Preparation method of lithium bis (fluorosulfonyl) imide solution

Abstract

The invention relates to the technical field of lithium ion battery material manufacturing, and discloses a preparation method of a lithium bis (fluorosulfonyl) imide solution, which comprises the following steps: (1) filling lithium salt particles into a filter column, pouring an organic solution dissolved with an amphiphilic block copolymer and a precursor into the filter column, and carrying out vacuum filtration to remove the organic solution to obtain a lithium bis (fluorosulfonyl) imide solution; taking out the lithium salt particles and calcining to obtain a salt-containing two-dimensional mesoporous material; and (2) in an inert gas atmosphere, filling the salt-containing two-dimensional mesoporous material into a filter column, then introducing an organic solution dissolved with bis (fluorosulfonyl) imide, and carrying out H < + > transfer exchange reaction to obtain a lithium bis (fluorosulfonyl) imide solution and the acid-adsorbing two-dimensional mesoporous material. New impurities are not introduced in the preparation process, and impurity acid generated along with the reaction is efficiently removed, so that the purity of the lithium bis (fluorosulfonyl) imide solution is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery material manufacturing, and particularly relates to a preparation method of a lithium bis(fluorosulfonyl)imide solution. Background Art

[0002] Lithium bis(fluorosulfonyl)imide (LiFSI) is a new type of lithium salt for lithium-ion battery electrolytes. Compared with LiPF 6 , LiFSI has higher thermal stability, electrochemical stability and conductivity, and can better cooperate with high-voltage, high-nickel, and high-rate batteries to meet the trends of high endurance, wide operating temperature, and high safety in future battery development. Liquid LiFSI has more advantages than solid LiFSI. Firstly, it is easy to combine with other components of the battery, simplifies the production process, and reduces costs. Secondly, for downstream electrolyte manufacturers, liquid products can reduce the pre-mixing process and improve production efficiency. In addition, liquid products avoid the post-treatment process of long-term distillation and desolvation of solid products, and the production process is more efficient and environmentally friendly.

[0003] Chinese Patent CN117069075A discloses a preparation method of lithium bis(fluorosulfonyl)imide. An aqueous solution of an alkali metal salt XFSI is passed through a cation exchange column to obtain an aqueous solution of LiFSI, and then a lithium salt that is insoluble in organic solvents is added. After distillation and concentration, an organic solvent is added, and water is removed by distillation to obtain liquid LiFSI. However, this method uses an alkali metal salt as a raw material, introducing other metal impurities and requiring additional impurity removal steps. Summary of the Invention

[0004] In order to solve the technical problem of the complex process route above, the present invention provides a preparation method of a lithium bis(fluorosulfonyl)imide solution, where the reactants do not introduce new impurities and the process route is simple.

[0005] The specific technical solution of the present invention is as follows: A preparation method of a lithium bis(fluorosulfonyl)imide solution, comprising the following steps: (1) Fill lithium salt particles into a filter column, pour an organic solution containing an amphiphilic block copolymer and a precursor into the filter column, vacuum filter to remove the organic solution, take out the lithium salt particles and calcine them to obtain a salt-containing two-dimensional mesoporous material; (2) In an inert gas atmosphere, fill the salt-containing two-dimensional mesoporous material into a filter column, and then pass an organic solution containing bis(fluorosulfonyl)imide to carry out an H + transfer exchange reaction to obtain a lithium bis(fluorosulfonyl)imide solution and a two-dimensional mesoporous material adsorbed with acid.

[0006] In the present invention, lithium salt particles serve as the substrate, and their surfaces serve as the assembly interface. Under vacuum conditions, the volatilization of the organic solvent induces the confined co-assembly of amphiphilic block copolymers and precursors on the surface of the lithium salt particles to form a coating. During the subsequent high-temperature calcination process, the organic block copolymer decomposes, and the inorganic framework precursor is transformed into the corresponding functional inorganic framework, resulting in a highly ordered two-dimensional mesoporous material containing salt. The two-dimensional mesoporous material containing salt reacts with bis(fluorosulfonyl)imide, and the unreacted inorganic acid is directly adsorbed on the two-dimensional mesoporous material, ultimately yielding a high-purity lithium bis(fluorosulfonyl)imide liquid. In the above process, a two-dimensional mesoporous material containing salt is prepared using lithium salt as the substrate. The initial material can be directly used as the raw material for preparing LiFSI without introducing new impurities, eliminating the need for corresponding impurity removal steps. Moreover, the unreacted inorganic acid is directly adsorbed on the two-dimensional mesoporous material, making the acid removal operation simple and efficient, and simplifying the process route. Secondly, the two-dimensional mesoporous material has a high specific surface area and pore volume, strong adsorption capacity, a large lithium salt loading capacity and uniform distribution, enabling the lithium salt to fully react with bis(fluorosulfonyl)imide, thereby improving the reaction efficiency and the yield of lithium bis(fluorosulfonyl)imide. In addition, using bis(fluorosulfonyl)imide containing a solvent as the reaction raw material reduces the corrosion hazard of pure HFSI and has high safety.

