Electrochemically Assisted (Bio)leaching of End-of-Life Lithium-Ion Batteries for Critical Metals Recovery

Reclaiming critical metals from end-of-life (EOL) lithium-ion batteries (LIBs) is necessary for achieving global decarbonization goals. We evaluated a novel recycling strategy that combines the advantages of electrochemically assisted leaching and organic acid leaching to recover critical metals from EOL LIBs. A gluconic acid (GA)-containing solution produced by the bacterium Gluconobacter oxydans was used as the electrolyte and lixiviant in an electrochemical system, wherein a reducing agent, ferrous iron, was continuously regenerated. A reductant is necessary for efficient solubilization of the LIB cathode metals (Co, Ni, and Mn) under acidic conditions. GA avoids some of the chemical neutralization and disposition issues associated with more corrosive mineral acids. Design of experiments modeling revealed the relative impacts of temperature, pulp density, and GA concentration on metal extraction efficiencies and predicted the net present value (NPV) of a LIB recycling operation based on the approach. While metal extraction efficiency was governed by the GA concentration, NPV was most reliant on the LIB pulp density. Although under today's market conditions, the current iteration of the integrated approach is not predicted to be profitable, our efforts to find an optimal balance between the extraction efficiency and NPV offer a template for improving the economic viability of critical metal recycling approaches.