JP2000082457A - Electric/electronic equipment and part safeguard, sealed battery safeguard using it and sealed battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrical/electronic equipment and part safeguard capable of preventing bursting as much as possible due to sharp increase of inner pressure arising in overcharge or a short circuit and preventing the release of generated decomposed gas to the outside and ensuring manufacture at a low cost, a safeguard for an electrolyte capacitor and a sealed battery for using it and a sealed battery using it. SOLUTION: A positive electrode cover 16 to be mounted at one end of an exterior can 11 consists of a pressure receiving plate 18 forming an innermost cover and to be connected to a positive electrode 13 of an electrode body 12 via a positive electrode lead 17, a shielding plate 20 for forming an intermediate cover and having a protruded contact portion 19 at the center for electrically contacting the pressure receiving plate and a sealing plate 21 forming an outermost cover and to be electrically connected to the shielding plate. A closed space 22 is formed between the pressure receiving plate 18 and the shielding plate 20, first and second communication portions 23, 24 are formed on the pressure receiving plate 18 and the shielding plate 20, which burst when pressure in the exterior can 11 and pressure in the closed space 22 which exceed a first set bursting pressure and a second set bursting pressure higher than the first set burst pressure, respectively, and a gas vent hole 31 is formed in the sealing plate 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for interrupting and generating a current path in an electric / electronic device / part when an internal pressure of the electric / electronic device / part such as a battery or an electrolytic capacitor rises due to a gas generated by overcharge or short circuit. The present invention relates to a safety device for electric / electronic devices and components capable of preventing explosion or explosion by releasing gas to the outside, a safety device for a sealed battery using the same, and a sealed battery using the same.

[0002]

2. Description of the Related Art In recent years, secondary batteries using a non-aqueous electrolyte for lithium batteries and lithium ion batteries using a non-aqueous electrolyte have been widely used in portable electronic devices and the like. Such a secondary battery has a feature of having a high electromotive force, but on the other hand, an electrode body including a positive electrode and a negative electrode housed in an outer can undergoes a chemical change to increase the internal pressure, which may cause rupture. For example, when a non-aqueous electrolyte battery such as a lithium secondary battery is overcharged or short-circuited due to misuse and a large current flows, the non-aqueous electrolyte in the electrode body is decomposed and gas May occur. Such a gas gradually fills the outer can, and when the internal pressure in the outer can increases, the battery eventually bursts.

In order to prevent such a rupture of the battery, various portable sealed batteries have been developed in the past, and as one form, a sealed battery having a structure shown in FIG. 5 has been proposed.

As shown in FIG. 5, a positive electrode 53, a separator 54 and a negative electrode 55 are provided in an outer can 51 also serving as a negative electrode terminal.
The electrode body 52 formed by spirally winding the laminate of the above is stored. A group of sealing lids 56 that also serves as an explosion-proof function and terminal
Is caulked and fixed to the upper end opening of the outer can 51 via an insulating gasket 57. The closing lid group 56 includes an intermediate lid 60 having a downwardly projecting portion 58 at the center and a downwardly extending annular projecting portion 59 formed outside the projecting portion 58. The plurality of linear grooves 61 are formed radially on the upper surface of the intermediate cover 60 located between the protrusion 58 and the annular protrusion 59. The bottom portion of the linear groove 61 functions as a valve membrane. The periphery of the hat-shaped closing lid 63 having the gas vent hole 62 is disposed on the intermediate lid 60,
The closing lid 63 is sandwiched by the intermediate lid 60 by bending the peripheral edge of the lid inward. Intermediate lid 60 and lid 6 for closing
The periphery of 3 is caulked and fixed to the upper end opening of the outer can 51 via an insulating gasket 57 in an airtight state. The lead stopper 64 made of an insulating material having a bottomed cylindrical shape is used to
Is fitted to the annular projection 59 of the first embodiment. Lead stopper 6
An insertion hole 65 into which the protrusion 58 of the intermediate lid 60 is inserted is opened at the center of the fourth cover 4. Multiple vent holes 66
Are formed in the lead stopper 64 concentrically around the insertion hole 65. The positive electrode lead plate 67 is attached to the back surface of the lead stopper 64 so as to cover at least the insertion hole 65, and the projection 58 of the intermediate lid 60 inserted into the insertion hole 65 is connected by welding. One end of the positive electrode lead 68 is connected to the positive electrode 53 of the electrode body 52, and the other end is connected to the positive electrode lead 68.

