JP2018200840A - Power storage device - Google Patents

Abstract

To provide a power storage device in which a tab group can be insulated from a case body.SOLUTION: A secondary battery 10 comprises an insulation sheet 43 comprising a projection 44 at a portion projecting closer to a lid 23 than a tab side end surface 12a of an electrode assembly 12. The projection 44's tip 43f in a direction projecting from the tab side end surface 12a is positioned closer to the lid 23 than second junction surfaces 32b, 42b of a positive electrode conductive member 32 and negative electrode conductive member 42 and is away from the lid 23's internal surface 23c. A penetration direction Y of a weld portion 22 between a case body 13 and the lid 23 is the lid 23's plate thickness direction. Part of the weld portion 22 is exposed on the lid 23's external surface 23e.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power storage device including an insulating sheet that insulates an electrode assembly from a case body.

  Secondary batteries are widely used as a power source because they can be recharged and used repeatedly. Generally, a secondary battery includes a case, and an electrode assembly and an electrolytic solution are accommodated in the case. The electrode assembly has a positive electrode, a negative electrode, and a separator that insulates the positive electrode from the negative electrode, and has a laminated structure in which a separator is interposed between the positive electrode and the negative electrode.

  In the secondary battery, the positive electrode has a positive tab made of metal foil, and the negative electrode has a negative tab made of metal foil. The plurality of positive electrode tabs are electrically connected to the positive electrode conductive member in a state where they are stacked to form a tab group, and a positive electrode terminal is connected to the positive electrode conductive member. Similarly, a plurality of negative electrode tabs are overlapped to form a tab group and are electrically connected to a negative electrode conductive member, and a negative electrode terminal is connected to the negative electrode conductive member.

  The case of the secondary battery includes a case main body and a lid that closes an opening of the case main body, and the case main body and the lid are joined. In general, a case made of a metal such as aluminum having excellent durability is often used for a case of a secondary battery. In order to insulate the metal case from the electrode assembly, an insulating sheet is disposed between the electrode assembly and the case body. An insulating sheet is arrange | positioned not only to the active material layer of an electrode assembly but the position of a tab group, and insulates the outermost layer of a tab group and a case main body (for example, refer patent document 1).

WO2014 / 002647

  By the way, like patent document 1, in the structure which insulates a tab group and a case main body with an insulating sheet, at the time of welding of a case main body and a lid, an insulating sheet may melt and it may become impossible to insulate a tab group and a case main body. .

  The objective of this invention is providing the electrical storage apparatus which can insulate a tab group and a case main body.

  A power storage device for solving the above problems is formed by alternately laminating positive and negative electrodes in an insulated state, and tabs having a shape protruding from a part of one side of the electrodes have the same polarity in the laminating direction. An electrode assembly having a group of tabs gathered together, a metal case body containing the electrode assembly and having an opening, and a metal flat plate joined to an end face surrounding the opening and closing the opening A case having a lid made of metal, a welded portion obtained by joining the end face of the case main body, a mating portion of the lid facing the mating face facing the end face, the inner surface of the lid, and the electrode having the tab group A conductive member disposed between the tab-side end surface of the assembly and joined to the tab group; and an insulating sheet that insulates the electrode assembly and the case main body, the insulating sheet being on the tab side From the end surface to the lid side A protruding portion is provided at a portion that protrudes and is interposed between the tab group and the case main body, and a tip of the protruding portion in the protruding direction from the end surface on the tab side is from a joint surface of the conductive member with the tab group. Is also located on the lid side and spaced from the inner surface of the lid, the penetration direction of the welded portion is the plate thickness direction of the lid, and a part of the welded portion is in the plate thickness direction of the lid The gist is that only the outer surface is exposed.

  According to this, the tab group exists between the tab side end surface and the joint surface of the conductive member. And a protrusion part protrudes from a tab side end surface, and the front-end | tip of a protrusion part exists in a lid | cover side rather than the joint surface of an electrically-conductive member. For this reason, a tab group can be insulated from a case main body by the protrusion part of an insulating sheet.

