Browsing by Author "Maritz, Roelof Frederick"

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    Comparing the environmental impact of different hydrometallurgical processes for the recycling of lithium-ion batteries using a life cycle assessment approach
    (Stellenbosch : Stellenbosch University, 2024-03) Maritz, Roelof Frederick; Dorfling, Christie; Akdogan, Guven; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering.
    ENGLISH ABSTRACT: Lithium-ion batteries (LIBs) have become commonplace for everyday use in consumer electronics. These batteries have also gained a lot of popularity recently for usage in larger scale application such as electric vehicles (EV). The LIB market is projected to grow from 700 GWh in 2022 to 4.7 TWh in 2030 (Fleischmann et al., 2023). The consequence of this rapidly increasing demand for LIBs is the formation of a fast-growing end-of-life (EOL) LIB waste stream. This waste stream includes valuable metals such as lithium, cobalt, nickel, and manganese to potentially be recycled, thus providing benefits in terms of waste management and income from the sale of these recovered metals. There is thus a clear need for EOL LIB recycling and a necessity to find out what is the best process technology available to recycle EOL LIBs. Traditionally LIBs have been recycled using pyrometallurgy, but the recent industry focus has shifted towards alternative process technologies such as hydrometallurgy. There is, however, no clear consensus on how these hydrometallurgical flowsheets should be arranged. As such, the purpose of this study was to compare the environmental impacts of implementing different hydrometallurgical process flowsheets designed for the recovery of metals from EOL LIBs. This comparative environmental study was performed using the life cycle assessment (LCA) framework and considered the use of three lixiviants (hydrochloric-, sulphuric-, and citric acid) alongside the use of three flowsheet options (sequential metal precipitation, mixed metal precipitation, and hybrid sequential precipitation - solvent extraction systems). Lastly, the process was modelled based on a mixed feed of LiCoO2, LiFePO4, and NMC111 batteries. The potential environmental impacts of mineral acid-based processes were found to generally be lower than that of organic acid-based processes by 18 to 61 percentage points. Furthermore, mixed metal precipitation provided the greatest environmental benefit of the flowsheet options considered by 46 to 117 percentage points when compared to the closest competitor. The LCA system was subsequently subjected to multivariate uncertainty analysis and a discernability analysis regarding process feed sensitivity which served to confirm the trends already observed. The LCA system was also subjected to a weak point analysis, where the consumption of NaOH and electricity were listed as the main concerns for process improvement. The process solutions recommended to address both weak points involve the integration of membrane technology and antisolvent crystallisation. Furthermore, the LCA system was compared for a South African and a European context, where it was determined that South Africa’s overreliance on hard coal for energy generation is the main difference between the two regions. Finally, the hydrometallurgical EOL LIB recycling processes were subjected to an additional LCA study regarding the use of recycled metals for resynthesizing NMC cathode materials. This additional study showed that integrating the sequential precipitation recycling process with solid-state synthesis of NMC622 cathode could save up to 70% on energy consumption during cathode synthesis. Meanwhile, integrating the mixed NMC precipitation recycling process with the solid-state synthesis of NMC622 cathode could reduce the environmental impact of NMC cathode production by up to 67%.