Abstract: A new lithium salt，lithium-difluoro（oxalato） borate was synthesized from the materials of lithium tetrafluoroborate （LiBF₄） and anhydrous oxalic acid assisted by silicon tetrachloride.The influences of reaction temperature，reaction time， mass ratio of the reaction materials，and mass ratio of the crystallization solvent methylene dichloride to concentrated product on the yield of product were investigated.The structures of the objective products were confirmed by FT-IR and TG.The best conditions were described as following：the reaction temperature was 30 ℃，the reaction time was 4 h，the mass ratio of the reaction materials was 1∶0.9，the mass ratio of the crystallization solvent/concentrated product was 50∶1，and crystallization solvent was methylene dichloride.Under the best conditions，the best yield was 98.3%.In addition，adding LiBF₂（C₂O₄） in electrolyte can effectively improve the cycle performance at room temperature and low temperature performance of battery.

Key words: lithium tetrafluoroborate, lithium-difluoro（oxalato） borate；reaction conditions；yield