Structure and lithium ion diffusion in lithium silicate glasses and at their interfaces with lithium lanthanum titanate crystals

Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Lithium containing glasses such as lithium silicate glasses have been widely studied due to their high ionic conductivity. Recently, lithium silicate glasses were introduced in polycrystalline lithium lanthanum titanate (LLT) ceramics as intergranular thin films between the crystalline grains to achieve higher lithium ion conductivities in these solid state electrolytes. In this work, we present investigations of the structure and diffusion behavior of lithium silicate glasses and their interfaces with LLT crystals using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces, as well as the effect of atomic structure on diffusion behaviors, were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. The interface lithium ion diffusion energy barrier was found to be dominated by the glass phase.