JP2949567B2 - Prismatic sealed battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed rectangular battery, and more particularly, to a sealed rectangular battery in which a short circuit due to contact between a positive electrode tab and a negative electrode plate is reduced.

[0002]

[Related technologies] Nickel-hydrogen secondary batteries and nickel-
Alkaline secondary batteries such as cadmium batteries have a hermetically sealed structure as a whole, and there are cylindrical and square shapes. Here, for example, a square sealed nickel-
The structure of the hydrogen secondary battery will be described with reference to FIG.

[0003] A prismatic nickel-hydrogen secondary battery has an outer can 1 accommodating an electrode plate group 3 therein, and is fitted into an opening 1a of the outer can 1 after accommodating the electrode plate group 3 therein. Part 1
and a lid plate 2 that seals a. The outer can 1 is a nickel-plated steel rectangular parallelepiped bottomed can having an opening 1a having a rectangular shape in plan view, and also serves as an external terminal of a negative electrode. In the present invention, the side of the opening 1a of the outer can is defined as the upper side, and the bottom side of the outer can is defined as the lower side. Therefore, also about the electrode group 3 mentioned later, the opening part 1a side is made up and the bottom side is made down in the state accommodated in the outer can.

The cover plate 2 is provided with a positive electrode terminal 21 at the center, and has a rectangular shape whose plan view conforms to the opening 1a of the outer can, and is connected to the positive electrode terminal at a predetermined position on the lower surface. Positive electrode lead plate is disposed. Electrode group 3
As shown in FIG. 2, a plurality of positive electrode plates (nickel electrodes) 31 and negative electrode plates (hydrogen storage alloy electrodes) 32 were stacked with an electrically insulating separator 33 interposed therebetween. It has a structure, and is inserted through the opening 1a of the outer can and is housed in the outer can 1. The electrode plate group 3 is generally formed in a substantially rectangular parallelepiped shape so as to conform to the inner shape of the outer can 1. In the present invention, the outer can 1
The portion corresponding to the short side (3a in FIG. 2) is referred to as the short side, and the portion corresponding to the long side of the outer can (3b in FIG. 2) is referred to as the long side.

As a positive electrode plate (nickel electrode) 31, for example, a porous conductive plate such as a sponge-like nickel plate is filled and coated with an active material mixture mainly composed of nickel hydroxide which operates as a positive electrode active material. Things are usually used.
The positive electrode plate 31 has a positive electrode tab on one side surface. The positive electrode tab 34 is, for example, a sheet-like small piece made of nickel, and is disposed so as to protrude upward from an upper portion of the electrode plate group by a predetermined length when assembled as an electrode plate group. (See FIG. 2).

As an example of the procedure for mounting the positive electrode tab, first, as shown in FIG.
a, 31b are compressed in the thickness direction by a press machine to form concave portions 31c, 31d, and the positive electrode tab 34 is formed in the concave portion 31d on one side surface (side surface 31b in the figure).
And one end of the positive electrode tab 34 is spot-welded to the recess 31d. At this time, the dimensions of the depth of the concave portion and the thickness of the positive electrode tab are determined by the side surface 31 of the positive electrode plate 31.
A predetermined dimension is set in advance so that b and the surface opposite to the welding surface of the positive electrode tab 34 are substantially flush.

As the negative electrode plate (hydrogen storage alloy electrode) 32, for example, a porous conductive plate such as a punched nickel plate or a nickel net, a conductive material powder such as a hydrogen storage alloy powder and a nickel powder, and a polyvinylidene fluoride A material obtained by filling and coating a mixture obtained by mixing a binder powder such as a ride at a predetermined ratio is usually used. Separator 33
For example, a sheet made of a porous synthetic resin having electrical insulation properties is generally used.

An example of the procedure for assembling the electrode plate group 3 is as follows.
First, the separator 33 is folded in two and formed into an envelope shape. The positive electrode plate 31 is inserted into the envelope with the positive electrode tab facing upward, and a combined body of the separator 33 and the positive electrode plate 31 is formed. And the negative electrode plate 32 are alternately superposed. At this time, each positive electrode plate 31 is arranged such that, for example, the side surface 31b of the first positive electrode plate to which the positive electrode tab is welded and the side surface 31a of the second positive electrode plate to which the positive electrode tab is not welded face each other. I do. The negative electrode plate is located at the outermost position. Then, as a whole, it is formed into a substantially rectangular parallelepiped shape as shown in FIG.

