Method for preparing lithium difluoromethylsulfonyl imide by taking lithium hydroxide as lithium source
By using lithium hydroxide to react with dichloromethane and difluoromethane and imine difluoromethane, combined with dichlorosulfonate removal and crown ether treatment, the long reaction time and long reaction time in the preparation of lithium difluoromethanesulfonylimide were solved. The problem of low product purity has achieved efficient preparation of high-purity lithium difluoromethylsulfonimide, meeting the high safety and high energy density requirements of lithium-ion batteries.
Patent Information
- Application Number
- CN202411214318.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-31
- Publication Date
- 2024-12-10
AI Technical Summary
The existing preparation method for lithium bisfluoromethylsulfonimide has problems such as long reaction time, incomplete reaction, and low purity of the product. Especially when lithium carbonate is used as the lithium source, it leads to viscous system and difficulty in stirring, and the product is Occasionally, lithium carbonate is wrapped, which affects product quality.
Lithium hydroxide is used as the lithium source, react with dichloromethane and difluoromethylsulfonate imine, control the temperature and stirring conditions, add dichlorosulfoxide to remove water, and use crown ether to reduce the impurity ion content, and finally obtain through drying. High purity lithium bisfluoromethylsulfonimide.
The reaction efficiency and product purity are improved, the problems of long reaction time and incomplete product are avoided, and the high purity and high safety requirements of lithium-ion battery electrolyte are met, with yield and purity reaching more than 98%.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lithium ion battery electrolyte preparation, and specifically is a method for preparing lithium bis(fluoromethylsulfonyl)imide by using lithium hydroxide as a lithium source. Background Art
[0002] In recent years, with the support of the state for the new energy vehicle industry, the new energy vehicle market has developed rapidly. With the decline of financial subsidies for new energy vehicles and the gradual strengthening of the market driving effect, the lithium-ion power battery industry is rapidly moving towards the path of high-quality development. Moreover, the state requires that future lithium batteries develop in the direction of higher safety and higher energy density, that is, the safety requirements for electrolytes are greatly improved. Under this environment, lithium bis(fluorosulfonyl)imide, a new electrolyte solute with higher safety and stability, has officially ushered in development opportunities. Lithium bis(fluoromethylsulfonyl)imide is an organic electrolyte lithium salt with good stability and one of the most widely used electrolytes for lithium-ion secondary batteries. At present, the synthesis of lithium bis(fluoromethylsulfonyl)imide uses lithium carbonate as a lithium source for reaction with bis(fluorosulfonyl)imide, but Li2CO3 contains less water and has insufficient solubility in Li2CO3 and bis(fluorosulfonyl)imide, which makes the system very viscous and difficult to stir during the reaction. At the same time, it was also found that the product occasionally encapsulated lithium carbonate, which affected the quality of the product. In addition, tracking the acidity of the reaction system and the bubbling phenomenon of the tail gas found that the reaction time was long when Li2CO3 was used as a lithium source, and there was an incomplete reaction. Summary of the invention
[0003] The purpose of the present invention is to solve the technical problems of long reaction time, incomplete reaction and low product purity in the existing preparation method of lithium bisfluoromethylsulfonyl imide, and to provide a method for preparing lithium bisfluoromethylsulfonyl imide using lithium hydroxide as a lithium source.
[0004] To achieve its purpose, the present invention adopts the following technical solution: The method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source comprises the following steps: (1) Place dichloromethane in a reaction flask and add lithium hydroxide monohydrate; (2) Place the reaction system in (1) at 0-5°C, add bis(fluoromethanesulfonic acid) imide under stirring and react for 2-4 hours; an equivalent amount of water will be produced during the reaction. If the reaction is carried out at a higher temperature, a decomposition reaction will occur, resulting in a low product yield and F - and SO4 2- The content of two ions exceeded the standard; (3) heating the reaction system to 20-25°C, adding thionyl chloride, stirring to remove water, filtering, adding dichloromethane and crown ether to the filter cake for pulping, and filtering to obtain a wet product of lithium bis(fluoromethylsulfonyl)imide; (4) Drying the wet product of lithium bis(fluoromethylsulfonyl imide) in step (3) to obtain a finished product of lithium bis(fluoromethylsulfonyl imide).
