Purification method of lithium diallyl malonate borate
By purifying lithium diallylmalonic acid borate using a mixed solvent of high-polar and low-polar organic solvents, the problem of by-product impurities in the existing process is solved, and the acquisition of high-purity products is achieved, meeting the purity requirements of lithium battery electrolyte.
Patent Information
- Application Number
- CN202311214058.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-20
- Publication Date
- 2025-03-21
AI Technical Summary
The existing synthesis process of lithium bimalonic acid borate contains by-product impurities, resulting in low product yield and low purity, which cannot meet the purity standards required for electrolytes in lithium battery electrolytes.
Purification is carried out using a mixed solvent containing high-polar organic solvent and low-polar organic solvent. The product and impurities are effectively separated through a two-step dissolution process to improve product purity.
It significantly improves the purity of lithium diallylmalonate borate, reduces the content of impurity metal ions, is simple to operate and low cost, and meets the use requirements of electrolyte additives.
Smart Images
Figure CN119661567A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of preparation of lithium ion battery electrolyte additives, and in particular to a method for purifying lithium bis(allylmalonate borate). Background Art
[0002] In recent years, with the vigorous development of the lithium-ion new energy industry, people have been continuously deepening their research on electrolyte lithium salts. Inorganic anion electrolyte lithium salts, such as lithium hexafluorophosphate and lithium tetrafluorophosphate, have high conductivity and cycle efficiency, but their defects are: they have strong hygroscopicity and poor thermal stability, and there are safety hazards at high temperatures or high current densities, which are not conducive to the development and application of lithium-ion batteries with high energy and power density. Therefore, organic anion electrolyte lithium salts with higher electrochemical stability and thermal stability, such as lithium bis(oxalatoborate) and lithium bis(malonateborate), have attracted extensive attention from researchers. Among them, lithium bis(malonateborate) has better extensibility because different groups can be introduced into its 2-position for modification and derivatization. Therefore, lithium bis(malonateborate) salts have important research significance and market value.
[0003] At present, the known synthesis process of lithium bismalonate borate, such as the lithium bismalonate borate prepared in patent CN 114989206 and document "Synthesis and Characterization of Network Type Single Ion Conductors", has one or more by-products such as lithium malonate, soluble oligomers, lithium fluoride, and lithium tetrafluoroborate. Since most impurities have very similar solubility to the target product in general solvents, they are difficult to separate, which will lead to low product yield and low purity, and cannot meet the required purity standard of electrolyte in lithium battery electrolyte. Therefore, after synthesizing lithium bismalonate borate, how to efficiently purify it to reduce the impurity salt, metal ion and moisture content is crucial for the research and development of this type of electrolyte lithium salt. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a method for purifying lithium bis(allylmalonate borate), which is simple to operate, can greatly reduce the content of metal ions and other ions, and greatly improve the purity of the product.
[0005] To solve the above problems, the technical solution adopted by the present invention is: a method for purifying lithium bis(allyl) boron malonate, comprising the following steps: 1. adding a first mixed solvent to a crude salt of lithium bis(allyl) boron malonate, the first mixed solvent comprising a high-polarity organic solvent and a low-polarity organic solvent, the mass ratio of the high-polarity organic solvent to the low-polarity organic solvent being 1:1-1:5, heating and stirring to dissolve, filtering while hot to remove organic impurities from the filtrate; 2. vacuum drying the filter cake and grinding it into fine powder, adding a second mixed solvent and cooling and stirring, the second mixed solvent comprising a high-polarity organic solvent and a low-polarity organic solvent, the mass ratio of the high-polarity solvent to the low-polarity solvent being 9:1-3:1; filtering while cold after dissolution to remove insoluble impurity salts; 3. concentrating the filtrate into granules, grinding it into fine powder and transferring it to a vacuum drying oven for drying to obtain a finished lithium bis(allyl) boron malonate. The first mixed solvent, in which the mass ratio of the high polar organic solvent to the low polar organic solvent is 1:1-1:5, can fully dissolve organic impurities but not dissolve lithium salts; the second mixed solvent, in which the mass ratio of the high polar solvent to the low polar solvent is 9:1-3:1, can dissolve the lithium bismalonate borate product but not dissolve the impurity lithium salt. Through two-step dissolution, the product and impurities can be effectively separated, thereby greatly improving the purity of the product.
[0006] Furthermore, in the aforementioned method for purifying lithium bis(allylmalonate borate), the low-polarity organic solvent is selected from one of dichloromethane, toluene, n-hexane, dichloroethane, and cyclohexane; the high-polarity organic solvent is selected from one of diethyl ether, methyl tert-butyl ether, acetone, acetonitrile, tetrahydrofuran, ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and ethylene glycol dimethyl ether.
