JPH0935692A - Square sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a square sealed battery with less welding failure caused by sloughed substance filled and coated on the surface of an electrode. SOLUTION: An electrode group 2 impregnated with alkaline electrolyte is housed in an outer jacket can with bottom 1A having a square opening part 1a, and a cover plate 3 is fit to the square opening part 1a, then welded thereto for sealing to obtain a square sealed battery. Mesa type narrow width parts 11, 11 protruding in the inner direction of the can are formed in a pair of can walls 1b, 1c facing an electrode plate positioning on the outermost side of the electrode group 2 among facing two pairs of can walls of the outer jacket can with bottom 1A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prismatic sealed battery, and more particularly to a prismatic sealed battery in which welding defects between an outer can and a cover plate are less likely to occur.

[0002]

[Related technology] Nickel-hydrogen secondary battery and nickel-
An alkaline secondary battery such as a cadmium battery has a sealed structure as a whole, and its shape has a cylindrical shape and a prismatic shape. Here, for example, rectangular closed type nickel-
The structure of the hydrogen secondary battery will be described with reference to FIG.

As shown in the exploded perspective view of FIG. 1, this battery has a rectangular parallelepiped outer can 1 having an electrode plate group 2 accommodated therein.
And a lid plate 3 which is fitted and mounted in the opening 1a of the outer can 1 and seals the opening 1a. The outer can 1 is a rectangular parallelepiped bottomed can made of nickel-plated steel,
The opening 1a has a rectangular shape when seen in a plan view, and also serves as an external terminal of the negative electrode.

This bottomed outer can 1 is usually prepared by deep drawing a steel plate plated with nickel and
An elliptic cylinder with a bottom is formed, then gradually deformed into a rectangular shape to obtain a can body, and finally, the upper portion of the can body is cut in order to make the height of the can body a predetermined size. At this time, at a position at a predetermined height from the bottom surface of the outer can, it is cut by a cutter so that its cut end is parallel to the bottom surface of the outer can.

In the electrode plate group 2, a plurality of positive electrode plates (nickel electrodes) 21 and negative electrode plates (hydrogen storage alloy electrodes) 22 are superposed with an electrically insulating separator 23 interposed therebetween. It is structured. Positive electrode plate (nickel electrode) 21
As such, for example, a porous conductive sheet such as a sponge-like nickel sheet in which an active material mixture mainly composed of nickel hydroxide that operates as a positive electrode active material is filled and applied is usually used.

As the negative electrode plate (hydrogen storage alloy electrode) 22, for example, a porous conductive sheet such as punched nickel sheet or nickel net, conductive material powder such as hydrogen storage alloy powder and nickel powder, and polyvinylidene fluoride are used. A mixture obtained by filling and mixing a mixture of a binder powder such as a ride powder at a predetermined ratio is usually used. As the separator 23, for example, a sheet made of a porous synthetic resin having electric insulation is usually used. still,
This separator has elasticity.

When assembling the electrode plate group 2, first, the separator 23 is folded in two and formed into an envelope shape, and the positive electrode plate 21 is inserted thereinto to separate the separator 23 and the positive electrode plate 21.
Form a bond with. Then, the combined body and the negative electrode plate 22 are alternately stacked so that the negative electrode plate 22 is located on the outermost side, and then the whole is molded into a rectangular parallelepiped shape so as to fit the inner shape of the outer can 1. Therefore, when the electrode plate group 2 is housed in the outer can 1, there is almost no gap between the side surface of the outermost negative electrode plate of the housed electrode plate 2 and the inner surface of the can wall of the outer can. It becomes a state.

Here, each positive electrode plate 21 is connected to a positive electrode terminal 31 described later via the positive electrode current collector 4 and the lead plate 31a, and each negative electrode plate 22 is made of a conductive sheet (not shown). Are electrically connected to each other, and in this state, for example, the outermost negative electrode plate of the electrode plate group is brought into contact with the outer can to be connected to the negative electrode terminal (outer can).

