CO₂-assisted selective lithium extraction and closed-loop regeneration of spent NCM cathodes toward cleaner battery...

The growing volume of spent lithium-ion batteries (LIBs) has increased the need to recover valuable materials while limiting environmental impacts. Conventional hydrometallurgical recycling of spent NCM cathodes generally dissolves Li, Ni, Co, and Mn together, resulting in complex downstream separation. Selective Li recovery and direct cathode regeneration are usually developed separately. Integrating them requires efficient Li removal while retaining a transition-metal matrix suitable for subsequent reconstruction. In this study, lignite carbothermal reduction was coupled with CO₂-assisted aqueous leaching and molten-salt relithiation. During roasting, lattice-bound Li was converted into leachable lithium-containing phases, whereas Ni, Co, and Mn were retained predominantly in water-insoluble phases. The carbonate/bicarbonate equilibrium established by dissolved CO₂ subsequently promoted the selective transfer of Li into the aqueous phase. Under the optimized conditions, lithium extraction reached 99.8% within 30 min, and Li₂CO₃ with a purity 98.6% was recovered. The transition-metal-rich residue was then subjected directly to molten-salt relithiation and calcination, avoiding complete dissolution and separate recovery of Ni, Co, and Mn. The regenerated cathode exhibited a well-defined α-NaFeO₂-type layered structure and delivered an initial discharge capacity of 202 mA h g^-1 at 0.5C, with 103 mA h g^-1 remaining after 100 cycles. A preliminary economic assessment estimated a net benefit of approximately USD 831.23 per ton of processed feedstock. This integration retains the value of both Li and the transition-metal residue while reducing downstream processing. Further work should focus on microstructural and interfacial control of the regenerated cathode and scale-up validation using compositionally variable feedstocks.