Method for manufacturing energy storage devices

Abstract

This effectively prevents laser glitches during welding. [Solution] The method for manufacturing an energy storage device disclosed herein includes a case preparation step S1, a sealing plate preparation step S2 for preparing a sealing plate, an electrode preparation step S3 for preparing an electrode body, an assembly step S4, a tack welding step S5 for tack welding the case and the sealing plate, and a final welding step S6 for welding the case and the sealing plate all around. The case prepared in the case preparation step S1 is curved such that a pair of wide surfaces are recessed toward the inside of the opening. In the can opening step S42 of the assembly step S4, the rear edge and front edge of the opening are opened toward the outside of the case. Thereafter, in the housing step S43, the electrode body is housed inside the case from the opening, and the sealing plate is attached to the opening.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a power storage device.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2013-187087 discloses a can sealing welding method for a sealed battery in which a lid is joined to an opening of a battery case by welding. A step for fitting the lid is formed on a part of the inner surface of the opening of the battery case. In this welding method, laser welding is started from a joint portion where the inner surface on which the step is formed and the lid are joined. According to Japanese Patent Application Laid-Open No. 2013-187087, by using such a welding method, laser leakage can be prevented. Laser leakage is a phenomenon in which the laser passes through the joint portion between the battery case and the lid and enters the inside of the battery case.

[0003] Furthermore, Japanese Patent Application Laid-Open No. 2013-187087 discloses a can sealing welding method for a sealed battery in which welding is performed by dividing the sealed battery into a front region and a rear region. In this welding method, with a pressing jig, laser welding is started in a state where the lid located in the front region of the sealed battery is pressed downward from above against the battery case, and the battery case and the lid in the rear region are welded. Next, the pressing 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 No. 2013-187087, by using such a welding method, it is possible to prevent the lid from lifting up from the battery case during welding.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventor of this invention aims to efficiently prevent laser glitches. [Means for solving the problem]

[0006] The method for manufacturing an energy storage device disclosed herein includes the steps of: preparing a rectangular case having a rectangular opening on one side; preparing a sealing plate to seal the opening; preparing a flat electrode body to be housed in the case; an assembly step of housing the electrode body into the case through the opening and attaching the sealing plate to the opening of the case; a tack welding step of irradiating a predetermined portion of the boundary between the case and the sealing plate with laser light from the outer surface side of the sealing plate to tack weld the case and the sealing plate; and a final welding step of operating laser light along the boundary between the case and the peripheral edge of the sealing plate to weld the case and the sealing plate all around. The case prepared in the step of preparing the case has a curved shape in which the central part of the edge of the opening along a pair of opposing side walls is concave toward the inside of the opening. In the assembly step, the electrode body is housed with the edges along the pair of opposing side walls open toward the outside of the case. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic perspective view showing the energy storage device 10. [Figure 2] Figure 2 is an exploded perspective view of the energy storage device 10. [Figure 3] Figure 3 is a flowchart showing an example of a manufacturing method for the energy storage device 10. [Figure 4] Figure 4 is a schematic enlarged view showing the boundary between case 11 and sealing plate 13 in a reference example. [Figure 5] Figure 5 is a plan view of case 11 as it was prepared in case preparation step S1. [Figure 6] Figure 6 is a schematic diagram showing the formation of the case 11 prepared in the case preparation process S1. [Figure 7]Figure 7 is a schematic diagram before opening the trailing edge 11d1 and leading edge 11d2. [Figure 8] Figure 8 is a schematic diagram showing the case when the trailing edge 11d1 and leading edge 11d2 are opened. [Figure 9] Figure 9 is a schematic diagram showing the electrode body 20 housed inside the case 11 and the sealing plate 13 attached to the opening 11d. [Figure 10] Figure 10 is a plan view of the case 11 and sealing plate 13 when the suction pad 61 has been removed. [Figure 11] Figure 11 is a schematic diagram illustrating the temporary welding process S5. [Figure 12] Figure 12 is a schematic diagram illustrating the welding process S6. [Modes for carrying out the invention]

[0008] Hereinafter, an embodiment of the technology disclosed herein will be described with reference to the drawings. The embodiment described herein is, of course, not intended to particularly limit the present invention. Each drawing is schematic and does not necessarily reflect the actual object. Furthermore, components and parts that perform the same function are appropriately denoted by the same reference numeral, and redundant descriptions are omitted as appropriate. Also, in this specification, notations such as "X~Y" indicating a numerical range mean "X or more and Y or less" unless otherwise specified.

