Rechargeable accumulator having a manganese dioxide electrode and an acid electrolyte

An accumulator which can be alternately charged and discharged having two electrodes of the first kind mounted on base material, wherein in said first kind electrodes all the active material passes into solution on discharge which comprises:

• (a) on the positive side, an electrode of the first kind mounted on a base material, said electrode containing manganese dioxide as active material, said base material having a coarsely porous structure with an average pore diameter of from 0.1 to 2 mm and a pore volume of from 20 to 70% and selected from the group consisting of titanium coated with titanium nitride, titanium coated with titanium carbide, and graphite;
• (b) on the negative side, an electrode of the first kind mounted on a base material, said electrode selected from the group consisting of zinc, cadmium, iron, manganese and lead as the active material, and said base material consisting of powdered graphite embedded in a plastics binder which is resistant to the electrolyte whereby said base material is non-porous;
• and
• (c) an acid electrolyte, said acid being selected from the group consisting of sulfuric acid, tetrafluoroboric acid, hexafluorosilicic acid, perchloric acid, and amidosulfonic acid, wherein said acids form soluble salts with the metals of the active materials and have oxidation resistant anions with the proviso that when lead is used as an active material on the negative side, sulfuric acid cannot be used.