(Invited) Harness the Interplay between Local Ordering and Lattice Strain for Boosting Na Ionic Conductivity

The state-of-art data-driven discovery of novel ionic conductors is mainly driven by the exploration of novel structural frameworks that deliver connected low-barrier diffusion channels for facile ion migration, or the optimization of diffusor/vacancy contents. An orthogonal design strategy is to engineer the key local structures that can be used to reshape the energy landscape. In this presentation, we will demonstrate the influence of two key local structures, e.g., local ordering and lattice strain, on optimizing Na ionic conductivity for solid-state electrolytes. It has been found that orders of magnitude higher ionic conductivity can be accomplished if the local ordering tendency is frustrated, or when the lattice distortion is appropriately optimized. Such a strategy can also induce orders of magnitude higher ionic conductivity without stuffing Na or creating Na vacancies. As instructed by these theoretical discoveries, we will also demonstrate several newly synthesized Na solid-state oxide conductors with ionic conductivity of more than 1 mS/cm.