Non-volatile, Li-doped ion gel electrolytes for flexible WO3-based electrochromic devices

Flexible electrochromic devices (ECDs) based on Li-doped ion gels and tungsten trioxide (WO3) arc demonstrated. Colored ECDs cannot be produced using conventional ion gels comprised of copolymers and room temperature ionic liquids (RTILs) due to a lack of cations that can be inserted into WO3. Based on considerations of the coloration mechanism, we developed Li-doped ion gels and applied these to devices.The effects of Li salt concentration are systematically examined, with respect to device dynamics, coloration efficiency, and transmittance contrast. In addition, the coloration/bleaching switching stability of the ECD produced using optimal Li salt content is investigated. The ECD exhibits distinct colored and bleached states even after 24 h operation in air. Using the described Li-doped ion gel electrolytes, flexible WO3 ECDs were successfully demonstrated with good bending stability and no electrolyte leakage. (C) 2018 Published by Elsevier Ltd.