JPH10214609A - Safety structure for sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safety structure for a sealed battery with improved safety by conducting current shutoff and sealing plate breakage simultaneously. SOLUTION: A battery lid 2, an insulation film 3, and a sealing plate 4 are at least provided successively from the outside toward the inside of the battery in the sealing portion 1 sealing the battery can 7 opening of a sealed battery 10. The battery lid 2 to be the external electrode is electrically connected to the sealing plate 4. The sealing plate 4 is equipped with a predetermined break portion W to be broken by the pressure rise of the inside of the battery, and a portion 5 surrounded by the predetermined break portion W of the sealing plate 4 is electrically connected to a battery inside power generation portion E at its inner side face. The insulation film 3 is placed at a position for obstructing the contact of the portion 5 surrounded by the predetermined break portion W and the battery lid 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety structure for coping with an abnormal increase in internal pressure and temperature in a sealed battery.

[0002]

2. Description of the Related Art A sealed battery is one in which a power generating element is sealed in a battery can. For example, a dry battery is a well-known embodiment. The power generation element referred to here is an electrochemical element of a battery for performing power generation and charge / discharge. Due to the structure of the sealed battery, when an abnormal temperature rise or expansion of the fluid occurs inside the sealed battery, the internal pressure may be abnormally increased, and eventually, an explosion may occur. Therefore, conventionally, a sealed battery is provided with a safety structure for evacuating a gas or the like having an internal high pressure to the outside to avoid such a situation.

FIG. 3 is a sectional view showing a typical example of a conventional safety structure. In the example shown in the figure, the opening of the battery can 37 is sealed by the sealing portion 31. In FIG.
Only the cross section is hatched. The sealing part 31
It has a metal battery lid 32, a sealing plate 34, and a connection plate 33, which are electrically connected to the internal power generation element E. Since the battery cover 32 is provided with the through-hole 32a, the sealing plate 34 serves as a partition for separating the internal pressure of the battery from the external pressure. The connection plate 33 has a shape having a convex portion at the center portion, and the sealing plate 3 is formed at the top of the convex portion.
4 and connected by welding. A through hole is provided in a central portion of the connection plate 33. In the sealing plate 34, the sealing plate 3
The thin portion W formed by removing the plate material from one side or both sides of the surface 4 is provided so as to draw an annular curve as a portion to be broken. 38 is a gasket.

In the structure shown in FIG. 3, when the pressure inside the battery rises to P1 due to an abnormal situation, the sealing plate 34
Is lifted, the welding connecting the sealing plate 34 and the connection plate 33 is peeled off, and the current is interrupted. At this stage, the sealing plate 34 is not broken, and still functions as a partition. Further, when the pressure increases and reaches P2, the thin-walled portion W breaks, and the high-pressure fluid inside is released to the outside to prevent the battery can from rupture. In general, P
2 is set to be 1.2 to 2.5 times P1.

[0005]

However, the sealing plate 34
The welding fracture strength of the connection part between
Requires a high welding technology, and it is very difficult to keep the error within a common-sense error range of ± 5% to ± 15%, and there is a problem of lack of reliability.

When the pressure inside the battery reaches P1 due to an abnormal situation and the current is interrupted but does not reach P2, the pressure inside the battery becomes at least 5 k
gf / cm ² or more, and when it is high, it reaches 15 kgf / cm ² or more. This legally corresponds to the pressure used for the high-pressure vessel, and it is not safe to maintain this state.

An object of the present invention is to solve the above problems and to provide a safety structure of a sealed battery having improved safety by simultaneously interrupting current and breaking a sealing plate.

[0008]

The safety structure of the sealed battery according to the present invention has the following features. (1) In a sealing portion for sealing an opening of a battery can of a sealed battery, a battery lid is arranged in order from the outside to the inside of the battery,
At least an insulating film and a sealing plate are provided, and the battery lid serves as an external electrode of the battery, and is electrically connected to the sealing plate, and the sealing plate increases a pressure inside the battery. The part surrounded by the part to be broken of the sealing plate is electrically connected to the power generating element inside the battery on the inner side surface, and the insulating film is A safety structure for a sealed battery, which can be installed at a position where contact between the portion surrounded by the portion to be broken and the battery lid is obstructed when the portion breaks.

