Electricity storage device manufacturing method and electricity storage device

Abstract

To increase the bonding strength between a case and a sealing plate. [Solution] The manufacturing method for an electricity storage device includes a case preparation step S01, a sealing plate preparation step S02, an assembly step S03, and a main welding step S05. In the case preparation step S01, a rectangular case having an opening is prepared. In the sealing plate preparation step S02, a sealing plate is prepared to be attached to the opening along the edge of the opening. In the assembly step S03, the sealing plate is attached to the case opening. In the main welding step S05, the case and the sealing plate are laser welded together along the entire periphery of the sealing plate. In the main welding step S05, the starting point of the laser welding is set inside the periphery of the sealing plate.

Description

[Technical Field]

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

[0002] Japanese Patent Application Publication No. 2018-202478 discloses a laser welding device that includes a means for splitting a laser beam into two and a means for translating the two split laser beams along the joining interface between two members. This laser welding device is configured to symmetrically position the two split laser beams at equal positions from the joining interface so that they do not enter the joining interface. According to Japanese Patent Application Publication No. 2018-202478, high-quality welding can be achieved by using this laser welding device when welding two members. For example, the laser welding device can be used to suppress spatter generation in the manufacture of a lithium battery that includes a container with an opening and a lid that is attached to the opening and welded to the container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-202478 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present invention would like to increase the bonding strength between the case and the sealing plate. [Means for solving the problem]

[0005] The method for manufacturing an electricity storage device disclosed herein includes the steps of: preparing a rectangular case having an opening; preparing a sealing plate to be attached to the opening along the edge of the opening; assembling the case to attach the sealing plate to the opening; and laser welding the case and the sealing plate along the entire periphery of the sealing plate. In the welding step, the starting point of the laser welding is set inside the periphery of the sealing plate. This manufacturing method can increase the bond strength between the case and the sealing plate. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view schematically illustrating an electricity storage device. [Figure 2] FIG. 2 is an exploded perspective view of the electricity storage device. [Figure 3] FIG. 3 is a flowchart showing an example of a method for manufacturing an electricity storage device. [Figure 4] FIG. 4 is a diagram for explaining the pre-welding step. [Figure 5] FIG. 5 is a diagram for explaining the main welding step. [Figure 6] FIG. 6 is a diagram schematically showing the vicinity of the starting point of laser welding in the main welding step. [Figure 7] FIG. 7 is a plan view schematically showing the case and the sealing plate after the main welding step has been completed. [Figure 8] FIG. 8 is an enlarged view of the area around the inner protrusion in FIG. [Figure 9] FIG. 9 is a diagram schematically showing the vicinity of the starting point of laser welding in the main welding step according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the technology disclosed herein will be described below with reference to the drawings. The embodiments described herein are, of course, not intended to limit the present invention. The drawings are schematic and do not necessarily reflect the actual product. Furthermore, identical reference numerals are used for components and parts performing the same function, and redundant descriptions will be omitted. The symbols X, Y, and Z in the drawings represent the front-to-rear, left-to-right, and up-to-down directions, respectively. The Y direction is perpendicular to the X direction. The Z direction is perpendicular to the X and Y directions. The symbols F, Rr, L, R, U, and D in the drawings represent the front, rear, left, right, top, and bottom directions, respectively. However, these directions are merely used for convenience of explanation and do not limit the installation form of the energy storage device. Furthermore, in this specification, a numerical range such as "X to Y" means "X or greater and Y or less" unless otherwise specified.

[0008] In this specification, the term "electricity storage device" refers to a device that can be charged and discharged. Electricity storage devices include batteries generally referred to as lithium ion batteries and lithium secondary batteries, as well as batteries such as lithium polymer batteries and nickel-metal hydride batteries. A secondary battery generally refers to a battery that can be repeatedly charged and discharged through the movement of charge carriers between the positive and negative electrodes. An electrolytic solution or a solid electrolyte may be used in an electricity storage device. For example, the secondary battery may be a secondary battery that uses a so-called liquid electrolyte, or a so-called all-solid-state battery that uses a solid electrolyte. Electricity storage devices also include capacitors such as electric double layer capacitors and lithium ion capacitors.

