Defining Diffusion Pathways in Intercalation Cathode Materials: Some Lessons from V2O5 on Directing Cation Traffic

The invention of rechargeable batteries has dramatically changed our landscapes and lives, underpinning the explosive worldwide growth of consumer electronics, ushering in an unprecedented era of electric vehicles, and potentially paving the way for a much greener energy future. Unfortunately, current battery technologies suffer from a number of challenges, e.g., capacity loss and failure upon prolonged cycling, limited ion diffusion kinetics, and a rather sparse palette of high-performing electrode materials. Here, we discuss the origins of diffusion limitations in oxide materials using V2O5 as a model system. In particular, we discuss constrictions in ionic conduction pathways, narrow energy dispersion of conduction band states, and the stabilization and self-trapping of polarons as local phenomena that have substantial implications for introducing multiscale compositional and phase heterogeneities. Strategies for mitigating such limitations are discussed such as reducing diffusion path lengths and the design of metastable frameworks yielding frustrated coordination and decreased barriers for migration of polarons.