Recovery of LiFePO4 from used lithium-ion batteries by sodium-bisulphate-assisted roasting

The use of eco-friendly and low-consumption regeneration technology to retrieve valuable components from lithium-ion batteries (LIBs) helps in alleviating resource shortages and environmental pollution. This paper details a sulphated roasting procedure for recycling spent LiFePO4 (LFP) batteries. Thermal performance characterisation and thermodynamic calculation results show that NaHSO4·H2O can promote lithium extraction from the Fe–P–O structure and convert it into a water-soluble sulphate. The remaining Fe, P, and O combine to form insoluble compounds. After solid-liquid separation, lithium-leaching solution and iron-containing residue were obtained for the preparation of Li3PO4 and FePO4. Here, a systematic study was conducted to determine the effects on Li leaching of the mass ratio of NaHSO4·H2O to LFP, roasting temperature, roasting time and water leaching time. The recovery technique offers a high degree of selectivity, enables acid-free leaching, and reduces environmental damage. In addition, the LFP produced by the recycled product has excellent physical and chemical properties, thus illustrating the feasibility of the process. Overall, this study offers a reliable reference for future environmental protection, selective recovery, and process design of spent LIBs.