Preparation of microporous carbon nanofibers from polyimide by using polyvinyl pyrrolidone as template and their capacitive performance

A self-supported and binder-free micro-porous polyimide (PI)-based carbon fibers are prepared by polymer blend electrospinning technology and subsequent thermal treatment without activation and evaluated electrochemically for supercapacitor application. Polyvinyl pyrrolidone (PVP) is successfully used as a pore forming template by controlling the crosslinking between PVP and PI precursor via imidization process. The maximal specific capacitance of 215 F g−1 based on a symmetrical two-electrode supercapacitor is achieved at 0.2 A g−1. The specific capacitance could still remain 113 F g−1 at 100 A g−1 with the retention ratio of 53%. It is noteworthy to mention that the energy density is 7.5 Wh kg−1 with power density of 0.05 kW kg−1 at a current density of 0.2 A g−1, and 5.0 Wh kg−1 with a high power density of 7.5 kW kg−1 at 30.0 A g−1. The maximum power density is 20.0 kW kg−1 with energy density of 3.0 Wh kg−1. The results indicate that the specific capacitance is not only attributed to optimized pore structures and surface chemistry but also attributed to the wettability of the electrolyte. The improved rate performance should be related to the reduced ion transportation distance derived from the nanofibers.