Planar on-chip micro-supercapacitors based on reduced graphene oxide and carbon nanotube by liquid–air interface self-assembly and photolithography

Abstract

Recently, the development of miniaturized electronic devices has accelerated the demand for the rate capability of planar on-chip micro-supercapacitors (POMSs). The POMSs based on reduced graphene oxide and carbon nanotube (rGO/CNT) composite electrodes (rGO/CNT-POMSs) were manufactured in the work and detailed electrochemical tests of devices were carried out over a wide range of scanning rates (0.01–10000 V s−1). The rGO/CNT composite electrode films without binder were prepared on silicon substrates by a modified liquid–air interface self-assembly method and a hydroiodic acid reduction method. The electrodes were fabricated into interdigital structure with 50 μm width of electrode and gap of electrode by photolithography. Interdigital POMSs based on different electrodes were prepared by gold sputtering on the electrode lugs. The area capacitance of the rGO/CNT-POMSs was 28.62 μF cm−2. They also had 0.004 μWh cm−2 of energy density and 1.068 μW cm−2 of power density. In addition, the charge–discharge time constant of the device was only 5.6 μs, and the charge–discharge rate was very quick. After 10,000 cycles of charge–discharge, the capacitance retention rate was still above 88%. At the ultra-high scan rate of 10000 V s−1, the devices still worked well. Compared with the POMSs based on reduced graphene oxide electrodes (rGO-POMSs) and the POMSs based on carbon nanotube electrodes (CNT-POMSs), the introduction of the CNT significantly increased the area capacitance, energy density and power density of rGO/CNT-POMSs, and significantly shortened the charge–discharge time constant. This indicated that the rGO/CNT composite electrodes had a good application prospect in the micro-chip accumulator devices.