[0009] Fig. 1 is a perspective view schematically showing an electricity storage device 10. Fig. 2 is an exploded perspective view of the electricity storage device 10. As shown in Figs. 1 and 2, the electricity storage device 10 includes a case 11 and a sealing plate 13.

[0010] The case 11 is a rectangular case formed in a substantially rectangular parallelepiped shape. When viewed from above, the case 11 has short sides extending in the X direction and long sides extending in the Y direction. The case 11 has a bottom surface 11a, a pair of narrow sides 11b, and a pair of wide sides 11c. The bottom surface 11a is formed in a rectangular shape having short sides and long sides. The pair of narrow sides 11b face each other in the Y direction. The pair of narrow sides 11b extend upward from both ends of the bottom surface 11a in the Y direction. The pair of wide sides 11c face each other in the X direction. The pair of wide sides 11c extend upward from both ends of the bottom surface 11a in the X direction. The pair of narrow sides 11b and the pair of wide sides 11c form side surfaces of the case 11. As shown in FIG. 2, the case 11 has a rectangular opening 11d at its top. Case 11 is formed of, for example, aluminum or an aluminum alloy mainly containing aluminum, from the viewpoint of ensuring light weight and required rigidity. Although not shown, an electrode assembly having a positive electrode and a negative electrode is housed inside case 11. Furthermore, although not shown, if electricity storage device 10 is a liquid battery, electrolyte is also housed inside case 11.

[0011] Sealing plate 13 is a member for closing opening 11d of case 11. Sealing plate 13 is attached to opening 11d along the edge of opening 11d of case 11. In the embodiment shown in FIG. 1, sealing plate 13 is a flat plate formed in a rectangular shape. Sealing plate 13 may be made of the same material as case 11. Sealing plate 13 may be made of, for example, aluminum or an aluminum alloy mainly containing aluminum.

[0012] The sealing plate 13 has a gas exhaust valve 14 for exhausting gas inside the case 11. The gas exhaust valve 14 is located in the center of the sealing plate 13 in the Y direction. The gas exhaust valve 14 is, for example, a thin-walled portion designed to break when the pressure inside the case 11 rises above a predetermined value. When the pressure inside the case 11 reaches or exceeds the predetermined value, the gas exhaust valve 14 breaks, and the gas inside the case 11 is exhausted to the outside of the case 11.

[0013] A pair of electrode terminals 17 are provided on both ends of the sealing plate 13 in the Y direction. The method for attaching the electrode terminals 17 to the sealing plate 13 is not particularly limited. For example, the electrode terminals 17 may be attached to the sealing plate 13 by using a crimping process. The electrode terminals 17 may also be integrally formed with the sealing plate 13. The electrode terminals 17 are electrically connected to the electrode body housed inside the case 11. One of the pair of electrode terminals 17 is a positive electrode terminal electrically connected to the positive electrode. The other of the pair of electrode terminals 17 is a negative electrode terminal electrically connected to the negative electrode.

[0014] In an electricity storage device 10 such as that shown in Fig. 1, with an electrode assembly housed inside the case 11, the case 11 and the sealing plate 13 are laser-welded along the entire periphery of a peripheral edge 13a of the sealing plate 13. This joins the case 11 and the sealing plate 13, and the inside of the case 11 is sealed. For example, if the electricity storage device 10 is a liquid-based battery, sealing the inside of the case 11 prevents the electrolyte from leaking from inside the case 11.

[0015] In the above-described electricity storage device 10, the case 11 may expand due to factors such as gas generation during charging and discharging. When the case 11 expands, a load is applied to the joint between the case 11 and the sealing plate 13. Therefore, the joint between the case 11 and the sealing plate 13 is required to have a predetermined level of joint strength. However, the present inventors have confirmed that the joint between the case 11 and the sealing plate 13 may not have the predetermined joint strength, particularly near the starting point of laser welding. The present inventors have conducted extensive research into the cause of this and have concluded the following.

