JP2014017159A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device in which a first separator and a second separator can be prevented from being peeled.SOLUTION: In an electrode assembly 14, a first separator 24 covers one side of a positive electrode sheet 21 and has a first extension 51 larger than the positive electrode sheet 21, and partially extending from the side face 21e thereof, and a second separator 25 covers the other side of the positive electrode sheet 21 and has a second extension 52 larger than the positive electrode sheet 21, and partially extending in the same direction as the first extension 51. A separator 23 has a folded portion 26 formed by folding the first extension 51 toward the positive electrode sheet 21 so as to be laminated each other, and has first and second welded portions welded to the folded portion 26 in the lamination direction.

Description

  In the present invention, a first electrode having an active material layer formed on at least one surface, a first separator and a second separator sandwiching the first electrode, and a second electrode having a polarity different from that of the first electrode are laminated. The present invention relates to a power storage device including an electrode assembly.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery as a power storage device that stores power supplied to the traveling motor. A secondary battery has, for example, a positive electrode sheet and a negative electrode sheet having active material layers formed on both sides, and a separator is interposed between the positive electrode sheet and the negative electrode sheet (see, for example, Patent Document 1).

  As shown in FIG. 9A, in Patent Document 1, the bag-shaped separator 80 that accommodates the electrode plate 90 is folded in half from the folding portion 87 to form two separator members 83 and 84. Further, the side edges of the separator members 83 and 84 are joined to each other on both sides of the bent portion 87 to form a joined portion 85, thereby forming a bag shape. As shown in FIG. 9B, upright portions 83a and 84a formed by bending the pair of side edges of the two separator members 83 and 84 in a direction perpendicular to the peripheral surfaces of the separator members 83 and 84, respectively. Is formed. And the joining part 85 positions a pair of standing part 83a of the other separator member 83 inside the pair of standing part 84a of one separator member 84, and joins two corresponding standing parts 83a and 84a. Is formed.

Japanese Patent Laid-Open No. 10-326608

By the way, in order to prevent the positive electrode plate 90 and the negative electrode plate 90 from directly facing each other, it is important to prevent the pair of separator members 83 and 84 from peeling off.
An object of the present invention is to provide a power storage device that can prevent the first separator and the second separator from being peeled off.

  In order to solve the above problem, the invention according to claim 1 is a first electrode having an active material layer formed on at least one surface, a first separator and a second separator sandwiching the first electrode, and the In the power storage device including an electrode assembly in which a second electrode having a polarity different from that of the first electrode is stacked, the first electrode has a side surface continuous with a surface on which the active material layer is formed, The first separator covers a first surface of the first electrode and has a first extension portion that is larger than the first electrode and partially extends from at least a part of the side surface of the first electrode. The second separator has a second extending portion that covers the other surface of the first electrode and that is larger than the first electrode and partially extends in the same direction as the first extending portion. Any one of the first extension part and the second extension part is the other The first extending portion and the second extending portion are stacked so that the first extending portion and the second extending portion are stacked, and the electrode assembly is welded to at least a part of the folded portion. The gist is to have a welded part.

  According to this, the welded portion is formed between the first extension portion and the second extension portion facing each other without being folded, and one of the extension portions is connected to the other side. A welded portion is also formed between the first extending portion and the second extending portion facing each other by folding back. For this reason, compared with the case where upright parts facing each other as in the background art are joined together, the number of places where the joined parts (welded parts) are formed increases, and as a result, the first extended part and the second extended part are welded. The area can be increased, and the first separator and the second separator can be prevented from peeling off. In addition, since the welded area is increased by folding back the extending portion, the folded portion is not enlarged in the extending direction from the first electrode.

  The first extension part and the second extension part have a resin layer and a ceramic layer coated with ceramics on one surface of the resin layer, and the outermost layer in the stacking direction in the folded part. The resin layer may be exposed on the inner surface of the extended portion that is positioned and folded back toward the first electrode.

According to this, since the resin layer is always exposed at the position where the first extension portion and the second extension portion face each other, that is, the position that becomes the welding portion, the welding between the extension portions can be performed more reliably. Can do.
In addition, the first separator and the second separator may be formed by bending a single separator.

