Battery

Abstract

A battery according to an embodiment of the present invention comprises an electrode group, a band bundle part, a conductive member, and a joint part. The band bundle part protrudes in a protruding direction intersecting with the stacking direction of a plurality of current collecting band parts in the electrode group. The band bundle part includes an overlap region in which all of the current collecting band parts overlap, and a non-overlap region in which one or more of the current collecting band parts do not overlap with the other current collecting band parts, and which is adjacent to the overlap region from a side where the protruding end is positioned. In the joint part of the band bundle part and the conductive member, the center of a first recess is positioned in the overlap region and the center of a second recess different from the first recess is positioned in the non-overlap region, among a plurality of recesses.

Description

Technical Field

[0001] Embodiments of the present invention relate to a battery.

Background Art

[0002] A battery such as a lithium-ion secondary battery includes an electrode group, and the electrode group includes a positive electrode and a negative electrode. In the electrode group, each of the positive electrode and the negative electrode includes a current collector, and in the current collector, a banding portion where a plurality of current collecting band portions are bundled is formed. In the electrode group, the banding portion protrudes, and in the battery, the banding portion of the current collector is electrically connected to an electrode terminal via a conductive member such as a lead. A conductive member such as a lead is joined to the banding portion by welding such as ultrasonic welding, and in the battery, a joint portion (welding mark) where the banding portion and the conductive member are joined is formed.

[0003] In the banding portion, the plurality of current collecting band portions are stacked in a stacking direction that intersects (orthogonal or substantially orthogonal) with the protruding direction of the banding portion. Also, in the banding portion, a shift may occur between the plurality of current collecting band portions with respect to the protruding amount in the protruding direction. In this case, in the banding portion, an overlap region where all of the current collecting band portions overlap, and a non-overlap region where one or more of the current collecting band portions do not overlap with other current collecting band portions are formed. And in the banding portion, the non-overlap region is adjacent to the overlap region from the side where the protruding end of the banding portion is located.

[0004] In a battery as described above, from the viewpoint of realizing high output, for example, the number of windings in a wound electrode group is increased, or the number of stacked electrode plates in a stacked electrode group is increased. In this case, the dimension of the electrode group in the thickness direction becomes large, and the number of current collecting band portions to be stacked increases in the banding portion of the current collector. In the banding portion, as the number of current collecting band portions to be stacked increases, the ratio occupied by the non-overlap region where one or more of the plurality of current collecting band portions do not overlap with other current collecting band portions increases. In the battery, even when the ratio occupied by the non-overlap region in the banding portion of the current collector increases, it is required that the banding portion be appropriately joined to the conductive member.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-77597 [Patent Document 2] Japanese Patent Publication No. 2012-209260 [Patent Document 3] International Publication No. 2016 / 204147 [Overview of the project] [Problems that the invention aims to solve]

[0006] The problem that the present invention aims to solve is to provide a battery in which the bundled currents portion is properly joined to a conductive member even when the proportion of the non-overlapping region, in which one or more of the multiple current-collecting portions do not overlap with other current-collecting portions, increases in the bundled currents portion of the current collector. [Means for solving the problem]

[0007] According to the embodiment, the battery comprises an electrode group, a bundle portion, a conductive member, and a joint portion. The bundle portion comprises a plurality of current-collecting strips bundled together in a stacked state relative to each other, and protrudes in a protruding direction that intersects with the stacking direction of the plurality of current-collecting strips in the electrode group. The bundle portion comprises an overlapping region where all of the current-collecting strips overlap, and a non-overlap region where one or more current-collecting strips do not overlap with other current-collecting strips and are adjacent to the overlapping region from the side where the protruding end is located. The conductive member is connected to the bundle portion of the electrode group. The joint portion comprises a plurality of recesses, each recessed in the stacking direction, and the bundle portion and the conductive member are joined at the joint portion. At the joint portion, the center of one or more of the first recesses is located in the overlapping region, and the center of one or more of the second recesses, separate from the first recesses, is located in the non-overlap region. Furthermore, the first recess and the second recess are provided adjacent to each other along the protruding direction of the bundle portion. [Brief explanation of the drawing]

[0008] [Figure 1]Figure 1 is a schematic diagram showing a battery according to the first embodiment in a cross-section perpendicular or substantially perpendicular to the depth direction. [Figure 2] Figure 2 is a schematic diagram showing an example of the configuration of the lead connection portion to one of the pair of unsupported portions of the electrode group in the battery according to the first embodiment, as viewed from one side in the longitudinal direction of the electrode group. [Figure 3] Figure 3 is a schematic diagram showing an example of the configuration of the lead connection portion to one of the pair of unsupported portions of the electrode group in the battery according to the first embodiment, as viewed from one side in the thickness direction of the electrode group. [Figure 4] Figure 4 is a schematic diagram illustrating an example of the process of connecting a lead to one of a pair of unsupported portions of the electrode group in the first embodiment, in a cross-section perpendicular or substantially perpendicular to the width direction of the electrode group. [Figure 5] Figure 5 is a schematic cross-sectional view showing the A1-A1 section of Figure 3. [Figure 6] Figure 6 is a schematic diagram showing an example of the configuration of the lead connection portion to one of the pair of unsupported portions of the electrode group in the battery according to the first embodiment, as viewed from one side in the thickness direction of the electrode group, as shown in Figure 3. [Figure 7] Figure 7 is a schematic diagram showing an example of the configuration of the lead connection portion to one of the pair of unsupported portions of the electrode group in the battery according to the first embodiment, as viewed from one side in the thickness direction of the electrode group, as shown in Figures 3 and 6. [Figure 8] Figure 8 is a schematic diagram showing an example of the configuration of the lead connection portion to one of the pair of unsupported portions of the electrode group in the battery according to the first modified example, as viewed from one side in the thickness direction of the electrode group. [Figure 9] Figure 9 is a schematic diagram showing an example of the configuration of the lead connection portion to one of the pair of unsupported portions of the electrode group in the battery according to the second modified example, viewed from one side in the longitudinal direction of the electrode group. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings.

[0010] (First embodiment) First, as an example of an embodiment, a first embodiment will be described. Figure 1 shows a battery 1 according to the first embodiment. In this embodiment, as shown in Figure 1, the battery 1 comprises an electrode group 2 and an outer casing 3. The outer casing 3 comprises an outer container 5 and a lid member 6. The outer container 5 and the lid member 6 are each made of a metal such as aluminum, aluminum alloy, iron, copper, or stainless steel. Here, the battery 1 and the outer casing 3 are defined in the depth direction (a direction perpendicular or approximately perpendicular to the plane of the paper in Figure 1), the lateral direction (directions indicated by arrows Y1 and Y2) that intersects (is perpendicular or approximately perpendicular to) the depth direction, and the height direction (directions indicated by arrows Z1 and Z2) that intersects (is perpendicular or approximately perpendicular to) both the depth direction and the lateral direction. In each of the battery 1 and the outer casing 3, the dimensions in the depth direction are smaller than the dimensions in the lateral direction and the dimensions in the height direction. Note that Figure 1 shows a cross-section perpendicular or approximately perpendicular to the depth direction.

