N,N-diethylpyrrolidine bisfluorosulfonimide salt, and preparation method and application thereof
The method for preparing N,N-diethylpyrrolidine bisfluorosulfonylimide salt solves the problems of insufficient conductivity and safety of traditional ionic liquids, and realizes the preparation of ionic liquids with high purity and high conductivity, which are suitable for battery electrolytes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LANDE (JIANGSU) NEW MATERIAL TECHNOLOGY CO LTD
- Filing Date
- 2026-05-08
- Publication Date
- 2026-07-10
AI Technical Summary
Traditional ionic liquids suffer from insufficient conductivity and safety in electrolytes.
Using potassium carbonate solution, tetrahydropyrrole, and bromoethane as raw materials, N,N-diethylpyrrole bromide was synthesized under specific temperature and catalyst conditions. Subsequently, it underwent an ion exchange reaction with lithium bisfluorosulfonylimide to prepare N,N-diethylpyrrole bisfluorosulfonylimide salt. Purity was ensured by activated carbon decolorization and organic solvent extraction.
This method improves the conductivity and safety of ionic liquids, reduces the introduction of impurity ions, simplifies the preparation process, and yields high-purity N,N-diethylpyrrolidine difluorosulfonylimide salt.
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Figure CN122355979A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ionic liquid materials technology, and in particular to an N,N-diethylpyrrolidine difluorosulfonyl imide salt, its preparation method, and its application. Background Technology
[0002] The history of ionic liquids dates back to 1914, when Walden reported (EtNH2). + HNO3 - The synthesis of ionic liquid (melting point 12℃) was achieved by reacting concentrated nitric acid with ethylamine. However, due to its instability in air and tendency to explode, its discovery did not initially attract much interest; it was the earliest known ionic liquid. Generally, ionic compounds require very high temperatures to overcome the ionic bonds and dissolve into liquids; this state is called a "molten salt." The ionic bonds in ionic compounds weaken as the radius of the cation increases, and the melting point decreases accordingly. For most substances, the melting point of a mixture is lower than that of the pure substance. For example, NaCl has a melting point of 803℃, while a mixture of 50% LiCl and 50% AlCl3 (mole fraction) has a melting point of only 144℃. By further increasing the volume and structural asymmetry of the cations or anions, weakening the forces between them, liquid ionic compounds at room temperature can be obtained. Based on this principle, in 1951, F.H. Hurley and T.P. Wiler first synthesized an ionic liquid that was liquid at ambient temperature. They chose N-ethylpyridine as the cation, and synthesized an ionic liquid that was a mixture of n-ethylpyridine bromide and aluminum chloride (molar ratio of aluminum chloride to ethylpyridine bromide was 1:2). However, the liquid temperature range of this ionic liquid was relatively narrow, and aluminum chloride ionic liquid releases hydrogen chloride upon contact with water, which is irritating to the skin. It wasn't until 1976 that Robert from Colorado State University, using AlCl3 / [N-EtPy]Cl as an electrolyte in his organic electrochemical research, discovered that this room-temperature ionic liquid was an excellent electrolyte, miscible with organic matter, proton-free, and with a wide electrochemical window. In 1992, Wilkes synthesized 1-methyl-3-ethylimidazole chloride using 1-methyl-3-ethylimidazole as the cation, achieving a melting point of 8°C in the presence of 50% AlCl3. Only after this did the application research of ionic liquids truly begin to be widely carried out.
[0003] In recent years, due to the rapid development of science and technology and industry, the application of ionic liquids has been increasing, including in electrolyte addition, pharmaceutical intermediates, and is particularly important in the battery industry. Traditional ionic liquids have certain drawbacks.
