A general fabrication approach on spinel MCo2O4 (M = Co, Mn, Fe, Mg and Zn) submicron prisms as advanced positive materials for supercapacitor

Abstract

The design and fabrication of advanced electrode materials for supercapacitor have been extensively explored recently. The spinel transition metal oxides have drawn considerable attentions because of their high theoretical capacity to store electrical charge. This work introduced a general hydrothermal assisted co-precipitation approach to fabricate five kinds of spinel MCo2O4 (M = Co, Mn, Fe, Mg and Zn) submicron prisms on nickel foams. Among these spinel MCo2O4 electrodes, the MgCo2O4 exhibited the highest specific capacity of 613.5 C g−1 (0.883 C cm−2) at a current density of 2 mA cm−2. All the specific capacities of bimetallic oxides were higher than single metal oxide Co3O4, indicating the enhanced electrochemical performance of bimetallic oxides. The correlations between peak currents and the square root of the scan rates of all prepared electrode materials showed OH− diffusion-controlled characteristic in their redox reactions. Furthermore, an assembled MgCo2O4//AC hybrid supercapacitor (HSC) achieved a specific capacity and a specific energy of 182.8 C g−1 at 0.5 A g−1 and 39.7 W h kg−1, respectively. More impressively, this MgCo2O4//AC HSC showed a subsequent increase about 21.1% in specific capacity after 5000 cycles, suggesting its promising characteristics for the next generation energy storage device.