JP2007227283A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery which has accurate current interrupting function, even if the exhaust area of a sealing plate is increased, with a weld area corresponding thereto. <P>SOLUTION: The sealing plate comprises a ring-like insulating gasket, a metal foil having a protruding portion at the center, and a metal cap used also as a terminal provided on the upper surface part of the metal foil, which are disposed in the inside or an upper part of a bottomed disk-shaped metal case having a gas port. The metal foil includes an engraved part and further a weld part at the protruding portion for ensuring electric conductivity with the metal case or another metal foil insulated therefrom by the insulating gasket at the protruding portion, and has the function of electric interruption by rupture of the weld part or the engraved part, and the welding of the weld part is formed of a plurality of spot welding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sealed battery, particularly a sealed battery used for a battery having a high energy density such as a lithium secondary battery.

  In recent years, as electronic devices have become portable and cordless, the demand for higher energy density and smaller size and weight of the secondary battery serving as a driving power source has become stronger. Non-aqueous electrolyte secondary batteries typified by lithium ion secondary batteries, which have extremely remarkable characteristics of being capable of rapid charging while having a small size and light weight and having a high energy density as a battery that meets such demands. Developed and mainstream.

  This non-aqueous electrolyte secondary battery is an electrode plate group in which a positive electrode using a lithium-containing transition metal compound as a positive electrode active material and a negative electrode using a carbon material as a negative electrode active material are wound with a separator interposed therebetween. A battery in which a non-aqueous electrolyte is housed in a battery case.

  However, with the increase in power consumption due to higher functionality of electronic devices, there is a strong demand for higher capacity, higher energy density, and longer life, and thinning separators and current collectors that do not contribute to capacity Since the packing density of the electrode plate is increased, the distance between the positive and negative electrodes is reduced, and the space volume in the battery is also reduced. Moreover, since each component is mounted with high density along with the downsizing of electronic equipment, the usage environment in which the battery is used with large heat generation may be severe conditions exceeding 60 ° C.

  Under such circumstances, it is important to ensure the safety of the battery even when the battery is overcharged due to the failure of the charger or the inability to control charging.

  Explosion-proof sealed batteries that activate the current interrupt mechanism when the internal pressure of the battery exceeds a predetermined value are known as a method to ensure the safety of the battery in the case of falling into an overcharged state. Gas is generated and filled due to a chemical change inside the battery, and the internal pressure of the battery increases due to the gas filling. Thereby, the progress of the abnormal reaction inside the battery is stopped, the sudden rise in battery temperature is prevented, and safety is ensured.

In general, a sealing plate having a safety mechanism has a metal foil overlapped with a ring-shaped insulating gasket in or on a bottomed dish-shaped metal case having a gas vent. The metal foil has a convex shape at the center, and the metal foil is electrically connected by welding at the convex part with a bottomed dish-shaped metal case insulated with a metal foil and an insulating gasket. ing. A metal cap that also serves as an external terminal is placed on the upper surface of the peripheral edge of the metal foil. In the current interruption mechanism, when the battery internal pressure rises, the metal foil receives the battery internal pressure and swells through the gas vent of the metal case. The metal foil has a ring-shaped stamped portion, and when the battery internal pressure reaches a predetermined value, the stamped portion is broken so as to tear the entire circumference, thereby interrupting the current. (For example, see Patent Document 1)
In addition to this, there is one that breaks the welded portion of the metal foil to interrupt the current. (For example, see Patent Document 2)
In addition, there is also a sealing plate in which a Positive Temperature Coefficientine (hereinafter referred to as PTC) element is stacked between a metal foil and a metal cap in order to cut off current when the temperature rises. (For example, see Patent Document 3)
Japanese Patent Laid-Open No. 10-021892 JP 09-199105 A Japanese Patent Laid-Open No. 06-215747

  As the electric capacity of the battery increases and the battery diameter increases, it is necessary to expand the exhaust area of the sealing plate. In the sealing plate blocking mechanism, when the exhaust area becomes large, the area where the metal foil receives pressure increases when the internal pressure rises. Therefore, the stamped portion breaking blocking mechanism increases the area where the metal foil extends, making it difficult to break the stamped portion. In the partial break interruption mechanism, the welded portion is easily broken even at a low pressure, and in both cases, the current interruption operation becomes difficult.

  Accordingly, the present invention solves such a conventional problem, and provides a sealed battery having an accurate current interruption mechanism and excellent safety even when the exhaust hole area of the sealing plate is enlarged. It is intended.

