A sustainable closed-loop method of selective oxidation leaching and regeneration for lithium iron phosphate cathode materials from spent batteries

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.