JP2014203737A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce variations in an opening shape and an opening area of a pressure release valve.SOLUTION: A power storage device has an intersection groove 23 in a valve body 21 of a pressure release valve 20. The intersection groove 23 has an intersection part P in which a straight groove 24 and a straight groove 25 intersect with each other. A region including the intersection part P is used as a first cleavage part 26 and a region not including the intersection part P is used as a second cleavage part 27. Then, mechanical strength of the first cleavage part 26 is made weaker than that of the second cleavage part 27.

Description

  The present invention relates to a power storage device having a pressure release valve that releases pressure inside a case to the outside of the case.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery such as a lithium ion battery as a power storage device that stores power supplied to an electric motor serving as a prime mover. This type of secondary battery is disclosed in Patent Document 1, for example. The secondary battery has an electrode assembly in which a negative electrode obtained by applying a negative electrode active material to a metal foil and a positive electrode obtained by applying a positive electrode active material to a metal foil are insulated with a separator and laminated in layers. And the electrode assembly and electrolyte solution are accommodated 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 releases the pressure inside the case to the outside of the case.

JP 2011-181214 A

When variation occurs in the position where the pressure release valve starts to be opened, the opening shape and the opening area of the valve also vary. As a result, there is a possibility that the pressure in the case cannot be sufficiently released.
The present invention has been made paying attention to such problems existing in the prior art, and an object thereof is to provide a power storage device capable of reducing variations in the opening shape and opening area of the pressure release valve. There is to do.

  A power storage device that solves the above-described problem is a power storage device that includes a pressure release valve that opens a pressure in the case to the outside of the case in which the electrode assembly is housed, and the pressure release valve includes a cleavage start point. 1 cleavage part and the 2nd cleavage part which does not contain the said cleavage origin, and said 1st cleavage part has mechanical strength lower than said 2nd cleavage part.

  According to this configuration, the first cleavage portion including the cleavage starting point can be determined as the position where the cleavage starts, and the cleavage is likely to start from the first cleavage portion. As a result, variations in the opening shape and opening area of the pressure release valve can be reduced.

  In the power storage device, the pressure release valve may include a cleavage groove, and the first cleavage part and the second cleavage part may include the cleavage groove. According to this configuration, the cleavage of the first cleavage portion and the second cleavage portion can be promoted by the cleavage groove. Accordingly, it is possible to improve the speed in releasing the pressure in the case.

  In the above power storage device, the cleavage groove may include an intersection groove, and the cleavage start point may be an intersection of the intersection groove. According to this configuration, at the initial stage of the opening of the pressure release valve, the cleavage of the pressure release valve can be radially expanded by the cross groove. Accordingly, it is possible to improve the speed in releasing the pressure in the case.

In the above power storage device, the first cleavage portion may be annealed. According to this structure, the site | part from which hardness differs by a simple method can be provided.
In the power storage device, the second cleavage portion may be shot peened. According to this structure, the site | part from which hardness differs by a simple method can be provided.

  According to the present invention, variations in the opening shape and opening area of the pressure release valve can be reduced.

The perspective view which shows the external appearance of a secondary battery. The top view which shows the surface of the pressure release valve of 1st Embodiment. FIG. The top view which shows the surface of the pressure release valve of 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment embodying a power storage device will be described with reference to FIGS.
As shown in FIG. 1, in a secondary battery 10 as a power storage device, an electrode assembly 12 is accommodated in a case 11. The case 11 also contains an electrolyte solution together with the electrode assembly 12. The case 11 includes a bottomed cylindrical case main body 13 and a flat lid 14 that closes an opening for inserting the electrode assembly 12 into the case main body 13. Both the case main body 13 and the lid body 14 are made of metal (for example, stainless steel or aluminum). In addition, the secondary battery 10 of this embodiment is a rectangular battery whose appearance is a rectangular shape because the case body 13 has a bottomed rectangular tube shape and the lid body 14 has a rectangular flat plate shape. Moreover, the secondary battery 10 of this embodiment is a lithium ion battery.

