New insights into the lithium-ion diffusion mechanism in vanadate compounds

Abstract

Vanadate as intercalation compounds are attracting considerable interest for use in electrochemical energy storage devices, such as lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries. However, the ion transport mechanism in vanadate compounds has never been clearly elucidated despite its overwhelming influence on electrochemical performance. Unlike previous reports, in this work, new insights into Li+ diffusion mechanisms for LiV3O8 are proposed, and the key points are as follows. First, Li+ tended to be transported along the b-axis direction via a knock-off mechanism rather than direct hopping along the c-axis direction, as argued by traditional views. Second, the lattice lithium ions in LiV3O8, which were previously thought to function via pillar effects, were proven to be electrochemically active by computational calculations. Moreover, further studies revealed that our conclusions were universal and could be widely applied to many other vanadate compounds. This work has provided a new understanding of ion diffusion in vanadate compounds, which enables researchers to develop more efficient strategies for performance optimization.