JP2018142428A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery in which variation in working pressure of a current interruption mechanism is reduced.SOLUTION: A current interruption mechanism 40 comprises: a deformation plate 50 connected to an external terminal 13; and a collector 60, connected to an electrode plate, which has a bonding part welded to the deformation plate. A peripheral part of the deformation plate is welded to a peripheral part of a conductor 30 connected to the external terminal. The peripheral part of the conductor is provided with a step part 31 having: a flat portion 32 on which the peripheral part of the deformation plate is placed; and a lateral wall portion 33 which comes into contact with an end face of the peripheral part of the deformation plate. With the end face of the peripheral part of the deformation plate making contact with the lateral wall portion of the step part, the deformation plate and the conductor are welded to each other. The conductor is formed into a rectangular shape having four sides and corner parts. The width of the flat portion formed on the four sides is narrower than that of the flat portion formed on the corner parts.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a secondary battery having a current interruption mechanism in a battery case.

  In secondary batteries such as lithium ion secondary batteries, secondary batteries having a current interruption mechanism that cuts off current when the pressure in the battery case increases due to overcharging or the like are known (for example, Patent Documents). 1).

  Such a current interruption mechanism is provided in the middle of a current path that electrically connects the external terminal and the electrode plate constituting the electrode body. Specifically, the deformation plate electrically connected to the external terminal, and the electrode It is comprised with the electrical power collector electrically connected to the board. The deformable plate and the current collector are joined to each other, and the current collector is provided with a thin portion or a notched portion such as a notch portion that is broken when a certain stress is applied. And when the pressure in a battery case rises more than predetermined value, a deformation | transformation plate will be displaced by the pressure, and the fracture | rupture scheduled part of an electrical power collector will fracture. Thereby, when a deformation | transformation board peels from a collector, the electric current path between a deformation | transformation board and a collector is interrupted | blocked.

JP 2010-212034 A

  In the current interruption mechanism configured as described above, the peripheral edge of the deformable plate is disposed in the battery case, and is fixed to the peripheral edge of the conductor electrically connected to the external terminal by welding.

  However, when the peripheral edge of the deforming plate is brought into contact with the peripheral edge of the conductor and welding is performed, the displacement of the deformable plate with the increase in pressure varies depending on the contact state. As a result, the pressure at which the current breakage portion of the current collector breaks fluctuates, which causes a problem that the operating pressure of the current interrupt mechanism varies.

  The present invention has been made in view of the above problems, and a main object thereof is to provide a secondary battery in which variation in operating pressure of a current interrupt mechanism is reduced.

  A secondary battery according to the present invention is a secondary battery in which a current interruption mechanism is arranged in a current path between an external terminal and an electrode plate accommodated in a battery case, and the current interruption mechanism is an external terminal. And a current collector electrically connected to the electrode plate and having a joint portion welded to the deformation plate. The peripheral edge of the deformable plate is disposed in the battery case and welded to the peripheral edge of the conductor electrically connected to the external terminal, and the conductor mounts the peripheral edge of the deformable plate on the peripheral edge. A step portion having a flat surface portion to be placed and a side wall portion that comes into contact with the end surface of the peripheral edge of the deformation plate is formed. The plate and the conductor are welded. The conductor is formed in a rectangular shape having four sides and four corners in plan view, and the width of the planar portion formed on each side of the four sides in the stepped portion is a plane formed in the corner portion. It is characterized by being narrower than the width of the part.

  According to the present invention, the contact state between the peripheral edge portion of the deformable plate and the peripheral edge portion of the conductor is stabilized, whereby variation in the operating pressure of the current interrupt mechanism can be reduced.

