Lithium Transport in Crystalline and Amorphous Cathode Coatings for Li-Ion Batteries

Cathode coating materials, encompassing metal oxides and fluorides, have demonstrated their efficacy in enhancing battery performance, particularly in terms of durability and safety. These coatings act as physical barriers or HF scavengers, impeding the electrode-electrolyte side reactions. However, a critical aspect that remains inadequately explored is the understanding of lithium transport within these coatings, a pivotal factor influencing battery cycling performance. In this study, we employ a hybrid approach, combining first-principles density functional theory calculations and statistical mechanics, to investigate lithium transport across a diverse range of coating materials, including both crystalline and amorphous forms. Lithium diffusivities are systematically calculated for 25 metal oxides and 19 metal fluorides, identified as promising coating materials through previous thermodynamic high-throughput screening. A total of 12 crystalline metal oxides, 6 amorphous metal oxides, and 8 amorphous metal fluorides exhibit promising capabilities for efficient lithium transport compared with typical solid-state materials used in Li-ion batteries. Notably, Y2O3, Sc2O3, ZnO, and Ga2O3 among these candidates exhibit low Li diffusion barriers in both crystalline and amorphous forms. However, some candidates display limited Li diffusivities due to unfavorable Li binding sites and relatively high diffusion barriers. A detailed examination of Li diffusion barriers in crystalline metal oxides reveals that those with similar crystal structures exhibit comparable lithium transport abilities. Surprisingly, no clear correlation is observed between Li diffusivity in the crystalline and amorphous forms. This comprehensive investigation contributes to a broader understanding of the battery performance enhancements associated with coatings. The identified promising cathode coating materials hold the potential to expedite the design and discovery of future materials, marking a significant step forward in advancing battery technology.