A preparation method of lithium bis(fluorosulfonyl)imide

Abstract

The present invention belongs to the technical field of lithium-ion battery electrolyte preparation, and specifically relates to a method for preparing lithium bis(fluorosulfonyl)imide, comprising: reacting a lithium source with bis(chlorosulfonyl)imide to obtain lithium bis(chlorosulfonyl)imide; and reacting the lithium bis(chlorosulfonyl)imide with a fluorination agent to obtain lithium bis(fluorosulfonyl)imide. The present invention provides a novel synthetic route for lithium bis(fluorosulfonyl)imide, utilizing lithiation followed by fluorination to prepare the lithium bis(fluorosulfonyl)imide. The method can be carried out under mild reaction conditions and does not require the use of high-temperature hydrogen fluoride, resulting in a simple process, low energy consumption, and high safety.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery electrolyte preparation, and particularly relates to a method for preparing lithium bis(fluorosulfonyl)imide. Background Art

[0002] Lithium bis(fluorosulfonyl)imide (LiFSI) is a new type of electrolyte that can be used in lithium-ion battery electrolytes. Compared with the traditional lithium salt lithium hexafluorophosphate (LiPF6), the lithium ions in lithium bis(fluorosulfonyl)imide are easier to dissociate, so it has higher conductivity; the decomposition temperature of LiFSI is higher than 200°C, and its thermal stability and safety performance are significantly better than LiPF6; in addition, LiFSI also has unique effects in improving high-temperature storage and low-temperature discharge, and LiFSI has excellent properties such as good compatibility with electrodes. Therefore, LiFSI is a lithium-ion battery electrolyte with good prospects.

[0003] Currently, the main method for preparing lithium bis(fluorosulfonyl)imide is to first fluorinate bis(chlorosulfonyl)imide at high temperature to synthesize bis(fluorosulfonyl)imide, which is then reacted with a lithium salt to prepare lithium bis(fluorosulfonyl)imide. For example, patent document CN113511639A discloses reacting sulfur trioxide, ammonia, and thionyl chloride to produce bis(chlorosulfonyl)imide, followed by sequential high-temperature fluorination and lithiation with HF to produce lithium bis(fluorosulfonyl)imide. This process uses high-temperature HF, consumes a lot of energy, and is highly hazardous. Summary of the Invention

[0004] The present invention aims to provide a method for preparing lithium bis(fluorosulfonyl)imide, so as to solve the problems of high energy consumption and high risk factor in the existing method for preparing lithium bis(fluorosulfonyl)imide.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A preparation method of lithium bis(fluorosulfonyl)imide comprises: reacting a lithium source with bis(chlorosulfonyl)imide to obtain lithium bis(chlorosulfonyl)imide; and reacting the lithium bis(chlorosulfonyl)imide with a fluorination agent to obtain lithium bis(fluorosulfonyl)imide.

[0007] The beneficial effects of the above technical solution are as follows: the present invention is an improved invention, which provides a new synthesis route for lithium bis(fluorosulfonyl)imide. The present invention adopts a method of first lithiation and then fluorination to prepare lithium bis(fluorosulfonyl)imide. The present invention can be carried out under mild reaction conditions. The present invention does not require the use of high-temperature hydrogen fluoride, and has the advantages of simple process, low energy consumption, and high safety. It solves the problems of high energy consumption and high risk factor in the existing preparation methods of lithium bis(fluorosulfonyl)imide. Moreover, the method of the present invention can obtain high-purity lithium bis(fluorosulfonyl)imide, which can meet the use requirements of lithium-ion battery electrolytes, improve the safety of battery products, and promote the development of the new energy vehicle industry. In addition, the method of the present invention also has the advantage of high yield and is suitable for promotion and application.

[0008] As a further improvement, the reacting of the lithium source with bischlorosulfonyl imide includes: mixing the lithium source with an organic solvent to obtain a lithium source dispersion, wherein the organic solvent is ethyl methyl carbonate or dimethyl carbonate, and then dropwise adding bischlorosulfonyl imide to the lithium source dispersion, and reacting after the dropwise addition is completed.

