Cleaner separation and recovery of valuable metals from spent ternary cathode via carbon dioxide synergetic thermite reduction strategy.

ABSTRACT

The low-carbon recycling of spent lithium-ion batteries has become crucial due to the increasing need to address resource shortages and environmental concerns. Herein, a low-carbon, facile, and efficient method was developed to separate and recover Li, Al, and transition metals from spent ternary cathodes. Initially, the cathode materials post-discharge and disassembly do not require pre-sorting. Instead of using carbonaceous materials, the Al foil in the cathode serves as the reducing agent during reduction roasting. The impact of different roasting atmospheres (air, N2, CO2) on phase transitions and the extraction of valuable metals was examined. The findings revealed that after synergistic thermite reduction in a carbon dioxide atmosphere, the cathode material is completely dissociated. Li is selectively converted to Li2CO3 rather than LiAlO2, and the reduced reactivity of the Al foil encourages the formation of lower-valence oxides of Ni and Co, rather than their metallic forms. Under optimal roasting conditions at 650 °C for 1.0 h, 91.4% of Li can be preferentially and selectively extracted through carbonation water leaching, with less than 0.1% of Al and transition metals dissolving. Subsequently, ∼98% of Al and ∼99% of Ni, Co, and Mn can be leached using alkaline and acidic solutions, respectively. Compared to the traditional carbon thermal reduction process, this process offers several advantages including the elimination of pre-sorting and additional reducing agents, lower carbon emissions, and higher recovery rates of valuable metals. Thus, this process makes the recovery of metals from spent lithium-ion batteries more environmentally sustainable, simple, cost-effective, and adaptable.