Fast Oxygen Redox Kinetics Induced by CoO₆ Octahedron With π‐Interaction in P2‐Type Sodium Oxides

Abstract

Enhancing the kinetics of lattice oxygen redox (LOR) in P2‐type layered sodium oxide cathodes is crucial for the advancement of sodium‐ion batteries (SIBs) with superior energy and power densities. Electronic structure regulation stands out as a highly effective approach to address the inherent limitations of P2‐type layered oxides with LOR, including sluggish kinetics, phase transitions, voltage hysteresis, and local structural distortion. Herein, a strategy involving the introduction of CoO6 octahedra with π‐interaction into Na0.6Li0.1Fe0.3−xCoxMn0.6O2 (x = 0, 0.15, 0.3) cathodes to facilitate Na‐ion transport is proposed. Furthermore, the impact of FeO6 octahedra with σ‐interaction in P2‐type cathodes on electrochemical performance is comprehensively investigated. Through multimodal in‐situ and ex‐situ characterization techniques, it is revealed that Co─O with π‐interaction effectively mitigates P2‐OP4 phase transitions by strengthening Na─O, reduces voltage hysteresis, and stabilizes the local structure. Consequently, Na0.6Li0.1Co0.3Mn0.6O2 demonstrates enhanced Na‐ion diffusion kinetics, leading to improved rate performance and a reversible capacity of 55 mAh g−1 at 10 C, significantly outperforming cathodes with Fe─O σ‐interaction. Moreover, when coupled with hard carbon, the full cell achieves a remarkable energy density of 395 Wh kg−1 (on cathode) at 0.1 C, with a capacity retention of 75% over 100 cycles at 1 C.