Deep fluorination-driven fast-charge and high-capacity sodium oxide cathode

Abstract

To advance the application of layered oxide cathodes in fast-charging sodium-ion batteries, it is crucial to not only suppress irreversible phase transitions but also improve the rate capability of cathode materials and optimize Na⁺ diffusion kinetics to ensure high capacity output at various charge-discharge rates. In this research, the targeted F-substitution with a heavy ratio in oxygen anion layer optimizes the Na⁺ diffusion path and electronic conductivity of the material, thereby decreasing the Na⁺ diffusion barrier and imparting high-rate performance. At a 20 C rate, the cathode achieves a capacity of over 80 mAh g⁻¹ with stable cycling performance. Additionally, the dual rivet effect between the transition metal layer and oxygen layer prevents significant phase transitions during charge/discharge within the 2–4.2 V range for the modified cathode. As a result, the F-substituted oxygen anion layer improved Na⁺ diffusion, electronic conductivity, and crystal plane structure stability, which led to the development of a high-performance, fast-charging sodium-ion battery (SIB), opening new avenues for commercial applications.