阅读说明：本技术 一种双氟磺酰亚胺锂的制备方法 (Preparation method of lithium bis (fluorosulfonyl) imide ) 是由 段宾 周阳 王�锋 郭琬 辛婉婉 李亚楠 王晓峰 耿梦湍 薛峰峰 闫春生 于 2021-09-18 设计创作，主要内容包括：本发明属于双氟磺酰亚胺锂的制备领域,具体涉及一种双氟磺酰亚胺锂的制备方法。该方法包括以下步骤：双氟磺酰亚胺与磷酸锂在非水溶剂中反应,得到含双氟磺酰亚胺锂的反应液,后处理得到双氟磺酰亚胺锂。本发明的双氟磺酰亚胺锂的制备方法,工艺简单,反应快速,不副产酸或水,省去降酸或除水等提纯过程,得到的双氟磺酰亚胺锂纯度高、收率高,且溶剂可循环利用。(The invention belongs to the field of preparation of lithium bis (fluorosulfonyl) imide, and particularly relates to a preparation method of lithium bis (fluorosulfonyl) imide. The method comprises the following steps: reacting the difluoride sulfimide with lithium phosphate in a non-aqueous solvent to obtain reaction liquid containing the difluoride sulfimide lithium, and performing post-treatment to obtain the difluoride sulfimide lithium. The preparation method of the lithium bis (fluorosulfonyl) imide provided by the invention has the advantages of simple process, quick reaction, no by-product of acid or water, no need of purification processes such as deacidification or dehydration, high purity and high yield of the obtained lithium bis (fluorosulfonyl) imide, and the solvent can be recycled.)

1. A preparation method of lithium bis (fluorosulfonyl) imide is characterized by comprising the following steps: reacting the difluoride sulfimide with lithium phosphate in a non-aqueous solvent to obtain reaction liquid containing the difluoride sulfimide lithium, and performing post-treatment to obtain the difluoride sulfimide lithium.

2. The method for preparing lithium bis (fluorosulfonyl) imide according to claim 1, wherein the molar ratio of bis (fluorosulfonyl) imide acid to lithium phosphate is 2: (1-1.8).

3. The method for preparing lithium bis (fluorosulfonyl) imide according to claim 1, wherein the reaction temperature is 0 to 60 ℃.

4. The method for preparing lithium bis (fluorosulfonyl) imide according to claim 3, wherein the reaction time is 1 to 5 hours.

5. The method for preparing lithium bis (fluorosulfonyl) imide according to any one of claims 1 to 4, wherein said reaction is carried out by: firstly, mixing lithium phosphate and a non-aqueous solvent to prepare a mixed solution, and then dropwise adding the bis-fluorosulfonyl imide into the mixed solution.

6. The method for producing lithium bis (fluorosulfonyl) imide according to claim 5, wherein the time for dropping bis (fluorosulfonyl) imide is at least 10% of the reaction time.

7. The method for preparing lithium bis (fluorosulfonyl) imide according to claim 1, wherein said non-aqueous solvent is one or more selected from the group consisting of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, dichloromethane, and dichloroethane.

8. The preparation method of lithium bis (fluorosulfonyl) imide according to any one of claims 1 to 4 and 7, wherein the post-treatment comprises filtration, and the obtained filtrate is concentrated, crystallized and dried to obtain a finished lithium bis (fluorosulfonyl) imide.

9. The method for producing lithium bis (fluorosulfonyl) imide according to claim 8, wherein said concentration crystallization is concentration under reduced pressure; the temperature of the reduced pressure concentration does not exceed 60 ℃.

10. The method for producing lithium bis (fluorosulfonyl) imide according to claim 8, wherein the lithium phosphate is produced by reacting the filter residue obtained by filtration with lithium carbonate or lithium hydroxide.

Technical Field

The invention belongs to the field of preparation of lithium bis (fluorosulfonyl) imide, and particularly relates to a preparation method of lithium bis (fluorosulfonyl) imide.

Background

In recent years, the electric automobile industry develops rapidly, wherein the lithium battery automobile develops fastest due to excellent comprehensive performance of the battery. The lithium bis (fluorosulfonyl) imide is a novel electrolyte lithium salt in the lithium battery electrolyte, and compared with the traditional electrolyte lithium hexafluorophosphate, lithium ions in the lithium bis (fluorosulfonyl) imide are easier to dissociate and have higher conductivity; the decomposition temperature is high, and the thermal stability and the safety performance are good; in addition, the material also has unique effect on improving the performances of high-temperature storage, low-temperature discharge and the like. In conclusion, the lithium bis (fluorosulfonyl) imide has excellent chemical properties and safety and good development prospect.

