WO2000062357A1

WO2000062357A1 - Safety device for enclosed cell and enclosed cell comprising the same

Info

Publication number: WO2000062357A1
Application number: PCT/JP2000/002355
Authority: WO
Inventors: Hiroaki Kawamura; Hiroaki Okamoto; Kinji Saijo
Original assignee: Toyo Kohan Co., Ltd.
Priority date: 1999-04-12
Filing date: 2000-04-11
Publication date: 2000-10-19
Also published as: TW511311B; AU3676900A

Abstract

A safety device comprising an anode cap that is attached to one end of a case and included a pressure receiving plate connected to an anode of an electrode body through a lead and being an innermost cap, a shielding plate electrically connected to the pressure receiving plate through a central contact section and being an intermediate cap, and a sealing plate electrically connected to the shielding plate and being an outermost cap is characterized in that a C-shaped groove is formed around a second flat contact surface being the central contact section of the shielding plate, a strength reducing groove is formed inside the C-shaped groove, and a narrow to-be-bent section is provided between the ends of the strength reducing groove and the portions spaced back from the ends of the C-shaped groove by predetermined distances. Therefore, rupture due to sharply increased inner pressure occurring on overcharging or short-circuit is completely prevented. The safety device for an enclosed cell is manufactured at low cost.

Description

Description Sealed battery safety device and sealed battery using the same ^ Technical Field

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

10 In recent years, secondary batteries using nonaqueous electrolytes for lithium batteries and lithium ion batteries using nonaqueous 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, a non-aqueous electrolyte battery such as a lithium secondary battery

I If the battery is overcharged or short-circuited due to misuse and a large current flows, the non-aqueous electrolyte in the electrode body may be decomposed to generate gas. Such gas gradually fills the outer can, and when the internal pressure in the outer can rises, the battery eventually explodes. In order to prevent such battery rupture, various types of hermetically sealed batteries have been developed in the past. One example of such a battery is described in Japanese Patent Application Laid-Open No. Hei 6-3382005. There are things that are.

In this method, a positive electrode lid attached to one end of an outer can is formed by forming a metal lid with an innermost lid and connected to the positive electrode of the electrode body via a positive electrode lead. A metal explosion-proof valve electrically connected to the metal perforated plate via a portion, and a metal cap terminal S forming an outermost lid and electrically connected to the metal explosion-proof valve. I have.

With the above configuration, it is possible to break the central welded part when the internal pressure of the battery rises. As a result, the electrical connection between the metal perforated plate and the metal explosion-proof plate is cut off, and the gas inside the battery is discharged to the outside due to the destruction of part of the metal explosion-proof valve. Can be prevented.

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 perforated metal plate to the center of the metal explosion-proof valve, but it is extremely difficult to perform uniform spot welding. Therefore, the welding strength varies for each sealed battery. As a result, the internal pressure of the battery, which interrupts the electrical connection between the metal perforated plate and the metal explosion-proof plate, is not constant.

! C Even if the breaking pressure has been reached, the electrical connection between the metal perforated plate and the metal explosion-proof plate may not be interrupted, which significantly impairs the reliability of the sealed battery. become.

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 shielding plate can be surely cut off.

\ It is an object of the present invention to provide a sealed battery safety device capable of sufficiently securing the safety of a closed battery and a sealed battery provided with the safety device. Disclosure of the invention