Therefore, in the obtained electrode plate group,
The positive electrode tab protrudes upward from the upper part. Here, one end of the conductive sheet 35 is joined at a predetermined position on the bottom side or the upper side (the upper side in FIG. 2) of each negative electrode plate. The other end of each conductive sheet 35 is converged and joined at one location, and the whole negative electrode is electrically connected.

Next, in manufacturing the battery, the other end 34a of the positive electrode tab 34 of the electrode plate group 3 is connected to the positive electrode terminal as shown in FIG. 4 which is a cross-sectional view taken along the line IV-IV in FIG. In order to facilitate the connection, they are gathered and joined at one location (convergence location J), whereby each positive electrode plate 31 is electrically united. The electrode plate group 3 in which the other end 34a of the positive electrode tab 34 is thus bundled is continuously inserted into the outer can 1 through the opening 1a of the outer can 1. Then, an alkaline electrolyte is injected into the outer can 1, and thereafter, the other end 34a of each positive electrode tab 34, which is focused at one location, and the positive electrode terminal 21 of the lid plate are disposed on the lower surface of the lid plate. Connected via a positive electrode lead plate.

Then, finally, the opening 1a of the outer can 1
In addition, a pulse type laser welding suitable for fine processing is usually performed on a portion (hereinafter, referred to as a fitting portion) where the cover plate 2 is fitted and mounted and the opening 1a of the outer can 1 and the cover plate 31 match (hereinafter, referred to as a fitting portion). Then, the outer can 1 and the lid plate 2 are sealed and welded to form a sealed rectangular battery.

[0012]

In the above-mentioned electrode group, the convergence point J at the other end 34a of each positive electrode tab 34 is located near the long side of the electrode group, and is usually shown in FIG. As described above, the portion is located on the side opposite to the side surface 31b on the side where the one end 34b of the positive electrode tab 34 in each positive electrode plate 31 is attached. Then, the other end 34a of each positive electrode tab 34
When focusing, the other end 34a of each positive electrode tab is
The other end 34a is focused at the focusing point J by pulling in the direction, and the whole is welded.

When the other end 34a of each positive electrode tab 34 is converged in the above-described state, as shown in FIG. 5, a force in the direction of arrow P is applied to the positive electrode tab 34, so that the positive electrode tab 34 is bent. Can be When the bending becomes large, the one end 34b of the positive electrode tab 34 is peeled off from the welded portion with the positive electrode plate, and the lower end of the one end 34b of the positive electrode tab may be hardly inserted into the adjacent separator 33. In the worst case, this lower end pierces the separator 33,
In addition, it may come into contact with the negative electrode plate 32 ahead of it, causing a short circuit accident.

[0014] The present invention solves the above-mentioned problem in the rectangular sealed battery. When the other end of the positive electrode tab is focused, the lower end of the positive electrode tab attached to the positive electrode plate breaks through the separator,
It is an object of the present invention to provide a rectangular sealed battery having a structure capable of preventing a short circuit from being caused by contact with a negative electrode plate.

[0015]

In order to achieve the above object, according to the present invention, a negative electrode plate and a positive electrode tab are provided on one side surface together with an alkaline electrolyte in a bottomed outer can having a rectangular opening. A large number of positive electrode plates each having one end attached thereto are disposed via a separator, and an integrated electrode plate group is accommodated therein.The rectangular opening is sealed with a lid plate having a positive electrode terminal, and In a rectangular sealed battery having the other end converged at one location and connected to the positive electrode terminal, one end of the positive electrode tab is closer to the other end of each of the positive electrode tabs on the side surface of the positive electrode plate. A rectangular sealed battery characterized by being mounted on a side surface is provided.

In the prismatic sealed battery according to the present invention, a positive electrode tab attached to the positive electrode plate of the electrode group is provided on each positive electrode plate by:
Since the other end of each positive electrode tab is welded to the surface closer to the focusing point, when the other end of the positive electrode tab is focused, a force is applied to the positive electrode tab toward the focusing point, and the positive electrode tab is Even if it bends, the lower end portion applies a force only in the direction pressed against the positive electrode plate to which the positive electrode tab is welded, so that the lower end portion of the positive electrode tab breaks through the separator and contacts the adjacent negative electrode plate. Things can be suppressed.

[0017]

FIG. 6 shows an example of an electrode group in a rectangular sealed battery according to the present invention. In the electrode plate group 3A, in each positive electrode plate 31, one end 34b of the positive electrode tab is welded to a concave portion 31c formed on a side surface 31a of the other end 34a of the positive electrode tab closer to the converging point J.

