Einfluss von Lithium-Eisen-Phosphat auf das Recycling von Lithium-Nickel-Kobalt-Manganoxid-Batterien

TThe increasing market ramp-up of electric vehicles is leading to a sharp rise in production and return of used lithium-ion batteries (LIB) with different cathode materials, depending on the respective area of application. The sustainable end-of-life management of these batteries poses a key challenge due to growing quantities and heterogeneous material compositions. Mixed recycling streams in particular increase the complexity of process control and require selective, robust, and scalable recycling routes. Hydrometallurgical processes generally enable high product quality and targeted metal recovery but are sensitive to contamination and changing material flows. This thesis investigates the influence of lithium iron phosphate (LFP) content on a hydrometallurgical recycling process for lithium nickel manganese cobalt (NMC) cathode material. For this purpose, two leaching systems, one with citric acid (CIT) and the other with methanesulfonic acid (MSA), were combined with a three-stage precipitation concept consisting of oxalic acid precipitation of transition metals, purification precipitation, and selective lithium precipitation. The MSA system shows higher and more stable leaching efficiencies for the valuable metals nickel, manganese, cobalt, and lithium, while in the CIT system, the strong complexation of iron by citrate complexes impairs the selectivity of the subsequent separation steps. Oxalic acid precipitation exhibits high selectivity for Ni, Mn, and Co in both systems. Purification precipitation proves to be significantly more effective in the MSA system, as iron and phosphates can be efficiently precipitated at a pH of 9, which favors subsequent lithium precipitation and achieves higher product purity. With increasing LFP content, especially from about 10¿20%, complexation effects, co-precipitation, and the stabilization of undesirable metal compounds increase, which reduces the selectivity of the precipitation and purification stages without targeted process adjustments. Based on the results obtained, process optimization approaches are derived, including acid selection, pH control, reaction time, temperature, and precipitate type, in order to maximize metal recovery and reduce the environmental impact of the hydrometallurgical process chain.