The lid plate 3 is a nickel-plated steel plate having a positive electrode terminal 31 in the center thereof and having a rectangular shape in plan view that fits into the opening 1a of the outer can. A positive electrode lead plate 31a connected to the positive electrode terminal is arranged at a predetermined position. The sealed nickel-
As an example of the procedure for manufacturing the hydrogen secondary battery, first, the electrode plate group 2 is once compressed in the short side direction. Then, the separator 23 interposed between the electrode plates contracts, and the dimension of the electrode plate group in the short side direction is slightly reduced. In this state, the electrode plate group 2 is inserted into the outer can 1 through the opening 1 a of the outer can 1.

Next, the alkaline electrolyte is injected into the outer can 1 containing the electrode plate group 2, and then the lid plate 3 is fitted and attached to the opening 1a of the outer can 1. And the outer can 1
The portion where the opening 1a and the lid plate 3 of (1) and the lid plate 3 match (hereinafter, referred to as a fitting portion) is usually subjected to pulse laser welding suitable for microfabrication, and the sealing welding of the outer can 1 and the lid plate 3 is performed. Then, a prismatic battery having a closed structure is formed.

[0011]

By the way, when the upper part of the outer can is cut by a cutter in order to adjust the height of the outer can to a predetermined size, the cut end of the outer can 1, which has been cut, that is, the inner edge of the opening 1a. 1e has a substantially right angle as shown in FIG. Then, the electrode plate group 2 is placed in such an outer can 1.
When inserting, for example, when the electrode plate group 2 is slightly tilted as shown in FIG. 2, the inner edge 1e of the opening 1a and the side surface of the electrode plate group 2 may come into contact with each other. is there. Even if the contracted separator returns to its original size due to its elasticity during insertion, the opening 1a
The inner edge 1e of the above may come into contact with the outer can 2.

As described above, when the inner edge 1e of the opening 1a of the outer can 1 and the electrode plate group 2 come into contact with each other, the hydrogen filled and applied to the surface of the negative electrode plate 22 located on the outermost side of the electrode plate group 2 is charged. The mixture containing the occlusion alloy powder will be scraped off. Then, the mixture containing the hydrogen storage alloy powder and the like scraped off adheres to the opening 1a and remains as it is. When the lid plate 3 is fitted and attached to the opening 1a, a metal different from the base material (the outer can and the lid plate) locally exists in the formed fitting portion. Therefore, at the time of sealing welding. In some cases, the dissimilar metals are locally welded to each other, and some portions are not welded, and welding failure may occur in the fitting portion.

When such defective welding occurs, the resulting battery has a poor sealing, problems such as leakage of alkaline electrolyte occur, the rate of defective batteries increases, and the yield in battery manufacturing decreases. . SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems in a prismatic sealed battery and to provide a prismatic sealed battery in which welding defects caused by scraping off the substance applied to the surface of the electrode plate are less likely to occur.

[0014]

In order to achieve the above object, according to the present invention, an electrode plate group is housed in a bottomed outer can having a rectangular opening in a state of being immersed in an alkaline electrolyte. In the rectangular sealed battery in which the rectangular opening is fitted and sealed with a welded cover plate, the outermost side of the electrode plate group out of the two pairs of facing can walls of the bottomed outer can. Provided is a prismatic sealed battery, characterized in that a pair of can walls facing the electrode plate located at is formed with a mesa-shaped narrow portion protruding inward of the can.

In the prismatic sealed battery according to the present invention, since the narrow width portion is formed on the inner surface of the can wall of the outer can, when the electrode plate group is inserted into the outer can, the electrode plate group has the narrow width portion. By being guided so as not to come into contact with the inner edge of the opening of the outer can and being inserted into the outer can, it is prevented that the hydrogen storage alloy powder or the like on the surface of the negative electrode plate is scraped off at the inner edge of the opening. It is possible to prevent hydrogen storage alloy powder and the like from remaining in the openings.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows the appearance of an example of a prismatic sealed battery according to the present invention. In this prismatic sealed battery, a part of the pair of can walls 1b and 1c on the long side protrudes inward of the can, and the space between the can walls 1b and 1c is narrower than other parts. It is the same as the conventional prismatic sealed battery except that the outer can 1A in which the narrow portions 11, 11 are formed is adopted.

