WO2017110246A1

WO2017110246A1 - Electrode assembly and manufacturing method for power storage device

Info

Publication number: WO2017110246A1
Application number: PCT/JP2016/082108
Authority: WO
Inventors: 真也奥田; 雅巳冨岡; 雅人小笠原
Original assignee: 株式会社豊田自動織機
Priority date: 2015-12-21
Filing date: 2016-10-28
Publication date: 2017-06-29
Also published as: JP6753416B2; JPWO2017110246A1

Abstract

This electrode assembly which includes an electrode having a tab, is provided with: a current collector; and a tab laminate which includes laminated tabs. The tab laminate is disposed on the current collector in the lamination direction of the tab laminate. The tab laminate includes a welded portion which is positioned on the inner side with respect to a first end surface, of the tab laminate, extending in the lamination direction of the tab laminate. In a plane orthogonal to the lamination direction of the tab laminate, the welded portion has a cross sectional area which monotonically increases, over the thickness of the tab laminate, toward the current collector. In a cross section, of the tab laminate, that includes the lamination direction of the tab laminate and is orthogonal to the first end surface of the tab laminate, the outer surface of the welded portion is inclined with respect to the lamination direction of the tab laminate such that the outer surface extends outwardly in approaching the current collector.

Description

Electrode assembly and method for manufacturing power storage device

One aspect of the present invention relates to an electrode assembly and a method for manufacturing a power storage device.

When manufacturing a lithium secondary battery, a method of welding a plurality of tabs stacked on a current collector using a laser is known (see Patent Document 1).

Japanese Patent Laying-Open No. 2015-74028

In the above method, a weld is formed on the end face of a tab laminate composed of a plurality of stacked tabs. On the other hand, the value of the current flowing through each tab of the tab laminate increases as it approaches the current collector. Therefore, it is preferable to increase the cross-sectional area of the welded portion orthogonal to the stacking direction of the tab laminate in accordance with the maximum current value flowing in the tab closest to the current collector.

An object of one aspect of the present invention is to provide an electrode assembly and a method of manufacturing a power storage device that can adjust the electrical resistance value of each tab in accordance with the value of current flowing through each tab of the tab laminate.

An electrode assembly according to an aspect of the present invention is an electrode assembly including an electrode including a tab, and includes a current collector and a tab stacked body including the stacked tabs, and the tab stacked body includes The tab laminated body is disposed on the current collector in the laminating direction of the tab laminated body, and the tab laminated body is located on the inner side from the first end surface of the tab laminated body extending along the laminating direction of the tab laminated body. The cross-sectional area of the welded portion in a plane perpendicular to the stacking direction of the tab laminate is monotonously increased as the current collector approaches the thickness of the tab laminate, In the cross section of the tab laminate that includes the lamination direction of the tab laminate and is orthogonal to the first end surface of the tab laminate, the outer surface of the welded portion is directed outward as it approaches the current collector. Inclined with respect to the lamination direction of the tab laminate To have.

In this electrode assembly, the cross-sectional area of the welded portion increases monotonously as it approaches the current collector over the thickness of the tab laminate. Therefore, the electrical resistance value of each tab of the tab laminate decreases as the current collector is approached. On the other hand, the value of the current flowing through each tab of the tab laminate increases as it approaches the current collector. Therefore, in the electrode assembly, the electrical resistance value of each tab can be adjusted according to the current value flowing through each tab of the tab laminate.

In the cross section of the tab laminate, the current collector may protrude outward from the first end face of the tab laminate.

In this case, the inclination angle of the outer surface of the welded portion with respect to the stacking direction of the tab laminate can be increased. As a result, the rate of increase in the cross-sectional area of the welded portion in the stacking direction of the tab laminate is increased.

The electrode assembly includes a plurality of electrodes, each of the plurality of electrodes including a main body and the tab protruding from one end of the main body, and the electrode assembly includes a plurality of stacked main bodies. The length of the tab between the electrode main body and the welded portion may become shorter as the current collector is approached.

When the length of the tab between the electrode body and the welded portion is short, the heat generated in the welded portion is easily transferred to the electrode body, so that the electrode body is easily affected by heat. Even in such a case, in this electrode assembly, since the current collector is located near the tab where the distance between the electrode body and the welded portion is short, the heat generated in the welded portion is generated by the electrode body. Before the current collector. As a result, it is difficult for heat to be transferred from the welded portion to the electrode body via the tab.

The tab laminated body may have a second end face that is disposed on the opposite side of the tab laminated body from the first end face.

