Low-temperature graphitization of lignin via Co-assisted electrolysis in molten salt

Abstract

The ever-growing energy demand and environmental issues have stimulated the development of sustainable energy technologies. Herein, an efficient and environmentally friendly electrochemical transformation technology was proposed to prepare highly graphitized carbon materials from an abundant natural resource - lignin (LG). The preparation process mainly includes pyrolytic carbonization of raw LG material and electrochemical conversion of amorphous carbon precursor. Interestingly, with the assistance of Co catalyst, the graphitization degree of the products was significantly improved, in which the mechanism was the removal of heteroatoms in LG and the rearrangement of carbon atoms into graphite lattice. Furthermore, tunable microstructures (nanoflakes) under catalytic effects could also be observed by controlling the electrolytic parameters. Compared with the products CN1 (without catalyst) and CN5 (with 10% catalyst), the specific surface area are 158.957 and 202.246 m2 g−1, respectively. When used as the electrode material for lithium-ion batteries, CN5 delivered a competitive specific capacity of ∼350 mAh g−1 (0.5 C) compared with commercial graphite. The strategy proposed in this work provides an effective way to extract value-added graphite materials from lignin and can be extended to the graphitization conversion of any other amorphous carbon precursor materials.