Layered-Structured Sodium-Ion Cathode Materials: Advancements through High-Entropy Approaches

High-entropy materials (HEMs) offer a novel approach in battery technology by utilizing multielement synergy–known as high-entropy and cocktail effects–to enhance material performance. In sodium-ion batteries (SIBs), HEMs hold promise for addressing key challenges in battery material performance. This review delves deeply into the mechanisms and specific characteristics of high-entropy effects, for the first time, scientifically connecting enhancements in the electrochemical performance of layered cathodes to the intrinsic properties of HEMs. We explore the mechanisms behind these improvements, particularly in O3 and P2-type layered oxides, where the high-entropy strategy contributes to maintaining the structural integrity, enhancing air resistance, and improving ion diffusion. Additionally, we analyze the limitations of this approach and discuss future development directions, incorporating advanced methods like element selection, computational techniques, and multiphase coexistence. This provides design guidelines and general considerations for optimizing high-entropy layered oxides, highlighting both their potential and challenges for SIB applications.