Method for manufacturing battery case

Abstract

To provide a method for manufacturing a battery case, capable of preventing an occurrence of notches due to burn-through of molten metal at a welded metal termination of a joint intersecting with an opening, in a battery case including a case body that is made of an aluminum material and joined by laser welding.SOLUTION: There is provided a method for manufacturing a battery case 1 that includes: a cylindrical case body 11 made of an aluminum material, having an opening 11K, into which an electrode body 2 is inserted, at least at one axial end 111 and having a first joint 11S which intersects with the opening and butt-joins ends 112 in a width direction together; and a sealing body 12 sealing the opening through a second joint 12S. The method includes: a first welding step S1 of performing laser-welding to the first joint up to just before the opening; and a second welding step S2 of connecting a welded metal termination 11YS laser-welded up to just before the opening of the first joint and a welded metal part 12Y of the second joint when laser welding is performed to the second joint along the opening.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a battery case. [Background technology]

[0002] For example, Patent Document 1 discloses a rectangular battery can (battery case) formed by laser welding at least two members made of steel plates, characterized in that a first linear joint is formed at the bottom and reaches the lower ends of the opposing side wall portions (case main body), and that a second linear joint and a third linear joint are formed on the opposing side wall portions, respectively, which are connected to the first joint and reach the openings at the upper ends of the respective side wall portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-59954 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the prismatic battery cans have the advantage of being easily adaptable to larger batteries, they have issues with corrosion resistance to electrolyte because they are made of steel plate. Furthermore, because they are made of steel plate, they have issues with not being able to meet the need for weight reduction. In this regard, forming the prismatic battery cans from aluminum offers a potential solution to the issues of corrosion resistance and weight reduction.

[0005] However, since the surface tension of aluminum material in molten metal is less than half that of steel plate, there was a problem in that excessive welding heat was accumulated at the ends of the weld metal of the second and third joints that intersect with the opening that seals the sealing body, making it easy for notches to occur due to melt-through of the molten metal.

[0006] The disclosed technology has been made in consideration of such problems, and aims to provide a method for manufacturing a battery case in which an aluminum case body is joined by laser welding, and which can prevent notches from occurring due to burn-through of molten metal at the end of the weld metal at the joint that intersects with the opening. [Means for solving the problem]

[0007] (1) One aspect of the disclosed technology for solving the above-described problems is a method for manufacturing a battery case including: a cylindrical case body made of aluminum, the case body having an opening at at least one axial end for inserting an electrode body, and a first joint that intersects with the opening and butt-joins the widthwise ends; and a sealing body that seals the opening via a second joint, the method including: a first welding process of laser-welding the first joint up to just before the opening; and a second welding process of laser-welding the second joint along the opening to connect a weld metal terminal end portion of the first joint that has been laser-welded up to just before the opening to a weld metal portion of the second joint.

[0008] (2) In the manufacturing method of a battery case described in (1), it is preferable that the case body has a convex portion that protrudes toward the outer surface along the widthwise end, and the first welding process melts the convex portions together to form a weld metal portion that protrudes in a curved shape toward the outer surface.

[0009] (3) In the manufacturing method of the battery case described in (1), it is preferable that the case body has a convex portion that protrudes outward along the widthwise end portion displaced toward the inner surface side relative to the general portion while maintaining the plate thickness of the case body, and the first welding process fuses the convex portions together to form a weld metal portion that protrudes in a curved shape toward the outer surface side.

[0010] (4) In the method for manufacturing a battery case described in (1), the case body has a convex portion that protrudes from the groove surface to the outer surface along the widthwise end portion where a groove surface that is recessed toward the inner surface of the outer surface of the case body is formed, and the first welding process preferably melts the convex portions together to form a weld metal portion that protrudes in a curved shape toward the outer surface.

