JP2021086651A - Power storage device - Google Patents

Abstract

To provide a power storage device capable of maintaining the airtightness of a case.SOLUTION: A cross section obtained by cutting a welded part 20 with a plane P perpendicular to an abutting direction Y where a tip end part 13c of a first peripheral wall 13b abuts on a tip end part 14c of a second peripheral wall 14b is defined as a first cross section. A cross section on the second peripheral wall 14b obtained by cutting a lid 14 with the plane P through an inner face 141a of a second bottom wall 14a which is farthest from a case body 13 along the abutting direction Y in a portion of the second bottom wall 14a exposed into a case 11 is defined as a second cross section. Here, the lid 14 has a thick part 30 which makes a cross sectional area of the second cross section larger than a cross sectional area of the first cross section.SELECTED DRAWING: Figure 4

Description

The present invention relates to a power storage device.

Conventionally, vehicles such as EVs (Electric Vehicles) and PHVs (Plug in Hybrid Vehicles) are equipped with power storage devices such as lithium-ion secondary batteries for storing power supplied to electric vehicles and the like. The secondary battery disclosed in Patent Document 1 has an outer container as a case. The outer container has a second container as a case body for accommodating the electrode body and a first container as a lid for closing the opening of the second container. The first container has a peripheral wall formed in a square tube shape and a bottom wall that closes an end portion of the peripheral wall opposite to the bottom wall of the first container. The peripheral wall of the first container projects from the bottom wall of the first container toward the second container. Therefore, the first container has a shape that opens toward the second container.

Further, the above-mentioned secondary battery has a welded portion in which the first container and the second container are welded together. The welded portion is formed at the boundary portion between the first container and the second container with the opening of the second container closed by the first container.

Japanese Unexamined Patent Publication No. 2015-060831

By the way, when the power storage device is used, the peripheral wall of the first container tends to be deformed toward the outside of the outer container as the internal pressure of the outer container increases. Specifically, the peripheral wall of the first container is likely to be deformed toward the outside of the outer container starting from the boundary portion with the bottom wall of the first container. Such deformation of the peripheral wall increases as the size of the power storage device increases. If the peripheral wall of the first container is deformed toward the outside of the outer container, cracks may occur in the welded portion between the first container and the second container, and the airtightness of the outer container may not be maintained.

An object of the present invention is to provide a power storage device capable of maintaining the airtightness of a case.

The power storage device for solving the above problems has a case body for accommodating the electrode body and a case having a lid for closing the opening of the case body, and the case body has a plate-shaped first bottom wall and the first. It has a tubular first peripheral wall extending from the edge of one bottom wall, and the lid has a plate-shaped second bottom wall and a tubular shape extending from the edge of the second bottom wall toward the first peripheral wall. A power storage device having the second peripheral wall of the above and having a welded portion in which the tip end portion of the first peripheral wall and the tip end portion of the second peripheral wall are welded, and the tip portion of the first peripheral wall and the second peripheral wall. The cross section when the welded portion is cut by a plane orthogonal to the abutting direction with the tip end portion of the peripheral wall is defined as the first cross section, and the portion of the second bottom wall exposed in the case is described along the abutting direction. When the part farthest from the case body is the farthest part, and the cross section of the second peripheral wall when the lid is cut in the plane so as to pass through the farthest part is the second cross section, the lid is It has a thick portion that makes the cross-sectional area of the second cross section larger than the cross-sectional area of the first cross section.

According to this, since the rigidity of the second peripheral wall can be improved as compared with the case where the lid does not have a thick portion, the second peripheral wall is less likely to be deformed toward the outside. Therefore, when the internal pressure of the case rises, stress is less likely to be generated in the welded portion, and cracks are less likely to occur in the welded portion. As a result, the airtightness of the case can be maintained.

In the power storage device, the cross-sectional area of the thick portion when the lid is cut on the flat surface is from the case body to the second bottom wall along the abutting direction with the cross-sectional area of the second cross section as the maximum. It should grow gradually as you go.

According to this, as compared with the case where the cross-sectional area of the thick portion changes abruptly, for example, since local stress does not act on the thick portion, it is easy to suppress the deformation of the lid.
In the power storage device, the second bottom wall has a long square plate shape, the second peripheral wall has a square tubular shape, and the thick portion extends in the longitudinal direction of the second bottom wall. It is preferable that the wall is provided over the entire length of the boundary between the wall and the second peripheral wall.

