GB660503A - Improvements in rechargeable electric cells - Google Patents

Abstract

660,503. Accumulators. MALLORY BATTERIES, Ltd. June 13, 1949 [June 12, 1948], No. 15732/49. Class 53. An accumulator comprises a positive electrode of silver, an electrolyte of a zinc or cadmium halide, and a negative electrode which is amalgamated with mercury to amalgamate the metal deposited from the electrolyte when the cell is charged. The positive electrode may be in the form of a rod or of a sheet of silver-plated copper which is sprayed with a coarse deposit of silver. The negative electrode may consist of a sheet of copper or copper-zinc alloy such as brass or bronze which may be zinc-plated and amalgamated, or a woven copper or copper alloy screen may be used. Alternatively the negative electrode may consist of a quantity of mercury surrounding a copper tube. To ensure a satisfactory deposit of zinc or cadmium when the cell is charged various substances may be added to the electrolyte, for example magnesium chromate, dichromates and chromates of sodium, potassium and lithium, zinc dichromate, and organic substances of the heterocyclic type such as quinaldine, furfural and beta - naphthaquinoline. When cadmium chloride is used as electrolyte a small quantity of sodium or potassium chloride may be added. One example of an accumulator comprises a positive electrode of compressed silver powder, an amalgamated negative electrode of copper or copper alloy and an electrolyte consisting of a solution of zinc bromide containing a small amount of magnesium chromate. Fig. 1 shows a step in the construction of a single cell accumulator comprising a silver-plated copper sheet 11 carrying a deposit of sprayed silver. On the sheet 11 is a sheet 12 of paper or cloth and a sheet 13 of parchment paper, above which is a corrugated sheet 14 of zinc plated and amalgamated copper. The sheets 11, 14 are offset so that when all the sheets are rolled up the sheets 11, 14 project at opposite ends as shown. The roll is placed in an open-ended cylinder of polythene or other insulating material which is inserted in a copper container silver-plated on the inside. The rolled sheet 11 makes contact with the bottom of the container, the sheet 14 being in contact with a dished zinc-covered copper plate which closes the top of the container. The top plate may be provided with a cut-out tongue which is normally pressed into position in the plate but which will partly lift and relieve any excess gas pressure. In a modification a copper can zinc-plated and amalgamated on its inside forms the negative electrode. In the centre of the can is a rod of compressed silver powder resting on an insulating disc and separated from the can by apertured mica plates. The can is filled with a jelly electrolyte consisting of a solution of zinc bromide mixed with sodium carboxymethyl cellulose or other thickening agent. Fig. 4 shows a further modification in which two cells are joined in series, each cell comprising a silver-plated copper dish 40 containing compressed precipitated silver 42 supporting a jelly electrolyte 47 above which is a zinc-plated and amalgamated copper screen 45 enclosed by an amalgamated copper or bronze cover 44. Fig. 6 shows a cell consisting of a copper container 70 silver-plated on the inside and enclosing a pressed silver powder cylinder 71, a solution of zinc bromide 76 and a porous cup 73 of sintered aluminium silicate or magnesium silicate. Within the cup 73 is a copper cup 74 and between the two cups is a quantity of mercury 75 constituting the negative electrode with which the zinc deposited during the charging of the cell combines.