JP3322566B2 - Explosion-proof sealing plate for sealed batteries - Google Patents

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, particularly used for sealing a battery having a high energy density such as a lithium battery or a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, portable and cordless (portable) electronic devices such as AV devices and personal computers have been rapidly advanced, and various types of high-capacity alkaline storage batteries and lithium batteries have been used as driving power supplies for these devices. A non-aqueous electrolyte (organic solvent-based electrolyte) secondary battery represented by a secondary battery is suitable. Furthermore, non-aqueous electrolyte secondary batteries are being promoted to be sealed batteries with high energy density and excellent load characteristics, and these sealed batteries are widely used as power sources for portable devices such as watches and cameras. Have been.

In a sealed nonaqueous electrolyte battery having a high energy density, when a device including a charger fails, is overcharged, or is erroneously used, a power generation element inside the battery undergoes a chemical change. For example, the electrolyte and the active material are decomposed by an abnormal reaction due to overcharging, short circuit, or the like, and abnormal gas is generated inside the battery, and the internal pressure of the battery becomes excessive. In such a case, the battery may explode or damage the equipment in use.For this type of battery, open the valve to release gas when the battery internal pressure exceeds the set value. Explosion-proof safety functions have been added. Furthermore, in non-aqueous electrolyte secondary batteries, there is a danger of ignition due to a sudden rise in temperature due to overcurrent.Therefore, by detecting the internal pressure of the battery, the current is completely cut off prior to gas discharge, causing ignition. There is an explosion-proof safety mechanism that reliably prevents

[0004] For example, an upper valve body and a terminal plate having a vent are placed in a conductive state through a welded portion at the center thereof, and when the internal pressure reaches a predetermined value, the internal pressure of the battery is reduced. An explosion-proof safety mechanism is known in which a valve received through an air hole is deformed in the direction of internal pressure, and the valve separates from a welded portion with a terminal plate, thereby shutting off an energizing current (JP-A-6-196150). Gazette).

However, in the above explosion-proof safety mechanism, it is necessary to set and weld a predetermined portion between the valve body and the terminal plate to a low welding strength that can be peeled off by a constant internal pressure of the battery. Ultrasonic welding that can be welded with high strength was adopted. However, in ultrasonic welding, only heat is generated on the surface of the joint portion of the workpiece by vibrating heat generation, so that there are many unstable factors, so that the welding strength varies inevitably. In the above explosion-proof safety mechanism, the current breaking pressure is set according to the welding strength. Therefore, the current breaking pressure differs according to the variation in the welding strength, and has a disadvantage that it cannot be set to a constant value. As a result, the current may be interrupted before the battery internal pressure rises to the predetermined value, or conversely, the current may not be interrupted even though the battery internal pressure has reached the predetermined value.

Therefore, when the current is interrupted due to an increase in the internal pressure of the battery, the current can be reliably interrupted when the internal pressure of the battery rises to a certain value without being affected by the welding strength between the valve body and the terminal plate. A sealing plate has been proposed. This explosion-proof sealing plate includes an upper metal foil 1 as a valve body and a lower metal foil 2 to which a positive electrode lead body 7 of an electrode plate group is connected via a metal case 8, as shown in a vertical sectional view of FIG. The peripheral portions are overlapped with a ring-shaped insulating gasket 3 interposed therebetween, and the central portions of the metal foils 1 and 2 are welded to each other to form a welded portion S.

FIG. 6A is a plan view of the lower metal foil 2, and FIG. 6B is a sectional view taken along the line BB of FIG. In the same figure, a pair of opposed rectangular ventilation holes 4 are formed around the center of the lower metal foil 2 where the above-mentioned welded portion S is formed in the disk-shaped center portion. The two parallel thin portions 6 connecting the edge portions of the holes are arranged to form a square.

