JP3056457B2 - Sealed secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed secondary battery, and more particularly to a sealed secondary battery in which conduction is interrupted inside the battery when the internal pressure of the battery rises abnormally during charging.
Next battery.

[0002]

2. Description of the Related Art As a sealed secondary battery of this type, for example, there is a non-aqueous lithium secondary battery, which can be reused by charging. The sealed secondary battery includes a cylindrical negative electrode can having a bottom on one end side, and a power generating element using lithium is stored in the negative electrode can, and the negative electrode side of the power generating element is connected to the negative electrode can. At the same time, the open end on the other end side of the negative electrode can is insulated and closed by a positive electrode terminal, and the positive electrode side of the power generating element is connected to this positive electrode terminal.

In such a sealed secondary battery, if the battery is overcharged due to an abnormality of a charger or the like, the battery temperature rises (about 100 ° C.), and the electrolyte impregnated into the power generating element is disturbed. May be decomposed to generate gas, and the internal pressure may rise significantly. When the internal pressure of the battery is abnormally increased, a problem such as leakage of the enclosed electrolytic solution to the outside occurs. Therefore, when the internal pressure exceeds a predetermined pressure, conduction inside the battery is cut off. A device equipped with an apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 5-34043 (Int.
01M 2/12).

In the above safety device, a safety valve is provided on the positive electrode terminal side, and the safety valve expands and deforms due to the internal pressure, thereby cutting off the conduction path of the positive electrode, so that further charging is automatically stopped. It has become. That is, Japanese Patent Application Laid-Open No.
The sealed secondary battery disclosed in Japanese Patent No. 343043 has a negative electrode can (exterior can) that houses the power generating element, and a positive electrode terminal (lid) attached to an open end of the negative electrode can via an insulating material.
A safety valve, which is formed of a conductive member disposed in a conductive state inside the positive electrode terminal and is deformed in the direction of the positive electrode terminal in accordance with the internal pressure, and is disposed between the safety valve and the power generating element; An intermediate member (a thin metal plate) that electrically connects the side to the safety valve, and a holding member (a disk, a disk holder) that prevents the intermediate member from moving toward the positive electrode terminal. The internal pressure causes the safety valve to bulge outward and separate from the intermediate member, thereby interrupting conduction between the safety valve and the intermediate member.

[0005]

However, in such a conventional sealed secondary battery, the safety valve is deformed due to an increase in battery internal pressure, and the conduction path on the positive electrode side is cut off.
Since the conduction path is blocked in this way, an abnormal current can be prevented from flowing into the battery.If the internal pressure decreases due to a drop in the battery temperature, for example, the safety valve that has swelled and deformed outwards returns. May become conductive again.
When re-conducted in this way, conduction is restored and an abnormal current flows again. Then, a phenomenon that heat is generated again to generate gas, and the internal pressure increases, is repeated, and the sealing performance of the battery itself is impaired, and there is a problem that the electrolyte leaks.

Therefore, the present invention has been made in view of such a conventional problem, and once the conduction state is interrupted by deformation of the safety valve, the conduction is restored by maintaining the interruption state of the safety valve. It is an object of the present invention to provide a sealed secondary battery that prevents the occurrence of the above problem.

[0007]

In order to achieve the above object, a sealed secondary battery of the present invention will be described below for each claim.

According to a first aspect of the present invention, there is provided a sealed secondary battery including a negative electrode can housing a power generating element, a positive electrode terminal attached to an open end of the negative electrode can via an insulating material, and a conductive member inside the positive electrode terminal. A safety valve that is arranged in a state and is deformed outward according to the internal pressure, an intermediate member that is disposed between the safety valve and the power generation element, and that connects the positive electrode side of the power generation element to the safety valve, A holding member that prevents the safety valve from moving in the direction of the safety valve, and when the internal pressure of the battery is abnormally increased, the internal pressure deforms the safety valve outward and separates from the intermediate member, thereby establishing conduction between the safety valve and the intermediate member. In a sealed type secondary battery in which the state is shut off, a state in which a spring member having a biasing force in a direction in which the two are separated from each other is interposed between the safety valve and the holding member, and the spring member is interposed With above safety valve And the intermediate member is constructed by coupling with a removable intensity when the battery internal pressure rises above a predetermined pressure.