[0004] Therefore, it is of great significance to provide an N,N-diethylpyrrolidine bisfluorosulfonyl imide salt with higher conductivity, safety and better performance. Summary of the Invention
[0005] To address the aforementioned technical problems, the present invention aims to provide an N,N-diethylpyrrolidine difluorosulfonyl imide salt, its preparation method, and its application.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt, comprising the following steps: 1) Potassium carbonate solution, tetrahydropyrrole and bromoethane were reacted in an inert atmosphere to obtain an intermediate product. The intermediate product was dissolved in an organic solvent, filtered and evaporated to dryness to obtain N,N-diethylpyrrole bromide. 2) Dissolve N,N-diethylpyrrolidine bromide in water, add activated carbon for decolorization treatment, and obtain an aqueous solution of N,N-diethylpyrrolidine bromide; 3) An aqueous solution of N,N-diethylpyrrolidine bromide is reacted with lithium difluorosulfonylimide in an organic solvent by an ion exchange reaction to obtain N,N-diethylpyrrolidine difluorosulfonylimide.
[0007] Furthermore, in step 1), the mass ratio of potassium carbonate to water in the potassium carbonate solution is 1:1.5~3.5; The molar ratio of potassium carbonate, tetrahydropyrrole, and bromoethane in the potassium carbonate solution is 0.5~1.5:1:2.4~3.0; The mass-to-volume ratio of the N,N-diethylpyrrolidine bromide salt to the organic solvent is 190~210g:200mL; The mass ratio of the intermediate product to water is 150~220:400.
[0008] Furthermore, in step 1), the reaction temperature is 40~50℃ and the reaction time is 12~36h; The drying temperature is 60~70℃.
[0009] Furthermore, in step 2), the amount of activated carbon added is 1 to 6% of the mass of N,N-diethylpyrrolidine bromide.
[0010] Furthermore, in step 2), the decolorization treatment temperature is 60~70℃, and the decolorization treatment time is 2~6h.
[0011] Furthermore, in step 3), the ratio of the N,N-diethylpyrrolidine bromide aqueous solution, lithium difluorosulfonyl imide, and organic solvent is 190~210g:37~94g:100mL; The mass fraction of the lithium difluorosulfonylimide is ≥99 wt.%.
[0012] Furthermore, in step 3), the temperature of the ion exchange reaction is 20~40℃, and the time of the ion exchange reaction is 3~5h.
[0013] Furthermore, the organic solvent in steps 2) and 3) is independently dichloromethane.
[0014] This invention provides an N,N-diethylpyrrolidine difluorosulfonyl imide salt prepared by the preparation method described above.
[0015] The present invention also provides the application of the aforementioned N,N-diethylpyrrolidine bisfluorosulfonylimide salt as an ionic liquid in battery electrolytes.
[0016] The beneficial effects of this invention are: This invention uses tetrahydropyrrole, bromoethane, and lithium bisfluorosulfonylimide as basic raw materials to prepare N,N-diethylpyrrole difluorosulfonylimide salt under specific temperature and catalyst conditions. A relatively simple and environmentally friendly post-processing method is then used to obtain N,N-diethylpyrrole difluorosulfonylimide salt with extremely high purity. The preparation method of this invention achieves liquid-solid separation of reaction products and byproducts, and the reaction does not introduce other impurity ions, greatly improving the purity of the product. Furthermore, this invention uses a solvent-free process, reducing the harmful effects of other organic solvents, and the preparation process is simple, yielding a product with extremely high purity. Attached Figure Description
[0017] Figure 1 NMR spectrum of N,N-diethylpyrrolidine difluorosulfonylimide salt prepared in Example 1; Figure 2 The ion chromatogram of N,N-diethylpyrrolidine difluorosulfonylimide salt prepared in Example 1; Figure 3 The image shows the physical product of N,N-diethylpyrrolidine difluorosulfonylimide salt prepared in Example 1. Detailed Implementation
[0018] This invention provides a method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt, comprising the following steps: 1) Potassium carbonate solution, tetrahydropyrrole and bromoethane were reacted in an inert atmosphere to obtain an intermediate product. The intermediate product was dissolved in an organic solvent, filtered and evaporated to dryness to obtain N,N-diethylpyrrole bromide. 2) Dissolve N,N-diethylpyrrolidine bromide in water, add activated carbon for decolorization treatment, and obtain an aqueous solution of N,N-diethylpyrrolidine bromide; 3) An aqueous solution of N,N-diethylpyrrolidine bromide is reacted with lithium difluorosulfonylimide in an organic solvent by an ion exchange reaction to obtain N,N-diethylpyrrolidine difluorosulfonylimide.
