Separation of Li and Co From LiCoO2 Cathode Material Through Aluminothermic Reduction: Investigation of the Thermite Reaction

Abstract

Aluminum can be used as a reductant for metal oxide reduction processes. This study investigates the reaction between Al with LiCoO2 in the context of recycling and separation of Li and Co from end-of-life battery cathode material. Specifically, this work attempts to investigate the initiation of the ignition of the thermite reaction. Both thermodynamic assessments and experimental work were carried out on the LiCoO2-Al system in the range of 750 °C to 1020 °C with three different amounts of Al additions in the sample, i.e., 11 wt pct, 20 wt pct, and 28 wt pct. It was found that the amount of Al (composition of the sample), the sample weight, and the initial heating temperature affect the occurrence of spontaneous ignition of the thermite reaction in the system leading to the partial/full melting of the sample. A function of Biot number and temperature was utilized to construct maps showing the onset of ignition where it was found that samples with large Biot numbers tend to ignite. In addition, higher Al addition, sample mass, and temperature were likely to generate ignition. The ignition was found to govern the type of end products of Li and Co; for example, the Li was distributed to gas as Li(g) and slag as LiAlO2 while Co could be extracted as Co metal or Co-Al alloy. The 11 wt pct and 20 wt pct Al addition to the samples resulted in a pure metallic cobalt product, whereas 28 wt pct Al addition resulted in CoAl alloy with a composition of 86.1 wt pct Co and 13.9 wt pct Al. The final product of the vaporized Li was in the form of Li(OH) due to the exposure to water vapor in the atmosphere upon collection. This aluminothermic approach is considered as a promising method to recover Li and Co from waste LiCoO2.