Synergistic Pyrolytic Recovery of Valuable Metals from Spent NCM Cathodes via MnCl2-Coffee Ground Co-Treatment

With the rapid increase in the number of retired lithium-ion batteries, the green recovery of valuable metals such as Li, Ni, Co, and Mn from spent ternary cathode materials has attracted extensive attention. Existing biomass-only pyrolysis processes suffer from the encapsulation of lithium salts by excessive biochar. At the same time, chloride roasting usually requires relatively high chloride dosages, which may introduce external impurities or lead to the co-leaching of transition metals. Therefore, to address the respective limitations of biomass-only pyrolysis and chloride roasting and fill the research gap in synergistic biomass–chloride roasting, this study proposed a synergistic pyrolysis system using trace MnCl2 and coffee grounds (CGs) to selectively recover valuable metals from spent NCM ternary cathode black mass (SNCM). The synergistic pyrolysis mechanism underlying the co-treatment of spent NCM cathodes with MnCl2 and CGs was verified for the first time. In the system, CGs provide the primary reducing environment, while trace MnCl2 synergistically promotes Li+ migration and lattice deconstruction via its Lewis acid effect. Lithium was converted into Li2CO3, Ni and Co ions were reduced to their metallic states, and manganese was converted into MnO. A Li leaching efficiency of 95.5% was achieved under the optimized conditions (SNCM:MnCl2:CGs mass ratio of 1:0.06:3, 650 °C, and 120 min). This halide salt–biomass synergistic pyrolysis approach enables selective lithium extraction coupled with high-efficiency transition metal recovery, demonstrating notable economic viability and offering a sustainable paradigm for the green valorization of spent lithium-ion batteries.