Polyacrylamide gel electrolyte for high-performance quasi-solid-state electrochromic devices

Electrolytes, especially the gel polymer electrolytes (GPEs) play an important role in an electrochromic device (ECD), and have received extensive attention in recent years. GPEs combine the advantages of both liquid and solid electrolytes, and provide a new solution for realizing solid-state ECDs. In this work, polyacrylamide (PAM) GPE with a high ionic conductivity of 6.4 × 10−2 S cm−1 at room temperature was synthesized by an in situ free radical polymerization in an ECD, where Prussian blue (PB) and tungsten trioxide (WO3) were used as electrochromic (EC) layers. The in situ polymerization realizes a much better match between the electrolyte layer and the EC film. A large optical modulation of 74.8% at 678 nm and a high coloration efficiency of 154.5 cm2·C−1 are achieved for the obtained PB/PAM GPE/WO3 device. Due to the high ionic conductivity and fast ion transport, the ECD also has a fast coloration time (tc) of 2.1 s and a bleaching time (tb) of 1.7 s. Additionally, the ECD maintains 90.6% of optical modulation after 13,500 cycles, demonstrating an excellent cycling stability.