SnS2 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 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+ ions with rapid transport kinetics
as well as inhibit the restacking 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 this state is the most suitable for fast ion transport. In addition,
numerous ultratiny 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 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.
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