Invited: Continuum Modeling of Interfacial and Transport Phenomena in Electrochemical Capacitors

Electrochemical capacitors are promising electrical energy storage devices bridging the gap between batteries and conventional dielectric capacitors. They can be divided in two categories: electric double layer capacitors (EDLCs) and pseudocapacitors. EDLCs store electric charge physically in the electric double layer forming at the interfaces between the electrolyte and nanoporous electrodes. During charging or discharging, ions are transported in the electrolyte under the combined influence of diffusion and electrostatic forces as well as steric effects. On the other hand, pseudocapacitors store energy not only via the electric double layer but also via fast surface redox reactions and possibly ion intercalation within the redox-active electrode.

This talk will present physical modeling of interfacial phenomena, transport phenomena, and redox reactions in electrochemical capacitors under charging and discharging conditions. The model accounts for finite ion size, asymmetric electrolytes, and three-dimensional electrode morphology. It also considers faradaic reactions and ion intercalation when simulating pseudocapacitors. Typical cyclic voltammetry measurements will be reproduced numerically for various electrolyte and electrode materials and different scan rates. The results will be used to provide detailed physical interpretation of experimental measurements. Special effort will be made to systematically compare model predictions with experimental data.