In-situ-selective-UV crosslinking fabrication of solid liquid host guest electrolyte: A facile one-step method realizing highly flexible electrochromic device

Flexible electrochromic devices (FECDs) are promising candidates for the next generation of wearable electronics due to their low operating voltage and energy consumption. For the flexible electrochromic devices, the electrolyte is an important component. Typically, the electrolyte needs to be formulated according to the device structure and usage scenario. A high-performance electrolyte involves consideration of many factors, including choosing the right polymer, solvent, curing agent, and ion type to satisfy particular device specifications. In this work, a ultraviolet-curable solid–liquid host–guest (UV-SLHG) electrolyte is developed. Several aspects of performance are improved by introducing the solid–liquid coexisting microstructure without changing the electrolyte formulation, including excellent adhesion, a 30% increase in tensile characteristics, and a seven-fold increase in ionic conductivity when compared to a fully cured solid-state electrolyte. More importantly, the unique advantage of SLHG electrolytes lies that the thickness will not change significantly during bending. The FECD made by using the UV-SLHG-based electrolyte sustained 10,000 bending cycles at the bending radius of 2.5 mm while maintaining outstanding optical modulation. A wearable ring-type ECD and a battery-free FECD wine label were made as demonstrators. The UV-SLHG strategy is not only suitable for the FECDs but also universally applicable to other electrolyte-based of flexible electronics such as flexible capacitors and batteries.