This thesis deals with the applicability of the pyrometallurgical reactor concept InduRed, developed at the Chair of Thermal Processing Technology, to the recycling of lithium-ion batteries (LIB). In this technology, unlike pyrometallurgical processes currently available on the market, lithium is not slagged but recovered via the gas stream. The research results with cathode materials from battery production look promising with regard to lithium utilization. However, experiments at the chair showed that the melting ability of the LIB active material from the waste stream, which is required by the InduRed concept, is not given. In addition to the cathode material, this LIB active material also consists of anode material (graphite) and impurities of the electrode conductor foils made of copper and aluminum. Further investigations with the cathode materials resulting from the aforementioned knowledge showed that the material behavior is unfavorably influenced mainly by the aluminum impurities and the carbon. Due to this, this work deals with the influence of aluminum and carbon on the commercially used cathode materials NMC (in the configuration 6:2:2), NCA, LCO, and LFP. With the help of a heating microscope, in-depth investigations were carried out regarding the material behavior at high-temperature application and with the addition of potential interfering elements such as aluminum and carbon. Consequently, the generated results were plotted in an Al-C cathode material system in three-dimensional space at a given temperature. Interpolation of the data points from the experiments created a surface in space. The described approach enables new possibilities of representation and, based on this, new possibilities of discussion and interpretation of the influence of aluminum and carbon on the behavior of the mentioned cathode materials. The most essential finding is that the carbon concentration required for the optimum melting point is lower than the stoichiometric carbon requirement. This, in turn, is attributed to the higher oxygen affinity of aluminum compared to carbon. In addition, the relationship between the C and Al concentrations shows that the allowable aluminum concentration can increase due to carbon reduction in the blends. However, carbon reduction can only occur up to a minimum carbon concentration. Thus, the limits of a meltable zone could be defined for each cathode material.
|Translated title of the contribution||Determination and analysis of aluminium- and carbon additives to cathode materials of lithium-ion batteries to recover valuable metals by the pyrometallurgical reactor concept InduRed|
|Award date||1 Jul 2022|
|Publication status||Published - 2022|