[0007] Preferably, in step (1), the mass ratio of the amphiphilic block copolymer, lithium salt, and precursor is 1:50 - 120:5 - 20.

[0008] Preferably, in step (1), the lithium salt is selected from one or more of lithium sulfate, lithium fluoride, lithium chloride, and lithium phosphate.

[0009] Preferably, in step (1), the amphiphilic block copolymer is selected from one or more of polyoxyethylene polyoxypropylene ether, polyethylene glycol-polystyrene, polyphenylene sulfide-polycaprolactone, polystyrene-b-polyvinylpyridine, and polyoxyethylene-polyoxypropylene; the precursor is selected from one or more of phenolic resin, EVA resin, tetrabutyl titanate, silicon oxide nanocrystals, and cerium oxide nanocrystals.

[0010] Preferably, in step (1), the vacuum degree of the vacuum filtration is 3 - 6 kPa, and the filtration time is 20 - 40 min.

[0011] Preferably, in step (1), the calcination temperature is 300 - 600 °C, the heating rate is 2 - 6 °C, and the calcination time is 12 - 24 h.

[0012] In the above technical solution, when the temperature is lower than 300 °C, the precursor cannot be fully converted into the corresponding functional inorganic framework, and the organic block copolymer is also difficult to completely decompose, resulting in an incomplete structure of the prepared two-dimensional mesoporous material; when the temperature is higher than 600 °C, the pore structure of the two-dimensional mesoporous material will be damaged and the active sites will decrease. When the heating rate is lower than 2 °C / min, the production cycle will be prolonged and the production cost will increase; when the heating rate is higher than 6 °C / min, rapid heating will generate large thermal stress inside the material, resulting in cracks or structural defects in the two-dimensional mesoporous material.

[0013] Preferably, in steps (1) and (2), the organic solution is selected from one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0014] Preferably, in step (2), in the organic solution dissolved with bis(fluorosulfonyl)imide, the concentration of bis(fluorosulfonyl)imide is 20-40 wt%.

[0015] Preferably, after step (2), the two-dimensional mesoporous material adsorbed with acid is washed with an organic solvent to remove the adsorbed acid, then immersed in a saturated aqueous solution of a lithium salt for salt adsorption, and then the solid is filtered and separated, and the solid is dried to obtain a regenerated two-dimensional mesoporous material containing salt.

[0016] In the above technical solution, after the reaction, the two-dimensional mesoporous material can be washed with acid by a solvent, impregnated and adsorbed with a lithium salt, and dried in vacuum, and then can be re-introduced into the reaction as a raw material, realizing recycling, improving the material utilization rate, and reducing waste generation.

[0017] Preferably, the impregnation temperature for salt adsorption is 20-40 °C, and the impregnation time is 8-24 h.

[0018] Preferably, after step (2), the lithium bis(fluorosulfonyl)imide solution is passed through a high-exchange-degree calcium-type molecular sieve column to remove water and acid.

[0019] In the above technical solution, a high-exchange-degree calcium-type molecular sieve column is used to further remove trace water and trace acid in the lithium bis(fluorosulfonyl)imide solution, improving the purity of the lithium bis(fluorosulfonyl)imide solution.

[0020] Compared with the prior art, the present invention has the following advantages: (1) The process route is simple: using a lithium salt as a substrate to prepare a salt-containing two-dimensional mesoporous material, the initial material can be directly used as a raw material for preparing LiFSI without introducing new impurities, and there is no need to set corresponding impurity removal steps. Moreover, the unreacted inorganic acid is directly adsorbed on the two-dimensional mesoporous material, and the acid removal operation is simple and efficient, simplifying the process route; (2) High product yield: The two-dimensional mesoporous material has a high specific surface area and pore volume, strong adsorption capacity, a large lithium salt loading capacity and uniform distribution. The lithium salt can fully react with bis(fluorosulfonyl)imide, improving the reaction efficiency and the yield of lithium bis(fluorosulfonyl)imide; (3) High method safety: Using bis(fluorosulfonyl)imide containing solvent as the reaction raw material reduces the corrosion hazard of pure HFSI; (4) High environmental friendliness and less waste: After the two-dimensional mesoporous material after the reaction is washed with acid with solvent, impregnated and adsorbed with lithium salt, and vacuum dried, it can be reused as a raw material in the reaction, realizing recycling, improving the material utilization rate, and reducing waste generation; (5) Low water content: Using a high exchange degree calcium type molecular sieve column to remove water can efficiently reduce the water content to a lower level, overcoming the limitation that the distillation efficiency drops rapidly after the water content drops to a certain value in distillation water removal. Specific embodiments

