 2

[0108] This comparative example is used to illustrate the preparation method of bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, and includes most of the operations in Example 1, except that:

[0109] The 7.5% KFSI acetonitrile solution was used instead of the 7.5% KFSI ethanol solution, and the sodium resin D was used instead of the sodium resin B;

[0110] K in the effluent + =7920.48ppm;

[0111] 114.13 g of white powdery product was obtained. + The content is too high and the ion exchange is not complete. The product is a mixture of KFSI and NaFSI. The NaFSI content is 31.17wt% calculated by ion detection, the yield is 28.55% (based on KFSI), and the moisture content is 183ppm.

[0112] Preparation Example 5, Sodium Resin E: The preparation method includes most of the operations in Preparation Example 1, except that:

[0113] Dimethyl carbonate was used instead of anhydrous ethanol solution for the final elution operation.

[0114] Comparative Example 3

[0115] This comparative example is used to illustrate the preparation method of bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, and includes most of the operations in Example 1, except that:

[0116] The 7.5% KFSI dimethyl carbonate solution was used to replace the 7.5% KFSI ethanol solution, and the sodium resin E was used to replace the sodium resin B;

[0117] K in the effluent + =8286.22ppm;

[0118] 114.39 g of white powdery product was obtained. + The content is too high and the ion exchange is not complete. The product is a mixture of KFSI and NaFSI. The NaFSI content is 28.17 wt % calculated by ion detection, the yield is 25.44% (based on KFSI), and the moisture content is 189 ppm.

[0119] From the preparation results of Examples 1 to 4, it can be seen that the preparation method provided by the present invention can directly prepare NaFSI from KFSI, and the preparation process is relatively environmentally friendly and safe. The obtained NaFSI has the characteristics of high yield and high purity. At the same time, from the comparison of Examples 1 to 4 and Comparative Examples 1 to 3, it can be seen that compared with other organic solvents, the present invention uses alcohol solvents as the elution solvent of the cation exchange resin and the medium system of ion exchange, which can effectively reduce the K in the effluent. + content and moisture content, thereby improving the final yield and purity of NaFSI, indicating that the use of alcohol solvents is beneficial to improving the ion exchange efficiency between KFSI and cation exchange resin, ensuring K + Full replacement.

[0120] Preparation Example 6, lithium resin A: The preparation method is as follows:

[0121] Measure about 300mL of strong acid cation exchange resin and add it to a 500mL chromatography column. Add 250mL of ultrapure water for elution. The conductivity of the effluent is 40μS / cm. Then add 250mL of 16% hydrochloric acid solution. The K + =0.2ppm, Na + =0.31ppm, Li + =0ppm, then add 1250mL ultrapure water to elute the resin column, the conductivity of the effluent is 152μS / cm, Cl - =1.40ppm; 1250mL of 6% LiOH solution was added, the effluent pH = 12, 2000mL of ultrapure water was added to elute the resin column, the effluent conductivity was 129μS / cm, and finally 1000mL of anhydrous ethanol solution was added to elute the resin column, and the water content in the effluent was 34350ppm.

[0122] Preparation Example 7, lithium resin B: The preparation method is as follows:

[0123] Measure about 300mL of strong acid cation exchange resin and add it to a 500mL chromatography column. Add 250mL of ultrapure water for elution. The conductivity of the effluent is 44μS / cm. Then add 250mL of 8% sulfuric acid solution. The K + =0.12ppm, Na + =0.57ppm, Li + =0ppm, then add 1750mL ultrapure water to elute the resin column, the conductivity of the effluent is 76μS / cm, SO4 2-=0.19ppm, 1400mL of 8% Li2CO3 solution was added, the pH of the effluent was 12, 2000mL of ultrapure water was added to elute the resin column, the conductivity of the effluent was 136μS / cm, and finally 1750mL of anhydrous ethanol solution was added to elute the resin column, and the water content in the effluent was 26223ppm.

[0124] Example 5

[0125] This example is used to illustrate the preparation method of the alkali metal salt of bis(fluorosulfonyl)imide disclosed in the present invention, which includes the following operations:

[0126] Prepare 1451g of 7.5% KFSI ethanol solution (water = 18354ppm) and add it to the chromatography column with lithium resin A. Control the flow rate to 40-90mL / h to obtain 1428g of effluent (K + =0.2ppm). The effluent was added to a flask and distilled under reduced pressure at 30°C for 45h to obtain 86.08g (0.4603mol) of a white powdery product with a yield of 92.63% (based on KFSI), a moisture content of 166ppm, and a main content of 99.87wt% LiFSI.

