WO2017073745A1

WO2017073745A1 - Electrode assembly

Info

Publication number: WO2017073745A1
Application number: PCT/JP2016/082105
Authority: WO
Inventors: 真也奥田; 雅人小笠原; 雅巳冨岡
Original assignee: 株式会社豊田自動織機
Priority date: 2015-10-29
Filing date: 2016-10-28
Publication date: 2017-05-04
Also published as: JPWO2017073745A1; JP6834972B2

Abstract

This electrode assembly, which has multiple electrodes each having a main body and a tab projecting from one edge of a main body, is provided with electrode main body having the multiple laminated main bodies, and a tab laminate having the multiple laminated tabs and projecting from the electrode main body. In the tab laminate, in the leading end portion in the direction of projection of the tab laminate, the leading ends of the tabs are arranged staggered in the projection direction. The tab laminate has a welded portion located inside from a first end surface of the tab laminate, which extends in the direction of lamination of the tab laminate and in the direction of projection of the tab laminate.

Description

Electrode assembly

One aspect of the invention relates to an electrode assembly.

A power storage device such as a lithium ion battery includes an electrode assembly in which a plurality of electrodes are stacked. Each electrode has a tab, and when manufacturing the electrode assembly, the tabs of the stacked electrodes are welded. Welding is performed, for example, by irradiating the end face of the stacked tabs with an energy beam. (See, for example, Patent Document 1).

JP 2002-313309 A

In the tip portion of the stacked tabs (hereinafter sometimes referred to as "tab stack"), there are many cases where the positions of the tips of the tabs are shifted. When an energy beam is applied to the front end portion of the tab stack while the front end of each tab is misaligned, a weld of a depth sufficient to join the plurality of tabs is inward from the front end of each tab There is a possibility that the joint strength between the tabs is insufficient.

An object of the present invention is to provide an electrode assembly in which bonding strength between a plurality of stacked tabs is secured even when the position of the tip of each tab is shifted.

An electrode assembly according to one aspect of the present invention is an electrode assembly having a plurality of electrodes each including a main body and a tab projecting from one end of the main body, the electrode main body having a plurality of stacked main bodies, A tab laminate having a plurality of tabs formed and projecting from the electrode body, in the tab laminate, the tips of the plurality of tabs are arranged to be offset in the protrusion direction at the tip portion of the tab laminate in the protrusion direction The tab stack has a weld located inwardly from the first end face of the tab stack extending along the stack direction of the tab stack and the protruding direction of the tab stack.

The above electrode assembly comprises an electrode body having a plurality of stacked bodies, and a tab laminate having a plurality of stacked tabs and projecting from the electrode body. The positions of the tips of the plurality of tabs are offset in the projecting direction at the tip end portion of the tab stack in the projecting direction. In the above-described electrode assembly, the tab laminate has the weld located inside from the first end face of the tab laminate extending along the stacking direction of the tab laminate and the projecting direction of the tab laminate. Unlike the leading end portion of the tab laminate, the first end face of the tab laminate has a small amount of displacement. Therefore, a weld of sufficient depth can be formed inward from the first end face of the tab stack. Thus, the bonding strength between the plurality of stacked tabs can be secured.

The tab stack may further include another weld extending along the stacking direction and the protruding direction and located inward from the second end surface different from the first end surface. Thereby, the joint strength between the stacked tabs can be enhanced as compared with the case where the welded portion is positioned on only one end face.

The plurality of tabs may be connected to one another by welds without using a member positioned across the tab stack in the stacking direction. For example, a method of improving the bonding strength between the plurality of tabs by using a member positioned across the tab stacks in the stacking direction may be considered, but according to the above-mentioned electrode assembly, a plurality of stacked layers by welding portions Such a member can be made unnecessary since the joint strength between the tabs is secured.

The electrode assembly is a laminated type, and the electrode assembly includes two electrode bodies having opposite polarities to each other, and the above-mentioned tab laminates project a plurality of stacked tabs from the electrode body having one polarity. A first tab stack having a plurality of tabs, and the electrode assembly is a second tab stack having a plurality of tabs protrudingly stacked from the electrode body having the other polarity, the second tab stack being stacked A second tab stack having a weld located inwardly from an end face of the second tab stack extending along the direction and the protruding direction of the second tab stack; In the body, the positions of the tips of the plurality of tabs in the second tab stack are offset in the direction of protrusion of the second tab stack at the tip portion of the second tab stack in the protrusion direction, Tab stack and the second tab stack are the same It protrudes toward, may first tab laminate and the second tab laminate is folded.

The electrode assembly further includes a current collector, and the tab stack is disposed on the current collector in the stacking direction, and the first end face of the tab stack in a cross section orthogonal to the protruding direction of the tab stack. The length of the weld in the inward direction may increase as it approaches the current collector. Thus, when the tab laminate is disposed on the current collector, the bonding strength of the stacked plurality of tabs to the current collector can be enhanced.

The tab laminate is disposed between the conductive member and the current collector in the lamination direction of the tab laminate, and the thickness of the conductive member in the lamination direction of the tab laminate is in the lamination direction of the tab laminate. It may be smaller than the thickness of the current collector.

In this case, since the thickness of the conductive member is relatively small, the difference between the heat capacity of the conductive member and the heat capacity of the tab can be reduced.

In the first end face of the tab laminate, the maximum length of the weld in a direction orthogonal to the lamination direction of the tab laminate is orthogonal to the lamination direction of the tab laminate and the lamination direction of the tab laminate When viewed from a direction orthogonal to both of the directions, it may be larger than the maximum length of the overlapping portion of the welded portion and the tab laminate in the laminating direction of the tab laminate.

In this case, at the first end face of the tab laminate, the weld extends in the direction intersecting the stacking direction of the tab laminate. As a result, when current flows in the stacking direction in the weld, the electrical resistance between the plurality of tabs can be reduced.

In a cross section of the tab laminate including the stacking direction of the tab laminate and orthogonal to the first end face of the tab laminate, the maximum welding depth of the weld in a direction orthogonal to the stacking direction of the tab laminate May be less than 2 mm.

When viewed in the normal direction of the first end face of the tab stack, the weld portion may have an outer shape including a curve.

In this case, since the stress is not easily concentrated at the curved portion of the outer shape of the welded portion, the welded portion is not easily peeled off.

According to one aspect of the present invention, an electrode assembly is provided in which bonding strength between a plurality of stacked tabs is secured even when the position of the tip of each tab is shifted.

FIG. 1 is an exploded perspective view of a power storage device provided with an electrode assembly according to the embodiment. FIG. 2 is a cross-sectional view of the storage battery taken along line II-II of FIG. FIG. 3 is a perspective view of an electrode assembly according to the embodiment. FIG. 4 is a view showing a part of the electrode assembly of FIG. 3 viewed from the Y-axis direction. FIG. 5 is a view showing a part of the electrode assembly of FIG. 3 as viewed in the X-axis direction. FIG. 6 is a diagram showing one step of the method of manufacturing the electrode assembly according to the embodiment. FIG. 7 is a diagram showing a process of the method of manufacturing the electrode assembly according to the embodiment. FIG. 8 is a view showing a part of an electrode assembly having a weld according to a modification. FIG. 9 is a diagram showing the evaluation results of the example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and the overlapping description is omitted. In the drawings, an XYZ orthogonal coordinate system is shown as needed. The Z-axis direction is, for example, the vertical direction, and the X-axis direction and the Y-axis direction are, for example, the horizontal direction.

