Enabling Full Conversion Reaction with High Reversibility to Approach Theoretical Capacity for Sodium Storage

Abstract Conversion‐type electrode materials are emerging as promising candidates for high‐energy rechargeable batteries, owing to their substantially higher theoretical capacity relative to intercalation‐based materials. Nevertheless, the full benefit from conversion‐type electrode materials remains out of reach in sodium‐ion batteries, due to the inadequate conversion reaction toward sodium and the poor reversibility during desodiation. Here, a full conversion reaction with high reversibility is demonstrated through promoting the initial sodium intercalation and subsequent reconversion kinetics by transition metal doping. The doping‐induced lowering of the sodium intercalation energy in thermodynamics effectively drives the full conversion reaction, while the metal transition of the doped element enhances reconversion kinetics in achieving high reversibility. The obtained results open a new avenue for the development of high‐performance conversion‐type electrodes and provide a novel understanding of the conversion reaction mechanism.