Electrodeposited V2O5·nH2O Thin Film with Superior Mg2+ Storage and Electrochromic Properites

Developing bifunctional materials with concurrent electrochromic and electrochemical energy storage capabilities is crucial for advancing the construction of energy-saving smart windows, smart sensors, implanted displays, and electronic skins. Herein, a layered V 2 O 5 · n H 2 O thin film is fabricated through a facile electrodeposition method with V 2 O 5 sol as electrolyte, and its Mg 2+ storage and electrochromic performances are explored for the first time. This layered V 2 O 5 film exhibits outstanding Mg 2+ storage performance, delivering an areal specific capacity of 17 μAh cm −2 at 0.5 mA cm −2 , showing no capacity decay during 500 cycles, and exhibiting superior rate performance. It achieves an optical contrast (Δ T ) of 64.63% at 769 nm wavelength (between orange-red and dark green) and a rapid switching speed. Notably, the color transition exhibits a distinct potential dependence and high optical distinguishability: it reversibly switches between green, orange, and red hues at discrete potential points during the electrochemical cycling process. The structure/performance relationship of the film is analyzed via in situ Raman, ex situ XRD, XPS, and DFT calculations. This study provides clues for developing Mg 2+ -intercalation-based electrochromic energy storage bifunctional materials.