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 proposed to treat the fine fraction of black mass (<100 mu m) 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 separation. In this work, the flotation performance of a pyrolyzed black mass obtained from an industrial recycling plant was improved by adding a pre-treatment step consisting of mechanical attrition with and without kerosene addition. The LMO 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 flotation behavior, the spent black mass from pyrolyzed LIBs was compared to a model black mass, comprising fully liberated 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 enhances the emulsification of kerosene, simultaneously increasing its (partial) spread on the LMOs, graphite, and residual binder, with a subsequent reduction in selectivity.

Automated summary

Froth flotation is proposed as a method to separate anodic graphite particles from cathodic lithium metal oxides (LMOs) in the fine fraction of black mass from spent lithium-ion batteries. The flotation performance of a pyrolyzed black mass was improved by adding a pre-treatment step consisting of mechanical attrition with and without kerosene addition. The recovery of LMOs increased significantly, but the selectivity decreased.