[0011] (5) In the method for manufacturing a battery case described in (1), it is preferable that the case body has a protrusion that protrudes toward both the outer surface side and the inner surface side along the widthwise end of the case body, and the first welding process melts the protrusions together to form a weld metal part that protrudes in a curved shape toward the outer surface side and the inner surface side. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view of a sealed storage battery including a battery case according to a first example embodiment, which is manufactured by a method for manufacturing a battery case according to one aspect of the present embodiment. [Figure 2] 2 is a flowchart showing a method for manufacturing the battery case shown in FIG. 1. [Figure 3] 2 is a perspective view of a rectangular cylindrical intermediate product used in the case body of the battery case shown in FIG. 1. FIG. [Figure 4] FIG. 2 is a partial perspective view of a state in which a first joint portion of a rectangular tubular intermediate product divided into two parts has been laser-welded up to just before the opening to form the case body of the battery case shown in FIG. [Figure 5] 2 is a partial perspective view showing a state in which laser welding is being performed on a second joint portion that joins the case body and the sealing body of the battery case shown in FIG. 1. FIG. [Figure 6A] FIG. 5 is an enlarged cross-sectional view of a first modified example of the first joint portion of the case body shown in FIG. 4 before laser welding. [Figure 6B] FIG. 5 is an enlarged cross-sectional view of a first modified example of the first joint portion of the case body shown in FIG. 4 after laser welding. [Figure 7A] FIG. 5 is an enlarged cross-sectional view of a second modified example of the first joint portion of the case body shown in FIG. 4 before laser welding. [Figure 7B] FIG. 5 is an enlarged cross-sectional view of a second modification of the first joint portion of the case body shown in FIG. 4, after laser welding. [Figure 8A] FIG. 5 is an enlarged cross-sectional view of a third modified example of the first joint portion of the case body shown in FIG. 4 before laser welding. [Figure 8B] FIG. 5 is an enlarged cross-sectional view of a third modification of the first joint portion of the case body shown in FIG. 4, after laser welding. [Figure 9A] FIG. 5 is an enlarged cross-sectional view of a fourth modified example of the first joint portion of the case body shown in FIG. 4 before laser welding. [Figure 9B] FIG. 5 is an enlarged cross-sectional view of a fourth modified example of the first joint portion of the case body shown in FIG. 4, after laser welding. [Figure 10A] FIG. 5 is an enlarged cross-sectional view of a fifth modified example of the first joint portion of the case body shown in FIG. 4 before laser welding. [Figure 10B] FIG. 5 is an enlarged cross-sectional view of a fifth modified example of the first joint portion of the case body shown in FIG. 4 after laser welding. [Figure 11] FIG. 10 is a schematic perspective view of a sealed storage battery including a battery case according to a second example embodiment, which is manufactured by a method for manufacturing a battery case according to one aspect of the present embodiment. [Figure 12A] 12 is a cross-sectional view of an intermediate product used in the case body of the battery case shown in FIG. 11. FIG. [Figure 12B] 12 is a cross-sectional view of the case body of the battery case shown in FIG. [Figure 13A] 12 is a cross-sectional view of an intermediate product used in Modification 1 of the case body of the battery case shown in FIG. [Figure 13B] 12 is a cross-sectional view of a first modified example of the case body of the battery case shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Manufacturing method of the present battery case> Next, the configuration of a battery case manufactured by a method for manufacturing a battery case according to one aspect of the embodiment of the disclosed technology will be described in detail with reference to the drawings. Fig. 1 shows a schematic cross-sectional view of a sealed storage battery including a battery case according to a first example, manufactured by the method for manufacturing a battery case according to one aspect of the present embodiment. The X direction indicates the longitudinal direction of the case body, the Y direction indicates the width direction of the case body, and the Z direction indicates the axial direction of the case body.

[0014] (Battery case of the first embodiment) As shown in Fig. 1, the battery case 1 of the first embodiment is made of aluminum and includes a cylindrical case body 11 having an opening 11K at at least one axial end 111 for inserting an electrode assembly 2, a first joint 11S that intersects with the opening 11K and butt-joins widthwise ends 112, and a sealing body 12 that seals the opening 11K via a second joint 12S. The aluminum material is not limited to aluminum material and includes aluminum alloy material. Here, the case body 11 is formed in a rectangular tube shape, but it may also be formed in a cylindrical shape.

