Carbon Nanotube Modified Zn–Co Bimetallic Selenide Composites for Lithium–Sulfur Batteries

Abstract

The cathode material of the lithium−sulfur (Li−S) battery poses several challenges, including inadequate conductivity, the "shuttle effect", and volume expansion, all contributing to its reduced cycle lifespan. To address these issues, high-performance Li−S batteries can be manufactured by using transition metal selenide nanomaterials. These nanomaterials exhibit polarity, porosity, electrochemical catalytic activity, and high conductivity, making them well-suited hosts for sulfur cathodes. In this study, a metal−organic framework material was employed as a precursor to produce hollow dodecahedral transition metal selenides. This involved combining the precursor with selenium powder and subjecting it to high-temperature calcination. By leveraging bimetallic synergism and incorporating carbon nanotubes, the material's conductivity was improved, providing a conductive pathway for electron transport. The hollow ZnSe/CoSe 2 structure's surface is interconnected by carbon nanotubes, forming a conductive network. This arrangement facilitates efficient sulfur utilization and prevents structural collapse during battery cycling. Moreover, ZnSe/CoSe 2 enhances the chemical anchoring of polysulfide, promotes polysulfide transformation, and induces homogeneous nucleation of Li 2 S. Experimental results demonstrate excellent electrochemical performance when 50 mg of carbon nanotubes. At a rate of 0.05 C, the initial discharge specific capacity reaches 1225.75 mA h•g −1 , while at 1 C, it is 439.35 mA h•g −1 . After 200 cycles, the battery exhibits a capacity retention of 71.25% with a reversible capacity of 313.08 mA h•g −1 .