Impact of Li<sub>2</sub>O<sub>2</sub> Particle Size on Li–O<sub>2</sub> Battery Charge Process: Insights from a Multiscale Modeling Perspective

We report a comprehensive multiscale model describing charge processes of Li–O<sub>2</sub> batteries. On the basis of a continuum approach, the present model combines mathematical descriptions of mass transport of soluble species (O<sub>2</sub>, Li<sup>+</sup>, LiO<sub>2</sub>) and elementary reaction kinetics, which are assumed to be dependent on the morphology of the Li<sub>2</sub>O<sub>2</sub> 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 Li<sub>2</sub>O<sub>2</sub> particles, which are determined by the applied current density during discharge. Therefore, the model underlines the strong link between discharge and charge processes.