In situ etching strategy to construct yolk–shell CoSe2@NiCoSe4-NC heterostructures for high-performance sodium ion battery

Abstract

A yolk–shell structure CoSe₂@NiCoSe₄-NC has been successfully synthesized through an in situ etching and ion exchange strategy, as well as the subsequent selenization process of the ZIF-67 dodecahedron precursor. Due to the unique yolk–shell structure and bimetallic synergistic effect, the CoSe₂@NiCoSe₄-NC heterostructure exhibits high conductivity and enhanced specific surface aera for the incorporation of electrode and electrolyte, which provide good charge transfer kinetics and facilitate Na⁺ transport, as well as accelerating the reaction kinetics. When used as an anode material for sodium-ion batteries, it exhibits promising electrochemical performance, including excellent rate capability and outstanding cycle stability. The yolk–shell structure CoSe₂@NiCoSe₄-NC shows a high specific capacity of 341.3 mA h g⁻¹ at a current density of 5 A g⁻¹ and can still deliver a 94.8% retention rate after 400 cycles at a current density of 1 A g⁻¹, which proves that the material is a good sodium-ion battery anode material. This simple and universal method can provide a new method for the preparation of bimetallic selenide and yolk–shell structure anode materials.