An Effective Tandem Leaching Method for Recovering Precious Metals from Depleted Ternary Lithium-Ion Batteries

The increasing volume of spent ternary lithium batteries necessitates the development of an environmentally friendly and efficient recycling process tailored for these batteries. This paper introduces an innovative leaching system that employs oxalic acid and its derivative, Deep Eutectic Solvents (DES), as leaching agents, specifically designed to selectively recover Li and other valuable metals from the cathode materials of discarded ternary lithium batteries, Li(NixCoyMn1-x-y)O2 (NCM). These findings indicate that oxalic acid is capable of selectively leaching Li without the need for reducing agents, whereas DES effectively segregates and leaches other valuable metals. The optimal parameters determined through orthogonal experiments for the initial leaching stage included a solid-to-liquid ratio of 15 g L−1, leaching duration of 3 h, temperature of 75 °C, and stirring speed of 400 rpm, resulting in a Li leaching rate of 99.95%. In the subsequent step, DES enabled the precipitation of Ni and the leaching of Co and Mn within 2 h at 110 °C, achieving recovery rate of 99.88% for Ni, 98.1% for Co, and 90% for Mn, while also significantly optimizing the recovery conditions. This breakthrough may offer an environmentally benign and effective method for the selective recovery of Li and other valuable metals.