At the end face located at the tip of the tab laminate (the end face connecting the first and second end faces arranged opposite to each other across the tab laminate), the end faces arranged opposite to each other across the tab laminate. The positional deviation between the tabs is often larger than that of the first and second end faces. When the positional deviation between the tabs is large, it is difficult to monotonously increase the cross-sectional area of the welded portion over the thickness of the tab laminate as the current collector is approached. When forming the welded portion on the end face located at the tip of the tab laminate, the length of each tab is adjusted in order to suppress displacement between the tabs. On the other hand, in this electrode assembly, it is not necessary to form a welded portion on the end face located at the tip of the tab laminate, so that it is not necessary to adjust the length of each tab.

The tab laminate is disposed between the conductive member and the 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 extends in a direction intersecting the stacking 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 stacked 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.

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

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

A method of manufacturing a power storage device according to one aspect of the present invention includes a case having a main body portion in which an opening is formed and a lid portion that closes the opening of the main body portion, and the above-described electrode assembly housed in the case. A method of manufacturing a power storage device comprising: a step of fixing the current collector to the lid portion; a step of arranging the tab laminate on the current collector; and the step of fixing the current collector to the lid portion. Forming the welded portion by irradiating the first end surface of the tab laminated body with an energy beam in a state where the tab laminated body is disposed on the current collector.

When welding the tabs of the tab laminate in a state where the tab laminate is arranged on the current collector fixed to the lid, when using resistance welding, the current collector and the tab laminate are paired with a pair of electrodes. It is necessary to pinch. In that case, the position of the electrode may interfere with the position of the lid. On the other hand, in this method for manufacturing a power storage device, the welded portion is formed by irradiation with an energy beam, so that an electrode necessary for resistance welding is not necessary. Therefore, the problem of interference due to the position of the electrode does not occur.

In the manufactured power storage device, the current collector may be an unbent flat plate.

In resistance welding, in order to avoid the problem of interference due to the position of the electrode, a bent current collector plate is used to separate the region fixed to the lid and the region to be resistance welded. On the other hand, in this power storage device manufacturing method, since the welded portion is formed by irradiation with an energy beam, welding can be performed even if an unbent flat plate is used as the current collector.

A method of manufacturing a power storage device according to another aspect of the present invention includes a case having a main body portion in which an opening is formed and a lid portion that closes the opening of the main body portion, and an electrode assembly accommodated in the case. The electrode assembly includes an electrode including a tab, and the electrode assembly includes a current collector and a tab stacked body including the stacked tabs. The tab laminated body is disposed on the current collector in the lamination direction of the tab laminated body, and the tab laminated body extends along the lamination direction of the tab laminated body. A method of manufacturing the power storage device, comprising: a step of fixing the current collector to the lid; and a step of disposing the tab laminate on the current collector. The tab laminate is disposed on the current collector fixed to the lid. State, by irradiating an energy beam to the first end face of the tab laminate, and forming the weld.

According to one aspect of the present invention, it is possible to provide an electrode assembly and a method for manufacturing a power storage device that can adjust the electrical resistance value of each tab in accordance with the value of current flowing through each tab of the tab laminate.

FIG. 1 is an exploded perspective view of a power storage device including the electrode assembly according to the first embodiment. FIG. 2 is a cross-sectional view of the power storage device taken along line II-II in FIG. FIG. 3 is a perspective view of the electrode assembly according to the first embodiment. 4 is a view showing a part of the electrode assembly of FIG. 3 as viewed from the X-axis direction. FIG. 5 is a view showing a part of the electrode assembly of FIG. 3 as viewed from the Y-axis direction. FIG. 6 is a diagram illustrating a step of the method of manufacturing the power storage device according to the first embodiment. FIG. 7 is a diagram illustrating one step in the method of manufacturing the power storage device according to the first embodiment. FIG. 8 is a diagram illustrating a step of the method of manufacturing the power storage device according to the first embodiment. FIG. 9 is a diagram illustrating a step of the method of manufacturing the power storage device according to the first embodiment. FIG. 10 is a diagram illustrating one step in the method of manufacturing the power storage device according to the first embodiment. FIG. 11 is a diagram illustrating a step of the method of manufacturing the power storage device according to the first embodiment. FIG. 12 is a diagram illustrating one process of the method for manufacturing the power storage device according to the second embodiment. FIG. 13 is a diagram illustrating a step of the method of manufacturing the power storage device according to the second embodiment. FIG. 14 is a diagram illustrating one process of the method for manufacturing the power storage device according to the third embodiment. FIG. 15 is a diagram illustrating a step of the method of manufacturing the power storage device according to the third embodiment. FIG. 16 is a diagram illustrating a part of an electrode assembly having a weld according to a modification. FIG. 17 is a diagram illustrating 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 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 first 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.