In the explosion-proof sealing plate, the two metal foils 1 and 2 are electrically connected only through the welded portion S at the center, and the current breaking pressure is determined by the breaking strength of the thin portion 6 of the lower metal foil 2. Is set by That is, when the internal pressure of the battery rises to a predetermined value, this pressure acts on the upper metal foil 1 through the air hole 4, and the thin portion 6 is broken by the stress that deforms the upper metal foil 1 in the internal pressure direction, and A portion of the metal foil 2 that is surrounded by the pair of ventilation holes 4 and the pair of thin portions 6 is hollowed out and integrated with the upper metal foil 1 to be separated from the lower metal foil 2, thereby interrupting the current flow. In this explosion-proof safety mechanism, there is no need to peel off the welded portion S, so that the welded portion S can be formed by laser welding capable of welding to a strong welding strength. Therefore, the current interrupting pressure is set by the breaking strength of the thin portion formed by the marking means or the like, and is not affected at all by the variation in the welding strength of the welded portion S.

[0009]

However, the above explosion-proof sealing plate has the following problems. That is, when a welded portion S having a high welding strength is formed by laser welding at the center of the metal foils 1 and 2, the welded portion S is particularly formed because the lower metal foil 2 has a pair of ventilation holes 4. It is necessary to secure a laser irradiation space corresponding to the laser nugget diameter as shown by a vertical parallel line in FIG. 6A around the central portion to be formed. For this reason, it is necessary to set the distance l between the two ventilation holes 4 and the distance W between the two thin parts 6 to be equal to or more than a predetermined value. Therefore, the thin part 6 has a relatively long dimension (that is, it corresponds to the distance l between the two ventilation holes 4). Becomes As a result, the thin portion 6 is set to have a breaking strength that breaks at a predetermined battery internal pressure in a long dimension, so that it is necessary to form the thin portion extremely thin, and a process for controlling the engraving means with high precision has been performed. In this case, the thickness tends to vary, and the reliability tends to be low. For example, the pair of thin portions 6 may be broken on one side during processing, or may be broken in a process of caulking the metal case 8 in the explosion-proof sealing plate inward, and there is a problem in that the manufacturing yield is poor.

Further, since the thin portion 6 is formed to have an extremely small thickness and is set so as to have a predetermined breaking strength as a whole, the welded portion S is formed by the distance 1 between the two ventilation holes 4 and the both thin portions 6. Is formed at the center portion of each of the intervals W, and the tensile force due to the deformation of the upper metal foil 1 acts on the thin portions 6 through the welded portions S as substantially uniform shearing forces over the entire thin portions 6. Need to be set to If the welded portion S is slightly deviated from the above-mentioned predetermined position, since the breaking strength of each portion in the thin portion 6 is very low, the thin portion 6 is applied at a pressure lower than the current interrupting pressure. Even if there is, the welded portion S is broken in a state of being peeled off from the displaced direction. That is, when the irradiation position of the laser beam shifts during the formation of the welded portion S, there is also a problem that the current interrupting pressure changes according to the shift.

In the case of a rigid body or a workpiece having a large thickness during laser welding, laser welding can be performed without any trouble since the material itself does not deform. However, since the above-mentioned metal foils 1 and 2 have a small thickness of about 0.05 to 0.15 mm and are easily deformed, when they are mutually welded by laser welding, FIG.
As shown in FIG. 5, the upper metal foil 1 is brought into contact with the lower metal foil 2 received on the flat upper surface of the fixing jig 9 by the fixing jig 10 having the lower central portion curved.
The laser light C is applied to those contact portions.

However, the fixing jig 10 on the side to be irradiated with the laser light C necessarily has a hole 10 through which the laser light C passes.
It is necessary to provide a space 9a in the fixing jig 9 on the other side, at least at a position opposed to the irradiation of the laser beam C to avoid thermal effects. for that reason,
The central part of the center of both metal foils 1 and 2 to be welded is
Due to the existence of the passage hole 10a and the space 9a, it cannot be directly pressed down, but only presses around them. Therefore, the location where both metal foils 1 and 2 should be welded is
Even if the jigs 10 and 11 are used, a gap is easily generated due to the deformation, and the gap causes insufficient heat conduction between the two metal foils 1 and 2, which causes inconveniences such as poor welding and drilling.

