Mechanistic and Kinetic Investigation of Synergistic Methanesulfonic and DL–Malic Acids Leaching System for Battery Cathode Recycling

ABSTRACT

Organic acids have been considered as eco‐friendly leaching agents, but their utilization has been limited due to low pulp density and high costs. In this study, methanesulfonic acid (MSA), with high acidity, and DL‐malic acid (MA), with excellent chelating ability and cost‐effectiveness, were combined to develop a novel hybrid organic leaching system. 2.4 M MSA–0.6 M MA exhibited superior leaching performance for LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , achieving leaching efficiencies for Li, Ni, Mn, and Co above approximately 93% within 1 h at a pulp density of 80 g L ⁻¹ , exhibiting the highest pulp density and superior cost‐effectiveness among various organic systems. The synergetic leaching mechanism combining acidolysis and complexolysis was not only investigated through theoretical kinetic modeling but also experimentally revealed through residue analysis using X‐ray photoelectron spectroscopy (XPS) and reductive ability analysis using cyclic voltammetry (CV). Based on the comprehensive examinations, it was revealed that MSA rapidly dissolved Li and low‐valence transition metals through acidolysis, while MA enhanced leaching efficiency through chelation and reduction of high‐valence transition metals. Consequently, mechanistic and kinetic insights into the hybrid organic leaching were theoretically and experimentally validated, and the findings are expected to provide a fundamental basis for developing sustainable organic acid‐based leaching technologies for next‐generation cathode recycling.