[0005] As a further preferred embodiment of the technical solution of the present invention, in step (1), the mass ratio of dichloromethane to lithium hydroxide monohydrate is 12-15:1; preferably 13.73:1.
[0006] Furthermore, in step (2), the equivalent ratio of lithium hydroxide monohydrate to bis(fluoromethanesulfonic acid) imide is 0.96-1.1:1. If the amount of lithium hydroxide monohydrate added is too much, LiCl will be generated when SOCl2 is subsequently added, resulting in Cl - The content increases and it is extremely difficult to remove; the stirring speed of the reaction of lithium hydroxide monohydrate and bis(fluoromethanesulfonic acid imide) is 600-800r / min.
[0007] Furthermore, in step (3), the liquid-solid mass ratio of the dichloromethane and the crown ether to the filter cake is 2.8-3.3:1. The mass ratio of the dichloromethane and the crown ether is 1000-5000:1.
[0008] Furthermore, in step (3), the crown ether is a mixture of 18-crown-6 and 15-crown-5, and the mixing ratio is 1:1-1.5.
[0009] Furthermore, in step (3), the stirring and dewatering speed is 400-800 r / min, and the stirring time is 10-15 h.
[0010] Furthermore, in step (4), the drying temperature is 130-160°C.
[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. From the perspective of production controllability and product quality, the present invention selects LiOH with its own crystal water as the lithium source. Compared with the Li2CO3 system, the water content in LiOH is high, which is 4 times the water content in Li2CO3. In addition, the solubility of lithium hydroxide itself is relatively high, which can avoid the problems of long reaction time, incomplete reaction, low product purity, etc. existing in the Li2CO3 system.
[0012] The technical principle is as follows: (FSO2)2NH+LiOH·H2O+2SOCl2→LiN(F2SO2)2+2SO2+4HCl.
[0013] 2. In order to prevent the water in the reaction system from affecting the product, the present invention adds thionyl chloride to remove water. At the same time, the crown ether is added to reduce the content of sodium ions and potassium ions, which are extremely difficult to remove impurities in the product, so that it meets the standards of the battery industry. Adding dichloromethane can dissolve the compounds formed by the crown ether and the sodium and potassium ions so as to separate them from the product. DETAILED DESCRIPTION
[0014] The present invention is described in detail below through specific examples.
[0015] Example 1 The method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source provided in this embodiment comprises the following steps: (1) Place 600 g of dichloromethane in a 1000 ml reaction bottle and add 43.7 g of lithium hydroxide monohydrate; (2) The reaction system in (1) was placed at 0°C, and 190.5 g of bis(fluoromethanesulfonic acid imide) was added under stirring at a speed of 300 r / min and reacted for 2 h; (3) The reaction system was heated to 23°C, 350 g of thionyl chloride was added dropwise, and the mixture was stirred at 300 r / min for 15 h to remove water. After the water was removed, the mixture was filtered, and the filter cake was slurried by adding 600 g of dichloromethane and 0.2 g of crown ether (0.1 g each of 18-crown-6 and 15-crown-5), and the potassium ions and sodium ions mixed into the system or contaminated were removed by filtration to obtain a wet product of lithium bis(fluoromethylsulfonyl)imide; (4) Drying the wet product of lithium bis(fluoromethylsulfonyl imide) in step (3) at 150° C. to obtain a finished product of lithium bis(fluoromethylsulfonyl imide) with a yield of 98% and a purity of 98.99%.
