Multi-slice nanostructured WS2@rGO with enhanced Li-ion battery performance and a comprehensive mechanistic investigation

Abstract

A thin nanoslice structured WS₂@reduced graphene oxide (rGO) composite was successfully fabricated by a facile hydrothermal synthesis method. The layered structure and morphology of the composite were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The WS₂@rGO composite structure demonstrated significantly enhanced rate capability performance in comparison with pristine WS₂ when used as an anode material for lithium-ion batteries (LIBs). The composite demonstrated a capacity of 565 mA h g⁻¹ after 100 cycles when cycled at 0.1 A g⁻¹ and it could still deliver a stable capacity of about 337 mA h g⁻¹ at 2 A g⁻¹. Electrochemical impedance spectroscopy (EIS) measurement showed that the synergistic effect between WS₂ and rGO could remarkably reduce the contact resistance and improve the corresponding electrochemical performances. In order to analyze and interpret the corresponding results from a theoretically sound perspective, first principles calculations was further performed to investigate the corresponding inner mechanisms of pristine WS₂ and WS₂@graphene composite. The nudged elastic band (NEB) method was used to investigate the diffusion properties of Li in the different structures. Molecular dynamics (MD) simulation and Young's modulus calculation were further employed to explore the stability and mechanical properties of the two structures for the first time. These new perspectives pave the way for the design and fabrication of graphene–TMDs based composites as the next generation of LIB anode materials with high power density and cycling stability.