Dual interface modifications enabling long-life and air-stable O3-type cathode for advanced sodium-ion batteries

O3-type layered oxide materials are generally regarded as the most potential cathode candidates for sodium-ion batteries (SIBs) owing to their exceptional energy density and suitable initial Coulombic efficiency. However, the development of the O3-type cathode materials in practical applications is hindered by their poor cyclic and air stability. Herein, we creatively develop a dual-layer interface modification strategy for the O3 cathode (NaNi_0.45Mn_0.4Cu_0.05Ti_0.1O₂), aimed at decreasing the diffusion barrier of Na⁺ and alleviating structural deterioration during the cycle process. The optimized sample (O3@P2@NAO) exhibits a comprehensive improvement in electrochemical properties, characterized by not only high capacity (150 mAh g^-1 at 0.1C) and superior rate capability (126.6 mAh g^-1 at 5C), but also extended cycling stability (90.5% capacity retention after 120 cycles). In addition, the O3@P2@NAO cathode delivers an excellent capacity retention of 85.5% after air exposure to wet air (40% RH) for 7 days. The physicochemical structure and electrochemical tests indicate that the unique double interface modification layers provide rapid Na⁺ transport channels and slow down the corrosion effects of the electrolyte and air on the cathode surface. This work provides a feasible approach for developing O3-type cathodes with application potential and accelerating advancements toward the commercialization of SIBs.