In the prior patents, the following reports about the preparation of lithium bis (fluorosulfonyl) imide are mainly found:

patents CN104925765B and CN105731399B all adopt bis-fluoro sulfonyl imide to react with alkaline lithium salt to obtain lithium bis-fluoro sulfonyl imide, and since acid-base neutralization can release heat violently, low-temperature reaction is required, energy consumption is high, and a large amount of water is produced as a byproduct, which greatly increases the difficulty of product purification and the difficulty of solvent recovery and purification.

In patent CN106276829B, firstly, dichlorosulfimide and an organic solvent are fully mixed and condensed, and then lithium fluoride and liquid hydrogen fluoride are sequentially added into a reactor to be heated and react to prepare the lithium difluorosulfimide. The method uses and produces hydrogen fluoride as a byproduct, so that the product has high acidity, high purification difficulty, high deacidification cost for solvent recovery, and special equipment is required, and the method is not beneficial to industrial production.

In patent application CN107416782A, bis-fluorosulfonyl imide is reacted with RLi to obtain lithium bis-fluorosulfonyl imide and an organic HR, organic byproducts and a reaction solvent are difficult to completely separate, the solvent is difficult to purify and recover, and environmental load and production cost are increased.

Patent application CN111533094A discloses a method for simply preparing high-purity lithium bis (fluorosulfonyl) imide, which comprises the steps of carrying out exchange reaction on bis (fluorosulfonyl) imide and special lithium salt to generate lithium bis (fluorosulfonyl) imide and gas HX, and then filtering, washing and vacuum-drying to obtain the high-purity lithium bis (fluorosulfonyl) imide. Although the method does not need to remove water and impurities, the methyl lithium and the lithium hydride used in the method have active properties and are easy to lose control of reaction, and the generated hydrogen is flammable and explosive gas, so that the potential safety hazard is huge.

The existing preparation method of the lithium bis (fluorosulfonyl) imide has the problems of water, acid, organic matters, flammable and explosive gases and the like as by-products, and the factors of high purification difficulty, high cost, high potential safety hazard and the like seriously restrict the industrialization process of the lithium bis (fluorosulfonyl) imide.

Disclosure of Invention

The invention aims to provide a preparation method of lithium bis (fluorosulfonyl) imide, which does not produce acid or water, omits purification processes such as deacidification or dehydration and the like, and has high purity and high yield of the obtained lithium bis (fluorosulfonyl) imide.

In order to realize the purpose, the technical scheme of the preparation method of the lithium bis (fluorosulfonyl) imide provided by the invention is as follows:

a preparation method of lithium bis (fluorosulfonyl) imide comprises the following steps: reacting the difluoride sulfimide with lithium phosphate in a non-aqueous solvent to obtain reaction liquid containing the difluoride sulfimide lithium, and performing post-treatment to obtain the difluoride sulfimide lithium.

The preparation method of the lithium bis (fluorosulfonyl) imide provided by the invention has the advantages of simple process, quick reaction, no by-product of acid or water, no need of purification processes such as deacidification or dehydration, high purity and high yield of the obtained lithium bis (fluorosulfonyl) imide, and the solvent can be recycled.

Preferably, the molar ratio of the bis-fluorosulfonyl imide acid to lithium phosphate is 2: (1-1.8).

Preferably, the reaction temperature is 0-60 ℃. More preferably, the reaction time is 1-5 h.

To further optimize the purity and yield of the product, preferably, the reaction is carried out in the following manner: firstly, mixing lithium phosphate and a non-aqueous solvent to prepare a mixed solution, and then dropwise adding the bis-fluorosulfonyl imide into the mixed solution. Further preferably, the time for dropping the bis-fluorosulfonyl imide is at least 10% of the reaction time. More preferably 10 to 35%. The reaction time was not counted.

Preferably, the non-aqueous solvent is selected from one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, dichloromethane and dichloroethane.

The post-treatment is to extract the lithium bis (fluorosulfonyl) imide from the reaction solution, and generally no chemical reaction occurs, such as filtration, concentration crystallization, drying and the like. Preferably, the post-treatment comprises filtration, and the obtained filtrate is concentrated, crystallized and dried to obtain the finished product of the lithium bis (fluorosulfonyl) imide. The concentration crystallization is decompression concentration; the temperature of the reduced pressure concentration does not exceed 60 ℃.