According to this, the rigidity of the lid can be effectively improved by providing the thick portion in the longitudinal direction in which the second bottom wall is more likely to bend than in the lateral direction.
In the power storage device, it is preferable that the second bottom wall has a long square plate shape and the second peripheral wall has a square tubular shape, and the thick portion is formed at the four corner portions of the second peripheral wall. ..

According to this, the rigidity of the lid can be improved as compared with the case where the thick portion is not provided.
In the power storage device, the second bottom wall has a long square plate shape and the second peripheral wall has a square tubular shape, and the meat is covered over the entire direction in which the second peripheral wall surrounds the second bottom wall. Thick parts should be formed.

According to this, the cross-sectional area of the second cross section can be increased as compared with the case where a thick portion is formed in a part of the second peripheral wall surrounding the second bottom wall, and the rigidity of the lid can be increased. Can be improved.

According to the present invention, the airtightness of the case can be maintained.

An exploded perspective view of the secondary battery. An exploded perspective view showing the components of the electrode body. Sectional drawing of the power storage device along the stacking direction. FIG. 5 is an enlarged cross-sectional view of a part of the power storage device according to the embodiment. FIG. 5-5 is a cross-sectional view taken along the line 5-5 in FIG. FIG. 6-6 is a sectional view taken along line 6-6 in FIG. FIG. 5 is an enlarged cross-sectional view of a part of the power storage device according to another embodiment. FIG. 5 is an enlarged cross-sectional view of a part of the power storage device according to another embodiment. FIG. 5 is an enlarged cross-sectional view of a part of the power storage device according to another embodiment. FIG. 5 is an enlarged sectional view of a part of the power storage device according to another embodiment. FIG. 5 is an enlarged sectional view of a part of the power storage device according to another embodiment. FIG. 5 is an enlarged cross-sectional view of a part of the power storage device according to another embodiment.

Hereinafter, an embodiment in which the power storage device is embodied will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1 or 2, the secondary battery 10 as a power storage device has a case 11 and an electrode body 12 housed in the case 11. The case 11 has a case body 13 for accommodating the electrode body 12 and a lid 14 for closing the opening of the case body 13. The case body 13 and the lid 14 are made of metal such as stainless steel or aluminum. Further, the case body 13 has a long square plate-shaped first bottom wall 13a and a square tubular first peripheral wall 13b extending from the edge of the first bottom wall 13a. The case body 13 is opened by the first peripheral wall 13b on the side opposite to the first bottom wall 13a. The secondary battery 10 of the present embodiment is a lithium ion secondary battery. Further, the secondary battery 10 of the present embodiment is a square battery having a square appearance.

The electrode body 12 has a plurality of positive electrode electrodes 21 as positive electrode electrodes, a plurality of negative electrode electrodes 22 as negative electrode electrodes, and a plurality of separators 23. The electrode body 12 has a rectangular parallelepiped shape because the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween.

The positive electrode electrode 21 has a rectangular sheet-shaped positive electrode metal foil 24 and positive electrode active material layers 25 existing on both sides of the positive electrode metal foil 24. The positive electrode metal foil 24 is, for example, an aluminum foil. The positive electrode electrode 21 has a rectangular positive electrode tab 26 protruding from a part of one of the edges along the pair of long sides. The positive electrode tab 26 does not have the positive electrode active material layer 25 and is composed of the positive electrode metal foil 24 itself.

The negative electrode electrode 22 has a rectangular sheet-shaped negative electrode metal foil 27 and negative electrode active material layers 28 existing on both sides of the negative electrode metal foil 27. The negative electrode metal foil 27 is, for example, a copper foil. The negative electrode electrode 22 has a rectangular negative electrode tab 29 protruding from a part of one edge of the edge along the pair of long sides. The negative electrode tab 29 does not have the negative electrode active material layer 28 and is composed of the negative electrode metal foil 27 itself.

