Metal-organic framework derived Co1-xS@C nanoboxes for long-life Na+ storage

Transition metal sulfides appear excellent electrochemical properties in the realm of anode for sodium-ion batteries and hold significant potential for practical application in large-scale devices in the future. However, their development is hindered by inferior inherent conductivity and tremendous volume strain during discharge and charge processes. In this study, Co1-xS@C nanoboxes were synthesized utilizing Co-Co PBA as a precursor. The electrochemical sodium storage performance of Co1-xS@C electrode was characterized, revealing an extremely long-life and stable performance. At 1.0 A g−1 and 2.0 A g−1, the electrode delivered capacities of 255.8 mAh g−1 and 197.6 mAh g−1 after 5000 and 10,000 cycles respectively, with negligible capacity attenuation. The pseudo-capacitance behavior of Co1-xS@C NBs electrode in sodium storage was quantitatively calculated through CV test at varying sweep speeds. The significant contribution of pseudo-capacitance resulted in its exceptional rate capacity and electrochemical stability. Furthermore, kinetic analysis revealed that the existence of a carbon shell enhanced the Na+ diffusion kinetics and charge transfer kinetics of Co1-xS@C NBs. This strategy provides a reference for enhancing the Na+ storage performance of other transition metal sulfides.