In Situ Growth of CoSe 2 Coated in Porous Carbon Layers as Anode for Efficient Sodium‐Ion Batteries

A novel composite material of CoSe 2 /N‐doped carbon box (CoSe 2 /NC) is successfully synthesized using zeolitic imidazolate frameworks‐67 as the sacrificial templates through a simple two‐step calcine process. The CoSe 2 nanoparticles are encapsulated in N‐doped carbon layers, which can seriously avoid agglomeration. When used CoSe 2 /NC as anode materials for sodium‐ion batteries (SIBs), it exhibits an excellent high reversible specific capacity and a superior cycling stability of 390.2 mA h g −1 at 5 A g −1 over 4000 cycles. The excellent performance of CoSe 2 /NC can be attributed to cooperation of CoSe 2 nanoparticles and N‐doped carbon layers. Carbon layers coated on the surface of CoSe 2 nanoparticles not only improve a well conductivity to facilitate the charge transfer, but also buffer the structure to expand during the Na + insertion/extraction process. Furthermore, this novel porous structure provides more active sites and increases contact areas between the materials and the electrolyte, thus increasing the specific capacity and cycle stability. This work provides a possibility of anode materials for SIBs with excellent electrochemistry performance.