JP2014232647A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device that is able to increase energy density by eliminating unnecessary space that does not contribute to battery capacity even in a configuration having a plurality of electrode units.SOLUTION: In an electrode assembly 12, a negative electrode 20 includes a pair of negative electrode active material layers 26 on both sides of a negative electrode metal foil 25 with a space between them in the longitudinal direction thereof, and also has a negative electrode exposure part 25a sandwiched between the spaced negative electrode active material layers 26. The negative electrode 20 is bent at the negative electrode exposure part 25a such that the negative electrode active material layers 26 face each other. The electrode assembly 12 has, between the opposite negative active material layers of the negative electrode 20, a plurality of electrode units 50 sandwiching an in-unit positive electrode 191 via a separator 21. The electrode assembly 12 is formed in layers such that an inter-unit positive electrode 192 is sandwiched between the electrode units 50 via the separator 21.

Description

  The present invention relates to a power storage device having an electrode assembly formed by laminating a first electrode and a second electrode via a separator in a case.

  Conventionally, lithium ion secondary batteries, nickel-hydrogen secondary batteries, and the like are well known as power storage devices mounted on vehicles such as EVs (Electric Vehicles) and PHVs (Plug-in Hybrid Vehicles). These power storage devices are formed by laminating positive and negative electrodes each having an active material layer (active material region) on the surface of a metal foil (current collector) with a separator interposed therebetween. A solid body is provided (for example, Patent Document 1).

  As shown in FIG. 6, in the battery of Patent Document 1, the positive electrode 80 has a positive electrode mixture 82 on one surface of an aluminum positive electrode current collector 81, and the positive electrode 80 is opposed to the positive electrode mixture 82. It is folded in half. In the positive electrode 80, the positive electrode mixture 82 is not provided in the folded portion. The negative electrode 83 has a negative electrode mixture 85 on both sides of a copper negative electrode current collector 84. The negative electrode 83 is surrounded by the separator 86 and is sandwiched between the folded positive electrode 80, and the positive electrode 80 and the negative electrode 83 are unitized. The separator 86 is disposed along the surface of the folded positive electrode current collector 81. The negative electrode current collector 84 of the negative electrode 83 is disposed opposite to the positive electrode mixture 82 of the positive electrode 80 via the separator 86, and a plurality of units are stacked to form an electrode assembly.

Japanese Patent Laid-Open No. 11-12016

  By the way, in the battery of Patent Document 1, units adjacent in the stacking direction of the electrode assembly are opposed to each other by the positive electrode current collectors 81. The part where the positive electrode current collectors 81 face each other does not contribute to the battery capacity, and the part where the positive electrode current collectors 81 face each other is a useless space.

  An object of the present invention is to provide a power storage device that can eliminate a useless space that does not contribute to the battery capacity and increase the energy density even when the configuration includes a plurality of electrode units.

  In order to solve the above problem, the power storage device according to claim 1 includes a first electrode having a first active material region on both sides of a first current collector, and a second current collector. Formed on both surfaces by laminating a second electrode having a second active material region different from the first active material region, and a separator interposed between the first electrode and the second electrode The first electrode is provided with a pair of the first active material regions spaced apart in one direction of the first current collector, and separated from each other. The exposed portion of the first current collector sandwiched between the first active material regions, the first active material regions spaced apart from each other are bent at the exposed portion, and the electrode The assembly includes the second electrode via the separator between the first active material regions opposed to the first electrode. A plurality comprises an electrode unit sandwiching a plurality of said electrode unit, and summarized in that is formed by laminating across the second electrode through the separator.

  According to this, since the first electrode is bent at the exposed portion, the first active material region is not bent, and a useless active material region that does not contribute to the battery capacity can be eliminated. The first active material region is provided on both sides of the first current collector. Therefore, in the electrode unit, the first active material region and the second active material region face each other on the inner surface side of the bent first electrode. In the electrode assembly, since the second electrode is sandwiched between the electrode units, the first active material region on both outer surface sides of the first electrode is opposed to the second active material region. ing. For this reason, even if the electrode assembly is configured by laminating a plurality of electrode units, a portion where the metal foils face each other does not occur, and a portion that does not contribute to the battery capacity does not occur. For this reason, even if it is a structure provided with two or more electrode units, the useless space which does not contribute to battery capacity can be eliminated, and an energy density can be enlarged.

