Constraining Interlayer Slipping in P2-Type Layered Oxides with Oxygen Redox by Constructing Strong Covalent Bonds.

Lattice oxygen redox (LOR) in P2-type layered oxides is an effective strategy to break through the limit of energy density of conventional cathodes due to its high redox potential (>4 V vs Na/Na) as well as extra capacity. Nevertheless, LOR-induced local structure distortion and irreversible phase transitions cause serious electrochemical performance degradation, hindering practical applications. Herein, we propose that the generation of the OP4 phase can be replaced with the Z phase by introducing the Sb element with a higher ionic potential and strong covalent bonds within the TMO octahedron. Z phase transition is realized by constraining interlayer slipping between adjacent transition metal (TM) layers compared to OP4, which reduces the strain in the layered structure, lowers the Na diffusion energy barrier, and creates more efficient Na diffusion channels. Consequently, Sb-substituted oxides demonstrate excellent kinetics, rate capability (79 mAh g at 1 A g) in half cells, and a high energy density of 487 Wh kg (on cathode) in full cells.