JP6833562B2 - Rechargeable battery - Google Patents

Description

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

In a secondary battery such as a lithium ion secondary battery, a secondary battery having a current cutoff mechanism that cuts off the current when the pressure inside the battery case rises due to overcharging or the like is known (for example, Patent Documents). 1).

Such a current cutoff mechanism is provided in the middle of the current path for electrically connecting the external terminal and the electrode plate constituting the electrode body. Specifically, the deformed plate electrically connected to the external terminal and the electrode It is composed of a current collector electrically connected to the board. The deformed plate and the current collector are joined to each other, and the current collector is provided with a thin-walled portion or a notch portion that breaks when a certain stress is applied. When the pressure inside the battery case rises above a predetermined value, the deformed plate is displaced by the pressure, and the planned breakage portion of the current collector breaks. As a result, the deformed plate is separated from the current collector, so that the current path between the deformed plate and the current collector is cut off.

Japanese Unexamined Patent Publication No. 2010-21024

In the current cutoff mechanism having the above configuration, the peripheral edge of the deformed plate is arranged in the battery case and fixed to the peripheral edge of the conductor electrically connected to the external terminal by welding.

However, when the peripheral edge of the deformed plate is brought into contact with the peripheral edge of the conductor for welding, the displacement of the deformed plate due to the increase in pressure varies depending on the state of contact. As a result, the pressure at which the planned break portion of the current collector breaks fluctuates, which causes a problem that the operating pressure of the current cutoff 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 variations in operating pressure of a current cutoff mechanism are reduced.

The secondary battery according to the present invention is a secondary battery in which a current cutoff mechanism is arranged in a current path between an external terminal and a plate housed in a battery case, and the current cutoff mechanism is an external terminal. It is provided with a deformed plate electrically connected to the plate and a current collector having a joint electrically connected to the electrode plate and welded to the deformed plate, and the peripheral portion of the deformed plate is inside the battery case. It is placed on the periphery of a conductor that is electrically connected to an external terminal. In the peripheral edge of the conductor, a stepped portion having a flat surface portion on which the peripheral edge portion of the deformable plate is placed and a side wall portion in contact with the peripheral edge portion end surface of the deformable plate is formed, and the peripheral edge portion end surface of the deformable plate Welding marks are formed at the boundary between the deformed plate and the conductive member in a state where the side wall portion of the step portion is in contact with each other, and the distance from the side wall portion to the radial inner end portion of the flat portion is D ₁ . When the distance from the side wall portion to the radial inner end portion of the weld mark is D ₂ , D ₁ ≤ ₂ D 2 is characterized.

According to the present invention, it is possible to reduce the variation in the operating pressure of the current cutoff mechanism by stabilizing the contact state between the peripheral edge portion of the deformed plate and the peripheral edge portion of the conductor.

It is a perspective view which showed typically the appearance of the secondary battery in one Embodiment of this invention. It is sectional drawing which shows typically the structure of the current cutoff mechanism in the section II-II of FIG. (A) is a cross-sectional view showing a joint state between the conductor and the deformed plate, and (b) is an enlarged view of the peripheral edge of the conductor. (A) to (c) are views showing the state in which the peripheral edge portion of the deformed plate is placed on the flat surface portion of the conductor. It is a graph which showed the result of having obtained the relationship between the displacement of the center of the protrusion of the deforming plate, and the pressure of a battery when the gap between a deforming plate and a flat surface part of a conductor is changed by simulation. (A) to (c) are diagrams showing the contact state between the deformed plate and the flat surface portion when the width of the flat surface portion of the conductor is reduced. (A) and (b) are diagrams explaining the optimum range of the width of the flat surface portion of the conductor. (A) and (b) are diagrams showing a modified example of the shape of the stepped portion at the peripheral edge portion of the conductor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments. In addition, changes can be made as appropriate without departing from the range in which the effects of the present invention are exhibited.

