Impact of Li2O2 Particle Size on Li-O2 Battery Charge Process: Insights from a Multiscale Modeling Perspective

We report a comprehensive multiscale model describing charge processes of Li-O-2 batteries. On the basis of a continuum approach, the present model combines mathematical descriptions of mass transport of soluble species (O-2, Li+, LiO2) and elementary reaction kinetics, which are assumed to be dependent on the morphology of the Li2O2 formed during discharge. The simulated charge curves are in agreement with previously reported experimental studies. The model along with the assumed reaction mechanisms provides physical explanations for the two-step charge profiles. Furthermore, it suggests that these charge profiles depend on the size of the Li2O2 particles, which are determined by the applied current density during discharge. Therefore, the model underlines the strong link between discharge and charge processes.