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 in which an opening is formed 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. 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 has a metal foil 14 made of, for example, 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 accommodates 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 first embodiment. 4 is a diagram (partial sectional view) showing a part of the electrode assembly of FIG. 3 as viewed from the X-axis direction. FIG. 5 is a view showing a part of the electrode assembly of FIG. 3 as viewed from the Y-axis direction. The electrode assembly 3 shown in FIG. 3 includes a plurality of positive electrodes 11 and a plurality of negative electrodes 12 that are stacked on each other 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. 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 together to form electrode

main bodies

40 and 42, respectively. That is, the electrode assembly 3 includes an electrode body 40 having a plurality of main bodies 14a stacked in the Z-axis direction, and an electrode body 42 having a plurality of main bodies 17a stacked in the Z-axis direction. 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 a tab laminate 21 having a plurality of tabs 14b laminated in the Z-axis direction and a tab laminate 25 having a plurality of tabs 17b laminated in the Z-axis direction. 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 extending 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 surfaces 21 a and 21 b (first and second end surfaces) 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 protective 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 in the Z-axis direction. 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 tab laminate 21. The thickness of the protective plate 23 is larger than the thickness of the tab 14 b and smaller than the thickness of the current collector plate 16. The electrode assembly 3 may not include the protection plate 23 and the current collector plate 16.

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 side from the end faces 21a and 21b of the tab laminated body 21, 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 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 FIG. 3). The maximum length W1 is smaller than the maximum length of the welded portion W in the Z-axis direction. The welded portion W extends to the inside of the current collector plate 16 and the protective plate 23 adjacent to the end surfaces 21a and 21b. 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.

As shown in FIG. 4, in the electrode assembly 3, the cross-sectional area of the welded portion W in a plane (for example, the XY plane) orthogonal to the stacking direction (for example, the Z-axis direction) of the tab stacked body 21 is The thickness increases monotonously as the current collector plate 16 is approached. For example, the cross-sectional area of the welded portion W is the product of the weld depth D of the welded portion W and the weld length L (see FIG. 3) in the X-axis direction. Further, the outer surface Ws of the welded portion W approaches the current collector plate 16 in the cross section (for example, the YZ cross section) of the tab laminated body 21 that includes the laminating direction of the tab laminated body 21 and is orthogonal to the end faces 21 a and 21 b of the tab laminated body 21. Accordingly, the tab laminated body 21 is inclined with respect to the stacking direction so as to go outward (in a direction away from the end faces 21a and 21b). The outer surface Ws of the welded portion W may be inclined with respect to the stacking direction of the tab laminate 21 so as to go outward as it approaches the current collector plate 16 over the thickness of the tab laminate 21. You may incline with respect to the lamination direction of the tab laminated body 21 so that it may go outside as it approaches the current collecting plate 16 over a part of thickness of 21. In the cross section of the tab laminate 21 (for example, the YZ cross section), the current collector plate 16 may protrude outward from the end faces 21 a and 21 b of the tab laminate 21, but inside the end faces 21 a and 21 b of the tab laminate 21. May be located.

In addition, in the cross section (for example, the YZ cross section) of the tab laminated body 21 including the Z axis direction and orthogonal to the end faces 21a and 21b of the tab laminated body 21, the boundary line Wa of the welded portion W is a direction H (perpendicular to the Z axis direction). For example, you may extend in the direction inclined with respect to both the lamination direction (Z-axis direction) of the tab laminated body 21 and the Y-axis direction. For example, the welded portion W has two boundary lines Wa, and the welded portion W depends on the shape of the molten pool formed around the energy beam B by irradiation with an energy beam B (see FIG. 8) described later. The distance between the two boundary lines Wa becomes narrower from the outer surface Ws toward the inner side. 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 Ws 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 in the tab laminate 21 may extend in parallel to the lamination direction of the tab laminate 21.

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 surfaces 25 a and 25 b (first and second end surfaces) are arranged on opposite sides of the tab laminate 25. The end surfaces 25a and 25b are surfaces along the XZ plane. The end surface 25 c is a surface that 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.

The tab laminate 25 is disposed between the current collector plate 19 and the protective plate 27 in the Z-axis direction. That is, 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 in the Z-axis direction. The protective plate 27 is not in contact with the current collector plate 19, and the protective plate 27 and the current collector plate 19 are separated with the tab laminate 25 sandwiched in the stacking direction. The tab laminate 25 is thicker than the protective plate 27, and the current collector plate 19 is thicker than the tab laminate 25. The thickness of the protection plate 27 is larger than the thickness of the tab 17 b and smaller than the thickness of the current collector plate 19. The electrode assembly 3 may not include the protection plate 27 and the current collector plate 19.

