JPS5914225B2 - Batteries with spiral electrode bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery equipped with a spiral electrode body, and an object thereof is to provide a current collecting structure that is inexpensive and has good strong discharge characteristics.

In a battery equipped with a spiral electrode body, for example, a sealed nickel-cadmium storage battery which is a typical example of a cylindrical battery, current is generally collected from the electrode terminal as follows.

That is, as shown in FIG. 4, a strip-shaped positive electrode 20 and a negative electrode 2
1 is wound in a spiral shape with a separator 22 interposed therebetween, and the lead terminal 23 of the positive electrode extends upwardly to expose the porous metal core disposed in the positive electrode, or is connected to the positive electrode plate. The current collecting lead is extended by spot welding and welded to a sealing plate 25 provided with a cap 24 which also serves as a positive terminal. On the other hand, in the case of the negative electrode, the porous metal core was extended and exposed downward in the same manner as the positive electrode, or the current collector lead was welded, and the current collector was welded to the inner bottom surface of the metal case 2T. As for the negative electrode, there is also a method in which current is collected to the metal case, which is the negative electrode terminal, by pressing the outermost periphery of the spiral electrode body as the negative electrode to the metal case without using a current collector. In the above-described method of collecting current between the electrode and each terminal, the discharge voltage of the battery decreases significantly during strong discharge, so the following proposals have been made to improve the current collecting method. That is, as shown in FIG. 5, the positive electrode 33 and the negative electrode 34
are wound in a spiral shape with a separator 35 interposed between them, slightly shifted in the vertical direction, to expose the porous core metal 3633T disposed in the positive and negative electrodes upward and downward, and place the porous core metal 3633T on the exposed core metal. As the metal current collectors 38 and 39, lath plates, nets,
This is a so-called tableless method in which a plate or the like is placed and the current collector and exposed core metal portion are connected by welding. This method has superior strong discharge characteristics compared to the above-mentioned commonly used current collection method. J This Tables method has an electrode structure in which an active material is held in sintered metal powder with a metal core disposed inside, with the metal core partially exposed.

When welding this exposed part with the current collector,
A width of at least about 0.5 □ is required; for this reason, when making the electrode, during the sintering process, the exposed part of only the core metal is removed in advance so that metal powder does not adhere to one end of the core metal. is making a profit. However, it is extremely difficult to industrially control the exposed area to a certain width, and in reality it is approximately 0.
．． There is a variation width of about 5 to 1.2 wrIn. Therefore, the exposed portion of the core metal is approximately 10 mm when the battery is configured. However, the width of the exposed portion of the metal core during electrode fabrication becomes larger than that, and the loss increases.

In addition, in this method, the exposed part of the core metal, which is not directly involved in the battery reaction, is located somewhere under the electrode, so in batteries where the electrode width is short, the exposed part of the core metal occupies a large proportion of the area. This has the disadvantage that the battery capacity inevitably decreases. The present invention eliminates these drawbacks of the conventional tapless method. An embodiment of the present invention will be described below.

A large area 0.7 m thick sintered Nitsukel positive electrode with a 0.06 m thick metal porous metal core (nickel-plated perforated steel plate) arranged approximately in the center was fabricated, and this was placed in a predetermined area. Cut to size and use as unit plates for battery construction. At the end face (cut end) of this unit electrode plate, the core metal layer and the active material layer formed by cutting are exposed on the same surface and coexist with each other. Next, the same core metal as the positive electrode is placed almost in the center, resulting in a thickness of 0.5? A paste-type cadmium negative electrode with a large area is prepared, and this is also cut into unit plates like the positive electrode. Similarly to the positive electrode, the active material layer and the core metal are exposed on the same surface and coexist on the end face (cut) of this negative electrode unit plate. A spiral electrode body is constructed using the positive and negative unit electrode plates after being cut.

In FIG. 1, a positive electrode 1 and a negative electrode 2 are spirally wound with a separator 3 made of a non-woven polyamide resin interposed between the two electrodes, with their positions slightly shifted from each other in the direction of the soil. A positive electrode current collector 4 made of nickel mesh is placed on the exposed positive end surface of this spiral electrode body, and the current collector 4 and the upper end surface of the positive electrode are welded at several locations. The strip-shaped lead-out portion 4' of the current collector is connected to a cap 5 which also serves as a positive terminal.
It is welded to a metal sealing plate 6 which is electrically connected to the metal sealing plate 6. On the other hand, a current collector 7 similar to the positive electrode current collector is welded to the exposed lower end surface of the negative electrode 2, and a tongue piece provided on a part of the current collector is welded to a metal case 8 which also serves as a negative electrode terminal. . 9
1 is an elastic valve body, and 10 is a gasket.

Reference numerals 11 and 12 are porous core materials disposed within the positive and negative electrodes, respectively. The relationship between the spiral electrode body and the current collectors welded above and below it is shown in FIG.

In other words, the spiral electrode body shown without the separator is
After its outer periphery is fixed with a fixing tape 13 and a positive electrode current collector 4 is disposed on the exposed end face of the positive electrode, a welding electrode is positioned at an arbitrary welding point 14 and welding is performed. Similarly, a negative electrode current collector 7 is welded to the exposed end face of the negative electrode at an arbitrary welding point 14. Note that a tongue piece 15 for welding to the metal case 8 is provided on a part of the negative electrode current collector 7 . In addition, it is easy to use the shape of the current collector as shown in Figure 2, which usually has a disk shape as the main part (the positive electrode side has a strip-shaped lead-out part and the negative electrode side has a tongue piece).
A square shape is convenient, but other shapes such as a square shape or a diamond shape may be used as long as the welding area can be appropriately selected and there is no risk of internal short circuit.

