JP2015015217A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device for making it possible to provide a gas generating member in a case while suppressing occurrence of electrode displacement caused by a gap between a case wall and electrode assembly.SOLUTION: A secondary battery 10 includes a case 11 for accommodating an electrode assembly 14 having a layered structure interposing a separator 27 between a positive electrode 21 and negative electrode 24. The case 11 includes a pressure release valve 15 which operates by pressure inside the case. Inside the case 11, foam members 35 including a foaming agent are arranged between third side faces 14c of the electrode assembly 14 and side walls 12b, 12d of a case main body 12 which are opposite to the third side faces 14c. The foam members 35 are arranged so as to be in contact with the third side faces 14c.

Description

  The present invention relates to a power storage device.

  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. The secondary battery includes an electrode assembly that is laminated with a separator interposed between a positive electrode having an active material layer and a negative electrode, and a case that houses the electrode assembly.

  In order to increase the capacity of the secondary battery, it is desirable that the size of the electrode assembly is approximately the same as the volume of the case. However, in order to insert the electrode assembly into the case when manufacturing the secondary battery, it is necessary to form the case slightly larger than the electrode assembly, and between the case wall constituting the case and the electrode assembly. A predetermined gap is generated. If there is a gap between the case wall and the electrode assembly, vibration is applied to the secondary battery and the positive electrode and the negative electrode are displaced, so that lithium is deposited on the positive electrode and the capacity of the secondary battery is reduced. There is a fear. In order to suppress electrode displacement caused by the gap between the case wall and the electrode assembly, in the secondary battery described in Patent Document 1, a support member is provided in the gap between the case wall and the electrode assembly. Yes.

JP 2010-50111 A

  By the way, when a pressure operating member that operates by pressure in the case, such as a pressure release valve or a current interrupting device (CID), is disposed in the case of the secondary battery, a gas generating member that generates gas by heat, such as a foaming agent. Is preferably provided in the case. However, when the support member is provided as described above, it is difficult to secure a space for disposing the gas generating member in the case, and there is room for improvement in this respect.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to suppress the occurrence of electrode displacement caused by the gap between the case wall and the electrode assembly. Meanwhile, an object is to provide a power storage device in which a gas generating member can be provided in a case.

  A power storage device for solving the above problems includes an electrode assembly stacked with a separator interposed between a positive electrode and a negative electrode having an active material layer, a case containing the electrode assembly, A pressure actuating member that is actuated by pressure. In the power storage device, a foaming member including a foaming agent is disposed between at least one side surface of the electrode assembly parallel to the stacking direction of the electrode assembly and a case wall constituting the case and facing the side surface. The foam member is in contact with the side surface.

  According to the above configuration, since the end face of each electrode that forms the side surface of the electrode assembly is supported by the foamed member, it is possible to suppress the occurrence of electrode displacement when vibration is applied to the power storage device. Moreover, in the said structure, the foaming member has a function as a support member which supports the side surface of an electrode assembly, and a function as a gas generation member which generate | occur | produces gas with a heat | fever. For this reason, the foaming member as a gas generating member can be arrange | positioned in a case, without securing the space for arrange | positioning a gas generating member separately in a case.

As the foaming agent, for example, one having a decomposition start temperature in the range of 80 ° C to 150 ° C can be employed.
For example, when the decomposition start temperature of the foaming agent is less than 80 ° C., the pressure actuating member may operate due to the thermal decomposition of the foaming agent being started in a situation where there is no risk of performance degradation of the power storage device. Further, in the power storage device, there is a risk that the performance of the power storage device is greatly deteriorated at around 200 ° C. In order to avoid the performance degradation as much as possible, the foaming agent is thermally decomposed before the temperature in the case reaches 200 ° C. It is desirable to operate. According to the above configuration, the foaming agent is thermally decomposed when the temperature in the case is higher than the temperature at which there is no risk of performance degradation of the power storage device and lower than the temperature at which the performance of the power storage device may be greatly reduced. And the pressure actuating member can be actuated appropriately.

