Method for manufacturing a welded structure and battery

Abstract

The present invention provides a method for manufacturing a welded structure and a battery. The method for manufacturing a welded structure includes: a step of preparing a laminate in which a plate-shaped first welded member formed of a first metal and a plate-shaped second welded member formed of a second metal are laminated; and a step of irradiating laser light from the side of the first welded member in such a manner as to form a plurality of annular weld marks having coaxial central axes. In the step of irradiating laser light, the laser light is irradiated in such a manner that the irradiation energy gradually decreases as it advances from a predetermined weld mark located inside toward the outermost peripheral side.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a welded structure in which a plate-shaped first welded member formed of a first metal and a plate-shaped second welded member formed of a second metal are welded, and a battery in which a plate-shaped positive terminal formed of a first metal and a plate-shaped negative terminal formed of a second metal are welded. Background Art

[0002] As a laser welding method in which thin plate-shaped welded members are overlapped and irradiated with laser to weld them, International Publication No. 2015 / 186168 discloses the following method: while irradiating laser along a preset multi-circular welding line, moving the laser, and moving the laser along the outer circular welding line prior to the movement of the laser along the inner circular welding line. Summary of the Invention

[0003] In the laser welding method disclosed in International Publication No. 2015 / 186168, the welding conditions are set to be constant so that the inner region of the welding line is sequentially reduced by a predetermined amount, and even if there is a gap between the thin plates, the thin plates can be reliably welded to each other. Due to the gap, welding is actually sometimes performed in the outermost peripheral region without knowing the state of the welded portion. When the thin plates are made of different metals, an unexpected alloy may be generated at the weld mark located at the outermost periphery. In this case, the strength of the joint may be reduced due to the formation of an alloy in the outermost peripheral portion where stress is likely to concentrate.

[0004] The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a method for manufacturing a welded structure that can suppress the formation of an alloy in the outermost periphery and maintain good joint strength, and a battery in which the terminals are well joined to each other.

[0005] The method for manufacturing a welded structure according to the present disclosure includes: a step of preparing a laminate in which a plate-shaped first welded member formed of a first metal and a plate-shaped second welded member formed of a second metal are laminated; and a step of irradiating laser from the side of the first welded member so as to form a plurality of circular weld marks having a coaxial central axis. In the step of irradiating the laser, the laser is irradiated in such a manner that the irradiation energy gradually decreases as it advances from a predetermined weld mark located inside toward the outermost peripheral side.

[0006] According to the above structure, laser is irradiated in such a manner that the irradiation energy gradually decreases as it advances from a predetermined weld mark located on the inner side toward the outermost peripheral side. Therefore, from the predetermined weld mark toward the outermost peripheral side, the alloy layer formed by laser irradiation can be gradually reduced. As a result, in the inner part where the applied stress is small, a certain degree of alloy layer can be allowed to strongly join the first welded member and the second welded member, and the alloy content in the weld mark located on the outermost periphery where stress is likely to concentrate can be reduced. Consequently, cracking at the outermost periphery where stress is likely to concentrate can be suppressed, and good joint strength can be maintained.

[0007] In the method for manufacturing a welded structure based on the above disclosure, it is preferable that in the step of irradiating the laser, the plurality of trajectories of the laser irradiated corresponding to the plurality of annular weld marks are discontinuous.

[0008] According to the above structure, by making the plurality of trajectories of the irradiated laser discontinuous, it is easy to change the irradiation energy of the laser for each of the trajectories.

[0009] In the method for manufacturing a welded structure based on the above disclosure, in the step of irradiating the laser, each of the plurality of trajectories may also be in a circular shape.

[0010] According to the above structure, laser irradiation can be performed uniformly in the entire circumferential direction.

[0011] In the method for manufacturing a welded structure based on the above disclosure, in the step of irradiating the laser, the plurality of annular weld marks may also be formed in such a manner that the depth of the weld marks gradually becomes shallower as it advances from the predetermined weld mark located on the inner side toward the outermost periphery.

[0012] According to the above structure, it is also possible to gradually reduce the depth of the weld marks as it advances from the predetermined weld mark toward the outermost periphery. As a result, in the inner part where the applied stress is small, a certain degree of alloy layer can be allowed to strongly join the first welded member and the second welded member, and the alloy content in the weld mark located on the outermost periphery where stress is likely to concentrate can be reduced.