[0009] The above technical solution has the beneficial effect of facilitating sufficient contact between the lithium source and bis(chlorosulfonylimide) by preparing a lithium source dispersion, thereby promoting the reaction. Adding bis(chlorosulfonylimide) to the lithium source system facilitates sufficient reaction of the bis(chlorosulfonylimide), further increasing the yield of the final product, lithium bis(fluorosulfonylimide).

[0010] As a further improvement, the lithium source is lithium chloride or lithium hydride, and the temperature for the reaction of the lithium source with bischlorosulfonyl imide is 10-20°C.

[0011] The above technical solution has the following beneficial effects: the reaction of the lithium source with bis(chlorosulfonyl)imide of the present invention has high reactivity, can occur under mild conditions, does not generate water, and reduces the content of impure water. The above temperature facilitates rapid lithiation reaction, which helps improve product yield and reaction efficiency. The lithiation reaction of the present invention can be carried out at a mild temperature, with low energy consumption and high safety. If the temperature is too low, the reaction rate will be slow, the reaction time will be too long, and the product yield will be low; if the temperature is too high, the byproducts will increase.

[0012] The reaction equation of the lithium source of the present invention and bis(chlorosulfonyl)imide is as follows:

[0013] HClSI+LiCl=LiClSI+HCl

[0014] HClSI+LiH=LiClSI+H2

[0015] As a further improvement, the molar ratio of the bischlorosulfonyl imide to the lithium source is 1:(1.05-1.1).

[0016] The beneficial effect of the above technical solution is that under the above conditions, bischlorosulfonylimide can be completely reacted, further improving the yield of the final product, lithium bisfluorosulfonylimide.

[0017] Furthermore, the mass ratio of bischlorosulfonyl imide to the organic solvent is 1:(2-2.4).

[0018] As a further improvement, the time for dropwise adding bischlorosulfonyl imide is 0.3 to 0.5 h, and the reaction time of the lithium source and bischlorosulfonyl imide is 1.5 to 2.5 h.

[0019] The beneficial effect of the above technical solution is that under the above conditions, all bischlorosulfonyl imide can be converted into lithium bischlorosulfonyl imide, further improving the yield of the lithium bisfluorosulfonyl imide product.

[0020] Furthermore, after the reaction between bischlorosulfonyl imide and the lithium source is completed, the method further comprises: filtering the solution after the reaction between bischlorosulfonyl imide and the lithium source, washing and drying the filter residue for reuse, the drying temperature of the filter residue being 80-90° C., the filtrate being lithium bischlorosulfonyl imide, and reacting the filtrate with a fluorination reagent.

[0021] As a further improvement, the fluorination agent is HF, and the reaction temperature of the lithium bis(chlorosulfonyl)imide and the fluorination agent is 35-70°C.

[0022] The beneficial effects of the above technical solution are as follows: under the above conditions, lithium bis(chlorosulfonylimide) can be caused to undergo a fluorination reaction with HF, thereby improving the yield and reaction efficiency of the product. The fluorination reaction of the present invention can be carried out at a mild temperature, with low energy consumption and high safety. If the reaction temperature is too low, the reaction rate slows down and the reaction yield decreases. If the reaction temperature is too high, the reaction is too intense and difficult to control.

[0023] The reaction equation of lithium bis(chlorosulfonyl)imide of the present invention and fluorination agent is as follows:

[0024] LiClSI+2HF=LiFSI+2HCl

[0025] As a further improvement, the molar ratio of the lithium bis(chlorosulfonyl)imide to the fluorination agent is 1:(2-2.2).

[0026] The beneficial effect of the above technical solution is that under the above conditions, lithium bis(chlorosulfonylimide) is completely converted into lithium bis(fluorosulfonylimide), further improving the yield of the final product, lithium bis(fluorosulfonylimide).

