Isatin anhydride as multifunctional film-forming additive to enhance cycle life of high-voltage Li-ion batteries at elevated temperature

High-voltage Ni-rich based lithium-ion batteries with long-term cycled life can be obtained by reasonable regulation of the nonaqueous electrolyte components. Herein, a novel multifunctional electrolyte additive , isatin anhydride (IAn) is dedicated to construct stable solid-electrolyte-interface (SEI) films on the both Ni-rich layered LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode and graphite anode in a high-voltage pouch cell. Electrochemical tests reveal that IAn can significantly enhance the long-term cycling performance of the graphite/NCM523 full-cell at high voltage and high temperature. The pouch cell containing 1.0 wt% IAn shows an excellent capacity retention of 92.3% after 200 cycles between 3.0 and 4.5 V at 1.0C under 45 °C condition. In contrast, the cell without IAn appears a lower cycle performance after 192 cycles while the capacity retention decrease to 18.3%. Such obvious improvement of electrochemical performance contributes from the formation of thin and stable SEI films at two electrodes’ surfaces, leading to restraining the electrolyte decomposition and protecting material structures on the both cathode and anode .