A method for preparing lithium bisfluorosulfonimide

Abstract

The application discloses a preparation method of lithium bisfluorosulfonimide, and aims to provide a preparation method of lithium bisfluorosulfonimide by using easily separated N-alkyl bisfluorosulfonimide instead of ammonium salt of lithium bisfluorosulfonimide, and lithium salt, wherein the preparation steps are short, the whole separation and purification process is simple and easy to implement, and the danger degree of materials is relatively low. The technical scheme is as follows: N-alkyl bisfluorosulfonimide and alkaline lithium salt are used as raw materials, and reaction is carried out in an organic solvent A at room temperature to obtain the product; and the application relates to the technical field of new energy.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of new energy, and relates to a preparation method of lithium salt lithium bisfluorosulfonylimide. BACKGROUND

[0002] Lithium bisfluorosulfonylimide (LiFSI) is an organic lithium salt, which contains a lithium ion and a bisfluorosulfonylimide group in the structure. Due to excellent thermal stability, high low-temperature resistance, excellent hydrolysis resistance, high ionic conductivity and an electrochemical window, lithium bisfluorosulfonylimide is widely applied in electrolytes of lithium batteries, can effectively reduce the high and low temperature resistance of the SEI layer formed on the surface of the electrode plate at low temperature, has good compatibility with the electrode, improves the low-temperature discharge and high-temperature storage performance, reduces the capacity loss of the lithium battery in the storage process, and thus improves the battery capacity and the electrochemical performance of the battery. Compared with lithium hexafluorophosphate, lithium in lithium bisfluorosulfonylimide is more easily dissociated, and therefore has higher conductivity. In the future, lithium bisfluorosulfonylimide is most likely to replace lithium hexafluorophosphate and become the second generation of lithium ion battery electrolyte.

[0003] However, as a lithium ion secondary battery electrolyte, lithium bisfluorosulfonylimide needs to meet the harsh requirements of high purity and waterlessness. If moisture is introduced, it is difficult to completely remove the moisture by means of heating, drying or even decomposition, and even if the moisture can be removed, a large yield loss is needed. Therefore, the preparation process of lithium bisfluorosulfonylimide has become a research hotspot in the field, and currently there are five main synthesis routes of lithium bisfluorosulfonylimide.

[0004] Method one: CN110155967A discloses that chlorosulfonic acid, aminosulfonic acid and dichlorosulfoxide are used as raw materials to prepare dichlorosulfonylimide HCSI; fluorination is performed to obtain bisfluorosulfonylimide HFSI; and HFSI is reacted with a corresponding lithium salt to obtain LiFSI. The raw materials of this method are simple, but a large amount of by-product gas is generated, which is difficult to handle.

[0005] Method two: CN201711030977.8 discloses that chlorosulfonic acid and chlorosulfonic acid isocyanate are used as raw materials to prepare dichlorosulfonylimide HCSI; fluorination is performed to obtain bisfluorosulfonylimide HFSI; and HFSI is reacted with a corresponding lithium salt to obtain LiFSI. This method greatly reduces the by-product gas, greatly improves the atomic economy, but chlorosulfonylisocyanate is expensive and difficult to obtain, and it is difficult to remove the chlorine ion in the product, which affects the quality of the product.

[0006] Method three: sulfuryl fluoride, ammonia and an organic amine are used as raw materials to prepare ammonium salt of bisfluorosulfonylimide by one-pot method; the obtained ammonium salt is reacted with an alkaline lithium salt to obtain LiFSI. This method has short steps and relatively low material risk, but the separation process is difficult, sulfuryl fluoride is difficult to obtain, and the recovery of the organic amine has certain difficulty.

[0007] Method four: when preparing LiFSI by reacting HClSI directly with LiF in US2004097757, a large amount of corrosive tail gas HF is generated, and the residual HF in the electrolyte will eventually have an adverse effect on lithium batteries; tail gas absorption also increases the difficulty of industrial operation; at the same time, excess LiF and LiFSI are not easy to separate, resulting in low purity of the final product LiFSI.

[0008] Method five: LiFSI is prepared by exchanging purified potassium bisfluorosulfonylimide with lithium perchlorate metal in CN202211548420.4, and the residual potassium ion in the product is often high, which affects the practical application of LiFSI, and there is a certain risk of explosion.

[0009] The intermediate products prepared by the above-mentioned various methods are ammonium salts of bisfluorosulfonylimide, which are difficult to separate, the post-treatment is complex, and the product purity is not high, which is difficult to meet the battery grade standard and cannot be directly industrialized. SUMMARY

[0010] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for preparing bisfluorosulfonylimide lithium by replacing the ammonium salt of bisfluorosulfonylimide with easily separable N-alkyl bisfluorosulfonylimide, which is prepared with lithium salt, the preparation steps are short, the whole separation and purification process is simple and easy to operate, and the material risk is relatively low.

[0011] To this end, the technical solution provided by the present application is as follows:

[0012] A method for preparing bisfluorosulfonylimide lithium, which is prepared by reacting N-alkyl bisfluorosulfonylimide and basic lithium salt in an organic solvent A, in which N-alkyl bisfluorosulfonylimide is used to prepare bisfluorosulfonylimide lithium, and the unreacted N-alkyl bisfluorosulfonylimide is easy to separate.

