Nitrogen-rich hierarchical porous carbon paper for a free-standing cathode of lithium sulfur battery

Abstract

A free-standing cathode without any binder, conductor, and current collector is attractive due to its reduced weight and cost. This study introduces nitrogen-rich and hierarchical porous carbon fibers in the form of a free-standing carbon paper synthesized by NaBH4-aided electrospinning and subsequent CO2 annealing. This modified process leads to a large mesopore volume of 1.007 cm(3) g(-1) and exposes the nitrogen inside the polymer to the surface of the fiber, resulting in the outstanding surface nitrogen content of 19.38 wt% with abundant pyridinic-N and pyrrolic-N of 16.24 wt% in total surface atoms, while eliminating any further treatment for increasing porosity or coating the polar active sites. The resultant material impregnated by sulfur and filtered by a graphene solution is directly employed as a cathode without any additives. As a result, the capacity is maintained at 696 mAh g(-1) up to the 500th cycle at 0.2 C, and 645 mAh g(-1) at a high current density of 5.0 C. Even with a high sulfur loading of 6.11 mg cm(-2), a remarkable areal capacity of 3.09 mAh cm(-2) is recorded after 500 cycles at 0.2 C with the free-standing form preserved.