It is the perspective view which showed typically the external appearance of the secondary battery in one Embodiment of this invention. It is sectional drawing which showed typically the structure of the electric current interruption mechanism in alignment with the II-II line | wire of FIG. (A) is sectional drawing which showed the joining state of a conductor and a deformation | transformation board, (b) is the figure which expanded the peripheral part of the conductor. (A)-(c) is the figure which showed the state which mounted the peripheral part of the deformation | transformation board in the plane part of the conductor. It is the graph which showed the result of having calculated | required the relationship between the displacement of the center part of the protrusion part of a deformation | transformation board when changing the clearance gap between a deformation | transformation board and a conductor, and the pressure of a battery by simulation. (A)-(c) is the figure which showed the contact state of a deformation | transformation board and a plane part when the width | variety of the plane part of a conductor is made small. (A)-(c) is the figure which showed typically the structure of the plane part of an electric conductor, (a) is a top view, (b) is the cross section along the VIIb-VIIb line of 7 (a). FIG. 4C is a cross-sectional view taken along line VIIc-VIIc in FIG. It is the top view which showed typically the other structure of the plane part of the conductor. (A), (b) is the figure explaining the optimal range of the width | variety of the plane part formed in the long side of a conductor. (A), (b) is the figure which showed the modification of the shape of the level | step-difference part in the peripheral part of a conductor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention.

  FIG. 1 is a perspective view schematically showing an external appearance of a secondary battery according to an embodiment of the present invention, and FIG. 2 schematically shows a configuration of a current interrupting mechanism along the line II-II in FIG. FIG. Here, the kind of the secondary battery in the present embodiment is not particularly limited, and includes, for example, a lithium ion secondary battery, a nickel-hydrogen secondary battery, and the like.

  As shown in FIG. 1, in the secondary battery 10 in the present embodiment, an electrode body (not shown) in which a positive electrode plate and a negative electrode plate are stacked or wound via a separator has an opening together with an electrolytic solution. Housed in the battery case 11, the opening is sealed with a sealing body 12. Further, the sealing body 12 is provided with a positive external terminal 13, a negative external terminal 14, a safety valve 15, and an injection part 16 for injecting an electrolytic solution. In addition, in the injection part 16, the injection hole (not shown) in which electrolyte solution is inject | poured is sealed with the sealing stopper (not shown).

  As shown in FIG. 2, a current interruption mechanism 40 that interrupts current when the pressure in the battery case 11 rises is provided inside the battery case 11. Here, the current interruption mechanism 40 includes a deformation plate 50 electrically connected to the (positive electrode) external terminal 13 and a current collector 60 electrically connected to a positive electrode (not shown) constituting the electrode body. It is configured. Further, the protruding portion 51 formed at the central portion of the deformable plate 50 is joined to the current collector 60 by welding. Further, the current collector 60 has a planned fracture portion (for example, a thin-walled portion or a notch portion) 62 on the radially outer side than the joint portion 61 with the deformable plate 50. The current collector 60 and the deformation plate 50 are electrically insulated by the insulating plate 22 except for the joint portion 61.

  The cylindrical portion 13 a of the external terminal 13 is inserted into openings formed in the gasket 20, the sealing body 12, the insulating plate 21, and the conductor 30, and the distal end portion thereof is caulked to be fixed to the sealing body 12. Yes. In addition, it is preferable that the caulked part in the front-end | tip part of the cylinder part 13a is welded to the conductor 30. FIG. Further, the peripheral edge of the deformable plate 50 is welded to the peripheral edge of the conductor 30. As a result, the external terminal 13 is electrically connected to the positive electrode via the conductor 30, the deformation plate 50, and the current collector 60. That is, the current interruption mechanism 40 in this embodiment is arranged in the current path between the external terminal 13 and the positive electrode.

  When the pressure in the battery case 11 rises, the protrusion 51 of the deformable plate 50 is displaced toward the outside of the battery case 11 (upper side in the figure), but the protrusion 51 is welded to the current collector 60. Therefore, when the pressure in the battery case 11 exceeds a predetermined value, the planned break portion 62 of the current collector 60 is broken. As a result, the deformation plate 50 is peeled off from the current collector 60, thereby interrupting the current path between the deformation plate 50 and the current collector 60.

  By the way, as shown in FIGS. 3A and 3B, the conductor 30 has a step portion 31 on which the peripheral portion of the deformable plate 50 is placed at the peripheral portion. That is, welding of the peripheral edge of the deformable plate 50 and the peripheral edge of the conductor 30 is performed in a state where the peripheral edge of the deformable plate 50 is placed on the stepped portion 31 of the conductor 30. Here, FIG. 3A is a cross-sectional view showing the joined state of the conductor 30 and the deformable plate 50 (the state shown in FIG. 2 and the state reversed in the axial direction), and FIG. These are the figures which expanded the peripheral part of the conductor 30. FIG.