[0127] Example 6

[0128] This example is used to illustrate the preparation method of the bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, which comprises the following steps:

[0129] Prepare 789g of 10% NaFSI ethanol solution (water = 14085ppm) and add it to the chromatography column with lithium resin A. Control the flow rate to 40-90mL / h to obtain a total of 770g of effluent (Na + =0ppm). The effluent was added to a flask and distilled under reduced pressure at 40°C for 17h to obtain 64.01g (0.3423mol) of a white powdery product with a yield of 88.04% (based on NaFSI), a moisture content of 132ppm, and a main content of 99.91wt% LiFSI.

[0130] Example 7

[0131] This example is used to illustrate the preparation method of the bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, which comprises the following steps:

[0132] Prepare 722g of 12.5% ​​KFSI ethanol solution (water = 10921ppm) and add it to the chromatography column with lithium resin B. Control the flow rate to 40-90mL / h to obtain 698g of effluent (K +=0.3ppm). The effluent was added to a flask and distilled under reduced pressure at 50°C for 18h to obtain 66.18g (0.3539mol) of a white powdery product with a yield of 85.87% (based on KFSI), a moisture content of 95ppm, and a main content of 99.85wt% LiFSI.

[0133] Example 8

[0134] This example is used to illustrate the preparation method of the bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, which comprises the following steps:

[0135] Prepare 3242g of 7.5% KFSI ethanol solution (water = 12437ppm) and add it to the chromatography column with lithium resin A. Control the flow rate of the effluent to 40-90mL / h. The final effluent contains Li + =88ppm, the lithium in the resin column was consumed; 1000mL ultrapure water, 5500mL 16% hydrochloric acid solution, 2250mL ultrapure water, 1250mL 6% LiOH solution, 2250mL ultrapure water, and 1500mL anhydrous ethanol were added to the resin column in sequence for elution to regenerate the resin column; the above effluent was added to the resin column, and 2134g of 7.5% KFSI ethanol solution was added again, and the effluent flow rate was controlled to 40-90mL / h; then the resin column was regenerated again; all the above effluents were added to the resin column, and the effluent flow rate was controlled to 40-90mL / h, to obtain a total of 5316g (K + =0.2ppm). The effluent was added to a flask and distilled under reduced pressure at 50°C for 95h to obtain 343.72g (1.8381mol) of a white powdery product with a yield of 99.84% (based on KFSI), a moisture content of 102ppm, and a main content of 99.89wt% LiFSI.

[0136] Preparation Example 8, Lithium Resin C: The preparation method includes most of the operations in Preparation Example 6, except that:

[0137] Ethyl methyl carbonate was used instead of anhydrous ethanol solution for the final elution operation.

[0138] Comparative Example 4

[0139] This comparative example is used to illustrate the preparation method of bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, and includes most of the operations in Example 5, except that:

[0140] A 7.5% KFSI ethyl methyl carbonate solution was used to replace a 7.5% KFSI ethanol solution, and lithium resin C was used to replace lithium resin A.

[0141] K in the effluent+ =8158.57ppm;

[0142] 95.98 g of white powdery product was obtained. + The content is too high and the ion exchange is incomplete. The product is a mixture of KFSI and LiFSI. The LiFSI content is calculated to be 31.84 wt% by ion detection, the yield is 32.88% (based on KFSI), and the moisture content is 175 ppm.

[0143] Preparation Example 9, Lithium Resin D: The preparation method includes most of the operations in Preparation Example 6, except that:

[0144] Acetonitrile was used instead of anhydrous ethanol solution for the final elution operation.

[0145] Comparative Example 5

[0146] This comparative example is used to illustrate the preparation method of bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, and includes most of the operations in Example 5, except that:

[0147] A 7.5% KFSI acetonitrile solution was used to replace a 7.5% KFSI acetonitrile solution, and a lithium resin D was used to replace a lithium resin A.

[0148] K in the effluent + =7730.62ppm;

[0149] 95.47 g of white powdery product was obtained. + The content was too high and the ion exchange was incomplete. The product was a mixture of KFSI and LiFSI. After ion detection, the LiFSI content was 35.06 wt%, the yield was 36.02% (calculated as KFSI), and the moisture content was 172 ppm.

[0150] Preparation Example 10, Lithium Resin E: The preparation method includes most of the operations in Preparation Example 6, except that:

[0151] Dimethyl carbonate was used instead of anhydrous ethanol solution for the final elution operation.

