JP6868221B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage device in which a case containing an electrode assembly is provided with a pressure release valve that releases pressure inside the case to the outside of the case.

Vehicles such as EVs (Electric Vehicles) and PHVs (Plug in Hybrid Vehicles) are equipped with secondary batteries such as lithium-ion batteries as storage devices for storing the power supplied to the electric motor that serves as the prime mover. This type of secondary battery is disclosed in, for example, Patent Document 1. The secondary battery has an electrode assembly in which a negative electrode having a negative electrode active material coated on a metal foil and a positive electrode electrode having a positive electrode active material coated on a metal foil are insulated by a separator and laminated in layers. Then, the electrode assembly and the electrolytic solution are housed in the case of the secondary battery. Further, the case of the secondary battery is provided with a pressure release valve (gas discharge valve) that cleaves when the pressure inside the case reaches the release pressure and releases the pressure inside the case to the outside of the case.

Japanese Unexamined Patent Publication No. 2014-203708

In such a pressure release valve, if the position where the cleavage starts (the opening point) varies, the opening shape and opening area of the opened valve also vary. As a result, the pressure inside the case may not be sufficiently released.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a power storage device capable of suppressing variations in the opening point of a pressure release valve.

The power storage device for solving the above problems is a power storage device provided with a pressure release valve for releasing the pressure inside the case to the outside of the case in a case containing the electrode assembly, and the pressure release valve is , The plurality of straight grooves intersect, and the width of the bottom surface of the straight groove in the lateral direction increases from the end of the straight groove toward the intersection of the straight groove. The gist is to become.

According to this, the thin region of the pressure release valve increases from the end of the straight groove toward the intersection, so that the vulnerability of the pressure release valve increases from the end of the straight groove toward the intersection. Become. Since the pressure release valve starts to open from the highly vulnerable part, the pressure release valve tends to open from the intersection of the straight groove. Therefore, it is possible to suppress variations in the opening point of the pressure release valve.

Further, with respect to the power storage device, the straight groove is erected from one end of the bottom surface in the lateral direction and the other end of the bottom surface in the lateral direction, and the first side surface is A second side surface on the opposite side is provided, and the shortest distance between the first side surface and the second side surface at a position along the surface of the pressure release valve is increased as the width of the bottom surface in the lateral direction increases. It is preferable that the size increases.

According to this, the width of the bottom surface in the lateral direction increases from the end to the intersection, whereas the straight groove is formed as compared with the case where the shortest distance between the first side surface and the second side surface is constant. Easy to form.

The power storage device for solving the above problems is a power storage device provided with a pressure release valve for releasing the pressure inside the case to the outside of the case in a case containing the electrode assembly, and the pressure release valve is , The plurality of straight grooves intersect, and the width of the bottom surface of the straight groove in the lateral direction decreases from the end of the straight groove toward the intersection of the straight groove. It is preferable to be.

According to this, the width of the bottom surface of the straight groove in the lateral direction becomes smaller from the end of the straight groove toward the intersection of the straight groove. Becomes thinner from the edge to the intersection. Therefore, the stress generated in the pressure release valve is concentrated at the intersection of the straight grooves. Since the opening of the pressure release valve starts from the part where the stress is concentrated, the pressure release valve is likely to open from the intersection of the straight grooves. Therefore, it is possible to suppress variations in the opening point of the pressure release valve.

Further, with respect to the power storage device, the straight groove is erected from one end of the bottom surface in the lateral direction and the other end of the bottom surface in the lateral direction, and the first side surface is The shortest distance between the first side surface and the second side surface at a position along the surface of the pressure release valve, which is provided with the second side surface on the opposite side, is as the width of the bottom surface in the lateral direction becomes smaller. It is preferable that the size becomes smaller.

According to this, the width of the bottom surface in the lateral direction decreases from the end to the intersection, whereas the straight groove is formed as compared with the case where the shortest distance between the first side surface and the second side surface is constant. Easy to form.

