Abstract: Surface residual lithium compounds severely affected the preparation and application of LiNi_0.80Co_0.15Al_0.05O₂ (NCA) cathode materials. Coating the NCA surface with Li-reactant agents is an efficient method for transforming these residual lithium compounds. Nonetheless, a singular coating technique is insufficient to satisfy all specified requirements. In this paper, the liquid phase and solid phase were combined. First, the LiOH on the surface of the NCA cathode material was washed with ethanol, and then Al₂O₃ was added. Combined with XRD, SEM, TEM and XPS analysis, the added Al₂O₃ reacted with the washed LiOH, not only generating a β-LiAlO₂ coating on the surface of the NCA cathode material, but also effectively reducing the amount of residual LiOH on the surface. Electrochemical performance tests revealed that β-LiAlO₂ coating could enhance the first discharge performance, rate capability, and cycle stability of the NCA cathode material. The capacity retention rate of LiAlO₂-NCA samples remained at 68.4%, after 200 cycles at 1 C. CV and EIS analyses showed that the improvement in the electrochemical performance of the LiAlO₂-NCA sample was attributed to the β-LiAlO₂ coating, which can not only enhance Li⁺ diffusion kinetics and conductivity of the cathode material but also reduce the interface side reactions between the electrode and electrolyte, thereby decreasing the R_ct.