According to this, a 1st separator and a 2nd separator can be manufactured easily.
One of the first extension part and the second extension part may be formed longer than the other, and the folded part may be formed by folding one of the extension parts.

  According to this, since only one extending portion is folded, the extending portion can be easily folded. In addition, since the extension part of one folded part is weak in the force to return to the shape before it is folded back, the extension part is maintained in a joined state to prevent the folded part from being separated into each extension part. can do.

  The folded portion may be formed by folding both the first extending portion and the second extending portion. According to this, the welding part is formed in three places in the lamination direction of the folding | returning part, and also a welding area can be increased.

  The first electrode has a tab protruding from a part of the first end, and the separator is formed with a bent portion at the bent position, and the tab is inserted into the bent portion. The folded portion may be formed by the extended portion on the opposite side of the bent portion, and the weld portion may be formed.

  According to this, the first electrode is inserted between the first separator and the second separator from the side opposite to the bent portion, and the tab of the first electrode is inserted into the notch of the separator, and then folded back to the side opposite to the bent portion. Part is formed. Therefore, even if it is set as the form inserted in the notch | incision, the 1st electrode is pinched | interposed between the bending part and the folding | turning part in the surface direction of the 1st electrode. Therefore, even if the first electrode tries to move in the surface direction toward the bent portion or the turned-up portion, the first electrode can contact the bent portion or the turned-up portion, and the movement can be restricted. Then, as a configuration for restricting the movement of the first electrode, the folded portion may be formed only on the side opposite to the folded portion. For example, compared with the case where the folded portion is formed on all remaining side portions other than the folded portion. And the structure which controls the movement of a 1st electrode can be made easily.

The folded portion may be formed in a region where the extending portion extends.
According to this, since the folded portion is not disposed on the surface of the first electrode, even when the folded portion is formed, the thickness in the stacking direction in the state where the first electrode is sandwiched between the first separator and the second separator is thick. Can be prevented.

The first electrode may be a positive electrode and the second electrode may be a negative electrode.
According to this, since it can prevent that a 1st separator and a 2nd separator peel, it can prevent that a 1st electrode opposes a 2nd electrode with a separator.

  The power storage device may be a secondary battery.

  According to this invention, it can prevent that a 1st separator and a 2nd separator peel.

The perspective view which shows the secondary battery of embodiment. The disassembled perspective view which shows an electrode assembly. The front view which shows the arrangement | positioning aspect of a separator and a positive electrode sheet. Sectional drawing which shows a sheet | seat assembly. Sectional drawing which shows another example of a folding | turning part. Sectional drawing which shows another example of a folding | turning part. Sectional drawing which shows another example of a folding | turning part. Sectional drawing which shows another example of a folding | turning part. (A) And (b) is a figure which shows background art.

  Hereinafter, an embodiment in which the present invention is embodied in a secondary battery mounted on a vehicle (for example, an industrial vehicle or a passenger vehicle) will be described with reference to FIGS. The secondary battery is used to drive a travel motor.

  As shown in FIG. 1, a secondary battery 10 as a power storage device includes a metal case 11 that forms an outer shell thereof. The case 11 includes a rectangular box-shaped container 12 and a rectangular flat lid 13 that closes the opening of the container 12. For this reason, the secondary battery 10 has a rectangular outer shape. The secondary battery 10 is a lithium ion secondary battery.

  The case 11 contains an electrode assembly 14 and an electrolytic solution (not shown) as an electrolyte. As shown in FIG. 2, in the electrode assembly 14, a positive electrode sheet 21 as a plurality of first electrodes and a negative electrode sheet 22 as a plurality of second electrodes can pass ions (lithium ions) related to electrical conduction. The separators 23 are alternately stacked via a separator 23 formed of a porous film. Specifically, the electrode assembly 14 is configured by alternately laminating a plurality of sheet assemblies 20 composed of positive electrode sheets 21 and separators 23 and a plurality of negative electrode sheets 22.