Further, with respect to the power storage device, the pressure release valve preferably includes a plurality of arc-shaped grooves having a bottom surface along an arc portion which is a part of the peripheral edge of the pressure release valve.
According to this, since the pressure release valve has an arcuate groove in addition to the straight groove, the linear groove and the arcuate groove are cleaved. Therefore, a sufficient opening area at the time of cleavage can be obtained. Further, by changing the width of the bottom surface of the arcuate groove in the lateral direction, the vulnerability of the pressure release valve in the arcuate groove can be adjusted.

According to the present invention, it is possible to suppress variations in the opening point of the pressure release valve.

Perspective view of the secondary battery. Top view of the pressure release valve of the first embodiment. (A) and (b) are cross-sectional views of the pressure release valve. The plan view of the pressure release valve of the 2nd Embodiment. (A) and (b) are cross-sectional views of the pressure release valve. (A) is a plan view of the pressure release valve of the first comparative example, (b) is a plan view of the pressure release valve of the second comparative example, (c) is a sectional view of the pressure release valve of the first comparative example, (d). ) Is a cross-sectional view of the pressure release valve of the second comparative example.

(First Embodiment)
Hereinafter, a first embodiment in which the power storage device is embodied in a secondary battery will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the secondary battery 10 as a power storage device includes a case 11. The secondary battery 10 includes an electrode assembly 12 housed in a case 11. The case 11 has a rectangular parallelepiped case body 13 and a rectangular flat plate-shaped lid 14 that closes the opening of the case body 13. The case body 13 and the lid 14 constituting the case 11 are both made of metal (for example, stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a square battery having a square appearance. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

The electrode assembly 12 has a positive electrode, a negative electrode, and a separator that insulates the positive electrode and the negative electrode. The positive electrode is formed by applying a positive electrode active material on both sides of a positive electrode metal foil (aluminum foil). The negative electrode is formed by applying a negative electrode active material to both sides of a negative electrode metal foil (copper foil). The electrode assembly 12 has a laminated structure in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated and a separator is interposed between the two electrodes. Further, the positive electrode terminal 15 and the negative electrode terminal 16 are electrically connected to the electrode assembly 12. Each part of the positive electrode terminal 15 and the negative electrode terminal 16 is exposed from the lid 14 to the outside of the case 11. Further, a ring-shaped insulating ring 17 for insulating from the case 11 is attached to the positive electrode terminal 15 and the negative electrode terminal 16, respectively.

The secondary battery 10 includes a pressure release valve 21 on the lid 14. The pressure release valve 21 is arranged between the positive electrode terminal 15 and the negative electrode terminal 16. The pressure release valve 21 opens when the pressure inside the case 11 reaches the release pressure, which is a predetermined pressure, so that the pressure inside the case 11 does not rise too much when gas is generated inside the case 11. The inside and outside of the case 11 are communicated with each other.

The pressure release valve 21 has a thin plate-shaped valve body 22 that is thinner than the plate thickness of the lid 14. The valve body 22 is located at the bottom of the recess 14a recessed in the outer surface of the lid 14 and is integrated with the lid 14.
As shown in FIG. 2, the pressure release valve 21 has a track-shaped peripheral edge in which two parallel straight portions 23 and 24 are connected by arc portions 25 and 26. The valve body 22 is connected to the peripheral edge of the pressure release valve 21 and has a track shape similar to the pressure release valve 21.

One end of the arc portion 25 is connected to one end of the straight portion 23, and the other end is connected to one end of the straight portion 24. One end of the arc portion 26 is connected to the other end portion of the straight line portion 23, and the other end portion is connected to the other end portion of the straight line portion 24. One end of the straight portions 23 and 24 is connected by an arc portion 25 having an arc shape as a whole, and the other end portion of the straight portions 23 and 24 is connected by an arc portion 26 having an arc shape as a whole. ing. In the pressure release valve 21, the portions where the ends of the straight portions 23 and 24 and the ends of the arc portions 25 and 26 are connected are the boundaries P1, P2, P3 and P4 of the straight portions 23 and 24 and the arc portions 25 and 26. Become.

