Improving separation efficiency in end-of-life lithium-ion batteries flotation using attrition pre-treatment

The comminution of spent lithium-ion batteries (LIBs) produces a powder containing the active cell components, commonly referred to as “black mass.” Recently, froth flotation has been pro-posed to treat the fine fraction of black mass (< 100µm) as a method to separate anodic graphite particles from cathodic lithium metal oxides (LMOs). So far, pyrolysis has been considered as an effective treatment to remove organic binders in the black mass in preparation for flotation sepa-ration. In this work, the flotation performance of a pyrolyzed black mass obtained from an indus-trial recycling plant was improved by adding a pre-treatment step consisting of mechanical attri-tion. The LMOs recovery in the underflow product increased from 70% to 85% and the graphite recovery remained similar, around 86% recovery in the overflow product. To understand the flo-tation behaviour, the spent black mass was compared to a model black mass, comprising fully lib-erated LMOs and graphite particles. In addition, ultrafine hydrophilic particles were added to the flotation feed as an entrainment tracer, showing that the LMO recovery in overflow products is a combination of entrainment and true flotation mechanisms. This study highlights that adding kerosene during attrition enhance the emulsification of kerosene, simultaneously increasing its (partial) spreading on LMOs, graphite and residual binder, with a subsequent reduction of selectivity.