In this research, NiO, a vital transition metal known for its excellent electrochemical properties, was successfully synthesized under alkaline conditions using the precipitation method. Alterations in calcination temperatures between 720 and 800°C in an argon atmosphere yielded different NiO crystal sizes. The smallest crystals, obtained at 760°C, exhibited the highest specific capacity, reaching 991.2 mAh g–1 at 0.5 C. The NiO electrode showed an impressive capacitance retention rate of approximately 98% over 300 cycles. This method offers high-performance NiO materials with extended life cycles, making it a strong candidate for use in lithium-ion battery anodes. Using saturated potassium hydroxide (KOH) aids in nickel oxide precipitation, improving performance. Recyclable KOH enhances potential for large-scale anode material production.