Solvation structure and dynamics of Li and LiO2 and their transformation in non-aqueous organic electrolyte solvents from first-principles simulations

Abstract

Density functional theory calculations together with ab initio molecular dynamics (AIMD) simulations have been used to study the solvation, diffusion and transformation of Li+ and LiO2 upon O2 reduction in three organic electrolytes. These processes are critical for the performance of Li-air batteries. Apart from studying the structure of the solvation shells in detail, AIMD simulations have been used to derive the diffusivity and together with the Blue Moon ensemble approach to explore LiO2 formation from Li+ and O2− and the subsequent disproportionation of 2LiO2 into Li2O2 + O2. By comparing the results of the simulations to gas phase calculations, the impact of electrolytes on these reactions is assessed which turns out to be more pronounced for the ionic species involved in these reactions.