Due to the rapid market capitalization and the demand for valuable and sometimes critical raw materials, lithium-ion batteries (LIBs) are among the most relevant topics for the recycling industry in the short, medium and likely long term. The continuous development of the LIB technology will undoubtedly mean that the rules of the game for recyclers will change frequently and that processes will have to be highly flexible. In general, the processing and recovery of valuable raw materials from LIBs is a complex task that often involves a chain of processes and procedures. The challenges and scientific questions concerning LIB recycling are pervasive, both in number and content. This thesis, however, addresses one specific issue. An intermediate product along the recycling chain of LIBs is so-called "black matter", a black powder enriched with valuable metal oxides, whose further processing can be regarded as one of the bottlenecks of LIB recycling. Recovering valuable metals such as nickel, cobalt, or lithium from this black matter can be achieved by various methods, with specific strengths and weaknesses. The present work focuses on the pyrometallurgical approach, which has, among many advantages, a very decisive cut. Lithium, which is now on the European Commission's list of critical raw materials, is almost entirely oxidized and slagged by the pyrometallurgical methods that are in use today. As the possibilities for later recovery from this slag are limited, primarily due to low concentrations, the lithium-containing slag is often utilized elsewhere. Thus, while pyrometallurgical processes can reliably recover nickel and cobalt, lithium is excluded and no longer useable for functional recycling, i.e. the production of new LIBs. As lithium's economic importance is high due to the predicted market growth in the LIB sector, and especially against the backdrop of future supply security, a more sustainable approach is probably inevitable in the future. The present work particularly addresses this problem, and investigates a possibility to achieve simultaneous recovery of nickel, cobalt, the other transition metals and lithium by pyrometallurgical means. For this purpose, the so-called InduRed reactor concept is to be used, which has favorable properties and has already been successfully applied for other industrial and municipal residues. The work aims to investigate whether the reactor concept could be an alternative to conventional pyrometallurgical approaches, at which point it should be optimally integrated into existing recycling chains, and what contribution it could make to the future sustainability of the LIB technology. To determine the essential suitability and to evaluate potentially achievable recovery rates as well as possibly necessary adaptations of the process, a series of research, tests and analyses were carried out. The results can roughly be divided into three sub-areas. The first part, which marked the start of the scientific work, deals with the high-temperature behaviour of currently used cathode materials. In several experimental series, the most common cathode materials with and without carbon addition, as well as black matter from a pre-treatment process, were examined in a heating microscope and subjected to thermogravimetric analyses. This showed that the desired reactions occur in a temperature range between 650°C and 900°C, which is compatible with the InduRed concept. However, a considerable difference in the behaviour of brand-new cathode materials and black matter from the pre-treatment step was identified. The research and investigations to clarify the underlying cause of this phenomenon comprise the results' second part. A state-of-the-art review highlighted how crucial black matter's chemical and structural properties could be for downstream processes. For example, the pyrolysis step was ident