[0013] In the method for manufacturing a welded structure based on the above disclosure, in the step of irradiating the laser, the laser may also be irradiated in such a manner that the alloy content of the first welded member and the second welded member in the weld mark located on the outermost periphery is less than the alloy content in the predetermined weld mark located on the inner side.

[0014] According to the above structure, it is also possible to allow a certain degree of alloy layer in the inner part where the applied stress is small to strongly join the first welded member and the second welded member, and reduce the alloy content in the weld mark located on the outermost periphery where stress is likely to concentrate.

[0015] In the method for manufacturing the welded structure based on the above-mentioned present disclosure, in the step of irradiating the laser, the laser may be irradiated in such a manner that the spot diameter gradually decreases as it advances from the above-mentioned predetermined weld bead located on the inner side toward the outermost peripheral side.

[0016] According to the above structure, it is also possible to allow a certain amount of alloy layer in the inner part where the applied stress is small, and strongly join the first welded member and the second welded member, while reducing the amount of alloy contained in the weld bead located on the outermost periphery where stress is likely to concentrate.

[0017] The battery based on the present disclosure includes: a battery laminate including a first single battery and a second single battery each having a plate-shaped positive electrode terminal formed of a first metal and a plate-shaped negative electrode terminal formed of a second metal, and the first single battery and the second single battery are laminated in such a manner that the positive electrode terminal and the negative electrode terminal are arranged in the lamination direction; and a plurality of annular weld beads for welding the positive electrode terminal and the negative electrode terminal. The plurality of annular weld beads are arranged such that the central axes are coaxial, and as it advances from a predetermined weld bead located on the inner side toward the outermost periphery, the depth of the weld bead gradually becomes shallower.

[0018] According to the above structure, among the plurality of annular weld beads for joining the positive electrode terminal and the negative electrode terminal, it is possible to allow a certain amount of alloy layer in the inner part where the applied stress is small, and strongly join the positive electrode terminal and the negative electrode terminal, while reducing the amount of alloy contained in the weld bead located on the outermost periphery where stress is likely to concentrate. As a result, it is possible to suppress cracks from occurring on the outermost periphery where stress is likely to concentrate, and join the positive electrode terminal and the negative electrode terminal while maintaining good joining strength.

[0019] In the battery based on the above-mentioned present disclosure, the amount of alloy of the positive electrode terminal and the negative electrode terminal contained in the weld bead located on the outermost periphery may also be less than the amount of alloy contained in the above-mentioned predetermined weld bead located on the inner side.

[0020] According to the above structure, among the plurality of annular weld beads for joining the positive electrode terminal and the negative electrode terminal, it is also possible to allow a certain amount of alloy layer in the inner part where the applied stress is small, and strongly join the positive electrode terminal and the negative electrode terminal, while reducing the amount of alloy contained in the weld bead located on the outermost periphery where stress is likely to concentrate.

[0021] In the battery based on the above-mentioned present disclosure, as it advances from the above-mentioned predetermined weld bead located on the inner side toward the outermost peripheral side, the width of the weld bead may gradually become smaller.

[0022] According to the above structure, among the plurality of annular weld marks joining the positive terminal and the negative terminal, in the inner part where the applied stress is small, a certain degree of alloy layer is allowed to strongly join the positive terminal and the negative terminal, and the alloy content contained in the weld mark located at the outermost periphery where stress is likely to concentrate is reduced.

[0023] According to the present disclosure, a method for manufacturing a welded structure capable of suppressing the formation of an alloy at the outermost periphery and maintaining good joint strength, and a battery in which terminals are well joined to each other can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the drawings, in which the same reference numerals denote the same elements, and as follows.

[0025] Figure 1 is a schematic perspective view showing a battery according to Embodiment 1.

[0026] Figure 2 is a plan view showing an enlarged joint portion between a positive terminal and a negative terminal of the battery according to Embodiment 1.

[0027] Figure 3 is along Figure 2 a schematic cross-sectional view taken along line III-III shown.

[0028] Figure 4 is a flowchart showing a manufacturing process of the battery according to Embodiment 1.

[0029] Figure 5 is a flowchart of a method for manufacturing a welded structure used in a process of welding a positive terminal and a negative terminal in a manufacturing process of the battery according to Embodiment 1.

[0030] Figure 6 is a view showing a process of irradiating a laser in the method for manufacturing a welded structure according to Embodiment 1.

