JPH09199117A - Positive plate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the separating of a positive electrode tab from its mounting part of a positive plate, in the case of focusing the other end of the positive electrode tab. SOLUTION: A positive plate 31A supports an active material compound and comprises a metal porous unit 31c of three-dimensional network structure provided with a tab mounting part 31c in a prescribed position and a positive electrode tab 34 spot-welding one end to the tab mounting part 31c. Here, the positive electrode tab 34 is provided with a return part 34c in one end, the return part 34c is opposed to be engaged with the positive electrode tab mounting part 31c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode plate incorporated in an electrode plate group housed in a prismatic sealed battery and a method of manufacturing the same, and more particularly to a positive electrode plate in which peeling of a positive electrode tab is less likely to occur and a method of manufacturing the same. .

[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 form has a cylindrical shape and a prismatic shape. Here, for example, the structure of a prismatic sealed type nickel-hydrogen secondary battery will be described with reference to FIG.

The prismatic nickel-hydrogen secondary battery is fitted and mounted in the outer can 1 which houses the electrode plate group 3 therein, and the opening 1a of the outer can 1 after housing the electrode plate group 3, and the opening thereof. Part 1
and a lid plate 2 for sealing a. The outer can 1 is, for example, a nickel-plated steel rectangular parallelepiped bottomed can, has an opening 1a having a rectangular shape in plan view, and also serves as an external terminal of the negative electrode plate.

The lid plate 2 is provided with a positive electrode terminal 21 in the center thereof and has a rectangular shape in plan view which fits the opening 1a of the outer can and is connected to the positive electrode terminal at a predetermined position on the lower surface thereof. A positive electrode lead plate (not shown) is provided. As shown in FIG. 2, the electrode plate group 3 includes a positive electrode plate (nickel electrode) 31B and a negative electrode plate (hydrogen storage alloy electrode) 32, and a separator 33 having electrical insulation and liquid retention therebetween. In this state, a plurality of sheets are stacked on top of each other, and are inserted from the opening 1 a of the outer can and housed in the outer can 1. The electrode plate group 3 is formed in a substantially rectangular parallelepiped shape so as to fit the inner shape of the outer can 1 as a whole.

As the positive electrode plate (nickel electrode) 31B, for example, a material in which a positive electrode active material mixture is carried on a porous metal body having a three-dimensional network structure such as a sponge-like nickel plate is usually used. As the positive electrode active material mixture, a mixed powder containing nickel hydroxide as a main component and, if necessary, powder of a cobalt compound such as cobalt oxide is used. On one side surface of the upper portion of the positive electrode plate 31B, for example, a positive electrode tab 34 made of a tape-shaped small piece made of nickel.
Are welded together, and the positive electrode tabs 34 are arranged so as to project upward from the upper part of the electrode plate group by a predetermined length when assembled as an electrode plate group (see FIG. 2).

An example of the method for manufacturing the positive electrode plate will be described below. First, a viscous paste-like active material mixture is prepared by adding an aqueous solution of a thickener prepared by dissolving carboxymethyl cellulose or methyl cellulose to the mixed powder of the positive electrode active material and stirring the whole. Then
For example, as shown in FIG. 3, a predetermined portion of the long nickel porous body sheet 30 is crushed in the thickness direction to form the concave portion 30a.
To form The recess 30a will be a tab attachment point described later. Then, the long-sized sponge-like nickel porous body sheet is continuously filled and coated with the paste-like active material mixture and then dried to solidify the active material mixture, thereby carrying the positive electrode active material mixture. The long sponge-like nickel porous sheet 30 is manufactured.

After that, in order to adjust the thickness of the nickel porous body sheet 30 and to more firmly support the active material mixture supported thereon and increase the packing density thereof, the nickel porous body sheet 30 is rolled. Give. And
The above-mentioned nickel porous sheet 30 that has been rolled
After removing the deposits in the recesses 30a (tab attachment points), the predetermined points indicated by the chain double-dashed line in FIG. 3 are cut with a cutter, and tab attachment points 31c (31d) are placed at the predetermined positions.
The strip-shaped positive electrode plate precursor 31 is prepared. The tab attachment portion 31c (31d) has a higher density than other portions, so that a good nugget portion can be formed at the time of spot welding performed in the subsequent stage.

Then, as shown in FIG. 4, a long positive electrode tab conductive tape T is supplied along the arrow S to the tab mounting portion 31d, and its tip portion t is superposed on the tab mounting portion 31d. After forming the welded portion by applying electricity to the welded portion while pressurizing the welded portion with the upper electrode 51 and the lower electrode 52 of the spot welding machine, the tip portion t of the tab conductive tape is spot-welded to the precursor 31. Then, during or after the welding, the long conductive tape T for positive electrode tab is cut into a desired length by a cutter 60 composed of an upper blade 61 and a lower blade 62, so that the tab mounting as shown in FIG. A positive electrode plate 31B is formed by welding the positive electrode tab 34 to the location 31d.

