Hierarchical CoS2/N-Doped Carbon@MoS2 Nanosheets with Enhanced Sodium Storage Performance.

We introduce a hierarchical nanostructure of CoS2/N-doped carbon@MoS2 comprising two transition-metal sulfides CoS2 and MoS2, with enhanced sodium storage performance in sodium-ion batteries. A micron-sized Co metal-organic framework (MOF) is transformed into a CoS2/N-doped carbon composite, followed by a solvothermal growth of MoS2 nanosheets on the surface. The resulting composite material offers several specific advantages for sodium storage: (i) accelerated sodium-ion diffusion kinetics due to its heterogeneous interface; (ii) shortened ion diffusion path and exposed active sites for sodium storage due to its hierarchical nanosheet architecture; and (iii) homogeneous nitrogen doping of the MOF-derived carbon, which is beneficial for electronic conductivity. Due to these merits, this composite exhibits excellent electrochemical performance with a specific capacity of 596 mAh g-1 after 100 cycles at 0.1 A g-1 and 395 mAh g-1 at 5.0 A g-1.