Abstract
The recovery of critical elements in recycling processes of complex high-tech products is often limited when applying only mechanical separation methods. A possible route is the pyrometallurgical processing that allows transferring of important critical elements into an alloy melt. Chemical rather ignoble elements will report in slag or dust. Valuable ignoble elements such as lithium should be recovered out of that material stream. A novel approach to accomplish this is enrichment in engineered artificial minerals (EnAM). An application with a high potential for resource efficient solutions is the pyrometallurgical processing of Li ion batteries. Starting from comparatively simple slag compositions such as the Li-Al-Si-Ca-O system, the next level of complexity is reached when adding Mg, derived from slag builders or other sources. Every additional component will change the distribution of Li between the compounds generated in the slag. Investigations with powder X-Ray diffraction (PXRD) and electron probe microanalysis (EPMA) of solidified melt of the five-compound system Li2O-MgO-Al2O3- SiO2-CaO reveal that Li can occur in various compounds from beginning to the end of the crystallization. Among these compounds are Li1−x(Al1−xSix)O2, Li1−xMgy(Al)(Al3/2y+xSi2−x−3/2y)O6, solid solutions of Mg1−(3/2y)Al2+yO4/LiAl5O8 and Ca-alumosilicate (melilite). There are indications of segregation processes of Al-rich and Si(Ca)-rich melts. The experimental results were compared with solidification curves via thermodynamic calculations of the systems MgO-Al2O3 and Li2O-SiO2-Al2O3.
Highlights
With respect to the development in electromobility as well as to the changes in circular energy systems, Li-ion batteries are of central importance
To better understand the results presented in this article, the existing information about the compounds of important binary and ternary systems containing Li2 O, MgO, Al2 O3, SiO2 and CaO is summarized
The compounds Li2 Al4 O7 synthesized by Kale et al [7] and Li3 AlO3 were found to be instable by Kale et al [7] and are not part of the data published by Konar et al [5]
Summary
With respect to the development in electromobility as well as to the changes in circular energy systems, Li-ion batteries are of central importance. The hydrometallurgical processing of Li enriched silicate slag has shown that Li recovery can reach 80–95% [2]. To better understand the results presented in this article, the existing information about the compounds of important binary and ternary systems containing Li2 O, MgO, Al2 O3 , SiO2 and CaO is summarized. This information serves as the starting point to analyze and improve the existing data and develop respective thermodynamic modeling strategies. Important Binary Phase Systems Containing Li. In the systems Li2 O-CaO and Li2 O-MgO, except for limited solid solution, no explicit phase reactions are reported (e.g., Konar et al [4]). The compounds Li2 Al4 O7 synthesized by Kale et al [7] and Li3 AlO3 were found to be instable by Kale et al [7] and are not part of the data published by Konar et al [5]
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