Freestanding and flexible graphene wrapped MnO2/MoO3 nanoparticle based asymmetric supercapacitors for high energy density and output voltage

Abstract

Asymmetric supercapacitors (ASC) based on freestanding membranes with high energy density and high output voltage by a simple pre-reduced and vacuum filtering method are reported. Reduced graphene oxide (rGO) coated MnO₂ nanospheres and rGO coated MoO₃ nanoparticle composites are selected as the positive and the negative materials of the devices, respectively. The ASC has a high operation voltage window of 2.0 V in a hydrogen electrolyte, a high energy density of 34.6 mW h cm⁻³ at a power density of 100 mW cm⁻³, and a high volumetric capacitance of 62.7 F cm⁻³ at a current density of 0.1 A cm⁻³. Especially, the ASC exhibits an excellent cycling performance of 94.2% capacitance retention after over 3000 cycles. This strategy of designing the hybridized structure for freestanding and flexible ASC provides a promising route for next-generation supercapacitors with high energy density and high output voltage.