Stabilizing Lattice Oxygen in a P2-NaMnFeO Cathode via an Integrated Strategy for High-Performance Na-Ion Batteries.

P2-type NaMnFeO (MF) has attracted great interest as a promising cathode material for sodium-ion batteries (SIBs) due to its high specific capacity and low cost. However, its poor cyclic stability and rate performance hinder its practical applications, which is largely related to lattice oxygen instability. Here, we propose to coat the cathode of SIBs with LiZrO, which realizes the "three-in-one" modification of LiZrO coating and Li, Zr co-doping. The synergy of LiZrO coating and Li/Zr doping improves both the cycle stability and rate performance, and the underlying modification mechanism is revealed by a series of characterization methods. The doping of Zr increases the interlayer spacing of MF, reduces the diffusion barrier of Na, and reduces the ratio of Mn/Mn, thus inhibiting the Jahn-Teller effect. The LiZrO coating layer inhibits the side reaction between the cathode and the electrolyte. The synergy of LiZrO coating and Li, Zr co-doping enhances the stability of lattice oxygen and the reversibility of anionic redox, which improves the cycle stability and rate performance. This study provides some insights into stabilizing the lattice oxygen in layered oxide cathodes for high-performance SIBs.