  The positive electrode sheet 21 includes a positive electrode metal foil (for example, an aluminum foil) 21a formed in a rectangular shape, and a positive electrode active material layer 21b formed by applying a positive electrode active material on both surfaces of the positive electrode metal foil 21a. Has been. The negative electrode sheet 22 includes a negative electrode metal foil (for example, copper foil) 22a formed in a rectangular shape, and a negative electrode active material layer 22b formed by applying a negative electrode active material on both surfaces of the negative electrode metal foil 22a. Has been.

  The positive electrode sheet 21 is formed with a positive electrode-side uncoated portion 21 d to which a positive electrode active material is not applied along the first end portion 21 c (one side direction (long side direction)) of the positive electrode sheet 21. The positive electrode-side uncoated portion 21 d is formed to have a width in the other side direction (short side direction) of the positive electrode sheet 21. A positive electrode current collecting tab 31 as a tab (projected) formed so as to protrude from the positive electrode metal foil 21 a is provided on a part of the first end portion 21 c of the positive electrode sheet 21. ing.

  Similarly to the positive electrode sheet 21, the negative electrode sheet 22 is not coated with the negative electrode active material along the one end portion 22 c (one side direction (long side direction)) of the negative electrode sheet 22. Is formed. The negative electrode side uncoated portion 22 d is formed to have a width in the other side direction (short side direction) of the negative electrode sheet 22. A negative electrode current collecting tab 32 formed by extending the negative electrode metal foil 22 a is provided on a part of the one end portion 22 c of the negative electrode sheet 22.

In the following description, it is assumed that the positive electrode sheet 21 includes the positive electrode-side uncoated portion 21d and excludes the positive electrode current collecting tab 31. The same applies to the negative electrode sheet 22.
In the positive electrode sheet 21 and the negative electrode sheet 22, the positive electrode current collecting tabs 31 are arranged in a row along the stacking direction, and the negative electrode current collecting tabs 32 are arranged in a row along the stacking direction at positions where the positive electrode current collecting tabs 31 do not overlap. It is laminated so that it may be arranged in a shape. As shown in FIG. 1, each positive electrode current collecting tab 31 is bent in a state of being collected (bundled) within a range from one end to the other end in the stacking direction of the electrode assembly 14. Specifically, each positive electrode current collecting tab 31 is gathered toward one end side in the stacking direction of the electrode assembly 14, and in the gathered state, other positive electrode current collecting tabs 31 are arranged in the stacking direction opposite to the one end side. It is folded toward the end side. And each positive electrode current collection tab 31 is electrically connected by welding the location where the each positive electrode current collection tab 31 has overlapped. The same applies to each negative electrode current collecting tab 32.

  The secondary battery 10 includes a positive terminal 41 and a negative terminal 42 for taking out electric power from the electrode assembly 14. Each terminal 41, 42 is attached in a state of penetrating through the case 11 through a through hole formed in the lid 13 of the case 11, and a part of the terminal 41 is exposed outside the case 11. The positive terminal 41 is electrically connected to the positive current collecting tab 31 by welding, and the negative terminal 42 is electrically connected to each negative current collecting tab 32 by welding. Thereby, the electric power of the electrode assembly 14 can be taken out of the case 11 and the electrode assembly 14 can be charged by supplying electric power to the electrode assembly 14.

Next, the detailed configuration and the like of the sheet assembly 20 will be described below together with detailed descriptions of the positive electrode sheet 21, the negative electrode sheet 22, and the separator 23.
As shown in FIG. 2, the positive electrode sheet 21 (rectangular portion excluding the positive electrode current collecting tab 31) and the negative electrode sheet 22 (rectangular portion excluding the negative electrode current collecting tab 32) have a similar shape. Yes. Specifically, the positive electrode sheet 21 is formed slightly smaller than the negative electrode sheet 22. The length of one side direction (long side direction) and the other side direction (short side direction) of the positive electrode sheet 21 (positive electrode metal foil 21a) is set shorter than the length of each direction of the negative electrode sheet 22 (negative electrode metal foil 22a). Has been.

