Enhanced sodium storage in strongly-combined MoS2/rGO nanocomposite: Constructed by ionic liquid induced layer-by-layer self-assembly

Abstract

Molybdenum disulfide (MoS2) is a promising anode material for sodium ion battery. Nevertheless, the semi-conductive feature and closely stacked nanostructure hinder its application. Moreover, the uncontrolled geometric structure and loose combination with high-conductive matrix lead to a limited Na+ diffusion path and easy-destroyed structure. Here, a strongly-combined MoS2/rGO nanosheet structure is realized by ionic liquid induced layer-by-layer self-assembly approach. The ionic liquid works well as bi-functional assisted solvent to induce the uniform growth of MoS2 on rGO layers and to maintain the large-scale morphology of rGO nanosheet. The enlarged interlayer distance between S–Mo–S adjacent planes facilitates the fast Na+ transport. The well-maintained rGO layer affords favorable tolerance to the volume change of MoS2 and increases the conductivity as well. Density function theory calculations demonstrate that the enlarged interlayer reduces the diffusion energy barriers of Na+ and accelerates the reaction kinetics. Benefitting from the strong bonding between few-layered MoS2 nanoflake and well-maintained 2D rGO nanosheet, the MoS2/rGO composite exhibits a high specific capacity (581.7 mA h g−1 after 100 cycles at 100 mA g−1), remarkable rate capability (309.2 mA h g−1 at 12.8 A g−1) and excellent cycling stability (263.2 mA h g−1 after 300 cycles at 3 A g−1).