Metal organic frameworks-derived multi-shell copper-cobalt-zinc sulfide cubes for sodium-ion battery anode

Transition metal sulfides (TMSs) have been considered as one type of promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacity and outstanding redox reversibility. However, the application of TMSs for SIB anode still faces the fatal challenge mainly pertaining to rapid capacity decay and slow reaction kinetics. Herein, we employ Cu/Zn co-doped ZIF-67 (Cu/Zn-ZIF-67) as the precursor to prepare multishell hollow carbon-coated Cu39S28-CoS2-ZnS@nitrogen doped carbon cubes (CCZS@NC@C-15), where the outer shell is a carbon coating layer, and the interior is the double shells formed by CU39S28, CoS2 and ZnS in a porous nitrogen-rich carbon matrix. The as-prepared CCZS@NC@C-15 with unique multi-shell structure can not only effectively buffer the volumetric stress during the sodium insertion/extraction processes, but also increase the volume utilization rate of anode materials. Additionally, the porous carbon cube structure not only increases the contact area between the anode materials and the electrolyte but also prevent the agglomeration of active particles effectively. Furthermore, the carbon coating layer combine with the internal N-rich carbon matrix increases the conductivity of anode and improve the electrochemical stability. As a result, the as-prepared CCZS@NC@C-15 anode shows the remarkable electrochemical stability and rate capability. Our research provides a new strategy for the rational design of TMSs with unique structure for high-performance SIBs.

Automated summary

This study presents a unique strategy for the rational design of transition metal sulfides (TMSs) with high-performance for sodium-ion batteries (SIBs) by utilizing Cu/Zn co-doped ZIF-67 as a precursor to prepare multi-shell hollow carbon-coated Cu39S28-CoS2-ZnS@nitrogen doped carbon cubes. The resulting electrode shows remarkable electrochemical stability and rate capability, attributed to the effective buffering of volumetric stress, increased volume utilization rate, improved conductivity, and prevention of active particle agglomeration provided by the unique multi-shell structure.