Vertically Aligned Graphene–Carbon Fiber Hybrid Electrodes with Superlong Cycling Stability for Flexible Supercapacitors

Graphene electrode-based supercapacitors are in high demand due to their superior electrochemical characteristics. A major bottleneck of using the supercapacitors for commercial applications lies in their inferior electrode cycle life. Herein, a simple and facile method to fabricate highly efficient supercapacitor electrodes using pristine graphene sheets vertically stacked and electrically connected to the carbon fibers which can result in vertically aligned graphene-carbon fiber nanostructure is developed. The vertically aligned graphene-carbon fiber electrode prepared by electrophoretic deposition possesses a mesoporous 3D architecture which enabled faster and efficient electrolyte-ion diffusion with a gravimetric capacitance of 333.3 F g-1 and an areal capacitance of 166 mF cm-2 . The electrodes displayed superlong electrochemical cycling stability of more than 100 000 cycles with 100% capacitance retention hence promising for long-lasting supercapacitors. Apart from the electrochemical double layer charge storage, the oxygen-containing surface moieties and α-Ni(OH)2 present on the graphene sheets enhance the charge storage by faradaic reactions. This enables the assembled device to provide an excellent gravimetric energy density of 76 W h kg-1 with a 100% capacitance retention even after 1000 bending cycles. This study opens the door for developing high-performing flexible graphene electrodes for wearable energy storage applications.