Investigation of Spent Coin Cells for Recovery of Li and Mn Values

Lithium-based coin cells are primarily used for portable electronic devices and comprise lithium and manganese in the electrode material as the LiMn₂O₄ phase. Various pre-treatment methods, such as thermal exposure, pyrolysis, and hydrogen reduction, are investigated for the selective recovery of Li and Mn. The effect of pre-treatment on phase dissociation and metal recovery is evaluated. Thermal treatment and pyrolysis result in partial phase dissociation in the 450–750 °C temperature range, causing lower Li extraction. However, hydrogen reduction at 650 °C is suitable for selective Li dissolution (~ 86% using 10% H₂ and ~ 96% in pure H₂ atmosphere). The dissociation of the LiMn₂O₄ phase, formation of LiOH, and microstructural features influence the Li extraction. For Mn recovery, reductant-free sulfuric acid leaching of the water-leached residue results in 95.0% and 99.3% extraction using 10% H₂ and pure H_2, respectively. Further, the manganese from the leach solution is recovered as manganese oxide (Mn₃O₄) nanoparticles (96% purity) by precipitation, which can be used as a precursor for battery and supercapacitor applications. It is calculated that 315 g of the coin cells (100 g of electrode material) will yield 17.8 g of Li₂CO₃ and 67.9 g of Mn₃O₄ nanoparticles.