A sustainable closed-loop method of selective oxidation leaching and regeneration for lithium iron phosphate cathode...

A sustainable closed-loop method for recovering waste lithium iron phosphate batteries is developed in this paper. Li⁺ was selectively leached from cathode materials in a system of NaHSO₄ and H₂O₂. Under the optimal conditions of leaching temperature of 65 °C, 1.1 times molar quantity NaHSO₄, 2 vol% H₂O₂, solid-liquid ratio of 100 g/L and leaching time of 15 min, the leaching efficiency of Li can reach 99.84%, while Fe is only 0.048%. Meanwhile, XRD, FTIR, XPS and TEM analysis were carried out to explore the conversion mechanism in the oxidation leaching process of the original raw and leaching products. Li⁺ in the filtrate was precipitated with Na₂CO₃ and converted into Li₂CO₃. The precipitated salty wastewater can be converted into leaching agent for recycling by adding a certain amount of sulfuric acid. The recycled products are used to synthesize LiFePO₄ materials, and regenerated LiFePO₄ materials show good electrochemical properties. The discharge capacity displays 141.3 mAhg^-1 at 1C, with the capacity retention rate of 99.4% after 200 cycles. This study provides a sustainable closed-loop process for recycling and reuse of waste LiFePO₄ batteries, which promotes resource conservation and environmental protection.