JPH01309252A - Seald battery - Google Patents

Abstract

PURPOSE:To make it possible to generate ripping at a desired pressure by forming a linear helical groove that is notched from both the inside and outside of a baseplate, the width of the groove being made larger on the inside than on the outside, and by forming two branch helical grooves at both edges of the linear helical groove. CONSTITUTION:A helical groove 3 notched from both the inside and outside of a baseplate is formed where it is passing through the center part of the baseplate, a helical groove 3 being made larger in its width on the inside than on the outside, and further, at least a pair of branch parts 4 are formed at both edges of the linear helical groove 3. A branch part 4 is a helical groove that plays a part in concentrating a deformation due to the pressure on a notched part at the center of the linear part 3 of a helical groove, thus the center part is ripped with a good reproducibility by notching on both sides. Thereby, a groove can be ripped at a desired pressure in the pressure range for which stability is ensured responsive to the increasing internal pressure of a cell.

Description

DETAILED DESCRIPTION OF THE INVENTION [17f Industrial Application Field] The present invention relates to an explosion-proof sealed battery. For more details,
This invention relates to an explosion-proof sealed battery that has a notch in the bottom plate of a metal battery can.

[Prior Art] Conventionally, in sealed batteries, specific notches are provided in advance to prevent the internal pressure of the battery from exceeding the limit pressure resistance of the battery can or battery sealing part, causing an explosion. Proposal to release the pressure by
For flat sealed batteries, a method in which cutouts are provided for the purpose of lowering the pressure resistance of the parts where stress is concentrated when the pressure inside the battery case increases relative to other parts (Utility Model No. 6)
0-65970), a method of forming a groove at the bottom of a battery container with a flat part at the bottom and an intersection at the center of the bottom (JP-A-63-86244, JP-A-6
3-86246), on the inner surface of the bottom of the battery container? 14
There is a method of attaching a mark (Japanese Patent Application Laid-open No. 53-86245).

Various overpressure release safety valves have also been proposed that operate when the internal battery scum pressure increases. As disclosed in JP-A No. 62-90883, a non-aqueous secondary battery uses a lithium composite metal oxide for the positive electrode, uses a specific carbon material for the negative electrode, uses lithium perchlorate as the electrolyte, and uses brobylene carbonate as the solvent. In case of no pressure during normal use? E-Battery does not fit inside the can. If the bipolar active material or electrolyte reacts with moisture or oxygen, the performance will be degraded, so a safety valve is not suitable, and it is preferable to seal the battery container with a hermetic seal and adopt a completely sealed structure. However, while the airtightness is improved and the storage capacity is improved, under abnormal environments such as being heated to high temperatures or being charged at high voltage, the internal pressure of the battery increases and the battery explodes with a popping sound. The contents may scatter and cause damage to battery-powered equipment. This hermetically sealed sealed battery also needs to have a notch to provide explosion-proof functionality.

Conventionally, press working has been used to form explosion-proof notches, but when stainless steel is used, the grooves undergo work hardening, and unless annealing is performed, the operating pressure for the explosion-proof function is unstable. A sharp V-shaped groove has the advantage of being easy to tear, but has the disadvantage of low durability of a punch for processing. 0.1~0.2n+mR at the bottom of the groove
There is also a method of rounding the surface (Utility Model Publication No. 58-26460), or it will become less sensitive to pressure increases.

[Problems to be Solved by the Invention] For batteries that function as negative terminals, a cross-shaped notch on the bottom of a battery can is inappropriate because it can be mistaken for a positive electrode terminal, and it is inappropriate to make a notch in the area where stress is concentrated. In this case, a stable tear-opening pressure cannot be obtained with a battery that does not receive any pressure at all under normal conditions.

By using a simple and highly economical press processing method, the desired position can be cut within a pressure range that ensures safety in response to increases in battery internal pressure, and it can also be cut at a desired position in a pressure range that does not operate during normal use. It is necessary to provide a notch.

An object of the present invention is to provide a sealed battery having a notch structure that allows the bottom of the battery can to exhibit a stable explosion-proof function when pressure increases under abnormal environments.

[Means for Solving the Problems] The present invention provides a sealed battery having a notch in the bottom plate of a metal battery can, in which a linear notch groove cut out from both the inside and outside of the bottom plate is provided at a position passing through the center of the bottom plate. The notched groove is characterized in that the groove width on the inner surface is larger than the groove width on the outer surface, and at least two branched notched grooves are provided each branching from both ends or near both ends of the linear notched groove. .

In the present invention, notches are provided on both sides of the bottom plate of a battery can made of metal such as stainless steel or nickel-plated carbon steel. The notch has a straight portion passing through the center of the bottom plate,
There are at least two straight line or circular arc branch parts at both ends of the straight part, which are located symmetrically with respect to the straight part, and each branch tip is at least 120 degrees and within 150 degrees, preferably at least 150 degrees with respect to the straight part. It is between 130 degrees and 145 degrees. The branch tip is at least 1 mm away from the can periphery.

Further, the branched portion may be in the shape of a broken line and may not necessarily be connected to the straight portion. In the cross section of the notches provided on both sides, the notch groove on the inside of the battery can is shallower and wider than the notch groove on the outside of the can.

By providing such a notch, the durability of the groove forming punch for press working is significantly improved compared to the case where a notch is provided only on one side.

The tip of the notch groove on the outside of the can may be rounded with a radius of o, oi to 0.04 mm.

The wall thickness of the notch is varied in the range of 20 μm to 50 μm to obtain a desired operating pressure in the battery can internal pressure range of 15 to 45 kg/cm 2 .

