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

Abstract

Manganese oxide (MnO₂) 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 MnO₂ domains into continuously interconnected carbon nanotube (CNT) networks, thus imparting both electrical conductivity and mechanical durability to MnO₂. In particular, we synthesize a fiber-shaped coaxial electrode with a nickel fiber as the current collector (Ni/CNT/MnO₂); the thickness of the CNT/MnO₂ 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/MnO₂ coaxial electrodes as cathode and anode together with a 1.0 M Na₂SO₄ 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.

Manganese dioxide is a promising material for energy storage applications, but is limited by its brittleness and poor conductivity. Here, manganese dioxide domains are electrochemically deposited onto carbon nanotube networks to produce flexible and conductive hybrid fiber-shaped supercapacitors.