Lignin-induced eutectogel electrolytes enabling wide-temperature tolerance and high energy density zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors (ZHS) have demonstrated tremendous potential in the field of energy storage for wearable electronics, as they combine the higher energy density of zinc-ion batteries with the superior power density of supercapacitors. However, conventional solid electrolytes with low conductivity, extreme environments intolerance, safety risks, and a time- and energy-consuming preparation process, which hinders the applications of ZHS. Herein, a self-catalytic system (SLS[sbnd]Fe³⁺) basing on sulfonated lignin (SLS) was used to rapidly (∼60 s) fabricate polyacrylamide-SLS hydrogels (PLH). Zinc perchlorate (Zn(ClO₄)₂) was used as hydrogen bond acceptor, ethylene glycol (EG) as hydrogen bond donor, and water as diluent to lower viscosity to create a metal salt-based ternary hydrated eutectic solvent (DES). PLH were immersed in the DES to obtain eutectogels. The prepared eutectogels displayed enhancing properties of mechanical strength (∼2160 % elongation), ionic conductivity (45.3 mS cm⁻¹), antifreeze/non-drying and flame-retardant (a LOI value of 47.3). The ZHS assembled with the eutectogel electrolyte exhibited a high energy density of 216.94 Wh kg⁻¹ at a high-power density of 712 W kg⁻¹. Meanwhile, the ZHS had long cycle stability at −20 °C, with 70 % capacity retention after 10,000 long cycles. This study provides an effective strategy for the preparation of full-performance eutectogel electrolytes.