Ultra‐Compact MXene/Alginate/PVA Composite Fibers by Intercalation and Chelation for Enhanced Flame Retardancy and Energy Harvesting

MXene fibers with electro-conductivity and electrochemical properties have drawn growing research interest for its promising applications in wearable electronics, flexible electrodes, and smart textiles. However, producing MXene fibers with high strength keeps challenging because loose MXene sheets are hard to compact tightly due to electrostatic repulsion. Herein, ultra-compact MXene-based fibers are produced by intercalating alginate and polyvinyl alcohol (PVA) layers into MXene nanosheets and chelating via metal ions (i.e., Ca²⁺). The hydrogen and ionic bond are beneficial to compact MXene nanosheets and decrease the interplanar spacing, which improves the tensile strength. These result in MXene-based fibers with low porosity (0.2 vol%) and a high orientation factor of 0.877 exhibiting high electrical conductivity (1006 S cm^‒1). In addition, flame retardancy is enhanced without smoldering owing to the synergistic effect of MXene and metal ions. Moreover, these compact MXene-based fibers with electromagnetic interference shielding, mechanical stability, acid, and alkali-resistant properties, and photo-thermal effect can be achieved for scale production. This strategy paves the way for the continuous production of compact functional fibers, applicable in flame retardant fabric, wireless communication, energy harvesting, and wearable flexible textiles.