Method for jointly preparing bis (fluorosulfonyl) imide and monofluorophosphate

Abstract

The invention belongs to the technical field of lithium ion battery electrolyte, and particularly relates to a method for jointly preparing bis (fluorosulfonyl) imide and monofluorophosphate. The preparation method comprises the following steps: reacting urea, chlorosulfonic acid and phosphorus pentafluoride serving as raw materials to generate a mixture of bis (fluorosulfonyl) imide acid and monofluorophosphoric acid, distilling to remove HCl and PF5 impurities in the mixture, and reacting the mixture with alkali metal salt under the poor solvent condition of monofluorophosphate to obtain a solid-liquid mixture; and carrying out solid-liquid separation on the solid-liquid mixture, and drying the obtained solid to obtain monofluorophosphate, and concentrating the obtained filtrate, adding a poor solvent for recrystallization, filtering and drying to obtain the bis (fluorosulfonyl) imide salt. According to the method, two acids can be synthesized through one-step reaction, the synthesis process flow is simple, the reaction time is short, the production efficiency can be remarkably improved, and the production cost is saved. And the prepared monofluorophosphate and bis (fluorosulfonyl) imide salt are high in quality and can be widely applied to lithium ion battery electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrolyte technology, specifically relating to a method for the combined preparation of bis(fluorosulfonyl)imide salt and monofluorophosphate. Background Technology

[0002] In recent years, with the rapid development of the new energy industry, lithium-ion batteries have been widely used in electronic products, electric vehicles, and grid energy storage as important energy storage products. The performance of lithium-ion batteries mainly depends on their electrolyte materials. Lithium hexafluorophosphate, as a common electrolyte material, has excellent electrochemical performance, but its thermal stability is poor, and it readily generates corrosive gases such as HF upon contact with water. Lithium bisfluorosulfonyl imide (LiFSI), due to its excellent thermal stability, good conductivity, and low toxicity, is considered a new electrolyte material to replace lithium hexafluorosulfonate. Lithium monofluorophosphate, as an electrolyte additive, can significantly improve the low-temperature cycle performance of lithium-ion batteries.

[0003] Currently, LiFSI is typically prepared by fluorination of dichlorosulfonylimide acid with a fluorinating agent, followed by reaction with an alkali metal salt. Patent document CN119503743A discloses a method for producing difluorosulfonylimide and lithium difluorosulfonylimide. This method uses aminosulfonic acid, chlorosulfonic acid, and thionyl chloride as raw materials, which undergo chlorination to obtain dichlorosulfonylimide. Then, using dichlorosulfonylimide and hydrofluoric acid or dichlorosulfonylimide and hydrogen fluoride gas as raw materials, a fluorination reaction is performed to obtain crude difluorosulfonylimide. A metal salt is then added to the crude difluorosulfonylimide, followed by melt crystallization and / or distillation. Finally, it reacts with the metal salt to generate lithium difluorosulfonylimide. This process is complex and costly.

[0004] Monofluorophosphates are typically prepared using hexafluorophosphate as a raw material. Patent document CN119430125A discloses a method for preparing lithium monofluorophosphate, which involves adding phosphorus pentoxide and sodium oxide to a reactor and mixing them thoroughly; mixing sodium hexafluorophosphate with a polar solvent to obtain a mixed solution; adding the mixed solution dropwise to the reactor; heating after the addition is complete to obtain a crude product; and purifying the crude product to obtain sodium monofluorophosphate. However, this process is difficult to control and has a low yield.