FIG. 1 is a perspective view schematically showing the appearance of the secondary battery according to the embodiment of the present invention, and FIG. 2 is a cross section schematically showing the configuration of the current cutoff mechanism in the cross section II-II of FIG. It is a figure. Here, the type 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 of the present embodiment, an electrode body (not shown) in which a positive electrode plate and a negative electrode plate are laminated or wound via a separator has an opening together with an electrolytic solution. It is housed in the battery case 11, and the opening is sealed by the sealing body 12. Further, the sealing body 12 is provided with a positive electrode external terminal 13, a negative electrode external terminal 14, a safety valve 15, and an injection unit 16 for injecting an electrolytic solution. In the injection unit 16, a liquid injection hole (not shown) into which the electrolytic solution is injected is sealed by a sealing plug (not shown).

As shown in FIG. 2, a current cutoff mechanism 40 is provided inside the battery case 11 to cut off the current when the pressure inside the battery case 11 rises. Here, the current cutoff mechanism 40 includes a deformed 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 deformed plate 50 is joined to the current collector 60 by welding. Further, the current collector 60 has a portion to be broken (for example, a thin-walled portion, a notch portion, etc.) 62 on the radial outer side of the joint portion 61 with the deformed plate 50. Except for the joint portion 61, the current collector 60 and the deformed plate 50 are electrically insulated by the insulating plate 22.

The tubular portion 13a of the external terminal 13 is inserted into the openings formed in the gasket 20, the sealing body 12, the insulating plate 21, and the conductor 30, respectively, and the tip portion thereof is crimped and fixed to the sealing body 12. There is. Further, the peripheral edge portion of the deformed plate 50 is welded to the peripheral edge portion of the conductor 30. As a result, the external terminal 13 is electrically connected to the positive electrode via the conductor 30, the deformed plate 50, and the current collector 60. That is, the current cutoff mechanism 40 in this embodiment is arranged in the current path between the external terminal 13 and the positive electrode.

When the pressure inside the battery case 11 rises, the protruding portion 51 of the deformed plate 50 is displaced toward the outside (upper side in the drawing) of the battery case 11, but the protruding portion 51 is welded to the current collector 60. Therefore, when the pressure in the battery case 11 exceeds a predetermined value, the planned breakage portion 62 of the current collector 60 breaks. As a result, the deformed plate 50 is separated from the current collector 60, so that the current path between the deformed plate 50 and the current collector 60 is cut off.

By the way, as shown in FIGS. 3A and 3B, a step portion 31 on which the peripheral edge portion of the deformed plate 50 is placed is formed on the peripheral edge portion of the conductor 30. That is, welding of the peripheral edge portion of the deformed plate 50 and the peripheral edge portion of the conductor 30 is performed in a state where the peripheral edge portion of the deformed plate 50 is placed on the stepped portion 31 of the conductor 30. Here, FIG. 3A is a cross-sectional view showing the joint state of the conductor 30 and the deformed plate 50 (the one shown in FIG. 2 and the state inverted in the axial direction), and FIG. 3B is shown in FIG. Is an enlarged view of the peripheral edge of the conductor 30.

As shown in FIG. 3B, the stepped portion 31 formed on the peripheral edge portion of the conductor 30 corresponds to the flat surface portion 32 on which the peripheral edge portion of the deformable plate 50 is placed and the peripheral edge portion end portion of the deformable plate 50. It has a side wall portion 33 in contact with the side wall portion 33. Then, the boundary between the deformed plate 50 and the conductor 30 is welded in a state where the peripheral end surface 52 of the deformed plate 50 and the side wall portion 33 of the stepped portion 31 are in contact with each other. The welding is preferably performed by irradiation with energy rays such as laser welding.

By the way, when the peripheral edge portion of the deformable plate 50 is placed on the flat surface portion 32 of the conductor 30, as illustrated in FIGS. 4A to 4C, the deformable plate 50 and the flat surface portion 32 of the conductor 30 There may be a gap between them. Here, FIG. 4A shows a state without a gap, and FIGS. 4B and 4C show a state with a gap. FIG. 4B shows an example in which a gap L is generated due to the protrusion 53 on the deformed plate 50, and FIG. 4C shows an example in which a gap L is generated due to the bending 54 on the deformed plate 50. Each is shown.

