Cycle life limit of carbon-based electrodes for rechargeable metal–air battery application

• Bifunctional electrodes were evaluated with different carbon and catalysts.
• The graphitization of the Vulcan more than doubled the electrode cycle life.
• The limiting factor for cycle life of electrodes was the corrosion of carbon support.
• The catalyst size/morphology also affected the performance degradation.
• Electrochemical impedance spectroscopy was used to assess failure mechanisms.

In this paper, the electrochemical performance and cyclic lifetime of bifunctional electrodes in an alkaline electrolyte were investigated as a function of the perovskite catalyst (La0.6Ca0.4CoO3 or Sr0.5Sm0.5CoO3−δ) and the carbon (as-received or graphitized Vulcan XC-72 carbon black). The electrochemical performance of the electrodes was essentially the same, regardless of the carbon and the catalyst; however, the cycle life was directly controlled by the carbon. The graphitized Vulcan-based electrodes had more than twice the cycle life of the as-received Vulcan-based electrodes, due to the better corrosion resistance of the graphitized carbon. The cycle life of the carbon-based electrodes was limited to 100–110 cycles under the testing conditions used in this investigation and the limiting factor was the carbon rather than the catalyst, i.e., the corrosion/oxidation of carbon under the anodic condition. Furthermore, the size/morphology of the catalyst powder affected the electrode performance degradation under cycling noticeably. The failure mechanisms of these electrodes under cycling were also assessed using impedance spectroscopy.