Fine grinding of pyrometallurgical battery slag and its influence on lithium dissolution

Abstract

Pyrometallurgical recycling of lithium-ion batteries (LIB) has established itself as a robust process in industrial practice due to its good scalability. A major drawback of this approach is the slagging of lithium, which limits its recovery and usually requires thermal energy and large amounts of leaching reagents using a hydrometallurgical recovery process in order to accomplish a return into the material cycle. To counteract this disadvantage, the present study investigates the fine grinding behaviour of battery slags in a stirred media mill and its possibility to increase the solubility of lithium containing slag phases. As the main influencing factors, the grinding media stress energy, processing time, and the pH value were investigated. The results show that by selecting suitable fine grinding process parameters, the specific surface area of the battery slag can be increased significantly from 0.2 m²/g to 55 m²/g and a lithium dissolution efficiency of up to 30 % can be reached in an aqueous environment. The variation of pH value during fine grinding enables a further process improvement with a dissolution efficiency of up to 90 % at pH=4. Particularly in the context of sustainable recycling process design, fine grinding offers a notable benefit in decreasing the quantity of leaching reagents required by as much as 76 % compared to standard leaching processes.