Three-Dimensionally Conducting Network in Graphene-Based Composite Fibers toward Enhanced Electrochemical and Toughness Performance in Fibrous Supercapacitors

As one of the most promising energy storage devices, graphene-based fibrous supercapacitors (FSSCs) are attracting intensive attention. However, the conflict between specific capacitance and intrinsic brittleness of pure graphene fibers hinders their practical applications. Herein, we develop a strategy to fabricate graphene-based ternary composite CNT/MXene/graphene (CMG) fiber electrodes with high toughness and high electrical and electrochemical performance. These resulting properties are attributed to the three-dimensional cross-linked conducting network within graphene sheets through covalent bonding and π–π interaction among acidified carbon nanotubes, graphene sheets, and MXene, which greatly contributes to the enhanced tensile strength, toughness, and electrical transport in the CMG fiber. The CMG fiber with the optimized mass ratio of different components shows a high toughness of ∼1.7 MJ m–3 and an electrical conductivity of 420 S cm–1, which is 4- and 2-fold that of reduced graphene oxide fiber, respectively. The assembled FSSC based on the optimized CMG fiber exhibits an areal capacitance of 237 mF cm–2 and a good rate performance of 85%.