The pressure release valve 21 has a plurality of grooves on the surface 22a of the valve body 22. The groove is composed of an intersecting groove 30, a plurality of arcuate grooves 41, 42 along the arc portions 25, 26, and a plurality of linear grooves 43, 44 along the straight line portions 23, 24. The thickness of the valve body 22 is thinner at the portion where the groove is present than at the portion where the groove is not present.

The intersecting groove 30 is located in a rectangular region in which adjacent boundaries P1 to P4 are connected by a straight line shown by a two-dot chain line in FIG. The intersecting groove 30 is formed by intersecting the first groove 31 and the second groove 32 as two straight grooves. The first groove 31 is located on a virtual straight line Y1 connecting the boundary P1 and the boundary P4. The first groove 31 includes a first end 31a at one end located on the boundary P1 side and a second end 31b at the other end located on the boundary P4 side. The second groove 32 is located on a virtual straight line Y2 connecting the boundary P2 and the boundary P3. The second groove 32 includes a first end 32a at one end located on the boundary P2 side and a second end 32b at the other end located on the boundary P3 side. The first groove 31 and the second groove 32 intersect at the center of the valve body 22. The portion where the first groove 31 and the second groove 32 intersect is called an intersection Q.

As shown in FIGS. 3 (a) and 3 (b), the first groove 31 and the second groove 32 are erected with the bottom surface 33 located at the deepest portion and the bottom surface 33 inclined from one end in the lateral direction. It is composed of a first side surface 34, and a second side surface 35 that is inclined from the other end of the bottom surface 33 in the lateral direction and is erected on the opposite side of the first side surface 34.

The width A of the bottom surface 33 of the first groove 31 in the lateral direction increases from the first end 31a toward the intersection Q, and increases from the second end 31b toward the intersection Q. That is, the width A of the first groove 31 in the lateral direction is the minimum at the first and second end portions 31a and 31b and the maximum at the intersection Q. In the present embodiment, the length of the first groove 31 from the first end 31a to the intersection Q and the length of the first groove 31 from the second end 31b to the intersection Q are 6 mm, respectively. The width Amin of the bottom surface 33 in the lateral direction at the first and second end portions 31a and 31b is set to 0.1 mm (see FIG. 3B), and the width Amax of the bottom surface 33 in the lateral direction at the intersection Q is set. It is set to 0.3 mm (see FIG. 3A). Therefore, the thin region of the valve body 22 becomes larger from the first end 31a toward the intersection Q, and becomes larger from the second end 31b toward the intersection Q. Further, the shortest distance C between the first side surface 34 and the second side surface 35 at a position along the surface 22a of the valve body 22 increases from the first end portion 31a toward the intersection Q, and the second end portion 31b. It becomes larger toward the intersection Q from. That is, the shortest distance C increases as the width A of the first groove 31 in the lateral direction increases.

The width B of the bottom surface 33 of the second groove 32 in the lateral direction increases from the first end 32a toward the intersection Q, and increases from the second end 32b toward the intersection Q. That is, the width B of the second groove 32 in the lateral direction is the minimum at the first and second end portions 32a and 32b and the maximum at the intersection Q. In the present embodiment, the length of the second groove 32 from the first end 32a to the intersection Q and the length of the second groove 32 from the second end 32b to the intersection Q are 6 mm, respectively. The width Bmin of the bottom surface 33 in the lateral direction at the first and second end portions 32a and 32b is set to 0.1 mm (see FIG. 3B), and the width Bmax of the bottom surface 33 in the lateral direction at the intersection Q is set. It is set to 0.3 mm (see FIG. 3A). Therefore, the thin region of the valve body 22 becomes larger from the first end 31a toward the intersection Q, and becomes larger from the second end 31b toward the intersection Q. Further, the shortest distance D between the first side surface 34 and the second side surface 35 at a position along the surface 22a of the valve body 22 increases from the first end portion 32a toward the intersection Q, and the second end portion 32b. It becomes larger toward the intersection Q from. That is, the shortest distance D increases as the width B of the second groove 32 in the lateral direction increases.

