Abstract
Spent lithium iron phosphate (LiFePO4, LFP) batteries contain considerable amounts of Fe; however, most conventional recycling processes primarily target Li recovery, while Fe is often discarded or utilized as a low-value residue. In this study, an integrated pyrometallurgical refining process was developed to recover and purify Fe from spent LFP battery-derived materials through sequential Cu and P removal. Following decarbonization and oxidative smelting, an FeO-rich slag was subjected to carbothermic reduction to produce an Fe–Cu–P alloy. Cu was subsequently removed by FeS-assisted sulfidation and slag refining, and the remaining P was removed by oxidative dephosphorization using Fe2O3 and a CaO–SiO2-based slag. The effects of reaction temperature, Cu molar ratio, and slag basicity were systematically investigated. The optimum Cu-removal condition was obtained at 1400 °C with a Cu molar ratio of 2:1, under which the Cu content decreased from 6.44 to 1.47 wt.%, corresponding to an estimated Cu-removal efficiency of 77.45%. Subsequent dephosphorization was strongly influenced by slag basicity. Increasing the CaO/SiO2 ratio from 2.0 to 3.0 decreased the residual P content from 1.33 to 0.042 wt.% and increased the phosphorus distribution ratio from 3.36 to 138.57. At a basicity of 3.0, the P removal efficiency reached 99.44%. Under the optimum conditions, the final metallic product exhibited a calculated Fe purity of 98.55% with an Fe recovery of 93.27%. The results demonstrate that sequential sulfidation and oxidative dephosphorization can effectively remove Cu and P while minimizing Fe loss, providing a feasible pyrometallurgical route for upgrading Fe recovered from spent LFP batteries into a reusable metallic resource.