The In-Situ Synthesis of a 3D SnS/N-Doped Graphene Composite with Enhanced Electrochemical Performance as a Low-Cost Anode Material in Sodium Ion Batteries

Abstract

SnS/N-doped graphene (SnS/NG) composites are promising anode materials for sodium ion batteries. Generally, SnS is synthesized from SnCl2·2H2O. However, SnCl2·2H2O is not suitable for large-scale production due to its high price. Compared with SnCl2·2H2O, SnCl4·5H2O has a lower price, more stable chemical properties and better water solubility. Until now, there have been no related reports on the synthesis of SnS from SnCl4·5H2O. In this work, the fabrication of SnS/NG in a facile, two-step process, which combines a hot water bath and thermal annealing and uses SnCl4·5H2O as a precursor, is described. The mechanism of phase transformation in the direct synthesis of SnS from Sn4+ is also discussed in detail. Applying our methodology, SnS nanoparticles were grown in-situ on graphene sheets and wrapped by N-doped graphene sheets to form a 3D SnS/NG composite. With 35.35% content of graphene in the SnS/NG composite, the reversible specific capacity remained at 417.8 mAh/g at 1000 mA/g after 100 cycles, exhibiting a high specific capacity and good cycling stability. In addition, the composite also had an excellent rate performance, with a specific capacity of 366.9 mAh/g obtained even at 5000 mA/g. Meanwhile, the fast sodium storage kinetics of SnS/NG were also analyzed, providing some theoretical support for further study.