In the process of attaching the positive electrode tab described above, normally, as shown in FIG. 4, the tip portion of the positive electrode tab conductive tape is placed at the tab attachment point 31d.
Is a cutting portion when the conductive tape T is cut by the cutter 60 in the process of attaching the positive electrode tab prior to this. When the tip portion t of the conductive tape T is overlapped with the tab attachment portion, the tip portion t of the conductive tape T is usually placed on the attachment portion (31d in the figure) formed on the upper surface side of the precursor 31. In this embodiment, the tab attachment point is on the bottom and the positive electrode tab conductive tape is on the top.

Here, as shown in FIG. 4, a portion where the tab mounting portion of the positive electrode plate precursor 31 is provided (welded portion).
When the long blade 61 is placed at a position far from the end face 31e and the lower blade 62 is placed at a position near the end face 31e, the tip end t after cutting is sharply sharpened upward in the drawing. A protruding portion (referred to as a burr portion in the present invention) 34c,
A curved surface portion (dull portion in the present invention) 34d is formed on the opposite side (lower side in the drawing) of the burr portion 34c.
That is, when the cutter 60 is arranged as described above,
A burr portion 34c is formed on the upper side and a dull portion 34d is formed on the lower side of the tip portion t after cutting. As described above, when the conductive tape T having the tip portion t in such a state is placed on the tab mounting portion 31d located on the upper surface of the precursor 31 to manufacture the positive electrode plate, the positive electrode plate 31B is obtained. As shown in FIG. 6, the positive electrode tab is attached with the burr portion 34c facing outward and the droop portion 34d being located on the tab attachment point 31d side. Therefore, the positive electrode plate 3
When 1B is incorporated in the electrode plate group described later, the burr portion 34 is formed.
Faces an adjacent separator.

In the production of the positive electrode plate, after the conductive tape for the positive electrode tab is spot-welded and then the conductive tape for the positive electrode tab is cut into a predetermined length by the cutter, the burr portion and the dull portion are separated. Since the newly provided tip portion t is newly formed, the new tip portion t is placed at the tab attachment position of the next positive electrode plate precursor, whereby the second positive electrode plate is manufactured. By repeating such a series of operations, the positive electrode plate is continuously manufactured.

As the negative electrode plate (hydrogen storage alloy electrode) 32 constituting the electrode plate group 3 as shown in FIG. 2, for example, a porous conductive plate such as a punching nickel plate or a nickel net, and a hydrogen storage alloy powder are used. A mixture obtained by filling and coating a conductive material powder such as nickel powder and a binder powder such as polyvinylidene fluoride at a predetermined ratio is generally used.

As the separator 33, for example,
A sheet made of a porous synthetic resin having electric insulation and liquid retention is usually used. Next, an example of an assembling procedure of the electrode plate group 3 will be described below. First, as shown in FIG. 7, the separator 33 is folded in half, and the positive electrode plate 31B is inserted therein with the positive electrode tab 34 facing upward, and the edges 33a, 33a along the longitudinal direction of the separator are mutually separated. The separator 33 is welded to form a bag, and an integrated product in which the positive electrode plate 31B is housed is manufactured. Then, the integrated product and the negative electrode plate 32 are alternately stacked. At this time, each positive electrode plate 31B has, for example, a surface 31b on which the positive electrode tab 34 of the first positive electrode plate is welded and a surface on which the positive electrode tab 34 of the second positive electrode plate is not welded. 31a is arranged so as to face each other. The negative electrode plate is located at the outermost part. Then, as a whole, it is formed into a substantially rectangular parallelepiped electrode plate group 3 which can be fitted and inserted into the outer can as shown in FIG.

Therefore, in the obtained electrode plate group 3, the positive electrode tab 34 projects upward from the upper part. Here, each negative electrode plate 32 has one end of the conductive tape 35 bonded to a predetermined position on the bottom side or the upper side (the upper side in FIG. 2), and each conductive tape 35 has the other end focused at one place. Are joined together, and the entire negative electrode is electrically connected.

Next, the other end 34a of the positive electrode tab 34 of the electrode plate group 3 facilitates connection with the positive electrode terminal as shown in FIG. 8 which is a sectional view taken along the line VIII-VIII of FIG. Therefore, the positive electrode plate 31B is electrically connected as a whole by being collected and bonded at one place (focusing place J). In this way, the electrode plate group 3 including the positive electrode plate having the other end 34a of the positive electrode tab 34 focused, the negative electrode plate 32 focused with the conductive tape 35, and the separator 33 continues to be as shown in FIG. Then, it is inserted into the outer can 1 through the opening 1 a of the outer can 1. Then, the alkaline electrolyte is injected into the outer can 1, and thereafter, the other ends 34a of the positive electrode tabs 34 and the positive electrode terminals 21 of the lid plate, which are focused in one place, are arranged on the lower surface of the lid plate 2. Connected via the positive electrode lead plate.

