NOVELTY - The elementary battery comprises a film of solid electrolyte containing a lithium salt between a film forming a positive electrode and a film forming a negative electrode, or by a stack of elementary batteries. The stack comprises two terminal elementary batteries between which intermediate elementary batteries are placed. The two protective films are formed by an elastic material, where one of the electrodes of the elementary battery or each terminal battery is in contact with a protective film constituted by an elastic material.    USE - Used as an elementary battery.    ADVANTAGE - The elementary battery ensures safe operation to the user by preventing contact between electrodes of opposite sign directly or through a sharp penetrating element.    DETAILED DESCRIPTION - The elementary battery comprises a film of solid electrolyte containing a lithium salt between a film forming a positive electrode and a film forming a negative electrode, or by a stack of elementary batteries. The stack comprises two terminal elementary batteries between which intermediate elementary batteries are placed. The two protective films are formed by an elastic material, where one of the electrodes of the elementary battery or each terminal battery is in contact with a protective film constituted by an elastic material. One of the protective films is in contact with a connection layer of an electrode having a thickness emax, where the film has a thickness eme as eme greater than emax/ame. The positive electrode is constituted of a current collector forming the connection layer and carrying a film of active material of positive electrode capable of inserting reversible lithium ions. The negative electrode is constituted by a film of a metal material forming the connection layer including lithium, lithium alloys and intermetallic lithium compounds and by a current collector forming the connection layer carrying active material film of negative electrode capable of inserting lithium ions reversibly. The group of elementary batteries is assembled in parallel or series. The positive electrodes of two adjacent elementary batteries are combined into one and formed by single current collector having a film of positive electrode active material on each of these faces. The negative electrodes of two adjacent elementary batteries are combined into one and formed either by a single current collector having a film of negative electrode active material on each of its faces, or by a film of a metal including lithium, lithium alloys and intermetallic lithium compounds. The protective film is placed on the upstream face of the positive current collectors, and on the downstream face of negative current collectors, where the upstream and downstream faces extend with respect to the direction of penetration of a pointed conducting element. The protective film not placed on the outside of a terminal electrode is formed by a material that has electronic conduction close to the electronic conductivity of the electrode material with which it is contacted and less than the electronic conductivity of the current collector. The material constituting the protective film is an elastic polymer material comprising a polymer, an agent of electronic conduction and optionally charges. The electronic conduction agent includes carbon black, acetylene black, optionally graphite in expanded form, where the carbon is present in the form of nanotubes. The protective film is placed between the current collector and the film of electrode active material.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an elementary battery.    Lithium film (1)    Electrolyte film (2)    Positive electrode active material film (3)    Positive electrode current collector (4)    Turning element. (5)