JP4121130B2 - Sealed battery - Google Patents

Description

  The present invention relates to a cylindrical sealed battery such as a lithium ion secondary battery provided with a cleavage vent.

  In recent years, with the miniaturization and higher functionality of electronic devices, there is a demand for higher capacity of sealed batteries used for power supplies. As a battery useful for these applications, a sealed battery using metallic lithium as a positive electrode active material has attracted attention. In such a sealed battery, a large amount of gas is generated in the battery due to incorrect handling such as abnormal charging / discharging due to troubles of electronic devices or dropping of the battery into the fire, resulting in excessive battery internal pressure. The battery may explode.

  On the other hand, Patent Documents 1 to 5 disclose that a circular sealing wall that seals the upper and lower surfaces of a cylindrical battery case is provided with a cleavage vent for preventing the battery from bursting. Such a cleavage vent forms a thin portion by providing a groove in the sealing wall so that when the internal pressure of the battery exceeds a predetermined value, the thin portion is cleaved and the gas inside the battery is quickly released. It has become.

Japanese Utility Model Publication No. 51-3376 (page 2, left column, lines 26-32, FIG. 3) Japanese Utility Model Publication No. 61-30276 (page 1, right column, lines 19-26, FIG. 2) JP-A-2-281552 (page 3, upper left column-upper right column, FIG. 3) JP-A-9-115497 (paragraph number 0012-0013, FIG. 2) Japanese Patent Laid-Open No. 11-213978 (paragraph number 0013, FIG. 1)

  In Patent Documents 1 to 3, the thin wall portion passes through the center of the sealing wall, and when the internal pressure of the battery rises and the sealing wall expands and deforms in a dome shape, the deformation near the center of the sealing wall is maximized, The thin part is cleaved starting from the central part of the sealing wall. For this reason, in patent documents 1-3, if a positive electrode terminal etc. are arranged in the center of a sealing wall, it will become difficult to cleave a thin part.

  In Patent Document 4, the thin wall portion is formed in a semicircular shape that is concentric with the periphery of the sealing wall, and when the sealing wall is inflated and deformed into a dome shape, the center side of the sealing wall is in a planar state by an elastic restoring force. To return, pull the thin part up and down and tear it off. In this case, a large opening is formed in the sealing wall. For this reason, in Patent Document 4, there is a possibility that part of the electrode, which is the contents, jumps out as the thin portion is cleaved, and the periphery of the battery is soiled or the object around the battery is damaged. Moreover, there is a possibility that the portion other than the thin portion may be cleaved, and in this case, the contents are more likely to jump out.

  Accordingly, an object of the present invention is to provide a sealed battery in which the contents are not easily ejected when the cleavage vent is actuated after ensuring the action of the cleavage vent.

As shown in FIG. 3, the sealed battery targeted by the present invention is such that the upper opening of a bottomed cylindrical battery case 1 is sealed by a circular sealing wall 2, and the center of the sealing wall 2 is caulking sealed. Terminal 5 is arranged, and one cleavage vent 7 is arranged so as to surround the terminal 5 . The cleavage vent 7 includes the thin portions 12 that are cleaved when the internal pressure of the battery is equal to or higher than a predetermined value by providing the grooves 10 and 11 with respect to the sealing wall 2. The thin-walled portion 12 extends in an arc shape that is concentric with the peripheral edge of the sealing wall 2, and has a vent angle θ <b> 1 defined by a virtual straight line connecting the center of the sealing wall 2 and both ends of one cleavage vent 7. , 90 ° to 150 °.

The thin-walled portion 12 of the cleavage vent 7 is formed by pressing grooves 10 and 11 on the front and back of the sealing wall 2 so as to face each other. The groove 10 on the surface side of the sealing wall 2 has an upward flat surface and is formed in a stepped shape that is one step lower than the surface of the sealing wall 2. The groove on the inner surface side of the sealing wall 2 is formed by two-step pressing, and has a flat surface facing downward, and is formed in a stepped shape that is one step lower than the inner surface of the sealing wall 2. The first-stage groove and a second-stage groove having a downward flat surface and being recessed in a stepped shape one step lower than the flat surface of the first-stage groove. The second-stage groove can be formed such that its flat surface is located at the center in the width direction of the flat surface of the first-stage groove.