(2) The safety structure for a sealed battery according to the above (1), wherein the insulating film is provided so as to be superposed on the outer side of the sealing plate.

(3) The safety structure for a sealed battery according to the above (1), wherein the insulating film is provided so as to overlap with the inside of the battery lid.

(4) The safety structure for a sealed battery according to the above (1), wherein the insulating film has air permeability.

[0012]

In the safety structure according to the present invention, the insulating film is provided at a position where it prevents the contact between the portion surrounded by the rupture portion and the battery lid when the rupture portion breaks. Therefore, the pressure inside the battery rises due to an abnormal situation, the part to be broken is broken, and the part surrounded by the part is partially or completely separated from the sealing plate with electrical connection with the power generation element. In this case, the portion cannot contact the battery lid by the insulating film. That is, the safety structure of the present invention can cut off or reduce the current inside the battery at the same time or almost at the same time as the breaking of the portion to be broken. In the present invention, unlike the conventional safety structure, there is no need to set the pressure in two stages,
The structure can be simplified.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing an example of the safety structure of the sealed battery according to the present invention. As shown in the example of FIG.
Sealing part 1 for sealing the opening of battery can 7 of sealed battery 10
A battery cover 2, an insulating film 3, and a sealing plate 4 are provided in this order from the outside of the sealed battery 10 to the inside. Battery cover 2
Is an external electrode of the sealed battery 10 and is electrically connected to the sealing plate 4. The sealing plate 4 has a rupture scheduled portion W that is ruptured due to a rise in pressure inside the battery. The portion surrounded by the breakable portion W is electrically connected to the power generating element E inside the battery on the inner side surface. When the portion to be broken is broken, the insulating film 3
It is installed at a position where the contact between the portion 5 surrounded by a circle and the battery lid 2 is obstructed. .

In the example shown in FIG. 1, the sealing portion 1 is attached to a battery can 7 via a gasket 8, and the battery lid 2 and the sealing plate 4 are overlapped at their peripheral edges and are electrically connected to each other. . The breakable portion W is formed in the center portion of the sealing plate 4 so as to draw an annular curve on the plate surface of the sealing plate (not shown). The insulating film 3 is placed on the outside of the sealing plate 4 so as to overlap. 6 is a through hole.

As shown in FIG. 2B, when the portion to be broken W is broken by the rise in pressure inside the battery and the portion 5 surrounded by the portion to be broken W is separated from the sealing plate 4, the insulating film is formed. 3
Can interrupt the connection between the portion 5 surrounded by the to-be-ruptured portion W and the battery lid 2, and can interrupt or reduce the current flowing between the portion 5 surrounded by the to-be-ruptured portion W and the battery lid 2.

FIG. 2 is a sectional view showing another example of the safety structure of the sealed battery according to the present invention. FIG. 1 shows a mode in which the insulating film 3 is attached and installed on the surface of the battery lid 2 on the inside of the battery. Other components other than the insulating film have the same mode as that of FIG. In FIG. 2 as well, the insulating film 3 can block or reduce the current flowing between the battery cover 2 and the portion 5 surrounded by the breakable portion W separated by the increase in the pressure inside the battery.

The insulating film used in the present invention can prevent the portion surrounded by the portion to be broken from being separated from the sealing plate and then contacting the portion with the battery lid, that is, preventing the portion from being electrically connected. There is no particular limitation as long as it is provided. The installation of the insulating film may be performed at a position where the contact between the portion and the sealing plate may be obstructed. For example, the insulating film may be superimposed on the outside of the sealing plate as shown in FIG. As shown in FIG. 2, it may be performed by superimposing on the inner side of the battery cover.

