Engineering cationic vacancies on sphere-like zinc cobaltite microstructures via self-assembly of silkworm-like interconnected nanoparticles for battery-type supercapacitors

Abstract

In this study, we utilized the solvothermal synthesis method to engender Zn vacancies on spinel ZnCo₂O₄ microspheres (V_Zn-ZCO), intending to improve their electrochemical performance. X-ray photoelectron spectroscopy was used to quantify the Zn vacancies, and this was supported by Rietveld refinement using X-ray diffraction data and energy-dispersive X-ray analysis. The resulting V_Zn-ZCO material had a high specific area of 53.60 m² g⁻¹ and an average pore diameter of 7.96 nm, which facilitated faster transport paths and greater surface area for rapid charge transfer. In terms of supercapacitor performance, the V_Zn-ZCO electrode exhibited battery-type behavior and achieved a high specific capacity of 367 C g⁻¹ at 1 A g⁻¹, as well as excellent rate capability with 82% of capacity retention. Furthermore, it displayed superior cycling stability with 76% retention of the maximum specific capacity after 5000 cycles. Therefore, our findings suggest that producing cationic vacancies is an effective strategy for improving the electrochemical performance of spinels.