Surface-Phase Engineering via Lanthanum Doping Enables Enhanced Electrochemical Performance of Li-Rich Layered Cathode

High-capacity Li-rich layered oxides (LLOs) hold giant promise as cathodes for Li-ion batteries but still suffer from cycling instability and voltage decay. The oxygen redox reaction and phase transformation to spinel are major incentives for performance deterioration. Hence, we propose a La-doping strategy to stabilize surface oxygen and reduce spinel phase components. The special La-O bond could exhibit not only an electrovalent characteristic bond but also a relative covalent property, which enhances the stability of lattice oxygen and the reversibility of oxygen redox. The spinel phase composition of surface area could be reduced through La doping, which suppresses capacity fade and voltage decay. Accordingly, the La-doping LLOs with Li and O vacancy defects forming at the surface area exhibit excellent reversible capacity (225 mA h/g at 1 C and 145 mA h/g at 5 C) and rate performance (80.68 and 81.76% capacity retention over 300 cycles at 1 and 5 C). This study could be extended to synthesize other advanced cathode materials for next-generation Li-ion batteries and even be helpful to the R & D of rare-earth utilization.