Therefore, the present invention can set the predetermined breaking strength while increasing the thickness of the thin portion of the lower metal foil, and can reliably maintain the predetermined current interruption pressure without accurately positioning the welded portions of the two metal foils. It is an object of the present invention to provide an explosion-proof sealing plate for a sealed battery having a configuration that can be set as follows.

[0014]

In order to achieve the above-mentioned object, an explosion-proof sealing plate for a sealed battery according to the present invention comprises an electrically conductive upper and lower metal foil having an insulating gasket between the peripheral edges thereof. A pair of ventilation holes that are stacked and interposed and electrically connected to each other through a welded portion in which each central portion is welded to each other, and that applies a battery internal pressure to the upper metal foil in the lower metal foil ; frangible thin portion 2 Article connecting the hole edge portion of the two positions facing each of the vent holes, the welding portion
Explosion-proof enclosure for sealed batteries formed in an annular shape to surround
A plate, at least one of the pair of ventilation holes
Is formed in a substantially U-shape in which a pair of projecting holes are continuously provided inward on both ends of the main body hole, and the two lines are easily broken.
The thinned portion has one end at the edge of the tip hole of the pair of protrusion holes.
Each is formed to be connected, and its breaking strength
However, it is set to a value that breaks when the internal pressure of the battery acting on the upper metal foil reaches a predetermined value.
And

According to the sealed battery in which the opening of the battery can is sealed by using the explosion-proof sealing plate of the invention, the internal pressure of the battery acts as a pushing force against the upper metal foil through the ventilation hole of the lower metal foil. When a large amount of gas is generated inside the battery due to an abnormal reaction due to overcharge or battery short circuit, when the battery internal pressure reaches a predetermined value set by the breaking strength of the thin portion of the lower metal foil, the upper metal foil The upward deforming force acts on the lower metal foil through the welded portion, and the thin portion breaks. Thereby, the annular portion surrounded by the pair of air holes and the two thin portions in the lower metal foil is hollowed away from the lower metal foil together with the upper metal foil,
The two metal foils, which have been conductive to each other only through the welded portion, are separated from each other, and the current is interrupted. As a result, in the initial stage of overcharging or short-circuit, the current is cut off and the chemical reaction stops, suppressing the rise in battery temperature and internal pressure due to the charging current or short-circuit current, and preventing the battery from firing or exploding I do.

In the explosion-proof sealing plate, at least one of the vent holes has a U-shape having a main body hole and a pair of projecting holes, and the two thin portions have a pair of projecting holes. Since it is provided so as to connect between the edge of the front end hole of the portion and the edge of the hole of the other ventilation hole, the length is significantly reduced. Therefore, the thickness of the thin portion can be increased by an amount corresponding to the shortened length when setting the predetermined breaking strength, so that the predetermined thickness can be easily determined without performing precise processing for controlling the marking means with high accuracy. It can be manufactured almost exactly to the breaking strength of, and the production yield is greatly improved.

Moreover, the welded portions formed at the respective central portions of the two metal foils are biased toward the protruding holes with respect to the thin portions, and the thin portions are broken by being pulled by the welded portions and peeling off. Is done. Therefore, even if the welded portion is formed slightly displaced from the predetermined portion, the welded portion is set at a position deviated from the beginning with respect to the thin portion, so that there is almost no influence on the current interrupting pressure. Therefore, the current interrupting pressure can always be set to a constant value, and the thin portion is reliably broken without variation when the battery internal pressure rises to a constant value. Further, if the distance between the main body hole of one of the vents and the other vent is set to a required value, a laser-irradiated portion of a necessary space when welding both metal foils by laser welding can be secured.