[0015] The electrode assembly 2 inserted through the opening 11K is formed by stacking a positive electrode body and a negative electrode body with a separator sandwiched between them. FIG. 1 illustrates a wound-type electrode assembly 2 in which long, stacked positive electrode bodies, negative electrode bodies, and a separator are wound flat. However, this is not a limitation. A laminated electrode assembly in which rectangular positive electrode bodies and negative electrode bodies are stacked with a separator sandwiched between them may also be used. The current collector foils 21 on the positive and negative sides of the electrode assembly 2 are connected to positive and negative current collector terminals 4, respectively. Each current collector terminal 4 includes an external terminal 41 protruding toward the outer surface 11G of the battery case 1 and an internal terminal 42 connected to the current collector foil 21 on the inner surface 11N of the battery case 1. The external terminals 41 are fixed to the sealing body 12 via an insulating member 3.

[0016] The electrode assembly 2, connected to the current collecting terminal 4 and fixed to the sealing body 12, is housed in the case body 11 through the opening 11K. After the electrode assembly 2 is housed in the opening 11K of the case body 11, it is sealed with the sealing body 12. A second joint 12S, which joins the opening 11K of the case body 11 to the sealing body 12, is formed by laser welding. The case body 11 is formed as a bottomed rectangular cylinder having a pair of long side walls 11a, 11a extending in the longitudinal direction (X direction), a pair of short side walls 11b, 11b extending in the width direction (Y direction), and a bottom wall 11c forming the cylinder bottom. A rectangular opening 11K is formed in one axial end 111 of the case body 11. The electrode body 2 is placed inside the case body 11 through the opening 11K, and after the opening 11K and the sealing body 12 are joined, the electrolyte 5 is injected through an injection port (not shown), and the sealed storage battery 10 is completed after initial charging, aging, etc.

[0017] (Manufacturing method of the battery case of the first embodiment) Fig. 2 shows a flowchart illustrating a method for manufacturing the battery case shown in Fig. 1. Fig. 3 shows a perspective view of a rectangular tubular intermediate product used for the case body of the battery case shown in Fig. 1. Fig. 4 shows a partial perspective view of a rectangular tubular intermediate product divided into two parts, in which a first joint portion has been laser-welded up to just before the opening to form the case body of the battery case shown in Fig. 1. Fig. 5 shows a partial perspective view of a part of the process of laser welding a second joint portion that joins the case body and the sealing body of the battery case shown in Fig. 1.

[0018] 1 to 5, a method for manufacturing a battery case 1 includes a cylindrical case body 11 made of aluminum, the case body 11 having an opening 11K at at least one axial end 111 for inserting an electrode assembly 2, and a first joint 11S that intersects with the opening 11K and butt-joins widthwise ends 112, and a sealing body 12 that seals the opening 11K via a second joint 12S, and includes a first welding step S1 and a second welding step S2. The first welding step S1 is a step of laser welding the first joint 11S, which butt-joins the widthwise ends 112 of the case body 11, up to just before the opening 11K. The second welding process S2 is a process in which, when laser welding along the opening 11K to the second joint 12S that joins the opening 11K of the case body 11 and the sealing body 12, the weld metal terminal end portion 11YS, which has been laser welded up to just before the opening 11K of the first joint 11S, is connected to the weld metal portion 12Y of the second joint 12S.

[0019] In the first welding step S1, for example, as shown in FIG. 3, a rectangular tubular intermediate product 11X having a hat-shaped cross section is press-formed from a flat aluminum plate. The short side wall 11b and the bottom wall 11c extend from the outer periphery (widthwise end 112), and the long side wall 11a constitutes the top plate. The rectangular tubular intermediate product 11X is then divided into two equal parts along a parting line that divides the rectangular tubular intermediate product 11X into two equal parts along the longitudinal direction (X direction). The parting line is formed at the position of the opening 11K of the case body 11. The forming method of the rectangular tubular intermediate product 11X is not limited to press forming, and may be die-casting, cold or warm forging, or the like. Furthermore, these forming methods may be combined with cutting, electric discharge machining, or the like.

