Hierarchical Porous Nitrogen-Doped Carbon Fiber Derived from Polyacrylonitrile for Advanced Lithium Sulfur Batteries

Abstract

A hierarchical porous nitrogen-doped carbon fiber (HPNCF) was synthesized while considering the advantages of its physical structure and chemical adsorption. The hierarchical porous structure of the HPNCF consists of both micro- and mesopores. The micropores can effectively confine and inhibit the dissolution of polysulfides, whereas the mesopores can effectively accommodate sulfur and provide sufficient space for volume expansion that occurs during the lithiation process. Nitrogen-doped carbon matrix not only can improve the wettability and accessibility of the electrolyte, but also strengthen the chemical interaction between polysulfides and carbon. In this study, a synthesized carbon matrix (HPNCF) was loaded with a high sulfur content (73%) and delivered a high initial discharge capacity of 1630 mAh g(-1) at 0.2 C with a retention capacity of 1325 mAh g(-1) after 50 cycles. Even at a high C-rate of 1 C, the capacity retention of 840 mAh g(-1) after 50 cycles was achieved. The outstanding electrochemical performance of HPNCF/S composite was attributed to the efficient utilization of elemental sulfur and the confinement of polysulfides by the hierarchical porous structure as well as chemical adsorption by nitrogen doping. Therefore, HPNCF/S composite is expected to be a superior cathode material used to improve the electrochemical performance of lithium sulfur batteries.