Evaluating Microstructure and Mineral Chemistry for an Economical Lithium Recovery from Slag

Established pyrometallurgical processes enable the recovery of many valuable metals from lithium-ion-batteries (LIB) (e.g. Ni, Cu, Co) as an alloy or a metal sulfide. However, lithium dissolves into the slag, from which it cannot currently be recovered economically. One recently discussed approach is called “Engineering of Artificial Minerals” where the lithium is collected in a specifically designed phase.^[1] A recent study demonstrated β-eucryptite as a lithium collector phase with high potential.^[2]

To achieve an economically feasible process, the collector phase requires optimized characteristics: 1) High lithium content; 2.) Low amounts of process impeding impurities; 3.) A suitable microstructure for liberation and sorting. The sampled crystalline slag was investigated using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to investigate these parameters.

The investigated lithium collector phase, β-eucryptite identified in slag from an industrial LIB recycler, shows a lithium content of 5.54 ± 0.19 mass %, close to the stoichiometric content of 5.51 mass %. Furthermore, it shows only minor amounts of cationic impurities, mostly iron and calcium. These impurities could be easily removed while coprocessing β-eucryptite with spodumene in a primary lithium converter.^[3] In addition to grain size distributions, for the quantitative description of the microstructure the implementation of the envelope parameters was tested. A more detailed quantification of the grain shape than conventionally used descriptors was demonstrated.

[1] Hampel, et al., ACS omega, 2024.

[2] Gantz, et al., Adv Energy and Sustain Res, 2024.

[3] Nandihalli, et al., Sustainability, 2024.