<p>NiO/CuO/Co₃O₄ ternary nanocomposites (TNCs) were synergistically designed via hydrothermal method to enhance interfacial charge transfer and redox activity for high-efficiency supercapacitor applications. The structural analysis using XRD confirmed the coexistence of cubic NiO, monoclinic CuO and spinal Co₃O₄ phases with an average crystallite size of ~ 21&#xa0;nm, indicating the formation of a well-defined ternary system. XPS analysis verified the presence of Ni²⁺/ Ni³⁺, Cu²⁺ and Co²⁺/Co³⁺ oxidation states along with oxygen vacancies. FESEM and HRTEM studies revealed a hexagonal plate-like morphology with well-defined lattice fringes and polycrystalline nature of the prepared material. BET analysis showed a high specific surface area of 131 m²g^− 1 with mesoporous structure (~ 1.93&#xa0;nm pore size), facilitating efficient electrolyte access and charge transport. Electrochemical measurements demonstrated excellent pseudocapacitive behaviour with a high specific capacitance of 1523&#xa0;F g^− 1 at 10 mV s^− 1 scan rate and 1160&#xa0;F g^− 1 at 2 A g^− 1 current density from CV and GCD curves, respectively. The electrode exhibited superior cyclic stability with 97.8% capacitance retention after 1000 cycles at 5&#xa0;A g^− 1. A symmetric supercapacitor device was fabricated, delivering a specific capacitance of 395&#xa0;F g^− 1 at 10 mV s⁻¹and an energy density of 69.7 Wh kg^− 1. The device also demonstrated practical applicability by successfully powering a red LED. These results highlight the potential of the NiO/CuO/Co₃O₄ TNCs as an efficient electrode material for next-generation high energy supercapacitors.</p>