A preparation method of lithium bis(fluorosulfonyl)imide
By introducing sulfuryl fluoride into the aqueous hydrofluoric acid solution of urea and reacting with lithium carbonate, the preparation process of lithium difluorosulfonimide is simplified, and the problems of complex process and low gas reaction efficiency in the prior art are solved, so as to achieve High-efficiency and low-cost preparation of lithium difluorosulfonimide.
Patent Information
- Application Number
- CN202310718202.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-16
- Publication Date
- 2024-12-06
- Estimated Expiration
- 2043-06-16
AI Technical Summary
The existing preparation method for lithium bisfluorosulfonimide is complex in technology, complicated in steps, and low in reaction efficiency between gas and gas, resulting in high production efficiency and cost.
Sulfyl fluoride is introduced into the aqueous hydrofluoric acid solution of urea, and the reaction is carried out under the action of the catalyst bismuth trifluoride to form a aqueous solution of difluorosulfonimide, and then react with lithium carbonate to prepare lithium difluorosulfonimide, which is filtered and Drying results in high-purity products, simplifying the process flow and improving the reaction efficiency.
It realizes contact reaction between gas and liquid, has high production efficiency, simple steps, easy control, reduces impurity content and production costs, and improves product purity and yield.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of ion battery materials, and in particular to a method for preparing lithium bis(fluorosulfonyl)imide. Background Art
[0002] The most widely used electrolyte lithium salt in lithium-ion batteries is lithium hexafluorophosphate, which has good ionic conductivity and electrochemical stability, but its disadvantages are poor heat resistance and water sensitivity. In comparison, lithium bis(fluorosulfonyl)imide has good thermal stability and hydrolysis stability and has been used as an additive in lithium battery electrolytes. With the advancement of lithium bis(fluorosulfonyl)imide preparation technology and the decline in prices, it is very likely to replace lithium hexafluorophosphate as the main salt in the future, and market demand will further explode.
[0003] At present, the method for producing lithium bis(fluorosulfonyl)imide in the industry is mainly divided into two steps, first preparing bis(fluorosulfonyl)imide, and then reacting it with lithium salt to obtain lithium bis(fluorosulfonyl)imide. There are many production processes for bis(fluorosulfonyl)imide, for example, PCT application WO2009123328A1 reports that chlorosulfonic acid isocyanate is first prepared by reacting cyanogen chloride with sulfur trioxide, then reacting with chlorosulfonic acid to obtain bis(chlorosulfonyl)imide, and then reacting with fluoride to obtain bis(fluorosulfonyl)imide. The Chinese patent "Preparation method of bis(fluorosulfonyl)imide and (perfluoroalkylsulfonylfluorosulfonyl)imide alkali metal salt" with publication number CN101747242A reports that sulfonamide is reacted with dichlorothionyl and chlorosulfonic acid to obtain bischlorosulfonyl imide, which is then reacted with antimony trifluoride to obtain bisfluorosulfonyl imide; the Chinese patent "A lithium bisfluorosulfonyl imide and its preparation method and application" with publication number CN113511639B reports that ammonia and sulfur trioxide are used to prepare iminodisulfonic acid, which is then chlorinated with thionyl chloride to obtain bischlorosulfonyl imide, which is then reacted with hydrogen fluoride to obtain bisfluorosulfonyl imide. These processes are long and complicated. There are other processes with simple processes suitable for industrialization. For example, the one-step method disclosed in the Chinese patent "A method for preparing bisfluorosulfonyl imide" with publication number CN115893338A directly generates hydrogen fluoride and bisfluorosulfonyl imide by reacting sulfuryl fluoride and ammonia. It requires less raw materials, less by-products, and fewer reaction steps, thus reducing production costs. However, the reaction raw materials sulfuryl fluoride and ammonia are both gases, and the production efficiency of gas-gas reaction is low. Although solvents are used to accelerate the reaction, the effect is still not ideal. Summary of the invention
[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a method for preparing lithium bis(fluorosulfonyl)imide.
[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:
[0006] A method for preparing lithium bis(fluorosulfonyl)imide comprises the following steps:
[0007] S1, sulfuryl fluoride is introduced into the hydrofluoric acid aqueous solution of urea, and reacts under the action of a catalyst to obtain a bis(fluorosulfonyl)imide aqueous solution; the catalytic reaction equation is as follows:
[0008] CO(NH2)2+4SO2F2+H2O→2NH(SO2F)2+CO2↑+4HF;
[0009] S2, adding lithium carbonate to the aqueous solution of bis(fluorosulfonyl)imide obtained in step S1, filtering and concentrating after the reaction to obtain crude lithium bis(fluorosulfonyl)imide.
