Trimetallic sulfides derived from tri-metal-organic frameworks as anode materials for advanced sodium ion batteries

Highly conductive metal sulfides with high theoretical capacities and good conductivity have been considered as anode material alternatives for sodium-ion batteries (SIBs). Unfortunately, the unsatisfactory cycling stability and poor rate performance are usually resulted from the sluggish electrochemical kinetics and volumetric expansion in the charge/discharge process, which severely restricts their applications. Herein, trimetallic sulfides embedded into the carbon matrix with a microsphere shape (denoted as CoNiZnS/C) were successfully prepared by a facile solid sulfidation of tri-metal-organic frameworks. The nanorods-assembled microsphere structure with abundant phase boundaries of multiphase in the CoNiZnS/C would provide abundant active sites and defects for storing sodium ions and rich voids to alleviate the volumetric strains. As the anode material of SIBs, the optimum composite named as CoNiZnS/C-2 in this work demonstrated high initial Coulombic efficiency (96.52% at 0.1 A g^-1), good cycling stability (maintaining 410.7 mA h g^-1 at the 960th cycle at 2.0 A g^-1) and excellent rate performance (477.0 mA h g^-1 at 5.0 A g^-1). Thus, such a multi-metal sulfide composite with special physical-chemical properties may offer a new insight to promote the electrochemical performance of sulfide-based anode materials for the SIBs.