  Here, the positive electrode active material layer 21b is formed in the entire region of the positive electrode sheet 21 other than the positive electrode side uncoated portion 21d. The negative electrode active material layer 22b is formed in the entire region of the negative electrode sheet 22 other than the negative electrode side uncoated portion 22d. For this reason, since the positive electrode sheet 21 is formed to be slightly smaller than the negative electrode sheet 22, the positive electrode active material layer 21b is formed to be slightly smaller than the negative electrode active material layer 22b. In the positive electrode sheet 21, the side surface 21 e of the positive electrode sheet 21 is formed by a surface that is continuous with and orthogonal to the surface facing the separator 23 among the surfaces on which the positive electrode active material layer 21 b is formed.

  As shown in FIG. 2 to FIG. 4, the separator 23 is formed by folding a separator-forming material having a belt shape as a whole from a fold line L in the center of one side direction (long side direction), It is formed by joining (welding) two short sides (free ends) extending in parallel. As shown in FIG. 4, the separator 23 has a sheet-like resin layer 23a and a ceramic layer 23b formed by coating ceramic on one surface of the resin layer 23a.

  As shown in FIG. 3, in the separator 23, the first separator 24 is entirely formed by a rectangular region extending from the fold line L at the fold portion 27 to one long side 23 d (side) extending in parallel to the fold line L. Is formed. In the separator 23, the second separator 25 is formed by the entire rectangular region from the fold line L to the other long side 23f (side edge) extending in parallel to the fold line L. As shown in FIG. 4, the separator 23 is bent so that the resin layer 23 a faces the inner surfaces of the first separator 24 and the second separator 25.

  As shown in FIG. 3, the first separator 24 and the second separator 25 are formed so that the first separator 24 is larger. Specifically, the length from the fold line L to one long side 23d is set longer than the length from the fold line L to the other long side 23f. The first separator 24 and the second separator 25 cover the positive electrode sheet 21 and have a larger area than the positive electrode sheet 21.

  In the bent portion 27 of the separator 23, an elongated hole-shaped cut 27 a is formed so as to extend linearly along the bending line L. The cuts 27 a are formed at positions spaced from the side edges of the separator 23 toward the center of the bent portion 27 along the bend line L. For this reason, the cut 27a is formed in an independent hole shape. That is, the cut 27 a is discontinuous with respect to both sides of the separator 23, and the cut 27 a has a shape closed on the bent portion 27.

  As shown in FIGS. 2 and 4, in the separator 23, the positive electrode sheet 21 is disposed between the first separator 24 and the second separator 25, and the positive electrode current collecting tab 31 of the positive electrode sheet 21 has a notch 27a. Has been inserted. The positive electrode sheet 21 is sandwiched between the first and second separators 24 and 25, and the positive electrode sheet 21 (positive electrode active material layer 21 b) is entirely covered with the first and second separators 24 and 25.

  Here, as already described, the positive electrode sheet 21 is formed slightly smaller than the first and second separators 24 and 25. For this reason, as shown in FIG. 2, in the aspect which comprises the sheet | seat aggregate | assembly 20, a part of 1st and 2nd separators 24 and 25 are outside from the side surface 21e of the positive electrode sheet 21 (direction orthogonal to the side surface 21e). ). In other words, when the first and second separators 24 and 25 are unitized with the positive electrode sheet 21 sandwiched therebetween, the first and second separators 24 and 25 cover the positive electrode sheet 21 and a part thereof protrudes from the side surface 21 e of the positive electrode sheet 21. Thus, it can be said that it is formed larger than the positive electrode sheet 21.

  As shown in FIG. 2, a part of the first separator 24 that extends from the side surface 21e of the positive electrode sheet 21 in the form constituting the sheet assembly 20 is used as a first extension portion 51 and extends from the side surface 21e. A part of the second separator 25 is a second extending portion 52. Each extending portion 51, 52 extends over the entire circumference of the first and second separators 24, 25 so as to surround the positive electrode sheet 21. In addition, as shown in FIG. 4, the extending portions 51 and 52 face each other in the thickness direction of the positive electrode sheet 21. Of the extended portions 51 and 52, the extended portions 51 and 52 are located on the long sides 23 d and 23 f side of the separator 23, and the extended portions 51 and 52 are located on the opposite side of the bent portion 27. The (free ends) are joined (welded) to each other. As a result, the sheet assembly 20 is formed by integrating the positive electrode sheet 21 with the separator 23.

