Maleic Anhydride and (Ethoxy)pentafluorocyclotriphosphazene as Electrolyte Additives for High-Voltage LiCoO₂/Si-Graphite Lithium-Ion Batteries

Anhydride additives including maleic anhydride and succinic anhydride are initially selected as additives in the commercial electrolytes for high-voltage lithium-ion batteries with a Si-based anode. The introduction of (ethoxy)pentafluorocyclotriphosphazene as a flame retardant realizes the nonflammability of electrolytes, and the conductivity of electrolytes exceeds 10 mS cm–1 at 25 °C. Maleic anhydride and (ethoxy)pentafluorocyclotriphosphazene jointly contribute to the exceptional performances of 4.45 V LiCoO2/Si-graphite pouch cells at 25 °C. The capacity retention at 1C of 300 cycles reaches 78%, and the discharge capacity ratio of 6C/1C is approximately 83%. These results suggest that this nonflammable electrolyte has good application prospect. Scanning electron microscopy and X-ray photoelectron spectroscopy measurements are implemented to analyze the interface properties of electrodes.