JPH04349347A - Sealed battery - Google Patents

Abstract

PURPOSE:To prevent any damage on air-tightness of a battery container due to an external impact and to operate the explosion preventing function of the battery container with good reproducibility and at a low pressure in the case that the inner pressure of the battery container rises. CONSTITUTION:Single or a plurality of ventilation holes formed in a part of a battery container made of a metal having at least 0.2mm thickness are closed by a metal sheet characterized by its thickness of less than 0.2mm and having a notch groove. In order to operate the explosion preventing function of the battery container stably at a lower pressure, a method wherein a material having a smaller rupture strength than the material of the battery container is used for the metal sheet and further a method wherein the notch groove is formed by pressing, wet-etching, laser-etching, etc., are used in parallel.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an explosion-proof sealed battery.

0002

2. Description of the Related Art Conventionally, various overpressure release safety valves have been proposed that operate when gas pressure inside a battery increases. However, for example, a nonaqueous secondary battery using a lithium composite metal oxide as a positive electrode active material disclosed in JP-A-55-136131, or JP-A-62-90863, JP-A-6
In the case of a non-aqueous secondary battery disclosed in No. 3-299056 etc., that is, a non-aqueous secondary battery using a lithium composite metal oxide as the positive electrode active material and a carbonaceous material as the negative electrode active material, etc. During normal use, the pressure inside the battery case hardly increases, but if the active materials of both electrodes, electrolyte, etc. react with moisture, oxygen, etc. that enter from the outside air, the performance of the battery gradually decreases. Safety valves are inappropriate for batteries. That is, for batteries whose performance is degraded by moisture, oxygen, etc., it is preferable to have a completely sealed structure.

However, although batteries with a completely sealed structure have improved sealing performance and excellent storage performance, they do not survive under abnormal conditions such as when heated to high temperatures or when charged with high voltage or large current. In this case, the pressure inside the battery increases, and as a result, the battery can ruptures and the contents of the battery are scattered, potentially causing personal injury or property damage.

Therefore, in sealed batteries, in order to prevent the pressure inside the battery from exceeding the limit pressure resistance of the battery can or the battery sealing part and causing an explosion, a notch is provided in advance and the pressure is reduced by cutting. Various proposals have been made to open up the world. One example of this method is a method in which a cross-shaped cut is made in a sealed alkaline button battery to control the wall thickness at the intersection point (Utility Model Publication No. 58-17332), which increases the pressure inside the battery can for flat sealed batteries. A method of forming a notch for the purpose of lowering the pressure resistance of the part where the stress is most concentrated relative to other parts when A method of forming a groove on the inner surface of the bottom of the battery container (Japanese Patent Application Laid-open No. 63-86244, JP-A No. 63-86246), a method of forming a groove on the inner surface of the bottom of the battery container (Japanese Patent Application Laid-Open No. 63-86244, Japanese Patent Application Laid-open No. 63-86246). Kaisho 63-8
6245), and a method of forming linear cut grooves branching at both ends in the bottom of the battery container (Japanese Patent Laid-Open Nos. 1-309252 and 1-309253).

By the way, even in completely sealed batteries,
It is necessary to make the pressure resistance of the battery container low enough to prevent the battery container from bursting and the contents scattering, but on the other hand, if an external impact is applied to the battery container, the battery can easily If the sealed state of the container is broken, it cannot be used. That is, a completely sealed battery needs to be structurally strong, and the battery container must have a sufficiently low withstand voltage and be stable.

However, in conventional completely sealed batteries, when the battery container is formed by drawing, if the wall thickness of the battery container is less than a certain value, processing defects, voids in the material, etc. may cause the battery container itself to deteriorate. However, depending on the shape of the battery container, the wall thickness of the battery container usually needs to be approximately 0.2 mm or more, and the battery container must have an explosion-proof notch. In a structure that forms a It is very important to set the pressure resistance of the battery container so that it will operate properly, and to ensure that the explosion-proof function of the battery container is not easily activated due to shocks applied during use or transportation of the battery. was difficult.

[0007]

SUMMARY OF THE INVENTION The present invention provides for the explosion-proof function of a battery container to operate stably at a desired pressure within a pressure range that ensures safety in response to an increase in internal pressure of the battery.
Another object of the present invention is to provide a completely sealed battery having an explosion-proof structure in which the explosion-proof function of the battery container is not easily activated by shocks applied during use or transportation of the battery.