The foam member may be in contact with the case wall.
According to the said structure, since a foaming member will be in the state which contact | connected both the side surface and case wall of the electrode assembly, generation | occurrence | production of electrode deviation can be suppressed more.

The foam member may be in contact from one end to the other end of the side surface in the stacking direction of the electrode assembly.
According to the said structure, since the end surface of all the electrodes laminated | stacked as an electrode assembly will be supported by the foaming member, generation | occurrence | production of electrode deviation can be suppressed more.

  For example, in a power storage device, one of the side surfaces parallel to the stacking direction of the electrode assembly has a positive electrode tab and a negative electrode tab protruding from the side surface, and the foam member has a positive electrode tab and a negative electrode tab. You may contact the side surface on the opposite side to the said side surface.

  Since each electrode tab of the electrode assembly is connected to the case, electrode misalignment hardly occurs in the vicinity of the side surface having the tab in the electrode assembly, but in the vicinity of the side surface opposite to the side surface having the tab in the electrode assembly. Then, since such a connection is not made, electrode misalignment is likely to occur. According to the said structure, generation | occurrence | production of the electrode shift | offset | difference in the vicinity of the side surface in which a shift | offset | difference tends to arise in an electrode assembly can be suppressed.

  An example of the power storage device is a secondary battery.

  According to the present invention, it is possible to provide the gas generating member in the case while suppressing the occurrence of electrode displacement due to the gap between the case wall and the electrode assembly.

The disassembled perspective view which shows a secondary battery. The perspective view which shows the external appearance of a secondary battery. The exploded perspective view of an electrode assembly. Sectional drawing which shows the cross-section of a secondary battery. Sectional drawing which expanded a part of secondary battery.

Hereinafter, an embodiment of a power storage device will be described with reference to FIGS.
As shown in FIG. 1, a secondary battery 10 as a power storage device includes a rectangular parallelepiped electrode assembly 14 and a case 11 in which an electrolytic solution is accommodated. The case 11 includes a bottomed cylindrical case main body 12 and a flat lid 13 that closes an opening 12 a into which the electrode assembly 14 is inserted into the case main body 12.

  As shown in FIG. 2, the case main body 12 includes a bottom wall 12f and four side walls 12b, 12c, 12d, and 12e provided upright on the bottom wall 12f. Of the four side walls 12b, 12c, 12d, and 12e, the side wall 12b and the side wall 12d are located facing each other, and the side wall 12c and the side wall 12e are located facing each other. In addition, the four side walls 12 b, 12 c, 12 d, 12 e of the case body 12, the bottom wall 12 f, and the lid body 13 constitute a case wall of the case 11. The opening 12a of the case body 12 and the lid 13 are joined by laser welding or the like. The case body 12 and the lid body 13 are both made of metal (for example, made of stainless steel or aluminum). The secondary battery 10 of this embodiment is a prismatic battery whose appearance is a rectangular shape because the case body 12 has a bottomed rectangular tube shape and the lid body 13 has a rectangular flat plate shape. Moreover, the secondary battery 10 of this embodiment is a lithium ion battery.

  As shown in FIGS. 1 and 2, the case 11 is cleaved when the pressure in the case 11 reaches an opening pressure that is a predetermined pressure so that the pressure in the case 11 does not increase excessively. 11 is provided with a pressure release valve 15 as a pressure actuating member for communicating inside and outside. In this embodiment, the pressure release valve 15 is located on the lid 13 of the case 11. The opening pressure of the pressure release valve 15 is set to a pressure at which the case 11 itself or the joint between the case body 12 and the lid 13 can be broken before a crack or breakage can occur. The pressure release valve 15 has a thin plate-like valve body 15 a that is thinner than the plate thickness of the lid body 13. The valve body 15 a is located at the bottom of a recess 13 c that is recessed on the upper surface of the lid body 13, and is molded integrally with the lid body 13. The pressure release valve 15 has a circular periphery. The valve body 15 a is connected to the periphery of the pressure release valve 15 and has a circular shape like the pressure release valve 15.

