Tailoring the dielectric and electrochemical properties of ZnO–CoO with Fe doping for energy storage devices

Metal oxides have been extensively researched due to their exceptional electrical conductivity and superior specific capacitance, making them pivotal materials in the study of supercapattery devices. In this study, zinc oxide mixed with cobalt oxide with a 50/50 weight, and (ZnO–CoO) nanocomposite was synthesized using a hydrothermal technique. Moreover, the effect of iron (Fe) incorporation into the ZnO–CoO heterostructure was investigated. Characterization of the Fe/ZnO–CoO nanoparticles involved X-ray diffraction (XRD) and scanning electron microscopy (SEM) to analyze their crystallinity and phase composition. The impact of iron doping on the dielectric properties of ZnO–CoO is also evaluated. The high dielectric constant values were observed at low frequencies in pure ZnO–CoO. Moreover, tan δ has larger values at lower frequencies and smaller values at higher frequencies. The Fe/ZnO–CoO composite exhibited superior electrochemical performance, with a specific capacity of 653 Cg−1 compared to 487 C/g for the simple ZnO–CoO composite. In hybrid device, Fe/ZnO–CoO//AC, the composite electrode showed a specific capacity of 164 Cg−1 at 1.0 Ag−1. The device demonstrated an extraordinary energy density of 57 Wh kg−1 and an improved power density of 3600 W/kg. Notably, the device exhibited excellent capacity retention (CR) of 97