Band Structure Engineering Promotes Anionic Redox Reversibility of Cobalt‐Free Li‐Rich Layered Oxides Cathodes
Xianggang Gao, Juanlang Guo, Shihao Li, Haiyan Zhang, Yi Zhang, Chaohong Guan, Mengran Wang, Yanqing Lai, Zhian Zhang
Abstract
Abstract Li‐rich layered oxides cathodes (LLOs) have prevailed as the promising high‐energy‐density cathode materials due to their distinctive anionic redox chemistry. However, uncontrollable anionic redox process usually leads to structural deterioration and electrochemical degradation. Herein, a Mo/Cl co‐doping strategy is proposed to regulate the relative position of energy band for modulating the anionic redox chemistry and strengthening the structural stability of Co‐free Li 1.16 Mn 0.56 Ni 0.28 O 2 cathodes. The incorporation of Mo with high d state orbit and Cl with low electronegativity can narrow the band energy gap between bonding and antibonding bands via increasing the filled lower‐Hubbard band (LHB) and decreasing the non‐bonding O 2p energy bands, promoting the anionic redox reversibility. In addition, strong covalent Mo─O and Mn─Cl bonding further increases the covalency of Mn─O band to further stabilize the O 2 n− species and enhance the reversible distortion of MnO 6 octahedron. The strengthening electronic conductivity, together with the epitaxial structure Li 2 MoO 4 facilitates the fast Li + kinetics. As a result, the dual doping material exhibits enhanced anionic redox reversibility and suppressed oxygen release with increased cyclic stability and excellent rate performance. This strategy provides some guidance to design high‐energy‐density LLOs with desirable anionic redox reversibility and stable crystal structure via band structure engineering.