Facile-synthesized NiCo2O4@MnMoO4 with novel and functional structure for superior performance supercapacitors

The optimized structure of composited materials decides the electrochemical performances of supercapacitors. Herein, the NiCo2O4@MnMoO4 particles with novel and functional structure were synthesized by two-step hydrothermal method process in this work, in which nickel foam (Ni foam) was employed as substrate. In the experiment process, the NiCo2O4 particles were prepared on the Ni foam and then the NiCo2O4@MnMoO4 particles were prepared on the NiCo2O4. According to the electrochemical tests, both the NiCo2O4 and NiCo2O4@MnMoO4 micro-particles prepared in this work have superior electrochemical performances including higher specific capacitances than most of the other NiCo2O4 and NiCo2O4@MnMoO4 researches. At the scan rate of 5 mA·cm−2, the area specific capacitance of the NiCo2O4 electrode is 4.73 F cm−2 (equivalent to 1152.4 F·g−1 mass specific capacitance), while that of the NiCo2O4@MnMoO4 electrode is 16.40 F cm−2 (equivalent to 2603.9 F·g−1 mass specific capacitance). The cycling performance of the NiCo2O4 and NiCo2O4@MnMoO4 at the current density of 5 mA·cm−2 were measured. After 3000 discharge–charge cycles, the specific capacitance of the NiCo2O4 micro-particles remains 112.2% of its initial value, and the NiCo2O4@MnMoO4 micro-particles remains 92.1%. The asymmetric supercapacitor is assembled by the NiCo2O4@MnMoO4 compounds and activated carbon (AC), which show high energy density of 44.16 Wh/kg at power density of 0.8 kW/kg. The results show that the NiCo2O4@MnMoO4 composite is an excellent candidate for electrode materials of energy storage devices.