Electrochromic study to quantify kinetics in PEDOT supercapacitors

Abstract

Filtering capacitors are essential components in electronic circuits for converting high frequency alternating current (AC) into direct current (DC) with minimal energy dissipation. Yet the bulkiness and rigid configuration of traditional filtering capacitors (e.g. Aluminum electrolyte capacitors) impose size restrictions. Supercapacitor offers the potential of high capacitance density to function as miniaturized filtering capacitors. However, the charging/discharging speed of supercapacitors tend to be slow below 100 Hz and limit their use in ac filtering. To understand the mechanisms of the charging/discharging process in electrode materials, this study measures electrochromic properties of the conducting polymer PEDOT, one of the most widely used electrode materials in organic supercapacitors. The contributions of redox reactions and electrical double layer to the total capacitance were quantified. We found that redox reactions were active and dominant when the switching frequency was higher than 100 Hz. The rate of redox reactions for PEDOT changes with different applied potential due to the changing conductivity of PEDOT . The main bottleneck to fast kinetics were due to the interfacial impedance between the Faradaic materials and the current collector electrode. These results will guide future optimization of the materials and morphology design for filtering capacitor electrode.