  In such a protrusion, if the tip is too close to the inner surface of the lid, depending on how the case body and the lid are welded, the tip side of the protrusion is melted by the heat generated during welding, and the protrusion is connected to the tab group and the case. There is a possibility that the tab group and the case main body cannot be insulated because they cannot be interposed between the main bodies. Therefore, the tip of the protruding portion is configured to be separated from the inner surface of the lid, and for welding, welding is performed so that the penetration direction is in the plate thickness direction of the lid so that a part of the welded portion is exposed only on the outer surface of the lid. A part was formed, and so-called vertical strike was made. For this reason, compared to the case where a welding portion is formed along the end surface of the case main body and the mating surface of the lid by performing a so-called horizontal welding method, the case main body is closer to the tab group than the end surface. The amount of heat transmitted can be suppressed, and the amount of heat transmitted from the case body to the protruding portion can be suppressed. Therefore, at the time of welding, it can suppress that a protrusion part fuse | melts from a front-end | tip, and can insulate a tab group and a case main body with a protrusion part.

  Further, in the power storage device, the tab group is bent from one end side in the stacking direction toward the other end side, from the tip end side in the protruding direction of the tab, from the other end side in the stacking direction to one end side. It is preferable that the distal end side bent portion is bent toward the end, and the protruding portion is interposed between the distal end side bent portion and the case body.

  According to this, when the front end side bent part is not provided in the tab group, the front end of the tab group may come into contact with the protruding part to break through the protruding part, and the tab group and the case main body may be short-circuited. However, by providing the distal end side bent portion, the tip of the tab group can be prevented from coming into contact with the protruding portion, and the protruding portion can be prevented from being damaged.

  In the power storage device, the lid includes a top plate portion having the mating surface, and an insertion portion that protrudes from the top plate portion toward the electrode assembly and is inserted into the case body. Also good.

According to this, the heat at the time of welding is transmitted from the top plate portion to the insertion portion, and the amount of heat transmitted to the portion closer to the tab group than the end surface in the case body can be further suppressed.
In the power storage device, the positive electrode and the negative electrode may be insulated by a separator, and the insulating sheet may be formed of a material having a higher melting point than the separator.

  According to this, in the separator, the portion closest to the welded portion is located on the tab side end surface, and the separator is not easily affected by heat during welding. On the other hand, an insulating sheet having a protruding portion is closer to a welded portion than a separator and is easily affected by heat. Even if it is a member which has the same insulation function, melting | fusing of a protrusion part can be suppressed by manufacturing an insulating sheet with a material with high melting | fusing point.

  The power storage device is a secondary battery.

  According to the present invention, the tab group and the case main body can be insulated.

The disassembled perspective view which shows the secondary battery of embodiment. (A) is sectional drawing which shows a secondary battery, (b) is an expanded sectional view which shows the welding part vicinity. The disassembled perspective view which shows the component of an electrode assembly. Sectional drawing which shows the inside of a secondary battery.

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 or FIG. 2A, a secondary battery 10 as a power storage device includes a rectangular parallelepiped case 11, and an electrode assembly 12 is accommodated in the case 11. The case 11 is made of metal with a bottomed rectangular tube shape (for example, made of aluminum or aluminum alloy), and includes a case main body 13 having an opening 13g and a lid 23 that closes the opening 13g of the case main body 13.

  The case main body 13 includes a rectangular bottom wall 13a, first wall portions 13b and 13c erected from a pair of long sides of the bottom wall 13a, and a second erected from a pair of short sides of the bottom wall 13a. It has wall parts 13d and 13e. Hereinafter, a direction in which the bottom wall 13 a of the case body 13 and the lid 23 are connected at the shortest distance is referred to as a depth direction X of the case 11.

  The lid 23 has a rectangular flat plate shape. The lid 23 includes a top plate portion 23 a that closes the opening 13 g of the case main body 13, and a rectangular plate-shaped insertion portion 23 b that is positioned inside the top plate portion 23 a and is inserted into the case main body 13. Have.

  As shown in FIG. 2B, the top plate portion 23a includes a mating surface 23d on a surface supported by an end surface 13f surrounding the opening 13g of the case body 13, and the mating surface 23d is a square surrounding the insertion portion 23b. Annular.

  The case 11 includes a welded portion 22 in which a mating portion F of the end surface 13f of the case main body 13 and the mating surface 23d of the top plate portion 23a (lid 23) is welded. The case main body 13 and the lid 23 are joined by a welded portion 22. The lid 23 includes an inner surface 23c on the end surface of the insertion portion 23b of one surface in the plate thickness direction D, and an outer surface 23e on the other surface in the plate thickness direction. The plate thickness direction D coincides with the depth direction X.

