All-solid-state batteries with non-flammable solid-state electrolytes have significant advantages over Li-ion or Na-ion batteries with liquid electrolytes. In this poster we will present our recent advances in understanding the fundamental relationship between crystal structure and ionic transport in fast Li-ion conductors [1]. We find that the topology of the sites along the lithium hopping path, and the volume per anion, largely control the activation energy for Li motion.  This topology is more favorable in compounds where the anions form a bcc lattice than in the typical close-packed fcc and hcp anion arrangements, explaining why most compounds are not fast-ion conductors.  Furthermore, an accurate and efficient first-principles computational methodology has been developed to evaluate thermodynamic stability of the solid-state electrolyte against battery electrodes [2]. These findings not only provide valuable insights towards the understanding of materials behaviors in discovered ionic conductors, but also serve as design principles for new Li and Na conducting materials and all-solid-state batteries. We will also report a few novel Li and Na ionic conductors that are predicted based on our design principles and experimentally confirmed by our collaborators.

[1] Y. Wang, et al., “Design principles for solid-state lithium superionic conductors,” Nat. Mater., 14, 1026-1031, (2015).

[2] W. Richards, et al., “Interface stability in solid-state batteries”, Chem. Mater., 28, 266-273, (2016).