<p>Black NiO nanoflakes synthesized using a simple co-precipitation method were investigated as supercapacitor electrode material. The structural, morphological, and compositional properties of the nanoflakes were analyzed, revealing a uniform size distribution and impurity-free composition. Electrochemical characterizations conducted in 6 M KOH electrolyte revealed that black NiO nanoflakes demonstrated a high specific capacitance of 340.21 F g⁻¹ at 2 A g⁻¹, a low bulk resistance of 1.41 Ω, and retaining 75% capacitance at higher current density. The electrode demonstrated excellent cycling stability, retaining 65.32% of its specific capacitance after 6000 GCD cycles. The comparison with previously reported works highlights the potential of black NiO nanoflakes as a promising material for future supercapacitor applications.</p>