As shown in FIG. 4, the narrow portions 11 and 11 of the outer can 1A usually have a rectangular shape in plan view which is substantially similar to the shape of the wall surface of the can, and its cross-sectional shape is shown in FIG. 5, which is a cross-sectional view taken along the line V-V of FIG.
At the positions opposite to each other, the inside of the can wall has a mesa-shaped protrusion toward the inside of the can. This narrow part 1
The upper end 11a of each of the first and the first parts 11 and 11 has a gentle curved surface or a tapered shape, and is provided with a flat surface 11b continuously thereunder.

When the rectangular sealed battery is manufactured according to the conventional manufacturing procedure by using the outer can 1A having the narrow portions 11 and 11, the electrode plate group 2 is inserted into the outer can 1A. As shown in FIG. 6, with the electrode plate group 2 slightly tilted,
Even when inserted, the electrode plate group 2 is guided by the narrow portion 11 formed inside the inner edge 1e of the opening 1a as shown by the chain double-dashed line, and is corrected into a state parallel to the can wall. However, since it is inserted into the outer can, contact between the outermost negative electrode plate 22 and the inner edge 1e of the opening 1a is suppressed.
Further, when the electrode plate group 2 is inserted, the narrow portion 11 presses the electrode plate group 2 in the short side direction, so that the electrode plate group 2 is prevented from returning to its original size due to the elasticity of the separator 23. To be Therefore, the electrode plate group 2 returns to the original size during insertion, and the opening 1a
The contact with the inner edge 1e of is extremely reduced. As described above, when the outer can 1A is adopted, the inner edge 1 of the opening 1a is
Since the contact between e and the electrode plate group 2 is avoided, the mixture containing the hydrogen storage alloy powder and the like on the surface of the negative electrode plate 22 located on the outermost side of the electrode plate group 2 is scraped off by the inner edge 1e of the opening 1a. Things are suppressed. Here, the upper end portion 1 of the narrow portion 11
Since 1a is not a right angle but a gentle curved surface, it is suitable for guiding the electrode plate group 2 and is positioned on the outermost side of the electrode plate group 2 at the upper end portion 11a during insertion of the electrode plate group 2. The mixture containing the hydrogen-absorbing alloy powder and the like is hardly scraped off from the negative electrode plate 22.

As described above, in the outer can 1A, the electrode plate group 2 can be accommodated in the outer can 1A without contacting the electrode plate group 2 and the inner edge 1e of the opening 1a.
The sealing welding of the lid plate can be performed in a state where the mixture containing the hydrogen storage alloy powder or the like does not remain in the opening 1a. Therefore, it is possible to obtain a good rectangular sealed battery with few welding defects. As a procedure for forming the narrow width portion 11 in the outer can 1A,
For example, as shown in FIG. 7, the can walls 1b and 1c facing each other on the long side of the outer can are pressed into a pressing jig 5 having a predetermined rectangular shape.
5, the can walls 1b and 1c are pushed inward by a predetermined amount by pressing them in the direction of arrow P, and the mesa-shaped narrow portion 11 protruding inside the can walls 1b and 1c toward the inside of the outer can. , 11 are formed.

When the ratio of the height dimension h of the narrow portion 11 to the height dimension H of the can wall 1b (1c) is 60% or more, the outer can of the outer can is projected when the can wall is projected inward. When the strain becomes large and the ratio becomes 40% or less, the narrow width portion 11 having a small height dimension is formed, so the electrode plate group 2 is guided to the lower portion of the outer can in a state parallel to the can wall. It becomes difficult to do. Therefore, the ratio of the height dimension h of the narrow portion 11 to the height dimension H of the can wall is
It is preferable to set in the range of 40 to 60% (see FIG. 4).

