JP3599967B2 - Sealed battery - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention has a battery sealing structure capable of processing an excessive internal pressure and shutting off an energizing circuit when a sealed battery having a high energy density such as a lithium secondary battery is abnormally used, particularly a lithium secondary battery. A sealed battery.
[0002]
[Prior art]
A sealed battery with a high energy density, such as a lithium secondary battery, may have abnormal internal gas due to abnormal gas generation inside the battery if the equipment or charger that uses this battery is broken or used improperly. May rise excessively. A gas venting mechanism is provided for discharging the gas that has occurred abnormally in preparation for such abnormal use. In addition, since the non-aqueous electrolyte secondary battery involves an abnormal temperature rise, a current interrupt mechanism for interrupting the current before the gas is discharged is provided.
[0003]
As prior art of a sealed battery provided with the gas release mechanism and the current cutoff mechanism, Japanese Patent Application Laid-Open Nos. Hei 5-335501, Hei 5-34043, Hei 8-306351, Hei 8-315798, Hei 9 JP-A-199105 and JP-A-9-199106 are known. The configurations disclosed in these documents deform the thin metal plate by an abnormally increased internal pressure, thereby interrupting the connection for electrical connection and cutting off the current, and removing an excessive current circuit that is a source of abnormal gas generation. It is configured to shut off.
[0004]
[Problems to be solved by the invention]
However, in order to completely shut off the energizing circuit when the battery internal pressure rises above a predetermined value, it is necessary to ensure that the precision at which the parts joined by welding for electrical connection are peeled off, or the predetermined battery internal pressure, Since the breaking accuracy of the easily breakable portion that breaks when added is required, there is a problem that it is difficult to control the material thickness, welding strength, and precision of the easily breakable portion of the joined portion, and the product yield is reduced.
[0005]
An object of the present invention is to provide a sealed battery provided with a highly reliable sealing plate, which improves the breaking accuracy at which an electrical junction is broken when the internal pressure of the battery increases.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a battery case in which an end opening of a battery case accommodating a power generation element is hermetically sealed by a sealing plate, and a metal cap provided on the inside of the battery from a metal cap forming an electrode portion of the sealing plate. In a sealed battery provided with a mechanism for interrupting an energizing circuit from a power generation element to a metal cap by deforming a thin plate due to an increase in battery internal pressure, an electric power is applied to the power generation element at a position of the sealing plate facing the inside of the battery. Provided connected, forming an opening only in the metal plate at the center of the clad material cold-welded by superimposing the metal plate and the metal foil, and the metal plate and the metal foil in the appropriate place of the clad material a composite metal plate formed with vent holes through, together with the peripheral portion is fixed and supported together with the composite metal plate through the outside of the battery-side insulating member of the composite metal plate, electrostatic the metal cap Manner by connecting provided, forming a bulging portion which gently bulge inside the battery side in the central portion, the central portion of the expanded portion is welded to the metal foil on the opening of the composite metal plate The metal sheet on the opening welded to the metal sheet by the abnormally increased internal pressure of the battery, and the metal sheet on the opening is turned to the outside of the battery, thereby forming a composite metal sheet. It is characterized in that it is configured so as to cut off an energizing circuit from to the metal cap .
[0007]
According to the above configuration, the opening provided at the center of the metal plate constituting the composite metal plate is formed by covering with the metal foil, and the center of the bulging portion of the metal thin plate is welded to this portion of the metal foil. Therefore, when the internal pressure of the battery abnormally rises enters through the ventilation hole formed in the composite metal plate and the pressure reaches the metal plate, the bulging portion of the pressed metal plate becomes the metal foil at the position of the welded opening. , And the electric circuit from the composite metal plate to the metal cap is cut off. In this configuration, the breaking accuracy of the current-carrying circuit due to the internal pressure of the battery depends on the breaking strength of the metal foil covering the opening, so the breaking strength related to the material and thickness of this metal foil may be controlled, and the metal foil may be fixed. If the quality is controlled to be as low as possible, it is possible to configure a current-carrying circuit cutoff structure that operates stably.
