Facile and efficient recycling of cathode materials of spent lithium manganate batteries

Abstract

A simple scheme of selective lithium leaching by direct oxidation was proposed. The thermodynamic feasibility of this new method was verified by the E–pH diagram of the Li–Mn–H₂O system. Sodium persulfate Na₂S₂O₈ was selected as the oxidant to oxidize LiMn₂O₄ to MnO₂, and subsequently, lithium was de-intercalated from the crystal lattice. The experimental results show that under the optimum conditions, 97% of Li is released into the solution in 120 min, while almost all the Mn remains in the leaching residue. The kinetic study results suggest that selective leaching of Li is controlled by a chemical reaction according to the Avarami model. Furthermore, XRD, XPS, and FT-IR spectroscopy were used to investigate the leaching mechanisms. The content of the LMO phase decreases gradually while the MnO₂ phase increases with the lithium extraction, but the spinel structure of lithium manganate is not damaged throughout the process. Finally, a closed-loop process for recycling spent lithium manganate batteries was proposed, which is also suitable for recycling other types of spent LIBs.