  As shown in FIG. 3, the electrode assembly 14 includes a positive electrode 21, a negative electrode 24, and a separator 27 that insulates the positive electrode 21 and the negative electrode 24. The positive electrode 21 has a positive electrode active material layer 23 on both surfaces of a positive metal foil 22 (for example, an aluminum foil). The first end face 21a of the positive electrode 21 has a positive electrode tab 31 which is made of the positive electrode metal foil 22 and has a shape protruding from the first end face 21a. The positive electrode 21 has a rectangular shape (rectangular shape) in a front view in which an end surface facing the first end surface 21a is a second end surface 21b, and a pair of end surfaces connecting the first end surface 21a and the second end surface 21b are third end surfaces 21c. It is. The positive electrode 21 has positive electrode chamfered portions 21g at the four corners.

  The negative electrode 24 has a negative electrode active material layer 26 on both surfaces of a negative electrode metal foil 25 (for example, a copper foil). Further, the first end face 24a of the negative electrode 24 has a negative electrode tab 32 made of the negative electrode metal foil 25 and protruding from the first end face 24a. The negative electrode 24 has a rectangular shape (rectangular shape) as viewed from the front, with the end face facing the first end face 24a as the second end face 24b and the pair of end faces connecting the first end face 24a and the second end face 24b as the third end face 24c. It is. The negative electrode 24 has negative electrode chamfered portions 24g at the four corners.

  The separator 27 also has a rectangular shape (rectangular shape) when viewed from the front, with the end surface facing the first end surface 27a as the second end surface 27b and the pair of end surfaces connecting the first end surface 27a and the second end surface 27b as the third end surface 27c. It is. The separator 27 has separator chamfered portions 27g at the four corners.

  In the present embodiment, the positive electrode 21, the negative electrode 24, and the separator 27 are formed in the same size. That is, the length in the longitudinal direction and the short direction of the positive electrode 21, the length in the longitudinal direction and the short direction of the negative electrode 24, and the length in the long direction and the short direction of the separator 27 are the same length. Yes.

  As shown in FIG. 1, the electrode assembly 14 has a stacked structure in which a plurality of positive electrodes 21 and a plurality of negative electrodes 24 are alternately stacked, and a separator 27 is interposed between the electrodes 21 and 24. . The electrode assembly 14 includes side surfaces 14a, 14b, and 14c parallel to the stacking direction X of the electrode assembly 14 by the end surfaces 21a to 21c of the positive electrode 21, the end surfaces 24a to 24c of the negative electrode 24, and the end surfaces 27a to 27c of the separator 27. have. The first side surface 14a, which is one of the side surfaces 14a, 14b, and 14c, includes a first end surface 21a provided with the positive electrode tab 31 in the positive electrode 21 and a first end surface 24a provided with the negative electrode tab 32 in the negative electrode 24. And a first end face 27 a of the separator 27. In other words, the first side surface 14a has a positive electrode tab 31 and a negative electrode tab 32 that protrude from the first side surface 14a. The surface opposite to the first side surface 14a is defined as a second side surface 14b, and the two opposing surfaces connecting the first side surface 14a and the second side surface 14b are defined as a third side surface 14c. The second side surface 14 b includes a second end surface 21 b of the positive electrode 21, a second end surface 24 b of the negative electrode 24, and a second end surface 27 b of the separator 27. The third side surface 14 c includes a third end surface 21 c of the positive electrode 21, a third end surface 24 c of the negative electrode 24, and a third end surface 27 c of the separator 27. In a state where the electrode assembly 14 is housed in the case 11, the first side surface 14 a of the electrode assembly 14 faces the lid 13, and the second side surface 14 b of the electrode assembly 14 is the bottom of the case body 12. The two third side surfaces 14c of the electrode assembly 14 are opposed to the side walls 12b and 12d of the case main body 12, respectively.