The pressure release valve 21 has two arc-shaped grooves 41 along the arc portion 25 and two arc-shaped grooves 42 along the arc portion 26 on the surface 22a of the valve body 22. The arcuate grooves 41 and 42 are erected from the bottom surface located at the deepest part, the first side surface inclined from one end in the lateral direction of the bottom surface, and the first side surface inclined from the other end in the lateral direction of the bottom surface. It is composed of two sides. Of the two arcuate grooves 41, one end of one arcuate groove 41 is connected to the first end portion 31a of the first groove 31, and one end of the other arcuate groove 41 is the second. It is connected to the second end portion 32b of the groove 32. Further, of the two arcuate grooves 42, one end of one arcuate groove 42 is connected to the second end portion 31b of the first groove 31, and one end of the other arcuate groove 42 is connected to the second end portion 31b of the first groove 31. It is connected to the first end portion 32a of the second groove 32. The pressure release valve 21 has one arcuate groove 41, 42 connected to the first groove 31 and one arcuate groove 41, 42 connected to the second groove 32.

The pressure release valve 21 has linear grooves 43 and 44 along the straight portion 23 and linear grooves 43 and 44 along the straight portion 24 on the surface 22a of the valve body 22. The linear grooves 43 and 44 are erected from the bottom surface located at the deepest part, the first side surface inclined from one end in the lateral direction of the bottom surface, and the other end inclined from the other end in the lateral direction of the bottom surface. It is composed of a second aspect. Of the two linear grooves 43, one end of one of the linear grooves 43 is connected to the first end 31a of the first groove 31, and one end of the other linear groove 43 is , It is connected to the second end portion 32b of the second groove 32. Further, of the two linear grooves 44, one end of one of the linear grooves 44 is connected to the second end 31b of the first groove 31, and one end of the other linear groove 44. The portion is connected to the first end portion 32a of the second groove 32. The pressure release valve 21 has one linear groove 43, 44 connected to the first groove 31 and one linear groove 43, 44 connected to the second groove 32, respectively.

Next, the operation of the pressure release valve will be described.
In the secondary battery 10 provided with the pressure release valve 21, if gas is generated inside the case 11 at the time of abnormality, the internal pressure of the case 11 increases accordingly. The pressure inside the case 11 is applied so as to expand the valve body 22 outward by making the back surface of the valve body 22 thinner than the plate thickness of the lid 14 a pressure receiving surface. At this time, stress is generated in the intersecting grooves 30, the arcuate grooves 41 and 42, and the linear grooves 43 and 44 of the valve body 22 due to the pressure applied from the inside of the case 11. Then, when the pressure of the case 11 exceeds the opening pressure, the pressure release valve 21 uses the intersection Q as the cleavage starting point, and the first groove 31, the second groove 32, the arcuate grooves 41, 42, and the linear grooves 43, 44 Cleaves. As a result, the valve body 22 is opened, and the pressure inside the case 11 is released to the outside.

Next, the effects of the first embodiment will be described together with the actions.
(1) The thin region of the valve body 22 of the pressure release valve 21 increases from the first end 31a and the second end 31b of the first groove 31 toward the intersection Q, so that the pressure release valve 21 has a thin region. The vulnerability increases from the first end 31a and the second end 31b of the first groove 31 toward the intersection Q. Further, the thin region of the valve body 22 of the pressure release valve 21 increases from the first end 32a and the second end 32b of the second groove 32 toward the intersection Q, so that the pressure release valve 21 is fragile. The property increases from the first end 32a and the second end 32b of the second groove 32 toward the intersection Q. Since the pressure release valve 21 starts to open from a highly fragile portion, the pressure release valve 21 tends to open from the intersection Q of the first groove 31 and the second groove 32. Therefore, the variation in the opening point of the pressure release valve 21 can be suppressed.

(2) The shortest distance C between the first side surface 34 and the second side surface 35 in the first groove 31 is such that the width A of the bottom surface 33 in the lateral direction is from the first end portion 31a and the second end portion 31b to the intersection Q. It gets bigger as it gets bigger. Further, the shortest distance D between the first side surface 34 and the second side surface 35 in the second groove 32 is such that the width B of the bottom surface 33 in the lateral direction is from the first end portion 32a and the second end portion 32b toward the intersection Q. It gets bigger as it gets bigger. Therefore, while the widths A and B of the bottom surface 33 in the lateral direction become large, the first groove 31 and the second groove 32 are more likely to be formed as compared with the case where the shortest distances C and D are kept constant.

