Three-dimensional knotting of W17O47@PEDOT:PSS nanowires enables high-performance flexible cathode for dual-functional electrochromic and electrochemical device

An efficient integration of electrochromic and electrochemical devices into one flexible entity enables both energy storage and energy-saving dual-functionalities. For this purpose, achieving both high electrochromic and electrochemical performance is the key aspect. Herein, a new 3D architecture is successfully made by knotting W17O47@PEDOT (poly(3,4-ethylenedioxythiophene)):PSS (poly(styrenesulfonate)) nanowires with NaWO3 nanoknots, and interestingly, the 3D W17O47/(NaWO3-knots)@PEDOT:PSS cathode thus-made simultaneously exhibits a large optical modulation (79.7% at 633 nm), an ultra-long cycling life (76% of original optical modulation retained after 12 400 cycles), and a high areal capacitance (55.1 mF cm(-2) at 0.1 mA cm(-2)). Our density functional theory (DFT) calculations demonstrate that the much improved dual-functional performance is correlated to the raised electronic conductivity and ion adsorption at the W17O47/(NaWO3 nanoknots) interface, together with the ion adsorption of PEDOT:PSS in the 3D-knotted architecture. As a proof-of-concept application, different-sized flexible dual-functional electrochromic/electrochemical devices (FDEDs) were assembled and investigated for various application scenarios, including a smart window (15 cm x 10 cm), a wearable wristband (20 cm x 2.5 cm), and a smart eyeglass. The smart window made of the FDED enables a large temperature difference of 27.6 degrees C confirm-tested in model houses, where the energy source also powers three light-emitting diodes (LEDs). The understandings of the key governing principles in the electrodes and dual-functionalities provide a timely foundation for the new generation flexible multifunctional devices.