CS209356B1 - Manufactring method of tabular or compact by plastic bonded electrodes with different shape of section,for electrochemical power supply units - Google Patents

Description

(54) Method for producing tubular or compact plastic bonded electrodes with different cross-sectional shapes, for electrochemical power sources

The present invention relates to a process for the manufacture of tubular or compact plastic bonded electrodes with different cross-sections for electrochemical power sources.

The extrusion method is suitable for the preparation of tubular or compact electrodes with different cross-sections as porous plastic bonded biphasic electrodes, especially those electrochemical power sources whose electrode system is housed in a cylindrical vessel of a height that is either comparable to the vessel diameter or rate. These are current sources in which either the coil arrangement of the electrode system or the stacked electrodes cannot be used for geometric reasons.

One prior art method for producing electrodes consists in preparing briquettes of various shapes from a pulverulent electrochemically active mass by pressing. The current collector is then pressed into these briquettes either in the form of a wire or a metal grid, which also serves as a mechanical electrode casing.

According to a further manufacturing process, the electrochemically active substance is deposited in a porous metallic matrix of various shapes using precipitation or other chemical methods.

Cs. No. 196572 describes a method for producing electrodes in which a mixture of an electrochemically active substance, a plastic and a plasticizer is rolled onto a metal collector (mesh, perforated sheet or expanded metal) to form a flat electrode usable either as such or as a coil.

The disadvantage of the first two production methods, which have been used so far for virtually all electrodes of primary and secondary electrochemical power sources, is the high labor associated with the pressing of the electrodes, while maintaining a uniform electrode porosity. In the second method, this entails high material costs associated with the preparation of the porous support metal skeleton.

These drawbacks are solved to a certain extent by the last of the above mentioned methods of electrode production, but the disadvantage is that it leads exclusively to plate-type or foil-type electrodes and does not allow the preparation of electrodes especially cylindrical or other geometrical shapes such as prisms or bodies with other possible cross-sectional shapes - ellipse, triangle, starfish, cross and so on.

A drawback common to all three manufacturing processes is the difficulty of producing cylindrical, tubular, or other compact electrodes of varying cross-section, which are housed in cylindrical vessels of electrochemical power sources with a vessel height that is either comparable or to a different extent of containers. The electrodes for this type of cells are used in the form of a central cylindrical, mostly positive, electrode, concentrically surrounded by a second, mostly negative, electrode. In particular, it is difficult to maintain an even porosity of the electrodes and therefore, for example, a central cylindrical electrode is usually produced by pressing in the form of two half-cylinders, which are then folded into the shape of a cylinder. Also, the tubular outer electrode is usually prepared from multiple segments, which are then folded into the shape of a hollow cylinder, respectively. tubing.

The above-mentioned disadvantages are overcome by the method of manufacturing a tubular or compact plastic bonded electrode having a different cross-sectional shape for electrochemical current sources consisting of an active mass provided with a plastic binder suitable for extrusion and a current collector according to the invention. The plastic binder of the liquid plasticizer and, if appropriate, the porosity agent is pre-homogenized and the slightly moistened bulk mixture thus treated is subjected to extrusion at normal temperature in the extrusion die to form a compact electrode body with different cross-sectional shape. The thus formed, yet plastic electrode body is pressed by pressing a collector of various shape made of metal or carbon material along the whole electrode height by pressing, after which the liquid plasticizer is removed. evaporation.

By extrusion at normal temperature it is possible to produce an electrode body, into which the collector made of carbon or metal material is pressed in a centrical manner, or the electrode body is pressed into a metal container of circular cross-section after the transverse dividing to the required length or height. in the form of strips or rods, it is pressed externally over the entire electrode height.

The advantage of the method of preparation of the electrodes according to the invention is that the whole production process, ie extrusion, dividing and pressing of the collector or pressing into the container, can be fully automated in contrast to the prior art, which not only has a positive impact on production economics, scattering in yeast produced electrodes.

The presence of the liquid plasticizer facilitates both the actual creep process in the extrusion die and positively affects the uniformity of the porosity of the final electrode. Upon completion of the extrusion operation and providing the electrode with a current collector, the liquid plasticizer is removed by simple evaporation.

The invention exploits the finding that by using a mixture of powdered electrochemically active material, plastic binder and liquid plasticizer, an extrusion process can be carried out at normal temperature using relatively low extrusion pressures, the resulting product in the form of a tube or compact body having different cross-sectional shape is characterized by uniform porosity This is achieved by uniformly distributing the electrochemical active component throughout the electrode body. In addition to a suitable liquid plasticizer, which also serves as a porosity agent, a plastic binder is selected which has a suitable shape and particle size which, during the extrusion process, is geometrically oriented to the shape of the fiber. This fibrous structure positively affects the mechanical properties of the resulting electrode and is the optimal solution for ion and electron transfer | in a plastic bonded electrode during its electrochemical function.

