JPH0644951A - Square nickel-hydrigen battery - Google Patents

Abstract

PURPOSE:To provide a highly reliable square nickel-hydrogen battery having improved sealing quality. CONSTITUTION:This battery comprises a bottomed square metal case 1, an electrode group 5, an alkaline electrolyte, a sealing plate 6, and an insulation sealing gasket 8. The case 1 has a bent section 3 and a stepped section 4, while the sealing plate 6 is caulked and fastened to the internal area of the case 1 enclosed with the sections 3 and 4. Furthermore, the bent angle of a corner section 17 at the open end 2 of a bent section 3 on the case 1 is taken between 80 and 100 degrees. In addition, the bent angle of a straight section 18 at the open end 2 on the bent section 3 of the case 1 is kept smaller than the bent angle of the corner section 17 at the open end 2 on the bent section 3 of the case 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a prismatic nickel metal hydride battery.

[0002]

2. Description of the Related Art Sealed prismatic batteries are sealed by, for example, a method called a crimping method (or crimping method) as described below. First, a stepped portion is formed by expanding the vicinity of the open end of a bottomed rectangular tubular metal case. Continuing,
A power generation element is housed in the metal case. Continued,
After inserting the sealing plate above the stepped portion in the metal case with the insulating sealing gasket made of synthetic resin interposed, the vicinity of the opening end of the metal case is contracted. Subsequently, the vicinity of the opening end of the metal case is curled inward and bent, whereby the sealing plate is caulked and fixed to the vicinity of the opening end in the metal case for sealing. In such a prismatic battery, the insulating sealing gasket interposed between the metal case and the sealing plate is put into a compressed state, and its repulsive elastic force is used to achieve an airtight and liquid-tight sealing.

Regarding the bent shape (curl shape) of the open end of the metal case in the prismatic battery, a shape in which it is bent inward uniformly over the entire circumference has been conventionally known. However, when a sealing method having a step of contracting the vicinity of the opening end of the metal case toward the center is adopted, when the contraction is performed, the corner portion (corner part) near the opening end of the metal case is thinned or Distortion is likely to occur,
Moreover, the corner portion of the opening end of the metal case extends above the straight portion (side portion). Further, since the corners of the opening end of the metal case are likely to be misaligned or distorted during the next bending, the corners of the opening end of the metal case are difficult to bend during this bending. There is. Therefore, when bending the straight part of the opening end of the metal case in the same way as the corner part when bending, the force applied from above to the corner part becomes excessive, and the force from above is applied to the body part and bottom of the metal case. The metal case cannot be supported, and as a result, the metal case is deformed such as dented or distorted, and the hermeticity is deteriorated.

By the way, as one of the prismatic batteries described above, an electrode group in which a nickel positive electrode plate and a hydrogen storage alloy negative electrode plate are alternately stacked with a separator interposed therebetween is placed in a bottomed rectangular cylindrical metal case together with an alkaline electrolyte. Various prismatic nickel metal hydride batteries having a structure housed in the inside have been studied.

The prismatic nickel metal hydride battery is another prismatic alkaline secondary battery (for example, prismatic nickel cadmium battery).
Since it is possible to achieve higher energy density, there is a demand for a measure capable of sufficiently ensuring excellent sealing property even under severe operating conditions such as high battery temperature.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a highly reliable prismatic nickel-hydrogen battery with improved hermeticity.

[0007]

DISCLOSURE OF THE INVENTION The present invention is directed to a metal case having a bottomed rectangular tube having a substantially quadrangular opening end at the top, a nickel positive electrode plate and a hydrogen storage alloy negative electrode plate housed in the metal case. And a group of electrodes alternately stacked via a separator, an alkaline electrolyte stored in the metal case, a substantially rectangular sealing plate for sealing the metal case, the metal case and the A prismatic nickel-hydrogen battery comprising an insulating sealing gasket made of synthetic resin interposed between the sealing plate and the sealing plate in a compressed state,

The metal case constitutes an opening end portion of the metal case, and has a bent portion which is bent inward over the entire circumference of the opening end, and is formed below the bent portion. And a step portion having a shape projecting inward, the sealing plate is fixed by caulking at a position surrounded by the bent portion and the step portion in the metal case,

The bending angle of the corner portion of the opening end of the bent portion of the metal case is 80 to 100 °, and the bending angle of the straight portion of the opening end of the bending portion of the metal case is the bending angle of the metal case. The prismatic nickel-hydrogen battery is characterized in that the bending angle is smaller than the bending angle of the corner portion of the opening end of the portion.

