JP2015191724A - power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of suppressing precipitation of ions.SOLUTION: In a secondary battery 10, a separator 27 is formed by welding a pair of separator sheets 27a confronting each other. The separator 27 has a junction 27g joining the edges. A gap filling member 50 is a laminate of a plurality of sheet members 51, and has a welded portion 50a where all sheet members 51 are welded, and a body 50b surrounded by the welded portion 50a. In the laminating direction of an electrode assembly 14, the body 50b is facing the entire surface of an active material layer 23 of a positive electrode 21 via a negative electrode 24.

Description

  The present invention relates to an electrode assembly in which negative electrodes and positive electrodes wrapped with a separator are alternately stacked, a case in which the electrode assembly is accommodated, at least one end face in the stacking direction of the electrode assembly, and the end face The present invention relates to a power storage device having a gap filling member that fills a gap with the inner surface of the case.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery such as a lithium ion battery as a power storage device that stores power supplied to an electric motor serving as a prime mover. A secondary battery includes, for example, an electrode assembly in which a rectangular positive electrode and a negative electrode each having an active material layer formed on both surfaces are stacked with a separator interposed therebetween.

  Among secondary batteries, for example, when manufacturing a square secondary battery, a positive electrode, a separator, and a negative electrode are stacked to form an electrode assembly, and then the electrode assembly applies a load in the stacking direction. The length in the stacking direction in the restrained state is measured. Then, it is determined whether or not the length of the electrode assembly in the stacking direction is within a predetermined value range.

  This is because if the length of the electrode assembly in the stacking direction is larger than the inner dimension of the case, the electrode assembly cannot be accommodated in the case. Further, if the length of the electrode assembly in the stacking direction is smaller than the inner dimension of the case, for example, a gap between the end surface of the electrode assembly in the stacking direction and the inner surface of the case facing the end surface in the case This is because the electrode assembly becomes too large and the electrode assembly moves in the stacking direction in the case, which is not preferable. Therefore, even when the length in the stacking direction of the electrode assembly is smaller than the inner dimension of the case, it is regarded as an unqualified product if the length in the stacking direction is not within the predetermined value range.

  On the other hand, when the length of the electrode assembly in the stacking direction is within a predetermined value range, the gap between the end surface of the electrode assembly and the inner surface of the case is filled with respect to the difference from the inner dimensions of the case. The member is filled and the gap is closed. The gap filling member includes one or a plurality of stacked sheet members, and the number of sheet members to be used is determined according to the size of the gap. In order to enhance the workability of the work of closing the gap, for example, as in Patent Document 1, it is preferable to previously weld and integrate a plurality of resin sheet members. This is because not only the handling of the plurality of sheet members is facilitated, but also the plurality of sheet members can be filled in the gap at once.

JP 2009-48966 A

  In a state where the gap filling member is filled in the gap, the electrode assembly is restrained in the stacking direction, and pressure is applied to the electrode assembly in the stacking direction. However, in the gap filling member in which the resin sheet members are welded and integrated, the welded portion is shrunk with welding, while the non-welded portion is not shrunk, and in the surface direction of the gap filling member. The thickness varies along. For this reason, the pressure applied to the electrode assembly from the gap filling member differs between the welded part and the non-welded part, and the pressure applied to the electrode assembly varies in the surface direction. The electrode assembly is manufactured so that the entire surface of the active material layer of the positive electrode faces the active material layer of the negative electrode through a separator from the viewpoint of suppressing a decrease in energy density in the secondary battery. For this reason, when the pressure applied to the electrode assembly varies in the plane direction, the distance between the active material layers of the positive electrode and the negative electrode in the stacking direction varies in the plane direction, which causes ion precipitation.

  An object of the present invention is to provide a power storage device that can suppress the precipitation of ions.

