This master's thesis investigates whether and to what extent the addition of slag formers has a positive influence on the meltability of black mass from lithium-ion batteries (LIB). On the other hand, it is being investigated whether the recovery rate of nickel (Ni), manganese (Mn) and cobalt (Co) in the obtained metal phase can be increased and the slagging of lithium (Li) still be kept low. Additionally, the extent to which the transfer coefficient of lithium into the gaseous phase changes is being investigated. The output of gaseous lithium during a pyrometallurgical recycling process for lithium-ion batteries is the unique selling point of the InduRed reactor concept, which was developed at the Chair of Thermal Processing Technology at Montanuniversität Leoben. In this thesis, the cathode materials LiNi1-y-zMnyCozO2 (NMC811), LiNi0.8Co0.15Al0.05O2 (NCA) and LiCoO2 (LCO) were analysed in more detail on the InduMelt system, the batch version of the InduRed reactor concept. In order to additionally investigate the robustness of the InduMelt recycling process against impurities, copper, aluminium and iron were added to the LIB black mass. The slag formers were summarised in two slag systems, CaO-SiO2-MgO (40-45-15) and Al2O3-CaO-SiO2 (15-25-60). The analysis results of the individual test series were compared and discussed in detail using diagrams. The most important finding of this work is that the addition of slag formers has a negative effect on the recovery of nickel, manganese and cobalt, reduces the lithium transfer coefficient into the gas phase and also leads to a safety risk for the MgO crucibles used.