Facile hydrothermal synthesis of copper oxide microspheres decorated with nickel sulfide nanoparticles battery-type electrode materials for high-energy-density hybrid supercapacitors

A novel binder-free copper oxide@nickel sulfide (CuO@NiS) composite electrode was successfully synthesized on Ni foam via a two-step hydrothermal method for high-performance supercapacitor applications. The hierarchical morphology of the CuO@NiS composite, consisting of CuO microspheres decorated with NiS nanoparticles, offers a large surface area and facilitates electrolyte ion diffusion. The electrode exhibited a high specific capacity of 130.09 mA h g- 1 at 1 A g- 1 and excellent cycling stability with 92.64 % capacity retention after 5000 cycles. A hybrid supercapacitor (HSC) assembled with CuO@NiS and activated carbon (AC) electrodes demonstrated a wide operating voltage of 1.6 V, a maximum energy density of 33.96 W h kg- 1 at 368.69 W kg- 1, and excellent cycling stability of 94.57 % over 5000 cycles. The superior performance of the CuO@NiS composite electrode is attributed to its unique morphology, enhanced electrolyte accessibility, and synergistic interaction between CuO and NiS components. These findings highlight the potential of CuO@NiS as a promising electrode material for high-performance supercapacitors.