Selective leaching process for efficient and rapid recycling of spent lithium iron phosphate batteries

With the continuous development of new energy vehicles, the number of decommissioned lithium iron phosphate (LiFePO₄) batteries has been constantly increasing. Therefore, it is necessary to recover metal from spent LiFePO₄ batteries due to the high potential for environmental protection and high resource value. In this study, sodium persulfate (Na₂S₂O₈) was selected as the oxidant to regulate and control the oxidation state and proton activity of the leaching solution through its high oxidizing ability. Selective recovery of lithium from LiFePO₄ batteries was achieved by oxidizing LiFePO₄ to iron phosphate (FePO₄) during the leaching process. This paper reports an extensive investigation of the effects of various factors, including the acid concentration, initial volume fraction of the oxidant, reaction temperature, solid-liquid ratio, and reaction time, on lithium leaching. Li⁺ reached a high leaching rate of 93.3% within 5 minutes even at a low concentration of sulphuric acid (H₂SO₄), and high-purity lithium carbonate (Li₂CO₃) was obtained through impurity removal and precipitation reactions. In addition, the leaching mechanism was analysed by both X-ray diffraction and X-ray photoelectron spectroscopy characterization. The results show that the obtained high lithium-ion (Li⁺) leaching efficiency and fast Li⁺ leaching time can be ascribed to the superior oxidizing properties of Na₂S₂O₈ and the stability of the crystal structure of LiFePO₄ during the oxidative leaching process. The adopted method has significant advantages in terms of safety, efficiency and environmental protection, which are conducive to the sustainable development of lithium batteries.