Ultrahigh rate sodium-ion storage of SnS/SnS2 heterostructures anchored on S-doped reduced graphene oxide by ion-assisted growth

Developing high-performance anode materials is very crucial for room-temperature sodium-ion batteries (SIBs). Sn-based compounds are promising SIB anode materials for their high theoretical capacities and low costs. However, the intrinsic low conductivity, poor infiltration and irreversible reactions of Sn-based compounds lead to poor rate and cycling performance. In order to address above issues, SnS/SnS2 heterostructures on sulfur-doped reduced graphene oxide (SG) are assembled via a facile alkali ion-assisted growth. As-synthesized SnS/SnS2 heterostructures on SG with assistance of K+, denoted as SnS/SnS2@SG-K, exhibits typical layer-stacked structure and high reversible capacities over 800 mAh g(-1) at 50 mA g(-1) and 241 mAh g(-1) even at a record high current density of 48 A g(-1), which are superior to most of the Sn-based SIB anode materials. The excellent rate and cycling performance of SnS/SnS2@SG-K could be ascribed to the layer-stacked structures of SG and heterojunctions between SnS and SnS2 which can accelerate semi-infinite diffusions of Na+ ions and electrons, alleviate polysulfide shuttling problems and reduce volume fluctuation effect. Meanwhile, the pseudocapacitance of oxygen and sulfurcontaining groups in SG also contribute to the unprecedented sodium storage performance of assynthesized SnS/SnS2@SG-K. (C) 2018 Published by Elsevier Ltd.