Method for manufacturing an electricity storage device

Abstract

To efficiently prevent laser beam loss. [Solution] A manufacturing method for an electricity storage device includes a temporary welding step, a main clamping step, and a main welding step. In the temporary welding step, the case 11 and the sealing plate 13 are temporarily welded together at a plurality of predetermined positions on the boundary between the case 11 and the sealing plate 13. In the main clamping step, an opening is clamped along a pair of wide surfaces 11c of the case 11. In the main welding step, with the opening clamped along the pair of wide surfaces 11c of the case 11, the case 11 and the sealing plate 13 are laser welded together along the entire periphery 13a of the sealing plate 13. In the main clamping step, portions of the case 11 formed by temporary welding where the spacing between the temporary welds is longer than a predetermined length are clamped.

Description

[Technical Field]

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

[0002] Japanese Patent Application Laid-Open Publication No. 2013-187087 discloses a method for sealing a sealed battery case, in which a lid is welded to the opening of the battery case. A step is formed on a portion of the inner surface of the opening of the battery case, into which the lid fits. In this welding method, laser welding begins at the joint where the inner surface with the step is joined to the lid. Japanese Patent Application Laid-Open Publication No. 2013-187087 claims that this welding method can prevent laser penetration. Laser penetration is a phenomenon in which the laser penetrates the joint between the battery case and the lid and enters the interior of the battery case.

[0003] Furthermore, Japanese Patent Application Laid-Open Publication No. 2013-187087 discloses a method for welding a sealed battery can in which a sealed battery is divided into a front region and a rear region and then welded. In this welding method, a holding jig is used to press the lid located in the front region of the sealed battery against the battery case from above to below, and laser welding is then initiated to weld the battery case and the lid in the rear region. Next, the holding jig is removed, and the battery case and the lid in the front region of the sealed battery are welded. According to Japanese Patent Application Laid-Open Publication No. 2013-187087, this welding method can prevent the lid from lifting off the battery case during welding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-187087 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present invention would like to efficiently prevent laser beam loss. [Means for solving the problem]

[0006] The method for manufacturing an electric storage device disclosed herein includes the steps of: preparing a rectangular case having a rectangular 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; pre-welding the case and the sealing plate at predetermined positions along the boundary between the case and the sealing plate; clamping the opening along a pair of side surfaces of the case; and laser-welding the case and the sealing plate along the entire periphery of the sealing plate with the opening clamped along the pair of side surfaces of the case. In the clamping step, the portion of the case where the spacing between the pre-welded pre-welds is longer than a predetermined length is clamped. This manufacturing method effectively prevents laser leakage. [Brief explanation of the drawings]

[0007] [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 temporary clamping step and the temporary welding step. [Figure 5] FIG. 5 is a plan view schematically showing the case and the sealing plate after the pre-welding step has been completed. [Figure 6] FIG. 6 is a diagram for explaining the main clamping step and the main welding step according to the reference example. [Figure 7] FIG. 7 is an enlarged view showing a schematic diagram of the boundary portion between the case and the sealing plate according to the reference example. [Figure 8] FIG. 8 is a diagram illustrating a main clamping step and a main welding step according to one embodiment. [Figure 9] FIG. 9 is a diagram for explaining a main clamping step and a main welding step according to another embodiment. [Figure 10] FIG. 10 is a diagram for explaining a main clamping step and a main welding step according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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, components and parts performing the same function are appropriately designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. 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, up, and down directions, respectively. However, these directions are merely used for convenience of explanation and do not in any way limit the installation form of the energy storage device. Furthermore, in this specification, a numerical range such as "X to Y" means "greater than or equal to X and less than or equal to Y" unless otherwise specified.

[0009] 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.

[0010] Fig. 1 is a perspective view that schematically shows 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, a sealing plate 13, and an electrode assembly 20.

[0011] 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. The case 11 is made of, for example, aluminum or an aluminum alloy containing aluminum as the main component, from the viewpoint of ensuring light weight and required rigidity.

[0012] 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.

[0013] 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.

