High-performance asymmetric supercapacitors using holey graphene electrodes and redox electrolytes

Construction of asymmetric supercapacitors with high energy and power densities using the same anode and cathode electrodes remains a great challenge. Herein, holey reduced graphene oxide (rGO) films are synthesized using a catalytic etching process and utilized as both cathode and anode electrodes for the supercapacitor construction. On the anode of an asymmetric supercapacitor, an electrical double layer capacitor is formed in 1 M Na2SO4, while on the cathode a pseudocapacitor is fabricated where redox electrolytes of [Fe(CN)6]3-/4- are added. The performance of as-formed asymmetric supercapacitors is varied with the pore sizes and densities on the holey rGO films. With a cell voltage of 2.0 V, a specific capacitance of as high as 101.25 F g−1, an energy density of 56.25 Wh kg−1, a power density of 35.83 kW kg−1, and excellent long cycle life (98% of its specific capacitance even at 5000 charge/discharge cycles) are achieved. Such performance is superior to most of graphene based supercapacitors. Therefore, these asymmetric supercapacitors are promising for applications of storage systems with double-high densities.