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 faces 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 sides from the end faces 25a and 25b of the tab laminated body 25, respectively. The end surface 25 b of the tab laminated body 25 faces the end surface 21 b of the tab laminated 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. 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 FIG. 3). The welded portion W extends to the inside of the current collector plate 19 and the protection 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.

As shown in FIG. 4, in the electrode assembly 3, the cross-sectional area of the welded portion W in a plane (for example, the XY plane) orthogonal to the stacking direction (for example, the Z-axis direction) of the tab stack 25 is The thickness increases monotonically as the current collector plate 19 is approached. In addition, the outer surface Ws of the welded portion W approaches the current collector plate 19 in the cross section (for example, the 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 25 a and 25 b of the tab laminated body 25. Accordingly, the tab laminated body 25 is inclined with respect to the lamination direction so as to go outward (in a direction away from the end faces 25a and 25b). The outer surface Ws of the welded portion W may be inclined with respect to the stacking direction of the tab laminate 25 so as to go outward as it approaches the current collector plate 19 over the thickness of the tab laminate 25. You may incline with respect to the lamination direction of the tab laminated body 25 so that it may face outside as it approaches the current collecting plate 19 over a part of thickness of 25. In the cross section of the tab laminate 25 (for example, the YZ cross section), the current collector plate 19 may protrude outward from the end faces 25a and 25b of the tab laminate 25, but inside the end faces 25a and 25b of the tab laminate 25. May be located.

In addition, in the cross section (for example, the YZ cross section) of the tab laminated body 25 that includes the Z axis direction and is 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 H (perpendicular to the Z axis direction). For example, you may extend in the direction inclined with respect to both the lamination direction (Z-axis direction) of the tab laminated body 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 in the tab laminate 25 may extend in parallel to the lamination direction of the tab laminate 25.

In the electrode assembly 3 according to the first embodiment, the cross-sectional area of the welded portion W in the XY plane increases monotonously as it approaches the

current collector plates

16 and 19 over the thickness of the tab laminates 21 and 25. Further, in the YZ section, the outer surface Ws of the welded portion W is inclined with respect to the stacking direction of the tab laminates 21 and 25 so as to go outward as the

current collector plates

16 and 19 are approached. The welded portion W having such a shape is formed by the molten material moving in the stacking direction of the tab laminates 21 and 25 by, for example, at least one of gravity and surface tension when the welded portion W is formed. obtain. Further, the extending direction of the boundary line Wa of the welded portion W is controlled by, for example, the irradiation direction of the energy beam B irradiated to the end faces 21a, 21b, 25a, and 25b of the tab laminates 21 and 25 as described above. .

Further, as shown in FIG. 5, the length of the tab 17 b between the electrode main body 42 and the welded portion W may be shortened as the current collector plate 19 is approached. The electrode body 42 has one end 42a and the other end 42b in the Z-axis direction, and the plurality of tabs 17b are bundled on the one end 42a side in the Z-axis direction. As a result, the end of the tab 17b becomes longer as it approaches the current collector plate 19, so that the end face 25c located at the end of the tab laminate 25 becomes an inclined surface. Similarly, in the tab laminate 21, the lengths of the plurality of tabs 14 b between the electrode main body 40 and the welded portion W may be shortened as the current collector plate 16 is approached. The length of the plurality of

tabs

14b, 17b between the electrode

main bodies

40, 42 and the welded portion W may be shortened as the

current collector plates

16, 19 are approached across the tab laminates 21, 25, It may be shortened as it approaches the

current collector plates

16 and 19 over a part of the tab laminates 21 and 25. Further, the lengths of the plurality of

tabs

14 b and 17 b between the electrode

main bodies

40 and 42 and the welded portion W may be shortened as the

protective plates

23 and 27 are approached. In this case, the plurality of

tabs

14b and 17b are bundled on the other end 42b side in the Z-axis direction.

As described above, in the electrode assembly 3 of the first embodiment, the cross-sectional area of the welded portion W increases monotonously as the

current collector plates

16 and 19 are approached over the thickness of the tab laminates 21 and 25. Yes. Therefore, as the

current collector plates

16 and 19 are approached, the electric resistance values of the

tabs

14b and 17b of the tab laminates 21 and 25 become smaller. On the other hand, the value of the current flowing through the

tabs

14 b and 17 b of the tab laminates 21 and 25 increases as the

current collectors

16 and 19 are approached. Therefore, in the electrode assembly 3, the electrical resistance value of each

tab

14b, 17b can be adjusted according to the value of the current flowing through each

tab

14b, 17b of the

tab laminate

21, 25.