Preferably, the filter residue obtained by filtering is reacted with lithium carbonate or lithium hydroxide to prepare lithium phosphate.

Detailed Description

The preparation method of the lithium bis (fluorosulfonyl) imide (LiFSI) mainly comprises the steps of obtaining lithium bis (fluorosulfonyl) imide and lithium dihydrogen phosphate (insoluble in a solvent) by utilizing the contact reaction of the lithium bis (fluorosulfonyl) imide and the lithium phosphate in a non-aqueous solvent, filtering, concentrating, crystallizing and drying a reaction liquid to obtain the lithium bis (fluorosulfonyl) imide, wherein the reaction principle is as follows: 2HFSI + Li₃PO₄＝2LiFSI+LiH₂PO₄。

The nonaqueous solvent preferably has a moisture content of less than 50 ppm. More preferably less than 30ppm, still more preferably less than 10 ppm; under the condition of low-moisture solvent, the product has less deterioration and the solvent is easy to recover. The non-aqueous solvent is preferably one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylene chloride, and dichloroethane, and more preferably dimethyl carbonate. The amount of the non-aqueous solvent is 700g per 1-1.5 mol of lithium phosphate.

After the reaction, the lithium bis (fluorosulfonyl) imide is easy to dissolve in the solvent, the excessive lithium phosphate and the byproduct lithium dihydrogen phosphate are insoluble in the solvent, separation can be realized by filtration, and the appropriate molar ratio can ensure complete reaction of the lithium bis (fluorosulfonyl) imide and can not cause waste of a large amount of raw materials. The molar ratio of bis-fluorosulfonylimide to lithium phosphate is preferably 2: (1 to 1.6), more preferably 2: (1.05 to 1.4), most preferably 2: (1.05-1.2).

The reaction is carried out at normal temperature or lower temperature, and can be 0-60 ℃, more preferably 0-40 ℃, and most preferably 10-30 ℃. The reaction time is preferably 1 to 5 hours, and more preferably 1.2 to 3 hours. At low temperature, the reaction activity of the raw materials is low, the reaction period is long, and the yield is low; at high temperature, the product is deteriorated and the side reaction is increased. The preferable reaction temperature is adopted, so that the product with high purity and yield can be obtained more favorably.

Filtering after reaction, concentrating, crystallizing and drying to obtain the lithium bis (fluorosulfonyl) imide; concentrating the crystals, preferably concentrating under reduced pressure; under the condition of solvent, the high-temperature concentration process is easy to generate side reaction, so that the purity of the product is low, and therefore, the temperature of the reduced pressure concentration is preferably not more than 60 ℃, and more preferably not more than 50 ℃. The pressure is-0.090 to-0.098 MPa, preferably-0.095 MPa. After concentration and crystallization, drying is preferred, wherein the drying temperature is preferably 70-140 ℃, more preferably 80-120 ℃, and further preferably 90-110 ℃; the drying is preferably carried out in a protective atmosphere; the protective atmosphere is preferably nitrogen.

The filter residue is mainly excessive lithium phosphate and byproduct lithium dihydrogen phosphate, lithium carbonate or lithium hydroxide is added for reaction to obtain lithium phosphate, the lithium phosphate can be reused for synthesis reaction, and the method is simple to operate, high in practicability, economical and environment-friendly. The relevant reaction principle is as follows: LiH₂PO₄+Li₂CO₃＝Li₃PO₄+H₂O+CO₂、LiH₂PO₄+2LiOH＝Li₃PO₄+2H₂O。

By adopting the preferable mode, the related products with the purity of the bis-fluorosulfonyl imide and the lithium phosphate both reaching more than 99.5 percent can be obtained.

The technical solutions will be clearly and completely described below with reference to the embodiments of the present invention, and it should be understood that the described embodiments are only a part of specific embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The specific embodiment of the preparation method of the lithium bis (fluorosulfonyl) imide of the present invention is as follows:

example 1

The preparation method of lithium bis (fluorosulfonyl) imide of the present embodiment includes the following steps: 60.9g of lithium phosphate is added into 350g of dimethyl carbonate (with 30ppm of water) at the temperature of 10 ℃ and stirred for dispersion, and bis (fluorosulfonyl) imide (181 g) is dropwise added under the constant temperature condition, the dropwise addition takes 0.5h, and the reaction lasts for 3h (the molar ratio of the bis (fluorosulfonyl) imide to the lithium phosphate is 2: 1.05). Filtering the reaction solution, concentrating the filtrate at 50 ℃ under reduced pressure (-0.095MPa) for crystallization, and drying the crystal at 100 ℃ under the protection of nitrogen to obtain pure product lithium bis (fluorosulfonyl) imide with the purity of 99.2% and the yield of 90.6%; adding lithium carbonate into the filter residue to react in water, filtering and drying to obtain the lithium phosphate with the purity of 99.5 percent and the yield of 92.4 percent.