In this way, when the peripheral edge portion of the deformable plate 50 and the peripheral edge portion of the conductor 30 are welded between the deformed plate 50 and the flat surface portion 32 of the conductor 30 in different contact states between the deformed plate 50 and the conductor 30. , There arises a problem that the operating pressure of the current cutoff mechanism 40 fluctuates.

The protrusion 53 illustrated in FIG. 4 (b) and the deflection 54 illustrated in FIG. 4 (c) are exaggerated (deformed) for easy understanding, and do not represent actual dimensions. ..

Further, the protrusion 53 illustrated in FIG. 4 (b) and the deflection 54 illustrated in FIG. 4 (c) may occur in a part of the peripheral edge portion of the deformed plate 50, or may occur in the entire peripheral edge portion. .. The protrusions 53 and the bends 54 are not intentionally formed, but are unintentionally generated.

FIG. 5 shows the displacement (μm) of the center of the protruding portion 51 of the deformed plate 50 when the gap L between the deformed plate 50 and the flat surface portion 32 of the conductor 30 is changed to 0 μm (no gap), 15 μm, and 30 μm. It is a graph which showed the result of having obtained the relationship between and the pressure (MPa) in a battery case 11 by a 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. The width of the flat surface portion 32 of the conductor 30 on which the peripheral edge portion of the deformed plate 50 is placed is set to 0.5 mm.

As shown in FIG. 5, the displacement at the center of the protruding portion 51 when the pressure inside the battery case 11 is the same decreases as the gap L between the deformed plate 50 and the flat surface portion 32 of the conductor 30 increases. There is. In other words, at the intersection of the straight line P showing 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 the curves A, B, and C. The pressure, that is, the operating pressure of the current cutoff mechanism 40, increases as the gap L between the deformation plate 50 and the flat surface portion 32 of the conductor 30 increases.

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

6 (a) to 6 (c) show the deformed plate 50 and the conductor 30 when the width of the flat surface portion 32 is smaller than the width of the conventional flat surface portion 32 illustrated in FIGS. 4 (a) to 4 (c). It is a figure which showed the contact state with the plane part 32 of. As shown in FIGS. 6 (b) and 6 (c), even if the deformed plate 50 has unintended partial protrusions 53 and bending 54 as illustrated in FIGS. 4 (b) and 4 (c), the deformed plate 50. There is no gap between the 50 and the flat surface portion 32 of the conductor 30.

As described above, when the deformation plate 50 has the protrusions 53, the bend 54, and the like, the larger the width of the flat surface portion 32, the easier it is for the protrusions 53, the bend 54, and the like to come into contact with the flat surface portion 32. That is, by reducing the width of the flat surface portion 32, the possibility that the protrusion 53, the deflection 54, or the like comes into contact with the flat surface portion 32 can be reduced. As a result, the contact state between the deformed plate 50 and the flat surface portion 32 of the conductor 30 is stabilized, and as a result, the variation in the operating pressure of the current cutoff mechanism 40 can be reduced.

The optimum range of the width of the flat surface portion 32 of the conductor 30 used in the present embodiment will be described with reference to FIGS. 7A and 7B.

FIG. 7A is an enlarged view of the peripheral edge portion of the conductor 30, and on the peripheral edge portion of the conductor 30, a flat surface portion 32 on which the peripheral edge portion of the deformable plate 50 is placed and an end surface 52 of the peripheral edge portion of the deformable plate 50 A stepped portion 31 having a side wall portion 33 that comes into contact with the side wall portion 33 is formed.

FIG. 7B is an enlarged view showing a state in which the deformed plate 50 and the conductor 30 are welded to each other in a state where the peripheral end surface 52 of the deformed plate 50 and the side wall portion 33 of the stepped portion 31 are in contact with each other. A welding mark 70 is formed at the boundary between the deformed plate 50 and the conductor 30.

