High performance flexible solid-state asymmetric supercapacitors from MnO₂/ZnO core-shell nanorods//specially reduced graphene oxide

With a view to developing flexible solid-state asymmetric supercapacitors, we have specially designed and nanoscopically engineered two types of electrodes: a MnO₂/ZnO core-shell nanorod array and a HI-reduced graphene oxide assembly, both deposited in situ on a carbon cloth. These materials were thoroughly characterized by structural and spectroscopic techniques. The flexible solid-state asymmetric supercapacitors with cathodes and anodes made of these materials have demonstrated superior performance characteristics. They can be cycled in a wide potential window of 0-1.8 V for 5000 cycles with only 1.5% capacitance loss. The demonstrated volumetric energy density of 0.234 mW h cm^-3 and volumetric power density of 0.133 W cm^-3 are much higher than those of similar devices reported previously in the literature.