  A power storage device for solving the above problems includes an electrode assembly in which a negative electrode and a positive electrode wrapped with a separator are alternately stacked, a case housing the electrode assembly, and a stacking direction of the electrode assembly A gap filling member filled in a gap between the end surface of the case and the inner surface of the case facing the end surface, wherein the separator welds the edges of a pair of separator sheets facing each other. The gap filling member is a laminate of a plurality of sheet members, and a welded portion in which edges of all the sheet members are welded together, and a main body portion surrounded by the welded portions, And the main body part faces the entire surface of the active material layer of the positive electrode through the negative electrode in the stacking direction of the electrode assembly.

  According to this, the main body portion of the gap filling member is not welded like the welded portion, and shrinkage or the like due to the welding is not generated. For this reason, there is no dispersion | variation in the thickness accompanying welding in the length (thickness) to the lamination direction in the main-body part in a gap filling member. And this main-body part has opposed the whole surface of the active material layer of the positive electrode through the negative electrode. For this reason, in the state where the gap filling member is filled in the gap, it is possible to uniformly apply pressure to the active material layer of the positive electrode along the surface direction. Therefore, the distance between the active material layers of the positive electrode and the negative electrode in the stacking direction of the electrode assembly does not vary in the plane direction, and ion precipitation can be suppressed.

Moreover, about the electrical storage apparatus, the said gap filling member may be welded over the perimeter by the edge parts of all the sheet members.
According to this, it is possible to suppress the plurality of sheet members from being shifted in the surface direction, and it is possible to suppress the fluctuation of the thickness of the main body portion.

  In the power storage device, the gap filling member is a laminate of a first sheet member and a second sheet member having a larger outer size than the first sheet member, and one or more first sheet members are It may be configured to be sandwiched between the second sheet members from both sides in the stacking direction of the stacked body, and an edge portion facing the stacking direction in the second sheet member may be welded.

  According to this, in the gap filling member, the first sheet member is simply sandwiched between the second sheet members, and the first sheet member and the second sheet member are not welded. That is, the welding part with which the gap filling member is provided is a part where only the edge part of the second sheet member is welded. For this reason, in the manufacture of the gap filling member, even if the number of the first sheet members is changed, the welding condition is not always changed by the welding of the opposing second sheet member. Therefore, there is no need to set welding conditions each time the number of stacked sheets changes, as in the case of welding all of the stacked first sheet member and second sheet member, and a plurality of types of gaps having different lengths in the stacking direction. The filling member can be manufactured without changing the welding conditions, and the gap filling member can be manufactured efficiently.

  The power storage device is a secondary battery.

  According to the present invention, precipitation of ions can be suppressed.

The disassembled perspective view which shows the secondary battery of embodiment. The perspective view which shows the external appearance of the secondary battery of embodiment. The disassembled perspective view which shows the component of an electrode assembly, and a gap filling member. The top view which shows a clearance gap filling member. Sectional drawing which shows an electrode assembly and a gap filling member. The perspective view which shows another example of a clearance gap filling member.

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 FIG. 1 and FIG. 2, the secondary battery 10 as a power storage device is a lithium ion secondary battery, and the secondary battery 10 includes a metal case 11 that constitutes an outer shell of the secondary battery 10. The case 11 has a bottomed rectangular parallelepiped case main body 12 having an opening 12 a on one surface, and a lid 13 that closes the opening 12 a of the case main body 12. The case body 12 includes a rectangular bottom plate 12b, a short side wall 12c erected from a pair of opposed short side edges of the bottom plate 12b, and a long side wall 12d erected from a pair of long side edges of the bottom plate 12b. With. The case 11 contains an electrode assembly 14 and an electrolytic solution (not shown) as an electrolyte. The electrode assembly 14 has a rectangular parallelepiped shape as a whole, corresponding to the internal space of the case body 12 having a rectangular parallelepiped shape. The lid 13 includes a liquid injection port 13a, and an electrolytic solution can be injected into the case 11 from the liquid injection port 13a. The liquid injection port 13a is sealed with a sealing plug 13c after the electrolyte solution is injected.

