JPWO2017073745A1 - Electrode assembly - Google Patents

Abstract

An electrode assembly having a plurality of electrodes each including a main body and a tab protruding from one end of the main body includes an electrode main body having a plurality of stacked main bodies, and a tab having a plurality of stacked tabs and protruding from the electrode main body A laminate. In the tab laminated body, the tips of the plurality of tabs are arranged so as to be shifted in the protruding direction at the leading end portion in the protruding direction of the tab laminated body. The tab laminate includes a weld portion located on the inner side from the first end surface of the tab laminate that extends along the stacking direction of the tab laminate and the protruding direction of the tab laminate.

Description

  One aspect of the present 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 an end surface of the stacked tabs with an energy beam. (For example, refer to Patent Document 1).

JP 2002-313309 A

  In the tip portion of the stacked tabs (hereinafter sometimes referred to as “tab laminate”), the positions of the tips of the tabs are often shifted. If the tip of the tab stack is displaced with the energy beam when the tip of each tab is misaligned, a weld that is deep enough to join the tabs will be inside from the tip of each tab. In other words, the bonding strength between the tabs may be insufficient.

  An object of one aspect of the present invention is to provide an electrode assembly in which the bonding strength between a plurality of stacked tabs is ensured even when the positions of the tips of the tabs are shifted.

  An electrode assembly according to an aspect of the present invention is an electrode assembly having a plurality of electrodes each including a main body and a tab protruding from one end of the main body, the electrode main body having a plurality of stacked main bodies, and a stack A tab laminated body that has a plurality of tabs and protrudes from the electrode body. The tab laminated body has a weld portion located on the inner side from the first end surface of the tab laminated body that extends along the lamination direction of the tab laminated body and the protruding direction of the tab laminated body.

  The electrode assembly includes an electrode body having a plurality of laminated main bodies, and a tab laminate having a plurality of laminated tabs and protruding from the electrode body. The positions of the tips of the plurality of tabs are shifted in the projecting direction at the tips of the tab laminate in the projecting direction. In the above electrode assembly, the tab laminated body has a weld portion located on the inner side from the first end surface of the tab laminated body extending along the lamination direction of the tab laminated body and the protruding direction of the tab laminated body. On the first end face of the tab laminate, the above-described deviation amount is small unlike the tip portion of the tab laminate. Therefore, a weld part having a sufficient depth can be formed inward from the first end face of the tab laminate. Therefore, it is possible to ensure the bonding strength between the stacked tabs.

  The tab laminate may further include another weld portion that extends along the stacking direction and the protruding direction and is located on the inner side from the second end surface that is different from the first end surface. Thereby, compared with the case where a welding part is located only in one end surface, the joint strength of laminated | stacked tabs can be raised.

  A plurality of tabs may be connected to each other by a welded portion without using a member positioned across the tab laminate in the stacking direction. For example, a method of improving the bonding strength between a plurality of tabs by using a member positioned across the tab laminate in the stacking direction is also conceivable. However, according to the above-described electrode assembly, a plurality of layers stacked by a welded portion are considered. Since the bonding strength between the tabs is ensured, such a member can be made unnecessary.

  The electrode assembly is a laminated type, and the electrode assembly includes two electrode bodies having opposite polarities, and the tab laminate includes a plurality of tabs protruding from the electrode body having one polarity and stacked. The electrode assembly is a second tab laminate having a plurality of tabs protruding from the electrode body having the other polarity and laminated, the second tab laminate being laminated. And a second tab laminate having a weld portion located inward from an end surface of the second tab laminate extending in the direction and the projecting direction of the second tab laminate. In the body, the positions of the tips of the plurality of tabs in the second tab laminated body are shifted in the protruding direction of the second tab laminated body at the distal end portion of the second tab laminated body in the protruding direction. The tab laminate and the second tab laminate are the same To protrude, may be the first tab laminate and the second tab laminate is folded.

  The electrode assembly further includes a current collector, and the tab stacked body is disposed on the current collector in the stacking direction, and a first end surface of the tab stacked body in a cross section orthogonal to the protruding direction of the tab stacked body. The length of the welded portion in the direction from the inside toward the inside may increase as the current collector is approached. Thereby, when a tab laminated body is arrange | positioned on a collector, the joining strength with respect to the collector of the some laminated | stacked tab can be raised.

  The tab laminate is disposed between a conductive member and a current collector in the stacking direction of the tab laminate, and the thickness of the conductive member in the stacking direction of the tab laminate is the stacking 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.

  The maximum length of the welded portion in the direction orthogonal to the stacking direction of the tab laminate at the first end surface of the tab laminate is orthogonal to the stacking direction of the tab laminate and the stacking direction of the tab laminate. When viewed from a direction orthogonal to both the directions, the maximum length of a portion where the welded portion and the tab laminate overlap in the stacking direction of the tab laminate may be larger.

  In this case, at the first end face of the tab laminate, the welded portion spreads in a direction intersecting with the lamination direction of the tab laminate. As a result, when current flows in the stacking direction at the welded portion, the electrical resistance value between the plurality of tabs can be reduced.

  The maximum weld depth of the weld in the direction perpendicular to the lamination direction of the tab laminate in the cross section of the tab laminate perpendicular to the first end surface of the tab laminate including the lamination direction of the tab laminate May be less than 2 mm.

  The welded portion may have an outer shape including a curve when viewed from the normal direction of the first end face of the tab laminate.

  In this case, the stress is difficult to concentrate on the curved portion of the outer shape of the welded portion, and therefore the welded portion is difficult to peel off.

  According to one aspect of the present invention, there is provided an electrode assembly in which the bonding strength between a plurality of stacked tabs is ensured even when the positions of the tips of the tabs are shifted.

