An novel electrolyte additive, 4-methylmorpholine-2,6-dione (MMD) with anhydride and amine functional groups, is come up with, which can not only construct a dense and stable cathode-electrolyte-interface (CEI) film on solid and electrolyte interphase that can automatically improve the cycling stability of lithium-ion batteries (LIBs) at high temperature and high voltage, but also effectively capture hydrofluoric acid and water in the electrolyte that can adequately inhibit carbonate decomposition and protect LiCoO₂ (LCO) internal structure. The capacity retention rate of Li||LCO cells increases from 65.8% to 83.5% after 200 cycles at 1C between 3.0 and 4.6 V after just adding a trace amount of 0.03% MMD to the baseline electrolyte. Even at ultra-high voltages of 4.7 V, the retained capacity of MMD-containing Li||LCO half-cell is improved from 91 to 122 mAh g⁻¹ after 200 cycles at 1C. Both theoretical calculation and experiments reveal that MMD can be preferentially oxidized ahead of those solvent through C–C bond breaking to construct a thin and robust CEI layer on LCO surface. Such a combination of anhydride and amine functional groups opens up a direction to exploit novel electrolyte additives for prolonging the cycle life of higher energy density LCO.