Lignin Functionalized with Catechol for Large-Scale Organic Electrodes in Bio-Based Batteries

Abstract

Lignin, obtained as a waste product in huge quantities from the large-scale cellulose processing industries, holds a great potential to be used as sustainable electrode material for large-scale electroactive energy storage systems. The fixed number of redox-active phenolic groups present within the lignin structure limits the electrochemical performance and the total energy storage capacity of the lignin-based electrodes. Herein, the way to enhance the charge storage capacity of lignin by incorporating additional small catechol molecules into the lignin structure is demonstrated. The catechol derivatives are covalently attached to the lignin via aromatic electrophilic substitution reaction. The increased phenolic groups in all functionalized lignin derivatives notably increase the values of capacitance compared to pristine lignin. Further, solvent fractionation of lignin followed by functionalization using catechol boosts three times the charge capacity of lignin electrode.