  As shown in FIG. 3, the electrode assembly 14 has a stacked configuration in which a plurality of positive electrodes 21 and a plurality of negative electrodes 24 are alternately stacked with separators 27 interposed therebetween. . The positive electrode 21 includes a rectangular positive electrode metal foil (in this embodiment, an aluminum foil) 22 and a rectangular positive electrode active material layer 23 provided on both surfaces of the positive electrode metal foil 22. The active material layers 23 on both surfaces of the positive electrode metal foil 22 have the same planar shape and the same thickness, and face each other with the positive electrode metal foil 22 interposed therebetween. The positive electrode 21 has a positive electrode uncoated portion 22d where the active material layer 23 is not provided and the positive electrode metal foil 22 is exposed along the first side 22c. In the positive electrode 21, the current collecting tab 31 for the positive electrode protrudes from a portion of the first side 22 c of the positive electrode uncoated portion 22 d. In the positive electrode 21, the opposite side of the first side 22c provided with the positive current collecting tab 31 is defined as a second side 22e, and a pair of sides connecting the first side 22c and the second side 22e is defined as a third side. Let it be side 22f.

  The negative electrode 24 has a rectangular negative electrode metal foil (copper foil in the present embodiment) 25 and a rectangular negative electrode active material layer 26 provided on both surfaces of the negative electrode metal foil 25. The active material layers 26 on both surfaces of the negative electrode metal foil 25 have the same planar shape and the same thickness. The negative electrode 24 has a negative electrode uncoated portion 25d where the active material layer 26 is not provided and the negative electrode metal foil 25 is exposed along the first side 25c. In the negative electrode 24, a negative electrode current collecting tab 32 protrudes from a part of the first side 25c of the negative electrode uncoated portion 25d. In the negative electrode 24, the opposite side of the first side 25c on which the negative current collecting tab 32 is provided is the second side 25e, and the pair of sides connecting the first side 25c and the second side 25e is the third side. Let it be side 25f.

  The positive electrode 21 is wrapped in a bag-like separator 27 with a part of the current collecting tab 31 protruding. The separator 27 is formed into a bag shape by welding all the edges except for the edge facing the current collecting tab 31 among the facing edges of the pair of rectangular separator sheets 27a. . Therefore, the separator 27 is integrated with the positive electrode 21.

  The separator 27 is made of a resin and is formed of a porous film having micropores through which ions related to electrical conduction (lithium ions) can pass. In the separator 27, the side extending along the first side 22 c of the positive electrode 21 is defined as a first side 27 c, the opposite side of the first side 27 c, and along the second side 22 e of the positive electrode 21. The extending side is defined as a second side 27e. In the separator 27, a pair of sides that connect the first side 27 c and the second side 27 e and extend along the third side 22 f of the positive electrode 21 are defined as a third side 27 f.

  As shown in FIGS. 3 and 5, the separator 27 has a joint portion 27 g welded to the edges of the separator sheet 27 a, and the joint portion 27 g is provided over the entire four sides excluding the current collecting tab 31. It is a square ring. In the joint portion 27g, the length L1 along the surface of the separator 27 and in the direction orthogonal to the sides 27c, 27e, and 27f is the same at any position on the entire circumference of the separator 27.

  The lengths 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) are the lengths of the two adjacent sides of the active material layer 23 of the positive electrode. 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 surface of the positive electrode active material layer 23.

  As shown in FIG. 1, the positive electrode 21, the negative electrode 24, and the separator 27 are positions where the positive current collecting tabs 31 are arranged in a row along the stacking direction and do not overlap the positive current collecting tab 31. The negative electrode current collecting tabs 32 are stacked so as to be arranged in a line along the stacking direction. In other words, the positive current collecting tab 31 and the negative current collecting tab 32 protrude to the same side of the electrode assembly 14. The current collecting tabs 31 and 32 are 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. By welding the locations where the current collecting tabs 31 of the respective positive electrodes are overlapped, the current collecting tabs 31 of the respective positive electrodes are electrically connected, and the positive electrode conductive member 41a is connected. A positive electrode terminal 41 b for taking out electricity from the electrode assembly 14 is connected to the positive electrode conductive member 41 a.

