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CN-116730352-B - Synthesis method of lithium tetrafluoroborate and electrolyte

CN116730352BCN 116730352 BCN116730352 BCN 116730352BCN-116730352-B

Abstract

The invention belongs to the field of new energy, and discloses a method for synthesizing lithium tetrafluoroborate, which comprises the following steps that step 1, lithium halide is added into a nonaqueous organic solvent, boron trichloride is introduced, and a solution containing the lithium tetrafluoroborate is obtained through reaction; and 2, introducing hydrogen fluoride into the solution obtained in the step 1, and reacting to obtain the solution containing lithium tetrafluoroborate. The method adopts a solvent method for synthesis, firstly adopts any available halogenated lithium and boron trichloride for reaction to obtain an intermediate product, and then carries out unified fluorination to obtain the lithium tetrafluoroborate, which can select various halogenated lithium to realize the scheme of the invention, can selectively enrich the raw materials, and simultaneously obviously reduces the production cost.

Inventors

  • HONG GUO
  • QIN XIAOKANG
  • Liu du

Assignees

  • 广州天赐高新材料股份有限公司
  • 九江天赐高新材料有限公司

Dates

Publication Date
20260508
Application Date
20230628

Claims (9)

  1. 1. The synthesis method of the lithium tetrafluoroborate is characterized by comprising the following steps of: Step1, adding lithium halide into a nonaqueous organic solvent, introducing boron trichloride, and reacting to obtain a solution containing lithium halogenoborate; Step 2, introducing hydrogen fluoride into the solution obtained in the step 1, and reacting to obtain a solution containing lithium tetrafluoroborate; the reaction equations of steps 1 and 2 are: ; wherein X is F, cl, br or I, a is 1,2, or 3;b is 1,2 or 3.
  2. 2. The method for synthesizing lithium tetrafluoroborate according to claim 1, wherein the molar ratio of the lithium halide to the boron trichloride is 1:0.9 to 1.1.
  3. 3. The method for synthesizing lithium tetrafluoroborate according to claim 1, wherein the mass ratio of the lithium halide to anhydrous hydrogen fluoride is 1:2-10.
  4. 4. The method for synthesizing lithium tetrafluoroborate according to claim 1, wherein the nonaqueous organic solvent is any one or a combination of several of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, vinylene carbonate, propylene carbonate, methyl carbonate, 1-fluoroethylene carbonate, ethyl acetate, butyl acetate, diethyl ether.
  5. 5. The method for synthesizing lithium tetrafluoroborate according to claim 1, wherein the reaction temperature in step 1 is 10 to 90 ℃ and the reaction time is 1 to 24 hours.
  6. 6. The method for synthesizing lithium tetrafluoroborate according to claim 1, wherein the reaction temperature in the step 2 is 0 to 90 ℃ and the reaction time is 3 to 10 hours.
  7. 7. The method for synthesizing lithium tetrafluoroborate according to claim 1, wherein the reaction pressure in the step 2 is 1 to 10 atm.
  8. 8. The method for synthesizing lithium tetrafluoroborate according to claim 1, further comprising step 3, wherein the step 3 is specifically to concentrate the solution obtained in the step 2 to obtain a lithium tetrafluoroborate crude product, and recrystallizing the lithium tetrafluoroborate crude product to obtain a lithium tetrafluoroborate crystal.
  9. 9. The method for synthesizing the lithium tetrafluoroborate according to claim 8, wherein the method for concentrating the solution obtained in the step 2 is that the solution obtained in the step 2 is concentrated by heating under reduced pressure, the crude lithium tetrafluoroborate is separated out from the solution, and the crude lithium tetrafluoroborate is obtained by filtering; the method for obtaining the lithium tetrafluoroborate crystal by recrystallizing the lithium tetrafluoroborate crude product comprises the following steps: Dissolving a lithium tetrafluoroborate crude product by using a good solvent, adding a poor solvent to separate out lithium tetrafluoroborate crystals, and drying under reduced pressure to obtain lithium tetrafluoroborate crystals; the good solvent is any combination of one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, propylene carbonate, methyl carbonate, 1-fluoroethylene carbonate, ethyl acetate, butyl acetate and diethyl ether; The poor solvent is one or any combination of several of toluene, xylene, trimethylbenzene, methylene dichloride, dichloroethane, n-hexane, cyclohexane and n-heptane.

