DE1160909B - Alkaline accumulator - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: H Ol m

German class: 21b-25/02

Number: 1160 909

File number: Y 447 VIb / 21b

Filing date: October 5, 1960

Opening day: January 9, 1964

The invention relates to an alkaline storage battery with positive electrodes, the active mass of which is mercury and contains a small amount of silver, and has a particularly useful structure for Object by which the rechargeability of the cells is ensured.

It is believed that the mercury cells used in primary cells do not recharge allow, but must be removed after unloading. The use of such primary cells however, is due to the high raw material cost despite the uniform discharge voltage limited to a few practical cases. Also the attempt to use mercury cells for accumulators making it unsuccessful because satisfactory recharging could not be achieved could. An electrical collector with an alkaline electrolyte has already been proposed whose positive electrodes consist of mercury and a small amount of silver. But also a completely reversible current-supplying reaction was not possible because of the mercury can not be oxidized by the known electrochemical route alone.

In contrast, the invention is based on the object to avoid these disadvantages and to make mercury cells rechargeable. Included the structure should be simple and cheap and the best possible use of the load capacity allow.

This object is achieved according to the invention in that the positive mass is made of mercury oxide and from a current-conducting mixture of silver powder and finely divided graphite and / or activated carbon. This structure provided according to the invention is more advantageous Way to ensure rechargeability. The mercury oxide is used when discharging Mercury oxydil is reduced, which easily converts to the oxide form when it is electrochemically charged can be traced back.

The mercury content in the positive mass is expediently between 50 and 70 percent by weight. It should be dimensioned according to the invention in a preferred embodiment so that it is about the twice the molecular weight of the amalgamated metal of the negative electrode, which is zinc or cadmium can be, corresponds. Further features of the invention relate to the addition of certain organic ones Acids to the electrolyte for the purpose of influencing the surface tension of that present in the electrolyte metallic mercury.

Alkaline accumulator

Applicant:

Yardney International Corporation,
New York, NY (V. St. A.)

Representative:

Dr.-Ing. G. Ackmann, patent attorney,

Duisburg, Zieglerstr. 32

Named as inventor:
Ricardo Salcedo, Madrid

Claimed priority:

Spain of October 8, 1959 (No. 252 527)

The subject matter of the invention is explained using a drawing.

1 shows a perspective view of a cell constructed according to the invention;

Fig. 2 shows a perspective view of an electrode;

F i g. 3 shows an electrode cover in a side view;

F i g. 4 shows a side view of an electrode set, and

5 shows a side view of a set of electrodes with metallic container and casing.

As already stated, mercury cells are generally not reversible because of the mercury compound is reduced to mercury metal and is not further oxidized by electrolytic means. According to the invention the reversibility can be achieved by using a negative electrode that for example, contains such an amount of zinc that this before the complete reduction of the positive Active mass is consumed. A positive electrode designed according to the invention essentially consists made of mercury oxide and a powder mixture of graphite and silver. The graphite acts as a Distributor and electrical conductor and the silver powder as a catalyst and electrical conductor. The one to achieve a powerful work in each individual cell can be the exact amount of substances required easily estimated © which can be determined by trial.

309 778/101

The Mercury overoxidation should make up 50 to 60 percent by weight of the total weight of the positive electrode mass. A mercury oxide content of 58 to 62 ⁰ zo is preferred. The graphite and the silver form the remaining 30 to 50 ⁰ O of the positive electrode mass, the proportion of which can be varied within the limits, provided that the sum of these components does not exceed 50 percent by weight. The various constituents should have an optimally effective grain size distribution.

Usually, the constituent parts of the positive electrode are in paste form and are more uniform for the purpose Distribution of the substances intimately mixed. For use in a cell, they are in a silver-plated Steel container or bag packed connected to the positive poles of some type.

The negative electrode mass which is used in a cell which needs the positive active mass in the described manner can be varied within wide limits in the composition of its two constituents according to type and amount. It is expediently composed of zinc or some other metal, for example iron, cadmium or tin, which is electrically more negative than mercury oxide and which essentially does not react directly with an alkaline electrolyte. However, zinc and cadmium are preferred. Amalgated zinc or cadmium with a low mercury content works well. The mercury content should not exceed 5 ⁰ Zo of the content of negative active material.

More advantageous results are achieved when the molar content of the mercury oxide contained in the positive active material is contained, approximately equivalent to twice the molar content of the zinc or Is cadmium, which is in the negative active mass. The amalgated zinc or cadmium can can be made by any of the known methods.

A particular for use with the described active composition electrolyte is an alkaline solution of potassium zincate, the od any small amount, about 1 to 5 ⁰ Zo of the weight of the solution, of an aromatic acid, such as p-toluic acid, terephthalic acid, isophthalic acid. Like., is added. The addition of these acids, which form soluble salts with the excess alkali contained in the electrolyte, overcomes the surface tension of the metallic mercury present in the electrodes and the accumulation of small drops and also regulates the proportion of zinc oxide dissolved in the electrolyte. Although other alkalis can be used, potassium hydroxide is preferred. A typical electrolyte, which is about 30 to 35 ⁰ Zo contains potassium hydroxide has 12 g of zinc oxide on 100 g of potassium hydroxide. In addition, terephthalic acid is added, namely 1 to 1.5 g per 100 cm ^{3 of} electrolyte solution.

