JP6417820B2 - Power storage device - Google Patents

Description

  The present invention relates to a power storage device in which a short-circuit unit is disposed between a flat surface of an electrode assembly and a wall portion of a 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. Some secondary batteries include an electrode assembly in which a positive electrode and a negative electrode each having an active material layer are stacked with a separator interposed therebetween, and a case for housing the electrode assembly.

  In such a secondary battery, when a foreign object is stuck in the case from the outside, the separator between the positive electrode and the negative electrode may be broken by the foreign object, and the positive electrode and the negative electrode may be short-circuited in the case. is there. When a short circuit occurs, heat is generated in the vicinity of the short circuit part, causing problems such as an increase in pressure in the battery due to gas generation.

  Therefore, there is a case where a short-circuit electrode is provided in a case in order to suppress the generation of heat in the electrode assembly when a foreign object is stabbed (for example, see Patent Document 1). A secondary battery described in Patent Document 1 includes an electrode assembly in which a positive electrode and a negative electrode are stacked, and a short-circuit positive electrode and a short-circuit that do not have an active material layer on both sides in the stacking direction of the electrode assembly. A dummy laminate (short-circuit unit) is provided in which the negative electrode and the short-circuit separator are sandwiched therebetween.

JP 2001-351670 A

  By the way, as a secondary battery, the flat surface of the both ends of the electrode assembly in the stacking direction is rectangular, and in the case, the wall portion facing the flat surface of the electrode assembly is rectangular. In such a secondary battery, a pressure along the stacking direction of the electrode assembly may act on the wall portion from the outer surface side. In this case, the case is easy to bend into a dogleg shape along the long side of the wall portion in the stacking direction. Then, the short-circuit separator of the short-circuit unit housed in the case and the separator of the electrode assembly are also bent into a dogleg shape following the bending of the case. Here, when the bending of the electrode assembly separator occurs before the short-circuit separator of the short-circuit unit due to such bending, the electrode assembly precedes the short-circuit between the short-circuit positive electrode and the short-circuit negative electrode in the short-circuit unit. There is a possibility that the positive electrode and the negative electrode in the short circuit.

  This invention was made paying attention to the problem which exists in the said prior art, and the objective can suppress that a separator for an assembly breaks before a short circuit separator in the case of bending. The object is to provide a power storage device.

In the following, means for achieving the above object and its effects are described.
A power storage device that solves the above problems includes an electrode assembly in which an assembly electrode having a metal foil and an active material layer is stacked with an assembly separator interposed therebetween, and a case that houses the electrode assembly And a short-circuit unit disposed outside a rectangular flat surface located at both ends in the stacking direction of the electrode assembly, wherein in the case, the wall portion facing the flat surface is The short-circuit unit is configured by sandwiching a short-circuit separator between the short-circuit electrodes not having the active material layer, and the short-circuit electrode has the same shape as the metal foil , The short-circuit separator has a direction in which the elongation rate until it breaks is lower than the other direction along the surface of the short-circuit separator, and the elongation rate until the break in the short-circuit separator is low. Become The direction is along the direction in which the long side of the wall extends, and the assembly separator has a higher elongation rate until it breaks than other directions among the directions along the surface of the assembly separator. The direction in which the elongation rate until breakage in the assembly separator is high is along the direction in which the long side of the wall extends, and the wall portion of the short-circuit separator The elongation rate until breaking along the direction in which the long side extends is lower than the elongation rate until breaking along the direction in which the long side of the wall portion of the assembly separator extends.

In the above configuration, pressure along the stacking direction of the electrode assembly may act on the wall portion of the case from the outer surface side. In this case, the long side of the wall portion of the case is bent in a dogleg shape along the stacking direction. At this time, the short-circuit separator also tends to be bent in a dogleg shape along the stacking direction of the electrode assembly. However, in the short-circuit separator, the side that is about to be bent into a square shape has a low elongation rate until it breaks . For this reason, the short-circuit separator is quickly damaged when it is bent into a square shape. As a result, at the time of bending, the short-circuiting separator can be damaged before the assembly separator is damaged, and the short-circuiting electrodes can be short-circuited.

