Environmentally Friendly Recovery of Li2CO3 from Spent Lithium-Ion Batteries by Oxidation and Selective Leaching Process

The extraction of valuable metals from spent Ni–Co–Mn oxide (NCM) cathodes typically encounters the use of strong acids or alkalis, often leading to secondary pollution. Herein, an environmentally friendly recovery route for the selective extraction of lithium (Li) by using sodium persulfate (Na₂S₂O₈) as the sole leaching agent was proposed. Under the optimized conditions, the leaching efficiency of Li achieved 98.02%, and the selective leaching efficiency of Li was 94.80%. Moreover, the lithium carbonate (Li₂CO₃) product was recovered from the Li-rich filtrate with a high purity of 99.5%. The mechanism of Li selective leaching was revealed by means of wet chemistry, kinetics, thermodynamics, and solid-phase analysis. During selective leaching, free radicals SO₄^•– and ^•OH, hydron ion (H⁺), and sodium ion (Na⁺) were generated by Na₂S₂O₈. These free radicals can increase the redox potential of the leaching system. Under these conditions, Co and Mn elements were both maintained in a high valence state and the cathode structure was collapsed, thus contributing to the leaching of Li. The proposed environmentally friendly recovery process of Li from spent NCM cathodes is promising for practical applications, offering significant economic benefits.