A.-M. Wang *, H.-Y. Liu, D.-D. Guo, N. Bai *, L.-B. Ben *, Z.-S. Wu, H. Liu, Y.-H. Shen, D. Cao

Chemical Engineering Journal, 2025, accepted.

P2-type NaxMnO2.05 (x ≤ 1) cathode materials suffer from severe structural degradation during electrochemical cycling, primarily attributed to Jahn–Teller distortion associated with Mn3+ ions and the instability of surface oxygen atoms in their close-packed layered framework. These issues critically limit their capacity retention and practical applicability in sodium-ion batteries. In this study, we propose a synergistic strategy to enhance both the surface and bulk stability of NMO cathode materials through surface fluorination and iron doping, respectively. This dual-modification is achieved via a facile solid-state sintering method, resulting in a core–shell structured material with an Fe-doped bulk and a fluorine-enriched surface layer. Comprehensive structural and electrochemical characterizations confirm the successful construction of the core–shell architecture and its positive impact on cycling durability. The optimized composition, NaxMn0.9Fe0.1O1.95F0.1 (FF10-NMO), delivers a high specific discharge capacity of 113 mAh g−1 at 5C and maintains 92% of its initial capacity after 600 cycles in half-cell configurations. Furthermore, when paired with commercial hard carbon in full-cell assemblies, FF10-NMO achieves a remarkable energy density of 163.01 Wh kg−1 and a power density of 542.18 W kg−1. These results highlight the effectiveness of the Fe/F co-modification approach in stabilizing P2-type layered structures and underscore the great promise of core–shell engineered cathode materials for high-performance sodium-ion batteries.