  In order to achieve the above object, the sealed battery of the present invention is a sealed battery formed by sealing an opening of a battery case containing a power generation element with a sealing plate, and the sealing plate has a gas vent. The inside or upper part of the bottomed dish-shaped metal case is composed of a ring-shaped insulating gasket, a metal foil having a convex portion at the center, and a metal cap that also serves as a terminal on the upper surface of the metal foil, The metal foil has a stamped portion, and the metal foil is further insulated from the metal case or other metal foil insulated from each other by the insulating gasket, in order to ensure electrical continuity at the convex portion. There is a welded part by spot welding on the convex part, and it is a sealed battery having a function of electrical interruption by breaking the welded part or the stamped part, and the welded part is constituted by a plurality of spot welds. It is.

  In this configuration, since there is a ring-shaped insulating gasket, electrical continuity is ensured by welding with the metal case or another metal foil only by the welded portion on the convex portion.

  In this configuration, by using a plurality of spot welds, the metal foil weld diameter necessary for the current interrupt mechanism can be easily obtained according to the exhaust area of the sealing plate. In particular, it is possible to cope with an increase in the sealing plate exhaust area accompanying an increase in battery diameter and battery capacity. In particular, if a large welding diameter is to be obtained by spot welding at one point, the temperature distribution in the welded portion becomes uniform and the thickness of the metal foil increases in accordance with the size of the welding diameter. There are many difficult issues such as narrowing. With respect to such a problem, if a plurality of spot welds are used, it is easy to stabilize the temperature distribution of the weld in one point of welding, and multiple points are welded under welding conditions that match the thickness of the metal foil to be welded. Stable welding can be performed while securing a necessary welding diameter according to the exhaust area of the plate.

  In the current interruption mechanism that breaks the stamped part of the metal foil, the metal foil swells due to the internal pressure of the battery, the surface receiving the pressure extends and the stamped part breaks, but when the sealing plate has a large exhaust area, the surface receiving the pressure If the metal foil is not expanded more greatly when the pressure is increased, it becomes difficult to break the stamped portion. Since the space for inflating the metal foil with the sealing plate is limited, in order to break the stamped portion even in such a case, the area in which the metal foil extends by increasing the pressure may be reduced. Therefore, by expanding the weld diameter of the central weld with multiple spot welds and expanding the fixed area, the area where the metal foil extends due to pressure rise can be reduced, and the engraved part can be easily broken, with a predetermined internal pressure. The current can be cut off.

In the current interruption mechanism due to the fracture of the central weld of the metal foil, the metal foil swells due to the internal pressure of the battery, and the force that separates the weld acts to break the weld. Therefore, it breaks easily even at a low pressure, and the storage stability such as high temperature deteriorates. Therefore, it is only necessary to ensure the strength of the weld according to the area that receives the pressure, so that the weld can be easily fractured by securing the required diameter of the central weld with multiple spot welds. The current can be reliably cut off at a predetermined internal pressure.

  Further, the diameter of the minimum circumscribed circle of the stamped portion is a stamped diameter, and the weld diameter of the entire welded portion is configured to be equal to or smaller than the stamped diameter. It is preferable to have such a configuration.

  In this configuration, it is possible to more reliably cut off the current at a predetermined internal pressure.

  Moreover, it is preferable to laminate | stack the ring-shaped metal plate or the PTC element which resistance value rises with a temperature rise between the said metal foil and the said metal cap.

  With this configuration, the metal foil having the convex portion can be stably operated.

  According to the present invention, when the sealing plate exhaust area increases as the battery diameter and the battery capacity increase, the weld diameter required for current interruption can be easily obtained, and the current can be reliably supplied with a predetermined internal pressure. Can be blocked.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  The sealed battery according to the present invention is characterized in that the sealing plate has a feature, and welding of the welded portion on the convex portion of the metal foil is spot welding, and is constituted by a plurality of spot weldings.

  FIG. 1 shows a schematic cross-sectional view of an example of an explosion-proof sealing plate for a sealed battery according to this embodiment.

  In FIG. 1, an explosion-proof sealing plate for a sealed battery includes a lower metal foil 2 that is in contact with the upper metal foil 1, a ring-shaped insulating gasket 3 that is interposed between the peripheral edges of the two metal foils 1 and 2, It is composed of a PTC 4 placed on the upper surface of the upper metal foil 1, a metal cap 5 placed on the upper surface of the PTC 4, and a bottomed dish-shaped metal case 6 having a gas vent hole for inserting and holding each member. ing. The upper metal foil 1 is provided with a concave bulge portion, and the lower metal foil 2 is provided with a convex bulge portion, both bulge portions being in contact with each other via an inner diameter 3a of the insulating gasket 3, The contact surface 7 is welded by a welded portion 7a. The upper metal foil 1 and the lower metal foil 2 are provided with ring-shaped marking portions 1a and 2a, respectively.