Further , when the long side of the wall portion is bent in a dogleg shape along the laminating direction, in the separator for an assembly, the side along the long side of the uneven plane is along the laminating direction of the electrode assembly, Bends in a U shape. However, in the separator for an assembly, the side that is bent into a square shape has a high elongation rate until it breaks . For this reason, the assembly separator can be flexibly stretched following the bending of the dogleg and can suppress the occurrence of breakage such as cracks in the assembly separator.

  In the above power storage device, a preferable example of the power storage device is a secondary battery.

  According to the present invention, it is possible to suppress breakage of the assembly separator prior to the short-circuit separator during bending.

The perspective view which shows the external appearance of a secondary battery. (A) is sectional drawing which shows the inside of a secondary battery, (b) is the elements on larger scale which show a short circuit unit. The disassembled perspective view which shows the component of an electrode assembly.

Hereinafter, an embodiment embodying a power storage device will be described with reference to FIGS.
As shown in FIGS. 1 and 2A, a secondary battery 10 as a power storage device includes a case 11 in which an electrode assembly 12 is accommodated. 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 a rectangular opening 13 a into which the electrode assembly 12 is inserted into the case main body 13. A positive electrode terminal 16 and a negative electrode terminal 17 are electrically connected to the electrode assembly 12. A ring-shaped insulating ring 18 for insulating from the case 11 is attached to each terminal 16, 17. Further, a part of each of the terminals 16 and 17 is exposed to the outside of the case 11 through a through hole formed in the lid body 14.

  The case body 13 includes a bottom wall 13b that faces the opening 13a, long side walls 13d and 13f that stand from the long side edge of the bottom wall 13b, and short side walls 13c and 13e that stand from the short side edge of the bottom wall 13b. And having. Both the case main body 13 and the lid body 14 are made of metal (for example, made of stainless steel or aluminum). Moreover, as for the secondary battery 10 of this embodiment, the case main body 13 is a bottomed square cylinder shape. The case body 13 has a rectangular bottom wall 13b. The long side walls 13d and 13f have a flat plate shape that is rectangular when viewed from the front. The long sides 131d and 131f of the long side walls 13d and 13f form the long sides of the opening 13a, respectively. The long sides 132d and 132f of the long side walls 13d and 13f are connected to the long side of the bottom wall 13b, respectively. The short sides 133d and 134d of one long side wall 13d and the short sides 133f and 134f of the other long side wall 13f are connected to the short side walls 13c and 13e, respectively.

In addition, since the lid body 14 has a rectangular flat plate shape, the secondary battery 10 is a square battery whose appearance is square. Moreover, the secondary battery 10 of this embodiment is a lithium ion battery.
As shown in FIG. 3, the electrode assembly 12 has a layered structure in which a plurality of electrode storage separators 25 and a plurality of negative electrodes 26 are alternately stacked. The electrode storage separator 25 has a bag shape. A positive electrode 21 is accommodated in the electrode storage separator 25 as an assembly electrode. In this embodiment, the electrode storage separator 25 is an assembly separator. The negative electrode 26 is an assembly electrode having a polarity different from that of the positive electrode 21. In the present embodiment, the positive electrode 21, the electrode storage separator 25, and the negative electrode 26 are all formed in a rectangular shape.

  The positive electrode 21 has a rectangular positive metal foil (for example, aluminum foil) 22 and a positive electrode active material layer 23 containing a positive electrode active material on both surfaces of the positive metal foil 22. A positive electrode tab 24 protrudes from the long side 21 a of the positive electrode 21.

  The negative electrode 26 has a rectangular negative metal foil (for example, copper foil) 27 and a negative electrode active material layer 28 containing a negative electrode active material on both surfaces of the negative electrode metal foil 27. A negative electrode tab 29 protrudes from the long side 26 a of the negative electrode 26.

  The electrode storage separator 25 includes a rectangular first separator member 25a and a rectangular second separator member 25b facing each other. The first separator member 25a and the second separator member 25b are both made of an insulating resin (for example, made of polyethylene). The first separator member 25a and the second separator member 25b are manufactured by cutting a long rectangular sheet-shaped separator original into a desired size. In this embodiment, since the separator raw material is manufactured by uniaxial stretching in which the separator material is stretched in one direction, the first separator member 25a and the second separator member 25b are in the machine direction at the time of manufacture, that is, in the MD direction (FIG. 3). The fiber is oriented in the direction of arrow MDA).

