Method 1: A preparation method of quality Lithium Tetrafluoroborate, including the following steps:

1) According to the molar ratio of H3BO3 to HF in the ratio of 1:4～6, add boric acid to hydrofluoric acid for reaction to obtain fluoroboric acid solution;
2) According to the ratio of the molar ratio of Li to B of 1.05-1.5:1, add the lithium compound to the fluoroboric acid solution obtained in step 1) for reaction to obtain a lithium tetrafluoroborate solution;
3) Concentrate the quality Lithium Tetrafluoroborate solution obtained in step 2), cool to crystallize, and filter to obtain lithium tetrafluoroborate crystals;
4) Dry the quality Lithium Tetrafluoroborate crystals obtained in step 3) to obtain crude lithium tetrafluoroborate;
5) The crude quality Lithium Tetrafluoroborate obtained in step 4) is placed in a reactor, and fluorine gas or a mixture of fluorine and nitrogen gas is introduced for reaction to obtain the lithium tetrafluoroborate.

Method 2: A preparation method of high-purity quality Lithium Tetrafluoroborate, including the following steps:

(1) Under the condition of -10℃～10℃, slowly add boric acid to the hydrofluoric acid solution, control the molar ratio of boric acid to anhydrous hydrofluoric acid: H3BO3:HF=1:(4～6), then continue Stir and react for 0.5 to 5 hours to prepare a fluoroboric acid solution;
(2) Under the condition of -10℃～15℃, add the lithium compound to the fluoroboric acid solution prepared in step (1) according to the molar ratio Li:B=1.05～1.5, stir and react for 0.5-5h to obtain quality Lithium Tetrafluoroborate solution;
(3) The quality Lithium Tetrafluoroborate solution is concentrated under the conditions of -0.05～-0.09MPa, 50℃～90℃, concentrated to 1/3～1/8 of the original volume of lithium tetrafluoroborate solution, and then reduced to room temperature Cool and crystallize, filter, and the obtained solid is lithium tetrafluoroborate crystals;
(4) The lithium tetrafluoroborate crystals are initially dried at 30-60°C for 2-8 hours, and then vacuum-dried at 50-100°C for 2-8 hours to obtain crude lithium tetrafluoroborate;
(5) Dissolve the crude lithium tetrafluoroborate obtained in step (4) in anhydrous hydrofluoric acid to obtain a reaction liquid, control the reaction temperature from 0°C to 15°C, and pass fluorine gas or a mixture of fluorine and nitrogen into the reaction liqui
(6) The said quality Lithium Tetrafluoroborate hydrofluoric acid mother liquor gradient cooling crystallization, the crystallization temperature is -40～0℃, filter, the crystalline product is dried at 30～80℃ under the protection of nitrogen to obtain high-purity lithium tetrafluoroborate product, filtrate Recycle for recycling.