Detection of Li in synthetic slags of Li-ion batteries by laser ablation inductively coupled plasma time of flight mass spectrometry (LA-ICP-ToF-MS)

Abstract

Lithium is one of the most important technological elements and is mainly used in Li-ion traction batteries (LIBs). Due to its high oxygen affinity, recovering this element from, e.g., batteries is a challenge. In pyrometallurgical processes, Li accumulates in the slag and is currently largely lost. A new pyrometallurgical approach, called “engineered artificial minerals” (EnAM), deals with the modification of slag to enrich elements such as Li in a single phase with a simple chemical structure and favourable properties for processing (e.g. morphology). To maximise the efficiency of this process, the first step is to characterise as accurately as possible the distribution of the target element (here Li) across the phases in the slag. In this article, a combination of an electron-optical and X-ray based method (electron probe microanalysis) with a spatially resolved mass spectrometric method (laser ablation inductively coupled plasma time-of-flight mass spectrometry) is presented to study the distribution of Li in a synthetically produced slag. The combination of LA-ICP-ToF-MS multi elemental imaging with backscattered electron (BSE(Z)) imaging allows the resolution of intricate fine structures and the unambiguous identification of crystalline phases in the slag. Electron optics (backscattered electrons) provides high spatial resolution and mass spectrometry offers high sensitivity to detect Li. This makes it possible to characterise not only the stoichiometrically identifiable phases but also the non-stoichiometric amorphous components. By combining different analytical methods (toolbox), three Li-bearing phases could be clearly identified: the residual melt, Mn₃O₄ and LiMnO₂.