In-situ synthesis of covalently-bonded SnS2/FeS2 heterostructures for high rate sodium storage

SnS2 has been regarded as a promising anode material of sodium ion batteries (SIBs) due to the large interlayer spacing which favors to the reversible ion intercalation and extraction, and thus contributing to the high specific capacity. However, the intrinsic weak van der Waals interactions in the interlayers of SnS2 nanosheets lead to the deficient electron transfer across interlayers and the poor stability of layered structure, which seriously deteriorates the electrochemical performance of SnS2 anode in SIBs. Herein, the covalently-bonded SnS2/FeS2 heterostructures anchored on reduced graphene oxide (rGO) (referred to as SnS2/FeS2@rGO) were prepared via the in-situ decomposition and subsequent sulfurization of FeSnO(OH)5 nanoparticles. Based on the experimental characterizations and density functional theory (DFT) calculation, the covalently-bonded SnS2/FeS2 interfaces could promote charge/electrons transfer and accelerate ion diffusion kinetics. When applied as the anode materials toward SIBs, SnS2/FeS2@rGO exhibits superior rate capability of 429.6 mA h g−1 at a high current density of 6 A/g along with excellent long cycle stability. This proposed in-situ synthesis strategy via FeSnO(OH)5 nanoparticles may offer a new way toward effective electron transfer for metal ions storage and transport applications.