DE193108C - - Google Patents

Description

IMPERIAL

PATENT OFFICE.

PATENT LETTERING

CLASS 21 b. GROUP

with alkaline electrolytes.

Patented in the German Empire on October 6, 1906.

The present invention relates to a method for increasing the capacity of putty-like effective masses made from finely divided magnetic metals such as iron, nickel and cobalt.

When powder of a magnetic metal, e.g. B. Nickel, with a suitable electrolyte, For example, a sulfuric acid solution of an ammonium salt to a paste or

ίο a paste and pour the mixture into the shape of a brick is pressed and exposed to the oxidizing effect of the air, the outermost layers of the nickel grains are transformed according to the following reaction:

Ni + H ₂ SO _i = H ₂ + Ni SO _i H ₂ + O = H ₂ O.

The nickel sulfate formed in this way combines with the ammonium salt to form a sparingly soluble double salt (NHJ ₂ Ni ₂ (SOJ ₂ , which crystallizes out on the nickel particles during drying and connects them closely. The oxygen in the air and the ammonium salt also contribute to the formation of oxygen-rich basic salts at.

As soon as the above-mentioned reaction is continued to a certain degree after repeated soaking of the brick with the acidified solution of the ammonium salt and subsequent drying, the brick loses its porosity and no longer absorbs any appreciable amount of solution. It consists of 35

40

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then from a conductive skeleton of nickel particles, the pores of which are coated with nickel animonium salts are filled.

The limit of effectiveness that can be given to the brick in this way is obvious thereby achieved.

When, such a brick is placed in an alkali solution and used as an anode of electrolysis the following reactions occur:

(NHJ ₂ Ni (SOJ ₂ + 4KOH = 2 NH ₃ + 2 H ₂ O ■ + Ni f OH) ₂ + 2K ₂ SO _i

and Ni (OH) ₂ + 0 + 2H ₂ O = Ni (OH) ₁ .

For the sake of simplicity, it is assumed here that the high electrolytic efficiency Nickel hydrate has this composition.

When the brick is freed from alkali hydrate by washing with water, and after that has dried, you notice that it has become porous again, so that it is liquid again can absorb. From this it follows that the nickel hydrate has less space than the nickel ammonium salts, that were previously included in it. In fact, after this operation the pores of the metal framework with a larger amount of electrolytically active nickel hydrate are filled.

It is clear, however, that when in the bricks all or part of the nickel particles

can be replaced by a light material, for example graphite, then that conductive framework, calculated as a unit of weight, has a much larger amount in its pores of effective mass.

It is therefore most expedient to proceed as follows:

. Finely divided nickel (nickel powder) or metallic nickel in the form of thin flakes

ίο is distributed with, preferably crystalline Mixed graphite, at least a part of which has been plated with nickel by electrodeposition, such as is described in German patent specification 158800.

This mixture is mixed with an ammonium salt solution (for example salmia) which is mixed with Sulfuric acid is mixed into a pulp or paste, which in the mesh a network provided with a suitable drainage or in perforated metal sheets is kneaded from pure nickel or a nickel alloy.

The electrode thus formed is dried and then soaked with the same solution; this is repeated until the putty has achieved sufficient strength and the Pores are filled with nickel ammonium salts. Then the electrode is immersed in an alkali solution used and subjected to electrolysis as an anode, after which already

OH

OH

This reaction takes place very slowly, and only after three or five days has all the hydrate of the nickel peroxide been reduced to Ni (OHJ _2. The galvanic reaction is facilitated if ungalvanized graphite is present. Instead of every molecule M (OH) ₁ are like this two molecules of M (OH) ₂ , which doubles the amount of nickel hydrate. The gradual increase also has a strong cementing effect on the surrounding particles, which increases the strength of the cement even more. Electrolysis as an anode in alkali then becomes lower nickel hydrate converted into higher depolarizing hydrates.

When repeating these operations, the pores of the electrodes with are electrolytic The nickel ammonium salts are gradually given to the active nickel hydrate by the electrolytically active nickel hydrate be replaced.

