Diffusion of ions and solvent in propylene carbonate solutions for lithium-ion battery applications

Abstract

Diffusion of lithium ions in organic solvent solutions is important to the performance of lithium ion batteries. In this article, fully atomistic molecular dynamics (MD) simulations were employed to study the diffusive behavior of LiPF6 electrolyte salt and propylene carbonate in solutions at different temperatures in direct comparison to experimental diffusivity data. Organic solutions at 1 M concentrations were considered at the operational conditions of Lithium ion batteries. We show that non-polarizable scaled charge force fields can predict, quantitatively, the diffusion of Li+ and PC solvent in a range of operational temperatures. Such type of force fields are much less computational demanding than polarizable or ReaxFF models. Diffusion follows an Arrhenius type of behavior. van Hove autocorrelation functions show a nonGaussian type of movement for ions and PC solvent. The Li+ is moving by a mixed-vehicular mechanism. Moreover, the nearest neighbour distances of the Li+- carbonyl oxygen in these PC solutions is predicted accurately using the scaled charges GAFF, in agreement to experiments. Furthermore, quantitative prediction of modeled ionic conductivity in comparison to experiments can be achieved in a range of temperatures.