Description

Synthesis method of lithium tetrafluoroborate and electrolyte Technical Field The invention belongs to the field of new energy, and particularly relates to a synthesis method of lithium tetrafluoroborate and an electrolyte. Background The preparation method of LiBF 4 mainly comprises a solid-gas phase contact method (CN 101863489), a nonaqueous solution method (CN 115260239A), an aqueous solution method (US 6623717) and an ion exchange method (CN 104030310). The solid-gas phase contact method is to synthesize the basic lithium salt serving as a raw material at a high temperature, and has high equipment requirement, strict process control requirement, high synthesis difficulty, low reaction efficiency and difficulty in realizing large-scale production. The nonaqueous solution method is to form suspension of lithium fluoride in an organic solvent and react with BF 3 to generate LiBF 4, but the method has high requirements on equipment, raw materials are not easy to obtain, and the production cost is high. The aqueous solution method adopts boric acid to react with HF aqueous solution to prepare tetrafluoroboric acid, then reacts with carbonate to obtain lithium tetrafluoroborate solution, and the lithium tetrafluoroborate solution is concentrated, crystallized and dried to obtain the product, however, in the preparation process of the method, lithium tetrafluoroborate exists in the form of monohydrate or trihydrate, the product purity is low, and drying and dehydration are difficult. The ion exchange method utilizes the difference of solubility of potassium tetrafluoroborate and the like and lithium tetrafluoroborate to obtain a crude product, and the crude product is further recrystallized to obtain a qualified product. The solid-gas phase contact method, the aqueous solution method and the ion exchange method are not widely adopted any more due to preparation difficulty, equipment requirements, purification requirements and the like, and the currently popular methods are a nonaqueous solution method and a rheological phase method. The following scheme is seen in detail: Nonaqueous solution method: The method comprises the steps of S1, mixing a solvent, anhydrous lithium fluoride and boron trifluoride solution, stirring and filtering to obtain a lithium tetrafluoroborate solution, S2, adding anhydrous oxalic acid and silicon tetrachloride into the lithium tetrafluoroborate solution, reacting to obtain crude lithium difluorooxalate, and S3, purifying the crude lithium difluorooxalate to obtain refined lithium difluorooxalate. D2: 114477201A discloses a process for preparing lithium tetrafluoroborate, comprising dissolving a complex of lithium fluoride (LiF) and boron trifluoride in DMC and reacting at 64-80 ℃. Fluid phase change method: CN107585776A discloses a method for synthesizing lithium tetrafluoroborate by a rheological phase method, which takes boron trichloride as a raw material, obtains an intermediate product boron trifluoride by anhydrous hydrogen fluoride fluorination, then reacts with a rheological body prepared by high-purity lithium fluoride solid powder and anhydrous hydrofluoric acid, and finally obtains the finished product lithium tetrafluoroborate by steps of concentration crystallization, separation, purification and the like. Whether non-aqueous, rheological or less commonly employed solid-gas phase contact, aqueous, ion exchange methods, the starting materials generally employed are at least lithium fluoride and/or boron trifluoride. In particular CN107585776a emphasizes the use of high purity lithium fluoride solid powders, the above process has the following common technical problems: 1. The raw materials are single in source, CN101863489 and CN115260239A, CN114477201A, CN107585776A both use boron trifluoride and lithium fluoride, the single raw material source means that the purity of the raw materials is very high, for example, CN107585776A clearly records that high-purity lithium fluoride solid powder is used, if other halogenated lithium is mixed in the powder, impurities are generated to influence the purity of a product, and meanwhile, the single raw material source means that the raw materials are very likely to be forced to be abandoned and used; 2. The price of boron trifluoride and lithium chloride is higher than that of boron trichloride and lithium chloride, and the price of rheological phase is higher than that of other solvent systems by taking the rheological phase as a reaction system; 3. The equipment requirement is high, and the scheme taking the rheological phase as the reaction system has higher corrosion protection requirement. Therefore, the technical problem to be solved in the project is how to make the raw material types become more abundant selectively and how to reduce the production cost in the process of producing lithium tetrafluoroborate. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a method for synthesiz