[0019] In this invention, in step 1), the mass ratio of potassium carbonate to water in the potassium carbonate solution is 1:1.5~3.5, preferably 1:1.8~3, and more preferably 1:2~2.5; The molar ratio of potassium carbonate, tetrahydropyrrole, and bromoethane in the potassium carbonate solution is 0.5~1.5:1:2.4~3.0, preferably 0.8~1.3:1:2.4~2.8, and more preferably 1.1:1:2.4~2.6; The mass-to-volume ratio of the N,N-diethylpyrrolidine bromide to the organic solvent is 190-210 g: 200 mL, preferably 194-205 g: 200 mL, and more preferably 198-200 g: 200 mL; The mass ratio of the intermediate product to water is 150~220:400, preferably 175~210:400, and more preferably 195~200:400.
[0020] In this invention, in step 1), the reaction temperature is 40~50℃, preferably 40~47℃, and more preferably 40~45℃; the reaction time is 12~36h, preferably 14~34h, and more preferably 16~32h. The drying temperature is 60~70℃, preferably 62~68℃, and more preferably 65℃.
[0021] In this invention, in step 2), the amount of activated carbon added is 1 to 6% of the mass of N,N-diethylpyrrolidine bromide, preferably 1.5 to 5.5%, and more preferably 2 to 5%.
[0022] In this invention, in step 2), the temperature of the decolorization treatment is 60~70℃, preferably 62~68℃, and more preferably 65℃; the time of the decolorization treatment is 2~6h, preferably 3~5h, and more preferably 4h.
[0023] In this invention, in step 3), the ratio of the N,N-diethylpyrrolidine bromide aqueous solution, lithium difluorosulfonyl imide, and organic solvent is 190~210g:37~94g:100mL, preferably 193~207g:40~90g:100mL, and more preferably 199~203g:45~85g:100mL; The mass fraction of the lithium difluorosulfonyl imide is ≥99 wt.%, preferably ≥99.2 wt.%, and more preferably ≥99.4 wt.%.
[0024] In this invention, in step 3), the temperature of the ion exchange reaction is 20~40℃, preferably 22~37℃, and more preferably 25~35℃; the time of the ion exchange reaction is 3~5h, preferably 3.5~4.5h, and more preferably 4h.
[0025] In this invention, the organic solvent in steps 2) and 3) is dichloromethane.
[0026] This invention provides an N,N-diethylpyrrolidine difluorosulfonyl imide salt prepared by the preparation method described above.
[0027] The present invention also provides the application of the aforementioned N,N-diethylpyrrolidine bisfluorosulfonylimide salt as an ionic liquid in battery electrolytes.