Finally, the opening 1a of the outer can 1
Then, the lid plate 2 is fitted and attached to the outer can 1, and the portion where the opening 1a of the outer can 1 and the lid plate 2 are matched is usually subjected to pulse laser welding suitable for microfabrication. Sealing welding with the plate 2 is performed to form a prismatic battery having a sealed structure.

[0017]

In the electrode plate group described above, the focusing point J of the other end 34a of each positive electrode tab 34 is normally attached to the positive electrode tab 34 of each positive electrode plate 31B as shown in FIG. It is a portion located on the side opposite to the side surface 31b on the side where the operation is performed. When the other end 34 a of each positive electrode tab 34 is focused, the other end 34 a of each positive electrode tab 34 is focused.
a in the direction of arrow P, and the other end 3 of them at the focusing point J
4a is focused and the whole is welded.

When the other end 34a of each positive electrode tab 34 is focused in the above-mentioned state, as shown in FIG. 9, a force in the direction of arrow P is applied to the positive electrode tab 34 and the positive electrode tab 34 bends. Sometimes. Then, when the deflection becomes large, the one end 34b of the positive electrode tab 34 is separated from the welded portion with the positive electrode plate, and the separator 33 adjacent to the burr portion 34c described above.
It can be difficult. Then, the burr portion 34c may pierce the separator 33 and further come into contact with the negative electrode plate 32 located in front of the separator 33 to cause a short circuit accident.

In order to solve such a problem, in the electrode plate group housed inside the outer can, the positive electrode tab is welded to the surface of each positive electrode plate at the other end of the positive electrode tab, which is closer to the focusing point. However, for example, it is proposed in Japanese Patent Application No. 7-192069. According to this method, when the other end of the positive electrode tab is focused, even if the positive electrode tab is pulled and the positive electrode tab is largely bent, as shown in FIG.
Is only pressed against the positive electrode plate to which the positive electrode tab is welded (in the direction of arrow Q), the burr portion 34c does not break through the adjacent separator and come into contact with the negative electrode plate.

However, in this method, when focusing the other end of the positive electrode tab, an upward force (direction of arrow U) may be applied to the positive electrode tab in the positive electrode plate close to the focusing point, so that the positive electrode The tab may be pulled up, shear stress may act on the positive electrode tab and the welded portion of the tab mounting portion, the phenomenon of peeling of the welded portion may occur, and the positive electrode tab may be dislocated from the tab mounting portion.

In order to strengthen the connection between the positive electrode tab and the positive electrode plate, the positive electrode tab is subjected to burring to form a burr-like protrusion, and the burr-like protrusion is penetrated in the thickness direction of the tab mounting portion. After that, a method of caulking and fixing the whole is disclosed in JP-A-4-36871. In this method, it is true that the positive electrode tab and the positive electrode plate are strongly bonded to each other and it is possible to prevent the welded portion between the positive electrode tab and the tab attachment portion from being separated, but since the burring process is performed, the manufacturing process As the number increases, the processing cost increases, and the economy of battery manufacturing deteriorates.

The present invention solves the above-mentioned problems in the positive electrode plate incorporated in the electrode plate group housed in the prismatic sealed battery, and when the other end of the positive electrode tab is focused, the positive electrode tab is moved from the tab mounting portion of the positive electrode plate. It is an object of the present invention to provide a positive electrode plate having a structure capable of preventing the peeling and the manufacturing method thereof.

[0023]

In order to achieve the above object, in the present invention, a metal porous body having a three-dimensional network structure carrying an active material mixture and provided with tab attachment points at predetermined positions. And a positive electrode tab having one end spot-welded to the tab attachment portion, the positive electrode tab has a burr portion at one end thereof, and the burr portion faces the positive electrode tab attachment portion. There is provided a positive electrode plate characterized by being engaged with each other.

Further, in the present invention, a tab attachment portion is provided by compressing a predetermined part of the continuous metal porous body sheet having a three-dimensional network structure, and then the continuous metal porous body sheet is filled with the paste-like active material mixture. Then, drying step; after rolling the metal porous body continuous sheet to remove deposits at the tab attachment points, the metal porous body continuous sheet is cut into strips having tab attachment points at the ends. A step of forming a positive electrode plate precursor; a step of forming a welded portion by superimposing a conductive tape for a positive electrode tab on a tab mounting portion of the positive electrode plate precursor, and spot welding the welded portion; A step of cutting the tape with a cutter arranged at a predetermined position; in the method of manufacturing the positive electrode plate, when the conductive tape for the positive electrode tab is cut when forming the welded portion. The back portion occurring at the tip of the-loop arranged so as to face the tab attachment point, pushing the back portion to the tab attachment point, the production method of the positive electrode plate, wherein the engaging is provided.

