ZnS-Sb2S3@C Core-Double Shell Polyhedron Structure Derived from Metal–Organic Framework as Anodes for High Performance Sodium Ion Batteries

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-Sb2S3@C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn2+ dissociated from ZIF-8 and S2– from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn2+ and Sb3+, in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and Sb2S3/C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex Sb2S3/C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices.