Synergistic regulation of pore structure in PAN-based carbon nanofibers with lignin and pitch for sodium-ion storage

Carbon nanofibers (CNFs) have attracted considerable attention due to their interconnected fibrous architecture and excellent electrical conductivity for sodium-ion batteries (SIBs) as anode materials. However, polyacrylonitrile (PAN)-based CNFs often exhibit limited sodium storage performance because of their insufficient pore structure. In this work, PAN was employed as a precursor, while low-cost lignin and pitch were introduced as synergistic modifiers to construct composite CNFs via electrospinning followed by pre-oxidation and carbonization. The influence of precursor composition on the structural evolution and sodium storage behavior of the CNFs was systematically investigated. During pyrolysis, lignin-rich oxygen-containing functional groups released gases to generate abundant open pores, whereas the melt rheology of pitch enhanced fiber adhesion, partially sealed open pores, and formed a compact three-dimensional network with closed pores. Benefiting from this synergistic structural regulation, the optimized PPL622-CNF exhibited a high reversible capacity of 238.9 mAh g −1 at 0.03 A g −1 with a significantly enhanced plateau capacity. Moreover, a capacity retention of 86.7% after 200 cycles at 0.2 A g −1 was achieved. This work demonstrated an effective strategy for tailoring the pore structure of PAN-based CNFs through lignin/pitch synergy, providing valuable insights for the development of low-cost, high-performance anode materials for SIBs.