JPH04366545A - Sealed battery - Google Patents

Abstract

PURPOSE:To form a thin part between outer surface and inner surface differences in level and enhance safety by providing a difference in level directing the outer surface of a case in an inside position from the most outside circumferential part of the bottom part on the bottom part outer surface of a battery case, and providing an inner surface difference in level directing the outward of the case in the same or inside position, compared with the outer surface difference in level on the bottom part inner surface. CONSTITUTION:A negative electrode 2 mainly consisting of lithium, a cylindrical positive electrode body 4 mainly consisting of a separator 3, and a needle collector 5 are disposed in a battery case 1, and a positive electrode terminal 7 to which thionyl chloride is injected as a positive electrode and electrolytic solution 6, a glass seal 8, and an upper lid consisting of a metal lid 9 are welded to the upper part of the case 1 and sealed. In this constitution, an outer surface difference in level 10 is provided on the bottom outer surface of the case 1, and an inner surface difference in level 11 in the same or inside position, compared with the difference in level 10 on the inner surface of the case to form a thin part 12 between the differences in level 10 and 11. The thickness of the bottom part, or the depth P of the inner surface difference in level 11 is regulated to set the thickness of the thin part 12 so that it can be certainly broken at a low pressure, and the internal pressure and a received material are released to the outside.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery using an oxyhalide having an explosion-proof function as an active material and sealed with a hermetic seal.

0002

[Prior Art] Lithium batteries that use a lithium-based negative electrode and thionyl chloride as a positive electrode and electrolyte solvent have a structure that is completely sealed with a hermetic seal because the active material is highly reactive with water. ing.

[0003] However, the above-mentioned sealed battery has a
The hermetic seal allows for high airtightness, making it excellent for storage. However, on the other hand, if an abnormal situation occurs such as being exposed to high temperature heating or being charged at a high voltage, the internal pressure of the battery will become abnormal. There is a risk that the battery will explode and damage equipment that uses the battery.

[0004] For this reason, it has been proposed to provide an explosion-proof function by forming a groove in the bottom of the battery case and providing a thin section.

A typical sealed battery with an explosion-proof function that has been proposed in the past will be explained with reference to FIG. As shown in the cross-sectional view of the battery in Figure 4, an example of a sealed battery has a battery case.
In the gas 21, there is a negative electrode 22 mainly composed of lithium, and a separator.
A cylindrical positive electrode body 24 mainly made of carbon, and a needle-like current collector 25 are arranged, and thionyl chloride is injected as a positive electrode/electrolyte solvent 26, a positive electrode terminal 27, and a glass seal. 28, attach the top cover made of metal cover 29 to the battery case.
It is welded to the upper circumference of the space 21 to seal it.

A cross-shaped groove 30 is machined in the bottom of the battery case 21, as shown in FIG. 5, and a thin wall portion is formed by this groove 30. That is, when the internal pressure of the battery begins to rise abnormally, the thin walled portion formed by the cross-shaped groove 30 ruptures, forming an opening and releasing the battery contents and internal pressure to the outside of the battery, thereby preventing the battery from bursting. It has become. (Refer to Japanese Patent Application Laid-Open No. 63-86243)

Since the explosion-proof function proposed in the past has the above-mentioned structure, for example, when the battery is thrown into a fire, the internal pressure of the battery rises rapidly, and the thin part formed by the groove 30 ruptures in a cross shape, causing the internal pressure to rise. Although it was planned that the contents of the battery would be released, in reality the opening area of the thin-walled part was not very large, and as a result, the battery contents such as the positive electrode body and bottom paper that were supposed to be released were released from the thin-walled part. There is a high risk of it getting stuck in an imperfect opening. When the opening becomes clogged with the contents and becomes occluded again,
Since the increased internal pressure of the battery was not sufficiently released, the internal pressure of the battery would rise again, and there was a risk of the battery bursting.

[0008] Furthermore, in order to form an opening due to internal pressure, etc., a notch groove having a wedge-shaped cross section or the like is formed in a cross shape on the outer surface of the bottom of the battery case, so when a tab-shaped terminal member is joined, the joining part is restrictions arise. That is, the tab is attached so that the notch groove is not buried.