[0031] Figure 7 is a plan view showing an enlarged joint portion between a positive terminal and a negative terminal of the battery according to Embodiment 2.

[0032] Figure 8 is along Figure 7 a schematic cross-sectional view taken along line VIII-VIII shown.

[0033] Figure 9 is a plan view showing an enlarged joint portion between a positive terminal and a negative terminal of the battery according to Embodiment 3.

[0034] Figure 10 is alongFigure 9 Schematic sectional view of the X-X line shown

[0035] Figure 11 It is a plan view showing the joint portion of the positive electrode terminal and the negative electrode terminal of the battery according to Embodiment 4 in an enlarged manner.

[0036] Figure 12 It is a plan view showing the joint portion of the positive electrode terminal and the negative electrode terminal of the battery according to Embodiment 5 in an enlarged manner. Detailed implementation mode

[0037] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, in the embodiments shown below, the same reference numerals are added to the same or common parts in the drawings, and the description thereof will not be repeated.

[0038] (Embodiment 1)

[0039] Figure 1 It is a schematic perspective view showing the battery according to Embodiment 1. Refer to Figure 1 , the battery according to Embodiment 1 will be described. A plurality of batteries according to Embodiment 1 are combined into a module and mounted on a vehicle such as a hybrid vehicle or an electric vehicle.

[0040] As Figure 1 shown, the battery 100 according to Embodiment 1 includes a first single cell 10A and a second single cell 10B. In addition, in the present embodiment, for convenience, the case where the number of single cells included in the battery 100 is 2 is illustrated, but the number of single cells is not limited to 2 and may be 3 or more.

[0041] The first single cell 10A and the second single cell 10B are, for example, laminated batteries. The first single cell 10A and the second single cell 10B include an electrode body 11, a housing 12, a positive electrode terminal 13, and a negative electrode terminal 14.

[0042] The electrode body 11 includes a positive electrode current collector foil provided with a positive electrode active material layer and a negative electrode current collector foil provided with a negative electrode active material layer. The positive electrode current collector foil and the negative electrode current collector foil may be laminated in multiple layers with a separator interposed therebetween, or may be laminated in multiple layers in such a manner that a solid electrolyte layer is sandwiched between the positive electrode active material layer and the negative electrode active material layer.

[0043] The housing 12 houses the electrode body 11 inside. The housing 12 is formed by fusing a laminated film at the peripheral portion. This laminated film is, for example, an aluminum alloy film whose surface is coated with a resin material. In addition, the laminated film may also be a resin film.

[0044] The positive terminal 13 is connected to a portion where a plurality of positive current collector foils are joined together, and is provided so as to protrude from the housing 12. The positive terminal 13 is a plate-like member formed of a first metal and corresponds to a first welded member. The positive terminal 13 is formed of, for example, aluminum.

[0045] The negative terminal 14 is connected to a portion where a plurality of negative current collector foils are joined together, and is provided so as to protrude from the housing 12. The negative terminal 14 is a plate-like member formed of a second metal different from the first metal and corresponds to a second welded member. The negative terminal 14 is formed of, for example, copper.

[0046] The first single cell 10A and the second single cell 10B are stacked in such a manner that the positive terminal 13 and the negative terminal 14 are arranged and disposed in the stacking direction. The first single cell 10A and the second single cell 10B are stacked in this way to form a battery stack.

[0047] In addition, the battery 100 includes a joint portion 15 that joins the positive terminal 13 and the negative terminal 14.

[0048] Figure 2 It is a plan view showing an enlarged view of the joint portion between the positive terminal and the negative terminal of the battery according to Embodiment 1. Figure 3 It is along Figure 2 The schematic cross-sectional view of the III-III line shown. Refer to Figure 2 And Figure 3 To explain the details of the joint portion 15.

[0049] As Figure 2 And Figure 3 Shown, the joint portion 15 includes a plurality of annular weld marks L1 to L6. The plurality of annular weld marks L1 to L6 are provided so that the central axes are coaxial. The plurality of annular weld marks L1 to L6 each have a substantially circular shape. The plurality of annular weld marks L1 to L6 increase in diameter (inner diameter) as they go to the outermost peripheral side.

[0050] As the plurality of annular weld marks L1 to L6 advance from a predetermined weld mark located inside toward the outermost periphery, the depth of the weld marks gradually becomes shallower. Specifically, with respect to the plurality of annular weld marks L1 to L6, the weld marks gradually become shallower as they advance from the innermost weld mark L1 toward the outermost weld mark L6.

