P2/O3 Biphase Integrated With Fence‐Type Superstructure Enables Robust Sodium Layered Oxide Cathodes

Abstract

ABSTRACT Layered oxides are promising cathode candidates for sodium‐ion batteries (SIBs) owing to their tunable compositions and high specific capacities. However, detrimental phase transitions, Jahn–Teller (J–T) distortion, and transition‐metal (TM) migration during cycling typically induce severe structural degradation and irreversible oxygen loss, ultimately resulting in rapid capacity fading. Herein, we propose a dual‐scale interlayer‐intralayer synergistic strategy to address these intrinsic challenges, which integrates a P2/O3 biphasic intergrowth architecture for interlayer stabilization and a fence‐type superstructure with enlarged superlattice spacing for intralayer regulation within TM slabs. The intergrown P2/O3 phases generate a robust interlocking effect that alleviates strain accumulation, further suppressing undesirable phase evolution, mitigating J–T distortion, and partially restraining out‐of‐plane TM migration. Meanwhile, the fence‐type superstructure, featuring an ultra‐wide interplanar spacing, inhibits the formation of vacancy clustering driven by in‐plane TM migration, thereby stabilizing the local oxygen environment and eliminating irreversible oxygen loss. Benefiting from this cooperative interlayer‐intralayer regulation, the as‐designed Na 0.668 Li 0.1 Ni 0.3 Mn 0.4 Ti 0.2 O 2 cathode delivers quasi‐solid‐solution reaction behavior and highly reversible oxygen redox, along with substantially enhanced structural stability and electrochemical performance. This work highlights the critical role of dual‐scale structural engineering in simultaneously modulating hierarchical structural motifs, providing a generalizable paradigm for the rational design of high‐energy‐density layered cathodes for SIBs.