Untersuchung der Fluorverteilung und -abtrennung in hydrometallurgischen Recyclingprozessen von Lithium-Ionen-Batterien

The growing demand for lithium-ion batteries (LIBs), particularly in the field of electromobility, is leading to an increasing need for efficient and sustainable recycling processes. Besides the recovery of strategically important metals such as lithium, nickel, cobalt and manganese, the fluorine content also poses a challenge. Fluorine enters the battery system primarily via the conductive salt lithium hexafluorophosphate (LiPF6) and via fluorine-containing binders such as polyvinylidene fluoride (PVDF). During hydrometallurgical recycling, fluorine can transfer into the leaching solution, where it can negatively impact metal recovery and product quality by forming stable fluoride compounds. Furthermore, this halogen has both environmentally problematic and health-hazardous properties. The aim of this work is to investigate the distribution of fluorine and the influence of various defluorination strategies on hydrometallurgical recycling processes for end-of-life lithium-ion batteries. For this purpose, two different black masses are analysed, one pyrolysed and one unpyrolysed sample. Mechanochemical treatment with calcium oxide in a planetary mill and wet chemical defluorination in an alcoholic potassium hydroxide solution were used as defluorination methods. After pre-treatment, the hydrometallurgical recycling process of the black masses starts by leaching with sulphuric acid and the addition of hydrogen peroxide as a reducing agent. The pregnant leach solutions is further processed using multi-stage precipitation processes to selectively recover nickel, cobalt, manganese and lithium. As part of the experimental investigation, the fluorine distribution in the individual process streams is analysed in order to evaluate the effects of the respective pre-treatment on the fluorine distribution.