A Robust UV-curable Ion-liquid Gel Electrolyte for High-performance Polymer-based Electrochromic Devices

Abstract

The electrolyte plays a vital role in balancing charges and facilitating ion transportation in electrochromic devices (ECDs). Meanwhile, mechanical performance is a crucial aspect worth noting in practical applications for preventing short circuit of the EC and counter electrode layers. Herein, a robust polymer framework quasi-solid gel electrolyte (GE) with high mechanical properties is constructed through a combination of “Soft chain” epoxy acrylate (EA) and “Hard chain” VEIMPF6 monomer with EMIMTFSI and LiTFSI as the ion source. After optimizing the component ratio, the electrolyte GE3-Li2 shows the best universal properties including a high ionic conductivity of 1.52×10-3 S/cm, over 85% of optical transmittance in visible band and good mechanical strength such as tensile strength of 0.56 MPa, adhesion strength of 1.385 MPa, and elongation at break of 426%. The resultant three polymer-based ECDs based on this electrolyte demonstrate outstanding electrochromic performance, which also retains electrochromic behaviors after hundreds of times of bending, flexing and pressing tests. All of these indicate a robust gel electrolyte for practical application in polymer-based ECDs has been designed and obtained.