Nitrogen-Doped Carbon Nanospheres Dispersed within Graphene Oxide to Fabricate Composite Fibers for High Performance Flexible Supercapacitors

Fiber-shaped supercapacitors have garnered significant interest in the field of flexible and wearable energy storage devices. Herein, a "ball bearing" structured nitrogen-doped hollow carbon spheres/graphene composite fiber is designed by integrating nitrogen-doped hollow carbon spheres into graphene sheets. The nitrogen-doped hollow carbon spheres promote the interfacial slip between graphene sheets during the stretching process, and a remarkable toughness of 4.5 MJ m–3 and a fracture strain of 16.38% are obtained. Due to the hierarchical mesoporous structure, elevated specific surface area, and N and O groups introduced by the nitrogen-doped hollow carbon spheres, the optimal nitrogen-doped hollow carbon spheres/graphene composite fiber electrode demonstrates distinctive specific capacitance (367 F cm–3 at 0.5 A cm–3) and excellent rate performance (retaining 65.61% capacity from 0.5 to 2 A cm–3). Furthermore, the symmetric all-solid-state supercapacitor attains a peak energy density of 24.99 mW h cm–3 and a volumetric power density of 822 mW cm–3. These NHCS/GF composite fibers hold tremendous potential for practical applications in wearable devices, flexible electronics, and smart textiles.