Characterization and beneficiation of pyrolyzed black mass: increasing the recycling recovery of spent lithium ion batteries

摘要

The lithium ion battery (LiB) market is growing rapidly which leads to considerable increase of LiB wastes. Despite the enhancement in graphite consumptions, there is no graphite recycling process from LiBs so far. Thus, graphite usually remains in slags from the metallurgical treatments. The LiB components contain cobalt (Co), lithium (Li) and graphite, counted as critical materials. The aim of the present work is to increase the recycling recovery of the LiBs by developing an innovative process minimizing metal losses. Mineral liberation analysis (MLA), X-ray fluorescence (XRF) and X-ray diffraction (XRD) were used for characterization of the black mass to understand the liberation behaviour of the crushed LiB particles. Flotation tests were carried out in an Outotec GTK lab cell while the main studied parameters wereattritioning rate, pH and the reagents dosages (Kerosene and MIBC). The characteristic analyses showed that graphite particles were fully liberated from the copper foils, and the organic layer on the active particles was removed which led to an increases in separation efficiency. However, only 62 wt. % of the cathode active particles were liberated from the aluminium foil. Based on the obtained characterization results particularly the liberation degrees, a new flowsheet was designed to concentrate all the active materials (graphite, Co, Ni, Mn and Li) in the < 50 urn fraction removing the foil particles. Flotation experiments showed that attritioning improved the process efficiency while preserving the spherical shape of graphite. Graphite recovery is 98 % with a grade of 72 wt. % and the tailings recover more than 90% of the precious metals Co, Ni and Li from the spent LiBS, with the respective grades 27 wt. % Co, 7 wt. % and 2.5 wt. % Li. Major impurities in concentrates were identified at fine particles from cathode active materials, which could be removed with a desliming process and flotation cleaner stage. This research is at its beginning, and is expected to bring about an innovative and useful process for the recycling industry, despite the challenges involved. This process can recover the graphite and the lithium, which are usually ending the slags. At present, there might be legitimate questions regarding the expense and benefits of graphite recycling. However, the treatment of LiBs will become necessary in the near future due to environmental issues as well as the scarcity and criticality of LiB components. Consequently, graphite will become a valuable and needed by-product from the metals recycling. The dependence on imports of graphite from China would be reduced, providing a solution to meet the significant predicted demand of battery grade graphite. Moreover, LiB as a key driver of the transition away from a carbon-based economy, it is necessary to ensure a truly positive impact over the lifecycle of LiB, and consequently to reach a closed-loop system.