(3) In addition to the first groove 31 and the second groove 32, the pressure release valve 21 includes a plurality of arc-shaped grooves 41 and 42 along the arc portions 25 and 26 and having a bottom surface. The second groove 32 and the arcuate grooves 41 and 42 are cleaved. Therefore, a sufficient opening area at the time of cleavage can be obtained. Further, the vulnerability of the valve body 22 of the pressure release valve 21 can be adjusted by changing the width of the bottom surfaces of the arcuate grooves 41 and 42 in the lateral direction.

(Second Embodiment)
Hereinafter, a second embodiment in which the power storage device is embodied in a secondary battery will be described with reference to FIGS. 4 and 5. The same configurations as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 4, the pressure release valve 21 has a plurality of grooves on the surface 22a of the valve body 22. The groove is composed of an intersecting groove 30, a plurality of arcuate grooves 41, 42 along the arc portions 25, 26, and a plurality of linear grooves 43, 44 along the straight line portions 23, 24.

The width A of the bottom surface 33 of the first groove 31 in the lateral direction becomes smaller from the first end 31a toward the intersection Q, and becomes smaller from the second end 31b toward the intersection Q. The width A of the first groove 31 in the lateral direction is maximum at the first and second end portions 31a and 31b and minimum at the intersection Q. That is, in a plan view of the pressure release valve 21 viewed from the thickness direction, the first groove 31 becomes thinner from the first end portion 31a and the second end portion 31b toward the intersection Q. In the present embodiment, the length of the first groove 31 from the first end 31a to the intersection Q and the length of the first groove 31 from the second end 31b to the intersection Q are 6 mm, respectively. The width Amax of the bottom surface 33 in the lateral direction at the first and second end portions 31a and 31b is set to 0.3 mm (see FIG. 5B), and the width Amin of the bottom surface 33 in the lateral direction at the intersection Q is set. It is set to 0.1 mm (see FIG. 5 (a)). Further, the shortest distance C between the first side surface 34 and the second side surface 35 in the first groove 31 becomes smaller from the first end portion 31a toward the intersection Q, and from the second end portion 31b toward the intersection Q. It gets smaller as it gets smaller. That is, the shortest distance C becomes smaller as the width A of the first groove 31 in the lateral direction becomes smaller.

The width B of the bottom surface 33 of the second groove 32 in the lateral direction becomes smaller from the first end 32a toward the intersection Q, and becomes smaller from the second end 32b toward the intersection Q. The width B of the second groove 32 in the lateral direction is maximum at the first and second end portions 32a and 32b and minimum at the intersection Q. That is, in a plan view of the pressure release valve 21 viewed from the thickness direction, the second groove 32 becomes thinner from the first end portion 32a and the second end portion 32b toward the intersection Q. In the present embodiment, the length of the second groove 32 from the first end 32a to the intersection Q and the length of the second groove 32 from the second end 32b to the intersection Q are 6 mm, respectively. The width Bmax of the bottom surface 33 in the lateral direction at the first and second end portions 32a and 32b is set to 0.3 mm (see FIG. 5B), and the width Bmin of the bottom surface 33 in the lateral direction at the intersection Q is set. It is set to 0.1 mm (see FIG. 5 (a)). Further, the shortest distance D between the first side surface 34 and the second side surface 35 in the second groove 32 becomes smaller from the first end portion 32a toward the intersection Q, and from the second end portion 32b toward the intersection Q. It gets smaller as it gets smaller. That is, the shortest distance D becomes smaller as the width B of the second groove 32 in the lateral direction becomes smaller.