In this manner, the positive electrode tab 34 is connected to the positive electrode plate 3.
1, when the other end 34a of the positive electrode tab is gathered at one location J, even if a force is applied to the positive electrode tab 34 in the direction of the arrow P and the positive electrode tab 34 is bent, FIG. As shown in (1), the lower end of one end 34b of the positive electrode tab 34 is only pressed against the positive electrode plate 34 to which the positive electrode tab is welded. Therefore, the lower end portion only presses the concave portion 31c of the positive electrode plate in the direction of arrow Q. Even if the lower end portion is peeled off at the welded portion, the lower end portion contacts the adjacent negative electrode plate 32 and causes a short circuit. Will not occur.

Therefore, even when this electrode plate group 3A is employed and a square sealed battery is assembled according to a conventional manufacturing process, an excellent square sealed battery with extremely few occurrences of short circuit accidents can be obtained. Here, in the electrode plate group 3A, for example, when the force at the time of converging the other end 34a of each positive electrode tab becomes extremely large, and when an excessive force is applied to the positive electrode tab 34, the positive electrode tab 34 which is greatly bent is formed. 7, the separator 33 is crushed at a portion S surrounded by a dotted circle in FIG. 7, and an end (hereinafter, simply referred to as an upper end) 3 of the adjacent negative electrode plate 32 on the opening side is pressed.
Contact with 2a can also occur. In order to prevent such a problem from occurring, for example, as shown in FIG. 8, the position of the upper end 32a of the negative electrode plate 32 may be lower than the position of the upper end 31e of the positive electrode plate 31. preferable.

In this way, even if the positive electrode tab 34 is largely bent when the other end 34a of the positive electrode tab is focused, the upper end 32a of the adjacent negative electrode plate is positioned below the upper end 31e of the positive electrode plate. Therefore, contact between the positive electrode tab 34 and the upper end 32a of the negative electrode plate is unlikely to occur. Therefore, when the electrode group (3B) as described above is employed, it is possible to obtain an excellent rectangular sealed battery with less occurrence of a short circuit. Here, if the vertical dimension difference between the upper end 32a of the negative electrode plate and the upper end 31e of the positive electrode plate is too small, when the positive electrode tab 34 is largely bent, the positive electrode tab contacts the upper end 32a of the negative electrode plate. May be. Conversely, if the difference between the dimensions is too large, the vertical dimension of the negative electrode plate is too small relative to the vertical dimension of the positive electrode plate, and the cross-sectional shape of the electrode plate group 3 when viewed from the long side direction Becomes comb-like, and the strength in the short side direction decreases at the upper part of the electrode group. Therefore, the magnitude of the vertical dimension difference between the upper end 32a of the negative electrode plate and the upper end 31e of the positive electrode plate is:
When the positive electrode tab 34 is largely bent, the positive electrode tab 34 is larger than the size at which the upper end 32a of the negative electrode plate contacts, and smaller than the size at which the predetermined strength cannot be secured in the short side direction of the electrode plate group 3. Is preferred.

In the present invention, the other end 3 of the positive electrode tab is used.
Although only the case where the focusing point J of 4a is set near the long side of the electrode group (left end in the figure) as shown in FIG. 6, the position of the focusing point J of the other end 34a of the positive electrode tab is , May be set arbitrarily. In that case, one end 34 of the positive electrode tab
b needs to be welded to the side closer to the converging point J in each positive electrode plate. For example, as shown in FIG. 9, when the convergence point J is set substantially above the middle between the positive plates 31A and 31B, one end 3 of each positive electrode tab 34 is formed.
4b is welded to the surface closer to the converging point J in each positive electrode plate. That is, in the positive electrode plate 31A, one end 34b of the positive electrode tab is welded to the concave portion 31d on the right side surface in the drawing, and in the positive electrode plates 31B and 31C, one end 34b of the positive electrode tab is welded to the concave portion 31c on the left side surface in the drawing. Is done.

[0022]

【Example】

Example 1 A positive electrode plate (nickel electrode) having a length of 50 mm, a width of 20 mm, and a thickness of 0.5 mm was manufactured. Then, a concave portion 31c having a substantially square shape in plan view is formed on the upper portion of the positive electrode plate by a press machine.
31d was formed to obtain a positive electrode plate having a concave portion as shown in FIG. The dimensions of the concave portions 31c and 31d are 5m in length.
m, width 5 mm, depth 0.1 mm. Next, length 10m
A positive electrode tab 34 made of a nickel sheet-like piece having a width of 3 mm and a width of 3 mm and a thickness of 0.1 mm is prepared, and one end 34b of the positive electrode tab is connected to the 31a side of the two concave portions of the positive electrode plate. Spot welding was performed on the concave portion 31c.