[0014] The sealing plate 13 is provided with a pair of electrode terminals 17, 18. The pair of electrode terminals 17, 18 are arranged at both ends of the sealing plate 13 in the Y direction. The method for attaching the electrode terminals 17, 18 to the sealing plate 13 is not particularly limited. For example, the electrode terminals 17, 18 may be attached to the sealing plate 13 by using a crimping process. The electrode terminals 17, 18 may be integrally formed with the sealing plate 13. The electrode terminal 17 includes an external terminal 17a and an internal terminal 17b. The external terminal 17a is attached to the upper side of the sealing plate 13. The internal terminal 17b is attached to the lower side of the sealing plate 13. Similarly, the electrode terminal 18 includes an external terminal 18a and an internal terminal 18b.

[0015] The electrode body 20 shown in FIG. 2 is housed inside the case 11 in the form shown in FIG. 1. Although not shown, the electrode body 20 has a positive electrode and a negative electrode. The positive electrode of the electrode body 20 is connected to the internal terminal 17b of the electrode terminal 17. Therefore, the electrode terminal 17 is a positive electrode terminal electrically connected to the positive electrode of the electrode body 20. The negative electrode of the electrode body 20 is connected to the internal terminal 18b of the electrode terminal 18. Therefore, the electrode terminal 18 is a negative electrode terminal electrically connected to the negative electrode of the electrode body 20. The configuration of the electrode body 20 is not particularly limited. Various conventionally known electrode bodies can be used for the electrode body 20.

[0016] Next, a method for manufacturing the electricity storage device 10 will be described. Fig. 3 is a flowchart showing an example of the 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 clamping step S04, a temporary welding step S05, a main clamping step S06, and a main welding step S07. The method for manufacturing the electricity storage device 10 may include steps other than these, but descriptions thereof will be omitted here.

[0017] 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. Note that in this specification, the width of the case 11 refers to the length of the case 11 in the Y direction. By preparing such a relatively large case, a relatively large electrode assembly can be accommodated inside the case 11, and therefore a high-capacity electricity storage device can be obtained.

[0018] In the sealing plate preparation step S02, a sealing plate 13 to be attached to the opening 11d of the case 11 is prepared along the edge of the opening 11d. The method for preparing the sealing plate 13 in the sealing plate preparation step S02 is not particularly limited. The sealing plate 13 is prepared, for example, by machining a rectangular flat plate, such as by drilling holes, and then attaching electrode terminals 17, 18, etc. The sealing plate 13 may also be prepared by being integrally molded with the electrode terminals 17, 18, etc. The sealing plate preparation step S02 may be performed before or after the case preparation step S01. The sealing plate preparation step S02 may also be performed simultaneously with the case preparation step S01.

[0019] 2, in the assembly step S03, the electrode body 20 is connected to the electrode terminals 17 and 18. More specifically, the positive electrode of the electrode body 20 is connected to the internal terminal 17b of the electrode terminal 17, and the negative electrode of the electrode body 20 is connected to the internal terminal 18b of the electrode terminal 18. Next, in the assembly step S03, with the electrode body 20 connected to the electrode terminals 17 and 18, the sealing plate 13 is attached to the opening 11d of the case 11. In this way, the electrode body 20 is housed inside the case 11, and the sealing plate 13 is attached to the opening 11d.

[0020] FIG. 4 is a diagram illustrating the temporary clamping step S04 and the temporary welding step S05. FIG. 4 illustrates the case 11 and the sealing plate 13 as viewed from above. Reference symbols C1 to C16 in FIG. 4 indicate positions where welding is performed in the temporary welding step S05. As shown in FIG. 4, reference symbols C1 to C4 are located near the gas exhaust valve 14. Reference symbols C5 to C8 are located near the electrode terminal 17. Reference symbols C9 to C12 are located near the electrode terminal 18. Reference symbols C1 to C12 are located on the long sides of the case 11. Reference symbols C13 and C14 are located on the left short side of the case 11. Reference symbols C15 and C16 are located on the right short side of the case 11. Reference symbols C1 to C16 are located symmetrically in the X and Y directions.

[0021] In the temporary clamping step S04, a plurality of predetermined positions of the boundary between the case 11 and the sealing plate 13 are clamped. In the temporary clamping step S04, positions where welding will be performed in the temporary welding step S05 are clamped. In the embodiment shown in Fig. 4, the positions indicated by the reference characters C1 to C16 are clamped in the temporary clamping step S04. Note that if the position where temporary welding will be performed in the temporary welding step S05 is changed, the positions clamped in the temporary clamping step S04 will change accordingly.