In the above invention, the upper metal foil is provided with a flexible concave portion whose central portion swells downward, and the lower metal foil has the flexibility of the central portion bulging upward. A convex portion having a convex portion is provided, and two protruding thin portions are formed on the convex portion, and the central portion of each of the concave portion and the convex portion is welded in a state of elastically contacting each other. In this case, a welded portion can be formed.

Accordingly, when the two metal foils are overlapped to form a welded portion at each central portion, the concave portion and the convex portion are slightly bent after their tip portions come into contact with each other. Due to the restoring force, the contact portions strongly press each other. Therefore, the tip portions of the concave portion and the convex portion are in pressure contact with each other, so that no gap is formed in the contact portion, so that the contact portion can be always laser-welded in a welded state without defects.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention. In this figure, the explosion-proof sealing plate for a sealed battery comprises a thin upper metal foil 11 having flexibility, a thin lower metal foil 12 provided opposite to the upper metal foil 11, and both metal sheets. A ring-shaped insulating gasket 13 interposed between the peripheral portions of the foils 11 and 12, and a ring-shaped PTC superposed on the upper surface of the peripheral portion of the upper metal foil 11;
(Positive Temperature Coefficient) element 14, metal cap 17 having four exhaust holes 17a mounted on PTC element 14, and four ventilation holes for inserting and holding the above members in a stacked state. 18a made of aluminum.

The upper metal foil 11 has a thickness of, for example, 0.15 m.
m, a flexible aluminum disk having an outer diameter of 12.7 mm and a concave portion 11a whose central portion bulges downward in a curved shape, and a C-shaped inscription is formed around the concave portion 11a. And a C-shaped easily breakable thin portion 11b.

FIG. 2A is a plan view of the lower metal foil 12,
(B) is a sectional view taken along line AA of (a). In the figure, a lower metal foil 12 is made of, for example, a flexible aluminum disk having a thickness of 0.1 mm and an outer diameter of 13.5 mm, and has a convex portion whose central portion bulges upwardly in a curved shape. It has a portion 12a. Further, the lower metal foil 12 is formed with two air holes 12b and 12c opposed to each other at symmetrical positions on both sides of the disk-shaped central portion, and one air hole 12c is formed as a main body hole 12d. It has a substantially U-shape having a pair of projecting holes 12e provided inwardly in a communicating state from both sides of the main body hole 12d, and the other ventilation hole 12b is formed in a rectangular shape. . Further, in the lower metal foil 12, a pair of easily breakable thin portions 12f are formed between the respective front edge portions of the two protruding hole portions 12e and the edge portions of the other ventilation holes 12b opposed thereto. These thin portions 12f have a breaking strength that breaks when the battery internal pressure reaches a predetermined value, and the thin portions 1f of the upper metal foil 11
The intensity is set lower than 1b.

The two metal foils 11 and 12 face each other at a relative position where the lower thin portion 12f is contained inside the upper C-shaped thin portion 11a. In addition, both metal foils 11 and 12
Are electrically connected only through a welded portion S formed by welding their central portions to each other by laser welding. The PTC element 14 is a resistance element having a positive temperature characteristic in which the electric resistance value increases by orders of magnitude when the temperature exceeds a predetermined temperature range due to the flow of a current equal to or more than a set value.

The above explosion-proof sealing plate for a sealed battery is made of two metal foils 11 and 12 which are superposed with an insulating gasket 13 interposed therebetween.
The PTC element 14 and the metal cap 17 are placed on top of each other and inserted into the metal case 18 in a stacked state.
8 is assembled by caulking the upper part inward.
When inserting the explosion-proof sealing plate into the battery can, the lead body 19 led out from one of the electrode plates (usually the positive electrode) of the electrode group housed in the battery can is inserted into the metal case 1 as shown in FIG.
After the electrolyte is injected into the electrode group, the explosion-proof sealing plate is mounted inside the opening of the battery can with an insulating gasket 20 interposed therebetween. After that, when the upper end portion of the battery can is caulked inward, the explosion-proof sealing plate seals the opening of the battery can.