[0011] The outer container 5 comprises a bottom wall 7 and a peripheral wall 8. Inside the outer container 5, an internal cavity 10 housing the electrode group 2 is defined by the bottom wall 7 and the peripheral wall 8. The bottom wall 7 is adjacent to the internal cavity 10 from one side in the height direction. One end of the peripheral wall 8 is connected to the bottom wall 7 and extends from the bottom wall 7 along the height direction. The peripheral wall 8 also surrounds the internal cavity 10 from the outer periphery. In the outer container 5, the internal cavity 10 opens in the height direction toward the side opposite to where the bottom wall 7 is located. The lid member 6 is attached to the peripheral wall 8 at the end opposite to the bottom wall 7. The lid member 6 closes the opening of the internal cavity 10 in the outer container 5. The lid member 6 and the bottom wall 7 face each other in the height direction, with the internal cavity 10 in between.

[0012] Electrode group 2 comprises a positive electrode 13A and a negative electrode 13B. In electrode group 2, a separator (not shown) is interposed between the positive electrode 13A and the negative electrode 13B. The separator is made of an electrically insulating material and electrically insulates the positive electrode 13A from the negative electrode 13B.

[0013] The positive electrode 13A includes a positive electrode current collector such as a positive electrode current collector foil as a current collector, and a positive electrode active material-containing layer supported on the surface of the positive electrode current collector as an active material-containing layer. The positive electrode current collector is, but not limited to, for example, an aluminum foil or an aluminum alloy foil. The thickness of the positive electrode current collector is about 10 μm to 20 μm. The positive electrode active material-containing layer includes a positive electrode active material and may optionally contain a binder and a conductive agent. The positive electrode active material is, but not limited to, for example, an oxide, a sulfide, and a polymer capable of occluding and releasing lithium ions. The positive electrode current collector includes an unloaded portion 15A on which the positive electrode active material-containing layer is not supported. The unloaded portion 15A is also referred to as a "positive electrode current collector tab".

[0014] The negative electrode 13B includes a negative electrode current collector such as a negative electrode current collector foil as a current collector, and a negative electrode active material-containing layer supported on the surface of the negative electrode current collector as an active material-containing layer. The negative electrode current collector is, but not limited to, for example, an aluminum foil, an aluminum alloy foil, or a copper foil. The thickness of the negative electrode current collector is about 10 μm to 20 μm. The negative electrode active material-containing layer includes a negative electrode active material and may optionally contain a binder and a conductive agent. The negative electrode active material is, but not limited to, for example, a metal oxide, a metal sulfide, a metal nitride, and a carbon material capable of occluding and releasing lithium ions. The negative electrode current collector includes an unloaded portion 15B on which the negative electrode active material-containing layer is not supported. The unloaded portion 15B is also referred to as a "negative electrode current collector tab".

[0015] The electrode group 2 includes the aforementioned unloaded portions 15A and 15B as a pair of unloaded portions (current collector tabs) 15. In one example, with a separator sandwiched between the positive electrode 13A and the negative electrode 13B, the positive electrode 13A, the negative electrode 13B, and the separator are wound around a winding axis to form a wound electrode group 2. In another example, with a separator interposed between a positive electrode plate serving as the positive electrode 13A and a negative electrode plate serving as the negative electrode 13B, a plurality of positive electrode plates and a plurality of negative electrode plates are alternately laminated to form a laminated electrode group 2.

[0016] In the internal cavity 10, an electrolytic solution (not shown) is held (impregnated) in the electrode group 2. The electrolytic solution may be a non-aqueous electrolytic solution in which an electrolyte is dissolved in an organic solvent, or may be an aqueous electrolytic solution such as an aqueous solution. Instead of the electrolytic solution, a gel electrolyte may be used, or a solid electrolyte may be used. When a solid electrolyte is used as the electrolyte, in the electrode group, the solid electrolyte is interposed between the positive electrode 13A and the negative electrode 13B instead of the separator. In this case, the positive electrode 13A is electrically insulated from the negative electrode 13B by the solid electrolyte.

[0017] In the battery 1 of an example in FIG. 1, positive electrode terminals 16A and negative electrode terminals 16B are provided as a pair of electrode terminals 16, and each of the electrode terminals 16 is attached to the lid member 6 of the exterior portion 3 in a state where a part thereof is exposed to the outside. Each of the electrode terminals 16 is formed of a conductive material such as metal. On the outer surface of the lid member 6, an insulating member 18 is provided between each of the electrode terminals 16 and the lid member 6. Each of the electrode terminals 16 is electrically insulated from the lid member 6 and the exterior container 5 by the insulating member 18.

[0018] Further, the battery 1 includes positive electrode side leads 20A and negative electrode side leads 20B as a pair of leads 20, and positive electrode side backup leads 21A and negative electrode side backup leads 21B as a pair of backup leads 21. The leads 20 which are conductive members and the backup leads 21 which are m clip members are formed of a conductive material such as metal, for example, formed of any of aluminum, stainless steel, copper, iron, etc. Further, the leads 20 and the backup leads 21 are disposed in the internal cavity 10 of the exterior portion 3.

[0019] In electrode group 2, the unsupported portion 15A of the positive electrode current collector is electrically connected to the positive electrode terminal 16A via the positive electrode lead 20A, etc., and the unsupported portion 15B of the negative electrode current collector is electrically connected to the negative electrode terminal 16B via the negative electrode lead 20B, etc. Therefore, each of the unsupported portions 15 is electrically connected to the corresponding electrode terminal 16 via the corresponding lead 20, etc., which are conductive members. Also, in the example in Figure 1, the positive electrode lead 20A is connected to the unsupported portion 15A of the positive electrode current collector via the positive electrode backup lead 21A, etc., and the negative electrode lead 20B is connected to the unsupported portion 15B of the negative electrode current collector via the negative electrode backup lead 21B. Each of the conductive lead 20 is connected to the corresponding one of the unsupported portions 15 via the corresponding backup lead 21, which are clip members.

[0020] Furthermore, in the internal cavity 10 of the outer casing 3, the unsupported portion 15, the lead 20, and the backup lead 21 are each prevented from contacting the outer casing 3, including the outer container 5 and the lid member 6, by one or more insulating members (not shown), and are electrically insulated from the outer casing 3. In the battery 1, one or both of a gas release valve and a liquid filling port (neither shown) may be formed on the lid member 6. If a liquid filling port is formed on the lid member 6, a sealing plate (not shown) that closes the liquid filling port is welded to the outer surface of the lid member 6.

[0021] As shown in Figure 1, the electrode group 2 has defined dimensions in the length direction (directions indicated by arrows L1 and L2), the width direction (directions indicated by arrows W1 and W2) that intersects (is perpendicular or nearly perpendicular to) the length direction, and the thickness direction (directions perpendicular or nearly perpendicular to the plane of the paper in Figure 1) that intersects (is perpendicular or nearly perpendicular to) both the length and width directions. In the electrode group 2, the dimensions in the thickness direction are smaller than the dimensions in the length direction and the dimensions in the width direction. In an example in Figure 1, the electrode group 2 is arranged in the internal cavity 10 such that the length direction coincides with or approximately coincides with the lateral direction of the battery 1, and the width direction coincides with or approximately coincides with the height direction of the battery 1. The electrode group 2 is then arranged in the internal cavity 10 such that the thickness direction coincides with or approximately coincides with the depth direction of the battery 1.

