DE1195381B - Electrodes for accumulators in which the active particles are embedded in thermoplastic binders - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

HOIm

German class: 21b-25/01

Number:
File number:
Registration date:
Display day:

1195 381
B70393VIb / 21b
January 19, 1963
June 24, 1965

Electrodes for accumulators, e.g. B. those with alkaline electrolytes, consist of an electrochemical inactive porous framework in whose pores the active material is embedded. In this z. B. by Sintered, metallically conductive frameworks, the active masses z. B. introduced by that one impregnates the framework with a nickel or cobalt salt solution and then the nickel precipitates with alkali as nickel or cobalt hydroxide. Then the plates are covered with water washed and dried. In order to achieve sufficient capacity, it is necessary to carry out these operations to repeat several times. It is also known that the nickel or cobalt hydroxide by cathodic Polarization of the porous electrode frameworks with nickel or cobalt salts in their pores have been introduced by soaking to precipitate. But this method is also used for the purpose of achieving this Repeat the impregnation and polarization process several times if there is sufficient capacity indispensable.

In the manufacture of electrodes for batteries with acidic electrolytes, e.g. lead batteries, a slurry of lead dioxide is introduced into the pores of a lead framework and then solidified. These electrodes have the disadvantage that they suffer a considerable loss over time suffer their mechanical strength and thus become unusable.

It is also known to filler compounds such as those used for the manufacture of negative plates for lead-acid batteries are used and which mainly consist of finely divided lead oxides, substances with add ion-exchanging properties.

Finally, positive and negative electrodes, especially for lead-acid batteries, have become known, in which the active particles, e.g. B. lead dust or lead oxide dust, by a thermoplastic Binders are held together, taking care that the electrode mass remains porous so that the active particles can be reached by the electrolyte. Such electrode bodies should not be too thick, otherwise the active mass will not be fully utilized. So z. B. at rapid charging of the electrode, the electrolyte path in the pores is blocked by the development of gas, which leads to a decrease in the capacitance of the electrode.

It has now been found that these disadvantages in electrodes made of active particles with thermoplastic Plastics exist, do not occur if they contain granular ion exchangers.

Electrodes for accumulators where the
active particles in thermoplastic
Binders are embedded

Applicant:

Aniline & Soda Factory in Baden
Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Harald Guthke, Frankenthal (Palatinate);

Wolfgang Habermann, Mainz;

Dr. Rolf Schellenberg, Mannheim

It was surprisingly found that such electrodes are mechanically very stable. Because of the property of the ion-exchanging substances to swell in electrolytes or generally in liquids, it was to be feared that the plastic-containing panels would be blown up. By the invention Incorporation of ion exchangers is also achieved, especially with thicker electrode plates, the surprising advantage that the in the active mass contained in the plates is fully utilized and that they are accordingly through a high load capacity. This effect was not to be expected without further ado, because the ion exchangers in the finished electrode are surrounded on all sides by the thermoplastic binder and it was to be expected that their function would be considerably impaired.

The inventive incorporation of ion exchangers prevents z. Belly with rapid charging, the electrolyte path in the pores is blocked by gas evolution, so that constant good contact between the electrolyte and the one in the depth of the electrode active mass is guaranteed. This good contact is also guaranteed when using thicker electrodes manufactures, e.g. B. those whose thickness exceeds 0.3 cm.

Both those of an inorganic nature, such as permutites, and those are suitable as ion exchangers synthetic organic nature, such as exchangers based on copolymers of styrene or styrene derivatives and divinylbenzene, which are used as charge-carrying groups e.g. B. sulfo groups, quaternary ammonium compounds, Contain hydroxyl groups and the like.

509 597/191

Depending on the intended use of the electrode, the thermoplastic binders selected are those that are resistant to either acids or alkalis. Durable electrodes with particularly good conductivity obtained when using polyvinyl carbazole or copolymers of vinyl carbazole and styrene and vinyl carbazole, styrene and acrylonitrile, respectively.

