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

Funding Information: This research has been funded by BATCircle2.0 project (Grant number 44886/31/2020 ) and the Finnish Steel and Metal Producers' Fund. This work made use of RawMatters Finland Infrastructure (RAMI) based in Aalto University and funded by the Academy of Finland. Publisher Copyright: © 2021 The Authors 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 kc = 21.8 × 10−3 min−1). However, such high chloride concentrations also significantly increased the Cu consumption and decreased its reductive efficiency.