Design, synthesis and characterization of urea-based hybrid gel polymer electrolyte for applications in electrochemical devices

Abstract

In this work, a novel highly conductive colorless and transparent hybrid gel polymer electrolyte (GPE) was synthesized by the sol-gel reaction of poly(propylene glycol) bis(2-aminopropyl ether) (2-APPG) with different molecular chain lengths, isophorone diisocyanate (IPDI), 3-isocyanatepropyltriethoxysilane (ICS) and swelled in the electrolyte containing lithium bis(trifluoromethylsulfonyl) imide (LiTFSI). The TGA results show that the polymer electrolyte samples have only 1–3% weight loss when the temperature reaches 180 °C, indicating the electrolytes have excellent thermal stability. The presentd GPE exhibits a maximum conductivity value of 1.43 × 10−3 S cm−1 and Li ion transference numbers (t+) reaching to 0.32 at 20 °C. The GPE shows excellent electrochemical stability and storage stability. Furthermore, the prototype of the electrochromic device (ECD) using the GPE sample as the conductive layer has good optical modulation behavior (optical density change (Δ(OD)) value is 0.274), excellent coloring efficiency of 278.6 cm 2 C−1, and satisfactory cycling performance (stable cycling 550 times between 3.2 V and −3.5 V). The results indicate that the GPEs are suitable for electrochromic application and offer remarkable prospective.