[0005] Therefore, developing a rapid and efficient method for preparing bis(fluorosulfonyl)imide salts and monofluorophosphates, and overcoming the technical shortcomings of existing processes that are complex and time-consuming, is an urgent problem to be solved. Summary of the Invention

[0006] Based on this, the purpose of this invention is to provide a method for the combined preparation of difluorosulfonyl imide salt and monofluorophosphate, which can obtain the synthesis of the two acids in one step; the overall process is simplified and the reaction time can be significantly shortened.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for the combined preparation of difluorosulfonyl imide salt and monofluorophosphate, comprising the following steps: S1, using urea, chlorosulfonic acid and phosphorus pentafluoride as raw materials, reacts to produce difluorosulfonylimide acid and monofluorophosphoric acid, obtaining a mixture A of difluorosulfonylimide acid and monofluorophosphoric acid, and removing impurities from the mixture A by distillation to obtain mixture B; S2, react the mixture B described in S1 with an alkali metal salt under unfavorable solvent conditions of monofluorophosphate to obtain a solid-liquid mixture; S3, the solid-liquid mixture described in S2 is separated into a solid and a filtrate. The solid is dried to obtain monofluorophosphate. The filtrate is concentrated and recrystallized to obtain difluorosulfonamide salt.

[0008] Furthermore, the molar ratio of urea, chlorosulfonic acid, and phosphorus pentafluoride in S1 is 1:4:1~4.5; the reaction is terminated when the residual chloride ion content in the reaction solution is <30ppm.

[0009] Further, in S1, the urea and chlorosulfonic acid are first added to the reaction vessel, mixed, and heated to 100~130°C to form a reaction solution. Then, the phosphorus pentafluoride is introduced into the reaction solution in two batches, with the flow rate ratio of the first batch to the second batch being 1:1.8~2.2.

[0010] Further, in step S1, the mixture A is first cooled to 55-65°C, and then impurities are removed by atmospheric distillation to obtain mixture B. The impurities include HCl generated in the reaction and excess raw material PF5.

[0011] The reaction equation in S1 is: CH4N2O+4ClSO2OH+PF5→2HN(SO2F)2+H2PO3F+CO2+4HCl Further, the total amount of the alkali metal salt added in S2 is the sum of the first part and the second part. The first part reacts with monofluorophosphoric acid in mixture B to obtain monofluorophosphate, and the molar ratio of the first part to monofluorophosphoric acid in mixture B is 1-1.05:1. The second part reacts with difluorosulfonylimide acid in mixture B to obtain difluorosulfonylimide salt, and the molar ratio of the second part to difluorosulfonylimide acid in mixture B is 1-1.05:2. The weight ratio of the unsuitable solvent of the monofluorophosphate to mixture B is 2-2.5:1.

[0012] Further, in S2, the undesirable solvents of the alkali metal salt and monofluorophosphate are first added to the reaction vessel, mixed, and cooled to 8-12°C to form a mixture. Then, the mixture B is added dropwise to the mixture. After the addition is completed, the reaction ends when the acidity of the supernatant is <100ppm.

[0013] Furthermore, the unsuitable solvents for the monofluorophosphate in S2 include dimethyl carbonate, acetonitrile, diethyl carbonate, ethylene carbonate, or propylene carbonate; the chemical formula of the alkali metal salt is M. + n X n- Where M is Li, Na or K, X is F, Cl, CO3, OH or SO4, and n is 1 or 2.

[0014] The reaction equation in S2 is: nHN(SO2F)2+M n X→nM[N(SO2F)2]+H n X; nH2PO3F+2M n X→nM2(PO3F)+2H n X, (when X is CO3, H) n X is CO2 + H2O.

[0015] Furthermore, the drying temperature described in S3 is 75~85℃, and the drying time is 10~15h.

[0016] Further, the recrystallization process in S3 is as follows: a poor solvent for difluorosulfonylimide salt is added to the concentrate of the filtrate to precipitate the difluorosulfonylimide salt solid, followed by solid-liquid separation to obtain the difluorosulfonylimide salt solid; the amount of poor solvent added is 5 to 7 times the mass of the concentrate. The filtrate is then concentrated to a mass ratio of 1:0.6 to 1 by rotary evaporation at 80±2℃ to obtain the concentrate.

[0017] Furthermore, the unsuitable solvents for the difluorosulfonyl imide salt in S3 include dichloromethane, dichloroethane, carbon tetrachloride, or n-hexane; the difluorosulfonyl imide salt solid is dried at 95~105℃ for 10~15h to obtain the difluorosulfonyl imide salt.

