Sandwich-like SnS/Graphene/SnS with Expanded Interlayer Distance as High-Rate Lithium/Sodium-Ion Battery Anode Materials.

SnS materials have attracted broad attention in the field of electrochemical energy storage due to their layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling leads to electrode structure instability and a severe capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS/graphene/SnS (SnS/rGO/SnS) composite with ultrathin SnS nanosheets covalently decorated on both sides of reduced graphene oxide sheets C-S bonds. Owing to the graphene sandwiched between two SnS sheets, the composite presents an enlarged interlayer spacing of ∼8.03 Å for SnS, which could facilitate the insertion/extraction of Li/Na ions with rapid transport kinetics as well as inhibit the restacking of SnS nanosheets during the charge/discharge cycling. The density functional theory calculation reveals the most stable state of the moderate interlayer spacing for the sandwich-like composite. The diffusion coefficients of Li/Na ions from both molecular simulation and experimental observation also demonstrate that this state is the most suitable for fast ion transport. In addition, numerous ultratiny SnS nanoparticles anchored on the graphene sheets can generate dominant pseudocapacitive contribution to the composite especially at large current density, guaranteeing its excellent high-rate performance with 844 and 765 mAh g for Li/Na-ion batteries even at 10 A g. No distinct morphology changes occur after 200 cycles, and the SnS nanoparticles still recover to a pristine phase without distinct agglomeration, demonstrating that this composite with high-rate capabilities and excellent cycle stability are promising candidates for lithium/sodium storage.