Three-Dimensional Arrays of 1D MnO2 Nanocrystals for All-Solid-State Asymmetric Supercapacitors

Reported is the synthesis of 3D hierarchical structures based on one-dimensional MnO2 nanobuilding blocks (nanorods, nanowires, and nanoneedles) by means of a facile and scalable coprecipitation method and their use as electrodes for the assembly of all-solid-state supercapacitors. Asymmetric devices were also assembled by using these nanostructured MnO2 materials as the positive electrode and reduced graphene oxide (rGO) as the negative electrode with a polymeric gel electrolyte. The asymmetric cells successfully extend the working voltage windows beyond 1.4V and allowed for a maximum voltage of 1.8V. An asymmetric device based on hierarchical nanoneedle-like MnO2 and rGO achieved a maximum specific capacitance of 99Fg(-1) at a scan rate of 10mVs(-1) with a stable operational voltage of 1.8V. This high value allowed for a large specific energy of 24.12Whkg(-1).