FIG. 1 is an exploded perspective view of a power storage device provided with an electrode assembly according to the embodiment. FIG. 2 is a cross-sectional view of the power storage device taken along line II-II of FIG. The power storage device 1 shown in FIGS. 1 and 2 is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery or an electric double layer capacitor.

As shown in FIGS. 1 and 2, the power storage device 1 includes, for example, a hollow case 2 having a substantially rectangular parallelepiped shape, and an electrode assembly 3 accommodated in the case 2. The case 2 is formed of, for example, a metal such as aluminum. The case 2 has a main body 2a opened on one side and a lid 2b closing the opening of the main body 2a. An insulating film (not shown) is provided on the inner wall surface of the case 2. For example, a non-aqueous (organic solvent based) electrolyte solution is injected into the inside of the case 2. In the electrode assembly 3, the positive electrode active material layer 15 of the positive electrode 11, the negative electrode active material layer 18 of the negative electrode 12, and the separator 13 described later are porous, and the pores are impregnated with the electrolyte solution . The positive electrode terminal 5 and the negative electrode terminal 6 are disposed apart from each other in the lid 2 b of the case 2. The positive electrode terminal 5 is fixed to the case 2 via the insulating ring 7, and the negative electrode terminal 6 is fixed to the case 2 via the insulating ring 8.

The electrode assembly 3 is a stacked electrode assembly. The electrode assembly 3 includes a plurality of positive electrodes 11 (electrodes), a plurality of negative electrodes 12 (electrodes), and a bag-like separator 13 disposed between the positive electrodes 11 and the negative electrodes 12. The positive electrode 11 and the negative electrode 12 have opposite polarities to each other. For example, the positive electrode 11 is accommodated in the separator 13. A plurality of positive electrodes 11 and a plurality of negative electrodes 12 are alternately stacked via the separator 13 in a state where the positive electrode 11 is accommodated in the separator 13.

The positive electrode 11 has a metal foil 14 made of, for example, aluminum foil, and a positive electrode active material layer 15 formed on both sides of the metal foil 14. The metal foil 14 of the positive electrode 11 includes a rectangular main body 14 a and a rectangular tab 14 b projecting from one end of the main body 14 a. The positive electrode active material layer 15 is a porous layer formed by containing a positive electrode active material and a binder. The positive electrode active material layer 15 is formed by supporting a positive electrode active material on at least a central portion of the main body 14 a on both sides of the main body 14 a.

Examples of the positive electrode active material include composite oxides, metallic lithium, sulfur and the like. The composite oxide includes, for example, at least one of manganese, nickel, cobalt and aluminum, and lithium. Here, as an example, the positive electrode active material is not supported on the tab 14 b. However, an active material may be supported on the base end portion of the tab 14 b on the main body 14 a side.

The tab 14b extends upward from the upper edge of the main body 14a, and is connected to the positive electrode terminal 5 through the current collector 16 (current collector). The current collector 16 is disposed between the tab 14 b and the positive electrode terminal 5. The current collector plate 16 is formed of, for example, the same material as the metal foil 14 of the positive electrode 11 in a rectangular flat plate shape. The plurality of stacked tabs 14 b are disposed between the current collector 16 and the protective plate 23 (conductive member) thinner than the current collector 16 (see FIG. 3). The protective plate 23 is made of, for example, the same material as the metal foil 14 of the positive electrode 11 in the shape of a rectangular flat plate.

The negative electrode 12 has, for example, a metal foil 17 made of copper foil and a negative electrode active material layer 18 formed on both sides of the metal foil 17. Similar to the metal foil 14 of the positive electrode 11, the metal foil 17 of the negative electrode 12 includes a rectangular main body 17a and a rectangular tab 17b protruding from one end of the main body 17a. The negative electrode active material layer 18 is formed by supporting the negative electrode active material on at least a central portion of the main body 17 a on both sides of the main body 17 a. The negative electrode active material layer 18 is a porous layer formed by containing a negative electrode active material and a binder.

As the negative electrode active material, for example, graphite, highly oriented graphite, meso carbon micro beads, hard carbon, carbon such as soft carbon, alkali metals such as lithium and sodium, metal compounds, SiO x (0.5 ≦ x ≦ 1.5) Etc., boron-added carbon, and the like. Here, as an example, the negative electrode active material is not supported on the tab 17 b. However, the active material may be supported on the proximal end portion of the tab 17b on the main body 17a side.

The tab 17b extends upward from the upper edge of the main body 17a, and is connected to the negative electrode terminal 6 via the current collector 19 (current collector). The current collecting plate 19 is disposed between the tab 17 b and the negative electrode terminal 6. The current collector 19 is formed, for example, in the shape of a rectangular flat plate from the same material as the metal foil 17 of the negative electrode 12. The plurality of stacked tabs 17 b are disposed between the current collecting plate 19 and the protective plate 27 (conductive member) thinner than the current collecting plate 19 (see FIG. 3). The protective plate 27 is made of, for example, the same material as the metal foil 17 of the negative electrode 12 in a rectangular flat plate shape.

The separator 13 accommodates the positive electrode 11. The separator 13 has a rectangular shape as viewed from the stacking direction of the positive electrode 11 and the negative electrode 12. The separator 13 is formed, for example, in a bag shape by welding a pair of long sheet-like separator members to each other. Examples of the material of the separator 13 include porous films made of polyolefin resins such as polyethylene (PE) and polypropylene (PP), and woven or non-woven fabrics made of polypropylene, polyethylene terephthalate (PET), methyl cellulose and the like.

FIG. 3 is a perspective view of an electrode assembly according to the embodiment. The electrode assembly 3 includes a plurality of positive electrodes 11 and a plurality of negative electrodes 12 stacked one on another via a separator 13. Each of the plurality of positive electrodes 11 includes a main body 14a extending in the XY plane, and a tab 14b protruding from one end of the main body 14a in the X-axis direction (direction orthogonal to the side surface S described later). Each of the plurality of negative electrodes 12 includes a main body 17a extending in the XY plane, and a tab 17b protruding in the X-axis direction from one end of the main body 17a. The

main bodies

14a and 17a are stacked on each other to constitute an electrode main body 20 as a whole. The electrode body 20 has a side surface S. The side surface S is constituted by one end of the stacked

main bodies

14a, 17a. The

tabs

14b and 17b are stacked on one another to form tab stacks 21 and 25, respectively. That is, the electrode assembly 3 includes an electrode body 20 having a plurality of 14a and 17b stacked in the Z-axis direction, a tab stack 21 having a plurality of tabs 14b stacked in the Z-axis direction, and the Z-axis direction. And a tab stack 25 having a plurality of stacked tabs 17b. The tab stacks 21 and 25 protrude from the side surface S of the electrode body 20 in the X-axis direction. The tab stacks 21 and 25 are arranged separately from each other in the Y-axis direction.

