Lithiothermic-Synchronous Construction of Mo-Li₂S-Graphene Nanocomposites for High-Energy Li₂S//Si-C Battery

Reducing the activation barrier and stabilizing the sulfur species of Li₂S cathodes can ultimately enhance cell efficiency and the cycle life of S-based Li-ion batteries (LIBs). Here, a unique synchronous synthesis method is established that can simultaneously construct Li₂S encapsulated in conductive protective layers, and accordingly propose a coordination effect of catalysis and domain restriction for Li₂S cathodes. Typically, based on the lithiothermic reaction of 8Li + MoS₂ + CS₂ = 4Li₂S + Mo + C, the obtained composite features abundant Mo nanocrystals embedded in crystalline Li₂S matrices and then wrapped by few-layer graphene. Notably, all three components derived from lithiothermic reaction are linked by the chemical bonding of Mo-S and C-S, forming a compact Mo-Li₂S-graphene triple heterostructure. Systematic studies reveal an unprecedented relevancy between charge overpotential and catalytic activation of Mo-Li₂S-graphene, whereas a low activation potential of 2.43 V is achieved. Further studies disclose the relationship between cycle stability and confinement effect of core-shell structure, whereas the improved confinement efficiency for polysulfides enables an excellent cycle life for the Li-S battery. Moreover, the Mo-Li₂S-graphene cathode demonstrates promising application for LIB, where the Mo-Li₂S-graphene//Si-C battery shows a high capacity of 764 mAh g⁻¹ and outstanding cycle stability.