Vertically grown MoS₂ nanosheets on graphene with defect-rich structure for efficient sodium storage

The synthesis of a perpendicular growth structure of MoS₂ nanosheets on graphene for efficient sodium storage is challenging yet ideal due to the benefits of open ion diffusion channels and high electronic conductivity. In this study, we have successfully fabricated a novel structure of vertical MoS₂ nanosheets on graphene, with ZnS nanoparticles serving as bonding points (MoS₂/ZnS/G), through a facile hydrothermal method. During the synthesis process, Zn²⁺ not only acts as a landing site for the vertical growth of MoS₂ nanosheets but also triggers the formation of a defect-rich structure in the final samples. This unique architecture of MoS₂/ZnS/G effectively combines the advantages of a vertically aligned geometry and a defect-rich structure for energy storage. The resulting structure displays shortened transport paths for electrons/ions, enhanced conductivity, improved structural integrity, and an increased number of active sites for promising electrochemical performance. As expected, when used as anode for sodium-ion batteries, the as-synthesized MoS₂/ZnS/G exhibits excellent rate capability (high capacity of 298 mAh·g⁻¹ at 5 A·g⁻¹) and good cycling stability (a capacity decay of 0.056% per cycle after 500 cycles at 1 A·g⁻¹). According to the kinetic investigations, the electrochemical process of the MoS₂/ZnS/G sample is primarily governed by a pseudocapacitive behavior, which enhances the charge/discharge kinetics and allows the MoS₂/ZnS/G structure to remain intact during cycling.