Secondary battery

Abstract

A secondary battery 1 comprises a plurality of current collectors 50 that are electrically connected to a plurality of electrodes, and a terminal joined to the plurality of current collectors 50, wherein: an outer surface of the terminal in a joint portion J between the plurality of current collectors 50 and the terminal has a first undulating region R1 having an undulating shape; the first undulating region R1 includes a first undulating pattern P1 having a plurality of first recessed portions U1, and two second undulating patterns P2 having a plurality of second recessed portions U2 having an area, in a plan view of the outer surface of the terminal, that is larger than that of the first recessed portions U1; and the first undulating pattern P1 is located between the two second undulating patterns P2 in a plan view.

Description

secondary battery

[0001] The present disclosure relates to secondary batteries.

[0002] Patent Document 1 discloses an ultrasonic bonding device including an anvil and a horn disposed opposite the anvil, and the ultrasonic bonding device ultrasonically bonds a plurality of objects to be bonded together by applying pressure and vibration to the objects, which are stacked on the anvil, using the horn.

[0003] In the ultrasonic bonding device of Patent Document 1, the height of the outermost protrusion of the multiple protrusions on at least one of the anvil and the horn is set smaller than the height of the inner protrusions. This prevents cracks from occurring at the boundary between the gripped area of ​​the workpieces that is clamped by the anvil and the horn and the non-gripped area that is not clamped by the anvil and the horn. This improves the strength of the bonded joint of the workpieces and stabilizes the bonded state of the joint.

[0004] Japanese Patent Application Laid-Open No. 2006-231402

[0005] However, in the ultrasonic bonding device of Patent Document 1, if the height of the outermost protrusions is smaller than the height of the inner protrusions, the inner protrusions will wear out earlier than the outermost protrusions. As a result, if the difference in height between the inner protrusions and the outermost protrusions becomes small, cracks may occur at the boundary between the gripped and non-gripped areas, reducing the strength of the bonded joint and causing variations in the bonded condition. This also applies when the bonded objects are multiple current collectors and terminals of a secondary battery.

[0006] The present disclosure has been made in view of the above, and aims to stabilize the bonding state between a plurality of current collectors and terminals in a secondary battery.

[0007] The secondary battery of the present disclosure comprises a laminate in which a plurality of electrodes are stacked, a plurality of current collectors electrically connected to a plurality of the electrodes, and a terminal joined to a plurality of the current collectors, wherein the outer surface of the terminal at the joint between the plurality of current collectors and the terminal has a first uneven region having an uneven shape, the first uneven region having a first uneven pattern having a plurality of first depressions, and two second uneven patterns having a plurality of second depressions whose area in a planar view of the outer surface of the terminal is larger than the first depressions, and the first uneven pattern is located between the two second uneven patterns in the planar view.

[0008] According to the secondary battery of the present disclosure, the bonded state between the multiple current collectors and the terminals can be stabilized.

[0009] FIG. 1 is a plan view of a secondary battery according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the secondary battery taken along line II-II shown in FIG. 1. FIG. 3 is a schematic diagram illustrating a process for joining a positive electrode terminal and multiple current collectors. FIG. 4 is a plan view of the support surface of an anvil. FIG. 5 is a view of the anvil as viewed from the arrow V shown in FIG. 4. FIG. 6 is a plan view of the pressing surface of a horn. FIG. 7 is a side view of the horn. FIG. 8 is a cross-sectional view of the horn taken along line VIII-VIII shown in FIG. 6. FIG. 9 is a cross-sectional view of the horn taken along line IX-IX shown in FIG. 6. FIG. 10 is a diagram illustrating the amount of wear on the support surface of the anvil according to the embodiment of the present disclosure shown in FIG. 4 and the amount of wear on the support surface of an anvil of a comparative example. FIG. 11 is a plan view of a joint between multiple current collectors and a positive electrode terminal, as viewed from the positive electrode terminal side. FIG. 12 is a partially enlarged view of a first uneven region showing the first uneven pattern shown in FIG. 11. FIG. 13 is a cross-sectional view of the joint. FIG. 14 is a partially enlarged view of a first concave-convex region showing the first concave-convex pattern, the second concave-convex pattern, and the third concave-convex pattern shown in FIG. 11 . FIG. 15 is a plan view of a joint between a plurality of current collectors and a positive electrode terminal, as seen from the current collector side. FIG. 16 is an enlarged view of the second concave-convex region shown in FIG. 15 . FIG. 17 is a cross-sectional view of the joint taken along line XVII-XVII shown in FIG. 16 . FIG. 18 is a cross-sectional view of the joint taken along line XVIII-XVIII shown in FIG. 16 . FIG. 19 is a plan view of an anvil used in a joining process according to a first modified example of the embodiment of the present disclosure. FIG. 20 is a view of the anvil as seen from the arrow XX shown in FIG. 19 . FIG. 21 is a plan view of an anvil used in a joining process according to a second modified example of the embodiment of the present disclosure. FIG. 22 is a plan view of an anvil used in a joining process according to a third modified example of the embodiment of the present disclosure. FIG. 23 is a plan view of an anvil used in a joining process according to a fourth modified example of the embodiment of the present disclosure. Fig. 24 is a plan view of an anvil used in a joining process according to a fifth modified example of an embodiment of the present disclosure. Fig. 25 is a plan view of an anvil used in a joining process according to a sixth modified example of an embodiment of the present disclosure. Fig. 26 is a side view of an anvil and a horn according to the sixth modified example of an embodiment of the present disclosure. Fig. 27 is a plan view of an anvil used in a joining process according to a seventh modified example of an embodiment of the present disclosure.FIG. 28 is a plan view of an anvil used in a joining process according to an eighth modified example of the embodiment of the present disclosure.

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Each embodiment is an example, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible.

[0011] Fig. 1 is a plan view of a secondary battery 1 according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view of the secondary battery 1 taken along line II-II shown in Fig. 1.

[0012] The secondary battery 1 is, for example, a lithium ion battery. As shown in FIG. 1 , the secondary battery 1 includes a laminate 10, a positive electrode terminal 20, a negative electrode terminal 30, an outer casing 40, and a current collector 50.

[0013] The laminate 10 is housed in an exterior body 40. As shown in Fig. 2, the laminate 10 has a laminated structure and includes a plurality of sheet-like positive electrodes 11 and a plurality of sheet-like negative electrodes 12, with the plurality of positive electrodes 11 and the plurality of sheet-like negative electrodes 12 alternately stacked with separators 13 interposed therebetween.

[0014] The positive electrode terminal 20 is in the form of a plate with an L-shaped cross section having a bent surface 21, and one end including the bent surface 21 is located inside the exterior body 40. The other end of the positive electrode terminal 20 is located outside the exterior body 40. The positive electrode terminal 20 may also be in the form of an unbent plate.

[0015] The positive electrode terminal 20 is electrically connected to each of the plurality of positive electrodes 11 via a plurality of current collectors 50. The current collectors 50 are metal foils. The positive electrode terminal 20 and the current collectors 50 connected to the positive electrode terminal 20 are made of the same metal (e.g., aluminum). The positive electrode terminal 20 and the plurality of current collectors 50 are electrically joined to form a joint J (details of which will be described later).

[0016] Like the positive electrode terminal 20, the negative electrode terminal 30 has an L-shaped cross section with a bent surface, and one end including the bent surface is located inside the exterior body 40. The other end of the negative electrode terminal 30 is located outside the exterior body 40. The negative electrode terminal 30 is electrically connected to each of the multiple negative electrodes 12 via multiple current collectors 50. The negative electrode terminal 30 and the current collectors 50 connected to the negative electrode terminal 30 are each formed of the same metal (e.g., copper). A joint J is formed by electrically joining the negative electrode terminal 30 and the multiple current collectors 50 (details will be described later). Note that the negative electrode terminal 30 and the current collectors 50 connected to the negative electrode terminal 30 may be formed of different metals. For example, the negative electrode terminal 30 may be made of copper, and the current collectors 50 connected to the negative electrode terminal 30 may be made of nickel, nickel-plated copper, nickel-clad copper, or the like.

[0017] 1, the exterior body 40 has a housing portion 41 that houses the laminate 10 and a flange portion 42 around the housing portion 41. The housing portion 41 houses an electrolyte (e.g., a non-aqueous electrolyte solution).

[0018] The exterior body 40 is formed by folding back a single film. A portion of the film is formed into a convex shape, for example, by press working, to form the storage section 41. The overlapping portions of the film around the storage section 41 are joined to form a flange section 42, which prevents leakage of the electrolyte.

[0019] Next, a detailed description will be given of the joint J between the positive electrode terminal 20 and the plurality of current collectors 50. Fig. 3 is a schematic diagram showing the process of joining the positive electrode terminal 20 and the plurality of current collectors 50.

