Subcontract Report: Diffusion Mechanisms and Bond Dynamics in Solid Electrolyte Ion-Conductors

We employ first-principles molecular dynamics simulations and Maximally Localized Wannier Function (MLWF) analysis to explore how halide substitution and nano-phase microstructures affect diffusivity, through the activation energy barrier - Ea and D0, in the solid electrolyte Li3InBr6-xClx. We find that nano-phase microstructures with x=3 (50-50 Br-Cl) mixed composition have a higher diffusivity compared to x=2 and x=3 solid solutions. There is a positive linear relationship between ln(D0.) and Ea, which suggests that for superionic conductivity optimizing both the activation energy and the D0 is important. Bond frustration due to mismatch in crystal geometry and ideal coordination number leads to especially high diffusivity through a high D0 in the x=3 composition.