  The welded portion 22 is formed by irradiating laser from the outer surface 23e of the top plate portion 23a toward the end surface 13f of the case main body 13 to melt and harden the top plate portion 23a and the case main body 13. The welded portion 22 is formed by so-called vertical strike. Therefore, the penetration direction Y of the welded portion 22 is the same as the plate thickness direction D of the lid 23. The penetration direction Y is orthogonal to the end surface 13f of the case body 13 and the mating surface 23d of the top plate portion 23a. Since the welded portion 22 is formed by vertical striking, the welded portion 22 that can be seen from the outside of the case 11 is only the portion exposed on the outer surface 23 e of the lid 23, and cannot be seen by the case main body 13.

An electrolyte (electrolytic solution) (not shown) is accommodated in the case 11. The secondary battery 10 of this embodiment is a lithium ion secondary battery.
As shown in FIG. 3, the electrode assembly 12 includes a plurality of electrode storage separators 20 that store the positive electrodes 14 and a plurality of negative electrodes 24. The electrode assembly 12 has a layered structure in which a plurality of electrode storage separators 20 and a plurality of negative electrodes 24 are alternately stacked. The positive electrodes 14 and the negative electrodes 24 are alternately stacked with the single-layer separator 21 of the electrode storage separator 20 interposed therebetween. In the present embodiment, the positive electrode 14, the single layer separator 21, and the negative electrode 24 are all rectangular. The direction in which the electrode storage separator 20 and the negative electrode 24 are stacked is defined as the electrode stacking direction.

  The positive electrode 14 includes a rectangular sheet-like positive metal foil (for example, aluminum foil) 15 and a positive electrode active material layer 16 present on both surfaces of the positive metal foil 15. The positive electrode 14 includes an uncoated portion 15a where the positive metal foil 15 is exposed along one edge portion 14a of the edge portions along the pair of long sides. The uncoated portion 15a includes a positive electrode tab 17 protruding from a part of the edge portion 14a. The uncoated portion 15a is a portion constituted by the positive electrode metal foil 15 itself without being coated with the positive electrode active material layer 16.

  The negative electrode 24 includes a rectangular sheet-like negative electrode metal foil (for example, copper foil) 25 and a negative electrode active material layer 26 present on both surfaces of the negative electrode metal foil 25. The negative electrode 24 has a negative electrode tab 27 protruding from a part of the edge 24a along one long side of the pair of long sides. The negative electrode tab 27 is a portion made of the negative electrode metal foil 25 itself without being coated with the negative electrode active material layer 26.

  The electrode storage separator 20 is made of an insulating resin (polyethylene in the present embodiment). The electrode assembly 12 is held in a laminated state by a holding tape (not shown), and the entire surface of the positive electrode active material layer 16 is maintained facing the negative electrode active material layer 26 via the single-layer separator 21. In the electrode assembly 12, the plurality of electrode storage separators 20 and the plurality of negative electrodes 24 are arranged such that the positive electrode tabs 17 are arranged in a row along the stacking direction, and the negative electrode tabs 27 are aligned along the stacking direction. They are stacked in a row.

  As shown in FIG. 1 or FIG. 2A, the electrode assembly 12 includes a tab-side end surface 12 a on an end surface facing the lid 23. The electrode assembly 12 includes a positive electrode tab group 17a and a negative electrode tab group 27a on the tab side end face 12a. The tab-side end surface 12a is configured by laminating the edge portion of the electrode storage separator 20 and the edge portion 24a of the negative electrode 24. The positive electrode tab group 17 a is configured by stacking the positive electrode tabs 17, and the negative electrode tab group 27 a is configured by stacking the negative electrode tabs 27.

  Next, the tab groups 17a and 27a will be described. In FIG. 4, the negative electrode tab group 27 a is illustrated, but the positive electrode tab group 17 a has the same structure, and thus the positive electrode tab group 17 a is omitted. In the following description, if the negative electrode is read as the positive electrode, the positive electrode tab group 17a is described.

  As shown in FIG. 4, in the tab group 27a, the tab 27 positioned at one end in the stacking direction is referred to as a first tab 271. In the tab group 27a, the tab 27 positioned at the other end in the stacking direction is referred to as a second tab 272.

  In the tab group 27a, the tabs 27 are gathered on one end side in the stacking direction so that the second tab 272 approaches the first tab 271. As a result, the tabs 27 that were independent in the stacking stage are collected on the first tab 271 side.

