Toward Low-Cost\nProduction of Battery-Grade Iron Phosphate:\nUnlocking the Value of Mill Scale

The utilization of iron from the\nmill scale for the production\nof battery-grade iron phosphate offers a solution for the high-value\nutilization of the mill scale. In this work, a cyclic copper powder\nreduction-enhanced leaching approach was proposed for the efficient\nextraction of iron from the mill scale to prepare battery-grade iron\nphosphate. Under the optimized conditions, the iron leaching rate\nreached 99.72%. The introduction of a copper reductant changed the\nleaching mechanism from a combination of internal diffusion and surface\nchemical reactions to solely internal diffusion. The copper can be\nrecycled with a recovery rate of 99.996%. After five cycles, the leaching\nrate of iron remained consistently above 90%. Meanwhile, aluminum\nwas effectively reduced to 43.83 mg/L. The as-synthesized iron phosphate\nmet the battery-grade standard and had excellent electrochemical performance\nwith almost no loss in discharge capacity after 100 cycles. This study\npioneers a novel approach for the reductive leaching technology and\nprovides a new insight for the sustainable utilization of mill scale.