Even if the insulating film has air permeability,
It may not be provided, but it is preferable that the gas or the like, which has become high pressure due to the increase in the pressure inside the battery, has gas permeability since it needs to escape to the outside. However, even if the material does not have air permeability, it is a preferable embodiment if the thickness, material, strength, and the like are set so as to be broken by the break of the portion to be broken. In addition, from the viewpoint of the reliability of the operation of the safety structure of the present invention, the insulating film having air permeability is superior, but the insulating film having no air permeability allows the sealing plate to be externally attached at normal times. This is better in terms of long-term reliability because it can protect from the atmosphere.

Examples of the material of the insulating film include plastic, rubber, paper and the like. If air permeability is to be imparted to the insulating film, the above-mentioned material may be subjected to a post-process such as punching to form holes and impart air permeability, or a porous insulating material such as a nonwoven fabric May be used. Examples of a method for forming the insulating film include punching with a press and injection molding, but are not particularly limited.

As shown in FIG. 1, the sealing plate is attached to the opening of the battery can and serves as a partition for separating the internal pressure of the battery from the external pressure. The sealing plate is superimposed on the battery lid at the peripheral edge, and the sealing plate and the battery lid are electrically connected. In the sealing plate, a portion to be broken is formed in a portion other than the peripheral edge portion, which is broken by a rise in pressure inside the battery. The breakable portion is formed in an annular shape on the surface of the sealing plate. The sealing plate is electrically connected to the power generation element on a surface inside the battery at a portion surrounded by the portion to be broken. As the material of the sealing plate, any material may be used as long as it is a conductive material, but a material having excellent corrosion resistance to an organic electrolytic solution is preferable. For example, a conductive material such as aluminum is plated (coated) on an aluminum alloy, a conductive plastic, or a plastic. And the like.

The portion to be broken may be any portion that breaks when the pressure inside the battery reaches a preset pressure. Examples of the breakable portion include a thin portion formed by reducing the thickness of a part of the sealing plate as shown in FIGS. In addition, if a sealing plate composed of a thin plate 42 and a thick plate 43 having an opening as shown in FIG. 4 is used as the sealing plate, the lower side of the opening (the side in contact with the thin plate 42).
The area of the thin plate 42 corresponding to the entire circumference of the area is a portion to be broken.
In this case, it is preferable to provide a cutting tool or the like as necessary on the entire lower circumference of the opening. FIG. 4 is a cross-sectional view of the sealing plate 41, and only the thick plate 43 is hatched.

The portion to be broken must be formed so that the portion surrounded by the portion to be broken is separated from the sealing plate after the break. It is preferable that the part is completely separated from the sealing plate. However, even when a part is partially separated except for a part, the connection resistance between the part and the sealing plate is several Ω.
If it reaches the level (below 10 mΩ before breaking), since the battery voltage is 3 V to 5 V, the current is sufficiently reduced, which is a preferable embodiment. If the portion to be broken is the thin portion described above, examples of a method for forming the portion to be broken include press forming, cutting, and etching. In the case shown in FIG. 4, there is a method of welding a thin plate to a perforated thick plate to form a portion to be broken.

The line drawn by the portion to be broken on the surface of the sealing plate preferably has an annular curve in terms of causing breakage. The ring-shaped curve referred to here is not limited to a completely closed curve, but may be a partially broken curve such as a “C-shaped”.
The shape of the circular curve may be set according to the application, such as a circle, an ellipse, a square, and a rhombus. The shape is not limited to a circle for a cylindrical battery and a square for a square battery, but also fits in a square cross section of a square battery. It may be circular. By selecting the size of the annular curve, the pressure at break can be adjusted.

The battery can is not particularly limited as long as it is generally used for a sealed battery. The shape of the cross section perpendicular to the longitudinal direction of the battery can is not particularly limited, and may be any of a round shape, a square shape, and the like.
The battery can often serves as a negative electrode, but is not particularly limited in the present invention, and may serve as a positive electrode. The battery can may be covered with an insulating tube or the like in a final product stage. Materials for the battery can include nickel-plated iron, stainless steel, aluminum and the like. As a method of forming a battery can, a method by multi-stage press molding,
A method by impact press molding, a method by deep drawing, and the like are exemplified.

