Shielded SnS2/SnS heterostructures on three-dimensional graphene framework for high-rate and stable sodium-ion storage

Abstract Tin sulfides are promising anode materials for sodium-ion batteries (SIBs) for their high theoretical capacity and fast kinetics for Na storage. However, the severe volume expansion and intrinsically low charge conductivity fundamentally compromise their electrochemical performance. Addressing at the issue, SnS2/SnS heterostructures are decorated on three-dimensional graphene nanosheets (3D GNS) framework, which is then shielded with a nanocarbon layer. In this nanocomposite, the SnS2/SnS p-n heterostructures induce an internal electric field on the heterointerfaces to promote the charge transfer inside the material, which effectively ensures the rate capability of the material. Moreover, the 3D GNS provides a porous conductive network to accelerate the long-range transport of electron further enhancing its rate performance. Meanwhile, the dual-carbon structure would alleviate the volume expansion of SnS2/SnS during cycling, ensuring improved stability. The integration of these merits leads to excellent battery performance for the material, including high reversible capacity, rate capability, and cycling stability. This concept of simultaneously enhancing the ionic, electronic, and mass conductivity as well as the structural stability by combining heterogeneous structures, 3D conductive networks, and protective shields can further shed light on not only SIB materials but also other energy storage materials or devices.