Hierarchical spheres constructed by ultrathin VS2 nanosheets for sodium-ion batteries

Abstract

In the present work, a one-step route was developed for synthesizing VS₂ microspheres in the absence of an additive, and they were assembled from ultrathin nanosheets. Such three-dimensional hierarchical VS₂ spheres could not only act as a reservoir for electrolyte diffusion but also provide sufficient void space for volume variation during the intercalation/de-intercalation process of Na⁺ ions. As a result, the material could exhibit a superior rate and long cycling stability. In detail, capacity of 565 mA h g⁻¹ was obtained after 1000 cycles at 2 A g⁻¹, making it a promising electrode material for electrochemical applications. Meanwhile, to further prove the excellent electrochemical performance, VS₂ nanosheets were also investigated by density-functional theory (DFT) calculations, indicating their metallic feature and large adsorption capacity for the intercalation of Na⁺ ions.