JP2017107655A - Electrode assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode assembly capable of reducing variation of a current flowing between a tab laminate and a terminal.SOLUTION: An electrode assembly 3 includes a plurality of negative electrodes 12 each including a tab 17b, and also includes a tab laminate 25 having a plurality of laminated tabs 17b. The tab laminate 25 has first and second weld portions W1, W2 for bonding a plurality of the tabs 17b. The weld portions W1, W2 are electrically connected to a negative electrode terminal 6. The length of a current path LC1 between the weld portion W1 and the negative electrode terminal 6 is shorter than the length of a current path LC2 between the weld portion W2 and the negative electrode terminal 6. In the cross section of the tab laminate 25 which is perpendicular to the lamination direction of the tab laminate 25, the conduction area S1 of the weld portion W1 is smaller than the conduction area S2 of the weld portion W2.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electrode assembly.

  There is known a secondary battery in which a plurality of current collector plates are connected to a terminal body (see, for example, Patent Document 1). In this secondary battery, the current collector plate is connected to the terminal main body portion by a welded portion in the current collector plate group close to the terminal main body portion among the plurality of current collector plates. Moreover, in the current collecting plate group far from the terminal body portion among the plurality of current collecting plates, the current collecting plates are connected to each other by a welding portion.

JP 2014-154272 A

  In the secondary battery, the welding area of the welded portion close to the terminal main body is larger than the weld area of the welded portion far from the terminal main body. Therefore, the current flowing through the welded portion close to the terminal main body portion increases, and the current flowing through the welded portion far from the terminal main body portion decreases. As a result, the current variation in the current collector plate as a whole increases.

  An object of one aspect of the present invention is to provide an electrode assembly that can reduce variation in current flowing between a tab laminate and a terminal.

  An electrode assembly according to an aspect of the present invention is an electrode assembly including a plurality of electrodes each including a tab, the electrode assembly including at least one tab laminate having the plurality of stacked tabs, and the at least one tab assembly. The tab laminate includes first and second joints that join the plurality of tabs, and the first and second joints are electrically connected to terminals, and the first The current path length between the junction and the terminal is shorter than the current path length between the second junction and the terminal, and is at least 1 perpendicular to the stacking direction of the at least one tab laminate. In a cross section of one tab laminate, the conduction area of the first joint is smaller than the conduction area of the second joint.

  Here, the current path length is the length of the shortest current path among the current paths between the junction and the terminal.

  When the conduction areas of the first and second junctions are the same, the current value flowing between the first junction and the terminal is larger than the current value flowing between the second junction and the terminal. growing. For this reason, the variation in current flowing between the tab laminate and the terminal increases. On the other hand, in the electrode assembly described above, the value of the current flowing between the first joint and the terminal and the second joint are compared with the case where the conduction areas of the first and second joints are the same. And the difference between the current value flowing between the terminal and the terminal can be reduced. Therefore, variation in current flowing between the tab laminate and the terminal can be reduced.

  The first and second joints may be first and second welds, respectively.

  The first and second welds may be located on an end surface of the at least one tab laminate that extends in the stacking direction of the at least one tab laminate.

  In this case, the first and second welds can be formed using an energy beam.

  The at least one tab laminate has first and second end surfaces disposed on opposite sides of the at least one tab laminate, and the first and second welds are Each may be located on the first and second end faces.

  In this case, even if an unwelded portion is generated between the plurality of tabs on either one of the first and second end surfaces, an unwelded portion is unlikely to be generated between the plurality of tabs on the other end surface.

  Each of the plurality of electrodes includes a main body and the tab protruding from one end of the main body, and the electrode assembly further includes an electrode main body having a plurality of stacked main bodies, When the resistance value between the electrode body passing through the joint and the terminal is R1, and the resistance value between the electrode body passing through the second joint and the terminal is R2, 0. 5 ≦ R2 / R1 ≦ 1.5 may be satisfied.

  In this case, since the difference between R1 and R2 can be reduced, the value of the current flowing between the electrode body and the terminal via the first joint and the electrode body and the terminal via the second joint. The difference from the current value flowing between them can be reduced. Therefore, the variation in the current flowing between the electrode body and the terminal can be reduced.

  According to one aspect of the present invention, it is possible to provide an electrode assembly that can reduce variation in current flowing between the tab laminate and the terminal.