In order to achieve the above object, the sealed battery safety device according to the present invention comprises a positive electrode cover attached to one end of the outer can connected to the positive electrode of the electrode body via a positive electrode lead while forming an innermost lid. A pressure receiving plate, a shielding plate forming an intermediate lid and being electrically connected to the pressure receiving plate via a central contact portion, and a sealing plate forming an outermost lid and being electrically connected to the shielding plate. The gas receiving hole is provided in the pressure receiving plate, the inner space of the outer can communicates with the contact space formed between the pressure receiving plate and the shielding plate, and the central contact portion is formed from the center of the pressure receiving plate. A protrusion protruding toward the shield plate and having a first flat contact surface, and a first protrusion provided at a central portion of the shield plate and elastically contacting the first flat contact surface of the protrusion. A C-shaped groove is formed concentrically around the second flat contact surface of the shielding plate with an arc angle of 180 ° or more around the second flat contact surface of the shielding plate, and the inside of the C-shaped groove of the shielding plate is A groove to reduce the strength is formed at the location where it is formed, and a narrow bent portion is formed between both ends of the groove for reducing the strength and a portion retracted by a predetermined distance from both ends of the C-shaped groove, and the pressure of the shielding plate is received. Metal foil ^ is joined to the side of the plate to form a valve membrane in each of the C-shaped groove and the strength reducing groove.If the pressure in the outer can exceeds the set current cutoff pressure, the shielding plate will The second flat contact surface of the shielding plate is separated from the first flat contact surface of the pressure receiving plate so that the electrical connection between the pressure receiving plate and the shielding plate is interrupted, and the current interrupting outer can When the internal pressure exceeds the set membrane break pressure, the valve membrane is broken.

^'C Therefore, at all times, in a closed space, the electrical conduction of the pressure receiving plate and the shielding plate, the first flat contact surface provided on the projection of the pressure receiving plate to a second planar contact surface of the elastically shield This is ensured by contact. 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 contact surface of the shielding plate to be separated from the first flat contact surface of the pressure receiving plate. The pressure plate and shield plate

1. Cut off the air conduction to prevent further generation of decomposition gas and prevent the decomposition gas from flowing out.

At this time, a narrow bent portion is provided between both ends of the strength reducing groove provided inside the C-shaped groove surrounding the second flat contact 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 part C, and the second flat contact surface rises, 1 quickly and quickly away from the flat contact surface. Therefore, the electrical continuity between the pressure receiving plate and the shield plate can be quickly and reliably interrupted by the set current cutoff pressure. At this time, since the shielding plate is plastically deformed, it is possible to reliably prevent the second flat contact surface from coming into contact with the first flat contact surface again.

^ 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, When the valve membrane provided on the shield plate breaks, the decomposed gas is released to the outside through the gas flow holes, contact space, valve membrane, and gas vent holes provided on the pressure receiving plate, and the sealed battery explodes. Can be prevented.

Here, preferably, the set current cutoff pressure is set to 4 to 5 kg / cm ² , and the set membrane breaking pressure is set to 20 kg Z cn ^

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.

1 ^{C (} 2) The strength reducing 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.

④The shielding plate and the metal foil are made of a clad metal plate with both clad, and the valve membrane is

I? It is formed by the portion of the metal foil covering the side annular groove and the outer annular groove.

Here, preferably, the thickness of the metal plate is about 50 m, and the thickness of the metal foil is about 10 m.

Moreover, such a clad metal plate, for example, as the applicant has disclosed in JP-1- 2 2 4 1 8 4 JP ^{above, 1 X 1 0 - 1 ~} 1 X 1 0- 4 Torr In a very low-pressure inert gas atmosphere, a metal substrate having a bonding surface and a metal foil are each grounded to one electrode A, and the other electrode B, which is insulated and supported, has an AC of 1 to 50 MHz. To produce a glow discharge, and the electrode area exposed to the plasma generated by the glow discharge is 1/3 or less of the area of the electrode B, and is manufactured by performing a sputter etching process. can do.

⑤ In addition to providing a C-shaped groove consisting of a bottomed groove with 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. 環状 A PTC thermistor element consisting of an annular plate is interposed between the shielding plate and the sealing plate.The PTC thermistor element increases the temperature of the safety device of the sealed battery and reduces the flow of current. From this point, the explosion due to overcurrent is also prevented.