The tab stack 21 includes end faces 21 a, 21 b, 21 c of the tab stack 21 extending along the stack direction (Z-axis direction) of the tab stack 21. The end surfaces 21a and 21b are surfaces sandwiching the tab stack 21, and the end surface 21c is a surface connecting the end surfaces 21a and 21b. That is, the end faces 21 a and 21 b are disposed on the opposite sides of the tab stack 21. The end surfaces 21a and 21b are surfaces along the XZ plane. The end surface 21 c is a surface inclined with respect to the XY plane so that the thickness of the tab laminate 21 decreases toward the tip of the tab laminate 21.

The tab stack 21 is disposed between the current collector 16 and the protective plate 23 in the Z-axis direction. That is, the tab stack 21 is disposed on the current collector 16 in the Z-axis direction. The protective plate 23 is disposed on the tab laminate 21 on the opposite side of the current collector plate 16 with the tab laminate 21 interposed therebetween. The protective plate 23 is not in contact with the current collector 16, and the protective plate 23 and the current collector 16 are separated by sandwiching the tab laminate 21 in the stacking direction. The tab laminate 21 is thicker than the protective plate 23, and the current collector 16 is thicker than the protective plate 23. The thickness of the protective plate 23 is larger than the thickness of the tab 14 b.

The length of the current collector plate 16 in the Y-axis direction is larger than the length of the tab laminate 21 in the Y-axis direction (the distance between the end faces 21a and 21b). In the Y-axis direction, the position of the outer end of the current collector plate 16 in the Y-axis direction coincides with the position of the end of the main body 14 a in the Y-axis direction. The length of the protective plate 23 in the Y-axis direction is substantially the same as the length of the tab laminate 21 in the Y-axis direction.

The tab laminate 21 has welds W located on the inner side from the end faces 21 a and 21 b of the tab laminate 21. The maximum length W2 of the weld W in the direction (for example, the X-axis direction) orthogonal to the lamination direction of the tab laminate 21 at the end faces 21a and 21b of the tab laminate 21 is the lamination direction of the tab laminate 21 (for example, Z-axis direction When viewed from the direction (for example, the Y-axis direction) orthogonal to both the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab laminate 21 (for example, the Z-axis direction) And the maximum length W1 of the overlapping portion of the welded portion W and the tab laminate 21 (see FIGS. 3 and 4). The weld portion W will be described in detail later with reference to FIG.

Similarly, the tab stack 25 includes

end surfaces

25a, 25b, 25c of the tab stack 25 extending along the stack direction (Z-axis direction) of the tab stack 25. The end surfaces 25a and 25b are surfaces sandwiching the tab stack 25, and the end surface 25c is a surface connecting the end surfaces 25a and 25b. That is, the end faces 25 a and 25 b are disposed on the opposite sides of the tab stack 25. The end surfaces 25a and 25b are surfaces along the XZ plane. Further, the end face 25 c is a surface inclined with respect to the XY plane so that the thickness of the tab laminate 25 decreases toward the tip of the tab laminate 25.

The tab stack 25 is disposed between the current collector 19 and the protective plate 27 in the Z-axis direction. The tab stack 25 is disposed on the current collector 19 in the Z-axis direction. The protective plate 27 is disposed on the tab laminate 25 on the opposite side to the current collector plate 19 with the tab laminate 25 interposed therebetween. The protective plate 27 is not in contact with the current collecting plate 19, and the protective plates 27 and 29 are separated by sandwiching the tab laminate 25 in the stacking direction. The tab laminate 25 is thicker than the protective plate 27, and the current collector 19 is thicker than the protective plate 27. The thickness of the protective plate 27 is larger than the thickness of the tab 17 b.

The length of the current collector plate 19 in the Y-axis direction is larger than the length of the tab laminate 25 in the Y-axis direction (the distance between the end surfaces 25a and 25b). The position of the outer end of the current collector plate 19 in the Y-axis direction in the Y-axis direction coincides with the position of the end in the Y-axis direction of the main body 17a. The length of the protective plate 27 in the Y-axis direction is substantially the same as the length of the tab laminate 25 in the Y-axis direction.

The tab laminate 25 has welds W located on the inner side from the end faces 25 a and 25 b of the tab laminate 25. The maximum length W2 of the weld W in the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab stack 25 at the end faces 25a and 25b of the tab stack 25 is the stacking direction of the tab stack 25 (for example, the Z-axis direction When viewed from a direction (for example, the Y-axis direction) orthogonal to both the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab laminate 25 (for example, the Z-axis direction) And the maximum length W1 of the overlapping portion of the welded portion W and the tab laminate 25 (see FIGS. 3 and 4). The maximum length W1 is smaller than the maximum length of the weld W in the Z-axis direction. The weld portion W will be described in detail later with reference to FIG.

One feature of this embodiment is the shape of the tab stacks 21, 25 and the position of the weld W in the tab stacks 21, 25. Here, examples of the shape of the tab laminate 25 and the positions of the welds W in the tab laminate 25 will be mainly described in detail with reference to FIGS. 4 and 5. The shape of the tab laminate 21 and the position of the welded portion W in the tab laminate 21 can be described in the same manner as in the case of the tab laminate 25 and thus detailed description will be omitted.

FIG. 4 is a view schematically showing the tab laminate 25 as viewed from the Y-axis direction. As described above, the tab stack 25 has a plurality of stacked tabs 17 b. The tab 17 b protrudes in the X-axis direction from one end of the main body 17 a. The end face 25 c of the tab laminate 25 is inclined with respect to the XY plane such that the thickness of the tab laminate 25 decreases toward the tip of the tab laminate 25. Hereinafter, the reason why the end face 25c is inclined will be specifically described.

As shown in FIG. 4, the tab laminate 25 protruding from the main body 17 a is roughly divided into a proximal end portion 251, a central portion 252 and a distal end portion 253 in order from the main body 17 a side in the protrusion direction of the tab laminate 25. . The proximal portion 251 is a portion connected to the main body 17a. In the proximal end portion 251, the spacing between the plurality of tabs 17b in the stacking direction of the tab stack 25 decreases in the direction in which the tab stack 25 protrudes. The central portion 252 is a portion having a proximal end portion 251 as a proximal end and extending in the projecting direction of the tab stack 25. In the central portion 252, the plurality of tabs 17b are arranged substantially without spacing. The leading end portion 253 is a portion connected to the central portion 252 in the protruding direction of the tab stack 25 and extending in the protruding direction of the tab stack 25. In the tip portion 253, the tips of the plurality of tabs 17b are arranged to be offset in the projecting direction. Therefore, the end face 25c configured by the end face of the tip of the plurality of tabs 17b is inclined with respect to the XY plane.

More specifically, in FIG. 4, n (n is an arbitrary integer of 2 or more) main bodies 17a of the main bodies 17a1 to 17an are illustrated as a plurality of stacked main bodies 17a. The plurality of main bodies 17a (a part of the positive electrode 11) and the plurality of main bodies 14a (a part of the negative electrode 12) are laminated to each other via the separator 13 and accordingly, the plurality of main bodies 17a (main bodies 17a1 to 17a3) , 17 an etc.) are arranged at intervals in the stacking direction. At a portion on the main body 17a side in the base end portion 251 of the tab laminate 25, the plurality of tabs 17b (tabs 17b1 to 17b3, 17bn, etc.) are arranged at an interval in the stacking direction similarly to the plurality of main bodies 17a. There is. The plurality of tabs 17 b are bundled (consolidated) in the stacking direction of the tab stack 25 so that the distance between the plurality of tabs 17 b narrows toward the central portion 252. In the central portion 252, the spacing between the plurality of tabs 17b may be substantially zero.

