Thermal-electrochemical lithium-ion battery simulations on microstructure and porous electrode scale

Heat production within a battery cell is governed by local fluxes of ions and electrical currents in the microstructure of the battery electrodes. These fluxes are strongly coupled with thermal transport, leading to a fully coupled reaction transport model for batteries [1-3]. By applying the volume-averaging technique to our thermal-electrochemical microscopic theory the corresponding thermal-electrochemical porous electrode theory can be derived [3]. Implementation of both models in our simulation software BEST [4] allows to compare the results of the homogenized theory with numerically averaged simulations on micro scale. Whereas the numerically averaged results agree very well with the results of porous electrode theory, strong fluctuations around this average (e.g. of the overpotential) are observed in microstructures. Our results raise the question to which extent porous electrode theory can be used to predict degradation phenomena in batteries.