A novel vanadium-mediated MoS2 with metallic behavior for sodium ion batteries: Achieving fast Na+ diffusion to enhance electrochemical kinetics

Molybdenum disulfide (MoS2), as a potential anode material for sodium ion batteries (SIBs), has attracted great attention due to its layer structure with high reversible capacity. However, its low electronic conductivity, sluggish electrochemical kinetics and volume expansion during charging/discharging process always lead to poor cycling stability as well as rate performance. In this study, vanadium was combined into the framework of MoS2 to form VMoS2 (VMS2) through a facile one-step hydrothermal method. Combined the experiment results with the density functional theory calculations, it is found that V mediating not only significantly increased the electronic conductivity due to metallic property but also decreased the energy barrier (0.069 eV) of sodium ion transportation when compared with that of the pure MoS2 (0.12 eV), resulting in excellent electrochemical performance with rapid electrochemical kinetics. Furthermore, the disordered structure with rich defects in the VMS2 could provide more active sites for Na+ storage. As a result, when it was used as the anode material of SIBs, a high specific capacity (548.1 mAh g(-1) at a current density of 100 mA g(-1)) with excellent cycling stability (451.6 mAh g(-1) retaining after 800 cycles at 2 A g(-1)) and superb rate performance (207.4 mAh g(-1) retained at 20 A g(-1)) was achieved.