All graphene electrode for high‐performance asymmetric supercapacitor

Summary “Electrode imbalance” is one of the major issues that hinders the potential performance of asymmetric supercapacitors (ASCs), which arises mainly due to the huge dissimilarities of the electrodes microstructures. Herein, an “all‐graphene” electrode system is designed by simple chemo‐thermal modification of graphene oxide. Chemically functionalized graphene (FG) cathode and two anodes based on thermally reduced graphene oxide (TrGO) and iodine‐doped graphene (IG) prepared via simple synthetic routes, followed by assembling into ASCs. The ASC comprising FG cathode‐IG anode delivers phenomenally high energy‐power (E‐P) density (91 W h kg−1 and 424.95 W kg−1) and a good capacitance retention after 10 000 cycles. This outcome is accredited to the similar chemistry of electrodes resulting in a minimal electrode imbalance. The developed scheme has capacity to be employed as all‐graphene hybrid energy storage system outputting enhanced performance and cyclic stability. A 1.7‐V asymmetric supercapacitor is fabricated by the integration and voltage balance of graphene‐based double‐layer supercapacitive cathode and pseudocapacitive anode. The combination of electrostatic and faradic charge storage in this all‐graphene asymmetric supercapacitor enables the device to deliver ultra‐high energy and power density as well as superior cyclic stability and rate performance.