[0022] In the temporary clamping step S04, a temporary clamping jig 40 is used. The temporary clamping jig 40 includes a pressing portion 41 and a drive unit 42. The pressing portion 41 is a portion that is pressed against the case 11. The pressing portion 41 is configured to clamp only a predetermined number of positions on the boundary between the case 11 and the sealing plate 13. In the embodiment shown in FIG. 4, the pressing portion 41 is configured to clamp only the positions indicated by the reference characters C1 to C16. The pressing portion 41 has portions that locally press against only a predetermined number of positions on the case 11. In the embodiment shown in FIG. 4, the pressing portion 41 that presses against the pair of wide surfaces 11c of the case 11 has six portions that intermittently press against the case 11. In the embodiment shown in FIG. 4, the pressing portion 41 that presses against the pair of narrow surfaces 11b of the case 11 has two portions that intermittently press against the case 11. The dimensions and shape of the pressing unit 41 can be changed as appropriate depending on the position where pre-welding is performed in the pre-welding step S05 and the dimensions of the case 11. The driving device 42 is a device that drives the pressing unit 41. The type of the driving device 42 is not particularly limited. The driving device 42 may be, for example, an air cylinder.

[0023] In the pre-welding step S05, the case 11 and the sealing plate 13 are pre-welded together with the sealing plate 13 attached to the opening 11d. The pre-welding is performed to position the sealing plate 13 relative to the opening 11d. In the pre-welding step S05, the case 11 and the sealing plate 13 are intermittently welded together. In the pre-welding step S05, the case 11 and the sealing plate 13 are pre-welded together at a plurality of predetermined positions on the boundary between the case 11 and the sealing plate 13. The pre-welding step S05 is performed with a plurality of predetermined positions on the boundary between the case 11 and the sealing plate 13 clamped. In the embodiment shown in FIG. 4, the positions indicated by the reference symbols C1 to C16 are pre-welded with the 16 positions indicated by the reference symbols C1 to C16 clamped. In the embodiment shown in FIG. 4, pre-welding is performed at positions symmetrical in the X and Y directions. In the embodiment shown in FIG. 4, predetermined positions near the gas release valve 14 are tack-welded at the boundary between the case 11 and the sealing plate 13, as indicated by reference characters C1 to C4. In the embodiment shown in FIG. 4, predetermined positions near the electrode terminals 17 and 18 are tack-welded at the boundary between the case 11 and the sealing plate 13, as indicated by reference characters C5 to C12. However, the positions and the number of tack-welded positions are not limited to those 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 tack-welding step S05 may be the same as or different from that used in the main welding step S07. Various conventionally known welding devices may be used in the tack-welding step S05.

[0024] FIG. 5 is a plan view schematically showing the case 11 and the sealing plate 13 after the pre-welding step S05. Reference symbols W1 to W16 in FIG. 5 indicate pre-welded portions. In FIG. 5, the pre-welded portions W1 to W16 are exaggerated. After the pre-welding step S05 is completed, the pre-welded portions W1 to W16 are formed at predetermined positions on the boundary between the case 11 and the sealing plate 13. In the embodiment shown in FIG. 5, the pre-welded portions W1 to W16 are formed at the same positions as the reference symbols C1 to C16 in FIG. 4. In the embodiment shown in FIG. 5, the pre-welded portions W1 to W16 are formed at positions symmetrical with respect to the X and Y directions. The pre-welded portions W1 to W16 are the portions where the case 11 and the sealing plate 13 are joined.

[0025] The symbol L1 in FIG. 5 indicates the spacing between tack welds W1 and W2. The symbol L2 in FIG. 5 indicates the spacing between tack welds W1 and W6. The symbol L3 in FIG. 5 indicates the spacing between tack welds W5 and W6. In the configuration shown in FIG. 5, the tack welds W1 to W16 are arranged symmetrically in the X and Y directions, so the spacing between tack welds W3 and W4 is equal to the spacing L1 between tack welds W1 and W2. The spacing between tack welds W4 and W7, the spacing between tack welds W2 and W9, and the spacing between tack welds W3 and W12 are equal to the spacing L2 between tack welds W1 and W6. The spacing between tack welds W7 and W8, the spacing between tack welds W9 and W10, and the spacing between tack welds W11 and W12 are equal to the spacing L3 between tack welds W5 and W6.

