VS4/MoS2 heterostructures grown along graphene to boost reaction kinetics and reversibility for high performance lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are regarded as one of the most promising next-generation energy storage systems due to their high theoretical volumetric and high weight energy density. However, there are severe problems in the application of lithium-sulfur batteries. The shuttle effect of soluble lithium polysulfide (LiPs) and the low conductivity of sulfur, which leads to slow redox kinetics, are hindering the more significant application of lithium-sulfur batteries. One of the viable solutions to the cathode problem of lithium-sulfur batteries is heterostructured materials. The built-in electric field provided by the heterostructure can significantly accelerate the kinetics of charge transport. In this work, we constructed a heterogeneous structure of G-VS4/MoS2 composites(PVM) modified by Polyvinylpyrrolidone(PVP) is constructed based on graphene, which consists of VS4 nanosheets and MoS2 nanosheets grown vertically on graphene lamellae. With weak van der Waals interactions, the one-dimensional (1D) chain-like VS4 crystal structure enables fast charge transfer in Li-ion batteries. The two-dimensional (2D) lamellar MoS2 crystals contain Mo-S bonds that also have adsorption effects on polysulfides. Density functional theory (DFT) calculations show that VS4 and MoS2 can increase the binding energy of the anode to the polysulfide. Therefore, the S@PVM cathode material provides a large capacity of 1061.4 mAh/g at 0.5 C and can still get to 808.3 mAh/g after 400th cycles. A capacity retention rate of 76.15% is obtained at the same time. It can also boast an initial discharge capacity of 834.8 mAh/g at 1 C. These works can provide more thoughts for developing cathode materials for lithium-sulfur batteries.