[0018] The beneficial effects of this invention are: 1. The combined preparation method provided by this invention can synthesize two acids in one step, which simplifies the synthesis process, shortens the reaction time, significantly improves production efficiency, and saves production costs.

[0019] 2. The combined preparation method provided by this invention uses simple and readily available raw materials and environmentally friendly, pollution-free solvents. The prepared monofluorophosphate and difluorosulfonyl imide salts are of high quality and can be widely used in lithium-ion battery electrolytes. The yield of monofluorophosphate is >92%, and can reach more than 97%, with a purity >99.5%; the yield of difluorosulfonyl imide salt is >98%, with a purity >99.9%. Attached Figure Description

[0020] To more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Appendix Figure 1 The monofluorophosphoric acid prepared in Example 1 of this invention 19 F-NMR spectrum; Appendix Figure 2 The difluorosulfonyl imide acid prepared in Example 1 of this invention 19 F-NMR spectrum; Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. All mentioned embodiments are implemented based on the technical solutions of the present invention, and detailed implementation processes are given. However, it should be stated that the scope of protection of the present invention is not limited to the following embodiments.

[0023] The following embodiments provide detailed implementation procedures for the technical solutions of the present invention. Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0024] Example 1 (1) Weigh 45g of urea and 351g of chlorosulfonic acid (purity > 98%) into a 1L PFA three-necked flask, stir and heat to 110℃, and then pass phosphorus pentafluoride gas at a flow rate of 1L / min for 30min. After that, adjust the flow rate to 2L / min and continue to pass phosphorus pentafluoride gas for 20min. The chloride ion content in the reaction solution was detected to be 8ppm, indicating that the reaction was complete. The solution temperature was then lowered to 60℃, and atmospheric distillation was used to remove HCl impurities and excess PF5. A mixed solution of difluorosulfonylimide acid and monofluorophosphoric acid was obtained, weighing 462g. The content of difluorosulfonylimide acid was 78.3% and the content of monofluorophosphoric acid was 21.7% by nuclear magnetic resonance fluorine spectroscopy. Figure 1 and Figure 2The NMR fluorine spectra of monofluorophosphate and difluorosulfonylimide acid are presented separately. From... Figure 1 As can be seen, the characteristic peak corresponding to the fluorine atom in monofluorophosphoric acid has a chemical shift of approximately -70 to -80 ppm, exhibiting a doublet due to coupling with ³¹P. From Figure 2 As can be seen, the characteristic peak chemical shift corresponding to the fluorine atom in difluorosulfonylimide acid is in the range of approximately 58-59 ppm. Since the two fluorine atoms are directly bonded to the sulfur atom, there is no direct spin coupling between them, so it appears as a single peak.

[0025] (2) Weigh 135g of lithium carbonate and 1000g of dimethyl carbonate into a 2L three-necked reaction flask, and control the temperature at about 10℃. Take 420g of the mixed solution of difluorosulfonyl imide and monofluorophosphoric acid from step (1) above, and slowly add it dropwise into the reaction flask using a constant pressure dropping funnel. After the addition is completed, take the supernatant and measure the acidity. If it is <100ppm, it is the endpoint of the reaction. After filtration, a solid insoluble ointment is obtained. Heat the ointment to 80℃ and dry it for 12h to obtain solid lithium monofluorophosphate with a mass of 95.47g, a yield of 93.6%, and a purity of 99.91%. The filtrate was a salt solution of lithium difluorosulfonylimide. The solution was heated to 80°C by rotary evaporation to concentrate the mass ratio of lithium difluorosulfonylimide to dimethyl carbonate to 1:0.8. Five times the volume of dichloromethane solution was slowly added dropwise to the solution, and a solid precipitated out. The solid was filtered to obtain the solid, and the obtained solid was dried at 100°C for 12 hours to obtain 333.53 g of lithium difluorosulfonylimide, with a yield of 98% and a purity of 99.95%.