[0013] Further, the above-mentioned method for preparing bisfluorosulfonylimide lithium comprises the following steps in sequence: under anhydrous and anaerobic conditions, organic solvent A, N-ethyl bisfluorosulfonylimide, and basic lithium salt solution are sequentially added to a reaction device, stirring is carried out at room temperature for 5-9h, after the reaction is completed, the first reduced pressure distillation is carried out under reduced pressure to concentrate to no liquid is distilled out, then a poor solvent is added, white solid is precipitated, and bisfluorosulfonylimide lithium can be obtained by filtration and drying.

[0014] Further, the above-mentioned method for preparing bisfluorosulfonylimide lithium, the basic lithium salt is at least one of lithium alcoholate, lithium amide, and lithium hydroxide.

[0015] Further, the above-mentioned method for preparing bisfluorosulfonylimide lithium, the solvent of the basic lithium salt solution is methanol or ethanol.

[0016] Further, in the above-mentioned method for preparing lithium bisfluorosulfonimide, the organic solvent A is at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, butyl acetate, and dimethoxyethane; preferably dimethyl carbonate, because dimethyl carbonate is a commonly used solvent in electrolyte, which can reduce the introduction of impurities, thereby ensuring the purity of the target product.

[0017] Further, in the above-mentioned method for preparing lithium bisfluorosulfonimide, the first reduced pressure distillation condition is -0.095 to -0.100 MPa and 45 to 50°C; the filtration is performed under reduced pressure at -0.095 to -0.100 MPa; and the drying is performed at 80 to 85°C and -0.095 to -0.100 MPa for 5 to 6 hours.

[0018] Further, in the above-mentioned method for preparing lithium bisfluorosulfonimide, the poor solvent is at least one of aromatic hydrocarbon solvents, preferably toluene, dichloromethane, dichloroethane, hexane 、 cyclohexane .

[0019] Further, in the above-mentioned method for preparing lithium bisfluorosulfonimide, the N-alkyl lithium bisfluorosulfonimide is prepared by reacting a sulfonyl compound with an amine-containing compound in an organic solvent B.

[0020] Further, in the above-mentioned method for preparing lithium bisfluorosulfonimide, the N-alkyl lithium bisfluorosulfonimide is prepared by the following method:

[0021] 1) under anhydrous and anaerobic conditions, an organic solvent B is added to a reaction vessel, which is cooled to -3 to -6°C, a sulfonyl compound is slowly introduced into the reaction vessel, an acid-binding agent is added with stirring, and then an amine-containing compound solution is slowly added dropwise into the flask, and the reaction temperature is maintained at -5 to 0°C;

[0022] 2) after the dropwise addition is completed, the temperature is maintained and stirring is continued for 0.8 to 1.2 hours, and then the reaction solution is returned to room temperature, and stirring is continued for 4 to 6 hours;

[0023] 3) after the reaction is completed, the solvent is removed by reduced pressure distillation under the second reduced pressure distillation condition, and the N-ethyl lithium bisfluorosulfonimide is obtained by post-treatment;

[0024] The molar ratio of the sulfonyl compound, the amine compound, and the acid-binding agent is 1:1:2.

[0025] In the scheme, the sulfuryl fluoride is first introduced into acetonitrile, then triethylamine is added, and then the ethylamine acetonitrile solution is slowly added dropwise; the reaction temperature is relatively low, -5-0℃, which avoids the occurrence of side reactions caused by high temperature, i.e. the other fluorine of the sulfuryl fluoride may also be replaced, so that the target product cannot be obtained, and the product purity is affected.

[0026] Further, in the above-mentioned preparation method of lithium bisfluorosulfonimide, the amine compound has the following general structure:

[0027] R1 is independently selected from one of phenyl, C1-C10 saturated hydrocarbon group, C2-C10 olefin group, C2-C10 alkyne group, C1-C10 halogenated saturated hydrocarbon group, C2-C10 halogenated olefin group, and C2-C10 halogenated alkyne group.

[0028] In the scheme, the alkylamine is more easily obtained, has a lower boiling point, and is easy to separate from the product; and the final generated alkyl alcohol also has a lower boiling point, is easy to separate and purify, and saves energy consumption.

[0029] Further, in the above-mentioned preparation method of lithium bisfluorosulfonimide, the acid binding agent is an organic amine, preferably triethylamine, which easily combines with protons through the lone pair of electrons on the N atom, and neutralizes the acid generated in the reaction.

[0030] Further, in the above-mentioned preparation method of lithium bisfluorosulfonimide, the organic solvent B is at least one of acetonitrile, dichloromethane, and dichloroethane, and acetonitrile is preferably used. In the scheme, acetonitrile is used as the solvent, which has a higher boiling point, is less volatile, and is more environmentally friendly; after the reaction is completed, the solvent can be removed by direct vacuum distillation to obtain the target N-ethyl bisfluorosulfonimide, and the operation is simple.

[0031] Further, in the above-mentioned preparation method of lithium bisfluorosulfonimide, the sulfuryl compound is sulfuryl fluoride or sulfuryl fluoride chloride.

[0032] Further, in the above-mentioned preparation method of lithium bisfluorosulfonimide, the second vacuum distillation condition is -0.095 to -0.100 MPa and 35-45℃.

[0033] Further, in the above-mentioned preparation method of lithium bisfluorosulfonimide, when the amine compound is benzylamine, the step 3) post-treatment is to add dichloromethane to the reaction residue, stir and dissolve, then wash with deionized water to remove the dichloromethane solution, obtain the organic phase, remove the organic phase, and continue vacuum drying to obtain white crystals.

