Recycling Li-ion Battery Cathode Materials in Iron Rich/Low Sulfate Cultures of Acidithiobacillus ferrooxidans

The continuous demand for lithium-ion batteries (LIBs) in consumer products and electric vehicles (EVs) has raised concerns about their environmental impact when not disposed of properly. Among the components of a spent LIB, the recovery of heavy metals such as Nickel, Manganese, and Cobalt from the cathode materials is the most critical. While this goal can be achieved through processes such as biohydrometallurgy, it relies on large quantities of chemicals such as FeSO4 for the energy source, which can limit the scalability. In this work, we seek to develop a modified biohydrometallurgy process that is self-sufficient. For this purpose, we examined the feasibility of replacing FeSO4 salt with metallic Fe, which is readily available and abundant in spent batteries as protective cases. The growth profile of the autotrophic bacterium Acidithiobacillus ferrooxidans (Atf) was studied after the initial acidification with H2SO4 or HCl. The resulting culture was then used to leach model cathode materials made of NMC622 (Ni:Mn:Co=6:2:2). Near-unity leaching efficiencies were measured on all four elements of interest, Li, Ni, Mn, and Co, when compared with those by aqua regia based digestion. This new bioleaching process opens the door to efficiently recovering cathode metals while further simplifying the cultivation process, promising scaled up applications.