[0010]

According to the present invention, the bending angle of the straight portion of the opening end of the bent portion of the metal case is made smaller than the bending angle of the corner portion of the opening end of the bending portion of the same metal case. Since the bendability of the corner portion of the opening end, which is the bent portion, is improved, it is possible to prevent the metal case from being deformed by the force applied from above during bending. Further, by setting the bending angle of the corner portion at the opening end of the bent portion of the metal case to be 80 to 100 °, it is possible to seal in a gas-tight and liquid-tight manner. In this way, a highly reliable prismatic nickel-hydrogen battery with improved hermeticity can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a top view of a prismatic nickel-hydrogen battery showing an embodiment of the present invention, and FIG. 2 is a diagonal line A of FIG.
It is sectional drawing which follows the -A line.

Reference numeral 1 in the figure denotes a metal case which also serves as a negative electrode terminal and has a bottomed rectangular tube shape. The metal case 1 has an opening end 2 of a substantially rectangular shape in the upper part, and a bent portion 3 having a shape in which the opening end 2 is bent inward over the entire circumference of the opening end 2.
Are formed. Below the bent portion 3 of the metal case 1, a step portion 4 having a shape protruding inward is formed.
In the metal case 1, the electrode group 5 is housed and the alkaline electrolyte is stored. A substantially rectangular sealing plate 6 is caulked and fixed at a position surrounded by the bent portion 3 and the step portion 4 in the metal case 1. The sealing plate 6 has a curvature at the corner portion and an exhaust hole 7 is formed at the center. An insulating sealing gasket 8 made of synthetic resin is interposed between the metal case 1 and the sealing plate 6 in a compressed state.
A positive electrode lead 9 derived from a nickel positive electrode plate of the electrode group 5 described later is welded to the lower surface of the sealing plate 6. A cap-shaped terminal cap 10 also serving as a positive electrode terminal is welded to the upper surface of the sealing plate 6 so as to cover the exhaust hole 7. The terminal cap 10 forms the valve chamber 11 together with the sealing plate 6,
An elastic valve element 12 is arranged in the valve chamber 11 in a compressed state so as to close the exhaust hole 7. The elastic valve body 12 is made of a material such as synthetic rubber. Above the sealing plate 6, a substantially rectangular insulating plate 13 having a hole in the center holds the flange part of the terminal cap 12 together with the sealing plate 6, and inserts the protruding part of the terminal cap 12 into the hole. It is located in. The outer peripheral surface of the metal case 1 is covered with an exterior tube 14 whose upper and lower openings are bent inward. The outer tube 14 is a tube made of heat-shrinkable resin, and fixes the insulating plate 13 by sandwiching the peripheral edge of the insulating plate 13 with the upper surface of the bent portion 3 of the metal case 1.

The open end 2 of the bent portion 3 of the metal case 1
As shown in Fig. 3, the bending angle of the corner is 8
It is 0 to 100 °, and the bending angle of the straight portion is smaller than the bending angle of the corner portion. This improves the bendability of the corner portion of the opening end 2 that becomes the bent portion 3 of the metal case 1, so that the metal case 1 is hermetically and liquid-tightly sealed without being deformed by the force applied from above during bending. It becomes possible to do. Therefore, the prismatic nickel-hydrogen battery described above has improved sealing performance and increased reliability. It is desirable that the metal case 1 satisfies the following formulas (1) and (2). 1.5tc ≦ Rc ≦ 4tc (1) Rb ≦ Rc (2)

(However, in the formulas (1) and (2), tc is the plate thickness of the corner portion of the metal case 1, and Rc is the metal case 1.
Radius of curvature in the vertical direction of the corner portion of the bent portion 3, and Rb is the vertical radius of curvature of the corner portion of the bent portion 15 on the peripheral edge of the bottom surface of the metal case 1)

The reason for this is that the metal case 1 satisfies the above-mentioned formulas (1) and (2), and the strength due to the plate thickness of the metal case 1 and the bent portion 15 at the peripheral edge of the bottom surface of the metal case 1. This is because sufficient strength is ensured, so that it is possible to more reliably prevent the metal case 1 from being deformed due to a force from above applied when the metal case 1 is bent in the vicinity of the opening end 2 that serves as the bent portion 3. For example, in the above formulas (1) and (2), tc is 0.4 mm and Rc is 1 m.
When m and Rb are 0.8 mm, it is possible to reliably prevent the metal case 1 from being deformed by the force applied from above during bending.