[0034] Further, the preparation method of the above-mentioned lithium bisfluorosulfonimide, when the amine compound is ethylamine, the post-treatment of step 3) is to continue to heat the product after removing the organic solvent B to 100-120 DEG C and distill under reduced pressure, and the colorless liquid is collected.

[0035] Compared with the prior art, the technical scheme provided by the present application has the following technical advantages:

[0036] 1. The technical scheme provided by the present application uses thionyl chloride or thionyl fluoride chloride as raw material, and does not generate difficult-to-separate ammonium salt of bisfluorosulfonimide, but generates easy-to-separate N-alkyl bisfluorosulfonimide, which is convenient for subsequent operation.

[0037] 2. In the technical scheme provided by the present application, the preparation of N-alkyl bisfluorosulfonimide is at-5-0 DEG C, so that the temperature is not too high, and a side reaction of generating two molecules of amino compound with both halogens being substituted may occur, and the temperature requirement is relatively low, which is helpful to reduce energy consumption and the requirement for reaction equipment.

[0038] 3. The technical scheme provided by the present application uses cationic N-alkyl bisfluorosulfonimide to prepare lithium bisfluorosulfonimide with lithium salt, the preparation steps are short, the whole separation and purification process is simple and easy to operate, and the material is relatively low in danger degree. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 N-ethyl bisfluorosulfonimide prepared in Example 1 1 H NMR spectrum;

[0040] Figure 2 Lithium bisfluorosulfonimide prepared in Example 1 19 F NMR spectrum;

[0041] Figure 3 N-ethyl bisfluorosulfonimide prepared in Example 2 1 H NMR spectrum;

[0042] Figure 4 Lithium bisfluorosulfonimide prepared in Example 2 19 F NMR spectrum;

[0043] Figure 5 Lithium bisfluorosulfonimide prepared in Example 3 19F NMR spectrum

[0044] Figure 6 N-benzyl bisfluorosulfonimide prepared in Example 4 1 H NMR spectrum;

[0045] Figure 7Lithium bisfluorosulfonimide prepared in Example 4 19 HNMR spectrum;

[0046] Figure 8 N-phenylfluorosulfonimide prepared in Comparative Example 1 1 HNMR spectrum. DETAILED DESCRIPTION

[0047] The technical solutions provided by the present application will be described in detail below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0048] Example 1

[0049] The present embodiment provides a preparation method of lithium bisfluorosulfonimide, which comprises the following steps in sequence:

[0050] 1) Preparation of N-ethyl bisfluorosulfonimide

[0051] Under anhydrous and anaerobic conditions, 150 mL of acetonitrile was added to a 500 mL flask, which was cooled to -5°C, and 51.00 g (0.5 mol) of sulfuryl fluoride was slowly introduced into the flask. While stirring, 50.05 g (0.5 mol) of triethylamine was added, and then 50 mL of acetonitrile solution containing 11.25 g (0.25 mol) of ethylamine was slowly added dropwise into the flask. The reaction temperature was maintained at -5-0°C, and after the dropwise addition was completed, the temperature was maintained for 1 h with stirring, and then the reaction solution was allowed to return to room temperature and was continuously stirred for 5 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40°C, and the temperature was further increased to 110°C, and then the reaction was distilled under reduced pressure at -0.097 MPa and 40°C. 43.23 g of colorless liquid was collected, with a yield of 82.73%, and its 1 HNMR spectrum Figure 1 . The reaction chemical formula is as shown in

[0052] Formula 1:

[0053]

[0054] 2) Preparation of lithium bisfluorosulfonimide

[0055] Under the condition of no water and no oxygen, 100 mL of dimethyl carbonate, 20.89 g (0.1 mol) of N-ethyl bisfluorosulfonimide, 100 mL of ethanolic lithium solution (1 mol / L) were sequentially added into a 250 mL flask, and the reaction was stirred at room temperature for 7 h. After the reaction was completed, the reaction solution was concentrated under reduced pressure at 45 °C to a liquid which was difficult to distill. Then, 100 mL of poor solvent toluene was added, and white solid was precipitated. The solid was collected by filtration under reduced pressure at -0.097 MPa. The collected solid was dried at 80 °C under a pressure of -0.099 MPa for 5 h to obtain 14.31 g of white crystals, with a yield of 76.52% (calculated based on ethanolic lithium). The reaction chemical formula is shown in Formula 2. 19 The H NMR spectrum is shown in Figure 2 , the acidity is 37 ppm, and the moisture content is 48 ppm. The reaction chemical formula is shown in Formula 2.

[0056]

[0057] Example 2

[0058] The present embodiment provides a preparation method of lithium bisfluorosulfonimide, which sequentially comprises the following steps:

[0059] 1) Preparation of N-ethyl bisfluorosulfonimide

[0060] Under the condition of no water and no oxygen, 150 mL of acetonitrile was added into a 500 mL flask, and the solution was cooled to -5 °C. Then, 59.02 g (0.5 mol) of sulfuryl fluoride chloride was slowly added into the solution, and 50.05 g (0.5 mol) of triethylamine was added into the solution while stirring. Then, 50 mL of acetonitrile containing 11.25 g (0.25 mol) of ethylamine was slowly added into the solution, and the reaction temperature was maintained at -5 to 0 °C. After the dropwise addition was completed, the temperature was maintained for 1 h. Then, the reaction solution was warmed to room temperature, and the stirring was continued for 5 h. During the reaction, white precipitates were generated. After the reaction was completed, the solid was removed by filtration, and the filtrate was collected. The solvent was removed by distillation under reduced pressure at -0.097 MPa and 40 °C. The temperature was further increased to 110 °C, and the distillation was continued under reduced pressure at -0.099 MPa for 4 to 6 h. Then, 37.56 g of colorless liquid was collected, with a yield of 71.88%. The reaction chemical formula is shown in Formula 3. 1 The H NMR spectrum is shown in Figure 3 . The reaction chemical formula is shown in Formula 3.

