Lithium transport in amorphous Al₂O₃ and AlF ₃ for discovery of battery coatings

Lithium batteries have become a dominant power source for portable electronic devices and also for electric vehicles because of their superior energy density. Electrode coating materials, including amorphous metal oxides and fluorides, are beneficial to improve battery performance such as durability and safety. We use methods that combine first principles density functional theory calculations and statistical mechanics to investigate Li transport in amorphous Al₂O₃ and AlF₃. Because of unfavorable Li binding sites and relatively high diffusion barriers, the Li diffusivities are found to be very low, about 1.1 × 10^-13 (2.7 × 10^-14) m²s^-1 at 600 K for a-AlF ₃ (a-Al₂O₃). The diffusivities are also much lower than those in benchmark materials, Li-β-alumina and LiFePO ₄, which have open channel structures. This work is one part of a framework for understanding the battery performance improvement associated with coatings and should aid in future discovering of coating materials.