Scalable non-liquid-crystal spinning of locally aligned graphene fibers for high-performance wearable supercapacitors

One-dimensional graphene fibers have attracted increasing interests due to their extraordinary mechanical strength, electrical conductivity and flexibility compared with two-dimensional graphene films/papers and three-dimensional foams/hydrogels/aerogels. Here, we developed a scalable non-liquid-crystal spinning process for the production of continuous graphene fibers with tailored structure for high-performance wearable supercapacitors. These fibers possessed surfaces with bark-like fine microstructure and different shaped cross-sections with locally aligned dense pores, depending on the jet stretch ratio (R) during spinning. Owing to this unique structure facilitating the access to, and diffusion of electrolyte ions, the specific capacitance reached 279 F g(-1) (340 F cm(-3)) at a current density of 0.2 A g(-1) (0.244 A cm(-3)) in 1 M H2SO4 when R = 1.0. A flexible solid-state fiber supercapacitor assembled from these fibers showed a specific capacitance and energy density of 226 F cm(-3) and 7.03 mWh cm(-3) at 0.244 A cm(-3), respectively. We further demonstrated the proof-of-concept of wearable energy-storage by sewing three solid-state yarn supercapacitors in series into a textile, which was able to power a light-emitting diode for more than 5 min after being charged. This non-liquid-crystal spinning strategy could be extended to the assembly of other two-dimensional nanomaterials into macroscopic fibers for applications in micro-devices, wearable electronics and smart textile. (C) 2015 Elsevier Ltd. All rights reserved.