Crystalline Structure Engineering of Metal Sulfides Toward Advanced Sodium‐Ion Storage

ABSTRACT Transition metal sulfides (TMSs) have garnered significant attention due to their unique physiochemical properties and high theoretical capacities. However, their poor intrinsic electronic conductivity hinders reaction kinetics. In this study, we propose a strategy of crystalline structure engineering to achieve metallic electronic conductivity, thereby significantly enhancing the electrochemical reaction kinetics during sodium‐ion storage. Our findings reveal that iron sulfides with different crystal structures exhibit distinct electrochemical behaviors in sodium‐ion batteries. Specifically, the metallic‐phase tetragonal FeS, characterized by its layered structure, demonstrates superior electronic conductivity, electrochemical reversibility, and fast reaction kinetics. These attributes result in a markedly higher sodium storage capacity and faster electrochemical reactivity compared to semiconducting hexagonal FeS. This study introduces a critical strategy for designing next‐generation sodium storage anodes with improved electrochemical performance.