Sea-Cucumber-like Microstructure Polyoxometalate/TiO(2) Nanocomposite Electrode for High-Performance Electrochromic Energy Storage Devices

The key challenge in the practical application of electrochromic energy storage devices (EESDs) is the fabrication of high-performance electrode materials. Herein, we deposited K(7)[La(H(2)O)(x)(α(2)-P(2)W(17)O(61))] (P(2)W(17)La) onto TiO(2) nanowires (NW) to construct an NW–P(2)W(17)La nanocomposite using a layer-by-layer self-assembly method. In contrast to the pure P(2)W(17)La films, the nanocomposite exhibits enhanced electrochromic and electrochemical performance owing to the 3D sea-cucumber-like microstructure. An EESD using the NW–P(2)W(17)La 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.