Method for manufacturing an electricity storage device

Abstract

To provide a manufacturing method of a power storage device that can reduce the amount of abrasion of the sealing corner compared to the conventional method even when "shaving of the sealing corner" occurs in a closing process.SOLUTION: A sealing plate 10 used in a closing process includes a pair of sealing long sides 11b and 11c in which the outer peripheral edge portion 11 has a rectangular ring shape, and that are parallel to each other, and a pair of sealing short sides 11d and 11e parallel to each other, and four arc-shaped sealing corners 11f to 11i connecting them. The outer peripheral end surface 14 located at the outermost side of the outer peripheral surface 13 of the sealing plate 10 has a form extending in parallel to the thickness direction DT of the sealing plate 10. The length LK in the thickness direction DT of the corner end surfaces 14f to 14i included in the sealing corners 11f to 11i among the outer peripheral end surfaces 14 is shorter than the length LL in the thickness direction DT of the long side end surfaces 14b, 14c included in the sealing long sides 11b, 11c.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an electricity storage device. [Background technology]

[0002] Patent Document 1 discloses an electricity storage device having an electrode assembly, a metal case that houses the electrode assembly, and a rectangular metal sealing plate that is inserted into a rectangular opening of the case to close the opening. In this electricity storage device, an opening wall that surrounds the opening of the case and an outer peripheral edge of the sealing plate are welded together along the entire periphery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-79476 A

[0004] The above-mentioned electricity storage device is manufactured as follows. First, in a closing step, the electrode body is housed inside the case, and a sealing plate is inserted into the opening of the case to close the opening with the sealing plate. Next, in a welding step, with the opening of the case closed with the sealing plate, the outer peripheral edge of the sealing plate and the opening wall of the case are laser welded all around.

[0005] The opening wall of the case used in the closing step has a rectangular ring shape and has a pair of parallel opening long sides, a pair of parallel opening short sides, and four arc-shaped opening corners connecting them. Furthermore, the closing step uses a sealing plate as follows. Specifically, the outer peripheral edge of the sealing plate has a rectangular ring shape and has a pair of parallel sealing long sides, a pair of parallel sealing short sides, and four arc-shaped sealing corners connecting them. Furthermore, the outer peripheral end face located on the outermost side of the outer peripheral surface of the sealing plate has a shape that extends parallel to the thickness direction of the sealing plate. Summary of the Invention [Problem to be solved by the invention]

[0006] In the closing step, when a sealing plate and a case having the above-mentioned shape are used, "shaving" may occur at the sealing corners of the sealing plate when the sealing plate is inserted into the opening of the case. Here, "shaving" of the sealing corners refers to the fact that, when the sealing plate is inserted into the opening of the case, a part of the sealing corners of the sealing plate overlaps the opening corners of the case in the thickness direction, and the sealing plate is inserted into the opening of the case, so that a part of the sealing corners (specifically, the part overlapping the opening corners in the thickness direction) is shaved. The shaving of the sealing corners generates metal powder, which accumulates on the surfaces of the sealing corners and the opening corners.

[0007] Specifically, for example, there are cases where the short side dimension of the inner peripheral surface of the opening wall of the case is equal to the short side dimension of the sealing plate, the long side dimension of the inner peripheral surface of the opening wall of the case is equal to the long side dimension of the sealing plate, and the outer radius of the sealing corner of the sealing plate is smaller than the inner radius of the opening corner of the case. In such cases, in the closing step, the sealing plate is inserted into the opening of the case so that a part of the sealing corner of the sealing plate overlaps the opening corner of the case in the thickness direction. As a result, a part of the sealing corner of the sealing plate (specifically, the part overlapping the opening wall of the case in the thickness direction) is scraped off, generating metal powder.

[0008] As described above, the metal powder generated by the scraping of the sealing corners accumulates on the surfaces of the sealing corners and the opening corners, and therefore, when the outer peripheral edge of the sealing plate and the opening wall of the case are laser-welded over the entire circumference in the welding process after the closing process, spatters and voids may occur due to the metal powder.

