JP6075640B2 - Secondary battery structure - Google Patents

Description

  The present invention relates to a secondary battery structure including a current interruption mechanism that interrupts current when a pressure in a battery case of a secondary battery exceeds a predetermined level.

2. Description of the Related Art Conventionally, some secondary batteries such as lithium ion batteries include a current interrupting mechanism that detects that the pressure in the battery case exceeds a predetermined level and interrupts the current.
The current interrupt mechanism is a mechanism that deforms the current collecting plate and the reversing plate joined to the rivet when the pressure in the battery case exceeds a predetermined level, and separates the connecting portion between the reversing plate and the current collecting plate. is there.

In the technique disclosed in Patent Document 1, a sealing material is disposed between the reversing plate and the positive electrode current collecting plate, and the convex portion of the lower gasket disposed on the outer side of the rivet is caulked, whereby the rivet and the reversing plate are arranged. , And fix the sealing material.
Thereby, in the technique disclosed in Patent Document 1, the sealing material is fixed in a compressed state to ensure the sealing performance inside the battery case.

In the technique disclosed in Patent Literature 1, there is a possibility that the current interrupting mechanism may rattle for the sake of caulking the convex portion of the lower gasket.
As a structure for suppressing such rattling, a structure in which a rivet and a lower gasket are insert-molded can be considered. In this case, there is a possibility that the sealing material cannot be fixed in a compressed state between the reversing plate and the positive electrode current collector plate, that is, the sealing material cannot be arranged.
In such a case, when the current is interrupted while the electrolyte is attached to the lower gasket or the like, the current may flow to the rivet through the electrolyte even after the current is interrupted. is there.

  As described above, in the prior art, it has been impossible to achieve both suppression of rattling of the current interrupt mechanism and improvement of insulation performance.

JP 2013-157200 A

  The present invention has been made in view of the above situation, and provides a secondary battery structure capable of achieving both suppression of rattling of the current interrupt mechanism and improvement of insulation performance.

  A secondary battery structure according to the present invention includes a rivet that fixes a lid of a secondary battery, an insulating member that covers the rivet, a current collector plate, and a reversing plate joined to the rivet, and the secondary battery. And a current interrupting mechanism for interrupting current by separating the connecting portion between the reversing plate and the current collector plate by deforming the reversing plate when the pressure in the battery case exceeds a predetermined level. In the secondary battery structure, the rivet and the insulating member are insert-molded to form an insert-molded member, and a recess or a gap is formed between the joint of the rivet and the reverse plate and the outer edge of the insert-molded member. Protrusions are provided.

  In the secondary battery structure according to the present invention, the joining portion of the rivet and the reversing plate is a welded portion formed by joining the rivet and the reversing plate by welding, and the secondary battery structure is A recess is provided between the weld and the outer edge of the insert-molded member.

  The present invention has an effect that it is possible to achieve both suppression of rattling of the current interrupt mechanism and improvement of insulation performance.

Sectional drawing which shows a secondary battery. Sectional drawing of an electric current interruption mechanism. The expanded sectional view which shows the welding part of an inversion board and a rivet. Explanatory drawing which shows the distance through which an electric current flows. Sectional drawing which shows the rivet in which a convex part is formed. Sectional drawing which shows another embodiment of a holder. (A) The figure which shows the holder in which a recessed part is formed. (B) The figure which shows the holder in which a convex part is formed. Sectional drawing which shows another embodiment of the shape of a recessed part. (A) The figure which shows the cross-sectional view substantially V-shaped recessed part. (B) The figure which shows the substantially semicircle-shaped recessed part seeing a cross section.

  Below, the secondary battery structure of this embodiment is demonstrated.

  As shown in FIG. 1 and FIG. 2, the secondary battery structure is a structure of the secondary battery 1 including a current interrupting mechanism 30 that detects that the pressure in the battery case 11 exceeds a predetermined level and interrupts the current. It is about.

  First, the configuration of the secondary battery 1 will be described.

  In addition, in this embodiment, although the secondary battery 1 shall be a lithium ion battery, it is not limited to this.

In the secondary battery 1, the electrode body 20 is housed in a bottomed rectangular tube-shaped battery case 11 having an open top surface, the battery case 11 is sealed with a lid 12, and an electrolyte is injected into the battery case 11. It is manufactured by.
The lid 12 supports a Z terminal 14 that is electrically connected to the external terminal 13 (a positive terminal and a negative terminal). An upper insulating member 15 is interposed between the lid 12 and the Z terminal 14.
The electrode body 20 is electrically connected to the current collector plate 16 by joining the current collector plate 16 to both ends.

