Sulfur-Enriched Pitch-Based Carbon Nanofibers With Lotus Root-Like Axial Pores for Boosting Sodium Storage Performance

Pitch is a promising precursor for preparing carbon materials for anode of sodium-ion batteries. Heteroatom doping is an effective way to increase the sodium storage capacity while constructing reasonable pores and nanosizing the carbon skeleton help to achieve a high-rate performance of anodes. In this work, sulfur-doped carbon nanofibers with lotus root-like axial pores were prepared using coal liquefaction pitch as the main precursor by electrospinning, pre-oxidation, sulfurization, and carbonization. A considerable content of 7.41 wt.% of sulfur was doped into the carbon skeleton after low-temperature gas-phase sulfurization and subsequent carbonization. The as-prepared sulfur-doped porous carbon nanofiber films, used as self-supporting electrodes of sodium-ion batteries, display high specific capacity (528.5 mAh g⁻¹ at 25 mA g⁻¹), high-rate performance (209.3 mAh g⁻¹ at 500 mA g⁻¹) and exceptional cycling stability (96.97% of retention at 500 mA g⁻¹ over 1000 cycles). With desirable flexibility and excellent sodium storage performance, the achieved sulfur-doped porous carbon nanofibers hold great promise for potential applications as self-supporting anodes of sodium-ion batteries.