WO2001011701A1

WO2001011701A1 - Safety device for closed cell and closed cell comprising the same

Info

Publication number: WO2001011701A1
Application number: PCT/JP2000/005283
Authority: WO
Inventors: Hiroaki Kawamura; Akira Kaneko; Hiroaki Okamoto; Kunio Nishimura
Original assignee: Toyo Kohan Co., Ltd.
Priority date: 1999-08-05
Filing date: 2000-08-07
Publication date: 2001-02-15
Also published as: TW471196B; AU6320200A; JP3983050B2

Abstract

A safety device for a closed cell, for preventing rupture due to a sudden increase of the inner pressure caused by overcharging and short circuit. The safety device can be manufactured at low cost and comprises a positive plate cap (16) including a pressure-receiving plate (18) constituting an innermost cap, a shield plate (20) constituting an intermediate cap, and a sealing plate (21) constituting an outermost cap. A projection (28) of the pressure-receiving plate (18), in a first flat joining face (27), is joined to a second flat joining face (29) of the shield plate (20), thus forming a central joining part (19). A C-shaped groove (31) is formed around the second flat joining face (29). A strength-weakening groove (32) bending in such a direction in which the groove (32) is opposed to the C-shaped groove (31) is formed surrounded by the C-shaped groove (31). Between both ends (32a) of the strength-weakening groove (32) and portions (31a) away from both ends of the C-shaped groove (31) by predetermined distance, narrow portions (33) to be bent are formed.

Description

Description Sealed battery safety device and sealed battery using the same

The present invention relates to a sealed battery safety device having an explosion-proof function and a sealed battery using the same. Background art

In recent years, secondary batteries using non-aqueous electrolytes for lithium batteries and lithium ion batteries using non-aqueous electrolytes have been widely used in portable electronic devices and the like.

Such a secondary battery has a characteristic 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 assembly is decomposed and gas May occur. Such gas gradually fills the outer can, and when the internal pressure in the outer can rises, the battery eventually explodes.

Conventionally, various types of sealed batteries have been developed to prevent such battery ruptures. One form of the battery is a scoring plate-shaped shield plate attached as a safety device. There is.

This consists of a positive electrode lid attached to one end of the outer can, a metal pressure receiving plate that forms the innermost lid and is connected to the positive electrode of the electrode body via a positive electrode lead, an intermediate lid, and a central welded part. And a metal cap terminal that is electrically connected to the metal pressure receiving plate via a metal cover, and a metal cap terminal that forms the outermost lid and is electrically connected to the metal shield plate. With the above configuration, when the internal pressure of the battery rises, the central welded portion is broken to cut off the electrical connection between the metal pressure receiving plate and the metal shielding plate, and also destroy the scored part of the metal shielding plate. As a result, the gas inside the battery can be discharged to the outside, and the battery can be prevented from exploding.

However, the conventional sealed battery described above still has the following problems to be solved. In other words, the center weld is formed by spot welding the center of the metal pressure plate to the center of the metal shield plate by spot welding, but the spot welding is performed so that the spot weld is broken. Since it is extremely difficult to achieve uniformity, the welding strength will vary from one sealed battery to another. As a result, the internal pressure of the battery that cuts off the electrical connection between the metal pressure receiving plate and the metal shielding plate is not constant.Depending on the sealed battery, even though the internal pressure of the battery has reached the set cutoff pressure, The state in which the electrical connection between the metal pressure receiving plate and the metal shielding plate is not interrupted may occur, which significantly impairs the reliability of the sealed battery for safety.

The present invention is intended to solve such a problem. When the internal pressure of the battery rises above a certain level, the electric connection between the pressure receiving plate and the shield plate can be surely cut off. An object of the present invention is to provide a sealed battery safety device capable of sufficiently ensuring safety and a sealed battery provided with the safety device. Disclosure of the invention

