JPH08306351A - Explosionproof sealing plate of sealed type battery - Google Patents

Abstract

PURPOSE: To provide an explosionproof sealing plate which can reliably prevent an accident such as ignition by electrically connecting two sheets of metal foils having thin parts by partly connecting the foils and cutting electric current with a prescribed pressure when the inner pressure of a battery rises. CONSTITUTION: Aluminum foils 1, 7 are welded in the center parts by ultrasonic welding and in the welded parts 11, a case 4 and a metal cap 6 are electrically connected. A thin part 7a can be ruptured by pressure equal tp or lower than the pressure with which the welded parts 11 can be parted and a thin part 1a can be ruptured. When the inner pressure of a battery rises, at first the foil 7 is expanded, a crack is formed in the thin part 7a, and then the foil 1 is expanded, the thin part 7a is ruptured, the two foils 1, 7 are parted, and thus electric current can be cut. In the case the inner pressure of a battery rises further, the thin part 1a is also ruptured and a gas evolved in the inside of the battery is released outside of the battery. Consequently, a constant current cutting pressure, which is independent of the strength of the joining parts of the metal foils, can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an explosion-proof sealing plate for a sealed battery provided with a current interruption and gas discharge mechanism.

[0002]

2. Description of the Related Art Conventionally, in a sealed battery, various explosion-proof sealing plates have been used as an explosion-proof mechanism against the risk of ignition and explosion due to internal pressure rise due to gas generated by chemical reaction or overcharge. There is. For example, JP-A-6-
Japanese Patent Laid-Open No. 196150 discloses an explosion-proof mechanism composed of a welding plate and a partition electrically conducted by ultrasonic welding.
In this explosion-proof mechanism, a welding plate having a ventilation hole is arranged on the inner side, that is, the power generation element side, and a partition wall for sealing the battery is arranged on the outer side thereof. When the pressure inside the battery rises, the partition arranged on the outside swells and a force pulling the welding plate on the inside is generated. When the pressure inside the battery further rises and this force exceeds the strength of the welded portion between the partition wall and the welding plate, the partition wall and the welding plate separate. Therefore, both are electrically insulated,
The current is cut off.

[0003]

In the above current interruption type explosion-proof mechanism, the pressure for interrupting the current when the internal pressure of the battery rises depends on the strength of the welded portion. Since it is difficult to precisely control the strength of the welded portion, the working pressure of the current interruption type explosion-proof sealing plate is not stable. It is an object of the present invention to provide an explosion-proof sealing plate of constant quality, which can accurately interrupt the current when the pressure inside the battery rises and prevent accidents such as ignition.

[0004]

An explosion-proof sealing plate for a sealed battery according to the present invention includes two inner and outer metal foils that are electrically connected to each other by partially bonding the central portion, and the inner metal foil is , A thin-walled portion that is arranged so as to surround the joint portion and that breaks at a pressure lower than the peeling pressure of the joint portion, and the outer metal foil is more than the pressure at which the thin-walled portion of the inner metal foil breaks. Also has a thin portion that breaks at high pressure.

[0005]

In the explosion-proof sealing plate of the sealed battery of the present invention, when the internal pressure of the battery rises, first the inner metal foil swells, and when this pressure reaches the pressure at which the inner metal foil is broken, the thin wall portion Tear occurs. The outer metal foil swells and pulls the bonded inner metal foil. The peeling pressure at the joint between the two metal foils is higher than the pressure at which the thin portion of the inner metal foil breaks, so the tearing of the thin portion of the inner metal foil progresses and the two metal foils The current is cut off by separating the two. When the pressure further rises and reaches the pressure at which the outer metal foil breaks, the outer metal foil breaks, the gas inside the battery is released to the outside, and the pressure inside the battery decreases. Therefore,
The current breaking pressure does not depend on the strength of the joint portion of the metal foil. Further, the pressure at which the thin portion is broken to break can be easily controlled, and the explosion-proof sealing plate having a constant current interruption pressure can be provided.

[0006]

The present invention will be described in detail below with reference to its examples. An embodiment of the explosion-proof sealing plate of the present invention is shown in FIG. An annular thin portion 1a was provided in the center of the aluminum foil 1 having a thickness of 0.15 mm and an outer diameter of φ12.7 mm by using a circular stamp with an outer diameter of 4.0 mm. On the other hand, the outer diameter φ is set at the center of the aluminum foil 7 having a thickness of 0.12 mm and an outer diameter of 12.7 mm.
An annular thin portion 7a having a circular stamp of 4.0 mm was provided. After sandwiching the insulating gasket 3 between the peripheral portions of these two aluminum foils 1 and 7, the central portions of the two aluminum foils 1 and 7 are ultrasonically welded, and these are placed in an aluminum case 4 having a vent hole. The metal cap 6 having a temperature resistor 5 and a ventilation hole on top of it, and the upper end of the case 4 was caulked to the peripheral edge of the metal cap 6 via the insulating gasket 3 to obtain an explosion-proof sealing plate. . This explosion-proof sealing plate is used by mounting it in the opening of a battery case accommodating a power-generating element with the lower part inside. A positive electrode lead is connected to the case 4.