[0025]

FIG. 11 shows an example of an electrode plate group 3A incorporating a positive electrode plate 31A of the present invention. In this electrode plate group 3A, in each of the positive electrode plates 31A, a burr portion 34c generated at one end 34b of the positive electrode tab when the positive electrode tab 34 (conductive sheet for the positive electrode tab) is cut is disposed so as to abut on the tab mounting portion 31c. In this state, the burr portion 34c is pushed into the tab attachment portion 31c and engaged therewith. Therefore, even when a force is applied to the positive electrode tab 34 in the direction of the arrow P when the other end 34a of the positive electrode tab 34 is focused on one place in the electrode plate group 3A, as shown in FIG.
The burr portion 34c of the one end 34b of the positive electrode tab 34 is only pressed against the tab attachment point 31c of the positive electrode plate 31 to which the positive electrode tab 34 is welded. Therefore, the burr portion 34c is provided at the tab attachment portion 3 of the positive electrode plate.
In 1c, the positive electrode tab 34 is pressed in the direction of the arrow Q and further digs into the tab mounting portion 31c, so that the positive electrode tab 34 is more firmly bonded to the tab mounting portion 31c and is less likely to be peeled off. In the present invention, the term "engagement" refers to the state in which the burr portion 34c bites into the tab mounting portion as shown in FIG.

Further, even if a force is applied in the direction of the arrow U, since the burr portion 34c bites into the tab mounting portion 31c like a wedge, the positive electrode tab 34 is prevented from peeling from the tab mounting portion 31c. To be done. Here, in order to prevent the positive electrode tab 34 from being pulled out in the direction of the arrow U even when a large force is applied in the direction of the arrow U, in order to effectively exhibit the wedge effect, the tab mounting portion 3
It is preferable that the angle α of the burr portion inside 1c (see the circle A in FIG. 11) be 90 degrees or less.

In the above description, the positive electrode tab 34 is used.
A concave portion 31c whose one end 34b is formed on the side surface 31a of the other end 34a of the positive electrode tab 34 near the focusing point J
However, in the positive electrode plate of the present invention, the present invention is not limited to this mode, and if the burr portion 34c of the positive electrode tab 34 is engaged with the tab attachment portion, the state shown in FIG. As shown, one side of the positive electrode tab 34 is located on the side surface 3 on the side farther from the focusing point J at the other end of the positive electrode tab.
It does not cause any inconvenience even if it is welded to the tab mounting portion 31d formed on 1b (positive electrode plate 31A '). in this case,
When the other end 34a of the positive electrode tab 34 is focused on the focusing point J, even if a force along the direction of the arrow P is applied to the positive electrode tab 34, the burr portion 34c is engaged with the tab attaching point 31d. Therefore, the positive electrode tab 34 is difficult to peel off. what if,
The positive electrode tab 34 bends, and accordingly, the positive electrode tab 3
Even if one end 34b of No. 4 is peeled off from the tab attachment portion and one end 34b of the positive electrode tab is pressed against the adjacent separator 33, the portion contacting the separator 33 is the curved drip portion 34d. Almost never break through. Therefore, the positive electrode tab 3
It is possible to effectively prevent the situation where the negative electrode plate 32 and the negative electrode 4 come into contact with each other to cause a short circuit.

When the electrode group 3A incorporating the positive electrode plate 31A of the present invention as described above is adopted and the prismatic closed battery is assembled in the conventional manner, an excellent prismatic closed battery with extremely few occurrence of short circuit accident can be obtained. it can. Here, a method for manufacturing the positive electrode plate 31A in the present invention will be described below. First, based on the conventional method, tab attachment points 31c, 3 are provided at predetermined positions.
A strip-shaped positive electrode plate precursor 31 having 1d is manufactured.

Then, as shown in FIG. 13, the positive electrode tab conductive tape T is supplied to the positive electrode plate precursor 31 along the arrow S, and the tip portion of the positive electrode tab tape is attached to the tab mounting portion 31c. The t are overlapped to form a weld. At this time, the burr portion 34c is arranged so as to face the tab attachment portion 31c. After that, the welding portion is pressed in the thickness direction by the pressing means, and the burr portion 34c is pushed into the tab mounting portion 31c to be engaged. Then, the welding portion is connected to the upper electrode 51 of the spot welding machine.
Then, current is applied while being pressed by the lower electrode 52, and the conductive tape T for the positive electrode tab is spot-welded to the precursor 31. Then, the upper blade 61 with the conductive tape for the positive electrode tab arranged at a predetermined position.
It is cut into a desired length by a cutter 60 including a lower blade 62 and a lower blade 62. In this way, the positive electrode plate 31A including the positive electrode tab 34 is formed.