In order to achieve the above object, a sealed battery safety device according to the present invention includes a positive electrode lid attached to one end of an outer can, which is formed with an innermost lid and connected to a positive electrode of an electrode body via a positive electrode lead. A pressure receiving plate, a shielding plate forming an intermediate lid and electrically connected to the pressure receiving plate via a central joint, and a sealing plate forming an outermost lid and being electrically connected to the shielding plate. Gas pressure holes are provided in the pressure receiving plate, and the inner space of the outer can communicates with the joint operating space formed between the pressure receiving plate and the shielding plate, and the central joint is shielded from the center of the pressure receiving plate. Projecting toward the plate and having a first flat joining surface The first flat joint surface of the projection provided at the center of the shield plate is formed from a second flat joint surface that abuts sexually, and the first flat joint surface of the projection is formed around the second flat joint surface of the shield plate. ° A C-shaped groove is provided concentrically with an arc angle of at least, and a strength reduction groove is formed at a position inside the C-shaped groove of the shielding plate, and both ends of the strength reduction groove and the C-shaped groove are formed. A narrow bent portion is formed between the portion that is receded a predetermined distance from both ends, and a metal foil is bonded to the side of the pressure receiving plate of the shielding plate to form a valve membrane in each of the C-shaped groove and the strength reducing groove. When the pressure in the outer can exceeds the set current interrupting pressure, the shield plate is bent in an upwardly protruding state along the portion to be bent, and the second flat joint surface of the shield plate receives the first pressure receiving plate. The electrical connection between the pressure receiving plate and the shielding plate is interrupted by breaking the thin film around the flat joint of the It said leaflets and the pressure exceeds the setting membrane rupture pressure is to be broken.

Therefore, in the enclosed space, the electrical continuity between the pressure receiving plate and the shield plate is always established by connecting the first flat joint surface provided on the projection of the pressure plate to the second flat joint surface of the shield plate by spot welding or the like. It is ensured by joining. On the other hand, when the internal pressure in the battery rises sharply and exceeds the set current cutoff pressure, the pressure of the decomposition gas causes the shielding plate, especially the second flat joining surface of the shielding plate to have the first flat surface of the pressure receiving plate. The breakage of the thin film around the joint surface cuts off the electrical continuity between the pressure receiving plate and the shielding plate, thereby preventing further generation of the decomposition gas and preventing the decomposition gas from flowing out. At this time, a narrow bent portion is formed between both ends of the strength reducing groove provided inside the C-shaped groove surrounding the second flat joint surface and a portion receded by a predetermined distance from both ends of the C-shaped groove. When the internal pressure in the battery suddenly rises and exceeds the set current cutoff pressure, the shielding plate is easily bent along the bent portion, and the material around the joint on the first flat joint surface is formed. By breaking, the second flat joint surface rises and quickly separates. Therefore, the electrical continuity between the pressure receiving plate and the shielding plate can be quickly and reliably interrupted by the set current interruption pressure. At this time, since the shielding plate is plastically deformed, it is necessary to reliably prevent the second flat joint surface from coming into contact with the first flat joint surface again. Can be. In addition to the shielding plate having such a C-shaped groove, the bottom thin portion of the concave groove may be formed by scoring or the like, and the bottom thin film may serve as a valve membrane. Next, despite the above-mentioned electrical interruption, if the chemical reaction in the outer can progresses to generate decomposition gas and the internal pressure further rises and exceeds the set membrane breaking pressure, the shielding plate When the provided valve membrane breaks, the decomposed gas is released to the outside through the gas flow holes, the joint operating space, the valve membrane, and the gas vent holes provided in the pressure receiving plate, preventing the sealed battery from exploding. it can. Here, preferably, the set current cutoff pressure is 1/2 of the set membrane break pressure. The set film breaking pressure is set to 10 to 30 kg / cm ² .

In addition, the safety device for a sealed battery according to the first aspect of the present invention has the following features.

(1) The strength-reducing groove is formed from an arc-shaped groove that is bent in the direction opposite to the C-shaped groove, and both ends of the strength-reducing groove are arranged in an overlapping state at both ends of the C-shaped groove.

(2) The low-strength groove may be formed by a linear groove that is arranged linearly and connects the portions that are recessed by a predetermined distance from both ends of the C-shaped groove.

③ The inside and outside of the C-shaped groove can be connected by a plurality of connecting tabs arranged in an arc.