The electrodes according to the invention can be manufactured in various ways. One can z. B. the fine-grained ion exchanger and the fine-grained active mass, which either consists of metals or oydic compounds of metals, with the fine-grained organic Mix the binder and the mixture at temperatures close to the softening point of the Press thermoplastic plastic to form a solid molded body. It is also possible to use the to produce electrodes according to the invention by the fact that the active material and the ion exchanger, so both of which should be in fine-grained form, in a solution or suspension of a binder suspended. The suspension is then applied to the surface of a shaped body and solidified there. The molded body can be made of plastic, ζ. Β. Polyvinyl carbazole or polystyrene, metal, z. B. nickel or iron, or made of glass and adapted to the respective type of accumulator Shape, e.g. that of plates, rods, foils.

In the manufacture of electrodes for alkaline batteries, where the active material is oxidic Low conductivity compounds such as B. those of nickel, cobalt and silver are used it is necessary to achieve sufficient conductivity within the electrode, to add electrically conductive substances to these during manufacture. For this come in particular the metals corresponding to the oxidic compounds, i.e. nickel, cobalt or silver, into consideration. However, semiconductors can also be used, e.g. B. iron (II), (III) oxide.

To increase the porosity of the electrodes according to the invention, it is possible to use the mixtures or Dispersions soluble compounds before they solidify, e.g. B. inorganic salts or in water soluble organic substances to be added, which are dissolved out with water after solidification.

The grain sizes of the ion exchangers, metal powder, metal oxide powder and the soluble compounds should expediently be below 500 μ in order to avoid layer formation in the Avoid electrode. The ratio of the active material to the organic binder can be within further limits can be varied and is chosen so that the finished electrode has sufficient capacity has sufficient mechanical stability. It is advisable to use, based on the electrode, about 1 to 10 percent by weight organic binder. For positive electrodes with alkaline Electrolytes are the two components mentioned advantageously fine-grained conductive connections, z. B. Metals such as nickel, added in an amount of 30 to 60 percent by weight. The addition to The ion exchanger is advantageously about 0.05 to 20 percent by weight, based on the electrode.

The electrodes according to the invention are characterized by a high capacitance, a high mechanical one Stability and good chemical resistance. As one in the manufacture of electrodes for alkaline Accumulators neither on a framework produced by sintering nor on the cumbersome multiple Soaking and precipitation is dependent, they are also characterized by a particularly simple Manufacturing method from.

example 1

A mixture of 9 parts by weight of carbonyl nickel powder with a grain size of about 5 μ, 4 parts by weight of nickel (III) oxide with a grain diameter of 50 μ, 1 part by weight of potassium nitrate, 0.5 part by weight of a basic ion exchanger, consisting of a styrene-divinylbenzene copolymer with quaternary ammonium groups, the grain size of which is about 40 μ, and 1 part by weight of polystyrene with a grain diameter of about 50 μ is pressed at a temperature of about 145 ° C to form a plate with a length of 40 mm and a thickness of 3 mm. After soaking, the electrode is ready for use. As a positive electrode in an alkaline electrolyte, this compact delivers about 8.5 Ah / dm ² .

Example 2

A suspension consisting of 9 parts by weight of carbonyl nickel with a particle size of about 5 μ, 3.5 parts by weight of nickel (II) hydroxide powder with a particle size of about 50 μ, 1.35 parts by weight of an ion exchanger made of a styrene-divinylbenzene copolymer with quaternary ammonium groups, whose grain size is about 40 μ, 8 parts by volume of a solution consisting of tetrahydrofuran with 100 g of polyvinyl carbazole per liter, is spread about 2.5 mm thick on a fine-meshed nickel wire netting and solidified by drying first at room temperature and then at + 80 ° C . After solidification, the electrode is soaked with distilled water. In 21% potassium hydroxide solution, it delivers 6.5 to 7 Ah / dm ² as a positive electrode.

Claims (2)

Patent claims: 1. Electrodes for accumulators, especially those with alkaline electrolytes which the active particles are embedded in thermoplastic binders, characterized in that that they contain granular ion exchangers. 2. Electrodes according to claim 1, characterized in that they the ion exchanger in in an amount of 0.05 to 20 percent by weight, based on the electrode. Considered publications:
German Auslegeschrift No. 1079 706;
British Patent No. 727429;
U.S. Patent No. 2,644,023. 509 597/191 6.65 © Bundesdruckerei Berlin