  In the power storage device, the first electrode is a negative electrode having a negative electrode active material layer as a first active material region, and the second electrode is a positive electrode active material as a second active material region. A positive electrode having a material layer, wherein the separator includes a first separator and a second separator facing each other, and has a storage portion for storing the positive electrode, and the first separator rather than the storage portion. And a joining portion that joins the first separator and the second separator on an edge side of the second separator, and the positive electrode sandwiched between the electrode units is connected to the separator. The positive electrode is supported on the inner bottom surface of the case through a bottom-side joint portion, and the positive-electrode edge of the positive-electrode active material layer is supported on the bottom-side joint portion. When the edge on the inner bottom surface side of the negative electrode active material layer on the outer surface side in the knit is a negative electrode edge, the length of the bottom-side joint portion along the height direction orthogonal to the inner bottom surface is the height It is set to be longer than the length from the inner bottom surface to the negative electrode edge along the vertical direction.

  According to this, in the positive electrode sandwiched between the electrode units, the positive electrode active material layer is disposed at a position separated from the inner bottom surface by the length of the bottom-side joint portion. Then, by setting the length of the bottom joint portion to a predetermined length, the positive electrode active material layer of the positive electrode sandwiched between the electrode units is opposed to the negative electrode active material layer without protruding from the negative electrode edge. Can be made.

  In the power storage device, the positive electrode sandwiched between the negative electrode active material layers in the electrode unit is supported on the inner bottom surface of the case through the exposed portion and the separator, and the separator is bonded to the bonding unit. The exposed portion side joint portion supported by the exposed portion of the portion, and the length of the exposed portion side joint portion and the thickness of the exposed portion along the height direction is in the height direction. It is set to be longer than the length from the inner bottom surface along the edge of the negative electrode.

  According to this, in the positive electrode sandwiched between the electrode units, the positive electrode active material layer is disposed at a position away from the inner bottom surface by a length that is a sum of the thicknesses of the exposed portion side joint portion and the exposed portion. Then, by setting the combined length of the exposed portion side joint and the exposed portion to a predetermined length, the positive electrode active material layer can be opposed to the negative electrode active material layer without protruding from the negative electrode edge. it can.

  The power storage device is a secondary battery.

  According to the present invention, even if the configuration includes a plurality of electrode units, useless space that does not contribute to battery capacity can be eliminated, and the energy density can be increased.

The disassembled perspective view which shows a secondary battery. The perspective view which shows the positive electrode and negative electrode which comprise an electrode assembly, and an electrode unit. The perspective view which shows the external appearance of a secondary battery. (A) is sectional drawing which shows an electrode unit, (b) is a front view which shows the positive electrode in a unit, (c) is a front view which shows the positive electrode between units. Sectional drawing which shows a part of electrode assembly accommodated in the case. The figure which shows background art.

Hereinafter, an embodiment in which the power storage device is embodied as a secondary battery will be described with reference to FIGS.
As shown in FIGS. 1 and 3, a secondary battery 10 as a power storage device includes an electrode assembly 12 accommodated in a case 11. The case 11 includes a bottomed square cylindrical case main body 13 and a rectangular flat plate-shaped lid member 15 that closes an insertion port 14 into which the electrode assembly 12 is inserted into the case main body 13. The case body 13 has a rectangular flat plate-like bottom wall T and side walls S erected so as to surround the four sides of the bottom wall T, and a resin that covers the bottom wall T and the side walls S on the inner surface of the case body 13. Layer G is provided. The inner bottom surface Ta of the case 11 includes a resin layer G that covers the bottom wall T. The case main body 13 and the lid member 15 constituting the case 11 are both made of metal (for example, stainless steel or aluminum). In addition, the secondary battery 10 of the present embodiment is a square battery whose appearance is a square, and is a lithium ion battery.

