A highly transparent and stretchable electrolyte with photoetching patterning function for electrochromic energy storage application

Abstract

Electrochromic devices (ECDs) are considered as the next-generation e-paper display and energy storage technology. However, the fabrication of ECDs is hindered by the requirements of the electrolyte, which necessitates transparency, a wide electrochemical window, high ionic conductivity, processability, and stability - all crucial factors in the EC field. At the same time, it is also the focus for an universal method to prepare patterned electrochromic films and devices. In this study, a UV-curable liquid gel electrolyte based on the PEGDA and PMMA which provides the rovide cross-linked skeleton is developed as a straightforward solution to these challenges. The resulting solid electrolyte exhibits high transparency (over 90 %), a wide electrochemical window (−2 to 2 V), a high ionic conductivity (approximately 3.2 × 10⁻⁴ S cm⁻¹) and exceptional stretchability with deformation extent exceeding 175 %. Besides, ECDs are successfully fabricated with excellent cycle stability (over 35,000 cycles) even in the absence of an ion storage layer. Surprising is that the patterning of electrolyte could pattern the cling electrochromic polymer film at the same time during the photocuring process. Furthermore, the cured electrolyte films which was flexible enough are also allowed for cutting, machining, rearrangement and combination with patterned EC films, showcasing its potential for efficient, low-cost production of high-quality patterned ECDs. In general, the unique electrolyte not only acts as an important part of the electrolyte layer in the ECDs, but also realizes the patterned display. This breakthrough not only paves the way for the wide application of polymer electrochromic products, but also provides ideas for the design of electrochemical energy storage devices in the future.