[0026] Example 2 The preparation of the mixed solution of difluorosulfonylimide acid and monofluorophosphoric acid in this embodiment is the same as in Example 1, except that: Weigh 135g of lithium carbonate and 1000g of diethyl carbonate into a 2L three-necked reaction flask, maintaining the temperature at approximately 10℃. Take 420g of the product and slowly add it dropwise into the reaction flask using a constant-pressure dropping funnel. After the addition is complete, measure the acidity of the supernatant; a value <100ppm indicates the endpoint of the reaction. Filter to obtain a solid insoluble ointment. Heat the ointment to 80℃ and dry for 12 hours to obtain solid lithium monofluorophosphate with a mass of 94.15g, a yield of 92.3%, and a purity of 99.95%. The filtrate was a salt solution of lithium difluorosulfonylimide. The solution was heated to 80°C by rotary evaporation to concentrate the mass ratio of lithium difluorosulfonylimide to diethyl carbonate to 1:0.8. Six times the volume of dichloromethane solution was slowly added dropwise to the solution, and a solid precipitated out. The solid was filtered to obtain the solid, and the obtained solid was dried at 100°C for 12 hours to obtain 337.28 g of lithium difluorosulfonylimide, with a yield of 99.1% and a purity of 99.96%.

[0027] Example 3 (1) Weigh 45g of urea and 351g of chlorosulfonic acid (purity > 98%) into a 1L PFA three-necked flask, stir and heat to 120℃, and then pass phosphorus pentafluoride gas at a flow rate of 0.5L / min for 30min. Adjust the flow rate to 1L / min and continue passing phosphorus pentafluoride gas for 55min. The reaction was considered complete when the chloride ion content in the reaction solution was 5ppm. The solution temperature was then lowered to 60℃, and HCl and PF5 impurities were removed by atmospheric distillation. A mixed solution of difluorosulfonyl imide and monofluorophosphoric acid was obtained (460.1g). Nuclear magnetic resonance fluorine spectroscopy showed that the content of difluorosulfonyl imide was 78.3% and the content of monofluorophosphoric acid was 21.7%.

[0028] (2) Weigh 140g of lithium carbonate and 1000g of acetonitrile into a 2L three-necked reaction flask, and control the temperature at about 10℃. Take 420g of the above product and slowly add it dropwise into the reaction flask using a constant pressure dropping funnel. After the addition is completed, take the supernatant and measure the acidity. If it is <100ppm, it is the endpoint of the reaction. After filtration, a solid insoluble ointment is obtained. The ointment is heated to 80℃ and dried for 12h to obtain solid lithium monofluorophosphate with a mass of 98.94g, a yield of 97%, and a purity of 99.89%. The filtrate was a salt solution of lithium difluorosulfonylimide. The solution was heated to 80°C by rotary evaporation to concentrate the mass ratio of lithium difluorosulfonylimide to dimethyl carbonate to 1:0.8. Six times the volume of dichloromethane solution was slowly added dropwise to the solution, and a solid precipitated out. The solid was filtered to obtain the solid, and the obtained solid was dried at 100°C for 12 hours to obtain 338.29 g of lithium difluorosulfonylimide, with a yield of 99.4% and a purity of 99.97%.

[0029] Example 4 The preparation of the mixed solution of difluorosulfonylimide acid and monofluorophosphoric acid in this embodiment is the same as in Example 1, except that: Weigh 200g of sodium carbonate and 1000g of diethyl carbonate into a 2L three-necked reaction flask, maintaining the temperature at approximately 30℃. Take 420g of the product and slowly add it dropwise into the reaction flask using a constant-pressure dropping funnel. After the addition is complete, measure the acidity of the supernatant; a value <100ppm indicates the endpoint of the reaction. Filter to obtain a solid insoluble ointment. Heat the ointment to 80℃ and dry for 12 hours to obtain solid sodium monofluorophosphate, with a mass of 129.73g, a yield of 99.0%, and a purity of 99.5%. The filtrate was a salt solution of sodium difluorosulfonylimide. The solution was heated to 80°C by rotary evaporation to concentrate the mass ratio of lithium difluorosulfonylimide to dimethyl carbonate to 1:0.8. Six times the volume of dichloromethane solution was slowly added dropwise to the solution, and a solid precipitated out. The solid was filtered to obtain the solid, and the obtained solid was dried at 100°C for 12 hours to obtain 367.9 g of sodium difluorosulfonylimide, with a yield of 99.6% and a purity of 99.99%.

