A battery equipped with a cathode composite (2), an anode composite or an anode (4), an electrolyte layer (3) and a sealing material (6); characterized by that a material such as an element belonging to VIII-group of periodic table such as palladium etc., for example, is included in an inside of the battery. Gas produced in the battery inside is absorbed to the above material or added to a residual reactive double bond in an ion-conductive high-molecular compound by the above material, so that a rise of battery inside pressure due to gas is restrained and expansion and bursting of the battery are thus prevented.