[0016] Laser welding is a technique for joining two components by irradiating the boundary between the two components with a laser beam to melt the two components. The joint strength of the two components depends on the weld depth. The weld depth is the depth of the melted portion of the components to be welded. A deeper weld depth results in a higher joint strength, while a shallower weld depth results in a lower joint strength. Therefore, to increase the joint strength of the joint between the case 11 and the sealing plate 13, laser welding must be performed to ensure a sufficiently deep weld depth. However, immediately after the start of laser welding, the temperatures of the case 11 and the sealing plate 13 may not rise sufficiently, and the case 11 and the sealing plate 13 may not melt sufficiently. As a result, the weld depth may be shallow near the starting point of laser welding.

[0017] Furthermore, due to factors such as manufacturing dimensional tolerances, the positional relationship between the case 11, sealing plate 13, and the laser used for laser welding may deviate from the ideal positional relationship. The "ideal positional relationship" here refers to the optimal positional relationship between the case 11, sealing plate 13, and the laser for proper laser welding. Furthermore, due to factors such as manufacturing dimensional tolerances, a gap may form between the case 11 and sealing plate 13 when the sealing plate 13 is attached to the case 11. According to the inventor's findings, when the laser is shifted toward the case 11 relative to the ideal positional relationship and a gap forms between the case 11 and sealing plate 13, the joint strength is likely to be low near the starting point of laser welding. According to the inventor's findings, when the laser, case 11, and sealing plate 13 are in such a positional relationship, the sealing plate 13 is particularly difficult to melt immediately after the start of laser welding, and therefore the weld depth is likely to be shallow near the starting point of laser welding.

[0018] Furthermore, according to the findings of the present inventors, when manufacturing a relatively large electricity storage device 10, such as one in which the width of the case 11 is 30 cm or more, the welding depth near the starting point of laser welding is likely to be particularly shallow. The present inventors believe the cause of this is as follows: When manufacturing a relatively large electricity storage device 10, the dimensional tolerances of the case 11 and the sealing plate 13 are likely to be large, which makes it easy for a relatively large gap to form between the case 11 and the sealing plate 13, and the laser is likely to be relatively misaligned toward the case 11 from the ideal positional relationship. According to the findings of the present inventors, for example, when the width of the case 11 is approximately 30 cm, a gap of approximately 0.2 mm may form between the case 11 and the sealing plate 13. Furthermore, according to the findings of the present inventors, for example, when the width of the case 11 is approximately 30 cm, the laser may be relatively misaligned toward the case 11 from the ideal positional relationship by approximately 0.2 mm. Note that, in this specification, the width of the case 11 refers to the length of the case 11 in the Y direction.

[0019] For the reasons described above, the inventors of the present application would like to perform welding with a sufficiently deep weld depth along the entire periphery of peripheral edge 13a of sealing plate 13, even when the laser, case 11, and sealing plate 13 are in the above-described positional relationship. More specifically, the inventors of the present application would like to sufficiently melt sealing plate 13 near the starting point of laser welding on peripheral edge 13a of sealing plate 13, even when the laser, case 11, and sealing plate 13 are in the above-described positional relationship.

[0020] 3 is a flowchart showing an example of a method for manufacturing the electricity storage device 10. The method for manufacturing the electricity storage device 10 includes a case preparation step S01, a sealing plate preparation step S02, an assembly step S03, a temporary welding step S04, and a main welding step S05. Note that the method for manufacturing the electricity storage device 10 does not necessarily have to include the temporary welding step S04.

[0021] In the case preparation step S01, a rectangular case 11 having an opening 11d is prepared. The method for preparing the case 11 in the case preparation step S01 is not particularly limited. The case 11 is prepared, for example, by bending and shaping a single rectangular flat plate. The width of the case 11 prepared in the case preparation step S01 may be 30 cm or more. By preparing such a relatively large case, a relatively large electrode assembly can be housed inside the case 11, and therefore a high-capacity electricity storage device can be obtained.

[0022] In the sealing plate preparation step S02, a sealing plate 13 is prepared that is to be attached to the opening 11d of the case 11 along the edge of the opening 11d. In the sealing plate preparation step S02, a sealing plate 13 is prepared that has electrode terminals 17 attached thereto. The method for preparing the sealing plate 13 in the sealing plate preparation step S02 is not particularly limited. For example, the sealing plate 13 is prepared by machining a rectangular flat plate, such as by drilling holes, and then attaching electrode terminals 17 and the like. The sealing plate 13 may also be prepared by being integrally molded with the electrode terminals 17 and the like. The sealing plate preparation step S02 may be performed before or after the case preparation step S01. The sealing plate preparation step S02 may be performed simultaneously with the case preparation step S01.

