Interfacial coordination engineering in MXene composites for mono and multivalent battery systems

Engineering MXene-based composites has become a strategic approach to overcoming kinetic limitations, volume expansion, and sluggish multivalent ion diffusion in advanced battery chemistries. Owing to their metallic conductivity, tunable interlayer spacing, redox-active surfaces, and chemically versatile terminations, MXenes transcend the traditional role of conductive additives and function as electrochemical regulators that govern ion transport, interfacial stability, and structural evolution. This review systematically analyzes the design principles, synthesis strategies, and mechanistic roles of MXene-based composites across Li + , Na + , K + , Mg 2+ , and Zn 2+ battery chemistries. It correlates synthesis methodologies including hydrothermal, solvothermal, CVD, ALD, electrochemical deposition, self-assembly, and mechanochemical routes with structural engineering outcomes such as interlayer expansion, heterostructure formation, and defect modulation. Emphasis is placed on the thermodynamic and redox origins of charge storage, distinguishing redox-active versus redox-silent MXenes and positioning these materials along the capacitor-battery continuum. In multivalent systems, MXenes mitigate sluggish kinetics and dendrite formation through interfacial ion regulation and uniform nucleation control, while in monovalent systems they buffer volume expansion and accelerate charge transfer. By integrating conductive scaffolding, ion hosting, and interphase engineering within a single material platform, MXene-based composites offer a unifying strategy for high-rate, high-capacity, and long-life batteries. This review concludes by identifying critical challenges in stability, oxidation resistance, scalable synthesis, and mechanistic ambiguity, and proposes future research directions aimed at realizing MXenes as central components of sustainable post‑lithium energy storage technologies.