  The shape of the marking portion in this configuration is preferably a ring shape, but may be a C shape.

  2 and 3 show the concept of the weld diameter of the entire weld. As shown in FIG. 2 or FIG. 3, the diameter of the smallest circumscribed circle 9 having the smallest area among the circles surrounding the plurality of spot welds 8, that is, the arbitrary circumscribed circle 9 is defined as the weld diameter.

  The embodiment shown in FIG. 1 is an example in which the insulating gasket 3, the metal foils 1 and 2, and the metal cap 5 are inside the metal case 6.

Insulating gaskets, metal foils, and metal caps inside the metal case, in addition to those shown in FIG. 1, for example, the insulating gasket 3, metal foil 10, and metal cap in the metal case 6 as shown in FIG. All the components such as 5 are arranged in the metal case 6, and a sealing plate structure in which the metal case 6 is caulked inward and sealed is included.

  On the other hand, if the insulation gasket, metal foil, and metal cap are on the upper part of the metal case, for example, as shown in FIG. The structure of the sealing board which is arrange | positioned at the upper part of the metal case 6 and was sealed by crimping the battery case inside is included.

  Further, the present invention includes a form in an intermediate state between these embodiments.

  Hereinafter, the present invention will be further described using specific examples.

  The weld diameter of the weld 7a with respect to the ring inner diameter of the insulating gasket 3 was examined. All spot welding was performed using laser welding in which the welding diameter at one point was 1 mm. In the embodiment, the weld diameter is 3 spot welding as shown in FIG. 3, the weld diameter is 2.15 mm, the gasket inner diameter is 12 mm, and the thickness of the metal foils 1 and 2 is 0.15 mm. Created.

  A current interruption test was conducted with 100 sealing plates of the example prepared as described above. In the test method, nitrogen gas is pressurized at 29.4 kPa / s from the bottom of a bottomed dish-shaped metal case having gas vents. The test was performed by packing the outer periphery of the bottom of the metal case so that no gas leaked, and applying pressure only from below the lower metal foil through the gas vent. As a result of the test, the occurrence rate of the sealing plate that was not properly interrupted was examined.

  As a result of the test, it was shown that all the current blocking mechanisms in the sealing plates of the examples were appropriately operated and that it was effective to obtain a necessary weld diameter by spot welding of the welded portion 7a.

  The sealed battery of the present invention is a sealed battery having an explosion-proof safety that is excellent in increasing capacity and size, and is useful in the field of high output from a portable power source or the like.

1 is a schematic cross-sectional view of an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention. Illustration of an example for explaining the weld diameter Explanatory drawing of other examples for explaining weld zone weld diameter Schematic sectional view of an explosion-proof sealing plate for a sealed battery according to a second embodiment of the present invention Schematic sectional view of an explosion-proof sealing plate for a sealed battery according to a third embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper metal foil 1a Upper metal foil stamping part 2 Lower metal foil 2a Lower metal foil stamping part 3 Insulating gasket 3a Insulating gasket inner diameter 4 PTC
5 Metal cap 6 Metal case 7 Contact surface of upper metal foil and lower metal foil 7a Welded portion 8 Spot welded portion 9 Minimum circumscribed circle 10 Metal foil 10a Metal foil stamped portion 11 Metal foil

Claims (3)

It is a sealed battery in which the opening of the battery case containing the power generation element is sealed with a sealing plate,
The sealing plate includes a ring-shaped insulating gasket, a metal foil having a convex portion at the center, and a terminal on the upper surface of the metal foil, in or on the bottomed metal case having a gas vent. Consists of a metal cap that doubles as
The metal foil has a marking portion, and the metal foil is electrically insulated from the metal case or other metal foil insulated from each other by the insulating gasket, and the convex portion. The convex part has a welded part by spot welding, and is a sealed battery having a function of electrical interruption by breaking the welded part or the stamped part,
The said welding part is a sealed battery comprised by several spot welding.   When the diameter of the minimum circumscribed circle of the stamped portion is the stamped diameter and the diameter of the minimum circumscribed circle of the entire welded portion is the weld diameter, the weld diameter of the entire welded portion is not larger than the stamped diameter. The sealed battery according to claim 1, which is configured and has a function of electrically interrupting by breaking the engraved portion.   3. The sealed battery according to claim 1, wherein a ring-shaped metal plate or a Positive Temperature Coefficientette element whose resistance value increases with increasing temperature is laminated between the metal foil and the metal cap.