Interlayer expanded SnS/N-doped carbon/SnS ultra-thin composite driven from layered tin chalcogenides as advanced anode for lithium and sodium ion battery

The unique 2D-layered structure of tin (II) sulfide (SnS) compounds has led to the emergence of strong intensities, showcasing their significant potential in lithium (LIBs) and sodium (SIBs) ion batteries. However, the commercialization process of SnS compounds remain hindered due to the poor cycle stability caused by its substantial volume expansion during cycling in battery applications. In this study, a simple and scalable synthesis of ultra-thin composite with a well-connected structure SnS/N-doped carbon/SnS (SnS/NC/SnS) is reported. The structure is directly derived from layered tin chalcogenides (A2Sn3S7·xH2O, where A represents an organic cation). Within this configuration, SnS nanosheets are decorated on the N-doped carbon material. The composite exhibits an expanded layer of 9.7 Å, enabling rapid movement of Na+ ions (approximately 7 times the diffusion coefficient of bulk SnS). This expansion also aids in accommodating volume changes during the discharging and charging processes. Concurrently, theoretical calculations demonstrate that the structure maintains a relatively stable state at the interlayer spacing mentioned. The SnS/NC/SnS composite material exhibited significant potential for application in both SIBs and LIBs. In SIBs, it demonstrated excellent long-term cyclic stability, maintaining a capacity of 190 mA h g−1 even under high current density conditions of 2.5 A g−1 after 300 cycles. In LIBs, it exhibit a superior discharge capacity of 990 mA h g−1 and retains 94.1 % of its capacity after 150 cycles at 0.2 A g−1. Notably, this synthesis method is versatile, as the interlayer spacing can be adjusted by varying the type of organic cations used in the process.