[0061]

[0062] 2) Preparation of lithium bisfluorosulfonimide

[0063] Under anhydrous and oxygen-free conditions, 100 mL of dimethyl carbonate, 20.89 g (0.1 mol) of N-ethylbisfluorosulfonylimide, and 80 mL of an ethanol solution of lithium ethoxide (1 mol / L) were added sequentially to a 250 mL flask. The mixture was stirred at room temperature for 7 h. After the reaction was completed, the mixture was concentrated under reduced pressure at -0.097 MPa and 45 °C until the liquid was difficult to distill off. Then, 100 mL of the solution was added, and the mixture was filtered under reduced pressure at -0.097 MPa to collect the solid. The solid was then dried under reduced pressure at 80 °C and -0.099 MPa for 5 h to obtain 13.76 g of white crystals, with a yield of 91.98% (based on lithium ethoxide). 19 See F NMR spectrum. Figure 4 The acidity is 42 ppm and the moisture content is 36 ppm. The chemical formula for the reaction is shown in Formula 4:

[0064]

[0065] Example 3

[0066] This embodiment provides a method for preparing lithium difluorosulfonylimide. Using N-ethyldifluorosulfonylimide prepared in Example 1, under anhydrous and oxygen-free conditions, 200 mL of dimethyl carbonate, 20.89 g (0.1 mol) of N-ethyldifluorosulfonylimide (prepared in Example 1), and 2.31 g (0.1 mol) of lithium aminoamide were added sequentially to a 250 mL flask. The mixture was stirred at room temperature for 7 h. After the reaction was completed, the mixture was concentrated by vacuum distillation at -0.097 MPa and 45 °C until the liquid was difficult to distill off. Then, 100 mL of the unsuitable solvent toluene was added, resulting in the precipitation of a white solid. The solid was collected by vacuum filtration at -0.097 MPa and then dried at 80 °C and -0.099 MPa for 5 h to obtain 16.02 g of white crystals, with a yield of 85.67% (calculated as lithium aminoamide), an acidity of 31 ppm, and a water content of 23 ppm. 19 See F NMR spectrum. Figure 5 The chemical formula for the reaction is shown in Formula 5:

[0067]

[0068]

[0069] Example 4

[0070] This embodiment provides a method for preparing lithium bis(fluorosulfonyl)imide, which includes the following steps in sequence:

[0071] 1) Preparation of N-benzylbisfluorosulfonylimide

[0072] Under the condition of no water and no oxygen, 150 mL of acetonitrile was added into a 500 mL flask, and the flask was cooled to -5°C. Then 51.07 g (0.5 mol) of sulfonyl fluoride was slowly introduced into the flask, and 50.08 g (0.5 mol) of triethylamine was added into the flask under stirring. Then 26.79 g (0.25 mol) of benzylamine was slowly added into the flask dropwise, and the reaction temperature was maintained at -5-0°C. After the dropwise addition was completed, the temperature was maintained for 1 h under stirring. Then the reaction liquid was restored to room temperature, and the stirring was continued for 5 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40°C. Then 200 mL of dichloromethane was added into the flask residue, and the dichloromethane solution was washed with 300 mL of deionized water for three times. The organic phase was collected, and the solvent was removed. Then the organic phase was dried under vacuum at -0.99 MPa and 50°C, and 56.61 g of white solid was obtained, with a yield of 83.57%. The product was identified by H NMR spectrum, and the reaction chemical formula was shown in formula 6. 1 H NMR spectrum was shown in Figure 1. Figure 6 The reaction chemical formula was shown in formula 6.

[0073]

[0074] 2) Preparation of lithium bisfluorosulfonimide

[0075] Under the condition of no water and no oxygen, 100 mL of dimethyl carbonate, 27.07 g (0.1 mol) of N-benzyl bisfluorosulfonimide, and 80 mL of ethanolic lithium solution (1 mol / L) were sequentially added into a 250 mL flask. The reaction was stirred at room temperature for 7 h. After the reaction was completed, the liquid was concentrated by distillation under reduced pressure at -0.097 MPa and 50°C until the liquid could not be distilled. Then 100 mL of poor solvent toluene was added, and white solid was precipitated. The solid was collected by filtration under reduced pressure at -0.097 MPa. Then the solid was dried under reduced pressure at -0.099 MPa and 80°C, and 14.49 g of white crystal was obtained, with a yield of 96.86% (calculated based on ethanolic lithium). The product was identified by F NMR spectrum, and the reaction chemical formula was shown in formula 7. 19 F NMR spectrum was shown in Figure 2. Figure 7 Acidity: 28 ppm, moisture: 43 ppm. The reaction chemical formula was shown in formula 7.

[0076]

[0077]

[0078] Example 5

[0079] The embodiment provides a preparation method of lithium bisfluorosulfonimide, and the method sequentially comprises the following steps.