[0021] The present invention will be described below through specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, the changes and advantages that those skilled in the art can think of are included in the present invention, and the scope of protection of the present invention is the appended claims and any equivalents thereof.

[0022] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. The raw materials and equipment used in the present invention are conventional raw materials and equipment in the art and can be obtained from conventional commercial channels without special instructions; the methods used in the present invention are conventional methods in the art without special instructions.

[0023] It should be noted that in each embodiment, for the determination of purity and content, the purity and LiFSI content of the LiFSI solution are detected by high performance liquid chromatography (HPLC); the metal impurities in the LiFSI solution are detected by inductively coupled plasma (ICP) technology; the water content in the LiFSI solution is detected by the Karl Fischer method.

[0024] Example 1: The present invention provides a method for preparing a lithium bis(fluorosulfonyl)imide solution, which includes the following steps.

[0025] Preparation of salt-containing two-dimensional mesoporous material: Dissolve 2 g of phenolic resin in 50 mL of dimethyl carbonate, add 0.2 g of polyoxyethylene polyoxypropylene ether, and mix evenly to obtain the prepared reaction solution. In a 50 mL filter column, fill 20 g of lithium sulfate, pour the prepared reaction solution into the filter column, and filter under a vacuum pressure of 3 kPa for 30 min to remove the excess solution. After the filtration, transfer the lithium sulfate particles to a tubular furnace, heat up to 400 °C at a rate of 3 °C / min, and then calcine for 16 h to obtain a two-dimensional mesoporous material containing lithium sulfate.

[0026] Preparation of LiFSI solution: Under an inert gas atmosphere, dissolve 65.91 g of HFSI in 197.7 g of dimethyl carbonate, and stir and mix evenly. Fill the two-dimensional mesoporous material containing lithium sulfate into a 50 mL filter column, and then use a peristaltic pump to pump the dimethyl carbonate solution dissolved with HFSI into the filter column at a speed of 50 rpm / min to carry out H + transfer exchange reaction to obtain 264.45 g of LiFSI solution and a two-dimensional mesoporous material adsorbed with acid.

[0027] Purification of LiFSI solution: Use a peristaltic pump to pump the above LiFSI solution into a high-exchange-degree calcium-type molecular sieve column at a speed of 50 rpm / min to remove trace amounts of water and unreacted HFSI, and obtain 263.13 g of LiFSI solution.

[0028] Detect the purified LiFSI solution. The product purity is 99.92%, the LiFSI content is 25.586%, the yield is 98.91%, the moisture content: 13.16 ppm, K + : 3.41 ppm, Ca + : 0.35 ppm, Na + : 2.87 ppm.

[0029] Example 2: The present invention provides a preparation method of a lithium bis(fluorosulfonyl)imide solution, which includes the following steps.

[0030] Preparation of two-dimensional mesoporous material: Dissolve 2 g of EVA resin in 50 mL of ethyl methyl carbonate, add 0.2 g of polyethylene glycol-polystyrene, and mix evenly to obtain the prepared reaction solution. In a 50 mL filter column, fill 10 g of lithium fluoride, pour the prepared reaction solution into the filter column, and filter under a vacuum pressure of 3 kPa for 30 min to remove the excess solution. After the filtration, transfer the lithium fluoride particles to a tubular furnace, heat up to 400 °C at a rate of 3 °C / min, and then calcine for 16 h to obtain a two-dimensional mesoporous material containing lithium fluoride.

[0031] Preparation of LiFSI solution: Under an inert gas atmosphere, 69.83 g of HFSI was dissolved in 209.5 g of ethyl methyl carbonate and stirred evenly. The two-dimensional mesoporous material containing lithium fluoride was filled into a 50 mL filter column, and then a peristaltic pump was used to pump the ethyl methyl carbonate solution dissolved with HFSI into the filter column at a speed of 50 rpm / min for H + transfer exchange reaction to obtain 280.20 g of LiFSI solution and the two-dimensional mesoporous material adsorbed with acid.