Next, a separator is prepared by molding a nylon sheet having a thickness of 0.1 mm into an envelope shape having a length of 55 mm and a width of 24 mm, and the positive electrode plate is inserted into the separator with the positive electrode tab facing upward. Then, a combined body of the positive electrode plate and the separator was manufactured. Next, a negative electrode plate (hydrogen storage alloy electrode) having a length of 50 mm, a width of 20 mm, and a thickness of 0.5 mm was manufactured.

Four negative electrode plates manufactured as described above and three of the combined bodies were prepared, and the negative electrode plate and the combined body were alternately overlapped so that the negative electrode plate was located at the outermost position. The electrode group 3A as shown was manufactured. In addition, the said electrode group finally uses a press machine so that length (vertical dimension) may be 52 mm, horizontal (dimension in a long side direction) 24 mm, so that it may match the inner shape of the outer can described later. Thickness (dimension in the short side direction)
It was shaped into a substantially rectangular parallelepiped of 4.1 mm.

Then, as shown in FIG. 6, the other end 34a of each positive electrode tab is pulled in the direction of arrow P, and above the separator (focusing point J) located on the leftmost side in the figure in the electrode plate group 3A. It was focused and the other end of each positive electrode tab was welded. After the welding at the converging point J was completed, the other end of the positive electrode tab that was left before the converging point J was cut off. As described above, an electrode group in which the other end of the positive electrode tab was focused was manufactured.

In the negative electrode plate, one end of the conductive sheet was welded to a predetermined position on the upper part of each negative electrode plate, and the other end of the sheet was focused at one place and welded. Thereby, each negative electrode plate is also electrically united. Next, it is made of a nickel-plated steel plate having a thickness of 0.5 mm, and has a rectangular opening having a dimension of 25 mm in the long side direction and 4.5 mm in the short side direction at the top, and a dimension in the vertical direction. Was 60 mm and a rectangular parallelepiped outer can was prepared. Then, the electrode plate group 3A provided with the positive electrode tab was inserted into the outer can through the opening. Subsequently, 1 cc of an alkaline aqueous solution containing KOH as a main component was injected into the outer can as an electrolytic solution.

Next, a positive terminal is provided at the center, and the dimension in the long side direction is 25 mm and the dimension in the short side direction is 4.5 m.
m, the positive electrode lead plate of the lid plate having a thickness of 0.5 mm and the convergence point J at the other end of the positive electrode tab are welded, and the positive electrode plate and the positive electrode terminal are electrically connected. The fitting was fitted to the opening of the outer can. Then, laser welding was performed over the entire circumference of the fitting portion to produce a square sealed nickel-hydrogen secondary battery. In addition, the said battery is 1000
0 were produced.

The occurrence rate of short circuit was determined for the obtained battery. The results are shown in Table 1. Here, the occurrence rate of the short circuit was obtained as follows. First, the obtained battery was charged, discharged, and aged, and after activating the battery, an open circuit voltage was obtained for each battery, and a battery having a voltage value equal to or lower than the standard voltage was extracted. Then, the removed battery is disassembled and the state of the positive electrode tab is observed, and the lower end of the positive electrode tab 34 has broken through the separator as shown in FIG. 5, or the upper end of the positive electrode tab and the negative electrode plate are in contact with each other. Are counted as batteries with a short circuit. Then, the total number of manufactured batteries (1000
0), the ratio of the number of batteries in which a short circuit occurred was determined, and this ratio was defined as a short circuit occurrence rate (%).

Example 2 A negative electrode plate having a length of 48 mm, a width of 20 mm, and a thickness of 0.5 mm was used. When assembled into an electrode plate group, the upper end of the negative electrode plate was positioned 2 mm below the upper end of the positive electrode plate. 10000 nickel-hydrogen secondary batteries were manufactured in the same manner as in Example 1 except that the above-described procedure was adopted. The occurrence rate of short circuit was determined for the obtained battery in the same manner as in Example 1. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 The procedure of Example 1 was repeated except that the positive electrode tab was welded to the 31b side of the positive electrode plate (see FIG. 3), that is, to the recess 31d formed on the side opposite to that of Example 1. 10000 nickel-hydrogen secondary batteries were manufactured in the same manner as described above.

The occurrence rate of short circuit was determined for the obtained battery in the same manner as in Example 1. The results are shown in Table 1.