Thus, when the plurality of tabs 17b are bundled in the proximal end portion 251 of the tab stack 25, the proximal end (end face to the proximal end) (end face) from the proximal end (one end connected to the main body 17a) in each tab 17b. The length of the range in which the tab 17b exists in the protrusion direction of the tab stack 25 up to one end constituting the 25c is different from each other. In the example shown in FIG. 4, the plurality of tabs 17 b are bundled so as to approach the current collecting plate 19 (located in the negative direction of the Z axis). In this case, as the tab 17b (tab 17b1 to 17b3 and so on) located far from the tab 17bn closest to the current collector plate 19 in the stacking direction of the tab stack 25 (located on the Z-axis positive direction side) Length in the For example, in the case where the plurality of tabs 17b are designed to have the same shape, the length of the distal end portion 253 in the projecting direction of the tab laminate 25 runs short as the length of the proximal end portion 251 increases. As a result, in the tip portion 253, the tips of the plurality of tabs 17b are arranged to be shifted in the projecting direction.

It is also conceivable to design and manufacture each tab 17 b in a different shape in advance so that the tips of the plurality of tabs 17 b are aligned in the tip portion 253 when the plurality of tabs 17 b are bundled. Take the trouble. Alternatively, it is conceivable to cut the end portion 253 so that the ends of the plurality of tabs 17b are aligned in the end portion 253 after bundling the plurality of tabs 17b, but also in that case, it takes time and effort.

In the tab laminate 25 as described above, the plurality of tabs 17 b are welded, for example, by irradiating the energy beam B (described later). At this time, if the end face 25c of the tab laminate 25 is irradiated with the energy beam B to weld the tab 17b, the following problem may occur. That is, when the energy beam B is applied to the front end portion 253 (that is, the end face 25c) of the tab laminate 25 in which the positions of the front ends of the plurality of tabs 17b are shifted, for example, the same length from the front end of each tab 17b The welds to be formed are respectively formed. At this time, if the tip of each tab 17b is shifted, the position of the weld formed inside from the tip of each tab 17b is also shifted. As a result, it is difficult to form a welded portion having a portion penetrating a plurality of (or all) tabs 17 b in the stacking direction of the tab stack 25. That is, a welded portion having a depth sufficient to join the plurality of tabs 17b is not formed inward from the tip of each tab 17b. As a result, the bonding strength between the tabs 17b may be insufficient.

Therefore, in the electrode assembly 3, the plurality of tabs 17 b are welded at an end face different from the end face 25 c of the tab laminate 25. The end face different from the end face 25c is, for example, at least one end face of the end faces 25a and 25b. As described above, the end surfaces 25a and 25b are surfaces along the XZ plane, and in the end surfaces 25a and 25b, the positions of the side ends of the plurality of tabs 17b are shifted about the positions of the tips of the plurality of tabs 17b on the end surface 25c. There is not. The welds W are located inward from the end faces 25a and 25b of such tab laminates 25 respectively.

The shape of the tab laminate 21 and the position of the welded portion W in the tab laminate 21 are similarly described. That is, in the tip end portion in the protrusion direction of the tab stack 21, the tips of the plurality of tabs 14b are arranged to be shifted in the protrusion direction. The reason is described in the same manner as the reason why the tips of the plurality of tabs 17b are shifted, and thus the detailed description is omitted here. In the end faces 21a and 21b of the tab laminate 21, the positions of the side ends of the plurality of tabs 14b are not shifted as much as the positions of the tips of the plurality of tabs 14b in the end face 21c. The welds W are located inward from the end faces 21a and 21b of such tab laminates 21, respectively.

The weld W will be described in more detail with reference to FIG.

FIG. 5 is a view showing a part of the electrode assembly of FIG. 3 as viewed in the X-axis direction. As shown in FIGS. 3 and 5, the end face 25 b of the tab laminate 25 faces the end face 21 b of the tab laminate 21. Thus, the end faces 21a, 21b, 25a, 25b of the tab stacks 21, 25 are arranged along the Y-axis direction.

In the tab laminate 25, the welded portion W extends to the inside of the current collector 19 and the protective plate 27 adjacent to the end faces 25 a and 25 b. Preferably, in the end faces 25a and 25b, the length of the weld W in the X-axis direction is substantially equal to the length of the protective plate 27 in the X-axis direction or shorter than the length of the protective plate 27 in the X-axis direction. Thus, the welded portion W can be stably formed even when the tab 17b of the tab laminate 25 is displaced in the X-axis direction (for example, when there is a displacement due to a tolerance). When the length of the welded portion W in the X-axis direction is substantially equal to the length of the protective plate 27 in the X-axis direction, there is a possibility that the welded portion W may protrude outside the protective plate 27 in the X-axis direction. When the length of the weld W in the X-axis direction is longer than the length of the protection plate 27 in the X-axis direction, the weld W protrudes outside the protection plate 27 in the X-axis direction. Even in those cases, it is possible to form the weld W.

Similarly, in the tab laminate 21, the welds W extend to the inside of the current collector 16 and the protective plate 23 adjacent to the end faces 21 a and 21 b. Preferably, in the end faces 21a and 21b, the length of the weld W in the X-axis direction is substantially equal to the length of the protective plate 23 in the X-axis direction or shorter than the length of the protective plate 23 in the X-axis direction. Thus, the welded portion W can be stably formed even when the tab 14b of the tab laminate 21 is displaced in the X-axis direction (for example, when there is a displacement due to a tolerance). When the length of the welded portion W in the X-axis direction is substantially equal to the length of the protective plate 23 in the X-axis direction, there is a possibility that the welded portion W may protrude outside the protective plate 23 in the X-axis direction. When the length of the weld W in the X-axis direction is longer than the length of the protective plate 23 in the X-axis direction, the weld W protrudes outside the protective plate 23 in the X-axis direction. Even in those cases, it is possible to form the weld W.

FIG. 5 can also be viewed as a cross section orthogonal to the protruding direction of the tab stacks 21, 25. In this case, in the tab laminates 21, 25, the length (welding depth) of the weld W in the direction from the end faces 21a, 21b, 25a, 25b of the tab laminates 21, 25 to the inside is the current collector plate 16, It becomes larger as it goes to 19. The welded portion W has a shape corresponding to the shape of the molten pool formed around the energy beam B by irradiation of the energy beam B (see FIG. 7) described later. The molten pool is, for example, formed to be tapered inward from the surface of the object to be irradiated with the energy beam B in the irradiation direction of the energy beam B. The shape of the welded portion W shown in FIG. 5 is a shape in the case where the energy beam B is irradiated from an obliquely upward direction of the tab laminate 25, assuming that the positive direction of the Z axis is the upward direction. The welded portion W is also formed on the current collector plate 19. The weld W is also formed on the protective plate 27.

As shown in FIG. 5, in the end faces 21a, 21b, 25a, 25b of the tab laminates 21, 25, the plurality of

tabs

14b, 17b are not deviated like the end face 21c and the end face 25c. Therefore, the welded portion W formed inward from the end faces 21a, 21b, 25a, 25b has a portion passing through the plurality of (all in this example)

tabs

14b, 17b in the stacking direction of the tab laminates 21, 25. doing. That is, welds W having a depth sufficient to join the plurality of

tabs

14b and 17b are formed inward from the end faces 21a, 21b, 25a and 25b. As a result, the bonding strength between the plurality of

tabs

14 b and 17 b can be increased.