[0026] In the embodiment shown in FIG. 5, the relationship between the distance L1 between the tack welds W1 and W2, the distance L2 between the tack welds W1 and W6, and the distance L3 between the tack welds W5 and W6 is L2 > L3 = L1. That is, in the embodiment shown in FIG. 5, the distance L1 between the tack welds W1 and W2 is equal to the distance L3 between the tack welds W5 and W6. The distance L2 between the tack welds W1 and W6 is longer than the distance L1 between the tack welds W1 and W2 and the distance L3 between the tack welds W5 and W6. Specifically, in the embodiment shown in FIG. 5, L1 = 40 mm, L2 = 80 mm, and L3 = 40 mm. Therefore, in the embodiment shown in FIG. 5, the sealing plate 13 tack-welded to the case 11 in the tack welding step S05 has four portions along the edge of the opening 11d of the case 11 where the distances between the tack welds W1 to W16 are longer than 40 mm.

[0027] FIG. 6 is a diagram illustrating the main clamping step S06 and the main welding step S07 according to a reference example. FIG. 6 illustrates the case 11 and the sealing plate 13 as viewed from above. The symbol WT in FIG. 6 indicates the welding trajectory in the main welding step S07. In the main clamping step S06, the opening 11d is clamped along a pair of side surfaces of the case 11. In the embodiment shown in FIG. 6, the main clamping jig 50 presses the entire wide surface 11c of the case 11 in the Y direction, thereby clamping the opening 11d. In the main welding step S07, the case 11 and the sealing plate 13 are main-welded together. This main welding is performed to seal the opening 11d. The main welding step S07 is performed with the opening 11d clamped along a pair of side surfaces of the case 11. In the embodiment shown in FIG. 6, the main welding step S07 is performed with the entire wide surface 11c of the case 11 pressed in the Y direction by the main clamping jig 50. In the main welding step S07, case 11 and sealing plate 13 are laser-welded along the entire periphery of peripheral edge 13a of sealing plate 13.

[0028] However, if a gap exists between the case 11 and the sealing plate 13, so-called laser leakage may occur when laser welding is performed in the main welding step S07. Laser leakage is a phenomenon in which laser light penetrates the gap between the case 11 and the sealing plate 13 and enters the inside of the case 11. Laser leakage can cause welding defects. Therefore, in the main welding step S07, it is preferable to perform laser welding so as to prevent laser leakage. The present inventors wish to efficiently prevent laser leakage. Therefore, the present inventors conducted various studies to determine under what welding conditions laser leakage is likely to occur. As a result, the present inventors discovered the following problem.

[0029] FIG. 7 is an enlarged view schematically illustrating the boundary between the case 11 and the sealing plate 13 according to a reference example. FIG. 7 illustrates the case 11 and the sealing plate 13 as viewed from above. In the main welding step S07, the temperature of the case 11 rises, causing the case 11 to expand. When the case 11 expands, as shown in FIG. 7, the case 11 deforms outward, which can locally widen the gap between the case 11 and the sealing plate 13. According to the findings of the present inventors, the gap between the case 11 and the sealing plate 13 is likely to widen and laser leakage is likely to occur in areas where the spacing between the temporary welds W1 to W16 is relatively long. Specifically, the present inventors found that the gap between the case 11 and the sealing plate 13 is particularly likely to widen and laser leakage is particularly likely to occur in areas where the spacing between the temporary welds W1 to W16 is longer than 40 mm. Furthermore, according to the findings of the present inventors, as main welding step S07 proceeds, the gap between case 11 and sealing plate 13 widens, making laser leakage more likely to occur. This is thought to be because the temperature of case 11 increases as main welding step S07 proceeds.

[0030] Furthermore, according to the findings of the present inventors, laser voids are particularly likely to occur when manufacturing a relatively large electricity storage device 10, such as when the width of the case 11 is 30 cm or more. 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. 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, when manufacturing a relatively large electricity storage device 10, it is easy for the spacing between the temporary welds W1 to W16 to be relatively long in some areas, which makes it easy for the gap between the case 11 and the sealing plate 13 to widen in some areas during main welding step S07.

[0031] FIG. 8 is a diagram illustrating the main clamping step S06 and the main welding step S07 according to this embodiment. In the main clamping step S06 according to this embodiment, the portions of the case 11 where the spacing between the pre-welded joints W1 to W16 formed by pre-welding is longer than a predetermined length are clamped. In the embodiment shown in FIG. 8, the portions of the boundary between the case 11 and the sealing plate 13 where the spacing between the pre-welded joints W1 to W16 on the case 11 is longer than 40 mm are partially clamped. Specifically, in the embodiment shown in FIG. 8, the portions clamped are the portion between the pre-welded joints W1 and W6, the portion between the pre-welded joints W2 and W9, the portion between the pre-welded joints W4 and W7, and the portion between the pre-welded joints W3 and W12. That is, in the embodiment shown in FIG. 8, the portions where the spacing between the pre-welded joints W1 to W16 is 80 mm are clamped.