  In the electrode storage separator 25, the MD direction of the first separator member 25a matches the MD direction of the second separator member 25b. In the electrode storage separator 25, a direction orthogonal (crossing) to the MD direction is a TD direction (shown as an arrow TDA in FIG. 3). Of the directions along the surface of the electrode storage separator 25, the elongation in the MD direction is higher than other directions other than the MD direction. That is, the electrode storage separator 25 has an MD direction having a higher elongation rate than the TD direction.

  The MD direction of the electrode storage separator 25 is along the long sides 251a and 252a of the first separator member 25a and the long sides 251b and 252b of the second separator member 25b, and more specifically, is parallel. Further, the TD direction of the electrode storage separator 25 is along the short sides 253a and 254a of the first separator member 25a and the short sides 253b and 254b of the second separator member 25b, and more specifically, is parallel.

  The first separator member 25 a and the second separator member 25 b have the same size and are slightly larger than the positive electrode 21. In the electrode storage separator 25, the long side 251 a of the first separator member 25 a, the long side 251 b of the second separator member 25 b, and the long side 21 a of the positive electrode 21 are along. In the electrode storage separator 25, the long side 252 a of the first separator member 25 a, the long side 252 b of the second separator member 25 b, and the long side 21 b of the positive electrode 21 are along. Further, in the electrode storage separator 25, the short side 253a of the first separator member 25a, the short side 253b of the second separator member 25b, and the short side 21c of the positive electrode 21 are along. Further, in the electrode storage separator 25, the short side 254a of the first separator member 25a, the short side 254b of the second separator member 25b, and the short side 21d of the positive electrode 21 are along.

  The first separator member 25 a and the second separator member 25 b have long sides 21 a and 21 b and a protruding portion 40 a that protrudes from the short sides 21 c and 21 d constituting the outer shape of the positive electrode 21.

  The electrode storage separator 25 has a joint portion 41 formed by welding the protruding portions 40a facing each other between the first separator member 25a and the second separator member 25b. Further, the positive electrode tab 24 of the positive electrode 21 is located between the surfaces of the protruding portions 40a, which are the opposed surfaces of the first separator member 25a and the second separator member 25b, and passes between the first separator member 25a and the first separator member 25a. It protrudes from the long sides 251a and 251b of 25a and the second separator member 25b. In the electrode storage separator 25, the first separator member 25a and the second separator member 25b are bonded to each other, so that the inside of the bonding portion 41 is an electrode storage portion.

  The negative electrode 26 and the electrode storage separator 25 are laminated such that the long side 26a of the negative electrode 26, the long side 251a of the first separator member 25a, and the long side 251a of the second separator member 25b are along. . The negative electrode 26 and the electrode storage separator 25 are stacked such that the long side 26b of the negative electrode 26, the long side 252a of the first separator member 25a, and the long side 252b of the second separator member 25b are along. ing. The negative electrode 26 and the electrode storage separator 25 are laminated such that the short side 26c of the negative electrode 26, the short side 253a of the first separator member 25a, and the short side 253b of the second separator member 25b are along. The negative electrode 26 and the electrode storage separator 25 are laminated such that the short side 26d of the negative electrode 26, the short side 254a of the first separator member 25a, and the short side 254b of the second separator member 25b are along. .

  In the electrode assembly 12, the same polarities of the tabs 24 and 29 of the electrodes 21 and 26 are arranged in a row in the stacking direction L. In the electrode assembly 12, the negative electrode 26 and the electrode storage separator 25 are stacked so that different polarities do not overlap in the stacking direction L. Each positive electrode tab 24 is electrically connected to the positive electrode terminal 16, and each negative electrode tab 29 is electrically connected to the negative electrode terminal 17.

  As shown in FIGS. 2A and 2B, the short-circuit unit 30 is disposed outside the both flat surfaces 12 a of the electrode assembly 12. The short-circuit unit 30 is disposed between the flat surface 12a and the long side walls 13d and 13f of the case body 13 facing the flat surface 12a. Accordingly, the short-circuit unit 30 is interposed between the flat surface 12a and the long side walls 13d and 13f.