As illustrated in FIG. 5, in the cross section (for example, the YZ cross section) of the tab stack 21 including the Z axis direction and orthogonal to the end faces 21 a and 21 b of the tab stack 21, the boundary line Wa of the weld W is in the Z axis direction. It extends in a direction inclined with respect to both the direction H (for example, the Y-axis direction) orthogonal to the direction Y and the stacking direction (the Z-axis direction) of the tab laminate 21. For example, the weld W has two boundary lines Wa, and depending on the shape of the molten pool formed around the energy beam B, the two boundaries go from the outer surface of the weld W inward. The distance between Wa is narrow. The weld pool is formed to be tapered inward from the surface of the object to be irradiated with the energy beam B in the irradiation direction of the energy beam B. The welded portion W is also formed on the current collector plate 16, but since the density of the current collector plate 16 is different from the density of the tab laminate 21, the depth of the weld pool formed on the current collector plate 16 and the tab laminate 21 The depth of weld pool formed is different. As a result, as described above, the distance between the two boundary lines Wa narrows inward from the outer surface of the weld W. That is, in the YZ cross section of tab laminate 21, the smaller angle of the angles formed by one boundary line Wa of welding portion W and direction H is α, and another boundary line Wa of welding portion W and direction H Let θ be α, where θ is the smaller of the angles formed by の, and the smaller of the angles formed by direction J and direction H when the irradiation direction of energy beam B is projected onto the YZ plane. It becomes a value between β and. For example, in the YZ cross section of tab laminate 21, the smaller angle of the angles between boundary line Wa in current collecting plate 16 and direction H is α, and the boundary line Wa in tab laminate 21 and direction H Assuming that the smaller one of the angles formed is β, and the smaller one of the angles formed by the direction J of the irradiation direction of the energy beam B projected onto the YZ plane and the direction H is θ, then α <θ <β Become. The boundary line Wa of the welding portion W may be parallel to the Z-axis direction in the YZ cross section.

Similarly, in the cross section (for example, the YZ cross section) of the tab stack 25 including the Z axis direction and orthogonal to the end faces 25a and 25b of the tab stack 25, the boundary line Wa of the weld W is orthogonal to the Z axis direction ( For example, it extends in a direction inclined with respect to both the Y axis direction) and the stacking direction (Z axis direction) of the tab stack 25. For example, weld portion W has two boundary lines Wa, and from the outer surface of weld portion W inward according to the shape of the molten pool formed around energy beam B by irradiation of energy beam B described later. The distance between the two boundary lines Wa narrows toward the direction of travel. The weld pool is formed to be tapered inward from the surface of the object to be irradiated with the energy beam B in the irradiation direction of the energy beam B. The welded portion W is also formed on the current collector plate 19, but since the density of the current collector plate 19 is different from the density of the tab laminate 25, the depth of the weld pool formed on the current collector plate 19 and the tab laminate 25 are The depth of weld pool formed is different. As a result, as described above, the distance between the two boundary lines Wa narrows inward from the outer surface of the weld W. That is, in the YZ cross section of tab laminate 25, the smaller angle of the angle between one boundary line Wa of weld W and direction H is α, the other boundary Wa of weld W and direction H Let θ be α, where θ is the smaller of the angles formed by の, and the smaller of the angles formed by direction J and direction H when the irradiation direction of energy beam B is projected onto the YZ plane. It becomes a value between β and. For example, in the YZ cross section of tab laminate 25, the smaller angle of the angles formed by boundary Wa in current collector plate 19 and direction H is α, and the boundary Wa in tab laminate 25 and direction H Assuming that the smaller one of the angles formed is β, and the smaller one of the angles formed by the direction J of the irradiation direction of the energy beam B projected onto the YZ plane and the direction H is θ, then α <θ <β Become. The boundary line Wa of the welding portion W may be parallel to the Z-axis direction in the YZ cross section.

In the electrode assembly 3, in the YZ cross section of the tab laminates 21 and 25, the boundary line Wa of the welding portion W extends in a direction inclined with respect to both the direction H and the Z-axis direction. The extending direction of the boundary line Wa is controlled by the irradiation direction of the energy beam B irradiated to the end faces 21a, 21b, 25a, 25b of the tab stacks 21, 25.

In the cross section (for example, the YZ cross section) of the tab laminate 21 including the stacking direction of the tab laminate 21 and orthogonal to the end faces 21 a and 21 b of the tab laminate 21, the welded portion W in the direction orthogonal to the stacking direction of the tab laminate 21 Maximum welding depth Wd may be less than 2 mm, may be 1.5 mm or less, may be 1.2 mm or less, may be more than 0.1 mm, 0 It may be 3 mm or more. Similarly, in the cross section (for example, the YZ cross section) of the tab laminate 25 including the stacking direction of the tab laminate 25 and orthogonal to the end faces 25 a and 25 b of the tab laminate 25, welding in the direction orthogonal to the lamination direction of the tab laminate 25 The maximum welding depth Wd of the part W may be less than 2 mm, may be 1.5 mm or less, may be 1.2 mm or less, and may be more than 0.1 mm. , 0.3 mm or more. When the maximum welding depth Wd is less than 2 mm, for example, generation of sputtered particles due to irradiation of the energy beam B can be suppressed. In particular, when the maximum welding depth Wd is 1.2 mm or less, generation of sputtered particles is significantly suppressed (see FIG. 9).

In the cross section (for example, the XY cross section) of the tab stack 21 orthogonal to the stack direction of the tab stack 21, the maximum area of the welded portion W is, for example, 4 to 40 mm ² . Similarly, in the cross section (for example, the XY cross section) of the tab stack 25 orthogonal to the stack direction of the tab stack 25, the maximum area of the weld W is, for example, 4 to 40 mm ² . When the maximum area of the weld W is 4 mm ² or more, the electrical resistance value of the weld W can be sufficiently reduced.

As described above, in the electrode assembly 3, the maximum length W2 of the weld W in the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab stack 21 at the end faces 21 a and 21 b of the tab stack 21 is the tab When viewed from a direction (e.g., Y-axis direction) orthogonal to both the stacking direction (e.g., Z-axis direction) of the stacked body 21 and the direction (e.g., X-axis direction) orthogonal to the stacking direction of the tab stacked body 21 The maximum length W1 of the portion where the welded portion W and the tab laminate 21 overlap in the stacking direction of the laminate 21 (for example, the Z-axis direction) is larger (see FIGS. 3 and 4). Therefore, at the end faces 21 a and 21 b of the tab laminate 21, the welded portion W spreads in the direction intersecting the stacking direction of the tab laminate 21. As a result, when the current flows in the stacking direction in the welding portion W, the electrical resistance value between the plurality of tabs 14 b can be reduced. Further, since the mechanical strength of the welded portion W is increased, the welded portion W is unlikely to be broken even if stress is generated in the electrode assembly 3 due to, for example, an assembly operation or an external force. Furthermore, since the thermal diffusion of the welded portion W is improved, generation of sputtered particles resulting from the irradiation of the energy beam B can be suppressed when forming the welded portion W. Similarly, the maximum length W2 of the weld W in the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab stack 25 at the end faces 25a and 25b of the tab stack 25 is the stacking direction of the tab stack 25 (for example, When viewed from the direction (for example, the Y-axis direction) orthogonal to both the Z-axis direction) and the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab laminate 25 It is larger than the maximum length W1 of the overlapping portion of the welded portion W and the tab laminate 25 in the Z-axis direction). Therefore, at the end faces 25 a and 25 b of the tab laminate 25, the welded portion W spreads in the direction intersecting the stacking direction of the tab laminate 25. As a result, when a current flows in the stacking direction in the welding portion W, the electrical resistance value between the plurality of tabs 17 b can be reduced. Further, since the mechanical strength of the welded portion W is increased, the welded portion W is unlikely to be broken even if stress is generated in the electrode assembly 3 due to, for example, an assembly operation or an external force. Furthermore, since the thermal diffusion of the welded portion W is improved, generation of sputtered particles resulting from the irradiation of the energy beam B can be suppressed when forming the welded portion W.

