Simultaneously Constructing Stable Cathode/Solid-Electrolyte Interphase by Trimethylsilyl Trifluoromethanesulfonate Additive for High-voltage Lithium-Metal Batteries

High-energy-density Li||NCM622 batteries often suffer from an unstable electrode-electrolyte interface (EEI) at high cut-off voltage. This instability EEI causes continuous interfacial side reactions, structural deterioration of the NCM622 cathode, and the formation of lithium dendrites on the Li anode, ultimately culminating in rapid battery failure. Herein, we introduce trimethylsilyl trifluoromethanesulfonate (TMSOTf) as an additive to the traditional carbonate electrolyte to address these issues. The introduction of the TMSOTf additive alters the solvation structure of Li⁺ and helps to generate homogeneous and mechanically stable EEI enriched with LiF and Li₂SO_x (x = 0, 3, 4). The LiF-rich EEI can inhibit the deterioration of the NCM622 cathode and the growth of lithium dendrites. Meanwhile, the Li₂SO_x (x = 0, 3, 4) components with high ionic conductivity facilitate accelerating the migration of Li⁺ in EEI. Moreover, the TMSOTf additive can scavenge HF in the electrolyte and effectively inhibit the corrosion of EEI and NCM622 cathode by HF. As expected, the Li||NCM622 battery with TMSOTf-contained electrolyte demonstrates excellent cycling stability and rate capability at a high cut-off voltage of 4.6 V.