According to the present invention, since the thin portion 12 is formed in an arc shape concentric with the periphery of the sealing wall 2, even if the positive terminal 5 or the like is arranged at the center of the sealing wall 2, the positive terminal 5 The cleavage vent 7 can be formed so as not to interfere with the above, and the cleavage vent 7 can be operated reliably .

  Since the vent angle θ1 of the cleavage vent 7 is set to 90 ° or more, the cleavage vent 7 can be easily processed, the operating pressure of the cleavage vent 7 does not become excessively high, and battery rupture can be prevented appropriately. In addition, since the vent angle θ1 is set to 150 ° or less, it is possible to reliably prevent the battery contents from popping out when the cleavage vent 7 is operated, and the battery contents are contaminated by the battery contents or damaged around the battery. This can be reliably prevented, and the area of the thin portion 12 does not become too large, and the operating pressure of the cleavage vent 7 is stabilized.

  When the thin wall portion 12 is formed by pressing at least one of the front and back grooves 10 and 11 in two steps, stress is concentrated on the thin wall portion 12 when the sealing wall 2 is expanded and deformed due to an increase in battery internal pressure. And the reliability of the operation of the cleavage vent 7 can be further increased, the accuracy of the thickness of the thin portion 12 can be increased, and a more stable operation pressure of the cleavage vent 7 can be obtained. Obtainable.

(Example 1) FIGS. 1 to 3 show Example 1 of a sealed battery targeted by the present invention, and as shown in FIG. 3, a bottomed cylindrical battery case 1 having an open top surface, A circular sealing plate (sealing wall) 2 that closes the upper surface opening of the battery case 1, an electrode winding body 3 and a non-aqueous electrolyte solution accommodated in the battery case 1 are included. The battery case 1 and the sealing plate 2 are formed of a cold rolled steel plate (SPCC).

  In the center of the sealing plate 2, a terminal mounting hole 6 through which the insulating gasket 4 and the positive electrode terminal 5 pass is provided in a penetrating manner. The sealing plate 2 is fitted into the upper surface opening of the battery case 1 and the outer peripheral edge of the sealing plate 2 is laser welded to the inner peripheral surface of the battery case 1 so that the opening of the battery case 1 is sealed with the sealing plate 2. ing. The positive terminal 5 is caulked and fixed to the periphery of the terminal mounting hole 6 via the insulating gasket 4.

  The electrode winding body 3 is formed by laminating a sheet-like positive electrode coated with a positive electrode active material and a sheet-shaped negative electrode coated with a negative electrode active material with a sheet-like separator made of a synthetic resin film sandwiched between them. A group of electrodes wound in a cylindrical shape is accommodated in the battery case 1. The positive electrode and the positive electrode terminal 5 of the electrode winding body 3, and the inner surface of the battery case 1 and the negative electrode of the electrode winding body 3 are connected to each other by a conductive tab.

  As shown in FIG. 1, the sealing plate 2 is provided with a cleavage vent 7 extending in an arc shape concentric with the periphery of the sealing plate 2. As shown in FIG. 2, the cleavage vent 7 is formed by pressing the grooves 10 and 11 on the front and back of the sealing plate 2 so as to face each other. The groove 10 provided on the front side of the sealing plate 2 is formed by one-step pressing, and the groove 11 provided on the back side of the sealing plate 2 is formed by two-step pressing. The thin portion 12 is formed between the bottom surfaces of the front and back grooves 10 and 11 by such pressing.

  As shown in FIGS. 1 and 2, the thin portion 12 of the cleavage vent 7 has a diameter L1 at the center line of 10.7 mm and an upper and lower thickness T1 of 0.05 mm. The groove 10 on the front side of the cleavage vent 7 has a width dimension L2 of 1.2 mm and a vertical depth dimension T2 of 0.25 mm. The width dimension L3 of the first-stage groove 11a in the groove 11 on the back side of the cleavage vent 7 is 1.2 mm, and the vertical depth dimension T3 of the groove 11a is 0.15 mm. The width dimension L4 of the second-stage groove 11b in the groove 11 on the back side of the cleavage vent 7 is 0.3 mm, and the vertical dimension T4 of the groove 11b is 0.15 mm. Incidentally, the upper and lower thickness dimension T5 of the sealing plate 2 is 0.6 mm, and the diameter of the sealing plate 2 is 16.1 mm.

