Conversion of Lignin Precursors to Carbon Fibers with Nanoscale Graphitic Domains

Lignin is one of the most abundant and inexpensive natural biopolymers. It can be efficiently converted to low cost carbon fiber, monolithic structures, or powders that could be used directly in the production of anodes for lithium-ion batteries. In this work, we report thermomechanical processing methods relevant for the conversion of lignin precursors into carbon fiber-based anode materials, the impact of lignin precursor modification on melt processing, and the microstructure of the final carbon material. Modification of softwood lignin produced functionalities and rheological properties that more closely resemble hardwood lignin thereby enabling the melt processing of softwood lignin in oxidative atmospheres (air). The conversion process encompasses melt spinning of the lignin precursor, oxidative stabilization, and a low temperature carbonization step in a nitrogen/hydrogen atmosphere. We determined resistivities of individual carbon fiber samples and characterized the microstructure by scanning electron microscopy. Neutron diffraction reveals nanoscale graphitic domains embedded in an amorphous carbon matrix. These unique structural characteristics make biomass-derived carbon fibers a suitable material for energy storage applications with enhanced electrochemical performance.