  In addition, the electrode assembly 14 having a laminated structure is provided with a positive electrode tab group 31a in which the positive electrode tabs 31 are stacked in a row along the stacking direction X of the electrode assembly 14, and the negative electrode tab 32 includes A negative electrode tab group 32 a is provided that is stacked in a row along the stacking direction X of the electrode assembly 14. In the electrode assembly 14, the positive electrode tab group 31a is electrically connected to the positive electrode terminal 14g, and the negative electrode tab group 32a is electrically connected to the negative electrode terminal 14h. The positive electrode terminal 14 g and the negative electrode terminal 14 h are partly exposed outside the case 11 from the lid 13. Further, a ring-shaped insulating ring 13b for insulating from the case 11 is attached to the positive terminal 14g and the negative terminal 14h, respectively.

  As shown in FIG. 4, the four corners formed by the side walls 12b, 12c, 12d, 12e and the bottom wall 12f on the inner surface of the case body 12 are rounded portions R. That is, inside the case main body 12, the inner surfaces of the side walls 12b, 12c, 12d, and 12e of the case main body 12 and the inner surface of the bottom wall 12f are connected by the rounded corners R at the four corners. Further, in the case main body 12, the inner surfaces of adjacent side walls 12 b, 12 c, 12 d, and 12 e among the side walls 12 b, 12 c, 12 d, and 12 e of the case main body 12 are connected by the rounded portions R at the four corners.

  The electrode assembly 14 is disposed inside the case body 12 of the case 11 in a state of being wrapped with an insulating sheet 16. That is, the insulating sheet 16 is disposed between the electrode assembly 14 and the side walls 12b, 12c, 12d, 12e and the bottom wall 12f of the case body 12. A gap J <b> 1 is formed between the portion of the insulating sheet 16 that contacts the second side surface 14 b of the electrode assembly 14 and the bottom wall 12 f of the case body 12. Further, a gap K <b> 1 is formed between a portion of the insulating sheet 16 that contacts the third side surface 14 c of the electrode assembly 14 and the side walls 12 b and 12 d of the case body 12.

  Between the side walls 12 b and 12 d and the bottom wall 12 f of the case body 12 and the insulating sheet 16, two foam members 35 including a foaming agent are disposed. That is, between the third side surface 14c of the electrode assembly 14 and the side walls 12b and 12d of the case body 12 as a case wall facing the third side surface 14c, the second side surface 14b of the electrode assembly 14, and the second side A foam member 35 is disposed between the bottom wall 12f of the case body 12 as a case wall facing the side surface 14b. The foaming agent contained in the foaming member 35 is, for example, an organic foaming agent, and is, for example, azobisisobutyronitrile. Azobisisobutyronitrile has the property of starting thermal decomposition at around 100 ° C., and generates gas such as nitrogen upon thermal decomposition.

  As shown in FIGS. 1 and 5, the foam member 35 includes a rectangular plate-shaped first member 36 and a rectangular plate-shaped second member 37 erected from a side extending in the longitudinal direction of the first member 36. doing. When the surface on the insulating sheet 16 side in the foam member 35 is an inner surface, the inner surface of the first member 36 and the inner surface of the second member 37 are connected by a rounded portion R1. In the stacking direction X of the electrode assembly 14, the first member 36 and the second member 37 of the foam member 35 have a width Y <b> 2 that is the same size as the width Y <b> 1 of the side surfaces 14 a to 14 c of the electrode assembly 14. The thickness J2 of the first member 36 of the foam member 35 has the same size as the gap J1 between the insulating sheet 16 and the bottom wall 12f of the case body 12. In addition, the thickness K2 of the second member 37 of the foam member 35 has the same size as the gap K1 between the insulating sheet 16 and the side walls 12b and 12d of the case body 12. The length of the first member 36 of the foam member 35 in the short direction (the length in the horizontal direction in FIG. 5) is shorter than the length of the electrode assembly 14 in the longitudinal direction. The length of the second member 37 of the foam member 35 in the short direction (the length in the vertical direction in FIG. 5) is shorter than the length of the electrode assembly 14 in the short direction.

