Oxysulfide Li2BeSO: A potential new material for solid electrolyte predicted from first principles

Abstract

Solid electrolytes with fast Li+ conductivity and high chemical stability are of particular interest for application in all-solid-state lithium ion batteries. Particle swarm optimization (PSO) here predicts a new material, Li2BeSO, with both high Li+ conductivity and a wide electrochemical window. Two polymorphs are found in different pressure ranges; a tP20 structure is stable from ambient pressure to 12.6 GPa, above which an oI10 structure is stable. Analysis of phonon dispersion and possible decomposition paths reveals that both Li2BeSO polymorphs are dynamically and chemically stable at ambient pressure. This new material is therefore quench recoverable if synthesized under different P–T conditions. Migration energy barriers for Li+ transport in the two polymorphs at 0 GPa are analyzed for different paths and hopping modes, and the optimal Li+ transition path is derived for each structure. Interestingly, oI10-Li2BeSO is found to have a low barrier of ∼70 meV, suggesting it could be a potentially useful solid-state electrolyte. In addition to discovering a new and efficient solid electrolyte, this study advances our understanding of superionic conductors.