  Similarly, the negative electrode current collecting tab 32 is electrically connected by welding the portions where the negative electrode current collecting tabs 32 are overlapped, and the negative electrode conductive member 42a is connected to the negative electrode current collecting tab 32. ing. A negative electrode terminal 42b for taking out electricity from the electrode assembly 14 is connected to the negative electrode conductive member 42a. The positive electrode terminal 41b and the negative electrode terminal 42b penetrate the lid body 13 and protrude out of the case 11, and the positive electrode terminal 41b and the negative electrode terminal 42b are insulated from the lid body 13 by the insulating ring 13b.

  When the length along the stacking direction of the electrode assembly 14 is the thickness of the electrode assembly 14, the electrode assembly 14 is set so that the thickness is slightly smaller than the inner dimension of the case 11. The inner dimension of the case 11 is a distance between the inner surfaces 12f of the opposed long side walls 12d. The electrode assembly 14 has rectangular end faces 44 in both the stacking directions.

  In the electrode assembly 14, all the positive electrodes 21, the negative electrodes 24, and the separators 27 are held in a mutually positioned state by the first holding tape 45 and the second holding tape 47. In addition, the electrode assembly 14 is configured so that the entire surface of the positive electrode active material layer 23 faces the negative electrode active material layer 26 with the separator 27 interposed therebetween, from the viewpoint of suppressing a decrease in energy density in the secondary battery 10. It is manufactured. Further, the positive electrode active material layer 23 and the negative electrode active material layer 26 are manufactured so as not to face each other beyond the edge of the separator 27. In order to prevent the electrode assembly 14 manufactured with high accuracy from shifting in the stacking direction or the direction along the end face 44, the electrode assembly 14 includes the first holding tape 45 and the second holding tape 47. Is held by. The electrode assembly 14 is stacked and pressurized, and then held by the first holding tape 45 and the second holding tape 47.

  As shown in FIG. 5, a gap filling member 50 fills a gap between one end surface 44 of the electrode assembly 14 and the inner surface 12 f (the inner surface of the case 11) of one long side wall 12 d facing the end surface 44. Has been. The gap filling member 50 is a laminated body configured by laminating a plurality of sheet members 51. In the gap filling member 50, the direction in which the plurality of sheet members 51 overlap is defined as the stacking direction, and the length in the stacking direction is defined as the thickness of the gap filling member 50. The gap filling member 50 has a different length in the stacking direction according to the number of stacked sheet members 51.

  As shown in FIGS. 3 and 4, the sheet member 51 has a rectangular shape with a predetermined thickness and is made of resin. The plurality of sheet members 51 have the same outer shape. The length of each side of the two adjacent sides of the sheet member 51 (the length in the longitudinal direction and the length in the short side direction) is the length of each side of the two adjacent sides of the positive electrode active material layer 23 (the longitudinal direction). And the length in the short direction). That is, the sheet member 51 is set to a size that can cover the entire surface of the positive electrode active material layer 23. Further, the length of each side of the two adjacent sides of the sheet member 51 (the length in the longitudinal direction and the length in the short side direction) is the length of each side of the two adjacent sides of the separator 27 (the length in the longitudinal direction). And the length in the short direction). That is, the gap filling member 50 and the separator 27 have the same outer size.

  The gap filling member 50 includes a welded portion 50a formed by welding edges along the four sides of all the sheet members 51, and a main body portion 50b that is a non-welded portion surrounded by the welded portion 50a. . The welded portion 50a is a quadrangular ring provided over the entire four sides of the gap filling member 50, and the main body portion 50b surrounded by the welded portion 50a has a quadrangular shape in front view. In the welded portion 50a, the lengths L2 along the surface of the gap filling member 50 and in the direction perpendicular to the four sides are all the same. Further, the welded portion 50 a is thermally contracted by welding, and the thickness of the welded portion 50 a is thinner than the sum of the thicknesses of all the sheet members 51. Furthermore, the length L2 of the welded portion 50a is shorter than the length L1 of the joint portion 27g at the separator 27. On the other hand, the main body portion 50b is not thermally contracted, and the thickness of the main body portion 50b is the same as the sum of the thicknesses of all the sheet members 51, and is substantially the same along the surface direction of the main body portion 50b. In the gap filling member 50, the welded portion 50a is thinner than the main body portion 50b.

