The sampling and phase characterisation of black mass

‘Black mass’ is the industry term used to describe a type of e-waste comprising crushed and shredded battery cells. It is an intermediate product in the recycling of spent, end-of-life, batteries. It comprises a mixture of metals including; lithium, manganese, cobalt and nickel, which are valuable recycling commodities, of increasing strategic and economic importance to meet future global demands in the ‘battery revolution’. The objective of this ‘phase characterisation’ investigation was to provide an indicative profile of the morphological characteristics, grain size, composition and textural variability for a natural state (unprepared) and prepared (powdered) sample of black mass from Europe. It is envisaged that this is relevant to: (a) develop a pragmatic sampling strategy to ensure a non-biased, representative sample is provided for assaying; (b) determine the optimal processing route (e.g., hydrometallurgical, pyrometallurgical); (c) identify the presence of payable phases; (d) identify phases that may hinder metal recovery or penalty components; (e) develop assay procedures; and (f) assist in the identification of hazards and the mitigation of risks. The techniques used were: (1) visual examination and binocular microscopy; (2) manual scanning electron microscopy (SEM); (3) automated scanning electron microscopy with linked energy dispersive spectrometers (SEM-EDS), to characterise the phases present and particle types (using AMICS); (4) X-ray computed tomography (X-CT) to provide the 3D morphology of the particles; and (5) laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) to detect and quantify the phases that cannot be detected using automated SEM-EDS and X-CT. The results demonstrated that automated SEM-EDS can be used to characterise and quantify the phases present, and the phase chemistry allows the particle types to be assigned back
to the primary battery components. Some phases identified are at present not linked back to the original components and further work is needed to refine the compositional groups, with the analysis of additional samples from different feeds/streams in Europe, China and USA. Interactive SEM-EDS analysis also demonstrated that there is a high-resolution chemical variability within the individual particle categories. X-CT imaging demonstrated the complex 3D textures and morphology of the particles, which is potentially significant during sample preparation and chemical analysis. Neither automated nor manual interactive analysis can determine the presence / abundance of the light
elements, such as lithium. However, LA-ICP-MS was successful in detecting and quantifying lithium. Furthermore, LA-ICP-MS was able to determine contents of 67 other non-metals and metals at a 20- micron scale with ppm to ppb level detection limits.