Bi‐Functional Oxygen Electrode Using Large Surface Area La1 − x Ca x CoO3 for Rechargeable Metal‐Air Battery

In order to develop an air electrode to be used for rechargeable metal‐air batteries, gas‐diffusion type carbon‐based electrodes have been tested for the electrochemical reduction and evolution of oxygen. The electrode, loaded with a large surface area of catalyst was found to show high bifunctional performance, i.e. , 3000 mA/cm 2 (oxygen reduction) and 1000 mA/cm 2 (oxygen evolution) at −125 and +700 mV vs. , respectively, in 30 w/o at 25°C. The oxide catalyst is considered to decompose effectively , an intermediate appearing in both oxygen reduction and oxygen evolution reactions. The air electrode was stable for 100 cycles of charge‐discharge test at a current density of 100 mA/cm 2 .