Metal–organic framework-derived nitrogen-doped carbon-confined CoSe2 anchored on multiwalled carbon nanotube networks as an anode for high-rate sodium-ion batteries

Abstract

Metal selenides, as potential alternative candidates for sodium storage, have promising applicability due to their high theoretical specific capacity. However, their huge volume change and sluggish electrode kinetics during sodium ion uptake and release processes can result in insufficient cycling life and inferior rate performance, hindering their practical application. Herein, nitrogen (N)-doped carbon-confined cobalt selenide anchored on multiwalled carbon nanotube networks (denoted as CoSe₂@NC/MWCNTs) was designed and successfully built through a selenization process with ZIF-67 MOF as the template. The existence of the interconnected MWCNT network plays a crucial role in not only enhancing the electronic conductivity and ion/electron-transfer efficiency but also ensuring structural stability. Consequently, the optimized CoSe₂@NC/MWCNTs composite delivers a high reversible capacity of 479.6 mA h g⁻¹ at a current rate of 0.2 A g⁻¹, accompanied by a 92.0% capacity retention over 100 cycles and a predominant rate performance of 227.4 mA h g⁻¹ even under 20 A g⁻¹ when examined as the anode in Na-ion batteries. Moreover, the kinetic behaviors were confirmed using CV profiles at various rates, as well as the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). Besides, the HRTEM images clearly reveal the sodium-ion storage mechanism of the CoSe₂ hybrid. These results make CoSe₂@NC/MWCNTs a prospective anode material in advanced sodium-ion batteries.