Modeling Activation-Controlled Discharge at a Pore Tip in Presence of Charge Redistribution for Electrochemical Capacitor Electrodes

Highly porous carbon is often used as the electrode material in electrochemical capacitors (ECs). During charging or discharging of an EC, the potential at the tip of the pores (closest to the counter electrode) will change more quickly than the potential at the base due to added solution resistance down the length of the pores. After charging (discharging) there will be a distribution of potentials along the electrode surface. Because the tip of the pore will be at a higher potential than the rest of the pore after charging, it would be expected that any Faradaic reactions would happen preferentially at the pore tip. As the pore tip discharges, charge will then redistribute back up the pore to equalize the potential. This work examines the potential profile of a model pore undergoing an activation-controlled discharge in the presence of charge redistribution. The aim is to identify the important characteristics of the discharge curve and use them to elucidate the mechanisms governing the self-discharge of an experimental system. A hardware transmission line circuit, based on de Levie’s transmission line model of a pore, is used as a pore model, with RE 1 and RE 8 representing the tip and base of the pore, respectively. [1