  A positive electrode terminal 16 and a negative electrode terminal 17 as electrode terminals are electrically connected to the electrode assembly 12. A ring-shaped insulating ring 18 for insulating from the case 11 is attached to each of the positive terminal 16 and the negative terminal 17.

  As shown in FIG. 2, the electrode assembly 12 includes a sheet-like negative electrode 20 as a first electrode, a sheet-like positive electrode 19 as a second electrode, and between the positive electrode 19 and the negative electrode 20. And a sheet-like separator 21 that insulates.

  The positive electrode 19 has a positive electrode metal foil (aluminum foil in this embodiment) 22 as a second current collector in the form of a rectangular sheet, and a positive electrode active material layer 23 as a second active material region on both surfaces thereof. Have Further, the positive electrode 19 is not provided with the positive electrode active material layer 23, has a positive electrode exposed portion 22 a exposed from the positive metal foil 22 on one side of the positive electrode 19, and protrudes from a part of the positive electrode exposed portion 22 a. The positive electrode current collection tab 24 is provided. The positive electrode current collecting tab 24 has the same shape in the positive electrode 19 constituting the electrode assembly 12 and is provided at the same position. The positive current collecting tab 24 is electrically connected to the positive terminal 16.

  The negative electrode 20 has a negative electrode metal foil (copper foil in the present embodiment) 25 as a rectangular sheet-shaped first current collector, and a negative electrode as a first active material region on both surfaces of the negative electrode metal foil 25. An active material layer 26 is provided. A pair of negative electrode active material layers 26 are provided on both sides of the negative electrode metal foil 25 so as to be separated from each other in the longitudinal direction (one direction) of the negative electrode metal foil 25. The negative electrode 20 has a negative electrode exposed portion 25a where the negative electrode metal foil 25 is exposed between the negative electrode active material layers 26 spaced in the longitudinal direction (one direction) on both surfaces of the negative electrode metal foil 25, and the negative electrode metal foil. 25 also have negative electrode exposed portions 25a at both ends in the longitudinal direction. The negative electrode 20 is provided with a negative electrode current collecting tab 27 made of the negative electrode metal foil 25 protruding from a part of the negative electrode exposed portion 25 a on both ends in the longitudinal direction of the negative electrode metal foil 25. The negative electrode current collecting tab 27 has the same shape in each negative electrode 20 constituting the electrode assembly 12 and is provided at the same position.

  The negative electrode 20 is folded in half from a negative electrode exposed portion 25a located in the center in the longitudinal direction, and has a negative electrode active material layer 26 on each of the inner surface side and the outer surface side of the negative electrode 20, and the negative electrode active material layer 26 on the inner surface side. While facing each other, the negative electrode current collecting tabs 27 at both ends in the longitudinal direction are also facing each other.

  The positive electrode 19 has a rectangular shape excluding the positive current collecting tab 24, and the negative electrode 20 has a rectangular shape except the negative current collecting tab 27. However, the length of each of the two adjacent sides of the negative electrode active material layer 26 (the length in the longitudinal direction and the length in the short direction) is the length of each side of the two adjacent sides of the positive electrode active material layer 23. It is set longer than (the length in the longitudinal direction and the length in the short direction). That is, the negative electrode active material layer 26 is set to a size that can cover the entire surface of the positive electrode active material layer 23.

  The positive electrode 19 is wrapped in a bag-like separator 21. The separator 21 has a first separator 21 a and a second separator 21 b that are opposite to each other and that cover both surfaces of the positive electrode 19 and have the same size, and a storage portion 21 c for the positive electrode 19. . The first and second separators 21 a and 21 b include a protruding portion 30 that protrudes from each end edge of the positive electrode 19 in a stacked state. The first and second separators 21a and 21b sandwiching the positive electrode 19 are formed by welding the protruding portions 30 to each other on the edge side of the first and second separators 21a and 21b with respect to the storage portion 21c. A joining portion 31 is provided.

