Abstract:With the continuous surge in the number of retired lithium-ion batteries, developing an environmentally friendly, cost-effective, and efficient recycling process for cathode materials has become a key scientific challenge for the sustainable development of the new energy industry. Conventional hydrometallurgical recycling technologies typically rely on strong acids combined with external reducing or oxidizing agents, which lead to high reagent consumption and operating costs and generate large volumes of metal-containing wastewater, posing significant environmental and disposal challenges. Therefore, it is of great scientific and practical significance to develop a novel recycling process that eliminates the need for external chemical additives while enabling the synergistic recovery of multiple components. In this study, an additive-free recycling strategy based on an intrinsic synergistic redox mechanism is proposed for a mixed system of spent LiFePO4 (S-LFP) and LiMn2O4 (S-LMO). This approach fully utilizes the electrochemical potential difference between different electrode materials to drive spontaneous electron transfer reactions under mildly acidic conditions, with acid consumption reduced by nearly half compared to conventional methods. Specifically, Fe2+ ions are first leached from S-LFP and act as internal reducing agents in the solution; these Fe2+ ions subsequently reduce Mn3+ to Mn2+ in S-LMO, thereby promoting the efficient co-leaching of Mn and Li. This process achieves a synergistic recycling of the spent materials, reaching nearly 100% leaching efficiency for Mn and Li under mild conditions (20 ℃, 40 min), demonstrating excellent reaction kinetics and synergistic effects. Meanwhile, Fe species are selectively converted into insoluble FePO4 precipitates, allowing for easy solid–liquid separation. The resulting FePO4 can directly serve as a precursor for regenerating LiFePO4 (R-LFP). The leachate is further processed by adjusting the pH with ammonia to precipitate Mn(OH)2, followed by the addition of Na2CO3 to obtain Li2CO3, thereby achieving the full recovery and reuse of Fe, Mn, Li, and P elements. The regenerated R-LFP exhibits a uniform spherical morphology with a narrow particle size distribution and a well-maintained crystal structure. Electrochemical testing of the regenerated material exhibits an excellent discharge capacity of 134.96 mA·h/g and a capacity retention of 99.4% after 200 charge-discharge cycles, indicating outstanding cycling stability and structural reversibility. This work systematically elucidates the self-driven redox mechanism between spent electrode materials and achieves closed-loop recovery of all constituent elements with high-value-added material regeneration. The entire process relies solely on spontaneous electron transfer among the waste materials, without the need for external oxidizing or reducing agents, significantly reducing energy consumption, reagent usage, and secondary pollution. The proposed synergistic redox strategy overcomes the limitations of conventional hydrometallurgical processes and provides a new theoretical foundation and practical pathway for the green, efficient, and sustainable recycling of multi-component spent lithium-ion batteries, showing great potential for large-scale industrial application. Close-