FIG. 1 is an exploded perspective view of a power storage device including the electrode assembly according to the embodiment. FIG. 2 is a cross-sectional view of the storage battery taken along line II-II in FIG. FIG. 3 is a perspective view of the electrode assembly according to the embodiment. 4 is a view showing a part of the electrode assembly of FIG. 3 as viewed from the Y-axis direction. FIG. 5 is a view showing a part of the electrode assembly of FIG. 3 as viewed from the X-axis direction. Drawing 6 is a figure showing one process of a manufacturing method of an electrode assembly concerning an embodiment. FIG. 7 is a diagram illustrating one step in 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 examples.

  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 redundant descriptions are omitted. In the drawing, an XYZ orthogonal coordinate system is shown as necessary. 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 including the electrode assembly according to the embodiment. FIG. 2 is a cross-sectional view of the power storage device taken along line II-II in FIG. The power storage device 1 shown in FIGS. 1 and 2 is a nonaqueous 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 a hollow case 2 having a substantially rectangular parallelepiped shape, for example, and an electrode assembly 3 accommodated in the case 2. The case 2 is made of a metal such as aluminum. The case 2 has a main body 2a that is open on one side and a lid 2b that closes the opening of the main body 2a. On the inner wall surface of the case 2, an insulating film (not shown) is provided. For example, a non-aqueous (organic solvent) electrolyte is injected into 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 electrolytic solution. . A positive electrode terminal 5 and a negative electrode terminal 6 are spaced apart from each other on the lid 2 b of the case 2. The positive electrode terminal 5 is fixed to the case 2 via an insulating ring 7, and the negative electrode terminal 6 is fixed to the case 2 via an 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-shaped 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. For example, the positive electrode 11 is accommodated in the separator 13. In a state where the positive electrode 11 is accommodated in the separator 13, the plurality of positive electrodes 11 and the plurality of negative electrodes 12 are alternately stacked via the separators 13.

  The positive electrode 11 includes, for example, a metal foil 14 made of an aluminum foil, and a positive electrode active material layer 15 formed on both surfaces of the metal foil 14. The metal foil 14 of the positive electrode 11 includes a rectangular main body 14a and a rectangular tab 14b protruding from one end of the main body 14a. The positive electrode active material layer 15 is a porous layer formed including 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 the central portion of the main body 14a on both surfaces of the main body 14a.

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

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

  The negative electrode 12 includes a metal foil 17 made of, for example, copper foil, and a negative electrode active material layer 18 formed on both surfaces 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 a negative electrode active material on at least a central portion of the main body 17a on both surfaces of the main body 17a. The negative electrode active material layer 18 is a porous layer formed including a negative electrode active material and a binder.

  Examples of the negative electrode active material include carbon such as graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, alkali metals such as lithium and sodium, metal compounds, SiOx (0.5 ≦ x ≦ 1.5 ) And the like, and boron-added carbon. Here, as an example, the tab 17b does not carry a negative electrode active material. However, an active material may be carried on the base 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 a current collector plate 19 (current collector). The current collector plate 19 is disposed between the tab 17 b and the negative electrode terminal 6. For example, the current collector plate 19 is formed in a rectangular flat plate shape from the same material as the metal foil 17 of the negative electrode 12. The plurality of stacked tabs 17b are disposed between the current collector plate 19 and a protective plate 27 (conductive member) thinner than the current collector plate 19 (see FIG. 3). For example, the protection plate 27 is formed in a rectangular flat plate shape from the same material as the metal foil 17 of the negative electrode 12.

  The separator 13 houses the positive electrode 11. The separator 13 has a rectangular shape when viewed from the stacking direction of the positive electrode 11 and the negative electrode 12. For example, the separator 13 is formed 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 a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven fabric or a non-woven fabric made of polypropylene, polyethylene terephthalate (PET), methylcellulose, and the like.

  FIG. 3 is a perspective view of the 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 on each other with a separator 13 interposed therebetween. 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 (a direction orthogonal to a 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 from one end of the main body 17a in the X-axis direction. The main bodies 14a and 17a are laminated with each other to constitute the 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 and 17a. The tabs 14b and 17b are laminated with each other to form tab laminated bodies 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 stacked body 21 having a plurality of tabs 14b stacked in the Z-axis direction, and a Z-axis direction. And a tab laminate 25 having a plurality of laminated tabs 17b. The tab laminates 21 and 25 protrude in the X-axis direction from the side surface S of the electrode body 20. The tab laminates 21 and 25 are arranged apart from each other in the Y-axis direction.

  The tab laminated body 21 includes end surfaces 21a, 21b, and 21c of the tab laminated body 21 that extend along the lamination direction (Z-axis direction) of the tab laminated body 21. The end surfaces 21a and 21b are surfaces that sandwich the tab laminate 21, and the end surface 21c is a surface that connects the end surfaces 21a and 21b. That is, the end faces 21 a and 21 b are arranged on opposite sides of the tab laminate 21. The end surfaces 21a and 21b are surfaces along the XZ plane. The end surface 21 c is a surface that is inclined with respect to the XY plane so that the thickness of the tab laminated body 21 becomes smaller toward the tip of the tab laminated body 21.

  The tab laminate 21 is disposed between the current collector plate 16 and the protection plate 23 in the Z-axis direction. That is, the tab laminate 21 is disposed on the current collector plate 16 in the Z-axis direction. The protection 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 plate 16, and the protective plate 23 and the current collector plate 16 are separated from each other with the tab laminate 21 sandwiched in the stacking direction. The tab laminate 21 is thicker than the protective plate 23, and the current collector plate 16 is thicker than the protective plate 23. The thickness of the protective plate 23 is larger than the thickness of the tab 14b.

  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 portion of the current collector plate 16 in the Y-axis direction coincides with the position of the end portion of the main body 14a 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 laminated body 21 has welded portions W located on the inner sides from the end faces 21 a and 21 b of the tab laminated body 21. The maximum length W2 of the welded portion W in the direction (eg, the X-axis direction) orthogonal to the lamination direction of the tab laminate 21 on the end faces 21a, 21b of the tab laminate 21 is the lamination direction (eg, the Z-axis direction) of the tab laminate 21. ) And 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-layered structure 21, the stacking direction (for example, the Z-axis direction) of the tab stacked body 21 ) Is larger than the maximum length W1 of the portion where the welded portion W and the tab laminate 21 overlap (see FIGS. 3 and 4). The welded portion W will be described in detail later with reference to FIG.