According to another aspect of the present invention, there is provided a sealed battery including the above-described safety device for a sealed battery. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration explanatory view of a safety device for a sealed battery according to an embodiment of the present invention in a normal use state. FIG. 2 is an arrow view along the line I_I in FIG. 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 the electrical connection between the pressure receiving plate and the 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 plan view of a shield plate of a safety device for a sealed battery according to a modification of the embodiment of the present invention. It is an area drawing. FIG. 6 is a plan view of a shield plate of a safety device for a sealed battery according to a modification of the 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.

20.

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 a positive electrode 13, a separator 14 and a negative electrode 15 is spirally wound. At the upper end opening of the outer can 11, a safety device for a sealed battery that has both an explosion-proof function and a terminal is provided. It is substantially formed by caulking and fixing a positive electrode lid 16 having the following configuration to an upper end opening of the outer can 11 via an 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 positive electrode lead 17. A shielding plate 20 that forms an intermediate lid and is electrically connected to the pressure receiving plate 18 via the central contact portion 19; and forms an outermost lid and is electrically connected to the shielding plate 20. The sealing plate 21 is provided. 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. A PTC thermistor element 23 is interposed.

Next, the configuration of each part of the positive electrode cover 16 having the above configuration will be described.

As shown in FIGS. 1 to 3 and FIG. 5, 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 1 are formed through the gas circulation holes 24. A contact part operating space 26 formed between the shield plate 20 and the shield plate 20 communicates with each other.

As shown in FIGS. 1 to 4, a central contact portion 19 that electrically connects 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 contact surface 27 together with the first flat contact surface 27 of the projection 28 provided at the center of the shielding plate 20 and visibly abutting. Formed by 29.

As shown in FIGS. 1 to 4, around the second flat contact surface 29 of the shielding plate 20, except for the connecting tab portion 30, there is a C-shaped groove 31 at 180 °. It is formed concentrically with the above arc angle Θ. 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 32 a of the strength reducing groove 32 and a portion 31 a retreated a predetermined distance from both ends of the C-shaped groove 31. Have been. 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 C-shaped groove 3 is formed by the gold foil 34. The valve membranes 35 and 36 are formed by covering the groove 1 and the groove 32 for reducing the strength, respectively.

The thicknesses of the valve membranes 35 and 36 are set so as to break when the pressure exceeds a set breaking pressure (for example, 20 kg 5 / cm or more. Specifically, a thick wall made of aluminum ( For example, when a metal foil 34 is clad on a shielding plate 20 made of a 50 m) metal substrate to form a clad metal plate, for example, a copper foil of 10 zm may be used as the metal foil 34. it can.

When the pressure in the outer can 1 ^ 1 increases and exceeds the set current cutoff pressure by using the above-described configuration of the central contact portion 19 and the shielding plate 20, as shown in FIG. 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 contact surface 29 is separated in parallel to the first flat contact surface 27 provided on the projection 28 of the pressure receiving plate 18. 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 is quickly separated from the pressure receiving plate 18. Even if the center of the shielding plate 20 rises slightly, the shielding plate 20 will be completely separated from the pressure receiving plate 18, and the electrical conduction between the pressure receiving plate 18 and the shielding plate 20 reliably and quickly. Can be shut off.

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

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 the present 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 contact part operation space 26 as shown in FIG. The first flat contact surface in which the second flat contact surface 29 of the plate 20 is formed on the projection 28 of the pressure receiving plate 18 27, and the electrical conduction between the pressure receiving plate 18 and the shielding plate 20 is immediately cut off. Therefore, it is possible to prevent further generation of the decomposition gas, to surely prevent the internal pressure of the outer can 11 from further increasing and exploding, and to break the valve membranes 35 and 36 still. Since it is not performed, decomposition gas harmful to the human body can be prevented from leaking out, and environmental protection can be achieved.

Furthermore, in spite of the above-mentioned interruption of the electrical conduction, a chemical reaction proceeds in the outer can 11 and further decomposed gas is generated to increase the internal pressure. As shown in the figure, one or both of the valve membranes 35 and 36 are broken, and the decomposition gas flows from the contact part operation space 26 to the space between the shielding plate 20 and the sealing plate 21 and the sealing plate.