[0080] 1) Preparation of N-benzyl bisfluorosulfonimide

[0081] Under the condition of no water and no oxygen, 150 mL of dichloromethane was added into a 500 mL flask, and cooled to -5°C, then 51.07 g (0.5 mol) of sulfuryl fluoride was slowly bubbled into the flask, 50.08 g (0.5 mol) of triethylamine was added under stirring, and 26.79 g (0.25 mol) of benzylamine was slowly dropped into the flask, the reaction temperature was kept between -5°C and 0°C, after the dropping was completed, the temperature was kept for 1 h under stirring, then the reaction liquid was restored to room temperature, and stirred for 5 h. Then, 50 mL of dichloromethane was added into the flask residue, and dissolved under stirring, then the dichloromethane solution was washed with 300 mL of deionized water for three times, the organic phase was collected, and the organic phase solvent was removed, then vacuum drying was carried out at -0.99 MPa and 50°C, and 54.23 g of white solid was obtained, with a yield of 80.04%.

[0082] The reaction chemical formula is shown in formula 6

[0083] 2) Preparation of lithium bisfluorosulfonimide

[0084] Under the condition of no water and no oxygen, 100 mL of methyl ethyl carbonate, 27.07 g (0.1 mol) of N-benzyl bisfluorosulfonimide, and 80 mL of ethanolic lithium solution (1 mol / L) were sequentially added into a 250 mL flask, and stirred at room temperature for 7 h, then the reaction was completed, and concentrated under reduced pressure at -0.097 MPa and 50°C until the liquid could not be distilled, then 100 mL of poor solvent toluene was added, and white solid was precipitated, the solid was collected by reduced pressure filtration at -0.097 MPa, and dried under reduced pressure at -0.099 MPa and 80°C, and 14.21 g of white crystal was obtained, with a yield of 94.99% (calculated based on ethanolic lithium), an acidity of 28 ppm, and a moisture content of 40 ppm. The reaction chemical formula is shown in formula 7.

[0085] Example 6

[0086] The embodiment provides a preparation method of lithium bisfluorosulfonimide, which sequentially comprises the following steps:

[0087] 1) Preparation of N-benzyl bisfluorosulfonimide

[0088] Under the condition of no water and no oxygen, 150 mL of dichloroethane was added into a 500 mL flask, and cooled to -5°C. Then 51.07 g (0.5 mol) of sulfonyl fluoride was slowly introduced into the flask, and 50.08 g (0.5 mol) of triethylamine was added under stirring. Then 26.79 g (0.25 mol) of benzylamine was slowly added dropwise into the flask, and the reaction temperature was maintained at -5-0°C. After the dropwise addition was completed, the temperature was maintained for 1 h under stirring. Then the reaction liquid was restored to room temperature, and was continuously stirred for 5 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40°C. Then 200 mL of dichloromethane was added into the flask residue, and was stirred to dissolve. Then the above dichloromethane solution was washed with 300 mL of deionized water for three times. The organic phase was collected, and the solvent was removed. Then the white solid was obtained by vacuum drying at -0.99 MPa and 50°C. The yield was 55.03 g, and the yield was 81.23%. The reaction formula is shown in formula 6.

[0089] 2) Preparation of lithium bisfluorosulfonimide

[0090] Under the condition of no water and no oxygen, 150 mL of dichloroethane was added into a 500 mL flask, and cooled to -5°C. Then 51.07 g (0.5 mol) of sulfonyl fluoride was slowly introduced into the flask, and 50.08 g (0.5 mol) of triethylamine was added under stirring. Then 26.79 g (0.25 mol) of benzylamine was slowly added dropwise into the flask, and the reaction temperature was maintained at -5-0°C. After the dropwise addition was completed, the temperature was maintained for 1 h under stirring. Then the reaction liquid was restored to room temperature, and was continuously stirred for 5 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40°C. Then 200 mL of dichloromethane was added into the flask residue, and was stirred to dissolve. Then the above dichloromethane solution was washed with 300 mL of deionized water for three times. The organic phase was collected, and the solvent was removed. Then the white solid was obtained by vacuum drying at -0.99 MPa and 50°C. The yield was 55.03 g, and the yield was 81.23%. The reaction formula is shown in formula 6.

[0091] Example 7

[0092] The embodiment provides a preparation method of lithium bisfluorosulfonimide, which sequentially comprises the following steps:

[0093] 1) Preparation of N-benzyl bisfluorosulfonimide

[0094] Under anhydrous and anaerobic conditions, 150 mL of acetonitrile was added into a 500 mL flask, which was cooled to -3 °C, and then 51.07 g (0.5 mol) of sulfuryl fluoride was slowly bubbled into the flask, while 50.08 g (0.5 mol) of triethylamine was added with stirring, and 26.79 g (0.25 mol) of benzylamine was slowly added dropwise into the flask, and the reaction temperature was maintained at -5-0 °C, and after the dropwise addition was completed, the temperature was maintained for 1 h with stirring, and then the reaction solution was allowed to return to room temperature, and stirring was continued for 5 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40 °C. Then, 200 mL of dichloromethane was added into the flask residue, which was stirred and dissolved, and then the dichloromethane solution was washed with 300 mL of deionized water in three portions, and the organic phase was collected, and the solvent of the organic phase was removed, and then vacuum drying was continued at -0.99 MPa and 50 °C, to obtain 56.65 g of white solid, with a yield of 83.62%. The reaction chemical formula is shown in Formula 6.