According to a second aspect of the present invention, a slide member is provided between the intermediate member and the holding member, the slide member being movable in a direction away from the positive electrode terminal while integrally holding the intermediate member. At the same time, a spring member having a biasing force in a direction away from the slide member and the safety valve is interposed between the slide member and the safety valve. With the spring member interposed, the safety valve and the intermediate member are connected to each other, and the internal pressure of the battery is reduced. It is configured by joining with a strength that can be released when the pressure rises to a predetermined pressure or more.

According to a third aspect of the present invention, there is provided a sealed secondary battery, wherein the insulating material used in the first or second aspect is formed with a reduced diameter portion which comes into contact with the lower end portion of the holding member or approaches the lower end portion with a slight gap.

The operation of the sealed secondary battery of the present invention having the above structure will be described below for each claim.

According to the first aspect, the positive electrode terminal attached to the open end of the negative electrode can is electrically connected to the positive electrode side of the power generating element via the safety valve and the intermediate member. Since the safety valve and the intermediate member were urged in a direction away from each other with a spring member interposed therebetween, the internal pressure of the battery rose to a predetermined pressure or more, and the safety valve swelled and deformed outward and was separated from the intermediate member. In this case, the urging force of the spring member acts on the safety valve in a direction that promotes the deformation of the safety valve. Therefore, when the internal pressure of the battery drops and the safety valve attempts to return due to conduction interruption due to the release of the safety valve from the intermediate member, the safety valve is prevented from completely returning by the urging force of the spring member, and is extended. Can reliably prevent the safety valve and the intermediate member from conducting.

According to a second aspect of the present invention, a slide member is provided between the intermediate member and the holding member, the slide member being movable in a direction away from the safety valve while integrally holding the intermediate member. Since the spring member is interposed between the slide member and the safety valve, the slide member and the safety valve are urged in a direction away from each other. Acts in a direction that promotes deformation of the safety valve, and moves the slide member away from the safety valve. At this time, since the intermediate member also moves along with the slide member, the distance between the intermediate member and the safety valve increases, so that even when the safety valve attempts to return due to a decrease in battery internal pressure, the spring member does not move. Since the urging force is acting and the intermediate member escapes from the safety valve, it is possible to more reliably prevent the safety valve and the intermediate member from conducting again.

According to a third aspect of the present invention, a reduced diameter portion is formed at the inner end of the insulating member so as to be in contact with or close to the lower end of the holding member with a small gap. When the holding member is released, the lower end portion of the holding member is supported by the reduced diameter portion to prevent the holding member from dropping. Thus, it is possible to eliminate the problem that this is short-circuited to the safety valve.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 show a first embodiment of a sealed secondary battery of the present invention. FIG. 1 is a cross-sectional view showing a main part of the battery during normal charging. FIG. FIG.

That is, a sealed secondary battery (hereinafter simply referred to as a battery) 10 to which the present invention is applied is as shown in FIG.
A negative electrode can 14 for accommodating the power generating element 12;
A positive electrode terminal 18 attached to the open end 14a of the battery via a gasket 16 as an insulating material;
8, a conductive member disposed in a conductive state inside,
A safety valve 20 that is deformed outward (toward the positive electrode terminal 18) in accordance with the internal pressure; and an intermediate member 22 that is disposed between the safety valve 20 and the power generation element 12 and that connects the positive electrode side of the power generation element 12 to the safety valve 20. And a holding member 24 for preventing the intermediate member 22 from moving in the direction of the safety valve 20. When the battery internal pressure rises abnormally, the internal pressure deforms the safety valve 20 outward and separates from the intermediate member 22. Then, the conduction state between the safety valve 20 and the intermediate member 22 is shut off.