  The gap filling member 50 is held integrally with the electrode assembly 14 by a holding tape (not shown). By using the gap filling member 50, the length in the stacking direction of the electrode assembly 14 and the gap filling member 50 is adjusted to be slightly shorter than the inner dimension of the case body 12.

  As shown in FIG. 5, the main body 50 b of the gap filling member 50 faces the entire surface of the positive electrode active material layer 23 with the negative electrode 24 interposed therebetween. The entire surface of the quadrangular annular welded portion 50 a of the gap filling member 50 is opposed to the quadrangular annular joint portion 27 g of the separator 27 via the negative electrode 24 in the stacking direction. Therefore, only the positive electrode active material layer 23 overlaps with all the layers in the stacking direction over the entire surface, and only the positive electrode active material layer 23 covers the entire surface in the stacking direction by the gap filling member 50 (main body portion 50b). Pressurized. Further, the movement of the electrode assembly 14 in the stacking direction is restricted by the gap filling member 50 in the case 11.

  In the case 11, the separator 27 that encloses the positive electrode 21 has a second side 27 e supported on the bottom plate 12 b of the case body 12, and the negative electrode 24 has a second side 25 e on the bottom plate 12 b of the case body 12. It is supported by. In the gap filling member 50, the lower end edge of the welded portion 50 a is supported on the bottom plate 12 b of the case body 12.

  In addition, a positive electrode conductive member 41a and a negative electrode conductive member 42a are disposed above the separator 27, the negative electrode 24, and the gap filling member 50 that enclose the positive electrode 21, and thereby, the separator 27, the negative electrode 24, and the gap filling. The upward movement of the member 50 is restricted. In addition, both the third sides 27f of the separator 27 that encloses the positive electrode 21, the third sides 25f of the negative electrode 24, and the left and right edges of the gap filling member 50 are opposed to the inner surfaces of both short side walls 12c, The movement of the separator 27, the negative electrode 24 and the gap filling member 50 in the left-right direction is restricted by the short side wall 12c. Therefore, in the case 11, the separator 27, the negative electrode 24, and the gap filling member 50 are restricted from moving in the vertical and horizontal directions, and the electrode assembly 14 and the gap filling member 50 are maintained facing each other in the stacking direction. Yes.

Next, the operation of the secondary battery 10 will be described.
In the secondary battery 10, the main body portion 50 b of the gap filling member 50 faces the entire surface of the positive electrode active material layer 23 via the negative electrode 24 and pressurizes in the stacking direction.

Next, a method for manufacturing the secondary battery 10 will be described.
First, a predetermined number of positive electrodes 21, negative electrodes 24, and separators 27 are stacked, a predetermined load is applied, and pressure is applied. The electrode assembly 14 is manufactured by positioning with the first holding tape 45 and the second holding tape 47 in a pressurized state. Next, the length of the electrode assembly 14 in the stacking direction is measured, the thickness of the gap filling member 50 is selected based on the length of the electrode assembly 14 in the stacking direction, and the gap filling having the selected thickness is selected. The member 50 is laminated on one end face 44 of the electrode assembly 14. Thereafter, the gap filling member 50 is integrated with the electrode assembly 14 with a holding tape (not shown), and the electrode assembly 14 and the gap filling member 50 are collectively inserted into the case body 12. Thereafter, the opening 12a of the case body 12 is closed with the lid 13 to manufacture the secondary battery 10.

