LiNi_{0.5}Co_{0.2}Mn_{0.3}O_{2} (NCM523) cathode materials can operate at extremely high voltages and have exceptional energy density. However, their use is limited by inherent structure instability during charge/discharge and exceptionally oxidizing Ni^{4+} at the surface. Herein, we have developed a citrate-assisted deposition concept to achieve a uniform lithium-conductive LiNbO_{3} coating layer on the NCM523 surface that avoids self-nucleation of Nb-contained compounds in solution reaction. The electrode–electrolyte interface is therefore stabilized by physically blocking the detrimental parasitic reactions and Ni^{4+} dissolution whilst still maintaining high Li+ conductivity. Consequently, the modified NCM523 exhibits an encouraging Li-storage specific capacity of 207.4 mAh g^{−1} at 0.2C and 128.9 mAh g^{−1} at 10C over the range 3.0–4.5 V. Additionally, a 92% capacity retention was obtained after 100 cycles at 1C, much higher than that of the pristine NCM523 (73%). This surface engineering strategy can be extended to modify other Ni-rich cathode materials with durable electrochemical performances