In order to introduce even more electrolytically active nickel hydrate into the pores, finds now the following operation takes place:

The electrode is washed with water to remove the attached alkali hydrate and then brought into a solution which contains a nickel salt, for example nickel sulfate and appropriately made slightly acidic (or possibly slightly ammoniacal).

When treated as an anode in alkali, the surfaces of the nickel particles become coated with a thin, well-covering layer of nickel hydrate, which is insoluble in alkali and, as is known, the oxidation of the underlying metal in this electrolyte prevented. The case is completely different if the electrode is immersed in the last-mentioned solution, z. B. of nickel sulfate is used, which is especially when it is slightly acidic, the layer of nickel hydrate 'slowly dissolves, so that the metallic nickel surface is exposed.

This creates a galvanic chain, on the one hand with metallic nickel and on the other hand with nickel hydrate, whereby (if the temporarily formed Ni (OHJ _{3 is} disregarded) the following schematic reaction occurs:

= 2Ni (OHJ ₂ + Ni S O ₄

completely filled and thus the capacity of the electrodes is multiplied.

In this operation, however, as is easy to understand, the manufacture of new nickel hydrate at the expense of the metallic nickel in the electrode itself.

If the reaction is carried out too far, the nickel particles that cause the will lose Conductive frameworks gradually form their mutual coherence, thereby reducing the Conductivity of the electrode is reduced.

If in the manufacture of the putty a relatively large amount of flake graphite has been used, it is more advantageous to sufficiently fill the pores that Electrode metallic to unite with a smooth nickel plate, which is also in the solution is pressed into it by nickel sulphate.

The nickel sheet is thereby dissolved, and

the released nickel migrates through the electrolyte into the pores of the electrode, where it precipitates as a hydrate. In this case it is advantageous to use the solution from Do not acidify nickel salt, but keep it completely neutral, as a result of the nickel particles the hydrate layer formed on the surface for as long as possible against oxidation to protect.

ίο What here about putty made from nickel particles with Nickel hydrates are said to also apply to putties made from iron, cobalt etc. or their hydrates.

An iron electrode can suitably be treated in the following ways:

The electrode is discharged until the greater part of the effective mass has been converted into iron hyperoxide hydrate ie (OHo,) . The electrode is then placed in a solution of chlorine iron ammonium and connected to an iron sheet located in the same bath.

This causes the following reaction:

2 Fe (OH) ₃ + Fe = 3 Fe (OH) ₂ .

If the graphite used in nickel electrodes is heavily coated with nickel (on 70 percent or more), it can be used alone. But you can also do one Use a mixture of heavily nickel-plated and non-nickel-plated (refnem) graphite.

By means of this procedure, the capacity of the putties of the type described is determined significantly increased and this capacity can be charged and discharged very quickly. In addition, the putties fully retain their strength and performance. "* ■

Claims (4)

. ₀ patent claims: I. Method of increasing the capacity of putty electrodes for electrical Collectors with alkaline electrolytes, which by treating finely divided nickel, iron or cobalt with a Putty-forming, possibly oxidizing electrolytes and through oxidation of the putty mass are obtained in the air and subsequent electrolysis as an anode in alkali, characterized in that the Electrode is first introduced into an electrolyte, which is a salt or another electrolytically separable connection of the one contained in the cement Contains metal, whereupon the electrode as anode is subjected to electrolysis in alkali is, and that if necessary, these measures are repeated, for the purpose of making the pores in the mass with more effective To fill mass. 2. The method according to claim 1, characterized in that the Kittelelectrode with a plate made of the same metal as that contained in the smock electrode, is metallically connected and both electrodes are placed in the same electrolyte will. 3. The method according to claim 1 and 2, characterized in that the finely divided Metals mixed with graphite particles, preferably crystalline graphite, which in its total amount or only partially coated, for example by galvanic means, with a thin layer of the metal contained in the putty (metallized) have been used. 4. The method according to claim 3, characterized in that in place of with Graphite of mixed metal, highly metallized graphite alone or with unmetallized Mixed graphite is used as a material for the manufacture of the smock electrode will.