TECHNOLOGY FOCUS - ELECTRONICS - Preferred Method: The metal-air battery and a module system is designed in a planar or tubular shape.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The metal-containing negative electrode comprises at least one metal, metal alloy or metal-containing compound, where the metal, metal alloy or metal-containing compound is in a molten, solid or semi-solid state, preferably molten state or in powder form. The metal is tin, bismuth, gallium, iron, copper, cobalt, nickel, lead, magnesium, zinc, antimony, indium, sodium, lithium or aluminum. The metal-containing electrode further comprises a mixed ion-electron or ion conducting porous matrix. The metal-containing negative electrode comprises: a mixture of a metal, metal alloy or metal-containing compound powder and a mixed ion-electron or ion-conducting powder or fiber; or a mixture of a liquid metal, metal alloy or metal-containing compound and a mixed ion-electron or ion-conducting powder or fiber. The ion conducting porous matrix comprises a fluorite-related oxygen ion conductor of formula (((A1-x-yA2xA3y)Os)1-z((Q1-vQ1v)O2)z-d). The mixed ion-electron conducting porous matrix comprises a fluorite-related oxygen ion conductor and/or a perovskite type transition metal oxide of formula ((E1-qE1q)1-a(Z1-rZ1r)1-bO3-d). The porous positive air electrode comprises a mixed electron and oxygen ion conductor. The mixed electron and oxygen ion conductor comprised in the porous air positive electrode is made of: perovskite type transition metal oxide of formula (Ln1-qMx)1-a(M11-yM2y)1-bO3-d); or a composite of a perovskite type transition metal oxide with the fluorite-related oxygen ion conductor which is (I).A, A2, A3 = at least one mono-, di- or trivalent element which is Y, Na, Sc, Sm, Gd, Ce, Ca, Mg, Al or Bi;Q, Q1 = at least one cation including Zr or Ce;v, x, y, z = 0-1;s = 0.5-1.5;a, b, d = site deviations from stoichiometry;E, E1 = Sr, Y, Sm, Ce, Bi, La, Gd, Nd, Pr, Ca, Ba, Mg or Pb;Z, Z1 = transition metal ions or Ga;q, r = 0-1;Ln = lanthanide cation including La, Pr, Nd, Sm or Gd;M = at least one alkaline-earth cation including Ca, Sr or Ba; andM1, M2 = Co, Fe, Cr, Cu or Mn.Provided that x+y is less than or equal to 1. The oxygen ion conductor electrolyte is a fluorite-related oxygen ion conductor which is (I). EXAMPLE - No suitable example given.