A positive electrode plate is manufactured by using the above-described procedure as one cycle. Therefore, after completing one cycle,
The tip portion t of the cut positive electrode tab conductive tape is subsequently moved in the direction of the arrow S to be overlapped with the tab attachment portion of the next positive electrode plate precursor to form a welded portion, and the above manufacturing procedure is repeated. In this way, positive electrode plates are continuously manufactured.

As described above, in the present invention, it is essential that the burr portion 34c of the positive electrode tab 34 is pushed into and engaged with the tab mounting portion 31c (or 31d) so as to face the tab mounting portion 31c (or 31d). Conductive tape for tab T
When the bar is cut, the burr portion 34c causes the tab mounting point 31
The upper blade 6 of the cutter 60 is formed so as to occur on the side facing c.
1 and the lower blade 62 are arranged. That is, as shown in FIG. 13, when the positive electrode tab is attached to the tab attaching portion 31c,
As the cutter 60, an upper blade 61 is provided at a position closer to the end surface 31e of the portion (welding portion) where the tab attachment portion of the positive electrode plate precursor 31 is provided, and a lower blade 62 is provided at a position farther from the end surface 31e. To arrange. Such a cutter 60
When the conductive tape T for the positive electrode tab is cut by means of the conductive tape T for the positive electrode tab, the tip portion t of the conductive tape for the positive electrode tab is provided with the burr 3 on the lower side in the drawing.
4c, a drip portion 34d is formed on the upper side in the drawing,
The burr portion 34c faces the tab attachment portion 31c. Therefore, when the positive electrode plate 31A is incorporated in the electrode plate group, the drip portion 34d faces the adjacent separator 33.

In the above-mentioned positive plate manufacturing procedure,
When the burr portion 34c is pushed into and engaged with the tab mounting portion 31c, a pressing means is used, but the method of the present invention is not limited to this procedure, and the upper electrode 51 and the lower electrode 52 of the spot welding machine are Also, by adopting a shape in which the burr portion 34c can also be pressed, the burr portion 34c may be pushed in during the pressing process during spot welding. In this case, the number of steps can be reduced, which is preferable.

Further, in the positive electrode plate precursor 31, since the tab attachment portions 31c and 31d are formed in a compressed state, the density is higher than that of the other electrode plate surfaces 31a and 31b. The quality is different from the point. In particular, since the material matching is poor at the boundary between the tab mounting portion 31c and the electrode plate surface, if excessive force is applied during spot welding, the material may break. Therefore, it is preferable to avoid the boundary portion as a portion where the burr portion of the positive electrode tab is pushed at the tab attachment portion.

Further, in the method for producing a positive electrode plate precursor according to the conventional method, after forming a concave portion to be a tab attachment point on a continuous sheet-shaped metal porous body, roll rolling for thickness adjustment is performed. The sheet is compressed in the thickness direction and two-dimensionally spreads in a direction orthogonal to the thickness direction by that amount. At this time, the recesses are in a highly densified state, have a different degree of extension from the electrode plate flat portion, and are in a state in which planar deformation in four directions is limited. Distortion occurs in the recess.
Therefore, when a continuous sheet in such a state is cut and a strip-shaped positive electrode plate precursor is used, undulation occurs at the tab attachment point, and when positive electrode tab spot welding is performed at such a tab attachment point. The tabs and the tab attachment points do not come into full contact with each other in a close contact state, and as a result, good spot welding may not be performed. Even in such a case, in the positive electrode plate manufacturing method of the present invention, since the burr portion of the positive electrode tab is pushed into and engaged with the tab attachment point, it is possible to prevent the positive electrode tab from peeling from the tab attachment point as much as possible. Can be suppressed.

[0035]

【Example】

Example 1 First, the pore size is 100 to 500 μm, and the porosity is 85 to 95%.
Then, a continuous sheet of sponge-like nickel porous body having a thickness of 1.1 mm and a width of 14 mm was prepared. And the long side dimension 10
mm, and a rectangular die having a short side dimension of 5 mm at a position displaced by 2 to 2.5 mm to the right from the center line in the width direction of the continuous sheet of the sponge-like nickel porous body, and the longitudinal direction of the sheet and the length of the die. The sheet was pressed at 75 mm intervals so that the sides were parallel to each other, and the sheet was compressed at predetermined positions as shown in FIG. 3 to form a plurality of rectangular recesses 30a. The reduction rate at this time was 80%.

Then, 70 parts by weight of spherical nickel hydroxide powder, 10 parts by weight of CoO powder, and 20 parts by weight of a 1% aqueous solution of carboxymethyl cellulose were mixed to prepare a paste-like positive electrode active material mixture. Then, the continuous nickel porous body sheet was filled with the paste positive electrode active material mixture by a vacuum impregnation method, and then dried at 100 ° C. for 0.5 hours.