Further, the lateral dimension w of the can wall 1b (1c)₀Against
Lateral dimension w of the narrow portion 11₁Ratio of 50% or more
When the can wall is projected inward, the outer can will be greatly distorted.
And the above ratio will be 20% or less
Then, the lateral dimension of the narrow portion 11 becomes small, and the flat surface 11b
The area (contact area with the electrode group) becomes small,
When the plate group 2 is accommodated, stress concentrates at the contact point,
The mixture containing the hydrogen storage alloy, etc. in the part of may be separated
There is. From this, the lateral dimension w of the can wall ₀Against
Lateral dimension w₁The ratio of 20% to 50%
Preferably (see FIG. 4). In addition, the narrow part on the can wall
When forming, the lateral dimension w of the narrow portion 11₁The center of the direction is
Make it approximately coincide with the center position of the long side of the can wall.

If the upper end 11a of the narrow width portion 11 is located too far below the opening 1a, the electrode plate group 2 will be separated from the inner edge 1e of the opening 1a before being guided by the narrow width portion 11. There is a possibility of contact. Also, the upper end portion 11a of the narrow portion
Is too close to the opening 1a, when forming the narrow portion,
The opening 1a is deformed, and it becomes impossible to obtain the opening as designed. For this reason, the dimension A from the opening 1a to the upper end 11a of the narrow portion 11 (see FIGS. 4 and 7) is longer than the dimension at which the opening 1a is deformed, and the electrode plate group 2 is guided. Set it within the range shorter than the dimension that makes it impossible.

Further, if the dimension B (see FIG. 7) between the opposed narrow portions 11 is too small, the electrode plate group 2 (when compressed in the short side direction) cannot be inserted into the outer can 1. . Further, if the dimension B is too large, rattling occurs between the electrode plate group 2 and the side surface of the electrode plate group 2 and the inner edge 1e of the opening 1a when the electrode plate group 2 is inserted into the outer can. It is possible that they come into contact with each other. Therefore, the dimension B between the narrow portions 11 facing each other
Is set to be equal to or greater than the short side dimension of the electrode plate group 2 when compressed in the short side direction and less than the length that makes it impossible to guide the electrode plate group 2.

Here, the outer can of a commonly used prismatic sealed battery is made of a 0.4 mm thick nickel-plated steel plate, has an opening of 16 mm in length and 6 mm in width, and has a high height. It is a bottomed can having a size of 46 mm. When the narrow portion in the present invention is formed on the outer can, the dimensions of the narrow portion are such that the height dimension h is 20 to 25 mm and the lateral dimension w ₁ is 5.
6 mm, the dimension B between the opposing narrow width portions 11 is 5.0 to 5.
Preferably, it is 5 mm. The dimension A from the opening 1a to the upper end 11a of the narrow portion 11 is 1.5 to
It is preferably 3.0 mm, more preferably 2.
0 mm.

In the present invention, as the narrow portion, only the case in which the can wall of the outer can is pressed from the outside so that the inside of the can wall is protruded into a mesa shape has been described.
As the narrow portion, another member having the same shape as the mesa-shaped protruding portion is joined to the inside of the can wall of the outer can, or the thickness of the can wall of the outer can is locally thickened, and A mesa-shaped protrusion may be formed. In such a case,
The narrow width portion is set to have dimensions that satisfy the above-mentioned conditions.

[0026]

【Example】

Example 1 For a 0.4 mm thick steel plate plated with nickel,
Deep drawing was performed to form a rectangular parallelepiped bottomed can body having an opening having a rectangular shape with a length of 16 mm and a width of 6 mm and a height of 55 mm. Then, with a cutter, raise the height of the can to 46 m.
Cut to m.