  The electrode assembly 12 includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode from the negative electrode. The positive electrode is configured by applying a positive electrode active material to both surfaces of a positive metal foil (aluminum foil). The negative electrode is configured by applying a negative electrode active material to both surfaces of a negative electrode metal foil (copper foil). The electrode assembly 12 has a stacked structure in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked and a separator is interposed between the electrodes. In addition, a positive electrode terminal 15 and a 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 to the outside of the case 11 from the lid body 14. Further, a ring-shaped insulating ring 17 a for insulating from the case 11 is attached to the positive terminal 15 and the negative terminal 16, respectively.

  In addition, the lid 14 of the case 11 is provided with a liquid injection hole 18 for injecting an electrolyte into the case 11 (case body 13). The liquid injection hole 18 is closed by a sealing member 19. Has been. The sealing member 19 is fixed to the surface 14 a (surface outside the case) of the lid body 14 and is exposed outside the case 11. Further, the pressure release valve 20 that is opened when the pressure in the case 11 reaches an open pressure, which is a predetermined pressure, and communicates the inside and outside of the case so that the pressure in the case 11 does not increase excessively. Is provided. In this embodiment, the pressure release valve 20 is located on the lid 14 of the case 11. Further, in the lid body 14, the sealing member 19 (the liquid injection hole 18) and the pressure release valve 20 are positioned side by side. The release pressure of the pressure release valve 20 is set to a pressure at which the case 11 itself and the joint between the case body 13 and the lid body 14 can be broken before cracks or breakage can occur. The pressure release valve 20 has a thin plate-like valve body 21 that is thinner than the plate thickness of the lid body 14. The valve body 21 is located at the bottom of a recess 22 that is recessed in the upper surface of the lid body 14, and is molded integrally with the lid body 14.

As shown in FIG. 2, the pressure relief valve 20 has a circular periphery. The valve body 21 is connected to the periphery of the pressure release valve 20 and has a circular shape like the pressure release valve 20.
The surface 21a of the valve body 21 has a cross groove 23 as a cleavage groove. The intersecting groove 23 includes two straight grooves 24 and 25 extending linearly between the peripheral edges of the valve body 21. The straight grooves 24 and 25 are grooves having the same shape, and are V-shaped grooves in this embodiment. The intersecting groove 23 has an intersecting portion P at a position where the two straight grooves 24 and 25 intersect. This intersecting portion P is likely to concentrate pressure applied from the inside of the case 11 and is assumed as a starting point of cleavage, which is a starting point when the valve body 21 starts to tear. In this embodiment, the intersection P of the intersection groove 23 is located at the center of the valve body 21.

  As shown in FIGS. 2 and 3, the valve body 21 includes a crossing portion P, surrounds the first cleaving portion 26 located around the crossing portion P, and the outer periphery of the first cleaving portion 26, And a second cleaving portion 27 located between the outer periphery and the periphery of the valve body 21. In FIG. 2 and FIG. 3, the first cleavage portion 26 is illustrated by dots, and the portion not attached with dots is the second cleavage portion 27. The 2nd cleavage part 27 is a site | part which does not contain the cross | intersection part P used as a cleavage origin. And the 1st cleavage part 26 and the 2nd cleavage part 27 are site | parts containing the groove surface of the linear grooves 24 and 25, as shown in FIG.

  As shown in FIG. 2, when the surface 21 a of the valve body 21 is viewed in plan, the area of the first cleavage part 26 is smaller than the area of the second cleavage part 27. Thereby, when the valve body 21 is viewed in plan, the first cleavage part 26 is a region smaller than the second cleavage part 27 and includes a part of the intersection part P in the region of the valve body 21. Located in the area. In addition, it is preferable that the area of the 1st cleavage part 26 is an area of 50% or less with respect to the area of the valve body 21, for example.

  In this embodiment, the first cleaving portion 26 is annealed. Due to this annealing, the mechanical strength of the first cleavage portion 26 is lower than the mechanical strength of the second cleavage portion 27. That is, the first cleaving portion 26 is a portion where a part of the metal portion in the valve body 21 is softened by annealing, and is softer than the second cleaving portion 27. Annealing includes high-frequency annealing and laser annealing. In this specification, the level of mechanical strength is based on the comparison of materials without depending on the shape.

