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

Abstract

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.

An energy-saving, bending sensitive, and self-healing PVA-borax-IL ternary hydrogel electrolyte for visual flexible electrochromic strain sensors

“…It's markedly lower than the power consumption of a liquid-state ECD. 64 The above results indicate that the ECD with PVA-borax-IL 0.3 as the conductive electrolyte and AVCOOEt as the ECM has the advantages of low coloration voltage, large optical modulation, high coloration efficiency, rapid response, good cycling stability, and low energy consumption compared with previous reports that used PAAm, 24 PVA-borax, 21,55,65 or P(GMA 2 -AAm 8 )borate 23 as the conductive electrolytes (Table 1). Compared to the ECD with P(VDF-co-HFP)-IL as the conductive electrolyte and CN-PV 2+ as the ECM, 66 it has slightly higher coloration voltage and power consumption, but has a faster response and a higher CE.…”

“…60 Water decomposition voltage is an important parameter in the operating voltage window of HGEs. In general, the theoretical decomposition voltage of water is 1.23 V, 23 which will seriously restrict the development of HGEs in exible sensors, energy storage equipment and other elds. The operating voltage windows of PVA-borax and PVA-borax-IL 0.3 HGEs were investigated by linear scanning voltammetry.…”

“…[20][21][22] In addition, related studies have shown that gel electrolytes also promote the improvement of electrochromic properties. [23][24][25][26] Hydrogels in gel electrolytes promise brand new applications in exible electronic elds such as stretchable ECDs, 27 ionic skin, [28][29][30][31] so robotics, 32,33 personal healthcare monitoring, 34 drug delivery, 35 articial organs, 36 and wearable electronics [37][38][39] due to their inherent excellent exibility, high optical transparency, high ionic conductivity, and good biocompatibility. PVA hydrogels have been widely studied due to their nontoxicity, biocompatibility, degradability, water retention, and low cost.…”

Emerging Electrochromic Materials and Devices for Future Displays

“…Thus, related materials for ISL must maintain good electrochemical reversibility, stability, capacity, and compatibility with EC materials. − The ion transport layer (ITL) has the function of transferring ions inside the device. The candidates for related ion-transport materials include electrolytes (e.g., lithium salt, ammonium salt, and ionic liquid)-doped gels/solutions/films, − polymers with ionic conductivity − such as poly­(ionic liquid) and Nafion, (ionic) liquid crystals, , etc. The ECL, which is mainly composed of EC materials, is the core of an ECD; it undertakes the task of color change and optical modulation.…”

Self-Healing Polymers for Electronics and Energy Devices

“…Electrochromic devices reversibly alter their optical properties (i.e., transmittance, absorbance, or reflectance) and emission color as a result of the electric-field-stimulated redox switching in electrochromic materials. Electrochromic devices have been used in various fields, including smart windows, antidazzling mirrors, and information displays. − A typical electrochromic device usually features a multilayer structure, including an electrochromic layer containing redox active materials with tunable optical properties, an ion storage layer containing redox active materials for charge balance, an ion transport layer containing electrolytes for ion transmission and two conducting electrodes. , Electrochromic materials based on conducting polymers have unique advantages over their inorganic counterparts (e.g., WO 3 , NiO, and V 2 O 5 ) in terms of high coloration efficiency, fast response speed, high color tunability, and low redox switching potential.…”