Recent advances in iron-based heterostructure anode materials for sodium ion batteries

Sodium ion batteries (SIBs), characterized by high energy density , prolonged cycle life, and cost-effectiveness, have garnered substantial attention as scalable energy storage devices. However, the primary challenge facing SIBs is the identification of suitable electrode materials capable of accommodating sodium ions reversibly and sustainably. To transition SIBs from the experimental stage to practical applications, the identification of electrode materials exhibiting satisfactory electrochemical performance is imperative. Iron (Fe), as a widely utilized metal element, exhibits considerable potential for application as anode materials in SIBs due to its abundance, cost-effectiveness, and high specific capacity. Nonetheless, Fe-based electrode materials suffer from low conductivity and significant volume changes during charge and discharge processes, leading to poor rate performance and cyclic stability, thereby restricting their widespread application in SIBs. Various modification strategies, such as nanosizing electrode materials, heteroatom doping , heterostructure construction, and combination with fast ion conductors , have been reported to address these challenges. Importantly, engineering Fe-based electrode materials with heterogeneous structures, integrating two or more components via van der Waals forces or chemical bonds, is crucial for creating intricate heterogeneous interfaces. These interfaces generate self-built electric fields that expedite ion transport, enhance reaction kinetics, and mitigate structural damage due to volume changes during cycling, thereby significantly improving the overall electrochemical performance of Fe-based materials in SIBs. Given the rapid advancements in the utilization of Fe-based materials in SIBs, a comprehensive review is necessary to not only summarize recent progress but also provide insight and guidance on their application in SIBs. This review offers a detailed overview of the research progress on Fe-based anode materials with heterostructure in SIBs. Emphasis is placed on synthesis methods, characterization techniques, and energy storage mechanisms of heterostructure Fe-based electrode materials. Additionally, the sodium ion storage characteristics, modification strategies, and strengthening mechanisms of Fe-based materials, including Fe-based oxides , sulfides , phosphides, selenides , as well as dual-anion Fe-based anode materials, are summarized. Finally, the remaining challenges and future development prospects of Fe-based heterostructure anode materials are discussed, aiming to promote the rapid development and practical application of these materials for SIBs.