High-efficiency recovery of lithium from waste lithium-ion batteries using a steam-assisted calcium-based carbon thermal reduction process

A novel steam‑calcium‑carbon source ternary synergistic reduction system was constructed for selective lithium extraction from spent NCM cathode materials. Under the optimized conditions (800 °C, 90 min, 15% C, 20% CaO, 0.3 mL/min water flow), the lithium leaching efficiency reached an ultrahigh level of 96.90%. • The dual function of CaO was clarified: immobilizing fluorine to prevent LiF formation and lithium loss, and fixing CO 2 to regulate reaction atmosphere and reduce carbon emissions; steam in-situ generated H 2 /CO via water-gas shift reaction as high-efficiency reducing agents. • This process replaced traditional acid-base reagents with water vapor, avoided toxic and hazardous substance introduction, and enabled recovery of gaseous products (H 2 /CO), achieving green and sustainable lithium recovery with low pollutant and greenhouse gas emissions. Lithium-ion batteries (LIBs) contain precious metals such as lithium, cobalt, and nickel, making their recycling crucial for resource conservation and environmental protection. However, existing recycling technologies typically rely on acidic or alkaline reagents, presenting issues such as high energy consumption and severe pollution. Conventional carbon thermal reduction or catalyst-based recovery technologies exhibit drawbacks such as harsh reaction conditions, poor selectivity, and limited lithium extraction efficiency, often resulting in fluoride pollution and substantial carbon emissions. This paper proposes a novel steam-assisted calcium-based calcination-reduction process, establishing a ternary synergistic reduction system involving a steam‑calcium‑carbon source to achieve highly efficient and selective extraction of lithium from spent ternary lithium battery cathode materials (SNCM). After optimizing key parameters, the optimal conditions were determined as follows: calcination temperature of 800 °C, duration of 90 min, carbon addition of 15%, CaO addition of 20%, and water flow rate of 0.3 mL/min. Under these conditions, the lithium leaching rate reached 96.90%. Combining multiple characterization techniques and thermodynamic calculations, the reaction mechanism was revealed: Water vapor generates H 2 and CO in situ via the water-gas shift reaction to serve as reducing agents. These agents synergistically decompose SNCM with carbon, converting lithium into water-soluble Li 2 CO 3 , reducing nickel and cobalt to metallic states, and transforming manganese into MnO. CaO sequesters fluorine to prevent lithium loss and traps CO 2 to reduce carbon emissions, ensuring selective lithium recovery. This process replaces traditional acid-base reagents with steam, eliminating the introduction of toxic or hazardous substances. The gaseous products are recoverable, reducing pollutant and greenhouse gas emissions. It provides a viable technical route for the efficient and environmentally friendly extraction of lithium from spent lithium-ion battery cathode materials.