[0009]
The composite metal plate can be formed by folding the outer peripheral portion of the metal plate in the centripetal direction and holding the peripheral portion of the metal foil in the folded portion, instead of using the clad material. The metal foil is welded to the center of the bulge of the metal sheet that has been advanced to the opening formed in the center of the metal sheet, so that when the metal sheet is reversed by the internal pressure of the battery and recedes from the opening, the metal foil is removed. The rupture range covers the opening, and the rupture strength of the metal foil can be set to a predetermined accuracy.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
[0011]
FIG. 1 shows the structure of a sealing plate portion of a sealed battery according to a first embodiment of the present invention as a cross-sectional structure. The sealed battery has a bottomed cylindrical shape in which a power generation element is accommodated in a lower part (not shown). The upper opening of the battery case 10 formed in the above is hermetically sealed with a sealing plate 1. The sealing plate 1 has a composite metal plate 6 in which a metal foil 6b is joined to a metal plate 6a by a cladding process, an insulating ring 5, and a central portion in a peripheral portion fixed to the battery case 10 by swaging. A thin metal plate 4 having a swelling portion 4a formed on the inside of the battery, a PTC 3 which is a ring-shaped critical temperature resistor, and a metal cap 9 having a vent 9a are arranged in this order. The battery case 10 is insulated from the battery case 10 and fixed to the battery case 10 by caulking. The lead 8 connected to the power generating element is joined to the metal plate 6a of the composite metal plate 6, and the metal foil 6b and the center of the bulging portion of the thin metal plate 4 are joined by welding. An energization circuit is formed which leads to the thin metal plate 4, the PTC 3, and the metal cap 9.
[0012]
As shown in FIG. 3, the composite metal plate 6 is a clad material obtained by cold pressing an aluminum foil (metal foil) 6b on the surface of an aluminum disk (metal plate) 6a having an opening 11 formed at the center position. After that, the vent 12 is formed by penetrating the aluminum plate 6a and the aluminum foil 6b.
[0013]
The thin metal plate 4 has a bulged portion 4a gently bulging toward the inside of the battery at the center, and an easily breakable portion 4b having a C-shaped thin portion formed on the bulged portion 4a. Is provided. To show this in a specific configuration example, an aluminum plate having a thickness of 0.15 mm is formed into a disk having a diameter of 12.7 mm, and a C-shaped stamp having a diameter of 4.0 mm is formed on the bulging portion 4a. The easily breakable portion 4b is formed by forming a thin portion having a U-shape. The thin metal plate 4 is laser-welded to the aluminum foil 6b at the center of the bulging portion 4a and at the center of the opening 12 of the composite metal plate 6.
[0014]
Further, a PTC (Positive Temperature Coefficient) 3 is a well-known critical temperature resistor, which has a negligible electric resistance value that can be ignored in a normal state. However, the temperature rises to a predetermined value due to a rise in temperature caused by the flow of an excessive current. Is a positive temperature coefficient resistance element whose electric resistance value rapidly increases when the temperature exceeds a critical temperature range (critical temperature).
[0015]
The sealed battery provided with the sealing plate 1 having the above-described structure can reduce the internal pressure due to gas or the like generated when a device using the sealed battery fails, or is improperly used due to improper use or external short circuit. An abnormal response operation corresponding to an abnormal increase or an abnormal temperature increase will be described below with reference to FIGS.
[0016]
Examples of abnormal use of batteries include a short circuit between the positive and negative electrodes due to a failure of the device that uses the battery, overcharging due to a charger failure, overload use ignoring battery capacity, and a positive or negative electrode due to intentional or unexpected situations. Short-circuiting, over-discharging due to multiple series connection, reverse charging, and the like can be considered. In order to cope with such abnormal use, three kinds of abnormal response operations are performed.
[0017]
First, in the first abnormal response operation, when an excessive current flows, the temperature of the PTC 3 rises due to the excessive current flowing, and when the PTC 3 reaches a critical temperature, its electric resistance value sharply increases. As a result, the supplied current is greatly reduced and maintained, and battery damage due to an external short circuit or erroneous use due to excessive current is prevented.
