This paper firstly revealed that the safety of lithium-ion battery could be greatly improved by using a novel electrolyte additive: ammonium perfluorocaprylate (APC). In a UL 94 flammability test, even with APC concentration in an organic electrolyte as low as 0.70 wt%, the flame propagation rate was significantly decreased by about 33%. The differential scanning calorimetry (DSC) analysis showed that less heat released in the reaction between lithiated Mesocarbon microbead (MCMB) anode and electrolyte, and the thermal unstable temperature of electrolyte increased from 138.0 to 167.5 ℃ by adding APC in the electrolyte. A lower charge-transfer resistance of an MCMB anode and a higher stability of SEI film were well determined by EIS in the APC-containing electrolyte system. The Li/MCMB cell with additive APC presented better capability of capacity retention and charge-discharge coulombic efficiency in cycling testing.

Key words: lithium-ion battery, electrolyte additive, ammonium perfluorocaprylate, flame-retardant