Directly grown carbon nano-fibers on nickel foam as binder-free long-lasting supercapacitor electrodes

Binder-free carbon nanofiber (CNF) electrodes are prepared using a facile one-step process on nickel foam (Ni-f). The amalgamation of the innate Ni-f pores and nanostructure caused by the growth of the CNF is found to show a good aerial capacitance. Cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy are used to electrochemically characterize these CNF/Ni-f supercapacitor electrodes. In a two-electrode cell using 6M KOH as an electrolyte, these electrodes show a good aerial capacitance of ca. 142 +/- 7 mF/cm(2) at 10 mA/cm(2) and a specific energy of 62 mWh/m(2) at a high-specific power of 82 W/m(2). The electrodes also show a 100% retention in capacitance even after 10000 cycles at 10 mA/cm(2). Simple one-step electrode preparation process with no external catalyst, reasonable aerial capacitance, excellent stability, and ideal retention of specific energy with an increase in specific power, makes this an interesting material for thin energy storage devices.