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 CoSe2/ZnSe nanospheres (CoSe2/ZnSe@C nanospheres) are fabricated by direct selenization of a delicately designed Co1.6Zn0.4-(benzimidazole)4 metal–organic framework (MOF) nanosheet precursor and used as the anode materials in sodium-ion batteries (SIBs). The fabricated CoSe2/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 CoSe2/ZnSe@C nanospheres could be mainly attributed to their ultrasmall particle sizes and the phase boundaries between CoSe2 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.