Here, the stresses generated in the first groove 31 and the second groove 32 of the pressure release valve 21 of the second embodiment, the pressure release valve 21a of the first comparative example, and the pressure release valve 21b of the second comparative example are compared. To do.
The pressure release valves 21a and 21b of the first and second comparative examples have a second width A of the bottom surface 33 of the first groove 31 in the lateral direction and a width B of the bottom surface 33 of the second groove 32 in the lateral direction. It is different from the pressure release valve 21 of the embodiment. As shown in FIGS. 6A and 6C, in the first comparative example, the width A of the bottom surface 33 of the first groove 31 in the lateral direction is from the first end portion 31a to the second end portion 31b. The width B of the bottom surface 33 of the second groove 32 in the lateral direction is constant from the first end portion 32a to the second end portion 32b. The widths A and B are set to 0.3 mm. As shown in FIGS. 6 (b) and 6 (d), in the second comparative example, the width A of the bottom surface 33 of the first groove 31 in the lateral direction is from the first end portion 31a to the second end portion 31b. The width B of the bottom surface 33 of the second groove 32 in the lateral direction is constant from the first end portion 32a to the second end portion 32b. The widths A and B are set to 0.1 mm.

At this time, in the second embodiment, the stress generated at the intersection Q is 194.2 [MPa], and the average stress generated at each end 31a, 31b, 32a, 32b is 61.8 [MPa]. Is. Therefore, the stress generated at the intersection Q is about 3.1 times the stress generated at the boundaries P1 to P4. In the first comparative example, the stress generated at the intersection Q is 188.4 [MPa], and the average stress generated at each end 31a, 31b, 32a, 32b is 108.8 [MPa]. Therefore, the stress generated at the intersection Q is about 1.7 times the stress generated at the boundaries P1 to P4. In the second comparative example, the stress generated at the intersection Q is 114.3 [MPa], and the average stress generated at each end 31a, 31b, 32a, 32b is 119.9 [MPa]. Therefore, the stress generated at the intersection Q is about 1.0 times the stress generated at the boundaries P1 to P4. From this, it can be seen that in the second embodiment, the stress is concentrated in the intersection Q rather than the boundaries P1 to P4 as compared with the first and second comparative examples.

In the second embodiment, in addition to the same effect as the effect (3) of the first embodiment, the following actions and effects can be obtained.
(4) Since the width A of the bottom surface 33 of the first groove 31 becomes smaller from the first end portion 31a and the second end portion 31b toward the intersection Q, the pressure release valve 21 is viewed in a plan view from the thickness direction. , The first groove 31 becomes thinner from the first end portion 31a and the second end portion 31b toward the intersection Q. Further, since the width B of the bottom surface 33 of the second groove 32 becomes smaller from the first end portion 32a and the second end portion 32b toward the intersection Q, the pressure release valve 21 is viewed in a plan view from the thickness direction. The second groove 32 becomes thinner from the first end portion 32a and the second end portion 32b toward the intersection Q. Therefore, the stress generated in the valve body 22 of the pressure release valve 21 is concentrated in the intersection Q. Since the opening of the pressure release valve 21 starts from the portion where the stress is concentrated, the pressure release valve 21 is likely to open from the intersection Q of the first groove 31 and the second groove 32. Therefore, the variation in the opening point of the pressure release valve 21 can be suppressed.

(5) The shortest distance C between the first side surface 34 and the second side surface 35 in the first groove 31 is such that the width A of the bottom surface 33 in the lateral direction is from the first end portion 31a and the second end portion 31b to the intersection Q. It becomes smaller as it goes toward it. Further, the shortest distance D between the first side surface 34 and the second side surface 35 in the second groove 32 is such that the width B of the bottom surface 33 in the lateral direction is from the first end portion 32a and the second end portion 32b toward the intersection Q. It becomes smaller as it becomes smaller. Therefore, while the widths A and B of the bottom surface 33 in the lateral direction are reduced, the first groove 31 and the second groove 32 are more likely to be formed as compared with the case where the shortest distances C and D are constant.

The first and second embodiments may be changed as follows.
○ The shape of the case 11 is not limited to a rectangular parallelepiped shape, and may be, for example, a cylindrical shape.
○ The electrode assembly 12 is not limited to the laminated type, and may be a wound type in which a band-shaped positive electrode and a band-shaped negative electrode are wound and laminated in a layered manner.