[0023] In the assembly step S03, the electrode body is inserted into the case 11. Thereafter, the sealing plate 13 is attached to the opening 11d of the case 11.

[0024] FIG. 4 is a diagram illustrating the tack welding step S04. FIG. 4 illustrates the case 11 and the sealing plate 13 as viewed from above. In the tack welding step S04, the case 11 and the sealing plate 13 are tack welded together while the sealing plate 13 is attached to the opening 11d. The tack welding is performed to position the sealing plate 13 relative to the case 11. In the tack welding step S04, the case 11 and the sealing plate 13 are intermittently welded together. In the embodiment shown in FIG. 4, 16 predetermined locations on the boundary between the case 11 and the sealing plate 13 are tack welded. Note that reference characters W1 to W16 in FIG. 4 indicate positions where tack welding is performed. In the embodiment shown in FIG. 4, as indicated by reference characters W1 to W4, predetermined locations on the boundary between the case 11 and the sealing plate 13 near the gas release valve 14 are tack welded. In the embodiment shown in Fig. 4, as indicated by the reference symbols W5 to W12, predetermined positions near the electrode terminal 17 are pre-welded at the boundary between the case 11 and the sealing plate 13. However, the positions and number of pre-welded positions are not limited to the embodiment shown in Fig. 4 and can be changed as appropriate depending on the dimensions of the case 11 and the sealing plate 13. The welding device used in the pre-welding step S04 may be the same as or different from the one used in the main welding step S05. Various conventionally known welding devices may be used in the pre-welding step S04.

[0025] FIG. 5 is a diagram illustrating the main welding step S05. FIG. 5 illustrates the case 11 and the sealing plate 13 as viewed from above. The arrow labeled WT in FIG. 5 indicates the welding path in the main welding step S05. The point labeled P1 in FIG. 5 is the start point of the main welding. Note that, in the following description, the start point of the main welding may be simply referred to as the start point P1. In the main welding step S05, the case 11 and the sealing plate 13 are main-welded together. This main welding is performed to seal the opening 11d. In the main welding step S05, the case 11 and the sealing plate 13 are laser-welded along the entire periphery 13a of the sealing plate 13. As shown in FIG. 3, the main welding step S05 includes a first step S05a and a second step S05b. Note that various conventionally known laser welding devices may be used in the main welding step S05.

[0026] FIG. 6 is a schematic diagram illustrating the vicinity of start point P1. Reference symbol P2 in FIG. 6 is the end point of first step S05a. Note that in the following description, end point P2 of first step S05a may be simply referred to as end point P2. Reference symbol D1 in FIG. 6 is the distance between start point P1 and end point P2. In this welding step S05, start point P1 of laser welding is set inside peripheral edge 13a of sealing plate 13. In the embodiment shown in FIG. 6, start point P1 is set to the left of left-side electrode terminal 17. In the embodiment shown in FIG. 6, start point P1 is set at the center of sealing plate 13 in the X direction. End point P2 is set at peripheral edge 13a of sealing plate 13. Distance D1 between start point P1 and end point P2 corresponds to the distance over which laser welding is performed in first step S05a. The distance D1 between the start point P1 and the end point P2 may be, for example, about 0.5 mm to 1.5 mm, but can be changed as appropriate depending on conditions such as the output value of the laser used in laser welding, the material of sealing plate 13, and the welding speed.

[0027] In the first step S05a, laser welding is performed from a starting point P1 toward the peripheral edge 13a of the sealing plate 13. In the embodiment shown in FIG. 6, in the first step S05a, laser welding is performed from the starting point P1 to the end point P2 toward the left. In the embodiment shown in FIG. 6, in the first step S05a, laser welding is performed so that the welding orbit WT and the peripheral edge 13a of the sealing plate 13 are perpendicular to each other. In the first step S05a, the output of the laser is controlled so that the output of the laser used for laser welding is increased as the welding position approaches the peripheral edge 13a of the sealing plate 13 from the starting point P1. In the first step S05a, the output of the laser is controlled so that the laser output becomes a predetermined value when the welding position reaches the end point P2.