[0010] Lithium carbonate is added to the bis(fluorosulfonyl)imide aqueous solution in step S1 to convert the bis(fluorosulfonyl)imide into lithium bis(fluorosulfonyl)imide. Meanwhile, hydrofluoric acid is converted into lithium fluoride precipitate, and bismuth trifluoride is precipitated. Lithium fluoride, bismuth trifluoride and excess lithium carbonate are removed by filtration.
[0011] Preferably, the catalyst is bismuth trifluoride, and the amount of the catalyst used is 0.06-1% of the weight of water in the urea hydrofluoric acid aqueous solution.
[0012] Preferably, in the hydrofluoric acid aqueous solution of urea, the weight ratio of hydrogen fluoride, urea and water is (2-5):(10-20):100. The purpose of adding hydrofluoric acid is to promote the dissolution of the catalyst bismuth trifluoride, which is soluble in inorganic acid aqueous solution and insoluble in neutral and alkaline solutions.
[0013] Preferably, the weight ratio of sulfuryl fluoride to urea is (690-720): 100. A slight excess of sulfuryl fluoride ensures that urea reacts fully, and the excess sulfuryl fluoride is discharged in the form of gas without forming impurities.
[0014] Preferably, the weight ratio of lithium carbonate to urea is (380-400): 100. A slight excess of lithium carbonate ensures that the intermediate product bisfluorosulfonyl imide is fully converted into lithium bisfluorosulfonyl imide, and at the same time, the solution is converted from acidic to neutral or weakly alkaline, and the catalyst bismuth trifluoride is precipitated; the bismuth trifluoride recovered by filtration can be reused.
[0015] Preferably, the reaction temperature of step S1 is 40-60°C, and the reaction pressure is 0.1-0.8 MPa. Too high a temperature will increase the side reactions and affect the impurity content, while too low a temperature will reduce the reaction rate; the pressure is 0.1-0.8 MPa, and increasing the pressure can increase the reaction rate.
[0016] Preferably, in step S2, alcohol is added before filtering; the amount of alcohol added is 1-3% of the weight of water in the hydrofluoric acid aqueous solution of urea. The alcohol is at least one of ethanol, methanol and propanol. Adding a small amount of alcohol before filtering can further reduce the solubility of lithium fluoride and lithium carbonate, allowing them to be fully precipitated, and reducing the impurity content in the subsequent filtrate.
[0017] Preferably, the crude lithium bis(fluorosulfonyl)imide obtained in step S2 is dissolved in a good solvent and then a poor solvent is added, and high-purity lithium bis(fluorosulfonyl)imide is obtained by filtering and drying.
[0018] Preferably, the amount of the good solvent is 1.2 to 2.0 times the weight of the crude lithium bis(fluorosulfonyl)imide product; the amount of the poor solvent is 5 to 7 times the weight of the crude lithium bis(fluorosulfonyl)imide product.
[0019] Specifically, the good solvent is any one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and tetrahydrofuran; the poor solvent is at least one of dichloroethane, dichloromethane, toluene, and anisole.
[0020] Preferably, the drying is vacuum drying; the drying temperature is 40 to 50° C. and the drying time is 6 to 10 hours. Too high a temperature will cause the lithium bis(fluorosulfonyl)imide to decompose.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] The reaction of the invention is a contact reaction between gas and liquid, with high production efficiency, mild reaction conditions and easy control; and the invention is a one-pot continuous reaction to prepare the target product, lithium bis(fluorosulfonyl)imide, which combines the separation of bis(fluorosulfonyl)imide and the combination of lithium into one, with simple steps. DETAILED DESCRIPTION
[0023] The present invention provides a method for preparing lithium bis(fluorosulfonyl)imide, comprising the following steps:
[0024] Sulfuryl fluoride is introduced into a hydrofluoric acid aqueous solution of urea, and the mixture is reacted at 40-60° C. for 8-16 hours under the action of a catalyst, bismuth trifluoride, to obtain a bisfluorosulfonyl imide aqueous solution, and then lithium carbonate is added to convert the bisfluorosulfonyl imide into lithium bisfluorosulfonyl imide. Meanwhile, hydrofluoric acid is converted into lithium fluoride precipitation, and bismuth trifluoride is precipitated. The lithium fluoride, bismuth trifluoride and excess lithium carbonate are removed by filtration, and the filtrate is concentrated to anhydrous state to obtain a crude lithium bisfluorosulfonyl imide. The crude lithium bisfluorosulfonyl imide is dissolved in a benign solvent, and then a poor solvent is added to reprecipitate the lithium bisfluorosulfonyl imide. The high-purity lithium bisfluorosulfonyl imide is obtained by filtration and drying.
