High-performance flexible supercapacitors with hierarchical structured cathode (NiCo2O4/Au/MnO2) and anode (NiCo2S4/PPy)

NiCo2O4 nanoflowers with high specific surface area were prepared on nickel foam (NF) by hydrothermal method and used as frameworks for developing cathode and anode of flexible asymmetric supercapacitor. With the unique nanoflower-like NiCo2O4 arrays as skeleton, the NiCo2O4/Au/MnO2 cathode was prepared by goldspraying and electrochemical deposition and the NiCo2S4/PPy anode was prepared by second-hydrothermal and electro-polymerization. The hierarchical structured electrodes offer sufficient redox sites and adequate channels for accelerating ion and electron transport between electrodes and electrolyte. Moreover, the NiCo2S4/ PPy was first reported as the anode, and its cycling stability (capacitance retention of 86.04 % after 5000 cycles) and specific capacitance (1612.5F/g at 1 A/g). The assembled flexible all-solid-state asymmetric supercapacitor (NiCo2O4/Au/MnO2 // NiCo2S4/PPy) displays a high energy density of 206.37 Wh kg-1 at a power density of 398.57 W kg- 1 and an outstanding cyclability (capacitance retention of 83.41 % after 5000 cycles).