First-principles thermal modeling of hybrid pseudocapacitors under galvanostatic cycling

Abstract

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.

Computational Insights into Materials and Interfaces for Capacitive Energy Storage

“…Pilon et al proposed a one‐dimensional continuum model to simulate the time‐dependent charging behavior of a hybrid capacitor consisting of a pseudocapacitive metal oxide electrode for lithium‐ion intercalation and a carbon electrode for EDL formation ( Figure a) . Ion diffusion, lithium‐ion intercalation, and redox reaction were simultaneously captured.…”

“…In the case of a thin‐film electrode of fast Li‐intercalation, the CV curve suggests that the Faradaic process dominates in the whole voltage range (Figure b). In the case of a thick oxide electrode where the kinetics is limited by Li intercalation, they found that the Faradaic region is at more negative potential, while the capacitive region is at high potential and dominated by the EDL formation and that the transition between Faradaic and capacitive behavior occurred between these two regions …”

In Operando Calorimetric Measurements for Activated Carbon Electrodes in Ionic Liquid Electrolytes under Large Potential Windows

“…Other physicochemical phenomena may also contribute to the irreversible and/or reversible heat generation rates. For example, in hybrid supercapacitors, redox reactions also contribute to the reversible heat generation upon charging/discharging . In addition, the overpotential at the redox active electrode necessary to drive the redox reactions is responsible for irreversible “polarization heating” .…”

“…For example, in hybrid supercapacitors, redox reactions also contribute to the reversible heat generation upon charging/discharging . In addition, the overpotential at the redox active electrode necessary to drive the redox reactions is responsible for irreversible “polarization heating” . Other possible sources of heat generation may be associated with ion solvation/desolvation and decomposition of the electrolyte at high potentials …”

A Review on Electrothermal Modeling of Supercapacitors for Energy Storage Applications

“…The total heat Q generated in Hybrid SC can also be deduced from one-dimensional Stern electrochemical model [69], which describes the heat generation process, and expressed as:…”