High‐Entropy Materials as Anodes in Sodium‐Ion Batteries: Current Status, Challenges, and Future Perspectives

Abstract Sodium‐ion batteries (SIBs) can act as an alternative to lithium‐ion batteries due to their similar working principle and sodium's higher abundance in the crust. However, sodium's larger ionic radius and higher relative atomic mass cause sluggish ion diffusion, structural degradation, and low anode capacity, impairing fast‐charging, cycling stability, and energy density of SIBs. High‐entropy materials (HEMs) have recently gained attention as a potential solution to these limitations. Nevertheless, a comprehensive review of HEMs as SIB anodes is still lacking. This review systematically summarizes recent advancements in HEM‐based SIB anodes. It first clarifies the definition, entropy‐based classification, and four core effects of HEMs, and discusses their sodium storage mechanisms, including insertion, conversion, alloying, and the recently proposed space‐charge mechanism. The review further explores six categories of HEM anodes—sulfides, oxides, selenides, phosphides, alloys, and MXenes, among which MXenes have rarely been discussed in previous reviews—discussing their structural characteristics and electrochemical performance. The review also highlights current synthesis strategies of HEMs in SIBs, addressing challenges such as elemental segregation, nanostructure control, and scalability. Finally, the review outlines current challenges of HEM anodes and proposes their future research directions focused on space‐charge mechanisms, compositions optimization, synthesis approaches, and wide‐temperature‐range adaptability.