Carbon nanofiber supercapacitors with large areal capacitances

We develop supercapacitor SC devices with large per-area capacitances by utilizing three-dimensional 3D porous substrates. Carbon nanofibers CNFs functioning as active SC electrodes are grown on 3D nickel foam. The 3D porous substrates facilitate a mass loading of active electrodes and per-area capacitance as large as 60 mg /cm2 and 1.2 F /cm2, respectively. We optimize SC performance by developing an annealing-free CNF growth process that minimizes undesirable nickel carbide formation. Superior per-area capacitances described here suggest that 3D porous substrates are useful in various energy storage devices in which per-area performance is critical. © 2009 American Institute of Physics. doi:10.1063/1.3273864