Formation of Hierarchical Cu‐Doped CoSe 2 Microboxes via Sequential Ion Exchange for High‐Performance Sodium‐Ion Batteries

Abstract Electrode materials based on electrochemical conversion reactions have received considerable interest for high capacity anodes of sodium‐ion batteries. However, their practical application is greatly hindered by the poor rate capability and rapid capacity fading. Tuning the structure at nanoscale and increasing the conductivity of these anode materials are two effective strategies to address these issues. Herein, a two‐step ion‐exchange method is developed to synthesize hierarchical Cu‐doped CoSe 2 microboxes assembled by ultrathin nanosheets using Co–Co Prussian blue analogue microcubes as the starting material. Benefitting from the structural and compositional advantages, these Cu‐doped CoSe 2 microboxes with improved conductivity exhibit enhanced sodium storage properties in terms of good rate capability and excellent cycling performance.