  Similarly, the tab laminate 25 includes end surfaces 25a, 25b, and 25c of the tab laminate 25 that extend along the lamination direction (Z-axis direction) of the tab laminate 25. The end surfaces 25a and 25b are surfaces that sandwich the tab laminate 25, and the end surface 25c is a surface that connects the end surfaces 25a and 25b. That is, the end faces 25a and 25b are disposed on the opposite sides of the tab laminate 25. The end surfaces 25a and 25b are surfaces along the XZ plane. Further, the end surface 25c is a surface inclined with respect to the XY plane so that the thickness of the tab laminated body 25 becomes smaller toward the tip of the tab laminated body 25.

  The tab laminate 25 is disposed between the current collector plate 19 and the protection plate 27 in the Z-axis direction. The tab laminate 25 is disposed on the current collector plate 19 in the Z-axis direction. The protection plate 27 is disposed on the tab laminate 25 on the opposite side of the current collector plate 19 with the tab laminate 25 interposed therebetween. The protection plate 27 is not in contact with the current collector plate 19, and the protection plates 27 and 29 are separated from each other with the tab laminate 25 sandwiched in the lamination direction. The tab laminate 25 is thicker than the protective plate 27, and the current collector plate 19 is thicker than the protective plate 27. The thickness of the protection plate 27 is larger than the thickness of the tab 17b.

  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). In the Y-axis direction, the position of the outer end portion of the current collector plate 19 in the Y-axis direction matches the position of the end portion of the main body 17a in the Y-axis direction. The length of the protection 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 laminated body 25 has welded portions W located on the inner side from the end faces 25a and 25b of the tab laminated body 25, respectively. The maximum length W2 of the welded portion W in the direction (eg, the X-axis direction) orthogonal to the lamination direction of the tab laminate 25 at the end faces 25a, 25b of the tab laminate 25 is the lamination direction (eg, the Z-axis direction) of the tab laminate 25 ) And 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-layered structure 25, the stacking direction (for example, the Z-axis direction) of the tab stacked body 25 ) Is larger than the maximum length W1 of the portion where the welded portion W and the tab laminate 25 overlap (see FIGS. 3 and 4). The maximum length W1 is smaller than the maximum length of the welded portion W in the Z-axis direction. The welded portion W will be described in detail later with reference to FIG.

  One feature of the present embodiment is the shape of the tab laminates 21 and 25 and the position of the welded portion W in the tab laminates 21 and 25. Here, an example of the shape of the tab laminate 25 and the position of the welded portion W in the tab laminate 25 will be mainly described in detail with reference to FIGS. 4 and 5. Since the shape of the tab laminated body 21 and the position of the welded portion W in the tab laminated body 21 can be described in the same manner as in the case of the tab laminated body 25, detailed description thereof is omitted.

  FIG. 4 is a diagram schematically showing the tab laminate 25 viewed from the Y-axis direction. As described above, the tab stacked body 25 includes a plurality of stacked tabs 17b. The tab 17b protrudes from the one end of the main body 17a in the X-axis direction. The end surface 25c of the tab laminated body 25 is inclined with respect to the XY plane so that the thickness of the tab laminated body 25 becomes smaller toward the tip of the tab laminated body 25. Hereinafter, the reason why the end face 25c is inclined will be described in detail.

  As shown in FIG. 4, the tab laminated body 25 protruding from the main body 17 a is roughly divided into a base end portion 251, a central portion 252 and a distal end portion 253 in order from the main body 17 a side in the protruding direction of the tab laminated body 25. . The proximal end portion 251 is a portion connected to the main body 17a. In the base end portion 251, the distance between the plurality of tabs 17 b in the stacking direction of the tab stacked body 25 decreases as it goes in the protruding direction of the tab stacked body 25. The central portion 252 is a portion having the base end portion 251 as the base end and extending in the protruding direction of the tab laminate 25. In the central portion 252, the plurality of tabs 17b are arranged with substantially no space therebetween. The tip portion 253 is a portion that is connected to the central portion 252 in the protruding direction of the tab laminated body 25 and extends in the protruding direction of the tab laminated body 25. In the tip portion 253, the tips of the plurality of tabs 17b are arranged so as to be shifted in the protruding direction. Therefore, the end surface 25c constituted by the end surfaces at the tips of the plurality of tabs 17b is inclined with respect to the XY plane.

  More specifically, FIG. 4 illustrates n (n is an arbitrary integer greater than or equal to 2) main bodies 17a of the main bodies 17a1 to 17an as a plurality of stacked main bodies 17a. Since 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 stacked on each other via the separator 13, the plurality of main bodies 17a (the main bodies 17a1 to 17a3) are correspondingly stacked. , 17an, etc.) are arranged at intervals in the stacking direction. A plurality of tabs 17b (tabs 17b1 to 17b3, 17bn, etc.) are arranged at intervals in the stacking direction in the portion on the main body 17a side in the base end portion 251 of the tab laminated body 25, like the plurality of main bodies 17a. Yes. The plurality of tabs 17b are bundled (aggregated) in the stacking direction of the tab stacked body 25 so that the distance between the plurality of tabs 17b becomes narrower toward the central portion 252. In the central portion 252, the size of the interval between the tabs 17b may be substantially zero.

  As described above, when the plurality of tabs 17b are bundled in the base end portion 251 of the tab laminate 25, from the base end (one end connected to the main body 17a) of each tab 17b, the tip opposite to the base end (end face) The length of the range in which the tab 17b exists in the protruding direction of the tab laminate 25 is different from each other up to one end constituting 25c. In the example shown in FIG. 4, the plurality of tabs 17 b are bundled so as to approach the current collector plate 19 (positioned on the Z-axis negative direction side). In this case, the proximal end portion 251 is closer to the tab 17b (tabs 17b1 to 17b3, etc.) located farther from the tab 17bn closest to the current collector plate 19 in the laminating direction of the tab laminate 25 (located on the Z axis positive direction side). The length at becomes larger. For example, when the plurality of tabs 17b are designed in the same shape, the tab 17b whose length at the proximal end portion 251 increases, the length in the protruding direction of the tab laminate 25 at the distal end portion 253 is insufficient. As a result, at the distal end portion 253, the distal ends of the plurality of tabs 17b are displaced in the protruding direction.

