Flexible all-solid-state supercapacitors based on an integrated electrode of hollow N-doped carbon nanofibers embedded with graphene nanosheets

A novel facile and scalable strategy is developed to prepare a hierarchical porous nonwoven of hollow N-doped carbon nanofibers embedded with graphene nanosheets (HN-CNFs/GNs) as an integrated electrode for flexible all-solid-state supercapacitors. It was found that graphene nanosheets (GNs) were curled inside the electrospun fibers, but freely expanded and connected adjacent CNFs in the form of nanosheets after carbonization, thereby increasing the electrochemical capacitance interface and conductivity as well. When the weight ratio of GNs is 2 wt%, the HN-CNFs/GNs delivers high capacitance of 249 F g(-1) at 1 A g(-1) in a three-electrode configuration. A two-electrode symmetrical cell delivers extraordinary cycling stability with no capacitance degradation after 5000 cycles. The symmetric all-solid-state supercapacitor provides a remarkable cycling stability with a capacity retention of 90% after 2000 cycles and high rate capacity. The device also displays outstanding flexibility with no obvious capacitance decay even when bent to 180 degrees. This research proves the potential application of the nonwoven of HN-CNFs/GNs in high efficient, wearable and flexible energy storage devices. (C) 2019 Elsevier Ltd. All rights reserved.