Visualization of Structures and Li-Ion Conduction Pathways in the Li 2 S-P 2 S 5 System Using Neutron Scattering

Abstract

Designing the next generation of lithium ion batteries (LIBs) requires fundamental information that surprisingly often is still unknown-for example, details of how ions actually move through a working device. Li7P3S11 crystal and (Li2S)x(P2S5)100-x glasses have received a great deal of attention as a solid electrolyte for all-solid-state LIBs because of its extremely high ionic conductivity of 10 to 10-2 S/cm at room temperature. The authors predict and visualize the conduction pathways of Li ions in Li7P3S11 crystal and (Li2S)x(P2S5)100-x glasses, using reverse Monte Carlo (RMC) modeling and the bond valence sum (BVS) approach with neutron diffraction data. The conduction pathways of Li ions can be classified into two types: relatively "stable" regions and "metastable" regions for Li ions. Furthermore, the authors use quasielastic neutron scattering to directly monitor the fast diffusion of Li ions in Li7P3Sn crystal. According to the jump diffusion model, Li ions migrate between stable regions within a jump length G 1 = 4.3 A along conduction pathways.