We report a coaxial fiber supercapacitor, which consists of carbon microfiber bundles coated
with multiwalled carbon nanotubes as a core electrode and carbon nanofiber paper as an outer
electrode. The ratio of electrode volumes was determined by a half-cell test of each electrode.
The capacitance reached 6.3 mF cm-1 (86.8 mF cm-2) at a core electrode diameter of 230 μm and
the measured energy density was 0.7 μWh cm-1 (9.8 μWh cm-2) at a power density of 13.7 μW
cm-1 (189.4 μW cm-2), which were much higher than the previous reports. The change in the
cyclic voltammetry characteristics was negligible at 180o bending, with excellent cycling
performance. The high capacitance, high energy density, and power density of the coaxial fiber supercapacitor are attributed to not only high effective surface area due to its coaxial structure
and bundle of the core electrode but also all-carbon materials electrodes which have high
conductivity. Our coaxial fiber supercapacitor can promote the development of textile electronic
in near future.