[0020] In the first welding step S1, for example, as shown in FIG. 4 , the first joint portion 11S of the rectangular tubular intermediate product 11X (an intermediate product of the case body 11) divided into two is laser-welded up to just before the opening 11K. Specifically, with the widthwise ends 112 of the rectangular tubular intermediate product 11X divided into two pieces butted against each other, a laser beam LS is irradiated onto the widthwise ends 112 from the outer surface 11G side of the rectangular tubular intermediate product 11X (case body 11). Here, the laser beam LS is moved relatively along the widthwise ends 112, but the widthwise ends 112 may also be moved relatively to the laser beam LS. The laser beam LS may be a single beam with a narrow beam width, but a multi-beam or annular beam with a wide beam width is preferable. When the laser beam LS is a single beam, it is preferable to move the tip of the beam relatively along the widthwise ends 112 while slightly vibrating the tip of the beam in the width direction (Y direction) of the widthwise ends 112. Then, the molten metal 11YK of the widthwise end 112, which has been irradiated with the laser light LS and melted, is welded to the first joint portion 11S up to just before the opening 11K.

[0021] 5 , for example, when laser welding is performed along the opening 11K to the second joint 12S that joins the opening 11K of the case body 11 and the sealing member 12, a weld metal terminal end 11YS, which has been laser-welded up to just before the opening 11K of the first joint 11S, is joined to the weld metal portion 12Y of the second joint 12S. Specifically, laser light LS is irradiated from the outer surface 11G side of the case body 11 along the opening 11K to the abutment portion between the axial end face of the opening 11K of the case body 11 and the inner surface of the outer peripheral edge of the sealing member 12. When the laser light LS is irradiated to the intersection between the first joint 11S and the second joint 12S, the weld metal terminal end 11YS of the first joint 11S is remelted, thereby joining the weld metal terminal end 11YS of the first joint 11S to the weld metal portion 12Y of the second joint 12S. The laser beam LS irradiation device (not shown) can be used in both the first welding step S1 and the second welding step S2.

[0022] As described above in detail, in the first welding step S1, the first joint portion 11S is laser-welded up to just before the opening 11K, so that an unwelded portion 11M (see FIG. 4) that is not melted by the laser welding remains near the opening 11K. Therefore, the welding heat is diffused from the weld metal terminal end 11YS of the first joint portion 11S to the surrounding area, including the unwelded portion 11M near the opening 11K, and the weld metal terminal end 11YS is cooled quickly. Furthermore, by cooling the weld metal terminal end 11YS, the surface tension of the molten metal 11YK at the weld metal terminal end 11YS increases, making it possible to prevent the formation of a notch due to burn-through of the molten metal 11YK. Furthermore, when laser welding is performed along the opening 11K in the second welding process S2, the weld metal terminal end portion 11YS, which has been laser welded up to just before the opening 11K of the first joint 11S, is connected to the weld metal portion 12Y of the second joint 12S, so that the unwelded portion 11M of the first joint 11S, which was not welded in the first welding process S1, can be welded in the second welding process S2.

[0023] Therefore, the first joint 11S and the second joint 12S can be laser welded continuously while avoiding the occurrence of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint 11S. Therefore, it is possible to provide a method for manufacturing a battery case 1 in which an aluminum case body 11 is joined by laser welding, which can avoid the occurrence of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint 11S that intersects with the opening 11K.

[0024] Fig. 6A shows an enlarged cross-sectional view of Variation 1 of the first joint portion of the case body shown in Fig. 4 before laser welding. Fig. 6B shows an enlarged cross-sectional view of Variation 1 of the first joint portion of the case body shown in Fig. 4 after laser welding. As shown in Fig. 6A, case body 11 has protrusions 11T that protrude toward outer surface 11G along widthwise end 112, and as shown in Fig. 6B, first welding step S1 may fuse protrusions 11T together to form weld metal portion 11Y that protrudes in a curved shape toward outer surface 11G.

[0025] Specifically, as shown in FIG. 6A, the protrusion 11T protrudes from the outer surface 11G of the case body 11 toward the outer surface 11G by a predetermined protrusion amount d1. The thickness t1 of the protrusion 11T is substantially the same as the thickness t1 of the case body 11, although some thickness variation occurs due to drawing. The outer peripheral edges 11TG of the widthwise ends 112 of the protrusion 11T, which are continuous with the inner surface 11N, abut against each other. Furthermore, as shown in FIG. 6B, the protrusion amount d1 of the protrusion 11T correlates with the protrusion amount d2 of the weld metal portion 11Y, which protrudes in a curved shape toward the outer surface 11G of the case body 11. That is, when the protrusion amount d1 of the protrusion 11T is increased, the protrusion amount d2 of the weld metal portion 11Y also increases.

