Pyrometallurgical recycling of lithium ion batteries: Preliminary experiments to investigate the behaviour of cathode materials under reducing conditions

Abstract

In this work, a brief overview of currently used lithium ion battery (LIB) cathode materials is given. These materials as well as active material, a fine powdered mixture from a pre-treatment step of spent LIBs, were investigated in a heating microscope. In order to estimate when reduction reactions of the lithium-metal-oxides start, another experimental series, in which highly reactive carbon powder was added to the samples, was performed. Since the said materials are very complex and thermodynamic data is hard to find, the gathered information and experience from these preliminary experiments are necessary for the development of a new pyrometallurgical approach to LIB recycling. For the basic reactor design, the state of the active material at high temperatures and, respectively, its solubility in a mineral slag is a crucial property, which was investigated in a third experimental series. The conducted experiments show that the reduction reactions of all tested cathode materials start at technologically manageable temperatures of about 800 °C. Furthermore, a significant difference between experiments in which carbon was added, compared to those with pure cathode materials could be observed. The behaviour of the active material from an existing pre-treatment process does not match the corresponding mixture of pure cathode materials. However, possible reasons could be identified and are the focus of the further research project.