MnCoO/NiS nanocomposite for hybrid supercapacitor with superior energy density and long-term cycling stability.

MnCoO is regarded as a good electrode material for supercapacitor due to its high specific capacity and good structural stability. However, its poor electrical conductivity limits its wide-range applications. To solve this issue, we integrated the MnCoO with NiS, which has a good electrical conductivity, and synthesized a MnCoO/NiS nanocomposite using a two-step hydrothermal process. Comparing with individual MnCoO and NiS, the MnCoO/NiS nanocomposite showed a higher specific capacity and a better cycling stability as the electrode for the supercapacitor. The specific capacity value of the MnCoO/NiS electrode was 904.7 C g at 1 A g with a potential window of 0-0.55 V. A hybrid supercapacitor (HSC), assembled using MnCoO/NiS and active carbon as the cathode and anode, respectively, showed a capacitance of 116.4 F g at 1 A g, and a high energy density of 50.7 Wh kg at 405.8 W kg. Long-term electrochemical stability tests showed an obvious increase of the HSC's capacitance after 5500 charge/discharge cycles, reached a maximum value of ∼162.7% of its initial value after 25,000 cycles, and then remained a stable value up to 64,000 cycles. Simultaneously, its energy density was increased to 54.2 Wh kg at 380.3 W kg after 64,000 cycles.