Preparation of MoS2/WS2 nanosheets by liquid phase exfoliation with assistance of epigallocatechin gallate and study as an additive for high-performance lithium-sulfur batteries

The two-dimensional transition metal dichalcogenides have wide application value in many fields. Herein, MoS2 and WS2 nanosheets are produced by liquid phase exfoliation method assisted by epigallocatechin gallate. The effects of epigallocatechin gallate concentration and stripping time are investigated by UV-vis. The morphology and structure characterization of exfoliated nanosheets are studied by XRD, Raman, SEM, HRTEM and AFM, the results showing that the nanosheets have few layers and the exfoliated solution is homogeneous dispersion and stable. The exfoliated nanosheets produced by 2 mg ml(-1) epigallocatechin gallate solution for 12 h have five monolayers approximately, presenting a phase transformation from 2H to 1T structure of MoS2 nanosheets. Then, Graphene aerogel composites are prepared with the exfoliated MoS2/WS2 nanosheets, which loaded sulfur and employed as the cathode of Li-S batteries. TEM results reveal that MoS2/WS2 nanosheets are embedded in reduced graphene oxide, and sulfur is evenly distributed in the composites. The composites containing MoS2/WS2 nanosheets achieve outstanding electrochemical performance, during to the polysulfide adsorption capability of MoS2/WS2 nanosheets and reducing the shuttle effect in Li-S batteries. It demonstrates a good application of exfoliated MoS2/WS2 nanosheets in Li-S batteries. (C) 2019 Elsevier Inc. All rights reserved.