Further, since the contact area between the

current collector plates

16 and 19 and the welded portion W is increased, the joint strength between the

current collector plates

16 and 19 and the welded portion W is increased. Further, since the outer surface Ws of the welded portion W is inclined with respect to the stacking direction of the tab laminates 21 and 25 so as to go outward as the

current collector plates

16 and 19 are approached, for example, the tab laminate 21 or Even when an external force is applied to 25, the tab laminates 21, 25 are difficult to peel from the

current collector plates

16, 19.

When the

current collector plates

16 and 19 protrude outward from the end surfaces 21a, 21b, 25a, and 25b of the tab laminates 21 and 25 in the cross section of the tab laminates 21 and 25 (for example, the YZ cross section), the tab laminate The inclination angle of the outer surface Ws of the welded portion W with respect to the stacking direction of 21 and 25 can be increased. As a result, the rate of increase in the cross-sectional area of the welded portion W increases in the stacking direction of the tab laminates 21 and 25. When the welded portion W is formed, the molten material easily moves outward from the end surfaces 21a, 21b, 25a, 25b along the surfaces of the

current collector plates

16, 19 due to, for example, at least one of gravity and surface tension. Therefore, the inclination angle of the outer surface Ws of the welded portion W increases.

If the lengths of the

tabs

14b and 17b between the

electrode bodies

40 and 42 and the welded portion W are short, the heat generated in the welded portion W is easily transferred to the

electrode bodies

40 and 42. It is easy to influence. Even in such a case, in the electrode assembly 3, the

current collector plates

16 and 19 are located near the

tabs

14b and 17b where the distance between the electrode

main bodies

40 and 42 and the welded portion W is short. The heat generated in the weld W is transmitted to the

current collector plates

16 and 19 before the

electrode bodies

40 and 42. As a result, it is difficult for heat to be transmitted from the welded portion W to the

electrode bodies

40 and 42 via the

tabs

14b and 17b. Therefore, melting of the separator 13 and alteration of the material of the

electrode bodies

40 and 42 can be suppressed. Furthermore, since the

current collecting plates

16 and 19 have a higher heat capacity than the

protective plates

23 and 27, the heat can be released more efficiently than when the heat is released to the

protective plates

23 and 27. .

In the end face 25c located at the tip of the tab laminated body 25, the positional deviation between the tabs 17b is often larger than the two end faces 25a and 25b arranged on the opposite sides of the tab laminated body 25 (see FIG. 3). Similarly, in the tab laminate 21, the positional deviation between the tabs 14b often increases on the end surface 21c. When the positional deviation between the

tabs

14b and 17b is large, it becomes difficult to monotonously increase the cross-sectional area of the welded portion W over the thickness of the tab laminates 21 and 25 as the

current collector plates

16 and 19 are approached. When the welded portion W is formed on the end surfaces 21c and 25c located at the tips of the tab laminates 21 and 25, the lengths of the

tabs

14b and 17b are adjusted in order to suppress the displacement between the

tabs

14b and 17b. ing. On the other hand, in the electrode assembly 3, since it is not necessary to form the welding part W in the end surfaces 21c and 25c located in the front-end | tip of the tab laminated

bodies

21 and 25, it is not necessary to adjust the length of each

tab

14b and 17b.

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. 17).

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 lamination direction of the laminate 21 (for example, the Z-axis direction) (see FIG. 3). 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 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 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 protective 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 to 11 are views showing one process of the method for manufacturing the power storage device according to the first embodiment. The power storage device 1 shown in FIGS. 1 and 2 is manufactured by, for example, the following method.

(Current collector fixing process)
First, as shown in FIG. 6, the

current collector plates

16 and 19 are fixed to the lid portion 2b. 6A is a diagram showing the lid 2b and the

current collector plates

16 and 19 seen from the X-axis direction, and FIG. 6B shows the lid 2b and the current collector 19 seen from the Y-axis direction. FIG. An insulating member 28 having a plurality of holes for allowing the positive electrode terminal 5 and the negative electrode terminal 6 to pass through can be disposed between the lid portion 2 b and the

current collector plates

16 and 19.
(Arrangement process of tab laminate)
Next, as shown in FIG. 7, the tab laminates 21 and 25 are disposed on the

current collector plates

16 and 19, respectively. The

current collector plates

16 and 19 are located between the tab laminates 21 and 25 and the lid portion 2b. 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. Thereafter, the

protective plates

23 and 27 may be 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. 8, the energy beam is applied to the end surface 25a of the tab laminate 25 in a state where the tab laminates 21 and 25 are respectively disposed on the

current collector plates

16 and 19 fixed to the lid portion 2b. B is irradiated. 8A is a diagram showing the tab laminates 21 and 25 viewed from the X-axis direction, and FIG. 8B 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 irradiating device 30 may be composed of 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 is also inclined with respect to the end face 25 a of the tab laminate 25. In the YZ plane, the smaller angle θ among the angles formed by the direction H and the direction J may be 5 to 85 °, 10 to 80 °, or 45 to 75 °. Good. The direction J may be parallel to the direction H. 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 irradiated 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 via the current collector plate 19 and the protective plate 27 by a jig, for example.

