The present investigation describes the synthesis of uniform sponge-like Ni(OH)2 nanoparticles on stainless steel substrates by a two-step successive ionic layer adsorption and reaction method; the study also explores electrochemical properties. The formation of the β-phase Ni(OH)2 and it’s nanocrystallinity are confirmed by X-ray diffraction and X-ray photoelectron spectroscopy studies. Scanning electron microscopy revealed the formation and random distributions of porous and sponge-like nanoparticles with high Brunauer–Emmett–Teller surface area of 56.4 m2 g−1. The maximum specific capacitance of 428 F g−1 was obtained at 5 mV s−1 in a 2 M KOH electrolyte, indicating promising supercapacitor applications with remarkable rate capability. These results suggest the importance of rational design and synthesis of thin nanomaterials for high-performance energy applications.