Next, the operation of the sealed battery in which the opening of the battery can is sealed by the explosion-proof sealing plate will be described.
The current is supplied from the electrode plate, the lead body 19, the metal case 18, and the lower electrode 12 to the upper metal foil 11, PT
It flows to the C element 14 and the metal cap 17, and functions as a battery. In this sealed battery, the explosion-proof safety function functions in three stages. First, the first explosion-proof safety function will be described. When an excessive current flows, the PTC element 14 reaches the operating temperature in a short time, the resistance value increases, and the conduction current is greatly reduced and maintained. Thereby, remarkable damage to the battery due to external short circuit or erroneous use with excessive current can be prevented.

In the case of a lithium secondary battery, if uncontrolled overcharge or reverse charge due to a charger failure or the like, or a large number of series overdischarges occur, a current value equal to or less than the operating current of the PTC element 14 is used. Even so, the battery's internal pressure often rises, exceeding the safety allowable current of the battery. In this case, if current continues to flow through the battery, the temperature of the battery rises sharply while decomposing the electrolytic solution and active material, generating a large amount of gas or vapor and causing ignition or explosion. May result in damage. Therefore, a second explosion-proof safety function that detects the internal pressure of the battery and completely shuts off the supplied current acts to prevent ignition or explosive damage.

That is, when the battery internal pressure rises to a predetermined value set by the breaking strength of the thin portion 12f of the lower metal foil 12, the upper metal foil 11, which receives this pressure through the ventilation holes 12b and 12c, has its concave portion 11a inverted. And deforms upward, whereby the thin portion 12 of the lower metal foil 12 is deformed.
A shear force acts on f, and the thin portion 12f breaks. As a result, as shown in FIG. 3, the portion of the lower metal foil 12 surrounded by the air holes 12b, 12c and the thin portions 12f shown by vertical and parallel lines in FIG. At the same time, the two metal foils 11 and 12 that have been conductive only through the welded portion S are separated from each other, and the current is interrupted. Here, since the thin portion 11b of the upper metal foil 11 is set to have a higher breaking strength than the thin portion 12f of the lower metal foil 12, the upper metal foil 11 maintains the same state at the time of current interruption and the electrolyte is removed. As it prevents leakage, the electrolyte adheres to the PTC element 14,
The electrolyte does not leak out and corrode the equipment.

Thereafter, if the internal pressure of the battery further increases, the third explosion-proof safety function operates. That is, when a large amount of gas or vapor is generated and the internal pressure of the battery reaches a predetermined value set by the breaking strength of the thin portion 11b of the upper metal foil 11, the thin portion 11b is cleaved and the filled gas becomes a metal. The battery is exhausted to the outside of the battery through the exhaust hole 17a of the cap 17 to prevent the battery from being ruptured.

Next, the features of the explosion-proof sealing plate will be described. This explosion-proof sealing plate has ventilation holes 12b and 12c and a thin portion 12f formed in the lower metal foil 12 as shown in FIG.
Is provided, even if the thin portion 12f is formed by easy processing that does not require high precision control,
A remarkable effect that the current cutoff pressure can be set accurately can be obtained. That is, as shown by the vertical and parallel lines in FIG. 2A, the portion of the lower metal foil 12 surrounded by both the air holes 12b and 12c and both the thin portions 12f has a battery internal pressure of a predetermined value as described above. It is a location that is hollowed out when it reaches, and a laser irradiation location when forming the welded portion S by laser welding.
By setting the distance L between the main body hole 12d of the ventilation hole 12c and the main body 2b to a required value, it is possible to secure substantially the same space as the laser irradiation location shown in FIG.

