Enhancing the interface stability of Li/NCM622 batteries by adding 3-trifluoromethyl pyrazole

In this study, 3-trifluoromethylpyrazole (TMPZ) was developed as a multifunctional electrolyte additive to enhance wettability between separator and electrolyte, CEI formation and remove HF to improve the performance of Li/NCM622 batteries by experiment and theoretical calculation. After 200 cycles at 30 °C, the discharge capacity retention of batteries at 1 C with 0.5 wt% TMPZ additive is remarkably enhanced from 68.3 % to 83.2 %. The enhanced electrochemical performance of the batteries by adding TMPZ additive is evaluated by the spectroscopic characterization and theoretical calculation. It is demonstrated that TMPZ can generate uniform and dense CEI film via ring-opening electrochemical polymerization of TMPZ on the NCM622 electrode surface. The CEI film helps to suppress the breakdown of LiPF₆ electrolyte and the leaching of transition metals, effectively avoiding harmful side reactions between the NCM622 electrode and the electrolyte. Furthermore, introducing TMPZ can enhance the wettability between separator and electrolyte, therefore providing more channels of Li⁺ to accelerate reaction kinetics of batteries.