In a non-aqueous electrolyte battery having such a configuration, when a current higher than usual, for example, a large current is applied due to an overcharge state, and the large current generates a decomposition gas,
The decomposed gas enters the space between the lead stopper 64 and the intermediate lid 60 and increases its internal pressure. As a result, the intermediate lid 60 is pressed toward the closing lid 63 by the internal pressure, so that the protruding portion 58 of the intermediate lid 60 welded to the positive electrode lead plate 67 is released, and the current path of the positive electrode is cut off. Further, the valve membrane corresponding to the plurality of linear grooves 61 of the intermediate lid 60 is broken by the internal pressure, and the decomposed gas escapes to the outside through the broken part of the valve membrane and the gas vent hole 62 opened in the closing lid 63. Therefore, the rupture of the battery is prevented beforehand due to the current interruption and the escape of the decomposition gas to the outside of the battery.

[0006]

However, in the conventional non-aqueous electrolyte battery provided with the sealing lid group 56 which also functions as an explosion-proof function and a terminal, when the valve membrane is broken, the decomposition gas is always released to the outside. It will harm the human body and pollute the environment.

Also, since this type of battery has a structure in which the internal pressure of the battery directly acts on the intermediate lid 60, the battery repeatedly contacts the welding contact portion consisting of the projection 58 and the lead stopper 68 each time the pressure fluctuates. A tensile stress is generated, and it becomes difficult to maintain a stable contact breaking pressure accuracy. Since both the welding strength of the contact and the strength of the intermediate cover 60 directly have the shut-off pressure accuracy, in order to realize a high-accuracy shut-off pressure accuracy, the protrusions 5 are required.
In addition to the size, shape, thickness of the intermediate lid 60, and other design constraints, a high-precision welding technique is required. Furthermore, in order to realize a burst pressure with a small variation in a valve membrane forming a burst mechanism, high-precision processing technology and stability are required.

Further, when a corrosive electrolytic solution is used for the battery solution, the contact portion is directly affected by the electrolytic solution or gas, and the contact portion is corroded.

The present invention is intended to solve such a problem, and it is possible to prevent bursting due to a sudden increase in internal pressure that occurs at the time of overfilling or short circuit while preventing outflow of decomposition gas, and It is an object of the present invention to provide a safety device for electric / electronic devices and parts which can be manufactured at low cost, an electrolytic capacitor using the same, a safety device for a sealed battery, and a sealed battery using the same.

[0010]

According to a first aspect of the present invention, there is provided a safety device for electric / electronic equipment / parts.
The current interrupting function part of the electric / electronic device / part is configured so that the contact portion is sealed with a pressure receiving plate, an insulating ring, a shielding plate, etc., and a communication hole communicating with the pressure receiving plate at a predetermined pressure is provided. With the communication, the internal pressure of the electric / electronic device / part is applied between the pressure receiving plate and the shielding plate, and the pressure causes the convex portion or the bent portion of the blocking plate to peel off and deform from the pressure receiving plate to interrupt the electrical conduction. It is characterized by having done.

Therefore, the contact portion is normally held in the closed space, so that the electrical connection between the pressure receiving plate and the shielding plate is reliably ensured through the convex portion or the bent portion. On the other hand, when the internal pressure in the battery rises sharply and exceeds the set breaking pressure, the communication hole communicates, and the convex portion or the bent portion is reversed or separated due to the internal pressure of the electric / electronic device or component, and the electric pressure between the pressure receiving plate and the shielding plate is increased. The conduction is cut off to prevent further generation of the decomposition gas and the like, and to prevent the decomposition gas from flowing out.

According to a second aspect of the present invention, there is provided a safety device for a sealed battery according to the present invention, wherein a positive electrode cover attached to one end of an outer can forms an innermost cover and is connected to an electrode body via a positive electrode lead. A pressure-receiving plate connected to the positive electrode, a shielding plate forming an intermediate lid and having a contact portion in the central portion that is in electrical contact with the pressure-receiving plate, and an outermost lid formed and electrically connected to the shielding plate A sealing space is formed between the pressure receiving plate and the shielding plate, and the pressure in the outer can is the first set breaking pressure and the pressure in the outer can, respectively, in the pressure receiving plate and the shielding plate. Second higher than the first set breaking pressure
The first and second communication portions that break when the set breaking pressure is exceeded are formed, and a gas vent hole is formed in the sealing plate.

