Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1984-09-12
1986-10-21
Walton, Donald L.
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
429238, 429239, 296231, H01M 470, H01M 476
Patent
active
046185496
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of making electrodes for storage batteries of the lead-acid class.
Further, the invention relates to an improved electrode for storage batteries of the lead-acid class, and to an improved storage battery comprising such electrodes.
2. Description of the Prior Art
Electrodes for lead acid batteries are made essentially according to two principles, viz. pasted electrodes and tubular electrodes.
The first mentioned type comprises a grid which holds a dough (paste) of a mixture of lead oxides, water and sulphuric acid. If the electrode is intended to constitute a negative electrode (i.e. being used as the anode in the battery during discharge) also carbon black, barium sulphate and lignine are added. The dough is pasted into the grid, either manually or by means of any suitable equipment. The grid is cast in one piece of lead or a lead alloy and has the tasks of carrying the paste, which in the formed condition constitutes the active material, and conducting current to and from the active material. The grid may have different configurations to serve its purpose. Very often some of its spines are mutually somehwat displaced to enhance the ability of the grid to hold the active material. The grid also has a lug for the connection of other electrodes of the same kind in parallel, via a post strap, to a post, where a cable can be connected.
Tubular electrodes have a different grid design in that a number of straight and parallel spines are connected to an upper frame which has a lug. Also this kind of grid is cast in one piece. Porous tubes with a round, elliptic or square cross-section are thread on to the spines. To locate the spines centrally of each tube, the spines are provided with small protrusions or fins. The length of the tube is at least the same as that of the spine. The tubes are fixed to the grid only by pushing them on to the upper, conical parts of the spines. The application of the material, which after electro-chemical formation will constitute the positive active material, is made by turning the open ends of the tubes upwardly and filling a powder or a slurry of leady oxides into the tubes. Since the filling material is usually not a free flowing material, grid and tubes have to be vigorously shaken and vibrated during this operation. When the appropriate amount of material has been filled into the tubes, the ends have to be sealed by means of a bottom bar of plastic, which is pressed into the tubes. For the subsequent operation it is necessary that the bottom bar is well anchored. The tubes may be used either individually--one for each spine--or as a group of tubes, sewn or woven together. There could also be more than one spine in a tube.
Sometimes another element is added to the tubular electrode, viz. an enclosure of plastic arranged around the upper frame to protect it against corrosion. Such an arrangement also decreases the amount of antimony that can be dissolved from the frame. Furthermore, the portion of the current which passes from the upper frame to the negative electrodes is first forced through the positive active material, which means a higher current efficiency.
The porous tubes are made from braided or woven glass or polyester. Glass is very resistant to oxidation in the environment created by oxygen evolved on lead dioxide during charging, but must be supported and protected by a perforated sheet of e.g. PVC. Polyester tubes are impregnated by fenolic resin for the same reason. Very often the tubes are made from felted (non-woven) materials such as polyester. The properties of the tubing material shall be: high porosity to permit fast acid diffusion into the electrode and good mechanical strength to support the active material and retain it in the electrode.
The dough or powder applied to the grids and comprising lead compounds, must be transformed to lead dioxide in the positive electrode and to porous lead in the negative one by an electro-chemical process (formation) before the
REFERENCES:
patent: 969876 (1910-09-01), Johnson
patent: 1509992 (1924-09-01), Allen
patent: 3247023 (1966-04-01), Geissbauer
patent: 4285121 (1981-08-01), Guimond et al.
patent: 4331747 (1982-05-01), Julian et al.
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