[0008]

[Means for Solving the Problems] The present invention provides a sealed battery made of a metal battery container, in which one or more ventilation holes provided in a part of the metal battery container with a wall thickness of 0.2 mm or more are replaced by It is characterized by being closed by a metal plate having a diameter of less than 0.2 mm and having a cutout groove. In the present invention, the battery container is formed of a sufficiently thick metal, and the metal plate that closes one or more ventilation holes provided in a part of the metal battery container has a thickness of 0.5 mm. Constructed from a thin metal plate less than 2mm thick. That is, by using a thick metal container, the battery container has enough strength to prevent it from being easily deformed by an external impact, an increase in internal pressure within the battery container, or the like. The wall thickness of the battery container in order to obtain the necessary strength for the battery container varies depending on the size and shape of the battery container, but it usually needs to be 0.2 mm or more. Therefore, by making the thickness of the metal plate formed in a part of the battery container that does not easily deform sufficiently thinner than the wall thickness of the battery container, it is possible to prevent the slight increase in pressure inside the battery container. Also, it is possible to make the displacement of the metal plate sufficiently larger than the displacement of the shape of the battery container due to the increase in internal pressure within the battery container, and It can be configured to be responsively displaced. Although it depends on the material of the metal plate, the thickness of the metal plate is preferably about 0.1 mm or less. Furthermore, in order to operate the explosion-proof function stably at low pressures, it is necessary to create weaker parts in the metal plate by, for example, forming notched grooves in the metal plate. . Furthermore, by changing the metal plate to a material that has a lower breaking strength than the material of the battery container, it is also possible to adjust the operating pressure of the explosion-proof function to be even lower.

In particular, the method of providing notched grooves in the metal plate is easier and more accurate than forming notched grooves directly in the metal container, so the explosion-proof function can be operated with higher precision at lower pressures. enable. The notch grooves can be formed by press working, wet etching, laser beam etching, etc., but any method may be used, and the shape of the notch grooves is not particularly limited. Further, the battery container is usually made of stainless steel, nickel-plated carbon steel, etc., but is not particularly limited as long as it does not impede corrosion resistance. In addition, the materials of the metal plate include stainless steel, nickel-plated carbon steel,
Nickel, copper, aluminum, copper alloy, aluminum alloy, etc. can be used. Joining methods for sealing include laser welding, ultrasonic welding, resistance welding, etc.
Especially when a thin plate of a metal different from the battery container is used as the metal plate, it is effective to use ultrasonic welding to join the battery container and the metal plate.

[0010]Furthermore, a structure in which ribs are provided around the part where the metal plate is welded so that external shocks are less likely to be directly applied to the metal plate, and a wall thickness of the battery container around the part where the metal plate is welded are adjusted. The explosion-proof function of the battery container can be improved by partially thickening the metal plate, or by applying shock-absorbing resin, rubber, paper, etc. to the outside of the metal plate after welding the metal plate to the battery case. It is possible to more reliably prevent erroneous operation due to external impact or the like.

[0011]

[Operation] According to the present invention, the airtightness of the battery container is not easily damaged by external impact, and when the internal pressure of the battery container increases, the explosion-proof function of the battery container is activated at low pressure with good reproducibility. can be done.

0012

[Example] Next, the present invention will be explained by giving examples.

[0013]

[Example 1] A 0.3 mm thick stainless steel bottom cover with perforated ribs was welded to a 0.3 mm thick cylindrical stainless steel pipe measuring 21 mm in diameter x 83 mm, and then press-formed. The thickness of the notched groove is 0.
A stainless steel disc with a diameter of 1 mm and a diameter of 20 mm.
A hole with a diameter of 5.7 mm made in the bottom cover was closed by laser welding. FIGS. 1 and 2 show cross-sectional views of the entire battery container without illustration of the contents of the battery. 1 is a battery can,
2 is a bottom lid with perforated ribs, 3 is a metal plate with notched grooves, 4 is a battery sealing lid with a glass-metal seal, and 5 is a thick flat plate with perforations. It is the bottom cover. The wall thicknesses of the battery can, bottom cover, metal plate, and sealing cover are exaggerated. As shown in FIG. 2, the bottom cover to which the thin metal plate with the notched grooves is welded does not need to be ribbed, and may be a flat plate with a thickness of about 0.4 to 2.0 mm.

FIG. 3 shows a metal plate with notched grooves. FIG. 4 shows an enlarged view of the cross section taken along the line X-X' in FIG. 3, and FIG. 5 shows an enlarged view of the cross section taken along the line Y-Y' in FIG. Cut grooves with residual thicknesses of 0.03 mm and 0.04 mm were formed in a circular thin plate of stainless steel with a thickness of 0.1 mm, an unfilled battery container was manufactured, and water pressure was applied. The cutting pressure was determined by Thickness of remaining wall is 0.03mm
For those with a thickness of 0.04 mm, the cutting rate is 21 to 23 kg/cm2, and for those with a residual thickness of 0.04 mm, it is 29 to 31 kg/cm2.
It was torn at m2. In the conventional case where a notch groove is formed directly on the bottom of a 0.3 mm thick stainless steel can, the cutting pressure is 16 to 24 kg/cm2 if the residual wall thickness is 0.03 mm. Yes, remaining thickness is 0
．． For the 04mm one, the cutting pressure is 35-45kg.
/cm2, the cutting pressure is within a much narrower range. Furthermore, the processing yield was significantly improved compared to the case where notch grooves were formed directly on the bottom of a 0.3 mm thick stainless steel can. Further, according to the present invention, even if the notch groove is formed with the side a shown in FIG. There was almost no change in pressure. Therefore, in the present invention, there is no problem whether the side a or the side b shown in FIG. 4 is inside the battery container. The shape of the notch groove is also not limited to the shape shown in FIG. 3, and FIG. 6 shows an example of the shape of the notch groove.