Hereinafter, the operation of this embodiment will be described.
The pressure in the case 11 is applied so that the valve body 21 is expanded outward when the back surface 21b of the valve body 21 becomes a pressure receiving surface. Further, stress is generated in the intersecting groove 23 of the valve body 21 by the pressure applied from the inside of the case 11.

  In this embodiment, the first cleaving portion 26, which is softer than the second cleaving portion 27, is positioned so as to surround the intersecting portion P of the intersecting groove 23 assumed as a cleaving start point. For this reason, the pressure applied from the inside of the case 11 is likely to concentrate in the intersecting groove 23 in the vicinity of the intersecting portion P in the first tearing portion 26, and the valve element 21 is likely to start to break starting from the intersecting portion P.

  When the pressure in the case 11 reaches the opening pressure, the intersecting groove 23 is cleaved starting from the intersecting portion P. When the intersecting groove 23 on the surface 21a of the valve body 21 is thus cleaved, the valve body 21 is turned up outside while being divided into a plurality of regions. Thereby, a large opening is generated in the pressure release valve 20. The pressure in the case 11 is released to the outside of the case 11 through an opening generated in the pressure release valve 20.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) By having the first cleaved portion 26 that is softer than the second cleaved portion 27 at a position including the intersecting portion P, the intersecting portion P can be determined as a position where the cleaving starts, and the intersecting portion P is the starting point. Cleavage is easy to start. As a result, variations in the opening shape and the opening area of the pressure release valve 20 can be reduced. Therefore, the pressure in the case 11 can be sufficiently released.

  (2) The first cleaved portion 26 and the second cleaved portion 27 include the intersecting grooves 23, respectively, so that the cleavage of the first cleaved portion 26 and the second cleaved portion 27 can be promoted. Accordingly, it is possible to improve the speed in releasing the pressure in the case 11.

  (3) By having the intersecting grooves 23, the cleavage can be radially expanded by the intersecting grooves 23 at the initial stage of the cleavage. Accordingly, it is possible to improve the speed in releasing the pressure in the case 11.

(4) Since the 1st cleaving part 26 is provided in the valve body 21 by annealing, the site | part from which hardness differs can be provided in the valve body 21 by a simple method.
(Second Embodiment)
Next, a second embodiment in which the power storage device is embodied will be described with reference to FIG.

Note that, in the embodiment described below, the same components as those already described in the embodiment are denoted by the same reference numerals, and redundant description thereof is omitted or simplified.
As shown in FIG. 4, the pressure release valve 30 of this embodiment has a track-shaped periphery in which two parallel straight portions 31 and 32 are connected by arc portions 33 and 34. The valve body 35 of the pressure release valve 30 is connected to the periphery of the pressure release valve 30 and has a track shape like the pressure release valve 30.

  The arc portion 33 has one end connected to one end of the straight portion 31 and the other end connected to one end of the straight portion 32. The arc portion 34 has one end connected to the other end of the straight portion 31 and the other end connected to the other end of the straight portion 32. That is, in this embodiment, one end portion of the straight portions 31 and 32 is connected by an arc portion 33 having an arc shape as a whole, and the other end portion of the straight portions 31 and 32 is an arc shape as a whole. Connected by the arc part 34. In the pressure release valve 30, the portion where the end portions of the straight portions 31, 32 and the end portions of the arc portions 33, 34 are connected is the boundary P1, P2, P3, P4 between the straight portions 31, 32 and the arc portions 33, 34. Become.

  The surface 35a of the valve body 35 has a cleavage groove. The cleavage groove includes an intersecting groove 36, a plurality of arc-shaped grooves 37 and 38 along the arc portions 33 and 34, and a plurality of linear grooves 39 and 40 along the straight portions 31 and 32. In this embodiment, the intersecting grooves 36, the arc-shaped grooves 37 and 38, and the linear grooves 39 and 40 are all V-shaped grooves.

