Computational Insights into Dion-Jacobson Type Oxide Ion Conductors

Dion-Jacobson type materials have recently emerged as a new structural family of oxide ion conductors, materials important for applications in a variety of electrochemical devices. While some attempts to improve their ionic conductivity have been reported, a detailed understanding of the underlying oxide ion diffusion mechanisms in these materials is still missing. To explore the structure-property relationships leading to the favorable properties, we carried out ab initio molecular dynamics simulations of oxide ion diffusion in CsBi₂Ti₂NbO_10-δ. Our computational study reveals significant out-of-plane dynamics, indicating that the dominant pathway for oxide ion migration is via jumps into and out of the (ab) crystallographic plane. This suggests that further improvement of oxide ion conductivity relative to CsBi₂Ti₂NbO_10-δ could be achieved by enhancing the rotational flexibility of the coordination polyhedra located in the inner perovskite layer, thereby facilitating faster out-of-plane motions.