It is a disassembled perspective view of an electrical storage apparatus provided with the electrode assembly which concerns on 1st Embodiment. It is sectional drawing of the electrical storage apparatus along the II-II line | wire of FIG. It is a perspective view of the electrode assembly concerning a 1st embodiment. FIG. 4 is a cross-sectional view of the electrode assembly taken along line IV-IV in FIG. 3. It is sectional drawing of the electrode assembly which concerns on 2nd Embodiment. It is sectional drawing of the electrode assembly which concerns on 3rd Embodiment. It is sectional drawing of the electrode assembly which concerns on 4th Embodiment.

  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.

  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. 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 first embodiment. 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 plurality of stacked main bodies 14 a and the plurality of stacked main bodies 17 a constitute an electrode body 20. 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 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 faces 21a and 21b are faces along the XZ plane. Further, 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 decreases 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 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 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 laminate 21 includes a first weld W1 (first joint) located on the end surface 21a of the tab laminate 21 and a second weld W2 (second) located on the end surface 21b of the tab laminate 21. A joint portion). The welds W1 and W2 join the plurality of tabs 14b in the Z-axis direction. The welds W1 and W2 are located over the thickness of the tab laminate 21 in the Z-axis direction. The welded portions W1, W2 extend to the inside of the current collector plate 16 and the protective plate 23 adjacent to the end faces 21a, 21b. In the end faces 21a and 21b, the lengths of the welded portions W1 and W2 in the X-axis direction are 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 welds W1 and W2 can be stably formed. When the length of the welded portions W1 and W2 in the X-axis direction is substantially equal to the length of the protective plate 23 in the X-axis direction, the welded portions W1 and W2 can protrude outside the protective plate 23 in the X-axis direction due to positional displacement. There is sex. Further, when the length of the welded portions W1 and W2 in the X-axis direction is longer than the length of the protective plate 23 in the X-axis direction, the welded portions W1 and W2 protrude outside the protective plate 23 in the X-axis direction. Even in those cases, it is possible to form the welds W1 and W2.

  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. The end surface 25c 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 protection 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 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 includes a first welded portion W1 located on the end surface 25a of the tab laminated body 25 and a second welded portion W2 located on the end surface 25b of the tab laminated body 25. The welded portions W1 and W2 join the plurality of tabs 17b. The welds W1 and W2 are located over the thickness of the tab laminate 25 in the Z-axis direction. The welds W1 and W2 extend 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 faces 25a and 25b, the length of the welded portions W1 and W2 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 portions W1 and W2 can be stably formed. When the lengths of the welded portions W1 and W2 in the X-axis direction are substantially equal to the length of the protective plate 27 in the X-axis direction, the welded portions W1 and W2 can protrude outside the protective plate 27 in the X-axis direction due to misalignment. There is sex. Further, when the length of the welded portions W1 and W2 in the X-axis direction is longer than the length of the protective plate 27 in the X-axis direction, the welded portions W1 and W2 protrude outside the protective plate 27 in the X-axis direction. Even in those cases, it is possible to form the welds W1 and W2.

  4 is a cross-sectional view of the electrode assembly taken along line IV-IV in FIG. As shown in FIG. 4, the welded portions W <b> 1 and W <b> 2 respectively positioned on the end surfaces 25 a and 25 b of the tab laminated body 25 are electrically connected to the negative electrode terminal 6 by, for example, a current collector plate 19. The current path length LC1 between the welded portion W1 and the negative electrode terminal 6 is shorter than the current path length LC2 between the welded portion W2 and the negative electrode terminal 6. The current path length Lt1 between the welded portion W1 and the electrode body 20 may be the same as the current path length Lt2 between the welded portion W2 and the electrode body 20. In the cross section (for example, XY cross section) of the tab laminated body 25 orthogonal to the lamination direction of the tab laminated body 25, the conduction area S1 of the welded portion W1 is smaller than the conduction area S2 of the welded portion W2. For example, when the welded portion W1 has a rectangular shape, the conduction area S1 of the welded portion W1 is a product of the length L1 of the welded portion W1 in the X-axis direction and the depth D1 of the welded portion W1 in the Y-axis direction. Similarly, when the welded portion W2 has a rectangular shape, the conduction area S2 of the welded portion W2 is a product of the length L2 of the welded portion W2 in the X-axis direction and the depth D2 of the welded portion W2 in the Y-axis direction. .

  When the resistance value between the electrode body 20 passing through the welded portion W1 and the negative electrode terminal 6 is R1, and the resistance value between the electrode body 20 passing through the welded portion W2 and the negative electrode terminal 6 is R2, 0. 5 ≦ R2 / R1 ≦ 1.5 may be satisfied, 0.8 ≦ R2 / R1 ≦ 1.2 may be satisfied, or 0.9 ≦ R2 / R1 ≦ 1.1 may be satisfied.