The invention further exploits the fact that, for example, in cylindrical encapsulated Ni-Cd accumulators, one compact positive electrode of cylindrical shape can be prepared without costly pressing two half-cylinder electrodes and packing them into, for example, a fine metal mesh, thereby reducing both labor and cost. fine metal, mostly nickel, mesh. and

The method of manufacturing the plastic bonded electrode according to the invention further utilizes the finding that the introduction of a current collector, for example in the form of a metal or aluminum oxide. of carbon darkness, can be carried out immediately after the electrode body has been extruded and separated, i.e., when the body is still in a plastic state, which allows easy insertion of the collector without damaging the electrode body, for example through cracking. The metal collector in the form of a mandrel can already be provided in the upper part with a battery cover, which allows further subsequent technological operations, or the electrode body provided with a central space for the current collector can be extruded to facilitate insertion of the collector.

The process for producing electrodes of, for example, a cylindrical shape according to the invention is therefore particularly suitable, for example, for preparing positive cylindrical electrodes; In the case of encapsulated Ni-Cd accumulators, the height of which is considerably higher than their diameter, i.e. when it is not possible to use the coil technology in the assembly of the electrode system.

The advantages of the manufacturing process are best illustrated by the practical examples of the invention, which are not intended to limit the invention in any way. All parts shown in the examples represent the weight / weight ratio security.

EXAMPLE 1 parts of powder active mass for the positive electrodes of alkaline Ni-Cd accumulators are thoroughly mixed with 1 part of powdered polytetrafluoroethylene and then the resulting mixture is moistened with 2 parts of ethanol. The resulting mixture is placed in an extrusion die in a hydraulic extruder and a cylindrical electrode body having a diameter corresponding to the positive electrode of cylindrical encapsulated Ni-Cd accumulators with a 14 mm canister diameter and capacities up to 900 mAh is extruded at normal temperature. The extruded electrode body is then divided directly beyond the mouth of the die into the required electrode length, followed by a centric pressing of the metal collector in the form of darkness over the entire electrode height. The produced electrodes are allowed to stand for 4 hours at 20 ° C.

EXAMPLE 2 parts of the active electrolyte cell electrolyte positive electrode solid mass are thoroughly mixed with 1 part powdered polytetrafluoroethylene, and then the resulting mixture is moistened with 1 part ethyl alcohol. The resulting mixture is placed in an extrusion die and a cylindrical electrode body of a diameter corresponding to the final electrode is extruded at normal temperature. The extruded electrode body is then divided into the desired electrode height, and in a plastic state, a carbon rod collector is pressed into the electrode. The electrodes so produced were allowed to stand at 40 ° C for 2 hours to remove the plasticizer.

Example 3 parts of powdered active mass for negative electrodes of alkaline Ag-Zn, HgO-Zn, MnO ₂ -Zn,

Claims (4)

SUBJECT Method for producing a tubular or compact plastic bonded electrode having a different cross-sectional shape for electrochemical power sources consisting of an active material provided with a plastic binder suitable for extrusion and a current collector, characterized in that the mixture of active material, plastic binder, liquid plasticizer and homogenize and thus a slightly damp bulk mixture is extruded at normal temperature in the extrusion die to form a compact electrode body with different cross-sectional shape, and then the extruded electrode body is laterally divided into the required electrode length or height. collector of various shape made of metal or carbon material over the entire electrode height The Ag-Cd, Ni-Cd cells were thoroughly mixed with 1 part powdered polytetrafluoroethylene and then the resulting mixture was moistened with 1 part ethyl alcohol. The resulting mixture is placed in an extrusion die and the tube-shaped electrode body is extruded at normal temperature, which is then divided into a desired electrode height, and then pressed into a metal cylindrical vessel of the cell. From the electrodes so produced, the plasticizer is removed by evaporation at 20 ° C after 4 hours. Example 4 The preparation of the electrode was carried out as in Example 1 except that the active mass for the positive electrodes of the Ag-Zn cells was used as the electrochemically active substance. Example 5 The preparation of the electrode was carried out as in Example 4, except that the electrochemically active substance used was an electrochemically active mass for the positive electrode of HgO-Zn cells. OF THE INVENTION, after which the liquid plasticizer is removed by evaporation. 2. A method according to claim 1, characterized in that a collector of metal or carbon material is pressed into the extruded, yet plastic electrode body. 3. A method according to claim 1, characterized in that the tube-shaped electrode body is pressed into a metal container of circular cross-section after the transverse separation into the required electrode length or height. 4. A method according to claim 1, wherein the metal or carbon collector in the form of strips or rods is molded externally pq over the entire height of the electrode.