[0032] In the final clamping step S06, a final clamping jig 50 is used, which has a portion that intermittently presses against portions of the case 11 where the spacing between the pre-welded portions W1 to W16 is greater than 40 mm. The final clamping jig 50 includes a pressing unit 51 and a drive unit 52. The pressing unit 51 is the portion that is pressed against the case 11. The pressing unit 51 is configured to intermittently press against portions of the case 11 where the spacing between the pre-welded portions W1 to W16 is greater than 40 mm. Specifically, in the embodiment shown in FIG. 8, the pressing unit 51 presses against portions where the spacing between the pre-welded portions W1 to W16 is 80 mm. In the embodiment shown in FIG. 8, the pressing unit 51 is configured to press against the entire portion where the spacing between the pre-welded portions W1 to W16 is 80 mm. 8, there are four portions where the spacing between the pre-welded portions W1 to W16 is greater than 40 mm, and therefore the pressing portion 51 has four portions that intermittently press against each other. The driving device 52 is a device that drives the pressing portion 51. The type of the driving device 52 is not particularly limited. The driving device 52 may be, for example, an air cylinder.

[0033] The main welding step S07 is performed with the opening 11d clamped along a pair of side surfaces of the case 11. In the embodiment shown in Fig. 8, the main welding step is performed with the pressing portion 51 pressed against the wide surface 11c of the case 11 at portions where the temporary welds W1 to W16 are spaced 80 mm apart, with the opening 11d clamped. In the main welding step S07, 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. Note that the main welding step S07 may use any of various conventionally known laser welding devices.

[0034] As described above, according to the inventors' findings, as the main welding step S07 progresses, the gap between the case 11 and the sealing plate 13 widens. Therefore, in the main welding step S07 according to the present embodiment, the force clamping the portions of the case 11 where the intervals between the temporary welds W1 to W16 are longer than a predetermined length is increased as the laser welding progresses. Specifically, in the present embodiment, the main welding step S07 includes a first step S07a and a second step S07b.

[0035] The first step S07a is performed in a state where the portions of the case 11 along the wide surface 11c thereof where the spacing between the temporary welds W1 to W16 is longer than a predetermined length are clamped with a predetermined force. Here, the predetermined force may be, for example, approximately 100 N to 300 N, or approximately 150 N to 250 N. In the first step S07a, for example, laser welding may be performed over approximately 40% to 60% of the entire circumference of the peripheral edge 13a of the sealing plate 13. In this embodiment, in the first step S07a, laser welding is performed over half the circumference of the peripheral edge 13a of the sealing plate 13. Note that the starting point of laser welding in the first step S07a is not particularly limited.

[0036] The second step S07b is performed immediately after the first step S07a. The second step S07b is performed in a state where the portions of the case 11 along the wide surface 11c where the intervals between the temporary welds W1 to W16 are longer than a predetermined length are clamped with a force greater than a predetermined force. That is, in the second step S07b, laser welding is performed in a state where the opening 11d is clamped with a force greater than that in the first step S07a. The force used to clamp the opening 11d in the second step S07b may be approximately 1.5 to 3 times, or may be approximately 2 to 2.5 times, the force used to clamp the opening 11d in the first step S07a. In the second step S07b, laser welding is performed on the portions of the peripheral edge 13a of the sealing plate 13 that were not laser welded in the first step S07a. In this embodiment, in second step S07b, laser welding is performed on the remaining half of peripheral edge 13a of sealing plate 13 that was not laser welded in first step S07a. As a result, in main welding step S07, laser welding is performed on the entire circumference of peripheral edge 13a of sealing plate 13.

[0037] The main welding step S07 is completed when the second step S07b is completed. When the main welding step S07 is completed, the case 11 and the sealing plate 13 are welded together around the entire periphery 13a of the sealing plate 13. This seals the inside of the case 11. When the main welding step S07 is completed, various steps are performed as appropriate, such as a liquid 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 period of time, and an inspection step of inspecting the electricity storage device 10 for internal short circuits, etc., to manufacture the electricity storage device 10.

