CO2-assisted ascorbic acid leaching for metal recovery from spent NCM cathodes and battery regeneration.

چکیده اصلی

The recovery of critical metals from spent Ni-Co-Mn (NCM) cathodes commonly requires concentrated acids, auxiliary reductants, or energy-intensive treatment. Here, pressurized CO2-ascorbic acid leaching was integrated with leachate-based NCM811 regeneration. Under the optimized condition, 0.30 mol/L ascorbic acid, 7 MPa CO2, a solid-to-liquid ratio of 20 g/L, and 25 °C, Li was completely extracted within 80 min, while the extraction efficiencies of Ni, Co, and Mn reached 98.3 %, 97.1 %, and 97.2 %, respectively, without a separately added reducing agent. Control experiments confirmed that the increase in metal extraction arose from the coupled action of pressurized CO2 and ascorbic acid rather than from physical pressurization or CO2 alone. Equilibrium analysis further indicated that ascorbic acid provided the principal acidity and reducing capacity, while the dissolved CO2/H2CO3/HCO3- equilibrium can maintain protons availability during lattice dissolution. Kinetic fitting showed that the leaching behavior was best described by the product-layer diffusion model. SEM-EDS, XRD, and XPS revealed particle fragmentation, progressive disruption of layered structural order, and changes in surface valence states. The Li/Ni/Co/Mn-rich leachate was further converted into regenerated NCM811, which delivered discharge capacity of 180 mAh/g initially, retained 150 mAh/g after 200 cycles, and maintained 55-60 mAh/g at 5C. This approach achieves high metal extraction at room temperature using a relatively low organic-acid concentration without separately added reducing agent, while returning the recovered metals to functional cathode production.

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