[0026] In this way, in Modification 1 of the first joint portion, convex portions 11T that protrude toward the outer surface 11G of the case body 11 are formed along the widthwise end portions 112, so that the volume of molten metal 11YK that can be melted in the first welding step S1 can be increased by the volume of the convex portions 11T. Furthermore, in the first welding step S1, after the convex portions 11T are butted against each other, laser light LS is irradiated onto the convex portions 11T from the outer surface 11G side of the case body 11 to melt the molten metal 11YK, and the weld metal portion 11Y that protrudes in a curved shape toward the outer surface 11G of the case body 11 is formed at the first joint portion 11S. Therefore, because the weld metal portion 11Y of the first joint portion 11S protrudes in a curved shape toward the outer surface 11G side, the sagging resistance of the weld metal portion 11Y toward the inner surface 11N side when melted is improved. This more reliably prevents the formation of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint 11S. Furthermore, since the thermal contraction occurring during solidification of the curved, raised weld metal portion 11Y is dispersed by the curved, raised weld surface 11YM, solidification cracking in the weld metal portion 11Y can also be reduced.

[0027] 6B, the weld metal portion 11Y preferably has a weld surface 11YM formed in an arc shape with a constant radius of curvature 115. This is because the surface tension of the weld metal portion 11Y when melted acts uniformly on the arc-shaped protruding weld surface 11YM toward the outer surface 11G, countering gravity, improving resistance to burn-through. Furthermore, the weld metal portion 11Y preferably has not only a front bead portion 11Y1 protruding toward the outer surface 11G, but also a back bead portion 11Y2 protruding toward the inner surface 11N by a smaller amount than the front bead portion 11Y1. This is because the back bead portion 11Y2 can prevent insufficient penetration due to unmelted metal on the inner surface 11N side, thereby increasing the joint strength of the first joint 11S.

[0028] 7A shows an enlarged cross-sectional view of the first joint portion of the case body shown in Fig. 4 before laser welding. Fig. 7B shows an enlarged cross-sectional view of the first joint portion of the case body shown in Fig. 4 after laser welding. As shown in Figs. 7A and 7B, case body 11 has convex portions 11T that protrude toward outer surface 11G along widthwise end portions 112B that are displaced toward inner surface 11N relative to general portion 113 while maintaining thickness t1 of case body 11. In first welding step S1, convex portions 11T may be melted together to form weld metal portion 11Y that protrudes in a curved shape toward outer surface 11G.

[0029] In this case, even if the protrusion amount d1 of the protrusion 11T shown in FIG. 7A is the same as the protrusion amount d1 of the protrusion 11T shown in FIG. 6A, the protrusion amount d3 of the protrusion 11T relative to the general portion 113 can be reduced by the amount that the widthwise end 112B is displaced toward the inner surface 11N relative to the general portion 113. Furthermore, the thickness t1 of the case body 11 can be maintained. Therefore, the amount of protrusion d2 of the welded metal portion 11Y toward the outer surface 11G shown in FIG. 7B is maintained, while the displacement amount d4 of the case body 11 relative to the general portion 113 is reduced, thereby suppressing expansion of the case body 11. Furthermore, the first joint portion 11S can be formed at the widthwise end 112B while maintaining the thickness t1 of the case body 11, thereby preventing a decrease in the strength of the case body 11. This suppresses expansion of the case body 11, avoids a decrease in strength, and more reliably prevents the formation of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint 11S. Furthermore, since thermal contraction during solidification of the curved, raised weld metal portion 11Y is dispersed by the curved, raised weld surface 11YM, solidification cracking in the weld metal portion 11Y can also be reduced. In this case, it is preferable that the weld metal portion 11Y have not only a front bead portion 11Y1 that protrudes toward the outer surface 11G, but also a back bead portion 11Y2 that protrudes toward the inner surface 11N by a smaller amount than the front bead portion 11Y1.

[0030] 8A shows an enlarged cross-sectional view of the first joint portion of the case body shown in Fig. 4 before laser welding. Fig. 8B shows an enlarged cross-sectional view of the first joint portion of the case body shown in Fig. 4 after laser welding. As shown in Figs. 8A and 8B, case body 11 has convex portions 11T that protrude from groove surfaces 114 to outer surface 11G along widthwise end portions 112C that are formed with groove surfaces 114 that are recessed toward inner surface 11N relative to outer surface 11G of case body 11. In first welding step S1, convex portions 11T may be melted together to form weld metal portions 11Y that protrude in a curved shape toward outer surface 11G.