通過 Since the gas is quickly discharged to the outside through the gas vent holes 37 provided in the mouth plate 21, 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, release of cracked gas outside the battery

^ Can be performed only in the unlikely event that the adverse effects on the human body and the environment can be minimized.

In addition, as shown in FIGS. 1 to 4, in the present embodiment, the PTC thermistor element 23 composed of an annular plate is interposed between the shielding plate 20 and the sealing plate 21. If the temperature of the safety device of the sealed battery rises due to the generation of gas, it will be difficult for the current to flow.

5 and 6 show shield plates 20A and 20B of a safety device for a sealed battery according to a modification of the embodiment of the present invention.

As shown in FIG. 5, in the shielding plate 2 OA, the strength reducing groove 40 is disposed on a straight line connecting the portions 31 a and 31 a withdrawn by a predetermined distance from both ends of the C-shaped groove 31. It is characterized by being formed from a straight ^ groove formed. Also in this case, the shielding plate 20 is bent in an upwardly convex state along the portion to be bent 3 3 which is the weakest part in strength, and the second flat contact is made. The surface 29 can be quickly separated from the first flat contact surface 27 provided on the projection 28 of the pressure receiving plate 18.

As shown in FIG. 6, the shielding plate 20B is characterized in that the inside and the outside of the C-shaped groove 31 are connected by a plurality of connecting tabs 41, 42. In this case, since the strength of the shielding plate 20 near the strength reducing groove ζ32 can be reduced, the second flat contact surface 29 is provided on the projection 28 of the pressure receiving plate 18. It can be more quickly separated from the flat contact surface 27 of 1. Industrial applicability

'C As described above, in the sealed battery safety device according to claim 1, when a normal current flows, the contact portion between the pressure receiving plate and the shielding plate is brought into airtight contact in the sealed space. The sealed battery can be operated normally, and when excessive current flows, the C-shaped groove and the strength-reducing groove cooperate with each other by utilizing the pressure of the generated decomposition gas. Is bent upward along the part to be bent.

1) Bending, the second flat contact surface provided at the center of the shield plate is quickly separated from the first flat contact surface on the protrusion provided at the center of the pressure plate, and the contact between the pressure plate and the shield plate When the pressure of the decomposition gas further increases, the valve membrane is broken and the gas can be released to the outside of the battery promptly, so that the current is cut off and the decomposition gas is discharged to the outside of the battery. Can reliably be released, and the sealed battery can be prevented from exploding. Furthermore, by releasing the cracked 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 minimized.

In the safety device for a sealed battery according to claim 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 both ends of the C-shaped groove. Since the portions are arranged in a superposed state, a narrow portion to be bent can be easily formed.

In the safety device for a sealed battery according to claim 3, the strength reducing groove is formed as a C-shaped groove. Since it is formed from linear grooves arranged in a straight line connecting portions receded by a predetermined distance from both ends, also in this case, a narrow portion to be bent can be easily formed. In the safety device for a sealed battery according to claim 4, the inside and the outside of the C-shaped groove are connected by a plurality of connecting tabs arranged in an arc shape, so that the vicinity of the expected bending portion ^ is The strength of the shield plate to be formed can be reduced, and the electrical connection between the pressure receiving plate and the shield plate can be more reliably cut off.

The safety device for a sealed battery according to claim 5, wherein the metal foil is clad on a metal substrate provided with a C-shaped groove and a strength-reducing groove, and a shield having a valve film that is reliably operated by a set film breaking pressure. Plates can be manufactured inexpensively.

! 0 In the sealed battery safety device according to claim 6, since the C-shaped groove and the strength reducing groove are formed from bottomed grooves having a concave cross-section, the clad structure is not required. The valve membrane can be formed at low cost.

