Revealing ion storage mechanisms of high-entropy anode materials through element selection and structure design

Abstract

High-entropy materials (HEMs) have gained significant research interest as potential anodes for rechargeable ion batteries (RIBs), attributed to their exceptional electrochemical performance. However, the ion storage mechanisms in HEMs remain complex and incompletely understood, primarily due to multi-element synergy. This perspective critically examines the ion storage mechanisms of HEMs, focusing on intercalation, conversion, alloying, and the less-explored space charge. Emphasis is placed on the critical role of element selection in governing these mechanisms: anion elements are necessary for conversion reactions; Sn, Bi, Sb, Zn, In, Ge, and Si enable alloying, while transition metals like Fe, Co, and Ni are pivotal for space charge. Furthermore, we analyze the correlation among capacity, cycling stability, and fast-charging performance in HEMs relative to element selection. Elements promoting conversion, alloying, and space-charge mechanisms enhance capacity, whereas non-converting elements improve cycling stability. Anions with high electrical conductivity and cations facilitating space-charge formation improve fast-charging performance. We further emphasize that effective structural design is crucial to fully exploit these four mechanisms. The key principle is accelerating intercalation and conversion reaction kinetics, thereby promoting finer metal nanoparticle formation to maximize alloying and space-charge mechanisms. Finally, we outline current challenges and future research directions for HEM anodes in RIBs.