Three-dimensional α-Fe2O3/carbon nanotube sponges as flexible supercapacitor electrodes

Flexible supercapacitors, which can sustain large deformations while maintaining normal functions and reliability, are playing an increasingly important role in portable electronic devices. Here we report the preparation of a three-dimensional alpha-Fe2O3/carbon nanotube (CNT@Fe2O3) sponge electrode with a porous hierarchical structure, consisting of a compressible, conductive CNT network, coated with a layer of Fe2O3 nanohorns. The specific capacitance of these hybrid sponges has been significantly improved to above 300 F g(-1), while the equivalent series resistance remains at about 1.5 Omega. The highly deformed CNT@Fe2O3 sponge retains more than 90% of the original specific capacitance under a compressive strain of 70% (corresponding to a volume reduction of 70%). The hybrid sponge still works stably and sustains a similar specific capacitance to the initial value even after 1000 compression cycles at a strain of 50%. The outstanding properties of this hybrid sponge make it a highly promising candidate for flexible energy devices.