[0020] The positive electrode terminal 20 and the multiple current collectors 50 are bonded using an ultrasonic bonding machine 2. The ultrasonic bonding machine 2 includes an anvil 3 having a support surface 3a for supporting a workpiece, a horn 4 having a pressing surface 4a for pressing the workpiece, and an ultrasonic vibration generator 5 for applying ultrasonic vibrations to the horn 4. The horn 4 presses the positive electrode terminal 20 and the multiple current collectors 50 in a pressing direction D1 along the thickness direction of the positive electrode terminal 20. The horn 4 also vibrates in a vibration direction D2 that is perpendicular to the pressing direction D1.

[0021] Fig. 4 is a plan view of the support surface 3a of the anvil 3. Fig. 5 is a view of the anvil 3 as seen from the arrow V shown in Fig. 4. Arrow V is aligned with a third straight line L3, which will be described later.

[0022] 4, the support surface 3a of the anvil 3 has a rectangular shape extending along a first straight line L1 perpendicular to the vibration direction D2 of the horn 4 in a plan view. The plan view of the support surface 3a is the support surface 3a viewed along the pressing direction D1. A plurality of first protrusions T1, a plurality of second protrusions T2, and a plurality of third protrusions T3 are arranged on the support surface 3a in a line-symmetrical shape with respect to the first straight line L1.

[0023] The first protrusion T1, the second protrusion T2, and the third protrusion T3 each have a truncated quadrangular pyramid shape. That is, the top and bottom surfaces of the first protrusion T1, the second protrusion T2, and the third protrusion T3 are flat. Note that the first protrusion T1, the second protrusion T2, and the third protrusion T3 that overlap the periphery of the support surface 3a in a planar view have shapes that are cut off by the periphery of the support surface 3a in a planar view. The shapes of the first protrusion T1, the second protrusion T2, and the third protrusion T3 that are not cut off by the periphery of the support surface 3a2 will be described below.

[0024] 5, the lower surfaces of the first protrusions T1, the second protrusions T2, and the third protrusions T3 are located on a first plane S1 that is perpendicular to the pressing direction D1. The upper surfaces of the first protrusions T1, the second protrusions T2, and the third protrusions T3 are located on a second plane S2 that is parallel to the first plane S1 (i.e., on the same plane). In other words, the heights of the first protrusions T1, the second protrusions T2, and the third protrusions T3 are all equal to one another.

[0025] As shown in Figure 4, the first range A1 in which the multiple first protrusions T1 are arranged is located in the center of the support surface 3a in the direction along the first straight line L1 in a plan view. The lower and upper surfaces of the first protrusions T1 are square in a plan view. The multiple first protrusions T1 are arranged adjacent to each other with their diagonals parallel to the first straight line L1. As a result, the multiple first protrusions T1 are arranged in a matrix along the second straight line L2 and the third straight line L3 that intersect with the first straight line L1 in a plan view.

[0026] In a plan view, the second line L2 and the third line L3 are perpendicular to each other, and the angles formed by the second line L2 and the third line L3 with the first line L1 are equal to each other, i.e., 45°. A side of the lower surface of the first protrusion T1 is parallel to one of the second line L2 and the third line L3.

[0027] In addition, the sides of the lower surfaces of two adjacent first protrusions T1 are in contact with each other, that is, the cross section between the two adjacent first protrusions T1 is V-shaped.

[0028] The second range A2, in which the plurality of second protrusions T2 are arranged, is disposed adjacent to the first range A1 on both sides of the first range A1 in the direction along the first straight line L1, and is located outside the ranges extending from the first range A1 along the second straight line L2 and the third straight line L3.

[0029] The lower and upper surfaces of the second protrusion T2 are square in plan view. In plan view, the length of the sides of the lower surface of the second protrusion T2 is longer than the length of the sides of the lower surface of the first protrusion T1 (specifically, twice as long). That is, in plan view, the area of ​​the lower surface of the second protrusion T2 is larger than the area of ​​the lower surface of the first protrusion T1 (specifically, four times as long). Also, in plan view, the area of ​​the upper surface of the second protrusion T2 is larger than the area of ​​the upper surface of the first protrusion T1.

[0030] The second protrusions T2 are arranged adjacent to one another with the diagonals of their lower surfaces parallel to the first line L1. As a result, the second protrusions T2 are arranged in a matrix along the second line L2 and the third line L3 in a plan view. The sides of the lower surfaces of the second protrusions T2 are parallel to one of the second line L2 and the third line L3.

[0031] Furthermore, the sides of the lower surfaces of two adjacent second protrusions T2 are in contact with each other. That is, the cross section between two adjacent second protrusions T2 is V-shaped. And, the vertices of the lower surfaces of the adjacent second protrusions T2 and first protrusions T1 are in contact with each other. That is, the cross section between the adjacent second protrusions T2 and first protrusions T1 is V-shaped.

[0032] The third range A3, in which the plurality of third protrusions T3 are arranged, is located in a range extending from the first range A1 along the second straight line L2 and the third straight line L3. The plurality of third ranges A3 are located between the first range A1 and the second range A2 in the direction along the first straight line L1. The third range A3 is adjacent to the first range A1 in the direction along one of the second straight line L2 and the third straight line L3. The plurality of third ranges A3 are adjacent to the second range A2 in the direction along one of the second straight line L2 and the third straight line L3.

[0033] The lower and upper surfaces of the third protrusion T3 are rectangular in plan view. In plan view, the area of ​​the upper surface of the third protrusion T3 is larger than the area of ​​the upper surface of the first protrusion T1 and smaller than the area of ​​the upper surface of the second protrusion T2.

[0034] The length of the long side and the short side of the underside of the third protrusion T3 is equal to the length of one side of the underside of the second protrusion T2, and the length of the short side is equal to the length of one side of the underside of the first protrusion T1. The multiple third protrusions T3 are arranged in a matrix along the second line L2 and the third line L3 in a plan view. The side of the underside of the third protrusion T3 is parallel to one of the second line L2 and the third line L3.

[0035] Furthermore, the sides of the lower surfaces of two adjacent third protrusions T3 are in contact with each other, that is, the cross section between the two adjacent third protrusions T3 is V-shaped.

[0036] The adjacent third protrusions T3 and first protrusions T1 are adjacent to each other in the direction along one of the second straight line L2 and the third straight line L3, and the adjacent third protrusions T3 and first protrusions T1 have their lower surfaces in contact with each other, i.e., the cross section between the adjacent third protrusions T3 and first protrusions T1 is V-shaped.

[0037] Furthermore, the adjacent third protrusions T3 and second protrusions T2 are adjacent to each other in the direction along one of the second straight line L2 and the third straight line L3, and the adjacent third protrusions T3 and second protrusions T2 have their lower surfaces in contact with each other, i.e., the cross section between the adjacent third protrusions T3 and second protrusions T2 is V-shaped.

[0038] The inclination angles of the side surfaces of the first protrusion T1, the second protrusion T2, and the third protrusion T3 are equal to one another. A support surface 3a having such a shape can simplify the manufacturing process. Specifically, the multiple V-shaped cross-sectional grooves formed by the side surfaces of the first protrusion T1, the second protrusion T2, and the third protrusion T3, respectively, are located between the first protrusion T1, the second protrusion T2, and the third protrusion T3 and are continuous from one side of the support surface 3a to the other side in a direction along one of the second straight line L2 and the third straight line L3. Therefore, the multiple first protrusions T1, the multiple second protrusions T2, and the multiple third protrusions T3 can be easily formed by grinding the support surface 3a by moving a grinding wheel having V-shaped cross-sectional corners from one side of the support surface 3a to the other side in a direction along the second straight line L2 and the third straight line L3.

[0039] Fig. 6 is a plan view of the pressing surface 4a of the horn 4. Fig. 7 is a side view of the horn 4. Fig. 8 is a cross-sectional view of the horn 4 taken along line VIII-VIII shown in Fig. 6. Fig. 9 is a cross-sectional view of the horn 4 taken along line IX-IX shown in Fig. 6.

[0040] The pressing surface 4a of the horn 4 has a rectangular shape extending along a fourth straight line L4 perpendicular to the vibration direction D2 in a plan view. The plan view of the pressing surface 4a is the pressing surface 4a viewed along the pressing direction D1. The corners of the pressing surface 4a are chamfered in a plan view. In a plan view, the area of ​​the pressing surface 4a is smaller than the area of ​​the support surface 3a.

[0041] A plurality of sixth protrusions T6 are arranged on the pressing surface 4a in line symmetry with the fourth line L4 as the axis of symmetry. The sixth protrusions T6 are arranged in a matrix along a fifth line L5 and a sixth line L6 that intersect with the fourth line L4 in a plan view.

[0042] In a plan view, the fifth line L5 and the sixth line L6 are perpendicular to each other, and the angles formed by the fifth line L5 and the sixth line L6 and the fourth line L4 are equal to each other, 45°. A side of the lower surface of the sixth protrusion T6 is parallel to one of the fifth line L5 and the sixth line L6.