[0009] The present invention has been made in consideration of the current situation, and aims to provide a manufacturing method for an electricity storage device that can reduce the amount of scraping of the sealing corner (i.e., the volume of the scraped sealing corner) compared to conventional methods, even if "scraping of the sealing corner" occurs during the closing process. [Means for solving the problem]

[0010] (1) One aspect of the present invention has an electrode body, a metal case that houses the electrode body, and a rectangular metal sealing plate that is inserted into a rectangular opening of the case to close the opening. In a method for manufacturing a power storage device in which an opening wall portion of the case surrounding the opening and an outer peripheral edge portion of the sealing plate are welded over the entire circumference, the electrode body is housed inside the case, and the sealing plate is inserted into the opening of the case to close the opening by the sealing plate. A closing step; and a welding step of laser-welding the outer peripheral edge portion of the sealing plate and the opening wall portion of the case over the entire circumference in a state where the opening of the case is closed by the sealing plate. The opening wall portion of the case used in the closing step has a rectangular ring shape, a pair of opening long side portions parallel to each other, a pair of opening short side portions parallel to each other, and four arc-shaped opening corner portions connecting the opening long side portion and the opening short side portion. The sealing plate used in the closing step has an outer peripheral edge portion having a rectangular ring shape, a pair of sealing long side portions parallel to each other, a pair of sealing short side portions parallel to each other, and four arc-shaped sealing corner portions connecting the sealing long side portion and the sealing short side portion. The outermost peripheral end surface of the outer peripheral surface of the sealing plate has a form extending parallel to the thickness direction of the sealing plate. Among the outer peripheral end surfaces, the length LK in the thickness direction of the corner end surface included in the sealing corner portion is shorter than the length LL in the thickness direction of the long side end surface included in the sealing long side portion. and a length LS of a short side end face included in the plug short side portion among the outer peripheral end faces in the thickness direction and the length LL satisfy the relationship LS≦LL. A method for manufacturing a power storage device.

[0011] In this manufacturing method, in the closing step of inserting a sealing plate into the opening of the case to close the opening, the following sealing plate is used. Specifically, the outer peripheral edge portion of the sealing plate has a rectangular ring shape, a pair of sealing long side portions parallel to each other, a pair of sealing short side portions parallel to each other, and four arc-shaped sealing corner portions connecting them. Further, the outermost peripheral end surface of the outer peripheral surface of the sealing plate has a form extending parallel to the thickness direction of the sealing plate. And the length LK in the thickness direction of the portion included in the sealing corner portion (referred to as the corner end surface) of the outer peripheral end surface is shorter than the length LL in the thickness direction of the portion included in the sealing long side portion (referred to as the long side end surface) of the outer peripheral end surface. That is, the relationship LK < LL is satisfied.

[0012] As a result, even if "scraping of the sealing corners" occurs when the sealing plate is inserted into the opening of the case in the closing step, the amount of scraping of the sealing corners (i.e., the volume of the scraped sealing corners) can be reduced compared to the conventional example in which LK = LL. This reduces the amount of metal powder generated by scraping of the sealing corners, and therefore the amount of metal powder that accumulates on the surface of the outer periphery of the sealing plate and the surface of the opening wall of the case. This makes it possible to reduce the generation of spatters and voids caused by metal powder when the outer periphery of the sealing plate and the opening wall of the case are laser welded over the entire circumference in the welding step after the closing step.

[0013] The "shaving" of the sealing corner refers to the fact that, in the closing step, a part of the sealing corner (specifically, the part that overlaps the opening corner in the thickness direction) is scraped off by the opening corner when the sealing plate is inserted into the opening of the case so that a part of the sealing corner of the sealing plate overlaps the opening corner of the case in the thickness direction. The scraping of the sealing corner generates metal powder, which accumulates on the surface of the sealing corner and the surface of the opening corner.

[0014] (2) Furthermore, in the method for manufacturing an electric storage device as described in (1), the sealing plate used in the closing step has a front surface facing one side in the thickness direction and a back surface facing the other side, the back surface side of the outer peripheral edge portion is chamfered along the entire circumference, and the sealing corner portions are chamfered more than the sealing long side portions, so that the length LK is shorter than the length LL, and in the closing step, the method for manufacturing an electric storage device may include inserting the sealing plate from the back surface side into the opening of the case.

[0015] In this manufacturing method, a sealing plate as described below is used in the closing step of inserting a sealing plate into the opening of the case. The back side of the outer peripheral edge of the sealing plate is chamfered all around. In detail, the sealing corners are chamfered more than the sealing long sides, so that the length LK is shorter than the length LL. The outer peripheral surface of the sealing plate is composed of the aforementioned outer peripheral end face and the surface of the chamfered portion. In the closing step, the sealing plate is inserted into the opening of the case from the back side (i.e., from the chamfered side), thereby reducing the amount of wear on the sealing corners.

