Abstract
Aurubis AG, Europe’s leading Copper producer and multi-metal recycler, has been developing a Hydrometallurgical process to recycle Li-ion Battery Black Mass (BM) since 2020. The process, comprising of leaching, precipitation, crystallisation processes, and flotation for recovery of Graphite was developed by Aurubis’ R&D Department and piloted at our Hamburg site until end of 2023 with results openly presented in 2024. At that point in time, the core process was well defined, with Pilot campaign results underpinning mass and energy balances with high accountability for value metals (e.g., Li, Ni, Co, Mn).
Pyrolysis is the preferred pre-treatment method for BM before entering a Hydromet process and purportedly removes Organics such as Battery electrolyte (e.g., Ethylene Carbonate) and destroys or converts Fluorine materials (e.g, PF6, PVDF). However, the energy usage and off-gas treatment requirements for Pyrolysis has a high economic and environmental barrier to entry, especially in the European context. Aurubis took a strategic view to adapt our process to accept non-pyrolysed BM, whereby the Organic electrolyte is only vacuum distilled, to enable competitive BM supply. However, this would result in a large increase in residual Organic Electrolyte entering the Process flowsheet and had potential to cause other operability issues (e.g., foaming). An increase in primary conducting salt, LiPF6, was also associated with the battery electrolyte. After a Pilot campaign with non-pyrolysed BM it was apparent that Organic carbon species and Fluorine species would accumulate in our Lithium recovery processes. A robust process must therefore deal with both Organic material and Fluorine species or risk infecting products and residues with both.
Initial pilot plant filtrate analyses and process modelling showed that a build-up of Organic content could cause problems throughout the entire flowsheet or require large bleed streams to disposal to control it, engendering recovery losses. Lab and Pilot test-work and analytics were conducted to understand process chemistry, Organic and Fluoride speciation and removal techniques that could apply to our process. Ultimately an organic removal concept was developed and integrated into the process design. It also converted PF6 species to desired by-products. Finally, Lithium recovery was optimised by recycling the treated residue from the bleed stream. We believe that this development is highly competitive with Pyrolysis pre-treatment when combined with our overall flowsheet. It is worth discussing in context of BM recycling, the opportunity to robustly treat pyrolysed and non-pyrolysed feed materials with Hydrometallurgical processes.