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

Abstract

SnS2 materials have attracted broad attention in the field of electrochemical energy storage due to its layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling would lead to electrode structure instability and serve capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS2/graphene/SnS2 (SnS2/rGO/SnS2) composite with ultrathin SnS2 nanosheets covalently decorated on both sides of reduced graphene oxide sheets via C‒S bonds. Owing to the graphene sandwiched between two SnS2 sheets, the composite presents an enlarged interlayer spacing of ~8.03 Å for SnS2, which could facilitate the insertion/extraction of Li+/Na+ ion with rapid transport kinetics, as well as inhibiting the re-stacking of SnS2 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 that this state is the most suitable for fast ions transport. In addition, numerous ultra-tiny SnS2 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 SnS2 nanoparticles still recover to pristine phase without distinct agglomeration, demonstrate that this composite with high rate capabilities and excellent cycle stability are the promising candidate for lithium/sodium storage.