Synergistical Coupling Interconnected ZnS/SnS2 Nanoboxes with Polypyrrole-Derived N/S Dual-Doped Carbon for Boosting High-Performance Sodium Storage.

Metal sulfides possess tremendous potentials owing to their high specific capacity for sodium storage. However, the huge volume expansion, accompanied with structural collapse and unsatisfied electric conductivity upon continuous cycling, always lead to inferior rate capability and severe cycling fading. In this work, binary metal sulfide (ZnS/SnS2 ) nanoboxes confined in N/S dual-doped carbon shell (ZSS@NSC) are fabricated through a facile co-precipitation method involving the wrapping of polypyrrole, and subsequent in situ sulfidation process. Such a well-designed heterogeneity between ZnS and SnS2 provides rapid Na+ insertion and enhanced charge transport by creating an electric field at the heterointerface. More significantly, the formation of polypyrrole-derived N/S dual-doped carbon is synergistically coupled with the ZnS/SnS2 to create a unique and robust architecture, further strengthening the interconnect function at the heterointerface, which improves electric/ion transfer and mitigates the volume variation during the long-term cycling process. Herein, this as-prepared ZSS@NSC exhibits satisfied specific capacity, excellent rate property, and superior cyclic stability (a reversible capacity of 456.2 mAh g-1 with excellent capacity retention of 97.2% after 700 stable cycles at ultrahigh rate of 5 A g-1 ). The boosted Na-storage properties demonstrate that the optimized strategy of structure-engineering has a broad prospect to promote energy storage applications.