Lignin-Derived Carbon Electrodes and Biofilm Electrolytes for Sustainable and Flexible Supercapacitors: Fabrication, Efficiency, and Life Cycle Analysis

Developing sustainable, flexible, high-performance energy storage devices is crucial for next-generation wearable and flexible electronics. In this study, we report the successful fabrication of an all-lignin-derived flexible supercapacitor comprising activated carbon electrodes and a lignin-based biofilm electrolyte. Activated carbon was synthesized using sodium (Na) and magnesium (Mg) metals as templating agents within the lignosulfonate (LS) matrix, enhancing the physicochemical and electrochemical characteristics of the resulting porous carbon. Structural and textural characterization confirmed that Mg-LS-derived activated carbon exhibited superior structural properties, with a 1954 m2/g surface area and a 1.63 cm3/g pore volume. The Mg-LS-derived carbon electrodes were assembled with a lignin-based biofilm electrolyte, developed through the chemical cross-linking of poly(ethylene glycol) diglycidyl ether (PEGDGE) and lignin. The electrochemical performance of the assembled flexible supercapacitor was evaluated through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) analyses in both three-electrode and two-electrode configurations. The device exhibited a specific capacitance of 267.26 F/g at a current density of 0.5 A/g, achieving a high energy density of 18.56 Wh/kg with a corresponding power density of 125.12 W/kg. The cyclic stability showed a capacitance retention of 94.72% after 10000 cycles. Furthermore, the life cycle analysis demonstrated the economic and environmental sustainability of the lignin-based supercapacitor, confirming its potential as a viable and eco-friendly alternative for flexible energy storage applications. This research highlights lignin-derived materials as promising candidates for sustainable, flexible supercapacitor technologies suitable for advanced electronic devices.