Metal-Organic Frameworks-Derived NiS2/CoS2/N-Doped Carbon Composites as Electrode Materials for Asymmetric Supercapacitor

Transition metal sulfides derived from metal-organic frameworks (MOFs) have received increasing attention as a potential energy storage electrode material. Here, a series of NiS2/CoS2/NC-T (T=temperature) have been successfully constructed by carbonizing and sulfuring the precursor of Ni/Co-MOF. It is worth emphasizing that N-doped carbon materials improve the conductivity of the electrode material. Moreover, NiS2/CoS2/NC-500 maintains the rod-like structure of the precursor and exhibits a high specific capacitance of 1325 F g(-1) at a current density of 1 A g(-1). Apart from high capacitance, the NiS2/CoS2/NC-500 also demonstrated excellent cycling stability with retention rate of 75 % after 5000 cycles at a current density of 5 A g(-1). The good performance could be attributed to the unique rod-like structure and pore-size distribution of NiS2/CoS2/NC-500. Moreover, an assembled asymmetric supercapacitor NiS2/CoS2/NC-500//AC displays a high energy density of 53.93 Wh kg(-1) at a power density of 800 W kg(-1) and good cycle stability with capacitance retention of 85.71 % after 20,000 cycles at 5 A g(-1). In particular, a red LED can be illuminated by the assembled ASC, indicating that as-synthesized NiS2/CoS2/NC-500 hold great potential for practical applications.