  Next, the joining aspect of the 1st separator 24 and the 2nd separator 25 is demonstrated. In the following description, the first extending portion 51 indicates the first extending portion 51 on the one long side 23d side of the first separator 24, and the second extending portion 52 is the other end of the second separator 25. The 2nd extension part 52 of the long side 23f side is shown.

  As shown in FIG. 3, the first extending portion 51 is longer than the second extending portion 52. And as shown in FIG. 4, the 1st extension part 51 is bent in the standing state from the position beyond the front-end | tip of the 2nd extension part 52. As shown in FIG. Further, the first extension 51 is bent with the tip of the second extension 52 as a fulcrum so that the tip of the first extension 51 faces the positive electrode sheet 21. That is, the first extension portion 51 that is one extension portion is folded back toward the second extension portion 52 that is the other extension portion, and the first extension portion 51 covers the second extension portion 52. It is bent toward the positive electrode sheet 21 so as to be covered. Then, the resin layer 23 a is exposed toward the second extending portion 52 on the inner surface of the folded first extending portion 51. The first extending portion 51 is bent toward the second extending portion 52, and the first extending portion 51 and the ceramic layer 23b of the second extending portion 52 face each other. The 1 extension part 51 and the 2nd extension part 52 are laminated | stacked on three layers, and the folding | turning part 26 is formed. The folded portion 26 is formed in a region where the first extending portion 51 and the second extending portion 52 extend (outside the side surface 21e of the positive electrode sheet 21). That is, the folded portion 26 is not on the surface of the positive electrode sheet 21.

  As shown by a two-dot chain line in FIG. 4, the folded portion 26 is welded in the stacking direction of the folded portion 26 by being heated by the heater 33 from both ends in the stacking direction, and the first welded portion is welded to the folded portion 26. P1 and the 2nd welding part P2 are formed. The first welding part P1 is formed between the extending parts 51 and 52 facing each other without being folded back, and the resin layers 23a are welded to each other at the first welding part P1. The second welded part P2 is formed between the two extended parts 51, 52 facing each other by folding back the first extended part 51. In the second welded part P2, the resin of the first extended part 51 is formed. The layer 23a and the ceramic layer 23b of the second extending portion 52 are welded. Further, the first and second welded portions P1 and P2 are formed over the entire direction along the long sides 23d and 23f of the separator 23, respectively.

  And the 1st separator 24 and the 2nd separator 25 are joined by the return part 26 by forming the 1st and 2nd welding parts P1 and P2 in the return part 26. Further, the folded portion 26 is formed on the opposite side of the notch 27a with the first and second separators 24 and 25 interposed therebetween. The positive electrode sheet 21 is sandwiched between the bent portion 27 and the folded portion 26.

  As shown in FIGS. 1 and 2, the electrode assembly 14 is configured by laminating a sheet assembly 20 and a negative electrode sheet 22 in a state where two adjacent sides overlap each other. Thereby, the positive electrode active material layer 21b and the negative electrode active material layer 22b are opposed to each other with the first separator 24 and the second separator 25 interposed therebetween. Specifically, the negative electrode active material layer 22b faces the entire positive electrode active material layer 21b in an overlapping state. A region where the positive electrode active material layer 21b and the negative electrode active material layer 22b face each other is a region contributing to charge / discharge.

The operation of the secondary battery 10 of the present embodiment will be described below.
In the sheet assembly 20, the folded portion 26 is formed with a first welded portion P <b> 1 between the first and second extending portions 51, 52 facing each other without being folded, and further, the first extending portion. A second welded part P2 is formed between the first and second extending parts 51 and 52 facing each other by folding the part 51 back. For this reason, the welded portion 26 is formed with two welded portions within the thickness in the stacking direction. Therefore, as compared with the case where the first separator 24 and the second separator 25 are welded at only one welded portion, the first extended portion 51 is folded back and the second welded portion P2 is formed. The welding area can be increased, and the bonding strength between the first separator 24 and the second separator 25 can be increased.