[0007] Furthermore, in the aforementioned method for purifying lithium bis(allyl)malonate borate, in the first step, the mass ratio of the crude lithium bis(allyl)malonate borate salt to the first mixed solvent is 1:5 to 1:10.
[0008] Furthermore, in the aforementioned method for purifying lithium bis(allyl) boromalonate, the crude lithium bis(allyl) boromalonate salt is stirred in the first mixed solvent at a temperature of 40° C. to 85° C. and a stirring time of 2 h to 5 h.
[0009] Furthermore, in the aforementioned method for purifying lithium bis(allyl)malonate borate, in the second step, the mass ratio of crude lithium bis(allyl)malonate borate salt to the second mixed solvent is 1:1 to 1:3.
[0010] Furthermore, in the aforementioned method for purifying lithium bis(allylmalonate borate), in the second step, the stirring temperature is -10°C to 5°C, and the stirring time is 0.5h to 2h.
[0011] Furthermore, in the aforementioned method for purifying lithium bis(allylmalonate borate), during the purification process, the temperature during evaporation and concentration is 30°C~60°C and the vacuum degree is 100Pa~1000Pa; during the purification process, the temperature during vacuum drying is 85°C~120°C and the vacuum degree is 5~100Pa.
[0012] The advantages of the present invention are as follows: the purification method of the lithium bis(allyl)malonate borate of the present invention adopts a mixed solvent containing a high-polarity organic solvent and a low-polarity organic solvent for dissolving and purifying the product lithium bis(allyl)malonate borate according to the difference in solubility of impurities and products in different solvents and at different temperatures, and the product has high purity and low impurity metal ion content, simple operation steps, low purification cost, and meets the use requirements of electrolyte additives. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 is the H NMR spectrum of the finished lithium bis(allyl)malonate borate in Example 2, 1 H NMR (400MHz, DMSO-d6)δ5.82~5.74 (1H,m), 5.07 (1H, d, J = 12 Hz), 4.99 (1H, d, J = 12 Hz),3.55 (1H, t, J = 4 Hz), 2.56 (2H, t, J = 4 Hz).
[0014] Figure 2 is the NMR carbon spectrum of the finished lithium bis(allylmalonate borate) in Example 2, 13 C NMR (100MHz, CDCl3) δ167.45, 135.19, 117.01, 47.41, 30.44. Implementation
[0015] The present invention is further described in detail below through specific examples.
[0016] Example 1: In a three-necked jacketed kettle equipped with a thermometer and a stirrer, 300 g of lithium bis(allyl)malonate borate block crude salt, 1000 g of dimethyl carbonate and 2000 g of toluene were added, the mixture was heated to 70° C. and stirred for 2 h, and filtered while hot.
[0017] The filter cake was vacuum dried at 100°C and 59 Pa for 12 h. After the dried filter cake was ground into fine powder, a mixture of 270 g acetonitrile and 30 g n-hexane was added, cooled to 0°C and stirred for 2 h, and filtered while cold.
[0018] The filtrate was evaporated and concentrated at 50°C and a vacuum degree of 800 Pa to remove the solvent and was in granular form. The crude product was ground into fine powder and transferred to a vacuum drying oven for vacuum drying at 105°C and 10Pa for 24 hours to obtain 225g of lithium bis(allylmalonic acid borate) finished product with a content of 99.58% and impurity metal ions less than 5ppm.
[0019] Example 2: In a three-necked jacketed kettle equipped with a thermometer and a stirrer, 500 g of lithium bis(allyl)malonate borate block crude salt, 1250 g of diethyl carbonate and 1250 g of dichloroethane were added, the mixture was heated to 60° C. and stirred for 3 h, and filtered while hot.
[0020] The filter cake was vacuum dried at 120°C and 100 Pa for 8 h. After the dried filter cake was ground into fine powder, a mixture of 1125 g acetonitrile and 375 g dichloromethane was added, cooled to 0°C and stirred for 2 h, and filtered while cold.
[0021] The filtrate was evaporated and concentrated at 30°C and vacuum degree of 200 Pa to remove the solvent and became granular. The crude product was ground into fine powder and transferred to a vacuum drying oven at 105°C and 10Pa for vacuum drying for 24 hours to obtain 411g of lithium bis(allyl)malonate borate finished product with a content of 99.61% and impurity metal ions less than 5ppm. The NMR hydrogen spectrum and NMR carbon spectrum of the product are as follows: Figure 1 , Figure 2 shown.