The work including the

current collecting plates

16 and 19, the tab laminates 21 and 25, and the

protection plates

23 and 27 is placed on a transport stage such as a belt conveyor, and is transported in the Y-axis direction to the irradiation position of the energy beam B. The

The energy beam B can be scanned along the direction (X-axis direction) intersecting the Z-axis direction on the end face 25a of the tab laminate 25. In the first 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 H1 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.

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 laminate 25 as shown in FIG. 9A is a diagram showing the tab laminates 21 and 25 viewed from the X-axis direction, and FIG. 9B is a diagram showing the tab laminate 25 viewed from the Y-axis direction.

Subsequently, as shown in FIG. 10, the energy beam B is similarly applied to the end face 21 b of the tab laminated body 21. Thereby, as shown in FIG. 11, the welded portion W is also formed from the end surface 21 b of the tab laminated body 21 to the inside.

The energy beam B is applied to the end face 21b in a state where the end face 25b of the tab laminated body 25 and the end face 21b of the tab laminated body 21 are arranged to face each other.

Subsequently, similarly to the end face 21b of the tab laminated body 21, the welded portion W is formed on the inner side from the end face 25b of the tab laminated body 25 by irradiating the end surface 25b of the tab laminated body 25 with the energy beam B (FIG. 4). reference). The energy beam B is applied to the end face 25b in a state where the end face 25b of the tab laminated body 25 and the end face 21b of the tab laminated body 21 are arranged to face each other. Then, similarly to the end surface 25b of the tab laminated body 25, the end surface 21a of the tab laminated body 21 is irradiated with the energy beam B, thereby forming a welded portion W from the end surface 21a of the tab laminated body 21 (see FIG. 4). ).

When the energy beam B is irradiated, the workpiece including the tab stacked

bodies

21 and 25 is transferred in the Y-axis direction to the irradiation position of the energy beam B by the transfer stage. The end surfaces 21a and 25b of the tab laminates 21 and 25 are irradiated with the energy beam B using the first irradiation device 30, and the end surfaces 21b and 25a of the tab laminates 21 and 25 are used using the second irradiation device 30. May be irradiated with the energy beam B. Further, the end surfaces 25a, 21b, 25b, and 21a may be sequentially irradiated with the energy beam B by moving one irradiation device 30 with a driving device such as a motor to change the irradiation direction of the energy beam B.
(Electrode assembly accommodation process)
Next, the obtained electrode assembly 3 is accommodated in the main body 2a of the case 2, and the tab laminates 21 and 25 are bent. As a result, the opening of the main body 2a is blocked by the lid 2b.

The power storage device 1 is manufactured through the above steps.

In the case where resistance welding is used when welding the tabs 17b of the tab laminate 25 with the tab laminates 21 and 25 arranged on the

current collector plates

16 and 19 fixed to the lid 2b, respectively, It is necessary to sandwich the plate 19 and the tab laminate 25 with a pair of electrodes. In that case, the position of the electrode may interfere with the position of the lid 2b. On the other hand, in the method for manufacturing the power storage device 1 of the present embodiment, since the welded portion W is formed by irradiation with the energy beam B, an electrode necessary for resistance welding is not necessary. Therefore, the problem of interference due to the position of the electrode does not occur.

In the manufactured power storage device 1, the

current collecting plates

16 and 19 may be flat plates that are not bent. That is,

current collector plates

16 and 19 may be flat plates that are not bent from the start to the end of manufacture of power storage device 1. In resistance welding, in order to avoid the problem of interference due to the position of the electrodes, a bent current collector plate is used to separate the region fixed to the lid and the region to be resistance welded. On the other hand, in the method for manufacturing the power storage device 1, since the welded portion W is formed by irradiation with the energy beam B, welding can be performed even if flat plates that are not bent are used as the

current collector plates

16 and 19. As a result, the degree of freedom in designing the power storage device 1 is increased. The

current collecting plates

16 and 19 are not flat plates that are not bent, but may be bent flat plates.

FIG. 12 to FIG. 13 are views showing one process of the manufacturing method of the electrode assembly according to the second embodiment. 12A and 13A are views showing the tab laminates 21 and 25 viewed from the X-axis direction, and FIGS. 12B and 13B are tab stacks viewed from the Y-axis direction. FIG. In 2nd Embodiment, the electrical storage apparatus 1 can be manufactured similarly to 1st Embodiment except the welding part W being formed in the end surfaces 21c and 25c (1st end surface) of the tab laminated

bodies

21 and 25, respectively. it can.