According to the above embodiment, the following effects can be obtained.
(1) In the separator 23, the first extending portion 51 of the first separator 24 is folded to form the folded portion 26, and the folded portion 26 is heated in the stacking direction so that the first and second welded portions P1, P2 are Formed. Accordingly, two welds are formed in the folded portion 26. For this reason, compared with the case where the standing upright portions facing each other are joined as in the background art, the number of places where the joining portions (welding portions) are formed increases, and as a result, the first and second extending portions 51 and 52 are in contact with each other. The welding area can be increased, and the first separator 24 and the second separator 25 can be prevented from peeling off. Moreover, since the welding area is increased by folding back the first extending portion 51, the folding portion 26 does not increase in size in the extending direction from the positive electrode sheet 21 even if the welding area is increased.

  (2) In the separator 23, the first separator 24 and the second separator 25 have the resin layer 23a facing each other. For this reason, when the 1st extension part 51 is turned up and the return part 26 is formed, the resin layer 23a of the 1st and 2nd extension parts 51 and 52 will be welded in the 1st welding part P1, and the 2nd welding part P2 will be carried out. Then, the resin layer 23 a of the first extension part 51 is welded to the ceramic layer 23 b of the second extension part 52. Therefore, the resin layer 23a can always be used as a welding allowance, and the first extending portion 51 and the second extending portion 52 can be reliably welded.

  (3) The first separator 24 and the second separator 25 are formed on the separator 23 by being bent from the bent portion 27. For this reason, the separator 23 having the first separator 24 and the second separator 25 can be easily manufactured. The positive electrode sheet 21 is sandwiched between the folded portion 27 and the folded portion 26 (welded portion) by providing the folded portion 26 with the first and second welded portions P1 and P2. Therefore, even if the positive electrode sheet 21 tries to move in the surface direction toward the folded portion 26 or the folded portion 27, the positive electrode sheet 21 can abut on the folded portion 27 or the folded portion 26 to restrict the movement thereof.

  (4) Since the folded portion 26 is formed by folding only the first extending portion 51, for example, the folded portion 26 is formed by folding both the first extending portion 51 and the second extending portion 52. Is easier to fold, and the folded portion 26 is easier to make. Moreover, compared with the case where both the 1st extension part 51 and the 2nd extension part 52 are folded back and the folding | returning part 26 is formed, the force which tries to return to the shape before the folded-back site | part will return will become weak. For this reason, the 2nd welding part P2 cannot peel easily, and the shape of the folding | returning part 26 can be maintained.

  (5) The folded portion 26 is formed by using the first extending portion 51 and the second extending portion 52 that are regions protruding from the side surface 21 e of the positive electrode sheet 21, and is not on the surface of the positive electrode sheet 21. . For this reason, by the folding | returning part 26, it can prevent that the thickness of the lamination direction in the state which pinched | interposed the positive electrode sheet 21 between the 1st separator 24 and the 2nd separator 25 becomes thick.

  (6) A cut 27a is formed in the bent portion 27 of the separator 23, and the positive electrode current collecting tab 31 of the positive electrode sheet 21 is inserted into the cut 27a. Further, in the first and second separators 24 and 25, a folded portion 26 is formed on the side opposite to the folded portion 27. For this reason, even if the positive electrode current collection tab 31 is inserted in the notch 27a of the separator 23, the movement of the positive electrode sheet 21 can be regulated by the bent portion 27 and the folded portion 26. The folded portion 26 is formed only on the side opposite to the folded portion 27. Therefore, for example, as compared with the case where the folded portions 26 are formed on all remaining side portions other than the bent portion 27, a configuration that restricts the movement of the positive electrode sheet 21 with respect to the separator 23 can be easily made.

