Synergetic interactions improve cobalt leaching from lithium cobalt oxide in microbial fuel cells. 
Cobalt leaching from lithium cobalt oxide is a promising reduction process for recovery of cobalt and recycle of spent lithium ion batteries, but suffers from consumption of large amount of reductants and energy, and generation of excess secondary polluted sludge.  Thus, effective and environmental friendly processes are needed to improve the existing process limitations.  Here we reported microbial fuel cells (MFCs) to effectively reduce Co(III) in lithium cobalt oxide with concomitant energy generation.  There was a synergetic interaction in MFCs, leading to a more rapid Co(III) leaching at a rate 3.4 times the sum of rates by conventional chemical processes and no-acid controls.  External resistor, solid/liquid ratio, solution conductivity, pH and temperature affected system performance.  This study provides a new process for recovery of cobalt and recycle of spent lithium ion batteries with concomitant energy generation from MFCs.