  In this embodiment, each tab 27 is formed in the same size. For this reason, in the stacking direction, the tab 27 that is separated from the first tab 271 has a shorter length of the tab 27 that is aggregated as the tab group 27a. For this reason, the conduction | electrical_connection part W for making all the tabs 27 conduct | electrically_connect is provided according to the superposition | polymerization area | region with the other tab 27 in the 2nd tab 272. FIG. Further, in the tab group 27a, all the tabs 27 are free ends on the distal end side with respect to the conduction portion W.

  The tab groups 17a and 27a include a proximal-side bent portion 37 on the tab-side end surface 12a side. In the tab groups 17a and 27a, the base end side bent portion 37 includes a portion gathered near one end side in the stacking direction and a portion bent from one end side in the stacking direction toward the other end side in the stacking direction. The tab groups 17a and 27a include an extending portion 38. The extending portion 38 is a portion that extends from the proximal end side bent portion 37 in the stacking direction of the electrode assembly 12. The extending portion 38 has a shape that extends in the stacking direction from the proximal-side bent portion 37 along the inner surface 23 c of the lid 23. The extension portion 38 is provided with the conduction portion W. Further, the tab groups 17a and 27a are provided with a distal end side bent portion 39 that is bent toward the one end side from the other end side in the stacking direction on the distal end side from the extending portion 38. The distal end side bent portion 39 is located on the distal end side with respect to the extending portion 38 in the protruding direction of the tabs 17 and 27 from the tab side end surface 12a.

  As shown in FIG. 1 or FIG. 2A, the secondary battery 10 includes a positive electrode conductive member 32. The positive electrode conductive member 32 electrically connects the electrode assembly 12 and the positive electrode terminal 30. The positive terminal 30 is joined to the positive conductive member 32. A part of the positive electrode terminal 30 penetrates the lid 23 and protrudes to the outside of the case 11. The positive electrode terminal 30 and the lid 23 are insulated by an insulating member (not shown).

  The positive electrode conductive member 32 includes a first bonding surface 32a on the surface to which the positive electrode terminal 30 is bonded. The positive electrode tab group 17a and the positive electrode conductive member 32 are welded in a state where the positive electrode conductive member 32 is in contact with the tab group 17a to form a conductive portion W and are electrically connected. Yes (conducted). The positive electrode conductive member 32 is a surface to which the tab group 17a is bonded, and includes a second bonding surface 32b on the surface on the tab side end surface 12a side.

  The secondary battery 10 includes a negative electrode conductive member 42. The negative electrode conductive member 42 electrically connects the electrode assembly 12 and the negative electrode terminal 40. The negative electrode terminal 40 is joined to the negative electrode conductive member 42. A part of the negative terminal 40 protrudes outside the case 11 through the lid 23. The negative electrode terminal 40 and the lid 23 are insulated by an insulating member (not shown).

  The negative electrode conductive member 42 includes a first bonding surface 42a on the surface to which the negative electrode terminal 40 is bonded. The negative electrode tab group 27a and the negative electrode conductive member 42 are welded in a state where the negative electrode conductive member 42 is in contact with the tab group 27a to form a conductive portion W and are electrically connected. Yes (conducted). The negative electrode conductive member 42 is a surface to which the tab group 27a is bonded, and includes a second bonding surface 42b on the surface on the tab side end surface 12a side.

  The secondary battery 10 includes an insulating sheet 43 that insulates the case body 13 and the electrode assembly 12. The insulating sheet 43 is formed in a square box shape by bending one film material. The insulating sheet 43 is made of homopolymerized polypropylene. The melting point of the homopolymerized polypropylene is higher than the melting point of polyethylene which is the material of the electrode housing separator 20.

  The insulating sheet 43 includes a rectangular bottom 43a, first side portions 43b and 43c extending from the long side of the bottom portion 43a toward the lid 23, and a second side portion 43d extending from the short side of the bottom portion 43a toward the lid 23. , 43e. The insulating sheet 43 is disposed in a part of the case body 13 that faces the electrode assembly 12.

  The bottom 43a of the insulating sheet 43 insulates the bottom wall 13a of the case main body 13 and the electrode assembly 12, and the first side parts 43b and 43c of the insulating sheet 43 are connected to the first wall 13b and 13c of the case main body 13 and the electrode. Insulate the assembly 12. Further, the second side portions 43 d and 43 e of the insulating sheet 43 insulate the second wall portions 13 d and 13 e of the case body 13 from the electrode assembly 12.

