A MOF-to-MOF conversion assisted formation of hierarchical hollow Zn-Co₁-_xS/C@C composite for efficient potassium-ion storage

Hollow structured composite can enhance the structural stability of metal sulfide anode by accommodating its volume variation, while the performance is still hindered by its poor electron/ion conductivity. Herein, we develop a hier-archical hollow structure to achieve superior electrochemical performance, from which a MOF-to-MOF conversion is utilized to generate hollow Zn-Co1-xS/C composite followed with additional carbon coating layer. For potassium storage, as-prepared hollow Zn-Co1-xS/C@C composite displays high capacities of 375 mA h g-1 after 100 cycles at 0.2 A g-1 and 201 mA h g-1 after 500 cycles at 1 A g-1. Moreover, it also manifests outstanding rate capability of 200 mA h g-1 at 10 A g-1, outperforming hollow Co1-xS@C and majority of the reported cobalt-based anodes. With illustration by kinetics analysis and theoretical calculation, both of Zn doping and internal carbon matrix are conductive to promote the charge transportation ability of Co1-xS, thus accounting for the good cycling behavior and excellent rate capacity of hierarchical hollow Zn-Co1-xS/C@C composite.