(4) The shielding plate is made of a metal foil and a clad metal plate clad with the metal plate, and the valve membrane is formed by a portion of the metal foil covering the inner annular groove and the outer annular groove. Preferably, the thickness of the metal plate is about 0.2 to 0.5 mm, and the thickness of the metal foil is about 20 to: L00 m.

Further, such a clad metal plate has, for example, an electrode of 13.3 to 0.013 Pa, as disclosed by the present applicant in Japanese Patent Application Laid-Open No. 1-2224184. In a low-pressure inert gas atmosphere, a metal substrate with a bonding 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 other electrode B that is insulated and supported. To cause a glow discharge, and exposure to plasma generated by the glow discharge. The area of the output electrode is 1 Z 3 or less of the area of the electrode B, and the electrode can be manufactured by performing a sputter etching process.

薄膜 By breaking the thin film around the first flat joint surface of the pressure receiving plate, the electrical conduction between the pressure receiving plate and the shielding plate is interrupted to prevent further generation of decomposed gas, Prevent it from leaking outside. The thickness of the joint surface of the pressure receiving plate may be about 20 to 150 / m. A1 foil, A] alloy foil, stainless steel foil, nickel foil, Cu or Ni plated steel foil or electrolytic iron foil may be used as the material. The flat joint surface is a circle with a diameter of about 2 mm, and is drawn out by drawing or flattening by about 1 mm by ironing or the like, as shown in Fig. 5, in which the thickness of the side wall is made thinner than the flat joint surface. . In addition, the flat joint surface is made by scoring the non-joint surface as shown in Fig. 6 to create a step in the thickness, or as shown in Fig. 7 by further extending the center to reduce the thickness. May be. The broken part is the side wall part in Fig. 5, the score added part in Fig. 6, and the overhang part in Fig. 7.

The method of joining the second flat joint surface of the shielding plate and the first flat joint surface of the pressure receiving plate may be welding at only one point by laser welding or the like.

と共に In addition to providing a C-shaped groove consisting of a groove with a bottom having a concave cross section and a groove for reducing strength, a valve membrane can be formed by a thin portion at the bottom of the groove.

P A PTC thermistor element consisting of an annular plate is interposed between the shielding plate and the sealing plate, and the PTC thermistor element increases the temperature of the safety device of the sealed battery and makes it difficult for current to flow. From this aspect, the explosion due to overcurrent is prevented. According to another embodiment of the present invention, there is provided a sealed battery including the above-mentioned safety device for a sealed battery. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram of a configuration of a safety device for a sealed battery according to an embodiment of the present invention in a normal use state. FIG. 2 is a view taken along the line I-I of FIG. Figure 3 FIG. 3 is a configuration explanatory view of a safety device for a sealed battery according to an embodiment of the present invention in a state where electrical connection between a pressure receiving plate and a shielding plate is cut off. FIG. 4 is a configuration explanatory view of a safety device for a sealed battery according to an embodiment of the present invention in a state where a valve membrane is broken. FIG. 5 is a sectional view of a pressure receiving plate of the safety device for a sealed battery according to one embodiment of the present invention. FIG. 6 is a sectional view of a pressure receiving plate of the safety device for a sealed battery according to one embodiment of the present invention. FIG. 7 is a cross-sectional view of a pressure receiving plate of the safety device for a sealed battery according to one embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail 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 FIG. 1 to FIG. 4, an electrode body 12 is housed in an outer can 11 also serving as a negative electrode terminal. The electrode body 12 has a configuration in which a laminate of the positive electrode 13, the separator 14, and the negative electrode 15 is spirally wound. At the upper end opening of the outer can 11, a safety device for a sealed battery that also serves as an explosion-proof function and a terminal is provided. The safety device substantially includes a positive electrode lid 16 having the following configuration, It is formed by caulking and fixing to the upper end opening of the outer can 11 via the insulating gasket 16a.

As shown in FIGS. 1 to 4, the positive electrode lid 16 substantially forms the innermost lid and is connected to the positive electrode 13 of the electrode body 12 via the 2 ′ positive electrode lead 17. A plate 18, a shielding plate 20 that forms an intermediate lid and is electrically connected to the pressure receiving plate 18 via the central joint portion 19, and an outer lid and an electrical connection to the shielding plate 20. It is provided with a sealing plate 21 that is electrically connected. In addition, the positive electrode cover 16 has an insulating plate 22 interposed annularly between the pressure receiving plate 18 and the shielding plate 20, and an annular plate between the shielding plate 20 and the sealing plate 21. The PTC thermistor element 23 is interposed.