[0030] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for the combined preparation of difluorosulfonyl imide salt and monofluorophosphate, characterized in that, Includes the following steps: S1, using urea, chlorosulfonic acid and phosphorus pentafluoride as raw materials, reacts to produce difluorosulfonylimide acid and monofluorophosphoric acid, yielding a mixture A of difluorosulfonylimide acid and monofluorophosphoric acid; the mixture A is then distilled to remove impurities, yielding a mixture B; S2, react the mixture B described in S1 with an alkali metal salt under unfavorable solvent conditions of monofluorophosphate to obtain a solid-liquid mixture; S3, the solid-liquid mixture described in S2 is separated into a solid and a filtrate. The solid is dried to obtain monofluorophosphate. The filtrate is concentrated and recrystallized to obtain difluorosulfonamide salt.

2. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, The molar ratio of urea, chlorosulfonic acid and phosphorus pentafluoride in S1 is 1:4:1~4.5; the reaction is terminated when the residual chloride ion content in the reaction solution is <30ppm.

3. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, In step S1, urea and chlorosulfonic acid are first added to a reaction vessel, mixed, and heated to 100-130°C to form a reaction solution. Then, phosphorus pentafluoride is introduced into the reaction solution in two batches, with the flow rate ratio of the first batch to the second batch being 1:1.8-2.

2.

4. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, In step S1, mixture A is first cooled to 55-65°C, and then impurities are removed by atmospheric distillation to obtain mixture B.

5. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, The total amount of the alkali metal salt added in S2 is the sum of the first part and the second part. The first part reacts with monofluorophosphoric acid in mixture B to obtain monofluorophosphate, and the molar ratio of the first part to monofluorophosphoric acid in mixture B is 1-1.05:

1. The second part reacts with difluorosulfonylimide acid in mixture B to obtain difluorosulfonylimide salt, and the molar ratio of the second part to difluorosulfonylimide acid in mixture B is 1-1.05:

2. The weight ratio of the unsuitable solvent of the monofluorophosphate to mixture B is 2-2.5:

1.

6. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, In step S2, the undesirable solvents of the alkali metal salt and monofluorophosphate are first added to the reaction vessel, mixed, and cooled to 8-12°C to form a mixture. Then, mixture B is added dropwise to the mixture. After the addition is complete, the reaction ends when the acidity of the supernatant is <100ppm.

7. The method for jointly preparing bis(fluorosulfonyl)imide salt and monofluorophosphate as described in claim 1, characterized in that, Poor solvents for the monofluorophosphates described in S2 include dimethyl carbonate, acetonitrile, diethyl carbonate, ethylene carbonate, or propylene carbonate; the chemical formula of the alkali metal salt is M. + n X n- Where M is Li or Na, X is F, Cl, CO3, OH or SO4, and n is 1 or 2.

8. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, The drying temperature described in S3 is 75~85℃, and the drying time is 10~15h.

9. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 1, characterized in that, The recrystallization process in S3 is as follows: a poor solvent for difluorosulfonyl imide salt is added to the concentrate of the filtrate to precipitate the solid difluorosulfonyl imide salt, and then solid-liquid separation is performed to obtain the solid difluorosulfonyl imide salt; the amount of poor solvent added to the difluorosulfonyl imide salt is 5 to 7 times the mass of the concentrate.

10. The method for jointly preparing difluorosulfonyl imide salt and monofluorophosphate as described in claim 9, characterized in that, The unsuitable solvents for the difluorosulfonyl imide salt in S3 include dichloromethane, dichloroethane, carbon tetrachloride, or n-hexane; the difluorosulfonyl imide salt solid is dried at 95~105℃ for 10~15h to obtain the difluorosulfonyl imide salt.

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