  In each foam member 35 disposed inside the case 11, the first member 36 faces the bottom wall 12f of the case body 12 and the second side surface 14b of the electrode assembly 14, and the second member 37 is the case. It faces the side walls 12 b and 12 d of the main body 12 and the two third side surfaces 14 c of the electrode assembly 14. Further, the first member 36 of the foam member 35 is in contact with the second side surface 14 b of the electrode assembly 14 through the insulating sheet 16 and is in contact with the bottom wall 12 f of the case body 12. The first member 36 of the foam member 35 is in contact with one end of the second side surface 14 b of the electrode assembly 14 from the other end in the stacking direction X of the electrode assembly 14. That is, the first member 36 of the foam member 35 is in contact with the entire width of the second side surface 14 b of the electrode assembly 14 in the stacking direction X of the electrode assembly 14. Further, in the foam member 35, the second member 37 is in contact with the two third side surfaces 14 c of the electrode assembly 14 through the insulating sheet 16, and is in contact with the side walls 12 b and 12 d of the case body 12. The second member 37 of the foam member 35 is in contact with one end of the third side surface 14 c of the electrode assembly 14 from the other end in the stacking direction X of the electrode assembly 14. That is, the second member 37 of the foam member 35 is in contact with the entire width of the third side surface 14 c of the electrode assembly 14 in the stacking direction X of the electrode assembly 14. The rounded portion R1 of the foam member 35 faces the positive electrode chamfered portion 21g, the negative electrode chamfered portion 24g, and the separator chamfered portion 27g through the insulating sheet 16. The foam member 35 is in contact with the rounded portion R of the case body 12 at the corner between the first member 36 and the second member 37, the surface opposite to the side where the rounded portion R1 is formed. . By disposing the foam member 35 in this way, in the electrode assembly 14, the two corners formed by the second side surface 14b and the third side surface 14c are the entire width Y1 in the stacking direction X of the electrode assembly 14. And covered with a foam member 35.

Next, the operation of the secondary battery 10 will be described.
When the secondary battery 10 is mounted on a vehicle and used, the vibration of the vehicle is applied to the secondary battery 10. If the foam member 35 is not disposed inside the case 11, the gap K1 between the electrode assembly 14 and the side walls 12b, 12c, 12d, and 12e of the case body 12 remains. In such a case, battery performance may be deteriorated due to the displacement of the positive electrode 21, the negative electrode 24, and the separator 27 due to the vibration of the vehicle.

  In the secondary battery 10 of the present embodiment, the foam member 35 is disposed inside the case 11, whereby the side surfaces 14 b and 14 c of the electrode assembly 14, that is, the end surfaces 24 b and 24 c of the positive electrode 21, and the negative electrode 24. The end surfaces 24 b and 24 c and the end surfaces 27 b and 27 c of the separator 27 are supported by the foam member 35.

  Further, when the temperature inside the case 11 becomes partially high, the inside of the case 11 may not become a high pressure up to the opening pressure of the pressure release valve 15. In the secondary battery 10 of the present embodiment, when the inside of the case 11 reaches a high temperature around 100 ° C., the foaming agent contained in the foam member 35 is thermally decomposed to generate a gas such as nitrogen. Even in a situation where the gas is generated in this manner, the pressure inside the case 11 may not reach the opening pressure of the pressure release valve 15 even though the inside of the case 11 is at a high temperature as described above. Since the inside of 11 becomes a high pressure, the operation of the pressure release valve 15 can be promoted.

According to the above embodiment, the following effects can be obtained.
(1) Since the end surfaces 24b and 24c of the positive electrode 21 forming the side surfaces 14b and 14c of the electrode assembly 14, the end surfaces 24b and 24c of the negative electrode 24, and the end surfaces 27b and 27c of the separator 27 are supported by the foam member 35. The occurrence of electrode displacement when vibration is applied to the secondary battery 10 can be suppressed. The foam member 35 has a function as a support member that supports the side surfaces 14b and 14c of the electrode assembly 14 and a function as a gas generation member that generates gas by heat. Therefore, the foam member 35 as the gas generating member can be disposed in the case 11 without securing a space for separately disposing the gas generating member in the case 11.

