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.

Keywords: Carbon dioxide synergy; Low-carbon recycling; Reduction roasting; Selective water-leaching; Spent lithium-ion batteries.