From stainless steel to batteries: industrial-scale closed-loop hydrometallurgical integration for ferronickel-to-precursor conversion

In lithium-ion battery (LIBs) production, raw material costs account for 60–80 % of total manufacturing expenses. The extraction of critical metals, as the first step in the entire process from mineral processing to battery fabrication, represents the most costly and pollutant-intensive stage. This work focuses on clean and low-cost preparation of LIBs cathode precursors through fundamental study and industrial validation. Using crude ferronickel derived from electric furnace smelting of laterite nickel ore as raw material, systematic investigations were conducted to optimize the roasting, acid leaching, and precipitation processes for preparing FePO 4 and mixed hydroxide precipitate (MHP)/nickel cobalt manganese oxide (NCM), and a novel hydrometallurgical integration flow path based on "atmosphere controlled roasting activation – atmospheric sulfuric acid leaching – gradient precipitation" was proposed. Under optimized laboratory conditions, leaching efficiencies exceeding 99 % for Ni, Co, and 96 % for Fe were achieved from ferronickel, and over 97 % of Fe was recovered as FePO 4 , while more than 98 % of Ni and Co were converted into MHP/NCM products. The world's first demonstration production line utilizing this technology has been commissioned, with detailed analysis of industrial processes and product characteristics. Compared to existing laterite nickel ore extraction technologies, this innovative approach enables short-process synthesis of cathode precursor materials, significantly reduces leaching temperature and tailing residue emissions, demonstrating substantial economic and environmental benefits. This work establishes a paradigm for sustainable battery material production, aligning with circular economy principles through multi-component utilization of laterite nickel resources.