Stabilizing the Reversible Oxygen Redox Reactions in Lithium-Rich Layered Cathodes Via the Surface-to-Bulk Enhanced D-P Hybridization

Abstract

The oxygen redox (OR) reaction in layered Li-rich oxide (LLO) cathode materials has been an attractive topic as it provides additional capacity. However, the suppression of the irreversible transition metal (TM) migration and oxygen release induced by the OR reaction is still a challenging issue, as it would lead to a severe capacity and voltage decay. Here, we introduce a surface-to-bulk structure modification strategy, namely surface Ni segregation and bulk Mo doping structure. Based on this strategy, the oxygen atoms near the surface are fully coordinated, and meanwhile the distortion of the metal–oxygen octahedron is alleviated in the bulk phase, thereby enhancing the degree of TM 3d and O 2p hybridization to stabilize the metal–oxygen framework for the OR reaction. It suppresses cation migration and oxygen release and maintains phase stability, allowing a reversible OR reaction. As a result, the capacity and voltage retention of the modified materials were significantly improved. This work gives an efficient method to stabilize the OR reaction through the surface-to-bulk enhanced d-p hybridization and provides new paths for the design of Li-rich cathodes.