Next, the configuration of each part of the positive electrode lid 16 having the above configuration will be described. As shown in FIGS. 1 to 4, a plurality of gas circulation holes 24 are formed in the pressure receiving plate 18, and the internal space 25 of the outer can and the pressure receiving plate 18 are formed through the gas circulation holes 24. The joint operating space 26 formed between the shield plate 20 and the shield plate 20 communicates.

As shown in FIG. 1 to FIG. 4, a central joint 19 electrically connecting the pressure receiving plate 18 and the shielding plate 20 protrudes from the central portion of the pressure receiving plate 18 toward the shielding plate 20. A projection 28 having a first flat joint surface 27 together with the first flat joint surface 27 of the projection 28 provided at the center of the shielding plate 20. Welded.

As shown in FIGS. 1 to 4, around the second flat joint surface 29 of the shielding plate 20, except for the connecting tab portion 30, the C-shaped groove 31 has an angle of 180 ° or more. It is formed concentrically with an arc angle of 0. Further, inside the C-shaped groove 31, a strength reducing groove 32 formed of an arc-shaped groove bent in a direction facing the C-shaped groove 31 is formed. Both ends of the strength reducing groove 32 are arranged on both ends of the C-shaped groove 31 in a superposed state. A narrow bendable portion 33 is formed between both ends 3 2 a of the strength reducing groove 32 and a portion 31 a recessed from the both ends of the C-shaped groove 31 by a predetermined distance. ing. In FIG. 2, 33a indicates a bending line.

Further, in the present embodiment, as shown in FIGS. 1 to 4, a metal foil 34 is joined to a side surface of the pressure receiving plate of the shielding plate 20, and the metal foil 34 is used to form a C-shaped groove 31. The valve membranes 35 and 36 are formed by covering the grooves 32 for low strength and low strength, respectively. The thicknesses of the valve membranes 35 and 36 are set so that the valve membranes 35 and 36 break when the pressure exceeds a set breaking pressure (for example, SO kg Z cm ² ). Specifically, when forming a clad metal plate by cladding a metal foil 34 on a shielding plate 20 made of a thick (for example, 50 / zm) metal substrate made of aluminum, the metal foil 34 may be used. For example, a 10 μm copper foil can be used.

Further, as the shielding plate, a metal plate having a thin portion at the bottom of the concave groove by score processing or the like may be used. For example, a metal plate made of aluminum, nickel or stainless steel with a thickness of 0.3 mm is scored so that the thickness of the thin part is about 30 μm. What was done can be used as a shielding plate. The type, thickness, or thickness of the thin portion of the metal may be appropriately selected depending on the set breaking pressure.

When the pressure inside the outer can 11 increases and exceeds the set current cutoff pressure by the above-described configuration of the central joint 19 and the shielding plate 20, as shown in FIG. 3, the valve membranes 35 s, 3 6 is plastically deformed, and the shielding plate 20 is bent along the bent portion 33, which is the weakest part in strength, in a state of being upwardly convex. As a result, the second flat joint surface 29 breaks around the welded portion, thereby separating from the first flat joint surface 27 provided on the projection 28 of the pressure receiving plate 18. The first flat joining surface 27 is preferably made of a material as thin as 20 to 150 m in thickness. As described above, when the pressure of the decomposition gas reaches the set current cutoff pressure, the C-shaped groove 31 and the strength reducing groove 32 are provided, so that the shielding plate 20 quickly separates from the pressure receiving plate 18 Therefore, even if the center of the shielding plate 20 rises slightly, the shielding plate 20 is completely separated from the pressure receiving plate 18, and the electrical connection between the pressure receiving plate 18 and the shielding plate 20 is surely and promptly made. The conduction can be cut off.

Next, the operation of the safety device for a sealed battery having the above-described configuration will be described with reference to FIG.