[0032] Purification of LiFSI solution: Using a peristaltic pump, the above LiFSI solution was pumped into a high-exchange-degree calcium-type molecular sieve column at a speed of 50 rpm / min to remove trace amounts of water and unreacted HFSI, obtaining 278.60 g of LiFSI solution.

[0033] The purified LiFSI solution was detected. The product purity was 99.95%, the LiFSI content was 25.528%, the yield was 98.62%, the moisture content: 15.71 ppm, K + : 4.25 ppm, Ca + : 0.59 ppm, Na + : 1.32 ppm.

[0034] Example 3: The present invention provides a preparation method of a lithium bis(fluorosulfonyl)imide solution, including the following steps.

[0035] Preparation of two-dimensional mesoporous material: 1 g of tetrabutyl titanate was dissolved in 50 mL of diethyl carbonate, and 0.2 g of polyphenylene sulfide-polycaprolactone was added and mixed evenly to obtain the prepared solution to be reacted. 15 g of lithium chloride was filled into a 50 mL filter column, and the prepared solution to be reacted was poured into the filter column. Under a vacuum pressure of 3 kPa, suction filtration was carried out for 30 min to remove the excess solution. After the suction filtration was completed, the lithium chloride particles were transferred to a tube furnace and heated to 300 °C at a rate of 2 °C / min, and then calcined for 24 h to obtain the two-dimensional mesoporous material containing lithium chloride.

[0036] Preparation of LiFSI solution: Under an inert gas atmosphere, 64.10 g of HFSI was dissolved in 256.4 g of diethyl carbonate and stirred evenly. The two-dimensional mesoporous material containing lithium chloride was filled into a 50 mL filter column, and then a peristaltic pump was used to pump the diethyl carbonate solution dissolved with HFSI into the filter column at a speed of 50 rpm / min for H + transfer exchange reaction to obtain 257.2 g of LiFSI solution and the two-dimensional mesoporous material adsorbed with acid.

[0037] Purification of LiFSI solution: Using a peristaltic pump, the above LiFSI solution was pumped into a high-exchange calcium-type molecular sieve column at a speed of 50 rpm / min to remove trace amounts of water and unreacted HFSI, obtaining 319.46 g of LiFSI solution.

[0038] The purified LiFSI solution was tested. The product purity was 99.93%, the LiFSI content was 20.511%, the yield was 98.898%, the water content was 18.23 ppm, K + : 3.95 ppm, Ca + : 1.28 ppm, Na + : 1.56 ppm.

[0039] Example 4: The present invention provides a method for preparing a lithium bis(fluorosulfonyl)imide solution, which includes the following steps.

[0040] Preparation of two-dimensional mesoporous material: 4 g of silica nanocrystals were dissolved in 50 mL of dimethyl carbonate, and 0.2 g of polystyrene-b-poly(4-vinylpyridine) was added and mixed evenly to obtain the prepared solution to be reacted. In a 50 mL filter column, 24 g of lithium phosphate was filled, and the prepared solution to be reacted was poured into the filter column. Under a vacuum pressure of 3 kPa, suction filtration was carried out for 30 min to remove the excess solution. After the suction filtration was completed, the lithium phosphate particles were transferred to a tube furnace and heated to 600 °C at a rate of 6 °C / min, and then calcined for 12 h to obtain a two-dimensional mesoporous material containing lithium phosphate.

[0041] Preparation of LiFSI solution: Under an inert gas atmosphere, 62.57 g of HFSI was dissolved in 93.8 g of dimethyl carbonate and stirred and mixed evenly. The two-dimensional mesoporous material containing lithium phosphate was filled into a 50 mL filter column, and then a peristaltic pump was used for H + transfer exchange reaction. The dimethyl carbonate solution dissolved with HFSI was pumped into the filter column at a speed of 50 rpm / min to obtain 251.07 g of LiFSI solution and a two-dimensional mesoporous material adsorbed with acid.

[0042] Purification of LiFSI solution: Using a peristaltic pump, the above LiFSI solution was pumped into a high-exchange calcium-type molecular sieve column at a speed of 50 rpm / min to remove trace amounts of water and unreacted HFSI, obtaining 156.7 g of LiFSI solution.

[0043] The purified LiFSI solution was tested. The product purity was 99.91%, the LiFSI content was 40.727%, the yield was 98.76%, the water content was 16.99 ppm, K+: 4.54 ppm, Ca + : 1.64 ppm, Na +: 2.79 ppm.

[0044] Example 5: This example is to regenerate the two-dimensional mesoporous material that adsorbs acid in Example 1, including the following steps.