In the battery 10 having such a configuration, the basic configuration of the present invention is that a taper spring 26 as a spring member having a biasing force in a direction in which the safety valve 20 and the holding member 24 are separated from each other. With the taper spring 26 interposed, the safety valve 20 and the intermediate member 2 are interposed.
2 is connected to the battery 2 with a strength that allows the battery 2 to be detached when the internal pressure of the battery rises above a predetermined pressure.

The battery 10 is configured as a non-aqueous lithium battery. The power generating element 12 includes a sheet-like positive electrode material and a negative electrode material with a separator impregnated with an electrode solution interposed therebetween. The three-layer structure of the separator and the separator are spirally wound to form a cylindrical shape as a whole. The power generation element 12 is accommodated in the negative electrode can 14.

The positive electrode terminal 18 has a central protruding portion 18a which is formed in a circular shape and bulges outward. The peripheral portion 18b of the central protruding portion 18a is formed by the peripheral portion of the safety valve 20 and the ring-shaped PTC. The element 28 and the negative electrode can 14 are caulked and fixed to the open side end 14a of the negative electrode can 14 via the gasket 16, and the caulking seals the open side end 14a. The gasket 16 is formed of an insulating material such as a synthetic resin, and has a positive electrode terminal 18 and a PTC element 28.
A cover 16a is provided to cover the outer periphery and upper and lower surfaces of the peripheral portion of the safety valve 20, and a reduced diameter portion 16b extends from the inner periphery of the lower end of the cover 16a. The reduced diameter portion 16b is in contact with the lower end of the holding member 24 or close to the lower end with a slight gap.

The positive electrode terminal 18 and the safety valve 20
The PTC element 28 interposed between the PTC element and the PTC element 28 has a property that the resistance increases as the temperature rises. When an excessive current flows due to a short circuit or the like, the resistance can be increased to reduce the current. The safety valve 20 is formed of a flat thin metal plate and swells and deforms according to the internal pressure of the battery.

The intermediate member 22 is formed of a metal plate, and has an end surface 22a facing the center of the safety valve 20, and a tapered portion gradually increasing in diameter from the periphery of the end surface 22a toward the inside of the negative electrode can 14. 22b and a flange 22c provided at the peripheral edge of the distal end of the tapered portion 22b are formed, and form a cup shape as a whole and are integrated with the holding member 24. The holding member 24 is formed of an insulating material such as a synthetic resin, and is integrally formed on the outer periphery of the intermediate member 22 by injection molding. The holding member 24 has an annular recess 24a opened toward the safety valve 20 around the intermediate member 22, and a thick peripheral wall 24b formed on a peripheral portion of the annular recess 24a has a battery. A plurality of openings 24c that are opened in the direction of the central axis are formed at equal intervals in the circumferential direction.

The tapered spring 26 is connected to the intermediate member 22.
The holding member 24 is housed in the annular concave portion 24a so as to surround the tapered portion 22b. The tapered spring 26 is set to be naturally higher than the end surface 22a of the tapered portion 22b when housed in the annular concave portion 24a.
2a is brought into contact with the safety valve 20, and these end faces 22a and the safety valve 20 are joined by laser welding P. As described above, the intermediate member 22 and the safety member 20 are laser-welded to the safety valve 20, so that the intermediate member 22 and the holding member 24 are connected to the peripheral portion of the safety valve 20, that is, the positive electrode terminal 18.
The intermediate member 22 is prevented from moving toward the positive electrode terminal 18 by the holding member 24 in this fixed state.

As described above, the power generating element 12 is formed by winding a three-layer structure of a positive electrode material, a negative electrode material, and a separator. The lead plate 30 on the positive electrode side is connected to the flange 22 c surface of the intermediate member 22, and the lead plate (not shown) on the negative electrode side is connected to the inside of the negative electrode can 12.