The end surface 25c of the tab laminated body 25 is located at the tip of the tab laminated body 25 and is a surface along the YZ plane. The end face 25c may be formed by cutting the tip end of the tab laminate 25, or may be formed by laminating the tab 17b using tabs 17b having different lengths.

As shown in FIG. 12, the direction J in which the irradiation direction of the energy beam B is projected onto a plane (for example, XZ plane) that is orthogonal to the end surface 25c of the tab laminate 25 and includes the lamination direction of the tab laminate 25 is the plane. In (for example, XZ plane), you may incline with respect to both the direction H (for example, X-axis direction) orthogonal to a Z-axis direction, and the lamination direction of the tab laminated body 25. FIG. The direction J is also inclined with respect to the end face 25 c of the tab laminate 25. The energy beam B is scanned along the Y-axis direction while being displaced (wobbling) in the Z-axis direction on the end face 25c. The irradiation spot of the energy beam B moves from the position P4 on the axis H1 along the Y-axis direction to the position P5 on the end face 25c. For example, the positions P4 and P5 are located at the center of the end face 25c in the Z-axis direction. For example, the energy beam B is scanned while moving the center point along the Y-axis direction on the end face 25c and rotating the irradiation spot of the energy beam B around the center point on the YZ plane.

As shown in FIG. 13, the welded portion W is formed on the inner side from the end surface 25 c of the tab laminated body 25 by the irradiation of the energy beam B. As shown in FIG. 13B, the cross-sectional area of the welded portion W in a plane (for example, the XY plane) orthogonal to the stacking direction (for example, the Z-axis direction) of the tab stack 25 extends over the thickness of the tab stack 25. As it approaches the current collector plate 19, it monotonously increases. Further, as the outer surface Ws of the welded portion W approaches the current collector plate 19 in the cross section (for example, the XZ cross section) of the tab laminated body 25 that includes the lamination direction of the tab laminated body 25 and is orthogonal to the end face 25c of the tab laminated body 25. It is inclined with respect to the stacking direction of the tab laminate 25 so as to go outward (in a direction away from the end face 25c). In the cross section of the tab laminated body 25 (for example, the XZ cross section), the current collector 19 may protrude outward from the end face 25c of the tab laminated body 25, but is positioned inside the end face 25c of the tab laminated body 25. Also good.

Similarly, by irradiating the end surface 21c of the tab laminated body 21 with the energy beam B, the welded portion W is also formed on the end surface 21c of the tab laminated body 21.

In the second embodiment, the same effects as those in the first embodiment can be obtained. Moreover, in 2nd Embodiment, since the welding part W is formed also in the end surface 25c in addition to the end surfaces 25a and 25b of the tab laminated body 25, the electrical resistance value between the tabs 17b can be reduced. Similarly, the electrical resistance value between the tabs 14b can also be reduced. The welded portion W may not be formed on the end surfaces 21a, 21b, 25a, and 25b of the tab laminates 21 and 25, and the welded portion W may be formed only on the end surfaces 21c and 25c of the tab laminates 21 and 25.

FIG. 14 to FIG. 15 are diagrams showing one process of the method for manufacturing the electrode assembly according to the third embodiment. 14A and 15A are views showing the tab laminate 25 viewed from the X-axis direction, and FIGS. 14B and 15B are tab laminates 25 viewed from the Y-axis direction. FIG. In the third embodiment, the electrode assembly 3 can be manufactured in the same manner as in the first embodiment, except that the wound electrode assembly 3 is manufactured instead of the stacked electrode assembly 3.

The wound electrode assembly 3 includes tab laminates 21 and 25, similar to the stacked electrode assembly 3. The tab laminates 21 and 25 are disposed on opposite sides in the X-axis direction. In the tab laminate 25, the tab 17b is wound around the axis in the X-axis direction and then compressed in the Z-axis direction. Therefore, the tab laminate 25 includes tabs 17b that are laminated in the Z-axis direction. Specifically, a plurality of portions in the tab 17b are stacked in the Z-axis direction. The welded portion W connects the stacked tabs 17b. Specifically, a plurality of portions in the tab 17b are connected by the welded portion W. In the wound electrode assembly 3, the tab laminate 25 does not include the end surfaces 25a and 25b, but includes only the end surface 25c located at the tip. Similarly, the tab laminate 21 does not include the end surfaces 21a and 21b, but includes only the end surface 21c located at the tip.

