DE1276769B - Negative electrode for accumulators and process for their manufacture - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN W7TW> PATENTAMT Int. CL:

HOIm

EDITORIAL

German class: 21b-25/02

Number: 1276 769

File number: P 12 76 769.0-45 (Y 429)

Filing date: July 7, 1960

Open date: September 5, 1968

The invention relates to a negative electrode for accumulators with one made of zinc or cadmium existing active layer resting on a conductive base plate, e.g. B. made of copper, silver or nickel, is applied as a fine-pored electrolytic precipitate. She has a particularly functional one Structure of the negative electrode and a method for its manufacture are the subject matter by which the performance and durability of the electrode is significantly improved.

To give the active coating of a negative electrode a particularly large surface, In addition to a highly porous application of powder particles, a galvanic coating is also proposed been. If the electrodes are made of electrolytically reduced metal oxides the disadvantage must be accepted that not all of the oxide is reduced and only insufficient utilization of the active material is possible. On the other hand, such electrodes have the disadvantage of a high initial resistance, which initially results in a large voltage drop when discharging has the consequence. Finally, it has also been found disadvantageous in electrodes of this type that the electrolytic precipitate does not adhere adequately to the conductive base plate. The invention lies the underlying task of eliminating these disadvantages and difficulties and the negative electrode designed in such a way that their performance and the adhesion of the active layer on the base plate is significantly improved.

According to the invention, this object is achieved in that the fine-pored active layer has a density from about 35 to 65%, based on the density of the compact metals zinc or cadmium, is condensed. This compression initially has the advantage that the performance per Unit volume of the active mass is significantly improved. Resistance is in from the start correspondingly low. Another advantage can be seen in the fact that through the compression a better adhesion of the active layer on the conductive base plate is guaranteed.

The active electrode is expediently produced in that to form a highly porous zinc or Cadmium precipitate with a density of about 15 to 40%, based on the density of the compact metals zinc or cadmium, one used for electrolysis a solution that is known in Contains larger amounts of other ions that do not correspond to the metal to be deposited, and in which the ion content of the deposited

Negative electrode for accumulators and
Process for their manufacture

Applicant:

Yardney International Corporation,

New York, N.Y. (V. St. A.)

Representative:

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

4100 Duisburg, Claubergstr. 24

Named as inventor:
_ao Kenneth Brown, Ashaway, R.L;

Otto Wagner, Matawan, N. J. (V. St. A.)

Claimed priority:
V. St. v. America 8 July 1959 (825 842)

Metal at a temperature below 50 ° C is significantly less than 10 percent by weight, and that one is the obtained precipitate to a density of about 35 to 65%, based on the density of the compact Metals, compressed.

With this process, a highly porous precipitate is initially formed, which then on a such density is compressed, which ensures the best possible electrochemical properties.

The subject matter of the invention is shown in the drawing using several exemplary embodiments. It shows

F i g. 1 is a diagram of ten successive process steps for the production of electrodes designed according to the invention,
F i g. 2 a schematic representation of a bath for the electrolytic deposition of the active metal on the electrodes,

3 shows a schematic representation of a device for the continuous production of electrodes of the new kind,

F i g. 4 shows a bath for the production of bimetal electrodes according to the invention and

880 599/194

3 4

Fig. 5 shows the performance diagram for electrodes and the covers in process stage 9, differently from one another Volume weight. men. The conductors are made in process stage 10

As shown in FIG. 1 it can be seen, the current- at the previously covered places on suitable conductive support on which the active material is attached. Then the active mat is brought is first charged in a suitable size, gially of the positive electrodes, cut. The supports can be from any one of Fig. 2 shows a bath tank 20 which has two

suitable electrically conductive material, the anodes 21 and 21 'and a cathode 22 includes the with the active material no galvanic element made of a conductive carrier 23 with deposits forms and from the electrolytic bath, from the 24, 24 'of the active material in microcrystalline the active material is deposited, there is no attackable shape on both sides. The anodes and the is cash. Preferably thin copper foil is used. Cathode are connected by positive and negative conductors 25, punched or unpunched, used, but there are also 26 and 26 'connected to power sources. The cathode other conductive metals, such as silver and nickel, 22 has a frame 27,27 ', two of which are correspondingly usable. Iron can also be used when corresponding frames 28, 28 'are opposite to a it is ensured that an evolution of hydrogen 15 results in a uniform deposition of the layers 29, 29 ' due to its very low overvoltage. The frames 28, 28 'and 27, 27' are made that will. Electroplating the surface of the non-conductive material, e.g. B. from suitable Iron prevents the evolution of hydrogen when plastics.

