Sustainable Self-Healing Gel Polymer Electrolyte Based on Water-in-Deep Eutectic Solvent for Flexible Supercapacitors

In this study, a durable fire-resistant and self-healing dual-network gel polymer electrolyte (GPE) comprising poly(vinyl alcohol) (PVA), sodium alginate (SA), NaCl, and a water-in-deep eutectic solvent (DES) system was prepared using a one-step freezing-thawing technique for flexible supercapacitors (FSCs). Various GPEs were synthesized to investigate the influences of choline chloride (ChCl) and ethylene glycol (EG) molar ratios, the comprising components of the DES, and the impact of NaCl. The developed DES-based GPEs were formed through noncovalent interactions, offering several advantages, including the absence of chemical initiators and binders, environmental compatibility, and a simple preparation process. The dual-network GPEs exhibited extraordinary ionic conductivity, mechanical strength, stretchability, and self-healing properties as a result of the synergistic interaction between DES and NaCl and the creation of physically entangled networks. The optimized GPE, which showed an impressive ionic conductivity of 104.27 mS cm–1 at room temperature, was utilized in the fabrication of carbon-based FSC by sandwiching it between two same-size carbon cloth electrodes. The resulting device exhibited an energy density of 181.47 mWh cm–2 at a power density of 350 mW cm–2, and exceptional durability with a cycle life exceeding 10,000 cycles while providing approximately 93.32% capacitance retention throughout the testing period. Moreover, the prepared FSC maintained its electrochemical performance characteristics to an acceptable extent even under 90 and 180° bending deformation. Furthermore, the device prepared based on the self-healed GPE maintained 93.85 and 91.35% of its initial capacitance after the fifth and seventh cycles of cutting/healing, respectively, due to the remarkable self-repairing ability of the developed GPE. Our findings provide valuable insight into the development of flexible and leakproof GPEs for FSCs with potential applications in wearable electronic devices.