Metal-organic framework(MOF)-derived selenidation strategy to prepare porous(Zn,Cu)CoSex micro/nanostructures for sodium-ion batteries

Owning to the wide distribution,low cost,and similar chemical-electrochemical properties with lithium,sodium-ion batteries(SIBs) have attracted much attention during recent years and may have the potential to replace the commercial lithium-ion batteries.Herein,facile and simple bottom-up approach has been rationally applied to fabricate carbon-encapsulated ZnSe@CoSe_(2)micro spheres and Cu_(2)Se@CoSe_(2)nanocubes.The as-prepared ZnSe@-CoSe_(2)microspheres and Cu_(2)Se@CoSe_(2)nanocubes composites inherited the original structure of ZnCo-MOF and CuCo-MOF,respectively.Herein,both ZnSe@CoSe_(2)micro spheres and Cu_(2)Se@CoSe_(2)nanocubes delivered excellent electrochemical performance when presented as anode materials for SIBs.Both ZnSe@CoSe2micro spheres and Cu_(2)Se@CoSe_(2)nanocubes electrode could display a long-term cycling stability with a reversible capacity of 525 and 423 mAh·g^(-1)at the current density of 1 A·g^(-1)after 500 cycles,respectively.Furthermore,even at a high current density of 5 A·g^(-1),ZnSe@CoSe_(2)microsphere could still maintain 520 mAh·g^(-1)after 500 cycles,demonstrating remarkable capacity and excellent cycling performance.Those high performances were beneficial from the unique hollow and porous structure of ZnSe@CoSe_(2)microspheres and Cu_(2)Se@CoSe_(2)nanocubes derived from the precursor which facilitate the transport of sodium ions,contributing to high capacity,improved excellent cycle stability and rate capability.