Advances in the Separation of Graphite from Lithium Iron Phosphate from End-of-Life Batteries Shredded Fine Fraction Using Simple Froth Flotation

Abstract

Olivine-type lithium iron phosphate (LiFePO4, LFP) lithium-ion batteries (LIBs) have become a popular choice for electric vehicles (EVs) and stationary energy storage systems. In the context of recycling, this study addresses the complex challenge of separating black mass of spent LFP batteries from its main composing materials to allow for direct recycling. In this study, 71% copper and 81% aluminium foil impurities were removed by sieving black mass to <250 µm. Next, the application of froth flotation as a separation technique was explored, examining the influence of chemical agents, pre-treatment, and multi-step processes. Frother agent addition improved material recovery in the froth, while collector addition influenced the separation efficiency and enhanced graphite recovery. Pre-treatment, particularly sonication, was found to break down agglomerates and further improve separation. Multi-step flotation increased the purity of recovered fractions. The optimized process for a black mass < 250 µm, involving sonication pre-treatment and double flotation, resulted in enriched carbonaceous material (80.3 mol%) in froth fractions and high LFP concentration (81.9 mol%) in tailings fractions. The recovered spent LFP cathode material contained 37.20 wt% Fe2P2O7, a degradation product of LiFePO4. This research offers valuable insights for the development of efficient battery recycling methods for LFP batteries.