Synergetic carbothermic reduction and selective hydrochlorination of spent Li-ion batteries black mass towards enhanced metal recovery

Abstract

The vast amount of Lithium-ion batteries (LIBs) reaching their end-of-life calls for effective recycling processes, given the low recycling efficiency in the industry. This paper proposes an innovative sequential carbothermic reduction-selective hydrochlorination process to attain metallization of Ni-Co alloy, selective chlorination of Li, Mn, and Cu, and the formation of Al2O3 to address some of the recycling challenges. The proposed process paves the way for short-range effective separation of the high-value metals in the LIB black mass based on magnetism and water solubility differences. After hydrochlorination at 1000 °C for 30 min with the material bed measuring 9 mm in thickness, Li and Mn water recovery reached 97.28% and 98.13%, respectively. The Ni and Co recoveries into the magnetic fraction reached 93.03% and 91.37%, respectively. Up to 95.28% Al, including graphite, reported to the non-magnetic fraction. Prolonged hydrochlorination time increased the chlorination degree despite negatively affecting the Ni-Co alloy recovering efficiency. Conversely, an increase in the thickness of the material bed had a reverse effect. Step-wise precipitation of the water-soluble product produced high-purity Li2CO3 (≥99.5%) and Mn3O4. Compellingly, graphite with morphology and characteristic diffraction peaks and Raman bands similar to commercial graphite was regenerated by NaOH dissolution of the non-magnetic fraction. These findings demonstrate that a black mass with a complex composition (Li, Ni, Mn, Co, and Al) could be comprehensively recycled using synergetic carbothermic reduction and hydrochlorination. Besides the high recovery rates, the proposed process minimizes recycling process steps and chemical usage, which is of utmost industrial significance.