  As shown in FIG. 1 and FIG. 4A, a positive electrode 19 wrapped with a separator 21 is disposed inside the negative electrode 20 folded in half, and the negative electrode 20 and the positive electrode 19 One electrode unit 50 is formed. The electrode assembly 12 is formed by alternately stacking the electrode units 50 and the positive electrodes 19 with the positive electrodes 19 wrapped with the separators 21 sandwiched between the electrode units 50.

  As shown in FIG. 5, in the electrode assembly 12, the electrode unit 50 has the negative electrode exposed portion 25 a of the negative electrode 20 supported on the inner bottom surface Ta of the case 11. Further, the positive electrode 19 sandwiched between the electrode units 50 is supported on the inner bottom surface Ta of the case 11 via the joint portion 31 of the separator 21.

  Here, in the positive electrode active material layer 23 of each positive electrode 19, the edge on the bottom wall T side of the case 11 is defined as a positive electrode edge 23 a, and the bottom wall T of the case 11 is formed in the negative electrode active material layer 26 of each negative electrode 20. The side edge is referred to as a negative electrode edge 26a. The direction perpendicular to the inner bottom surface Ta of the case 11 is defined as the height direction. In this case, the length N1 along the height direction from the inner bottom surface Ta of the case 11 to the positive electrode edge 23a and the length N2 along the height direction from the inner bottom surface Ta to the negative electrode edge 26a are long. The length N1 is longer than the length N2. Therefore, on the bottom wall T side of the case 11, the positive electrode active material layer 23 is disposed inside the negative electrode active material layer 26 in the direction along the surface of the negative electrode active material layer 26.

  The positive electrode 19 sandwiched between the negative electrode active material layers 26 in the electrode unit 50 is referred to as an intra-unit positive electrode 191, and the positive electrode 19 sandwiched between the electrode units 50 is referred to as an inter-unit positive electrode 192. The in-unit positive electrode 191 is indirectly supported on the inner bottom surface Ta of the case 11 through the bent negative electrode exposed portion 25 a in the electrode unit 50.

  As shown in FIG. 4B, in the separator 21 that encloses the positive electrode 191 in the unit, the four sides of the joint portion 31 that surrounds the positive electrode 19 are disposed on the bottom wall T side of the case 11, and the negative electrode exposed portion 25 a The joint part 31 on one side to be supported is referred to as an exposed part side joint part 32. The positive electrode 191 in the unit is positioned in the separator 21 with the positive electrode edge 23 a of the positive electrode active material layer 23 supported by the exposed portion side joint portion 32.

  On the other hand, the inter-unit positive electrode 192 is directly supported on the inner bottom surface Ta of the case 11. As shown in FIG. 4C, in the separator 21 that encloses the inter-unit positive electrode 192, the four sides of the joint 31 that surrounds the inter-unit positive electrode 192 are arranged on the bottom wall T side of the case 11, and A joint 31 on one side that is directly supported by the inner bottom surface Ta of 11 is a bottom joint 33. The inter-unit positive electrode 192 is positioned in the separator 21 with the positive electrode edge 23 a of the positive electrode active material layer 23 supported by the bottom-side joint portion 33.

  Here, as shown in FIG. 5, in the exposed portion side joint portion 32, an end edge supported by the inner surface of the negative electrode exposed portion 25 a is set as an exposed side end edge 32 a, and in the bottom side joint portion 33, Let the edge supported by the inner bottom face Ta be the bottom side edge 33a.

