Constructing CoS Nanosheets Coating N-Doped Carbon Nanofibers as Freestanding Sulfur Host for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have shown great potential as a rival for next generation batteries, for its relatively high theoretical capacity and eco-friendly properties. Nevertheless, blocked by the shuttle effect of lithium polysulfides (LPSs, LiS-LiS) and insulation of sulfur, LSBs show rapid capacity loss and cannot achieve the practical application. Herein, a composite of carbon nanofibers coated by CoS nanosheets (denoted as CNF@CoS) is successfully synthesized as freestanding sulfur host to optimize the interaction with sulfur species. The combination of the two materials can lead extraordinary cycling and rate performance by alleviating the shuttle of LPSs effectively. N-doped carbon nanofibers serve as long-range conductive networks and CoS nanosheets can accelerate the conversion of LPSs through its electrocatalytic and chemical adsorption ability. Benefiting from the unique structure, the transporting rate of Li can be enhanced. Distribution of Li is uniform for enough exposed negative active sites. As a result, the cell with CNF@CoS as sulfur host is able to stabilize at 710 mA h g at 1 C after 200 cycles with average coulombic efficiency of 97.8% in a sulfur loading of 1.7 mg cm and deliver 4.1 mA h cm at 0.1 C even in 6.8 mg cm for 100 cycles.