[0017] Incidentally, the long side of the opening of the case is more easily deformed elastically than the corner of the opening. Therefore, even if the insertion of the sealing plate into the opening of the case is started in the closing step in a positional relationship in which a part of the sealing long side of the sealing plate overlaps the long side of the opening of the case in the thickness direction, when the sealing long side comes into contact with the long side of the opening, the opening long side elastically deforms outward following the sealing long side, so that the sealing plate tends to be inserted into the opening of the case without overlapping the opening long side in the thickness direction. This suppresses the "scraping" of the sealing long side.

[0018] In addition, the opening short side of the case is more easily deformed elastically than the opening corner. Therefore, the sealing short side of the sealing plate is less likely to be "scraped" than the sealing corner. However, since the opening short side of the case is less likely to be deformed elastically than the opening long side, it can be said that the sealing short side of the sealing plate is more likely to be "scraped" than the sealing long side. Therefore, it is preferable to satisfy the relationship LS≦LL. By doing so, even if "scraping" occurs at the sealing short side when the sealing plate is inserted into the opening of the case, the amount of scraping at the sealing short side can be made equal to or less than that of the conventional example in which LS=LL.

[0019] In the present application, "shaving" refers to a situation in which the sealing plate is inserted into the opening of the case in the closing step so that at least a portion of the outer periphery of the sealing plate overlaps with at least a portion of the opening wall of the case in the thickness direction, thereby shaving off the portion of the outer periphery of the sealing plate that overlaps with the opening wall in the thickness direction. This "shaving" generates metal powder, which accumulates on the surface of the outer periphery and the surface of the opening wall. [Brief description of the drawings]

[0020] [Figure 1] 1 is a plan view (top view) of an electricity storage device according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of FIG. [Diagram 3] FIG. 2 is a plan view of a sealing plate according to the embodiment. [Figure 4] 4A to 4C are cross-sectional views taken along lines CC, DD, EE, and FF in FIG. [Diagram 5] FIG. 5 is a cross-sectional view of FIG. [Figure 6] FIG. 4 is a cross-sectional view of FIG. 3 . [Figure 7] FIG. 2 is a plan view of a case according to the embodiment. [Figure 8] FIG. [Figure 9] 11A to 11C are diagrams illustrating a closing step according to the embodiment. [Figure 10] FIG. 11 is another view illustrating the closing step. [Figure 11] FIG. 11 is an enlarged view of a portion J in FIG. [Figure 12] FIG. 12 is a cross-sectional view of FIG. [Figure 13] FIG. 11 is another view illustrating the closing step. [Figure 14] FIG. 2 is a diagram illustrating a welding process according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Next, an embodiment of the present invention will be described. The electricity storage device 1 of this embodiment is a lithium ion secondary battery. This electricity storage device 1 includes an electrode body 50, a case 20 that houses the electrode body 50, and a sealing plate 10 that closes an opening 20b of the case 20 (see FIGS. 1 and 2). The case 20 is a metal hard case in the shape of a rectangular parallelepiped box, and has a rectangular opening 20b (see FIGS. 7 and 8). The sealing plate 10 is made of metal in the shape of a rectangular plate, and is inserted into the opening 20b of the case 20 to close the opening 20b (see FIGS. 1 and 2).

[0022] The opening wall 21 of the case 20 and the outer peripheral edge 11 of the sealing plate 10 are welded around the entire circumference to form an annular weld W (see FIG. 2). Here, the opening wall 21 of the case 20 is a portion that surrounds the opening 20b of the case 20, and has a rectangular ring shape in plan view (see FIG. 7). The outer peripheral edge 11 of the sealing plate 10 is a portion that includes the outer peripheral surface 13 of the sealing plate 10, and has a rectangular ring shape in plan view (see FIGS. 3 to 6).

[0023] The electrode body 50 has a positive electrode plate 51, a negative electrode plate 52, and a separator 53 interposed between the positive electrode plate 51 and the negative electrode plate 52 (see FIG. 2). More specifically, the electrode body 50 is a flat wound type electrode body including a strip-shaped positive electrode plate 51, a strip-shaped negative electrode plate 52, and a strip-shaped separator 53, in which the positive electrode plate 51 and the negative electrode plate 52 are wound with the separator 53 sandwiched therebetween. An electrolyte (not shown) is contained inside the electrode body 50. An electrolyte (not shown) is also contained on the bottom side inside the case 20.

