In Situ Surface Coating and Oxygen Vacancy Dual Strategy Endowing a Li-Rich Li1.2Mn0.55Ni0.11Co0.14O2 Cathode with Superior Lithium Storage Performance

Lithium-rich Mn-based cathode materials are widely regarded as the next-generation cathode materials for high-energy-density lithium-ion batteries owing to their low cost and high specific capacity. Nonetheless, their commercial application is seriously hindered by low initial Coulombic efficiency, capacity loss, and voltage drop during long-term cycling. Herein, surface phosphorus doping and a mixture protective layer with oxygen vacancies (OVs) which consists of Li3PO4 and LiMnPO4 as a surface-coating layer on the Li1.2Mn0.55Ni0.11Co0.14O2 cathode material through a facile solid–gas reaction treatment, which can simultaneously optimize the surface chemical structure and deplete lithium impurity, is proposed. What is more, the dual strategy of surface engineering and OVs can improve electronic conductivity and regulate the ion diffusion rate. The dual-modified sample expresses a discharge capacity of 180.9 mA h g–1 with a capacity retention of 89.2% at 0.5 C after 250 cycles, which is better than that of the pristine sample (63.7%). This work provides a facile and effective method for surface coating design to improve other Li-rich manganese-based cathodes for rechargeable batteries.