The tab laminate 21 is disposed between the protective plate 23 and the current collector plate 16 in the lamination direction of the tab laminate 21, and the thickness of the protective plate 23 in the lamination direction of the tab laminate 21 is the lamination of the tab laminate 21. It may be smaller than the thickness of the current collector 16 in the direction. In this case, since the thickness of the protective plate 23 is relatively small, the difference between the thermal capacity of the protective plate 23 and the thermal capacity of the tab 14 b can be reduced. Therefore, the quality of the welding part W in the contact location of the protective plate 23 and the tab 14b improves. The thickness of the protective plate 23 in the stacking direction of the tab stack 21 may be larger than the thickness of the tab 14 b in the stacking direction of the tab stack 21.

The thickness of the protective plate 23 may be 0.1 to 0.5 mm or 0.1 to 0.2 mm. If the thickness of the protective plate 23 is less than 0.1 mm, the force with which the protective plate 23 presses the tab 14b will be small, so the tab 14b tends to move easily during welding. If the thickness of the protective plate 23 is more than 0.5 mm, the energy for melting the protective plate 23 at the time of welding tends to be large. When the output of the energy beam B is increased to increase the energy, sputtered particles resulting from the irradiation of the energy beam B tend to be generated. The thickness of the tab 14b is, for example, 5 to 30 μm. The thickness of the tab laminate 21 may be, for example, 0.3 to 2.4 mm, or 0.6 to 1.0 mm.

Similarly, the tab laminate 25 is disposed between the protective plate 27 and the current collector plate 19 in the lamination direction of the tab laminate 25, and the thickness of the protective plate 27 in the lamination direction of the tab laminate 25 is the tab laminate It may be smaller than the thickness of the current collector 19 in the stacking direction of 25. In this case, since the thickness of the protective plate 27 is relatively small, the difference between the thermal capacity of the protective plate 27 and the thermal capacity of the tab 17b can be reduced. Therefore, the quality of the welding part W in the contact location of the protective plate 27 and the tab 17b improves. The thickness of the protective plate 27 in the stacking direction of the tab stack 25 may be larger than the thickness of the tab 17 b in the stacking direction of the tab stack 25.

The thickness of the protective plate 27 may be, for example, 0.1 to 0.5 mm, or 0.1 to 0.2 mm. If the thickness of the protective plate 27 is less than 0.1 mm, the force with which the protective plate 27 presses the tab 17b will be small, so the tab 17b tends to move easily during welding. If the thickness of the protective plate 27 is more than 0.5 mm, the energy for melting the protective plate 27 at the time of welding tends to be large. When the output of the energy beam B is increased to increase the energy, sputtered particles resulting from the irradiation of the energy beam B tend to be generated. The thickness of the tab 17b is, for example, 5 to 30 μm. The thickness of the tab laminate 25 may be, for example, 0.3 to 2.4 mm or 0.6 to 1.0 mm.

FIG.6 and FIG.7 is a figure which shows 1 process of the manufacturing method of the electrode assembly which concerns on embodiment. The electrode assembly 3 shown in FIG. 3 is manufactured, for example, by the following method.

(Step of preparing tab laminate)
First, as shown in FIG. 6, a plurality of tab stacks 21 and 25 are prepared. FIG. 6A is a view showing the tab stacks 21 and 25 as viewed from the X-axis direction, and FIG. 6B is a view showing the tab stack 25 as viewed from the Y-axis direction. For example, first, the tab stacks 21 and 25 are formed by laminating the

tabs

14 b and 17 b respectively on the

current collectors

16 and 19. Thereafter, the

protective plates

23 and 27 are placed on the tab stacks 21 and 25, respectively. The tab stacks 21 and 25 are pressed by the jig via the

protective plates

23 and 27, for example, but may not be pressed.

(Welding process)
Next, as shown in FIG. 7, the end face 25 a of the tab stack 25 is irradiated with the energy beam B. FIG. 7A is a view showing the tab stacks 21 and 25 as viewed from the X-axis direction, and FIG. 7B is a view showing the tab stack 25 as viewed from the Y-axis direction. The energy beam B is emitted from the irradiation device 30 toward the end face 25 a of the tab stack 25. The irradiation device 30 is, for example, a scanner head including a lens and a galvano mirror. A beam generator is connected to the scanner head via a fiber. The irradiation device 30 may be composed of, for example, an optical system of a dioptric system such as a prism or a diffractive system such as a diffractive optical element (DOE).

The direction J in which the irradiation direction of the energy beam B is projected onto a plane (for example, YZ plane) orthogonal to the end face 25a of the tab laminate 25 and including the lamination direction of the tab laminate 25 is Z in the plane (for example, YZ plane). It may be inclined with respect to both the direction H orthogonal to the axial direction (e.g., the Y-axis direction) and the stacking direction of the tab stack 25. The direction J may also be inclined with respect to the end face 25 a of the tab stack 25. When the direction J is inclined as described above, the smaller one of the angles formed by the direction H and the direction J in the YZ plane may be 5 to 85 °, or 10 to 80. It may be ° or 45 to 75 °. The energy beam B is a high energy beam that can perform welding. The energy beam B is, for example, a laser beam or an electron beam. The irradiation of the energy beam B is performed in the atmosphere of the inert gas G supplied from the nozzle 32.

The energy beam B is applied to the end face 25 a of the tab laminate 25 in a state where the tab laminate 25 is pressed in the Z-axis direction via the current collecting plate 19 and the protective plate 27 by a jig, for example.

The energy beam B is scanned at the end face 25 a of the tab stack 25 along a direction (X-axis direction) intersecting the Z-axis direction. In the embodiment, the energy beam B is scanned along the X-axis direction while being displaced in the Z-axis direction. For example, the energy beam B is scanned along the X axis direction while reciprocating (wobbling) in the Z axis direction. The displacement of the irradiation spot of the energy beam B in the Z-axis direction is larger than the thickness of the tab stack 25. The irradiation spot of the energy beam B moves from the position P1 on the axis along the X-axis direction to the position P2 on the end face 25a of the tab stack 25. For example, the positions P1 and P2 are located at the center of the end face 25a of the tab stack 25 in the Z-axis direction. For example, the energy beam B is moved while moving the central point along the X-axis direction at the end face 25a of the tab stack 25 and rotating the irradiation spot of the energy beam B in the XZ plane about the central point. If the diameter of rotation is larger than the thickness of the tab laminate 25, it is preferable because the end face 25a of the tab laminate 25, the current collector plate 19 and the protective plate 27 can be welded as a whole. Further, the energy beam B may be irradiated to the part of the end face 25 a of the tab stack 25 on the protective plate 27 side, and the energy beam B may not be irradiated to the remaining part on the current collector plate 19 side. In this case, the welding portion W is not formed on the remaining portion of the end face 25 a of the tab stack 25 on the current collecting plate 19 side. However, the weld W extends in the thickness direction of the tab stack 25 inside the tab stack 25 by the weld W extending in the irradiation direction of the energy beam B inside the end face 25 a of the tab stack 25. It will be. The plurality of tabs 17 b and the current collector plate 19 can be welded by causing the welded portion W to reach the current collector plate 19.

