Decoration of defective graphene with MoS2 enabling enhanced anchoring and catalytic conversion of polysulfides for lithium–sulfur batteries: a first-principles study

The potential of carbon materials for electrochemical processes could be largely activated by the delicate regulation of their intrinsic defects, and this prospect could be further enhanced after hybridizing with other functional components. Herein, we, for the first time, systematically combine graphene possessing different intrinsic defects with MoS2 as a host material for sulfur in lithium–sulfur batteries using first-principles calculations. After introducing the intrinsic defects in graphene, the heterostructures provide moderate binding affinity to lithium polysulfides (LiPSs) and facilitate their chemical reactions due to the unsaturated coordination of defective carbon and the charge rearrangement inside the heterostructures. Specifically, graphene with intrinsic defects increases the active sites and improves the conductivity, while MoS2 can not only improve the adsorption for LiPSs, but also provide smooth Li diffusion pathways and catalyze the rapid conversion of LiPSs. Among all the calculated heterostructures, the single vacancy graphene/MoS2 heterostructure is considered to be the most promising sulfur host due to the strongest binding strength to LiPSs (3.10–0.72 eV) and the lowest free energy barrier for the sulfur reduction reaction (1.36 eV), which is attributed to the spin polarization near the carbon defect. This work could afford fruitful insights into the rational design of defect engineering in heterostructures.