Tailoring the “accessible sites” of nitrogen-doped graphene fibers via balancing the hydrogen bonds and π-π attraction towards superior volumetric capacitance

Fiber supercapacitors (FSCs) composed of graphene nanosheets are promising energy storage devices as instantaneous power supply for wearable electronics. However, the electrochemical performance of graphene fibers is still far away from satisfactory. The reasons are attributable to the generation of “electrolyte inaccessible volume” such as crumples, voids and pores which are stemmed from the π-π conjugation between the graphitic domains in reduced graphene oxide nanosheets. Herein, we propose a strategy for tailoring the “accessible sites” of nitrogen-doped graphene fibers (NGFs) via balancing the hydrogen bonds and π-π attraction during the dehydration of the hydrothermally assembled hydrogel fibers. The optimized NGF-G shows significant improvement in electrochemical properties, achieving an excellent specific capacitance of 571.4 F cm⁻³ (equivalent to 476.2 F g⁻¹), promising rate performance with 68 % retained at 1.0 A cm⁻³, and a high strength of 227.6 MPa. In addition, the solid-state FSC assembled based on NGF-G fibers provides an improved energy density of 20.6 mWh cm⁻³ and power density of 500.0 mW cm⁻³, exceeding the values previously reported for other fibrous materials. This research offers a viable strategy to enhance the electrochemical performances of GFs without compromising their mechanical properties through the modulation of assembling structure of graphene nanosheets.