Mg2+ doping into Li sites to improve anionic redox reversibility and thermal stability of lithium-rich manganese-based oxides cathode

Abstract

As a low cost and low atomic mass dopant, Mg2+ doping is often used to improve the electrochemical performance of lithium-rich manganese-based layered oxides (LRMO) cathode materials. However, the Mg2+ doping site is still controversial and its mechanism is not clear. In this work, Mg-doped LRMO was synthesized by a spray-drying method. It was proved that the Mg2+ is doped into the Li sites of the Li layers substituting partial ‘Li–O–Li’ with a stronger ‘Li–O–Mg’ configuration. The Mg-doped LRMO possesses a stable lattice structure and high reversibility of anionic redox reaction, which shows a high initial Coulombic efficiency of 89.0%, enhanced specific capacity (305.3 mAh/g at 0.1 C), cycling performance, and thermal stability in comparison with the pristine sample. The first-principle calculations reveal that the top of the O2p band of Mg-doped LRMO is lower about 0.81 eV, which implies a more stable lattice oxygen structure.