Three-Dimensional Porous Nitrogen-Doped Carbon Nanosheet with Embedded NiCo_3-S₄ Nanocrystals for Advanced...

The shuttle effect of lithium polysulfides (Li₂S) 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 NiCo_3-S₄ 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 NiCo_3-S₄ nanocrystals with high polarity act as strong "traps" for the immobilization of Li₂S, which leads to an effective suppressing of the shuttle effect and promotes efficient utilization of sulfur. The NiCo_3-S₄/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 Li₂S species on bimetallic sulfide hybrid materials and reveals an attractive route to design the highly desirable cathode materials for Li-S batteries.