[0043] The sixth protrusion T6 has a square-shaped underside, and its width narrows toward the protrusion end. The edges of the undersides of two adjacent sixth protrusions T6 are in contact with each other. Furthermore, as shown in FIGS. 7, 8, and 9, the undersides of the sixth protrusions T6 are positioned on a third plane S3 that is perpendicular to the pressing direction D1.

[0044] 6, the sixth protrusions T6 are arranged such that a diagonal line of their lower surfaces is parallel to the fourth straight line L4 in a plan view. Hereinafter, among the sixth protrusions T6, the sixth protrusion T6 whose upper surface overlaps the fourth straight line L4 in a plan view will be referred to as the seventh protrusion T7, and the sixth protrusions T6 on both sides of the seventh protrusion T7 in the vibration direction D2 will be referred to as the eighth protrusion T8.

[0045] As shown in Figure 7, in a side view perpendicular to the vibration direction D2, the pressing surface 4a has an arc C that passes through the periphery of the pressing surface 4a in the vibration direction D2 and is convex toward the outside of the horn 4. The seventh protrusion T7 does not overlap with the arc C in side view. The seventh protrusion T7 has a truncated cone shape with quadrangular (specifically, square) upper and lower surfaces. As shown in Figures 7 and 8, the upper and side surfaces of the seventh protrusion T7 are linear in cross section.

[0046] On the other hand, the eighth protrusion T8 has an arc shape that follows the arc C in side view. That is, as shown in Figures 8 and 9, the top surface and side surface of the eighth protrusion T8 have a shape that follows the arc C in cross section. Specifically, the eighth protrusion T8 has the same truncated cone shape as the seventh protrusion T7, with the top surface cut away by a curved surface that forms the arc C in side view. As a result, the heights H2a and H2b of the eighth protrusion T8 are lower than the height H1 of the seventh protrusion T7.

[0047] Furthermore, among the multiple eighth protrusions T8, the closer the eighth protrusions T8 are to the periphery of the pressing surface 4 a in the vibration direction D2 (in other words, the farther they are from the center in the vibration direction D2), the lower their heights become. Specifically, the eighth protrusions T8 shown in Fig. 8 are closer to the periphery of the pressing surface 4 a in the vibration direction D2 than the eighth protrusions T8 shown in Fig. 9, and the height H2b of the eighth protrusions T8 shown in Fig. 8 is lower than the height H2a of the eighth protrusions T8 shown in Fig. 9.

[0048] Furthermore, the height H1 of the seventh protrusion T7 is greater than the heights of the first protrusion T1, the second protrusion T2 and the third protrusion T3 of the anvil 3 (i.e., the distance between the first plane S1 and the second plane S2).

[0049] Next, a process of joining the positive electrode terminal 20 and the plurality of current collectors 50 (hereinafter referred to as the joining process) will be described. As shown in Fig. 3 , the positive electrode terminal 20 is placed with the surface opposite to the folded surface 21 of the positive electrode terminal 20 in contact with the support surface 3a of the anvil 3. Furthermore, the plurality of current collectors 50 are arranged in a stacked state on the folded surface 21 of the positive electrode terminal 20.

[0050] In addition, in a plan view seen along the pressing direction D1, the support surface 3 a and the pressing surface 4 a face each other and overlap with each other, and in this case, the first area A1, the second area A2, and the third area A3 of the support surface 3 a overlap with the sixth protrusions T6 of the pressing surface 4 a, respectively.

[0051] Next, the multiple current collectors 50 are pressed in the pressing direction D1 by the pressing surface 4 a of the horn 4, and the horn 4 is further vibrated in the vibration direction D2, whereby the positive electrode terminal 20 and the multiple current collectors 50 are welded together and integrated to form a joint J. Note that the negative electrode terminal 30 and the multiple current collectors 50 are also similarly joined using the ultrasonic joining machine 2 to form a joint J.

[0052] As described above, the horn 4 extends along the fourth straight line L4, which is perpendicular to the vibration direction D2. As a result, on both sides of the horn 4 in the direction along the fourth straight line L4, the vibration of the horn 4 during the joining process occurs not only along the vibration direction D2 but also along the pressing direction D1. Therefore, on the support surface 3a of the anvil 3, the load acting on the support surface 3a in the joining process is greater on both sides of the support surface 3a in the direction along the first straight line L1, which is perpendicular to the vibration direction D2, than on the central portion of the support surface 3a in the direction along the first straight line L1, which is perpendicular to the vibration direction D2, and this may result in greater wear of the support surface 3a.

[0053] To address the issue of wear on the support surface 3a, as described above, a plurality of first protrusions T1 are located in the center of the support surface 3a in the direction along the first straight line L1, and a plurality of second protrusions T2 are located at both ends of the support surface 3a in the direction along the first straight line L1. Furthermore, in a plan view, the area of ​​the upper surface of the second protrusions T2 is larger than the area of ​​the upper surface of the first protrusions T1. Therefore, the load acting on the support surface 3a during the joining process is prevented from concentrating at both ends of the support surface 3a in the direction along the first straight line L1, and wear on the support surface 3a can be suppressed.

[0054] Furthermore, as described above, the heights of the first protrusions T1, the second protrusions T2, and the third protrusions T3 are all equal to one another. This prevents the load from concentrating on the first protrusions T1, the second protrusions T2, and the third protrusions T3. This allows the wear amounts of the first protrusions T1, the second protrusions T2, and the third protrusions T3 to be uniform.

[0055] In this way, wear of the support surface 3 a can be suppressed at both ends of the support surface 3 a in the direction along the first straight line L1, and the amount of wear of the first protrusions T1, the second protrusions T2, and the third protrusions T3 can be made uniform, thereby stabilizing the joint state between the current collectors 50 and the positive electrode terminal 20 at the joint J.

[0056] 10 is a diagram showing the amount of wear on the support surface 3 a of the anvil 3 according to the embodiment of the present disclosure shown in FIG. 4 and the amount of wear on the support surface of the anvil 6 of the comparative example. The vertical axis of FIG. 10 represents the average amount of wear on the protrusions T1, T2, and T3, and the horizontal axis of FIG. 10 represents the number of times the current collector 50 and the positive electrode terminal 20 are joined (the so-called number of shots).

[0057] The anvil 6 of the comparative example differs from the anvil 3 of the above embodiment in that the entire support surface is formed by the first protrusion T1. In other words, the first protrusion T1 is disposed over the entire support surface of the anvil 6 of the comparative example.

[0058] As shown in Fig. 10 , the average wear amount of the support surface 3a in the anvil 3 of this embodiment is less than the average wear amount of the support surface in the anvil 6 of the comparative example. Furthermore, the greater the number of joining operations, the greater the difference between the average wear amount of the support surface 3a in the anvil 3 of this embodiment and the average wear amount of the support surface in the anvil 6 of the comparative example. In other words, Fig. 10 shows that the average wear amount of the support surface 3a in the anvil 3 of this embodiment is suppressed by suppressing the wear of the support surface 3a at both ends of the support surface 3a in the direction along the first straight line L1 as described above, and by uniforming the wear amounts of the multiple first protrusions T1, the multiple second protrusions T2, and the multiple third protrusions T3.

[0059] Next, the state of the outer surface of the joint J between the positive electrode terminal 20 and the plurality of current collectors 50 will be described in detail.

[0060] 11 is a plan view of joints J between a plurality of current collectors 50 and the positive electrode terminal 20, as seen from the positive electrode terminal 20 side. The plan view of joints J shown in FIG. 11 is a diagram showing a plan view of joints J seen from the positive electrode terminal 20 side along the thickness direction of the positive electrode terminal 20. The plan view of joints J means that joints J are seen along the thickness direction of the positive electrode terminal 20.

[0061] The outer surface of the positive electrode terminal 20 at the joint J has a first uneven region R1 that is uneven and has a plurality of depressions that are recessed in the thickness direction of the positive electrode terminal 20. The two-dot chain line shown in Fig. 11 indicates the periphery of the first uneven region R1. The first uneven region R1 is formed by pressing the current collector 50 with the horn 4 along the pressing direction D1 while the positive electrode terminal 20 is supported on the support surface 3a of the anvil 3.

[0062] The first uneven region R1 extends along a first direction W1. When the joint J is supported by the anvil 3 during welding, the first direction W1 is substantially perpendicular to the pressing direction D1 and the vibration direction D2. The first uneven region R1 has a first uneven pattern P1, two second uneven patterns P2, and four third uneven patterns P3. A seventh line L7, an eighth line L8, a ninth line L9, and a tenth line L10 shown in FIG. 11 indicate the boundaries between the first uneven pattern P1, the second uneven pattern P2, and the third uneven pattern P3 (details will be described later).

