Understanding Ionic Transport in LiFeO2 Polymorphs: Pathways to Enhancing Lithium-Ion Battery Performance.

We compare the ionic transport properties of six LiFeO2 polymorphs side by side to assess their potential as intercalation cathodes for lithium-ion batteries (LIBs). Employing two established methods, Bond Valence Site Energy (BVSE) calculations and Crystal Analysis by Voronoi Decomposition (CAVD), with identical settings for all six structures, we analyze how structural variations affect Li-ion diffusion pathways, dimensionalities, and migration barriers. Within this comparison, the ordered rock salt phase shows the most favorable transport characteristics, combining the lowest energy barriers of the six polymorphs with three-dimensional Li-ion conduction. The tetrahedral polymorph also has a three-dimensional void network, but its lowest-energy migration is one-dimensional, and the network connects in all three dimensions only at considerably higher energy. In contrast, layered and corrugated structures enable quasi-two-dimensional diffusion but are limited by high out-of-plane barriers. The goethite and γ phases are the most constrained. Goethite confines low-energy migration to a single axis, and in γ-LiFeO2, high barriers in every direction leave the geometrically connected network kinetically ineffective. Together, the results provide a consistent structure-transport comparison across the six polymorphs that can guide the choice of LiFeO2 phases for further cathode development.