  The intersecting groove 36 includes two straight grooves 41 and 42. The straight grooves 41 and 42 are positioned on virtual straight lines Y1 and Y2 that intersect the arc portions 33 and 34 that are the peripheral edges of the pressure release valve 30, respectively. The virtual straight lines Y1 and Y2 intersect the virtual line indicated by the two-dot chain line in the diagram connecting the boundaries P1 and P3, and the virtual line indicated by the two-dot chain line in the diagram connecting the boundaries P2 and P4. The intersecting groove 36 has an intersecting portion P at a position where the two straight grooves 41 and 42 intersect. The intersection P includes intersections of virtual straight lines Y1 and Y2. In this embodiment, the intersection P of the intersection groove 36 is located at the center of the valve body 35.

  The surface 35 a of the valve body 35 has two arc-shaped grooves 37 along the arc portion 33 and two arc-shaped grooves 38 along the arc portion 34. Of the two arc-shaped grooves 37, one arc-shaped groove 37 is connected to one end located on the boundary P <b> 1 side in the linear groove 41, and extends in an arc shape along the arc portion 33. Of the two arc-shaped grooves 38, one arc-shaped groove 38 is connected to one end located on the boundary P <b> 2 side in the linear groove 42, and extends in an arc shape along the arc portion 34. . Of the two arc-shaped grooves 37, the other arc-shaped groove 37 is connected to the other end located on the boundary P <b> 3 side in the linear groove 42, and extends in an arc shape along the arc portion 33. . Of the two arc-shaped grooves 38, the other arc-shaped groove 38 is connected to the other end located on the boundary P <b> 4 side in the linear groove 41, and extends in an arc shape along the arc portion 34. . Each arcuate groove 37, 38 bisects the valve body 35 in a direction in which the position of the end opposite to the end connected to the straight grooves 41, 42 is orthogonal to the direction in which the straight portions 31, 32 extend. The length is a position that is separated from the bisector L1 indicated by a one-dot chain line in the inside at a predetermined distance. That is, the arc-shaped grooves 37 and 38 are provided along a part of the arc portions 33 and 34.

  Further, the surface 35 a of the valve body 35 has two linear grooves 39 and 40 along the linear portion 31 and two linear grooves 39 and 40 along the linear portion 32. Of the two linear grooves 39, one linear groove 39 is connected to one end located on the boundary P <b> 1 side in the linear groove 41, and extends linearly along the linear part 31. Yes. Of the two linear grooves 40, one linear groove 40 is connected to one end located on the boundary P <b> 2 side in the linear groove 42, and extends linearly along the linear part 31. doing. Of the two linear grooves 39, the other linear groove 39 is connected to the other end located on the boundary P <b> 3 side in the linear groove 42, and extends linearly along the linear portion 32. doing. Of the two linear grooves 40, the other linear groove 40 is connected to the other end located on the boundary P <b> 4 side in the linear groove 41, and extends linearly along the linear part 32. doing.

  The straight grooves 39 and 40 are located from a perpendicular line L2 that passes through the intersection of the virtual straight lines Y1 and Y2 at the end opposite to the ends connected to the straight grooves 41 and 42 and perpendicularly intersects the bisector L1. The length is a position that is separated by a predetermined distance. That is, each linear groove 39 and 40 is provided along a part of the linear portions 31 and 32. As a result, the valve body 35 has one linear groove 39, 40 connected to the linear groove 41 and one linear groove 39, 40 connected to the linear groove 42.

  Then, on the surface 35 a of the valve body 35, assuming virtual straight lines Y <b> 1 and Y <b> 2 along the intersecting grooves 36, a plurality of regions S <b> 1, S <b> 2, S <b> 3 surrounded by the virtual straight lines Y <b> 1 and Y <b> 2 and the periphery of the pressure release valve 30. S4 is assumed. In the region S1, the portion of the virtual straight line Y1 located between the intersection P of the intersection groove 36 and the intersection where the virtual straight line Y1 intersects the arc 33, and the intersection P and the virtual straight line Y2 intersect the arc 34. This is a region partitioned by the portion of the virtual straight line Y2 located between the intersecting portion and the straight portion 31. In addition, the region S2 includes a portion of the virtual straight line Y2 located between the intersection P and the intersection where the virtual straight line Y2 intersects the arc 33, and an intersection where the intersection P and the virtual straight line Y1 intersect the arc 34. This is a region partitioned by the portion of the imaginary straight line Y1 located between the straight portion and the straight portion 32. The region S1 and the region S2 are point symmetric with respect to the intersection of the virtual straight line Y1 and the virtual straight line Y2.