  Similarly, the welded portions W1 and W2 located on the end surfaces 21a and 21b of the tab laminate 21 are electrically connected to the positive electrode terminal 5 by, for example, a current collector plate 16. The current path length LC1 between the welded portion W1 and the positive electrode terminal 5 is shorter than the current path length LC2 between the welded portion W2 and the positive electrode terminal 5. The current path length Lt1 between the welded portion W1 and the electrode body 20 may be the same as the current path length Lt2 between the welded portion W2 and the electrode body 20. 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 conduction area S1 of the welded portion W1 is smaller than the conduction area S2 of the welded portion W2. For example, the conduction area S1 of the welded portion W1 is a product of the length L1 of the welded portion W1 in the X-axis direction and the depth D1 of the welded portion W1 in the Y-axis direction. Similarly, the conduction area S2 of the welded portion W2 is a product of the length L2 of the welded portion W2 in the X-axis direction and the depth D2 of the welded portion W2 in the Y-axis direction.

  When the resistance value between the electrode main body 20 passing through the welded portion W1 and the positive electrode terminal 5 is R1, and the resistance value between the electrode main body 20 passing through the welded portion W2 and the positive electrode terminal 5 is R2, 0. 5 ≦ R2 / R1 ≦ 1.5 may be satisfied, 0.8 ≦ R2 / R1 ≦ 1.2 may be satisfied, or 0.9 ≦ R2 / R1 ≦ 1.1 may be satisfied.

  As described above, in the electrode assembly 3 of the present embodiment, in the tab laminate 25, the conduction area S1 of the welded portion W1 is smaller than the conduction area S2 of the welded portion W2. When the conduction area S1 of the welded portion W1 is the same as the conduction area S2 of the welded portion W2, the current value flowing between the welded portion W1 and the negative electrode terminal 6 is the current flowing between the welded portion W2 and the negative electrode terminal 6. Larger than the value. For this reason, the variation in current flowing between the tab laminate 25 and the negative electrode terminal 6 increases. On the other hand, in the electrode assembly 3 described above, the value of the current flowing between the welded portion W1 and the negative terminal 6 and the welded portion W2 are compared with the case where the conduction areas S1 and S2 of the welded portions W1 and W2 are the same. The difference from the current value flowing between the negative electrode terminal 6 can be reduced. Therefore, variation in current flowing between the tab laminate 25 and the negative electrode terminal 6 can be reduced. For example, when the resistance value between the welded portion W1 and the negative electrode terminal 6 is Ra, and the resistance value between the welded portion W2 and the negative electrode terminal 6 is Rb, 0.5 ≦ Rb / Ra ≦ 1.5 is satisfied. It may be satisfied, 0.8 ≦ Rb / Ra ≦ 1.2 may be satisfied, or 0.9 ≦ Rb / Ra ≦ 1.1 may be satisfied. When Rb / Ra = 1, the difference between the current value flowing between the welded portion W1 and the negative electrode terminal 6 and the current value flowing between the welded portion W2 and the negative electrode terminal 6 is zero. That is, the current flowing between the tab laminate 25 and the negative terminal 6 is uniform in the width direction of the current path. Similarly, in the tab laminate 21, the conduction area S1 of the welded portion W1 is smaller than the conduction area S2 of the welded portion W2. Therefore, the variation in the current flowing between the tab laminate 21 and the positive electrode terminal 5 can be reduced.

  When the welds W1 and W2 are positioned on the end faces 25a and 25b of the tab laminate 25, the welds W1 and W2 can be formed using an energy beam such as a laser beam or an electron beam. Similarly, when the welded portions W1 and W2 are positioned on the end surfaces 21a and 21b of the tab laminate 21, the welded portions W1 and W2 can be formed using an energy beam such as a laser beam or an electron beam. it can.

  In addition, when the welded portions W1 and W2 are positioned on the end surfaces 25a and 25b of the tab laminated body 25, respectively, an unwelded portion is generated between the plurality of tabs 17b on either one of the end surfaces 25a and 25b. Even if it exists, an unwelded part does not arise easily between several tab 17b in the other end surface. Similarly, when the welded portions W1 and W2 are positioned on the end surfaces 21a and 21b of the tab laminate 21, unwelded portions are generated between the tabs 14b on either one of the end surfaces 21a and 21b. Even so, unwelded portions are unlikely to occur between the plurality of tabs 14b on the other end face.