[0022] In the example shown in Figure 1, in electrode group 2, the unsupported portion 15A of the positive electrode current collector protrudes to one side in the longitudinal direction relative to the negative electrode active material-containing layer and separator, etc. The unsupported portion 15B of the negative electrode current collector protrudes in the longitudinal direction of electrode group 2 toward the opposite side from the side toward the positive electrode active material-containing layer and separator, etc., from which the unsupported portion 15A protrudes. Therefore, in electrode group 2 arranged in the internal cavity 10 of battery 1, the pair of unsupported portions 15, which are a pair of current-collecting tabs, protrude toward opposite sides of each other in the lateral direction of battery 1.

[0023] Figures 2 and 3 show an example of the configuration of the connection portion of the lead 20 to one of the pair of unsupported portions 15 of the electrode group 2. Figure 4 illustrates an example of the process of connecting the lead 20 to one of the pair of unsupported portions 15 of the electrode group 2. In Figures 2 and 4, the directions indicated by arrows T1 and T2 correspond to the thickness direction of the electrode group 2, and the directions indicated by arrows X1 and X2 in Figure 2 correspond to the depth direction of the battery 1. Figure 2 shows the battery 1 viewed from the side, i.e., from one side in the length direction of the electrode group 2, and Figure 3 shows the battery 1 viewed from the depth direction, i.e., from one side in the thickness direction of the electrode group 2. Figure 4 shows a cross-section perpendicular or approximately perpendicular to the width direction of the electrode group 2.

[0024] The following describes the connection portion of the lead 20, which is a conductive member, to one of the pair of unsupported portions 15 (15A, 15B) of the electrode group 2. In this embodiment, the connection portion of the lead 20, etc., to the other of the pair of unsupported portions 15 will have the same configuration as described below. As shown in Figures 2 to 4, a bundle portion 25 is formed on the unsupported portion 15 of the current collector. In one example in Figures 2 to 4, only one bundle portion 25 is formed on one unsupported portion 15. The bundle portion 25 is formed from a plurality of current collector bands 26, and the plurality of current collector bands 26 are bundled together in the bundle portion 25. Therefore, in one example in Figures 2 to 4, only one bundle portion 25, to which a plurality of current collector bands 26 are bundled, is formed on one unsupported portion 15. Each of the plurality of current collector bands 26 constituting the bundle portion 25 is formed from a part of the unsupported portion 15 of the current collector.

[0025] In this embodiment, as described above, the unsupported portion 15 protrudes from the electrode group 2. Therefore, the bundle portion 25 protrudes from the electrode group 2. In this embodiment, one side of the electrode group 2 in the longitudinal direction coincides with or approximately coincides with the protruding direction of the bundle portion 25, and in the electrode group 2, the bundle portion 25 protrudes to one side of the battery 1 in the lateral direction. In the bundle portion 25 of the unsupported portion 15, the multiple current collector strips 26 are bundled together in a stacking direction relative to each other. The stacking direction of the multiple current collector strips 26 intersects (orthogonal or approximately orthogonal to) the protruding direction of the bundle portion 25. In this embodiment, the stacking direction of the multiple current collector strips 26 in the bundle portion 25 coincides with or approximately coincides with the thickness direction of the electrode group 2 and coincides with or approximately coincides with the depth direction of the battery 1. Furthermore, the bundle portion 25 that protrudes in the protruding direction (longitudinal direction of the electrode group 2) in the electrode group 2 has a protruding end Pa of the protruding portion.

[0026] The backup lead 21, which is a clip member, is attached to the bundle portion 25 by sandwiching it from both sides in the stacking direction (thickness direction of the electrode group 2). The backup lead 21 is also attached to the bundle portion 25 from the side where the bundle portion 25 protrudes (outside in the longitudinal direction of the electrode group 2) and is close to the protruding end Pa of the bundle portion 25. In the bundle portion 25, a width direction is defined that intersects (is perpendicular or approximately perpendicular to) both the stacking direction and the protruding direction. In this embodiment, the width direction of the bundle portion 25 coincides with or approximately coincides with the width direction of the electrode group 2 and coincides with or approximately coincides with the height direction of the battery 1.

[0027] When the backup lead 21 is attached to the bundle portion 25, the backup lead 21 takes on a U-shape or a nearly U-shape in a cross section perpendicular or nearly perpendicular to the width direction of the bundle portion 25 (the width direction of the electrode group 2). The U-shaped or nearly U-shaped opening of the backup lead opens inward along the length direction of the electrode group 2, that is, away from the side from which the bundle portion 25 protrudes.

[0028] The conductive member, lead 20, is connected to the current collector's bundle portion 25 by contacting the backup lead 21 from one side in the stacking direction of the current collector's bundle portion 26. Lead 20 is connected to the bundle portion 25 by being joined to the backup lead 21 and the bundle portion 25. The joining of lead 20 to the backup lead 21 and the bundle portion 25 is performed by welding, such as ultrasonic welding. As described above, since lead 20 is connected to the current collector's bundle portion 25, a joint portion 30 is formed at the connection point between the bundle portion 25 and lead 20 as a weld mark where the bundle portion 25, lead 20 and backup lead 21 are joined.

[0029] In the bundle portion 25 of this embodiment, a difference occurs among the multiple current collector band portions 26 in terms of the amount of protrusion in the protruding direction (the longitudinal direction of the electrode group 2). As a result, in the bundle portion 25, an overlapping region 41 is formed where all of the current collector band portions 26 overlap, and a non-overlapping region 42 is formed where one or more of the current collector band portions 26 do not overlap with other current collector band portions 26. In the bundle portion 25, the non-overlapping region 42 is adjacent to the overlapping region 41 from the side where the protruding end Pa of the bundle portion 25 is located.

[0030] Here, in the bundled portion 25, a protruding end Pa is formed by the protruding end of the current collector band portion 26 with the largest amount of protrusion in the protruding direction. Also, in the bundled portion 25, an overlapping region 41 is formed over the range from the base position of the protruding portion to the protruding end of the current collector band portion 26 with the smallest amount of protrusion. Furthermore, in the bundled portion 25, a non-overlapping region 42 is formed over the range from the protruding end of the current collector band portion 26 with the smallest amount of protrusion to the protruding end Pa of the bundled portion 25. In one example, in the bundled portion 25, the current collector band portion 26 located on the inside of the bundled portion 25 in the stacking direction (thickness direction of the electrode group 2) has a larger amount of protrusion in the protruding direction.

[0031] Furthermore, in the bundle portion 25 of the current collector, a dimensional change portion 45 and a relay portion 46 are formed in the overlap region 41. In the overlap region 41, the relay portion 46 is adjacent to the dimensional change portion 45 from the side where the protruding end Pa of the bundle portion 25 is located. In the overlap region 41, the dimensional change portion 45 extends from the base position of the protruding portion of the bundle portion 25 to the boundary with the relay portion 46, and the relay portion 46 extends from the boundary with the dimensional change portion 45 to the boundary with the non-overlap region 42. Therefore, in the bundle portion 25, the space between the dimensional change portion 45 and the non-overlap region 42 in the protruding direction (length direction of the electrode group 2) is relayed by the relay portion 46.

[0032] In the dimensional change section 45 of the overlap region 41, the dimensions of the bundled portion 25 in the stacking direction (thickness direction of the electrode group 2) decrease toward the side where the protruding end Pa of the bundled portion 25 is located. Also, in the intermediate section 46, the dimensions of the bundled portion 25 in the stacking direction become uniform or nearly uniform over the range from the boundary with the dimensional change section 45 to the boundary with the non-overlapping region 42.

