Wet spinning of hollow graphene fibers with high capacitance

• The effective reduction of graphene oxide enables the robust hollow structure. • The hollow structure with enhanced interface promotes the ion transport. • The assembled supercapacitor exhibits ultra-high capacitance and energy density. Herein, we report a facile coaxial wet-spinning strategy to continuously produce hollow graphene fibers (HGF) with the merits of high conductivity, excellent flexibility, and enhanced electrode-electrolyte contact. The hollow structure is achieved by introducing reductant-containing coagulant solution into the fiber core with a composition identical to the spinning bath. The produced fibers were assembled into a supercapacitor device with an ultra-high specific capacitance of 711 mF/cm 2 (i.e. 33.5 mF/cm or 190 F/cm 3 ). The combination of outstanding electrochemical and mechanical properties makes this HGF a promising candidate for use in wearable supercapacitors and electronics