[0028] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0029] Example 1
[0030] 152.03 g of potassium carbonate (99 wt.%) was dissolved in 304 g of deionized water to obtain a potassium carbonate solution. The potassium carbonate solution and 71.12 g of tetrahydropyrrole (99 wt.%) were placed in an ice bath, with the temperature controlled below 10 °C. Then, 272.4 g of bromoethane (99 wt.%) was added, and the temperature was raised to 40 °C for a reaction time of 24 h. After the reaction, the solvent water and unreacted bromoethane were removed by rotary evaporation at 85 °C to obtain an intermediate product. The intermediate product was dissolved in 200 ml of dichloromethane; the insoluble matter was the byproduct potassium bromide. The filtrate was filtered, and the dichloromethane was removed by rotary evaporation at 65 °C to obtain 198.3 g of N,N-diethylpyrrole bromide. The purity was determined by high-performance liquid chromatography (HPLC), with a yield of 95.26%. 198.3g of N,N-diethylpyrrolidine bromide was dissolved in 400g of deionized water. Activated carbon was added at 5% of the mass of N,N-diethylpyrrolidine bromide for decolorization treatment at 65℃ for 4 hours. After decolorization, the solution was filtered through a Buchner funnel, yielding a colorless and transparent aqueous solution of N,N-diethylpyrrolidine bromide. 199.4 g of N,N-diethylpyrrolidine bromide aqueous solution and 61.73 g of 99 wt.% lithium difluorosulfonyl imide were subjected to an ion exchange reaction in 100 mL of dichloromethane at a temperature of 25 °C for 4 h. After the reaction was completed, the mixture was allowed to stand, and the lower organic layer was obtained by extraction and separation. The organic layer was washed five times with 10 mL of deionized water to obtain the organic layer. The solvent was removed by rotary evaporation to obtain N,N-diethylpyrrolidine difluorosulfonyl imide.
[0031] The N,N-diethylpyrrolidine difluorosulfonylimide salt prepared in Example 1 was tested by ion chromatography, and the test results are as follows: Figures 1-2 As shown in Table 1, the N,N-diethylpyrrolidine difluorosulfonyl imide salt prepared in Example 1 was analyzed, and the results are shown in Table 2. The ion chromatograms are shown in Table 2.
[0032] Table 1. Detection results of N,N-diethylpyrrolidine difluorosulfonyl imide salt prepared in Example 1
[0033] Table 2. Ion chromatogram of N,N-diethylpyrrolidine difluorosulfonylimide salt from Example 1
[0034] Example 2
[0035] The difference between Example 1 and Example 2 is that the amount of bromoethane used in Example 2 is 2.6 mol.
[0036] Examples 3-4
[0037] Compared with Example 1, the difference is that the reaction temperatures of potassium carbonate solution, tetrahydropyrrole and bromoethane in Examples 3 and 4 are 45°C and 50°C, respectively.
[0038] Comparative Examples 1-2
[0039] Compared with Example 1, the difference is that the amount of bromoethane used in Comparative Examples 1 and 2 is 2.0 mol and 2.2 mol, respectively.
[0040] The purity and yield of Examples 1-2 and Comparative Examples 1-2 were tested, and the test results are shown in Table 3.
[0041] Table 3 Test results of Examples 1-2 and Comparative Examples 1-2
[0042] As shown in Table 3, the yield of bromine salt synthesis gradually increases with the increase of the molar number of bromoethane. When the molar number reaches 2.4, both the product quality and yield reach their peak. As the number continues to increase, the yield and quality remain basically unchanged. Considering all factors, choosing 2.4 of bromoethane is the most economical.
[0043] Comparative Examples 3-4
[0044] Compared with Example 1, the difference is that the reaction temperatures of potassium carbonate solution, tetrahydropyrrole and bromoethane in Comparative Examples 3 and 4 are 30°C and 35°C, respectively.
[0045] The purity and yield of Examples 1, 3-4 and Comparative Examples 3-4 were tested, and the test results are shown in Table 4.
[0046] Table 4 Test results of Examples 1, 3-4 and Comparative Examples 3-4
[0047] As shown in Table 4, when other variables are kept constant, the product purity gradually increases with the increase of reaction temperature, and the yield also increases with the increase of temperature, eventually stabilizing. However, when the temperature rises to 50℃, the product color darkens and the product quality decreases. Therefore, considering all factors, 40~45℃ is the most appropriate.
[0048] Comparative Examples 5-6
[0049] Compared with Example 1, the difference is that the number of water washes in Comparative Examples 5 and 6 is 1 and 3, respectively.
[0050] The results of bromide ion residues in Examples 1 and Comparative Examples 5-6 are shown in Table 5.
