Eco-Friendly Recovery and Alloying of Metals from Spent Lithium-ion Batteries

With growing environmental concerns and the critical need for sustainable resources, metal recovery from secondary sources has gained importance. Among the techniques applied for this purpose, pyrometallurgy, which involves high-temperature processing, is a widely used method. However, this method faces challenges when recovering elements from spent Li-Ion Batteries (LIBs). Black Mass (BM), the residue left after mechanical shredding and physical separation of spent LIBs, is rich in valuable elements such as Co, Ni, and Li. This study investigates the pyrometallurgical recycling of BM from various types of LIBs. Initially, the high-temperature behavior of BM was examined to identify the critical reduction temperatures. A temperature of 600 °C was identified as critical. This temperature ensures the complete transformation of the cathode material into its constituent metal oxides (MeOs). Additionally, thermodynamic modeling indicated that up to 600 °C Li is present as Li2O or Li2CO3, while at higher temperatures, it forms LiAlO2 by reacting with Al. A temperature of 800 °C was found to fully reduce Co and Ni oxides to their metallic forms. Furthermore, it was also observed that heating the BM up to 700 °C, regardless of the atmosphere's oxidizing properties, resulted in evaporation of less than 10 % of the F in the BM. After investigating the high-temperature behavior of BM, in-situ alloying was introduced as an approach for recovering Co and Ni as alloying elements. This was achieved by the addition of Fe2O3/CuO to the BM, and consequently, the production of Fe/Cu-based alloys. The effect of mechanical activation on BM reduction and in-situ alloying was also examined, revealing varying effects across different BMs. While ball milling showed no effect on some BM samples, it enhanced the reduction rate in others by decreasing particle size. The variation in BM susceptibility to ball milling may result from the technique employed in producing the BM or the rate-influencing factors in its reduction. In samples where the reduction rate improved, ball milling resulted in lower C consumption and, consequently, reduced CO2 emission. In the final phase of this study, slag was incorporated into the in-situ alloying system, and Li and F evaporation were tracked under various slag conditions. Basicity was found to be a significant parameter, with a linear positive effect on Li evaporation and a quadratic effect on F evaporation.