Modified carbon-free silver electrodes for the use as cathodes in lithium-air batteries with an aqueous alkaline electrolyte

Kurzfassung

Gas diffusion electrodes with silver catalysts show a high activity towards oxygen reduction reaction in alkaline media but a rather poor activity towards oxygen evolution reaction. For the use in future lithium eair batteries with an aqueous alkaline electrolyte the activity of such electrodes must be improved significantly. As Co3O4 is a promising metal oxide catalyst for oxygen evolution in alkaline media, silver electrodes were modified with Co3O4. For comparison silver electrodes were also modified with IrO2. Due to the poor stability of carbon materials at high anodic potentials these gas diffusion electrodes were prepared without carbon support to improve especially the long-term stability. Gas diffusion electrodes were electrochemically investigated in an electrochemical half-cell arrangement. In addition to cyclic voltammograms electrochemical impedance spectroscopy (EIS) was carried out. SEM and XRD were used for the physical and morphological investigations. Investigations showed that silver electrodes containing 20 wt.% Co3O4 exhibited the highest performance and highest long-term stability. For comparison, rotating e ring e disc e electrode experiments have been performed using model electrodes with thin catalyst layers, showing that the amount of hydrogen peroxide evolved is negligible.