Transparent succinonitrile-modified polyacrylate gel polymer electrolyte for solid electrochromic devices

Transparent gel electrolytes have the advantage of optical transparency, higher ionic conductivity, and better electrode adhesion compared with solid inorganic electrolytes, which is of great significance in solid-state electrochromic glass and other electrochemical applications. Here, succinonitrile-modified polyacrylate gel polymer electrolyte (SN-GPE) has been successfully synthesized via an in-situ thermal polymerization under mild conditions. Adopted succinonitrile significantly improves ionic conductivity from 0.02 mS·cm−1 to 4.02 mS·cm−1, maintaining advantageous features such as high transparency and excellent electrochemical performance. The optimized SN-GPEs with good adhesion to both counter and working electrodes were assembled in semi-devices with a configuration of glass/FTO/WO3/SN-GPE/FTO/glass, which showed an excellent optical modulation (ΔT) of 34.5 % at λ = 633 nm and fast response time 4 s/20 s for bleaching/coloration by applying a bias voltage ± 2.8 V, and promising cycling stability with ΔT maintaining 90 % of the original after 2840 cycles, indicative of an extensive potential in the applications of the solid or flexible electrochromic devices. This work significantly broadens the transparent electrolyte family for advanced large-scale electrochromic devices.