Thereafter, the entire sheet was rolled at a rolling reduction of 50% to adjust the thickness of the nickel porous sheet 30 to 0.55 to 0.65 mm. Next, the nickel porous sheet 30 whose thickness has been adjusted is cut at intervals of 40 mm from the end, and as shown in FIG. 3, a strip-shaped positive electrode plate precursor 3 having tab attachment points 31c.
1 was produced. At this time, the nickel porous sheet 3
As the cutting point of 0, for example, as shown in FIG.
It was set so as to include the center of the long side of the rectangular recess 30a. The size of the tab attachment point 31c (31d) is
The length is 5 mm, the width is 5 mm, and the depth is 0.2 mm.

Then, the tab mounting portion 31c (31
The deposits adhering to the surface of d) were removed by the deposit removing means. Next, a nickel tape having a width of 3 mm and a thickness of 0.1 mm was prepared, and the tip thereof was cut by a cutter 60 composed of an upper blade 61 and a lower blade 62 arranged as shown in FIG. Burr part 34c, upper part 3
4d was formed. Then, the front end of the tape is moved in the direction along the arrow S, and the front end portion t of the tape is moved to three of the two tab attachment points of the positive electrode plate precursor 31.
The tab attachment portion 31c on the side 1a was overlaid to form a welded portion. At this time, the burr portion 34c was brought into contact with the tab attachment portion 31c so as to face it.

After that, the welded portion is pressed by the upper electrode 51 and the lower electrode 52 of a predetermined shape of the spot welding machine, and the burr portion 34c is pushed so as to face the tab attachment point 31c, and at the same time, the current is supplied to the welded portion. The spot was spot welded.
Next, the tape was cut by the cutter 60 at a position 5 mm from the end of the positive electrode plate precursor to manufacture a positive electrode plate 31A having a positive electrode tab 34 having a length of 8 mm.

A plurality of positive electrode plates 31A were manufactured by repeating the above procedure. 2000 pieces of the positive electrode plates thus obtained were subjected to a peeling test of a positive electrode tab having the following specifications. Peeling test: First, the electrode plate portion of the positive electrode plate 31A and the positive electrode tab were attached to the upper and lower chucks of the peeling tester, respectively, and pulled along the longitudinal direction of the positive electrode plate until the tensile force reached 1 kgf. Then, when the pulling force was less than 1 kgf and the positive electrode tab was peeled off, it was determined that the positive electrode tab peeled off, and the product that did not peel off was regarded as a good product.

By this peeling test, the number of positive electrode plates from which the positive electrode tab was peeled off was counted. Then, the ratio of the number of positive electrode plates from which the positive electrode tab was peeled (a product having peeling generated) was obtained, and the obtained results are also shown in Table 1 with the ratio as the peeling occurrence ratio (%) of the positive electrode tab. Thickness 0.1mm, length 85mm, width 18m
The separator 33 made of a nylon sheet of m is folded in two, and the positive electrode plate 31A obtained by the above manufacturing procedure is inserted into the separator 33 with the positive electrode tab 34 facing upward, and the edge portion of the separator 33 is welded. An integrated product of the positive electrode plate 31A and the separator 33 was manufactured (see FIG. 7).

Next, a vertical length of 40 mm manufactured by the conventional method,
Four negative electrodes (hydrogen storage alloy electrodes) having a width of 14 mm and a thickness of 0.5 mm and three integrated products are prepared, and the negative plates and the integrated products are alternately arranged so that the negative plates are located at the outermost part. By superposing, the electrode plate group 3A as shown in FIG. 14 was manufactured.
In addition, the electrode plate group 3A finally uses a press machine so as to fit the inner shape of the outer can described later, and the vertical length (vertical dimension) is 42 mm, and the horizontal length dimension is 15 m.
m, and the thickness (dimension in the short side direction) of 4.1 mm was formed into a substantially rectangular parallelepiped shape.

Then, as shown in FIG. 14, the other end 34a of each positive electrode tab is pulled in the direction of the arrow P, and above the separator 33 located at the leftmost side in the drawing in the electrode plate group 3A (focusing point J). Then, the other end of each positive electrode tab 34 was welded. After the welding at the focusing point J was completed, the other end of the positive electrode tab 34, which was left before the focusing point J, was cut off.

As described above, the electrode plate group 3A in which the other end of the positive electrode tab was focused was manufactured. Even in the negative electrode plate,
One end of the conductive tape was welded to a predetermined position on the upper portion of each negative electrode plate, and the other ends of the tape were converged at one location and welded. Thereby, each negative electrode plate is also electrically integrated. Next, it consists of a nickel-plated steel plate with a thickness of 0.5 mm, and the upper dimension is 1
A rectangular parallelepiped outer can having a rectangular opening having a length of 8 mm and a dimension of 4.5 mm in the short side direction and a dimension of 50 mm in the vertical direction was prepared. Then, the electrode plate group 3A provided with the positive electrode tab was inserted into the inside from the opening of the outer can. Continued
As an electrolytic solution, an alkaline aqueous solution containing KOH as a main component 1
cc was injected into the outer can.

