MOF-Derived MoC/WC Heterostructure as Bidirectional Catalyst for Lithium Polysulfide Enables High-Performance Lithium-Sulfur Batteries.

Since lithium-sulfur (Li-S) batteries have high energy density and environmental friendliness, they have garnered a lot of attention as a new type of energy storage technology. However, the shuttle effect of lithium polysulfides (LiPSs) and low utilization of sulfur (S) in Li-S batteries reduce the cycle stability and energy efficiency and limit their practical application. Therefore, it is urgent to achieve simultaneous immobilization and conversion of LiPSs utilizing catalysts. Herein, a metal-organic framework (MOF)-derived MoC/WC@NC heterojunction is synthesized as a bidirectional catalyst for LiPSs in high-performance Li-S batteries. Experimental and theoretical calculations indicate that the catalyst is expected to improve the catalytic activity for reduction and oxidation reactions of LiPSs, thereby accelerating the kinetics of Li-S batteries. In conclusion, with the incorporation of the novel catalyst between the cathodes and separators in Li-S batteries, the assembled batteries demonstrate excellent rate performance, with an initial discharge capacity of 1752.1 mAh g at 0.1 C, and a discharge-specific capacity of 783.2 mAh g even at 2 C. More significantly, the coulombic efficiency stayed above 99% and the capacity of 589.1 mAh g after 1000 cycles at 1 C with a decay rate of only 0.062% each cycle.