  The short-circuit unit 30 is configured by sandwiching a short-circuit separator 35 between a first metal member 31 and a second metal member 36. The short-circuit unit 30 is laminated in the order of the second metal member 36, the short-circuit separator 35, and the first metal member 31 from the flat surface 12 a of the electrode assembly 12 toward the long side walls 13 d and 13 f of the case body 13. Has been. That is, in the short-circuit unit 30, the second metal member 36 faces the flat surface 12 a of the electrode assembly 12. Therefore, in the present embodiment, the second metal member 36 constitutes one surface of the short-circuit unit 30.

  The first metal member 31, the short-circuit separator 35, and the second metal member 36 are all rectangular. The first metal member 31 is made of, for example, aluminum foil, and functions as a positive electrode short-circuiting electrode that does not have the positive electrode active material layer 23 on both surfaces. The second metal member 36 is made of, for example, copper foil, and functions as a negative electrode short-circuiting electrode that does not have the negative electrode active material layer 28 on both surfaces.

  As shown in FIG. 3, the first tab 34 protrudes from the long side 31 a of the first metal member 31. A second tab 39 protrudes from the long side 36 a of the second metal member 36. In addition, the 1st metal member 31 can use the thing of the same shape as the positive electrode metal foil 22 of the positive electrode 21 in the electrode assembly 12. FIG. As the second metal member 36, a member having the same shape as the negative electrode metal foil 27 of the negative electrode 26 in the electrode assembly 12 can be used.

  The short-circuit separator 35 is made of an insulating resin (for example, polyethylene). Further, the short-circuit separator 35 is manufactured by cutting a separator raw material manufactured by uniaxial stretching, like the separator members 25 a and 25 b in the electrode assembly 12. Therefore, in the short-circuit separator 35, the fibers are oriented in the machine direction at the time of manufacture, that is, in the MD direction (shown as an arrow MDU in FIG. 3).

  In the short-circuit separator 35, a direction orthogonal (crossing) to the MD direction is a TD direction (shown as an arrow TDU in FIG. 3). Of the directions along the surface of the short-circuit separator 35, the elongation in the TD direction is lower than other directions other than the TD direction. That is, the short-circuit separator 35 has a TD direction having a lower elongation than the MD direction.

  In addition, the TD direction of the short-circuit separator 35 of the present embodiment is along the long sides 35a and 35b of the short-circuit separator 35, and more specifically, is parallel. Further, the MD direction of the short-circuit separator 35 is along the short sides 35c and 35d of the short-circuit separator 35, and more specifically, is parallel.

  In the short-circuit unit 30, the long side 31 a of the first metal member 31, the long side 35 a of the short-circuit separator 35, and the long side 36 a of the second metal member 36 are along. In the short-circuit unit 30, the long side 31 b of the first metal member 31, the long side 35 b of the short-circuit separator 35, and the long side 36 b of the second metal member 36 are along. Further, in the short-circuit unit 30, the short side 31 c of the first metal member 31, the short side 35 c of the short-circuit separator 35, and the short side 36 c of the second metal member 36 are along. In addition, in the short-circuit unit 30, the short side 31 d of the first metal member 31, the short side 35 d of the short-circuit separator 35, and the short side 36 d of the second metal member 36 are along.

  In the short-circuit unit 30, the first tab 34 of the first metal member 31 is electrically connected to the positive terminal 16 together with the positive tabs 24 of the positive electrode 21. Similarly, in the short-circuit unit 30, the second tab 39 of the second metal member 36 is electrically connected to the negative electrode terminal 17 together with the negative electrode tabs 29 of the negative electrode 26.

  In the secondary battery 10, the long side 26 a of the negative electrode 26, the long side 251 a of the first separator member 25 a, and the long side 251 b of the second separator member 25 b are along the long side of the lid body 14. The long side 26b of the negative electrode 26, the long side 252a of the first separator member 25a, and the long side 252b of the second separator member 25b are along the long side of the bottom wall 13b.

  In the secondary battery 10, the long side 31 a of the first metal member 31, the long side 35 a of the short-circuit separator 35, and the long side 36 a of the second metal member 36 are along the long side of the lid body 14. Yes. Further, the long side 31 b of the first metal member 31, the long side 35 b of the short-circuit separator 35, and the long side 36 b of the second metal member 36 are along the long side of the bottom wall 13 b of the case body 13.

