Revealing the mechanisms of electrolyte additive PTS on Ni-rich electrode: Tolerance to high temperature (50 °C) and high voltage (4.6 V)

Ni-rich (Ni≥0.8) LiNi_xCo_yMn_1−x−yO₂ (NCM) cathode materials have attracted great interest for high-energy-density lithium ion batteries (LIBs). However, layered oxides of Ni-rich CAMs are suffering from the notorious structural and interfacial degradation in the liquid electrolyte, especially at high state-of-charge (voltage) and temperature, which leads to electrochemical performance deterioration and thermal runaway of the cell. This work systematically and comprehensively reveals the underlying mechanism of the electrolyte additive phenyl trifluoromethyl sulfide (PTS) to enhance the electrochemical property of Ni-rich layered oxides at high voltage (∼4.6 V) and high-temperature (∼50 °C). Specifically, PTS observably encourages the electrode stability via cathode-electrolyte interface strengthening and reactive oxygen species deactivating mechanism, which facilitates the NCM811 cathode to adapt to the deep charging state as well as the highly oxidized environment. The binding energy calculation results reveal that the superoxide radical could steadily adsorb on the S radical or Li⁺ sites by interacting with Li⁺, thus making the superoxide radical deactivated. With the interface strengthening of PTS, the Ah-level NCM811||Gr pouch cell exhibits excellent cycling stability. This work affords a guide to designing electrolytes for Ni-rich LIBs towards high-voltage and high-temperature.