The separator 23 is made of a rectangular sheet-shaped insulating material. The separator 23 insulates the positive electrode 21 and the negative electrode 22.
As shown in FIG. 1 or 3, the electrode body 12 has a positive electrode tab group 15 in which the positive electrode tabs 26 are gathered together, and a negative electrode tab group 15 in which the negative electrode tabs 29 are gathered together.

The secondary battery 10 has terminal portions 16 of each polarity for extracting electricity from the electrode body 12. Each terminal portion 16 has a rectangular conductive member 16a and an electrode terminal 16b protruding from the conductive member 16a. The conductive member 16a of the terminal portion 16 of the positive electrode is joined to the tab group 15 of the positive electrode, and the conductive member 16a of the terminal portion 16 of the negative electrode is joined to the tab group 15 of the negative electrode. Each electrode terminal 16b penetrates the lid 14 and projects to the outside of the case 11 and is fixed to the lid 14. An external device (not shown) that electrically connects the secondary batteries 10 to each other can be fixed to the tip of each electrode terminal 16b. The secondary battery 10 has an insulating ring 17 for insulating the lid 14 and the electrode terminals 16b of each terminal portion 16.

The secondary battery 10 has an insulating sheet 18 that covers the electrode body 12. The insulating sheet 18 insulates the electrode body 12 and the case body 13.
As shown in FIG. 1 or 4, the lid 14 has a long square plate-shaped second bottom wall 14a and a square tubular second peripheral wall 14b extending from the edge of the second bottom wall 14a toward the first peripheral wall 13b. And have.

The secondary battery 10 has a welded portion 20 in which the case body 13 and the lid 14 are welded together. The welded portion 20 joins both the tip portions 13c and 14c in a state where the tip portion 13c of the first peripheral wall 13b and the tip portion 14c of the second peripheral wall 14b are butted against each other. The welded portion 20 is indicated by dot hatching. In the following description, the direction in which the tip portion 13c of the first peripheral wall 13b and the tip portion 14c of the second peripheral wall 14b are abutted is defined as the abutting direction Y. In the second bottom wall 14a, the surface facing the inside of the case 11 is the inner surface 141a, and the surface exposed to the outside of the case 11 is the outer surface 140a. In a plan view of the second bottom wall 14a as viewed from the outer surface 140a, the direction in which the long side of the second bottom wall 14a extends is defined as the longitudinal direction X of the lid 14, and the direction in which the short side extends is defined as the lateral direction Z of the lid 14. ..

The second peripheral wall 14b has a thin portion 31 closer to the tip portion 14c along the abutting direction Y, and also has a thick portion 30 closer to the second bottom wall 14a than the thin portion 31 in the abutting direction Y. The thin portion 31 is a portion of the second peripheral wall 14b having a constant thickness along the abutting direction Y. The wall thickness portion 30 is a portion of the second peripheral wall 14b in which the thickness gradually increases from the thin wall portion 31 toward the second bottom wall 14a along the abutting direction Y. Of the second peripheral wall 14b, the surface facing the inside of the case 11 is the inner surface 141b, and the surface exposed to the outside of the case 11 is the outer surface 140b. Of the inner surface 141b of the second peripheral wall 14b, the inner surface of the thin portion 31 is described as the inner surface 310, and the inner surface of the thick portion 30 is described as the inner surface 300. In the cross section of the lid 14 cut along the abutting direction Y, the inner surface 310 of the thin portion 31 is parallel to the outer surface 140b. In the cross section in which the lid 14 is cut along the abutting direction Y, the inner surface 300 of the thick portion 30 is inclined so as to gradually separate from the outer surface 140b from the thin portion 31 toward the second bottom wall 14a along the abutting direction Y. It has a tapered shape.

Therefore, the thin portion 31 is provided over the entire second peripheral wall 14b, and the thick portion 30 is provided over the entire length of the long side of the second peripheral wall 14b and the overall length of the short side of the second peripheral wall 14b. It is provided over. That is, the thick portion 30 is provided over the entire direction in which the second peripheral wall 14b surrounds the second bottom wall 14a.

