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MXenes, as a 2D planar structure nanomaterial, were first reported in 2011. Due to their large specific surface area, high ductility, high electrical conductivity, strong hydrophilic surface, and high mechanical flexibility, MXenes have been extensively explored in the development of various functional materials with desired performances. This review is aimed to summarize the current progress in synthesis, modification, and applications of MXene‐based composite films as electrode materials of flexible energy storage devices. In the synthesis of MXenes, the evolution and exploration of etchants are emphasized. Furthermore, in order to develop MXene‐based composite films, the components used to modify the MXene nanoflakes, including 0D, 1D, and 2D nanomaterials, are summarized, and the perspectives and research direction of such materials are also discussed.

Poor rate capability due to the sheet self‐stacking of conventional MXene electrode limits their electrochemical application to some extent. Herein, incorporating reduced graphene oxide into Ti3C2Tx MXene is reported to improve the electrochemical performance, cycle lifetime, and mechanical flexibility significantly. Graphene oxide is reduced by thermal heating, by which it can release gas locally to induce micro‐surface structure. The resulting film with an introduction of 20 wt% graphene oxide exhibits an expansion of the interlayer space to multiply the active sites and thereby lead to a specific capacitance of up to 322 F g−1 at 1 A g−1 in 3 m H2SO4 electrolyte. In addition, the fabricated composite electrode also exhibits an excellent cycle stability and mechanical flexibility even after 32 000 charge/discharge cycles. This work provides a progressive strategy to synthesize micro‐structural and flexible MXene‐based electrode for the future application in flexible energy storage devices.

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