[0022] Example 3: In a three-necked jacketed kettle equipped with a thermometer and a stirrer, 350 g of lithium bis(allylmalonate borate) block crude salt, 420 g of acetone and 1680 g of dichloromethane were added, the mixture was heated to 40°C and stirred for 4 h, filtered while hot, and the filter cake was vacuum dried at 85°C and 95 Pa for 12 h.
[0023] After the dried filter cake was ground into fine powder, 600 g of ethylene glycol dimethyl ether and 100 g of cyclohexane were added, the mixture was cooled to -10°C and stirred for 1.5 h, and filtered while cold.
[0024] The filtrate was evaporated and concentrated at 60°C and a vacuum degree of 150 Pa to remove the solvent and was in granular form. The crude product was ground into fine powder and transferred to a vacuum drying oven for vacuum drying at 120°C and 5Pa for 18 hours to obtain 296g of lithium bis(allylmalonic acid borate) finished product with a content of 99.73% and impurity metal ions less than 5ppm.
[0025] Example 4: 800 g of lithium bis(allylmalonate borate) block crude salt, 1000 g of propylene carbonate and 3000 g of toluene were added to a three-necked jacketed kettle equipped with a thermometer and a stirrer, the mixture was heated to 85° C. and stirred for 5 h, and filtered while hot.
[0026] The filter cake was vacuum dried at 110°C and 60 Pa for 24 h. After the dried filter cake was ground into fine powder, 1400 g of ethyl acetate and 200 g of n-hexane were added, the mixture was cooled to 5°C and stirred for 0.5 h, and filtered while it was cold.
[0027] The filtrate was evaporated and concentrated at 60°C and a vacuum degree of 500 Pa to remove the solvent and was in granular form. The crude product was ground into fine powder and transferred to a vacuum drying oven for vacuum drying at 105°C and 45Pa for 20 hours to obtain 687g of lithium bis(allylmalonic acid borate) finished product with a content of 99.82% and impurity metal ions less than 5ppm.
[0028] Example 5: In a three-necked jacketed kettle equipped with a thermometer and a stirrer, 600 g of lithium bis(allyl)malonate borate block crude salt, 1200 g of methyl tert-butyl ether and 2400 g of dichloroethane were added, the mixture was heated to 55° C. and stirred for 3 h, and filtered while hot.
[0029] The filter cake was vacuum dried at 90°C and 86 Pa for 8 h. After the dried filter cake was ground into fine powder, 1500 g of tetrahydrofuran and 300 g of n-hexane were added, the mixture was cooled to -5°C and stirred for 1 h, and filtered while cold.
[0030] The filtrate was evaporated and concentrated at 60°C and a vacuum degree of 1000 Pa to remove the solvent and was in granular form. The crude product was ground into fine powder and transferred to a vacuum drying oven for vacuum drying at 115°C and 30Pa for 12 hours to obtain 509g of lithium bis(allylmalonic acid borate) finished product with a content of 99.64% and impurity metal ions less than 5ppm.
[0031] Example 6: Into a three-necked jacketed kettle equipped with a thermometer and a stirrer, 900 g of lithium bis(allylmalonate borate) block crude salt, 2700 g of ethylene carbonate and 2700 g of toluene were added, the mixture was heated to 80° C. and stirred for 5 h, and filtered while hot.
[0032] The filter cake was vacuum dried at 120°C and 35 Pa for 8 h. After the dried filter cake was ground into fine powder, a mixture of 800 g acetonitrile and 100 g n-hexane was added, cooled to 0°C and stirred for 0.5 h, and filtered while cold.
[0033] The filtrate was evaporated and concentrated at 55°C and a vacuum degree of 600 Pa to remove the solvent and was in granular form. The crude product was ground into fine powder and transferred to a vacuum drying oven for vacuum drying at 110°C and 28Pa for 24 hours to obtain 793g of lithium bis(allylmalonic acid borate) finished product with a content of 99.78% and impurity metal ions less than 5ppm.
[0034] Example 7: Into a three-necked jacketed kettle equipped with a thermometer and a stirrer, 450 g of lithium bis(allyl)malonate borate block crude salt, 1200 g of ethyl methyl carbonate and 2400 g of ethylene dichloride were added, the mixture was heated to 75° C. and stirred for 4 h, and filtered while hot.
[0035] The filter cake was vacuum dried at 120°C and 50 Pa for 12 h. After the dried filter cake was ground into fine powder, a mixture of 750 g of ethylene glycol dimethyl ether and 150 g of n-hexane was added, cooled to -10°C, stirred for 1 h, and filtered while cold.
