Lithium-Induced Inverted Honeycomb-Ordered Superlattice Enables Durable O3-Type Sodium Oxide Cathodes

O3-type layered sodium transition-metal oxides, such as NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM), suffer from detrimental phase transitions, irreversible oxygen release, and unstable interfaces during high-voltage operation, which severely hinder their practical application. Herein, we report a lithium-induced inverted honeycomb-superlattice engineering strategy that constructs a layered-superlattice composite structure within NFM, resulting in a locally distributed yet long-range-ordered inverted honeycomb superlattice. In this structure, the transition-metal (TM)-dominant columns occupy the centers of hexagonal motifs, surrounded by mixed Li/TM vertex sites. This distinctive superlattice rigidly anchors the transition-metal slabs, strengthens TM-O covalency, and suppresses irreversible interlayer gliding. It further regulates the high-voltage structural and redox evolution by enabling highly reversible anionic oxygen redox and introducing a reversible O1 intermediate phase during cycling. Concurrently, the in situ formed Li₃PO₄ (LP) coating effectively suppresses side reactions, further improving interfacial stability. The resulting NFM@LP cathode delivers 94.0% capacity retention after 500 cycles at 4.5 V, and the NFM@LP||hard carbon pouch full cell maintains 95.5% capacity retention over 200 cycles within 2.0-4.2 V. This work demonstrates that lithium-induced inverted honeycomb superlattice engineering provides a promising design strategy for constructing high-energy and durable O3-type sodium cathodes.