○ The pressure release valve 21 may be a separate part from the case 11. In this case, for example, the pressure release valve 21 is joined to the case 11 by laser welding.
○ The shape of the pressure release valve 21 is not limited to the track shape, and may be a circular shape.

○ The crossing groove 30 may be changed to, for example, a Y-shape in which one ends of the three straight grooves intersect at one place, or an asterisk shape in which the central parts of the three straight grooves intersect at one place.
○ The pressure release valve 21 may have a groove on the back surface of the valve body 22.

○ In the first embodiment, the width A of the bottom surface 33 of the first groove 31 may increase from the first end portion 31a and the second end portion 31b toward the intersection Q, and the amount of change may be appropriately changed. You can do it. Further, the width B of the bottom surface 33 of the second groove 32 may be increased from the first end portion 32a and the second end portion 32b toward the intersection Q, and the amount of change may be appropriately changed.

○ In the second embodiment, the width A of the bottom surface 33 of the first groove 31 may become smaller from the first end portion 31a and the second end portion 31b toward the intersection Q, and the amount of change may be appropriately changed. You can do it. Further, the width B of the bottom surface 33 of the second groove 32 may become smaller from the first end portion 32a and the second end portion 32b toward the intersection Q, and the amount of change may be appropriately changed.

○ The shortest distance C between the first side surface 34 and the second side surface 35 in the first groove 31 may be constant. Similarly, the shortest distance D between the first side surface 34 and the second side surface 35 in the second groove 32 may be constant.

○ The arcuate grooves 41 and 42 may be omitted.
○ The cross groove 30 and the arcuate grooves 41 and 42 do not have to be connected.
○ The linear grooves 43 and 44 may be omitted.

○ The cross groove 30 and the linear grooves 43 and 44 do not have to be connected.
The arcuate grooves 41, 42 and the linear grooves 43, 44 may be grooves having a V-shaped cross section and do not have a bottom surface.

○ 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 and the negative electrode active material layer and charge is transferred. Further, a capacitor may be used as the power storage device.

○ The secondary battery 10 may be mounted on an automobile as a vehicle power supply device, or may be mounted on an industrial vehicle. Further, it may be applied to a stationary power storage device.

10 ... Secondary battery as a power storage device, 11 ... Case, 12 ... Electrode assembly, 21 ... Pressure release valve, 22a ... Surface, 25, 26 ... Arc part, 31 ... First groove as a straight groove, 32 ... Straight line 2nd groove as a groove, 31a, 32a ... 1st end as an end, 31b, 32b ... 2nd end as an end, 33 ... bottom surface, 34 ... 1st side surface, 35 ... 2nd side surface, 41 , 42 ... Arc groove, Q ... Intersection, A, B ... Width, C, D ... Shortest distance.

Claims (1)

A power storage device in which a case containing an electrode assembly is provided with a pressure release valve for releasing the pressure inside the case to the outside of the case.
The pressure release valve has a thin plate-like valve body thinner than the plate thickness of the case.
The valve body is formed in a track shape in which two parallel straight portions are connected by an arc portion, and on the surface thereof, a plurality of linear grooves having a bottom surface along the two straight portions and the arc are formed. A first linear and bottomed portion that is connected to a plurality of arcuate grooves having a bottom surface along the portion and intersects the linear groove and the arcuate groove at the center of the valve body to form an intersection . With a groove and a second groove ,
The first groove and the second groove are inclined from one end of the bottom surface in the lateral direction to stand upright, and from the other end of the bottom surface in the lateral direction to the opposite side of the first side surface. With a second side to stand up
Wherein the first groove and the lateral direction of the width of the bottom surface of the second groove, continuously increases toward the front Ki交difference portion from the joined ends to said linear grooves and said arcuate groove, and, The shortest distance between the first side surface and the second side surface at a position along the surface of the pressure release valve is continuously increased as the width of the bottom surface in the lateral direction is continuously increased. As a result, the fragility of the pressure release valve is increased from the ends of the first groove and the second groove connected to the linear groove and the arcuate groove toward the intersection. Power storage device.

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