As shown in FIG. 14, the energy beam B is applied to the end face 25 c of the tab laminate 25 as in the second embodiment.

As shown in FIG. 15, similarly to the second embodiment, the welded portion W is formed on the inner side from the end surface 25 c of the tab laminated body 25 by the irradiation of the energy beam B.

In the third embodiment, the same operational effects as in the second embodiment can be obtained.

FIG. 16 is a view showing a part of an electrode assembly having a weld according to a modification. FIG. 16A is a diagram showing a tab laminate 25 as viewed from the Y-axis direction, which has a welded portion W according to a first modification. FIG. 16B is a view showing the tab laminate 25 having the welded portion W according to the second modified example as seen from the Y-axis direction. 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. 16A, the maximum length W2 of the welded portion W in the direction (X-axis direction) orthogonal to the stacking direction of the tab stacked body 25 on the end surface 25a of the tab stacked body 25 is the tab stacked body 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. 16B, 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.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. The components of the above embodiments can be arbitrarily combined.

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

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 to 5, the number of sputtered particles was remarkably increased compared to Examples 1 to 3. Moreover, the electrical resistance value of the weld W was measured. A in the table shown in FIG. 17 indicates that good results were obtained, and B indicates that results that were not better than A were obtained. In Examples 2 to 4, good results were obtained as compared to Examples 1 and 5. According to the evaluation result of FIG. 17, when the maximum welding depth Wd of the welded portion W is 0.3 to 1.5 mm, the number of sputtered particles is reduced. Further, when the maximum welding depth Wd is 0.3 to 1.2 mm, the number of sputtered particles is remarkably reduced, and the electric resistance value of the welded portion W is a good value.

DESCRIPTION OF SYMBOLS 1 ... Power storage device, 2 ... Case, 2a ... Main body part, 2b ... Cover part, 3 ... Electrode assembly, 11 ... Positive electrode (electrode), 12 ... Negative electrode (electrode), 14a, 17a ... Main body, 14b, 17b ... Tab , 16, 19 ... current collector plate (current collector), 21, 25 ... tab laminate, 21a, 21b, 21c, 25a, 25b, 25c ... end face, 23, 27 ... protective plate (conductive member), 40, 42 ... electrode body, B ... energy beam, W ... weld, Ws ... outer surface.

Claims

An electrode assembly comprising an electrode including a tab,
A current collector,
A tab laminate having the tabs laminated;
With
The tab laminate is disposed on the current collector in the stacking direction of the tab laminate,
The tab laminate has a weld portion located on the inner side from the first end surface of the tab laminate extending along the lamination direction of the tab laminate,
The cross-sectional area of the welded portion in a plane perpendicular to the stacking direction of the tab laminate is monotonously increased as the current collector approaches the thickness of the tab laminate,
In the cross section of the tab laminate that includes the lamination direction of the tab laminate and is orthogonal to the first end surface of the tab laminate, the outer surface of the welded portion is directed outward as it approaches the current collector. An electrode assembly that is inclined with respect to the stacking direction of the tab stack.
2. The electrode assembly according to claim 1, wherein in the cross section of the tab laminate, the current collector projects outward from a first end face of the tab laminate.
The electrode assembly comprises a plurality of electrodes;
Each of the plurality of electrodes includes a main body and the tab protruding from one end of the main body,
The electrode assembly further comprises an electrode body having a plurality of stacked bodies,
The electrode assembly according to claim 1 or 2, wherein a length of the tab between the electrode main body and the welded portion is shortened as the current collector is approached.
The tab laminated body according to any one of claims 1 to 3, wherein the tab laminated body has a second end face that is disposed on a side opposite to the first end face of the tab laminated body with the tab laminated body interposed therebetween. Electrode assembly.
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 4, wherein a thickness of the conductive member in the stacking direction of the tab laminate is smaller than a thickness of the current collector in the 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 to 5, wherein when viewed from a direction orthogonal to both of 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 is larger. 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 any one of claims 1 to 6, wherein is less than 2 mm.
The electrode assembly according to any one of claims 1 to 7, 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.
9. A case having a main body portion in which an opening is formed and a lid portion that closes the opening of the main body portion, and an electrode assembly according to any one of claims 1 to 8 accommodated in the case. A method for manufacturing a power storage device, comprising:
Fixing the current collector to the lid,
Arranging the tab laminate on the current collector;
Forming the welded portion by irradiating the first end face of the tab laminate with an energy beam in a state where the tab laminate is disposed on the current collector fixed to the lid portion; ,
A method for manufacturing a power storage device, comprising:
10. The method of manufacturing a power storage device according to claim 9, wherein in the manufactured power storage device, the current collector is a flat plate that is not bent.