Nitrogen-enriched meso-macroporous carbon fiber network as a binder-free flexible electrode for supercapacitors

In order to maximize supercapacitor performances, it is essential to engineer the electrode architecture with shortened ion-diffusion paths and high content of pseudocapacitive sites. By incorporating redox-active species into low-dimensional carbon materials, both the specific capacitances and rate capabilities can be improved. In this study, a self-sustaining, flexible mat consisting of nitrogen-enriched carbon fiber (NCF) network was successfully produced through the co-electrospinning of a polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP)/SiO2 blended solution, followed by pyrolysis and SiO2 removal processes. Despite its low surface area (<60 m2/g), the NCF exhibits high nitrogen content (17.3 wt%) and interconnected meso-macroporous nanostructure, resulting in high pseudocapacitance (242 F/g at 0.2 A/g), fast rate capability, and excellent cycling performance (99% of initial capacitance after 5000 cycles). The electrical double-layer capacitance and pseudocapacitance can be easily decoupled. The binder-free NCF based symmetric supercapacitor demonstrates a purely capacitive responses and high rate handling. We attribute the excellent electrochemical performances to the good conductivity and shortened ion diffusion paths of carbon fiber backbone, and pseudocapacitive edge-concentrated nitrogen species.