Rational Design of Hierarchically Structured CoS₂@NCNTs from Metal–Organic Frameworks for Efficient Lithium/Sodium Storage Performance

In this report, hierarchically structured CoS2 was formed with ZIF-67 as a template. CoS2 nanoparticles are prepared through two processes, including carbonization and sulfurization. At the same time, the ZIF-67 precursor is converted into a nitrogen-doped carbon polyhedron at the temperature from 550 to 750 °C. Due to the catalytic activity of cobalt, the surface of the carbon polyhedron framework catalytic formation of N-doped carbon nanotubes (NCNTs). We optimized the CoS2@NCNT composite material by controlling the carbonization temperature; the study found that the sample obtained at a temperature of 650 °C has a large specific surface area and a moderate degree of graphitization. When evaluated as a secondary battery anode material, CoS2@NCNTs-650 exhibits excellent lithium/sodium storage performance. Discharge specific capacities of 1057.4 mA h g–1 [lithium-ion batteries (LIBs)] and 621.5 mA h g–1 [sodium-ion batteries (SIBs)] are maintained after 200 cycles (0.5 A g–1). In addition, because of the higher capacitance contribution rate and lower electrochemical impedance of the CoS2@NCNTs-650 electrode, excellent rate performance is exhibited for both LIBs and SIBs.