[0033] In the non-overlap region 42, the number of overlapping current collector bands 26 decreases toward the side where the protruding end Pa of the bundled band 25 is located. Therefore, in the non-overlap region 42, the dimensions of the bundled band 25 in the stacking direction decrease as you approach the protruding end Pa of the bundled band 25. In the non-overlap region 42, one or more steps are formed that reduce the dimensions of the bundled band 25 in the stacking direction toward the side where the protruding end Pa is located. And in the non-overlap region 42, at each of the one or more steps, the number of overlapping current collector bands 26 decreases toward the side where the protruding end Pa is located. As described above, one or more steps are formed in the non-overlap region 42, so the non-overlap region 42 is also called the "step-forming region".

[0034] In this embodiment, the backup lead 21, which is a clip member, clamps the bundle portion 25 from both sides in the stacking direction only in the intermediate portion 46 of the overlap region 41 and the non-overlap region 42, but does not clamp the bundle portion 25 in the dimensional change portion 45 of the overlap region 41. Furthermore, in the bundle portion 25, the joint portion 30, which is a weld mark where the lead 20 and the backup lead 21 are joined, is formed in the intermediate portion 46 and the non-overlap region 42, but not in the dimensional change portion 45. As described above, the joint portion 30 is formed so that it spans both the overlap region 41 and the non-overlap region 42 in the bundle portion 25. In the overlap region 41, the joint portion 30 is formed only in the intermediate portion 46, and not in the dimensional change portion 45.

[0035] Figure 5 shows the A1-A1 cross-section of Figure 3. In Figure 5, a cross-section perpendicular or nearly perpendicular to the width direction of the electrode group 2 (width direction of the bundled portion 25) is shown. Also in Figure 5, the bundled portion 25 is shown with detailed components such as the multiple current collector bands 26 omitted. As shown in Figures 3 and 5, the joint portion 30, which is a weld mark, has multiple recesses 31. In the joint portion 30, each of the multiple recesses 31 is recessed toward the lead 20, which is a conductive member. That is, each of the recesses 31 is recessed toward the side where the lead 20 is located in the stacking direction (thickness direction of the electrode group 2). And each of the recesses 31 opens toward the opposite side of the side where the lead 20 is located in the stacking direction of the current collector band 26.

[0036] In one example, as shown in Figures 3 and 5, each opening of the recess 31 is formed on the outer surface facing away from the side of the backup lead 21 where the lead 20 is located. In one example, each of the recesses 31 is formed, passing through the backup lead 21, the bundle portion 25, and the backup lead 21 in sequence, all the way to the lead 20. In this case, each of the recesses 31 is recessed from the opening to the lead 20 in the direction of stacking the current collector bundle portion 26.

[0037] Each of the recesses 31 comprises a recessed bottom surface 32 and a recessed circumferential surface 33. In each of the recesses 31, the deepest part of the bottom is formed by the recessed bottom surface 32. In one example, each recessed bottom surface 32 of the recess 31 is perpendicular or approximately perpendicular to the stacking direction. In addition, each of the recesses 31 has an outer perimeter formed by a recessed circumferential surface 33, which extends from the opening edge to the recessed bottom surface 32. In each of the recesses 31, the recessed circumferential surface 33 is inclined with respect to the stacking direction (the thickness direction of the electrode group 2). In each recessed circumferential surface 33 of the recess 31, the depth increases as it moves away from the opening edge, that is, as it approaches the recessed bottom surface 32.

[0038] In each of the recesses 31, the center is defined by a central axis C that runs along the stacking direction. In each of the recesses 31, the central axis C passes through the recessed bottom surface 32, and the center is located on the recessed bottom surface 32. Therefore, in each of the recesses 31, the center is located at the bottom where the depth is greatest. In an example such as Figure 3, when viewed from the opposite side of where the leads 20 are located in the stacking direction (thickness direction of the electrode group 2), each of the recesses 31 has a rectangular or approximately rectangular shape. In each of the recesses 31, the intersection of the diagonals of the rectangular or approximately rectangular shape is defined as the center.

[0039] In one example, when viewed from the opposite side of where the lead 20 is located in the stacking direction, each of the recesses 31 will be one of the following shapes: triangular, polygonal (pentagonal or more), circular, or elliptical, and will be different from a quadrilateral. In this case as well, similar to the example in Figure 3, the center of each recess 31 is located at the deepest part of the bottom (recessed bottom surface 32). For example, if each of the recesses 31 is circular when viewed from the opposite side of where the lead 20 is located, the center of each recess 31 is defined as the center of the circle. Also, if each of the recesses 31 is elliptical when viewed from the opposite side of where the lead 20 is located, the intersection of the major and minor axes of the ellipse is defined as the center of each recess 31.

[0040] In this embodiment, the multiple recesses 31 of the joint 30 are composed of recesses (first recesses) 31A whose center (central axis C) is located in the relay portion 46 of the overlap region 41, and recesses (second recesses) 31B whose center (central axis C) is located in the non-overlapping region 42. Therefore, in the joint 30, one or more of the multiple recesses 31 are recesses 31A whose center is located in the overlap region 41, and one or more of the multiple recesses 31 whose center is located in the non-overlapping region 42. In an example such as Figure 3, three recesses 31A and three recesses 31B are provided, and the number of recesses (second recesses) 31B is the same as the number of recesses (first recesses) 31A.

[0041] In the embodiments, it is sufficient that one or more recesses 31A and 31B are provided, and the number of recesses 31A and 31B in the joint portion 30 is not particularly limited. For example, the number of recesses (second recesses) 31B may be less than the number of recesses (first recesses) 31A, or greater than the number of recesses 31A. However, it is preferable that the number of recesses 31B whose centers are located in the non-overlapping region 42 is equal to or greater than the number of recesses 31A whose centers are located in the overlapping region 41.

[0042] Furthermore, in an example such as Figure 3, multiple recesses 31A are provided, each centered in the overlapping region 41, and at the joint 30, a row of recesses (first recess row) 35A is formed, in which multiple recesses (first recesses) 31A are arranged in the width direction of the bundled portion 25 (width direction of the electrode group 2). Then, multiple recesses 31B are provided, each centered in the non-overlapping region 42, and at the joint 30, a row of recesses (second recess row) 35B is formed, in which multiple recesses (second recesses) 31B are arranged in the width direction of the bundled portion 25 (width direction of the electrode group 2). The row of recesses 35B is located on the side of the row of recesses 35A where the protruding end Pa of the bundled portion 25 is located.

[0043] In the example shown in Figure 3, one recess row 35A and one recess row 35B are formed. The recess row (second recess row) 35B is adjacent to the recess row (first recess row) 35A from the side where the bundle portion 25 protrudes. Also in the example shown in Figure 3, the number of recesses 31A forming the recess row 35A is the same as the number of recesses 31B forming the recess row 35B. Each of the recesses 31A forming the recess row 35A has a corresponding recess 31B forming the recess row 35B adjacent to it from the side where the protruding end Pa is located.

