N-doped reduced graphene oxide (rGO) wrapped carbon microfibers as binder-free electrodes for flexible fibre supercapacitors and sodium-ion batteries

In this study, N-doped reduced graphene oxide (rGO) wrapped carbon micro fibres (CFs) were synthesized by one-step high temperature pyrolysis method. Free-standing binder-free electrodes of N-doped rGO on CF were fabricated to apply in extended flexible fibrous supercapacitors and sodium-ion batteries (NIBs). The results showed that the attachment of N-doped graphene onto CF led to high electrochemical capacitance properties. The micro-fibre electrodes showed high performance supercapacitor behaviour of 18.7 F cm−3 at a current density of 1 A cm−3 as a flexible solid-state energy storage device. In parallel with the supercapacitance properties, the micro-fibre electrode shows impressive electrochemical performances when evaluated as anode for NIB, delivering a reversible capacity of 400 mAh/g with capacity retention approaching 100% after 100 cycles. The excellent performances are attributed to defects induced by N-doping along with large surface area of hierarchical porous architecture that can facilitate the storage and diffusion of Na+ and prevent the restacking of rGO during cycling. Thus, these N-doped rGO fibrous materials have substantial promise for fabricating extended flexible cable electronics and NIBs with superior strength and performance.