Closed-Loop Recycling of Spent LiNi_<i>x</i>Co_<i>y</i>Mn_{1–<i>x</i>–<i>y</i>}O₂ Batteries Based on Liquid-Phase Reduction-Driven Delithiation Conversion

The recycling of spent lithium-ion batteries (LIBs) is critical to the sustainable development of the new energy industry. However, traditional recycling processes often face challenges, such as high-energy consumption, complex procedures, and excessive use of corrosive reagents. In this study, an advanced liquid-phase reduction-driven strategy is employed to selectively extract Li from spent LiNi_<i>x</i>Co_<i>y</i>Mn_{1-<i>x</i>-<i>y</i>}O₂ (NCM) batteries and regenerate the NCM cathode materials. During the delithiation process, Li⁺ is leached into the liquid phase from spent NCM material, while the Ni, Co, and Mn elements remain in the solid phase, with N₂H₄·H₂O serving as the sole reagent. Under optimal reaction conditions, the Li leaching efficiency reaches 98.9%. Thermodynamic analysis and XRD results reveal that the delithiation reaction involves the transformation of spent NCM into a layered Ni-Co-Mn hydroxide (Ni/Co/Mn(OH)₂). Additionally, the Li-rich leachate can be recovered as Li₂CO₃ products, while the Ni-, Co-, and Mn-enriched residues serve as the precursor for regenerating NCM cathode materials. The regenerated NCM exhibits a discharge-specific capacity of 183.0 mAh g^-1 at 1C with a retention rate of 79.9% after 300 cycles. Overall, this work provides novel insights into the efficient closed-loop recycling of spent NCM batteries by leveraging the delithiation conversion technique.