Ru Single Atom Dispersed on MoS 2 /MXene for Enhanced Sulfur Reduction Reaction in Lithium-Sulfur Batteries.

The high theoretical energy density (2600 Wh kg -1 ) and low cost of lithium-sulfur batteries (LSBs) make them an ideal alternative for the next-generation energy storage system. Nevertheless, severe capacity degradation and low sulfur utilization resulting from shuttle effect hinder their commercialization. Herein, Single-atom Ru-doped 1T/2H MoS 2 with enriched defects decorates V 2 C MXene (Ru-MoS 2 /MXene) produced by a new phase-engineering strategy employed as sulfur host to promote polysulfide adsorption and conversion reaction kinetics. The Ru single atom-doped adjusts the chemical environment of the MoS 2 /MXene to anchor polysulfide and acts as an efficient center to motivate the redox reaction. In addition, the rich defects of the MoS 2 and ternary boundary among 1T/2H MoS 2 and V 2 C accelerate the charge transfer and ion movements for the reaction. As expected, the Ru-MoS 2 /MXene/S cathode-based cell exhibits a high-rate capability of 684.3 mAh g -1 at 6 C. After 1000 cycles, the Ru-MoS 2 /MXene/S cell maintains an excellent cycling stability of 696 mAh g -1 at 2 C with a capacity degradation as low as 0.02% per cycle. Despite a high sulfur loading of 9.5 mg cm -2 and a lean electrolyte-to-sulfur ratio of 4.3, the cell achieves a high discharge capacity of 726 mAh g -1 .