Hydrogel, the Next-Generation Electrolyte for Electrochromic Devices

Electrolytes have become a research frontier in the electrochromic community owing to their widespread applications in advanced electronic devices especially in electrochromic devices (ECDs). However, traditional ECDs with liquid electrolytes commonly suffer from inflexibility, complicated configurations, and poor electrochromic properties. To achieve solid- or flexible-state ECDs, an alternative method is to employ polymer electrolyte gels, which integrate the virtues of both liquid- and solid-state electrolytes. In this review, first, the device configurations of conventional ECDs are introduced, where the classification of electrolytes for ECDs is comprehensively introduced. Then the current situation and applications of hydrogels for ECDs, where it is expected to reveal the developing trends of hydrogel-based ECDs are specially reviewed. Finally, the insights on the design methods of hydrogel electrolytes for flexible and efficient ECDs are proposed. Electrolytes play an important role in transporting metal ions and even determining the performance of electrodes and electrochromic devices. Hydrogel electrolytes integrate the advantages of liquid- and solid-state electrolytes showing good performance in transparency, conductivities, flexibility, and interfacial stabilities, and have wide applications in electrochromic wearable devices, electrochromic smart windows, electrochromic displays, and electrochromic batteries.image (c) 2023 WILEY-VCH GmbH