High‐Entropy 2D MXenes: A New Paradigm for Energy Storage

ABSTRACT Two‐dimensional (2D) MXenes, a family of transition metal (TM) carbides and nitrides, have rapidly reshaped the landscape of electrochemical energy storage owing to their rich chemistry and outstanding charge‐storage performance. High‐entropy MXenes (HE‐MX), which integrate five or more near‐equimolar TMs within a single two‐dimensional (2D) lattice, extend this platform by introducing entropy‐stabilised multielement configurations inspired by high‐entropy alloys (HEAs). In these materials, configurational entropy, lattice distortion and “cocktail” effects cooperatively enhance electrochemical stability, activity and durability. This review explores the development of HE‐MX, tracing their evolution from the foundational concepts of HEA to sophisticated multi‐component architectures with adjustable structures and functional properties. It emphasises advancements in synthesis, such as the selective etching of complex precursors and in the management of lattice strain and surface terminations. By combining insights from in situ spectroscopy, multiscale simulations and electrochemical measurements, we clarify how features such as cation ordering, tailored surface terminations and entropy‐stabilised phases govern capacitive behaviour, ion transport kinetics and cycling robustness. Building on these entropy–structure–property relationships, this review outlines the design principles for atomic‐level control of the composition and interfaces and identifies strategies to improve stability under extreme operating conditions and enable scalable manufacturing. HE‐MX thus emerges as a versatile platform to alleviate the longstanding trade‐off between energy density and durability in next‐generation electrochemical energy storage systems.