  Further, when 0.5 ≦ R2 / R1 ≦ 1.5 is satisfied in the tab laminate 25, the difference between R1 and R2 can be reduced, so that the electrode body 20 and the negative electrode terminal 6 are connected via the welded portion W1. The difference between the current value flowing between the electrode body 20 and the negative electrode terminal 6 via the welded portion W2 can be reduced. Therefore, variation in the current flowing between the electrode body 20 and the negative electrode terminal 6 can be reduced. When R2 / R1 = 1, the current value flowing between the electrode body 20 and the negative electrode terminal 6 via the welded portion W1 and the current value flowing between the electrode body 20 and the negative electrode terminal 6 via the welded portion W2. The difference from the value is zero. That is, the current flowing between the electrode body 20 and the negative terminal 6 is uniform in the width direction of the current path. Similarly, when 0.5 ≦ R2 / R1 ≦ 1.5 is satisfied in the tab laminate 21, the variation in current flowing between the electrode body 20 and the positive electrode terminal 5 can be reduced. As a result, in the tab laminates 21 and 25, heat generation and reaction unevenness in the electrode assembly 3 due to current variation are suppressed.

  FIG. 5 is a cross-sectional view of the electrode assembly according to the second embodiment. The electrode assembly 3A shown in FIG. 5 has the same configuration as the electrode assembly 3 of the first embodiment except that the shapes of the welded portions W1 and W2 are different. In electrode assembly 3A, welded portion W2 includes a plurality of welded regions W21 and W22 that are spaced apart. For example, the welding regions W21 and W22 have the same shape. The welding part W1 has the same shape as each welding area W21 and W22. Therefore, the conduction area S1 of the welded portion W1 is the same as the conduction area of each welding region W21, W22. Therefore, in the present embodiment, the conduction area S1 of the welded portion W1 is half of the conduction area S2 of the welded portion W2 (the total conduction area of the welding regions W21 and W22). In this embodiment, the same effect as that of the first embodiment can be obtained.

  The welded portion W2 may include three or more welded regions, and the welded portion W1 may include a plurality of welded regions. Moreover, the conduction area of each welding area | region may differ.

  FIG. 6 is a cross-sectional view of the electrode assembly according to the third embodiment. The electrode assembly 3B shown in FIG. 6 has the same configuration as the electrode assembly 3 of the first embodiment except that the shape of the welded portion W2 is different. In the electrode assembly 3B, the welded portion W2 has, for example, a triangular shape. The conduction area S1 of the welded portion W1 is smaller than the conduction area S2 of the welded portion W2. In this embodiment, the same effect as that of the first embodiment can be obtained.

  FIG. 7 is a cross-sectional view of the electrode assembly according to the fourth embodiment. The electrode assembly 3 </ b> C shown in FIG. 7 has the same configuration as the electrode assembly 3 of the first embodiment except that the plurality of tab laminates 25 are provided. In the electrode assembly 3 </ b> C, the first tab stacked body 25 among the plurality of tab stacked bodies 25 has a welded portion W <b> 1 that joins the plurality of tabs 17 b, and the second tab stacked body 25 includes The tab laminate 25 has a welded portion W2 for joining the plurality of tabs 17b. The welded portion W1 includes a welding region W11 located on the end surface 25a of the first tab laminate 25 and a welding region W12 located on the end surface 25b of the first tab laminate 25. In the first tab laminate 25, the welding regions W11 and W12 are arranged apart from each other. The welded portion W2 includes a welding region W21 located on the end surface 25a of the second tab laminate 25 and a welding region W22 located on the end surface 25b of the second tab laminate 25. Also in the second tab laminate 25, the welding regions W21 and W22 are arranged apart from each other. The welds W1 and W2 are electrically connected to the negative electrode terminal 6 by, for example, a current collector plate 19. The current path length LC1 between the welded portion W1 (welded region W11) and the negative electrode terminal 6 is shorter than the current path length LC2 between the welded portion W2 (welded region W21) and the negative electrode terminal 6. In the XY cross section, for example, the welding regions W11 and W12 have the same shape, and the welding regions W21 and W22 have the same shape, for example. In the XY cross section, the conduction area of each welding region W11, W12 is smaller than the conduction area of each welding region W21, W22. Therefore, the conduction area S1 of the welded portion W1 is smaller than the conduction area S2 of the welded portion W2.

  The electrode assembly 3 </ b> C may include a plurality of tab laminates 21 having the same configuration as the plurality of tab laminates 25. The electrode assembly 3C may include three or more tab laminates.

