PNNL

Abstract

To study the discharge performance of Li–O2 batteries, we propose a multiscale modeling framework that links models in an upscaling fashion from the nanoscale to mesoscale and finally to the device scale. We have effectively reconstructed the microstructure of a Li–O2 air electrode in silico, conserving the porosity, surface-to-volume ratio, and pore size distribution of the real air electrode structure. The mechanism of rate-dependent morphology of Li2O2 growth is incorporated into the mesoscale model. The correlation between the active-surface-to-volume ratio and averaged Li2O2 concentration is derived to link different scales. The proposed approach’s accuracy is first demonstrated by comparing the predicted discharge curves of Li–O2 batteries with experimental results at the high current density. Next, the validated modeling approach effectively captures the significant improvement in discharge capacity due to the formation of Li2O2 particles. Finally, it predicts the discharge capacities of Li–O2 batteries with different air electrode microstructure designs and operating conditions.