As shown in FIGS. 7A and 7B, the distance (width of the flat surface portion 32) from the side wall portion 33 to the radial inner end 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 inner end in the direction is D ₂ , the width D ₁ of the flat surface portion 32 preferably satisfies _{D 1} ≤ _{2 D 2. When the width D 1} of the flat surface portion 32 is within such a range, the contact state between the deformed plate 50 and the flat surface portion 32 of the conductor 30 is stabilized, and as a result, the operating pressure of the current cutoff mechanism 40 varies. It can be reduced. _{If the width D 1} of the flat surface portion 32 is too small, the deformed plate 50 may enter the inside of the conductor 30 when the deformed plate 50 is assembled to the stepped portion 31 of the conductor 30. Therefore, in order to reduce this possibility, it is more preferable that _{the width D 1} of the flat surface portion 32 is D ₁ ≧ 0.5 D _2.

Further, the radial inner end portion of the welding mark 70 may be located flush with the radial inner end portion of the flat surface portion 32 or radially inside the radial inner end portion of the flat surface portion 32. More preferred.

_{The distance D 2} from the side wall portion 33 to the radial inner end of the welding mark 70 is preferably 2 mm or less, more preferably 0.1 mm to 1 mm, and 0.1 mm to 0.5 mm. It is more preferable to have.

There may be a gap between the deformed plate 50 and the flat surface portion 32 of the conductor 30. If the size of the gap is stable, that is, if the contact state between the deformed plate 50 and the conductor 30 is stable, the operating pressure of the current cutoff mechanism 40 is also stable.

Although the present invention has been described above in terms of preferred embodiments, such a description is not a limitation, and of course, various modifications can be made. 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 composed of one component.

Further, in the above embodiment, the current cutoff mechanism is provided in the middle of the current path for electrically connecting the positive electrode external terminal 13 and the positive electrode, but the current path for electrically connecting the negative electrode external terminal 14 and the negative electrode Of course, it may be provided in the middle.

The shape of the stepped portion 31 at the peripheral edge of the conductor 30 is not particularly limited as long as it has the flat surface portion 32 and the side wall portion 33 specified in the present invention. For example, in addition to the shape shown in FIG. 7 (b), the shape may be as shown in FIGS. 8 (a) and 8 (b).
Further, in the present embodiment, the materials of the conductor 30, the deformed plate 50, and the current collector 60 are not particularly limited, but are preferably made of aluminum or an aluminum alloy, respectively.

10 Rechargeable battery
11 Battery case
12 Sealed body
13 (Positive electrode) External terminal
13a Cylinder
14 Negative electrode external terminal
15 Safety valve
16 Injection part
20 gasket
21, 22 Insulation plate
30 Conductor
31 Steps
32 flat surface
33 Side wall
40 Current cutoff mechanism
50 Deformation plate
51 Protruding part
52 Peripheral end face
53 protrusions
54 Flexion 60 Current collector
61 Joint
62 Expected fracture
70 Weld marks

Claims (4)

A secondary battery in which a current cutoff mechanism is arranged in the current path between the external terminal and the electrode plate housed in the battery case.
The current cutoff 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. ,
The peripheral edge of the deformed plate is arranged in the battery case and welded to the peripheral edge of a conductor electrically connected to the external terminal.
The conductor has a stepped portion having a flat surface portion on which the peripheral edge portion of the deformed plate is placed and a side wall portion that abuts on the peripheral edge portion end surface of the deformed plate.
Welding marks are formed at the boundary between the deformed plate and the conductor in a state where the peripheral end surface of the deformed plate and the side wall portion of the stepped portion are in contact with each other.
Wherein the distance from the side wall portion to the radially inner end of the flat portion D1, when the distance from the side wall portion to the radially inner end of the welding mark and D2, Ri D1 ≦ 2D2 der, D1 ≧ 0.5D2,
Secondary battery . The radial inner end of the weld mark is located flush with the radial inner end of the flat surface or radially inward with the radial inner end of the flat surface.
The secondary battery according to claim 1. The joint portion between the deformed plate and the current collector is formed in the central portion of the current collector.
The current collector has a portion to be fractured radially outside the joint portion.
The secondary battery according to any one of claims 1 and 2. The conductor and the external terminal are one component.
The secondary battery according to any one of claims 1 to 3.

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