A superior sodium-ion anode material from PAN/Lignin-derived carbon nanofibers with inter-connected structure prepared through phosphoric acid induced cross-linking

A feasible route to fabricate phosphorus-doped carbon nanofibers (P-CNFs) with an inter-connected structure has been demonstrated through electrospinning, stabilization, and subsequent phosphoric acid impregnation and carbonization processes using polyacrylonitrile and lignin as carbon sources. The results illustrate that the phosphoric acid induced cross-linking could be beneficial to acquire the closed-pore structure and the heteroatom-doped surface chemistry of nanofibers. As a result, the P-CNFs exhibit higher interlayer spacing of graphite and lower BET specific surface area compared to the pristine CNFs. The P-CNFs as an anode material for sodium-ion batteries (SIBs) present a high reversible capacity 278 mA h g−1 at 0.2 A g−1 and a superior initial Coulomb efficiency (ICE) of 78.86 %. Moreover, the reversible capacity of P-CNFs can be stably maintained near the initial capacity after 5000 cycles at 1 A g−1, showing exceptional structural stability and cycling durability. Meanwhile, the sodium storage mechanism of P-CNFs was investigated using in-situ Raman and ex-situ XRD analysis to understand the exceptional structural stability and Na+ adsorption capacity of P-CNFs. This work provides valuable insights for the design of carbon nanofibers with an inter-connected structure as anode materials for SIBs, exhibiting outstanding electrochemical properties.