  As shown in FIG. 3B, the step portion 31 formed on the peripheral portion of the conductor 30 includes a flat portion 32 on which the peripheral portion of the deformable plate 50 is placed, and a peripheral end portion 52 of the deformable plate 50. And a side wall portion 33 that abuts. Then, the boundary between the deformable plate 50 and the conductor 30 is welded in a state where the peripheral edge of the deformable plate 50 and the side wall 33 of the stepped portion 31 are in contact with each other. In addition, it is preferable that the said welding is performed by irradiation of energy rays, such as laser welding.

  By the way, when the peripheral part of the deformation | transformation board 50 is mounted in the plane part 32 of the conductor 30, as illustrated in FIG.4 (a)-(c), the deformation | transformation board 50 and the plane part 32 of the conductor 30 and There may be a gap between the two. Here, Fig.4 (a) shows a state without a clearance gap, and FIG.4 (b), (c) shows a state with a clearance gap. FIG. 4B shows an example in which the gap L is generated due to the protrusion 53 on the deformable plate 50, and FIG. 4C shows an example in which the gap L is generated due to the bend 54 on the deformable plate 50. Each is shown.

  Thus, when the peripheral part of the deformation | transformation board 50 and the peripheral part of the conductor 30 are welded in the state from which the deformation | transformation board 50 and the conductor 30 differ, the problem that the working pressure of the electric current interruption mechanism 40 fluctuate | varies. Arise.

  Note that the protrusions 53 illustrated in FIG. 4B and the flexures 54 illustrated in FIG. 4C are exaggerated for easy understanding, and do not represent actual dimensions. .

  Further, the protrusion 53 illustrated in FIG. 4B and the flexure 54 illustrated in FIG. 4C may occur in a part of the peripheral edge of the deformation plate 50 or may occur in the entire peripheral edge. . The protrusion 53 and the flexure 54 are not formed intentionally, but are generated unintentionally.

  FIG. 5 shows the displacement (μm) at the center of the protrusion 51 of the deformable plate 50 when the gap L between the deformable plate 50 and the flat portion 32 of the conductor 30 is changed to 0 μm (no gap), 15 μm, and 30 μm. FIG. 6 is a graph showing the results of the relationship between the pressure and the pressure (MPa) in the battery case 11 obtained by simulation. Here, the curve A shows the case where the gap L is 0 μm, the curve B shows the case where the gap L is 15 μm, and the curve C shows the case where the gap L is 30 μm. In addition, the width | variety of the plane part 32 of the conductor 30 which mounts the peripheral part of the deformation | transformation board 50 was 0.5 mm.

  As shown in FIG. 5, the displacement at the center of the protrusion 51 when the pressure in the battery case 11 is the same decreases as the gap L between the deformation plate 50 and the flat portion 32 of the conductor 30 increases. Yes. In other words, at the intersection of the straight line P indicating the displacement (0.27 mm) at which the planned breaking portion 62 of the current collector 60 breaks when the gap L is 0 μm (no gap), and each of the curves A, B, and C. The pressure, that is, the operating pressure of the current interrupt mechanism 40 increases as the gap L between the deformation plate 50 and the flat portion 32 of the conductor 30 increases.

  In order to reduce the variation in the operating pressure of the current interrupt mechanism 40 due to the contact state between the deformable plate 50 and the flat portion 32 of the conductor 30, the present invention places the peripheral portion of the deformable plate 50. The planar portion 32 of the conductor 30 is a narrower one than the conventional one.

  6A to 6C show the deformed plate 50 and the conductor 30 when the width of the plane portion 32 is made smaller than the width of the conventional plane portion 32 illustrated in FIGS. 4A to 4C. It is the figure which showed the contact state with the plane part 32. As shown in FIGS. 6B and 6C, even if the deformation plate 50 has unintentional partial projections 53 and bends 54 as illustrated in FIGS. 4B and 4C, the deformation plate There is no gap between 50 and the flat portion 32 of the conductor 30.