An electrode group 5 housed in the metal case 1
Is a metal case 1 in which a plurality of hydrogen storage alloy negative electrode plates and a plurality of nickel positive electrode plates wrapped with a bag-shaped separator are alternately stacked vertically and the hydrogen storage alloy negative electrode plates are arranged on both sides. Are laminated so as to be in pressure contact with the inner surface of the long side (not shown). The hydrogen storage alloy negative electrode plate uses a hydrogen storage alloy as an active material and is connected to each other by a negative electrode lead (not shown). The separator is impregnated with an alkaline electrolyte. The nickel positive electrode plate uses nickel hydroxide as an active material.

The alkaline electrolyte stored in the metal case 1 is mainly composed of potassium hydroxide. The volume of the alkaline electrolyte mainly composed of potassium hydroxide is the volume occupied by the electrode group 5 (height of the electrode group 5 ×
90 ml% or less of the void volume obtained by subtracting the actual volume (excluding porosity) of the nickel positive electrode plate, the hydrogen storage alloy negative electrode plate and the separator from the bottom area in the metal case 1) and 2 ml per 1 Ah of battery capacity. The above is desirable. This is because, for example, as shown in Table 1, the amount of the alkaline electrolyte is 90% with respect to the void volume of the electrode group 6.
When the volume% is less than or equal to 2 ml with respect to the battery capacity of 1 Ah (Examples 1 to 3), the oxygen gas generated from the positive electrode during charging can be quickly absorbed on the negative electrode surface, which suppresses an increase in battery internal pressure and is excellent. This is because it is possible to simultaneously secure charge / discharge cycle characteristics.

[0018]

[Table 1]

The processing step of caulking and fixing the sealing plate 6 at a position surrounded by the bent portion 3 and the step portion 4 in the metal case 1 is performed as follows. First, as shown in FIG. 4, the step portion 16 is formed by expanding the vicinity of the opening end 2 of the metal case 1 to the outside. Open end 2 of this metal case 1
Has a substantially rectangular shape including four corner portions 17 and four straight portions 18 connecting the corner portions 17. Subsequently, as shown in FIG. 5A, after inserting the sealing plate 6 above the step 16 in the metal case 1 through the insulating sealing gasket 6, the drawing die 19 is lowered from above the metal case 1. . As a result, as shown in FIG. 5B, the vicinity of the pre-expanded opening end 2 of the metal case 1 is reduced to the size of the body of the metal case 1 and the insulating sealing gasket 8 is compressed in the lateral direction. At the same time, the step portion 16 moves inward, and the step portion 4 having a shape protruding inward is formed. Subsequently, as shown in FIG. 6A, the folding die 20 is lowered from above the metal case 1. As a result, FIG.
As shown in (b), a bent portion 3 having a shape in which the opening end 2 of the metal case 1 is bent inward over the entire circumference of the opening end 2.
And the bent portion 3 and the stepped portion 4 in the metal case 1 are formed.
The sealing plate 6 is caulked and fixed at a position surrounded by and.
In addition, as described above, this bending process is performed by changing the bending angle of the corner portion 17 of the opening end 2 of the metal case 1 to 80 degrees.
The bending angle of the straight portion 18 of the opening end 2 of the metal case 1 is smaller than the bending angle of the corner portion 17 of the opening end 2 of the metal case 1. Further, the shrinking process and the bending process are performed in a state where the bottom part of the metal case 1 is fitted in a lower mold conforming to the shape of the bottom part.

As a material for the insulating sealing gasket 8, a polyamide resin such as nylon 66 mixed with carbon black or graphite is desirable. This is due to the following reasons. Since the insulating sealing gasket 8 molded from such a polyamide resin has carbon black or graphite as a crystal nucleating agent during molding to increase the crystallinity, the compression rebound characteristics (compression creep characteristics) are improved and the weather resistance and oxidation resistance are improved. The property is improved. Therefore, the airtightness of the battery can be further improved.
For example, as shown in FIG. 7, an insulating sealing gasket 8 made of nylon 66 with 0.2% by weight of carbon black added.
In the case of using, the leakage rate of the battery becomes smaller than that in the case of using the insulating sealing gasket 8 made of nylon 66.

As a compression state of the insulating sealing gasket 8, the compression ratio of the straight portion (the portion located between the straight portion of the metal case 1 and the sealing plate 6) is 15 to 4
It is desirable that the volume ratio is 0% by volume, and the compression rate of the corner portion (the portion located between the corner portion of the metal case 1 and the sealing plate 6) is equal to or less than the compression rate of the straight portion. This is due to the following reasons. The insulating sealing gasket 8 in such a compressed state prevents overcompression of the corner portion, and has full repulsive elastic force even when the straight portion near the opening end 2 of the battery case 1 bulges outward due to an increase in battery internal pressure. Well maintained over the lap. Therefore, the battery can be provided with more stable hermeticity.