[0044] In the example shown in Figure 3, the boundary between the recessed rows 35A and 35B in the protruding direction of the bundled portion 25 is not shifted, or is hardly shifted, from the boundary between the overlapping region 41 and the non-overlapping region 42. Here, the area αA formed in the overlapping region 41 and the area αB formed in the non-overlapping region 42 of the joint 30, which is a weld mark, are defined. In the example shown in Figure 3, the ratio of area αA to area αB is 1 or close to 1.

[0045] Furthermore, regarding the protruding direction of the bundled portion 25, the boundaries of the recessed rows 35A and 35B may be offset from the boundary between the overlapping region 41 and the non-overlapping region 42. In an example shown in Figure 6, which is different from the example in Figure 3, the boundaries of the recessed rows 35A and 35B are located closer to the protruding end Pa than the boundary between the overlapping region 41 and the non-overlapping region 42. Therefore, the area αA is smaller than the area αB. However, even in a configuration where the boundaries of the recessed rows 35A and 35B are closer to the protruding end Pa than the boundary between the overlapping region 41 and the non-overlapping region 42, the center of the recess 31A of recessed row 35A is located in the overlapping region 41, and the center of the recess 31B of recessed row 35B is located in the non-overlapping region 42. Therefore, the ratio of area αA to area αB is greater than 1 / 3.

[0046] In the example shown in Figure 7, which is different from the examples in Figure 3 and Figure 6, the boundary between recess rows 35A and 35B is located further from the protruding end Pa than the boundary between the overlapping region 41 and the non-overlapping region 42. Therefore, the area αA is larger than the area αB. However, even in the configuration where the boundary between recess rows 35A and 35B is further from the protruding end Pa than the boundary between the overlapping region 41 and the non-overlapping region 42, the center of the recess 31A of recess row 35A is located in the overlapping region 41, and the center of the recess 31B of recess row 35B is located in the non-overlapping region 42. Therefore, the ratio of area αA to area αB is less than 3. Note that in Figures 6 and 7, the configuration of the connection portion of the lead 20 to one of the pair of unsupported portions 15 of the electrode group 2 is shown as viewed from one side in the thickness direction (stacking direction of the current collector portion 26) of the electrode group 2.

[0047] As described above, if one recess row 35A and one recess row 35B are formed, and the number of recesses 31A forming recess row 35A is the same as the number of recesses 31B forming recess row 35B, then the center of the recess 31A of recess row 35A is located in the overlapping region 41, and the center of the recess 31B of recess row 35B is located in the non-overlapping region 42. Furthermore, the ratio of area αA to area αB is greater than 1 / 3 and less than 3.

[0048] Furthermore, the dimensions of the bundle portion 25 are defined as follows: the protruding length D1 in the electrode group 2, that is, the dimension in the protruding direction (lengthwise direction of the electrode group 2) from the base position of the protruding portion to the protruding end Pa.The dimensions of the joint portion 30 in the protruding direction (lengthwise direction of the electrode group 2) of the bundle portion 25, D2, and the dimensions of the non-overlapping region 42 in the protruding direction of the bundle portion 25, D3.Dimension D3 corresponds to the distance from the boundary between the non-overlapping region 42 and the overlapping region 41 to the protruding end Pa.In one example, the ratio of dimension D2 to the protruding length D1 is 0.3 or more and 0.4 or less.The ratio of dimension D3 to the protruding length D1 is 0.2 or more and 0.5 or less.

[0049] In the non-overlapping region 42, it is preferable that the joint portion 30 is formed over more than half of the area when viewed from the side opposite to the side where the lead 20 is located in the stacking direction (thickness direction of the electrode group 2). Furthermore, the area β of the recessed bottom surface 32 in each recess 31 when viewed from the side opposite to the side where the lead 20 is located in the stacking direction is defined. In one example, in each recess 31, the ratio of the area β of the recessed bottom surface 32 to the total area of ​​the recess 31 is 5% or more and 10% or less.

[0050] In one example, when connecting the bundled portion 25 to the lead 20, as shown in Figure 4, the bundled portion 25 is sandwiched between backup leads 21 from both sides in the stacking direction of the current collector band portion 26. At this time, only the relay portion 46 and the non-overlapping region 42 are sandwiched by the backup leads 21, and the dimensional change portion 45 is not sandwiched by the backup leads 21. Then, the lead 20 is brought into contact with the backup lead 21 from one side in the stacking direction (thickness direction of the electrode group 2), and the horn (ultrasonic horn) 50 is brought into contact with the backup lead 21 from the opposite side of the stacking direction from the lead 20. Then, a retaining member 51 such as an anvil is brought into contact with the lead 20 from the opposite side of the stacking direction from the horn 50, and the lead 20, backup lead 21 and bundled portion 25 are sandwiched between the horn 50 and the retaining member 51.

[0051] Then, with the lead 20 and the bundle portion 25 sandwiched between the horn 50 and the retaining member 51, the horn 50 is ultrasonically vibrated, and the lead 20, the bundle portion 25 and the backup lead 21 are joined by ultrasonic welding. This forms a joint portion 30 as a weld mark. In this embodiment, as shown in Figure 4, one or more protrusions 52A and 52B are formed on the horn 50 as protrusions 52. In ultrasonic welding, the horn 50 is ultrasonically vibrated with each of the protrusions 52A and 52B in contact with the backup lead 21. At this time, the protrusion 52B is brought into contact with the backup lead 21 at a position closer to the protruding end Pa in the protruding direction of the bundle portion 25 compared to the protrusion 52A.

[0052] In one example shown in Figure 4, ultrasonic welding is performed as described above, resulting in the formation of a recess 31A whose center is located in the overlapping region 41 by the protrusion 52A, and a recess 31B whose center is located in the non-overlapping region 42 by the protrusion 52B. In one example, in the horn 50, multiple protrusions 52A are arranged in a direction perpendicular or approximately perpendicular to the plane of Figure 4, and multiple protrusions 52B are arranged in a direction perpendicular or approximately perpendicular to the plane of Figure 4. In this case, a row of recesses 35A is formed by the multiple protrusions 52A, and a row of recesses 35B is formed by the multiple protrusions 52B.

[0053] As described above, in this embodiment, each bundle portion 25 of the positive electrode 13A and the negative electrode 13B includes an overlapping region 41 where all of the current collection band portions 26 overlap, and a non-overlap region 42 where one or more of the current collection band portions 26 do not overlap with other current collection band portions 26 and are adjacent to the overlapping region 41 from the side where the protruding end Pa is located. The joint portion (weld mark) 30 to which the bundle portion 25 and the conductive member lead 20 are joined includes one or more recesses (first recess) 31A whose center is located in the overlapping region 41, and one or more recesses (second recess) 31B whose center is located in the non-overlap region 42. By forming the recess 31A whose center is located in the overlapping region 41 in the joint portion 30, it is effectively prevented that there are current collection band portions 26 of the bundle portion 25 that are not joined to the lead 20.

[0054] In the bundled band 25, all of the multiple current collector bands 26 are joined to the lead 20, thereby ensuring the durability of the joint 30 in fatigue tests, impact tests, and other tests conducted after the lead 20 is connected to the bundled band 25. This increases the pass rate in fatigue tests, impact tests, and other tests, improving the yield in the manufacture of the battery 1.