[0038] The manufacturing method for electricity storage device 10 of this embodiment includes a temporary welding step S05, a main clamping step S06, and a main welding step S07. In the temporary welding step S05, case 11 and sealing plate 13 are temporarily welded together at a plurality of predetermined positions on the boundary between case 11 and sealing plate 13. In the main clamping step S06, a portion of case 11 where the intervals between temporary welds W1 to W16 are longer than a predetermined length are clamped. In the main welding step S07, case 11 and sealing plate 13 are laser-welded together along a pair of side surfaces of case 11 around the entire periphery of peripheral edge 13a of sealing plate 13, with opening 11d clamped.

[0039] According to this manufacturing method, the spacing between the temporary welds W1 to W16 is relatively long, and main welding is performed in a state where only the areas where laser beam leakage is likely to occur are clamped. This allows the areas where laser beam leakage is likely to occur to be sufficiently clamped even with a smaller force than when the entire wide surface 11c of the case 11 is clamped, as in the configuration shown in Fig. 6. This makes it possible to efficiently prevent laser beam leakage.

[0040] As described above, according to the inventors' findings, gaps tend to widen during final welding in areas where the spacing between pre-welded joints W1 is greater than 40 mm. According to the manufacturing method of this embodiment, in final clamping step S06, the areas of the boundary between case 11 and sealing plate 13 where the spacing between pre-welded joints W1 to W16 on case 11 is greater than 40 mm are clamped. This makes it possible to efficiently prevent laser leakage.

[0041] According to this embodiment, electrode terminals 17, 18 are provided on sealing plate 13 prepared in sealing plate preparation step S02. In pre-welding step S05, predetermined positions near electrode terminals 17, 18 are pre-welded at the boundary between case 11 and sealing plate 13. This allows final welding to be performed with the areas near electrode terminals 17, 18 fixed, and therefore the positions of electrode terminals 17, 18 are less likely to vary after final welding.

[0042] According to this embodiment, the sealing plate 13 prepared in the sealing plate preparation step S02 has a gas release valve 14. In the pre-welding step S05, a predetermined position near the gas release valve 14 in the boundary between the case 11 and the sealing plate 13 is pre-welded. This allows main welding to be performed with the area near the gas release valve 14 fixed, making it less likely that the position of the gas release valve 14 will vary after main welding.

[0043] According to this embodiment, the method for manufacturing electricity storage device 10 includes a temporary clamping step S04 in which a plurality of predetermined positions of the boundary between case 11 and sealing plate 13 are clamped. In a temporary welding step S05, case 11 and sealing plate 13 are temporarily welded together in a state in which a plurality of predetermined positions of the boundary between case 11 and sealing plate 13 are clamped. This allows the temporary welding to be performed appropriately.

[0044] As described above, according to the inventors' findings, as the main welding step S07 progresses, the gap between the case 11 and the sealing plate 13 widens, making laser leakage more likely to occur. However, according to the present embodiment, in the main welding step S07, as the laser welding progresses, the force clamping the portion of the case 11 where the intervals between the temporary welds W1 to W16 are longer than a predetermined length is increased. Specifically, the main welding step S07 includes a first step S07a and a second step S07b. In the first step S07a, the case 11 and the sealing plate 13 are laser-welded together while the case 11 is clamped with a predetermined force. In the second step S07b, the case 11 and the sealing plate 13 are laser-welded together while the case 11 is clamped with a force greater than the predetermined force. This prevents the gap from widening even in the latter half of the main welding step S07, when the gap between the case 11 and the sealing plate 13 is likely to widen, thereby efficiently preventing laser leakage.

[0045] According to this embodiment, the sealing plate 13 that is pre-welded to the case 11 in the pre-welding step S05 has multiple portions along the edge of the opening 11d of the case 11 where the spacing between the pre-welded parts W1 to W16 is longer than 40 mm. In the final clamping step S06, a final clamping jig 50 is used that has portions that intermittently press against the portions of the case 11 where the spacing between the pre-welded parts W1 to W16 is longer than 40 mm. This makes it possible to prevent laser leakage even when there are multiple portions where the spacing between the pre-welded parts W1 to W16 is longer than 40 mm.