[0009] In this specification, "energy storage device" refers to a device capable of charging and discharging. Energy 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 refers to a battery in general that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes. Energy storage devices may use either an electrolyte or a solid electrolyte. For example, a secondary battery may be a secondary battery using a so-called liquid electrolyte, or a so-called all-solid-state battery using a solid electrolyte. Energy storage devices also include capacitors such as electric double-layer capacitors and lithium-ion capacitors.

[0010] Figure 1 is a schematic perspective view of the energy storage device 10. Figure 2 is an exploded perspective view of the energy storage device 10. In this embodiment, the energy storage device 10 is a lithium-ion secondary battery. In the following description, the symbols F, Rr, L, R, U, and D in the drawings represent front, back, left, right, top, and bottom, respectively, and the symbols X, Y, and Z in the drawings represent the thickness direction of the energy storage device 10, the width direction perpendicular to the thickness direction, and the up and down direction perpendicular to the width direction and thickness direction, respectively. As shown in Figures 1 and 2, the energy storage device 10 comprises a case 11, a sealing plate 13, and an electrode body 20.

[0011] Case 11 is a rectangular case having a rectangular opening on one side. In this embodiment, case 11 is formed in a substantially rectangular parallelepiped shape. As shown in Figure 2, case 11 has a rectangular opening 11d at the top. When viewed from above, case 11 has a short side extending in the thickness direction X and a long side extending in the width direction Y. Case 11 has a bottom surface 11a, a pair of narrow surfaces 11b, and a pair of wide surfaces 11c. The bottom surface 11a faces the opening 11d. The bottom surface 11a is formed in a rectangular shape with a short side and a long side. The pair of narrow surfaces 11b face the width direction Y. The pair of narrow surfaces 11b extend upward from both ends of the bottom surface 11a in the width direction Y (i.e., the short side of the bottom surface 11a). The pair of wide surfaces 11c face the thickness direction X. The pair of wide surfaces 11c extend upward from both ends of the bottom surface 11a in the thickness direction X (i.e., the long sides of the bottom surface 11a). The case 11 is formed of, for example, aluminum or an aluminum alloy mainly composed of aluminum, in order to ensure both lightness and the required rigidity.

[0012] As shown in Figure 2, the opening 11d is enclosed by a rear edge 11d1, a front edge 11d2, a left edge 11d3, and a right edge 11d4. The rear edge 11d1 and the front edge 11d2 extend in the Y direction. The rear edge 11d1 is located behind the front edge 11d2. The left edge 11d3 and the right edge 11d4 extend in the X direction. The left edge 11d3 is located to the left of the right edge 11d4. The left edge 11d3 connects the left end of the rear edge 11d1 to the left end of the front edge 11d2. The right edge 11d4 connects the right end of the rear edge 11d1 to the right end of the front edge 11d2. In the following explanation, the rear edge 11d1, front edge 11d2, left edge 11d3, and right edge 11d4 may be collectively referred to simply as the "edge of the opening 11d."

[0013] The sealing plate 13 is a member that seals the opening 11d of the case 11. The sealing plate 13 is attached to the opening 11d along the edge of the opening 11d of the case 11. The sealing plate 13 is a flat plate formed in a rectangular shape in a plan view. Although details will be described later, the opening 11d is sealed by welding the peripheral portion 13a of the sealing plate 13 along the edge of the opening 11d. The sealing plate 13 may be formed of the same material as the case 11. The sealing plate 13 may be formed of, for example, aluminum or an aluminum alloy mainly composed of aluminum.

[0014] The sealing plate 13 has a gas discharge valve 14 for discharging the gas inside the case 11. The gas discharge valve 14 is disposed at the center in the width direction Y (i.e., the direction orthogonal to the thickness direction X) of the sealing plate 13. The gas discharge 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 becomes equal to or higher than the predetermined value, the gas inside the case 11 is discharged to the outside of the case 11 by the breakage of the gas discharge valve 14.

[0015] A pair of electrode terminals 17, 18 are provided on the sealing plate 13. The pair of electrode terminals 17, 18 are disposed at both ends in the width direction Y of the sealing plate 13. The method of 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 caulking. Note that 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 has an external terminal 18a and an internal terminal 18b.