  In the secondary battery 10, the extending directions of the long sides 131 d, 131 f, 132 d, 132 f of the long side walls 13 d, 13 f of the case body 13 are parallel to the TD direction of the short-circuit separator 35 of the short-circuit unit 30. The extending directions of the long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f of the case body 13 are parallel to the MD direction of the first separator member 25a and the second separator member 25b of the electrode assembly 12. It has become.

Hereinafter, the operation of the secondary battery 10 of the present embodiment will be described.
In the secondary battery 10 in which the long side walls 13d and 13f of the case 11 are rectangular, when a pressure in the stacking direction L is applied from the outer surface side of the long side walls 13d and 13f, as shown by a two-dot chain line in FIG. The long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f and the long side of the lid body 14 are easily deformed so as to be bent along the stacking direction L into a dogleg shape. Then, the electrode assembly 12 also bends in the shape of a dogleg along the laminating direction L of the long side of the flat surface 12a. At this time, the long sides 35 a and 35 b of the short-circuit separator 35 also tend to be bent in a dogleg shape along the stacking direction L. However, the direction in which the long sides 35a and 35b of the short-circuit separator 35 extend is the TD direction, which is the direction in which the elongation rate is low. For this reason, the short-circuit separator 35 is damaged when pulled when it is to be bent into a dogleg shape.

  Further, the long sides 251 a, 251 b, 252 a, 252 b of the electrode storage separator 25 are bent in a dogleg shape along the stacking direction L of the electrode assembly 12. However, the extending direction of the long sides 251a, 251b, 252a, 252b of the electrode storage separator 25 is the MD direction, and the elongation rate is high. For this reason, the electrode storage separator 25 is flexibly extended following the bending of the character.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) In the short-circuit separator 35 of the short-circuit unit 30, the TD direction with a low elongation is along the direction in which the long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f in the case 11 extend. For this reason, when the long sides 131d, 131f, 132d, and 132f of the long side walls 13d and 13f of the case 11 are bent in a dogleg shape along the stacking direction L, the short-circuit separator 35 is difficult to stretch and easily breaks. . Therefore, before the electrode housing separator 25 of the electrode assembly 12 is damaged such as a crack, the short-circuit separator 35 is damaged, and the first metal member 31 and the second metal member 36 in the short-circuit unit 30 are short-circuited. Can do.

  (2) The extending direction of the long sides 251a, 251b, 252a, 252b of the electrode storage separator 25 has a high elongation rate. For this reason, the electrode storage separator 25 is flexibly extended following the bending of the character. Therefore, it is possible to prevent the electrode housing separator 25 from being damaged such as a crack before the short-circuit separator 35 when the case 11 is bent.

  (3) In the electrode storage separator 25, a joint portion 41 between the first separator member 25 a and the second separator member 25 b is formed around the storage portion of the positive electrode 21. In such an electrode storage separator 25, when the case 11 and the electrode assembly 12 are bent, the joint portion 41 is caught by the short sides 21c and 21d of the positive electrode 21, and is easily pulled greatly in the long side direction. However, by causing the MD direction in which the electrode housing separator 25 has a high elongation along the direction in which the long sides 251a, 251b, 252a, and 252b extend, it is possible to prevent the electrode housing separator 25 from being damaged such as a crack. .

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
The short-circuit separator 35 may be formed such that the TD direction is along a direction other than the direction along the long sides 35a and 35b. For example, the short-circuit separator 35 may be formed such that the TD direction is along the short sides 35c and 35d. Even in such a configuration, the extending direction of the short sides 35c and 35d only needs to be along the extending direction of the long sides 131d, 131f, 132d, and 132f of the long side walls 13d and 13f in the case 11.

  ○ The short-circuit separator 35 may have a shape other than a rectangular shape. Even in such a case, the direction in which the elongation rate of the short-circuit separator 35 is low may be arranged in a state along the direction in which the long sides of the opposed wall portions of the flat surface 12a extend.

  O The separator raw material may be manufactured by the biaxial extending | stretching which makes the separator material 35 extend | stretch the separator material to the both directions of an orthogonal direction for the short-circuit separator 35 in the said embodiment, and the short-circuit separator 35 in the said modification. Also in this form, if the elongation rate in one direction is lower than the elongation rate in the other direction among the elongation rates of the short-circuit separator in the biaxial direction orthogonal to the surface of the short-circuit separator, The direction in which the elongation rate decreases is arranged in a state along the extending direction of the long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f.

