Lithium recovery from mixed spent LFP-NMC batteries through atmospheric water leaching

Selective lithium recovery from a mixture of LFP-NMC spent lithium batteries presents significant challenges due to differing structures and elemental compositions of the batteries. These differences necessitate a distinct recycling pathway for each, complicating the process for the mixture. This study explored a carbothermal reduction approach combined with water leaching under atmospheric conditions to achieve a selective lithium recovery. For individual NMC black mass, at the optimal carbothermal conditions (950 °C, 15 °C/min, 2 h), lithium recovery of 95.7 ± 0.31% with 100% selectivity could be achieved. However, when the black mass was mixed with that of LFP in a 50:50 ratio, the recovery dropped to 9.78 ± 0.44%. Solid-state reactions during carbothermal process resulted in the formation of highly insoluble Li₃PO₄, and Fe-Ni-Co/Ni-Co alloys, which hinder lithium dissolution. To address these challenges, Na₂CO₃ was introduced as an additive to suppress Li₃PO₄. The addition of Na₂CO₃ to the 50:50 ratio of LFP-NMC black mass, increased lithium recovery to 59.47% with 100% selectivity. This enhancement was due to the stabilization of lithium as Li₂CO₃, a water-soluble compound. The results demonstrated that addition of Na₂CO₃ is a promising strategy for improving lithium recovery from mixed LFP-NMC batteries, providing a potential pathway for a more efficient recycling process.