  In addition, it may be possible to design and manufacture each tab 17b in a different shape in advance so that the tips of the plurality of tabs 17b are aligned at the tip portion 253 when the plurality of tabs 17b are bundled. Take the trouble. Alternatively, after bundling a plurality of tabs 17b, it may be possible to cut the front end portion 253 so that the front ends of the plurality of tabs 17b are aligned at the front end portion 253.

  In the tab laminate 25 as described above, the plurality of tabs 17b are welded by, for example, irradiating with an energy beam B (described later). At this time, if the end surface 25c of the tab laminate 25 is irradiated with the energy beam B and the tab 17b is welded, the following problem may occur. That is, when the energy beam B is irradiated to the tip portion 253 (that is, the end face 25c) of the tab laminated body 25 in which the positions of the tips of the plurality of tabs 17b are shifted, for example, the same length from the tip of each tab 17b to the inside. Each welded portion is formed. At this time, if the tips of the tabs 17b are displaced, the positions of the welded portions formed on the inside from the tips of the tabs 17b are also displaced. As a result, it is difficult to form a welded portion having a portion that penetrates a plurality of (or all) tabs 17b in the stacking direction of the tab stacked body 25. That is, a weld portion having a depth sufficient to join the plurality of tabs 17b is not formed on the inner side 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, a plurality of tabs 17 b are welded to an end surface different from the end surface 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. In the end surfaces 25a and 25b, the positions of the side ends of the plurality of tabs 17b are shifted from the positions of the tips of the plurality of tabs 17b on the end surface 25c. No. The welds W are located on the inner sides from the end faces 25a, 25b of such a tab laminate 25, respectively.

  The shape of the tab laminate 21 and the position of the welded portion W in the tab laminate 21 will be described in the same manner. In other words, at the tip end portion in the protruding direction of the tab laminate 21, the tips of the plurality of tabs 14b are shifted in the protruding direction. The reason will be described in the same manner as the reason why the tips of the plurality of tabs 17b are shifted, so detailed description thereof will be omitted here. In the end surfaces 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 on the end surface 21c. The welds W are located on the inner sides from the end faces 21a and 21b of such a tab laminate 21.

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

  FIG. 5 is a view showing a part of the electrode assembly of FIG. 3 as viewed from the X-axis direction. As shown in FIGS. 3 and 5, the end surface 25 b of the tab stacked body 25 faces the end surface 21 b of the tab stacked body 21. Therefore, the end faces 21a, 21b, 25a, and 25b of the tab laminates 21 and 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 plate 19 and the protective plate 27 adjacent to the end surfaces 25a and 25b. In the end surfaces 25a and 25b, the length of the welded portion W in the X-axis direction is preferably 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. Thereby, even if the tab 17b of the tab laminated body 25 is displaced in the X-axis direction (for example, when there is a displacement due to tolerance), the welded portion W can be stably formed. 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, the welded portion W may protrude outside the protective plate 27 in the X-axis direction due to positional displacement. When the length of the welded portion W in the X-axis direction is longer than the length of the protective plate 27 in the X-axis direction, the welded portion W protrudes outside the protective plate 27 in the X-axis direction. Even in those cases, the welded portion W can be formed.

  Similarly, in the tab laminate 21, the welded portion W extends to the inside of the current collector plate 16 and the protection plate 23 adjacent to the end surfaces 21 a and 21 b. In the end faces 21a and 21b, the length of the welded portion W in the X-axis direction is preferably 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. Thereby, even if the tab 14b of the tab laminated body 21 is displaced in the X-axis direction (for example, when there is a displacement due to tolerance), the welded portion W can be stably formed. If 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, the welded portion W may protrude outside the protective plate 23 in the X-axis direction due to positional displacement. Further, when the length of the welded portion W in the X-axis direction is longer than the length of the protective plate 23 in the X-axis direction, the welded portion W protrudes outside the protective plate 23 in the X-axis direction. Even in those cases, the welded portion W can be formed.

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

  As shown in FIG. 5, in the end surfaces 21a, 21b, 25a, and 25b of the tab laminates 21 and 25, the plurality of tabs 14b and 17b are not shifted like the end surfaces 21c and 25c. Therefore, the welded portion W formed on the inner side from the end faces 21a, 21b, 25a, 25b has a portion penetrating a plurality (all in this example) of the tabs 14b, 17b in the stacking direction of the tab stacks 21, 25. doing. That is, a welded portion W having a depth sufficient to join the plurality of tabs 14b and 17b is formed on the inner side from the end surfaces 21a, 21b, 25a, and 25b. As a result, the bonding strength between the plurality of tabs 14b and 17b can be increased.

