Tailoring Lithium Aluminate Phases Based on Thermodynamics for an Increased Recycling Efficiency of Li-Ion Batteries

The increased usage of Li-ion batteries (LIBs) requires innovative recycling processes, allowing recovering Li with a high recycling efficiency. Different research groups have developed several recycling technologies in the past. One promising technology is the pyrometallurgical combined with the hydrometallurgical process route. To increase the recycling efficiency of this technology, it is of high relevance to artificially engineer high lithium-containing phases by tailoring slag solidification with process parameters and composition. The significant challenge thereby is the complex interrelationship between composition, process temperature, and high lithium-containing phases such as LiAlO2. Especially, the influence of Mg impurities in the feed is crucial for the phase formation. Consequently, the question arises to what extend the Mg content should be artificially adjusted in combination with CaO as a slag builder to design LiAlO2. To overcome this challenge, a comprehensive thermodynamic model framework is presented in this work, which allows tailoring the slag composition and temperature such that the LiAlO2 amount can be engineered. The model is validated successfully by experimental data. For the first time, this study presents the role and potential of combined MgO and CaO tailoring for this complex system to gain high amounts of the desired LiAlO2. This lays a valuable base for significantly increasing the recycling efficiency in the pyrometallurgical recycling of LIBs by taking into account unavoidable feed impurities.