DE2459856A1 - Electrode for alkaline accumulator - comprises grid like structure with porous sinter coating on web - Google Patents

Abstract

Electrode, particularly for an alkaline accumulator comprising a grid-type structure the webs of which are provided with a highly porous sinter coating, the pores of which contain active matl. and the remaining openings in the structure being provided with additional sprayed- or pasted-in active matl. particularly one contg. added depolarising matl. The construction reduces the scattering of surface capacity compared to the usual sintered electrode plate, and combines the advantage of sintered and solid electrodes without resulting in manufacturing difficulties.

Description

Electrode for galvanic elements, especially for alkaline batteries The invention relates to an electrode for galvanic elements, in particular for alkaline alkalis.

In galvanic elements, especially in alkaline batteries, of the nickel / cadmium system are ground electrodes as well as sintered electrodes used and optionally also combined with one another in AkkumvAatorenzellen.

The active mass penetrates the highly porous sintered electrode framework introduced chemical or electrolytic processes.

Such sintered electrodes have the great advantage of only minor ones Polarization ~ and are therefore very resilient. In the preparation of However, there are high capacitance spreads, since the amount of active material that is introduced in the impregnation process, cannot be dosed with sufficient accuracy. The introduction of the so-called antipolar mass also helps with these electrodes Trouble with yourself.

To increase the capacity of such sintered electrodes it is already known to provide cavities within the. Sintered body, which a capacity reservoir should form (DT-PS 1 300 598). In such an arrangement, however, depending on the practically uncontrollable residual gas content in these cavities more or less active mass precipitated.-This leads to strong scattering of the surface capacities such plates.

If the cavities contain too much positive mass, so can it due to their swelling ability to form bubbles and thus to tear open the sintered structure to lead.

In addition, it is known to use sintered electrodes for stabilization Make recesses to prevent the panels from tearing during the impregnation process to prevent (DT-PS 650 621).

To the known ground electrodes, for example tube electrodes, Folded tape electrodes and pocket electrodes, also include so-called tape electrodes, in which the active masses are pasted into a metal mesh or expanded metal or be pressed in. Such ground electrodes are easy to manufacture, they have however, a stronger polarization than sintered electrodes and their load capacity is therefore limited. Their advantage lies in the fact that they provide an accurate dosage of the Allow active mass and that electrodes are produced with only a small capacity spread can be. The addition of antipolar mass can with these electrodes through simple admixture of the corresponding active material can be carried out. Furthermore is also the self-discharge of such ground electrodes is relatively low.

To combine the advantages of both types of electrodes, is it is known that positive sintered electrodes work together with negative ground electrodes allow. These arrangements have advantages in terms of electrical behavior of the accumulators with them. However, there are disadvantages due to the increased effort in the manufacture of such combinations.

The invention is therefore based on the object of providing an electrode develop which combine the advantages of sintered electrodes and ground electrodes combined and which compared to known electrodes no increased manufacturing difficulties brings with it.

This object is achieved according to the invention in that the electrode consists of a lattice-like metal framework, the webs of which with a highly porous Sinter support are provided, whose Pores contain active mass and provided the remaining framework openings with pasted active material are.

In particular, the pasted-in active material can be the usual Contains addition of antipolar mass.

The subject matter of the invention is set out below with reference to FIGS to 6 explained in more detail.

The starting point for the production of the electrode is a metallic grid-like one Framework, for example an expanded metal, the cross section of which is shown in FIG is, and which has the webs 1 and the connecting legs-2. These webs are provided with a sintering layer 3 according to FIG. 2 in conventional processes. In addition For example, a nickel powder slurry is applied, the viscosity of which is adjusted in this way is that only the webs are covered, while the larger scaffolding spaces or Most of the meshes remain free. The expanded metal coated in this way is sintered and the highly porous sintered body adhering to the webs is then after known method filled with the active positive or negative mass. In the remaining free spaces or meshes are then additional in a further work step active mass 4 according to Figure 3 sprinkled or pasted. Then the electrode can can still be pressed or rolled to hold the powdery masses firmly in the mesh to anchor.

Figure 4 shows the electrode of Figure 3 after such a pressing or. Rolling process. If necessary, the littered or

Pasted mass contain an antipolar additive, which in particular is applied to the positive electrode. The electrode arresters can be used or attached to the electrode framework after the sintered layer has been applied.

An advantageous method for producing such electrodes results from the fact that a thin metal foil 5 (Figure 5), which optionally is perforated by needles, provided with a nickel sintered layer 6 on both sides will. The metal foil should have a thickness of in .05 to 0.15 mm and after applying the sintered layer, the film should have a total thickness from 0.65 to 0.80 mm. This metal foil is then applied using conventional methods Device processed to expanded metal, as shown in Figure 6, and then, as already mentioned above, active material is sprinkled or pasted in.

For example, a piece of needle-perforated nickel foil is used with a thickness of 0.1 mm on both sides in a known manner with a highly porous nickel sintered layer from 0.25 to 0.30 mm and made into expanded material with a mesh size of 2 x 4 mm and a web height of 1.5 mm. In the highly porous sintered layer a positive mass amount of approx.

9 g / dm2 nickel hydroxide using known impregnation and precipitation processes brought in. In the remaining meshes, an additional 7.5 g / dm2 positive nickel hydroxide / graphite mass introduced. After that the plate pressed or rolled to a thickness of 0.8 mm.

As a positive electrode, this plate delivers after appropriate formation an amount of current of 3.0 to 3.3 Ah / dm2. The proportion of the pasted mass to the total mass can and can be varied within wide limits via the mesh size of the expanded metal expediently 25 to 50% of the total mass amount.

By introducing a precisely specified amount of mass into the cavities between the sintered bars the spread of the surface capacity is compared to the usual Reduced sintered electrode plates. A swelling of this introduced active material does not cause any destruction of the sinter framework, but only a minor one Increase in thickness of the entire plate, electrodes of the type described are in particular Can be used in gas-tight alkaline accumulators in order to reduce the To replace ground electrodes, as they represent a considerable increase in performance compared to ground electrodes entail, without having the disadvantages of pure sintered electrodes.

- patent claims -

Claims (3)

Claims 1. Electrode for galvanic elements, in particular for alkaline batteries, characterized in that they consist of a grid-like The framework consists of the webs of which are provided with a highly porous sinter layer, whose pores contain active material, and whose framework openings remain free with additional sprinkled or pasted active material are provided. 2. Electrode according to claim 1, characterized in that the into the The active material introduced into the framework openings that remain free, an addition of antipolar Contains mass. 3. A method for producing an electrode according to claim 1 or 2, characterized in that a sintered layer is applied to a metal foil is that the metal foil with sintered layer is processed into expanded metal and that then into the pores of the sintered metal and into the framework openings that remain free active mass is introduced.