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.