such carrier used in a zinc bath. According to Fig. 3, a washed and degreased one is used

will. 30 carrier 31 in tape form with covered surface

The cut beams are removed in step 2 for the later attachment of the ladder from greased and washed, e.g. B. by chlorine vapors and a role 30 on guide rollers through a subsequent rinsing in a water bath. Out to electroplating bath 32 and happens in the process the adherence of the electrolytic precipitates of a number of anodes 34 made of active metal. That active material on supports of certain types, e.g. B. as bath 32 is equipped with filters 35 for removing im made of silver, to improve the surface can easily electrolyte 33 and insoluble impurities to be etched. a cooling system, not shown, for upright

In stage 3, the areas where the desired bath temperature is maintained are provided Later, the conductors are to be attached to the carrier, in From the electroplating bath 32, the tape-compatible one arrives Way covered. 30-shaped carrier 36 with the deposited on it

The carriers prepared in this way are in stage 4 active metal by means of adjustable pressure rollers 37, then hung in the electrolytic bath and after which the electrodeposited active metal a sufficiently thick deposit of the active compacted to the desired extent. After that, will Material removed from the bath. the tape at 38 in strips 39 of the usual length

To achieve the highest discharge currents, the cells 35 cut.

len or batteries are the precipitates or the strips 39 are in holder 40 of any type

Electrodes put together by pressing them together and then placed in a washing container 41 Process stage 5 condensed. This compacting submerges the hot water of around 60 to 90 ° C can be done by rolling or by pressing. contains. The holders move from the washing container

In the next process stage 6, the 40 or frames 40 are placed in an amalgamation bath 42, up to maxi-electrodes neutralized and washed to ensure they are absorbed by 5% mercury times. Connecting Remnants of the electrolytic deposition bath ßend the strips 39 are rinsed in a bath 43 to clean. In the case of zinc electrodes, these are dried in and in a drying device 44. Stage 7 treated with dissolved mercury salts. The strips 39 are now removed from the racks 40

so amalgamated. Since most of the usual negatives 45 are taken out and placed in a cutting device 45 tive electrodes cut to electrode size more electronegatively than mercury. The covers the mercury will be on the surface of the attachment points for the ladder Electrolytically deposited microcrystalline actively removed and the conductors in a solder or welding vein Reduced mass. The amalgamation is applied to the now finished electrodes 48 in front of device 46 all applied to the hydrogen overvoltage 50 attached.

the electrodeposited active material to For the electrodeposition of the active

Increase, also for this reason, by any possible damage. Examples are given below: amalgamate impurities and create a surface

the same potential, which is not for example 1

There is a tendency for gas formation and self-discharge. In general 55

nen an addition of ¹ U to 5 percent by weight is sufficient. An electroplating bath is used

Contains mercury to achieve the desired we- 30% KOH and 5% ZnO dissolved in water, kungen. It has been found that the Amalga zinc anodes have a purity of mation in connection with the microcrystalline 99.9%. The cathodes consist of full or solid structure of the active mass the discharge depolar 60 perforated copper or brass sheets. The distance sation prevents which the life of the cells between anode and cathode is about 10 to belittles. 15 cm and the voltage difference 5 V. The effective

The amalgamation takes place by immersion in the same tension on the Kahodenfläche during the the amalgamating solution for a certain time electrolytic metal deposition lies between or until the required increase in weight is 65 1.85 to 2.25 V. The temperature of the bath is enough. After amalgamation, the electrodes are kept below 50 ° C, preferably at 25 ° C ± 5 ° C rinsed and dried in step 8. You th. The electrolyte becomes during the metal deposition Cut to the final dimensions manure continuously filtered, but the drain too

Claims (1)