  (7) The positive electrode sheet 21 is sandwiched between the first separator 24 and the second separator 25, the folded portion 26 is formed on the free end sides of the first separator 24 and the second separator 25, and the first separator 24 and the second separator 25 are I tried not to peel it off. As a result, the separator 23 can prevent the positive electrode sheet 21 from directly facing the negative electrode sheet 22.

  (8) The positive electrode sheet 21 is sandwiched between the first separator 24 and the second separator 25 of the separator 23. The first separator 24 and the second separator 25 include first and second extending portions 51 and 52 that cover the positive electrode sheet 21 and partially extend from the side surface 21 e of the positive electrode sheet 21. And the folding | returning part 26 was formed using a part of 1st and 2nd extension parts 51 and 52. As shown in FIG. For this reason, the dead space of the 1st and 2nd separators 24 and 25, such as the 1st and 2nd extension parts 51 and 52, is used effectively, a welding area is increased and the 1st separator 24 and the 2nd separator 25 peel. Can be prevented.

In addition, you may change the said embodiment as follows.
In the embodiment, the folded portion 26 is formed by folding only the first extending portion 51 out of the first extending portion 51 and the second extending portion 52, but is not limited thereto. As shown in FIG. 5, the extension length from the positive electrode sheet 21 of the 1st extension part 51 and the 2nd extension part 52 is made the same, and both the 1st extension part 51 and the 2nd extension part 52 are used. The folded portion 34 may be formed by folding. In this case, one first extending portion 51 is folded back to the other second extending portion 52 side. In this case, the separator 23 is formed of only the resin layer 23a. If comprised in this way, a welding part will be formed in three places in the lamination direction of the folding | returning part 34. FIG. That is, between the first extension part 51 and the second extension part 52 that are not folded back, between the second extension part 52 that is not folded back and the second extension part 52 that is folded back, and the first extension that is folded back. A welded portion is formed between the portion 51 and the second extending portion 52. In this case, the resin layer 23 a is exposed on the inner surface of the first extending portion 51 located in the outermost layer among the first and second extending portions 51 and 52 folded back toward the positive electrode sheet 21. As the separator 23, a resin layer 23a provided with a ceramic layer 23b may be used.

  In the embodiment, the separator 23 is bent so that the resin layer 23a faces the inner surfaces of the first separator 24 and the second separator 25, but the reverse is also possible. As shown in FIG. The inner surfaces of the first separator 24 and the second separator 25 may face each other, and the ceramic layer 23 b may face the positive electrode sheet 21.

  In the embodiment, the first separator 24 and the second separator 25 are bent and formed on the separator 23, but the present invention is not limited to this. As shown in FIG. 7, the first separator 24 and the second separator 25 are separated from each other, and the folded portion 26 is formed at at least two opposite sides of the four side portions of the first and second separators 24 and 25. May be. In this case, as shown in FIG. 7, one of the first extending portion 51 and the second extending portion 52 (the first extending portion 51 in FIG. 7) is replaced with the other (the second extending portion 52 in FIG. 7). The folded portion 26 may be formed by folding back only one of the extended portions having a longer extension length.

  As shown in FIG. 8, the first separator 24 and the second separator 25 are separated, and the folded portions 26 are formed at at least two opposite sides of the four side portions of the first and second separators 24 and 25. May be. In this case, the extension length of the 1st extension part 51 and the 2nd extension part 52 is made the same, both the 1st extension part 51 and the 2nd extension part 52 are folded back, and the folding | returning part 26 is formed. Also good.

  In the embodiment, the first electrode is the positive electrode sheet 21 and the second electrode is the negative electrode sheet 22, but the reverse may be possible, and the first electrode may be the negative electrode sheet 22 and the second electrode may be the positive electrode sheet 21.

  In the embodiment, the folded portion 26 is formed only on the side opposite to the folded portion 27. In addition, the folded portion 26 is formed on at least one of the pair of side portions sandwiched between the folded portion 27 and the folded portion 26. Also good. Further, the folded portion 26 may be formed on at least one of the side sides on both sides of the folded portion 27 without forming the folded portion 26 on the side opposite to the folded portion 27.

