Boosting the performance of cobalt molybdate nanorods by introducing nanoflake-like cobalt boride to form a heterostructure for aqueous hybrid supercapacitors.

Binary transition metal oxides have received extensive attention because of their multiple oxidation states. However, due to the inherent vices of poor electronic/ionic conductivities, their practical performance as supercapacitor material is limited. Herein, a cobalt molybdate/cobalt boride (CoMoO/Co-B) composite is constructed with cobalt boride nanoflake-like as a conductive additive in CoMoO nanorods using a facile water bath deposition process and liquid-phase reduction method. The effects of CoMoO/Co-B mass ratios on its electrochemical performance are investigated. Remarkably, the CoMoO/Co-B composite obtained at a mass ratio of 2:1 shows highly enhanced electrochemical performance relative to those obtained at other ratios and exhibits an optimum specific capacity of 436 F g at 0.5 A g. This kind of composite could also display great rate capacity (294 F g at 10 A g) and outstanding long cycle performance (90.5% capacitance retention over 10 000 cycles at 5 A g). Also, the asymmetric supercapacitor device is prepared by using CoMoO/Co-B composite as the anode with the active carbon as the cathode. Such a device demonstrates an outstanding energy density of 23.18 Wh kg and superior long-term stability with 100% initial specific capacity retained after 10,000 cycles. The superior electrochemical properties show that the CoMoO/Co-B electrode material has tremendous potential in energy storage equipment applications.