[0063] The first concave-convex pattern P1 is located in the center of the first concave-convex region R1 in the first direction W1. The first concave-convex pattern P1 is located between two second concave-convex patterns P2 in a plan view. Specifically, the first concave-convex pattern P1 is located between two second concave-convex patterns P2 in the first direction W1. The first concave-convex pattern P1 has a plurality of first recesses U1.

[0064] Note that with respect to the first recess U1, and the second recess U2 and third recess U3 described below, the first recess U1, the second recess U2, and the third recess U3 that overlap the periphery of the first uneven region R1 in a plan view have shapes that are cut off by the periphery of the first uneven region R1 in a plan view. Below, the shapes of the first recess U1, the second recess U2, and the third recess U3 will be described in terms of the shapes when they are not cut off by the periphery of the first uneven region R1.

[0065] The first recesses U1 are arranged in a matrix along a second direction W2 and a third direction W3 that intersect with each other in a plan view. In this embodiment, the second direction W2 and the third direction W3 are perpendicular to each other in a plan view. The second direction W2 and the third direction W3 each intersect with the first direction W1.

[0066] FIG. 12 is a partial enlarged view of the first concave-convex region R1 showing the first concave-convex pattern P1 shown in FIG. 11 . FIG. 12 is an enlarged view of the area indicated by the rectangular frame XI in FIG. 11 . The bottom B1 of the first recess U1 corresponds to the shape of the upper surface of the first protrusion T1 of the support surface 3a. Specifically, the bottom B1 of the first recess U1 is planar and square in plan view. Note that, in this specification, "planar" refers to a range having a predetermined surface roughness that is sufficiently smaller than the step between the periphery of the bottom B1 of the first recess U1 and the bottom B1 in the pressing direction D1. The sufficiently small predetermined surface roughness is 1 / 10 or less of the step between the periphery of the bottom B1 of the first recess U1 and the bottom B1 in the pressing direction D1. The surface roughness can be measured by measuring and analyzing the three-dimensional shape of the surface of the bottom B1 using a non-contact surface roughness measuring device such as a laser microscope. The non-contact surface roughness measuring instrument is set to a magnification of 200x, and a measurement range of 0.05 mm in diameter is set near the center of the bottom B1 of the first recess D1 to obtain the surface roughness. For example, when the measured roughness Ry (μm) is 20 μm or less, the bottom B1 can be determined to be flat. Note that the roughness Ry is the maximum height specified in JIS B 0601 (1994) and JIS B 0031 (1994). In each of the second direction W2 and the third direction W3, the distance between the bottoms B1 of two adjacent first recesses U1 (specifically, the distance between the center points of the bottoms B1 of the first recesses U1 in a planar view) is equal to each other.

[0067] 13 is a cross-sectional view of the joint J. As described above, the top surfaces of the first protrusions T1 are positioned on the same plane, and therefore the bottoms B1 of the first recesses U1 are positioned on the fourth plane S4 (i.e., on the same plane).

[0068] 11 , the second concave-convex pattern P2 is located adjacent to the first concave-convex pattern P1 on both outer sides of the first concave-convex pattern P1 in the first direction W1. The second concave-convex pattern P2 is located outside the range extending from the first concave-convex pattern P1 in the second direction W2 and the third direction W3 in a plan view. The second concave-convex pattern P2 has a plurality of second recesses U2.

[0069] The second recesses U2 are aligned along one of the second direction W2 and the third direction W3 in a plan view. In this embodiment, the second recesses U2 are aligned in a matrix along the second direction W2 and the third direction W3 in a plan view. In a plan view, the area of ​​the second recesses U2 is larger than the area of ​​the first recesses U1.

[0070] 14 is a partial enlarged view of the first concave-convex region R1 showing the first concave-convex pattern P1, the second concave-convex pattern P2, and the third concave-convex pattern P3 shown in FIG. 11 . FIG. 14 is an enlarged view of the area indicated by the rectangular frame XIV shown in FIG. 11 . The bottom B2 of the second recess U2 corresponds to the shape of the upper surface of the second protrusion T2 of the support surface 3a. Specifically, the bottom B2 of the second recess U2 is flat and square in plan view. The area of ​​the bottom B2 of the second recess U2 is larger than the area of ​​the bottom B1 of the first recess U1. Furthermore, the length of the bottom B2 of the second recess U2 in the first direction W1 is longer than the length of the bottom B1 of the first recess U1.

[0071] In each of the second direction W2 and the third direction W3, the distance between the bottoms B2 of two adjacent second recesses U2 (specifically, the distance between the centers of the bottoms B2 of the second recesses U2 in a plan view) is equal to one another, and the distance between the bottoms B2 of two adjacent second recesses U2 is greater than the distance between the bottoms B1 of two adjacent first recesses U1.

[0072] 13, the bottoms B2 of the second recesses U2 are located on the fourth plane S4 (i.e., on the same plane) as the bottoms B1 of the first recesses U1. As described above, the top surfaces of the first protrusions T1 and the top surfaces of the second protrusions T2 are located on the same plane, so that the bottoms B1 of the first recesses U1 and the bottoms B2 of the second recesses U2 are located on the same plane.

[0073] As shown in Figure 11, the third concave-convex pattern P3 is located in a range extending from the first concave-convex pattern P1 along both the second direction W2 and the third direction W3. The third concave-convex pattern P3 is located between the first concave-convex pattern P1 and the second concave-convex pattern P2 in the first direction W1. The third concave-convex pattern P3 is adjacent to the first concave-convex pattern P1 in either the second direction W2 or the third direction W3. The third concave-convex pattern P3 is also adjacent to the second concave-convex pattern P2 in either the second direction W2 or the third direction W3. The third concave-convex pattern P3 has a plurality of third recesses U3.

[0074] The third recesses U3 are aligned along at least one of the second direction W2 and the third direction W3 in a plan view. In a plan view, the area of ​​each third recess U3 is larger than the area of ​​each first recess U1 and smaller than the area of ​​each second recess U2.

[0075] 14 corresponds to the shape of the upper surface of the third protrusion T3 of the support surface 3a. Specifically, the bottom B3 of the third recess U3 is flat and rectangular in plan view. The area of ​​the bottom B3 of the third recess U3 is larger than the area of ​​the bottom B1 of the first recess U1 and smaller than the area of ​​the bottom B2 of the second recess U2.

[0076] The distance between the bottoms B3 of two adjacent third recesses U3 in the second direction W2 (specifically, the distance between the center points of the bottoms B3 of the third recesses U3 in a planar view) is different from the distance between the bottoms B3 of two adjacent third recesses U3 in the third direction W3.

[0077] Specifically, for the third uneven pattern P3 adjacent to the first uneven pattern P1 in the second direction W2, the distance between the bottoms B3 of two adjacent third recesses U3 in the second direction W2 is equal to the distance between the bottoms B2 of two adjacent second recesses U2 in the second direction W2 and the third direction W3, and the distance between the bottoms B3 of two adjacent third recesses U3 in the third direction W3 is equal to the distance between the bottoms B1 of two adjacent first recesses U1 in the second direction W2 and the third direction W3.

[0078] Furthermore, for the third uneven pattern P3 adjacent to the first uneven pattern P1 in the third direction W3, the distance between the bottoms B3 of two adjacent third recesses U3 in the second direction W2 is equal to the distance between the bottoms B1 of two adjacent first recesses U1 in the second direction W2 and the third direction W3, and the distance between the bottoms B3 of two adjacent third recesses U3 in the third direction W3 is equal to the distance between the bottoms B1 of two adjacent first recesses U1 in the second direction W2 and the third direction W3.

[0079] 13 , the bottoms B3 of the third recesses U3 are located on the fourth plane S4 (i.e., on the same plane), as are the bottoms B1 of the first recesses U1 and the bottoms B2 of the second recesses U2. As described above, the top surfaces of the first protrusions T1, the second protrusions T2, and the third protrusions T3 are located on the same plane, so that the bottoms B1 of the first recesses U1, the second recesses U2, and the third recesses U3 are located on the same plane.

[0080] The seventh line L7 and the ninth line L9 are parallel to the second direction W2. The seventh line L7 and the ninth line L9 also pass between the first recess U1 and the third recess U3, and the third recess U3 and the second recess U2, which are adjacent to each other in the third direction W3. The eighth line L8 and the tenth line L10 are parallel to the third direction W3. The eighth line L8 and the tenth line L10 also pass between the first recess U1 and the third recess U3, and the third recess U3 and the second recess U2, which are adjacent to each other in the second direction W2. In other words, the seventh line L7, the eighth line L8, the ninth line L9, and the tenth line L10 correspond to the ridges between the first concave-convex pattern P1, the second concave-convex pattern P2, and the third concave-convex pattern P3, which are adjacent to each other.