  (2) For example, when the decomposition start temperature of the foaming agent is less than 80 ° C., the pressure release valve 15 may operate due to the thermal decomposition of the foaming agent being started in a situation where there is no risk of performance degradation of the secondary battery 10. There is. Further, in the secondary battery 10, there is a possibility that the performance of the secondary battery 10 is greatly deteriorated at around 200 ° C. In order to avoid the performance degradation as much as possible, the foaming agent is thermally decomposed before the temperature in the case 11 reaches 200 ° C. It is desirable to operate the pressure release valve 15. According to the embodiment, when the temperature in the case 11 is higher than the temperature at which the performance of the secondary battery 10 is not likely to deteriorate, and is lower than the temperature at which the performance of the secondary battery 10 may be greatly reduced. The foaming agent can be pyrolyzed and the pressure relief valve 15 can be actuated appropriately.

  (3) Since the foam member 35 is in contact with both the side surfaces 14b and 14c of the electrode assembly 14 and the side walls 12b and 12d and the bottom wall 12f of the case body 12, the occurrence of electrode displacement can be further suppressed. it can.

  (4) All the positive electrodes 21, negative electrodes 24, and end surfaces 21b, 21c, 24b, 24c, 27b, 27c of the separator 27 stacked as the electrode assembly 14 are supported by the foam member 35, so that the electrode displacement occurs. Can be further suppressed.

  (5) Since the tabs 31 and 32 of the electrodes 21 and 24 of the electrode assembly 14 are connected to the lid 13 of the case 11, the electrodes in the vicinity of the first side surface 14 a having the tabs 31 and 32 in the electrode assembly 14 are provided. Deviation is unlikely to occur. On the other hand, in the vicinity of the second side surface 14b opposite to the first side surface 14a in the electrode assembly 14, since such a connection is not made, electrode displacement is likely to occur. According to the foam member 35 of the above-described embodiment, it is possible to suppress the occurrence of electrode displacement in the vicinity of the second side surface 14b in which the electrode assembly 14 is likely to be displaced.

It should be noted that the above-described embodiment can be implemented with the following modifications.
The formation of the positive electrode chamfered portion 21g of the positive electrode 21, the negative electrode chamfered portion 24g of the negative electrode 24, and the separator chamfered portion 27g of the separator 27 may be omitted. Moreover, in this form, it is also possible to omit the formation of the rounded portion R1 in the foam member 35 and connect the first member 36 and the second member 37 by a corner portion.

  ○ One foam member 35 may be disposed in the case 11. In this embodiment, for example, the first member 36 of the foam member 35 is formed to a size that covers the entire second side surface 14 b of the electrode assembly 14, and the second members 37 are provided on both sides of the first member 36. To do. According to the foam member 35, one foam member 35 can be disposed so as to contact the entire second side surface 14b of the electrode assembly 14 and a part of the third side surface 14c. Moreover, it is good also considering the foam member 35 arrange | positioned in the case 11 as three or more.

  The foam member 35 may be disposed at positions where the foam members 35 are in contact with the surfaces of both ends of the electrode assembly 14 in the stacking direction X in addition to the positions where the foam members 35 are in contact with the side surfaces 14b, 14c of the electrode assembly 14. In addition, the foam member 35 is disposed at a position where the electrode assembly 14 is in contact with the side surfaces 14b, 14c, and a support member that does not include a foaming agent is disposed at a position where the electrode assembly 14 is in contact with both surfaces in the stacking direction X. May be. In this embodiment, the foam member 35 and the support member that are disposed at positions that come into contact with both end surfaces of the electrode assembly 14 in the stacking direction X may be in contact with the side walls 12c and 12e of the case body 12. You may face without touching.

