In-situ exfoliation and integration of vertically aligned graphene for high-frequency response on-chip microsupercapacitors

Fast response on-chip micro-supercapacitors (MSCs) with large energy storage capabilities are highly in demand for high-frequency circuits and systems such as alternating current (AC) line filters. Devices with vertically aligned graphene thin-film electrodes were shown to be promising in maintaining close-to-ideal capacitive behavior at high frequencies due to low ionic and electric resistances. This study investigates a novel in-situ integration of vertically aligned graphene layers with micro-sized gold current collectors in which a modified bipolar electrochemistry method has been applied. The electrochemical analysis revealed a high average capacitance of 640 mu F cm(-2) (C.V(-1)cm(-2)) at a scan rate of 2 mV s(-1) for the fabricated MSCs and their excellent stability even after 50000 successive charge-discharge cycles by constant current. Most notably, the electrochemical impedance spectroscopy results revealed that the MSCs exhibited very fast response and close-to-ideal capacitive behavior even at around 1000 Hz. Specifically, the phase angle and specific capacitance measured at 120 Hz were -81.2 deg and 65.2 mu F cm(-2), respectively, in addition to a cut-off frequency of 3486 Hz at which the impedance angle is -45 deg. The device was tested as the capacitive energy storage component in a standard AC line filter, and its performance was found comparable to a commercial off-the-shelf aluminum electrolytic capacitor.

Automated summary

This study investigates fast response and stable on-chip micro-supercapacitors with unique integration of vertically aligned graphene and gold current collectors, enhancing capacitive behavior at high frequencies. Electrochemical impedance spectroscopy results show excellent performance of the micro-supercapacitors at high frequencies, and they function effectively as the capacitive energy storage component in AC line filters.