A MOF-to-MOF conversion assisted formation of hierarchical hollow Zn-Co_(1-x)S/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-Co_(1-x)S/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 Co_(1-x)S@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 Co_(1-x)S,thus accounting for the good cycling behavior and excellent rate capacity of hierarchical hollow Zn-Co1.xS/C@C composite.