[0009]

[Problems to be Solved by the Invention] The present invention aims to solve the above-mentioned problems.It is an object of the present invention to provide an opening for releasing the internal battery pressure and contents to the outside when the internal pressure of the battery increases. An object of the present invention is to provide a battery case having a large area and improved safety.

0010

[Means for Solving the Problems] The structure of the present invention, which has been made for the purpose of solving the above-mentioned problems, is a sealed battery in which a power generating material is housed in a battery case and a top cover is welded. A step toward the outside of the battery case is provided on the outer surface of the bottom of the battery case at a position inside the outermost periphery of the bottom, and a step toward the outside of the battery case is provided on the inside of the bottom at a position equal to or inside the outer surface step. By providing an inner surface step toward the outside,
This device is characterized in that a portion thinner than the battery case material is formed between the outer surface step and the inner surface step.

When looking at the outer surface of the bottom of this battery case from above,
The thin portion had a substantially circular shape, but a non-thin portion without a step was left on the outer periphery of the thin portion.

0012

[Operation] The explosion-proof function of this invention is such that when the internal pressure of the battery rises abnormally and the thin-walled part is torn, the inner surface of the circular thin-walled part is torn when the outer surface of the bottom of the battery case is viewed from above. Open your mouth. In addition, the area of the opening formed in this way is large enough to prevent the battery contents from clogging when they are discharged to the outside of the battery, so that the internal pressure and contents of the battery can be reliably discharged to the outside. can.

[0013] Also, when looking at the outer surface of the bottom of the battery case from above,
Since the thin part is formed into a substantially circular shape and a part of it is left as an unthinned part, that is, a joint part, this unthinned part (joint part) becomes a fulcrum when opening, and the opposite side of this fulcrum Since the internal pressure is concentrated on the thin-walled part of the cylinder, the explosion-proof function operates more reliably at a lower internal pressure than when the entire circumference of the circular shape is made of thin-walled parts.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of implementing the present invention will be explained below with reference to the drawings. FIG. 1 is a cross-sectional view of an example of a sealed battery formed according to the present invention. In FIG. A body 4 and a needle-like current collector 5 are arranged, thionyl chloride is injected as a positive electrode and an electrolytic solvent 6, and an upper lid consisting of a positive electrode terminal 7, a glass seal 8, and a metal lid 9 is placed in the upper circle of the battery case 1. It is sealed by welding around the circumference.

The battery case 1 has an outer step 10 on the outer surface of the bottom, and an outer step 10 on the inner surface of the battery case 1.
Inner surface steps 11 are provided at the same or inner positions as compared to 0, and by this structure, a thin wall portion 12 is formed between the outer surface step 10 and the inner surface step 11 at the bottom of the battery case 1.

FIG. 2 is an enlarged sectional view of the thin walled part 12 at the bottom of the battery case 1 of the present invention formed by press working. The mold D provides an outer surface step 10 at the bottom of the battery case 1, and an inner surface step 11 is provided on the inner surface of this bottom at the same or inner position than the outer surface step 10, so that the outer surface step 10 and the inner surface step 11 are A thin wall portion 12 is formed in between.

FIG. 3 is a top plan view of the bottom of the battery case 1 according to the present invention, in which the thin wall portion 12 is formed in a substantially circular shape, but there is a part of the non-thin wall portion 13 without a step. The mold P or D is formed so as to remain.

In FIG. 2, the rising radius R1 of the outer surface step 10 is R1=0.1 mm, and the rising radius R of the inner surface step 11 is R1=0.1 mm.
2 is R2 = 0.2 mm, the outer and inner diameters D1 and D2 of both the steps 10 and 11 are D1 = D2, and the wall thickness of the bottom of the case,
In other words, by adjusting the depth P of the inner surface step 11, the thickness of the thin portion 12 can be arbitrarily set. In addition, by reducing R1 and increasing R2, internal pressure is concentrated in the thin wall portion, making it easier to tear and ensuring reliable operation at low pressure. The results of experiments on the relationship between changes in R1 and R2 and working pressure are shown below.

It is shown in [Table 1]. In addition, the thickness of the thin part is 0.05 mm, D1=D
It was set as 2.

[0019]

[Table 1]

[0020] As a result, if R1 and R2 are set to 0.1 mm or less, cracks tend to occur in thin-walled parts during press processing.
In addition, it was found that the mold had a large amount of wear. Therefore, R1
, R2 is preferably 0.1 mm or more. Also

From the results in [Table 1], R1 = 0.1 mm and R2 = 0.2 because the working pressure can be lowered and press working can be performed stably.
It was set to mm.

