Activated carbon nanofibers derived from polyimides containing aryl imidazole and hydroxyl groups for high-performance supercapacitors

In this work, the carbon nanofibers (CNFs) are first prepared by electrospinning the poly(amic acid) (PAA) solution containing aryl imidazole and hydroxyl groups, followed by thermal imidization, rearrangement and carbonization. Then, the CNFs are further treated with KOH to obtain activated CNFs. The effects of the PAA concentration, rearrangement time, carbonation temperature and mass ratio of CNFs/KOH on the electrochemical properties are investigated. The results show that the sample HPI-CNF-20-2-800 displays the best electrochemical performance. After activation, the A-HPI-CNF-1/3 exhibits a maximum specific surface area of 1762 m2 g-1 and pore volume of 0.92 cm3 g- 1, leading to a high specific capacitance of 325.0 F g-1 at 0.5 A g-1. Moreover, the specific capacitance can reach 234.6 F g-1 when the current density is 20 A g-1. Furthermore, the symmetric supercapacitor fabricated by A-HPI-CNF-1/3 shows a maximum energy density of 29.17 Wh kg-1, coupled with a power density of 500.0 W kg-1. The capacitance retention rate of the supercapacitor maintains about 99.95% after 20,000 charge-discharge cycles at 1 A g-1. Therefore, this work provides a novel rearrangeable precursor for the preparation of activated CNFs with a considerable electrochemical performance, which will be considered as excellent electrode materials for supercapacitors.