GB449687A - Improvements in or relating to secondary cells - Google Patents

Abstract

449,687. Batteries. HOCHWALD, F., 13a, Tauentzienstrasse, Berlin. Jan. 1, 1935, Nos. 37 and 38. Convention dates, May 3, 1934 and June 19, 1934. [Class 53] An accumulator employing an electrolyte of zinc iodide or bromide has a positive electrode containing active carbon in sufficient quantity to absorb at least three quarters of the iodine or bromine set free during charging, the quantity of combined halogen in the electrolyte amounting to 1 to 2À5 grms to each gram of active carbon. The electrode may consist of a carbon or metal core covered with active carbon or the latter may be deposited on or within a porous carrier such as pumice. Graphite may be added to the carbon to increase the conducitivitv of the electrode. The active carbon may be subjected to a preliminary treatment with the halogen in gaseous or liquid form or in solution, or by means of electrolysis. The cell works with an electrolyte of a pH value between 3À5 and 6 to suppress the evolution of oxygen as much as possible. The distance between the surface of the active carbon and the cathode is not more than three times the thickness of the carbon layer and the thickness of the latter is not more than that of the carbon core. The electrolyte may be separated from the positive electrode by a perforated partition and the electrolyte may contain conductive salts such as halides of the alkali metals and oxides or hydroxides of metals such as zinc, magnesium and aluminium may be added to form a jelly. The negative electrodes may consist of iron or zinc-coated iron or nickel. The positive electrodes may be constructed to allow circulation of electrolvte bv providing them with perforations or grooves or making them in the form of grids or gauzes. The diameters and the distance between the perforations should not exceed 4 mms.