Crosslinked carbon nanofiber films with hierarchical pores as flexible electrodes for high performance supercapacitors
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Flexible, cross-linked carbon nanofibers (CNFs) film with hierarchical micro-meso-macro-porous structure is prepared by carbonization of the elestrospun polyacrylonitrile (PAN)/NaN3 composite nanofiber mats. The gas liberation of NaN3 during the carbonization is responsible for the tuning of both specific surface area and the pore size distribution. In addition, the exothermal decomposition of NaN3 at the heating stage of carbonization leads to the melting of the PAN/NaN3 composite fibers, resulting in a cross-linked CNF structure. The CNF film with 5 wt% NaN3 carbonized at 900 °C (CNF-5-900) shows a high specific capacitance of 222.92 F g− 1, nearly twice as high as that of the CNF film without NaN3 (CNF-0-900). It also shows an excellent capacitance retention ratio of 81.97% of its initial capacitance from 0.5 A/g to 50 A/g, much superior to the value of 51.02 % for CNF-0-900. Moreover, it has an excellent cycling stability with cycling retention ratio achieves 94.5% after 10,000 charge-discharge cycles. Coupled with its excellent mechanical stability (only 1.6% conductivity loss after bending of CNF-5-900 film at curvature radii (r) = 2.5 × 10− 3 m for 10,000 cycles) and facile fabrication process, the flexible, cross-linked CNF films with hierarchical micro-meso-macro-porous structure is a potential electrode materials and/or backbone to support other active materials for various application, including the flexible energy storage and electrocatalytic.