[0024] The electricity storage device 1 further has a positive electrode current collecting member 60 connected to the positive electrode plate 51 of the electrode body 50, and a negative electrode current collecting member 70 connected to the negative electrode plate 52 of the electrode body 50 (see FIG. 2). The electricity storage device 1 further has a positive electrode terminal member (not shown) connected to the positive electrode current collecting member 60 and exposed to the outside of the electricity storage device 1 through a first through hole (not shown) formed in the sealing plate 10. The electricity storage device 1 further has a negative electrode terminal member (not shown) connected to the negative electrode current collecting member 70 and exposed to the outside of the electricity storage device 1 through a second through hole (not shown) formed in the sealing plate 10.

[0025] Next, a method for manufacturing the electricity storage device 1 of this embodiment will be described. First, the lid structure 100 is formed. Specifically, a positive electrode current collecting member 60, a negative electrode current collecting member 70, a positive electrode terminal member (not shown), and a negative electrode terminal member (not shown) are assembled to the sealing plate 10 to form the lid structure 100 in which these are integrated. Next, an electrode body 50 is prepared, and the positive electrode current collecting member 60 of the lid structure 100 is connected to the positive electrode plate 51 of the electrode body 50, and the negative electrode current collecting member 70 of the lid structure 100 is connected to the negative electrode plate 52 of the electrode body 50, thereby integrating the lid structure 100 and the electrode body 50 (see FIG. 9).

[0026] Next, in the closing step, the electrode body 50 integrated with the lid structure 100 is accommodated inside the case 20 through the opening 20b, and the sealing plate 10 is inserted into the opening 20b of the case 20 to close the opening 20b of the case 20 (see FIG. 9). The sealing plate 10 is inserted into the opening 20b of the case 20 from the rear surface 10c side. The opening wall 21 of the case 20 subjected to the closing step has a rectangular ring shape and has a pair of opening long sides 21b, 21c parallel to each other, a pair of opening short sides 21d, 21e parallel to each other, and four arc-shaped opening corners 21f to 21i connecting them (see FIG. 7). The opening corners 21f are portions connecting the opening long side 21b and the opening short side 21d. The opening corners 21g are portions connecting the opening long side 21c and the opening short side 21d. Moreover, the opening corner 21h is a portion that connects the opening long side portion 21c and the opening short side portion 21e, and the opening corner 21i is a portion that connects the opening long side portion 21b and the opening short side portion 21e.

[0027] The sealing plate 10 used in the sealing step has the following configuration. Specifically, the outer peripheral edge 11 of the sealing plate 10 has a rectangular ring shape and has a pair of parallel sealing long side portions 11b, 11c, a pair of parallel sealing short side portions 11d, 11e, and four arc-shaped sealing corner portions 11f-11i connecting them (see Figs. 3-6). The sealing corner portion 11f is a portion connecting the sealing long side portion 11b and the sealing short side portion 11d. The sealing corner portion 11g is a portion connecting the sealing long side portion 11c and the sealing short side portion 11d. The sealing corner portion 11h is a portion connecting the sealing long side portion 11c and the sealing short side portion 11e. The sealing corner portion 11i is a portion connecting the sealing long side portion 11b and the sealing short side portion 11e. Additionally, an outer peripheral end face 14 located on the outermost side of the outer peripheral surface 13 of the sealing plate 10 has a shape that extends parallel to the thickness direction DT of the sealing plate 10 (see FIGS. 3 to 6). The outer peripheral surface 13 of the sealing plate 10 is composed of the outer peripheral end face 14 and the surface of a chamfered portion 15, which will be described later.