  The region S3 includes a portion of the virtual straight line Y1 located between the intersection P and the intersection where the virtual straight line Y1 intersects the arc 33, and an intersection where the intersection P and the virtual straight line Y2 intersect the arc 33. This is a region partitioned by the portion of the virtual straight line Y2 located between and the arc portion 33. In addition, the region S4 includes a portion of the virtual straight line Y2 located between the intersection P and the intersection where the virtual straight line Y2 intersects the arc 34, and an intersection where the intersection P and the virtual straight line Y1 intersect the arc 34. This is a region partitioned by the portion of the imaginary straight line Y1 located between the portion and the arc portion 34. The region S3 and the region S4 are point symmetric with the intersection of the virtual straight line Y1 and the virtual straight line Y2 as the center of symmetry.

  In this embodiment, the regions S1 and S2 are regions including the straight portions 31 and 32, and are in contact with the entirety of the straight portions 31 and 32, but are slightly in contact with the arc portions 33 and 34. On the other hand, in this embodiment, the areas S3 and S4 are areas including the arc portions 33 and 34, and are in contact with almost the entire arc portions 33 and 34. In this embodiment, the regions S1 and S2 are the second regions with few portions in contact with the arc portions 33 and 34, and the regions S3 and S4 are the first regions with many portions in contact with the arc portions 33 and 34. The area of the four regions S1 to S4 on the surface 35a of the valve element 35 is such that the regions S3 and S4 having more portions in contact with the arc portions 33 and 34 have less portions in contact with the arc portions 33 and 34. , Larger than S2.

  As shown in FIG. 4, the valve body 35 of this embodiment includes a crossing portion P and surrounds the first cleaving portion 43 positioned around the crossing portion P and the outer periphery of the first cleaving portion 43. , And a second cleaving portion 44 located between the outer periphery and the periphery of the valve body 35. In FIG. 4, the first cleavage portion 43 is illustrated by dots, and the portion not provided with dots is the second cleavage portion 44. The 1st cleavage part 43 contains each part of area | region S1-S4, and is located over these area | regions S1-S4. Further, the first cleavage part 43 is a part including a part of the groove surfaces of the linear grooves 41 and 42. Moreover, the 2nd cleavage part 44 contains each one part of area | region S1-S4, and is located over these area | regions S1-S4. The second cleaving portion 44 includes a part of groove surfaces of the straight grooves 41 and 42 not included in the first cleaving portion 43, a groove surface of the arc-shaped grooves 37 and 38, and a groove of the linear grooves 39 and 40. And a part including the surface. And the 2nd cleavage part 27 is a site | part which does not contain the cross | intersection part P used as a cleavage origin.

  As shown in FIG. 4, when the surface 35 a of the valve body 35 is viewed in plan, the area of the first cleavage part 43 is smaller than the area of the second cleavage part 44. Thereby, the first cleaving portion 43 is an area smaller than the second cleaving portion 44 when the valve body 35 is viewed in a plan view, and includes a part of the intersection portion P in the area of the valve body 35. Located in the area. In addition, it is preferable that the area of the 1st cleavage part 43 is an area of 50% or less with respect to the area of the valve body 35, for example.

  In this embodiment, the first cleaving portion 43 is annealed similarly to the first cleaving portion 26 of the first embodiment. Thereby, the mechanical strength of the first cleaving portion 43 is lower than the mechanical strength of the second cleaving portion 44. That is, the first cleaving portion 43 is softer than the second cleaving portion 44.

Hereinafter, the operation of this embodiment will be described.
In this embodiment, the first cleaving portion 43, which is softer than the second cleaving portion 44, is positioned so as to surround the intersecting portion P of the intersecting groove 36 that is assumed as a cleaving start point. For this reason, the pressure applied from the inside of the case 11 is likely to concentrate in the intersecting groove 36 in the vicinity of the intersecting portion P in the first tearing portion 43, and the valve body 35 is likely to be cleaved starting from the intersecting portion P.