In the battery 10 of the present embodiment having the above-described configuration, the positive electrode side of the power generating element 12 is a lead plate 30, an intermediate member 22 to which the lead plate 30 is connected, and laser welding to the intermediate member 22. Safety valve 20 and PTC
The electrical connection to the positive electrode terminal 18 is made via the element 28, and the negative electrode side of the power generating element 12 is electrically connected to the negative electrode can 14 via a lead plate (not shown).

At this time, since the safety valve 20 and the intermediate member 22 are connected with a predetermined fixing force by laser welding, if the internal pressure of the battery rises to a predetermined pressure or more due to the occurrence of an excessive current during charging, etc. When an outward pressure acts on the laser welding 20 and the laser welding P portion peels off, the safety valve 20 bulges outward and separates from the intermediate member 22 as shown in FIG. 20
And the intermediate member 22 is interrupted.

When the conduction is cut off as described above, the internal pressure of the battery is reduced, and the safety valve 20 attempts to return again. However, in the battery 10 of the present embodiment, the safety valve 20 and the holding member 24 The safety valve 20 and the intermediate member 22 are urged in a direction separating the safety valve 20 and the intermediate member 22 from each other, so that the urging force of the taper spring 26 acts in a direction to promote the deformation of the safety valve 20. Will be. For this reason, when the internal pressure of the battery drops and the safety valve attempts to return due to the conduction interruption due to the separation between the safety valve 20 and the intermediate member 22, the safety valve 20 is prevented from completely returning by the urging force of the taper spring 26. can do.
Therefore, since the safety valve 20 is not completely restored in this way, the safety valve 20 and the intermediate member 22 do not become conductive, and it is possible to reliably prevent gas from being generated again and the internal pressure from rising. Thus, it is possible to prevent the internal electrolyte from leaking outward due to the repeated increase and decrease of the internal pressure.

As described above, in the battery 10 of the present embodiment, the current is not restored even when the battery is overcharged, so that the occurrence of rejected products in the liquid leakage test can be significantly reduced. The following table shows the results of a liquid leakage test of a conventional battery and a battery of the present embodiment, in which energization may be restored, and 50 batteries were overcharged and tested.

[0028]

[Table 1] That is, as is clear from this table, the conventional battery has 10
%, Whereas the battery 10 of the present embodiment can eliminate the occurrence of defective products, and can greatly improve the yield.

When the safety valve 20 and the intermediate member 22 are separated from each other, the fixing force of the holding member 24 is lost.
Since the lower end of the holding member 24 can be supported by the reduced diameter portion 16b of the gasket 16, the holding member 24 is prevented from dropping, and in some cases, the intermediate member 22 is dropped.
Can be eliminated, which can cause a short-circuit to the safety valve 20.

In this embodiment, the case where the tapered spring 26 is used as the spring member has been disclosed. However, the present invention is not limited to this, and a normal coil spring having the same diameter as the whole may be used. Any urging means that urges the member 22 in the direction away from the member 22 may be used.

FIGS. 3 and 4 show a second embodiment of the present invention. FIG. 3 is a sectional view showing a main part of the battery during normal charging.
Is a cross-sectional view showing a main part of the battery at the time of conduction interruption, and the same components as those in the above embodiment are denoted by the same reference numerals, and redundant description will be omitted.

That is, in the battery 10 of this embodiment, a slide member 32 movable between the intermediate member 22 and the holding member 24 in a direction away from the safety valve 20 while integrally holding the intermediate member 24 is provided. At the same time, a coil spring 34 as a spring member having a biasing force in a direction separating the slide member 32 and the safety valve 20 is interposed between the slide member 32 and the safety valve 20, and the safety valve 20 and the safety valve 20 are interposed with the coil spring 34 interposed therebetween. The intermediate member 22 is connected to the intermediate member 22 with sufficient strength to be detachable when the internal pressure of the battery rises above a predetermined pressure.