[0031] In this case, the protrusion 11T shown in Fig. 8A protrudes from the groove surface 114 to the outer surface 11G, and the protrusion amount d5 of the protrusion 11T is smaller than the plate thickness t1 of the case body 11. Therefore, as shown in Fig. 8B, the protrusion amount d6 of the curved protruding weld metal portion 11Y is also reduced, and the curved protruding weld metal portion 11Y is less likely to protrude from the outer surface 11G of the case body 11. This makes it possible to more reliably prevent the formation of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint portion 11S while keeping the outer dimensions of the case body 11 compact. Furthermore, by making the width w1 of the protrusion 11T larger than the protrusion amount d5, the weld surface 11YM of the weld metal portion 11Y can be formed into a more gently curved surface (an arcuate surface with a large radius of curvature 115C), which distributes the surface tension of the weld metal portion 11Y during melting over a wider area and improves the burn-through resistance per unit volume of the weld metal portion 11Y. Furthermore, since the thermal contraction of the curved, raised weld metal portion 11Y during solidification is dispersed by the curved, raised weld surface 11YM, solidification cracking in the weld metal portion 11Y can also be reduced. In this case, it is preferable that the molten metal portion 11Y have not only a front bead portion 11Y1 that protrudes toward the outer surface 11G, but also a back bead portion 11Y2 that protrudes toward the inner surface 11N by a smaller amount than the front bead portion 11Y1.

[0032] 9A shows an enlarged cross-sectional view of Variation 4 of the first joint portion of the case body shown in Fig. 4 before laser welding. Fig. 9B shows an enlarged cross-sectional view of Variation 4 of the first joint portion of the case body shown in Fig. 4 after laser welding. As shown in Figs. 9A and 9B, case body 11 has protrusions 11T that protrude toward both outer surface 11G and inner surface 11N along widthwise end 112D of case body 11, and first welding step S1 may fuse protrusions 11T together to form weld metal portion 11Y that protrudes in a curved shape toward outer surface 11G and inner surface 11N.

[0033] In this case, the protrusion amount d9 of the front bead portion 11Y1, which protrudes in a curved shape toward the inner / outer surface 11G of the weld metal portion 11Y, can be ensured, while the protrusion amount d10 of the back bead portion 11Y2, which protrudes in a curved shape toward the inner surface 11N, can be increased. Therefore, the strength of both the front bead portion 11Y1 and the back bead portion 11Y2 improves the burn-through resistance toward the inner surface 11N when the weld metal portion 11Y melts, and this more reliably prevents the formation of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint 11S. Furthermore, because thermal contraction during solidification of the curvedly protruding weld metal portion 11Y is dispersed by the curvedly protruding weld surface 11YM, solidification cracking in the weld metal portion 11Y can also be reduced. Preferably, the protrusion amount d8 of the inner protrusion 11T2 is smaller than the protrusion amount d7 of the outer protrusion 11T1, and the outer protrusion 11T1 and the inner protrusion 11T2 are each formed so that the tip end is narrower than the base end, because this prevents the cross-sectional area of ​​the weld metal portion 11Y from becoming excessively large and increasing the gravity acting on the molten metal 11YK.

[0034] FIG. 10A shows an enlarged cross-sectional view of the first joint portion of the case body shown in FIG. 4 before laser welding. FIG. 10B shows an enlarged cross-sectional view of the first joint portion of the case body shown in FIG. 4 after laser welding. As shown in FIG. 10A, the protrusion 11T may be formed so that its protrusion amount increases at the opening 11K where the axial end 111 and the widthwise end 112 of the case body 11 intersect. That is, the protrusion 11T may include a protrusion 11T3 having a constant protrusion amount and a protrusion 11T4 whose protrusion amount gradually increases toward the opening 11K. In this case, as shown in FIG. 10B, the first joint portion 11S can have a weld metal portion 11Y3 having a constant protrusion amount and a weld metal portion 11Y4 whose protrusion amount gradually increases toward the opening 11K. The weld metal portion 11Y4 is formed up to just before the opening 11K.

