High-nickel ternary cathode materials such as LiNi0.8Co0.1Mn0.1O2 (NCM811) are among the most promising cathode materials due to their high capacity and low cost. However, irreversible phase transition and interfacial side reactions over cycles remain critical concerns. In this paper, a two-step carbon coating process is developed to suppress the adverse phase transition and excessive side reactions at the electrode-electrolyte interface. Sucrose is melted firstly at mild temperature to be coated onto the particle surface, which is converted into carbon in situ at elevated temperature under oxygen atmosphere. Both the cyclic (96.7% capacity retention after 100 cycles at 1 C) and rate performance (130 mAh g−1 at 5 C) of the NCM811 cathode are effectively improved by the carbon coating treatment.