[0095] 2) Preparation of lithium bisfluorosulfonimide

[0096] Under anhydrous and anaerobic conditions, 150 mL of acetonitrile was added into a 500 mL flask, which was cooled to -3 °C, and then 51.07 g (0.5 mol) of sulfuryl fluoride was slowly bubbled into the flask, while 50.08 g (0.5 mol) of triethylamine was added with stirring, and 26.79 g (0.25 mol) of benzylamine was slowly added dropwise into the flask, and the reaction temperature was maintained at -5-0 °C, and after the dropwise addition was completed, the temperature was maintained for 1 h with stirring, and then the reaction solution was allowed to return to room temperature, and stirring was continued for 5 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40 °C. Then, 200 mL of dichloromethane was added into the flask residue, which was stirred and dissolved, and then the dichloromethane solution was washed with 300 mL of deionized water in three portions, and the organic phase was collected, and the solvent of the organic phase was removed, and then vacuum drying was continued at -0.99 MPa and 50 °C, to obtain 56.65 g of white solid, with a yield of 83.62%. The reaction chemical formula is shown in Formula 6.

[0097] Example 8

[0098] The present embodiment provides a method for preparing lithium bisfluorosulfonimide, which comprises the following steps in sequence:

[0099] 1) Preparation of N-benzyl bisfluorosulfonimide

[0100] Under the condition of no water and no oxygen, 150 mL of acetonitrile was added into a 500 mL flask, and the flask was cooled to -6°C. Then 51.07 g (0.5 mol) of sulfuryl fluoride was slowly introduced into the flask, and 50.08 g (0.5 mol) of triethylamine was added into the flask under stirring. Then 26.79 g (0.25 mol) of benzylamine was slowly added into the flask dropwise, and the reaction temperature was maintained at -5-0°C. After the dropwise addition was completed, the temperature was maintained for 0.8 h under stirring. Then the reaction liquid was restored to room temperature, and the stirring was continued for 4 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.10 MPa and 35°C. Then 200 mL of dichloromethane was added into the flask residue, and the dichloromethane solution was washed with 300 mL of deionized water for three times. The organic phase was collected, and the solvent was removed. Then the white solid was obtained by vacuum drying at -0.99 MPa and 50°C. The yield was 53.38 g, and the yield was 78.79%. The reaction formula is shown in Formula 6.

[0101] 2) Preparation of lithium bisfluorosulfonimide

[0102] Under the condition of no water and no oxygen, 100 mL of dimethyl carbonate, 27.07 g (0.1 mol) of N-benzyl bisfluorosulfonimide, and 80 mL of an ethanolic solution of lithium ethoxide (1 mol / L) were sequentially added into a 250 mL flask. The reaction was stirred at room temperature for 5 h. After the reaction was completed, the liquid was concentrated by distillation under reduced pressure at -0.10 MPa and 45°C until the liquid could not be distilled. Then 100 mL of a poor solvent, toluene, was added, and a white solid was precipitated. The solid was collected by filtration under reduced pressure at -0.10 MPa. Then the white solid was dried under reduced pressure at -0.099 MPa and 80°C. The yield was 13.57 g, and the yield was 90.71% (calculated based on lithium ethoxide). The acidity was 30 ppm, and the moisture was 41 ppm. The reaction formula is shown in Formula 7.

[0103] Example 9

[0104] The example provides a method for preparing lithium bisfluorosulfonimide. The method sequentially comprises the following steps:

[0105] 1) Preparation of N-ethyl bisfluorosulfonimide

[0106] Under anhydrous and anaerobic conditions, 150 mL of acetonitrile was added into a 500 mL flask, cooled to -5°C, 51.00 g (0.5 mol) of sulfuryl fluoride was slowly introduced into the flask, 50.05 g (0.5 mol) of triethylamine was added under stirring, and then 50 mL of acetonitrile solution containing 11.25 g (0.25 mol) of ethylamine was slowly added dropwise into the flask, the reaction temperature was maintained at -5-0°C, after the dropwise addition was completed, the temperature was maintained for 1.2 h under stirring, and then the reaction liquid was returned to room temperature and stirred for 6 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.10 MPa and 45°C, and then the temperature was increased to 120°C, and the solvent was removed by distillation under reduced pressure at -0.10 MPa and 45°C, 43.61 g of colorless liquid was collected, and the yield was 83.46%. The reaction chemical formula is shown in Formula 1.

[0107] 2) Preparation of lithium bisfluorosulfonimide

[0108] Under anhydrous and anaerobic conditions, 100 mL of dimethyl carbonate, 20.89 g (0.1 mol) of N-ethyl bisfluorosulfonimide, and 100 mL of ethanolic solution of lithium ethoxide (1 mol / L) were sequentially added into a 250 mL flask, and the reaction was stirred at room temperature for 9 h, after the reaction was completed, the solvent was removed by distillation under reduced pressure, the liquid was difficult to distill at -0.097 MPa and 45°C, then 100 mL of poor solvent toluene was added, and white solid was precipitated, the solid was collected by filtration under reduced pressure at -0.095 MPa, and then dried at 80°C under the condition of -0.095 MPa for 6 h, 14.75 g of white crystal was obtained, the yield was 78.88% (calculated based on lithium ethoxide), the acidity was 36 ppm, and the moisture was 48 ppm. The reaction chemical formula is shown in Formula 2.

