Construction of Ternary Zn 0.5 Cu 0.5 Co 2 O 4 Spinel Structure on Nickel Foam: A Comprehensive Theoretical and Experimental Study from Single to Ternary Metal Oxides for High‐Energy‐Density Asymmetric Supercapacitor Application

Developing nanostructured multi-transition metal-based spinel architectures represents a strategic approach for boosting the energy density of supercapacitors while preserving high power density. Here, the influence of incorporating Zn and Cu into Co₃O₄ spinel systems on supercapacitor performance is investigated by synthesizing single (ZnO, CuO, Co₃O₄), binary (ZnCo₂O₄, CuCo₂O₄), and ternary (Zn_0.5Cu_0.5Co₂O₄) oxides on nickel foam substrates. Theoretical and experimental analyses highlight that the flower-like structures of Zn_0.5Cu_0.5Co₂O₄, comprising nanowires and nanoribbons, effectively reduced transport barriers and enhanced ion adsorption, thereby improving electron/ion reaction kinetics. Oxygen vacancies induced defect states in Zn_0.5Cu_0.5Co₂O₄, shifting the d- and p-band center values closer to the Fermi level and enhancing electrochemical performance. The Zn_0.5Cu_0.5Co₂O₄ exhibits a specific capacity of 271 mA h g^-1 (1776 F g^-1) at 1 A g^-1 with 97% capacity retention after 5 000 charge/discharge cycles. In a Zn_0.5Cu_0.5Co₂O₄//activated carbon configuration, the device demonstrates superior energy and power densities of 122.2 Wh kg^-1 and 800 W kg^-1, respectively, maintaining 91% capacitance after 10 000 cycles at 30 A g^-1 with high coulombic efficiency. This study presents an effective strategy to enhance ion/charge transfer and adsorption in multi-transition metal spinel architectures, advancing the development of supercapacitor electrodes.