[0016] Example 2 The method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source provided in this embodiment comprises the following steps: (1) Place 150 g of dichloromethane in a 1000 ml reaction bottle and add 10.925 g of lithium hydroxide monohydrate; (2) The reaction system in (1) was placed at 0°C, 47.625 g of bis(fluoromethanesulfonic acid imide) was added under stirring at a speed of 600 r / min and the reaction was continued for 4 h; (3) The reaction system was heated to 23°C, 87.5 g of thionyl chloride was added dropwise, and the mixture was stirred at 600 r / min for 10 h to remove water. After the water was removed, the mixture was filtered, and the filter cake was slurried by adding 150 g of dichloromethane and 0.2 g of crown ether (0.1 g each of 18-crown-6 and 15-crown-5), and the potassium ions and sodium ions mixed into the system or contaminated were removed by filtration to obtain a wet product of lithium bis(fluoromethylsulfonyl)imide.
[0017] (4) Drying the wet product of lithium bis(fluoromethylsulfonyl)imide in step (3) at 150° C. to obtain a finished product of lithium bis(fluoromethylsulfonyl)imide with a yield of 98% and a purity of 98.89%.
[0018] Embodiment 3-8 The other steps of Example 3-8 are the same as those of Example 1, except that the mass ratio of dichloromethane to lithium hydroxide monohydrate in step (1) is changed. The conversion rate of the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 1.
[0019] It can be seen from the above examples that when the mass ratio of dichloromethane to lithium hydroxide monohydrate is 12-15:1, the conversion rate of the product is relatively high. The preferred mass ratio is 13.7-15:1. Considering the saving of solvent, the most preferred ratio is 13.7:1.
[0020] Examples 9-13 The other steps of Examples 9-13 are the same as those of Example 1, except that the equivalent ratio of lithium hydroxide monohydrate to bis(fluoromethylsulfonyl)imide in step (2) is changed. The purity of the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 2.
[0021] From the above examples, it can be seen that when the equivalent ratio of lithium hydroxide monohydrate to bisfluoromethanesulfonimide is 0.96-1.1:1, the purity of the product is relatively high. Therefore, it is only necessary to control the equivalent ratio of lithium hydroxide monohydrate to bisfluoromethanesulfonimide to be 0.96-1.1:1, preferably 0.99-1:1.
[0022] Examples 14-18 Examples 14-18 are the same as Example 1 in other steps, except that the stirring speed of the reaction between lithium hydroxide monohydrate and bis(fluoromethylsulfonyl)imide in step (2) is changed. The purity of the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 3.
[0023] From the above examples, it can be seen that when the stirring speed of the reaction of lithium hydroxide monohydrate and bis(fluoromethanesulfonyl)imide is 600-800 r / min, the purity of the product is higher. Therefore, it is only necessary to control the stirring speed of the reaction of lithium hydroxide monohydrate and bis(fluoromethanesulfonyl)imide to be 600-800 r / min.
[0024] Examples 19-23 The other steps of Examples 19-23 are the same as those of Example 1, except that the reaction temperature in step (3) is changed. The purity of the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 4.
[0025] It can be seen from the above examples that when the reaction temperature is 20-25°C, the purity of the product is relatively high, and the preferred reaction temperature is 23-25°C.
[0026] Examples 24-28 Examples 24-28 are the same as Example 1 in other steps, except that the mass ratio of dichloromethane and crown ether to the filter cake in step (3) is changed. When the mass ratio of dichloromethane and crown ether to the filter cake is other values, the total amount of sodium ions and potassium ions in the product lithium bis(fluoromethylsulfonyl)imide is as shown in Table 5.
[0027] It can be seen from the above examples that when the mass ratio of dichloromethane and crown ether to filter cake is 2.8-3.3:1, the sodium ions and potassium ions in the product lithium bisfluoromethylsulfonyl imide are both low, and the preferred mass ratio is 3.1-3.3:1.
[0028] Examples 29-33 Examples 29-33 are the same as Example 1 in other steps, except that the mass ratio of dichloromethane to crown ether in step (3) is changed. The total amount of sodium ions and potassium ions in the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 6.
