Graphene–bismuth oxide nanotube fiber as electrode material for constituting flexible supercapacitors using a PVA/H3PO4 gel electrolyte is reported with a high specific capacitance (Ca) of 69.3 mF cm−2 (for a single electrode) and 17.3 mF cm−2 (for the whole device) at 0.1 mA cm−2, respectively. Our approach opens the door to metal oxide–graphene hybrid fibers and high-performance flexible electronics.
