Subtle Local Structural Details Influence Ion Transport in Glassy Li Thiophosphate Solid Electrolytes.

Many of the promising, high-performing solid electrolytes for lithium-ion batteries are amorphous or contain an amorphous component, particularly in the Li thiophosphate LiS-PS (LPS) compositional series. An explicit study of the local structure in four samples of ostensibly identically prepared 70LiS-30PS glass reveals substantial variation in the ratio between the two main local structural units in this system: PS3 tetrahedra and PS corner-sharing tetrahedral pairs. Local structural and compositional probes including Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray pair distribution function analysis are employed here to arrive at a consistent description of the relative amounts of isolated tetrahedral units, which vary by 13% across the samples measured.