Li−O₂ batteries have attracted significant attention due to their high theoretical capacity up to ~3000 Wh/kg, but they are still facing many challenges which avoid their penetration in practical applications. Their high charging voltage, which usually reaches 3.8 V and even more than 4 V, leads to problems such as poor round-trip efficiency, unfavorable parasitic reactions and a large potential gap between charge and discharge, resulting in an intrinsic loss of energy efficiency from source to end. The major part of this potential gap is due to large charge overpotential. Therefore, it is important to develop better understanding of the charge process.

In this work, a comprehensive multiscale model is reported to describe charge processes of Li−O₂ batteries. On the basis of a continuum approach, the present model combines mathematical descriptions of mass transport of soluble species (O₂, Li⁺, LiO₂) and detailed elementary reactions. The decomposition kinetics of the Li₂O₂ particles are assumed to be morphology dependent and the simulated charge curves are in good agreement with experimental studies reported in literature previously.¹ The model along with the assumed reaction mechanisms provides physical explanations for the characteristic two-step charge profiles. Moreover, since the morphology of Li₂O₂depends strongly on the applied current density during discharge and operation history upon cycling, the model underlines the strong link between discharge and charge processes. The experimental validation and comparison will be also discussed in the talk.

 [1] Zhai, D.; Wang, H.-H.; Yang, J.; Lau, K. C.; Li, K.; Amine, K.; Curtiss, L. A. J. Am. Chem. Soc. 2013, 135, 15364–15372.

 [2] Y. Yin, C. Gaya, A.Torayev ,V. Thangavel, A. A. Franco. J. Phys. Chem. Lett., 2016, 7 (19), 3897–3902