Electrodeposition of Ni-Co-S nanosheet arrays on N-doped porous carbon nanofibers for flexible asymmetric supercapacitors

In this work, a novel flexible electrode material for supercapacitor is prepared by electrodeposition of Ni-Co-S interconnected nanosheet arrays on N-doped hierarchical porous carbon nanofibers (Ni-Co-S@N-pCNFs). The electrode exhibits a remarkable specific capacitance of 520.2 F g-1 at the current density of 0.2 A g−1 and 670 F g-1 at 2 mV s−1. The activated charcoal (AC) loaded N-doped porous carbon nanofibers (AC@N-pCNFs) as electrode is also prepared which exhibits a specific capacitance of 257.2 F g-1 at 0.2 A g−1, as well as excellent cycling stability with a capacitance retention of 92.6% after 5000 cycles. Furthermore, the Ni-Co-S@N-pCNFs as the positive electrode, active carbon loaded N-doped hierarchical porous carbon nanofibers (AC@N-pCNFs) as negative electrode, and KOH/NKK hybrids as both the electrolyte and separator are assembled into flexible asymmetric supercapacitor. The assembled supercapacitor device without using any current collectors or binders shows a high energy density of 21.6 Wh·kg−1 at a power density of 134.9 W kg−1 and robust long-term cycling stability retaining over 90.0% after 3000 cycles at 1.0 A g−1. The as-assembled asymmetric supercapacitors (ASCs) have an outstanding mechanical flexibility and electrochemical stability and no significant attenuation occurred during cycling under different bending states.