[0035] Generally, welding heat of the first joint portion 11S tends to accumulate near the opening 11K where the axial end portion 111 and the widthwise end portion 112 of the case body 11 intersect. Furthermore, when the temperature of the molten metal 11YK is high, the surface tension decreases, making it more likely for the molten metal 11YK to burn through. Therefore, it is often necessary to employ a control method in which the output of the laser beam LS is reduced as it approaches the opening 11K.

[0036] However, by providing the protrusion 11T4 whose protrusion amount gradually increases toward the opening 11K, it is not necessary to reduce the output of the laser beam LS toward the opening 11K, and the weld metal part 11Y4 gradually increases in protrusion amount toward the opening 11K, thereby increasing its resistance to burn-through. Therefore, it is possible to more reliably prevent the formation of a notch due to burn-through of the molten metal 11YK at the weld metal terminal end 11YS of the first joint part 11S.

[0037] (Battery case of the second embodiment) Fig. 11 is a schematic perspective view of a sealed storage battery including a battery case according to a second example embodiment manufactured by a battery case manufacturing method according to one aspect of the present embodiment. As shown in Fig. 11, the battery case 1B of the second example embodiment is made of aluminum and includes a cylindrical case body 11B having openings 11BK at both axial ends 111B for inserting electrode bodies 2, first joint portions 11S that intersect with the openings 11BK and butt-join widthwise ends 112, and two sealing bodies 12B that seal the openings 11BK via second joint portions 12BS.

[0038] The electrode assembly 2, connected to the current collector terminal 4 (41) and fixed to the sealing body 12B, is housed in the case body 11B through the opening 11BK. After the electrode assembly 2 is housed in the opening 11BK of the case body 11B, it is sealed by the sealing body 12B and the second joint 12BS. The first joint 11S and the second joint 12BS are each joined by laser welding. The case body 11B is formed as a bottomless rectangular cylinder having a pair of long side walls 11Ba, 11Ba extending in the longitudinal direction (X direction) and a pair of short side walls 11Bb, 11Bc extending in the width direction (Y direction). After the electrode assembly 2 is housed in the case body 11B through the opening 11BK and the opening 11BK is joined to the sealing body 12B, the electrolyte 5 is injected through an inlet (not shown). Initial charging, aging, and other processes are performed to complete the sealed storage battery 10B.

[0039] (Method of manufacturing the battery case of the second embodiment) 12A shows a cross-sectional view of an intermediate product used for the case body of the battery case shown in FIG. 11. FIG. 12B shows a cross-sectional view of the case body of the battery case shown in FIG.

[0040] 2, 4, 5, 11, 12A, and 12B, the method for manufacturing a battery case 1B of the second embodiment, similar to the method for manufacturing the battery case 1 of the first embodiment, is a method for manufacturing a battery case 1B including a cylindrical case body 11B made of aluminum, the cylindrical case body 11B having openings 11BK at both axial ends 111B for inserting electrode bodies 2, and a sealing body 12B having a first joint portion 11S that intersects with the openings 11BK and butt-joins the widthwise ends 112 of the case body 11B, and the sealing body 12B that seals the openings 11BK via a second joint portion 12BS. The first welding step S1 is a step of laser welding the first joint portion 11S, which butt-joins the widthwise ends 112 of the case body 11B, up to just before the openings 11BK. The second welding step S2 is a step of connecting the weld metal terminal end portion 11YS, which has been laser-welded up to just before the opening 11BK of the first joint portion 11S in the first welding step S1, to the weld metal portion 12Y of the second joint portion 12S when laser welding is performed along the opening 11BK to the second joint portion 12BS that joins the opening 11BK of the case body 11B and the sealing body 12B. Here, the method for manufacturing the battery case 1B of the second embodiment will be described, focusing on the differences from the method for manufacturing the battery case 1 of the first embodiment.