[0028] The second step S05b is performed consecutively with the first step S05a. In the second step S05b, after the first step S05a is completed, the case 11 and the sealing plate 13 are laser-welded along the entire periphery of the peripheral edge 13a of the sealing plate 13. In the second step S05b, laser welding is started from the end point P2 of the first step S05a. In the second step S05b, the laser output is controlled so as to be maintained at a predetermined value. In the embodiment shown in FIG. 6, in the second step S05b, laser welding is performed clockwise from the end point P2 of the first step S05a. Note that in the second step S05b, laser welding may be performed counterclockwise from the end point P2 of the first step S05a. In second step S05b, the laser welding is completed after traveling from end point P2 of first step S05a around peripheral edge 13a of sealing plate 13 and reaching end point P2 of first step S05a again. The completion of second step S05b completes main welding step S05. When main welding step S05 is completed, case 11 and sealing plate 13 are welded together without any gaps, and the interior of case 11 is sealed.

[0029] FIG. 7 is a plan view schematically illustrating the case 11 and the sealing plate 13 after the completion of the main welding step S05. In FIG. 7, the hatched portion indicates a weld mark 30 formed by the laser welding performed in the main welding step S05. In FIG. 7, the weld mark 30 is exaggerated. The weld mark 30 is formed around the entire periphery of the peripheral edge 13a of the sealing plate 13. The weld mark 30 has an inner protrusion 30a and a main body portion 30b. As shown in FIG. 7, the main body portion 30b is formed in an annular shape along the entire periphery of the peripheral edge 13a of the sealing plate 13. The main body portion 30b is a weld mark formed by the laser welding performed in the second step S05b. The inner protrusion 30a protrudes from the main body portion 30b. The inner protrusion 30a protrudes inward from the peripheral edge 13a of the sealing plate 13. The inner protrusion 30a is a weld mark formed by the laser welding performed in the first step S05a.

[0030] Figure 8 is an enlarged view of the vicinity of the inner protrusion 30a in Figure 7. The dashed line in Figure 8 indicates the peripheral edge 13a of the sealing plate 13. The symbol D2 in Figure 8 is the distance from the peripheral edge 13a of the sealing plate 13 to the end of the inner protrusion 30a. The distance D2 from the peripheral edge 13a of the sealing plate 13 to the end of the inner protrusion 30a is the length of the weld mark formed by the laser welding in the first step S05a.

[0031] In the vicinity of the starting point P1 shown in FIG. 6, the temperature of the sealing plate 13 may not rise sufficiently, causing the sealing plate 13 to not melt, and therefore no weld mark may be formed. In such a case, the distance D2 from the peripheral edge 13a of the sealing plate 13 to the end of the inward protrusion 30a is shorter than the distance D1 between the starting point P1 and the end point P2. On the other hand, if the temperature at the starting point P1 rises sufficiently, the sealing plate 13 melts at the starting point P1, causing a weld mark to be formed at the starting point P1 as well. Furthermore, in such a case, a portion of the sealing plate 13 inside the starting point P1 may also melt, forming a weld mark. As a result, the distance D2 from the peripheral edge 13a of the sealing plate 13 to the end of the inward protrusion 30a may be equal to or greater than the distance D1 between the starting point P1 and the end point P2. For these reasons, distance D2 from peripheral edge 13a of sealing plate 13 to the end of inward protrusion 30a may be shorter, equal to, or longer than distance D1 between start point P1 and end point P2. That is, the relationship between the length of the weld mark formed by laser welding in first step S05a and the distance over which laser welding is performed in first step S05a varies depending on conditions such as the laser output, the material of sealing plate 13, and the welding speed. For example, if distance D1 between start point P1 and end point P2 is approximately 1 mm, distance D2 from peripheral edge 13a of sealing plate 13 to the end of inward protrusion 30a may be approximately 0.5 mm to 2 mm.