[0055] Furthermore, in batteries with increased output power, such as by increasing the number of turns in the wound electrode group 2 or increasing the number of stacked electrode plates in the laminated electrode group 2, the dimensions of the electrode group 2 in the thickness direction become larger. In this case, the number of stacked current collector strips 26 increases in each of the bundled strips 25 of the positive electrode 13A and the negative electrode 13B, and the proportion of non-overlapping regions 42 in which one or more of the current collector strips 26 do not overlap with other current collector strips 26 increases. As the proportion of non-overlapping regions 42 in the bundled strip 25 increases, if the joint 30 is formed only in the overlapping region 41, the dimensions of the joint 30 in the protruding direction of the bundled strip 25 become smaller.

[0056] In this embodiment, both a recess 31A whose center is located in the overlapping region 41 and a recess 31B whose center is located in the non-overlapping region 42 are formed at the joint. Therefore, even if the proportion of the non-overlapping region 42 in the bundled portion 25 increases, the dimensions of the joint 30 in the protruding direction of the bundled portion 25 do not decrease, and the area of ​​the joint 30 is appropriately secured. As a result, in the battery 1 in which the leads 20 are joined to the bundled portion 25, strength such as tensile strength is ensured at the connection portion of the leads 20 to the bundled portion 25, including the joint 30.

[0057] Furthermore, in the overlapping region 41, the number of stacked current collector bands 26 is greater than in the non-overlapping region 42, and the dimensions (thickness) of the bundled band 25 in the stacking direction are larger. For this reason, the recess 31A formed in the overlapping region 41 tends to be formed deeper than the recess 31B formed in the non-overlapping region 42. On the other hand, in the non-overlapping region 42, the number of stacked current collector bands 26 is smaller, so the area of ​​the recess 31B tends to be larger than that of the recess 31A. In the recess 31A, the increased depth increases the bonding strength between the bundled band 25 and the lead 20. And in the recess 31B, the increased area allows the bundled band 25 and the lead 20 to be bonded over a wider area.

[0058] In this embodiment, the joint portion 30 is formed with both a recess 31A that joins the bundle portion 25 and the lead 20 with high bonding strength, and a recess 31B that joins the bundle portion 25 and the lead 20 over a wide area. This improves the strength of the connection portion of the lead 20 to the bundle portion 25, including the joint portion 30, and improves the durability of the joint portion 30 in tests such as fatigue tests and impact tests. As described above, in this embodiment, even if the proportion of the non-overlapping region 42 in the bundle portion 25 of the current collectors of the positive electrode 13A and the negative electrode 13B increases, the bundle portion 25 is properly joined to the lead 20, which is a conductive member.

[0059] Furthermore, in a preferred example of this embodiment, the number of recesses 31B is greater than or equal to the number of recesses 31A. Also, in a preferred example of this embodiment, when viewed from the stacking direction, the joint portion 30 is formed over more than half of the area of ​​the non-overlapping region 42. By adopting these configurations, the area of ​​the joint portion 30 that joins the bundle portion 25 and the lead 20 is further increased. This further improves the strength of the connection portion of the lead 20 to the bundle portion 25.

[0060] Furthermore, in an example such as Figure 3 of this embodiment, a row of recesses 35A, in which a plurality of recesses 31A are arranged along the width direction of the bundled band 25, and a row of recesses 35B, in which a plurality of recesses 31B are arranged along the width direction of the bundled band 25, are formed in the joint portion 30. With this configuration, the dimensions of the joint portion 30 in the width direction of the bundled band 25 are also increased. As a result, the area of ​​the joint portion 30 that joins the bundled band 25 and the lead 20 is further increased, and the strength of the connection portion of the lead 20 to the bundled band 25 is further improved.

[0061] Furthermore, in this embodiment, the overlapping region 41 of the bundled portion 25 includes the aforementioned dimensional change portion 45 and relay portion 46, and in the overlapping region 41, the joint portion 30 is formed only in the relay portion 46. Since the joint portion 30 is not formed in the dimensional change portion 45, where the dimensions of the bundled portion 25 in the stacking direction decrease toward the side where the protruding end Pa is located, the lead 20 and the bundled portion 25 are properly joined in the portion of the joint portion 30 that is formed in the overlapping region 41.

[0062] (modified version) In the embodiments described above, one recess row 35A and one recess row 35B are formed, but in one modified example, multiple recess rows 35B are formed, each consisting of multiple recesses 31B arranged along the width direction. In the first modified example shown in Figure 8, one recess row (first recess row) 35A and two recess rows (second recess row) 35B are formed in the joint 30. In this modified example as well, the recess row 35B is located on the side where the protruding end Pa of the bundled portion 25 is located, relative to the recess row 35A. In this modified example, in the joint 30, the recess row 35B, recess row 35B, and recess row 35A are formed in that order from the side closest to the protruding end Pa. Furthermore, in this modified example, the number of recesses (second recesses) 31B whose centers are located in the non-overlapping region 42 is greater than the number of recesses (first recesses) 31A whose centers are located in the overlapping region 41. Figure 8 shows the configuration of the connection portion of the lead 20 to one of the pair of unsupported portions 15 of the electrode group 2, as viewed from one side in the thickness direction (stacking direction of the current collector portion 26) of the electrode group 2.

[0063] As shown in the modified example in Figure 8, by forming multiple rows of recesses 35B in the joint 30, the dimensions of the joint 30 in the direction of protrusion of the bundle 25 are further increased. This further increases the area of ​​the joint 30 that joins the bundle 25 and the lead 20, and further improves the strength of the connection portion of the lead 20 to the bundle 25.

[0064] Furthermore, in the embodiments described above, only one bundle portion 25 is formed in each of the unsupported portions 15, but in a certain modified example, multiple bundle portions 25 may be formed in each of the pair of unsupported portions 15. In the second modified example shown in Figure 9, in one unsupported portion 15, two (or more) bundle portions 25 are formed in which multiple current collector band portions 26 are bundled together. In this modified example, in the unsupported portion 15, the two bundle portions 25 are located apart from each other in the thickness direction of the electrode group 2. And, similar to the embodiments described above, an overlapping region 41 and a non-overlapping region 42 are formed in each of the two bundle portions 25. Note that Figure 9 shows the configuration of the connection portion of the lead 20 to one of the pair of unsupported portions 15 of the electrode group 2, viewed from one side in the length direction of the electrode group 2.

[0065] In this modified example, backup leads 21 are attached to each of the two bundled portions 25 in the same manner as in the previously described embodiment. Then, in the unsupported portion 15, each of the two bundled portions 25 is joined to the lead 20, which is a conductive member, with the backup leads 21 in between. Therefore, in this modified example, two backup leads 21 are provided for one unsupported portion 15.

[0066] In this modified example, each of the bundled portions 25 is joined to the lead 20 in the same manner as in the embodiments described above, and a joint portion 30 similar to any of the embodiments described above is formed in each of the bundled portions 25. Therefore, in the joint portion 30 to which each of the bundled portions 25 is joined to the lead 20, both a recess (first recess) 31A whose center is located in the overlapping region 41 and a recess (second recess) 31B whose center is located in the non-overlapping region 42 are formed. For this reason, this modified example also produces the same functions and effects as the embodiments described above. That is, even if the proportion of the non-overlapping region 42 in each of the bundled portions 25 increases, the bundled portions 25 are properly joined to the lead 20, which is a conductive member.

