Formation of 2D Amorphous Lithium Sulfide Enabled by Mo₂C Clusters Loaded Carbon Scaffold for High-Performance Lithium Sulfur Batteries.

Abstract

Lithium-sulfur (Li-S) batteries, operated through the interconversion between sulfur and solid-state lithium sulfide, are regarded as next-generation energy storage systems. However, the sluggish kinetics of lithium sulfide deposition/dissolution, caused by its insoluble and insulated nature, hampers the practical use of Li-S batteries. Herein, leaf-like carbon scaffold (LCS) with the modification of Mo₂C clusters (Mo₂C@LCS) is reported as host material of sulfur powder. During cycles, the dissociative Mo ions at the Mo₂C@LCS/electrolyte interface are detected to exhibit competitive binding energy with Li ions for lithium sulfide anions, which disrupts the deposition behavior of crystalline lithium sulfide and trends a shift in the configuration of lithium sulfide toward an amorphous structure. Combining the related electrochemical study and first-principle calculation, it is revealed that the formation of amorphous lithium sulfides shows significantly improved kinetics for lithium sulfide deposition and decomposition. As a result, the obtained Mo₂C@LCS/S cathode shows an ultralow capacity decay rate of 0.015% per cycle at a high mass loading of 9.5 mg cm^-2 after 700 cycles. More strikingly, an ultrahigh sulfur loading of 61.2 mg cm^-2 can also be achieved. This work defines an efficacious strategy to advance the commercialization of Mo₂C@LCS host for Li-S batteries.