[0027] As a further improvement, the reaction of the lithium bis(chlorosulfonyl)imide with the fluorination agent is carried out in a conventional reactor or a microchannel reactor, and the pressure of the reaction of the lithium bis(chlorosulfonyl)imide with the fluorination agent is 0.1-0.5 MPa.

[0028] The above technical solution has the beneficial effect of facilitating the complete reaction of lithium bis(chlorosulfonylimide) with the fluorination agent under the above conditions, further increasing the yield of lithium bis(fluorosulfonylimide). If the reaction pressure is too low, the reaction becomes more difficult to carry out; if the reaction pressure is too high, the reaction yield and reaction rate cannot be significantly improved, and a significant safety hazard may arise.

[0029] As a further improvement, the reaction time of the lithium bis(chlorosulfonyl)imide and the fluorination agent is 0.4 to 6 hours.

[0030] The beneficial effect of the above technical solution is that under the above conditions, it is conducive to the complete reaction of lithium bis(chlorosulfonylimide) and the fluorination agent, and further improves the yield of the final product lithium bis(fluorosulfonylimide).

[0031] As a further improvement, the reaction of lithium bis(chlorosulfonyl)imide and the fluorination agent is carried out in a microchannel reactor.

[0032] The beneficial effects of the above technical solution are: compared with conventional reactors, microchannel reactors enable more complete contact between materials, accelerating mass and heat transfer between materials. The reaction of lithium bis(chlorosulfonyl)imide with a fluorination agent in a microchannel reactor can shorten the reaction time and improve reaction efficiency.

[0033] Furthermore, after the reaction of lithium bis(chlorosulfonylimide) and the fluorination agent is completed, the method further includes purging the reacted solution with nitrogen to obtain lithium bis(fluorosulfonylimide). For example, the nitrogen purge temperature is 5 to 10°C and the nitrogen purge time is 0.3 to 0.6 hours. The nitrogen purge can remove the byproduct hydrogen chloride and unreacted hydrogen fluoride gas. DETAILED DESCRIPTION

[0034] The preparation method of lithium bis(fluorosulfonyl)imide in an embodiment of the present invention comprises: reacting a lithium source with bis(chlorosulfonyl)imide to obtain lithium bis(chlorosulfonyl)imide; and reacting the lithium bis(chlorosulfonyl)imide with a fluorination agent to obtain lithium bis(fluorosulfonyl)imide.

[0035] The present invention provides a new synthesis route for lithium bis(fluorosulfonyl)imide. The present invention adopts a method of first lithiation and then fluorination to prepare lithium bis(fluorosulfonyl)imide. The present invention has the advantages of simple process, low energy consumption and high safety.

[0036] The technical solution of the present invention is further described in detail below with reference to specific embodiments. The raw materials in the following embodiments are all conventional commercially available products.

[0037] Example 1

[0038] At 10° C., 44.63 g (1.05 mol) of lithium chloride was added to 440 g of dimethyl carbonate (water 10 ppm) with stirring and dispersion, and 214 g (1 mol) of bis(chlorosulfonyl)imide was added dropwise at a constant temperature for 0.5 h, and the mixture was reacted for 2.5 h to obtain a reaction solution; the reaction solution was filtered, the filter cake was dried at 90° C., and 330 g of the filtrate (containing 110 g, 0.5 mol of lithium bis(chlorosulfonyl)imide) and 0.2 g (1.01 mol) of HF were simultaneously fed through a microchannel reactor for reaction at a reaction temperature of 40° C., a pressure of 0.2 MPa, and a reaction time of 0.6 h; after completion of the reaction, the temperature was lowered to 10° C. and nitrogen was purged for 0.5 h to obtain a liquid salt, namely lithium bis(fluorosulfonyl)imide, with a purity of 99.9% and a yield of 95.4%.

