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

Abstract

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.