There is provided a mother-battery containing at least the following films: an anode of metallic lithium or sodium, a polymer electrolyte which is conductive towards the alkaline ions of the anode and also acts as a separator between the electrodes, and a composite cathode consisting of a compound which is reducible to lithium or sodium, an additive of electronic conduction and a polymer electrolyte binder. The mother battery also includes an electronically conductive thin coating on the external face of the anode and, possibly of the cathode, in which the conductive material is chemically inert towards the electrode material and which also serves to establish permanent electrical contacts on the external faces. The laminated mother-battery of larger surface area and at least partially charged is thereafter subjected to a sharp mechanical cutting out to give thin polymer electrolyte batteries with lithium or sodium anode. The thus cut out batteries preserve substantially their voltage after mechanical cutting out which is recovered by a mechanism of self-healing.