Therefore, normally, in the closed space, the electrical continuity between the pressure receiving plate and the shielding plate is reliably ensured through the protruding contact portion. On the other hand, when the internal pressure in the battery rises sharply and exceeds the first set breaking pressure, the first communication portion is broken, and the contact portion is deformed by the pressure of the decomposition gas, and the electrical connection between the pressure receiving plate and the shielding plate is performed. To prevent further generation of the decomposed gas and to prevent the decomposed gas from flowing out. Next, in spite of the above-mentioned electrical interruption, if a chemical reaction in the outer can progresses to generate decomposition gas and the internal pressure further increases and exceeds the second set breaking pressure,
When the second communication portion breaks, the decomposition gas is converted into the first gas.
Of the sealed battery is prevented from exploding through the communication part, the closed space, the second communication part, and the gas vent hole. Here, the set breaking pressure of the first and second communication portions is set to, for example, 4 to 30 kgf / cm ² . In addition,
These set breaking pressures can be arbitrarily set by changing the hole diameters and shapes of the first and second communication portions, the material and thickness of the metal foil.

The safety device for a sealed battery according to the second aspect of the present invention also has the following features. The pressure receiving plate is formed of a clad metal plate in which a metal foil is laminated and adhered to a metal substrate provided with a predetermined hole, and the first communication portion includes:
It will be formed by the portion of the metal foil that seals the hole. Here, aluminum, iron, copper,
Stainless steel or the like can be used, and its thickness is 0.1
mm to about 0.6 mm. On the other hand, as the metal foil, nickel, aluminum, copper, or the like can be used, and its thickness is about 10 μm to 50 μm. The shielding plate is also made of a clad metal plate in which a metal foil is laminated and adhered to a metal substrate provided with a predetermined hole, and the second communication portion is
It will be formed by the portion of the metal foil that seals the hole. Here, the thickness of the metal plate is 50 μm to 0.2 μm.
mm and the thickness of the metal foil is about 10 μm to 50 μm.

In the above description, the clad metal plate may be, for example, 1 × 10 ^-1 to 1 × 10 ^-4 Torr as disclosed by the present applicant in Japanese Patent Application Laid-Open No. 1-2224184.
In a very low pressure inert gas atmosphere, a metal substrate having a joint surface and a metal foil are each grounded to one electrode A, and an alternating current of 1 to 50 MHz is applied between the electrode A and the other electrode B which is insulated and supported. Then, the glow discharge is performed, and the area of the electrode exposed to the plasma generated by the glow discharge is 1/3 or less of the area of the electrode B.

By sealing an inert gas such as an argon gas or a nitrogen gas in the closed space, it is possible to more reliably prevent the protruding contact portion of the shielding plate from being corroded and the conduction with the pressure receiving plate from being deteriorated. . The contact portion of the shielding plate may be spot-welded or brazed to the pressure receiving plate, or may be brought into contact with the pressure receiving plate by utilizing the elastic force of the contact portion. In addition, the shape of the contact portion of the shielding plate may be a projection, and welding or brazing may be performed. PTC (Po) consisting of an annular plate between the shielding plate and the sealing plate
The PTC thermistor element is interposed, and the PTC thermistor element raises the temperature of the safety device of the sealed battery and makes it difficult for the current to flow, thereby preventing the explosion due to the overcurrent from this aspect. I have to. A sealed battery according to a second aspect of the present invention for achieving the above object includes the above-described safety device for a sealed battery.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to an embodiment shown in the accompanying drawings. First,
A configuration of a safety device for a sealed battery according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 to 3, an electrode body 12 is housed in an outer can 11 also serving as a negative electrode terminal. The electrode body 12 includes a positive electrode 13,
The laminate of the separator 14 and the negative electrode 15 is spirally wound. A safety device for a sealed battery having both an explosion-proof function and a terminal is provided at an upper end opening of the outer can 11, and the safety device is substantially provided with a positive electrode lid 16 having the following configuration by using an insulating gasket. It is configured by caulking and fixing to the upper end opening of the outer can 11 via 16a.

In the safety device for a sealed battery having the above-described structure, as shown in FIGS.
A pressure receiving plate 18 which substantially forms the innermost lid and is connected to the positive electrode 13 of the electrode body 12 via the positive electrode lead 17;
A shielding plate 20 forming an intermediate lid and having a protruding contact portion 19 at the center thereof for electrically contacting the pressure receiving plate 18; and a sealing plate forming an outermost lid and electrically connected to the shielding plate 20. 21.

