All-porous heterostructure of reduced graphene oxide–polypyrrole–nanoporous gold for a planar flexible supercapacitor showing outstanding volumetric capacitance and energy density

Abstract

A facile electrochemical method for the fabrication of a planar, all-solid-state flexible supercapacitor with a reduced graphene oxide–polypyrrole hybrid platform has been explored. Three-dimensional reduced graphene oxide (3DrGO) followed by a conducting polymer, polypyrrole (PPy) network has been deposited on a pristine nanoporous gold (npAu) chip. The all-solid-state, flexible, symmetric supercapacitor (PPy–3DrGO/npAu) exhibited a very high areal capacitance of 29.21 mF cm⁻². The all-porous morphology of the electrode with in-plane geometry renders an overwhelming volumetric stack capacitance of 245.34 F cm⁻³ of the device. The solid-state device was assembled under ambient conditions with an aqueous gel electrolyte without a “dry room”, required for packaging of all commercial capacitors. An unprecedented energy density of about 98.48 mW h cm⁻³ was observed with the highest power density of 19.68 W cm⁻³. The PPy–3DrGO based in-plane supercapacitor device also showed excellent cycling stability with retention of 85.9% with respect to the initial capacitance after 10 000 galvanostatic charge–discharge cycles, which is one of the highest cycling performances reported to date with conducting polymer-based symmetric devices. A negligible change in the current response of the continuously bent flexible MSC shows its excellent mechanical robustness and durability for long-run device performances. Interestingly, the fully charged device was able to show excellent storage properties for a long period of time and could light up a commercial LED, making it a potential power source option to be implemented in wearable or portable commercial electronic devices.