  As shown in FIG. 5, in the cross section (for example, YZ cross section) of the tab laminated body 21 including the Z axis direction and orthogonal to the end faces 21 a and 21 b of the tab laminated body 21, the boundary line Wa of the welded portion W is Extending in a direction inclined with respect to both the direction H (for example, the Y-axis direction) perpendicular to the direction and the stacking direction (Z-axis direction) of the tab laminate 21. For example, the welded portion W has two boundary lines Wa, and depending on the shape of the molten pool formed around the energy beam B, the two boundary lines are moved toward the inside from the outer surface of the welded portion W. The interval of Wa is narrow. The welding pool is formed so as to taper inward from the surface of the irradiation object of the energy beam B in the irradiation direction of the energy beam B. Although the welded portion W is also formed on the current collector plate 16, the density of the current collector plate 16 is different from the density of the tab laminate 21, so the depth of the weld pool formed on the current collector plate 16 and the tab laminate 21 The depth of the weld pool formed is different. As a result, as described above, the distance between the two boundary lines Wa becomes narrower from the outer surface of the welded portion W toward the inside. That is, in the YZ cross section of the tab laminate 21, the smaller one of the angles formed by one boundary line Wa of the weld W and the direction H is α, and the other boundary line Wa of the weld W and the direction H Is the smaller angle of θ, and θ is the smaller angle of the angles formed by the direction J and the direction H projected from the irradiation direction of the energy beam B on the YZ plane. It becomes a value between β. For example, in the YZ cross section of the tab laminated body 21, the smaller angle among the angles formed by the boundary line Wa in the current collector plate 16 and the direction H is α, and the boundary line Wa in the tab laminated body 21 and the direction H are Of the angles formed, β is the smaller angle, and θ is the smaller angle among the angles formed by the direction J and the direction H in which the irradiation direction of the energy beam B is projected on the YZ plane, so that α <θ <β. Become. The boundary line Wa of the welded portion W may be parallel to the Z-axis direction in the YZ section.

  Similarly, in the cross section (for example, YZ cross section) of the tab laminated body 25 including the Z axis direction and orthogonal to the end faces 25a and 25b of the tab laminated body 25, the boundary line Wa of the welded portion W is a direction orthogonal to the Z axis direction ( For example, it extends in a direction inclined with respect to both the stacking direction (Z-axis direction) of the tab laminate 25 and the Y-axis direction. For example, the welded portion W has two boundary lines Wa, and depending on the shape of the molten pool formed around the energy beam B by irradiation of the energy beam B described later, the welded portion W is inward from the outer surface. The distance between the two boundary lines Wa becomes narrower as it goes. The welding pool is formed so as to taper inward from the surface of the irradiation object of the energy beam B in the irradiation direction of the energy beam B. Although the welded portion W is also formed on the current collector plate 19, the density of the current collector plate 19 is different from the density of the tab laminate 25, so the depth of the weld pool formed on the current collector plate 19 and the tab laminate 25 The depth of the weld pool formed is different. As a result, as described above, the distance between the two boundary lines Wa becomes narrower from the outer surface of the welded portion W toward the inside. That is, in the YZ cross section of the tab laminate 25, the smaller one of the angles formed by one boundary line Wa of the welded portion W and the direction H is α, and the other boundary line Wa of the welded portion W and the direction H are Is the smaller angle of θ, and θ is the smaller angle of the angles formed by the direction J and the direction H projected from the irradiation direction of the energy beam B on the YZ plane. It becomes a value between β. For example, in the YZ cross section of the tab laminate 25, the smaller one of the angles formed by the boundary line Wa in the current collector plate 19 and the direction H is α, and the boundary line Wa in the tab laminate 25 and the direction H are Of the angles formed, β is the smaller angle, and θ is the smaller angle among the angles formed by the direction J and the direction H in which the irradiation direction of the energy beam B is projected on the YZ plane, so that α <θ <β. Become. The boundary line Wa of the welded portion W may be parallel to the Z-axis direction in the YZ section.

  In the electrode assembly 3, the boundary line Wa of the welded portion W extends in a direction inclined with respect to both the direction H and the Z-axis direction in the YZ section of the tab laminates 21 and 25. 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 laminates 21, 25.

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

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

  As described above, in the electrode assembly 3, the maximum length W2 of the welded portion W in the direction (eg, the X-axis direction) orthogonal to the stacking direction of the tab stacked body 21 on the end faces 21a and 21b of the tab stacked body 21 is When viewed from a direction (for example, the Y-axis direction) orthogonal to both the stacking direction (for example, the Z-axis direction) of the stacked body 21 and the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab stacked body 21 It is larger than the maximum length W1 of the portion where the welded portion W and the tab laminate 21 overlap in the stacking direction (for example, the Z-axis direction) of the stack 21 (see FIGS. 3 and 4). Therefore, on the end faces 21 a and 21 b of the tab laminated body 21, the welded portion W spreads in a direction intersecting with the lamination direction of the tab laminated body 21. As a result, when current flows in the welding direction at the welded portion W, the electrical resistance value between the plurality of tabs 14b can be reduced. Further, since the mechanical strength of the welded portion W is increased, the welded portion W is not easily broken even if stress is generated in the electrode assembly 3 by, for example, an assembly operation or an external force. Furthermore, since the thermal diffusibility of the welded portion W is improved, the generation of sputtered particles due to the irradiation of the energy beam B can be suppressed when forming the welded portion W. Similarly, the maximum length W2 of the welded portion W in the direction (for example, the X-axis direction) orthogonal to the stacking direction of the tab stacked body 25 on the end surfaces 25a and 25b of the tab stacked body 25 is the stacking direction of the tab stacked body 25 (for example, When viewed from a direction (for example, the Y-axis direction) orthogonal to both the Z-axis direction) and a direction (for example, the X-axis direction) orthogonal to the stack direction of the tab stack 25, the stack direction of the tab stack 25 (for example, 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). Therefore, on the end faces 25 a and 25 b of the tab laminated body 25, the welded portion W spreads in a direction intersecting with the lamination direction of the tab laminated body 25. As a result, when the current flows in the stacking direction in the welded portion W, the electrical resistance value between the plurality of tabs 17b can be reduced. Further, since the mechanical strength of the welded portion W is increased, the welded portion W is not easily broken even if stress is generated in the electrode assembly 3 by, for example, an assembly operation or an external force. Furthermore, since the thermal diffusibility of the welded portion W is improved, the generation of sputtered particles due to the irradiation of the energy beam B can be suppressed when forming the welded portion W.

