Fabrication of a snail shell-like structured MnO2@ CoNiO2 composite electrode for high performance supercapacitors

For the first time, we develop a cost-effective and facile one-step hydrothermal approach to directly grow MnO2@ CoNiO2 snail shell-like, CoNiO2 nanoflake-like, and MnO2 nanoflower-like structures on nickel foam as electrode for supercapacitor applications. Cyclic voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy are used to investigate the electrochemical responses of the electrodes. The MnO2@ CoNiO2 composite electrode exhibits a high specific capacitance and energy density of 1605.4 F g (-1) and 51.37 W h kg (-1), respectively, at 20 mA cm (-2) in 3 M KOH aqueous solution, as well as an attractive cycling ability ( 98.87% even after 3000 cycles at 40 mA cm (-2)), which are much better than those of the CoNiO2 and MnO2 electrodes. Such superior electrochemical performance of the MnO2@ CoNiO2 electrode is attributed to the combination of two active materials with an improved surface morphology, which can offer more pathways for electron transport and enhance the utilization of the electrode materials. These results show that the MnO2@ CoNiO2 composites are promising positive electrode materials for practical supercapacitors.