Tailoring Surface Chemistry for Robust and Ambient-Stable Sodium Layered Oxide Cathodes

Layered transition metal oxides represent a pivotal class of cathode materials for high-energy sodium-ion batteries (SIBs), yet their practical application is severely hindered by interfacial instability. To circumvent these degradation pathways, we demonstrate a novel synergistic Nb-Ti surface modification strategy to construct a multifunctional surface on Na_2/3Mn_2/3Cu_1/3O₂ (NMCO) cathode. Through comprehensive multimodal characterizations, we provide direct evidence that the in situ constructed Nb-Ti modified surface layer serves as a "defense barrier" that suppresses irreversible lattice oxygen redox and transition metal dissolution. Consequently, the tailored surface architecture significantly reinforces the structural integrity and facilitates Na-ion diffusion kinetics, resulting in exceptional cycling stability and ambient robustness. Theoretical calculations further corroborate that the preferential adsorption of Nb/Ti species at active lattice sites significantly elevates the energetic barriers for surface degradation. This synergistic modification strategy offers a promising and extensible approach to achieving high-performance layered oxide cathodes for sustainable energy storage.