  In this case, in the exposed portion side joint portion 32, the joint portion length L1 along the height direction from the exposed side edge 32 a to the positive electrode end edge 23 a of the positive electrode active material layer 23, and the bottom side joint portion 33, the bottom side The junction length L1 is shorter than the junction length L2 from the edge 33a to the cathode edge 23a of the cathode active material layer 23. Therefore, in the height direction, the exposed portion side joined portion 32 is shorter than the bottom side joined portion 33, and the joined portion length L1 is equal to the thickness W of the negative electrode exposed portion 25a than the joined portion length L2. It is getting shorter. In the exposed portion side joining portion 32 and the bottom side joining portion 33, the exposed portion side joining portion 32 has a smaller area of the joined protruding portion 30.

  Therefore, the joint length L2 of the bottom side joint 33 is longer than the length N2 from the inner bottom surface Ta to the negative electrode edge 26a. Further, the joint portion length L1 of the exposed portion side joint portion 32 is longer than the joint portion length L1 from the inner bottom surface Ta to the negative electrode edge 26a. The combined length L1 of the exposed portion-side bonded portion 32 and the thickness W of the negative electrode exposed portion 25a are the same as the bonded portion length L2 of the bottom-side bonded portion 33, and from the inner bottom surface Ta. It is longer than the length N2 to the negative electrode edge 26a.

  Therefore, in a state where the in-unit positive electrode 191 is supported by the negative electrode exposed portion 25a and the inter-unit positive electrode 192 is supported by the inner bottom surface Ta, the positive electrode edge 23a is arranged on the same straight line, and the positive electrode edge 23a. Is disposed inside the negative electrode edge 26a.

  In the electrode assembly 12 having the above-described configuration, the entire surface of the positive electrode active material layer 23 of the in-unit positive electrode 191 faces the negative electrode active material layer 26 on the inner surface side of each electrode unit 50, and The entire surface of the positive electrode active material layer 23 of each unit positive electrode 192 adjacent to the electrode unit 50 is opposed to each of the negative electrode active material layers 26. Therefore, all the positive electrode active material layers 23 face the negative electrode active material layer 26 over the entire surface, and the negative electrode active material layer 26 covers the entire surface of the positive electrode active material layer 23.

Next, the operation of the secondary battery 10 will be described.
In the stacking direction of the electrode assembly 12, the positive electrode active material layer 23 is opposed to each negative electrode active material layer 26, and even in the electrode assembly 12 using a plurality of electrode units 50, the positive electrode metal foils 22 Or there is no site | part which the negative electrode metal foil 25 opposes.

According to the above embodiment, the following effects can be obtained.
(1) The electrode assembly 12 includes an electrode unit 50 in which the negative electrode 20 is folded in half and the in-unit positive electrode 191 is sandwiched between the electrode unit 50 and the inter-unit positive electrode 192 sandwiched between the electrode units 50. Are laminated. Therefore, the positive electrode active material layer 23 of the in-unit positive electrode 191 is opposed to the negative electrode active material layer 26 on the inner surface side of the electrode unit 50, and the negative electrode active material layer 26 on the outer surface side of the electrode unit 50 is between the units. The positive electrode active material layer 23 of the positive electrode 192 is opposed. For this reason, in the electrode assembly 12, the site | part which metal foil opposes does not arise, and the site | part which does not contribute to battery capacity does not arise in the electrode assembly 12. FIG. For this reason, even if the electrode assembly 12 includes a plurality of electrode units 50, it is possible to eliminate a useless space that does not contribute to the battery capacity and increase the energy density.

  (2) The electrode unit 50 is folded at the negative electrode exposed portion 25a and folded in two. For this reason, the negative electrode active material layer 26 does not exist in the bent portion that does not contribute to the battery capacity, and there is no waste of the active material.