As shown in FIGS. 4 to 6, the cross section when the welded portion 20 is cut along the plane P orthogonal to the butt direction Y is defined as the first cross section A1. In the case 11, the cross-sectional area of the first cross section A1 is minimized. Further, assuming that the portion of the second bottom wall 14a exposed in the case 11 that is farthest from the case body 13 along the abutting direction Y is the farthest portion, in the present embodiment, the farthest portion is the first portion. 2 The inner surface 141a of the bottom wall 14a. The cross section when the lid 14 is cut by the plane P so as to pass through the inner surface 141a is referred to as the second cross section A2. The lid 14 is provided with the thick portion 30, so that the cross-sectional area of the second cross section A2 is larger than the cross-sectional area of the first cross section A1.

As described above, the thick portion 30 gradually becomes thicker from the thin portion 31 toward the second bottom wall 14a along the abutting direction Y, so that the cross-sectional area of the thick portion 30 is the second from the thin portion 31 side. It gradually increases toward the bottom wall 14a and reaches the maximum in the second cross section A2.

As shown in FIG. 5 or 6, the second cross section A2 is larger than the first cross section A1. The thick portion 30 is provided at all the boundary portions between the second bottom wall 14a and the second peripheral wall 14b.
Next, the operation of the secondary battery 10 will be described.

When the secondary battery 10 is used, a large pressure acts on the second bottom wall 14a and the second peripheral wall 14b of the lid 14 as the internal pressure of the case 11 rises. At this time, since the cross-sectional area of the second cross section A2 is larger than the cross-sectional area of the first cross section A1, the rigidity of the second peripheral wall 14b is improved. As a result, even if a large pressure is applied to the second peripheral wall 14b, the second peripheral wall 14b is less likely to be deformed outward.

According to the above embodiment, the following effects are obtained.
(1) Since the thick portion 30 of the lid 14 suppresses the second peripheral wall 14b from being significantly deformed toward the outside of the case 11, the stress generated in the welded portion 20 can be suppressed, and the welded portion 20 can be formed. It is possible to suppress the occurrence of cracks. As a result, the airtightness of the case 11 can be maintained. Even if the case 11 is enlarged, the deformation of the second peripheral wall 14b of the lid 14 can be suppressed, so that the airtightness of the case 11 can be maintained.

(2) The cross-sectional area of the thick portion 30 is gradually increased from the case main body 13 toward the second bottom wall 14a along the abutting direction Y with the cross-sectional area of the second cross section A2 as the maximum. According to this, for example, in a cross-sectional view in the butt direction Y, the inner surface 300 of the thick portion 30 is cut off without interfering with other parts inside the case 11 as compared with the case where the inner surface 300 is not tapered but has a quadrangular shape. The area can be increased.

(3) The thick portion 30 is formed over the entire direction in which the second peripheral wall 14b surrounds the second bottom wall 14a. For example, the cross-sectional area of the second cross section A2 is larger than that in the case where the thick portion 30 is formed only on a part of the second peripheral wall 14b. Therefore, the rigidity of the second peripheral wall 14b is further improved. As a result, the airtightness of the case 11 can be further maintained.

The above embodiment can be modified and implemented as follows. The above embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

○ As shown in FIG. 7, the shape of the thick portion 30 may be a shape that is curved and recessed from the thin portion 31 toward the second bottom wall 14a in a cross-sectional view along the abutting direction Y. Specifically, the thick portion 30 does not protrude from the virtual line L connecting the end portion 311 intersecting with the second bottom wall 14a and the end portion 312 intersecting with the second peripheral wall 14b, and is provided in a rounded shape. You may.

○ As shown in FIG. 8, the shape of the thick portion 30 may be a shape that bulges while curving from the thin portion 31 toward the second bottom wall 14a in a cross-sectional view along the abutting direction Y. Specifically, the thick portion 30 protrudes from the virtual line L connecting the end portion 311 intersecting with the second bottom wall 14a and the end portion 312 intersecting with the second peripheral wall 14b, and is provided in a rounded shape. May be good.

○ As shown in FIG. 9, the thick portion 30 includes the first thick surface 313, which is closer to the case body 13 than the inner surface 141a of the second bottom wall 14a and is parallel to the inner surface 141a, and the second peripheral wall. It may be formed by a second thick surface 314 which is located inside the inner surface 141b of 14b and is a surface parallel to the inner surface 141b.