  As shown in FIG. 2A or 4, the insulating sheet 43 includes a square annular projecting portion 44 at a portion projecting from the tab side end surface 12 a of the electrode assembly 12 toward the lid 23. In the depth direction X, the distal end 43 f of the protrusion 44 is located closer to the lid 23 than the second joint surface 32 b of the positive electrode conductive member 32 and the second joint surface 42 b of the negative electrode conductive member 42. Further, the distal end 43 f of the projecting portion 44 is located closer to the electrode assembly 12 than the first joint surface 32 a of the positive electrode conductive member 32 and the first joint surface 42 a of the negative electrode conductive member 42. Therefore, the tip 43 f of the protrusion 44 is located within the thickness of the positive electrode conductive member 32 and the negative electrode conductive member 42.

  One first side portion 43b of the insulating sheet 43 insulates the proximal end side bent portion 37 and the first wall portion 13b in the tab groups 17a and 27a, and the other first side portion 43c is in the tab groups 17a and 27a. The distal end side bent portion 39 and the first wall portion 13c are insulated.

  The distal end 43f of the protruding portion 44 is at a position farther away from the welded portion 22 in the depth direction X toward the tab side end surface 12a. The tip 43f of the protrusion 44 is in a position where it does not melt due to heat generated when welding the case body 13 and the lid 23 (hereinafter referred to as welding heat). The welding heat varies depending on the laser output, irradiation time, irradiation angle, and the like. The position of the tip 43f of the protrusion 44 is adjusted according to the laser welding conditions. The smaller the amount of welding heat generated, the closer the distal end 43f of the projecting portion 44 can be to the lid 23 along the depth direction, and the proximal end side bent portion 37 and the distal end side bent portion 39 come into contact with the case body 13. The fear can be reduced.

Next, the operation of the secondary battery 10 will be described.
In the insulating sheet 43, the base end side bent portion 37 and the distal end side bent portion 39 of the tab groups 17 a and 27 a are insulated from the case body 13 by the protruding portion 44 protruding from the tab side end surface 12 a of the electrode assembly 12 to the lid 23 side. it can.

According to the above embodiment, the following effects can be obtained.
(1) The tip 43f of the projecting portion 44 is positioned closer to the lid 23 than the first joint surfaces 32a and 42a of the conductive members 32 and 42, and the tab groups 17a and 27a are insulated from the case body 13. Further, the distal end 43f of the protruding portion 44 was separated from the inner surface 23c of the lid 23, and the welded portion 22 was vertically hit. For this reason, compared to the case where the welded portion 22 is formed along the end surface 13f of the case body 13 and the mating surface 23d of the lid 23, the portion of the case body 13 that is closer to the tab groups 17a and 27a than the end surface 13f. Therefore, the amount of heat transmitted to the protrusion 44 can be suppressed from the case body 13. Therefore, it can suppress that the protrusion part 44 fuse | melts from the front-end | tip 43f at the time of welding, Even if it is the structure which protruded the protrusion part 44 from the tab side end surface 12a, the tab groups 17a and 27a and the case main body 13 can be insulated.

  (2) By protruding the protruding portion 44 of the insulating sheet 43 from the tab side end surface 12a toward the lid 23, the tab groups 17a and 27a and the case main body 13 can be insulated. Therefore, compared with the case where the tab groups 17a and 27a and the case main body 13 are insulated by components other than the insulating sheet 43, the tab groups 17a and 27a and the case main body 13 can be insulated with a simple configuration.

  (3) The tab groups 17 a and 27 a include a distal end side bent portion 39. For this reason, it can suppress that the front-end | tip of tab group 17a, 27a contacts the protrusion part 44, and can suppress that the protrusion part 44 is damaged.

  (4) The lid 23 includes a top plate portion 23a and an insertion portion 23b, and the insertion portion 23b is a portion that is thicker than the top plate portion 23a. And when welding the case main body 13 and the lid | cover 23, welding heat is transmitted to the insertion part 23b from the top-plate part 23a, and suppresses the calorie | heat amount transmitted to the part close | similar to the tab groups 17a and 27a rather than the end surface 13f in the case main body 13. Can do. Therefore, the protruding portion 44 can be further hardly melted.

