Surface Reconstruction‐Integrated Bulk Defect Engineering Beyond Conventional Chemical Modulation for Na‐Layered Oxide Cathodes

ABSTRACT As the most prospective cathode material for sodium‐ion batteries (SIBs), layered oxides persistently suffer from detrimental phase transitions, irreversible oxygen loss, and severe interfacial degradation during cycling. Herein, utilizing O3‐NaNi 1/3 Fe 1/3 Mn 1/3 O 2 cathode as prototype, we propose an integrated modification strategy beyond conventional chemical modulation to simultaneously boost the bulk, surface and interfacial properties. The Y‐enriched NaYO 2 (NYO) coating derived via surface reconstruction facilitates site‐selective bulk substitution whilst inducing suitably quantized local oxygen vacancy (O V ) defects through charge balancing. The synergistic interaction between Y─O─TM strong bond and the O V 's charge‐buffering effect jointly modulates O 2p orbital electronic band configuration, preventing excessive O oxidation and formation of O─O dimers arising from charge concentration. Moreover, the perovskite‐phase NYO surface serves as an inherent fast Na + conductor ensuring efficient ion transport at interface, whilst also providing a robust rigid mechanical barrier that effectively suppresses interfacial side reactions and dissolution of transition metals. As a result, anion redox reversibility and local chemical environment stability are elevated, thereby comprehensively boosting electrochemical reaction kinetics and charge transfer efficiency, as confirmed by theoretical calculations and advanced synchrotron characterization. This research establishes a novel paradigm for the advancement of high‐performance Na‐layered oxide cathodes incorporating synergistic multi‐mechanism modification.