An enclosed space 22 is formed between the pressure receiving plate 18 and the shielding plate 20, and an inert gas such as an argon gas or a nitrogen gas is sealed in the enclosed space. In this closed space 22, the sealing plate 21 and the contact portion 19 are electrically connected to each other by welding to the pressure receiving plate 18, and the contact portion 19 of the shielding plate 20 is corroded by a decomposition gas or the like described later, The conduction with the plate 18 is prevented from being deteriorated.
The shape of the contact portion 19 may be formed as a protrusion as shown in FIG. 6 and connected to the pressure receiving plate 18. in this case,
Welding may or may not be performed at the contact portion 19. FIGS. 7 and 8 correspond to FIGS. 2 and 3 when the contact portion 19 is connected to the pressure receiving plate 18 by making the shape of the contact portion 19 into a protruding shape.
FIG. 9 shows a case where a PCT thermistor is provided corresponding to FIG.

The pressure receiving plate 18 and the shielding plate 20 have the outer can 11
And the pressure in the closed space 22 are respectively set to a first set breaking pressure P1 (for example, 4 to 5 kgf / cm ² ),
The first and second communication portions 23 and 24 are formed such that the first and second communication portions 23 and 24 are broken when the pressure becomes equal to or higher than the set breaking pressure P2 (for example, 20 kgf / cm ² ). The pressure receiving plate 18 has a thin (for example, 0.4 mm) metal substrate 26 having a communication hole 25 on the lower surface of a thin (for example, aluminum) metal substrate 26.
20 μm) by bonding a metal foil 27 using a cladding technique or the like.
Is formed by the communication hole 25 and a portion of the metal foil 27 that seals the communication hole 25.

The shielding plate 20 is also made of a thick (for example, 0.1 mm) metal substrate 29 made of nickel and having a communication hole 28.
Is made of thin aluminum (for example, 20 μm)
m) by adhering the metal foil 30 using a cladding technique or the like, and the second communication portion 24 is formed by the communication hole 28 and the portion of the metal foil 30 that seals the communication hole 28. You. The contact portion 19 of the shielding plate 20 is
The contact portion 19 can be contacted with the pressure receiving plate 18 by spot welding or brazing, or by utilizing the elastic force of the contact portion 19. In addition, as shown in FIG. 1, the contact portion 19 projects downward when not receiving the pressure of the later-described decomposition gas.
As shown in FIG. 2, the decomposition gas flows into the closed space 22 and is turned upside down to protrude upward.

A plurality of gas vent holes 31 are formed in the sealing plate 21. Next, the operation of the safety device for a sealed battery having the above configuration will be described with reference to FIGS. In the above sealed battery, as long as a normal current flows, no decomposition gas is generated in the outer can 11, and even if a small amount of gas is generated, the hermeticity of the sealed space 22 is completely ensured. Therefore, it is possible to reliably prevent the protruding contact portion 19 of the shielding plate 20 from being corroded and the conduction with the pressure receiving plate 18 from being deteriorated, and the battery function can always be normally maintained.

On the other hand, for example, when a large current flows due to an overcharged state, a decomposition gas having high corrosiveness is generated in the outer can 11 due to the large current, and the pressure in the outer can 11 increases. The sealed battery will explode.
However, in the present embodiment, the pressure in the outer can 11 is the first pressure.
When the pressure exceeds the first set breaking pressure P1 of the communication portion 23, the metal foil 27 in the first communication portion 23 as shown in FIG.
Is broken first, the decomposition gas flows into the closed space 22 from the inner space of the outer can 11, and the pressure of the decomposition gas causes the contact portion 19 to be inverted and convex upward, so that the pressure receiving plate 18 and the shielding plate 20 And the electrical continuity is quickly interrupted. Therefore, preventing further generation of decomposition gas,
It is possible to reliably prevent the internal pressure of the outer can 11 from further increasing and exploding, and to prevent the decomposition gas harmful to the human body from flowing out to the outside because the second communication portion 24 has not been broken yet. Can be prevented, and environmental protection can be achieved.

