Zinc positioning’s impact on electrochemical stability of γ-Al₂O₃ for supercapacitor efficiency

The electrochemical properties exhibited by the zinc-doped alumina nanoparticles suggest their potential as another viable alternative for supercapacitor electrode applications. The strategic placement of Zn²⁺ ions within the interstices of the alumina lattice forms potential barriers between Al³⁺ and Zn²⁺ ions, acting as effective centers for trapping charges. The structural changes report a decrease in the average crystallite size from 9 to 5 nm. The formation of trapping centers is confirmed by the enhancement in optical band gap value from 1.89 to 4.21 eV. The XPS data confirms the oxidation state of + 3 and + 2 for Al and Zn ions, respectively. A prolonged charge retention and an increased energy storage density are evidenced by the observed value of 1237 F g^–1 at 1 A g^–1. Furthermore, the stability of alumina gets enhanced on doping, demonstrating for the first time an impressive 92% stability over 10,000 cycles. The 5% Zn-doped Al₂O₃ electrode has the highest diffusion coefficient of 8.9 × 10^–12 cm² s^–1, showing efficient active sites for electrolyte ion intercalation. The asymmetric supercapacitor device analysis with 5% Zn-doped alumina as one of the electrodes attains a stability of 85% after 5000 repeated cycles. The device achieves a better energy density value of 47.63 W h kg^–1 at a power delivery rate of 996.9 W kg^–1. This study offers valuable insights into the electrochemical performance of zinc-doped alumina nanoparticles, underscoring their potential for high-performance energy storage applications in supercapacitor devices.