[0081] The ranges of the first uneven pattern P1, the second uneven pattern P2, and the third uneven pattern P3 can be determined by drawing the periphery of the first uneven region R1, the seventh line L7, the eighth line L8, the ninth line L9, and the tenth line L10 on an image of the outer surface of the joint J magnified, for example, at 100 times. The distance between the centers of the bottoms B1 of the first recesses U1, the distance between the centers of the bottoms B2 of the second recesses U2, the distance between the centers of the bottoms B3 of the third recesses U3, the area of ​​the first recesses U1, the area of ​​the second recesses U2, the area of ​​the third recesses U3, the area of ​​the bottoms B1 of the first recesses U1, the area of ​​the bottoms B2 of the second recesses U2, and the area of ​​the bottoms B3 of the third recesses U3 can also be measured using an image of the outer surface of the joint J magnified, for example, at 100 times.

[0082] As described above, in the joining process, on both sides of the horn 4 in the first direction W1, which is orthogonal to the vibration direction D2 like the first straight line L1, the vibration of the horn 4 in the joining process occurs not only along the vibration direction D2 but also along the pressing direction D1. Therefore, the load acting on the first uneven region R1 in the first direction W1 during the joining process is greater on both sides of the first uneven region R1 in the first direction W1 than on the center of the first uneven region R1 in the first direction W1, which may cause cracks to occur in the joint J.

[0083] To address the issue of cracks at the joint J, as described above, a plurality of first recesses U1 are located in the center of the first uneven region R1 in the first direction W1, and a plurality of second recesses U2 are located at both ends of the first uneven region R1 in the first direction W1. Furthermore, in a plan view, the area of ​​the second recesses U2 is larger than the area of ​​the first recesses U1. Therefore, the load acting on the joint J during the joining process is prevented from concentrating at both ends of the first uneven region R1 in the first direction W1.

[0084] Furthermore, when the plurality of second recesses U2 are located at both ends of the first uneven region R1 in the first direction W1, the area of ​​the second recesses U2 is larger than the area of ​​the first recesses U1, thereby preventing local compression of the joint J at both ends of the first uneven region R1. This prevents cracks from occurring at the joint J, and stabilizes the bond between the plurality of current collectors 50 and the positive electrode terminal 20 at the joint J.

[0085] Furthermore, as described above, the bottoms B1 of the first recesses U1, the bottoms B2 of the second recesses U2, and the bottoms B3 of the third recesses U3 are located on the same plane. This reduces local compression of the joint J compared to when the bottoms B1 of the first recesses U1, the bottoms B2 of the second recesses U2, and the bottoms B3 of the third recesses U3 are located on different planes. This reduces the risk of cracks occurring at the joint J, and stabilizes the bond between the current collectors 50 and the positive electrode terminal 20 at the joint J.

[0086] 15 is a plan view of a joint J between a plurality of current collectors 50 and the positive electrode terminal 20, as viewed from the current collector 50 side. In other words, the plan view of the joint J shown in FIG. 15 is a view showing a plan view of the joint J as viewed from the current collector 50 side along the thickness direction of the positive electrode terminal 20.

[0087] The outer surface of the current collector 50 at the joint J has a second uneven region R2 having an uneven shape with multiple depressions recessed in the thickness direction of the positive electrode terminal 20. The second uneven region R2 is formed by pressing the current collector 50 with the horn 4 along the pressing direction D1 while the positive electrode terminal 20 is supported on the support surface 3a of the anvil 3. The second uneven region R2 extends along the first direction W1. The second uneven region R2 has a plurality of sixth depressions U6.

[0088] Fig. 16 is an enlarged view of the second uneven region R2 shown in Fig. 15. Fig. 17 is a cross-sectional view of the joint J taken along line XVII-XVII shown in Fig. 16. Fig. 18 is a cross-sectional view of the joint J taken along line XVIII-XVIII shown in Fig. 16.

[0089] The sixth recesses U6 correspond to the shapes of the sixth protrusions T6 (seventh protrusions T7 and eighth protrusions T8: see FIGS. 7, 8, and 9 ) on the pressing surface 4 a. Specifically, the sixth recess U6 located in the center of the second uneven region R2 in the vibration direction D2 corresponds to the shape of the seventh protrusion T7 of the horn 4. The sixth recesses U6 located on both sides of the second uneven region R2 in the vibration direction D2 correspond to the shape of the eighth protrusion T8. As shown in FIG. 16 , the sixth recesses U6 are arranged in a matrix along the second direction W2 and the third direction W3.

[0090] As described above, the height of the eighth protrusion T8 of the horn 4 is lower than the height of the seventh protrusion T7. Furthermore, the depth of the sixth recess U6 decreases as one approaches the periphery of the second uneven region R2 in the vibration direction D2. Therefore, as shown in Figures 17 and 18, when the seventh straight line L7 connecting the peripheries E of the second uneven region R2 on both sides in the vibration direction D2 is used as a reference, the depth of the bottom B6a of the sixth recess U6 located in the center of the vibration direction D2 is the deepest among the multiple sixth recesses U6. Furthermore, the depth of the bottom of the sixth recess U6 decreases as one approaches the periphery E of the second uneven region R2 in the vibration direction D2.

[0091] 17 and 18, the bottom B6a of the sixth recess U6 located in the center of the vibration direction D2 shown in Fig. 17, the bottom B6b of the sixth recess U6 located outside the center in the vibration direction D2 shown in Fig. 18, and the bottom B6c of the sixth recess U6 located outside the center in the vibration direction D2 shown in Fig. 17 are closer to the periphery E of the second uneven region R2 in the vibration direction D2 in this order. The depths of the bottom B6a, the bottom B6b, and the bottom B6c become shallower in this order.

[0092] As a result, the compression ratio of the joint J at the bottom of the sixth recess U6 decreases toward the periphery E of the second uneven region R2 in the vibration direction D2. In other words, damage to the current collector 50 at the periphery E of the second uneven region R2 in the vibration direction D2 is suppressed during the joining process. Therefore, the joining state between the multiple current collectors 50 and the positive electrode terminal 20 can be stabilized.

[0093] As described above, the eighth protrusion T8 of the horn 4 has an arc-shaped cross section that follows the arc C that passes through the periphery of the pressing surface 4a in the vibration direction D2. Therefore, as shown in Figures 17 and 18, in the sixth recess U6 that is located outside the center in the vibration direction D2 and that overlaps the periphery E of the second uneven region R2, the outer surface that connects the periphery E of the second uneven region R2 to the bottom has an arc-shaped cross section that follows the arc C.

[0094] As a result, in the sixth recess U6 that overlaps the periphery of the second uneven region R2 in the vibration direction D2, the compressibility of the joint J decreases from the bottom toward the periphery E of the second uneven region R2. In other words, damage to the current collector 50 at the periphery of the second uneven region R2 in the vibration direction D2 is suppressed during the joining process. Therefore, the joining state between the multiple current collectors 50 and the positive electrode terminal 20 can be stabilized.

[0095] As described above, the seventh protrusion T7 of the horn 4 has a flat upper surface. Therefore, the bottom B6a of the sixth recess U6 located in the center of the vibration direction D2 shown in FIG. 16 is flat.

[0096] As a result, the current collectors 50 are compressed into a flat shape at the joint J, which has a high compression ratio in the center in the vibration direction D2, and this prevents the current collectors 50 from being damaged. Therefore, the joint state between the multiple current collectors 50 and the positive electrode terminal 20 can be stabilized.

[0097] Furthermore, as described above, the height H1 of the seventh protrusion T7 corresponding to the second uneven region R2 is greater than the heights of the first protrusion T1, second protrusion T2, and third protrusion T3 corresponding to the first uneven region R1. As a result, as shown in FIG. 13 , the depth De1 corresponding to the depths of the first recess U1, second recess U2, and third recess U3 in the first uneven region R1 is shallower than the depth De2 corresponding to the depth of the deepest portion (i.e., bottom B6a) of the sixth recess U6 in the second uneven region R2. In other words, the depth of the first uneven region R1 is shallower than the depth of the second uneven region R2. This results in a lower compressibility of the joint J on the positive electrode terminal 20 side than the joint J on the current collector 50 side. This prevents cracks from occurring in the joint J on the positive electrode terminal 20 side, thereby stabilizing the bond between the multiple current collectors 50 and the positive electrode terminal 20 at the joint J.

[0098] The joining of the plurality of current collectors 50 and the negative electrode terminal 30 is performed in the same manner as the joining of the plurality of current collectors 50 and the positive electrode terminal 20. That is, the first uneven region R1 and the second uneven region R2 are formed at the joint J between the plurality of current collectors 50 and the negative electrode terminal 30, similar to the joint J between the plurality of current collectors 50 and the positive electrode terminal 20. Therefore, the joint J between the plurality of current collectors 50 and the negative electrode terminal 30 can stabilize the joint state between the plurality of current collectors 50 and the negative electrode terminal 30, similar to the joint J between the plurality of current collectors 50 and the positive electrode terminal 20.

