Low-acid leaching of lithium-ion battery active materials in Fe-catalyzed Cu-H₂SO₄ system

Leaching of active cathode materials of Li-ion batteries (LIB) is a hotly contested topic. In the published literature, the best processes utilize concentrated acid (e.g. 2–3 M H₂SO₄) and elevated temperatures for waste LIB leaching, along with unstable reduction reagents such as H₂O₂. In this study, we demonstrate the dissolution of LiCoO₂ (LCO) in a low-acid leaching system that utilizes typical battery elements which can be found in impure, recycled black masses; Fe²⁺ as a reducing agent towards LCO, and Cu as a reducing agent towards Fe³⁺. We show for the first time that the Cu-Fe²⁺-H₂SO₄ system can provide an excellent performance in dissolving LCO materials at low acid environment and near-room temperature (T = 30 °C), even to the point where the acidity of the solution decreases to pH = 1.89 while reaching Co extraction of 92%. To the best of our knowledge, such high leaching efficiency has not been previously reported under such mild conditions. Nowadays, recyclability of the process waters may also be important, and herein we highlighted the influence of Na₂SO₄ on leaching of LCO active materials as well in this system. Minimization of the lixiviant concentration and temperature is beneficial in allowing decrease in chemical and energy consumption. High pH operation also can support further downstream processing, helping to avoid the problem of sodium accumulation towards the end-stage where lithium is recovered.