Sustainable Recovery of Cathode Materials from Spent Lithium-Ion Batteries Using Lactic Acid Leaching System

An environmentally friendly leaching process for recycling valuable metals from spent lithium-ion batteries is developed. A sol-gel method is utilized to resynthesize LiNi_1/3Co_1/3Mn_1/3O₂ from the leachate. Lactic acid is chosen as a leaching and chelating agent. The leaching efficiency is investigated by determining the contents of metal elements such as Li, Ni, Co, and Mn in the leachate using inductively coupled plasma optical emission spectroscopy. The spent cathode materials for the pretreatment process and the regenerated and freshly synthesized materials are examined using X-ray diffraction and scanning electronic microscopy. The results show that the leaching efficiencies of Li, Ni, Co, and Mn reached 97.7, 98.2, 98.9, and 98.4%, respectively. The optimum conditions are lactic acid concentration of 1.5 mol L^-1, solid/liquid ratio of 20 g L^-1, leaching temperature of 70 °C, H₂O₂ content of 0.5 vol %, and reaction time of 20 min. The leaching kinetics of cathode scrap in lactic acid fit well to the Avrami equation. Electrochemical analysis indicate that the regenerated LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials deliver a highly reversible discharge capacity, 138.2 mA h g^-1, at 0.5 C after 100 cycles, with a capacity retention of 96%, comparable to those of freshly synthesized LiNi_1/3Co_1/3Mn_1/3O₂ cathodes.