Synthesis of Ni(Co)MoO4 with a mixed structure on nickel foam for stable asymmetric supercapacitors

In this work, the Ni(Co)MoO4 (NMO-Co) hybrid materials with nanoneedle and nanosheet structure were prepared on nickel foam (NF) by the hydrothermal method for high-stability supercapacitors. The effect of Co presence on the structure and electrochemical properties of NMO-Co was investigated. As the molar of Cobalt increased, more nanoneedles grew on the surface of NiMoO4/NF. The combination of the Ni-doped CoMoO4 nanoneedles and Co-doped NiMoO4 nanosheets was irregularly arranged on the surface of NF, which emerged an improvement of the cycling performance. When the molar ratio of Co: Ni: Mo was 0.5: 1: 1, the capacitance retention of the hybrid electrode was 80.1% after 10,000 cycles at 10 A g−1, while the pure NiMoO4 electrode was 53.1%. Moreover, an asymmetric supercapacitor device displayed high energy density and power density. The maximum energy density and power density could reach 55.71 Wh kg−1 and 14,999 W kg−1, respectively. The hybrid electrode's good electrochemical performance is due to the combination of mutual doping of Ni and Co with a mixed morphology.