  (5) The insulating sheet 43 was made of homopolymerized polypropylene, and the electrode storage separator 20 was made of polyethylene. While the electrode storage separator 20 is not easily affected by heat during welding, the tip 43f of the protrusion 44 is easily affected by heat during welding. For this reason, even if it is the polypropylene and polyethylene which have the same insulation, the melting of the protrusion part 44 can be suppressed by manufacturing the insulating sheet 43 with the polypropylene with the higher melting point.

In addition, you may change the said embodiment as follows.
○ The material of the insulating sheet 43 may be polyethylene or other insulating material.

The separator is the bag-shaped electrode storage separator 20, but may be a sheet-shaped single-layer separator 21 that is not a bag.
The lid 23 may not be provided with the insertion portion 23b, and may have only the top plate portion 23a.

The tab groups 17a and 27a may not include the distal end side bent portion 39. Further, the distal end side of the conduction portion W may not be bent.
The front end 43f of the projecting portion 44 is closer to the lid 23 than the second joint surface 32b of the positive electrode conductive member 32 and the second joint surface 42b of the negative electrode conductive member 42, and the first joint surface 32a of the positive electrode conductive member 32 and the negative electrode The conductive member 42 may be located closer to the lid 23 than the first joint surface 42a.

  The negative electrode 24 has the negative electrode active material layer 26 on both sides of the negative electrode metal foil 25, but may have the negative electrode active material layer 26 only on one side of the negative electrode metal foil 25. Similarly, the positive electrode 14 has the positive electrode active material layer 16 on both sides of the positive electrode metal foil 15, but may have the positive electrode active material layer 16 only on one side of the positive electrode metal foil 15.

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 material may be used as long as ions move between the positive electrode active material and the negative electrode active material and transfer charge.

  F ... mating part, Y ... penetration direction, 10 ... secondary battery as a power storage device, 11 ... case, 23 ... lid, 12 ... electrode assembly, 12a ... tab side end face, 13 ... case main body, 13f ... end face, 13g ... opening, 14 ... positive electrode as electrode, 17, 27 ... tab, 17a, 27a ... tab group, 20 ... electrode storage separator as separator, 22 ... weld, 23 ... lid, 23a ... top plate, 23b ... insertion portion, 23c ... inner surface, 23d ... mating surface, 23e ... outer surface, 24 ... negative electrode as an electrode, 32 ... positive electrode conductive member as a conductive member, 32b ... second joint surface, 39 ... tip side bent portion, 42 ... Negative electrode conductive member as a conductive member, 42b ... Second joint surface, 43 ... Insulating sheet, 43f ... Tip, 44 ... Projection.

Claims (5)

An electrode assembly having a tab group in which positive and negative electrodes are alternately stacked in an insulated state, and tabs having shapes protruding from a part of one side of the electrode are gathered in the stacking direction with the same polarity. ,
A case that has a metal plate body that accommodates the electrode assembly and has an opening, and a metal plate lid that is joined to an end surface surrounding the opening and closes the opening;
A welded portion that joins a mating portion between the end surface of the case body and a mating surface facing the end surface in the lid;
A conductive member disposed between the inner surface of the lid and the tab side end surface of the electrode assembly in which the tab group exists, and joined to the tab group;
An insulating sheet for insulating the electrode assembly and the case body,
The insulating sheet protrudes from the tab side end surface to the lid side, and includes a protruding portion at a portion interposed between the tab group and the case body,
The tip of the protruding portion in the protruding direction from the tab side end surface of the protruding portion is located closer to the lid than the joint surface with the tab group of the conductive member, and is separated from the inner surface of the lid,
The welding direction of the welded portion is the plate thickness direction of the lid, and a part of the welded portion is exposed only on the outer surface in the plate thickness direction of the lid.   The tab group is bent from one end side in the stacking direction toward the other end side, and is bent toward the tip end side in the protruding direction of the tab and from the other end side in the stacking direction toward the one end side. The power storage device according to claim 1, further comprising a side bent portion, wherein the protruding portion is interposed between the tip side bent portion and the case body.   The said lid | cover has a top plate part which has the said mating surface, and the insertion part which protrudes toward the said electrode assembly from the said top plate part, and is inserted in the said case main body. Power storage device.   The electrical storage according to any one of claims 1 to 3, wherein the positive electrode and the negative electrode are insulated by a separator, and the insulating sheet is formed of a material having a melting point higher than that of the separator. apparatus.   The power storage device according to any one of claims 1 to 4, wherein the power storage device is a secondary battery.