Utilizing Cu⁺ as catalyst in reductive leaching of lithium-ion battery cathode materials in H₂SO₄–NaCl solutions

In this study, we introduce a novel waste battery leaching system that utilizes elemental copper both as a reductant and catalyst in a sulfuric acid-based lixiviant. Adding chloride ions into the solution stabilizes Cu⁺ species as complexes, which facilitates their use as catalysts for electron transfer between LiCoO₂ and copper. With this leaching system, Co, and Li dissolutions of over 90% were achieved within two hours under mild conditions (1 M H₂SO₄, 0.2 M NaCl, and 30 °C), thereby avoiding the use of high temperatures, concentrated acids, and external reductants – like H₂O₂ – that are commonly utilized in battery recycling studies. The XRD analyses of leach residues showed that Cu dissolution proceeded via an intermediate step where solid CuCl precipitated on the surface of Cu, inhibiting the dissolution of both Cu and LiCoO₂. The detrimental effects of CuCl precipitation were avoided by increasing the chloride concentration to ≥1.6 M, which allowed for very fast leaching kinetics (reaction rates up to k_c = 21.8 × 10⁻³ min⁻¹). However, such high chloride concentrations also significantly increased the Cu consumption and decreased its reductive efficiency.