Nickel-oxide-based supercapacitors with high aspect ratio concentric cylindrical electrodes

This study reports the fabrication and characterization of a metal-oxide-based supercapacitor with a high surface area 3D microelectrode. This microelectrode is comprised of high aspect ratio SU-8 pillars that are fabricated using backside exposure and coated with alternating Ni and Cu layers via a sequential electrodeposition process. High surface area Ni electrodes are obtained by selective removal of the Cu sacrificial interlayers. Through subsequent electrochemical deposition and heat treatment techniques, these electrodes are conformally coated with nickel oxide. Performance tests are carried out via cyclic voltammetry. Devices were cycled in excess of 400 times with insignificant capacitance degradation. The estimated areal capacitance is found to be 270 mF/cm² which is among the highest areal capacitance values reported for MEMS supercapacitors.