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.