[0099] Next, the joint J according to the first modified example of the embodiment of the present disclosure will be described, mainly focusing on the differences from the joint J according to the above embodiment.

[0100] Fig. 19 is a plan view of the anvil 3 used in the joining step according to the first modified example of the embodiment of the present disclosure. Fig. 20 is a view of the anvil 3 as seen from the arrow XX shown in Fig. 19. The arrow XX is aligned in the third direction W3.

[0101] In the support surface 3a1 of the anvil 3 according to the first modification, the first protrusions T1 are pyramidal in shape. The third protrusions T3 are triangular in cross section with a square lower surface. The second protrusions T2 are truncated pyramidal in shape, similar to the second protrusions T2 of the above embodiment.

[0102] By performing the joining process using such an anvil 3, the bottom B1 of the first recess U1, the bottom B2 of the second recess U2, and the bottom B3 of the third recess U3 of the first uneven region R1 of the joint J have the following shapes. That is, the bottom B1 of the first recess U1, which corresponds to the shape of the first protrusion T1, has a V-shaped cross section. The bottom B3 of the third recess U3, which corresponds to the shape of the third protrusion T3, also has a V-shaped cross section. Note that the bottom B2 of the second recess U2, which corresponds to the shape of the second protrusion T2, is flat, like the bottom B2 of the second recess U2 in the above embodiment, and is square in plan view.

[0103] Next, a joint J according to a second modified example of the embodiment of the present disclosure will be described, mainly focusing on differences from the joint J according to the first modified example of the embodiment. Fig. 21 is a plan view of an anvil 3 used in the joining step according to the second modified example of the embodiment of the present disclosure.

[0104] The support surface 3a2 of the anvil 3 according to the second modification further includes a plurality of fourth protrusions T4 and a plurality of fifth protrusions T5 in addition to a plurality of first protrusions T1, a plurality of second protrusions T2, and a plurality of third protrusions T3. The fourth protrusions T4 and the fifth protrusions T5, which overlap with the periphery of the support surface 3a2 in a plan view, have shapes that are cut off by the periphery of the support surface 3a2 in a plan view. The shapes of the fourth protrusions T4 and the fifth protrusions T5 when not cut off by the periphery of the support surface 3a2 will be described below.

[0105] The fourth range A4, in which the plurality of fourth protrusions T4 are arranged, is disposed adjacent to the two second ranges A2 on both outer sides thereof in the direction along the first straight line L1, and is located at a position deviated from the direction extending from the second range A2 along the second straight line L2 and the third straight line L3.

[0106] The multiple fourth protrusions T4 are shaped like quadrangular pyramids. That is, the upper and lower surfaces of the fourth protrusions T4 are flat. The lower and upper surfaces of the multiple fourth protrusions T4 are square in plan view. In plan view, the length of the sides on the lower surfaces of the fourth protrusions T4 is longer than the length of the sides on the lower surfaces of the second protrusions T2 (specifically, twice as long). That is, in plan view, the area of ​​the lower surfaces of the fourth protrusions T4 is larger than the area of ​​the lower surfaces of the second protrusions T2 (specifically, four times as long). Furthermore, in plan view, the area of ​​the upper surfaces of the fourth protrusions T4 is larger than the area of ​​the upper surfaces of the second protrusions T2.

[0107] The fourth protrusions T4 are arranged adjacent to one another with the diagonal of their lower surfaces parallel to the first line L1. As a result, the fourth protrusions T4 are arranged in a matrix along the second line L2 and the third line L3 in a plan view. The sides of the lower surfaces of the fourth protrusions T4 are parallel to one of the second line L2 and the third line L3.

[0108] Furthermore, the sides of the lower surfaces of two adjacent fourth protrusions T4 are in contact with each other. That is, the cross section between two adjacent second protrusions T2 is V-shaped. The vertices of the lower surfaces of the adjacent fourth protrusions T4 and second protrusions T2 are in contact with each other. That is, the cross section between the adjacent fourth protrusions T4 and second protrusions T2 is V-shaped.

[0109] The fifth area A5, in which the plurality of fifth protrusions T5 are arranged, is adjacent to the second area A2 in the directions along the second straight line L2 and the third straight line L3, and is also adjacent to the fourth area A4 in the directions along the second straight line L2 and the third straight line L3.

[0110] The fifth protrusions T5 each have a triangular cross section with a square bottom surface. The bottom and top surfaces of the fifth protrusions T5 are rectangular in plan view. In plan view, the area of ​​the top surface of the fifth protrusions T5 is larger than the area of ​​the top surface of the second protrusions T2 and smaller than the area of ​​the top surface of the fourth protrusions T4.

[0111] Furthermore, the length of the long side and the short side of the lower surface of the fifth protrusion T5 is equal to the length of one side of the lower surface of the fourth protrusion T4, and the length of the short side is equal to the length of one side of the lower surface of the second protrusion T2. ​​The multiple fifth protrusions T5 are arranged along one of the second straight line L2 and the third straight line L3 in a plan view. The sides of the lower surfaces of the multiple third protrusions T3 are parallel to one of the second straight line L2 and the third straight line L3. Note that the multiple fifth protrusions T5 may be arranged in a matrix along the second straight line L2 and the third straight line L3 in a plan view.

[0112] Furthermore, the sides of the lower surfaces of two adjacent fifth protrusions T5 are in contact with each other, that is, the cross section between the two adjacent fifth protrusions T5 is V-shaped.

[0113] The adjacent fifth protrusions T5 and T5 are adjacent to each other in the direction along one of the second line L2 and the third line L3, and the sides of the lower surfaces of the adjacent fifth protrusions T5 and T5 are in contact with each other. In other words, the cross section between the adjacent fifth protrusions T5 and T5 is V-shaped.

[0114] Furthermore, the adjacent fifth protrusion T5 and fourth protrusion T4 are adjacent to each other in the direction along one of the second line L2 and the third line L3, and the adjacent fifth protrusion T5 and fourth protrusion T4 have their lower surfaces in contact with each other, i.e., the cross section between the adjacent fifth protrusion T5 and fourth protrusion T4 is V-shaped.

[0115] The inclination angles of the side surfaces of the first protrusion T1, the second protrusion T2, the third protrusion T3, the fourth protrusion T4, and the fifth protrusion T5 are all equal to one another. Therefore, the manufacturing process of the support surface 3a2 having such a shape can be simplified. Specifically, the V-shaped cross-sectional grooves between the first protrusion T1, the second protrusion T2, the third protrusion T3, the fourth protrusion T4, and the fifth protrusion T5 are continuous from one side to the other of the support surface 3a2 in the direction along the second straight line L2 and the third straight line L3. Therefore, by moving a grinding wheel having a V-shaped cross-section corner in a direction along the second straight line L2 and the third straight line L3 from one side of the support surface 3a2 to the other side, the above-mentioned number of first protrusions T1, multiple second protrusions T2, multiple third protrusions T3, multiple fourth protrusions T4 and multiple fifth protrusions T5 can be easily formed.

[0116] By performing the joining process using such an anvil 3, the first uneven region R1 of the joining portion J of this second modified example further has, in addition to the above-mentioned first uneven pattern P1, second uneven pattern P2 and third uneven pattern P3, two fourth uneven patterns (not shown) and four fifth uneven patterns (not shown).

[0117] The fourth concave-convex pattern is located adjacent to the first concave-convex pattern P1 on both sides of the two second concave-convex patterns P2 in the first direction W1. In other words, the two second concave-convex patterns P2 are located between the two fourth concave-convex patterns in the first direction W1. Furthermore, the fourth concave-convex pattern is located outside the range extending from the second concave-convex patterns P2 along the second direction W2 and the third direction W3 in a plan view. The fourth concave-convex pattern has a plurality of fourth recesses (not shown).

[0118] The fourth recesses are aligned along one of the second direction W2 and the third direction W3 in a plan view. The fourth recesses may be aligned in a matrix along the second direction W2 and the third direction W3 in a plan view. The area of ​​the fourth recesses is greater than the area of ​​the second recesses U2 in a plan view.

[0119] The bottom of the fourth recess corresponds to the shape of the upper surface of the fourth protrusion T4 of the support surface 3a2. Specifically, the bottom of the fourth recess is flat and square in plan view. The area of ​​the bottom of the fourth recess is larger than the area of ​​the bottom of the fourth recess.

[0120] The distance between the bottoms of two adjacent fourth recesses in each of the second direction W2 and the third direction W3 (specifically, the distance between the center points of the bottoms of the fourth recesses in a plan view) is equal to each other, and the distance between the bottoms of two adjacent fourth recesses in each of the second direction W2 and the third direction W3 is greater than the distance between the bottoms B2 of two adjacent second recesses U2.

