Confined Hydrothermal Assembly of Hierarchical Porous MXene/RGO Composite Fibers with Enhanced Oxidation Resistance for High‐Performance Wearable Supercapacitors

Abstract MXene fibers have emerged as a promising material for energy storage applications due to their exceptional electrical conductivity and surface chemistry. However, the inherent challenges of oxidation instability and severe restacking of MXene nanosheets significantly limit their practical applications in flexible energy storage devices. Here, an innovative confined hydrothermal strategy combined with chemical crosslinking to construct 3D hierarchical porous MXene/reduced graphene oxide (RGO) composite fibers is reported. This rationally designed architecture effectively prevents MXene stacking while creating efficient ion transport channels. Notably, thiourea serves dual roles as both a chemical cross‐linker and selective reducing agent, while RGO nanosheets act as physical barriers, synergistically enhancing the composite's oxidation resistance. The optimized composite fiber exhibits outstanding electrical conductivity (862.2 S cm −1 ), mechanical strength (93.1 MPa), and remarkable oxidation resistance (90.5% conductivity retention after 60 days). The assembled solid‐state supercapacitor achieves excellent mechanical flexibility, superior cycling stability, and impressive energy density (13.5 mWh cm −3 ) and power density (1.9 W cm −3 ). This work provides a novel and effective strategy for developing high‐performance flexible wearable energy storage devices.