  As described above, when the protrusions 53 and the bends 54 are present on the deformable plate 50, the protrusions 53, the bends 54 and the like are likely to come into contact with the flat surface portion 32 as the width of the flat surface portion 32 is larger. That is, by reducing the width of the planar portion 32, the possibility that the projection 53, the flexure 54, etc. will contact the planar portion 32 can be reduced. As a result, the contact state between the deformable plate 50 and the flat portion 32 of the conductor 30 is stabilized, and as a result, variations in the operating pressure of the current interrupt mechanism 40 can be reduced.

  By the way, as shown in FIGS. 3A and 3B, the peripheral edge of the deformable plate 50 and the peripheral edge of the conductor 30 are welded to the stepped portion of the conductor 30. This is performed in a state where it is placed on the flat surface portion 32 in FIG. Therefore, if the width of the flat portion 32 is narrow, the deformable plate 50 may fall from the flat portion 32 of the conductor 30 when the deformable plate 50 is assembled to the conductor 30.

On the other hand, the conductor 30 is formed in a rectangular shape having four sides and four corners in plan view, and the peripheral portion of the deformable plate 50 is the four sides and four corners of the conductor 30. It is welded to. And when the pressure in the battery case 11 rises, the deformation | transformation board 50 will displace the protrusion part 51 of the deformation | transformation board 50 by using the welding part of the corner part of the four sides and four corners of the conductor 30 as a fulcrum. At this time, the deformation of the deformable plate 50 with the welds at the four sides of the conductor 30 as fulcrums is larger than the deformation with the welds at the corners of the four corners as fulcrums. As a result, the deformation of the deformation plate 50 with the welds on the four sides of the conductor 30 as fulcrums limits the breakage of the planned breakage portion 62 of the current collector 60.
Therefore, the influence of the contact state between the deformable plate 50 and the flat portions 32 on the four sides of the conductor 30 on the operating pressure of the current interrupt mechanism 40 is greater than the contact state between the flat portions 32 of the corner portions at the four corners. Is considered large.

  From such knowledge, the present invention employs a configuration in which the width of the flat portion 32 formed on each of the four sides of the conductor 30 is narrower than the width of the flat portion 32 formed in the corner portion. Thereby, by reducing the width of the flat surface portion 32 on the four sides of the conductor 30, the contact state between the deformable plate 50 and the flat surface portion 32 of the conductive material 30 is stabilized, and as a result, the operation of the current interruption mechanism 40 is performed. Variation in pressure can be reduced. On the other hand, in the corner portions at the four corners of the conductor 30, the assemblability of the deformable plate 50 to the conductor 30 can be improved by increasing the width of the plane portion 32.

Further, when the conductor 30 is formed in a rectangular shape having a long side and a short side in a plan view, the deformation plate 50 is more deformed with the welded portion on the long side of the conductor 30 as a fulcrum. It becomes larger than the deformation with the welding point at the short side as a fulcrum. As a result, the deformation of the deformable plate 50 with the welded portion on the long side of the conductor 30 as a fulcrum limits the breakage of the planned breakage portion 62 of the current collector 60.
From this, the influence of the contact state between the deformable plate 50 and the long side flat portion 32 of the conductor 30 on the operating pressure of the current interrupting mechanism 40 is less than the contact state between the short side flat portion 32. It is considered large. Therefore, the variation in the operating pressure of the current interrupting mechanism 40 is reduced by making the width of the flat portion 32 formed on the long side of the conductor 30 smaller than the width of the flat portion 32 formed on the short side. On the other hand, the assembling property of the deformable plate 50 to the conductor 30 can be further improved.

  7A to 7C are diagrams schematically showing the configuration of the planar portion 32 of the conductor 30 in the present embodiment. FIG. 7A is a plan view, and FIG. 7B is a diagram. 7A is a cross-sectional view taken along line VIIb-VIIb, and FIG. 7C is a cross-sectional view taken along line VIIc-VIIc in FIG.