Next, a positive electrode terminal is provided at the center, and the dimension in the long side direction is 18 mm and the dimension in the short side direction is 4.5 m.
m, and the positive electrode lead plate of the lid plate having a thickness of 0.5 mm and the focusing point J at the other end of the positive electrode tab are welded to electrically connect the positive electrode plate and the positive electrode terminal, and then the lid plate is removed. It was fitted and mounted in 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. The above battery is 2000
Individually manufactured.

With respect to the obtained battery, the occurrence rate of short circuit was determined according to the following specifications. Occurrence rate of short circuit: First, the obtained battery is charged, discharged, and aged to activate the battery, and then the open circuit voltage is obtained for each battery, and the voltage value is below the standard voltage. I pulled out the battery. Next, disassemble the battery that has been taken out and observe the state of the positive electrode tab, the lower end of the positive electrode tab has peeled off and broke through the separator, or the positive electrode tab has come off the tab attachment point and has contact with the negative electrode side member. Those which were doing were counted as the battery in which the short circuit occurred. Then, the ratio of the number of short-circuited batteries to the total number of manufactured batteries (2000) was determined, and this ratio was defined as a short-circuit occurrence rate (%).

The above results are also shown in Table 1. Comparative Example 1 The positive electrode tab 34 has a tab mounting portion 3 with its dull portion 34d.
1d except that they are abutted so as to face each other and the burr portion 34c is not engaged with the tab attachment portion 31c.
A positive electrode plate was manufactured in the same manner as in Example 1. With respect to the obtained positive electrode plate, the peeling occurrence rate of the positive electrode tab was determined in the same manner as in Example 1, and the results are also shown in Table 1.

Further, the positive electrode plate in which the burr portion of the positive electrode tab is not engaged with the tab mounting portion as described above is used, and when the other end of the positive electrode tab is focused, the positive electrode is provided on the surface far from the focusing point. 2000 nickel-hydrogen secondary batteries were manufactured in the same manner as in Example 1 except that the electrode group was assembled so that the tabs were positioned (see FIGS. 8 and 9). For the obtained battery, the occurrence rate of short circuit was determined in the same manner as in Example 1. The results are shown in Table 1.

[0049]

[Table 1]

As is clear from the results shown in Table 1, Example 1
In the positive electrode plate, the incidence of peeling of the positive electrode tab is 0%. That is, it shows that the positive electrode tab is not peeled off. This is because the burr portion of the positive electrode tab is pressed against and engaged with the tab attachment portion. Further, the battery employing the positive electrode plate of Example 1 has a short circuit occurrence rate of 0%. That is, it is shown that the positive electrode tab of the electrode plate group and the negative electrode plate did not come into contact with each other, and a good product in which a short circuit accident did not occur was obtained. This is because the positive electrode tab is engaged with the tab attachment point, so that even if a force is applied to the positive electrode plate during assembly of the electrode plate group, the positive electrode tab does not peel off, and the positive electrode tab and the member on the negative electrode side do not separate. This is because the contact with is suppressed.

On the other hand, in the positive electrode plate of Comparative Example 1, the rate of occurrence of peeling of the positive electrode tab was as high as 5%. This is because, in the positive electrode plate of Comparative Example 1, since the burr portion of the positive electrode tab is not engaged with the tab attaching portion, the connection between the positive electrode tab and the tab attaching portion depends only on the joining force of spot welding. This is because some of them peel off when a tensile force is applied.

The battery using the positive electrode plate of Comparative Example 1 has a high short circuit occurrence rate of 10%. This is because the burr portion of the positive electrode tab does not engage with the tab attachment point, so the welded portion of the positive electrode tab is easily peeled off, and the positive electrode tab peeled off from the welded portion came off the positive electrode plate and contacted the member on the negative electrode side. Is. Further, in the positive electrode plate of Comparative Example 1, since the burr portion of the positive electrode tab projects toward the outside of the positive electrode plate, a force is applied to the positive electrode tab when focusing the other end of the positive electrode tab, and accordingly, This is because, when the positive electrode tab is largely bent and the lower end portion of the positive electrode tab is peeled off, the burr portion located at the lower end portion pierces the adjacent separator and comes into contact with the tip of the negative electrode plate.

