Sea-Cucumber-like Microstructure Polyoxometalate/TiO₂ Nanocomposite Electrode for High-Performance Electrochromic...

The key challenge in the practical application of electrochromic energy storage devices (EESDs) is the fabrication of high-performance electrode materials. Herein, we deposited K₇[La(H₂O)_x(α₂-P₂W₁₇O₆₁)] (P₂W₁₇La) onto TiO₂ nanowires (NW) to construct an NW-P₂W₁₇La nanocomposite using a layer-by-layer self-assembly method. In contrast to the pure P₂W₁₇La films, the nanocomposite exhibits enhanced electrochromic and electrochemical performance owing to the 3D sea-cucumber-like microstructure. An EESD using the NW-P₂W₁₇La film as the cathode exhibited outstanding electrochromic and energy storage properties, with high optical modulation (48.6% at 605 nm), high switching speeds (t_coloring = 15 s, t_bleaching = 4 s), and high area capacitance (5.72 mF cm^-2 at 0.15 mA cm^-2). The device can reversibly switch between transparent and dark blue during the charge/discharge process, indicating that electrochromic contrast can be used as a quantitative indicator of the energy storage status.