A polyacrylic acid/polyacrylamide-based hydrogel electrolyte containing gelatin for efficient electrochromic device with outstanding cycling stability and flexible compatibility

Hydrogel electrolytes have been attracted intense research interest due to their widespread applications in advanced electronic devices. In this work, we developed a new hydrogel electrolyte to overcome two critical issues in electrochromic devices, involving long-term cycling stability and flexible compatibility. Briefly, gelatin was introduced into a hydrogel polymer matrix based on polyacrylic acid/polyacrylamide, resulting in high transparency, high electronic conductivity, durable electrochemical stability, inherent adhesiveness. Complementary electrochromic devices employing the present hydrogel electrolyte exhibited efficient performance with high optical contrast over 85 %, short response time, high coloration efficiency of 205.7 cm2/C. Remarkably, an excellent operation stability was achieved with less than 3 % loss of the initial optical contrast after 15,000 cycles switching, which was the best case among those based on the same electrochromic materials reported so far. Moreover, the efficient adhesiveness of the present hydrogel electrolyte enabled the compatibility with flexible device and improved the device bending stability. These findings might shed light on the development of durable and flexible electrochromic devices toward practical application.