In the sealed battery described above, for example, when a large current flows due to an overcharged state, a corrosive highly decomposed gas is generated in the outer can 11 due to the large current, and the pressure in the outer can 11 increases, If left unattended, the sealed battery will explode. However, in this embodiment, when the pressure of the decomposed gas in the outer can 11 exceeds the set current cutoff pressure, the decomposed gas flows into the joint operating space 26 as shown in FIG. The second flat joint surface 20 of 20 is broken and quickly separated from the first flat joint surface 27 formed on the projection 28 of the pressure receiving plate 18, and the pressure receiving plate 18 and the shielding plate 20 Electrical continuity is quickly interrupted. Therefore, further generation of the decomposition gas can be prevented, and the internal pressure of the outer can 11 can be further prevented from further rising and exploding, and the valve membranes: 35, 36 are still broken. As a result, it is possible to prevent the decomposition gas harmful to the human body from leaking out, and to protect the environment. Furthermore, in spite of the above-mentioned interruption of electrical conduction, a chemical reaction proceeds in the outer can 11 and further decomposed gas is generated, causing the internal pressure to rise and exceeding the set membrane breaking pressure. As shown in Fig. 7, one or both of the valve membranes 35 and 36 are broken, and the decomposition gas flows from the joint operating space 26 to the space between the shielding plate 20 and the sealing plate 21 and the sealing plate 2. Since the gas is quickly discharged to the outside through the gas vent holes 37 provided in 1, the explosion of the sealed battery can be reliably prevented.

As described above, by using the safety device for the sealed battery according to the present embodiment, it is possible to reliably perform the current interruption and release the decomposition gas to the outside of the battery, thereby preventing the sealed battery from being ruptured. can do. Furthermore, by releasing the decomposed gas to the outside of the battery only in the unlikely event, adverse effects on the human body and the environment can be suppressed as much as possible.

In addition, as shown in FIGS. 1 to 4, in the present embodiment, since the PTC thermistor element 23 composed of an annular plate is interposed between the shielding plate 20 and the sealing plate 21, the decomposition gas When the temperature of the safety device of the sealed battery rises due to the occurrence of the current, it becomes difficult for the current to flow, and from this aspect, the explosion due to the overcurrent can be prevented.

5 to 7 show cross-sectional views of the overhang portion of the pressure receiving plate. As shown in FIG. 5, the pressure receiving plate 18 is ironed so as to reduce the thickness of the side wall of the projection, and the second flat portion is joined to the first flat portion of the shielding plate at one point. . When the internal pressure of the decomposed gas rises, the side wall of the thinned projection breaks, blocking the electrical conduction between the pressure receiving plate and the shielding plate to prevent further generation of the decomposed gas.

As shown in FIG. 6, the pressure receiving plate 18 has a step in the thickness of the second flat portion, and the second flat portion is joined to the first flat portion of the shielding plate at one point. When the internal pressure of the cracked gas rises, the thin part around the weld at the second flat part breaks, blocking the electrical conduction between the pressure receiving plate and the shield plate and preventing further generation of cracked gas I do.

As shown in FIG. 7, the pressure receiving plate 18 further projects the second flat portion, reduces the thickness of the projecting portion, and joins the first flat portion of the shielding plate at one point. Cracked gas When the internal pressure rises, the welded area around the thinned overhang is broken, blocking the electrical continuity between the pressure receiving plate and the shielding plate to prevent further generation of decomposition gas. The thickness of the pressure receiving plate may be 20 to 150 m. If the internal pressure of the cracked gas rises, the thickness of the material at the rupture location should be determined appropriately according to the internal pressure at which the electrical continuity between the pressure receiving plate and the shielding plate should be shielded.

