Reagent-minimized selective lithium extraction from spent LiMn2O4 and LiFePO4 batteries via self-driven redox for closed-loop regeneration

To address high chemical reagent consumption and poor selective lithium extraction in recycling mixed cathode materials from spent LiMn 2 O 4 (LMO) and LiFePO 4 (LFP) batteries, this study proposes a synergistic hydrometallurgical process without external oxidants/reductants, inspired by the Li-ion intercalation/deintercalation mechanism in lithium-ion batteries (LIBs). The process achieves efficient and selective Li leaching via the coupled redox reaction between LMO and LFP in an acidic system. Single-factor experiments determined the optimal leaching conditions: 0.8 mol/L HCl, LMO: LFP mass ratio of 1.6:1, liquid-to-solid ratio of 12 mL/g, 90 °C, and 6 h. Under these conditions, Li leaching efficiency reached 99.19 ± 0.93%, while Fe and Mn leaching efficiencies were only 0.41 ± 1.25% and 25.07 ± 0.84%, respectively. Kinetic analysis shows Li leaching is controlled by solid product layer diffusion, with an apparent activation energy of 6.94 kJ/mol. Thermodynamic and characterization analyses confirm that in the acidic environment, LMO reduction and LFP oxidation occur simultaneously; Mn and Fe precipitate into the slag phase as MnO 2 , Mn 3 (PO 4 ) 2 , and FePO 4 , facilitating efficient Li release. Subsequent pH adjustment of the leachate enabled the preparation of Li 2 CO 3 and Mn 3 O 4 , as well as LMO regeneration. Life cycle assessment indicates this self-driven redox process for preferential Li recovery from mixed spent LIBs has advantages of low energy consumption, minimal reagent usage, high profitability, and significant environmental benefits. It provides an efficient solution for synergistic treatment and closed-loop recycling of mixed spent LIBs, aligning with green chemistry and circular economy principles.