Iron‐Based Materials for Advanced Lithium/Sodium‐Ion Batteries

Lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) help meet the growing global demand for sustainable energy storage due to their high energy density, portability, and rechargeability. As a key component of secondary battery systems, the anode material largely determines their overall performance. However, commercial graphite is limited by its low theoretical capacity (372 mAh·g^-1) and poor Na⁺ storage capacity, necessitating the exploration of alternative anode materials. Among the numerous candidate materials, iron-based compounds (including oxides, sulfides, and porous materials derived from metal-organic frameworks (MOFs)) stand out due to their high theoretical specific capacity, natural abundance, and environmental friendliness. However, severe volume expansion and structural instability during repeated charge-discharge cycles lead to rapid capacity decay, severely hindering their practical application. This review systematically summarizes the recent progress in iron-based compounds as anodes for LIBs and SIBs. The electrochemical properties of iron oxides, iron sulfides, and porous iron-based derivatives are highlighted, with particular attention paid to the challenges posed by volume expansion. Furthermore, a comprehensive analysis of the strategies developed to mitigate volume expansion, such as nanostructure design, carbon composites, hollow/porous structure engineering, and interface optimization, is presented. Finally, current limitations and future research opportunities are outlined, aiming to provide guidance for the rational design of high-performance iron-based anode materials for next-generation rechargeable batteries.