[0053]

According to the positive electrode plate of the first aspect, since the burr portion of the positive electrode tab is engaged with the tab mounting portion, the positive electrode tab and the tab mounting portion are firmly coupled. For this reason,
It is possible to prevent the welded portion of the positive electrode tab from peeling off, and prevent the occurrence of inconvenience caused by the positive electrode tab coming off the positive electrode plate. Further, in the positive electrode plate of the present invention, since the burr portion of the positive electrode tab engages with the tab mounting portion as described above, the sagging portion having the curved surface portion is located on the opposite side thereof. Therefore, when the positive electrode plate of the present invention is incorporated in the electrode plate group, the drooping portion contacts the adjacent separator. Therefore, even when the other end of the positive electrode tab is focused, a force is applied to the positive electrode tab, the positive electrode tab is largely bent, and even if the lower end portion of the positive electrode tab is peeled off, the curved sag portion of the positive electrode tab is separated. The positive electrode tab does not break through the separator and come into contact with the negative electrode plate because it is only pressed against the negative electrode plate. Therefore, when a battery is assembled using the positive electrode plate of the present invention, a situation in which the negative electrode plate and the positive electrode tab are short-circuited 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 reduced. improves.

According to a second aspect of the present invention, there is provided a method of manufacturing a positive electrode plate, which comprises a positive electrode tab and a tab attaching portion by a simple method in which a burr portion generated by cutting the positive electrode tab conductive tape with a cutter is pressed against the tab attaching portion. The bond of can be strengthened. That is, the method for producing a positive electrode plate of the present invention exhibits excellent effects without increasing the number of steps such as newly processing the positive electrode tab in order to improve the bonding force of the positive electrode tab. Therefore, the manufacturing method of the positive electrode plate of the present invention is excellent in economical efficiency when manufacturing a non-defective battery.

[Brief description of drawings]

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

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

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

FIG. 4 is a schematic configuration diagram when a positive electrode tab conductive tape is superposed on a tab mounting portion of a positive electrode plate.

FIG. 5 is a perspective view showing a configuration of a positive electrode plate.

6 is a cross-sectional view taken along line VI-VI in FIG.

FIG. 7 is a perspective view showing a structure of an integrated body of a positive electrode plate and a separator.

FIG. 8 is a cross-sectional view showing a configuration of a conventional electrode plate group.

FIG. 9 is a cross-sectional view showing a configuration of a mounting portion of a conventional positive electrode tab.

FIG. 10 is a cross-sectional view showing a configuration of another aspect of a conventional positive electrode tab mounting portion.

FIG. 11 is a cross-sectional view showing a configuration of a mounting portion of the positive electrode tab of the present invention.

FIG. 12 is a cross-sectional view showing the configuration of another aspect of the attachment portion of the positive electrode tab of the present invention.

FIG. 13 is a schematic configuration diagram when a positive electrode tab conductive tape is superposed on a tab attachment portion of a positive electrode plate in the present invention.

FIG. 14 is a cross-sectional view showing a configuration of an electrode plate group of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 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 precursor 31A positive electrode plate (in the present invention) 31B positive electrode plate (conventional) 31a , 31b Side surfaces 31c, 31d Tab attachment point 32 Negative electrode plate 33 Separator 34 Positive electrode tab 34a Positive electrode tab other end 34b Positive electrode tab one end 34c Burr part 34d Droop part J Focusing point

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Shioda, Haniwa Shimo-Funao-cho, Iwaki City, Fukushima Prefecture 23-6 Furukawa Battery Co., Ltd. Iwaki Plant (72) Inventor Kiyomasa Yoshinaga Joban-Funao Town, Iwaki City, Fukushima Prefecture 23-6 Fukukawa Battery Co., Ltd. Furukawa Battery Co., Ltd. (72) Inventor Hitoshi Kato Joban Shimofunao, Iwaki City, Fukushima Prefecture 23-6 Furukawa Battery Co., Ltd. Iwaki Co., Ltd.

Claims (2)

[Claims] 1. A metal porous body having a three-dimensional network structure, which carries an active material mixture and has tab attachment points at predetermined positions, and a positive electrode tab having one end spot-welded to the tab attachment points. In the positive electrode plate, the positive electrode tab is provided with a burr portion at one end thereof, and the burr portion is engaged with the positive electrode tab mounting portion so as to face the positive electrode tab. 2. A tab attachment portion is provided by compressing a predetermined portion of a continuous metal porous body sheet having a three-dimensional network structure, and then,
A step of filling the metal porous body continuous sheet with a paste-like active material mixture and then drying; rolling the metal porous body continuous sheet to remove deposits at the tab attachment points, and then the metal porous body continuous sheet A step of cutting into a strip shape in which a tab attachment point is located at an end to obtain a positive electrode plate precursor; a positive electrode tab conductive tape is superposed on a tab attachment point of the positive electrode plate precursor to form a welded portion, In the method for manufacturing a positive electrode plate, which comprises spot welding the welded portion; and cutting the conductive tape for a positive electrode tab with a cutter arranged at a predetermined position, when forming the welded portion, When the conductive tape for the positive electrode tab is cut, the burr portion generated at the tip portion of the tape is arranged so as to face the tab attachment point, and the burr section is pushed into the tab attachment point, Process for producing a positive electrode plate, characterized in that to.