[0028] Of the outer peripheral end surface 14, a portion included in the sealing long side portion 11b is referred to as a long side end surface 14b, and a portion included in the sealing long side portion 11c is referred to as a long side end surface 14c (see FIG. 6). Of the outer peripheral end surface 14, a portion included in the sealing short side portion 11d is referred to as a short side end surface 14d, and a portion included in the sealing short side portion 11e is referred to as a short side end surface 14e (see FIG. 5). Of the outer peripheral end surface 14, a portion included in the sealing corner portion 11f is referred to as a corner end surface 14f, a portion included in the sealing corner portion 11g is referred to as a corner end surface 14g, a portion included in the sealing corner portion 11h is referred to as a corner end surface 14h, and a portion included in the sealing corner portion 11i is referred to as a corner end surface 14i (see FIG. 4). The long side end faces 14b, 14c, the short side end faces 14d, 14e, and the corner end faces 14g to 14i are all flat surfaces extending in the thickness direction DT of the sealing plate 10 (the up-down direction in FIGS. 4 to 6).

[0029] In this embodiment, the case 20 and the sealing plate 10 have a dimensional relationship in which at least one of the sealing corners 11f-11i of the sealing plate 10 can overlap in the thickness direction DT with at least one of the opening corners 21f-21i of the case 20 when the sealing plate 10 is inserted into the opening 20b of the case 20 in the closing step. More specifically, the case 20 and the sealing plate 10 have a relationship in which at least one of the opening corners 21f-21i and at least one of the sealing corners 11f-11i can overlap in the thickness direction DT due to a dimensional difference within the dimensional tolerance range between the outer radius R1 of the sealing corners 11f-11i and the inner radius R2 of the opening corners 21f-21i (see FIGS. 11 and 12).

[0030] Here, the closing step of this embodiment will be described in detail. Here, a case will be described in which the sealing corner 11f of the sealing plate 10 overlaps the opening corner 21f of the case 20 in the thickness direction DT when the sealing plate 10 is inserted into the opening 20b of the case 20 in the closing step. As shown in FIG. 9, first, the electrode body 50 integrated with the lid structure 100 is accommodated inside the case 20 through the opening 20b. Furthermore, the sealing plate 10 constituting the lid structure 100 is inserted into the opening 20b of the case 20 (in other words, inside the opening wall 21), and the opening 20b of the case 20 is closed by the sealing plate 10.

[0031] FIG. 10 is a diagram showing the positional relationship between the sealing plate 10 and the case 20 when the sealing plate 10 is inserted into the opening 20b of the case 20, and is a plan view seen from the front surface 10b side of the sealing plate 10. FIG. 11 is an enlarged view of a portion J in FIG. 10, showing the positional relationship between the sealing corner 11f of the sealing plate 10 and the opening corner 21f of the case 20 when the sealing plate 10 is inserted into the opening 20b of the case 20. As shown in FIG. 11, in this example, the outer radius R1 of the sealing corner 11f of the sealing plate 10 is smaller than the inner radius R2 of the opening corner 21f of the case 20. The inner radius R2 of the opening corner 21f is the radius of a circular arc of the inner peripheral surface 23f of the inner peripheral surface 23 of the opening wall 21, which is included in the opening corner 21f, when viewed in plan. Moreover, the outer radius R1 of the sealing corner 11f is the radius of a circular arc of a corner end face 14f included in the sealing corner 11f of the outer circumferential end face 14 of the sealing plate 10 in a plan view.

[0032] 12, in the closing step, the sealing plate 10 is inserted into the opening 20b of the case 20 so that part of the sealing corner 11f of the sealing plate 10 overlaps with the opening corner 21f of the case 20 in the thickness direction DT (the up-down direction in FIG. 12). As a result, when the sealing plate 10 is inserted into the opening 20b of the case 20, "scraping" occurs at the sealing corner 11f of the sealing plate 10.

[0033] Here, "shaving" of sealing corner 11f refers to a situation in which a portion of sealing corner 11f of sealing plate 10 (specifically, overlapping portion 11f1, which is a portion that overlaps opening corner 21f of case 20 in the thickness direction DT) of sealing plate 10 is shaved off when sealing plate 10 is inserted into opening 20b of case 20 so that a portion of sealing corner 11f of sealing plate 10 overlaps opening corner 21f of case 20 in the thickness direction DT. As shown in Fig. 13, overlapping portion 11f1 of sealing corner 11f is shaved off to become metal powder MP, and this metal powder MP accumulates on the surface of sealing corner 11f and the surface of opening corner 21f.