  In this embodiment, when the cleavage starts from the intersection P and the end of the straight grooves 41 and 42 reaches the end connected to the arc-shaped grooves 37 and 38, the straight grooves and the arc-shaped grooves 37 and 38 are broken. Cleavage of 39, 40 also begins. By this cleavage, the valve body 35 is divided into four regions S1 to S4 along the grooves that define the regions S1 to S4.

  At this time, in this embodiment, the areas of the regions S3 and S4 having many portions in contact with the arc portions 33 and 34 are made larger than the areas of the regions S1 and S2 having many portions in contact with the straight portions 31 and 32. . That is, the areas S3 and S4 have a larger pressure receiving area than the areas S1 and S2. For this reason, the pressure receiving amount of the pressure applied from the inside of the case 11 to the back surface of the valve body 35 is larger in the regions S3 and S4 than in the regions S1 and S2.

  Therefore, according to this embodiment, in addition to the effects (1) to (4) of the first embodiment, the following effects can be obtained. In addition, the effects (1) to (4) are as follows. “Valve 21” is “Valve 35”, “Cross groove 23” is “Cross groove 36”, and “First cleavage part 26” is “First”. And “second cleavage part 27” are read as “second cleavage part 44”, respectively.

  (5) The arc-shaped grooves 37 and 38 are harder to cleave than the straight grooves 41 and 42. For this reason, by increasing the area of the regions S3 and S4 with many portions in contact with the arc portions 33 and 34 as compared with the areas of the regions S1 and S2 with few portions in contact with the arc portions 33 and 34, the regions S3 and S4 The amount of pressure received increases. Therefore, even if the pressure release valve 30 has the arc-shaped grooves 37 and 38 along the arc portions 33 and 34 in order to enlarge the opening of the pressure release valve 30, the cleavage of the arc-shaped grooves 37 and 38 is promoted to promote the region. S3 and S4 are easily opened outward. As a result, the balance of the opening of the pressure release valve 30 is improved, and the opening of the pressure release valve 30 can be increased. That is, the pressure in the case 11 can be quickly released.

  Incidentally, when the amount of pressure received in the regions S3 and S4 in contact with the arc portions 33 and 34 is small, the arc-shaped grooves 37 and 38 may not be sufficiently cleaved. That is, if the balance of the opening of the pressure release valve 30 is poor, the arc-shaped grooves 37 and 38 are not sufficiently cleaved, and as a result, the opening of the pressure release valve 30 is also reduced. Therefore, the quickness in releasing the pressure in the case 11 is impaired.

  (6) The intersecting groove 36 has two linear grooves 41 and 42. For this reason, the cleavage is promoted by the linear grooves 41 and 42 at the initial stage of the cleavage of the valve body 35. Accordingly, it is possible to improve the speed in releasing the pressure in the case 11.

  (7) By making the pressure release valve 30 into a track shape, the opening of the pressure release valve 30 can be set larger than when the pressure release valve 30 has a square shape. Accordingly, it is possible to improve the speed in releasing the pressure in the case 11.

  (8) Since the straight grooves 41 and 42 are extended to the vicinity of the boundaries P1 to P4, the arc-shaped grooves 37 and 38 can be arranged along the arc portions 33 and 34. Therefore, when each groove of the valve body 35 is cleaved, the opening of the pressure release valve 30 can be increased.

  (9) Since the linear grooves 41 and 42 and the arc-shaped grooves 37 and 38 are connected, the arc-shaped grooves 37 and 38 can be promptly transferred after the linear grooves 41 and 42 are cleaved. The pressure release valve 30 is divided into the regions S1 to S4 by the cleavage of the linear grooves 41 and 42, and an opening is generated when the valve body 35 is turned up to the outside in accordance with the progress of the cleavage, and the pressure is applied to the case 11 from the opening. Open to the outside. For this reason, the opening amount of the pressure release valve 30 can be sufficiently secured by promptly shifting the cleavage from the straight grooves 41 and 42 to the arc-shaped grooves 37 and 38.