[0109] Example 10

[0110] 1) Preparation of N-ethyl bisfluorosulfonimide

[0111] Under anhydrous and anaerobic conditions, 150 mL of acetonitrile was added into a 500 mL flask, cooled to -5°C, 51.00 g (0.5 mol) of sulfuryl fluoride was slowly introduced into the flask, 50.05 g (0.5 mol) of triethylamine was added under stirring, and then 50 mL of acetonitrile solution containing 11.25 g (0.25 mol) of ethylamine was slowly added dropwise into the flask, the reaction temperature was maintained at -5-0°C, after the dropwise addition was completed, the temperature was maintained for 1.2 h under stirring, and then the reaction liquid was returned to room temperature and stirred for 6 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.10 MPa and 45°C, and then the temperature was increased to 120°C, and the solvent was removed by distillation under reduced pressure at -0.10 MPa and 45°C, 43.61 g of colorless liquid was collected, and the yield was 83.46%. The reaction chemical formula is shown in Formula 1.

[0112] 2) Preparation of lithium bisfluorosulfonimide

[0113] Under anhydrous and anaerobic conditions, 100 mL of dimethyl carbonate, 20.89 g (0.1 mol) of N-ethyl bisfluorosulfonimide, and 80 mL of an ethanolic solution of lithium ethoxide (1 mol / L) were sequentially added to a 250 mL flask. The reaction was stirred at room temperature for 5 h. After the reaction was completed, the liquid was concentrated by distillation under reduced pressure at -0.097 MPa and 45 °C until it became difficult to distill. Then, 100 mL was added, and the solid was collected by filtration under reduced pressure at -0.097 MPa. The solid was then dried under reduced pressure at 80 °C and -0.099 MPa for 4 h to obtain 13.16 g of white crystals with a yield of 87.97% (calculated based on lithium ethoxide), an acidity of 43 ppm, and a moisture content of 38 ppm. The reaction chemical formula is shown in Formula 4.

[0114] Comparative Example 1

[0115] 1) Preparation of N-phenylfluorosulfonimide

[0116] Under anhydrous and anaerobic conditions, 150 mL of acetonitrile was added to a 500 mL flask, which was cooled to -5 °C. Then, 51.13 g (0.5 mol) of sulfuryl fluoride was slowly introduced into the flask while stirring. Subsequently, 50.11 g (0.5 mol) of triethylamine was added, and 23.31 g (0.25 mol) of aniline was slowly added dropwise to the flask. The reaction temperature was maintained at -5 to 0 °C. After the addition was completed, the temperature was maintained for 0.8 to 1.2 h, and then the reaction liquid was allowed to return to room temperature. The stirring was continued for 4 to 6 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure at -0.097 MPa and 40 °C. The triethylamine was still detected in the solvent. Then, 200 mL of dichloromethane was added to the residue in the flask, and the mixture was stirred and dissolved. The dichloromethane solution was washed with 300 mL of deionized water in three portions. The organic phase was collected, and the solvent was removed. The residue was dried under vacuum at -0.99 MPa and 50 °C to obtain 37.49 g of white solid, which was far less than the theoretical amount. The product structure was N-phenylfluorosulfonimide, and the yield was 85.7% as determined by liquid chromatography-mass spectrometry. The reaction chemical formula is shown in Formula 8. 1 The H NMR spectrum is shown in Figure 8 . The reaction chemical formula is shown in Formula 8.

[0117]

[0118] Comparative Example 2

[0119] The preparation method of lithium bisfluorosulfonimide provided in this comparative example is different from that of Example 1 in that an equal amount of pyridine was used instead of triethylamine as the acid-binding agent in the preparation of N-ethyl bisfluorosulfonimide. The other substances and parameters were completely consistent with those provided in Example 1. The yield of N-ethyl bisfluorosulfonimide obtained was 52.25%.

[0120] As can be seen from Examples 1 to 10, the technical scheme provided in the present application generates intermediate N-alkyl bisfluorosulfone imide. After the reaction is completed, only simple vacuum distillation is required to remove the solvent, and then the organic phase solvent is removed by washing and vacuum drying to obtain N-alkyl bisfluorosulfone imide. The yield of the generated N-alkyl bisfluorosulfone imide is relatively high, greater than 71.89%.

[0121] As can be seen from Examples 1 to 10, the technical scheme provided in the present application generates the final product lithium bisfluorosulfone imide. The yield of the final product is greater than 76.52%, the acidity is less than 40 ppm, the water content is less than 50 ppm, and the purity is more than 99.5%, which can reach the standard of battery grade.

[0122] As can be seen from Examples 5 to 8, the technical scheme provided in the present application uses acetonitrile, dichloromethane, and dichloroethane as the organic solvent B, and the cooling temperature is -3 to -6℃. The reaction temperature is maintained at -5 to 0℃. After the dropwise addition is completed, the temperature is continuously maintained and stirred for 0.8 to 1.2h, and then the reaction liquid is restored to room temperature and continuously stirred for 4 to 6h. In this case, the yield of N-benzyl bisfluorosulfone imide is more than 78%. The reaction time has a certain influence on the yield. Under the same conditions, if the temperature is continuously maintained and stirred for 0.8h after the dropwise addition is completed, and then the reaction liquid is restored to room temperature and continuously stirred for 4h, the yield is 78.79%. If the temperature is continuously maintained and stirred for 1.2h after the dropwise addition is completed, and then the reaction liquid is restored to room temperature and continuously stirred for 6h, the yield is 83.62%. It can be seen that as the reaction time is prolonged, the yield also increases. However, compared with 5h and 6h, the yield increases from 86.56% to 83.62%, and the increase rate is not high. Considering the energy consumption, it is preferred to restore the reaction liquid to room temperature and continuously stir for 5h.