[0051] At the weld mark L1, the aluminum forming the positive terminal 13 and the copper forming the negative terminal 14 melt, and the molten aluminum penetrates into the copper side. Thus, a considerable amount of alloy layer is formed at the weld mark L1. At the weld marks L2 to L5, the depth of penetration of the molten aluminum into the copper side gradually becomes smaller.

[0052] At the weld L6 located at the outermost periphery, the molten aluminum does not reach the copper, and the copper is not melted. Therefore, no alloy layer is formed at the weld L6. Thus, the amount of alloy contained in the weld L6 is less than that contained in the weld L1. In addition, at the weld L6, it is preferable that no alloy layer is formed, but it is also possible that a small amount of the molten aluminum reaches the copper to form a small amount of alloy layer.

[0053] Thus, by providing the welds L1 to L6, it is possible to allow a certain degree of alloy layer in the inner portion where the applied stress is small, and strongly join the positive terminal 13 and the negative terminal 14, and reduce the alloy layer (amount of alloy) contained in the welds located at the outermost periphery where stress is likely to concentrate. As a result, it is possible to suppress cracking from occurring at the outermost periphery where stress is likely to concentrate, and the positive terminal and the negative terminal can be joined while maintaining good joining strength.

[0054] Figure 4 is a flowchart showing the manufacturing process of the battery according to Embodiment 1. Refer to Figure 4 and the manufacturing method of the battery 100 according to Embodiment 1 will be described.

[0055] As Figure 4 shown, the manufacturing method of the battery 100 includes: a step (S10) of laminating the first single cell 10A and the second single cell 10B; and a step (S20) of joining the positive terminal 13 and the negative terminal 14.

[0056] When manufacturing the battery 100, first, in the step (S10), the first single cell 10A and the second single cell 10B are laminated such that the positive terminal 13 and the negative terminal 14 are arranged and disposed in the lamination direction. Next, in the step (S20), the positive terminal 13 and the negative terminal 14 are joined using the manufacturing method of the welding structure according to Embodiment 1. In the step (S20), as described later, the steps (S21) (refer to Figure 5 ) and the step (S22) (refer to Figure 5 ).

[0057] Figure 5 is a flowchart of the manufacturing method of the welding structure used in the step of welding the positive terminal and the negative terminal in the manufacturing process of the battery according to Embodiment 1.

[0058] As Figure 5 shown, the manufacturing method of the welding structure according to Embodiment 1 includes: a step (S21) of preparing a laminate in which a first welded member and a second welded member are laminated; and a step (S22) of irradiating the first welded member side with laser light so as to form a plurality of annular welds whose central axes are coaxial.

[0059] Specifically, in step (S21), a laminate is prepared by laminating a plate-shaped first welded member formed of a first metal and a plate-shaped second welded member formed of a second metal. More specifically, as described above, the battery laminate in which the positive terminal 13 and the negative terminal 14 are arranged in the lamination direction is set at the laser irradiation position.

[0060] Figure 6 It is a diagram showing the step of irradiating laser in the manufacturing method of the welded structure body according to Embodiment 1.

[0061] Next, as Figure 5 and Figure 6 shown, in step (S22), laser is irradiated to the positive terminal 13 in such a manner that a plurality of annular weld marks L1 to L6 having coaxial central axes are formed.

[0062] At this time, laser is irradiated in such a manner that the irradiation energy gradually decreases as it advances from a predetermined weld mark (specifically, the innermost weld mark L1) toward the outermost peripheral side. As a result, a plurality of annular weld marks L1 to L6 are formed in such a manner that the depth of the weld mark gradually becomes shallower as it advances from the innermost weld mark L1 toward the outermost periphery.

[0063] In addition, from the innermost weld mark L1 toward the outermost peripheral side, the alloy layer generated by laser irradiation can be gradually reduced. That is, the alloy amount contained in the outermost weld mark L6 can be made smaller than the alloy amount contained in the innermost weld mark L1.

[0064] Therefore, in the inner part where the applied stress is small, a certain degree of alloy layer can be tolerated to strongly join the positive terminal 13 and the negative terminal 14, and the alloy amount contained in the outermost weld mark where stress is likely to concentrate can be reduced. As a result, cracking at the outermost periphery where stress is likely to concentrate can be suppressed, and good joining strength can be maintained.

