Abstract: Surface deterioration occurs more easily in nickel-rich cathode materials with the increase of nickel content. To simultaneously prevent deterioration of active cathode materials and improve the electrochemical performance of the nickel-rich cathode material, the surface of nickel-rich LiNi_0.6Co_0.2Mn_0.2O₂ cathode material is decorated with the stable structure and conductive Li₃PO₄ by a facile method. The LiNi_0.6Co_0.2Mn_0.2O₂–1wt%, 2wt%, 3wt%Li₃PO₄ samples deliver a high-capacity retention of more than 85% after 100 cycles at 1 C under a high voltage of 4.5 V. The effect of different coating amounts (0–5wt%) for the LiNi_0.6Co_0.2Mn_0.2O₂ cathode is analyzed in detail. Results show that 2wt% coating of Li₃PO₄ gives better performance compared to other coating concentrations. Detailed analysis of the structure of the samples during the charge−discharge process is performed by in-situ X-ray diffraction. It is indicated that the modification for LiNi_0.6Co_0.2Mn_0.2O₂ cathode could protect the well-layered structure under high voltages. In consequence, the electrochemical performance of modified samples is greatly improved.