First-principles thermal modeling of hybrid pseudocapacitors under galvanostatic cycling

This study presents a theoretical framework developed from first principles for predicting the spatiotemporal thermal behavior of hybrid pseudocapacitors under galvanostatic cycling. It accounts for irreversible and reversible heat generation in the electrolyte and in the electrodes due to Joule heating, electric double layer (EDL) formation, and redox reactions. Detailed numerical simulations were performed to investigate the different local heat generation rates and the temperature as functions of time and cycling current. Numerical predictions showed good qualitative agreement with the limited experimental data available in the literature. Such numerical simulations can be used to physically interpret experimental measurements. Indeed, the present results suggest that a distinctive endothermic peak observed in the experimental heat generation rate resulted from cation starvation in the electrolyte reducing the faradaic current density. In addition, heating due to EDL formation significantly affected the local temperature and must be accounted for. The thermal model and the present results will help define safe modes of operation and develop thermal management strategies for pseudocapacitors.