Highly Strong and Conductive Carbon Fibers Originated from Bioinspired Lignin/Nanocellulose Precursors Obtained by Flow-Assisted Alignment and In Situ Interfacial Complexation

Composite filaments comprised of lignin and cellulose nanofibers (CNFs) were fabricated by a microfluidic spinning technique together with in situ interfacial complexation. The hierarchical assembly of well-ordered lignin/CNFs cross-linked using chitosan by ionic bonds resulted in the high orientation degree and compact microstructure of the filament, which was a promising precursor of carbon fibers. After stabilization and carbonization, bio-based carbon fibers with fine graphite microcrystals were obtained and carbon lattice was highly oriented along the fiber direction, contributing to the superior macro-performance. When the content of lignin was 75 wt %, the tensile strength and electrical conductivity of the carbon fibers reached 1648 MPa and 185.3 S/cm, respectively, surpassing the most reported values in the literature. Furthermore, a combined TG-FTIR approach was applied to further analyze the carbonization process of lignin/CNF precursors. The excellent mechanical and electrical performance of the bio-based carbon fibers would broaden their applications as a reinforcing agent and an electrical device. The demonstrated spinning technology also offered an avenue for the fabrication of high-performance filaments and carbon fibers.