[0046] As described above, according to the findings of the inventors of the present application, laser leakage is particularly likely to occur when manufacturing a relatively large electricity storage device 10 in which the width of the case 11 is 30 cm or more. This is because a relatively large gap is likely to occur between the case 11 and the sealing plate 13 in a relatively large electricity storage device 10, and the gap between the case 11 and the sealing plate 13 is likely to widen in the main welding step S07. However, according to the manufacturing method of this embodiment, the portion where the gap between the case 11 and the sealing plate 13 is likely to widen is efficiently clamped in the main welding step S07, so laser leakage can be efficiently prevented. Therefore, the manufacturing method of this embodiment can be used particularly effectively when manufacturing a relatively large electricity storage device 10.

[0047] In this specification, "the portions of the temporary welds W1 to W16 where the spacing is longer than a predetermined length are clamped" means that the effect of preventing the gap between the case 11 and the sealing plate 13 from widening during the final welding step S07 is achieved, and the embodiment of the final clamping step S06 is not limited to the above. For example, in the embodiment shown in Fig. 8, the entire portions of the temporary welds W1 to W16 where the spacing is longer than a predetermined length are clamped. However, in the final clamping step S06, the portions of the temporary welds W1 to W16 where the spacing is longer than a predetermined length may be partially clamped.

[0048] 9 and 10 are diagrams illustrating the final clamping step S06 and the final welding step S07 according to another embodiment. In the embodiment shown in FIGS. 9 and 10, in the final clamping step S06, only a portion of the portion where the spacing between the pre-welded portions W1 to W16 is longer than a predetermined length is clamped. Specifically, in the embodiment shown in FIG. 9, the pressing portion 51 is configured to press only against the center of the portion where the spacing between the pre-welded portions W1 to W16 is 80 mm. Specifically, in the embodiment shown in FIG. 10, the pressing portion 51 is configured to press intermittently against one portion where the spacing between the pre-welded portions W1 to W16 is 80 mm.

[0049] In the above embodiment, the force clamping the case 11 is increased once in the main welding step S07. However, the force clamping the case 11 may be increased in stages in two or more steps in the main welding step S07. For example, if the force clamping the case 11 is increased three times in the main welding step S07, the force clamping the case 11 may be increased as one-fourth of the entire circumference of the peripheral edge portion 13a of the sealing plate 13 is welded. Furthermore, in the main welding step S07, the force clamping the case 11 may be increased continuously as the laser welding progresses.

[0050] 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.

[0051] Section 1: providing a rectangular case having a rectangular 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 pre-welding step of pre-welding the case and the sealing plate at a plurality of predetermined positions in a boundary portion between the case and the sealing plate; a main clamping step of clamping the opening along a pair of side surfaces of the case; a main welding process of laser welding the case and the sealing plate along a pair of side surfaces of the case along the entire periphery of the sealing plate with the opening clamped, In the main clamping step, The method for manufacturing an electricity storage device includes clamping a portion of the case where the interval between the pre-welded portions formed by the pre-welding is longer than a predetermined length.

[0052] Section 2: the sealing plate prepared in the step of preparing the sealing plate is provided with an electrode terminal; In the temporary welding step, Item 2. The method for manufacturing an electricity storage device according to item 1, wherein the boundary between the case and the sealing plate is pre-welded at a predetermined position near the electrode terminal.

[0053] Section 3: the sealing plate prepared in the step of preparing the sealing plate has a gas exhaust valve for exhausting gas inside the case, In the temporary welding step, Item 3. The method for manufacturing an electricity storage device according to item 1 or 2, wherein the boundary between the case and the sealing plate is pre-welded at a predetermined position near the gas release valve.

[0054] Section 4: The method further includes a temporary clamping step of clamping the predetermined positions of the boundary portion between the case and the sealing plate, In the temporary welding step, Item 4. The method for manufacturing an electricity storage device according to any one of items 1 to 3, wherein the case and the sealing plate are pre-welded together in a state where the predetermined positions of the boundary portion between the case and the sealing plate are clamped.

[0055] Section 5: In the main welding process, Item 5. The method for manufacturing an electricity storage device according to any one of items 1 to 4, wherein as laser welding progresses, a force for clamping a portion of the case where the spacing between the temporary welds is longer than the predetermined length is increased.