○ As shown in FIG. 10, the thick portion 30 may have a stepped cross-sectional shape. Specifically, the thick portion 30 protrudes inward from the inner surface 141b of the second peripheral wall 14b and inward from the inner surface 141b. It may have a shape having a second thick portion 30b and a third thick portion 30c protruding from the inner surface 141b from the second thick portion 30b.

○ As shown in FIG. 11, the tip portion 40 of the second peripheral wall 14b may have a stepped shape in which the inner surface side in the thickness direction protrudes in the abutting direction Y from the outer surface side. The tip portion 40 has a first tip portion 41 on the inner surface side in the thickness direction and a second tip portion 42 on the outer side of the first tip portion 41. In this case, the inner surface 13d of the first peripheral wall 13b and the outer surface 41a of the first tip portion 41 are in contact with each other, the tip portion 13c of the first peripheral wall 13b and the second tip portion 42 are abutted, and the first peripheral wall 13b The tip portion 13c of the tip portion 13c and the second tip portion 42 are welded to form the welded portion 20.

○ As shown in FIG. 12, a wall thickness portion 30 may be provided at four corner portions at the boundary between the second bottom wall 14a and the second peripheral wall 14b.
○ In the embodiment, the electrode body 12 is a laminated type electrode body in which the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween, but for example, a long sheet-shaped positive electrode. It may be a winding type electrode body in which a long sheet-shaped negative electrode is wound with a long sheet-shaped separator 23 interposed therebetween.

○ The secondary battery 10 is not limited to the lithium ion secondary battery, and may be another secondary battery. In short, it is sufficient that ions move between the positive electrode active material layer 25 and the negative electrode active material layer 28 and charge is transferred.

○ The power storage device can be applied to a power storage device other than the secondary battery 10 such as a capacitor.

10 ... Secondary battery as a power storage device, 11 ... Case, 12 ... Electrode body, 13 ... Case body, 13a ... First bottom wall, 13b ... First peripheral wall, 13c ... Tip, 14 ... Lid, 14a ... Second Bottom wall, 14b ... 2nd peripheral wall, 14c ... Tip part, 20 ... Welded part, 30 ... Thick part, 31 ... Thin part, A1 ... 1st cross section, A2 ... 2nd cross section, P ... Plane, Y ... Butting direction ..

Claims (5)

It has a case body for accommodating the electrode body and a case having a lid for closing the opening of the case body.
The case body has a plate-shaped first bottom wall and
It has a tubular first peripheral wall extending from the edge of the first bottom wall.
The lid has a plate-shaped second bottom wall and
It has a tubular second peripheral wall extending from the edge of the second bottom wall toward the first peripheral wall.
A power storage device having a welded portion obtained by welding the tip end portion of the first peripheral wall and the tip end portion of the second peripheral wall.
The cross section when the welded portion is cut by a plane orthogonal to the abutting direction between the tip end portion of the first peripheral wall and the tip end portion of the second peripheral wall is defined as the first cross section.
Of the parts exposed in the case on the second bottom wall, the part farthest from the case body along the abutting direction is the farthest part, and the lid is placed on the plane so as to pass through the farthest part. When the cross section of the second peripheral wall when cut is taken as the second cross section,
The lid is a power storage device having a wall thickness portion that makes the cross-sectional area of the second cross section larger than the cross-sectional area of the first cross section. The first aspect of the present invention is characterized in that the cross-sectional area of the thick portion gradually increases from the case body toward the second bottom wall along the abutting direction with the cross-sectional area of the second cross section as the maximum. The power storage device described. The second bottom wall has a long square plate shape and the second peripheral wall has a square tubular shape, and the thick portion includes the second bottom wall extending in the longitudinal direction of the second bottom wall and the second bottom wall. The power storage device according to claim 1 or 2, wherein the power storage device is provided over the entire length of the boundary with the peripheral wall. The claim is characterized in that the second bottom wall has a long square plate shape and the second peripheral wall has a square tubular shape, and the thick portion is formed at four corner portions of the second peripheral wall. The power storage device according to claim 1 or 2. The second bottom wall has a long square plate shape and the second peripheral wall has a square tubular shape, and the thick portion is formed over the entire direction in which the second peripheral wall surrounds the second bottom wall. The power storage device according to claim 1 or 2, wherein the power storage device is characterized by the above.

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