Role of interlayer distance on the ionic and electronic transport in V₂O₅ cathodes

Vanadium pentoxide (V₂O₅) is a promising multi-valent battery cathode material due to its layered structure, which facilitates the intercalation of various ions (e.g., Li⁺, Na⁺, K⁺,  Ca²⁺, Mg²⁺, Zn²⁺). Pre-intercalation with other cations or even small molecules, like H₂O, can modify the distance between V₂O₅ layers. This structural change directly influences key transport properties: both ionic diffusion and electronic conduction, where the latter occurs through polaron hopping, as free carriers localize while deforming the lattice to form small polarons. To decouple the pure geometric effect of interlayer expansion from the chemical influence of specific pre-intercalants, we performed a detailed density functional theory (DFT) study using the nudged elastic band (NEB) method to systematically investigate the impact of interlayer spacing on ionic diffusion barriers, polaron localization, and polaron hopping. Our calculations reveal distinct migration pathways and quantify the ionic diffusibility and polaronic behavior, providing a fundamental understanding of the relationship between structure and battery performance. These results establish design principles for optimizing V₂O₅-based cathodes for next-generation energy storage.