[0036] The filtrate was evaporated and concentrated at 60°C and a vacuum degree of 120 Pa to remove the solvent and was in granular form. The crude product was ground into fine powder and transferred to a vacuum drying oven for vacuum drying at 120°C and 16 Pa for 18 hours to obtain 376 g of lithium bis(allylmalonic acid borate) finished product with a content of 99.69% and impurity metal ions less than 5 ppm.
[0037] Comparative Example 8: In a three-necked kettle equipped with a thermometer and a stirrer, 288 g of allylmalonic acid, 103 g of lithium tetrafluoroborate and 1200 g of acetonitrile were added, stirred evenly, heated to 50°C, 258 g of dimethyldichlorosilane was added dropwise, the addition was completed over 2 h, and the reaction was kept at 50°C for 7 h, and then the reaction was stopped.
[0038] The reaction solution was filtered to obtain 90 g of a crude solid product, which was washed with 360 g of dichloromethane for 3 h and then filtered. The filter cake was vacuum dried at 100° C. for 20 h to obtain 62 g of lithium bis(allylmalonic acid) propionate with a content of 85.79% and impure metal ions less than 5 ppm.
[0039] The experimental results of Comparative Example 8 show that the raw material lithium tetrafluoroborate and the reaction by-products lithium fluoride, lithium allyl malonate and other impurity salts cannot be completely removed by crystallization of the reaction solution and washing with a single solvent of dichloromethane. This method has the disadvantages of large loss, low yield, many by-products and low purity.
[0040] It can be seen from the above embodiments that the method for purifying lithium bis(allyl)malonate borate of the present invention adopts a mixed solvent containing a high-polarity organic solvent and a low-polarity organic solvent to dissolve and purify the product lithium bis(allyl)malonate borate, according to the difference in solubility of impurities and products in different solvents and at different temperatures. The product has high purity, low impurity metal ion content, simple operation steps, low purification cost, and meets the requirements for the use of electrolyte additives.
Claims
1. A method for purifying lithium bis(allylmalonate borate), comprising the following steps:
1. Add a first mixed solvent to the crude lithium bis(allyl)malonate borate salt, wherein the first mixed solvent comprises a high-polarity organic solvent and a low-polarity organic solvent, wherein the mass ratio of the high-polarity organic solvent to the low-polarity organic solvent is 1:1-1:5, heat and stir to dissolve, and filter the filtrate while hot to remove organic impurities; 2. Grind the filter cake into fine powder after vacuum drying, add a second mixed solvent, cool and stir, wherein the second mixed solvent comprises a high-polarity organic solvent and a low-polarity organic solvent, wherein the mass ratio of the high-polarity solvent to the low-polarity solvent is 9:1-3:1; after dissolving, filter while cold to remove insoluble impurity salts; 3. Concentrate the filtrate into granules, grind into fine powder, and transfer to a vacuum drying oven for drying to obtain a finished lithium bis(allyl)malonate borate.
2. The method for purifying lithium bis(allylmalonate borate) according to claim 1, characterized in that: The low-polarity organic solvent is selected from one of dichloromethane, toluene, n-hexane, dichloroethane, and cyclohexane; the high-polarity organic solvent is selected from one of diethyl ether, methyl tert-butyl ether, acetone, acetonitrile, tetrahydrofuran, ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and ethylene glycol dimethyl ether.
3. A method for purifying lithium bis(allylmalonate borate) according to claim 1 or 2, characterized in that: In the first step, the mass ratio of the crude lithium bis(allylmalonate borate) salt to the first mixed solvent is 1:5 to 1:
10.
4. A method for purifying lithium bis(allylmalonate borate) according to claim 1 or 2, characterized in that: The crude lithium bis(allylmalonic acid borate) salt is stirred in the first mixed solvent at a temperature of 40° C. to 85° C. and a stirring time of 2 h to 5 h.
5. A method for purifying lithium bis(allylmalonate borate) according to claim 1 or 2, characterized in that: In the second step, the mass ratio of crude lithium bis(allylmalonate borate) salt to the second mixed solvent is 1:1 to 1:
3.
6. A method for purifying lithium bis(allylmalonate borate) according to claim 1 or 2, characterized in that: In the second step, the stirring temperature is -10°C to 5°C, and the stirring time is 0.5h to 2h.
7. A method for purifying lithium bis(allylmalonate borate) according to claim 1 or 2, characterized in that: During the purification process, the temperature for evaporation and concentration is 30°C~60°C and the vacuum degree is 100Pa~1000Pa; during the purification process, the temperature for vacuum drying is 85°C~120°C and the vacuum degree is 5~100Pa.