As described above, a pair of projecting holes 12e is formed in the ventilation hole 12c while setting a portion surrounded by the two ventilation holes 12b and 12c and the two thin portions 12f as a required laser irradiation space. Therefore, both thin portions 12f are
The length D is much shorter than in the case of FIGS. 5 and 6, and when the breaking strength is set to be equal to that of FIGS. 5 and 6, the thickness is reduced by the length D. Can be increased. The thin portion 12 thus formed to have a relatively large thickness
f can be manufactured almost exactly to a predetermined breaking strength without performing processing for controlling the marking means with high precision. Thereby, the conventional problem that the thin portion 12f on one side is broken during processing or the thin portion 12f is broken in the step of caulking the metal case 18 in the explosion-proof sealing plate inward can be solved. Manufacturing yield is greatly improved.

On the other hand, the formation site of the welded portion S in the lower metal foil 12 is substantially the same as that of FIGS.
It is set at an intermediate position (L / 2) of the distance L between the hole b and the body hole 12d of the ventilation hole 12c, that is, at the center of each of the metal foils 11 and 12. However, the formation site of the welded portion S is:
Since the thin portion 12f is deviated rightward in FIG. 2A with respect to the thin portion 12f, the thin portion 12f is pulled by the welded portion S deviated rightward in the drawing and is torn off.
Therefore, even if the welded portion S of the lower metal foil 12 is formed slightly displaced from the predetermined portion, the welded portion S is formed in the thin portion 12f.
Because it is set to a position biased from the beginning,
There is almost no effect on the current interruption pressure.

Therefore, the current interrupting pressure can always be set to a constant value, and the thin portion 12f is reliably broken when the battery internal pressure rises to a constant value.

In the explosion-proof sealing plate, the current breaking pressure is set by the breaking strength of the thin portion 12f of the lower metal foil 12, so that the welded portion S of the two metal foils 11, 12 is firmly welded by laser welding. Can be formed. Next, the means for forming the welded portion S will be described with reference to FIG.
As shown in FIG. 4A, the concave dimension from the lower surface of the flat peripheral portion of the upper metal foil 11 to the tip of the concave portion 11a is d.
1, the convex portion 1 from the upper surface of the flat peripheral portion of the lower metal foil 12
2a, the protrusion dimension up to the tip is d2, and the insulating gasket 13
Is E, the explosion-proof sealing plate has d1 + d2
> E.

When forming the welded portion S, FIG.
As shown in FIG. 1B, the upper and lower fixing jigs 21 and 22 are formed by interposing the peripheral edges of both metal foils 11 and 12 with an insulating gasket 13 therebetween.
And fix it. At this time, as is clear from the dimensional relationship of d1 + d2> E, after the central portions of the concave portions 11a and the convex portions 12a, that is, the respective tip portions, come into contact with each other, and then the two metal foils 11, 12 further approach each other. As a result, the concave portion 11a and the convex portion 12a are slightly bent, and the respective contact portions of the concave portion 11a and the convex portion 12a are strongly pressed against each other by a restoring force due to bending, and there is no gap. Ensure contact with the condition. Since laser welding is performed by irradiating the laser beam C from the laser welding machine 23 to each contact portion of the concave portion 11a and the convex portion 12a, there is no poor contact or perforation, and the welding portion has a strong welding strength. S can be formed with good yield.

In the above embodiment, only one vent hole 12c of the pair of vent holes 12b and 12c has a U-shape. However, both vent holes have a U-shape. For example, in the lower metal foil 12, the length of the thin portion 12f can be further shortened while securing a laser irradiation portion having a space necessary for forming the welded portion S, and a more reliable thin wall can be obtained. The part 12f can be formed.