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

  The protective plate 23 may have a thickness of 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 becomes small, and thus the tab 14b tends to move during welding. If the thickness of the protective plate 23 is more than 0.5 mm, the energy for melting the protective plate 23 during welding tends to increase. When the output of the energy beam B is increased to increase the energy, sputtered particles due to the irradiation of the energy beam B are likely 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 laminated body 25 is disposed between the protective plate 27 and the current collector plate 19 in the laminating direction of the tab laminated body 25, and the thickness of the protective plate 27 in the laminating direction of the tab laminated body 25 is determined by the tab laminated body. It may be smaller than the thickness of the current collector plate 19 in the 25 stacking direction. In this case, since the thickness of the protection plate 27 is relatively small, the difference between the heat capacity of the protection plate 27 and the heat capacity of the tab 17b can be reduced. Therefore, the quality of the welding part W in the contact location of the protection board 27 and the tab 17b improves. The thickness of the protection plate 27 in the stacking direction of the tab laminate 25 may be larger than the thickness of the tab 17b in the stacking direction of the tab stack 25.

  The thickness of the protection plate 27 may be, for example, 0.1 to 0.5 mm or 0.1 to 0.2 mm. When the thickness of the protection plate 27 is less than 0.1 mm, the force with which the protection plate 27 presses the tab 17b is reduced, and thus the tab 17b tends to move during welding. If the thickness of the protective plate 27 is more than 0.5 mm, the energy for melting the protective plate 27 during welding tends to increase. When the output of the energy beam B is increased to increase the energy, sputtered particles due to the irradiation of the energy beam B are likely 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.

  6 and 7 are views showing a step of the method of manufacturing the electrode assembly according to the embodiment. The electrode assembly 3 shown in FIG. 3 is manufactured, for example, by the following method.

(Preparation process of tab laminate)
First, as shown in FIG. 6, a plurality of tab laminates 21 and 25 are prepared. 6A is a diagram showing the tab laminates 21 and 25 viewed from the X-axis direction, and FIG. 6B is a diagram showing the tab laminate 25 viewed from the Y-axis direction. For example, first, tab laminates 21 and 25 are formed by laminating tabs 14b and 17b on current collector plates 16 and 19, respectively. Thereafter, the protection plates 23 and 27 are placed on the tab laminates 21 and 25, respectively. The tab laminates 21 and 25 are pressed through the protective plates 23 and 27 by a jig, for example, but may not be pressed.

(Formation process of welded part)
Next, as shown in FIG. 7, the end surface 25 a of the tab laminate 25 is irradiated with the energy beam B. FIG. 7A is a diagram showing the tab laminates 21 and 25 viewed from the X-axis direction, and FIG. 7B is a diagram showing the tab laminate 25 viewed from the Y-axis direction. The energy beam B is irradiated from the irradiation device 30 toward the end surface 25a of the tab laminate 25. The irradiation device 30 is a scanner head including a lens and a galvanometer mirror, for example. A beam generator is connected to the scanner head via a fiber. The irradiation device 30 may be configured by a diffractive optical system such as a refractive type such as a prism or a diffractive optical element (DOE).

  A 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 surface 25a of the tab stack 25 and including the stacking direction of the tab stack 25 is Z in the plane (for example, YZ plane). You may incline with respect to both the direction H (for example, Y-axis direction) orthogonal to an axial direction, and the lamination direction of the tab laminated body 25. FIG. The direction J may also be inclined with respect to the end face 25a of the tab laminate 25. When the direction J is inclined as described above, the smaller angle θ among the angles formed by the direction H and the direction J in the YZ plane may be 5 to 85 °, or 10 to 80. The angle may be 45 ° or 45 ° to 75 °. The energy beam B is a high energy beam that can be welded. The energy beam B is, for example, a laser beam or an electron beam. The irradiation with the energy beam B is performed in an atmosphere of an inert gas G supplied from the nozzle 32.

  The energy beam B is applied to the end surface 25a of the tab laminated body 25 in a state where the tab laminated body 25 is pressed in the Z-axis direction through the current collector plate 19 and the protective plate 27 with a jig, for example.

  The energy beam B is scanned along the direction intersecting the Z-axis direction (X-axis direction) on the end surface 25a of the tab laminate 25. In the embodiment, scanning is performed along the X-axis direction while displacing the energy beam B in the Z-axis direction. For example, the energy beam B is scanned along the X-axis direction while being reciprocally displaced (wobbled) in the Z-axis direction. The amount of displacement of the irradiation spot of the energy beam B in the Z-axis direction is larger than the thickness of the tab laminate 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 laminate 25. For example, the positions P1 and P2 are located at the center of the end face 25a of the tab laminate 25 in the Z-axis direction. For example, the energy beam B is scanned while moving the center point along the X-axis direction on the end face 25a of the tab laminate 25 and rotating the irradiation spot of the energy beam B around the center point on the XZ plane. It is preferable that the diameter of rotation is larger than the thickness of the tab laminate 25 because the end face 25a, the current collector plate 19 and the protective plate 27 of the tab laminate 25 can be welded as a whole. Moreover, the energy beam B does not need to be irradiated to the part by the side of the protective plate 27 among the end surfaces 25a of the tab laminated body 25, and the energy beam B does not have to be irradiated to the remaining part by the side of the current collecting plate 19. In this case, the welding part W is not formed in the remaining part by the side of the current collecting plate 19 among the end surfaces 25a of the tab laminated body 25. FIG. However, the welded portion W extends in the irradiation direction of the energy beam B on the inner side of the end surface 25 a of the tab laminated body 25, so that the welded portion W extends in the thickness direction of the tab laminated body 25 inside the tab laminated body 25. It will be. By causing the welded portion W to reach the current collector plate 19, the plurality of tabs 17 b and the current collector plate 19 can be welded.

  By irradiating the energy beam B as described above, the welded portion W is formed on the inner side from the end surface 25a of the tab laminated body 25 as described above with reference to FIGS.

  Subsequently, the end surface 21b of the tab laminate 21 is also irradiated with the energy beam B, and a welded portion W is formed on the inner side from the end surface 21b. Similarly, the end face 25b of the tab laminated body 25 and 21a of the tab laminated body 21 are also irradiated with the energy beam B, and the welded portion W is formed inside the end faces 25b and 21a.

  The electrode assembly 3 is manufactured through the above steps.

