Cathode‐Electrolyte Interphase: Evolution, Identification and Modulation Strategies for High‐Voltage Dual‐Ion Batteries

Abstract Dual‐ion batteries (DIBs) have garnered considerable attention in the emerging electrochemical energy storage field due to their cation‐anion synergistic energy storage mechanism and high working voltage. However, the high cathode potential and the relatively large anions endow the formation of cathode‐electrolyte interphase (CEI), making it challenging to balance structural stability and efficient anion transport. In this review, a brief introduction is first given on the history of DIBs and the CEI evolution in DIBs. Then, the accurate CEI identification with advanced characterization techniques is comprehensively discussed. Furthermore, some representative CEI modulation strategies for rationally regulating morphology, composition, and reaction mechanisms are critically summarized. Finally, the current challenges and the focus for future research are introduced. It is expected that this review provides a crucial roadmap to accurately identify CEI composition, structure, and dynamic evolution, guide the design of advanced CEIs that are simultaneously robust and ionically conductive, and pave the way for positioning DIBs as potential complements to conventional lithium‐ion batteries.