Study on the Mechanism of Using DES Containing Lignin as the Gel Electrolyte for Supercapacitors

In this study, a high-strength organogel was successfully prepared using a ternary deep eutectic solvent containing choline chloride, glycerol, and aluminum chloride after the pretreatment of lignocellulose (pine wood). This organogel is based on poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA). When assembled into a capacitor, the gel electrolyte exhibited an excellent electrochemical performance. This strategy provides a novel recycling method for the high-value utilization of lignin-rich pretreatment waste liquids. The DES-based gel containing lignin forms cross-links between the deep eutectic solvent (DES) and the polymer using lignin as an anchor point through redox reactions, significantly enhancing the mechanical properties of the organogel. The maximum breaking strength reached 0.67 MPa. The highest compressive strength was 1.45 MPa, and the highest compressive modulus was 10.85 MPa. The gel electrolyte was assembled in a supercapacitor, with an ionic conductivity as high as 63.43 mS cm–1. It exhibited a high specific capacitance of 212 F g–1 at a current density of 1 A g–1 and maintained a capacitance retention rate of 71.37% at −40 °C. This study integrates DES in biomass pretreatment and supercapacitor energy storage, enabling high-value use of waste liquid and sustainable resource development. The biomass waste-based method reduces dependence on nonrenewable resources, offering a new sustainable development perspective.