  As shown in FIG. 7A, the conductor 30 is formed in a rectangular shape having a long side 30A, a short side 30B, and four corners 30C in plan view. Here, the widths Wa and Wb of the plane part 32 formed on the long side 30A and the short side 30B are narrower than the width Wc of the plane part 32 formed on the corner part 30C. Thereby, the wide flat surface portion 32 formed in the corner portion 30C maintains the assembling property of the deformable plate 50 to the conductor 30, while the width of the flat surface portion 32 formed in the long side 30A and the short side 30B. By narrowing Wa and Wb, variations in the operating pressure of the current interrupt mechanism 40 can be reduced. Further, by reducing the width Wa of the flat portion 32 formed on the long side 30A to be smaller than the width Wb of the flat portion 32 formed on the short side 30B, the variation in the operating pressure of the current interrupting mechanism 40 is reduced. Further, the assembling property of the deformable plate 50 to the conductor 30 can be further improved.

  FIG. 8 is a plan view schematically showing another configuration of the flat portion 32 of the conductor 30 in the present embodiment.

  As shown in FIG. 8, the conductor 30 is formed in a square shape having four sides 30A and four corner portions 30C having the same length in plan view. Here, the width Wa of the flat surface portion 32 formed on the four sides 30A is narrower than the width Wc of the flat surface portion 32 formed on the corner portion 30C. As a result, the wide flat surface portion 32 formed in the corner portion 30C maintains the assemblability of the deformable plate 50 to the conductor 30, while the width Wa of the flat surface portion 32 formed on the four sides 30A is reduced. Thus, variation in the operating pressure of the current interrupt mechanism 40 can be reduced.

  In the present embodiment, the width Wc of the flat surface portion 32 formed in the corner portion 30C is the maximum distance among the distances between the radially outer end portion and the radially inner end portion of the flat surface portion 32.

  Next, the optimum range of the width of the flat portion 32 formed on the long side of the conductor 30 will be described with reference to FIGS. 9A and 9B.

  FIG. 9A is an enlarged view of the long side peripheral portion of the conductor 30, and the flat portion 32 on which the peripheral portion of the deformation plate 50 is placed on the long side peripheral portion of the conductor 30, and the deformation plate A stepped portion 31 having a side wall portion 33 in contact with the peripheral edge portion 52 of 50 is formed.

  FIG. 9B is an enlarged view showing a state in which the peripheral edge face 52 of the deformation plate 50 and the side wall 33 of the step portion 31 are in contact with each other and the deformation plate 50 and the conductor 30 are welded. A welding mark 70 is formed at the boundary between the deformable plate 50 and the conductor 30.

As shown in FIGS. 9A and 9B, the distance from the side wall portion 33 to the radially inner end of the flat surface portion 32 (the width of the flat surface portion 32) is D ₁ , and the diameter of the welding mark 70 from the side wall portion 33. when the distance to the inward end portion and a _{D 2,} the width _{D 1} of the flat portion 32 preferably satisfies the _{D 1} ≦ 2D _2. Width D ₁ of the flat portion 32, by which is in this range, the state of contact between the flat portion 32 of the deformable plate 50 and the conductor 30 is stabilized, as a result, variations in the operating pressure for interrupting current mechanisms 40 Can be reduced. If the width D ₁ of the flat portion 32 is too small, the deformable plate 50 may enter the inside of the conductor 30 when the deformable plate 50 is assembled to the stepped portion 31 of the conductor 30. Therefore, in order to reduce this fear, it is more preferable that the width D ₁ of the plane portion 32 satisfies D ₁ ≧ 0.5D ₂ .

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, in the above-described embodiment, the widths Wa and Wb of the plane part 32 formed on the long side 30A and the short side 30B are narrower than the width Wc of the plane part 32 formed on the corner part 30C. May not be formed on the long side 30A, but only on the short side 30B. As a result, the peripheral edge of the deformable plate 50 does not come into contact with the flat surface portion 32 at the long side of the conductor 50, so that current interruption caused by the contact state between the deformable plate 50 and the flat surface portion 32 of the electric conductor 30 is prevented. Variations in the operating pressure of the mechanism 40 can be greatly reduced. In this case, the width Wb of the flat portion 32 formed on the short side 30B is preferably set to a size that does not impair the assembling property of the deformable plate 50 to the conductor 30.

  In the above embodiment, the conductor 30 is a separate member from the external terminal 13, but the conductor 30 and the external terminal 13 may be composed of a single component.