The slide member 32 is formed in a cylindrical shape.
The flange 22c of the cup-shaped intermediate member 22 is integrally attached to the bottom of the slide member 32, and the tapered portion 22b of the intermediate member 22 is disposed in the slide member 32. At this time, the end surface 22a at the tip of the tapered portion 22b and the end surface 32a of the slide member 32 are formed flush. A flange 32 is provided on the outer periphery of the slide member 32.
The flange 32b is fitted to the inner periphery of the holding member 24 so as to be slidable in the central axis direction, and is locked by a small diameter portion 24d formed at the upper end of the holding member 24. And further movement is prevented. Further, in a state where the flange portion 32b is locked to the small diameter portion 24d, the end surface 32a of the slide member 32 and the end surface 24e of the holding member 24 are formed flush.

The coil spring 34 is housed in the inner periphery of the slide member 32, and the end face 22 a of the intermediate member 22 is laser welded P to the safety valve 20 in a state where the coil spring 34 is compressed. Thus, the intermediate member 22
The slide member 32 and the holding member 24 are fixed by laser welding of the safety valve 20 and the safety valve 20.

Accordingly, in the battery 10 of this embodiment, when the safety valve 20 expands and deforms and separates from the intermediate member 22 due to an increase in battery internal pressure, the urging force of the coil spring 34 promotes the deformation of the safety valve 20. And moves the slide member 32 along the inner periphery of the holding member 24 in a direction away from the positive electrode terminal 18, that is, the safety valve 20. At this time, the intermediate member 22 also moves with the slide member 32, and the distance between the intermediate member 22 and the safety valve 20 increases. Therefore, even when the battery internal pressure decreases due to the conduction interruption caused by the separation between the safety valve 20 and the intermediate member 22 and the safety valve 20 attempts to return due to the decrease in the internal pressure, the urging force of the coil spring 34 acts. Since the intermediate member 22 escapes from the safety valve 20, the safety valve 20 and the intermediate member 22 can be more reliably prevented from conducting again. Therefore, even in this embodiment, the same result as the test shown in Table 1 of the first embodiment could be obtained.

Also in this embodiment, the reduced diameter portion 16b of the gasket 16 is in contact with the lower end of the holding member 24 with a slight gap or close to the lower end of the holding member 24. Even if the fixing force is lost, the holding member 24 can be prevented from falling, and the intermediate member 22 can be prevented from being inclined and short-circuited with the safety valve 20. Further, although the coil spring 34 is used as a spring member for urging the safety valve 20 and the intermediate member 22 in the separating direction,
Of course, other urging means may be used.

[0037]

As described above, the sealed secondary battery of the present invention has the following advantages.

According to the first aspect of the present invention, there is provided a sealed secondary battery comprising a safety valve which deforms in response to an internal pressure to cut off conduction and a holding member which holds the intermediate member so as to prevent the intermediate member from moving in the direction of the safety valve. A spring member having a biasing force in a direction in which the two are separated from each other is interposed, and with the spring member interposed, the safety valve and the intermediate member are separated from each other with a strength capable of separating when the battery internal pressure rises to a predetermined pressure or more. Since the internal pressure of the battery rises above a predetermined pressure, the safety valve expands and deforms outward and separates from the intermediate member, so that the urging force of the spring member is applied to the safety valve in a direction that promotes the deformation. Can work. Therefore, when the safety valve is detached from the intermediate member and the conduction is cut off, when the internal pressure of the battery decreases and the safety valve attempts to return, the safety valve is prevented from completely returning by the urging force of the spring member, As a result, it is possible to reliably prevent the safety valve and the intermediate member from being electrically connected again. By preventing re-conduction in this way, it is possible to prevent the internal pressure of the battery from rising and falling repeatedly,
Leakage of the internal electrolyte can be eliminated.