[0152] Comparative Example 6

[0153] This comparative example is used to illustrate the preparation method of bis(fluorosulfonyl)imide alkali metal salt disclosed in the present invention, and includes most of the operations in Example 5, except that:

[0154] A 7.5% KFSI dimethyl carbonate solution was used to replace a 7.5% KFSI dimethyl carbonate solution, and a lithium resin E was used to replace a lithium resin A.

[0155] K in the effluent+ =8087.29ppm;

[0156] 95.89 g of white powdery product was obtained. + The content is too high and the ion exchange is incomplete. The product is a mixture of KFSI and LiFSI. After ion detection, the LiFSI content is 32.37wt%, the yield is 33.41% (calculated as KFSI), and the moisture content is 180ppm.

[0157] From the preparation results of Examples 5 to 8, it can be seen that the preparation method provided by the present invention can directly prepare LiFSI through KFSI or NaFSI, and the preparation process is relatively environmentally friendly and safe. The obtained LiFSI has the characteristics of high yield and high purity. At the same time, from the comparison of Examples 5 to 8 and Comparative Examples 4 to 6, it can be seen that compared with other organic solvents, the present invention uses alcohol solvents as the elution solvent of the cation exchange resin and the medium system of ion exchange, which can effectively reduce the K in the effluent. + Or Na + content and moisture content, thereby improving the final yield and purity of LiFSI, indicating that the use of alcohol solvents is beneficial to improving the ion exchange efficiency between KFSI or NaFSI and cation exchange resin, ensuring K + Or Na + Full replacement.

[0158] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a bis(fluorosulfonyl)imide alkali metal salt, characterized in that: The steps include: An alcohol solution of an alkali metal salt XFSI is provided, wherein X represents a first alkali metal ion and FSI represents a bis(fluorosulfonyl)imide anion; Provided is a cation exchange resin column, wherein the cation exchange resin column is filled with a strong acid cation exchange resin, and the strong acid cation exchange resin adsorbs a second alkali metal ion Z, wherein the ionic radius of the second alkali metal ion Z is smaller than the ionic radius of the first alkali metal ion X; Ion exchange: The alcohol solution of the alkali metal salt XFSI is passed through a cation exchange resin column for ion exchange, and the first alkali metal ion X on the alkali metal salt XFSI is replaced by the second alkali metal ion Z to obtain an alcohol solution containing the alkali metal salt ZFSI, which is then purified to obtain the alkali metal salt ZFSI.

2. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The second alkali metal ion Z is selected from sodium or lithium.

3. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The first alkali metal ion X is selected from potassium or sodium.

4. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: In the alcohol solution of the alkali metal salt XFSI, the alcohol includes one or more of methanol, ethanol and isopropanol.

5. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The mass concentration of the alkali metal salt XFSI in the alcohol solution of the alkali metal salt XFSI is 1% to 30%, and the water content is 5% or less.

6. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The cation exchange resin column is prepared by the following preparation method: After the strongly acidic cation exchange resin is loaded into the column, the cation exchange resin column is eluted with water, an acid solution, water, a hydroxide or alkaline salt solution of the second alkali metal ion Z, water and an alcohol solvent in sequence.

7. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: When water is used to elute the cation exchange resin, the elution end sign is when the conductivity of the effluent is less than 200 μS / cm.

8. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: When an acid solution is used to elute the cation exchange resin, the cation content in the effluent is less than 100 ppm, which is used as the end of the elution.

9. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: When the cation exchange resin is eluted with the hydroxide or alkaline salt solution of the second alkali metal ion Z, the pH of the effluent > 8 is used as the end mark of the elution.

10. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: When using alcohol solvents to elute cation exchange resins, the water content in the effluent is <80000ppm is the sign of the end of elution.

11. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, 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%.

12. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: The hydroxide or alkaline salt solution of the second alkali metal ion Z is selected from ZOH, Z2CO3, ZHCO3, C n H 2n+1 One or more of the OZ solutions, wherein n is 1 or 2; the mass concentration of the hydroxide or alkaline salt in the hydroxide or alkaline salt solution is 0.1% to 50%.

13. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: The alcohol solvent includes one or more of methanol, ethanol and isopropanol.

14. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 6, characterized in that: When the second alkali metal ion Z of the effluent is less than 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.

15. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The alcohol solution containing the alkali metal salt ZFSI is concentrated under reduced pressure, filtered and dried to obtain the alkali metal salt ZFSI, wherein the temperature of the reduced pressure concentration is 5° C. to 80° C.

16. The method for preparing bis(fluorosulfonyl)imide alkali metal salt according to claim 1, characterized in that: The strongly acidic cation exchange resin is selected from sulfonic acid type cation exchange resin.

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