One-pot UV-polymerized cellulose-reinforced eutectogel electrolytes for flexible supercapacitors

A green one-pot strategy is reported to fabricate cellulose-reinforced eutectogel (C-Eutectogel) electrolytes via UV polymerization of acrylamide (AM) in a ZnCl₂-formic acid-H₂O ternary deep eutectic solvent (T-DES), which simultaneously dissolves microcrystalline cellulose (MCC) and serves as the ionic conductive medium. Without high-temperature pretreatment, the T-DES disrupts MCC crystallinity via hydrogen-bond reconstruction and in-situ esterification, enabling uniform dispersion. Upon UV-triggered acrylamide polymerization, a semi-interpenetrating network forms, with cellulose chains as physical crosslinkers and DES as ion-transport highways. At 6 wt% MCC, the eutectogel achieves 26.3 mS cm^-1 ionic conductivity, ~320% elongation, a - 62 °C freezing point, self-healing, adhesion, and flame retardancy. Flexible electric double-layer capacitors using this electrolyte deliver a 1.6 V window, 27.99 F g^-1 at 0.2 A g^-1, 84.3% capacitance retention after 180° bending, and stable operation from -20 to 25 °C with 67.4% retention at -20 °C. Devices remain functional under physical damage. This work offers an energy-efficient route for high-performance eutectogel electrolytes and integrates cellulose into flexible energy storage.