[0021] The thickness of the thin part 12 is 0.04
The working pressure was tested by setting it to mm, 0.05 mm, 0.06 mm, and 0.08 mm. This result

[Table 2] shows. In addition, in this experiment, R1 = 0.1 mm,
R2=0.2 mm and D1=D2.

[0022]

[Table 2]

[0023] Above

As a result of manufacturing AA-sized lithium thionyl chloride batteries with the thickness dimensions of each thin wall part shown in [Table 2] and testing the operating state of the explosion-proof function in a fire, the thickness of the thin wall part was 0.04 m.
In the case of 0.05 mm, the thin wall part was completely opened in a substantially circular shape, and the internal pressure and contents of the battery were completely discharged to the outside. However, the thickness of the thin part is 0.06 mm and 0.08 mm.
Some of the batteries exploded within about one minute after being dropped into the fire. From this, the thickness of the thin part is 0.0
It is preferably 5 mm or less.

[0024] Regarding D1 and D2, D1=8.0mm
In this experiment, D2 was set to 7.7 mm, 8.0 mm, and 8.3 mm, respectively, and the operating pressure was tested. The result

It is shown in [Table 3]. Note that the thin part thickness is 0.05 mm, R1 = 0.1
mm, R2=0.2 mm.

From the results in Table 3, it was found that the operating pressure could be set low if D1≧D2.

[0025]

[Table 3]

In all of the above experiments, the unthinned portion 13, that is, the connecting portion, functioned to prevent the open circular stepped portion from scattering. In addition, in the above example, a thionyl chloride lithium battery was used as a sealed battery, but
Even with other types of batteries, as long as they are sealed batteries, the same effects as those of the above example can be obtained by applying the present invention. However, the appropriate operating pressure for the explosion-proof function differs depending on the type of battery active material and battery case material. In addition, inside,
Although the planar shape of the outer surface step may be oval or polygonal in addition to circular without any particular problem, a circular shape is preferable.

[0027]

[Effects of the Invention] As explained above, according to the present invention,
Since the opening area for releasing the internal battery pressure and contents to the outside when the explosion-proof function is activated can be large, a highly safe explosion-proof function can be obtained. Furthermore, since the easily opened inner and outer step portions are formed of flat surfaces such as substantially circular shapes, terminal members such as tabs can be easily joined.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of an example of a sealed battery to which the present invention is applied.

[Figure 2] Battery case made by pressing the battery shown in Figure 1
An enlarged view of the thin section at the bottom of the space.

FIG. 3 is a plan view of the bottom of the battery case in FIG. 2;

FIG. 4 is a front sectional view of a battery with an explosion-proof function according to the prior art.

FIG. 5 is a plan view of the bottom of a battery case with an explosion-proof function according to the prior art.

[Explanation of symbols]

1,21 Battery case 2,22 Lithium 3,23 Separator 4,24 Cylindrical positive electrode body 5,25 Positive electrode current collector 6,26 Thionyl chloride 7,27 Positive electrode terminal 8,28 Glass seal 9, 29 Metal lid 10 Step portion 11 on the surface of the battery case
Step portion 12 on the inner surface of the battery case
Thin wall portion 13 Non-thin wall portion 30 Cross-shaped groove portion

Claims (3)

[Claims] Claim 1: In a sealed battery in which a power generating material is housed in a battery case and a top cover is welded, the battery case is located on the outer surface of the bottom of the battery case at a position inside the outermost periphery of the bottom. By providing a step toward the outside of the battery case and also providing an inner step toward the outside of the battery case at the same or inner position than the outside step on the inner surface of the bottom, the battery A sealed battery characterized by having a thinner part than the case material. 2. The planar shape of the step formed on the inner and outer surfaces of the bottom of the battery case is approximately circular, and a part of the circumference of the circular step is left where the thickness is not formed. The sealed battery according to claim 1, characterized in that: 3. The thin wall portion formed by the step formed on the inner and outer surfaces of the bottom of the battery case rounds the rising angle of the step, and the roundness of the rising angle of the outer step is larger than that of the inner step. The sealed battery according to claim 1 or 2, characterized in that: