Enhanced Transport Kinetics of Electrochromic Devices by W18O49 NW/Ti3C2Tx Composite Films

Abstract Electrochromic devices can facilitate the realization of a wide set of future applications, ranging from energy‐saving windows to smart wearables and stealth. Historically, tungsten oxides have been the most studied materials for electrochromism, albeit with bottlenecks like limited conductivity, high charge transport barrier, and low ion diffusivity. Here, inspired by the recent MXene materials, the study has engineered an electrochromic composite of MXene nanosheets (Ti 3 C 2 T x ) and W 18 O 49 nanowires (NWs). A transparent conductive electrode is fabricated by co‐assembly of Ag and W 18 O 49 NWs, followed by depositing W 18 O 49 NW/Ti 3 C 2 T x layers for the fabrication of the electrochromic device. The incorporation of Ti 3 C 2 T x nanosheets enhances the transport of electrons and ions within the electrochromic layer, leading to a significant improvement in the electrochromic performance. Noteworthily, the film structure comprising 15 layers of W 18 O 49 NW/Ti 3 C 2 T x composite reveals enhanced transmittance modulation (61%), rapid response time (4.5 s coloration, 6.5 s bleaching), and high coloration efficiency (139.1 cm 2 C −1 ). Moreover, the electrode also presents a high diffusion coefficient of Li + and good cycling stability (96.66% after 250 switching cycles). Finally, a large‐scale (15 × 20 cm 2 ) flexible electrochromic device with a solid electrolyte is successfully fabricated and utilized as a smart window and a flexible stealth patch.