Circular Potential of Lithium-Ion Battery Recycling Slags: Quantifying Microstructure and Elemental Distribution for...

Extractive pyrometallurgy is an established process for recycling lithium-ion batteries (LIB). One approach to recover lithium from slags produced by pyrometallurgical recycling of LIB involves accumulating lithium in an engineered artificial mineral (EnAM) facilitating recovery. β-Eucryptite (LiAlSiO₄) is a promising EnAM-candidate as it is chemically similar to the primary lithium ore spodumene (LiAlSi₂O₆) making co-processing a viable option. However, for economic recycling the β-eucryptite must have a high lithium content, a high purity, and display a favorable microstructure. The presented work aims to quantify all three parameters. An industrial pyrometallurgical slag was analyzed using scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS). The analyzed β-eucryptite shows a high lithium content of 5.45 mass % while containing only low amounts of iron (0.64 mass %) and calcium (0.2 mass %). However, small mean grain sizes (< 21 µm) and unfavorable grain shapes impede the separation of β-eucryptite. It was discovered that chromium and vanadium were accumulated in spinel phases of the chromite-coulsonite solid solution series. Producing a Cr, V-bearing spinel concentrate would enable the recycling of both metals as well as improving the quality of the residual lithium-depleted slag as a by-product.