Structural Analysis and Li Migration Pathways in Ramsdellite Li₂Ti₃O₇: A Theoretical Study

Ramsdellite Li₂Ti₃O₇, which is an interesting material both for lithium ion batteries and fundamental lithium diffusion studies, has been discussed as a possible one-dimensional Li-ion conductor in the literature. In order to shed light on the question of dimensionality of Li diffusion, a theoretical investigation has been performed at periodic density-functional theory level. The cation distribution and Li diffusion are investigated theoretically. Migration pathways along the crystallographic b direction and in the ac plane are compared. The calculated activation energies for both directions are similar. However, the potential energy landscape for Li migration within the ac plane is highly nonsymmetric with large energy differences between initial and final structures. This makes long-range migration in the ac plane kinetically less favorable than along the b direction.