A cell designed according to the invention consists, as shown in FIG. 1, of a housing 11 made of polyvinyl chloride. However, the housing can also be made of other materials that are arbitrarily resistant to alkali attack consist of plastic materials, for example methacrylate. The housing contains the spacers 12 and 12 ', which are arranged between the electrodes 13, 13' and 14. For the professional it can easily be seen that the number of electrodes depends on the number desired for each cell Capacity can be changed. To create an electrical unit between the electrodes, is designed to be filled with a sufficient amount of electrolyte, usually around 10 ". ο of volume is given, sufficient space is provided. The housing 11 has a cover 15 with Poles 16 and 16 'attached to it and electrically and mechanically connected to the positive and negative Electrodes connected ind. The poles have screw threads and protrude through the cover and through metallic ones Connecting bridges 17, 17 'and 17 ", which are usually made of silver-plated steel and which are soldered to the positive and negative electrode containers 18, 18 'and 18 ". The poles 16 and 16 'are of screw nuts 19, 19', 20 and 20 'at a relative distance to both Lid 15 as well as to the connecting bridges 17, 17 'and 17 ″ held in position. In this way and Way, the electrodes are fixed to the lid and

kept so safe. The lid is made with either resin or attached by soldering. In the version with a small number of electrodes According to Fig. 1, the pole 16 'protrudes down to the contact with the electrode 14, on the surface he's soldered on.

The illustrated in Fig. 2 typical embodiment of a container is used to accommodate the negative or positive active mass. Usually the container is made of steel plates with side and sides End walls which are finely perforated at 24 for the passage of the electrolyte. The top and bottom Covers 25 and 26 are wider and longer than the side and end walls and form for the jackets 27 or 27 'an approach or a carrier. The inner sheath 27 is on the perforated Surface of the container attached and in the embodiment of FIG. 5 with a Resin tightly attached to the imperforate surface of the container. The casing 27 forms a semipermeable Membrane and consists of regenerated cellulose or similar substances. The second sheath 27 ', on the other hand, consists of cotton fabric. It gives the first sheath 27 a firm fit on the perforated surface of the container. This sheath 27 'can either with the help of an adhesive or by means of cellulose tapes 28, as shown in FIG. 5 shows; be attached. Provided the container has positive ground it is made of silver-plated steel. In the other case where the container is the to absorb negative mass, it can consist of heavily galvanized steel or brass. In the During the manufacturing process, the positive or negative active material is placed in the container, the covers are applied and then either sealed with solder, adhesive or simply by pressure. The sheaths are then placed in the container in the manner described. The ones made in this way Electrodes are then inserted into the housing 11. However, the invention is not limited to the one described construction of the cells is limited. Rather, for those according to the invention Composite electrodes also find other cell designs use, for example by pressing the electrode mass into plates so that no containers are necessary.

The electrochemical designed according to the invention Cell has many advantages. She is not only efficient at work, but can also work for

can be recharged for further use. In addition, it is relatively simple in structure and cheap to manufacture. Without the theoretical basics about the work process according to the To list exhaustively the cell designed in accordance with the invention, silver should only act as a catalyst for the Mercury act and its share in the crushed active mass is not viewed as critical will. Even small amounts of silver were found to be effective. In this respect, any participation of silver in the electrochemical reaction can be viewed as secondary. So it doesn't wear for the storage and delivery of electrical energy. In addition, the silver is unlikely to be enter into electrical connection with the mercury oxide, so that it is therefore referred to as relatively inactive can be.

The graphite to be preferred in an electrode according to the invention serves primarily as a dispersant, to prevent the reduced mercury from sticking together excessively during discharge, although it also acts as a non-metallic conductor of relatively inactive character. Since that too finely divided silver acts like a dispersant and like a conductor, graphite can in extreme cases be completely replaced by silver. In practice, however, it should be more economical, a relative one to use a large amount of graphite and a correspondingly small amount of silver as a dispersant.

Instead of graphite, similar carbonaceous masses can also be used, in particular Activated carbon or mixtures thereof with graphite.

Claims (4)

Patent claims: 1. Alkaline accumulator with positive electrodes, whose active mass is mercury and contains a small amount of silver, characterized in that the positive mass from mercury oxide and from a current-conducting mixture of silver powder and finely divided material Graphite and / or activated carbon is made. 2. Accumulator according to claim 1, characterized in that the mercury oxide content in of the positive mass is between 50 and 70 percent by weight. 3. Accumulator according to claim 1 and 2, characterized in that the mercury oxide content in the positive mass about twice the molecular weight of the amalgamated metal of the negative electrode, which is zinc or cadmium can be, corresponds. 4. Accumulator according to claim 1 to 3, characterized in that the alkaline Electrolytes 1 to 5 percent by weight of toluic acid, terephthalic acid or isophthalic acid were added are. Considered publications:
German Patent Nos. 273143, 159 393;
British Patent No. 808 007. 1 sheet of drawings 309 778/101 12.63 ® Bundesdruckerei Berlin