[0032] After the main welding step S05 is completed, an injection step of injecting the electrolyte into the case 11, an aging step of charging the electricity storage device 10 and leaving it for a predetermined time, and an inspection step of inspecting the electricity storage device 10 for internal short circuits, etc. are carried out as appropriate, and the electricity storage device 10 is manufactured.

[0033] The method for manufacturing electricity storage device 10 of this embodiment includes a main welding step S05 in which case 11 and sealing plate 13 are laser-welded together along the entire periphery of peripheral edge 13a of sealing plate 13. Main welding step S05 includes a first step S05a and a second step S05b. In main welding step S05, a start point P1 of laser welding is set inside peripheral edge 13a of sealing plate 13. In first step S05a, laser welding is performed from start point P1 toward end point P2, which is set on peripheral edge 13a of sealing plate 13. In second step S05b, case 11 and sealing plate 13 are laser-welded together along peripheral edge 13a of sealing plate 13 from end point P2.

[0034] According to the manufacturing method of this embodiment, in the first step S05a, the laser beam is irradiated to a portion inside the peripheral edge 13a of the sealing plate 13, which makes it easy for the temperature of the sealing plate 13 to rise. Therefore, when the welding position reaches the end point P2, which is the end position of the first step S05a, the sealing plate 13 is sufficiently melted at the end point P2. Furthermore, the second step S05b is performed immediately after the end of the first step S05a. Therefore, the second step S05b is started when the temperature of the sealing plate 13 has sufficiently risen. This allows the second step S05b to perform welding with a sufficiently deep welding depth around the entire periphery of the peripheral edge 13a of the sealing plate 13. In particular, the welding with a sufficiently deep welding depth can be performed even at the end point P2, which is the start position of the second step S05b. Therefore, the bonding strength between the case 11 and the sealing plate 13 can be increased.

[0035] According to this embodiment, in first step S05a, the output of the laser used for laser welding is increased as the welding position by laser welding moves from starting point P1 toward peripheral edge 13a of sealing plate 13. This prevents a sudden increase in the temperature of sealing plate 13, thereby suppressing the occurrence of spatter.

[0036] As described above, according to the findings of the present inventors, when manufacturing a relatively large electricity storage device 10, such as one in which the width of the case 11 is 30 cm or more, a relatively large gap is likely to occur between the case 11 and the sealing plate 13, and the laser is likely to be relatively significantly misaligned toward the case 11 from an ideal positional relationship. Therefore, when manufacturing a relatively large electricity storage device 10, the welding depth at the starting point of laser welding is likely to be shallow. On the other hand, a particularly high joint strength is required for a relatively large electricity storage device 10. Therefore, when manufacturing a relatively large electricity storage device 10, even if the laser, the case 11, and the sealing plate 13 are in the above-described positional relationship, it is necessary to perform the main welding so that the welding depth is sufficiently deep around the entire periphery 13 a of the sealing plate 13. According to the manufacturing method of this embodiment, welding with a sufficiently deep welding depth can be performed around the entire periphery 13 a of the sealing plate 13 without any omissions. Therefore, the manufacturing method of this embodiment can be particularly effectively used when manufacturing a relatively large battery.

[0037] Although one embodiment of the technology proposed here has been described above, the above embodiment is merely an example and the technology can be implemented in other modes.

[0038] 9 is a diagram schematically illustrating the vicinity of starting point P1 of laser welding in main welding step S05 according to another embodiment. In the embodiment shown in Fig. 9, in first step S05a, laser welding is performed obliquely on peripheral edge 13a of sealing plate 13. Here, the angle θ formed between the welding orbit WT and peripheral edge 13a of sealing plate 13 in first step S05a is preferably about 30° to 150°, and more preferably about 45° to 135°, from the viewpoint of sufficiently increasing the temperature of sealing plate 13.

[0039] In the embodiment shown in FIG. 6, the start point P1 is set to the left of the left electrode terminal 17. However, the position of the start point P1 is not limited to the embodiment shown in FIG. 6. For example, the start point P1 may be set to the right of the right electrode terminal 17. In this case, in the first step S05a, laser welding may be performed from the start point P1 toward the right to the peripheral edge 13a of the sealing plate 13. Alternatively, the start point P1 may be set between the gas release valve 14 and the left electrode terminal 17. In this case, in the first step S05a, laser welding may be performed from the start point P1 toward the front or rear to the peripheral edge 13a of the sealing plate 13. Similarly, the start point P1 may be set between the gas release valve 14 and the right electrode terminal 17.