[0065] In addition, preferably, the plurality of trajectories of the laser irradiated corresponding to the plurality of annular weld marks are discontinuous. Thereby, it is easy to change the irradiation energy of the laser for each trajectory. Moreover, each trajectory is preferably circular. Thereby, laser irradiation can be performed uniformly in the entire circumference.

[0066] In addition, when the output ratio at the outermost irradiation is set to 1, the output ratio at the innermost irradiation is set to 2, and the irradiation energy is appropriately adjusted therebetween.

[0067] Through the above steps, the first welded member and the second welded member can be joined, and the battery 100 can be manufactured.

[0068] (Embodiment 2)

[0069] Figure 7 is a plan view showing an enlarged view of the joint portion between the positive electrode terminal and the negative electrode terminal of the battery according to Embodiment 2. Figure 8 is along Figure 7 the schematic cross-sectional view of line VIII-VIII shown. Refer to Figure 7 and Figure 8 , and the battery 100A according to Embodiment 2 will be described.

[0070] As Figure 7 and Figure 8 shown, in the case where the battery 100A according to Embodiment 2 is compared with the battery 100 according to Embodiment 1, the structure of the joint portion 15A is different. Other structures are substantially the same.

[0071] In Embodiment 2, the joint portion 15A also includes six weld marks L1 to L6, but the laser irradiation method is different, and thus the depths of the weld marks L1 to L6 also change.

[0072] In Embodiment 2, as moving from the innermost weld mark L1 toward the predetermined weld mark L4, the depth of the weld mark gradually becomes deeper, and as moving from the predetermined weld mark L4 toward the outermost periphery side (weld mark L6), the depth of the weld mark gradually becomes shallower.

[0073] At the weld mark L1, the aluminum constituting the positive electrode terminal 13 melts to a position where it does not reach the copper constituting the negative electrode terminal 14, or slightly reaches the copper position. Thus, there is no alloy layer or there is a small amount of alloy layer. At the weld marks L2 to L4, the depth gradually becomes deeper, and the depth of the molten aluminum invading the copper also gradually becomes deeper. Thus, at the weld marks L2 to L4, the alloy layer gradually increases. Particularly at the weld mark L4, a certain degree of alloy layer is allowed and the positive electrode terminal 13 and the negative electrode terminal 14 are strongly joined. As moving from the weld mark L4 toward the outermost peripheral weld mark L6, the depth of the molten aluminum invading the copper side gradually becomes smaller.

[0074] At the outermost peripheral weld mark L6, the molten aluminum does not reach the copper, and in addition, the copper does not melt. Therefore, at the weld mark L6, no alloy layer is formed. Thus, the amount of alloy contained in the weld mark L6 is less than the amount of alloy contained in the weld mark L4. In addition, at the weld mark L6, it is preferable that no alloy layer is formed, but it is also possible that the molten aluminum slightly reaches the copper and a small amount of alloy layer is formed.

[0075] The battery 100A of Embodiment 2 is also manufactured according to the manufacturing method of the battery according to Embodiment 1. That is, the manufacturing method of the welded structure according to the manufacturing method of the welded structure according to Embodiment 1 is implemented.

[0076] In Embodiment 2, in step (S22), laser is irradiated in such a manner that the irradiation energy gradually increases as it advances from the innermost weld mark L1 toward the weld mark L4 located at a predetermined inner side. Subsequently, laser is irradiated in such a manner that the irradiation energy gradually decreases as it advances from the predetermined weld mark L4 toward the outermost periphery. In this case, when the output ratio when irradiating the outermost side is set to 1, the output ratio when irradiating the predetermined inner side (the irradiation region corresponding to the weld mark L4) is set to 2, and the irradiation energy is appropriately adjusted therebetween.

[0077] In such a configuration, in the battery 100A and the manufacturing method of the welded structure according to Embodiment 2, substantially the same effects as those of the battery 100 and the manufacturing method of the welded structure according to Embodiment 1 can also be obtained.

[0078] (Embodiment 3)

[0079] Figure 9 is a plan view showing an enlarged view of the joint portion between the positive terminal and the negative terminal of the battery according to Embodiment 3. Figure 10 is along Figure 9 The schematic sectional view of the X-X line shown. Refer to Figure 9 and Figure 10 , the battery 100B according to Embodiment 3 will be described.

