Sandwich-like SnS2/Graphene/SnS2 with Expanded Interlayer Distance as High-Rate Lithium/Sodium-Ion Battery Anode Materials

Abstract

SnS 2 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 2 /graphene/SnS 2 (SnS 2 /rGO/SnS 2 ) composite with ultrathin SnS 2 nanosheets covalently decorated on both sides of reduced graphene oxide sheets via C–S bonds. Owing to the graphene sandwiched between two SnS 2 sheets, the composite presents an enlarged interlayer spacing of ∼8.03 Å for SnS 2, which could facilitate the insertion/extraction of Li + /Na + ions with rapid transport kinetics as well as inhibit the restacking of SnS 2 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 2 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 –1 for Li/Na-ion batteries even at 10 A g –1 . No distinct morphology changes occur after 200 cycles, and the SnS 2 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.