Next, the can walls 1b and 1c on the long side of the can body.
On the other hand, as shown in FIG. 6, the pressing surfaces of the can walls 1b and 1c are
Press in the direction of arrow P with jigs 5 and 5 that are rectangular.
So that the can walls 1b and 1c project inwardly of the can,
A mesa-shaped narrow portion 11 was formed inside b and 1c. This
The narrow portion 11 has a height dimension h of 23.5 mm and a lateral dimension w.
₁Has a rectangular shape with a width of 5.5 mm
The dimension B between 11 and 11 is 5.0 mm. In addition, this narrow
The width portion 11 extends from the opening portion 1a of the outer can 1 to the narrow width portion 11 above.
It was formed at a position where the dimension A up to the end was 2.0 mm.
In this way, a can having a narrow portion inside the can wall of the long side
The body was used as an outer can 1A.

Next, a positive electrode plate (nickel electrode) and a negative electrode plate (hydrogen storage alloy electrode) were laminated with an electrically insulating separator interposed therebetween to produce an electrode plate group. still,
The electrode plate group has a long side dimension of 15.5 mm and a short side dimension of 6.5.
mm, and a height of 42 mm. Then, the obtained electrode plate group is compressed in the short side direction to obtain the short side dimension of 5.0.
In the state of mm, it was inserted into the outer can through the opening of the outer can. Then, as an electrolytic solution, KO
1.10 cc of an alkaline aqueous solution containing H as a main component was injected into the outer can.

Finally, the positive electrode terminal is provided at the center, and the size of the cover plate is 16.0 mm in length, 6.0 mm in width, and 0.4 mm in thickness.
Then, the lid plate was fitted and attached to the opening of the outer can. Then, laser welding was performed over the entire circumference of the fitting portion to manufacture a prismatic closed type nickel-hydrogen secondary battery.
It should be noted that 1000 batteries were manufactured. The occurrence rate of laser welding failure was determined for the obtained battery. The results are shown in Table 1.

Here, the occurrence rate of laser welding defects was determined as follows. First, the battery manufactured as described above was kept in an atmosphere having a temperature of 60 ° C. and a relative humidity of 80% and left for 30 days. Next, the presence or absence of leakage was confirmed by dropping the phenolphthalein solution into the fitting part of the battery after 30 days and observing the discoloration of the solution. That is, when the phenolphthalein solution turned red, the alkaline electrolyte was present in the fitting portion, so that the battery in which the solution turned red was considered to have leaked. Then, the ratio of the battery in which the liquid leakage occurred to the whole of the manufactured batteries was obtained, and this ratio was taken as the incidence of laser welding failure. Example 2 The dimension A from the opening 1a to the upper end of the narrow portion 11 is set to 3.
1000 nickel-hydrogen secondary batteries were manufactured in the same manner as in Example 1 except that the thickness was 0 mm.

For the obtained battery, the incidence of laser welding failure was determined in the same manner as in Example 1. The results are also shown in Table 1. Example 3 The dimension A from the opening 1a to the upper end of the narrow portion 11 is 1.
1000 nickel-hydrogen secondary batteries were manufactured in the same manner as in Example 1 except that the thickness was 5 mm.

For the battery thus obtained, the incidence of laser welding defects was determined in the same manner as in Example 1. The results are also shown in Table 1. Comparative Example 1 1000 nickel-hydrogen secondary batteries were manufactured in the same manner as in Example 1 except that the narrow portion was not formed in the outer can.

For the obtained battery, the incidence of laser welding failure was determined in the same manner as in Example 1. The results are also shown in Table 1. Comparative Example 2 The dimension A from the opening 1a to the upper end of the narrow width portion 11 is set to 4.
1000 nickel-hydrogen secondary batteries were manufactured in the same manner as in Example 1 except that the thickness was 0 mm.

With respect to the obtained battery, the incidence of laser welding failure was determined in the same manner as in Example 1. The results are also shown in Table 1.

