Enhanced sodium ion storage capability through integrated functionality within conductive PPy coated MoS2/SnS composite

Abstract

Metal sulfide anodes exhibit excellent electrochemical performance in sodium ion batteries, primarily attributed to their high theoretical capacity and the facilitated conversion reactions. Nevertheless, the severe change in volume throughout cycling directly leads to the degradation of their electrochemical performance. In this study, a heterogeneous structure of polypyrrole (PPy) encapsulated MoS₂/SnS is successfully synthesized via a solvothermal method, resulting in MoS₂/SnS@PPy composite. The highly conductive PPy encapsulation layer not only significantly enhances the charge transfer rate of the composite, effectively improving their electrochemical performance, but also effectively alleviates volume expansion/shrinkage, thus remarkably strengthening the structural durability and resilience. The electrochemical analysis results of MoS₂/SnS@PPy demonstrate that this composite exhibits excellent cyclic stability and outstanding rate performance. It delivers an initial specific capacity of 755.3 mA h g⁻¹ at a current density of 1 A g⁻¹, and retains a specific capacity of 535.7 mA h g⁻¹ after 250 cycles. Even at a high density of 10 A g⁻¹, its specific capacity remains at 247.5 mA h g⁻¹. The exceptional electrochemical performance can be credited to the combined and mutually reinforcing action of the two metal sulfides in the composite and the enhanced structural robustness and conductivity of the composite achieved through PPy coating.