Metal–organic framework–derived ultrasmall nitrogen-doped carbon-coated CoSe2/ZnSe nanospheres as enhanced anode materials for sodium-ion batteries

Ultrasmall nitrogen-doped carbon-coated CoSe 2 /ZnSe nanospheres (CoSe 2 /ZnSe@C nanospheres) are fabricated by direct selenization of a delicately designed Co 1.6 Zn 0.4 -(benzimidazole) 4 metal–organic framework (MOF) nanosheet precursor and used as the anode materials in sodium-ion batteries (SIBs). The fabricated CoSe 2 /ZnSe@C nanospheres deliver a remarkable rate performance (395 mAh g −1 at 0.1 A g −1 and 341 mAh g −1 at 5.0 A g −1 ) and excellent long-term durability (346 mAh g −1 after 2500 cycle at 2.0 A g −1 ). The superior Na storage performance of the fabricated CoSe 2 /ZnSe@C nanospheres could be mainly attributed to their ultrasmall particle sizes and the phase boundaries between CoSe 2 and ZnSe, which improve the kinetics of the electrode, relieve the volume change during the charge/discharge process, and provide extra Na + storage sites. This work opens up possibilities to fabricate metal selenide–based hybrid materials with desired nanostructures and compositions from rationally designed multimetal MOF precursors for high-performance anode materials in SIBs.