By irradiating the energy beam B as described above, as described above with reference to FIGS. 3 and 5, the welded portion W is formed inside from the end face 25a of the tab laminate 25.

Subsequently, the energy beam B is also irradiated to the end face 21 b of the tab laminate 21 to form a welded portion W inside from the end face 21 b. Similarly, the energy beam B is applied also to the end face 25b of the

tab laminate

25 and 21a of the tab laminate 21 to form a welded portion W inside from the end faces 25b and 21a.

Through the above steps, the electrode assembly 3 is manufactured.

Thereafter, the tab stacks 21 and 25 are folded as shown in FIG. 3, for example, and the folded electrode assembly 3 is accommodated in the case 2, whereby the power storage device 1 can be manufactured.

The bending of the tab laminates 21 and 25 may be completed, for example, in a process of preparing the tab laminates prior to the process of forming the welds. In that case, the welded portion W is formed by the irradiation of the energy beam B to the end faces 21a, 21b, 25a, 25b in a state where the tab laminates 21, 25 are bent. In addition, the protrusion direction of the tab laminated body in the state by which the tab laminated body was bent points out the direction along the shape of the tab laminated body which was bend | folded. In the example shown in FIG. 1, for example, the tab stacks 21 and 25 are bent at the bending portion F. In this case, the projecting direction of the tab laminates 21 and 25 is a direction away from the side surface S of the electrode body 20 at a portion closer to the electrode main body 20 than the bent portion F of the tab laminates 21 and 25. In the portion of the tab laminates 21 and 25 closer to the

current collectors

16 and 19 than the bent portion F, the tab laminates 21 and 25 protrude from the bent portion F toward the

current collectors

16 and 19. It is considered to be the direction towards.

As described above, the electrode assembly 3 includes the electrode body 20 having the plurality of

stacked bodies

14 a and 17 a and the tab laminate 21 having the plurality of stacked

tabs

14 b and 17 b and protruding from the electrode body 20. , 25. The positions of the tips of the plurality of

tabs

14 b and 17 b are shifted in the protrusion direction at the tip portions (the tip portions 253 and the like) of the tab stacks 21 and 25 in the protrusion direction. In the electrode assembly 3, the tab stacks 21 and 25 extend along the stack direction (Z-axis direction) of the tab stacks 21 and 25 and the protrusion direction of the tab stacks 21 and 25. The welding portion W is positioned inward from the end faces 21a, 21b (first end face, second end face), 25a, 25b (first end face, second end face). In the end faces 21a, 21b, 25a, 25b of the tab laminates 21, 25, unlike the tip portions (the tip portions 253, etc.) of the tab laminates 21, 25, the above-mentioned deviation amount is small. Therefore, welds W of sufficient depth can be formed from the end faces 21a, 21b, 25a, 25b of the tab stacks 21, 25 inward. Thus, the bonding strength between the plurality of stacked

tabs

14b and 17b can be secured.

In the tab laminate 21, the welded portion W is located not only on one end face (for example, end face 21 a) but also on the inner side from the other end face (for example, end face 21 b). The bonding strength between the stacked tabs 14b can be further enhanced. Similarly, in the tab laminate 25, the welded portion is provided not only on one end face (for example, end face 25 a) but also on the inner side from the other end face (for example, end face 25 b). The bonding strength between the stacked tabs 17b can be increased more than in the case where it is carried out.

As described above with reference to FIGS. 3 and 5, the welding portion W is formed on the inner side from the end faces 21 a and 21 b of the tab laminate 21 and is also formed on the current collector plate 16 and the protective plate 23. Ru. In this case, the tab laminate 21, the current collector plate 16, and the protective plate 23 can be firmly connected by the welded portion W. For this reason, in the electrode assembly 3, the protective plate is used without using a member (for example, a member connecting the protective plate 23 and the current collector plate 16) positioned across the tab laminate 21 in the stacking direction of the tab laminate 21. 23, the plurality of tabs 14b and the current collector plate 16 are connected to each other by the welding portion W. Therefore, the member positioned across the tab stacks 21 as described above can be eliminated. Similarly, without using a member (for example, a member connecting the protective plate 27 and the current collector plate 19) positioned across the tab laminated body 25 in the laminating direction of the tab laminated body 25, the protective plate 27 and the plurality of tabs 17b And the current collectors 19 are connected to each other by the weld W. Therefore, a member positioned across the tab stack 25 as described above can be eliminated.

In the laminated electrode assembly 3, the tab laminate 21 and the tab laminate 25 protrude in the same direction from the electrode body 20, and the tab laminates 21 and 25 may be bent. An electrode assembly in which two tab laminates 21 and 25 (a first tab laminate and a second tab laminate) having opposite polarities (a positive electrode and a negative electrode) in this manner protrude in the same direction and are bent. Even in a three-dimensional structure, the tab laminates 21 and 25 have welds W positioned on the inner side from the end faces 21a, 21b, 25a and 25b, thereby joining the plurality of stacked

tabs

14b and 17b. The strength can be secured.

In addition, in the case where the tab laminates 21 and 25 are bent before the welded portion W is formed by the irradiation of the energy beam B, the following advantages are also obtained. That is, the tab laminates 21 and 25 may be bent, which may further increase the positional deviation of the tips of the plurality of

tabs

14 b and 17 b at the tip portions (the tip portions 253 and the like) of the tab laminates 21 and 25. There is. Even in that case, in the electrode assembly 3 according to the embodiment, the tab stacks 21 and 25 have the welds W positioned inside from the end faces 21a, 21b, 25a and 25b, so the plurality of

tabs

14b and 17b Even when the position of the front end of the above is shifted, the bonding strength between the stacked

plural tabs

14b and 17b can be secured.

In the electrode assembly 3, the length of the weld W in the direction from the end faces 21a, 21b, 25a, 25b of the tab laminates 21, 25 in the cross section orthogonal to the projecting direction of the tab laminates 21, 25 The (welding depth) increases as the

current collectors

16 and 19 are approached. Thereby, the joint strength with respect to

current collection plates

16 and 19 of a plurality of

laminated tabs

14b and 17b can be raised.