  (3) The inter-unit positive electrode 192 is supported on the inner bottom surface Ta of the case 11 via the bottom-side joint portion 33 of the separator 21. The junction length L2 of the bottom junction 33 is set to be longer than the length N2 from the inner bottom surface Ta of the case 11 to the negative electrode edge 26a of the negative electrode active material layer 26. In order to prevent dendrite precipitation in a lithium ion battery, the negative electrode active material layer 26 is set larger than the positive electrode active material layer 23 so that the negative electrode active material layer 26 exists outside the outer peripheral edge of the positive electrode active material layer 23. It is preferable to arrange in. At this time, the positioning accuracy between the negative electrode active material layer 26 and the positive electrode active material layer 23 is important. However, the inter-unit positive electrode 192 is supported by the bottom-side joint portion 33, and the negative electrode active material layer 26 is negative. It is located inside the extreme edge 26a in the direction along the surface. Therefore, the positive electrode active material layer 23 does not protrude from the negative electrode active material layer 26, and the positive electrode active material layer 23 and the negative electrode active material layer 26 can be reliably opposed to each other.

  (4) The in-unit positive electrode 191 is supported by the negative electrode exposed portion 25 a of the negative electrode 20 through the exposed portion side joint portion 32 of the separator 21. The combined length L1 of the exposed portion-side bonded portion 32 and the thickness W of the negative electrode exposed portion 25a are longer than the length N2 from the inner bottom surface Ta to the negative electrode edge 26a. Therefore, the in-unit positive electrode 191 is positioned on the inner side in the direction along the surface of the negative electrode edge 26a of the negative electrode active material layer 26 while being supported by the exposed portion-side bonding portion 32, and the positive electrode active material The layer 23 does not protrude from the negative electrode active material layer 26, and the positive electrode active material layer 23 and the negative electrode active material layer 26 can be reliably opposed to each other.

  (5) The length of the joint portion L1 of the exposed portion side joint portion 32 and the length of the joint portion length L2 of the bottom side joint portion 33 are set different from each other. Thus, even if the in-unit positive electrode 191 is indirectly supported by the negative electrode exposed portion 25a and the inter-unit positive electrode 192 is directly supported by the inner bottom surface Ta of the case 11, the negative electrode active material layer is formed on the bottom wall T side. In the direction along the surface 26, the positive electrode active material layer 23 can be prevented from protruding.

  (6) The joining portion length L1 of the exposed portion side joining portion 32 and the joining portion length L2 of the bottom side joining portion 33 are adjusted by adjusting the length and joining area of the protruding portion 30 when the separator 21 is manufactured. It can be set to a predetermined length. Therefore, by setting the junction length L1 and the junction length L2 during the manufacture of the separator 21, the opposing area between the positive electrode active material layer 23 and the negative electrode active material layer 26 can be made as large as possible to enable battery capacity. It becomes possible to increase as much as possible.

In addition, you may change the said embodiment as follows.
In the separator 21 that encloses the in-unit positive electrode 191, the joint length L <b> 1 of the exposed portion-side joint 32 may be changed as appropriate. For example, the combined length L1 of the exposed portion side bonded portion 32 and the thickness W of the negative electrode exposed portion 25a may be the same as the length N2 from the inner bottom surface Ta to the negative electrode edge 26a, It may be shortened.

  In the separator 21 that wraps the inter-unit positive electrode 192, the joint length L2 of the bottom joint 33 may be changed as appropriate. For example, the junction length L2 of the bottom side junction 33 may be the same as or shorter than the length N2 from the inner bottom surface Ta to the negative electrode edge 26a.

  The positive electrode active material layer 23 of the in-unit positive electrode 191 is not positioned by the exposed portion side joint portion 32, and the positive electrode edge 23 a is placed on the inner side of the negative electrode edge 26 a due to the binding force in the stacking direction of the electrode assembly 12. It may be positioned so as to be positioned.

  The positive electrode active material layer 23 of the inter-unit positive electrode 192 is not positioned by the bottom-side joint portion 33, and the positive electrode edge 23a is positioned inside the negative electrode edge 26a by the restraining force in the stacking direction of the electrode assembly 12. It may be positioned to

  In the electrode unit 50 that is located at the side end of the electrode assembly 12 in the stacking direction and faces the side wall S, the negative electrode active material layer 26 on the surface facing the side wall S may be omitted.

