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Despite significant progress in the field of Li-ion battery development over the past 30 years, challenges associated with the gradual shift from small-scale to large-scale battery applications necessitate the search for better electrode materials. In particular, Ni-rich layered oxide cathode materials (NCM) feature high specific capacities but suffer from inferior high-temperature cycling performance because of poor surface stability. Herein, we use ammonium sulfate (AS) to form a bifunctionalized cathode–electrolyte interface and thus improve NCM surface stability, revealing that thermal treatment of NCM in the presence of AS affords an artificial cathode–electrolyte interface comprising sulfonate and amino functional groups and thus effectively hinders electrolyte decomposition and Ni dissolution. The modified NCM feature surfaces with well-developed artificial cathode–electrolyte interfaces (which do not compromise structural stability) exhibit good high-temperature cycling performance. The modified NCM at 400 °C features a capacity retention of 75.6% after 100 cycles at 45 °C, whereas a much lower value of 52.2% is observed for the bare counterpart under identical conditions. Cycling-induced electrolyte decomposition, cracking, and Ni dissolution are strongly suppressed in cells with surface-modified NCM, which implies that residual hydrogen fluoride removal by the bifunctionalized artificial cathode–electrolyte interface improves NCM surface stability. Thus, the use of a bifunctionalized artificial cathode–electrolyte interface modified by task-specific AS is concluded to improve the surface properties of NCM and their high-temperature electrochemical performance.

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