  In this embodiment, the same effect as that of the first embodiment can be obtained. In the present embodiment, even if the number of stacked tabs 17b is increased, the thickness of each tab stacked body 25 can be reduced by increasing the number of tab stacked bodies 25. Moreover, in this embodiment, each welding part W1, W2 may be provided with one welding area | region and may be provided with three or more welding area | regions.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment. The components of the above embodiments can be arbitrarily combined.

  In each said embodiment, the welding part W1 may be located in the place away from the end surfaces 21a and 25a of the tab laminated bodies 21 and 25, for example. In this case, the welded portion W1 can be formed by, for example, resistance welding or ultrasonic welding. Similarly, the welded portion W2 may be positioned away from the end surfaces 21b and 25b of the tab laminates 21 and 25. Further, the welded portions W1, W2 may be located on the end surfaces 21c, 25c in addition to the end surfaces 21a, 21b, 25a, 25b of the tab laminates 21, 25. The welded portions W1 and W2 may be formed on two end surfaces of one end surface 21c and 25c of 21b, 25a and 25b, or the welded portions W1 and W2 may be formed on all three end surfaces. . The welded portions W1 and W2 may be positioned only on the end faces 21c and 25c, and may include three or more weld regions in which the conduction area increases as the current path length increases. When the welded portions W1 and W2 are located on the end surfaces 21c and 25c, the end surfaces 21c and 25c are surfaces along the YZ plane. Such end faces 21c and 25c may be formed by cutting the tips of the tab laminates 21 and 25, or formed by stacking the tabs 14b and 17b using the tabs 14b and 17b having different lengths. May be.

  In each of the above-described embodiments, each of the welded portions W1 and W2 may be a joint portion such as a caulking portion formed using, for example, a rivet.

  In each of the above embodiments, the electrode assemblies 3, 3A, 3B may be of a wound type. The wound electrode assemblies 3, 3 </ b> A, 3 </ b> B include tab laminates 21, 25, similar to the stacked electrode assemblies 3, 3 </ b> A, 3 </ b> B. The tab laminates 21 and 25 are disposed on opposite sides in the X-axis direction. In the tab laminate 25, the plurality of tabs 17b are wound around the axis in the X-axis direction and then compressed in the Z-axis direction. Therefore, the tab laminate 25 has a plurality of tabs 17b stacked on the current collector plate 19 in the Z-axis direction. Therefore, in the wound electrode assemblies 3, 3A, 3B, the tab laminate 25 does not include the end surfaces 25a, 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. Therefore, in the wound electrode assemblies 3, 3A, 3B, the welded portions W1, W2 are located only on the end faces 21c, 25c.

  3, 3A, 3B, 3C ... electrode assembly, 5 ... positive electrode terminal (terminal), 6 ... negative electrode terminal (terminal), 11 ... positive electrode (electrode), 12 ... negative electrode (electrode), 14a, 17a ... main body, 14b, 17b ... tab, 20 ... electrode body, 21,25 ... tab laminate, 21a, 21b, 21c, 25a, 25b, 25c ... end face, W1 ... first welded portion (first joint), W2 ... second Welded part (second joint part).

Claims (5)

An electrode assembly comprising a plurality of electrodes each including a tab,
Comprising at least one tab laminate having a plurality of the tabs stacked;
The at least one tab laminate includes first and second joining portions that join the plurality of tabs;
The first and second joints are electrically connected to terminals;
The current path length between the first junction and the terminal is shorter than the current path length between the second junction and the terminal,
An electrode set in which a conduction area of the first joint portion is smaller than a conduction area of the second joint portion in a cross section of the at least one tab laminate perpendicular to the lamination direction of the at least one tab laminate. Solid.   The electrode assembly according to claim 1, wherein the first and second joints are first and second welds, respectively.   The electrode set according to claim 2, wherein the first and second welds are located on an end surface of the at least one tab laminate extending in a stacking direction of the at least one tab laminate. Solid. The at least one tab laminate has first and second end faces disposed on opposite sides of the at least one tab laminate;
The electrode assembly according to claim 2, wherein the first and second welds are located on the first and second end faces, respectively. 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 includes an electrode body having a plurality of stacked bodies.
When the resistance value between the electrode body and the terminal passing through the first joint is R1, and the resistance value between the electrode body and the terminal passing through the second joint is R2. The electrode assembly according to any one of claims 1 to 4, wherein 0.5 ≦ R2 / R1 ≦ 1.5 is satisfied.

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