Phosphorus-Doped Hard Carbon Nanofibers Prepared by Electrospinning as an Anode in Sodium-Ion Batteries

Phosphorus-doped hard carbon nanofibers with macroporous structure were successfully synthesized by electrospinning followed by a thermal treatment process using polyacrylonitrile and H3PO4 as carbon and phosphorus precursors, respectively. X-ray photoelectron spectroscopy analysis reveals that the doped phosphorus atoms can incorporate into the carbon framework and most of them are connecting with carbon atoms to form P–C bond. The (002) plane interlayer spacing was taken from the X-ray diffraction pattern, which shows a large spacing of 3.83 Å for the obtained P-doped hard carbon nanofibers. When used as an anode in sodium-ion batteries, the as-prepared P-doped hard carbon nanofibers can deliver a reversible capacity of 288 and 103 mAh g–1 at a current density of 50 mA g–1 and 2 A g–1, respectively. After 200 cycles at 50 mA g–1, the capacity retention of P-doped hard carbon nanofibers still reaches 87.8%, demonstrating good cycling durability. These excellent electrochemical performances of P-doped hard carbon nanofibers can be attributed to the macroporous structure, large interlayer spacing, and the formation of P–C bond.