An integrated study on pyrolysis, flotation, and leaching for optimized recycling of industrial battery materials

• Pyrolysis, flotation and leaching of black mass systematically combined. • Pyrolysis increased the separation efficiency of both flotation and leaching. • Flotation enriched metal content of leaching feed by removal of graphite. • Both flotation and pyrolysis increased dissolved metal content. The increasing demand for lithium-ion batteries (LIBs) to support the global efforts in reducing carbon emissions have also made necessary the search for more efficient battery recycling technologies to prevent the depletion of raw materials. Pyrolysis, flotation and leaching are potential recycling unit processes that have recently drawn the attention as pretreatment, separation and dissolution methods in processes aimed at the recovery of materials from spent batteries. However, a study which systematically investigates the advantages and limitations resulting from the integration of these operations is still missing. In this work, an integrated experimental approach was applied to evaluate the recycling efficiency of pyrolysis, flotation and leaching together with their various combinations for the treatment of an industrially produced black mass. The results show that pyrolysis decreased the presence of cathode material in the graphite concentrate, increasing graphite purity from 60 to 80 %, although with a negative impact on graphite recovery from 60 to 50 %. Furthermore, the use of pyrolysis increased the leaching yield of metals from 40 to above 80 %. Additionally, the leaching yields of Ni and Co were further increased by nearly 5 % when flotation was applied, even without pyrolysis. With the combination of pyrolysis and flotation prior to leaching, an increased dissolution yield of metals from black mass was found for all the metals, particularly Ni (from 13.7 g/L to 19.8 g/L). The sole exception to this trend was Li, likely due to its dissolution in the flotation water. A rationalized explanation of this behavior is presented, supported by the characterization of the feed and product materials obtained under each different scenario. This work thus demonstrates that properly designed recycling stages can have a tangible impact in the process efficiency.