[0039] Example 2

[0040] At 20° C., 46.75 g (1.1 mol) of lithium chloride was added to 513.3 g of ethyl methyl carbonate (water 5 ppm) with stirring and dispersion, and 214 g (1 mol) of bis(chlorosulfonyl)imide was added dropwise at a constant temperature for 0.3 h, and the mixture was reacted for 1.5 h to obtain a reaction solution; the reaction solution was filtered, the filter cake was dried at 90° C., and 366.67 g of the filtrate (containing 110 g, 0.5 mol of lithium bis(chlorosulfonyl)imide) and 0.1 g (1.005 mol) of HF were simultaneously fed through a microchannel reactor for reaction at a reaction temperature of 35° C., a pressure of 0.1 MPa, and a reaction time of 1 h; after completion of the reaction, the temperature was lowered to 8° C. and nitrogen was purged for 0.6 h to obtain a liquid salt, i.e., lithium bis(fluorosulfonyl)imide, with a purity of 99.94% and a yield of 96.8%.

[0041] Example 3

[0042] At 15° C., 8.8 g (1.1 mol) of lithium hydride was added to 440 g of dimethyl carbonate (water 5 ppm) with stirring and dispersion, and 214 g (1 mol) of bis(chlorosulfonyl)imide was added dropwise at a constant temperature for 0.4 h, and the mixture was reacted for 2 h to obtain a reaction solution; the reaction solution was filtered, the filter cake was dried at 80° C., and 330 g of the filtrate (containing 110 g, 0.5 mol of lithium bis(chlorosulfonyl)imide) and 0.2 g (1.01 mol) of HF were simultaneously fed through a microchannel reactor for reaction at a reaction temperature of 50° C., a pressure of 0.3 MPa, and a reaction time of 0.4 h; after completion of the reaction, the temperature was lowered to 5° C. and nitrogen was purged for 0.3 h to obtain a liquid salt, namely lithium bis(fluorosulfonyl)imide, with a purity of 99.92% and a yield of 96.0%.

[0043] Example 4

[0044] At 20 ° C, 44.63 g (1.05 mol) of lithium chloride was added to 440 g of dimethyl carbonate (water 10 ppm) with stirring and dispersion, and 214 g (1 mol) of bischlorosulfonyl imide was added dropwise at a constant temperature for 0.5 h, and the reaction was carried out for 2.5 h to obtain a reaction solution; the reaction solution was filtered, and the filter cake was dried at 90 ° C; lithium bischlorosulfonyl imide and HF were reacted in a conventional reactor at a reaction temperature of 40 ° C and a pressure of 0.2 MPa. 330 g of the filtrate (containing 110 g, 0.5 mol of lithium bischlorosulfonyl imide) was stirred and 20.2 g (1.01 mol) of HF was pumped into the reaction for 1 h and the reaction time was 6 h; after the reaction was completed, the temperature was lowered to 10 ° C and nitrogen was purged for 0.5 h to obtain a liquid salt, i.e. lithium bisfluorosulfonyl imide, with a purity of 95.1% and a yield of 85.0%.

[0045] Example 5

[0046] At 20 ° C, 8.8 g (1.1 mol) of lithium hydride was added to 513.3 g of ethyl methyl carbonate (water 5 ppm) with stirring and dispersion, and 214 g (1 mol) of bischlorosulfonyl imide was added dropwise at a constant temperature for 0.3 h, and the reaction was carried out for 1.5 h to obtain a reaction solution; the reaction solution was filtered, and the filter cake was dried at 90 ° C; lithium bischlorosulfonyl imide and HF were reacted in a conventional reactor at a reaction temperature of 70 ° C and a pressure of 0.5 MPa. 330 g of the filtrate (containing 110 g, 0.5 mol of lithium bischlorosulfonyl imide) was stirred and 20.2 g (1.01 mol) of HF was pumped into the reaction for 0.8 h and the reaction time was 4 h; after the reaction was completed, the temperature was lowered to 10 ° C, and nitrogen was purged for 0.5 h to obtain a liquid salt, i.e. lithium bisfluorosulfonyl imide, with a purity of 97.9% and a yield of 89.3%.

