Biotreatment for the spent lithium-ion battery in a three-module integrated microbial-fuel-cell recycling system

A bio-electrochemically (BE) recycling platform was assembled to recover Li and Co from the cathodic materials of spent LIBs in one integrated system. The BE platform consists of three microbial-fuel-cell (MFC) subsystems, including MFC-A, MFC-B, and MFC-C. Co and Li were smoothly recovered from the cathodic materials in the assembled platform. The initial pH and the loading ratios of LiCoO₂ both significantly influenced the leaching efficiencies of Li and Co in MFC-A. Approximately 45% Li and 93% Co were simultaneously released through the reduction of LiCoO₂ at the initial pH of 1 and the loading ratios of LiCoO₂ of 0.2 g/L. The (NH₄)₂C₂O₄-modified granular activated carbons (GAC) with a thickness of 1.5 cm was favorably stacked adjacent to the cathode of the MFC-B system. About 98% of removal efficiency (RE_Co1) and 96% of recovery efficiency (RE_Co2) of Co were achieved in MFC-B under optimum conditions. The dosing concentration of Li⁺ lower than 2 mg/L and the (NH₄)₂CO₃ of 0.01-0.02 M were conducive to enhancing the recovery of Li from raffinate and guaranteed the higher power output and coulombic efficiencies in MFC-C. The continuous release of CO₂ caused by exoelectrogenic microorganisms on the biofilm facilitated the precipitation of Li₂CO₃.