[0032]

[Table 1]

As is clear from the results in Table 1, Example 1
Battery has a very low incidence of short circuits. In other words, this indicates that a non-defective product in which the positive electrode tab and the negative electrode plate of the electrode plate group are not in contact with each other and in which short-circuiting is less likely to be obtained. This is because the positive electrode tab is welded to the surface of the positive electrode plate that is closer to the focusing point at the other end of the positive electrode tab, so that when the other end of the positive electrode tab is focused, force is applied to the positive electrode tab in the direction toward the focusing point. Is added, only the lower end of the positive electrode tab is pressed against the positive electrode plate, and contact between the negative electrode plate and the positive electrode tab is suppressed.

It can also be seen that the battery of Example 2 has a lower short-circuit occurrence rate than the battery of Example 1. this is,
Since the electrode plate group is formed so that the upper end of the negative electrode plate is located below the upper end of the positive electrode plate, when the other end of the positive electrode tab is focused, excessive force is applied to the positive electrode tab, and the positive electrode tab is This is because, even if bent greatly, it was possible to prevent the upper end of the negative electrode plate from contacting the positive electrode tab.

On the other hand, the battery of Comparative Example 1 has a higher short-circuit occurrence rate than the battery of the present invention. this is,
In the battery of Comparative Example 1, since the conventional electrode group was employed, when the other end of the positive electrode tab was focused, a force was applied to the positive electrode tab, and the positive electrode tab was greatly bent,
This is because the welded portion at the lower end of the positive electrode tab was dislodged, and the lower end pierced the adjacent separator and came into contact with the negative electrode plate ahead.

[0036]

According to the first aspect of the present invention, the positive electrode tab is welded to a surface of the electrode plate group housed in the outer can that is closer to the converging point at the other end of the positive electrode tab in each positive electrode plate. Therefore, when focusing the other end of the positive electrode tab, even if a force is applied to the positive electrode tab and the positive electrode tab is largely bent,
Since the lower end of the positive electrode tab is only pressed against the positive electrode plate to which the positive electrode tab is welded, it is possible to avoid breaking through the adjacent separator and coming into contact with the negative electrode plate. Therefore, a short circuit between the negative electrode plate and the positive electrode tab is suppressed, so that the occurrence of defective products due to a short circuit accident is extremely reduced, and the yield in battery production is improved.

In the prismatic sealed battery according to the second aspect, in the electrode plate group, the upper end of the negative electrode plate is assembled so as to be located lower than the upper end of the positive electrode plate. Even if an excessive force is applied to the positive electrode tab and the positive electrode tab is greatly bent, contact with the upper end of the adjacent negative electrode plate and short circuit are suppressed as much as possible. Therefore, occurrence of defective products due to a short circuit accident is further reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a rectangular sealed battery.

FIG. 2 is a perspective view illustrating a configuration of an electrode group.

FIG. 3 is a perspective view showing a configuration of a positive electrode plate.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2;

FIG. 5 is a cross-sectional view showing a configuration of a mounting portion for a positive electrode tab in a conventional electrode plate group.

FIG. 6 is a cross-sectional view showing a configuration of an electrode group according to the present invention.

FIG. 7 is a cross-sectional view illustrating a configuration of a mounting portion of a positive electrode tab of an electrode plate group according to the present invention.

FIG. 8 is a cross-sectional view showing a configuration of a mounting portion of a positive electrode tab of another embodiment of the electrode plate group according to the present invention.

FIG. 9 is a cross-sectional view showing another embodiment of the configuration of the electrode group in the present invention.

[Explanation of symbols]

 Reference Signs List 1 outer can 1a opening 2 lid plate 21 positive electrode terminal 3 electrode plate group (conventional) 3A electrode plate group (in the present invention) 31 positive electrode plate 31a, 31b side surface 31c, 31d concave portion 32 negative electrode plate 33 separator 34 positive electrode tab 34a positive electrode The other end of the tab 34b One end of the positive electrode tab J Focusing point

Claims (2)

(57) [Claims] 1. A negative electrode plate and a large number of positive electrode plates having one end of a positive electrode tab attached to one side surface, together with an alkaline electrolyte, are arranged via a separator in a bottomed outer can having a rectangular opening. The integrated electrode plate group is accommodated, the rectangular opening is sealed with a cover plate having a positive electrode terminal, and the other end of each of the positive electrode tabs is focused at one location and connected to the positive electrode terminal. The sealed rectangular battery according to claim 1, wherein one end of the positive electrode tab is attached to a side surface of the side surface of the positive electrode plate which is closer to a focusing point at the other end of each of the positive electrode tabs. 2. The sealed rectangular battery according to claim 1, wherein the end of the negative electrode plate on the opening side is located closer to the bottom of the outer can than the end of the positive electrode plate on the opening side.