[0047] Example 6

[0048] At 20° C., 46.75 g (1.1 mol) of lithium chloride was added to 513.3 g of ethyl methyl carbonate (water 5 ppm) with stirring and dispersion, and 214 g (1 mol) of bis(chlorosulfonyl)imide was added dropwise at a constant temperature for 0.3 h, and the mixture was reacted for 1.5 h to obtain a reaction solution; the reaction solution was filtered, the filter cake was dried at 90° C., and 366.67 g of the filtrate (containing 110 g, 0.5 mol of lithium bis(chlorosulfonyl)imide) and 20 g (1 mol) of HF were simultaneously fed through a microchannel reactor for reaction at a reaction temperature of 35° C., a pressure of 0.1 MPa, and a reaction time of 1 h; after completion of the reaction, the temperature was lowered to 8° C. and nitrogen was purged for 0.6 h to obtain a liquid salt, i.e., lithium bis(fluorosulfonyl)imide, with a purity of 99.97% and a yield of 93.2%.

[0049] Example 7

[0050] At 20° C., 46.75 g (1.1 mol) of lithium chloride was added to 513.3 g of ethyl methyl carbonate (water 5 ppm) with stirring and dispersion, and 214 g (1 mol) of bis(chlorosulfonyl)imide was added dropwise at a constant temperature for 0.3 h, and the mixture was reacted for 1.5 h to obtain a reaction solution; the reaction solution was filtered, the filter cake was dried at 90° C., and 366.67 g of the filtrate (containing 110 g, 0.5 mol of lithium bis(chlorosulfonyl)imide) and 22 g (1.1 mol) of HF were simultaneously fed through a microchannel reactor for reaction at a reaction temperature of 35° C., a pressure of 0.1 MPa, and a reaction time of 1 h; after completion of the reaction, the temperature was lowered to 8° C. and nitrogen was purged for 0.6 h to obtain a liquid salt, i.e., lithium bis(fluorosulfonyl)imide, with a purity of 99.9% and a yield of 97.7%.

Claims

1. A method for preparing lithium bis(fluorosulfonyl)imide, characterized in that: include: reacting a lithium source with bischlorosulfonyl imide to obtain lithium bischlorosulfonyl imide; reacting the lithium bis(chlorosulfonylimide) with a fluorination agent to obtain lithium bis(fluorosulfonylimide); The fluorination agent is HF, and the reaction temperature of the lithium bis(chlorosulfonyl)imide and the fluorination agent is 35-70°C.

2. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, wherein The reacting of the lithium source with bischlorosulfonyl imide comprises: mixing the lithium source with an organic solvent to obtain a lithium source dispersion, wherein the organic solvent is ethyl methyl carbonate or dimethyl carbonate; then dropwise adding bischlorosulfonyl imide into the lithium source dispersion; and reacting after the dropwise addition is completed.

3. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 2, wherein: The lithium source is lithium chloride or lithium hydride, and the reaction temperature of the lithium source and bischlorosulfonyl imide is 10-20°C.

4. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 2, wherein: The molar ratio of the bischlorosulfonyl imide to the lithium source is 1:(1.05-1.1).

5. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 2, wherein: The time for dropwise addition of bischlorosulfonyl imide is 0.3-0.5 h, and the reaction time of the lithium source and bischlorosulfonyl imide is 1.5-2.5 h.

6. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, wherein: The molar ratio of the lithium bis(chlorosulfonyl)imide to the fluorination agent is 1:(2-2.2).

7. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, wherein: The reaction of the lithium bis(chlorosulfonyl)imide with the fluorination agent is carried out in a conventional reactor or a microchannel reactor, and the pressure of the reaction of the lithium bis(chlorosulfonyl)imide with the fluorination agent is 0.1-0.5 MPa.

8. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 1, wherein: The reaction time of the lithium bis(chlorosulfonyl)imide and the fluorination agent is 0.4 to 6 hours.

9. The method for preparing lithium bis(fluorosulfonyl)imide according to claim 7, wherein: The reaction of lithium bis(chlorosulfonyl)imide and the fluorination agent is carried out in a microchannel reactor.