[0035]

[Table 1]

As is clear from the results shown in Table 1, the batteries of Examples 1, 2, and 3 had a laser welding defect occurrence rate of 0%.
It has become. This means that when the lid plate is sealed and welded to the opening of the outer can, there is no mixture containing the hydrogen storage alloy powder in the fitting portion, and good welding can be performed, so that there is no welding failure. It shows that a good product was obtained.
That is, since the narrow width portion is formed at a predetermined position inside the can wall, the electrode plate group is guided into the narrow width portion and inserted into the outer can, and the negative electrode plate positioned at the outermost part of the electrode plate group. This makes it possible to avoid contact between the inner edge of the opening and the inner edge of the opening, thereby preventing the mixture containing the hydrogen storage alloy powder and the like from being scraped from the negative electrode plate.

On the other hand, the battery of Comparative Example 1 has a higher incidence of laser welding defects than the battery of the present invention. This is because the battery of Comparative Example 1 uses the conventional outer can, so that the negative electrode plate comes into contact with the inner edge of the opening.
The mixture containing the hydrogen storage alloy powder etc. was scraped off, the mixture containing the hydrogen storage alloy powder etc. was present in the fitting part, and the hydrogen storage alloy etc. adversely affected the sealing welding, and there was a part that was not welded. Is.

The battery of Comparative Example 2 also has a high incidence of laser welding failure. This is because the dimension A from the inner edge 1e of the opening 1a to the upper end of the narrow portion 11 is large and the narrow portion 11 is located in the lower portion of the can wall, so the electrode plate group is guided by the narrow portion. Before, it comes into contact with the inner edge of the opening, the mixture containing hydrogen storage alloy powder, etc. is scraped off at the inner edge of the opening, the mixture is present in the fitting part, and at the time of sealing welding, there is a part that is not welded. Because it happened.

[0039]

In the prismatic sealed battery according to the first aspect of the invention, since the narrow portion is formed inside the can wall of the outer can, when the electrode plate group is inserted into the outer can, the electrode plate group is slightly inclined. Even when inserted in a state, the electrode plate group is corrected to be in a state parallel to the outer can by the narrow portion, so that the inner edge of the opening of the outer can and the negative electrode plate located on the outermost side of the electrode plate are. Contact is prevented. Therefore, the mixture containing the hydrogen storage alloy powder or the like is suppressed from being scraped from the negative electrode plate, and the occurrence of welding defects due to the presence of the mixture containing the hydrogen storage alloy powder or the like in the fitting portion is suppressed. Therefore, the occurrence of defective products due to defective sealing is extremely reduced, and the yield in battery manufacturing is improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing the configuration of a prismatic sealed battery.

FIG. 2 is a cross-sectional view showing how an electrode plate group is inserted into an outer can.

FIG. 3 is a perspective view showing a configuration of a prismatic sealed battery according to the present invention.

FIG. 4 is a perspective view showing an outer can of a prismatic sealed battery according to the present invention.

FIG. 5 is a sectional view taken along the line VV of FIG. 3;

FIG. 6 is a cross-sectional view showing how an electrode plate group is inserted into an outer can according to the present invention.

FIG. 7 is a cross-sectional view showing a structure of an outer can according to the present invention.

DESCRIPTION OF SYMBOLS 1 outer can (conventional) 1A outer can (invention) 1a opening 1b, 1c can wall 11 narrow width 11a upper end 11b flat surface 2 electrode plate group 3 lid plate 31 positive electrode terminal

Claims (1)

[Claims] 1. A bottomed outer can having a rectangular opening,
In a prismatic closed battery in which a plate group is accommodated in a state of being immersed in an alkaline electrolyte, the rectangular opening is fitted therein, and which is sealed with a welded cover plate, the relative of the bottomed outer can. Of the two pairs of can walls facing each other, a pair of can walls facing the outermost electrode plate of the electrode plate group has a mesa-shaped narrow portion protruding inward of the can. The feature is a prismatic sealed battery.