As shown in FIG. 8, the insulating sealing gasket 8 has a substantially L-shaped vertical cross section, and has a bottom portion 8a and a rising wall portion 8 provided on the periphery of the bottom portion 8a.
b, and an undercut portion (inward protruding portion) for temporarily fixing the sealing plate 6 in contact with a corner portion of the upper surface of the sealing plate 6.
One having 8c on the inner surface is exemplified. In the case of the insulating sealing gasket 8 having such an undercut portion 8c, the undercut portion 8c located at the corner portion is removed from the viewpoint of improving moldability, sealing performance when assembled in a battery, and insertability of the sealing plate. It is desirable to remove or make it smaller than the undercut portion 8c located in another portion (straight portion). More preferably, only the undercut portion 8c for temporarily fixing the long side of the sealing plate 6 or
Alternatively, it is desirable to make the undercut portion 8c for temporarily fixing the short side of the sealing plate 6 smaller than the undercut portion 8c for temporarily fixing the long side of the sealing plate 6. For example, Table 2 below
As shown in Fig. 6, the undercut portion 8c located at the corner is removed, and the undercut portion 8c for temporarily fixing the short side of the sealing plate 6 is made smaller than the undercut portion 8c for temporarily fixing the long side. The sealing gasket 8 (example 1) and the insulating sealing gasket 8 (example 2) in which only the undercut portion 8c for temporarily fixing the long side of the sealing plate 6 is used,
The moldability, the sealing property when assembled in the battery, and the insertability of the sealing plate are good.

[0023]

[Table 2]

The insulating sealing gasket 8 is preferably injection molded from at least two gates. For example, as shown in FIG. 9, a frame-shaped injection molding die 21.
By injecting and molding resin from two gates at positions symmetrical to each other, the temperature difference and the density difference of the resin at the time of molding become smaller as compared with the case of injection molding from one gate. Weld lines generated in the insulating sealing gasket 8 are reduced. Therefore, it is possible to prevent a decrease in strength of the insulating sealing gasket 8 due to the weld line.

Further, the insulating sealing gasket 8 is preferably injection molded from a gate located at the bottom 8a as shown in FIG. This is due to the following reasons. Since the resin near the gate has a difference in density and crystallinity from other portions, cracks are likely to occur when compressed or extended at the time of sealing. Therefore, by injection-molding the insulating sealing gasket 8 from the gate near the bottom portion 8a, it is possible to prevent the strength of the rising wall portion 8b of the insulating sealing gasket 8 to which the most force is applied at the time of sealing from being lowered, so that the battery sealing property is further improved. Can be made.

As shown in FIG. 11, the terminal cap 10 has four corners on the lower surface of the collar 10a at positions symmetrical with respect to the projecting portions 10b.
A projection 22 for resistance welding projecting toward the sealing plate 6 is provided, the projection dimension of each projection 22 is 0.5 to 2 times the plate thickness, and the radius of curvature of each projection 22 is the plate thickness. 1.5-2.4
It is desirable to be doubled. This is due to the following reasons. By providing the four projections 22 having the specific shape as described above at the respective corner portions of the lower surface of the collar portion 10a, the attachment strength of the terminal cap 10 against the shearing force from the long side is increased and the fusion dimension of the projection 22 at the time of welding. Variation is reduced and the dimension between the sealing plate 6 and the terminal cap 10 is stabilized,
The reliability of the battery can be further increased.

The elastic valve body 12 has a tensile strength of 1
00 kg / cm ² It is desirable that the deterioration rate of the tensile strength after the ozone resistance deterioration test (50 ppm, 40 ° C., 72 hours) is 2% or less and the oxidation resistance is at the level of 2% or less. In this case, further, as shown in FIG.
It is desirable that the radius of curvature of the corner portion (R) of the exhaust hole 7 of the sealing plate 6 that comes into contact with is 0.05 mm or more. This is due to the following reasons. By setting the material of the elastic valve body 12 and the radius of curvature of the corner portion (R) of the exhaust hole 7 of the sealing plate 6 as described above, the elastic valve body can be used for a long period of time even in an oxidizing atmosphere in an overcharged state. Since it is possible to suppress deterioration of physical properties due to oxidation of 12 and prevent loss of the safety valve function due to cracking of the elastic valve body 12, it is possible to further improve battery reliability.

