JPH03201367A - Manufacture of paste type electrode - Google Patents

Abstract

PURPOSE:To efficiently and stably form a highly reliable paste type electrode for use in an alkaline storage battery by continuously welding a ribbon-shaped metal piece by means of ultrasonic seam. CONSTITUTION:The portion of a nickel sintered fiber base serving as a current collecting portion is initially compressed into a sheet metal by a roller to form a plain portion 2, the nickel sintered fiber base being a conductive porous base of three-dimensional structure. The nickel sintered fiber base is filled with a paste containing active material and then the paste on the plain portion 2 is removed and the base is dried and pressed to fabricate a filled base 1. A ribbon-shaped metal piece 3 formed of a nickel-plated steel plate serving as both a current collector and a reinforcing material is made to abut on the rotating chip 4 of an ultrasonic seam welding machine and is given ultrasonic vibration in such a manner as making the piece 3 perpendicular to the longitudinal direction of the plain portion 2, and the base 1 is moved at A speed of 1m/1min and then welding is carried out. Thereby a highly reliable paste type electrode is efficiently and stably obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a paste-type electrode used in an alkaline storage battery, and in particular to a method for welding a ribbon-shaped metal piece to a conductive porous substrate. This is related to process improvement.

(Conventional technology and problems) Conventionally, electrodes for alkaline storage batteries, typified by nickel-cadmium storage batteries, have been made by applying a slurry of metallic nickel powder with a diameter of several μm to a perforated steel plate, and then sintering it to form a conductive porous substrate. Therefore, sintered electrodes in which the substrate is impregnated with an active material, such as nickel hydroxide, have been widely used. However, such a sintered electrode has a complicated manufacturing method, and not only cannot a reduction in cost be expected, but also the substrate occupies a large volume relative to the electrode volume, which is an obstacle to increasing the capacity.

For this reason, there has recently been an active development of non-sintered electrodes in which a paste-like material containing an active material is filled into a conductive porous substrate with a three-dimensional structure, such as a sintered metal fiber substrate or a metal-plated fiber substrate. It is being done.

However, non-sintered electrodes usually use sintered metal fiber substrates, metal plating substrates, etc. as conductive porous substrates, but these substrates have mechanical strength that is lower than that of conventional sintered substrates. It is inferior, and the electrical resistance is also large when compared on a unit volume basis. As a result, when performing tab type current collection or tableless current collection using lead drawers, which are electrode current collection methods, the problem is that this substrate has high electrical resistance in the former case, and weak mechanical strength in the latter case. .

Therefore, in order to make an electrode that can withstand practical use, before filling a conductive porous substrate with a three-dimensional structure with a paste-like material, the part of the core that will become the current collector is compressed into a sheet metal shape with a roller etc. After that, the paste-like material is filled, the paste-like material on the uncoated part is removed, and a ribbon-shaped metal piece, such as a nickel ribbon or a ribbon-shaped nickel-plated steel plate, which serves as a current collector and a reinforcing material is added to the uncoated part. etc. are welded.

The above-described welding of a nickel ribbon and a nickel-plated steel plate to a plain area is performed by passing an electric current between the welding base materials in spot welding, and joining is achieved by heat generation caused by the contact resistance.

For this reason, for example, a small amount of paste-like material remains in the uncoated area, resulting in the occurrence of an A splash phenomenon, resulting in the problem that good welding strength cannot be obtained. In addition, the resistance welding is
Only a welding mark (nugget) with a size of about 1/2 to 173 of the width is formed, and its strength is extremely weak, so when the paste-type electrode is wound, the ribbon-shaped metal piece may peel off. There was a problem.

In order to solve the above problems, a method using ultrasonic metal welding has recently been proposed. In ultrasonic metal welding, high-frequency vibrations are applied horizontally to the welding surface while applying pressure, and the resulting frictional heat raises the temperature to near the recrystallization temperature, causing plastic deformation and welding. Therefore, since no current is required, even if a small amount of insulating material such as a paste-like material is present on the welding surface, it is scattered by the ultrasonic vibration and welding can be performed without splashing. Furthermore, since the size of the nugget is the same as the contact area of the welding tip, it is possible to weld the width of the ribbon-shaped metal piece.

However, the ultrasonic metal welding is spot welding, that is, spot welding. For example, tableless current collectors require welding at more than ten points depending on the size, making them unsuitable for mass production, and a new problem has arisen in that this welding process becomes rate-limiting.

[Structure of the Invention] (Means for Solving the Problems) The present invention involves stacking a ribbon-shaped metal piece as a current collector on the uncoated portion of a conductive porous substrate having a three-dimensional structure, and applying ultrasonic waves to the ribbon-shaped metal piece. This is a method for manufacturing a paste-type electrode that is continuously welded by welding, and the ultrasonic welding machine is equipped with a rotating tip.

The direction of the ultrasonic vibration at this time is preferably horizontal to the weld matrix surface, as in the case of spot welding.

Examples of the conductive porous substrate having the three-dimensional structure include a foamed metal, a sintered metal fiber substrate, a metal-plated fiber substrate, and the like.