[0067] Furthermore, in the embodiments described above, the bundle portion 25 of the current collector is joined to a conductive member such as a lead 20 via a backup lead 21, but this is not the only possible configuration. In one modified example, the backup lead 21 is not provided. In this case, the bundle portion 25 of the current collector is directly connected to a conductive member such as a lead 20. In this modified example, when connecting the lead 20 to the bundle portion 25, the lead 20 is brought into contact with the bundle portion 25 from one side in the stacking direction of the multiple current collector bundle portions 26. Then, the horn 50 is brought into contact with the bundle portion 25 from the opposite side of the stacking direction from the lead 20, and the retaining member 51 is brought into contact with the lead 20 from the opposite side of the stacking direction from the horn 50. As a result, the lead 20 and the bundle portion 25 are sandwiched between the horn 50 and the retaining member 51, and the lead 20 and the bundle portion 25 are joined by ultrasonic welding.

[0068] Even in this modified example, where the backup lead 21 is not provided, the bundle portion 25 includes the overlapping region 41 and the non-overlapping region 42 described above. At the joint portion 30 where the bundle portion 25 and the lead 20 are joined, both a recess (first recess) 31A whose center is located in the overlapping region 41 and a recess (second recess) 31B whose center is located in the non-overlapping region 42 are formed. Therefore, this modified example also provides the same functions and effects as the embodiments described above. That is, even if the proportion occupied by the non-overlapping region 42 in each of the bundle portions 25 increases, the bundle portion 25 is properly joined to the lead 20, which is a conductive member.

[0069] In one modified example, in the internal cavity 10 of the battery 1, the electrode group 2 is arranged such that its width coincides with or substantially coincides with the lateral direction of the battery 1, and its thickness coincides with or substantially coincides with the depth direction of the battery 1. Then, as in Patent Document 2 (Japanese Patent Publication No. 2012-209260), a pair of unsupported portions 15, namely the unsupported portion 15A of the positive electrode current collector and the unsupported portion 15B of the negative electrode current collector, protrude from the same side relative to each other in the longitudinal direction of the electrode group 2. In the battery 1, the pair of unsupported portions 15 protrude toward the side where the lid member 6 is located in the height direction. Therefore, in this modified example, the side where the lid member 6 is located in the height direction is the side from which the bundled portion 25 protrudes in each of the unsupported portions 15.

[0070] Furthermore, the exterior of the battery 1 is not limited to a configuration formed from an outer container 5 and a lid member 6. In one modified example, as described in Patent Document 3 (International Publication No. 2016 / 204147), the exterior is formed from a first metal exterior member and a second metal exterior member. In this case, the first exterior member has a bottom wall and a peripheral wall, and in the first exterior member, a flange protrudes outward from the end of the peripheral wall opposite to the bottom wall. The second exterior member is then attached to the flange of the first exterior member. In another modified example, the exterior of the battery may be formed from a three-layer laminate film in which a metal layer is sandwiched between resin layers.

[0071] In all of the modifications described above, the bundled portion 25 formed on each of the unsupported portions 15 includes the overlapping region 41 and the non-overlapping region 42 described above. At the joint portion 30 to which the bundled portion 25 and the lead 20 are joined, both a recess (first recess) 31A whose center is located in the overlapping region 41 and a recess (second recess) 31B whose center is located in the non-overlapping region 42 are formed. Therefore, the same functions and effects as those of the embodiments described above are achieved.

[0072] Furthermore, only one of the current collectors, the positive electrode 13A and the negative electrode 13B, may have a bundle portion 25 in which an overlapping region 41 and a non-overlapping region 42 are formed. In this case as well, the bundle portion 25 in which the overlapping region 41 and the non-overlapping region 42 are formed is joined to a conductive member such as a lead 20 in the same manner as in the embodiments described above, and a joint portion 30 similar to any of the embodiments described above is formed. Therefore, it is sufficient that at least one of the current collectors, the positive electrode 13A and the negative electrode 13B, has a bundle portion 25 in which an overlapping region 41 and a non-overlapping region 42 are formed, and a joint portion 30 having a recess (first recess) 31A and a recess (second recess) 31B is formed in the bundle portion 25 of the positive electrode 13A and / or the negative electrode 13B.

[0073] (Verification related to the embodiment, etc.) In addition, the following verification was performed as part of the verification related to the embodiments described above. In the verification, multiple aluminum foils were stacked to form a stacked body as a current collector. In the stacked body, the stacked aluminum foils were divided into eight blocks, and the aluminum foils were stacked with the eight blocks offset by 0.5 mm each. This created overlapping regions 41 and non-overlapping regions 42 in the stacked body, similar to the bundled portion 25 in the embodiments described above. The stacked body was then sandwiched from both sides in the stacking direction with backup leads, and conductive leads were attached to the backup leads using cellophane tape (registered trademark). This formed a test piece.

[0074] In the test piece, the direction corresponding to the stacking direction of the bundle portion 25 was defined as the stacking direction of the aluminum foil, and the direction corresponding to the protruding direction of the bundle portion 25 was defined as the length direction. Furthermore, in the test piece, the direction corresponding to the width direction of the bundle portion 25 was defined as the width direction. Then, as described above in the embodiments, the stacked body was joined to the lead in the test piece by ultrasonic welding using a horn.

[0075] In Example 1, a horn was used in which two rows of protrusions, each consisting of three protrusions, were formed. In the horn, the depth direction was defined as the direction that intersects (orthogonal or nearly orthogonal to) both the direction of protrusion of the protrusions and the direction of arrangement of the rows of protrusions. In Example 1, a horn was used in which the two rows of protrusions were adjacent to each other in the depth direction. In addition, the dimensions of each of the six protrusions in the depth direction of the horn were 1.25 mm. In Example 1, when joining the stacked body and the lead, the six protrusions formed six recesses at the joint. At this time, the protrusions were brought into contact with the backup lead in such a state that the depth direction of the horn coincided with or nearly coincided with the length direction of the test piece, and the arrangement direction of the rows of protrusions coincided with or nearly coincided with the width direction of the test piece.

[0076] In Example 1, three recesses, centered in the overlapping region, were formed by three protrusions forming one of the two rows of protrusions, similar to the recess (first recess) 31A in the embodiment. Then, three recesses, centered in the non-overlapping region, were formed by three protrusions forming the remaining row of the two rows of protrusions, similar to the recess (second recess) 31B in the embodiment. Therefore, in Example 1, the test piece had three recesses centered in the overlapping region and three recesses centered in the non-overlapping region at the joint between the stacked body and the lead.

[0077] In Comparative Example 1, a horn was used in which only one row of protrusions, each consisting of three protrusions, was formed. In the Comparative Example horn as well, the direction that intersects (orthogonal or nearly orthogonal to) both the protrusion direction of the protrusions and the arrangement direction of the row of protrusions was defined as the depth direction. In the horn of Comparative Example 1, the dimension of each of the three protrusions in the depth direction was 2.50 mm. Therefore, the dimension of each protrusion in the depth direction in the horn of Comparative Example 1 was twice that of the horn of Example 1. In Comparative Example 1, when joining the stacked body and the lead, three recesses were formed at the joint by the three protrusions. At this time, the protrusions were brought into contact with the backup lead when the depth direction of the horn coincided with or nearly coincided with the length direction of the test piece, and the arrangement direction of the row of protrusions coincided with or nearly coincided with the width direction of the test piece.