  In the embodiment, the separator 23 is the one in which the ceramic layer 23b is provided on only one surface of the resin layer 23a. However, the separator 23 in which the ceramic layer 23b is formed on both surfaces of the resin layer 23a is used. Also good.

  In the embodiment, the first and second welded portions P1 and P2 are formed over the entire folded portion 26, but the first and second welded portions P1 and P2 are formed only on a part of the folded portion 26. Alternatively, it may be formed at a plurality of positions at intervals.

In the embodiment, the positive electrode sheet 21 has the positive electrode active material layer 21b on both sides, but the positive electrode sheet 21 may have the positive electrode active material layer 21b only on one side.
In the embodiment, the negative electrode sheet 22 has the negative electrode active material layer 22b on both sides, but the negative electrode sheet 22 may have the negative electrode active material layer 22b only on one side.

  In the embodiment, the positive electrode current collecting tab 31 and the negative electrode current collecting tab 32 are folded in a state of being collected (bundled) within a range from one end to the other end in the stacking direction of the electrode assembly 14. However, the positive electrode current collecting tab 31 and the negative electrode current collecting tab 32 may not be collected.

The number of the positive electrode sheet 21 and the negative electrode sheet 22 constituting the electrode assembly 14 may be changed as appropriate.
The shape of the case 11 may be formed in a columnar shape or an elliptical column shape that is flat in the left-right direction.

  The present invention may be embodied as a nickel hydride secondary battery as an electricity storage device or an electric double layer capacitor.

  P1 ... first welding part, P2 ... second welding part, 10 ... secondary battery as power storage device, 14 ... electrode assembly, 21 ... positive electrode sheet as first electrode, 21b ... positive electrode active material as active material layer Layer, 21c ... first end, 21e ... side surface, 22 ... negative electrode sheet as second electrode, 23 ... separator, 23a ... resin layer, 23b ... ceramic layer, 24 ... first separator, 25 ... second separator, 26 , 34 ... folded part, 27 ... bent part, 27a ... notch, 31 ... positive electrode current collecting tab as a tab, 51 ... first extension part, 52 ... second extension part.

Claims (9)

A first electrode having an active material layer formed on at least one surface;
A first separator and a second separator sandwiching the first electrode;
And a power storage device including an electrode assembly in which a second electrode having a polarity different from that of the first electrode is laminated,
The first electrode has a side surface continuous with the surface on which the active material layer is formed,
The first separator has a first extending portion that covers one surface of the first electrode, is larger than the first electrode, and partially extends from at least a portion of the side surface of the first electrode. And
The second separator has a second extending portion that covers the other surface of the first electrode and that is larger than the first electrode and partially extends in the same direction as the first extending portion,
One of the first extension part and the second extension part has a folded part formed by stacking the first extension part and the second extension part by folding back to the other side. And a power storage device having a welded portion welded in at least a part of the folded portion in the stacking direction of the electrode assembly.   The first extension part and the second extension part have a resin layer and a ceramic layer coated with ceramics on one surface of the resin layer, and are located in the outermost layer in the stacking direction in the folded part. 2. The power storage device according to claim 1, wherein the resin layer is exposed on an inner surface of an extending portion that is folded back toward the first electrode.   3. The power storage device according to claim 1, wherein the first separator and the second separator are formed by bending a single separator.   4. The power storage device according to claim 3, wherein one of the first extension part and the second extension part is formed longer than the other, and the folded part is formed by folding one extension part.   The power storage device according to claim 3, wherein the folded portion is formed by folding both the first extending portion and the second extending portion.   The first electrode has a tab protruding from a part of the first end, and the separator has a notch in which a bent portion is formed at the bent position and the tab is inserted into the bent portion. The power storage device according to any one of claims 3 to 5, wherein the folded portion is formed by the extending portion on the opposite side to the bent portion, and the welded portion is formed.   The power storage device according to claim 1, wherein the folded portion is formed in a region where the extending portion extends.   The power storage device according to any one of claims 1 to 7, wherein the first electrode is a positive electrode and the second electrode is a negative electrode.   The power storage device according to any one of claims 1 to 8, wherein the power storage device is a secondary battery.