According to a second aspect of the present invention, a slide member is provided between the intermediate member and the holding member, the slide member being movable in a direction away from the positive electrode terminal while integrally holding the intermediate member. Since a spring member is interposed between the slide member and the safety valve to urge the slide member and the safety valve away from each other, when the safety valve separates from the intermediate member due to an increase in battery internal pressure, The biasing force of the spring member acts in a direction that promotes the deformation of the safety valve, and the slide member itself moves in a direction away from the safety valve, thereby moving an intermediate member to increase the distance between the safety member and the safety valve. be able to. Therefore, even when the safety valve attempts to return due to a decrease in the battery internal pressure, the safety valve and the intermediate member are re-established because the urging force of the spring member is acting and the intermediate member has escaped from the safety valve. Conduction can be more reliably prevented.

According to the third aspect of the present invention, since the reduced diameter portion which is in contact with the lower end portion of the holding member or is close to the lower end portion of the holding member with a small gap is formed in the insulating material, the connection between the safety valve and the intermediate member is made. When the holding member is released, the lower end of the holding member is supported by the reduced diameter portion to prevent the holding member from falling. In turn, the falling of the holding member causes the intermediate member to tilt. By doing so, it is possible to eliminate the problem that this is short-circuited to the safety valve.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a battery during normal charging according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the battery during conduction interruption according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of a battery during normal charging according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main part of a battery during conduction interruption according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 sealed secondary battery 12 power generation element 14 negative electrode can 16 gasket (insulating material) 16b reduced diameter portion 18 positive electrode terminal 20 safety valve 22 intermediate member 24 holding member 26 taper spring (spring member) 32 slide member 34 coil spring (spring member)

Continuation of front page (56) References JP-A-10-334883 (JP, A) JP-A-10-154530 (JP, A) JP-A-10-188945 (JP, A) JP-A-9-106803 (JP) JP-A-9-7573 (JP, A) JP-A-5-343043 (JP, A) JP-A-5-347154 (JP, A) JP-A-8-162094 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 2/34

Claims (3)

(57) [Claims] 1. A negative electrode can for accommodating a power generating element, a positive electrode terminal attached to an open end of the negative electrode can via an insulating material, and a conductive state disposed inside the positive electrode terminal. An outwardly deforming safety valve, an intermediate member disposed between the safety valve and the power generating element, for conducting the positive electrode side of the power generating element to the safety valve, and preventing the intermediate member from moving in the safety valve direction. A sealing member that has a holding member, and when the battery internal pressure rises abnormally, the internal pressure deforms the safety valve outward and separates from the intermediate member, thereby interrupting conduction between the safety valve and the intermediate member. In the type secondary battery, a spring member having a biasing force in a direction separating them is interposed between the safety valve and the holding member, and the safety valve and the intermediate member are interposed with the spring member interposed therebetween. ,
A sealed secondary battery characterized in that the batteries are connected with a detachable strength when the battery internal pressure rises above a predetermined pressure. 2. A negative electrode can for accommodating a power generating element, a positive electrode terminal attached to an open end of the negative electrode can via an insulating material, and a conductive state disposed inside the positive electrode terminal. An outwardly deforming safety valve, an intermediate member disposed between the safety valve and the power generating element, for conducting the positive electrode side of the power generating element to the safety valve, and preventing the intermediate member from moving in the safety valve direction. A sealing member that has a holding member, and when the battery internal pressure rises abnormally, the internal pressure deforms the safety valve outward and separates from the intermediate member, thereby interrupting conduction between the safety valve and the intermediate member. In the secondary battery, a slide member is provided between the intermediate member and the holding member, the slide member being movable in a direction away from the safety valve while integrally holding the intermediate member, and the slide member and the safety valve are provided. A spring member having a biasing force in a direction in which the two are separated from each other is interposed, and the safety valve and the intermediate member can be disengaged with the spring member interposed when the internal pressure of the battery rises above a predetermined pressure. A sealed secondary battery characterized in that it is bonded with a high strength. 3. The closed mold 2 according to claim 1, wherein a reduced diameter portion is formed in the insulating material so as to be in contact with the lower end portion of the holding member or to approach the lower end portion with a slight gap.
Next battery.