Polysulfide-derived anion heterogeneous interfaces engineering to facilitate high-efficiency sodium ion storage

Abstract

Poor structural stability and inherent low conductivity of the transition metal polysulfides often trigger continuous capacity decay. Here, an anionic heterogeneous modification engineering of the VS4 system is achieved by employing one-step strategy. The prepared layered V1.11S2/V1.13Se2/C heterostructure (VSSe/C) exhibits expanded layer distance (5.926 Å) and improved metallicity properties. Furthermore, the constructed built-in electric field achieves lower free energy and effective adsorption of reaction products. Resultantly, when applied to the sodium-ion battery anode, a high specific capacity of 784.9 mA h g−1 is achieved with 500 cycles at a current density of 2 A g−1. Impressively, a high capacity retention of 553.2 mA h g−1 is performed after 1000 cycles at 10 A g−1, which is significantly better than the unmodified VS4 electrode. Additionally, the assembled sodium ion capacitor exhibits excellent energy densities of 89.1 W h kg−1 at 380 W kg−1 and an ultra-high capacity retention rate of 96.6% over 2000 cycles at a high power density of 3800 W kg−1. Ex-situ XRD and XPS results reveal a stable disulfide/selenide conversion process, and no intermediate polysulfide formation. The design of anionic heterostructures using polysulfide derivatives may provide a reference for improving the structural properties of anion-rich based anode materials.