A yolk–shelled Co9S8/MoS2–CN nanocomposite derived from a metal–organic framework as a high performance anode for sodium ion batteries

Abstract

Sodium-ion batteries (SIBs) are considered as a promising energy storage device, and anode materials are proved to essentially affect their electrochemical performance. In this work, a yolk–shell structured Co₉S₈/MoS₂ polyhedron with N-doped carbon composite (Co₉S₈/MoS₂–CN) was designed and synthesized through a step by step process using ZIF-67 as the precursor. And this composite is demonstrated to be an excellent electrode candidate material for SIBs due to the magnificent yolk–shelled structures, in situ CN coating and the synergistic effect of the binary sulfides. The Co₉S₈/MoS₂–CN composite electrode shows highly stable cycling performance and delivers a reversible discharge capacity of 438 mA h g⁻¹ within 150 cycles at a current density of 1.0 A g⁻¹, which is much higher than that of Co₉S₈–CN or MoS₂ electrodes. Even at a high current density of 2.0 A g⁻¹, it can also deliver an impressively stable capacity of 421 mA h g⁻¹ within 250 cycles.