NOVELTY - A galvanic cell structure comprises a pressure vessel having cell components disposed in an interior volume of the vessel. The components include a metal hydride anode (31); at least one membrane separator (23) positioned on opposite sides of the metal hydride anode; at least one oxygen electrode (17) acting as a cathode, positioned near the separator on sides opposite to the metal hydride anode; insulator plates (29) positioned in contact with the oxygen electrode; and an electrolyte in contact with the metal hydride anode, the oxygen electrode, the insulator plate and/or the separator.    USE - As a galvanic cell structure e.g. a rechargeable fuel cell unit or a metal/air battery cell unit (claimed); useful in a rechargeable fuel cell and a metal/air battery.    ADVANTAGE - As galvanic cell components are enclosed in the pressure vessel, access to the interior of the galvanic cell structure from outside environment is restricted/blocked, thus preventing exchange of carbon dioxide and water in or out of the closed galvanic cell structure. Hence, the galvanic cell structure reduces/eliminates the effects of carbon dioxide poisoning and water evaporation, due to no contact with air and carbon dioxide. Susceptibility of hydrogen embrittlement for the pressure vessel material is reduced or eliminated. The gas enclosed in the vessel can be oxygen instead of hydrogen, where the oxygen use reduces/eliminates metal vessel embrittlement. Oxygen channel is defined by a space between the galvanic cell components and inner surface of the pressure vessel wall. In a cathode facing stacking model of galvanic cell units, the rechargeable fuel cell or metal/air battery can easily share the oxygen channel for each pair of single cells. In addition, there is greater charging and discharging power due to double cathode area; and the anode is insulated from oxygen allowing increased ease of stacking. Short-circuiting of the anode by direct oxidation is prevented. In a circulation-stacking model for galvanic cell units, electrical connections are simplified as compared to other models. The oxygen storing materials provides increased oxygen-storage ability in the closed space of pressure vessel such as in the oxygen channel.    DETAILED DESCRIPTION - Galvanic cell structure comprises a pressure vessel having cell components disposed in an interior volume of the vessel. The components include a metal hydride anode (31); at least one membrane separator (23) positioned on opposite sides of the metal hydride anode; at least one oxygen electrode (17) acting as a cathode, positioned adjacent to the separator on sides opposite to the metal hydride anode; insulator plates (29) positioned in contact with the oxygen electrode; and an electrolyte in contact with the metal hydride anode, the oxygen electrode, the insulator plate and/or the separator. The vessel is preferably a high-pressure container that is operable to contain a pressure of greater than 1 atmosphere. The oxygen electrode preferably includes a catalyst layer (21) and a diffusion layer (19) having an oxygen storage material. The insulator plates define several apertures. The galvanic cell unit includes at least one bipolar plate and an oxygen barrier layer, instead of the insulator plates. The bipolar plate surface has one portion in contact with a surface of the oxygen electrode, and another portion in contact with a surface of the metal hydride anode. The barrier layer contacts and shields a portion of the metal hydride anode surface that is not in contact with the bipolar plate. The catalyst layer of oxygen electrode includes a catalyst, a conductive particulate and a binder. The metal hydride anode comprises a metal hydride as active material, a binder and at least one conductive additive.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of a cathode-facing stacking model for rechargeable fuel cells or metal/air batteries.    oxygen electrode (17)    diffusion layer (19)    catalyst layer (21)    separator (23)    lead connections (25)    oxygen channel (27)    insulator plates (29)    metal hydride anode. (31)