Carbon nanotubes and manganese oxide hybrid nanostructures as high performance fiber supercapacitors

Abstract Manganese oxide (MnO 2 ) has long been investigated as a pseudo-capacitive material for fabricating fiber-shaped supercapacitors but its poor electrical conductivity and its brittleness are clear drawbacks. Here we electrochemically insert nanostructured MnO 2 domains into continuously interconnected carbon nanotube (CNT) networks, thus imparting both electrical conductivity and mechanical durability to MnO 2 . In particular, we synthesize a fiber-shaped coaxial electrode with a nickel fiber as the current collector (Ni/CNT/MnO 2 ); the thickness of the CNT/MnO 2 hybrid nanostructured shell is approximately 150 μm and the electrode displays specific capacitances of 231 mF cm −1 . When assembling symmetric devices featuring Ni/CNT/MnO 2 coaxial electrodes as cathode and anode together with a 1.0 M Na 2 SO 4 aqueous solution as electrolyte, we find energy densities of 10.97 μWh cm −1 . These values indicate that our hybrid systems have clear potential as wearable energy storage and harvesting devices.