A hybrid gel polymer electrolyte with imide groups modified by the coupling agent and its application in electrochromic devices

Herein, a new class of hybrid gel polyelectrolytes (GPEs) through sol–gel technology has been synthesized and characterized. The reaction mechanism of gel polymer electrolyte is based on the hydrosilylation and sol–gel reactions of poly(propylene glycol) bis(2-aminopropyl ether), pyromellitic dianhydride, glycidoxypropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. The gel polymer electrolyte exhibits excellent ion-conductive and thermostability performance. The maximum ionic conductivity value of 3.1 × 10⁻⁴ S cm⁻¹ and Li-ion transference numbers (t⁺) reaching 0.49 at 25 °C are achieved for the gel polymer electrolyte. The thermogravimetric analysis results show that the electrolyte samples are nearly 1% weight loss when the temperature reaches up to 100 °C. The gel polymer electrolytes display a prominent electrochemical stability, which could bear potential up to 10 V. In addition, the prototype electrochromic device using electrolyte sample as the conductive layer presents excellent coloration efficiency of 198.9 cm² C⁻¹, stable cycle of 125 periods under 5-V high-voltage environment, and stable cycling performance (achieving 300 stable cycles from the voltage of −3.5 to 2.5 V). As a result, the GPEs exhibit an excellent electrochemical performance, which is suitable for electrochromic application and offers a remarkable prospective.