Comparison of Correlated Li+ Diffusion from Molecular Dynamics of Promising Solid Electrolytes

Abstract

Li-ion batteries (LIBs) have been steadily improving since the first LIBs were commercially developed in the 1990s. Batteries with higher volumetric and gravimetric energy density using all-solid-state materials could revolutionize the LIB market. However, known superionic solid electrolytes are limited by a number of materials properties. Engineering better materials is especially limited by the lack of understanding of diffusion mechanisms, demanding novel analysis of diffusion using molecular dynamics. Molecular dynamics (MD) provides insight into correlated motion between Li-ions and correlated motion with the lattice. Correlated motion of Li-ions is common in the most promising superionic electrolytes. The results presented will be a broad survey of correlated motion using novel analysis tools developed by the authors and their collaborators. Diffusion in some of the most promising electrolytes, such as lithium borohydrides, lithium germanium thiophosphate, amorphous lithium thiophosphate, lithium lanthanum zirconium oxide, and the lithium rich anti-perovskites will be compared. Molecular dynamics of these systems will be performed either by ab-initio MD or classical MD. The Haven ratio and the Distinct Van Hove Analysis will be presented for each material. The novel analysis will focus on computational atomistic insights into the diffusion mechanisms of Li-ions, especially correlated motion.