[0040] The manufacturing method for the electricity storage device 10 may include steps other than those described above. For example, the manufacturing method for the electricity storage device 10 may include a clamping step of pressing the case 11 against the sealing plate 13 before the main welding step S05. This makes it possible to prevent laser leakage. Laser leakage is a phenomenon in which laser light passes through a gap between the case 11 and the sealing plate 13 and penetrates into the inside of the case 11. Similarly, the manufacturing method for the electricity storage device 10 may also include a clamping step before the temporary welding step S04.

[0041] The technology disclosed herein has been described in various ways. Unless otherwise specified, the embodiments and the like described herein do not limit the present invention. Furthermore, the technology disclosed herein can be modified in various ways, and as long as no particular problems arise, each component and each process described herein can be omitted or combined as appropriate. Furthermore, this specification includes the disclosures described in the following sections.

[0042] Section 1: providing a rectangular case having an opening; preparing a sealing plate to be attached to the opening along an edge of the opening; an assembly process of attaching the sealing plate to the opening of the case; a main welding step of laser welding the case and the sealing plate along the entire periphery of the sealing plate, In the main welding process, A method for manufacturing an electricity storage device, wherein a starting point of laser welding is set inside the peripheral edge portion of the sealing plate.

[0043] Section 2: The main welding process includes: a first step of laser welding from the starting point toward the peripheral edge portion of the sealing plate; Item 1. The method for manufacturing an electricity storage device according to item 1, further comprising: a second step, after completion of the first step, of laser welding the case and the sealing plate along the entire periphery of the sealing plate.

[0044] Section 3: In the main welding process, Item 3. The method for manufacturing an electricity storage device according to item 1 or 2, wherein the output of the laser used for laser welding is increased as the welding position approaches the peripheral edge portion of the sealing plate from the starting point.

[0045] Section 4: 4. The method for manufacturing an electricity storage device according to any one of items 1 to 3, wherein the case prepared in the case preparation step has a width of 30 cm or more.

[0046] Section 5: An electricity storage device obtained by the electricity storage device manufacturing method according to any one of items 1 to 4, a welding mark is formed along the entire periphery of the peripheral edge portion of the sealing plate, The welding mark has an inward protruding portion that protrudes inward beyond the peripheral edge portion of the sealing plate. [Explanation of symbols]

[0047] 10. Energy storage devices 11 cases 13 Sealing plate 13a Periphery of sealing plate 30 Weld marks 30a Inner protrusion S01 Case preparation process S02 Sealing plate preparation process S03 Assembly process S04 Temporary welding process S05 Main welding process S05a 1st process S05b 2nd process P1 Start point of main welding

Claims

1. providing a rectangular case having an opening; preparing a sealing plate to be attached to the opening along an edge of the opening; an assembly process of attaching the sealing plate to the opening of the case; a main welding process of laser welding the case and the sealing plate along the entire periphery of the sealing plate; Including, In the main welding process, A starting point of laser welding is set inside the peripheral edge portion of the sealing plate. A method for manufacturing an electricity storage device.

2. The main welding process includes: a first step of laser welding from the starting point toward the peripheral edge portion of the sealing plate; a second step of laser welding the case and the sealing plate along the entire periphery of the sealing plate after the first step is completed; The method for manufacturing the electricity storage device according to claim 1 , comprising:

3. In the main welding process, The method for manufacturing an electricity storage device according to claim 1 , wherein an output of a laser used for laser welding is increased as a welding position by laser welding approaches the peripheral edge portion of the sealing plate from the starting point.

4. The method for manufacturing an electricity storage device according to claim 1 , wherein the case prepared in the case preparation step has a width of 30 cm or more.

5. An electricity storage device obtained by the electricity storage device manufacturing method according to claim 1, a welding mark is formed along the entire periphery of the peripheral edge portion of the sealing plate, The welding mark has an inward protruding portion that protrudes inward beyond the peripheral edge portion of the sealing plate.

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