  The foam member 35 may be disposed so as to cover two corners formed by the first side surface 14a and the third side surface 14c in the electrode assembly 14. In this embodiment, the first member 36 of the foam member 35 contacts the first side surface 14 a of the electrode assembly 14 and the lid body 13 of the case 11. That is, the thickness J <b> 2 of the first member 36 of the foam member 35 has the same size as the gap between the first side surface 14 a of the electrode assembly 14 and the lid 13 of the case 11. Further, the second member 37 of the foam member 35 contacts the third side surface 14 c of the electrode assembly 14 and the side walls 12 b and 12 d of the case body 12. The foam member 35 includes two corners formed by the second side surface 14b and the third side surface 14c and two corners formed by the first side surface 14a and the third side surface 14c in the electrode assembly 14. You may arrange | position so that.

  The size of the first member 36 and the second member 37 of the foam member 35 can be freely set. For example, the length of the foam member 35 is set so as to be able to come into contact with the entire length of the electrode assembly 14 (the horizontal direction in FIG. 4) and the length in the short direction (the vertical direction in FIG. 4). May be. Further, in the stacking direction X of the electrode assembly 14, the width Y2 of the foam member 35 may be set so as to be able to contact a part of the width Y1 of the side surfaces 14a to 14c of the electrode assembly 14.

  ○ If the foam member 35 is in a range where the electrode assembly 14 and the side walls 12b and 12d and the bottom wall 12f of the case body 12 and the lid body 13 are preferably in contact with each other, the thickness J2 of the first member 36 of the foam member 35 May be formed larger than the gap J1 between the insulating sheet 16 and the bottom wall 12f of the case body 12 and the gap between the first side surface 14a of the electrode assembly 14 and the lid 13 of the case 11. . Similarly, the thickness K2 of the second member 37 of the foam member 35 may be formed larger than the gap K1 between the insulating sheet 16 and the side walls 12b and 12d of the case body 12.

  ○ The thickness J2 of the first member 36 of the foam member 35 is set such that the gap J1 between the insulating sheet 16 and the bottom wall 12f of the case main body 12, the first side surface 14a of the electrode assembly 14, and the lid 13 of the case 11 You may form smaller than the clearance gap between. In this embodiment, the foam member 35 is attached to the second side surface 14b and the first side surface 14a of the electrode assembly 14 so as to contact the second side surface 14b and the first side surface 14a of the electrode assembly 14. Arranged. The foam member 35 is arranged so as to face the bottom wall 12f of the case body 12 and the lid 13 of the case 11 without contacting. Further, the thickness K2 of the second member 37 of the foam member 35 may be formed smaller than the gap K1 between the insulating sheet 16 and the side walls 12b, 12d of the case body 12. In this embodiment, the foam member 35 is attached to the third side surface 14c of the electrode assembly 14 so as to be in contact with the third side surface 14c of the electrode assembly 14. And the foaming member 35 is arrange | positioned so that it may not contact with the side walls 12b and 12d of the case main body 12, and faces.

(Circle) the foaming member 35 is good also as an aspect which contacts the side surfaces 14b and 14c of the electrode assembly 14 directly, without passing through the insulating sheet 16. FIG.
The first member 36 and the second member 37 of the foam member 35 may be separate members each having a plate shape.

  The foam member 35 is not limited to the shape having the first member 36 and the second member 37, for example, the entire foam member 35 is composed of the plate-like first member 36. In other words, the shape of the foam member 35 can be freely set as long as the shape can be arranged in a state of being in contact with at least the surfaces facing each other among the side surfaces 14a to 14c, such as the third side surface 14c of the electrode assembly 14. . In addition, the foam member 35 in this embodiment is disposed at a position in contact with the surfaces facing each other among the side surfaces 14a to 14c of the electrode assembly 14, and can be freely disposed at other positions.

  In the above modification, the foam member 35 is disposed so as to contact at least one of the side surfaces 14a to 14c of the electrode assembly 14, and the side wall 12b of the case main body 12 as a case wall facing the side surface. 12d, the bottom wall 12f, and the lid 13 may be disposed.