[0056] Item 6: The main welding process includes: a first step of laser welding the case and the sealing plate together along a pair of side surfaces of the case, in a state where a portion of the case where the interval between the temporary welds is longer than the predetermined length is clamped with a predetermined force; Item 6. The method for manufacturing an electricity storage device according to any one of items 1 to 5, further comprising: a second step, after the first step, of laser-welding the case and the sealing plate together along a pair of side surfaces of the case, in a state where portions of the case where the spacing between the temporary welds is longer than the predetermined length are clamped with a force greater than the predetermined force.

[0057] Section 7: In the main clamping step, 7. The method for manufacturing an electricity storage device according to any one of items 1 to 6, wherein a portion of the boundary between the case and the sealing plate where the spacing between the temporary welds on the case is longer than 40 mm is clamped.

[0058] Section 8: The sealing plate pre-welded to the case in the pre-welding step has a plurality of portions along an edge of the opening of the case, the intervals between the pre-welded portions being longer than 40 mm, In the main clamping step, Item 8. The method for manufacturing an electricity storage device according to any one of items 1 to 7, wherein the clamping jig has a portion that intermittently presses against a portion of the case where the spacing between the temporary welds is longer than 40 mm.

[0059] Section 9: Item 9. The method for manufacturing an electricity storage device according to any one of items 1 to 8, wherein the case prepared in the case preparation step has a width of 30 cm or more. [Explanation of symbols]

[0060] 10. Energy storage devices 11 cases 11d aperture 13 Sealing plate 13a Periphery of sealing plate 14 Gas exhaust valve 17, 18 Electrode terminal 50 clamping fixtures S01 Case preparation process S02 Sealing plate preparation process S03 Assembly process S04 Temporary clamping process S05 Temporary welding process S06 Main clamping process S07 Main welding process S07a 1st process S07b 2nd process W1~W16 Temporary welds

Claims

1. providing a rectangular case having a rectangular 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 pre-welding step of pre-welding the case and the sealing plate at a plurality of predetermined positions in a boundary portion between the case and the sealing plate; a main clamping step of clamping the opening along a pair of side surfaces of the case; a main welding process of laser welding the case and the sealing plate along a pair of side surfaces of the case along the entire periphery of the sealing plate with the opening clamped, In the main clamping step, The method for manufacturing an electricity storage device includes clamping a portion of the case where the interval between the pre-welded portions formed by the pre-welding is longer than a predetermined length.

2. the sealing plate prepared in the step of preparing the sealing plate is provided with an electrode terminal; In the temporary welding step, The method for manufacturing an electricity storage device according to claim 1 , wherein the boundary between the case and the sealing plate is pre-welded at a predetermined position near the electrode terminal.

3. the sealing plate prepared in the step of preparing the sealing plate has a gas exhaust valve for exhausting gas inside the case, In the temporary welding step, The method for manufacturing an electricity storage device according to claim 1 , wherein the boundary between the case and the sealing plate is pre-welded at a predetermined position near the gas release valve.

4. The method further includes a temporary clamping step of clamping the predetermined positions of the boundary portion between the case and the sealing plate, In the temporary welding step, The method for manufacturing an electricity storage device according to claim 1 , wherein the case and the sealing plate are pre-welded together in a state where the predetermined positions of the boundary portion between the case and the sealing plate are clamped.

5. In the main welding process, The method for manufacturing an electricity storage device according to claim 1 , wherein a force for clamping a portion of the case where the interval between the temporary welds is longer than the predetermined length is increased as the laser welding progresses.

6. The main welding process includes: a first step of laser welding the case and the sealing plate together along a pair of side surfaces of the case, in a state where a portion of the case where the interval between the temporary welds is longer than the predetermined length is clamped with a predetermined force; 2. The method for manufacturing an electricity storage device according to claim 1, further comprising: a second step, after the first step, of laser welding the case and the sealing plate together along a pair of side surfaces of the case, in a state in which portions of the case where the spacing between the temporary welds is longer than the predetermined length are clamped with a force greater than the predetermined force.

7. In the main clamping step, The method for manufacturing an electricity storage device according to claim 1 , wherein the clamping is performed at a portion of the boundary between the case and the sealing plate where the spacing between the temporary welds on the case is greater than 40 mm.

8. The sealing plate pre-welded to the case in the pre-welding step has a plurality of portions along an edge of the opening of the case, the intervals between the pre-welded portions being longer than 40 mm, In the main clamping step, The method for manufacturing an electricity storage device according to claim 1 , wherein the clamping jig has a portion that intermittently presses against a portion of the case where the interval between the temporary welds is longer than 40 mm.

9. 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.

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