According to the above embodiment, the following effects can be obtained.
(1) The main body portion 50 b of the gap filling member 50 faces the entire surface of the positive electrode active material layer 23 with the negative electrode 24 in the stacking direction of the electrode assembly 14. In other words, the entire surface of the welded portion 50 a of the gap filling member 50 faces the joint portion 27 g of the separator 27 through the negative electrode 24 in the stacking direction of the electrode assembly 14. The main body 50b of the gap filling member 50 is not welded, and there is no variation in thickness due to welding. Therefore, even if the gap filling member 50 has the welded portion 50a, the main body portion 50b can uniformly apply pressure to the entire surface of the active material layer 23 of the positive electrode. As a result, the distance between the active material layers 23 and 26 of the positive electrode and the negative electrode in the stacking direction of the electrode assembly 14 does not vary in the plane direction, and lithium ion precipitation can be suppressed.

  (2) The gap filling member 50 is a laminate of a plurality of sheet members 51, all of which are integrated. For this reason, a plurality of sheet members 51 can be handled collectively, and the productivity of the secondary battery 10 is increased as compared with the case where the sheet members 51 are handled one by one and the gap is filled.

  (3) The gap filling member 50 has a quadrangular annular welded portion 50 a that surrounds the main body portion 50 b, and the welded portion 50 a is provided over the entire circumference of the gap filling member 50. For this reason, it is possible to suppress the plurality of sheet members 51 from shifting in the surface direction, and to prevent the thickness of the main body 50b from fluctuating. Therefore, in the case 11, it is possible to maintain a state in which the entire surface of the main body portion 50 b is opposed to the entire surface of the positive electrode active material layer 23 via the negative electrode 24.

In addition, you may change the said embodiment as follows.
As shown in FIG. 6, the gap filling member 60 includes a plurality of first sheet members 61 as sheet members, and two second sheet members 62 as sheet members having a larger outer size than the first sheet members 61. It is good also as a laminated body which laminated | stacked. In the gap filling member 60, the direction in which the plurality of first sheet members 61 and the two second sheet members 62 overlap is defined as a stacking direction.

  The first sheet member 61 has a rectangular shape with a predetermined thickness and is made of resin. The lengths of the two adjacent sides of the first sheet member 61 (the length in the longitudinal direction and the length in the short direction) are the lengths of the two adjacent sides of the active material layer 23 of the positive electrode ( The length in the longitudinal direction and the length in the short direction are set slightly longer. That is, the first sheet member 61 is set to a size that can cover the surface of the positive electrode active material layer 23.

  The second sheet member 62 has a rectangular shape with a predetermined thickness and is made of resin. The lengths of the two adjacent sides of the second sheet member 62 (the length in the longitudinal direction and the length in the short direction) are the two adjacent sides of the positive electrode active material layer 23 and the first sheet member 61. Is set longer than the length of each side (the length in the longitudinal direction and the length in the short direction). That is, the outer size of the second sheet member 62 is larger than the outer size of the first sheet member 61, and the second sheet member 62 is set to a size that can cover the entire surface of the first sheet member 61.

  The second sheet member 62 includes a protruding portion 62a that protrudes toward the end edge of the second sheet member 62 rather than the four sides (four end edges) of the first sheet member 61 in the stacked state. The gap filling member 60 heat-bonds the opposite edge portions (protruding portions 62a) of the second sheet member 62 with the plurality of first sheet members 61 sandwiched between the two second sheet members 62. Is formed.

  The gap filling member 60 includes a welded portion 60a formed by welding the protruding portions 62a facing each other. The welded portion 60 a is a quadrangular ring surrounding the plurality of first sheet members 61. In the welded portion 60a, the lengths L2 along the surface of the gap filling member 60 and in the direction perpendicular to the four sides are all the same. The length L2 of the welded portion 60a is shorter than the length L1 of the joint portion 27g at the separator 27. Further, the gap filling member 60 has a main body 63 having a quadrangular shape in plan view surrounded by the welded portion 60a. The main body 63 is a laminated body in which the first sheet member 61 and the second sheet member 62 are combined.

