Multi-scale electrochemical thermal model of Electric Double Layer Capacitor under galvanostatic cycling

Electric Double Layer Capacitors (EDLC) have a wide spectrum of application with internal heat generation which may lead to thermal runaway or accelerated aging. This study proposes a multi-scale electrochemical thermal model of EDLCs. Energy equation is solved for cylindrical EDLC device with averaged reversible heat generation rate calculated from local heat generation rate near single carbon nanoparticles derived from first principle. The numerical heat generation and temperature profile resemble experimental results with a prediction error less than 15%. The temperature is uniform across the jelly roll but shows a major drop across the air gap. The reversible heat generation profile is asymmetric and features a sharper peak for exothermic process compared with endothermic process. This is attributed to the relative fast heat dissipation from the EDLC device to the surrounding during exothermic process. Furthermore, detailed contribution of heat generation rate near the electrode/electrolyte interface is analyzed. Negative heat of mixing is observed at the start of charging. This can be attributed to the deviation of flux direction due to the existence of a curved surface. This comprehensive model can be used to study the detailed effect of nanoparticle phenomena on the heat generation and temperature profiles of commercial EDLC devices.