Example 2

The preparation method of lithium bis (fluorosulfonyl) imide of the present embodiment includes the following steps: 63.8g of lithium phosphate is added into 350g of dimethyl carbonate (water content is 10ppm) at the temperature of 20 ℃ and stirred for dispersion, bis (fluorosulfonyl) imide (181 g) is dropwise added under the constant temperature condition, the dropwise addition takes 0.5h, and the reaction lasts for 2h (the molar ratio of the bis (fluorosulfonyl) imide to the lithium phosphate is 2: 1.1). Filtering the reaction solution, concentrating the filtrate at 50 ℃ under reduced pressure (-0.095MPa) for crystallization, and drying the crystal at 95 ℃ under the protection of nitrogen to obtain pure product lithium bis (fluorosulfonyl) imide with the purity of 99.5% and the yield of 94.3%; adding lithium carbonate into the filter residue to react in water, filtering and drying to obtain the lithium phosphate with the purity of 99.6 percent and the yield of 95.1 percent.

Example 3

The preparation method of lithium bis (fluorosulfonyl) imide of the present embodiment includes the following steps: 69.6g of lithium phosphate is added into 350g of dimethyl carbonate (water content is 10ppm) at the temperature of 20 ℃ and stirred for dispersion, and bis (fluorosulfonyl) imide (181 g; dropwise addition takes 0.5h) is added at constant temperature and reacted for 1.5h (molar ratio of bis (fluorosulfonyl) imide to lithium phosphate is 2: 1.2). Filtering the reaction solution, concentrating the filtrate at 50 ℃ under reduced pressure (-0.095MPa) for crystallization, and drying the crystal at 90 ℃ under the protection of nitrogen to obtain pure product lithium bis (fluorosulfonyl) imide with the purity of 99.8% and the yield of 91.5%; adding lithium carbonate into the filter residue to react in water, filtering and drying to obtain the lithium phosphate with the purity of 99.6 percent and the yield of 96.7 percent.

Example 4

The preparation method of lithium bis (fluorosulfonyl) imide of the present embodiment includes the following steps: 63.8g of lithium phosphate is added into 350g of dimethyl carbonate (water content is 10ppm) at the temperature of 60 ℃ and stirred for dispersion, and bis (fluorosulfonyl) imide (181 g; dropwise addition takes 0.5h) is added at constant temperature and reacted for 1.5h (molar ratio of bis (fluorosulfonyl) imide to lithium phosphate is 2: 1.1). Filtering the reaction solution, concentrating the filtrate at 50 ℃ under reduced pressure (-0.095MPa) for crystallization, and drying the crystal at 95 ℃ under the protection of nitrogen to obtain a pure product of the lithium bis (fluorosulfonyl) imide, wherein the purity is 96.6 percent, and the yield is 88.2 percent; adding lithium carbonate into the filter residue to react in water, filtering and drying to obtain the lithium phosphate with the purity of 97.4 percent and the yield of 91.9 percent.

Example 5

The preparation method of lithium bis (fluorosulfonyl) imide of the present embodiment includes the following steps: 63.8g of lithium phosphate is added into 350g of dimethyl carbonate (water content is 10ppm) at the temperature of 20 ℃ and stirred for dispersion, and bis (fluorosulfonyl) imide (181 g; dropwise addition takes 0.1h) is added at constant temperature and reacted for 2h (molar ratio of bis (fluorosulfonyl) imide to lithium phosphate is 2: 1.1). Filtering the reaction solution, concentrating the filtrate at 50 ℃ under reduced pressure (-0.095MPa) for crystallization, and drying the crystal at 95 ℃ under the protection of nitrogen to obtain pure product lithium bis (fluorosulfonyl) imide with the purity of 98.2% and the yield of 90.5%; adding lithium carbonate into the filter residue to react in water, filtering and drying to obtain the lithium phosphate with the purity of 98.7 percent and the yield of 92.1 percent.

In other embodiments of the method for preparing lithium bis (fluorosulfonyl) imide of the present invention, other non-aqueous solvents defined in the present invention, such as ethyl methyl carbonate, diethyl carbonate, etc., can be selected to achieve corresponding improvement effects.