Further, in spite of the interruption of the electrical conduction, a chemical reaction proceeds in the outer can 11,
When the decomposed gas is further generated and the internal pressure rises and exceeds the second set breaking pressure P2, as shown in FIG. 3, the portion of the metal foil 27 in the second communication portion 24 is broken, and the decomposed gas is discharged. Since the gas is quickly discharged from the sealed space 22 to the outside through the space between the shielding plate 20 and the sealing plate 21 and the gas vent hole 31 provided in the sealing plate 21, the explosion of the sealed battery is reliably prevented. be able to. As described above, by using the safety device for a sealed battery according to the present embodiment, it is possible to reliably shut off the current and release the decomposed gas to the outside of the battery, thereby preventing the sealed battery from exploding. be able to. Further, by releasing the decomposed gas to the outside of the battery only in the unlikely event that the gas is depleted, adverse effects on the human body and the environment can be suppressed as much as possible.

FIG. 4 shows a modification of the safety device for a sealed battery according to the present embodiment. As shown in the drawing, the present modified example is configured such that, in the sealed battery safety device described with reference to FIGS. 1 to 3, between the shielding plate 20 and the sealing plate 21,
Further, a PTC thermistor element 32 made of an annular plate is provided. With this configuration, when the temperature of the safety device of the sealed battery rises due to the generation of the decomposition gas, it is difficult to flow the current, and the explosion due to the overcurrent can be prevented from this aspect.

[0026]

As described above, the safety device for electric / electronic devices and parts according to the first aspect of the present invention adopts a sealed structure at the contact portion, so that current can be reduced without requiring high-precision processing or welding. The variation of the cutoff pressure is reduced, and the contacts are not corroded by the electrolyte or the like. Further, when an excess current flows, the electric connection between the pressure receiving plate and the contact between the pressure receiving plate and the shielding plate can be quickly interrupted by utilizing the pressure of the generated gas to communicate with the communication hole. By preventing generation, explosion and explosion of electric and electronic devices and parts can be surely prevented.

In the safety device for a sealed battery according to the second aspect, when a normal current flows, the contact portion between the pressure receiving plate and the shield plate is brought into airtight contact with the sealed space in the sealed space to normally operate the sealed battery. In addition to being able to operate, when an excess current flows, the first communication portion is broken by utilizing the pressure of the generated decomposition gas to quickly cut off the electrical connection between the pressure receiving plate and the contact of the shielding plate. At the same time, when the pressure of the decomposition gas further increases, the second communication portion is broken and can be quickly discharged to the outside of the battery, so that the current is cut off and the decomposition gas is discharged to the outside of the battery reliably. Therefore, the rupture of the sealed battery can be prevented.
Further, by releasing the decomposed gas to the outside of the battery only in the unlikely event that the gas is depleted, adverse effects on the human body and the environment can be suppressed as much as possible.

In the safety device for a sealed battery according to the third aspect, a pressure-receiving plate that operates reliably by cladding a metal foil on a metal substrate provided with a predetermined hole can be easily manufactured. In the safety device for a sealed battery according to the fourth aspect, it is possible to easily manufacture a shielding plate that reliably operates by cladding a metal foil on a metal substrate provided with a predetermined hole. In the safety device for a sealed battery according to the fifth aspect, when the inert gas such as argon gas or nitrogen gas is sealed in the sealed space, the protruding contact portion of the shielding plate is corroded, and the sealing member is in contact with the pressure receiving plate. Deterioration of conduction can be prevented, and normal operation of the battery at normal times can be ensured. In the safety device for a sealed battery according to claim 6, the protruding contact portion of the shielding plate is spot-welded or brazed to the pressure receiving plate until the conduction is interrupted by generation of decomposition gas. Reliable conduction can be achieved. Also, by using the clad material, only the metal foil causes plug breakage at the time of peeling of the welded portion, so that a hole is not opened at the time of interruption (there is no risk of liquid leakage). Furthermore, since welding conditions can be widely set, it is possible to adopt a low-precision welding method such as spot welding. Claim 7
In the above-described safety device for a sealed battery, the structure of the contact portion can be simplified by making contact with the pressure receiving plate using the elastic force of the contact portion. Claim 8
In the safety device for a sealed battery described in the above, a PTC thermistor element composed of an annular plate is interposed between the shielding plate and the sealing plate, and the PTC element makes it difficult for current to flow. Explosion can be prevented. In the sealed battery according to the ninth aspect, by providing the sealed battery safety device according to the third to eighth aspects, a sealed battery with high performance and high safety can be manufactured at low cost.
Although the above description has mainly been given of a sealed battery, the present invention can be applied to other electric / electronic devices and components such as an electrolytic capacitor having a similar structure.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a safety device for a sealed battery which is an example of a safety device for electric / electronic devices and components according to an embodiment of the present invention in a normal use state.

