A Solvent-Free Synthesis of Lignin-Derived Renewable Carbon with Tunable Porosity for Supercapacitor Electrodes

Synthesis of multiphase materials from lignin, a biorefinery coproduct, offers limited success owing to the inherent difficulty in controlling dispersion of these renewable hyperbranched macromolecules in the product or its intermediates. Effective use of the chemically reactive functionalities in lignin, however, enables tuning morphologies of the materials. Here, we bind lignin oligomers with a rubbery macromolecule followed by thermal crosslinking to form a carbon precursor with phase contrasted morphology at submicron scale. The solvent-free mixing is conducted in a high-shear melt mixer. With this, the carbon precursor is further modified with potassium hydroxide for a single-step carbonization to yield activated carbon with tunable pore structure. A typical precursor with 90 % lignin yields porous carbon with 2120 m²  g^-1 surface area and supercapacitor with 215 F g^-1 capacitance. The results show a simple route towards manufacturing carbon-based energy-storage materials, eliminating the need for conventional template synthesis.