<p>Nickel is a critical metal widely used in lithium-ion batteries and stainless steel production. Traditional nickel–iron alloy processing relies on pyrometallurgical methods involving sulfurization and complex extraction steps, while hydrometallurgical approaches often require extensive grinding and sulfurization to enhance leaching efficiency, leading to high energy consumption and costs. This study introduces an innovative oxidative pressure acid leaching process that directly extracts nickel from large-particle nickel–iron alloys without pre-sulfurization or grinding. By optimizing parameters such as acid concentration, temperature, and oxygen pressure, the process achieves 98.39% nickel leaching efficiency, with iron leaching as low as 1.62%. The selective extraction is attributed to the stabilization of iron oxide phases under controlled conditions, minimizing iron dissolution while promoting nickel recovery. This streamlined hydrometallurgical approach significantly reduces energy consumption and operational complexity, offering a greener, cost-effective solution. In addition, the iron-rich residue (mainly Fe₂O₃) is efficiently utilized to synthesize lithium iron phosphate (LFP) battery materials via a short-route method. The synthesized LFP demonstrated excellent electrochemical performance, including a high and stable discharge capacity of 125 mAh/g. This integrated process provides a sustainable pathway for converting nickel–iron alloys into high-value battery materials, reducing industrial waste and simplifying processing steps.</p> Graphical Abstract <p></p>