Dynamically Cross-Linked Hydrogel Electrolyte with Remarkable Stretchability and Self-Healing Capability for Flexible Electrochromic Devices

It is desired to develop self-healing gel electrolytes for flexible electrochromic devices (ECDs) due to the demand of healing damages caused during operations. We here report a hydrogel electrolyte with remarkable self-healing capability, excellent stretchability, and ionic conductivity. The hydrogel electrolyte was synthesized via one-step copolymerization of glycerol monomethacrylate (GMA) and acrylamide (AAm) in the presence of borate. Within the hydrogel electrolyte, dynamic cross-linking is expected to be formed due to the borate-didiol complexation and hydrogen-bonding interactions. As a result, the hydrogel electrolyte demonstrates an excellent self-healing efficiency of up to 97%, a fracture strain of 1155%, a fracture toughness of 136.6 kJ m^-3, and a fracture stress of 13.0 kPa. Additionally, a flexible ECD based on the hydrogel electrolyte and an electrochromic layer of poly(3,4-(2,2-dimethyl-propylenedioxy)thiophene) (PProDOT-Me₂) was assembled and evaluated. The device is found to be stable in both mechanical and optical properties over 1000 operation cycles. This study may provide a promising way for self-healing electrolyte gels to be utilized in a variety of flexible electrochemical devices, including ECDs, supercapacitors, and batteries.