The case 4 is electrically connected to the aluminum foil 7 by the welded portion 11. Further, the metal cap 6 is electrically connected to the aluminum foil 1 via the temperature resistor 5. That is, the case 4 and the metal cap 6 are in an electrically connected state via the welded portions 11 of the two aluminum foils 1 and 7. Here, the thin portion 7
"a" is designed to be broken at a pressure below the pressure at which the welded portion 11 peels off and the pressure at which the thin portion 1a breaks.

Next, the operation mechanism of the explosion-proof sealing plate of this sealed battery will be described. When the pressure inside the battery rises, first, the aluminum foil 7 on the inner side swells, and the thin portion 7a
Torn. Next, since the aluminum foil 1 arranged on the outer side swells and the joined inner aluminum foil 7 is pulled, the tear of the thin portion 7a progresses, leading to breakage. By separating the two aluminum foils in this manner, the current is cut off. After that, when the battery internal pressure further rises, the thin portion 1a of the outer aluminum foil 1 is broken, so that the gas generated inside the battery is released to the outside of the battery and the internal battery pressure is lowered.

Next, a conventional explosion-proof sealing plate, which is a comparative example, will be described. A cross-sectional view of the explosion-proof sealing plate of this comparative example is shown in FIG. Same thickness as the example, 0.15 mm, outer diameter φ1
Outer diameter φ4.0 in the center of the 2.7 mm aluminum foil 13.
An annular thin portion 13a was provided by using a circular stamp of mm. Furthermore, a protrusion 2 having an outer diameter of 1.0 mm is formed at the center of the aluminum foil 2 having a ventilation hole having a thickness of 0.3 mm and an outer diameter of 12.7 mm.
a is provided. After sandwiching the insulating gasket 3 between the two aluminum foils 13 and the peripheral portions of the two aluminum foils 13, the central portion of the aluminum foil 13 and the projection 2a of the aluminum foil 2 are ultrasonically welded to each other, and an aluminum case having a ventilation hole is formed between them. 4, a temperature resistor 5 and a cap 6 having a ventilation hole are placed on the upper portion thereof, and the upper end portion of the case 4 is caulked to the peripheral edge portion of the metal cap 6 via the insulating gasket 3 to prevent the explosion-proof sealing plate. Got Similar to the embodiment, the case 4 and the cap 6 are electrically connected via the two aluminum foils 13 and 2.

The explosion-proof sealing plates of Examples and Comparative Examples are shown in FIG.
Evaluation was performed by the following method using the device shown in FIG. Electrode 8a
And 8b, the periphery of the explosion-proof sealing plate 12 is airtightly sandwiched, and a voltage is applied between both electrodes to energize between the two aluminum foils via the case 4 and the cap 6. Then, high-pressure air is sent from the high-pressure air inlet 10 below the case 4, and the lower part of the explosion-proof sealing plate is moved to 0.6 per second.
Pressurize while pressurizing with kgf / cm ² . 2 at this time
The air pressure at which the current is cut off between the aluminum foil sheets,
It measured using the pressure sensor 9. The respective results are shown in Table 1.

[0011]

[Table 1]

As can be seen from Table 1, the explosion-proof sealing plate of the embodiment has greatly improved the variation in pressure (σ (n-1)) for interrupting current. In the conventional explosion-proof sealing plate, which is a comparative example, the two aluminum foils 2 and 13 are separated from each other by the protrusions 2a that are welded portions to interrupt the current, so that the current interruption pressure depends on the strength of the welded portions. Therefore, variations in the strength of the welded portion greatly affect the current breaking pressure. On the other hand, in the explosion-proof sealing plate of the embodiment, the current is cut off by breaking the thin portion 7a. The pressure at which the thin portion of the aluminum foil breaks can be easily and accurately controlled by marking or the like. Therefore, the explosion-proof sealing plate of the sealed battery of the present invention has a small variation and can interrupt the current at a constant pressure.

[0013]

As described above, according to the present invention, an explosion-proof sealing plate for a sealed battery that shuts off the current at a constant pressure when the internal pressure of the battery rises and more reliably prevents accidents such as ignition. Can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an explosion-proof sealing plate according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of an explosion-proof sealing plate of a comparative example.

FIG. 3 is a vertical cross-sectional view of an apparatus for evaluating the current interruption performance of the explosion-proof sealing plate.

[Explanation of symbols]

 1 Aluminum foil 1a Thin part 2 Aluminum foil 2a Projection part 3 Insulation gasket 4 Aluminum case 5 Temperature resistor 6 Metal cap 7 Aluminum foil 7a Thin part 8a Electrode 8b Electrode 9 Pressure sensor 10 High pressure air inlet 11 Welding part 12 Explosion-proof sealing plate 13 Aluminum foil 13a Thin part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Hirakawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. An inner and outer metal foil, which is electrically connected by partially joining the central portion, wherein the inner metal foil is arranged so as to surround the joining portion, and An explosion-proof sealing plate for a sealed battery having a thin-walled portion that breaks at a pressure lower than the peeling pressure, and an outer metal foil having a thin-walled portion that breaks at a pressure higher than the pressure at which the thin-walled portion of the inner metal foil breaks. .