Formation of Lithium-Manganates in a Complex Slag System Consisting of Li2O-MgO-Al2O3-SiO2-CaO-MnO—A First Survey

Abstract

Due to the increasing demand for electromobility, the recovery of technologically relevant elements from spent Li-ion batteries is becoming increasingly important. Pyrometallurgical processing can deal with a broad range of input materials. Unfortunately, ignoble elements such as Li and Mn enter the slag. A novel approach to facilitate this processing is the Engineered Artificial Minerals (EnAM) strategy for the recovery of critical elements. The aim of this study is to investigate whether it is possible to stabilize Li in Li-manganates as the first crystallizate. For this purpose, synthetic oxide slags (Li, Mg, Al, Si, Ca, Mn) of varying compositions were made. The constituting compounds were identified using inductively coupled plasma optical emission spectrometry, powder X-ray diffraction, X-ray absorption near-edge structure analysis, and electron probe microanalysis. These results provide an understanding of the solidification process and the behavior of the elements of concern. Lithium-manganate(III) (LiMnO2) crystallized first, next to hausmannite (Mn2+Mn3+2O4) in a matrix consisting of wollastonite (CaSiO3) and larnite (Ca2SiO4). Within the structure of LiMnO2, Li and Mn can replace each other in certain proportions. By adding Al and Mg spinel, solid solutions between Mn2+Mn3+2O4, MnAl2O4, MgAl2O4 and LiMnO2 are expected and described by the stoichiometry formula: (Li(2x),Mg(1x),Mn(2+(1–x)))1+x(Al(2–z),Mn3+(z))2O4.