Investigating the interfacial interactions in CoSe2@CNTs for improved sodium storage performance†

Abstract

The most effective method of resolving the issue of inadequate conductivity and significant volume expansion of the converted sodium storage anode material is to hybridize/combine the electroactive material with a conductive carbon material to form a carbonaceous nanocomposite material. Herein, a one-step solvothermal method was employed to construct a cobalt diselenide@carbon nanotube (CoSe₂@CNTs) composite with a heterojunction structure. The incorporation of CNTs not only enhances the overall conductivity of the composite but also effectively mitigates the expansion of CoSe₂ during charging and discharging, providing structural support to the material. Moreover, the electronic coupling effect between the distinct elements at the interface between CoSe₂ and CNTs optimizes the electronic structure and charge distribution of the composite, establishing a built-in electric field within the composite and enhancing the rapid transport of sodium ions. X-ray photoelectron spectroscopy (XPS) tests and density functional theory (DFT) calculations further substantiate these findings. Among all the prepared samples, the optimized CoSe₂@CNTs-2 electrode demonstrates outstanding sodium storage properties, characterized by ultrahigh long-term cycling stability (345.8 mA h g⁻¹ at 2 A g⁻¹ after 1750 cycles). Finally, the Na₃V₂(PO₄)₃@C//CoSe₂@CNTs-2 full battery was investigated, retaining a reversible capacity of 164.2 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹. This finding provides important theoretical support for the optimization and design of conversion anode materials for sodium storage.