[0029] From the above examples, it can be seen that when the mass ratio of dichloromethane to crown ether is 1000-5000:1, the sodium ions and potassium ions in the product lithium bisfluoromethylsulfonyl imide are relatively low, and the mass ratio of dichloromethane to crown ether is preferably 1000-3000:1.
[0030] Examples 34-38 Examples 34-38 are the same as Example 1 in other steps, except that the mixing ratio of the crown ether in step (3) is changed. The total amount of sodium ions and potassium ions in the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 7.
[0031] From the above examples, it can be seen that when the mass ratio of 18-crown ether to 15-crown ether is 1:1-1.5, the sodium ion and potassium ion in the product are relatively low. Therefore, it is only necessary to control the mass ratio of 18-crown ether to 15-crown ether to be 1:1-1.5.
[0032] Examples 39-43 The other steps of Examples 39-43 are the same as those of Example 1, except that the stirring speed in step (3) is changed. The purity of the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 8.
[0033] It can be seen from the above embodiments that when the stirring speed in step (3) is 400-800 r / min, the purity of the product is relatively high, and the preferred stirring speed is 600-800 r / min.
[0034] Examples 44-49 Examples 44-49 are the same as Example 1 except that the drying temperature in step (4) is changed. The moisture content of the product lithium bis(fluoromethylsulfonyl)imide is shown in Table 9.
[0035] From the above examples, it can be seen that when the drying temperature is 130-160°C, the moisture content of the product lithium bis(fluoromethylsulfonyl)imide is relatively low. Therefore, it is only necessary to control the drying temperature to 130-160°C.
[0036] Comparative Example 1 Comparative Example 1 is the same as Example 1 in other steps, except that the lithium source is changed from lithium hydroxide to lithium carbonate. The yield and purity of the obtained product, lithium bisfluoromethylsulfonyl imide, are shown in Table 10.
Claims
1. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source, characterized in that: The following steps are involved: (1) Place dichloromethane in a reaction flask and add lithium hydroxide monohydrate; (2) Place the reaction system in (1) at 0-5°C, add bis(fluoromethanesulfonic acid) imide under stirring and react for 2-4 hours; (3) heating the reaction system to 20-25°C, adding thionyl chloride, stirring to remove water, filtering, adding dichloromethane and crown ether to the filter cake for pulping, and filtering to obtain a wet product of lithium bis(fluoromethylsulfonyl)imide; (4) Drying the wet product of lithium bis(fluoromethylsulfonyl imide) in step (3) to obtain a finished product of lithium bis(fluoromethylsulfonyl imide).
2. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 1, characterized in that: In step (1), the mass ratio of dichloromethane to lithium hydroxide monohydrate is 12-15:
1.
3. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 2, characterized in that: In step (1), the mass ratio of dichloromethane to lithium hydroxide monohydrate is 13.73:
1.
4. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 1, characterized in that: In step (2), the equivalent ratio of lithium hydroxide monohydrate to bis(fluoromethanesulfonic acid) imide is 0.96-1.1:
1.
5. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 4, characterized in that: In step (2), the stirring speed is 300-800 r / min.
6. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 1, characterized in that: In step (3), the liquid-to-solid mass ratio of the dichloromethane and crown ether to the filter cake is 2.8-3.3:
1.
7. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 6, characterized in that: In step (3), the mass ratio of dichloromethane to crown ether is 1000-5000:
1.
8. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 7, characterized in that: In step (3), the crown ether is a mixture of 18-crown-6 and 15-crown-5, and the mixing mass ratio is 1:1-1:1.
5.
9. A method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source as claimed in claim 8, characterized in that: In step (3), the stirring and dewatering speed is 300-800 r / min, and the stirring time is 10-15 h.
10. The method for preparing lithium bis(fluoromethylsulfonyl)imide using lithium hydroxide as a lithium source according to claim 1, characterized in that: In step (4), the drying temperature is 110-160°C.