High-energy and long-life O3-type layered cathode material for sodium-ion batteries

O3-type cathodes for sodium-ion batteries have attracted significant attention owning to their low cost and high energy density. However, their applications are restricted by rapid capacity degradation during long-term cycling, with uneven Na⁺ distribution and microcrack formation being key contributing factors. In this study, a customized reconstruction layer integrating a fast ion conductor NaCaPO₄ coating with gradient Ca²⁺ doping was developed to enhance the surface chemical and mechanical stability of the layered cathodes. The gradient Ca²⁺ doped interphase facilitated uniform phase transformation within the particles, minimized lattice mismatch, ensured even Na⁺ distribution, and mitigated microcrack formation through a pinning effect. Consequently, the optimized cathode delivered excellent rate performance (105.3 mAh g^{− 1} at 10 C), long-term cycling stability (81.0% capacity retention after 300 cycles at 0.5 C), and robust reliability under high-voltage conditions and across a wide operating temperature range (− 10 to 50°C). The practical feasibility of a pouch-type Na-ion full cell paired with a hard carbon anode was demonstrated by a high capacity retention of 82.9% after 300 cycles at 1 C. This scalable interface modification strategy can provide valuable insights into the development of advanced oxide cathode materials for sodium-ion batteries.