Lithium-conductive LiNbO3 coated high-voltage LiNi0.5Co0.2Mn0.3O2 cathode with enhanced rate and cyclability

Abstract

LiNi0.5Co0.2Mn0.3O2 (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 Ni4+ at the surface. Herein, we have developed a citrate-assisted deposition concept to achieve a uniform lithium-conductive LiNbO3 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 Ni4+ 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 0.2 C and 128.9 mAh g−1 at 10 C over the range 3.0–4.5 V. Additionally, a 92% capacity retention was obtained after 100 cycles at 1 C, 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.

Keywords

• NCM523
• Surface coating
• Confined synthesis
• Cycling stability
• Li-ion batteries