Good. For example, when the thickness of the break is 80 μm, the operating pressure is 9.5 kg / cm \ 100 m, the operating pressure is 11.0 kg Z cm ² , and when the thickness is 150 m, the operating pressure is 1 1 . a 8 kg / cm ^2. Industrial applicability

As described above, in the sealed battery safety device of the present invention, when a normal current flows, the sealed portion of the pressure receiving plate and the shield plate is joined in a sealed space in an airtight state by sealing in the sealed space. Batteries can be operated normally, and when excessive current flows, the shielding plate is bent by using the pressure of the generated decomposition gas to cooperate with the C-shaped groove and the strength reduction groove. Since the first flat joint surface on the projection provided at the center of the pressure receiving plate is broken along the projected portion in a state of upward protrusion, the second flat joint surface provided at the center of the shield plate is quickly To quickly break the electrical connection between the pressure receiving plate and the shield plate, and if the decomposition gas pressure further rises, the valve membrane can be broken and released immediately to the outside of the battery. , Current interruption and decomposition gas Can be performed emitted to the outside reliably, the rupture of the sealed type battery can be prevented. Furthermore, by releasing the decomposed gas to the outside of the battery only in the unlikely event that the gas is released, 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 present invention, the strength-reducing groove is formed from an arc-shaped groove that is bent in a direction opposite to the C-shaped groove, and both ends of the strength-reducing groove are both ends of the C-shaped groove. Since they are arranged in a superposed state, it is possible to easily form a narrow portion to be bent. r In the safety device for a sealed battery according to the present invention, the strength-reducing groove is formed by a linear groove formed in a straight line connecting portions receding a predetermined distance from both ends of the C-shaped groove. Also in this case, a narrow bent portion can be easily formed. In the safety device for a sealed battery according to the present invention, since the inside and the outside of the c-shaped groove are connected by a plurality of connecting tabs arranged in an arc shape, the shielding plate near the portion to be bent is provided. Therefore, the electrical connection between the pressure receiving plate and the shielding plate can be more reliably cut off.

In the safety device for a sealed battery according to the present invention, a metal plate provided with a C-shaped groove and a groove for reducing strength is clad with a metal foil, and a shield plate having a valve membrane which operates reliably by a set film breaking pressure is inexpensive. Can be manufactured.

In the safety device for a sealed battery according to the present invention, since the C-shaped groove and the strength reducing groove are formed from bottomed grooves having a concave cross section, the valve membrane can be formed at low cost without using a clad structure. can do.

Further, the pressure receiving plate is formed of a metal plate having a cylindrical projection, and is broken when the decomposed gas falls within a certain pressure range, so that the safety is high.

In addition, the cylindrical projection has a first flat joint surface having a thickness of 20 to 150 m, and when the decomposed gas is in a certain pressure range, a thin film portion around the joint is broken, and High in nature.

Further, the cylindrical projection is made of a metal plate in which the thickness of the side wall of the projection is reduced by ironing, and when the decomposition gas falls within a certain pressure range, the thin portion of the side wall is broken, and safety is reduced. high.

In addition, the cylindrical projection forms a step in the thickness at the first flat joint surface by scoring or the like, and when the decomposition gas falls within a certain pressure range, the thin portion at the first flat joint surface becomes thin. It breaks and is highly safe.

Further, since the first flat joint surface of the cylindrical protrusion has a further protruding flat portion having a reduced thickness, the first flat joint surface has a first flat joint surface when the decomposition gas is in a certain pressure range. The overhanging part is broken and the safety is high.

In the sealed battery safety device according to the present invention, an annular plate is provided between the shielding plate and the sealing plate. By interposing a PTC thermistor element, it is possible to make it difficult for the PTC element to flow current, and to prevent explosion due to overcurrent from this aspect.

Since the sealed battery of the present invention is equipped with the above-described safety device for a sealed battery, a sealed battery with high performance and high safety can be manufactured at low cost.

Claims

The scope of the claims

1. The positive electrode lid attached to one end of the outer can is connected to the pressure receiving plate connected to the positive electrode of the electrode body via the positive electrode lead, forming the innermost lid, and forming the intermediate lid and via the central joint. A shielding plate electrically connected to the pressure receiving plate, and a sealing plate electrically connected to the shielding plate while forming an outermost lid.

