Functional sulfur-doped zinc-nickel-cobalt oxide nanorods materials with high energy density for asymmetric supercapacitors

Abstract Transition metal oxides as the most promising electrode materials for supercapacitors has attracted widespread attention. However, their applications are limited by their sluggish charge transfer kinetics and insufficient active sites. Herein, we report the preparation of sulfur-doped zinc-nickel-cobalt oxides (S-ZNCO) using the synergistic effect of heteroatom doping and defect engineering by hydrothermal treatment and sulfurization method. The morphology and microstructure are characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy dispersive spectrometry (EDS) mapping, X-ray photoelectron spectroscopy (XPS) and Raman spectra. The results demonstrate the successful doping of sulfur atoms and introduction of oxygen vacancies, which increases the redox reaction active sites and further improves the electrochemical kinetics of the electrode material, giving rise to a high specific capacitance (2919.60 F g-1 at 1 A g-1) and better electrical conductivity of the S-ZNCO electrode. Furthermore, the assembled S-ZNCO-NF//AC device achieves a high energy density of 72.97 W h kg-1 at a power density of 825 W kg-1. This work opens up new opportunities to design of advanced transition metal compounds for supercapacitors.