FIG. 8 is a view showing a part of an electrode assembly having a weld according to a modification. FIG. 8A is a view showing the tab laminate 25 seen from the Y-axis direction, having the weld portion W according to the first modification. FIG. 8 (B) is a view showing the tab laminate 25 seen from the Y-axis direction, having the weld portion W according to the second modification. In the first and second modifications, as viewed in the normal direction of the end face 25 a of the tab stack 25, the weld W has an outer shape including a curve. Therefore, the stress is not easily concentrated at the curved portion of the outer shape of the welded portion W, so the welded portion W is hardly peeled off. The weld W may have an outer shape surrounded by a curve, or may have an outer shape surrounded by a curve and a straight line. The external shape of the welded portion W does not include corner portions where the stress tends to concentrate (portions where straight lines intersect).

The external shape of the welding portion W according to the first modification includes, for example, a part of an ellipse. As shown in FIG. 8A, the maximum length W2 of the weld W in the direction (X-axis direction) orthogonal to the stacking direction of the tab stack 25 at the end face 25a of the tab stack 25 is the tab stack 25 When viewed from the direction (Y-axis direction) orthogonal to both the stacking direction (Z-axis direction) and the direction (X-axis direction) orthogonal to the stacking direction of the tab stack 25 It is larger than the maximum length W1 of the portion where the welded portion W and the tab laminate 25 overlap in the (Z-axis direction).

The external shape of the welding portion W according to the second modification includes, for example, a part of a circle. As shown in FIG. 8B, the maximum length W2 of the weld W in the direction (X-axis direction) orthogonal to the stacking direction of the tab stack 25 at the end face 25a of the tab stack 25 is the tab stack 25 When viewed from the direction (Y-axis direction) orthogonal to both the stacking direction (Z-axis direction) and the direction (X-axis direction) orthogonal to the stacking direction of the tab stack 25 It is larger than the maximum length W1 of the overlapping portion of the welded portion W and the tab laminate 25 in (Z-axis direction). The maximum length W2 may be equal to or less than the maximum length W1.

Also in at least one of end face 25b of tab laminate 25 and end faces 21a and 21b of tab laminate 21, weld W has the same shape as weld W according to the first modification or the second modification. May be

Hereinafter, the present invention will be more specifically described based on examples, but the present invention is not limited to the following examples.

Example 1
The weld portion W was formed such that the maximum weld depth Wd of the weld portion W was 0.1 mm.

(Example 2)
The welded portion W was formed in the same manner as in Example 1 except that the maximum welding depth Wd of the welded portion W was 0.3 mm.

(Example 3)
A welded portion W was formed in the same manner as in Example 1 except that the maximum welding depth Wd of the welded portion W was 1.2 mm. The output of the laser used to form the weld W was 1500 W, and the scanning speed was 24.9 mm / sec.

(Example 4)
The welded portion W was formed in the same manner as in Example 1 except that the maximum welding depth Wd of the welded portion W was set to 1.5 mm. The power of the laser used to form the weld W was 1500 W, and the scanning speed was 8.3 mm / sec.

(Example 5)
The welded portion W was formed in the same manner as in Example 1 except that the maximum welding depth Wd of the welded portion W was 2 mm.

(Evaluation results)
The evaluation results of Examples 1 to 5 are shown in FIG. The situation where the laser beam was irradiated to the end face of the tab laminate was imaged, and the number of sputtered particles resulting from the irradiation of the laser beam was counted from the obtained image. In Examples 4 to 5, the number of sputtered particles was significantly increased as compared with Examples 1 to 3. Moreover, the electrical resistance value of the welding part W was measured. A in the table shown in FIG. 9 indicates that a good result was obtained, and B indicates that a result that was not better than A was obtained. Good results were obtained in Examples 2 to 4 as compared with Examples 1 and 5. According to the evaluation result of FIG. 9, when the maximum welding depth Wd of the welded portion W is 0.3 to 1.5 mm, the number of sputtered particles decreases. Furthermore, when the maximum welding depth Wd is 0.3 to 1.2 mm, the number of sputtered particles is significantly reduced, and the electrical resistance value of the welded portion W becomes a good value.

DESCRIPTION OF SYMBOLS 3 ... Electrode assembly, 14a, 17a ... Main body, 14b, 17b ... Tab, 16, 19 Current collection board (current collector), 20 ... Electrode

main body

21, 21 ... Tab laminated body, 21a, 21b, 21c, 25a, 25b, 25c ... end face, 23, 27 ... protection plate (conductive member), W ... welded portion.

Claims

An electrode assembly comprising a plurality of electrodes each including a body and a tab projecting from one end of the body, the electrode assembly comprising:
An electrode body having a plurality of stacked bodies;
A tab stack having a plurality of stacked tabs and protruding from the electrode body;
Equipped with
In the tab laminate, the tips of the plurality of tabs are arranged to be offset in the projecting direction at the distal end portion of the tab laminate in the projecting direction,
The tab laminate has a welding portion located inward from a first end face of the tab laminate extending in the stacking direction of the tab laminate and the protruding direction of the tab laminate.
Electrode assembly.
The tab laminate further includes another weld portion extending along the stacking direction and the protruding direction and positioned inward from a second end surface different from the first end surface.
An electrode assembly according to claim 1.
The electrode assembly according to claim 1, wherein the plurality of tabs are connected to one another by the weld without using a member positioned across the tab stack in the stacking direction.
The electrode assembly is a laminated type,
The electrode assembly includes two electrode bodies having opposite polarities.
The tab stack is a first tab stack having a plurality of tabs protruding and stacked from an electrode body having one polarity,
The electrode assembly is a second tab laminate having a plurality of tabs projecting and stacked from an electrode body having the other polarity, and the stacking direction of the second tab laminate and the second tab laminate And a second tab laminate having a weld located inward from the end face of the second tab laminate extending along the direction in which the body protrudes.
In the second tab laminate, positions of tips of the plurality of tabs in the second tab laminate at a tip portion in the protrusion direction of the second tab laminate are a protrusion direction of the second tab laminate. It is placed off the
The first tab stack and the second tab stack project in the same direction,
The electrode assembly according to any one of the preceding claims, wherein the first tab stack and the second tab stack are folded.
The electrode assembly further comprises a current collector,
The tab laminate is disposed on the current collector in the stacking direction,
In a cross section orthogonal to the projecting direction of the tab laminate, the length of the weld in a direction from the first end face of the tab laminate toward the inside becomes larger as it approaches the current collector. An electrode assembly according to any one of Items 1 to 4.
The tab laminate is disposed between the conductive member and the current collector in the stacking direction of the tab laminate,
The electrode assembly according to any one of claims 1 to 5, wherein the thickness of the conductive member in the stacking direction of the tab stack is smaller than the thickness of the current collector in the stacking direction of the tab stack.
In the first end face of the tab laminate, the maximum length of the weld in a direction orthogonal to the lamination direction of the tab laminate is orthogonal to the lamination direction of the tab laminate and the lamination direction of the tab laminate 7. The method according to any one of claims 1 to 6, wherein when viewed from a direction orthogonal to both the direction, the maximum length of the overlapping portion of the welded portion and the tab laminate in the laminating direction of the tab laminate is greater. An electrode assembly according to one of the preceding claims.
In a cross section of the tab laminate including the stacking direction of the tab laminate and orthogonal to the first end face of the tab laminate, the maximum welding depth of the weld in a direction orthogonal to the stacking direction of the tab laminate The electrode assembly according to any one of the preceding claims, wherein is less than 2 mm.
The electrode assembly according to any one of claims 1 to 8, wherein the weld has an outer shape including a curve when viewed in the normal direction of the first end face of the tab laminate.