[0034] Note that the opening corner portions 21f to 21i of the case 20 are less likely to elastically deform than the opening long side portions 21b, 21c and the opening short side portions 21d, 21e. For this reason, when the insertion of the sealing plate 10 into the opening 20b of the case 20 is started in the positional relationship as shown in FIG. 12, that is, in the positional relationship where a part of the sealing corner portion 11f of the sealing plate 10 overlaps with the opening corner portion 21f of the case 20 in the thickness direction DT, the opening corner portion 21f does not elastically deform outward (left side in FIG. 12) following the sealing corner portion 11f. For this reason, while the overlapping portion 11f1 of the sealing corner portion 11f of the sealing plate 10 is being scraped off by the opening corner portion 21f of the case 20, the sealing plate 10 is inserted into the opening 20b of the case 20.

[0035] Incidentally, the metal powder MP generated by the scraping of the sealing corner portion 11f accumulates on the surface of the sealing corner portion 11f and the surface of the opening corner portion 21f (see FIG. 13). For this reason, after the closing process, in the welding process, when the outer peripheral edge portion 11 of the sealing plate 10 and the opening wall portion 21 of the case 20 are laser-welded over the entire circumference, sputtering or voids may occur due to this metal powder MP.

[0036] On the other hand, in the present embodiment, with respect to the sealing plate 10 used in the closing process, among the outer peripheral end faces 14, the length LK in the thickness direction DT of the corner end faces 14f to 14i included in the sealing corner portions 11f to 11i is made shorter than the length LL in the thickness direction DT of the long side end faces 14b, 14c included in the sealing long side portions 11b, 11c. That is, the relationship LK < LL is satisfied (see FIGS. 4 and 6).

[0037] More specifically, the sealing plate 10 used in the closing process has a front surface 10b facing one side in the thickness direction DT and a back surface 10c facing the other side, and by chamfering the back surface 10c side of the outer peripheral edge portion 11 over the entire circumference, a chamfered portion 15 is formed on the back surface 10c side of the outer peripheral edge portion 11. Among the chamfered portions 15, the portions included in the sealing long side portions 11b, 11c are the long side chamfered portions 15b, 15c, the portions included in the sealing short side portions 11d, 11e are the short side chamfered portions 15d, 15e, and the portions included in the sealing corner portions 11f to 11i are the corner chamfered portions 15f to 15i (see FIGS. 4 to 6).

[0038] Specifically, since the sealing corners 11f to 11i are chamfered more than the sealing long side portions 11b and 11c, the length LK is made shorter than the length LL. Specifically, for example, when the thickness T of the sealing plate 10 is 1.4 mm, the chamfering dimension (i.e., the dimension of the long side chamfered portions 15b and 15c) ML of the sealing long side portions 11b and 11c is set to "C0.3". On the other hand, the chamfering dimension (i.e., the dimension of the corner chamfered portions 15f to 15i) MK of the sealing corners 11f to 11i is set to "C0.7". As a result, while the length LL = 1.1 mm, the length LK = 0.7 mm, and the relationship LK < LL can be satisfied.

[0039] In addition, also in the embodiment of JP-A-2012-79476 (this is taken as a conventional example), the back surface side of the outer peripheral edge portion of the sealing plate is chamfered over the entire circumference. Specifically, it is chamfered with a constant chamfering dimension over the entire circumference of the back surface side of the outer peripheral edge portion of the sealing plate. Specifically, when the thickness T of the sealing plate is 1.4 mm, the chamfering dimensions of the sealing long side portion, the sealing short side portion, and the sealing corner are all set to C0.3. Therefore, in the conventional example, LK = LL = 1.1 mm.

[0040] Therefore, in the present embodiment, in the closing step, when the sealing plate 10 is inserted into the opening 20b of the case 20 from the back surface 10c side (i.e., from the side that is C-chamfered), even if "chipping" occurs at the sealing corners 11f to 11i of the sealing plate 10, the chipping amount of the sealing corners 11f to 11i can be reduced as compared with the above-described conventional example. Here, the chipping amount of the sealing corners 11f to 11i refers to the volume of the chipped portion among the sealing corners 11f to 11i.

[0041] 11 to 13, the amount of metal powder MP generated by scraping of sealing corners 11f is smaller than in the conventional example described above, and this reduces the amount of metal powder MP that accumulates on the surface of outer circumferential edge 11 of sealing plate 10 and the surface of opening wall 21 of case 20. As a result, when outer circumferential edge 11 of sealing plate 10 and opening wall 21 of case 20 are laser welded over the entire circumference in the welding step after the closing step, it is possible to reduce the generation of spatters and voids caused by metal powder MP.

