Stability of Crystalline Compounds in Slag Systems Mainly Composed of Li2O-SiO2-CaO-MnOx

Abstract The challenge of obtaining sufficient raw materials is a major concern when it comes to extracting lithium from spent lithium-ion batteries. One way to address this is through pyrometallurgical processing, which leaves undesirable elements such as lithium, aluminum and manganese in the slag. The engineered artificial minerals approach focuses on the effective recovery of critical elements. Different slag systems have been studied in the literature, and understanding the phase relationships in the $$\text {Li}_2{\text {O}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mtext>Li</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> <mml:mtext>O</mml:mtext> </mml:mrow> </mml:math> - $$\text {SiO}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>SiO</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:math> -CaO- $$\text {MnO}_x$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>MnO</mml:mtext> <mml:mi>x</mml:mi> </mml:msub> </mml:math> system can lead to optimization of the recycling process. In this context, the stability of undesirable silicates can affect the maximum separation of Li from the slag. In order to contribute to the development of the Li recycling process, the stability of crystalline compounds was experimentally investigated in the present work for different slag compositions. The melted and solidified microstructures were characterized by SEM/EDX, EPMA, and XRD. Phase diagram data of binary and ternary systems were used to describe the solidification paths. As a result of solidification, crystals of $$\text {Li}_{2}\text {SiO}_{3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mtext>Li</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mtext>SiO</mml:mtext> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math> and $$\text {LiMnO}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>LiMnO</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:math> were observed in a matrix consisting of $$\text {Ca}_{3}\text {Si}_{2}\hbox {O}_{7}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mtext>Ca</mml:mtext> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mtext>Si</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mtext>O</mml:mtext> <mml:mn>7</mml:mn> </mml:msub> </mml:mrow> </mml:math> and $$\text {CaSiO}_{3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>CaSiO</mml:mtext> <mml:mn>3</mml:mn> </mml:msub> </mml:math> .