Compositional and Structural Engineering of MAX Phases and Their Derivatives for Electrochemical Energy Storage and Conversion.

MAX phases feature exceptional compositional and structural tunability, serving as a versatile materials platform for electrochemical energy storage and conversion, both as direct active materials and as chemical precursors for an array of functional derivatives. However, a unified framework connecting compositional and structural evolution across the MAX-phase platform materials with electrochemical functionality remains underdeveloped. Here, we review recent advances in MAX phases and their derivatives for electrochemical energy storage and conversion. We focus on compositional design, structural modulation, and derivative engineering and their roles in shaping charge-storage mechanisms, reaction kinetics, and long-term stability across secondary batteries, supercapacitors, and electrocatalysis. Finally, we outline future perspectives and design principles based on compositional-structural-functional relationships to guide the rational design of MAX-based materials for electrochemical applications.