Microscopic insights on ion transport in Li3OCl1−xBrx anti-perovskites from metadynamics simulations

Abstract

The recently discovered anti-perovskites of the formula, Li3OCl1−xBrx, where x=0 to 1, have been garnering interest as potential candidates for solid electrolytes in battery applications. It is observed that the Li ion transport in these solids is rather slow, and unaccessible within typical molecular dynamics time scales. However, by judicially augmenting it with the accelerated sampling technique of metadynamics, the present study derives fresh insights on the nature of Li ion transport in these systems. The microscopic of ion migration along intra- and inter-octahedral channels, suggests that intra-octahedral channels account for over 95% Li transport in the system. The bromide end member offers lower free energy barriers, due to entropic factors resulting from the expansion of the lattice. However, the large free energy barriers estimated in the present work suggest that the undoped Li3OCl1−xBrx anti-perovskites are unlikely to exhibit superionic behavior.