The current interruption mechanism 30 is disposed between the Z terminal 14 on the positive electrode side (left side in FIG. 1) of the secondary battery 1 and the current collector plate 16. The current interruption mechanism 30 before operation as shown in FIG. 2 electrically connects the Z terminal 14 and the current collector plate 16. Further, when the current interrupt mechanism 30 is operated, the Z terminal 14 and the current collector plate 16 are electrically disconnected.
The secondary battery structure is used for the secondary battery 1 having such a current interruption mechanism 30.

  Next, the structure of the electric current interruption mechanism 30 in which a secondary battery structure is used is demonstrated.

  As shown in FIG. 2, the current interrupt mechanism 30 includes an insert molding member 40, a gasket 51, and a reversing plate 52.

  The insert molding member 40 is a member composed of a rivet 41 and a holder 42.

The rivet 41 is formed using aluminum or the like as a material.
The rivet 41 is a substantially cylindrical member having a lower inner diameter dimension and an outer diameter dimension larger than the upper inner diameter dimension and the outer diameter dimension, and a small diameter portion 41a that is an upper small diameter portion; It has a large-diameter portion 41b which is the lower large-diameter portion.

  The small diameter portion 41 a of the rivet 41 has an upper end protruding upward from the lid body 12 (more specifically, the Z terminal 14 and the upper insulating member 15 placed on the lid body 12).

  The large-diameter portion 41 b of the rivet 41 is disposed below the lid 12, that is, inside the battery case 11. The lower end portion of the large-diameter portion 41b has an inner diameter dimension and an outer diameter dimension that are larger than the inner diameter dimension and the outer diameter dimension of other portions (two points shown inside the welded portion 52a in FIG. 2). (See chain line).

  In the secondary battery structure, the concave portion 41c is formed at the lower end portion of the large diameter portion 41b. The recess 41c is a substantially circular groove when viewed from the bottom. The recess 41c is formed in a substantially U shape in cross section.

The rivet 41 integrally fixes the Z terminal 14, the upper insulating member 15, the lid 12, and the gasket 51 by caulking the upper end portion of the small diameter portion 41 a.
Thereby, the rivet 41 is electrically connected to the Z terminal 14.

The holder 42 is made of resin.
The holder 42 is formed in a shape that is recessed upward in a circular shape. The holder 42 opens on the upper side smaller than the lower side.
The inner diameter dimension of the holder 42 is formed to be equal to the outer diameter dimension of the large diameter portion 41 b of the rivet 41. The large diameter portion 41 b of the rivet 41 is disposed inside the holder 42.

  That is, the holder 42 of this embodiment is an insulating member that covers the rivet according to the present invention.

In the secondary battery structure, the insert molding member 40 is formed by insert molding the rivet 41 and the holder 42.
That is, in the secondary battery structure, the rivet 41 is inserted into the mold, the molten resin is injected into the space between the mold and the rivet 41, and the holder 42 that covers the rivet 41 is formed.

The gasket 51 is formed using a resin or the like as a material.
The gasket 51 is formed in a substantially cylindrical shape having a substantially L shape in cross-section in which the upper outer diameter dimension is smaller than the lower outer diameter dimension, and is interposed between the lid body 12 and the rivet 41. The outer diameter dimension of the lower side (large diameter part side) of the gasket 51 is formed to be equal to the inner diameter dimension of the opening part on the upper side of the holder 42. The lower outer peripheral surface of the gasket 51 is in contact with the upper opening of the holder 42.

  As described above, the holder 42 and the gasket 51 are interposed between the lid body 12 and the rivet 41 to electrically insulate the lid body 12 and the rivet 41.

The reversing plate 52 is formed in a substantially disc shape made of aluminum.
The substantially central portion of the reversing plate 52 is recessed downward. As shown in FIG. 3, the thickness (vertical length dimension) of the reversing plate 52 is substantially the same as the depth (vertical length dimension) of the recess 41 c of the rivet 41.

When connecting the reversing plate 52 to the rivet 41, the reversing plate 52 is disposed inside the lower end portion of the large-diameter portion 41 b of the rivet 41. At this time, a predetermined gap is formed between the inner peripheral surface of the lower end portion of the large-diameter portion 41b and the outer peripheral surface of the reversing plate 52 (see the two-dot chain line shown inside the welded portion 52a in FIG. 3). .
The reversing plate 52 disposed at the lower end portion of the large diameter portion 41b of the rivet 41 is joined to the lower end portion of the large diameter portion 41b of the rivet 41 by welding the outer peripheral edge portion without gaps over the entire circumference. They are electrically connected (see the laser and the welded portion 52a shown by black triangles in FIG. 3).