For a cylindrical battery measuring φ21 mm x 83 mm and weighing approximately 80 g, if a notch groove is formed directly on the bottom of a 0.3 mm thick can as in the conventional case, if the battery is dropped from a height of 1 m onto a concrete floor, In some cases, the notched grooves on the bottom of the can can be easily torn by the impact of one or two drops, but in the structure shown in Figures 1 and 2, the metal plate with the notched grooves Unless the can was directly pierced by a foreign object on the floor, the notch groove in the metal plate welded to the bottom of the can would not be torn by the impact of about 10 drops.

[0016]

[Example 2] A 0.3 mm thick ribbed glass-metal sealing lid is welded to a 0.3 mm thick stainless steel bottomed long cylindrical can of 14 mm x 41 mm x 42 mm. φ2 drilled in a part of the metal sealing lid
The 0.1 mm thick hole was covered with a stainless steel thin plate having a thickness of 0.1 mm in which a cutout groove was formed by wet etching, and the hole was closed by laser welding. FIG. 7 shows a cross-sectional view of the entire battery container without showing the contents of the battery. Reference numeral 10 denotes a battery sealing lid with a glass-metal seal, and a hole is partially formed. The battery sealing lid may be reinforced with ribs or may be made of a thick flat plate. In Figure 8,
8 shows an external appearance of the battery container shown in FIG. 7 when viewed from above. The wall thicknesses of the battery can, metal plate, and sealing lid are exaggerated. Fig. 9 shows a metal plate with cut grooves, Fig. 10 shows an enlarged cross-sectional view taken along the line x-x' in Fig. 9, and Fig. 11
9 shows an enlarged view of the y-y' line cross section in FIG. The outer shape of the metal plate with the notched grooves does not need to be the shape shown in FIG. 9 at all, and may be circular, oval, rectangular, or the like.

[0017] Notches with remaining thicknesses of 0.02 mm and 0.03 mm were formed in a thin stainless steel plate with a thickness of 0.1 mm, an unfilled battery container was fabricated, and water pressure was applied. The cutting pressure was determined by Thickness of remaining meat is 0.02
If the thickness of the remaining thickness is 0.03 mm, the cutting rate will be 18 to 22 kg/cm2.
Cut at cm2.

Similarly, a notch groove with a remaining thickness of 0.02 mm was formed in a thin stainless steel plate with a thickness of 0.05 mm, an unfilled battery container was manufactured, and a water pressure was applied. When the cutting pressure was calculated, it was 7 to 9 kg/cm2.
When the thin metal plate forming the notched groove was thinner, there was a tendency for the cutting pressure to decrease, albeit slightly.

In other words, with the conventional method of forming notch grooves directly on the bottom of stainless steel cans, it was impossible to stably set the tearing pressure below 10 kg/cm2. According to the invention, as mentioned above, it is not only possible to stably set the tearing pressure to 10 kg/cm2 or less, but also to reduce the possibility of the explosion-proof function malfunctioning when an impact such as a fall is applied. was able to reduce it significantly.

[0020]

[Effects of the Invention] According to the present invention, the airtightness of the battery container is not easily damaged by external impact, and when the internal pressure of the battery container increases, the explosion-proof function of the battery container is achieved with good reproducibility and even at low pressure. can be operated.

[Brief explanation of drawings]

FIG. 1 is an example of a cross-sectional view of a battery container according to an embodiment of the present invention.

FIG. 2 is an example of a cross-sectional view of a battery container according to an embodiment of the present invention.

[Fig. 3] An example of a metal plate with notched grooves.

FIG. 4 is an enlarged view of a cross section taken along line XX' in FIG. 3;

FIG. 5 is an enlarged view of a line cross section taken along YY' in FIG. 3;

FIG. 6 is an example of the shape of a notched groove.

FIG. 7 is an example of a cross-sectional view of a battery container according to an embodiment of the present invention.

FIG. 8 is an example of a top view of the battery container in FIG. 7;

FIG. 9 is an example of a metal plate with notched grooves.

FIG. 10 is an enlarged view of a cross section taken along line xx' in FIG. 9;

FIG. 11 is an enlarged view of a line cross section taken along y-y' in FIG. 9;

[Explanation of symbols]

1. battery can. 2. Perforated ribbed bottom lid. 3. A metal plate with notched grooves. 4. Battery sealing lid with glass-metal seal. 5. Glass-metal seal. 6. Perforated thick flat plate bottom lid. 7. Straight notch groove. 8. Branch notch groove. 9. Thin wall part of notch groove. 10. Perforated battery lid with glass-metal seal. 11. A metal plate without cut grooves.

Claims (1)

[Claims] Claim 1: In a sealed battery made of a metal battery container, one or more ventilation holes provided in a part of the metal battery container with a wall thickness of 0.2 mm or more are replaced by a metal battery container with a wall thickness of 0.2 mm or more.
1. A sealed battery, which is closed by a metal plate having a diameter of less than 1,000 yen, and which is characterized by being provided with a notched groove.