[0121] The bottoms of the fourth recesses are located on a fourth plane S4 (see FIG. 13 ). Therefore, the bottoms B1 of the first recesses U1, the bottoms B2 of the second recesses U2, the bottoms B3 of the third recesses U3, and the bottoms of the fourth recesses are located on the same plane.

[0122] The fifth concave-convex pattern is located in a range extending from the second concave-convex pattern P2 along both the second direction W2 and the third direction W3. The fifth concave-convex pattern is located between the second concave-convex pattern P2 and the fourth concave-convex pattern in the first direction W1. The fifth concave-convex pattern is adjacent to the second concave-convex pattern P2 in either the second direction W2 or the third direction W3. The fifth concave-convex pattern is adjacent to the fourth concave-convex pattern in either the second direction W2 or the third direction W3. The fifth concave-convex pattern has a plurality of fifth recesses (not shown).

[0123] The fifth recesses are aligned along at least one of the second direction W2 and the third direction W3 in a plan view, and the area of ​​each fifth recess is greater than the area of ​​each second recess U2 and smaller than the area of ​​each fourth recess U3 in a plan view.

[0124] The bottom of the fifth recess corresponds to the shape of the upper surface of the fifth protrusion T5 of the support surface 3a. Specifically, the bottom of the fifth recess is flat and rectangular in plan view. The area of ​​the bottom of the fifth recess is larger than the area of ​​the bottom B2 of the second recess U2 and smaller than the area of ​​the bottom of the fourth recess.

[0125] The distance between the bottoms of two adjacent fifth recesses in the second direction W2 (specifically, the distance between the center points of the bottoms of the fifth recesses in a planar view) is different from the distance between the bottoms of two adjacent fifth recesses in the third direction W3.

[0126] Specifically, for the fifth uneven pattern adjacent to the second uneven pattern P2 in the second direction W2, the distance between the bottoms of two fifth recesses adjacent to each other in the second direction W2 is equal to the distance between the bottoms of two fourth recesses adjacent to each other in the second direction W2 and the third direction W3, and the distance between the bottoms of two fifth recesses adjacent to each other in the third direction W3 is equal to the distance between the bottoms B2 of two second recesses U2 adjacent to each other in the second direction W2 and the third direction W3.

[0127] Furthermore, for the fifth uneven pattern adjacent to the second uneven pattern P2 in the third direction W3, the distance between the bottoms of two fifth recesses adjacent to each other in the third direction W3 is equal to the distance between the bottoms of two fourth recesses adjacent to each other in the second direction W2 and the third direction W3, and the distance between the bottoms of two fifth recesses adjacent to each other in the second direction W2 is equal to the distance between the bottoms B2 of two second recesses U2 adjacent to each other in the second direction W2 and the third direction W3.

[0128] The bottoms B3 of the third recesses U3 are located on a fourth plane S4 (see FIG. 13 ). Therefore, the bottoms B1 of the first recesses U1, the bottoms B2 of the second recesses U2, the bottoms B3 of the third recesses U3, the bottoms of the fourth recesses, and the bottoms of the fifth recesses are located on the same plane.

[0129] Next, a joint J according to a third modified example of the embodiment of the present disclosure will be described, mainly focusing on differences from the joint J according to the above-described embodiment. Fig. 22 is a plan view of an anvil 3 used in the joining step according to the third modified example of the embodiment of the present disclosure.

[0130] In the support surface 3a3 of the anvil 3 according to the third modification, the first protrusion T1, the second protrusion T2, and the third protrusion T3 each have a truncated quadrangular pyramid shape with rectangular upper and lower surfaces. In addition, because the lower surface of the first protrusion T1 is rectangular, the shape of the third protrusion T3 located in the third range A3 adjacent to the first range A1 in the second direction W2 is different from the shape of the third protrusion T3 located in the third range A3 adjacent to the first range A1 in the third direction W3.

[0131] By performing the joining process using such an anvil 3, the bottom B1 of the first recess U1, the bottom B2 of the second recess U2, and the bottom B3 of the third recess U3 of the first uneven region R1 of the joint J have the following shapes: That is, the bottom B1 of the first recess U1 corresponding to the shape of the first protrusion T1, the bottom B2 of the second recess U2 corresponding to the shape of the second protrusion T2, and the bottom B3 of the third recess U3 corresponding to the shape of the third protrusion T3 are each flat and rectangular in plan view.

[0132] Next, a joint J according to a fourth modified example of the embodiment of the present disclosure will be described, mainly focusing on differences from the joint J according to the above-described embodiment. Fig. 23 is a plan view of an anvil 3 used in the joining step according to the fourth modified example of the embodiment of the present disclosure.

[0133] In the support surface 3a4 of the anvil 3 according to the fourth modification, the second line L2 and the third line L3 intersect each other but are not perpendicular to each other in a plan view. The angle between the second line L2 and the first line L1 and the angle between the third line L3 and the first line L1 are equal, e.g., 60°. As a result, the first protrusion T1 and the second protrusion T2 each have a quadrangular pyramid shape with a diamond-shaped lower surface and upper surface. The third protrusion T3 also has a quadrangular pyramid shape with a parallelogram-shaped lower surface and upper surface.

[0134] By performing the joining process using such an anvil 3, the second direction W2 and the third direction W3 intersect each other without being perpendicular to each other in a plan view.

[0135] The bottom B1 of the first recess U1, the bottom B2 of the second recess U2, and the bottom B3 of the third recess U3 of the first uneven region R1 of the joint J have the following shapes: The bottom B1 of the first recess U1, which corresponds to the shape of the first protrusion T1, and the bottom B2 of the second recess U2, which corresponds to the shape of the second protrusion T2, are each flat and rhombic in plan view. The bottom B3 of the third recess U3, which corresponds to the shape of the third protrusion T3, are each flat and parallelogram in plan view.

[0136] Next, a joint J according to a fifth modified example of the embodiment of the present disclosure will be described, mainly focusing on differences from the joint J according to the above-described embodiment. Fig. 24 is a plan view of an anvil 3 used in the joining step according to the fifth modified example of the embodiment of the present disclosure.

[0137] In the support surface 3a5 of the anvil 3 according to the fifth modification, the second line L2 and the third line L3 intersect each other but are not perpendicular to each other in a plan view. The angle between the second line L2 and the first line L1 is different from the angle between the third line L3 and the first line L1. The angle between the second line L2 and the first line L1 is, for example, 45°, and the angle between the third line L3 and the first line L1 is, for example, 60°. As a result, the first protrusion T1, the second protrusion T2, and the third protrusion T3 each have a truncated quadrangular pyramid shape with a parallelogram-shaped lower surface and upper surface.

[0138] Furthermore, since the lengths of the two adjacent sides on the underside of the first protrusion T1 are different, the shape of the third protrusion T3 located in the third range A3 adjacent to the first range A1 in the second direction W2 is different from the shape of the third protrusion T3 located in the third range A3 adjacent to the first range A1 in the third direction W3.

[0139] By performing the joining process using such an anvil 3, the second direction W2 and the third direction W3 intersect each other but are not perpendicular to each other in a plan view. In addition, the angle between the second direction W2 and the first direction W1 is different from the angle between the third direction W3 and the first direction W1.

[0140] The bottom B1 of the first recess U1, the bottom B2 of the second recess U2, and the bottom B3 of the third recess U3 of the first uneven region R1 of the joint J have the following shapes: The bottom B1 of the first recess U1, which corresponds to the shape of the first protrusion T1, the bottom B2 of the second recess U2, which corresponds to the shape of the second protrusion T2, and the bottom B3 of the third recess U3, which corresponds to the shape of the third protrusion T3, are each flat and have a parallelogram shape in a planar view.

[0141] Next, a description will be given of a joint J according to a sixth modified example of the embodiment of the present disclosure, mainly focusing on differences from the joint J according to the first modified example of the embodiment. Fig. 25 is a plan view of an anvil 3 used in the joining step according to the sixth modified example of the embodiment of the present disclosure.

[0142] The support surface 3a6 of the anvil 3 according to the sixth modified example has two first areas A1, three second areas A2, and eight third areas A3.

[0143] The two first ranges A1 are spaced apart from each other in the direction along the first straight line L1. The three second ranges A2 are located between the two first ranges A1 in the direction along the first straight line L1 and on both sides of the two first ranges A1 in the direction along the first straight line L1. The third range A3 is located between the first range A1 and the second range A2 in the direction along the first straight line L1. The third range A3 is adjacent to the first range A1 in the direction along one of the second straight line L2 and the third straight line L3. The third range A3 is adjacent to the second range A2 in the direction along one of the second straight line L2 and the third straight line L3.

[0144] 26 is a side view of an anvil 3 and a horn 4 according to a sixth modified example of the embodiment of the present disclosure. The horn 4 of this sixth modified example has two pressing surfaces 4a. In the joining process, the two pressing surfaces 4a each overlap one first area A1, two second areas A2 adjacent to the one first area A1, and four third areas A3 adjacent to the one first area A1 in a plan view.

