Preparation method and application of electrolyte additive composition

The invention discloses a preparation method and application of an electrolyte additive composition, and the additive composition is a mixture of mono-substituted difluorophosphate lithium trifluoroborate and lithium tetrafluoroborate as shown in the formula (I). The preparation method comprises the following steps: taking lithium difluorophosphate, boron trifluoride or a boron trifluoride complex as raw materials, and reacting in an organic solvent at the temperature of 50-60 DEG C for 1-2 hours to obtain the electrolyte additive composition. Under the action of a reaction accelerator, the additive composition is prepared, and the reaction accelerator is lithium tetrafluoroborate. The additive composition has the advantages of reducing battery impedance, improving high-temperature cycle, normal-temperature cycle and high-temperature storage performance of the battery, improving long-term storage stability of the battery and the like when being used in the electrolyte. 本发明公开了一种电解液添加剂组合物的制备方法及应用，所述添加剂组合物为下式结构(