[0018]
However, in the case of a lithium secondary battery, which is an example of a sealed battery, in the case of uncontrolled overcharging due to a failure of a charger or the like, reverse charging, overdischarging in a large number of series connections, etc., the PTC 3 reaches a critical temperature. Even if the current does not increase the temperature, the internal pressure of the battery may increase beyond the safe capacity of the battery. That is, when such an abnormal current continues to flow, the battery temperature rises rapidly with the decomposition of the electrolytic solution and the active material, and a large amount of gas or vapor is generated. Therefore, when the battery internal pressure rises above a predetermined pressure, a second abnormality handling operation for interrupting the current supply circuit is started.
[0019]
The state of each component of the sealing plate 1 shown in FIG. 1 is a normal state, and when the internal pressure in the battery case 10 rises, the internal pressure enters through the vent 12 formed in the composite metal plate 6. When the internal pressure exceeds a predetermined value, the bulging portion 4a of the thin metal plate 4 is welded at the opening 11 of the composite metal body 6 at its center position as shown in FIG. The metal foil 6b is torn and its bulging direction is reversed. Due to the reversal of the bulging portion 4a, the conduction between the composite metal plate 6 and the thin metal plate 4 is cut off, and the energizing circuit is cut off. The source of the rise is eliminated.
[0020]
However, even if the abnormal current is interrupted, the temperature does not drop instantaneously, the generation of gas or steam does not subside instantaneously, and if the internal pressure of the battery continues to increase, the third abnormal response operation is performed. to start. That is, when a large amount of gas or vapor is generated and the internal pressure of the battery reaches a predetermined value set based on the breaking strength of the easily breakable portion 4b provided on the thin metal plate 4, the easily breakable portion 4b breaks and the thin metal plate 4 The central portion of the metal cap 8 is cleaved, and the gas or vapor filling the inside of the battery is discharged outside from the vent 8a of the metal cap 8.
[0021]
Next, a configuration of a sealed battery according to a second embodiment of the present invention will be described with reference to FIGS. This configuration shows a modification of the composite metal plate 6 in the configuration of the first embodiment, and other components are common. Therefore, common components are denoted by the same reference numerals, and description thereof is omitted.
[0022]
In FIG. 4, a composite metal plate 13 is provided on the inside of the battery of the sealing plate 1a. As shown in FIG. 6, the composite metal plate 13 has a metal disk (metal) having an opening 14 in the center as shown in FIG. A metal foil 13b having a thickness of 0.01 mm to 0.1 mm is superimposed on the metal plate 13 and the metal disk 13a is folded back from the periphery in the centripetal direction at the outer periphery, and the periphery of the metal foil 13b is clamped and fixed. A ventilation hole 15 penetrating through the metal foil 13a and the metal foil 13b is formed.
[0023]
As shown in FIG. 4, the composite metal plate 13 is disposed such that the metal foil 13b is located on the inside of the battery at the center, and the metal metal 13 protrudes into the opening 14 formed at the center of the metal disk 13a. The center of the bulging portion 4a of the thin plate 4 is welded to the metal foil 13b.
[0024]
In this configuration, when the battery internal pressure rises abnormally, the battery internal pressure that enters the sealing plate 1a through the ventilation hole 15 formed in the composite metal plate 13 reaches the metal thin plate 4, and as shown in FIG. Is inverted. At this time, the metal foil 13b welded to the bulging portion 4a of the thin metal plate 4 is torn off by the bulging portion 4a which is inverted. The breaking strength of the metal foil 13b can be set as the strength at which the metal foil 13b covering the opening 14 formed in the metal disk 13a breaks at the peripheral portion of the opening 14, so that the material and the thickness of the metal foil 13b are reduced. By controlling, the breaking accuracy can be maintained constant. Therefore, since it does not depend on the peel strength of the welded portion which is hard to be processed to a constant joining strength, a stable energizing circuit cutoff structure can be configured.
[0025]
Note that the configuration of the PTC 3 in this configuration for suppressing an excessive current and for releasing the gas to the outside when the battery internal pressure is abnormally increased after the current interruption is the same as the operation of the configuration of the first embodiment described above. Omitted.
[0026]
In the above embodiment, the cylindrical battery is described. However, the present invention can be similarly applied to a prismatic battery or a battery similar thereto.
