JP2018142427A - 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 between itself and the deformation plate. A peripheral part of the deformation plate is welded to a peripheral part of a conductor 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, a welding mark 70 is formed at a boundary between the deformation plate and the conductor. When a distance from the lateral wall portion to a radially inner end of the flat portion is denoted as D, and a distance from the lateral wall portion to a radially inner end of the welding mark is denoted as D, the following equation holds true: D≤2D.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. A deformation plate electrically connected to the electrode plate, and a current collector electrically connected to the electrode plate and welded between the deformation plate, and the peripheral portion of the deformation plate is disposed inside the battery case. And is welded to the peripheral portion of the conductor electrically connected to the external terminal. In the peripheral portion of the conductor, 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 portion of the peripheral portion of the deforming plate is formed. In the state where the side wall portion of the stepped portion is in contact, a welding mark is formed at the boundary between the deformable plate and the conductive member, and the distance from the side wall portion to the radially inner end of the flat portion is D ₁ When the distance from the side wall portion to the radially inner end portion of the welding mark is D ₂ , D ₁ ≦ 2D ₂ .

  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 the II-II cross section 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), (b) is the figure explaining the optimal range of the width | variety of the plane part 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 is a cross-sectional view schematically showing a configuration of a current interruption mechanism in a II-II cross section 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. In addition, the current collector 60 has a planned fracture portion (for example, a thin-walled portion, a notch portion, etc.) 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. 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. 3 (b), the step portion 31 formed on the peripheral portion of the conductor 30 has a flat portion 32 on which the peripheral portion of the deformation plate 50 is placed, and a peripheral portion end portion of the deformation plate 50. And a side wall portion 33 in contact therewith. The boundary between the deformable plate 50 and the conductor 30 is welded in a state in which the peripheral edge surface 52 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 deformation plate 50 and the peripheral portion of the conductor 30 are welded between the deformation plate 50 and the flat portion 32 of the conductor 30 in a contact state where the deformation plate 50 and the conductor 30 are different from each other. There arises a problem that the operating pressure of the current interrupt mechanism 40 varies.

  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.

  With reference to FIGS. 7A and 7B, the optimum range of the width of the flat portion 32 of the conductor 30 employed in the present embodiment will be described.

  FIG. 7A is an enlarged view of the peripheral portion of the conductor 30. In the peripheral portion of the conductor 30, the flat portion 32 on which the peripheral portion of the deformable plate 50 is placed and the peripheral end face 52 of the deformable plate 50. A step portion 31 having a side wall portion 33 that abuts on the surface is formed.

  FIG. 7B is an enlarged view showing a state in which the peripheral edge surface 52 of the deformation plate 50 and the side wall portion 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. 7A and 7B, the distance from the side wall 33 to the radially inner end of the flat portion 32 (the width of the flat portion 32) is D ₁ , and the diameter of the welding mark 70 from the side wall 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 .

  In addition, the radially inner end of the welding mark 70 may be positioned flush with the radially inner end of the flat portion 32 or on the radially inner side of the radially inner end of the flat portion 32. More preferred.

The distance _{D 2} from the side wall portion 33 to the radially inner end of the welding mark 70 is preferably 2mm or less, more preferably 0.1 mm to 1 mm, in 0.1mm~0.5mm More preferably it is.

  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.

  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 embodiment, the conductor 30 is a separate member from the external terminal 13, but the conductor 30 and the external terminal 13 may be configured as one 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. 7B, the shape shown in FIGS. 8A and 8B may be used.
Moreover, in this embodiment, although the material of the conductor 30, the deformation | transformation board 50, and the electrical power collector 60 is not specifically limited, It is preferable to consist of aluminum or 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
31 Stepped 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 (5)

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 having a joint electrically connected to the electrode plate and 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,
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,
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 ₁ ≦ 2D ₂ , Secondary battery. 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 ₁ ≧ 0.5D ₂ The secondary battery according to claim 1, wherein   The radially inner end portion of the welding mark is located flush with the radially inner end portion of the planar portion, or is located radially inward of the radially inner end portion of the planar portion. Or the secondary battery of 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 any one of claims 1 to 3, wherein the current collector has a planned fracture portion on a radially outer side than the joining portion. The secondary battery according to claim 1, wherein the conductor and the external terminal are one part.

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