  In the above embodiment, the current interrupting mechanism is provided in the middle of the current path that electrically connects the positive external terminal 13 and the positive electrode. However, the current interrupt mechanism is electrically connected to the negative external terminal 14 and the negative electrode. Of course, it does not matter if it is provided in the middle.

  In addition, the shape of the stepped portion 31 in the peripheral portion of the conductor 30 is not particularly limited as long as it has the flat portion 32 and the side wall portion 33 defined in the present invention. For example, in addition to the shape shown in FIG. 9B, the shape shown in FIGS. 10A and 10B may be used.

The distance D ₂ from the side wall 33 to the radially inner end of the weld mark 70 is preferably 2 mm or less, more preferably 0.1 mm to 1 mm, and more preferably 0.1 mm to 0.5 mm. More preferably.

  Further, the width Wc of the flat surface portion 32 formed in the corner portion 30C is preferably 2 mm or less, more preferably 0.2 mm to 1 mm, and further preferably 0.2 mm to 0.5 mm. .

A gap may exist between the deformation plate 50 and the flat portion 32 of the conductor 30. If the size of the gap is stable, that is, if the contact state between the deformation plate 50 and the conductor 30 is stable, the operating pressure of the current interrupt mechanism 40 is also stabilized.
The conductor 30, the deformation plate 50, and the current collector 60 are preferably made of aluminum or an aluminum alloy, respectively.

10 Secondary battery
11 Battery case
12 Sealing body
13 (Positive electrode) External terminal
13a Tube part
14 Negative external terminal
15 Safety valve
16 Injection part
20 Gasket
21, 22 Insulating plate
30 Conductor
30A long side (four sides)
30B short side
30C Corner part 31 Step part
32 Plane section
33 Side wall
40 Current interrupt mechanism
50 deformation plate
51 Protrusion
52 Edge of peripheral edge
53 Protrusions
54 Deflection 60 Current collector
61 joints
62 Scheduled break
70 Weld marks

Claims (7)

A secondary battery in which a current interruption mechanism is arranged in a current path between an external terminal and an electrode plate housed in a battery case,
The current interrupt mechanism includes a deformable plate electrically connected to the external terminal, and a current collector electrically connected to the electrode plate and having a joint portion welded to the deformable plate,
A peripheral portion of the deformable plate is disposed in the battery case and welded to a peripheral portion of a conductor electrically connected to the external terminal;
In the peripheral portion, the conductor has a stepped portion having a flat portion on which the peripheral portion of the deforming plate is placed and a side wall portion in contact with the end surface of the peripheral portion of the deforming plate,
With the peripheral edge of the deformation plate and the side wall of the stepped portion in contact with each other, the deformation plate and the conductor are welded,
The conductor is formed in a rectangular shape having four sides and four corners in plan view,
In the step portion, the width of the flat portion formed on each of the four sides is smaller than the width of the flat portion formed on the corner portion. The conductor is formed in a rectangular shape having a long side and a short side,
2. The secondary battery according to claim 1, wherein, in the stepped portion, a width of the planar portion formed on the long side is narrower than a width of the planar portion formed on the short side. The conductor is formed in a rectangular shape having a long side and a short side,
The secondary battery according to claim 1, wherein in the stepped portion, the planar portion is formed only on the short side. In the state where the peripheral edge of the deformation plate and the side wall of the stepped portion are in contact, a welding mark is formed at the boundary between the deformation plate and the conductor,
On the long side, when the distance from the side wall part to the radially inner end of the flat part is D ₁ and the distance from the side wall part to the radially inner end of the welding mark is D ₂ , D _The secondary battery according to claim ₂ , wherein ₁ ≦ 2D ₂ . On the long side, when the distance from the side wall part to the radially inner end of the flat part is D ₁ and the distance from the side wall part to the radially inner end of the welding mark is D ₂ , D _The secondary battery according to claim 4, wherein ₁ ≧ 0.5D ₂ . The joint between the deformable plate and the current collector is formed at the center of the current collector,
The secondary battery according to claim 1, wherein the current collector has a planned fracture portion on a radially outer side than the joint portion.   The secondary battery according to claim 1, wherein the conductor and the external terminal are one part.

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