[0042] Incidentally, the opening long side portions 21b, 21c of the case 20 are more easily elastically deformed than the opening corner portions 21f to 21i. Therefore, even when the sealing plate 10 starts to be inserted into the opening 20b of the case 20 in a positional relationship in which the sealing long side portions 11b, 11c of the sealing plate 10 overlap the opening long side portions 21b, 21c of the case 20 in the thickness direction DT, when the sealing long side portions 11b, 11c come into contact with the opening long side portions 21b, 21c, the opening long side portions 21b, 21c elastically deform outward following the sealing long side portions 11b, 11c, so that the sealing plate 10 is inserted into the opening 20b of the case 20 without overlapping the opening long side portions 21b, 21c in the thickness direction DT. This prevents the sealing long sides 11b and 11c from being chipped.

[0043] In addition, the opening short side portions 21d, 21e of the case 20 are also more easily elastically deformed than the opening corner portions 21f-21i. Therefore, the sealing short side portions 11d, 11e of the sealing plate 10 are less likely to be "shaved" than the sealing corner portions 11f-11i. In this embodiment, "shaving" refers to a situation in which the sealing plate 10 is inserted into the opening 20b of the case 20 in the closing step so that at least a part of the outer peripheral edge portion 11 of the sealing plate 10 overlaps with at least a part of the opening wall portion 21 of the case 20 in the thickness direction DT, and the part of the outer peripheral edge portion 11 of the sealing plate 10 that overlaps with the opening wall portion 21 in the thickness direction DT is scraped. This "shaving" generates metal powder MP, which accumulates on the surface of the outer peripheral edge portion 11 and the surface of the opening wall portion 21.

[0044] However, the short sides 21d and 21e of the opening of the case 20 are less likely to undergo elastic deformation than the long sides 21b and 21c of the opening. For this reason, it can be said that the short sides 11d and 11e of the sealing plate 10 are more likely to be "scraped" than the long sides 11b and 11c of the sealing plate.

[0045] In contrast, in the present embodiment, with respect to the sealing plate 10 used in the closing process, among the outer peripheral end faces 14, the length LS in the thickness direction DT of the short side end faces 14d and 14e included in the short sides 11d and 11e of the sealing plate and the length LL in the thickness direction DT of the long side end faces 14b and 14c included in the long sides 11b and 11c of the sealing plate satisfy the relationship LS < LL (see FIGS. 5 and 6). Specifically, for example, when the thickness T of the sealing plate 10 is 1.4 mm, the chamfer dimension (i.e., the dimension of the long side chamfer portions 15b and 15c) ML of the long sides 11b and 11c of the sealing plate is set to "C0.3". On the other hand, the chamfer dimension (i.e., the dimension of the short side chamfer portions 15d and 15e) MS of the short sides 11d and 11e of the sealing plate is set to "C0.5". As a result, the length LL becomes 1.1 mm, while the length LS becomes 0.9 mm, and the relationship LS < LL can be satisfied.

[0046] By doing so, in the closing process, when the sealing plate 10 is inserted into the opening 20b of the case 20, even if "scraping" occurs at the short sides 11d and 11e of the sealing plate, the amount of scraping at the short sides 11d and 11e of the sealing plate can be reduced compared to the above-described conventional example. Note that the amount of scraping at the short sides 11d and 11e of the sealing plate refers to the volume of the portion that is scraped at the short sides 11d and 11e of the sealing plate.

[0047] Next, in the welding process, with the opening 20b of the case 20 closed by the sealing plate 10, the outer peripheral edge portion 11 of the sealing plate 10 and the opening wall portion 21 of the case 20 are laser welded over the entire circumference. Specifically, as shown in FIG. 14, a laser beam LB is irradiated from the surface 10b side of the sealing plate 10 (i.e., from above in FIG. 14) to the outer peripheral edge portion 11 of the sealing plate 10 and the opening wall portion 21 of the case 20 to weld the outer peripheral edge portion 11 of the sealing plate 10 and the opening wall portion 21 of the case 20. Thereby, the case 20 and the sealing plate 10 are joined and integrated.

[0048] As described above, in the closing step of the present embodiment, the amount of metal powder MP deposited on the surface of the outer peripheral edge portion 11 of the sealing plate 10 and the surface of the opening wall portion 21 of the case 20 is reduced. Therefore, after the closing step, in the welding step, when the outer peripheral edge portion 11 of the sealing plate 10 and the opening wall portion 21 of the case 20 are laser welded over the entire circumference, the generation of spatter and the generation of voids due to the metal powder MP can be reduced.