  In the above embodiment, in the secondary battery 10, the short-circuit unit 30 is interposed outside the flat surfaces 12a at both ends in the stacking direction L of the electrode assembly 12, but this is not a limitation. For example, the short-circuit unit 30 may be interposed only outside the flat surface 12 a at one end of the electrode assembly 12 in the stacking direction L.

  ○ Although the short-circuit unit 30 is configured by laminating the first metal member 31, the short-circuit separator 35, and the second metal member 36 one by one, the first metal member 31, the short-circuit separator 35, and the second metal member The number of stacked 36 may be changed as appropriate.

  The MD direction of the electrode storage separator 25 may be formed along a direction other than the direction along the long sides 251a, 251b, 252a, 252b. For example, the MD direction of the electrode storage separator 25 may be formed along the short sides 253a, 253b, 254a, 254b. Also in such a form, the MD direction in which the elongation rate of the electrode storage separator 25 is increased may be arranged in a state along the extending direction of the long side of the opposed wall portion of the flat surface 12a.

  The electrode storage separator 25 may have a shape other than a rectangular shape. For example, a square shape or the like may be used. Even in such a case, the electrode storage separator 25 only needs to be arranged in a state in which the direction in which the elongation rate is high is along the direction in which the long sides of the opposed wall portions of the flat surface 12a extend.

  The electrode storage separator 25 is a long separator that is folded in half from the middle in the longitudinal direction, and the positive electrode 21 or the negative electrode 26 is sandwiched between the portions facing each other in the folded state. It may be.

  The electrode storage separator 25 is formed by folding a single long separator from a plurality of locations along the longitudinal direction, and in the folded state, the positive electrode 21 or the negative electrode 26 between the portions facing each other. It is good also as what inserts.

The electrode stored in the electrode storage separator 25 may be changed to the negative electrode 26.
In place of the electrode storage separator 25, a sheet-like assembly separator may be adopted. In this embodiment, a sheet-like assembly separator is interposed between the positive electrode 21 and the negative electrode 26. Also in this case, the MD direction in which the elongation rate of the assembly separator is increased is made to extend along the direction in which the long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f of the case body 13 extend.

  (Circle) the separator raw material may be manufactured by the biaxial extending | stretching which the separator material in the said embodiment and the separator for assemblies in the said modification extend | stretches separator material to both directions of an orthogonal direction. Also in this embodiment, if the elongation rate in one direction is higher than the elongation rate in the other direction among the elongation rates in the biaxial directions perpendicular to the surface of the assembly separator, the elongation The direction in which the rate is increased is arranged in a state along the extending direction of the long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f.

  The first separator member 25a and the second separator member 25b in the above-described embodiment and the assembly separator in the above-described modified example are not necessarily in the direction in which the elongation rate of each separator is high, and the long sides 131d and 131f of the long side walls 13d and 13f. , 132d, and 132f may not be parallel to the extending direction. For example, the direction in which the elongation percentage of each separator is high and the long sides 131d, 131f, 132d, 132f of the long side walls 13d, 13f may intersect.

The electrodes 21 and 26 and the metal members 31 and 36 may have a shape other than a rectangular shape. For example, a square shape or the like may be used.
○ Only one side of the positive electrode 21 may have the positive electrode active material layer 23.

○ Only one side of the negative electrode 26 may have the negative electrode active material layer 28.
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.

  The case 11 of the secondary battery 10 is not limited to a metal, and a laminate film may be used as the case. The present invention is also applicable to a laminate cell in which an electrode assembly is wrapped with a laminate film. In this case, the electrode assembly has rectangular flat surfaces at both ends in the stacking direction, and in the laminate film, the wall portion facing the flat surface of the electrode assembly is rectangular. And the separator for short circuit is arrange | positioned in the state in which the direction where the elongation rate became low follows the direction where the long side of the wall part which opposes the flat surface extends in a laminate film.

  The shape of the case 11 can be changed if the wall portion facing the flat surface 12a of the electrode assembly 12 is rectangular. For example, the case 11 has a cylindrical shape having an elliptical bottom wall, and in this case, a wall portion erected from the long side of the ellipse has a rectangular shape on the flat surface of the electrode assembly 12. .

