Abstract: A sealed galvanic cell which has high power and energy densities, a low self discharge, and an open circuit voltage which is related to state of discharge, and which is useful for supplying electrical power to an implantable device, such as a defibrillator and a nerve stimulator, with a large current consumption, and method of making same. The galvanic cell includes a casing; a cathode unit having at least one electrode composed of a mixture of at least one metal oxide and at least one lead compound; an anode unit having at least one electrode comprised of an alkali metal; and an organic electrolyte comprised of a mixture of (a) ethylene- and/or propylene carbonate, (b), 2-dimethoxyethane, and (c) a conducting salt. The mixture of the cathode unit is one of (a) a mixture of CrO.sub.x (x=2.5 to 2.7) and at least one lead compound from among PbCrO.sub.4, PbMoO.sub.4 and PbO, (b) a mixture of CrO.sub.x (x=2.5 to 2.7), MnO.sub.2, and at least one lead compound from among PbCrO.sub.4, PbMoO.sub.