In the safety device for a sealed battery according to claim 7, a current flows through the PTC element by interposing a PTC thermistor element composed of an annular plate between the shielding plate and the sealing plate. It is possible to prevent explosion due to overcurrent from this aspect.

The sealed battery according to claim 8 can provide a high-performance and highly safe sealed battery at low cost by providing the sealed battery safety device according to claims 1 to 7. .

Claims

The scope of the claims

1. The positive electrode cover attached to one end of the outer can is made up of a 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 that forms an intermediate lid and has a central ^ A shielding plate electrically connected to the pressure receiving plate through a sealing plate, and a sealing plate electrically connected to the shielding plate while forming an outermost lid,

A gas flow hole is provided in the pressure receiving plate, and an internal space of the outer can communicates with a contact portion operation space formed between the pressure receiving plate and the shielding plate,

A projection having a first flat contact surface when the center contact portion projects from the center of the pressure receiving plate toward the shielding plate; and a first projection of the projection provided at the center of the shielding plate. A flat contact surface is formed from a second flat contact surface that resiliently contacts,

C-shaped grooves are provided concentrically around the second flat contact surface of the shielding plate at an arc angle of 180 ° or more,

A strength reducing groove is formed at a position inside the C-shaped groove of the shielding plate, and 5 "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. To form a narrow bending section,

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 cutoff pressure, the shielding plate is bent in an upwardly convex state along the bent portion, and the second flat contact surface of the shielding plate is subjected to the pressure receiving pressure. The electrical connection between the pressure receiving plate and the shielding plate is cut off from the first flat contact surface of the plate, and the valve film breaks when the pressure in the current interrupting outer can exceeds a set film breaking pressure. A safety device for a sealed battery, wherein the safety device is adapted to be operated.

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 on both ends of the c-shaped groove in a superposed state. The safety device for a sealed battery according to claim 1, wherein the safety device is provided.

3. The sealed battery according to claim 1, wherein the strength-reducing groove is formed by a linear groove that is linearly arranged to connect portions receding a predetermined distance from both ends of the C-shaped groove. Safety device.

4. The safety device for a sealed battery according to claim 1, wherein the inside and outside of the C-shaped groove are connected to each other by a plurality of connection 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 and the metal foil are formed of a clad metal plate.

6. The positive electrode lid attached to one end of the outer can is formed by the innermost lid, the pressure receiving plate connected to the positive electrode of the electrode body through the positive electrode lead, the intermediate lid, and the central i 0 contact part. A shielding plate electrically connected to the pressure receiving plate through a sealing plate, and a sealing plate electrically connected to the shielding plate while forming an outermost lid,

When the center contact portion protrudes from the center of the pressure receiving plate toward the shielding plate, a projection having a first flat contact surface is also provided; and a first of the projections provided at the center of the shielding plate. Formed from a second flat contact surface where the flat contact surface of

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

(0) A strength-reducing groove composed of a bottomed groove having a concave cross section is formed in a portion inside the C-shaped groove of the shielding plate, and a valve membrane is formed by a bottom thin portion of the strength-reducing groove,

Forming a narrow bendable portion between both ends of the strength reducing groove and a portion receded by a predetermined distance from both ends of the C-shaped groove;

When the pressure in the outer can exceeds the set current cutoff pressure, the shielding plate is bent in an upwardly convex state along the bent portion, and the second flat contact surface of the shielding plate is turned forward. When the electrical connection between the pressure receiving plate and the shielding plate is interrupted at a distance from the first flat contact surface of the pressure receiving plate, and the pressure in the current interrupting outer can exceeds a set membrane breaking pressure, the valve membrane is closed. A safety device for a sealed battery, wherein the safety device is broken.

7. The sealed battery according to any one of claims 1 to 6, wherein a PTC thermistor element formed of an annular plate is interposed between the shielding plate and the sealing plate. Safety equipment.

8. A sealed battery provided with the safety device for a sealed battery according to any one of claims 1 to 7.