• Energy Research

The present work offers a study on the engineering implications of the recovery of valuable fractions from industrially collected lithium battery (LIB) waste by mechanical and hydrometallurgical processes in HCl media. Direct leaching of LIB waste provides a possibility for Li extraction, a component that is lost into the slag fraction in the state-of-art high temperature processes. The challenges arising from the heterogeneous composition of industrial battery waste are highlighted, and the behavior of main metals present such as Co, Cu, Li, Mn, Ni and Al is observed. It is shown that mechanical separation processes can form fractions rich on Cu and Al, although subsequent refining stages are necessary. Regarding direct leaching, fast kinetics were found, as complete Li dissolution can be achieved in ca. 120 min. Furthermore, high solid/liquid ratio (>1/10) is required to increase metal value concentrations, resulting in a viscous slurry due to the graphite, plastics and other undissolved materials, which challenges filtration and washing of leach residue. Neutralization of the product liquid solution (PLS) result in co-precipitation of valuable battery metals along with Fe and Al. The highest value of LIBs lies in Co, subjected for solvent extraction (SX) or direct precipitation to make an intermediate product. SX can provide selectivity whereas Na2CO3 precipitation provides a fast route for Co-Ni bulk production. Li2CO3 precipitation from the remaining PLS is possible as zabuyelite - however, due to heterogeneity of the battery waste, the recovery of Li2CO3 with battery-grade purity remains a difficult task to be achieved by direct precipitation route.

The principle of the circular economy is to reintroduce end-of-life materials back into the economic cycle. While reintroduction processes, for example, recycling or refurbishing, undoubtedly support this objective, they inevitably present material losses or generation of undesired by-products. Balancing losses and recoveries into a single and logical assessment has now become a major concern. The present work broadens the use of relative statistical entropy and material flow analysis to assess the recycling processes of two lithium-ion batteries previously published in the literature. Process simulation software, that is, HSC Sim®, was employed to evaluate with a high level of accuracy the performance of such recycling processes. Hereby, this methodology introduces an entropic association between the quality of final recoveries and the pre-processing stages, that is, shredding, grinding, and separation, by a parameter based on information theory. The results demonstrate that the pre-processing stages have a significant impact on the entropy value obtained at the final stages, reflecting the losses of materials into waste and side streams. In this manner, it is demonstrated how a pre-processing system capable of separating a wider number of components is advantageous, even when the final quality of refined products in two different processes is comparable. Additionally, it is possible to observe where the process becomes redundant, that is, where processing of material does not result in a significant concentration in order to take corrective actions on the process. The present work demonstrates how material flow analysis combined with statistical entropy can be used as a parameter upon which the performance of multiple recycling processes can be objectively compared from a material-centric perspective.