[0025] The catalytic reaction equation of sulfuryl fluoride SO2F2 and urea CO(NH2)2 under the action of catalyst is:
[0026] CO(NH2)2+4SO2F2+H2O→2NH(SO2F)2+CO2↑+4HF.
[0027] In the hydrofluoric acid aqueous solution of urea, the weight ratio of hydrogen fluoride, urea and water is (2-5):(10-20):100, and the purpose of adding hydrofluoric acid is to promote the dissolution of the catalyst bismuth trifluoride.
[0028] The dosage of the catalyst bismuth trifluoride is 0.06-1% of the weight of water. Bismuth trifluoride is soluble in inorganic acid aqueous solution and insoluble in neutral and alkaline solutions.
[0029] The weight ratio of sulfuryl fluoride to urea is (690-720):100. A slight excess of sulfuryl fluoride ensures that the urea reacts fully, and the excess sulfuryl fluoride is discharged in the form of gas without forming impurities.
[0030] Sulfuryl fluoride reacts with urea at 40-60°C. Too high a temperature will lead to more side reactions and affect the impurity content, while too low a temperature will reduce the reaction rate. The pressure is 0.1-0.8MPa, and increasing the pressure can increase the reaction rate.
[0031] The weight ratio of lithium carbonate to urea is (380-400):100, with a slight excess of lithium carbonate to ensure that the intermediate product bisfluorosulfonyl imide is fully converted into lithium bisfluorosulfonyl imide, and at the same time, the solution is converted from acidic to neutral or weakly alkaline, and the catalyst bismuth trifluoride is precipitated; the bismuth trifluoride recovered by filtration can be reused.
[0032] Preferably, a small amount of alcohol can be added before filtration to further reduce the solubility of lithium fluoride and lithium carbonate, so that they can be fully precipitated and the impurity content in the subsequent filtrate can be reduced; the amount of alcohol added is 1 to 3% of the weight of water in the urea hydrofluoric acid aqueous solution, and can be any one or a combination of ethanol, methanol, and propanol;
[0033] The good solvent is any one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and tetrahydrofuran, and the amount used is 1.2 to 2.0 times the weight of the crude lithium bis(fluorosulfonyl)imide; the poor solvent is one or any combination of dichloroethane, dichloromethane, toluene, and anisole, and the amount used is 5 to 7 times the weight of the crude lithium bis(fluorosulfonyl)imide;
[0034] The drying is performed by heating at 40-50° C. for 6-10 hours under vacuum. Too high a temperature may cause decomposition of lithium bis(fluorosulfonyl)imide.
[0035] The present invention is further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.
[0036] Example 1
[0037] A method for preparing lithium bis(fluorosulfonyl)imide comprises the following steps:
[0038] 300 g of pure water, 30 g of urea, 6 g of anhydrous hydrogen fluoride and 0.18 g of bismuth trifluoride were added to a sealed container, stirred until completely dissolved, and then 207 g of sulfuryl fluoride gas was introduced, heated to 40 ° C for reaction for 16 h, and the pressure was controlled at 0.1 MPa to obtain a bisfluorosulfonyl imide aqueous solution, cooled to room temperature, and the generated carbon dioxide and excess sulfuryl fluoride were discharged, and then 114 g of lithium carbonate was added, and precipitation and gas were generated while stirring, and 3 g of ethanol was added to further precipitate lithium fluoride and lithium carbonate, and insoluble matter was removed by filtration. The obtained filtrate was concentrated to anhydrous to obtain 176.9 g of crude lithium bisfluorosulfonyl imide; the crude lithium bisfluorosulfonyl imide was dissolved in 213 g of dimethyl carbonate with stirring, and then 885 g of dichloroethane was added, and the lithium bisfluorosulfonyl imide was re-precipitated under stirring, filtered, and vacuum dried at 40 ° C for 10 h to obtain 164.7 g of high-purity lithium bisfluorosulfonyl imide.
[0039] The yield of this example is 88.1%, and the NMR analysis shows 19 F NMR: 51.3 ppm (solvent deuterated acetonitrile), purity 99.66%, acidity 8.2 ppm, water 16 ppm.