[0027]
【The invention's effect】
As described above, according to the present invention, the center of the swelling portion of the thin metal plate is welded to the metal foil covering the opening of the metal plate constituting the composite metal plate, and the structure for interrupting the current-carrying circuit due to an abnormal rise in the internal pressure of the battery. Is formed, when the bulging portion of the thin metal plate is reversed by the internal pressure of the battery, the metal foil covering the opening is torn off by the bulging portion which is reversed, and the energizing circuit is cut off. Therefore, it is possible to control the breaking strength of the metal foil covering the opening without depending on the peeling of the welded part where it is difficult to obtain a constant joining strength. A highly accurate energizing circuit shutoff structure can be configured.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a sealing plate of a sealed battery according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a state in which the operation of interrupting the energizing circuit has been performed from the normal state shown in FIG. 1;
FIGS. 3A and 3B are a plan view and a cross-sectional view taken along line AA of the composite metal plate according to the first embodiment.
FIG. 4 is a sectional view showing a configuration of a sealing plate of a sealed battery according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a state in which an operation of interrupting an energizing circuit is performed from the normal state shown in FIG. 4;
6A is a plan view showing a configuration of a composite metal plate according to a second embodiment, and FIG. 6B is a cross-sectional view taken along line AA.
[Explanation of symbols]
1, 1a sealing plate 3 PTC
Reference Signs List 4 metal thin plate 4a bulging portion 4b easily breakable portion 6, 13 composite metal plate 6a, 13a metal plate 6b, 13b metal foil 9 metal cap 10 battery case 11, 14 opening 12, 15 vent hole

Claims (2)

The end opening of the battery case accommodating the power generation element is hermetically sealed by a sealing plate, and a metal thin plate provided near the inside of the battery from a metal cap forming an electrode portion of the sealing plate is deformed by an increase in battery internal pressure. , In a sealed battery equipped with a mechanism for shutting off an energizing circuit from a power generating element to a metal cap,
The sealing plate is provided at a position facing the inside of the battery so as to be electrically connected to the power generating element, and an opening is formed only in the metal plate at a central portion of the clad material that is formed by laminating a metal plate and a metal foil and cold-pressing the metal plate. And a composite metal plate having a ventilation hole formed through a metal plate and a metal foil at an appropriate position in the clad material ,
Together with the peripheral portion is fixed and supported together with the composite metal plate via an insulating member in the battery outside of the composite metal plate, the metal cap is provided with electrically connected loosely to the battery inner side in the central portion Forming a swelling portion that swells, comprising a metal sheet whose central portion is welded to a metal foil on the opening of the composite metal plate ;
Due to the abnormally increased internal pressure of the battery, the bulging portion of the thin metal plate tears off the metal foil on the opening welded to the thin metal plate and turns over to the outside of the battery, so that an energizing circuit from the composite metal plate to the metal cap is formed. A sealed battery characterized in that the battery is shut off . The end opening of the battery case accommodating the power generation element is hermetically sealed by a sealing plate, and a metal thin plate provided near the inside of the battery from a metal cap forming an electrode portion of the sealing plate is deformed by an increase in battery internal pressure. , In a sealed battery equipped with a mechanism for shutting off an energizing circuit from a power generating element to a metal cap,
The sealing plate is provided at a position facing the inside of the battery so as to be electrically connected to the power generating element. The metal plate and the metal foil are overlapped so that the former is on the outside of the battery, and the outer peripheral portion of the metal plate is placed in the centripetal direction. The composite plate is made of a composite plate in which the peripheral portion of the metal foil is pressed and held at the folded portion. At the center of the composite plate, an opening is formed only in the metal plate. A composite metal plate with ventilation holes formed through the foil,
A peripheral portion of the composite metal plate is fixedly supported on the outside of the battery via an insulating member together with the composite metal plate, and is provided so as to be electrically connected to the metal cap. Forming a swelling portion that swells, comprising a metal sheet whose central portion is welded to a metal foil on the opening of the composite metal plate;
Due to the abnormally increased internal pressure of the battery, the bulging portion of the thin metal plate tears off the metal foil on the opening welded to the thin metal plate and turns over to the outside of the battery, so that an energizing circuit from the composite metal plate to the metal cap is formed. A sealed battery characterized in that the battery is shut off.

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