  (10) The straight grooves 39 and 40 promote the turning up of the regions S1 and S2 outward. That is, the regions S1 and S2 are easily opened outward by the cleavage of the linear grooves 39 and 40. As a result, the balance of the opening of the pressure release valve 30 is improved, and the opening of the pressure release valve 30 can be increased. That is, the pressure in the case 11 can be quickly released.

  (11) The arc-shaped grooves 37 and 38 are provided along part of the arc portions 33 and 34. Further, the straight grooves 39 and 40 are provided along a part of the straight portions 31 and 32. For this reason, even if each groove | channel cleaves and it turns up outside, the valve body 35 is connected in the location in which the groove | channel is not provided. Therefore, it is possible to prevent the fragments of the valve body 35 from scattering.

In addition, you may change this embodiment as follows.
○ Instead of annealing the first cleavage parts 26 and 43, the second cleavage parts 27 and 44 may be shot peened. According to shot peening, work hardening occurs in the metal parts of the valve bodies 21 and 35. For this reason, the second cleavage parts 27 and 44 subjected to shot peening are harder than the first cleavage parts 26 and 43 not subjected to shot peening. That is, the first cleavage parts 26 and 43 have lower mechanical strength and are softer than the second cleavage parts 27 and 44. Therefore, the same effect as that of the embodiment can be obtained.

  In addition to the annealing of the first cleavage parts 26 and 43, the second cleavage parts 27 and 44 may be shot peened. According to this, while the 1st cleavage parts 26 and 43 are softened by annealing, the 2nd cleavage parts 27 and 44 are hardened by shot peening. For this reason, the first cleavage parts 26 and 43 are softer than the second cleavage parts 27 and 44. Therefore, the same effect as that of the embodiment can be obtained.

The annealing process and the shot peening process may be performed on both the front and back surfaces of the valve bodies 21 and 35.
The cross grooves 23 and 36 may be changed to a Y shape instead of the X shape.

○ The cross-sectional shape of each cleavage groove may be changed.
○ The shape of the case 11 may be changed. For example, the case 11 may be cylindrical.
The pressure release valves 20 and 30 may be separate parts from the case 11, and the pressure release valves 20 and 30 may be joined to the case 11. Joining is performed by welding (for example, laser welding), for example.

The electrode assembly 12 is not limited to the laminated type, and may be a wound type in which a belt-like positive electrode and a belt-like negative electrode are wound and laminated in layers.
The secondary battery 10 is a lithium ion secondary battery, but is not limited thereto, and may be another secondary battery. In short, any ion may be used as long as ions move between the positive electrode active material layer and the negative electrode active material layer and transfer charge. Further, a capacitor may be used as the power storage device.

(Circle) the secondary battery 10 may be mounted in a motor vehicle as a vehicle power supply device, and may be mounted in an industrial vehicle. Further, the present invention may be applied to a stationary power storage device.
(Circle) you may provide the 1st cleaving parts 26 and 43 and the 2nd cleaving parts 27 and 44, without providing a crevice groove in the front and back both surfaces of the valve bodies 21 and 35. According to this configuration, the first cleavage portions 26 and 43 can be determined as positions where the cleavage starts, and the cleavage is easily started from the first cleavage portions 26 and 43 as the starting point.

(Circle) you may provide a cleavage groove in the back surface of the valve bodies 21 and 35. FIG.
O You may change the shape of the cleavage groove provided in the valve bodies 21 and 35. For example, a single linear groove or a groove having no intersection, such as a “C” -shaped groove, may be used. And in the valve bodies 21 and 35 having these grooves, the region including the position assumed as the cleavage starting point is defined as the first cleavage portions 26 and 43, and the region not including the position assumed as the cleavage starting point is defined as the second cleavage region. It is set as the cleavage parts 27 and 44. In this case, the first cleaved portions 26 and 43 may be provided by annealing, or the second cleaved portions 27 and 44 may be provided by shot peening.

  In the second embodiment, the imaginary straight lines Y1 and Y2 may be defined as lines passing through the center of the opening width of the groove or as lines passing through the opening end of the groove. In any case, the virtual straight lines Y1 and Y2 are lines extending along the groove.

