Lithium Tetrafluoroborate has a molecular formula of LiBF4 and a molecular weight of 93.74. It is mainly used as an electrolyte lithium salt for lithium ion battery electrolyte. With the rapid development of mobile communications and portable electrical appliances in modern society, lithium-ion secondary batteries are widely used in people’s daily lives due to their high energy density, high working voltage, small memory effect, low self-discharge rate, lightness and convenience, etc. application. At present, the classic electrolyte system used in lithium-ion secondary batteries is that electrolyte salts are dissolved in organic aprotic solvents. As one of the basic materials of lithium-ion batteries, the electrolyte directly affects the working performance of lithium-ion batteries.
Lithium Tetrafluoroborate has good chemical and thermal stability, and is not very sensitive to moisture, but its poor conductivity limits the application of LiBF4-based electrolyte systems. LiBF4 is mainly used as an additive in LiPF6-based electrolyte system to improve cycle life and improve the performance of lithium-ion batteries. In addition, the passivation ability of LiBF4 on aluminum foil is also quite excellent, so as a film-forming additive, LiBF4 has been widely used in current electrolytes. Moreover, the addition of Lithium Tetrafluoroborate can broaden the operating temperature range of lithium-ion batteries and improve the high and low temperature discharge performance of the battery. LiBF4 is more suitable for use in extreme environments (high temperature or low temperature) than LiPF6.
At present, the preparation methods of Lithium Tetrafluoroborate include aqueous solution method, gas-solid reaction method and non-aqueous solution method. The aqueous solution method uses hydrofluoric acid, boric acid and lithium carbonate as raw materials, the process conditions are mild, no explosive chemicals are involved, and the synthesis is simple and safe; however, the product obtained after the aqueous solution method reaction is Lithium Tetrafluoroborate monohydrate, which will easily dissolve in its own crystals when heated. The water turns into a molten state, making it difficult to dehydrate, and the content of insoluble matter is relatively high.