[0051] Table 5. Results of bromide ion residue tests in Examples 1 and 5-6
[0052] As shown in Table 5, necessary water washing is essential. As the number of water washings increases, the bromide ion content gradually decreases. When the number of water washings reaches 5, there is basically no bromide ion residue. Therefore, choosing 5 times is the most suitable for product purity.
[0053] As can be seen from the above embodiments, the present invention provides an N,N-diethylpyrrolidine difluorosulfonylimide salt, its preparation method, and its application. The preparation method of the N,N-diethylpyrrolidine difluorosulfonylimide salt of the present invention includes the following steps: reacting potassium carbonate solution, tetrahydropyrrole, and bromoethane in an inert atmosphere; then dissolving the reaction product in an organic solvent, filtering, and evaporating to obtain N,N-diethylpyrrolidine bromide; dissolving the N,N-diethylpyrrolidine bromide in water, adding activated carbon for decolorization treatment, and obtaining an aqueous solution of N,N-diethylpyrrolidine bromide; and performing an ion exchange reaction between the aqueous solution of N,N-diethylpyrrolidine bromide and lithium difluorosulfonylimide in an organic solvent to obtain the final product. The preparation method of the present invention separates the reaction product and by-product into liquid and solid phases, and the reaction does not introduce other impurity ions, greatly improving the purity of the product.
[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt, characterized in that, Includes the following steps: 1) Potassium carbonate solution, tetrahydropyrrole and bromoethane were reacted in an inert atmosphere to obtain an intermediate product. The intermediate product was dissolved in an organic solvent, filtered and evaporated to dryness to obtain N,N-diethylpyrrole bromide. 2) Dissolve N,N-diethylpyrrolidine bromide in water, add activated carbon for decolorization treatment, and obtain an aqueous solution of N,N-diethylpyrrolidine bromide; 3) An aqueous solution of N,N-diethylpyrrolidine bromide is reacted with lithium difluorosulfonylimide in an organic solvent by an ion exchange reaction to obtain N,N-diethylpyrrolidine difluorosulfonylimide.
2. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 1, characterized in that, In step 1), the mass ratio of potassium carbonate to water in the potassium carbonate solution is 1:1.5~3.5; The molar ratio of potassium carbonate, tetrahydropyrrole, and bromoethane in the potassium carbonate solution is 0.5~1.5:1:2.4~3.0; The mass-to-volume ratio of the N,N-diethylpyrrolidine bromide salt to the organic solvent is 190~210g:200mL; The mass ratio of the intermediate product to water is 150~220:
400.
3. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 2, characterized in that, In step 1), the reaction temperature is 40~50℃ and the reaction time is 12~36h; The drying temperature is 60~70℃.
4. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 2 or 3, characterized in that, In step 2), the amount of activated carbon added is 1 to 6% of the mass of N,N-diethylpyrrolidine bromide.
5. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 4, characterized in that, In step 2), the temperature of the decolorization treatment is 60~70℃, and the time of the decolorization treatment is 2~6h.
6. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 5, characterized in that, In step 3), the ratio of the N,N-diethylpyrrolidine bromide aqueous solution, lithium difluorosulfonyl imide, and organic solvent is 190~210g:37~94g:100mL. The mass fraction of the lithium difluorosulfonylimide is ≥99 wt.%.
7. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 6, characterized in that, In step 3), the temperature of the ion exchange reaction is 20~40℃, and the time of the ion exchange reaction is 3~5h.
8. The method for preparing N,N-diethylpyrrolidine difluorosulfonylimide salt according to claim 7, characterized in that, The organic solvent used in steps 2) and 3) is dichloromethane.
9. An N,N-diethylpyrrolidine difluorosulfonyl imide salt prepared by the preparation method according to any one of claims 1 to 8.
10. The application of the N,N-diethylpyrrolidine bisfluorosulfonylimide salt of claim 9 as an ionic liquid in a battery electrolyte.