  In the second embodiment, the positions where the virtual straight lines Y1, Y2 intersect the arc portions 33, 34 are positions further away from the respective boundaries P1-P4 toward the arc portions 33, 34, and these virtual straight lines Y1, Y2 The straight grooves 41 and 42 may be provided along the line. In this case, the virtual straight lines Y1 and Y2 intersect the peripheral edges of the arc portions 33 and 34. In this case, the regions S1 to S4 are provided such that the area of the region with many portions in contact with the arc portions 33 and 34 is larger than the area of the region with few portions in contact with the arc portions 33 and 34. Even in this case, the same effect as the embodiment can be obtained.

  In the second embodiment, the straight grooves 41 and 42 are not limited to being located on the virtual straight lines Y1 and Y2 intersecting with the arc portions 33 and 34, but are located on the boundary side ends located on the same straight portions 31 and 32. You may be located in the area | region where parts approach. The virtual straight lines Y1, Y2 in this case are extended along the straight grooves 41, 42 and intersect the straight portions 31, 32. Even in this case, the same effect as the embodiment can be obtained.

  In 2nd Embodiment, if the shape of the pressure release valve 30 is a shape which has an arc part, you may change into another shape. For example, it may be oval or circular. Moreover, the shape which connected one edge part of the linear parts 31 and 32 with the arc part, and connected the other edge part with the linear part may be sufficient. Moreover, you may vary the shape of the arc part connected to one edge part of the linear parts 31 and 32, and the arc part connected to the other edge part of the linear parts 31 and 32. As shown in FIG. Even in this case, the same effect as the embodiment can be obtained.

  In the second embodiment, the arc-shaped grooves 37 and 38 and the linear grooves 39 and 40 may be provided without being connected to the linear grooves 41 and 42. Even in this case, the same effect as the embodiment can be obtained.

  In the second embodiment, the cleavage grooves provided in the valve body 35 are the intersecting grooves 36 and the arc-shaped grooves 37 and 38, and the linear grooves 39 and 40 may not be provided. In this case, the intersecting groove 36 and the arc-shaped grooves 37 and 38 may be connected as in the embodiment, or may not be connected as in the above-described another example. Even in this case, the same effect as the embodiment can be obtained.

Next, a technical idea that can be grasped from the above embodiment and another example will be added below.
(A) A part of the periphery of the pressure relief valve has an arc portion, the pressure relief valve has a cleavage groove including a cleavage start point, and the cleavage groove is connected to the cross groove and the end of the cross groove and the arc portion. A plurality of arc-shaped grooves extending along the intersecting grooves, and an imaginary straight line that intersects with the peripheral edge of the pressure release valve is surrounded by the virtual straight line and the peripheral edge of the pressure release valve, and the arc portion A first region having a large number of portions in contact with each other, and a second region surrounded by a virtual straight line and the periphery of the pressure release valve and having a small number of portions in contact with the arc portion. It is larger than the area of the region.

  (B) The peripheral edge of the pressure release valve has a track shape in which parallel straight portions are connected by an arc portion.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 12 ... Electrode assembly, 20, 30 ... Pressure release valve, 21, 35 ... Valve body, 21a, 35a ... Surface, 23, 36 ... Cross groove, 26, 43 ... 1st , 27, 44 ... second cleavage part, P ... crossing part.

Claims (5)

In a power storage device having a pressure release valve for releasing the pressure in the case to the outside of the case in the case in which the electrode assembly is accommodated,
The pressure relief valve has a first cleavage part including a cleavage starting point, and a second cleavage part not including the cleavage starting point,
The power storage device, wherein the first cleavage portion has lower mechanical strength than the second cleavage portion. The pressure relief valve has a cleavage groove;
The power storage device according to claim 1, wherein the first cleavage portion and the second cleavage portion include the cleavage groove. The cleavage groove includes a cross groove,
The power storage device according to claim 2, wherein the cleavage starting point is an intersecting portion of the intersecting groove.   The power storage device according to any one of claims 1 to 3, wherein the first cleavage portion is annealed.   The power storage device according to any one of claims 1 to 4, wherein the second cleavage portion is shot peened.