[Function] According to the present invention, it is possible to stably tear the bottom of the battery can near the center. The branch notch serves to concentrate the deformation due to the pressure of the notch to the center of the straight part of the notch groove, and the notches on both sides cause the central part to be cut with good reproducibility. In particular, the width of the groove in the straight portion is wide on the inner surface and narrow on the outer surface, so that when the pressure inside the can increases, cutting is stably performed due to the notch effect of the notch on the outer surface.

[Example code] Next, the present invention will be explained with reference to Examples.

Example 1 A notch was formed in the bottom of a 0.3 mm thick bottomed cylindrical can made of stainless steel by press working.

FIG. 1 shows a cross-sectional view of the entire battery container without showing the contents of the battery. 1 is a battery can, and 2 is a battery sealing lid with a glass-metal seal. The thickness of the battery can 1 is shown slightly exaggerated.

FIG. 2 is a bottom view of the battery can 1, that is, a diagram showing the bottom plate portion of the battery can. As shown in the figure, the bottom plate is provided with a cutout groove consisting of a straight part 3 and symmetrical branch parts 4 at both ends thereof. FIG. 3 is an enlarged view of the cross section taken along line XX' in FIG. 2, and FIG. 4 is a cross section taken along line Y-Y' in FIG. Can bottom diameter 2
5m+n, the length of the straight part was 7 mm, and the length of one side of the branched part was 6IIIa+.

In FIG. 3, the notch width a on the inside of the battery can was 0.78 mm, and the width of the notch groove on the outside of the battery can was 0.37 mm. The thickness t of the thin portion 5 thus formed was 30 μm. FIG. 5 shows the angle α of the branch portion 40 with respect to the main straight line 3, and the angle was 138 degrees. When pressure was applied to the unfilled battery can using air pressure and the pressure at which the bottom of the battery can was torn was determined, it was 18 kg/c.
+n2-24 kg/cm2, and was cut at the center of the straight section 3.

Example 2 A notch was formed in the bottom of a bottomed cylindrical can made of nickel-plated carbon steel and having a thickness of 0.3 mm by press working. 6th
The figure shows the bottom of a battery can with a cutout. In this embodiment, the notch grooves are a straight part 3 and a symmetrical arc-shaped branch part 6.
It has a notch on both the inside and outside of the bottom plate. For a can bottom diameter of 15 mm, the length of the straight part 3 is 5 mm, and the straight line distance between the tip of the arc of the branch part 6 and the branch base point is 3.0 mm.
mm. The width of the notch groove inside the battery can is 0.80mm.
The width of the notch groove on the outside of the battery can was 0.36 mm. The thickness of the thin portion was 45 μm. As shown in Figure 7,
The angle of the branch tip with respect to the main straight line was 132 degrees.

When we applied air pressure to the unfilled battery can and determined the pressure at which the bottom of the battery can was torn, all 10 cases fell within the range of 17 kg/cm'-27 kg/cm2, and the center of the basic straight line It was torn apart.

In order for the cutting to be performed stably, the bifurcation must be symmetrical with respect to the straight line, regardless of its shape, and the angle between the straight line connecting the tip of the bifurcation and the bifurcation point must be 1.
The angle is preferably 20 degrees or more and 160 degrees or less, and more preferably 130 degrees or more and 145 degrees or less.

If this angle is less than 120 degrees or more than 160 degrees, stable tearing at the center of the straight portion will not occur.

The thickness of the thin walled portion formed by the notch is determined by the material of the battery can and the set pressure for causing the tear.

Comparative Example 1 A notch was formed in the bottom of a bottomed cylindrical can made of stainless steel and having a thickness of 0.3++ lIn by press working. FIG. 8 shows the bottom of a battery can provided with a notch. ×−×′
An enlarged view of the line cross section is shown in FIG.

The length of the straight portion 7 is 7 mm for a can bottom diameter of 25 mm.

The length of one side of the branch portion 8 was 6 mm. The notch was made only from the outside of the can. The angle of the branch tip to the straight part 7 is 9
It was 0 degrees.

The notch width C on the outside of the battery can in FIG. 9 was 0.37 mm. The thickness t of the thin portion 9 was 30 μm.

When air pressure was applied to an unfilled battery can to determine the pressure at which the bottom of the battery can was torn, it was found that the bottom of the battery was torn in a straight line, but the position of the rupture was not constant, and the pressure range at which it would break was determined. The temperature was also 12 kg/cm" - 35 kg/cm2, and it was not stable.

Even when the notch was provided only on the inner surface of the can, the situation of tearing was unstable.

[Effects of the Invention] As explained above, in the present invention, the linear portion of the notched groove has notches on both sides, the notched groove on the inside of the battery can is made larger than the notched groove on the outside of the can, and the notched groove is made on both ends of the straight portion. By providing a branch at a predetermined angle, it was possible to cut with the desired pressure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a battery container according to an embodiment of the present invention, FIG. 2 is a bottom view of the battery container, and FIGS. 3 and 4 are enlarged sectional views taken along line X-X' in FIG. 5 is a plan view showing the angle between the branch notch groove and the straight notch groove, FIG. 6 is a bottom view of another embodiment of the present invention, and FIG. 7 is a branch notch groove. 8 is a bottom view of a comparative example, and FIG. 9 is a sectional view taken along line XX' in FIG. 8. 1...Battery can, 2...Battery sealing lid with glass-metal seal, 3...
Notch groove, 4... Branch notch groove, 5... Thin wall portion. Figure 1

Claims (1)

[Claims] In a sealed battery having a notch in the bottom plate of a metal battery can, a linear notch groove cut out from both the inside and outside of the bottom plate is provided at a position passing through the center of the bottom plate, and the notch groove has a groove width on the inner surface. 1. A sealed battery comprising at least two branch notched grooves each having a width larger than the groove width on the outer surface and branching from both ends or near both ends of the linear notched groove.