Enhanced Transport Kinetics of Electrochromic Devices by W₁₈O₄₉ NW/Ti₃C₂T_x 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 (Ti₃C₂T_x) and W₁₈O₄₉ nanowires (NWs). A transparent conductive electrode is fabricated by co‐assembly of Ag and W₁₈O₄₉NWs, followed by depositing W₁₈O₄₉ NW/Ti₃C₂T_x layers for the fabrication of the electrochromic device. The incorporation of Ti₃C₂T_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 W₁₈O₄₉ NW/Ti₃C₂T_x composite reveals enhanced transmittance modulation (61%), rapid response time (4.5 s coloration, 6.5 s bleaching), and high coloration efficiency (139.1 cm² 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 cm²) flexible electrochromic device with a solid electrolyte is successfully fabricated and utilized as a smart window and a flexible stealth patch.