  When comprised in this way, in addition to the effect similar to (1)-(2) of embodiment, the effect as described below can be acquired. That is, the gap filling member 60 is formed by sandwiching the first sheet member 61 between the two second sheet members 62. Even if the number of the first sheet members 61 is changed to adjust the thickness of the gap filling member 60, only the two second sheet members 62 are always welded. Therefore, the gap filling member 60 having a different thickness can be manufactured without changing the welding conditions, and the manufacturing of the gap filling member 60 can be made more efficient.

The number of sheet members 51 sandwiched between the two second sheet members 62 may be one, or the number of sheets may be appropriately changed according to the thickness of the gap filling member 60.
Moreover, as long as the external size of the 1st sheet member 61 pinched | interposed into the 2nd sheet member 62 is larger than the active material layer 23 of a positive electrode, you may differ in 1st sheet members 61 laminated | stacked.

The welding parts 50a and 60a of the gap filling members 50 and 60 may not be heat welding, but may be ultrasonic welding, vibration welding, induction welding, high frequency welding, laser welding, spin welding, and the like.
○ The gap filling members 50 and 60 were filled in the gap between one end surface 44 of the electrode assembly 14 and the inner surface 12f of one long side wall 12d, but both end surfaces 44 of the electrode assembly 14 and each end surface 44 The gap filling members 50 and 60 may be filled in the gap between the opposed long side wall 12d and the inner surface 12f.

The electrode assembly 14 is not limited to the laminated type, and may be a wound type in which a belt-like positive electrode and a belt-like negative electrode are wound and laminated in layers.
The positive electrode 21 has the active material layer 23 on both surfaces of the positive electrode metal foil 22, but may have the active material layer 23 only on one surface of the positive electrode metal foil 22. Similarly, the negative electrode 24 has the active material layer 26 on both sides of the negative electrode metal foil 25, but may have the active material layer 26 only on one side of the negative electrode metal foil 25.

The power storage device may be applied not to the secondary battery 10 but to another power storage device such as an electric double layer capacitor.
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.
(Circle) you may arrange | position the insulating sheet for preventing a short circuit between the electrode assembly 14 and the case main body 12. FIG. In this case, the gap filling member 50, the electrode assembly 14, the gap filling members 50, 60, and the length in the stacking direction including the insulating sheet are slightly shorter than the inner dimension of the case body 12. Adjust 60.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) The power storage device in which the welding portion is formed by heat welding.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery as a power storage device, 11 ... Case, 12f ... Inner surface, 14 ... Electrode assembly, 21 ... Positive electrode, 23, 26 ... Active material layer, 24 ... Negative electrode, 27 ... Separator, 27a ... Separator sheet , 44 ... end face, 50, 60 ... gap filling member, 50a, 60a ... welded part, 50b ... main body part, 51 ... sheet member, 61 ... first sheet member, 62 ... second sheet member, 63 ... main body part.

Claims (4)

An electrode assembly in which negative electrodes and positive electrodes wrapped with separators are alternately stacked;
A case containing the electrode assembly;
A gap filling member filled in a gap between an end face of the electrode assembly in the stacking direction and an inner face of the case facing the end face,
The separator is formed by welding edges of a pair of separator sheets facing each other,
The gap filling member is a laminate of a plurality of sheet members, and a welded portion in which edges of all the sheet members are welded together,
A main body part surrounded by the welding part,
In the stacking direction of the electrode assembly, the main body portion faces the entire surface of the active material layer of the positive electrode via the negative electrode.   The power storage device according to claim 1, wherein the gap filling member is welded over the entire circumference between edges of all the sheet members.   The gap filling member is a laminate of a first sheet member and a second sheet member having a larger outer size than the first sheet member, and one or more first sheet members are laminated in the laminate. 2. The power storage device according to claim 1, wherein the power storage device is configured to be sandwiched by the second sheet member from both sides in a direction, and an edge portion facing the stacking direction is welded to the second sheet member.   The power storage device according to any one of claims 1 to 3, wherein the power storage device is a secondary battery.