[0123] As can be seen from Examples 5 to 8, the technical scheme provided in the present application uses dimethyl carbonate, methyl ethyl carbonate, and ethylene glycol dimethyl ether as the organic solvent A to dissolve N-ethyl bisfluorosulfone imide, and the yield of the reaction with lithium ethoxide is relatively high. The reaction time is 5 to 9h, and the yield will increase. However, the yield growth rate is small when the reaction time is prolonged to 9h. Considering the energy consumption, it is preferred to use a reaction time of 7h.

[0124] As can be seen from Examples 1 and 9, and Examples 2 and 10, the prolongation of the reaction time can slightly increase the yield of the intermediate product and the final product.

[0125] As can be seen from Examples 1 to 10 and Comparative Example 1, when aniline is used to prepare the intermediate product, the final product is N-phenyl fluorosulfone imide, which contains only one fluorosulfone group. Therefore, the expected intermediate product bisfluorosulfone imide cannot be obtained, and thus the final product cannot be obtained.

[0126] As can be seen from Examples 1 to 10 and Comparative Example 2, when pyridine is used as the acid-binding agent, the yield of N-ethyl bisfluorosulfonylimide is significantly lower than when triethylamine is used as the acid-binding agent. It is believed that the lone pair of electrons on the N atom of triethylamine easily binds to the proton, neutralizing the acid generated in the reaction, and thus the yield is higher.

Claims

1. A method for producing lithium bisfluorosulfonimide, characterized by, The N-alkyl bisfluorosulfonimide is prepared by the following method: The basic lithium salt is at least one of lithium alcoholate, lithium amide and lithium hydroxide; The N-alkyl bisfluorosulfonimide is prepared by the following method: Under the condition of no water and no oxygen, the organic solvent B is added into the reaction container and cooled to-3~-6℃, the sulfuryl compound is slowly introduced into the container, the acid binding agent is continuously added under stirring, and then the solution of the amine compound is slowly added into the flask, and the reaction temperature is kept between-5~0℃; After the dropping is completed, the temperature is continuously maintained and stirred for 0.8~1.2h, and then the reaction liquid is returned to room temperature and continuously stirred for 4~6h. After the reaction is completed, the solvent is removed by vacuum distillation under the second vacuum distillation condition, and the N-alkyl bisfluorosulfonimide is obtained by post-treatment.

2. The method for producing lithium bisfluorosulfonimide according to claim 1, characterized by, The method comprises the following steps in sequence: under the condition of no water and no oxygen, the organic solvent A, the N-alkyl bisfluorosulfonimide and the basic lithium salt solution are sequentially added into the reaction device, the reaction is stirred at room temperature for 5~9h, after the reaction is completed, the concentrated solution is concentrated by vacuum distillation under the first vacuum distillation condition until no liquid is distilled out, then the poor solvent is added, white solid is precipitated, and the lithium bisfluorosulfonimide is obtained by filtration and drying.

3. The method for producing lithium bisfluorosulfimide according to claim 1 or 2, characterized by, The solvent of the basic lithium salt solution is at least one of methanol or ethanol; and the organic solvent A is at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, butyl acetate and dimethoxyethane.

4. The method for producing lithium bisfluorosulfonimide according to claim 2, characterized by, The first vacuum distillation condition is-0.095~-0.100MPa and 45~50℃; the filtration is performed under the condition of-0.095~-0.100MPa; and the drying is performed under the condition of 80~85℃ and-0.095~-0.100MPa for 5~6h.

5. The method for producing lithium bisfluorosulfonimide according to claim 2, characterized by, The poor solvent is an aromatic hydrocarbon solvent.

6. The method for preparing lithium bisfluorosulfonimide according to claim 1, characterized by, The amine compound has the following general structure: ; R1 is independently selected from one of phenyl, C1-C10 saturated hydrocarbon group, C2-C10 olefin group, C2-C10 alkyne group, C1-C10 halogenated saturated hydrocarbon group, C2-C10 halogenated olefin group and C2-C10 halogenated alkyne group.

7. The method of preparing lithium bisfluorosulfimide according to claim 1, characterized in that, The molar ratio of the sulfuryl compound, the amine compound and the acid binding agent is 1:1:

2.

8. The method of claim 1, wherein the lithium bisfluorosulfimide is prepared by the process comprising: reacting lithium fluoride with sulfur dioxide in the presence of a solvent to form lithium bisfluorosulfimide; and removing the solvent from the lithium bisfluorosulfimide. The acid binding agent is an organic amine.

9. The method of claim 1, wherein the lithium bisfluorosulfimide is prepared by the process comprising: reacting lithium fluoride with sulfur dioxide in the presence of a solvent to form lithium bisfluorosulfimide; and removing the solvent from the lithium bisfluorosulfimide. The sulfuryl compound is sulfuryl fluoride or sulfuryl fluoride chloride.

10. The method of preparing lithium bisfluorosulfonimide according to claim 1, wherein The second vacuum distillation condition is-0.095~-0.100MPa and 35~45℃.

11. The method of preparing lithium bisfluorosulfonimide according to claim 1, characterized in that, When the amine compound is benzylamine, the post-treatment of step 3) is that dichloromethane is added into the reaction residue, the dichloromethane solution is removed by washing with deionized water, the obtained organic phase is removed, and the white crystal is obtained by continuously vacuum drying.

12. The method of preparing lithium bisfluorosulfonimide according to claim 1, wherein When the amine compound is triethylamine, the post-treatment of step 3) is that the product after the removal of the organic solvent B is continuously heated to 110℃ and vacuum distilled, and the colorless liquid is collected.

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