METAL OXYGEN BATTERY

There is provided a metal oxygen battery which uses an oxygen-storing material containing YMnOas a positive electrode material, and can reduce the discharge overpotential. The metal oxygen battery has a positive electrode to which oxygen is applied as an active substance, a negative electrode to which metallic lithium is applied as an active substance, and an electrolyte layer interposed between the positive electrode and the negative electrode . The positive electrode contains, as an oxygen-storing material, a composite metal oxide obtained by crushing and mixing a yttrium salt, a manganese salt and an organic acid, primarily calcining the mixture, and thereafter, adding a zirconium salt to the obtained primarily calcined material, and secondarily calcining the mixture, the composite metal oxide containing YMnOand ZrO.