[0040] Example 2
[0041] A method for preparing lithium bis(fluorosulfonyl)imide comprises the following steps:
[0042] 300 g of pure water, 60 g of urea, 15 g of anhydrous hydrogen fluoride and 3.0 g of bismuth trifluoride were added to a sealed container, stirred until completely dissolved, and then 432 g of sulfuryl fluoride gas was introduced, heated to 60 ° C for reaction for 8 h, and the pressure was controlled at 0.8 MPa to obtain a bisfluorosulfonyl imide aqueous solution, cooled to room temperature, and the generated carbon dioxide and excess sulfuryl fluoride were discharged, and then 240 g of lithium carbonate was added, and precipitation and gas were generated while stirring, and then 9 g of ethanol was added to further precipitate lithium fluoride and lithium carbonate, and insoluble matter was removed by filtration. The obtained filtrate was concentrated to anhydrous to obtain 370.1 g of crude lithium bisfluorosulfonyl imide; the crude lithium bisfluorosulfonyl imide was dissolved in 740 g of diethyl carbonate with stirring, and then 2590 g of toluene was added, and the lithium bisfluorosulfonyl imide was re-precipitated under stirring, filtered, and vacuum dried at 50 ° C for 6 h to obtain 343.2 g of high-purity lithium bisfluorosulfonyl imide.
[0043] The yield of this example is 91.8%, and the NMR analysis shows 19 F NMR: 51.5 ppm (solvent deuterated acetonitrile), purity 99.84%, acidity 8.5 ppm, water 15 ppm.
[0044] Example 3
[0045] A method for preparing lithium bis(fluorosulfonyl)imide comprises the following steps:
[0046] 300 g of pure water, 40 g of urea, 11 g of anhydrous hydrogen fluoride and 0.24 g of bismuth trifluoride were added to a sealed container, stirred until completely dissolved, and then 280 g of sulfuryl fluoride gas was introduced, heated to 40 ° C for reaction for 12 h, and the pressure was controlled at 0.4 MPa to obtain a bisfluorosulfonyl imide aqueous solution, cooled to room temperature, and the generated carbon dioxide and excess sulfuryl fluoride were discharged. Then 156 g of lithium carbonate was added, and precipitation and gas were generated while stirring. 6 g of ethanol was added to further precipitate lithium fluoride and lithium carbonate, and insoluble matter was removed by filtration. The obtained filtrate was concentrated to anhydrous to obtain 243.5 g of crude lithium bisfluorosulfonyl imide; the crude lithium bisfluorosulfonyl imide was dissolved in 390 g of ethyl methyl carbonate with stirring, and 1460 g of dichloromethane was added. The lithium bisfluorosulfonyl imide was re-precipitated under stirring, filtered, and dried in vacuo at 45 ° C for 8 h to obtain 225.4 g of high-purity lithium bisfluorosulfonyl imide.
[0047] The yield of this example is 90.5%, and the NMR analysis shows 19 F NMR: 51.3 ppm (solvent deuterated acetonitrile), purity 99.76%, acidity 8.4 ppm, water 16 ppm.
[0048] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.
Claims
1. A method for preparing lithium bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: S1, sulfuryl fluoride is introduced into the hydrofluoric acid aqueous solution of urea, and reacts under the action of a catalyst to obtain a bis(fluorosulfonyl)imide aqueous solution; the catalytic reaction equation is as follows: CO(NH2)2+4SO2F2+H2O→2NH(SO2F)2+CO2↑+4HF; S2, adding lithium carbonate to the aqueous solution of bis(fluorosulfonyl)imide obtained in step S1, filtering and concentrating after the reaction to obtain a crude product of lithium bis(fluorosulfonyl)imide; The catalyst is bismuth trifluoride.
2. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The amount of the catalyst used is 0.06-1% of the weight of water in the urea hydrofluoric acid aqueous solution.
3. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: In the hydrofluoric acid aqueous solution of urea, the weight ratio of hydrogen fluoride, urea and water is (2-5):(10-20):
100.
4. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The weight ratio of sulfuryl fluoride to urea is (690-720):
100.
5. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The weight ratio of lithium carbonate to urea is (380-400):
100.
6. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The reaction temperature of step S1 is 40-60° C., and the reaction pressure is 0.1-0.8 MPa.
7. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: In the step S2, alcohol is added before filtering; the amount of the alcohol added is 1-3% of the weight of water in the hydrofluoric acid aqueous solution of urea.
8. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, characterized in that: The crude lithium bis(fluorosulfonyl)imide obtained in step S2 is dissolved in a good solvent and then a poor solvent is added, and high-purity lithium bis(fluorosulfonyl)imide is obtained through filtering and drying.
9. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 8, characterized in that: The dosage of the good solvent is 1.2 to 2.0 times the weight of the crude lithium bis(fluorosulfonyl)imide product; the dosage of the poor solvent is 5 to 7 times the weight of the crude lithium bis(fluorosulfonyl)imide product.
10. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 8, characterized in that: The drying is vacuum drying; the drying temperature is 40-50° C., and the drying time is 6-10 hours.