[0080] As Figure 9 and Figure 10 shown, in comparison with the battery 100 according to Embodiment 1, the structure of the joint portion 15B of the battery 100B according to Embodiment 3 is different. Other structures are substantially the same.

[0081] The joint portion 15B includes three weld marks L1 to L3, and the laser irradiation method is also different from that of the joint portion 15 of Embodiment 1.

[0082] In Embodiment 3, as it advances from the innermost weld mark L1 toward the predetermined weld mark L2, the depth of the weld mark gradually becomes deeper, and as it advances from the predetermined weld mark L2 toward the outermost periphery (weld mark L3), the depth of the weld mark gradually becomes shallower.

[0083] At the innermost weld mark L1, the aluminum constituting the positive terminal 13 melts to reach a position slightly reaching the copper constituting the negative terminal 14. At the weld mark L2, this aluminum reaches the copper deeper than the weld mark L1, and a certain degree of alloy layer is allowed to strongly join the positive terminal 13 and the negative terminal 14. At the weld mark L3, this aluminum melts to a position shallower than the weld mark L2. Accordingly, the alloy amount contained in the weld mark L3 is less than the alloy amount contained in the predetermined weld mark L2.

[0084] The battery 100B of Embodiment 3 is also manufactured according to the manufacturing method of the battery according to Embodiment 1. In this case, the manufacturing method of the welded structure according to the manufacturing method of the welded structure according to Embodiment 1 is implemented.

[0085] In Embodiment 3, in step (S22), the laser is irradiated in such a manner that the irradiation energy gradually increases as it advances from the innermost weld mark L1 toward the weld mark L2 located at a predetermined inner side. Then, the laser is irradiated in such a manner that the irradiation energy gradually decreases as it advances from the predetermined weld mark L2 toward the outermost periphery.

[0086] In such a configuration, in the manufacturing method of the battery 100B and the welded structure according to Embodiment 3, effects substantially the same as those of the battery 100 and the manufacturing method of the welded structure according to Embodiment 1 can also be obtained.

[0087] (Embodiment 4)

[0088] Figure 11 is a plan view showing an enlarged view of the joint portion between the positive electrode terminal and the negative electrode terminal of the battery according to Embodiment 4. Refer to Figure 11 , and the battery 100C according to Embodiment 4 will be described.

[0089] As Figure 11 shown, compared with the battery 100 according to Embodiment 1, the battery 100C according to Embodiment 4 has different shapes of the positive electrode terminal and the negative electrode terminal, and thus the shapes of the plurality of weld marks are also different.

[0090] In the positive electrode terminal and the negative electrode terminal, the length in the protruding direction protruding from the electrode body is shorter than the length in the width direction orthogonal to the protruding direction. As a result, the plurality of weld marks are not circular shapes, but rectangular shapes with rounded corners. In this case, regarding the depth of the plurality of weld marks, it may gradually become shallower as it advances from the innermost side toward the outermost side as in Embodiment 1, or the weld marks may gradually become deeper as it advances from the innermost side toward the weld mark located at a predetermined inner side and gradually become shallower as it advances from the weld mark located at a predetermined inner side toward the outermost periphery as in Embodiments 2 and 3.

[0091] In Figure 11 , in the manufacturing process of the battery, the manufacturing method of the welded structure according to the manufacturing method of the welded structure according to Embodiment 1 may be implemented, or the manufacturing method of the welded structure according to the manufacturing method of the welded structure according to Embodiment 2 may be implemented. In either case, the plurality of laser trajectories are rectangular shapes with rounded corners.

[0092] In such a configuration, in the battery 100C and the manufacturing method of the welded structure according to Embodiment 4, effects substantially the same as those of the battery 100 and the manufacturing method of the welded structure according to Embodiment 1 can also be obtained.

[0093] (Embodiment 5)

[0094] Figure 12 is a plan view showing an enlarged view of the joint portion between the positive terminal and the negative terminal of the battery according to Embodiment 5. Refer to Figure 12 , the battery 100D according to Embodiment 5 will be described.

[0095] As Figure 12 shown, compared with the battery 100 according to Embodiment 1, the battery 100D according to Embodiment 5 has different shapes of the positive terminal and the negative terminal, and thus the shapes of the plurality of weld marks are also different.

