Regulating the Ion Transport in the Layered V₂O₅ Electrochromic Films with Tunable Interlayer Spacing

Abstract Unveiling the ion transport mechanism to design and explore efficient and stable ion transport pathways for high‐performance transition metal oxide (TMO)−based electrochromic materials is highly desired yet challenging. Herein, this study has demonstrated that the interlayer spacing of layered vanadium penoxide (V₂O₅) films can be tuned by inserting different amounts of lithium−ion (Li⁺) within host V₂O₅ material, as well as adjusting ion transport behavior and electrochromic performance. These results show that V₂O₅ with a small amount of ion insertion delivers a stable ion transport process and electrochromic properties. Increasing the amount of inserted Li⁺ will enlarge the interlayer spacing, which provides abundant active sites and efficient ion transport channels, and thus reversible and rich color variation of yellow−green−blue−olive green−orange is realized. Nevertheless, an excess of ion insertion results in the crystal structure collapse and cyclic stability degradation. These findings give a rationale for the evolution of electrochromic properties during different electrochemical reaction stages. This work provides considerable insight into the ion transport behavior within the layered V₂O₅ films, which gives fundamental theoretical guidance for developing and designing superior layered TMO electrochromic materials.