  Thus, the joint part of the rivet 41 and the reverse plate 52 is a welded part 52a formed by joining the rivet 41 and the reverse plate 52 by welding.

  Hereinafter, a gap (a distance along the radial direction of the reversing plate 52) between the inner peripheral surface of the lower end portion of the large-diameter portion 41b and the outer peripheral surface of the reversing plate 52 formed before welding is referred to as “welding portion gap C”. ".

In the secondary battery structure of the present embodiment, the reversing plate 52 and the lower end portion of the large diameter portion 41b of the rivet 41 are zigzag welded. That is, in the secondary battery structure, welding is performed so as to wave along the circumferential direction of the reversing plate 52.
As a result, the secondary battery structure can locally weld the outer peripheral edge portion of the reversal plate 52 even when the weld gap C varies depending on the phase of the reversal plate 52, thereby stabilizing the weld penetration depth. it can.

As shown in FIG. 2, the central portion of the reversing plate 52 is joined to the upper surface of the current collecting plate 16 by welding without gaps over the entire circumference, and is electrically connected to the current collecting plate 16 ( (See the welded portion 52b shown in FIG. 2).
That is, the reverse plate 52 is joined to the current collector plate 16 and the rivet 41 by welding.

  The thickness of the portion of the current collector plate 16 that is joined to the reversing plate 52 is partially reduced. Further, a notch portion 16 a is formed outside the welded portion 52 b of the current collector plate 16.

  As described above, in the secondary battery structure, the holder 42 is fixed to the lid body 12 without the caulking of the holder 42 to the current collector plate 16 by insert molding of the rivet 41 and the holder 42.

  According to this, in the secondary battery structure, rattling of the current interrupt mechanism 30 can be suppressed as compared with the case where the holder 42 is caulked and fixed to the current collector plate 16.

  When the pressure of the battery case 11 of the secondary battery 1 having such a current interrupting mechanism 30 rises, a pressure difference is generated between the lower space and the upper space of the reversing plate 52.

When the pressure on the lower side of the reversing plate 52 (pressure in the battery case 11) exceeds a predetermined level, the current interrupting mechanism 30 faces the reversing plate 52 upward due to the pressure difference between the lower side and the upper side of the reversing plate 52. Deform to warp.
As a result, the current interrupt mechanism 30 breaks the current collector plate 16 at the notch 16a and separates the connection portion between the reversing plate 52 and the current collector plate 16 to interrupt the current.

  Here, when the electrolytic solution adheres to the holder 42 or the like, it is collected via the electrolytic solution adhered to the holder 42 or the like even after the current interrupting mechanism 30 interrupts the current (after the reversing plate 52 is deformed). There is a possibility that current flows from the electric plate 16 to the rivet 41.

  Therefore, in the secondary battery structure, a undulation is provided on the lower surface of the rivet 41 by forming a recess 41 c at the lower end of the large-diameter portion 41 b of the rivet 41.

According to this, as shown in FIG. 4, the secondary battery structure can extend the creeping distance of the rivet 41.
That is, in the secondary battery structure, a distance L that is the sum of the distance along the vertical direction from the current collector plate 16 to the holder 42 and the creepage distance between the lower surfaces of the insert molding member 40 and the reverse plate 52, that is, current flows. The distance can be extended.
Therefore, since the secondary battery structure can make it difficult for the current to flow through the electrolyte after the current interrupt mechanism 30 interrupts the current, the insulation performance of the current interrupt mechanism 30 can be improved.

  As described above, in the secondary battery structure, by forming the recess 41c in the rivet 41 formed by insert molding, it is possible to achieve both suppression of rattling of the current interrupt mechanism 30 and improvement of insulation performance.

  In the secondary battery structure, the rivet 41 or the holder 42 may be provided with unevenness outside the lower end portion of the rivet 41 or the welded portion 52a of the lower end portion of the insert molding member 40.

For example, as shown in FIG. 5, in the secondary battery structure, a convex portion 141c may be formed on the rivet 41 instead of the concave portion 41c.
In addition, as shown in FIG. 6, in the secondary battery structure, the holder 42 may be formed with a concave portion 142 a or a convex portion 242 a.

