Three-Dimensional Porous Nitrogen-Doped Carbon Nanosheet with Embedded NixCo3-xS4 Nanocrystals for Advanced Lithium-Sulfur Batteries.

The shuttle effect of lithium polysulfides (Li2Sn) in electrolyte and the low conductivity of sulfur are the two key hindrances of lithium sulfur (Li-S) batteries. In order to address the two issues, we propose a three-dimensional porous nitrogen-doped carbon nanosheet with embedded NixCo3-xS4 nanocrystals derived from metal-organic frameworks for the durable-cathode host material in Li-S batteries. Experiments and density functional theory simulations show that the large porosity, robust N-doped carbon framework, and evenly embedded NixCo3-xS4 nanocrystals with high polarity act as strong "traps" for the immobilization of Li2Sn, which leads to an effective suppressing of the shuttle effect and promotes efficient utilization of sulfur. The NixCo3-xS4/N-doped carbon hybrid material exhibits a high reversible capacity of 1122 mAh g-1 at a current density of 0.5 C after 100 cycles. Even at high areal sulfur loadings of 10 and 12 mg cm-2, the hybrid cathode materials can maintain good areal capacities of 7.2 and 7.6 mAh cm-2 after 100 cycles. The present study sheds light on the principles of the anchoring behaviors of Li2Sn species on bimetallic sulfide hybrid materials and reveals an attractive route to design the highly desirable cathode materials for Li-S batteries.