Electrochemical micro-capacitors of patterned electrodes loaded with manganese oxide and carbon nanotubes

MnO2 and carbon nanotubes (CNT) composite electrodes have been built on the interdigital stack layers of Fe–Al/SiO2 and Fe–Al/Au/Ti/SiO2 for the electrochemical micro-capacitors, using photolithography and thin-film technologies. The electrode properties and the performance of micro-cells are measured and analyzed with cyclic voltammetry (CV), impedance spectroscopy, and galvanostatic charge/discharge test in 0.1 M Na2SO4 electrolyte. The vertically aligned CNT, grown on Fe–Al/SiO2, is more suitable for supporting the pseudocapacitive MnO2 than the random CNT on Fe–Al/Au/Ti/SiO2, but ohmic resistance of the former electrode is higher. We have prepared three cells on each stack layer with different electrode materials. The Ragone plot shows systematic variations in power and energy performance, reflecting their differences in electrode structure and polarization loss. The asymmetric cell of a pseudocapacitive positive electrode, loaded with MnO2 and CNT, exhibits a small IR drop and a high specific energy during discharge. Built on Fe–Al/SiO2, this asymmetric cell discharges at specific power 0.96 kW kg−1 with specific energy 10.3 Wh kg−1; while on Fe–Al/Au/Ti/SiO2, the asymmetric cell discharges at power 1.16 kW kg−1 with energy 5.71 Wh kg−1.

Electrochemical micro-capacitors of planar configuration have been prepared on the comb-like stack layer. The asymmetric cell with a positive MnO2 electrode, MnO2(+)_CNT, performs with a high specific energy.Figure optionsDownload as PowerPoint slideHighlights
► Electrochemical micro-capacitors of planar configuration have been built on two comb-like stack layers.
► The electrodes are loaded with vertically aligned CNT, augmented with manganese oxide.
► Asymmetric cells with a positive MnO2–CNT electrode outperform other cells in power and energy.
► Polarization losses of the cells are analyzed to account for their performance.