5 6 the filters and the reflux from the filters so applied 103 forms the common order for both chambers that the movement of the electrolyte between the cathode. When the circuits are switched on, the anode and cathode are as small as possible. That is, a porous zinc deposit 104 on the right bath voltage is created independently of the right side and a silver deposit 105 on the current density by increasing the voltage up to the left side of the foil 103 . the point of onset of gas evolution- When the electrolytic deposits 104,105 obtain. have reached the desired thickness, the If the 1 2 metal deposition is interrupted. The bath tank " 100 can now serve to close the silver layer 105 A bath is used which oxidizes from 25% Ammo ίο, z. B. by replacing the electrolyte liquid chloride, 5% cadmium oxide and 6% excess chlorine in the left compartment with a KOH solution, acid in an aqueous solution. The pH value of the bath, with the film 103 placed at a positive potential, is kept in the range from 3 to 5. and the silver anode 102 by a cathodically-ge The bath temperature is below 30 ⁰ C and the bath turned inert electrode, for example of stainless current density at 10 Amp./cm ^{2 is} held. The chip-free steel, is replaced. After completion of the oxynation at the cathode is 1.5 to 1.85 V. The dation can be the foil 103 with the layers 104,105 current density and the total voltage is because of the removed from the bath tank and as a tendency of this bath, the hydrogen overvoltage bimetal electrode for dry chargeable electrical to degrade cadmium, to regulate carefully. Cells or batteries are used. Of course, the addition of about 1% gelatin can largely eliminate this inclination on one side of the film 103 in one go. In this bath, an electrolytic coating of cadmium instead of cadmium electrodes provided results in a zinc discharge in a bath with a composition approximately in the range from 1.5 to 3 amps / dm ² . This is essential to be provided according to Example 2,
borrowed better than with electrodes made of pressed cad- The electrodes according to the invention are after mium powder and / or impregnated with cadmium 25 of the electrolytic deposition of the active metal sintered nickel plates. an active metal particle size of 1 to 8 microns. The active metal is so porous that its Example 3 Density approximately between 15 and 40% of the density of the . solid metal lies and is after the electrical In a bath of the following composition: _{30 p} i _at animals to about 35 to 65% of the solid metal KOH increased by 25%. AgCN 5% in Fig. 5 is the result of a series of tests KCN 15% shown in the diagram, with the performance in K ₂ CO ₃ 2% ampere-hours per cubic centimeter of negative active Wasse'r 35 ver mass is based on the volume weight. It deals zinc electrodes in a 30 per cent silver has been treated by common silver anodes on a KOH solution. The volume weight Copper cathode with an anode-cathode distance of the zinc precipitate was prior to sintering and of 25 mm and an anode-cathode potential pressing 15%, based on the density of the compact difference of 1 to 2.5 V electrodeposited. 40 zinc metal. The electroplating temperature was The bath current is about 5 amps / cm ² . The deposit was 25 ° C. The zinc precipitate received a 1% strength potential under these conditions is in the amalgamation and the discharge current had a Maintained range from 2.5 to 3 V. Density of about 0.3 amps / cm ² . The diagram shows After a sufficient amount of silver has been deposited, a compaction of 35 to 65% that is, the electrode is taken out of the bath, 45 particularly good performance is obtained,
pressed, washed and loaded in an aqueous KOH solution. The subsequent discharge of the Electrode results in a silver utilization approximately patent claims:
corresponding to the theoretical optimum of 2.0 g / Ah. 50 1. Negative electrode for accumulators with In contrast, electrodes made from a common zinc or cadmium active tertiary silver or silver oxides and a subsequent layer that is placed on a conductive base plate, Charge a silver utilization of not less than e.g. B. made of copper, silver or nickel, as a fine 2.6 g / Ah. porous electrolytic precipitate applied In Fig.4 is a method and an apparatus 55 is characterized in that the for the production of both positive and negative fine-pored active layers to a density Bimetal electrodes shown. In a bath tank of about 35 to 65%, based on the density 100 is a removable foil 103 made of the highly compact metals zinc or cadmium, Conductive metal, preferably made of silver, is compressed angeord-. net, which acts as a partition to subdivide the 60 2nd method of making a negative Bath container in a (right) zinc bath and an electrode for accumulators according to claim 1, (left) silver bath is used and the carrier of the herzu- characterized in that to form a forming the bimetal electrode. The electrolytes of highly porous zinc or cadmium precipitate Example 1 with a volume weight between 15 and 40%, and 3 correspond. A zinc anode 101 based on the density of the compact metals ten chamber and a silver anode 102 in the left zinc or cadmium, one for electrolysis Chamber are connected to suitable power sources solution used in a known manner and connected to the positive pole. The vagina- larger amounts of others to be separated from- the metal does not contain ions corresponding to, and in which the ion content of the metal to be deposited at a temperature below 50 ° C is much less than 10 percent by weight, and that the resulting precipitate to a density of about 35 to 65%, based on the density of the compact metals, condensed. Considered publications: German patent specifications No. 373 662, 578146, 214; French Patent No. 350 898; British Patent No. 561820; U.S. Patent No. 2,013,379; Willi Machu, Modern Electroplating, Weinheim / Bergstrasse, 1954, pp. 206, 207. 1 sheet of drawings S80 S99 / 194 8.68 © Bundesdruckerei Berlin