[0045] Place the two-dimensional mesoporous material that adsorbs acid in 50 mL of dimethyl carbonate, stir and wash for 20 min to remove the adsorbed acid, filter, put it in a drying oven, and dry it at 130 °C until constant weight. Subsequently, add it to 100 mL of saturated aqueous solution of lithium sulfate, stir and impregnate at 30 °C for 12 h, filter, and dry the solid at 100 °C under 3 kPa vacuum until the water content < 0.1% to obtain the regenerated two-dimensional mesoporous material containing lithium sulfate.

[0046] Example 6: This example is to regenerate the two-dimensional mesoporous material that adsorbs acid in Example 2, including the following steps.

[0047] Place the two-dimensional mesoporous material that adsorbs acid in 50 mL of dimethyl carbonate, stir and wash for 20 min to remove the adsorbed acid, filter, put it in a drying oven, and dry it at 130 °C until constant weight. Subsequently, add it to 100 mL of saturated aqueous solution of lithium fluoride, stir and impregnate at 20 °C for 24 h, filter, and dry the solid at 100 °C under 3 kPa vacuum until the water content < 0.1% to obtain the regenerated two-dimensional mesoporous material containing lithium fluoride.

[0048] Example 7: This example is to regenerate the two-dimensional mesoporous material that adsorbs acid in Example 3, including the following steps.

[0049] Place the two-dimensional mesoporous material that adsorbs acid in 50 mL of dimethyl carbonate, stir and wash for 40 min to remove the adsorbed acid, filter, put it in a drying oven, and dry it at 130 °C until constant weight. Subsequently, add it to 100 mL of saturated aqueous solution of lithium chloride, stir and impregnate at 40 °C for 8 h, filter, and dry the solid at 100 °C under 3 kPa vacuum until the water content < 0.1% to obtain the regenerated two-dimensional mesoporous material containing lithium chloride.

[0050] The raw materials and equipment used in the present invention are all common raw materials and equipment in the field without special instructions; the methods used in the present invention are all conventional methods in the field without special instructions.

[0051] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a lithium bis(fluorosulfonyl)imide solution, characterized in that: The following steps are involved: (1) filling lithium salt particles into a filter column, pouring an organic solution containing an amphiphilic block copolymer and a precursor into the filter column, removing the organic solution by vacuum filtration, taking out the lithium salt particles and calcining them to obtain a salt-containing two-dimensional mesoporous material; (2) In an inert gas atmosphere, the salt-containing two-dimensional mesoporous material is loaded into a filter column, and then an organic solution containing bis(fluorosulfonyl)imide is introduced to perform H + Transfer exchange reaction yields lithium bis(fluorosulfonyl)imide solution and two-dimensional mesoporous material with adsorbed acid.

2. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 1, characterized in that: In step (1), the mass ratio of the amphiphilic block copolymer, the lithium salt and the precursor is 1:50-120:5-20.

3. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 1, characterized in that: In step (1), the lithium salt is selected from one or more of lithium sulfate, lithium fluoride, lithium chloride and lithium phosphate.

4. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 1, characterized in that: In step (1), the amphiphilic block copolymer is selected from one or more of polyoxyethylene polyoxypropylene ether, polyethylene glycol-polystyrene, polyphenylene sulfide-polycaprolactone, polystyrene-b-polyvinyl pyridine and polyoxyethylene-polyoxypropylene; the precursor is selected from one or more of phenolic resin, EVA resin, n-butyl titanate, silicon oxide nanocrystals and cerium oxide nanocrystals.

5. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 1, characterized in that: In step (1), the calcination temperature is 300-600° C., the heating rate is 2-6° C., and the calcination time is 12-24 hours.

6. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 1, characterized in that: In steps (1) and (2), the organic solution is selected from one or more of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

7. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 1, characterized in that: In step (2), the concentration of bis(fluorosulfonyl)imide in the organic solution containing bis(fluorosulfonyl)imide is 20 to 40 wt %.

8. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to any one of claims 1 to 7, characterized in that: After step (2), the two-dimensional mesoporous material that adsorbs acid is washed with an organic solvent to remove the adsorbed acid, dried, and then placed in a saturated aqueous solution of lithium salt to impregnate the adsorbed salt, then filtered to separate the solid, and dried to obtain a regenerated salt-containing two-dimensional mesoporous material.

9. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claim 8, characterized in that: The immersion temperature of the immersion adsorption salt is 20-40° C., and the immersion time is 8-24 hours.

10. The method for preparing a lithium bis(fluorosulfonyl)imide solution according to claims 1 to 7, characterized in that: After step (2), the lithium bis(fluorosulfonyl)imide solution is passed into a high exchange calcium molecular sieve column to remove water and acid.