[0145] By performing the joining process using such an anvil 3 and horn 4, two first uneven regions R1 shown in Figure 11 are formed on the outer surface of the positive electrode terminal 20 at the joint J, and two second uneven regions R2 are formed on the outer surface of the current collector 50 at the joint J.

[0146] Next, a joint J according to a seventh modified example of the embodiment of the present disclosure will be described, mainly focusing on differences from the joint J according to the above-described embodiment. Fig. 27 is a plan view of an anvil 3 used in the joining step according to the seventh modified example of the embodiment of the present disclosure.

[0147] The support surface 3a7 of the anvil 3 according to the seventh modification does not have the third area A3. The second areas A2 are located adjacent to the first area A1 on both sides of the first area A1 in the direction along the first straight line L1.

[0148] The multiple grooves with a V-shaped cross section between the first protrusion T1 and the second protrusion T2 in the seventh modified example include a groove G1 (a groove shown by a dashed line in FIG. 27 ) that is not continuous from one side of the support surface 3 a to the other side in the direction along the second straight line L2 and the third straight line L3. In this case, even if a grinding stone having a V-shaped corner in cross section is moved from one side of the support surface 3 a to the other side in the direction along the second straight line L2 and the third straight line L3, the groove G1 cannot be formed, and the number of processing steps for the support surface 3 a is increased compared to the above embodiment.

[0149] By performing the joining process using such an anvil 3, the first concave-convex region R1 does not have the third concave-convex pattern P3. The second concave-convex pattern P2 is located adjacent to the first concave-convex pattern P1 on both outer sides of the first concave-convex pattern P1 in the first direction W1.

[0150] Next, a description will be given of a joint J according to an eighth modified example of the embodiment of the present disclosure, mainly focusing on differences from the joint J according to the seventh modified example of the embodiment. Fig. 28 is a plan view of an anvil 3 used in the joining step according to the eighth modified example of the embodiment of the present disclosure.

[0151] In the support surface 3a8 of the anvil 3 according to the eighth modification, the first straight line L1 and the second straight line L2 overlap in a plan view. Similar to the seventh modification, the second range A2 is located adjacent to the first range A1 on both sides of the first range A1 in the direction along the first straight line L1.

[0152] The multiple V-shaped grooves between the first protrusion T1 and the second protrusion T2 in this eighth modification include a groove G2 (shown by a dashed line in FIG. 28 ) located inside the periphery of the support surface 3 a in the direction along the second straight line L2. In this case, it is difficult to form the groove G2 using a grindstone with a V-shaped cross-section, and the machining direction of the support surface 3 a becomes more complex than in the above embodiment. The groove is formed by, for example, electric discharge machining.

[0153] By performing the joining process using such an anvil 3, the first uneven region R1 does not have the third uneven pattern P3. The second direction W2 is the same as the first direction W1. The first uneven region R1 is located adjacent to the first uneven pattern P1 on both outer sides of the first uneven pattern P1 in the first direction W1.

[0154] Like the joint J in the above embodiment, the joint J in each of the above modified examples can stabilize the joint state between the multiple current collectors 50 and the positive electrode terminal 20, and the joint state between the multiple current collectors 50 and the negative electrode terminal 30.

[0155] The above-described embodiments are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present disclosure.

[0156] For example, the laminate 10 may be a wound type. The laminate 10 may also constitute an all-solid-state battery. In this case, the laminate 10 has a positive electrode and a negative electrode, and the housing portion 41 houses a solid electrolyte.

[0157] Furthermore, it goes without saying that the support surface 3a is not limited to a rectangular shape in a plan view, and may be, for example, a square or circular shape in a plan view.

[0158] In addition, the plurality of first protrusions T1, the plurality of second protrusions T2, the plurality of third protrusions T3, the plurality of fourth protrusions T4, and the plurality of fifth protrusions T5 may each be arranged with their lower surfaces separated from each other.

[0159] Furthermore, the sixth protrusions T6 on the pressing surface 4a may be formed by the seventh protrusions T7 without the eighth protrusions T8. In this case, the bottoms of the sixth recesses U6 in the second concave-convex region R2 correspond to the shapes of the seventh protrusions T7 and are located on the same plane.

[0160] The first and second uneven regions R1 and R2 may not extend along the first direction W1, but may have equal lengths in two directions perpendicular to each other in a plan view, such as a square or a circle. In this case, the pressing surface 4a of the horn 4 may have a square or a circle in a plan view.

[0161] The present disclosure may also be implemented as a combination of the following configurations.

[0162] (1) A secondary battery comprising: a laminate in which a plurality of electrodes are stacked; a plurality of current collectors electrically connected to the plurality of electrodes; and terminals joined to the plurality of current collectors, wherein an outer surface of the terminal at a joint between the plurality of current collectors and the terminal has a first uneven region having an uneven shape, the first uneven region having: a first uneven pattern having a plurality of first recesses; and two second uneven patterns having a plurality of second recesses whose area in a plan view of the outer surface of the terminal is larger than that of the first recesses, and the first uneven pattern is located between the two second uneven patterns in the plan view.

[0163] (2) The secondary battery according to (1), wherein the first uneven region extends along a first direction in the plan view, and the first uneven pattern is located between two of the second uneven patterns in the first direction.

[0164] (3) The secondary battery according to (1) or (2), wherein the plurality of first recesses are arranged in a matrix along a second direction and a third direction that intersect with each other in the plan view.

[0165] (4) The secondary battery according to (3), wherein the second recesses are arranged along one of the second direction and the third direction in the plan view.

[0166] (5) The secondary battery described in (3) or (4), wherein the first uneven region further has a third uneven pattern having a plurality of third recesses each having an area in the plan view that is larger than the first recess and smaller than the second recess, the third uneven pattern being adjacent to the first uneven pattern in one of the second direction and the third direction, and the second uneven pattern being located outside the range extending from the first uneven pattern along the second direction and the third direction in the plan view.

[0167] (6) The secondary battery according to any one of (1) to (5), wherein the outer surface of the current collector at the joint has a second uneven region having an uneven shape, and the depth of the first uneven region is shallower than the depth of the second uneven region.

[0168] (7) The secondary battery according to any one of (1) to (6), wherein the plurality of electrodes include a positive electrode and a negative electrode, and the laminate has a laminate structure in which the positive electrode and the negative electrode are laminated with a separator interposed therebetween.

[0169] REFERENCE SIGNS LIST 1 secondary battery 10 laminate 11 positive electrode (electrode) 12 negative electrode (electrode) 13 separator 20 positive electrode terminal (terminal) 30 negative electrode terminal (terminal) 50 current collector B1 bottom of first recess B2 bottom of second recess B3 bottom of third recess J joint P1 first concave-convex pattern P2 second concave-convex pattern P3 third concave-convex pattern R1 first concave-convex region R2 second concave-convex region T1 first protrusion U1 first recess U2 second recess U3 third recess W1 first direction W2 second direction W3 third direction

Claims

1. A laminate in which a plurality of electrodes are laminated; A plurality of current collectors electrically connected to the plurality of electrodes; and terminals joined to the plurality of current collectors, an outer surface of the terminal at a joint between the current collectors and the terminal has a first uneven region having an uneven shape; The first uneven area is a first concave-convex pattern having a plurality of first concave portions; and two second concave-convex patterns each having a second concave portion having an area in a plan view of an outer surface of the terminal that is larger than the first concave portion, The first concave-convex pattern is located between two of the second concave-convex patterns in the plan view. Secondary battery.

2. The first uneven region extends along a first direction in the plan view, The first concave-convex pattern is located between two of the second concave-convex patterns in the first direction. The secondary battery according to claim 1 .

3. the first recesses are arranged in a matrix along a second direction and a third direction that intersect with each other in the plan view; The secondary battery according to claim 1 .

4. The second recesses are aligned along one of the second direction and the third direction in the plan view. The secondary battery according to claim 3 .

5. the first concave-convex region further includes a third concave-convex pattern including a plurality of third concave portions each having an area in the plan view that is larger than that of the first concave portions and smaller than that of the second concave portions; the third concave-convex pattern is adjacent to the first concave-convex pattern in one of the second direction and the third direction, the second uneven pattern is located outside a range extending from the first uneven pattern along the second direction and the third direction in the plan view; The secondary battery according to claim 3 .

6. the outer surface of the current collector at the joint portion has a second uneven region having an uneven shape; The depth of the first uneven region is shallower than the depth of the second uneven region. The secondary battery according to claim 1 .

7. The plurality of electrodes include a positive electrode and a negative electrode, The laminate has a laminate structure in which the positive electrode and the negative electrode are laminated with a separator interposed therebetween. The secondary battery according to claim 1 .