Local structure and lithium-ion diffusion pathway of cubic Li7La3Zr2O12 studied by total scattering and the Reverse Monte Carlo method

Abstract

The lithium-ion conducting solid electrolyte Li₇La₃Zr₂O₁₂ has one crystalline phase that has the cubic garnet structure, and this phase has one of the highest room temperature lithium-ion conductivities of any oxide. Neutron and X-ray total scattering data, analysed by the Reverse Monte Carlo method, have been used to examine the distribution of lithium ions over a wide range of temperatures, and to explore aspects of the stability and flexibility of the basic oxide structure. We compare the results with those from supporting molecular dynamics simulations. Unlike previous work, our method requires no prior assumptions about the Li ion distribution. Using total scattering rather than solely Bragg scattering, we obtain much higher real-space resolution than previously available. The combination of X-ray and neutron scattering allows detailed characterisation of both the mobile and immobile sublattices. Only a small fraction of Li ions are mobile at any one time; diffusion occurs primarily by movement between Li₂ sites via empty Li₁ sites.