Formation of Co-Mn mixed oxide double-shelled hollow spheres as advanced electrodes for hybrid supercapacitors

Complex hollow nanostructures have attracted tremendous attention as advanced electrode designs for high-performance hybrid supercapacitors. Delicate control of the interior configuration is quite challenging but critical to the performance optimization of hollow nanostructures. In this work, we have developed a facile self-templated strategy for the construction of Co-Mn mixed oxide double-shelled hollow spheres (Co-Mn-DHSs). The transformation from the solid precursor to this unique hollow structure is achieved through a redox reactionmediated Ostwald ripening process. Of note, this protocol could be extended to synthesize other metal oxide hollow architectures with similar structural features. As a battery-type electrode in alkaline solution, the crystalline Co-Mn-DHS sample after annealing treatment manifests remarkable electrochemical properties in terms of high specific capacitance and good cycling stability. Moreover, the derived hybrid supercapacitor device shows enhanced energy/power densities with long life.