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

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.