  Thereafter, the tab laminates 21 and 25 are bent, for example, as shown in FIG. 3, and the bent electrode assembly 3 is accommodated in the case 2 to manufacture the power storage device 1.

  The bending of the tab laminates 21 and 25 may be completed, for example, in the preparation step of the tab laminate before the weld formation step. In that case, the welded portion W is formed by irradiating the end surfaces 21a, 21b, 25a, 25b with the energy beam B in a state where the tab laminates 21, 25 are bent. In addition, the protruding direction of the tab laminated body in a state where the tab laminated body is bent refers to a direction along the shape of the bent tab laminated body. In the example shown in FIG. 1, for example, the tab laminates 21 and 25 are bent at the bent portion F. In this case, the protruding direction of the tab laminates 21 and 25 is the direction away from the side surface S of the electrode body 20 in the portion of the tab laminates 21 and 25 closer to the electrode body 20 than the bent portion F. Further, in the portions of the tab laminates 21 and 25 closer to the current collector plates 16 and 19 than the bent portion F, the protruding direction of the tab laminates 21 and 25 is from the bent portion F to the current collector plates 16 and 19 side. It is said that the direction is heading.

  As described above, the electrode assembly 3 includes the electrode body 20 having a plurality of stacked main bodies 14a and 17a, and the tab stacked body 21 having a plurality of stacked tabs 14b and 17b and protruding from the electrode body 20. , 25. The positions of the tips of the plurality of tabs 14b and 17b are shifted in the protruding direction at the tip portions (the tip portion 253 and the like) in the protruding direction of the tab laminates 21 and 25. In the electrode assembly 3, the tab laminates 21 and 25 are tab laminates 21 and 25 extending along the stacking direction (Z-axis direction) of the tab laminates 21 and 25 and the protruding direction of the tab laminates 21 and 25. End portions 21a, 21b (first end surface, second end surface), and 25a, 25b (first end surface, second end surface). On the end surfaces 21a, 21b, 25a, and 25b of the tab laminates 21 and 25, unlike the tip portions (the tip portions 253 and the like) of the tab laminates 21 and 25, the above-described deviation amount is small. Therefore, a weld portion W having a sufficient depth can be formed inward from the end faces 21a, 21b, 25a, 25b of the tab laminates 21, 25. Therefore, it is possible to ensure the bonding strength between the stacked tabs 14b and 17b.

  In the tab laminate 21, when the welded portion W is located not only on one end surface (for example, the end surface 21a) but also on the inner side from the other end surface (for example, the end surface 21b), the welded portion W is located only on one end surface. Rather, the bonding strength between the stacked tabs 14b can be increased. Similarly, in the tab laminate 25, the welded portion W is located only on one end surface by having a welded portion not only on one end surface (eg, end surface 25a) but also on the inner side from the other end surface (eg, end surface 25b). It is possible to increase the bonding strength between the stacked tabs 17b as compared with the case of doing so.

  As described above with reference to FIGS. 3 and 5, the welded portion W is formed on the inner side from the end surfaces 21 a and 21 b of the tab laminated body 21, and is also formed on the current collector plate 16 and the protection plate 23. The 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. Therefore, 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 stacked body 21 in the stacking direction of the tab stacked body 21. 23, the plurality of tabs 14b and the current collector plate 16 are connected to each other by the welded portion W. Therefore, a member located across the tab laminate 21 as described above can be made unnecessary. Similarly, without using a member (for example, a member connecting the protection plate 27 and the current collector plate 19) positioned across the tab laminate 25 in the stacking direction of the tab laminate 25, the protection plate 27, the plurality of tabs 17b. And the current collector plate 19 are connected to each other by the welded portion W. Therefore, a member positioned across the tab laminate 25 as described above can be eliminated.

  In the stacked electrode assembly 3, the tab stacked body 21 and the tab stacked body 25 protrude from the electrode body 20 in the same direction, and the tab stacked bodies 21 and 25 may be bent. In this way, an electrode set having a configuration in which two tab laminates 21 and 25 (first tab laminate and second tab laminate) having opposite polarities (positive electrode and negative electrode) protrude in the same direction and are bent. Even in a three-dimensional structure, each tab laminate 21, 25 has a welded portion W located on the inner side from the end faces 21 a, 21 b, 25 a, 25 b, thereby joining the plurality of stacked tabs 14 b, 17 b to each other. Strength can be secured.

  Further, when the tab laminates 21 and 25 are bent before the welded portion W is formed by irradiation of the energy beam B, there are the following advantages. That is, when the tab laminates 21 and 25 are bent, the amount of displacement of the positions of the tips of the plurality of tabs 14b and 17b may be further increased at the tip portions (tip portions 253, etc.) of the tab laminates 21 and 25. There is. Even in that case, in the electrode assembly 3 of the embodiment, the tab laminates 21 and 25 have the welded portions W located on the inner side from the end faces 21a, 21b, 25a, and 25b, and therefore, the plurality of tabs 14b and 17b. Even if the positions of the tips of the tabs are shifted, it is possible to ensure the bonding strength between the stacked tabs 14b and 17b.

  In the electrode assembly 3, the length of the welded portion W in the direction inward from the end faces 21 a, 21 b, 25 a, 25 b of the tab laminates 21, 25 in a cross section orthogonal to the protruding direction of the tab laminates 21, 25. The (welding depth) increases as the current collector plates 16 and 19 are approached. Thereby, the joint strength with respect to the current collecting plates 16 and 19 of the some laminated | stacked 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 diagram showing the tab laminate 25 as viewed from the Y-axis direction, having the welded portion W according to the first modification. FIG. 8B is a view showing the tab laminate 25 as viewed from the Y-axis direction, having the welded portion W according to the second modification. In the first and second modified examples, when viewed from the normal direction of the end face 25a of the tab laminate 25, the welded portion W has an outer shape including a curve. For this reason, the stress is difficult to concentrate on the curved portion of the outer shape of the welded portion W, so that the welded portion W is difficult to peel off. The welded portion 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 outer shape of the welded portion W does not include a corner portion (a portion where straight lines intersect) where stress is likely to concentrate.