Providing a gas flow hole in the pressure receiving plate, communicating the internal space of the outer can with a joint operating space formed between the pressure receiving plate and the shielding plate,

A cylindrical projection having a first flat joint surface and projecting from the central portion of the pressure receiving plate toward the shielding plate; and a cylindrical projection provided at the central portion of the shielding plate. The projections are formed from a second flat bonding surface to which the first flat bonding surface is bonded, and are concentrically C-shaped around the second flat bonding surface of the shielding plate at an arc angle of 180 ° or more. With a groove,

A strength-reducing groove is formed at a position inside the C-shaped groove of the shielding plate, and i IT, between the both ends of the strength-reducing groove and a portion receded by a predetermined distance from both ends of the C-shaped groove. To form a narrow bending section,

A metal foil is bonded to the side of the pressure receiving plate of the shielding plate to form a valve membrane in each of the C-shaped groove and the strength reducing groove.

When the pressure in the outer can exceeds a set current cut-off pressure, a joining portion of the first flat joining surface of the pressure receiving plate is broken, and an electrical connection between the pressure receiving plate and the shielding plate is cut off. A safety device for a sealed battery, wherein the valve membrane is ruptured when the pressure in the current interruption outer can exceeds a set membrane rupture pressure.

2. The strength-reducing groove is formed from an arc-shaped groove that is bent in a direction opposite to the C-shaped groove, and both ends of the strength-reducing groove are arranged in an overlapping state on both ends of the C-shaped groove. The safety device for a sealed battery according to claim 1, wherein

3. The parts where the strength-reducing groove has receded a predetermined distance from both ends of the C-shaped groove 2. The safety device for a sealed battery according to claim 1, wherein the safety device is formed from linear grooves that are linearly arranged.

4. The safety device for a sealed battery according to claim 1, wherein the inside and outside of the C-shaped groove are connected by a plurality of connecting tabs arranged in an arc shape.

5. The safety device for a sealed battery according to any one of claims 1 to 4, wherein the shielding plate is formed of a clad metal plate of a metal foil and a metal plate.

6. The positive electrode cover attached to one end of the outer can is connected to the pressure-receiving plate that forms the innermost lid and is connected to the positive electrode of the electrode body via the positive electrode lead, and the intermediate lid is formed and the center joint is connected. A shielding plate electrically connected to the pressure receiving plate, and a sealing plate electrically connected to the shielding plate while forming an outermost lid.

A cylindrical projection having a first flat joint surface and projecting from the central portion of the pressure receiving plate toward the shielding plate; and a cylindrical projection provided at the central portion of the shielding plate. The first flat joint surface of the protrusion is formed from a second flat joint surface elastically abutting,

Forming a C-shaped groove formed of a bottomed groove having a concave cross-section concentrically at an arc angle of 180 ° or more around the second flat joint surface of the shielding plate, and forming the C-shaped groove Bottom part The valve membrane is formed by the thin part,

Forming a strength-reducing groove formed of a bottomed groove having a concave cross section in a portion inside the C-shaped groove of the shielding plate, and forming a valve membrane by a bottom thin portion of the strength-reducing groove;

A narrow bent portion is formed between both ends of the strength reducing groove and a portion receded by a predetermined distance from both ends of the C-shaped groove, and a joint portion of the first flat joint surface of the pressure receiving plate is formed. When the pressure in the current interrupting outer can exceeds a set membrane breaking pressure, the valve membrane is broken when the electrical connection between the pressure receiving plate and the shielding plate is interrupted. Sealed battery safety device.

7. The safety device for a sealed battery according to any one of claims 1 to 6, wherein the pressure receiving plate is made of a metal plate having a cylindrical projection.

8. The safety device for a sealed battery according to any one of claims 1 to 7, wherein the cylindrical projection has a first flat joint surface having a thickness of 20 to 150; / m. .

9. The safety device for a sealed battery according to any one of claims 1 to 7, wherein the cylindrical projection has a side wall thickness of the projection reduced by ironing. Claims

10. The safety device for a sealed battery according to any one of claims 1 to 7, wherein the cylindrical protrusion has a step in thickness at the first flat joint surface.

The sealing according to any one of claims 1 to 7, wherein the cylindrical projection has a further projecting flat portion whose first flat joining surface has a reduced thickness. Battery safety device.

12. The safety of the sealed battery according to any one of claims 1 to 11, wherein a PTC thermistor element composed of an annular plate is interposed between the shielding plate and the sealing plate. apparatus.

13. A sealed battery comprising the safety device for a sealed battery according to any one of claims 1 to 12.