[0036]

As described above, according to the explosion-proof sealing plate for a sealed battery of the present invention, at least one of the ventilation holes of the pair formed in the lower metal foil is formed by the main body hole and the pair of projecting holes. And the two thin portions are provided so as to connect between the end edge of the pair of protrusion holes and the edge of the other ventilation hole, respectively. The length of the thin portion of the strip becomes significantly shorter. As a result, the thin portion can be set to a predetermined breaking strength by increasing the thickness by the reduced length. Therefore, a highly reliable thin portion can be formed by easy processing, and the production yield is greatly improved. In addition, the welded portions formed at the respective central portions of the two metal foils are biased toward the protruding hole with respect to the thin portion, and the thin portion is pulled from one side and broken in a state where the thin portion is peeled off. Thereby, even if the welded portion is formed slightly displaced from the predetermined portion,
Since there is almost no effect on the current cutoff pressure, the current cutoff pressure can always be set to a constant value. Also, by setting the distance between the main body hole of one of the ventilation holes and the other ventilation hole to a required value, it is possible to secure a laser irradiation location having a space necessary for welding both metal foils by laser welding. it can.

Further, a flexible concave portion is provided in the central portion of the upper metal foil, and a flexible convex portion is provided in the central portion of the lower metal foil, and each of the concave portion and the convex portion is provided. If the welded portion is formed in a state where the central portions are in elastic contact with each other, the concave portion and the convex portion are slightly bent after the respective tip portions come into contact with each other, and the contact portion is restored by the restoring force. Are strongly pressed against each other, so that the respective leading end portions of the concave portion and the convex portion surely come into contact with no gap, so that a welded portion without defects can always be formed at the contact portion by laser welding.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention.

FIG. 2 shows the lower metal foil of the explosion-proof sealing plate,
2 is a plan view, and FIG. 2B is a sectional view taken along line AA of FIG.

FIG. 3 is a longitudinal sectional view of the explosion-proof sealing plate in the operating state.

4A and 4B show a step of forming a welded portion on both metal foils of the explosion-proof sealing plate, wherein FIG. 4A is a longitudinal sectional view of a step of laminating two metal foils, and FIG. FIG. 4 is a longitudinal sectional view of a welding process.

FIG. 5 is a longitudinal sectional view showing a conventional explosion-proof sealing plate for a sealed battery.

FIG. 6 shows a lower metal foil of the explosion-proof sealing plate according to the first embodiment;
2 is a plan view, and FIG. 2B is a sectional view taken along line BB of FIG.

FIG. 7 is a longitudinal sectional view of a welding step of welding two metal foils on the explosion-proof sealing plate.

[Explanation of symbols]

 Reference Signs List 11 upper metal foil 11a concave portion 12 lower metal foil 12a convex portion 12b other ventilation hole 12c one ventilation hole 12d main body hole 12e projecting hole 12f thin portion 13 insulating gasket S welding portion

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-203818 (JP, A) JP-A-6-169139 (JP, A) JP-A-9-129195 (JP, A) JP-A 8- 115714 (JP, A) JP-A-8-115715 (JP, A) JP-A-9-161753 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/12 101 H01M 2/34

Claims (2)

(57) [Claims] An upper and a lower conductive metal foil are stacked with an insulating gasket interposed between their peripheral edges, and are electrically connected to each other via a welded portion in which respective central portions are welded to each other. The lower metal foil has a pair of air holes for applying a battery internal pressure to the upper metal foil, and two easy-to-break thin portions connecting between two opposing edge portions of the air holes. but sealed battery for proof which is formed annularly to surround the weld portion
At least one of the pair of ventilation holes is formed in a substantially U-shape in which a pair of projecting holes are continuously provided inward on both ends of the main body hole . One end of the two easily breakable thin-walled portions has the pair of protrusion holes.
Are formed so as to be connected to the edge of the tip hole of
The breaking strength is set to a value that breaks when the internal pressure of the battery acting on the upper metal foil reaches a predetermined value.
Anti爆封port plate for a sealed battery wherein the are. 2. The upper metal foil is provided with a flexible concave portion whose central portion swells downward, and the lower metal foil has a flexible convex whose central portion swells upward. A convex portion is provided, and two easily rupturable thin portions are formed in the convex portion, and the central portion of each of the concave portion and the convex portion is welded and welded in a state of elastically contacting each other. The explosion-proof sealing plate for a sealed battery according to claim 1, wherein a portion is formed.