A novel method for carbon removal and valuable metal recovery by incorporating steam into the reduction-roasting process of spent lithium-ion batteries

Abstract

Oxygen-free roasting could efficiently achieve the recovery of valuable metals from spent lithium-ion batteries (LIBs), but the roasted products have the drawbacks of a high carbon (C) content and a complex separation process. Hence, in this study, a new method incorporating steam (H2O) into the reduction-roasting recovery process of spent LIBs (steam roasting) was proposed to realize carbon removal and valuable metal recovery simultaneously. The influence of steam on the reduction-roasting process of spent LiNi0.6Co0.2Mn0.2O2 batteries (NCM) was investigated through experimental methods and thermodynamic analysis. The results indicated that the addition of steam could dramatically facilitate the decomposition and reduction process of spent NCM, and the carbon removal efficiency could reach 84%. H2O only acted on the reaction process of the anode material, and the main component C could be efficiently gasified by steam to produce hydrogen (H2) and carbon monoxide (CO), which could significantly accelerate the reduction process of CoO and NiO. The optimal conditions for valuable metal recovery and carbon removal were a H2O/C mole ratio of 5:1 and a reduction-roasting temperature of 1123 K. After steam roasting, the magnetic recovery efficiencies of Co and Ni were as high as 90% and 93%, respectively. The final recovery products were Co, Ni, and Li2CO3 with high purities. Therefore, this study is expected to provide a novel approach to achieve efficient disposal and recovery of metals from spent LIBs.