Metal-organic framework derived core-shell structured Cu-doped Co0.85Se@NC@C microcubes as advanced anodes for sodium-ion batteries

Recently, transition-metal selenides have appealed to extensive attention because of their high energy density and theoretical capacity; nevertheless, their weak cycling stability and inferior rate performance hinder the practical application of the materials as the anodes for sodium-ion batteries (SIBs). Herein, Cu-doped Co 0.85 Se nanoparticles embedded in N-doped carbon microcubes with the coating of carbon layer (CDCS@NC@C) have been synthesized using zeolite imidazole framework-67 as the template by the combined process of room-temperature coprecipitation and in-situ polymerization. The porous micro-nano structure of the material is beneficial to accommodating to the volume variation of the electrode during discharging and charging and facilitating the penetration of electrolyte, while the doping of Cu improves the electrical conductivity of the material by modulating the electronic structure. In addition, the rigid skeleton derived from carbonized resorcinol-formaldehyde enhances the structural stability of the material during sodiation/desodiation. Consequently, the CDCS@NC@C reveals satisfactory initial capacity of 465.2 mA h g −1 at 0.1 A g −1 , outstanding long lifetime of 251.3 mA h g −1 at 5A g −1 after 500 cycles with the capacity decay of 0.0755% per cycle and remarkable rate performance with a specific capacity of 248.9 mA h g −1 at 5 A g −1 . This study proposes an effective strategy to develop advanced anodes with high conductivity and excellent structural stability for SIBs by encapsulating active materials into a carbon matrix with the protection of rigid skeleton.