[0096] The positive terminal and the negative terminal have a substantially L-shaped configuration. Accordingly, the plurality of weld marks are not circular, but have a substantially L-shaped ring shape with rounded corners. In this case, regarding the depth of the plurality of weld marks, it may gradually become shallower as moving from the innermost side toward the outermost side as in Embodiment 1, or may gradually become deeper as moving from the innermost side toward the weld mark located at a predetermined inner side and gradually become shallower as moving from the weld mark located at a predetermined inner side toward the outermost peripheral side as in Embodiments 2 and 3.

[0097] In Figure 12 , in the manufacturing process of the battery, the manufacturing method of the welded structure according to the manufacturing method of the welded structure according to Embodiment 1 may be implemented, or the manufacturing method of the welded structure according to the manufacturing method of the welded structure according to Embodiment 2 may be implemented. In either case, the plurality of laser tracks form a substantially L-shaped ring shape with rounded corners.

[0098] In such a configuration, in the battery 100D and the manufacturing method of the welded structure according to Embodiment 5, effects substantially the same as those of the battery 100 and the manufacturing method of the welded structure according to Embodiment 1 can also be obtained.

[0099] (Other Variation Examples)

[0100] In the above Embodiments 1 to 4, the case where the positive terminal 13 is the first welded member and the negative terminal 14 is the second welded member has been described as an example, but it is not limited thereto. The first welded member may be a plate-like member made of a first metal, and the second welded member may also be a plate-like member made of a second metal different from the first metal.

[0101] In addition, in the above-described Embodiments 1 to 4, in the step of irradiating the laser (S22), the laser may be irradiated in such a manner that the spot diameter gradually decreases as it advances from a predetermined weld mark located on the inner side toward the outermost peripheral side.

[0102] As described above, the embodiments disclosed this time are merely illustrative and not restrictive in all respects. The scope of the present invention is shown by the claims and includes meanings equivalent to the claims and all modifications within the scope.

Claims

1. A method for manufacturing a welded structure, comprising: a step of preparing a laminate formed by laminating a plate-shaped first welded member made of a first metal and a plate-shaped second welded member made of a second metal; and A step of irradiating laser light from the side of the first member to be welded in such a manner as to form a plurality of annular weld marks having a common central axis, wherein, a plurality of circular weld beads, with three or more circular weld beads, In the step of irradiating the laser, the laser is irradiated in such a manner that the irradiation energy gradually decreases as it advances from the innermost weld bead toward the outermost peripheral side, so that the depth of the weld bead gradually becomes shallower as it advances from the innermost weld bead toward the outermost periphery, thereby forming a plurality of circular weld beads.

2. The method for manufacturing a welded structure according to claim 1, wherein in the step of irradiating the laser, the plurality of trajectories of the laser irradiated corresponding to the plurality of circular weld beads are discontinuous.

3. The method for manufacturing a welded structure according to claim 2, wherein in the step of irradiating the laser, the plurality of trajectories are each circular in shape.

4. The method for manufacturing a welded structure according to any one of claims 1 to 3, wherein in the step of irradiating the laser, the laser is irradiated in such a manner that the alloy content of the first welded member and the second welded member contained in the outermost weld bead is less than the alloy content contained in the innermost weld bead.

5. The method for manufacturing a welded structure according to any one of claims 1 to 3, wherein in the step of irradiating the laser, the laser is irradiated in such a manner that the spot diameter gradually decreases as it advances from the innermost weld bead toward the outermost peripheral side.

6. A battery, comprising: a battery laminate including a first single cell and a second single cell each having a plate-shaped positive terminal made of a first metal and a plate-shaped negative terminal made of a second metal, and the first single cell and the second single cell are laminated in such a manner that the positive terminal and the negative terminal are arranged in the lamination direction; and A plurality of annular weld beads that weld the positive terminal and the negative terminal, wherein, the plurality of circular weld beads, with three or more circular weld beads, a plurality of circular weld beads are provided with their central axes being coaxial, and the depth of the weld bead gradually becomes shallower as it advances from the innermost weld bead toward the outermost periphery.

7. The battery according to claim 6, wherein the alloy content of the positive terminal and the negative terminal contained in the outermost weld bead is less than the alloy content contained in the innermost weld bead.

8. The battery according to claim 6 or 7, wherein the width of the weld bead gradually becomes smaller as it advances from the innermost weld bead toward the outermost peripheral side.

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