Synergetic Electrochemical Behavior of NiO and Activated Carbon Composites for Advanced Supercapacitors

Nickel oxide (NiO) nanoparticles were prepared using the co-precipitation method, and then activated carbon (AC) powder was blended with NiO with percentages of 25, 50, and 75%. X-ray diffraction patterns confirmed the formation of both NiO and NiO/AC nanocomposite structures. The NiO and NiO/AC nanocomposite powders were also fully characterized by Brunauer–Emmett–Teller (BET), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), which evidenced that the nanoparticles were uniformly distributed with the AC. The NiO and NiO/AC nanocomposite powders were investigated as supercapacitor electrode materials in a 6 M KOH aqueous solution. NiO nanoparticles electrode delivered a specific capacitance of 235 F g^− 1 at a current density of 1 A g^− 1. In comparison, it was found that the AC50 (NiO/AC 50/50%) nanocomposite possessed the best electrochemical performance. It achieved specific capacitances of 325 F g^− 1 and 215 F g^− 1 at current densities of 1 and 5 A g^− 1, respectively. For practical application, the AC50 nanocomposite coin cell was assembled in 1 M TEABF₄/PC organic electrolyte with good electrochemical performance. It delivered a specific capacitance of 72 F g^− 1 at 1 mA g^− 1. It demonstrates remarkable electrochemical reversibility with 99.3% coulombic efficiency and 89.9% capacitance retention after 4000 cycles at the current density of 5 mA g^− 1. It also reveals a high specific energy of 62.5 Wh kg^− 1 and a specific power of 638 W kg^− 1 at a current density of 0.5 A g^− 1. Still, it exhibits a specific energy of 8.7 Wh kg^− 1 and a specific power of 6944 W kg^− 1 at a current density of 5 A g^− 1, estimating this material’s potential for use in supercapacitors.