Conducting polymer‐based hybrid electrochemical capacitor utilizing potassium iodide redox electrolyte with controlled self‐discharge

This paper reports on the application of poly (3,4-ethylenedioxythiophene)/carbon nanotubes (PEDOT/CNT) material for the construction of a hybrid supercapacitor utilizing iodide redox-active electrolyte. To address the advantages in terms of electrochemical performance, comparison has been made to the system using conventional activated carbon (AC) electrodes. Despite limited specific surface area, the PEDOT/CNT cell demonstrates reasonably high electrical parameters (vs. highly porous AC), especially those normalized per volume or total mass of the device. Interestingly, it also exhibits more stable self-discharge characteristics over operation time which shall be assigned to smaller fraction of free polyiodides generated in the cell in the presence of the low-surface-area polymer electrode, in addition to their strong confinement in the polymer network, thus supressing redox-shuttling. Pursuing the mechanistic studies, we have managed to detect (using the electrocatalytic WO3-based voltammetric probe) the presence of undesirable iodates but at lower concentrations in a case of the PEDOT/CNT-based capacitor.