High Fire‐Safety and Multifunctional Eutectogel for Flexible Quasi‐Solid‐State Supercapacitors

Abstract The preparation of high‐performance and fire‐safe electrolytes for flexible quasi‐solid‐state supercapacitors is challenging. In this work, a novel fire‐safe and multifunctional deep eutectic solvent gel (DESG) is fabricated using acrylic acid and urea as hydrogen bond donors and choline chloride as a hydrogen bond acceptor. DESG shows a high ionic conductivity (0.552 S m −1 ), good electrochemical performance (specific capacitance: 106.8 F g −1 ), and a wide operating temperature range (−20–90 °C), being a promising candidate for flexible solid‐state supercapacitors. Furthermore, it exhibits a good thermoelectric conversion capability (Seebeck coefficient: 1.56 mV K −1 ), being ideal for thermoelectric capacitors and fire‐warning sensors. The prepared DESG rapidly self‐extinguishes after removal from fire, reaching a limiting oxygen index value of 38.0% and demonstrating its excellent flame retardancy. In addition, DESG has a good self‐healing performance (healing efficiency of 84.3%). The work provides new insights into the preparation and application of high fire‐safety and multifunctional eutectogels for flexible quasi‐solid‐state supercapacitors.