[0041] In the first welding step S1 of the second embodiment, first, as shown in Fig. 12A, a flat aluminum plate is bent to form protrusions 11T protruding toward the outer surface 11G at both widthwise ends 112, forming a rectangular tubular intermediate product 11BX in which the protrusions 11T abut against each other. Then, as shown in Fig. 12B, laser light LS is irradiated onto the protrusions 11T from the outer surface 11G side of the intermediate product 11BX to melt the molten metal 11YK, forming a weld metal portion 11Y that curves toward the outer surface 11G side of the case body 11B at the first joint portion 11S up to just before the opening 11K. Next, in the second welding step S2, the second joint portion 12BS that joins the opening 11BK of the case body 11B to the sealing body 12B is laser-welded along the opening 11BK. 5 and 11, the weld metal terminal end 11YS, which is laser-welded up to just before the opening 11BK of the first joint 11S, is connected to the weld metal portion 12Y of the second joint 12S. This completes the battery case 1B of the second embodiment. While the example described here has a protrusion 11T formed at the widthwise end 112 that protrudes toward the outer surface 11G, the widthwise end 112 may not have the protrusion 11T.

[0042] FIG. 13A shows a cross-sectional view of an intermediate product used in Variation 1 of the case body of the battery case shown in FIG. 11. FIG. 13B shows a cross-sectional view of Variation 1 of the case body of the battery case shown in FIG. 11. In the intermediate product 11BZ shown in FIG. 12A, the protrusion 11T is formed at the widthwise end 112 located at the widthwise center of the short side wall 11Bb, but the position of the protrusion 11T is not limited thereto. For example, as shown in FIG. 13A, the protrusion 11T may be formed at the widthwise end 112C located at the intersection of the short side wall 11Cb and the long side wall 11Ca. In this case, the weld metal portion 11Y of the first joint 11S is not located at the widthwise center of the short side wall 11Cb, which has the advantage of making it easier to form an electrolyte inlet, a safety valve, etc. It goes without saying that modifications 2 to 5 shown in FIGS. 7A to 10B can be applied to the protrusions 11T shown in FIGS. 12A and 13A and the welded metal parts 11Y shown in FIGS. 12B and 13B. [Explanation of symbols]

[0043] 1. 1B battery case 2 Electrode body 10, 10B sealed storage battery 11, 11B case body 11G External surface 11K, 11KB opening 11N inner surface 11T convex part 11S 1st joint 11Y, 12Y welded metal parts 11YK Molten Metal 11YS Weld metal end 12, 12B Sealing body 12S, 12BS 2nd joint 111 Axial end 112, 112B, 112C Width end 112D Width end 113 General section 114 Concave groove surface LS laser light S1 First welding process S2 2nd welding process

Claims

1. a cylindrical case body made of aluminum, having an opening at at least one axial end portion for inserting an electrode body, and a first joint portion that intersects with the opening portion and butt-joins widthwise ends of the case body; a sealing body that seals the opening via a second bonding portion, a first welding step of laser welding the first joint portion up to just before the opening; a second welding process in which, when laser welding is performed along the opening to the second joint portion, a weld metal terminal end portion laser-welded up to just before the opening of the first joint portion is connected to a weld metal portion of the second joint portion; A method for manufacturing a battery case comprising:

2. The method for manufacturing a battery case according to claim 1, The case body includes a protrusion that protrudes outward along the widthwise end portion, The first welding step fuses the protrusions together to form a weld metal portion that protrudes in a curved shape toward the outer surface. A method for manufacturing a battery case.

3. The method for manufacturing a battery case according to claim 1, The case body includes a protrusion that protrudes outward along a widthwise end portion that is displaced inward relative to a general portion while maintaining the thickness of the case body, The first welding step fuses the protrusions together to form a weld metal portion that protrudes in a curved shape toward the outer surface. A method for manufacturing a battery case.

4. The method for manufacturing a battery case according to claim 1, the case body includes a convex portion that protrudes from a concave groove surface that is concave toward an inner surface relative to an outer surface of the case body along the width direction end portion, the concave groove surface being formed in the width direction end portion, the convex portion protruding from the concave groove surface to the outer surface, The first welding step fuses the protrusions together to form a weld metal portion that protrudes in a curved shape toward the outer surface. A method for manufacturing a battery case.

5. The method for manufacturing a battery case according to claim 1, The case body includes a protrusion that protrudes toward both an outer surface side and an inner surface side along the width direction end of the case body, The first welding step fuses the protrusions together to form a weld metal portion that protrudes in a curved shape toward the outer surface side and the inner surface side. A method for manufacturing a battery case.

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