  The outer shape of the welded 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 welded portion W in the direction (X-axis direction) orthogonal to the stacking direction of the tab stack 25 on the end surface 25a of the tab stack 25 is the tab stack 25. Direction of the tab laminate 25 when viewed from a direction (Y-axis direction) perpendicular to both the direction of lamination (Z-axis direction) and the direction orthogonal to the direction of lamination of the tab laminate 25 (X-axis direction). 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 outer shape of the welded 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 welded portion W in the direction (X-axis direction) orthogonal to the stacking direction of the tab stack 25 on the end surface 25a of the tab stack 25 is the tab stack 25. Direction of the tab laminate 25 when viewed from a direction (Y-axis direction) perpendicular to both the direction of lamination (Z-axis direction) and the direction orthogonal to the direction of lamination of the tab laminate 25 (X-axis direction). 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 maximum length W2 may be equal to or less than the maximum length W1.

  In at least one of the end face 25b of the tab laminate 25 and the end faces 21a and 21b of the tab laminate 21, the welded portion W has the same shape as the welded portion W according to the first modified example or the second modified example. May be.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to a following example.

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

(Example 2)
A weld W was formed in the same manner as in Example 1 except that the maximum weld depth Wd of the weld W was 0.3 mm.

(Example 3)
A weld W was formed in the same manner as in Example 1 except that the maximum weld depth Wd of the weld W was 1.2 mm. The power of the laser used for forming the weld W was 1500 W, and the scanning speed was 24.9 mm / sec.

Example 4
A weld W was formed in the same manner as in Example 1 except that the maximum weld depth Wd of the weld W was 1.5 mm. The output of the laser used for forming the weld W was 1500 W, and the scanning speed was 8.3 mm / sec.

(Example 5)
A welded portion W was formed in the same manner as in Example 1 except that the maximum weld 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 state of irradiating the end surface of the tab laminate with a laser beam was imaged, and the number of sputtered particles resulting from the laser beam irradiation was counted from the obtained image. In Examples 4-5, the number of sputtered particles increased remarkably compared with Examples 1-3. Moreover, the electrical resistance value of the weld W was measured. A in the table shown in FIG. 9 indicates that good results were obtained, and B indicates that results that were not better than A were obtained. In Examples 2 to 4, better results were obtained than in Examples 1 and 5. According to the evaluation results in FIG. 9, the number of sputtered particles was reduced when the maximum weld depth Wd of the welded portion W was 0.3 to 1.5 mm. Further, when the maximum welding depth Wd is 0.3 to 1.2 mm, the number of sputter particles is remarkably reduced, and the electric resistance value of the welded portion W is a good value.

  3 ... Electrode assembly, 14a, 17a ... Main body, 14b, 17b ... Tab, 16, 19 ... Current collector (current collector), 20 ... Electrode body, 21, 25 ... Tab laminated body, 21a, 21b, 21c, 25a, 25b, 25c ... end faces, 23, 27 ... protective plates (conductive members), W ... welds.

Claims (9)

An electrode assembly having a plurality of electrodes each including a main body and a tab protruding from one end of the main body,
An electrode body having a plurality of stacked bodies;
A tab laminate having a plurality of laminated tabs and protruding from the electrode body;
With
In the tab laminate, the tips of the plurality of tabs are displaced in the protruding direction at the tip portion in the protruding direction of the tab laminate,
The tab laminate includes a welded portion located on the inner side from a first end surface 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 that extends along the stacking direction and the protruding direction and is located on the inner side from a second end surface different from the first end surface.
The electrode assembly according to claim 1.   The electrode assembly according to claim 1 or 2, wherein the plurality of tabs are connected to each other by the welded portion without using a member positioned across the tab laminate in the lamination direction. The electrode assembly is a laminated type,
The electrode assembly includes two electrode bodies having opposite polarities,
The tab laminate is a first tab laminate having a plurality of tabs protruding from an electrode body having one polarity and laminated,
The electrode assembly is a second tab laminate having a plurality of tabs protruding from the electrode body having the other polarity and laminated, the second tab laminate being stacked in the second tab laminate and the second tab laminate. The second tab laminate having a weld portion located on an inner side from an end surface of the second tab laminate extending along a protruding direction of the body,
In the second tab laminate, the positions of the tips of the plurality of tabs in the second tab laminate at the tip portion in the protrusion direction of the second tab laminate are the protruding direction of the second tab laminate. It is arranged to shift to
The first tab laminate and the second tab laminate protrude in the same direction,
The electrode assembly according to claim 1, wherein the first tab laminated body and the second tab laminated body are bent. The electrode assembly further includes a current collector,
The tab laminate is disposed on the current collector in the lamination direction;
In a cross section orthogonal to the protruding direction of the tab laminate, the length of the welded portion in the direction from the first end surface to the inside of the tab laminate increases as the current collector is approached. Item 5. The 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 a thickness of the conductive member in a stacking direction of the tab laminate is smaller than a thickness of the current collector in a stacking direction of the tab laminate.   The maximum length of the welded portion in the direction orthogonal to the stacking direction of the tab laminate at the first end surface of the tab laminate is orthogonal to the stacking direction of the tab laminate and the stacking direction of the tab laminate. Any one of Claims 1-6 which is larger than the maximum length of the part which the said welding part and the said tab laminated body overlap in the lamination direction of the said tab laminated body when it sees from the direction orthogonal to both the said directions. The electrode assembly according to one item.   The maximum weld depth of the weld in the direction perpendicular to the lamination direction of the tab laminate in the cross section of the tab laminate perpendicular to the first end surface of the tab laminate including the lamination direction of the tab laminate The electrode assembly according to claim 1, wherein is less than 2 mm.   The electrode assembly according to any one of claims 1 to 8, wherein the welded portion has an outer shape including a curve when viewed from the normal direction of the first end face of the tab laminate.

Images