FIG. 2 is a configuration explanatory view of a safety device for a sealed battery according to one embodiment of the present invention in a state where a first communication portion is broken.

FIG. 3 is a configuration explanatory view of a safety device for a sealed battery according to one embodiment of the present invention in a state where a second communication portion is broken.

FIG. 4 is a configuration explanatory view of a safety device for a sealed battery according to a modification of the embodiment of the present invention, which includes a PTC thermistor element.

FIG. 5 is a configuration explanatory view of a conventional safety device for a sealed battery.

FIG. 6 is a configuration explanatory view of a safety device for a sealed battery, which is an example of a safety device for electric / electronic devices / parts according to another embodiment of the present invention when a contact portion has a projection shape.

FIG. 7 is a configuration explanatory view of a safety device for a sealed battery according to another embodiment of the present invention in a state where a first communication portion is broken when a contact portion is formed in a projecting shape.

FIG. 8 is a configuration explanatory view of a safety device for a sealed battery according to another embodiment of the present invention in a state where a second communication portion is broken when a contact portion is formed in a projecting shape.

FIG. 9 is a configuration explanatory view of a safety device for a sealed battery according to a modification of another embodiment of the present invention including a PTC thermistor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Outer can 12 Electrode body 13 Positive electrode 16 Positive electrode cover 17 Positive electrode lead 18 Pressure receiving plate 19 Contact part 20 Shielding plate 21 Sealing plate 22 Sealed space 23 First communicating part 24 Second communicating part 25 Communication hole 26, 29 Metal substrate 27 Metal foil 28 Communication hole 30 Metal foil 31 Gas vent hole 32 PTC thermistor element

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuyuki Okamoto 1302 Higashitoyoi, Kudamatsu City, Yamaguchi Prefecture Toyo Kohan Co., Ltd. (72) Inventor Hiroaki Hironaka 1302 Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture Toyo Kohan Co., Ltd. F-term in the Kudamatsu Plant (Reference)

Claims (9)

[Claims] 1. A current interrupting function portion of an electric / electronic device or component is configured such that a contact portion is sealed with a pressure receiving plate, an insulating ring, a shielding plate, or the like, and a communication hole communicating with the pressure receiving plate at a predetermined pressure is provided. With the communication of the communication hole, the internal pressure of the electric / electronic device / part is caused to act between the pressure receiving plate and the shielding plate,
A safety device for electric / electronic equipment / parts, wherein a convex portion or a bent portion of the blocking plate is peeled and deformed from the pressure receiving plate by the pressure to cut off electrical conduction. 2. A positive electrode lid attached to one end of an outer can forms a pressure receiving plate which forms an innermost lid and is connected to a positive electrode of an electrode body through a positive electrode lead, forms an intermediate lid, and has a A shielding plate having a contact portion that is in electrical contact with the pressure receiving plate, and a sealing plate that forms an outermost lid and is electrically connected to the shielding plate, between the pressure receiving plate and the shielding plate. A sealed space is formed in the pressure receiving plate and the shielding plate, and the pressure receiving plate and the shielding plate break when the pressure in the outer can exceeds a first set breaking pressure and a second set breaking pressure higher than the first set breaking pressure, respectively. A safety device for a sealed battery, wherein first and second communication portions are formed, and a gas vent hole is formed in the sealing plate. 3. The pressure receiving plate comprises a clad metal plate in which a metal foil is clad on a metal substrate provided with a predetermined hole, and the first communication portion is formed by a portion of the metal foil that seals the hole. The safety device for a sealed battery according to claim 2, wherein the safety device is formed. 4. The shielding plate is made of a clad metal plate in which a metal foil is laminated and adhered to a metal substrate provided with a predetermined hole, and the second communication portion is a portion of the metal foil that seals the hole. The safety device for a sealed battery according to claim 3, wherein the safety device is formed by: 5. The safety device for a sealed battery according to claim 3, wherein an inert gas is sealed in the sealed space. 6. The contact portion of the shielding plate is spot-welded or brazed to the pressure-receiving plate.
6. The safety device for a sealed battery according to any one of 5. 7. The safety device for a sealed battery according to claim 1, wherein a contact portion of the shield plate is in contact with the pressure receiving plate by an elastic force held by the contact portion. 8. The safety of a sealed battery according to claim 1, wherein a PTC thermistor element formed of an annular plate is interposed between the shielding plate and the sealing plate. apparatus. 9. A sealed battery comprising the safety device for a sealed battery according to claim 1.