Multi-heterostructured SnO/SnS embedded in carbon framework for high-performance sodium-ion storage.

Heterostructure materials, as newborn electrode materials for rechargeable batteries, are attracting increasing attention due to their robust architectures and superior electrochemical performances. It is widely believed that the inner electric field induced at the interface can improve the electric conductivity and ion diffusion kinetics, thus enhancing the long-term stability and high-rate performance of the batteries. Although much progress is made on heterostructure construction, the performance of the batteries is still far from satisfying the commercial applications. In this work, a new type of SnO/SnS (x = 1, 1.5) heterostructure embedded in carbon framework (C@SnO/SnS) is constructed via a facile sulfidation process. Compared to a single heterojunction, the multi-heterojunctions generated at SnO/SnS interface can induce an intensified built-in electric field, which promotes charge transportation and reaction kinetics of the electrode for Na-ions storage. Upon the sodiation process, the induced intensified electric field drives Na ions from SnS or SnO to SnS, while an inverse transportation of Na ions are accelerated upon the desodation process. As a result, C@SnO/SnS exhibits an outstanding reversible capacity of 510 mA h g after 300 cycles at 200 mA g.