Inner porous carbon nanofibers as binder-free electrodes for high-rate supercapacitors

In most of the porous carbon based electrode materials reported to date, the pores were open and directly exposed to electrolyte, and the materials suffered from a huge stress during long-term cycle at a large current density. These would inevitably cause an irreversible damage to the material structure, resulting in a dramatic capacity fade. In this work, the metal oxides composite nanofibers are first fabricated using an electrospinning technique, and then an oxidative polymerization of dopamine and a subsequent calcination are conducted to form a protecting shell. The inner carbon nanofibers have been obtained after removing the metal oxides nanoparticles. Owing to the robust dense carbon shell and inner porous carbon framework as well as intrinsic nitrogen doping, the prepared nanofibers electrode delivers high capacitances of 328 F g(-1) at 1 A g(-1) and 160 Fg(-1) even at an extremely high current density of 100 A g(-1) in a 6 M KOH aqueous solution. The electrode maintains 77% of the initial capacity after 5000 cycles at 5 A g(-1) . The assembled symmetric supercapacitor exhibits a high capacitance of 97.9 F g(-1) at 1 A g(-1) and still maintains at 60 F g(-1) even at a high current density of 50 A g(-1) . 73% of the initial capacitance is remained after 5000 cycles at a current density of 10 A g(-1) . The experimental results reveal that the inner porous carbon nanofibers may be a promising electrode material for high-rate supercapacitors. (C) 2017 Elsevier Ltd. All rights reserved.