  ○ The foaming agent contained in the foaming member 35 is an organic foaming agent other than azobisisobutyronitrile, such as N, N′-dinitroso-N, N′-dimethylphthalamide and p-toluenesulfonyl hydrazide. May be. Further, an inorganic foaming agent such as an azide compound may be used. It should be noted that a foaming agent having a decomposition start temperature in the range of 80 ° C. to 150 ° C. is desirable in that the performance deterioration of the secondary battery 10 is appropriately detected by the operation of the pressure release valve 15.

  The positive electrode 21, the negative electrode 24, and the separator 27 may be formed with different sizes. For example, the length in the longitudinal direction and the short direction of the positive electrode 21 is set to be shorter than the length in the longitudinal direction and the short direction of the negative electrode 24 and the separator 27, and the longitudinal direction of the negative electrode 24 and the separator 27. The lengths in the short direction may be the same. When the positive electrode 21, the negative electrode 24, and the separator 27 are formed in such a size, the end surfaces 24 a to 24 c of the negative electrode 24 and the end surfaces 27 a to 27 c of the separator 27 are parallel to the stacking direction X of the electrode assembly 14. Side surfaces 14a, 14b, and 14c are formed. Even in such a form, if the foam member 35 is disposed in contact with the side surfaces 14a to 14c of the electrode assembly 14, the same effect as that obtained in the above embodiment can be obtained.

The pressure release valve 15 may be disposed on the side walls 12b, 12c, 12d, 12e and the bottom wall 12f of the case body 12.
The secondary battery 10 may be provided with a current interrupt device (CID) that interrupts current when the pressure in the case 11 exceeds a threshold value, instead of the pressure release valve 15. Moreover, you may make it provide both the pressure release valve 15 and CID.

○ The shape of the case 11 may be changed. For example, the case 11 may be cylindrical.
The electrode assembly 14 is not limited to the laminated type, but 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.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 12 ... Case main body, 12b, 12c, 12d, 12e ... Side wall, 12f ... Bottom wall, 13 ... Lid body, 14 ... Electrode assembly, 14a ... First side surface, 14b ... First 2 side surfaces, 14c ... 3rd side surface, 15 ... pressure release valve, 21 ... positive electrode, 21a, 24a, 27a ... 1st end surface, 21b, 24b, 27b ... 2nd end surface, 21c, 24c, 27c ... 3rd end surface, DESCRIPTION OF SYMBOLS 23 ... Positive electrode active material layer, 24 ... Negative electrode, 26 ... Negative electrode active material layer, 27 ... Separator, 31 ... Positive electrode tab, 32 ... Negative electrode tab, 35 ... Foaming member.

Claims (6)

An electrode assembly laminated with a separator interposed between a positive electrode and a negative electrode having an active material layer, a case that houses the electrode assembly, and a pressure operating member that operates according to the pressure in the case A power storage device comprising:
A foaming member containing a foaming agent is disposed between at least one side surface of the electrode assembly parallel to the stacking direction of the electrode assembly and a case wall constituting the case and facing the side surface,
The power storage device, wherein the foam member is in contact with the side surface.   The power storage device according to claim 1, wherein the foaming agent has a decomposition start temperature in a range of 80 ° C. to 150 ° C. 2.   The power storage device according to claim 1, wherein the foam member is in contact with the case wall.   The power storage device according to any one of claims 1 to 3, wherein the foam member is in contact from one end to the other end of the side surface in the stacking direction of the electrode assembly. One of the side surfaces parallel to the stacking direction of the electrode assembly has a positive electrode tab and a negative electrode tab protruding from the side surface,
The power storage device according to any one of claims 1 to 4, wherein the foamed member is in contact with a side surface opposite to the side surface having the positive electrode tab and the negative electrode tab.   The power storage device according to any one of claims 1 to 5, wherein the power storage device is a secondary battery.