[0078] In Comparative Example 1, three recesses were formed by three protrusions, with their centers located in the non-overlapping region. Therefore, in Comparative Example 1, in the test piece, only three recesses with their centers located in the non-overlapping region were formed at the joint between the stacked body and the lead. In Comparative Example 1 as well, the joint between the stacked body and the lead was formed spanning both the overlapping and non-overlapping regions. Furthermore, in both Example 1 and Comparative Example 1, the load from the horn was set to 500N, the amplitude of the ultrasonic vibration to 90% of the maximum possible amplitude, and the horn depth was set to 1.1mm during ultrasonic welding. These conditions were the same in both Example 1 and Comparative Example 1.

[0079] In both Example 1 and Comparative Example 1, the joint between the stacked body and the lead was clamped with a jig, and the test piece with the joint formed was pulled at a speed of 100 mm / s. In both Example 1 and Comparative Example 1, the peak strength value at the time the test piece broke was measured using a push-pull gauge. For verification, the joint and strength measurements on the test piece described above were performed four times each in both Example 1 and Comparative Example 1. In both Example 1 and Comparative Example 1, the average value of the strength at the time the test piece broke was calculated from the four measurements.

[0080] In Example 1, the average strength over four measurements was 196 N, while in Comparative Example 1, the average strength over four measurements was 167 N. Therefore, it was demonstrated that forming both a recess centered in the overlapping region and a recess centered in the non-overlapping region at the joint improves the joint strength compared to the case where only a recess centered in the non-overlapping region is formed at the joint.

[0081] According to at least one of these embodiments or examples, the bundle portion comprises an overlapping region where all current-collecting strip portions overlap, and a non-overlapping region where one or more current-collecting strip portions do not overlap with other current-collecting strip portions and are adjacent to the overlapping region from the side where the protruding end is located. At the joint between the bundle portion and the conductive member, among a plurality of recesses, the center of the first recess is located in the overlapping region, and the center of a second recess, separate from the first recess, is located in the non-overlapping region. Even if the proportion of the non-overlapping region, where one or more of the plurality of current-collecting strip portions do not overlap with other current-collecting strip portions, occupies an increased amount in the bundle portion of the current collector, it is possible to provide a battery in which the bundle portion is properly joined to the conductive member.

[0082] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. The following are additional notes. [1] Electrode group and, The electrode group comprises a plurality of current collector bands bundled together in a stacked state relative to each other, and a bundle of bands that protrudes in a protruding direction intersecting the stacking direction of the plurality of current collector bands, the bundle of bands comprising an overlapping region where all of the current collector bands overlap, and a non-overlapping region where one or more of the current collector bands do not overlap with other current collector bands and are adjacent to the overlapping region from the side where the protruding end is located, A conductive member connected to the bundle portion of the electrode group, A joint comprising a plurality of recesses, each recessed in the stacking direction, to which the bundle portion and the conductive member are joined, wherein the center of one or more first recesses of the plurality of recesses is located in the overlapping region, and the center of one or more second recesses, separate from the first recesses of the plurality of recesses, is located in the non-overlapping region, A battery that is equipped with the following. [2] The battery of [1], wherein the number of second recesses whose centers are located in the non-overlapping region is equal to or greater than the number of first recesses whose centers are located in the overlapping region. [3] When viewed from the stacking direction, the joint is formed over more than half of the area of ​​the non-overlapping region of the bundled material. [1] The battery. [4] In the joint, a first row of recesses is formed, in which a plurality of the first recesses are arranged along the width direction intersecting both the stacking direction and the protruding direction of the bundled portion, and a second row of recesses is formed, in which a plurality of the second recesses are arranged along the width direction. The second row of recesses is located on the side of the first row of recesses where the protruding end of the bundle is located. One of the batteries [1] through [3]. [5] The overlapping region of the bundled portion is A dimensional change portion is provided, toward the side where the protruding end of the bundle portion is located, such that the dimensions of the bundle portion in the stacking direction decrease, A relay portion extends from the side where the protruding end of the bundle portion is located, adjacent to the dimensional change portion, to the boundary with the non-overlapping region, Equipped with, In the overlapping region, the joint is formed only in the relay portion. One of the batteries [1] through [3]. [6] An electrode terminal electrically connected to the bundle portion of the electrode group with the conductive member in between, An outer casing to which the electrode terminals are attached and which houses the electrode group inside, A battery further comprising any one of [1] to [3]. [7] The electrode group comprises a positive electrode and a negative electrode, Each of the positive electrode and the negative electrode is equipped with a current collector. The current collector of at least one of the positive electrode and the negative electrode includes the bundle portion in which the overlapping region and the non-overlapping region are formed, The joining portion having the first recess and the second recess is formed in the bundle portion of the positive electrode and / or the negative electrode. One of the batteries [1] through [3].

Claims

1. Electrode group and, The electrode group comprises a plurality of current collector bands bundled together in a stacked state relative to each other, and a bundle of bands that protrudes in a protruding direction intersecting the stacking direction of the plurality of current collector bands, the bundle of bands comprising an overlapping region where all of the current collector bands overlap, and a non-overlapping region where one or more of the current collector bands do not overlap with other current collector bands and are adjacent to the overlapping region from the side where the protruding end is located, A conductive member connected to the bundle portion of the electrode group, A joint portion to which the bundle portion and the conductive member are joined, comprising a plurality of recesses that are recessed in the stacking direction, wherein the center of one or more of the plurality of recesses, which is a first recess, is located in the overlapping region, and the center of one or more of the plurality of recesses, which is separate from the first recess, is located in the non-overlapping region, and the first recess and the second recess are provided adjacent to each other along the protruding direction of the bundle portion, A battery that is equipped with the following.

2. The battery according to claim 1, wherein the number of second recesses whose centers are located in the non-overlapping region is equal to or greater than the number of first recesses whose centers are located in the overlapping region.

3. Viewed from the stacking direction, the joint is formed over more than half of the area in the non-overlapping region of the bundled material. The battery according to claim 1.

4. In the joint, a first row of recesses is formed, in which a plurality of the first recesses are arranged along the width direction intersecting both the stacking direction and the protruding direction of the bundled portion, and a second row of recesses is formed, in which a plurality of the second recesses are arranged along the width direction. The second row of recesses is located on the side of the first row of recesses where the protruding end of the bundle is located. A battery according to any one of claims 1 to 3.

5. The overlapping region of the aforementioned bundle portion is A dimensional change portion is provided, toward the side where the protruding end of the bundle portion is located, such that the dimensions of the bundle portion in the stacking direction decrease, A relay portion extends from the side where the protruding end of the bundle portion is located, adjacent to the dimensional change portion, to the boundary with the non-overlapping region, Equipped with, In the overlapping region, the joint is formed only in the relay portion. A battery according to any one of claims 1 to 3.

6. An electrode terminal electrically connected to the bundle portion of the electrode group with the conductive member in between, An outer casing to which the electrode terminals are attached and which houses the electrode group inside, A battery according to any one of claims 1 to 3, further comprising the above.

7. The electrode group comprises a positive electrode and a negative electrode, Each of the positive electrode and the negative electrode is equipped with a current collector. The current collector of at least one of the positive electrode and the negative electrode includes the bundle portion in which the overlapping region and the non-overlapping region are formed, The joining portion having the first recess and the second recess is formed in the bundle portion of the positive electrode and / or the negative electrode. A battery according to any one of claims 1 to 3.

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