  As a result, the secondary battery structure can extend the distance of the current flowing through the electrolytic solution (the distance L) after the current interrupting mechanism 30 interrupts the current, so that the insulation performance of the current interrupting mechanism 30 is improved. It can be improved.

  As described above, in the secondary battery structure, the concave portions 41 c and 142 a or the convex portions 141 c and 242 a are provided between the joint portion (welded portion 52 a) of the rivet 41 and the reversing plate 52 and the outer edge portion of the insert molding member 40.

  In addition, the cross-sectional shape of the recessed part or convex part formed in an insert molding member is not limited to this embodiment. The cross-sectional shape of the concave portion or the convex portion formed in the insert molding member is, for example, a substantially V shape such as a concave portion 241c shown in FIG. 7A, and a substantially semicircular shape such as a concave portion 341c shown in FIG. It does not matter.

Here, when the insert molding member 40 is formed by the rivet 41 and the holder 42 as in this embodiment, the rivet 41 may be pulled due to the shrinkage variation of the resin. Further, the rivet 41 may be deformed due to a temperature rise during insert molding.
In other words, when the insert molding member 40 is molded as in the present embodiment, the shape of the rivet 41, that is, the tolerance of the weld gap C may vary.

  Therefore, as shown in FIGS. 2 and 3, in the secondary pond structure of the present embodiment, the recess 41 c is formed in the lower end portion of the large-diameter portion 41 b of the rivet 41, so that air is formed in the lower end portion of the large-diameter portion 41 b. Forming a layer.

  According to this, in the secondary battery structure, when the rivet 41 and the holder 42 are insert-molded to form the insert-molded member 40, the heat shrink variation of the holder 42 that is a resin member is reduced and made constant. be able to.

Thereby, the secondary battery structure can reduce the variation of the tolerance of the weld gap C and can be made constant.
For this reason, the secondary battery structure can stabilize the welding depth at the welded portion between the rivet 41 and the reverse plate 52 even when the joint between the rivet 41 and the reverse plate 52 is the welded portion 52a.
That is, the secondary battery structure can improve welding quality and reduce welding defects.

Further, the secondary battery structure can reduce the heat capacity of the welded portion 52a by forming the recess 41c at the lower end portion of the insert molding member 40, thereby reducing the amount of heat input to the welded portion 52a during welding. The deformation of the rivet 41 due to heat generated by welding can be suppressed.
Further, since heat generated by welding of the rivet 41 and the reversing plate 52 can be released from the recess 41c, the deformation of the rivet 41 can be suppressed and the penetration depth during welding can be kept to the thickness of the reversing plate 52. it can.

  As described above, in the secondary battery structure, when the joint between the rivet 41 and the reversing plate 52 is the welded portion 52a, the current blocking mechanism 30 is formed by forming the concave portion 41c at the lower end portion of the insert molding member 40. In addition to achieving both suppression of rattling and improvement in insulation performance, the operating pressure of the current interrupt mechanism 30 can also be stabilized.

  Furthermore, the secondary battery structure can reduce the equipment cost required for welding the rivet 41 and the reverse plate 52 by reducing the amount of heat input to the welded portion 52a during welding.

  As described above, in the secondary battery structure, the concave portion 41 c is provided between the welded portion 52 a and the outer peripheral edge portion (outer edge portion) of the insert molding member 40.

DESCRIPTION OF SYMBOLS 1 Secondary battery 11 Battery case 12 Cover body 16 Current collecting plate 30 Current interruption mechanism 40 Insert molding member 41 Rivet 41c Concave part 42 Holder (insulating member)
52 Reverse plate 52a Welding part (joining part)
141c Convex part

Claims (2)

A rivet for fixing a lid of the secondary battery; an insulating member that covers the rivet; a current collector; and a reversing plate joined to the rivet, wherein the pressure in the battery case of the secondary battery is at a predetermined level. A secondary battery structure comprising a current interrupting mechanism for interrupting current by separating the connecting part between the inversion plate and the current collector plate by deforming the inversion plate when exceeding,
Insert molding the rivet and the insulating member to form an insert molding member,
Providing a concave or convex portion between the joint of the rivet and the reversing plate and the outer edge of the insert molded member;
Secondary battery structure. The joint of the rivet and the reversing plate is
A welded portion formed by joining the rivet and the reverse plate by welding;
The secondary battery structure is:
Providing a recess between the weld and the outer edge of the insert molded member;
The secondary battery structure according to claim 1.

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