The first electrode may be the positive electrode 19, and the second electrode may be the negative electrode 20.
The separator 21 may be a type in which the four sides of the first and second separators 21a and 21b are not joined, but one side on the positive electrode current collecting tab 24 side is not joined, and the remaining three sides are joined. Alternatively, one side of the positive electrode current collecting tab 24 side and two sides connected to the one side may not be joined, and only the bottom wall T side may be joined.

  The first active material region may not be layered like the negative electrode active material layer 26, and may be one in which an active material is supported on a mesh current collector as the first current collector. Similarly, the second active material region may not be layered like the positive electrode active material layer 23, and may be one in which an active material is supported on a mesh current collector as a second current collector.

The secondary battery 10 is a lithium ion secondary battery, but is not limited thereto, and may be another secondary battery such as nickel metal hydride.
The power storage device is not limited to the secondary battery 10 and may be a capacitor such as an electric double layer capacitor or a lithium ion capacitor.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) A power storage device in which the length of each of the two adjacent sides of the first active material region is set longer than the length of each of the two adjacent sides of the second active material region.

  N1, N2 ... length, Ta ... inner bottom surface, W ... thickness, 10 ... secondary battery as power storage device, 11 ... case, 12 ... electrode assembly, 19 ... positive electrode as second electrode, 20 ... first Negative electrode as 1 electrode, 21 ... Separator, 21a ... First separator, 21b ... Second separator, 21c ... Storage section, 22 ... Positive metal foil as second current collector, 23 ... Second Positive electrode active material layer as active material region, 23a ... positive electrode edge, 25 ... negative electrode metal foil as first current collector, 25a ... negative electrode exposed portion, 26 ... negative electrode active material layer as first active material region 26a ... negative electrode edge, 31 ... junction, 32 ... exposed portion side junction, 33 ... bottom side junction, 50 ... electrode unit.

Claims (4)

A first electrode having a first active material region on both sides of the first current collector;
A second electrode having a second active material region opposite to the first active material region on both surfaces of the second current collector;
A power storage device having an electrode assembly in a case formed by laminating a separator interposed between the first electrode and the second electrode,
The first electrode includes a pair of the first active material regions spaced apart in one direction of the first current collector, and the first electrode sandwiched between the spaced apart first active material regions. An exposed portion of the current collector, and the first active material region spaced apart is bent at the exposed portion,
The electrode assembly includes a plurality of electrode units that sandwich the second electrode through the separator between the first active material regions opposed to the first electrode, and
A power storage device, wherein a plurality of the electrode units are formed to be stacked with the second electrode interposed between the separators. The first electrode is a negative electrode having a negative electrode active material layer as a first active material region, and the second electrode is a positive electrode having a positive electrode active material layer as a second active material region. The separator includes a first separator and a second separator that face each other, and has a storage portion that stores the positive electrode, and the first separator and the second separator rather than the storage portion. Having a joint for joining the first separator and the second separator on the edge side of
The positive electrode sandwiched between the electrode units is supported on the inner bottom surface of the case through a bottom-side joint portion of the joint portions of the separator, and the positive electrode is a positive electrode of the positive electrode active material layer. An extreme edge is supported by the bottom joint,
When the edge on the inner bottom surface side of the negative electrode active material layer on the outer surface side in the electrode unit is a negative electrode edge, the length of the bottom-side joint along the height direction orthogonal to the inner bottom surface is: The power storage device according to claim 1, wherein the power storage device is set to be equal to or longer than a length from the inner bottom surface to the negative electrode edge along the height direction. The positive electrode sandwiched between the negative electrode active material layers in the electrode unit is supported on the inner bottom surface of the case via the exposed portion and the separator, and the separator is the exposed portion of the joint portion. Having an exposed portion side joint supported by
The total length of the exposed portion-side joint along the height direction and the thickness of the exposed portion is set to be equal to or greater than the length from the inner bottom surface to the negative electrode edge along the height direction. The power storage device according to claim 2.   The power storage device according to any one of claims 1 to 3, wherein the power storage device is a secondary battery.