  The shape of the case 11 can be changed if the wall portion facing the flat surface 12a of the electrode assembly 12 is rectangular. For example, the case 11 has a cylindrical shape having an elliptical bottom wall. In this case, on the flat surface of the electrode assembly, a wall portion standing from the long side of the ellipse is rectangular on the bottom wall.

  As the electrode assembly 12, it is also possible to employ a wound body in which a belt-like positive electrode and a belt-like negative electrode are wound. In such a secondary battery, for example, a strip-shaped assembly separator is wound together with a positive electrode and a negative electrode to form an electrode assembly. In such a wound-type secondary battery, the long side wall of the case faces the uneven plane. In addition, a short-circuit unit in which a sheet-like short-circuit separator is sandwiched between short-circuit electrodes is interposed between a flat surface located at least one end in the stacking direction of the electrode assembly and the wall portion of the case. . Also in a secondary battery having such a wound electrode assembly, the long side of the long side of the case extends in the direction of low elongation of the short-circuit separator. Even if comprised in this way, the effect similar to the effect (1) obtained by the said embodiment can be acquired. Moreover, if the direction in which the long side of the long side wall in the case extends is along the direction in which the elongation rate of the assembly separator is high, the same effect as the effect (2) obtained in the above embodiment can be obtained.

The present invention may be embodied in a power storage device such as an electric double layer capacitor.
Next, a technical idea that can be grasped from the above embodiment and another example will be additionally described.
(A) an electrode assembly in which an assembly electrode having an active material layer is stacked with an assembly separator interposed therebetween, and a case for housing the electrode assembly, the electrode assembly comprising: A power storage device in which a short-circuit unit is disposed between a flat surface located at both ends in the stacking direction and a wall portion of the case facing the flat surface, and one surface of the short-circuit unit is opposed to the flat surface. In the case, the wall portion facing the uneven plane has a rectangular shape, and the short-circuit unit is configured by sandwiching a short-circuit separator between the short-circuit electrodes not having the active material layer, The short-circuit separator has a direction in which the elongation percentage is lower than the other directions among the directions along the surface of the short-circuit separator, and the direction in which the elongation ratio in the short-circuit separator is low, Long side of the wall Power storage device, characterized in that along the direction of extension.

  (B) The assembly separator has a direction in which the elongation rate is higher than the other direction among the directions along the surface of the assembly separator, and the elongation rate of the assembly separator is 2. The power storage device according to claim 1, wherein the heightened direction is along a direction in which a long side of the wall extends.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery as an electrical storage device, 11 ... Case, 12 ... Electrode assembly, 12a ... Flat surface, 13d, 13f ... Long side wall as a wall part, 21 ... Positive electrode as an electrode for assemblies, 23 ... Active Positive electrode active material layer as material layer, 25 ... Electrode storage separator as assembly separator, 26 ... Negative electrode as assembly electrode, 28 ... Negative electrode active material layer as active material layer, 30 ... Short-circuit unit, 31 ... 1st metal member as an electrode for short circuit, 35 ... Separator for short circuit, 36 ... 2nd metal member as an electrode for short circuit.

Claims (2)

An electrode assembly in which an assembly electrode having a metal foil and an active material layer is laminated with an assembly separator interposed therebetween;
A case for housing the electrode assembly;
A short-circuit unit disposed outside a rectangular flat surface located at both ends in the stacking direction of the electrode assembly, and a power storage device comprising:
In the case, the wall portion facing the uneven plane is rectangular.
The short-circuit unit is configured by sandwiching a short-circuit separator between short-circuit electrodes not having the active material layer,
The shorting electrode has the same shape as the metal foil ,
The short-circuit separator has a direction with a low elongation rate until it breaks than other directions along the surface of the short-circuit separator,
The direction in which the elongation rate until the break in the short-circuit separator is reduced is along the direction in which the long side of the wall extends.
The assembly separator has a direction in which the elongation rate is higher than the other direction among the directions along the surface of the assembly separator;
The direction in which the elongation rate until breakage in the assembly separator is high is along the direction in which the long side of the wall extends.
Elongation rate until break along the direction in which the long side of the wall portion of the short-circuit separator extends is greater than elongation rate until break along the direction in which the long side of the wall portion of the assembly separator extends A power storage device characterized by being low. It said power storage device, a power storage device according to claim 1 is a secondary battery.