  The vent angle θ1 between the imaginary straight lines connecting the center O of the sealing plate 2 shown in FIG. 1 and both ends of the cleavage vent 7 is 120 °. As shown in FIG. 2, the opening angle of the side surface in the width direction in the front-side groove 10 The opening angle θ3 of the side surface in the width direction of the first-stage groove 11a in the back-side groove 11 is 60 °, and the opening angle θ3 of the side surface in the width direction of the second-stage groove 11b is 60 °.

  When the internal pressure of the battery suddenly increases and exceeds a certain value, such as when abnormal charging / discharging is performed or when the battery is dropped into the fire, the thin portion 12 of the cleavage vent 7 is at the internal pressure of the battery. It is possible to prevent a situation in which the battery is ruptured by releasing the gas in the battery and bursting.

(Example 2) In Example 2, the vent angle θ1 was set to 90 °. Since the other points are the same as those of the first embodiment, description thereof is omitted.

(Example 3) In Example 3, the vent angle θ1 was set to 150 °. Since the other points are the same as those of the first embodiment, description thereof is omitted.

(Comparative Example 1) In Comparative Example 1, the vent angle θ1 was set to 180 °. Since the other points are the same as those of the first embodiment, description thereof is omitted.

(Comparative Example 2) In Comparative Example 2, the vent angle θ1 was 240 °. Since the other points are the same as those of the first embodiment, description thereof is omitted.

(Comparative example 3) In the comparative example 3, the groove | channel 11 on the back side was formed by one-step press work. The width of the groove 11 on the back side is 1.2 mm, and the vertical depth is 0.275 mm. The front groove 10 has a width dimension of 1.2 mm and a vertical depth dimension of 0.275 mm. Incidentally, the upper and lower thickness T1 of the thin portion 12 is 0.05 mm. Since the other points are the same as those of the first embodiment, description thereof is omitted.

Comparative Example 4 In Comparative Example 4, the width dimension of the front-side groove 10 and the width dimension of the back-side groove 11 were each set to 0.3 mm. The other points are the same as those in Comparative Example 3, and thus the description thereof is omitted.

  Five batteries according to Examples 1 to 3 of the present invention and five batteries of Comparative Examples 1 to 4 were prepared, respectively, and the operating pressure test of the cleavage vent 7 and the confirmation of the degree of cleavage during the operation of the cleavage vent 7 were performed. And performed.

(Operating pressure test of the cleavage vent 7) In the operation pressure test of the cleavage vent 7, a test hole is provided in the bottom wall of the battery case 1 in a state where the electrode winding body 3 is not mounted in the battery case 1. Water was poured into the battery from the hole, and the sealing plate 2 was pressurized from the inside by water pressure. Table 1 shows the average value of the operating pressure of the cleavage vent 7 and the standard deviation value, which are the test results.

  As shown in the test results of Examples 1 to 3 and Comparative Examples 1 and 2, as the vent angle θ1 increased, the operating pressure of the cleavage vent 7 decreased and the standard deviation value increased. The reason why the operating pressure of the cleavage vent 7 is decreased is considered to be that the area of the thin portion 12 increases as the vent angle θ1 increases. The reason why the standard deviation value is increased is considered that the variation in the thickness of the thin portion 12 increases with the increase in the area of the thin portion 12.

  As for the test results of Comparative Examples 3 and 4, the vent angle θ1 was 120 ° as in Example 1, but the standard deviation value of Comparative Examples 3 and 4 was larger than that of Example 1. In Comparative Examples 3 and 4, since the thin portion 12 was formed by one-stage pressing, it is considered that the variation in the thickness of the thin portion 12 became large. That is, in one-stage pressing, it is difficult to perform pressing with high dimensional accuracy of the thickness of the thin portion 12.