The battery lid serves as an external electrode of the battery, and is not particularly limited as long as it is generally used for a sealed battery like a battery can. The shape of the battery cover may be determined according to the battery can, and may be any of a round shape, a square shape, and the like. The battery cover usually serves as a positive electrode, but is not particularly limited in the present invention, and may serve as a negative electrode. The material of the battery lid is not particularly limited as long as it is a conductive material, but metal-nickel plated iron, stainless steel, aluminum, conductive plastic,
A material obtained by plating (applying) a conductive material such as nickel on a plastic may be used. Examples of the method for forming the battery can include pressing, injection molding, casting, cutting, and combinations thereof.

Although the safety structure according to the present invention is useful for any sealed battery, it is useful for a high-capacity lithium-ion secondary battery used as a rechargeable power source for notebook PCs, mobile phones, portable video cameras and the like. This is particularly useful for ensuring safety. The safety structure according to the present invention operates favorably in the following abnormal situations regarding the sealed battery. In other words, overcurrent or overcurrent caused by environmental changes outside the battery, such as an increase in
Evaporation of electrolyte due to abnormal temperature rise inside the battery caused by environmental changes inside the battery such as overvoltage, external short circuit, internal short circuit, electrolyte reaction, external destruction such as impact or penetration, and thermal expansion of gas This is an increase in the pressure inside the battery. The safety structure according to the present invention is useful not only for a general cylindrical (including a button type) sealed battery, but also for a battery of any shape such as a square battery.

[0027]

EXAMPLE A safety structure shown in FIG. 1 was provided to a sealing portion (= positive electrode terminal portion) of a lithium ion secondary battery having an outer diameter of about 18 mm. The insulating film has a thickness of 50 μm and a strength of 4.5 g /
D to 7.5 g / D (D: denier) polypropylene was used and placed on the sealing plate as shown in FIG. As the sealing plate, the one shown in FIG. 4 was used. Specifically, a thick plate (thickness: 0.5 mm, material: aluminum) provided with an opening having a diameter of 6 mm at the center,
A stack of thin plates (thickness: 0.04 mm, material: aluminum) was used.

When the internal pressure of the lithium ion secondary battery was raised by raising the temperature of the external environment, the sealing plate was broken at the portion to be broken at a stable temperature with little variation. It was confirmed that the internal current was interrupted, and the internal pressure was released before the battery can burst.

[0029]

According to the safety structure of the present invention, the interruption of the current and the breaking of the sealing plate are performed almost at the same time. Can be. Further, the number of components can be reduced as compared with the conventional one, so that the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a safety structure of a sealed battery according to the present invention.

FIG. 2 is a sectional view showing another example of the safety structure of the sealed battery according to the present invention.

FIG. 3 is a sectional view showing a typical example of a conventional safety structure.

FIG. 4 is a sectional view showing another example of the sealing plate used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealing part 2 Battery cover 3 Insulating film 4 Sealing plate 5 Part surrounded by a part to be broken 7 Battery can 10 Sealed battery W Part to be broken E Power generating element

Claims (4)

[Claims] At least a battery cover, an insulating film, and a sealing plate are provided in order from an outside of the battery to an inside thereof in a sealing portion for sealing an opening of a battery can of the sealed battery, The battery lid serves as an external electrode of the battery, and is electrically connected to the sealing plate. The sealing plate has a rupture portion that is ruptured due to a rise in pressure inside the battery, and the rupture of the sealing plate The part surrounded by the scheduled part is electrically connected to the power generating element inside the battery on the inner side surface, and the insulating film is
A safety structure for a sealed battery, which can be installed at a position where contact between a portion surrounded by the rupture portion and the battery lid is obstructed when the rupture portion breaks. 2. The safety structure for a sealed battery according to claim 1, wherein the insulating film is provided so as to be superposed on the outer side of the sealing plate. 3. The safety structure for a sealed battery according to claim 1, wherein the insulating film is provided so as to overlap with the inside of the battery cover. 4. The safety structure for a sealed battery according to claim 1, wherein the insulating film has air permeability.