All-solid-state flexible micro-supercapacitor arrays with patterned graphene/MWNT electrodes

We report on the fabrication of all-solid-state flexible micro-supercapacitor (MSC) arrays with electrodes consisting of patterned multilayer graphene (MG) and functionalized multi-walled carbon nanotubes (MWNTs), and polyvinyl alcohol (PVA)–H3PO4 gel electrolyte. The fabricated MSC exhibited areal capacitance of 2.54 mF/cm2 at a scan rate of 10 mV/s, which is ∼150 times higher than that of MSC with MG electrode. The areal energy and power density were also dramatically improved via using MG/MWNT electrodes. In addition, there was no deterioration of the electrical performance over repetitive convex and concave bending with a bending radius of 2.3 mm. Furthermore, both the output voltage and the total capacitance of the MSC could be controlled via the serial or parallel connection of multiple planar-type MSCs to operate high-voltage light-emitting diodes.