(Confirmation of the degree of cleavage of the cleavage vent 7) In confirmation of the degree of cleavage of the cleavage vent 7, the side of the battery case 1 is cleaved by a simulated fire test in which the side surface of the battery case 1 is heated with a gas burner. The presence or absence of the contents such as the electrode winding body 3 was visually confirmed. Table 2 shows the results.

  In Examples 1 to 3 and Comparative Examples 3 and 4, the cleavage degree of the cleavage vent 7 was small or moderate, so that the contents did not pop out. In Comparative Examples 1 and 2, the cleavage vent 7 Because of the large degree of cleavage, a part of the contents were exposed in Comparative Example 1, and a large part of the contents were exposed in Comparative Example 2. The reason why the contents are exposed in Comparative Examples 1 and 2 is considered to be because the cleavage angle increases because the vent angle θ1 is large, and the contents are easily ejected.

  When the vent angle θ1 is smaller than 90 °, the area of the thin portion 12 becomes too small, so that it is difficult to press the cleavage vent 7 and the operating pressure of the cleavage vent 7 becomes excessively high. When the vent angle θ1 is larger than 150 °, the contents are likely to jump out as shown in Comparative Examples 1 and 2.

  Further, as the vent angle θ1 is increased, the stress generated at the end portion in the arc direction of the cleavage vent 7 is reduced, so that the stress generated at the end portion of the cleavage vent 7 before the thin-walled portion 12 is cleaved is applied to the sealing plate 2. It can be prevented that the allowable stress is exceeded. That is, the crushing generated at the center portion in the arc direction of the cleavage vent 7 stops at the end portion in the arc direction of the cleavage vent 7 and does not break to a portion other than the cleavage vent 7. On the other hand, if the vent angle θ1 becomes too large, the contents are likely to pop out when the cleavage vent 7 is broken as described above.

  For example, when the sealing plate 2 is the cold-rolled steel plate, when the vent angle θ1 is set to 120 °, the portion other than the cleavage vent 7 is not broken and the content does not jump out. Incidentally, the allowable stress of the sealing plate 2 is 300 MPa. The vent angle θ1 is most preferably 120 °, but is preferably in the range of 110 to 130 °, and may be in the range of 90 ° to 150 °.

Opening the upper and lower surfaces of the batteries case 1, it may be sealed each of these upper and lower surfaces with a sealing plate (sealing wall).

Plan view AA line sectional view of FIG. Longitudinal front view

Explanation of symbols

1 Battery Case 2 Sealing Plate 7 Cleavage Vent 10/11 Cleavage Vent Groove 12 Thin Wall

Claims (2)

The upper opening of the bottomed cylindrical battery case is sealed with a circular sealing wall,
A crimp-sealed terminal is arranged at the center of the sealing wall, and one cleavage vent is arranged so as to surround the terminal ,
The cleavage vent, by providing the groove with respect to the sealing wall, and Nde including a thin portion of the battery internal pressure is cleaved in the case of more than a predetermined value,
The thin portion extends in an arc shape that is concentric with the periphery of the sealing wall,
A sealed battery characterized in that a vent angle defined by imaginary straight lines connecting the center of the sealing wall and both ends of the one cleavage vent is set in a range of 90 ° to 150 °. The thin portion of the cleavage vent is formed by pressing the groove on the front and back of the sealing wall in an opposing manner,
The groove on the surface side of the sealing wall has an upward flat surface, and is formed in a stepped shape that is one step lower than the surface of the sealing wall,
The groove on the inner surface side of the sealing wall is formed by two-stage pressing, has a flat surface facing downward, and is formed in a stepped shape that is one step lower than the inner surface of the sealing wall. A first-stage groove and a second-stage groove having a downward flat surface and being recessed in a stepped shape one step lower than the flat surface of the first-stage groove. And
2. The sealed battery according to claim 1, wherein the second-stage groove is formed such that a flat surface thereof is positioned at a center portion in a width direction of the flat surface of the first-stage groove .

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