As shown in FIG. 13, the terminal cap 1
The shape of the protruding portion 10b of 0 is a flat shape (or a substantially square shape)
And the shape of the hole of the insulating plate 13 is the terminal cap 1.
It is desirable to make the shape of the protruding portion 10b of 0 substantially equal. This is due to the following reasons. By setting the shape of the protruding portion 10b of the terminal cap 10 and the shape of the hole of the insulating plate 13 as described above, when the insulating plate 13 is inserted into the protruding portion 10b of the terminal cap 10, the insulating plate 13 is naturally guided to a proper position. In addition, since the insulating plate 13 is prevented from rotating even after the insertion, it is possible to reduce defects such as detachment of the insulating plate 12, so that the reliability of the battery can be improved and the production efficiency can be improved.

[0029]

As described in detail above, according to the present invention, a highly reliable prismatic nickel-hydrogen battery with improved hermeticity is provided.

[Brief description of drawings]

FIG. 1 is a plan view of a prismatic nickel metal hydride battery showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view for explaining the bending angle of the open end of the metal case.

FIG. 4 is a perspective view showing a metal case before sealing.

FIG. 5 is a cross-sectional view for explaining a process for forming a constriction near the opening end in the metal case.

FIG. 6 is a cross-sectional view for explaining a bending process near the opening end in the metal case.

FIG. 7 is a characteristic diagram showing changes in the liquid leakage rate with respect to the number of months of storage.

FIG. 8 is a sectional view for explaining the shape of an insulating sealing gasket.

FIG. 9 is an explanatory view showing a mold for injection molding of an insulating sealing gasket.

FIG. 10 is a cross-sectional view for explaining a gate position for injection molding of an insulating sealing gasket.

FIG. 11 is a bottom view showing the terminal cap.

FIG. 12 is a cross-sectional view for explaining a corner portion of the exhaust hole of the sealing plate that comes into contact with the elastic valve body.

FIG. 13 is a plan view showing a protruding portion of a terminal cap and an insulating plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal case, 2 ... Open end of metal case, 3 ... Bent part of metal case, 4 ... Step part of metal case, 5 ... Electrode group (internal omitted), 6 ... Sealing plate, 7 ... Exhaust hole, 8 ... Insulation sealing gasket, 8a ... Bottom of insulation sealing gasket, 8b ... Standing wall of insulation sealing gasket, 8c ... Undercut portion of insulation sealing gasket, 10 ... Terminal cap, 10
a ... collar of terminal cap, 10b ... projection of terminal cap, 11 ... valve chamber, 12 ... elastic valve body, 13 ... insulating plate, 14
... Exterior tube, 15 ... Bent part of bottom edge of metal case, 17 ... Corner part of open end of metal case, 18 ...
Straight part of the open end of the metal case, 19 ... diaphragm type,
20 ... Bending mold, 21 ... Mold for injection molding of insulation sealing gasket, 22 ... Projection for resistance welding of terminal cap.

Claims (4)

[Claims] 1. A bottomed rectangular metal case having a substantially quadrangular open end at the top, and a nickel positive electrode plate and a hydrogen storage alloy negative electrode plate housed in the metal case are alternately arranged with a separator interposed therebetween. An electrode group having a superposed structure, an alkaline electrolyte stored in the metal case, a substantially rectangular sealing plate for sealing the metal case, and a compressed state between the metal case and the sealing plate. A prismatic nickel-hydrogen battery comprising an insulating sealing gasket made of synthetic resin interposed between the metal case and the metal case, which constitutes an opening end portion of the metal case, and is bent inward over the entire circumference of the opening end portion. A bent part with a curved shape,
A step portion formed below the bent portion and projecting inward thereof, and the sealing plate is located at a position surrounded by the bent portion and the step portion in the metal case. It is fixed by crimping, the bending angle of the corner portion at the opening end of the bent portion of the metal case is set to 80 to 100 °, and the bending angle of the straight portion at the opening end of the bent portion of the metal case is set to the folding angle of the metal case. A prismatic nickel-hydrogen battery characterized in that it is smaller than the bending angle of the corner portion at the opening end of the curved portion. 2. An alkaline electrolyte mainly comprising potassium hydroxide is used, and the amount of the alkaline electrolyte is 90% by volume or less with respect to the void volume of the electrode group, and the battery capacity is 1 Ah. The prismatic nickel-hydrogen battery according to claim 1, wherein the amount is 2 ml or more per unit. 3. The prismatic nickel-hydrogen battery according to claim 1, wherein the insulating sealing gasket is made of a polyamide resin mixed with carbon black or graphite. 4. The compressibility of the insulating sealing gasket located between the straight portion of the metal case and the sealing plate is 15 to 40% by volume, and between the corner portion of the metal case and the sealing plate. 2. The rectangular nickel metal hydride according to claim 1, wherein the compression rate of the insulating sealing gasket located at is less than or equal to the compression rate of the insulating sealing gasket located between the straight portion of the metal case and the sealing plate. battery.