Water-dispersible graphene–wrapped MnO 2 nanospheres and their applications in coin cell supercapacitors

A highly stable and more water-dispersible graphene (WDG) was synthesized using microwave-assisted ball milling technique. The WDG-wrapped MnO 2 nanocomposites were prepared for two mass ratios of nanospheres and graphene sheets using reflux method. Comprehensive characterization of the prepared WDG-Mn1 and WDG-Mn2 hybrid nanocomposites was carried out to explore the electrochemical capacitance behaviors. The WDG-Mn1 and WDG-Mn2 electrodes showed capacitance performance of 130 F g −1 at 0.5 A g −1 and 178 F g −1 at 0.5 A g −1 , respectively. The WDG-Mn2 electrode revealed enhanced capacitance performance, that is, 84% of its initial capacitance was retained even after repeating the cyclic voltammetry test for 3000 cycles. This study reveals the enhanced capacity performance in WDG-Mn2 nanocomposite hybrid materials for supercapacitors.