New sodium battery cathode keeps 80% capacity after 200 cycles

Researchers at Central South University have developed a novel sodium-ion battery cathode with a radial gradient structure that significantly improves air stability and cycling durability. Sodium-ion batteries, valued for their low cost and potential in large-scale energy storage, have been hindered by cathode degradation caused by exposure to moisture and carbon dioxide. The team addressed this by creating a cathode with a mixed-phase outer layer that increases the oxidation state of transition metals, forming a protective barrier against environmental damage, while maintaining a stable inner core for strong sodium storage capacity. This design enables the cathode to retain about 80% of its capacity after 200 charge-discharge cycles, compared to only 21% for conventional cathodes. The new cathode also demonstrated enhanced resistance to real-world conditions, maintaining over 103 mAh/g capacity after 10 hours in humid air with carbon dioxide, with capacity loss reduced from over 50% in standard materials to just above 12%. The gradient structure facilitates faster sodium-ion transport, improving