The above paste-like material is a positive-electrode paste consisting of a positive electrode active material such as nickel hydroxide, a binder such as carboxymethylcellulose, methylcellulose, or sodium polyacrylate, and a solvent such as water, cadmium oxide, etc. An example of a paste-like material for negative electrodes is a negative electrode active material composed of a negative electrode active material, a binder such as polyvinyl alcohol, and a solvent such as ethylene glycol.

(Function) By using the ultrasonic seam welding machine of the present invention, ribbon-shaped metal pieces can be firmly welded, and highly reliable paste-type electrodes for alkaline storage batteries can be mass-produced more reliably than ever before. becomes possible.

There are two methods of ultrasonic seam welding: 1) a method in which the tip rotates and the welding base material moves, and 2) a method in which an ultrasonic horn and tip move over the welding base material, but the method can be used as appropriate depending on the production method. All you have to do is choose.

Figure 1 shows a schematic diagram of the ultrasonic welding machine in case 1>, and
The same schematic diagram for case 2) is shown in the figure.

(Example) Hereinafter, an example of the present invention will be described in detail based on FIGS. 1 and 2.

Example 1 A mixture of nickel hydroxide as the main ingredient, nickel powder as a conductive material, carboxymethyl cellulose as a thickener, and polytetrafluoroethylene as a binder in predetermined proportions was mixed with pure water and kneaded to form a paste. I prepared something.

Next, a portion of the nickel sintered fiber substrate, which is a conductive porous substrate having a three-dimensional structure, is compressed in advance into a sheet metal shape using a roller to form a plain portion 2 with a width of 3 squares and a thickness of 0.15 mm. was formed. Subsequently, after filling the nickel sintered fiber substrate with a paste-like material containing the active material, the paste-like material on the uncoated area 2 is removed, dried, and pressed to a length of l.
A filled substrate 1 having a width of 60 ms was prepared. Subsequently, a ribbon-shaped metal piece 3 made of a nickel-plated steel plate, which also serves as a current collector and a reinforcing material, is applied to the uncoated area 2 of the filled substrate 1 by a rotary tip 4 of an ultrasonic seam welding machine having the mechanism shown in FIG. Welding was performed by moving the filled substrate 1 at a speed of 1 m/min while applying ultrasonic vibrations so as to make contact with the uncoated portion 2 and in a direction perpendicular to the longitudinal direction of the uncoated portion 2. The ultrasonic welding conditions at this time were a frequency of 30 kHz.

The pressing force was 50 kg/c+n, the rotating tip diameter was 50 mm, and the tip width was 3 mm.

Example 2 A device was manufactured in the same manner as in Example 1, except that the apparatus shown in FIG. 2 in which the filled substrate 1 was fixed and the ultrasonic welding machine was moved was used.

Comparative Example 1 After manufacturing a filled substrate similar to Example 1, ultrasonic spot welding was performed over the entire length. At this time, the tip diameter is 3II
The product was manufactured in the same manner as in Example 1 except that No. I11 was used, and the other conditions were the same as in Example 1.

Comparative Example 2 After manufacturing a filled substrate similar to Example 1, electric resistance seam welding was performed over the entire length. The conditions at this time were a welding time of 101 Sv and a welding current of 2.5 kA.

Each of the above Examples 1.2 and Comparative Example 1.2 was
, B, CSD, and its filling substrate has a width of 1 at one end of the long side.
．． Harm
The lead was cut into a size of 40 mm and the tensile strength was measured by pulling the lead in the direction shown by the arrow in FIG. At the same time, the time required to weld the entire length of 1 m was measured. Each measurement was n-10, and the average value is shown in Table 1.

As can be seen from Table 1, the Examples are more advantageous than the Comparative Examples in both tensile strength and time required for welding. FIG. 4 shows the relationship between tensile strength and tensile distance using waveforms.

FIG. 4 also shows that the example of the present invention has a larger waveform area than the comparative example, and the intensity is correspondingly larger.

[Effects of the Invention] As described in detail above, the continuous ultrasonic seam welding manufacturing method of the present invention makes it possible to firmly attach a ribbon-shaped metal piece to a conductive porous substrate having a three-dimensional structure. It is possible to provide a method for efficiently and stably manufacturing paste-type electrodes for alkaline storage batteries that can be welded quickly and reliably and are highly reliable.

[Brief explanation of drawings]

Figures 1 and 2 are schematic perspective views of an apparatus for ultrasonic seam welding of ribbon-shaped metal pieces of a paste-type electrode of the present invention, Figure 3 is a principle diagram of a tensile strength test, and Figure 4 is a diagram of this embodiment A. , B and Comparative Examples C and D, respectively. 1... Filled substrate 2... Plain part 3...
Ribbon-shaped metal piece 4... Rotating chip 5... Ultrasonic horn

Claims (1)

[Claims] A ribbon-shaped metal piece is overlapped and welded as a current collector on the plain part of a conductive porous substrate having a three-dimensional structure, which has a part filled with a paste-like substance containing an active material and a plain part without the paste-like substance. A method for manufacturing a paste-type electrode, characterized in that the ribbon-shaped metal piece is continuously ultrasonic seam welded.