The battery shown in FIG. 1 has an electrode width of 8 TafL and a battery capacity of 100 mAh.

FIG. 3 shows the discharge capacity when this battery was charged at a rate of 10 hours for 15 hours and then discharged at each discharge current. In Fig. 3, A is the product of the present invention, B is a conventional general current collection method, and the battery is configured similarly to the configuration shown in Fig. 4, and C is the conventional core material exposed part shown in Fig. 5. Battery C uses a tapless current collection method, and the electrode width of this battery C is 8 m including the exposed core material, and the effective electrode reaction equivalent area is 7 m. It is. As is clear from FIG. 3, the product of the present invention has a large discharge capacity compared to B and C even when the discharge current becomes large.

The feature of the present invention is that the core material and the active material layer are exposed on the same surface and coexist, whereas in the conventional tapeless current collection method, the current collector is welded to the exposed part of the core material at the edge of the electrode. The purpose is to weld a current collector to the end face of the electrode in the current state.

Then, a conductive portion between the current collector and the electrode is formed using the metal core as the main element and the active material layer as a secondary element. Generally speaking, on the electrode end surface,
When the core metal and the active material layer coexist on the same surface and weld them together by placing a current collector on this part, if the electrode edge has poor conductivity, sparks may occur during welding. Therefore, welding between the current collector, the core material, and the active material layer tends to be insufficient.
In the above example, at the edge of the positive electrode, the metal core material of the nickel-plated steel plate, the sintered powder of nickel, and the active material of nickel hydroxide are exposed on the same surface and coexist. If the sintered powder undergoes oxidation and reduction steps in an alkaline solution during electrode production, the surface of the sintered powder may become partially oxidized. Furthermore, if the core material is left at a high temperature after being cut into unit electrode plates, the cut cross section of the core material may oxidize, resulting in poor conductivity at the electrode edge. In such cases, sufficient contact between the current collector and the edge and current collection can be ensured by polishing the edge of the electrode to which the current collector is welded before or after winding it around the spiral electrode body. be done. In addition, in order to ensure reliable contact with the electrode core material and active material, the current collector should be porous and have protrusions or irregularities, such as netting, lath plate, expanded metal, or punched metal, rather than a smooth strip. is preferable, and in cases where sufficient unevenness does not exist during the manufacturing process of the metal, such as the punched metal or expanded metal, it is preferable to intentionally create the unevenness by deburring or embossing.

Note that if the conductivity at the electrode edge is extremely good and the active material layer and core material are exposed on the same surface, no special conductivity improvement measures such as polishing the electrode edge should be used. It is possible to weld the edge of the electrode and the current collector and collect current, and a paste-type cadmium negative electrode is an example of this.

Paste-type cadmium negative electrodes are usually made of cadmium oxide, which also contains nickel powder and a binder as conductive materials.This is due to so-called chemical formation, and as metallic cadmium is always present near the core metal, it is difficult to use large-sized cadmium negative electrodes. The edge of the unit electrode plate, which is made by cutting an electrode into a predetermined size, has a core material and cadmium, a metal with good conductivity, in the vicinity, and welding between the current collector and the edge of the electrode can be easily and sufficiently performed. .

In the above embodiments, the core metal and the active material layer of both the positive and negative electrodes were exposed on the same surface and the current collectors were welded to the parts where they coexisted, but the present invention , in a spiral electrode body in which negative electrodes are wound with their positions shifted vertically from each other, at least one electrode end surface of each of the positive and negative electrodes is in a state in which a porous metal core and an active material layer coexist on the same surface, It is sufficient if a current collector is welded to the end face of the electrode. Therefore, in the battery system as well, the nickel
The present invention can also be applied to other battery systems having a structure including a spiral electrode body other than cadmium-based, a porous core metal whose edge of one electrode can be welded to a current collector, and an active material layer. Furthermore, as for the current collector, in addition to metal mesh as mentioned above, any material with burrs or irregularities such as a lath plate or punched metal can be used as long as it can be welded to surround the electrode end surface. .
Furthermore, in the present invention, a desired unit electrode can be made by simply preparing a large-sized electrode and cutting it to the required size at the required location.
Unlike conventional tablets type electrodes, it does not require an exposed part of the core material, so when making electrodes of various sizes, the complicated process of forming the exposed part of the core material can be eliminated, making it easier to work. I can do it. As described above, the present invention can provide an inexpensive battery with good strong discharge characteristics while maintaining a large battery capacity by improving the current collecting structure of the spiral electrode body.

[Brief explanation of the drawing]

FIG. 1 is a half-cut side view of a battery in an embodiment of the present invention;
Figure 2 is a diagram showing the arrangement and welding locations of the spiral electrode body and current collector of the same battery, Figure 3 is a diagram showing the discharge current-discharge capacity characteristics of the same battery, Figures 4 and 5 are It is a half-cut side view of a conventional battery. 1...Positive electrode, 2...Negative electrode, 3...
...Separator, 4...Positive electrode current collector, 7...
... Negative electrode current collector, 11, 12 ... Porous core metal.

Claims (1)

[Claims] 1. An electrode body in which a band-shaped positive electrode and a negative electrode are vertically shifted from each other and are wound in a spiral with a separator interposed therebetween, and the electrode body is exposed at the top and bottom of the spiral electrode body, respectively. A porous metal core and an active material layer are exposed on the same surface of at least one of the positive and negative electrode end surfaces, and a current collector is welded to the exposed electrode end surfaces of the positive and negative electrodes. A battery with a spiral electrode body. 2. A battery comprising a spiral electrode body according to claim 1, wherein the exposed end faces of the positive and negative electrodes are polished. 3. A battery comprising a spiral electrode body according to claim 1, wherein the current collector is a porous strip having uneven parts.