Hierarchical porous "skin/skeleton"-like MXene/biomass derived carbon fibers heterostructure for self-supporting, flexible all solid-state supercapacitors

Two-dimensional transition metal carbide and nitride are promising energy storage materials. However, the aggregation and rearrangement of two-dimensional nanosheets limit their electrochemical performance. In this paper, a novel hierarchical porous ?skin/skeleton?-like MXene/biomass derived carbon fibers (MXene/CF) heterostructure is prepared by one-step pyrolysis, which efficiently weakens the stacking of MXene nanosheets. Moreover, MXene/CF has a well-defined hierarchical porous structure, thereby facilitating electrolyte penetration and providing efficient and stable channels for rapid diffusion/transfer of ions to the electrode and producing functional MXene-based electrodes. When MXene/CF heterostructure is applied as a self-supporting electrode for supercapacitors, the electrode has high volumetric capacitance of 7.14 F cm-3, good rate characteristics (63.9% from 0.5 to 100 A g-1), and excellent cyclic stability (99.8% after 5000 cycles). In addition, all solid-state symmetric supercapacitors based on MXene/CF electrodes are also assembled, which not only exhibits high capacitance and rate performance, but also has good flexibility and long durability. The device still maintains structural integrity and steady capacitance even after 2500 cycles at different bending angles. This work is expecting to guide the design of the next generation of flexible, portable and highly integrated supercapacitors with high capacity and rate performance to further meet the requirements of sustainable development.