[0049] Thereafter, an electrolytic solution (not shown) is injected into the case 20 through a liquid injection hole (not shown) formed in the sealing plate 10. Thereafter, by sealing the liquid injection hole, the power storage device 1 is completed.

[0050] As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and it goes without saying that the present invention can be appropriately modified and applied without departing from the gist thereof.

[0051] For example, in the embodiment, as a specific example of the sealing plate 10 used in the closing step, when the thickness T of the sealing plate 10 is 1.4 mm, the length LL = 1.1 mm and the length LK = 0.7 mm, and an example satisfying the relationship LK < LL is shown. However, the present invention is not limited to such a specific example, and as long as the relationship LK < LL is satisfied, the lengths of LK and LL can be any lengths. Also, the thickness T of the sealing plate is not limited to 1.4 mm and can be any thickness dimension.

[0052] Furthermore, in the embodiment, as a specific example of the sealing plate 10 used in the closing step, when the thickness T of the sealing plate 10 is 1.4 mm, the length LL = 1.1 mm and the length LS = 0.9 mm, and an example satisfying the relationship LS < LL is shown. However, the present invention is not limited to such a specific example, and the lengths of LS and LL can be any lengths. The present invention includes not only the case where the relationship LS < LL is satisfied, but also the case where the relationship LS = LL is satisfied and the case where the relationship LS > LL is satisfied. However, it is preferable that the relationship LS ≦ LL is satisfied.

Explanation of reference numerals

[0053] 1. Energy storage devices 10 Sealing plate 11 Outer periphery 11b,11c Sealing long side 11d,11e Sealing short side 11f~11i Sealing corner 13 Outer surface 14 Outer edge 14b, 14c Long side end surface 14d, 14e Short side end face 14f,14g,14h,14i Corner end face 15 Chamfered part 20 cases 20b opening 21 Opening wall 21b, 21c Opening long side 21d, 21e Short side of opening 21f~21i Opening corner 50 Electrode body 60 Positive electrode current collector 70 Negative electrode current collector

Claims

1. A method for manufacturing an electricity storage device comprising: an electrode assembly; a metal case that houses the electrode assembly; and a rectangular metal sealing plate that is inserted into a rectangular opening of the case to close the opening, wherein an opening wall portion of the case that surrounds the opening and an outer peripheral edge portion of the sealing plate are welded together along an entire periphery, a closing step of housing the electrode body inside the case and inserting the sealing plate into the opening of the case to close the opening with the sealing plate; a welding process for laser-welding the outer peripheral edge portion of the sealing plate and the opening wall portion of the case along an entire periphery thereof in a state in which the opening of the case is closed by the sealing plate, The opening wall portion of the case used in the closing step has a rectangular ring shape, and has a pair of opening long side portions parallel to each other, a pair of opening short side portions parallel to each other, and four arc-shaped opening corner portions connecting the opening long side portions and the opening short side portions, The sealing plate used in the closing step is The outer peripheral edge portion has a rectangular ring shape and includes a pair of parallel sealing long side portions, a pair of parallel sealing short side portions, and four arc-shaped sealing corner portions connecting the sealing long side portions and the sealing short side portions, an outer peripheral end face located at the outermost position of an outer peripheral surface of the sealing plate has a shape extending parallel to a thickness direction of the sealing plate, Among the outer peripheral end faces, a length LK in the thickness direction of a corner end face included in the sealing corner portion is shorter than a length LL in the thickness direction of a long side end face included in the sealing long side portion, The length LS of the short side end face included in the plug short side portion in the thickness direction of the outer peripheral end face and the length LL satisfy the relationship LS≦LL. A method for manufacturing an electricity storage device.

2. A method for producing the electricity storage device according to claim 1, comprising the steps of: The sealing plate used in the closing step is The plate has a front surface facing one side in the thickness direction and a back surface facing the other side, The back surface side of the outer peripheral edge portion is chamfered over the entire circumference, The plug corner portion is chamfered larger than the plug long side portion, so that the length LK is shorter than the length LL, In the closing step, the sealing plate is inserted into the opening of the case from the back side. A method for manufacturing an electricity storage device.

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