[0016] The electrode body 20 has a flat shape and is housed inside the case 11. The electrode body 20 has a positive electrode and a negative electrode. The electrode body 20 is, for example, a wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated via a strip-shaped separator and wound in the longitudinal direction around a winding axis. However, the configuration of the electrode body 20 is not particularly limited. Various conventionally known electrode bodies can be used for the electrode body 20. The electrode body 20 may be, for example, a laminated electrode body in which a rectangular positive electrode and a rectangular negative electrode are stacked in an insulated state. Here, the electrode body 20 is housed in the case 11 with the winding axis substantially parallel to the width direction Y. In FIG. 1, the electrode body 20 is housed inside the case 11. Note that the electrode body 20 may be housed inside the case 11 with the winding axis substantially parallel to the vertical direction Z. The number of electrode bodies 20 housed in the case 11 may be one, or two or more (plural).

[0017] The positive electrode of the electrode body 20 is connected to the internal terminal 17b of the electrode terminal 17 shown in FIG. 2. 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.

[0018] Although illustration is omitted, the positive electrode has a positive electrode current collector and a positive electrode composite layer fixed on the positive electrode current collector. The positive electrode current collector is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode current collector is made of aluminum. The positive electrode composite layer typically contains a positive electrode active material (for example, a lithium transition metal composite oxide) capable of reversibly occluding and releasing charge carriers and a binder (for example, polyvinylidene fluoride (PVdF)).

[0019] Although not shown in the diagram, the negative electrode comprises a negative electrode current collector and a negative electrode composite layer fixed on the negative electrode current collector. The negative electrode current collector is made of a conductive metal such as copper, copper alloy, nickel, or stainless steel. In this case, the negative electrode current collector is made of copper. The negative electrode composite layer typically contains a negative electrode active material (e.g., a carbon material such as graphite) capable of reversibly intercepting and releasing charge carriers, and a binder (e.g., styrene-butadiene rubber (SBR) or carboxymethylcellulose (CMC)).

[0020] The electrode body 20 is impregnated with an electrolyte (not shown). The electrolyte is, in this case, a non-aqueous liquid electrolyte (non-aqueous electrolyte) containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, for example, carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). The supporting salt is, for example, a fluorine-containing lithium salt such as LiPF6. However, the electrolyte may be in solid form (solid electrolyte) and integrated with the electrode body 20. Also, any excess electrolyte that cannot be impregnated into the electrode body 20 may be stored inside the case 11.

[0021] Next, a method for manufacturing the energy storage device 10 will be described. Figure 3 is a flowchart showing an example of a method for manufacturing the energy storage device 10. The method for manufacturing the energy storage device 10 includes a case preparation step S1, a sealing plate preparation step S2, an electrode preparation step S3, an assembly step S4, a tack welding step S5, and a final welding step S6. The method for manufacturing the energy storage device 10 may include other steps, but their explanation will be omitted here. In the method for manufacturing the energy storage device 10 shown in Figure 3, the case 11 (see Figure 2) and the peripheral edge 13a of the sealing plate 13 (see Figure 2) are laser-welded.

[0022] Incidentally, when manufacturing a relatively large energy storage device 10, such as one with a case width of 30 cm or more, the opening 11d of the sealing plate 13 and the case 11 become larger. Also, to facilitate the installation of the sealing plate 13, the opening 11d of the case 11 has a shape in which the central part in the width direction Y bulges outward. Furthermore, in a relatively large energy storage device 10, the dimensional tolerances of the sealing plate 13 and the opening of the case 11 may also be set to be larger. As a result, for example, when the sealing plate 13 is installed in the case 11, a larger gap may occur between the sealing plate 13 and the opening 11d of the case 11 than in a small energy storage device, such as in the middle part of the sealing plate 13 in the width direction Y.

[0023] Figure 4 is a schematic enlarged view showing the boundary between case 11 and sealing plate 13. In Figure 4, case 11 and sealing plate 13 are shown as viewed from above, and tack welds Wa and Wb are formed between the sealing plate 13 and the edge of the opening of case 11. Tack welds Wa and Wb are areas where case 11 and the peripheral edge 13a of sealing plate 13 are locally welded to position case 11 and sealing plate 13 before full-circumferential welding of case 11 and sealing plate 13a. The symbol WT1 in Figure 4 indicates the welding trajectory of the laser welding in the main welding. In large energy storage devices 10, the distance between the tack welds Wa and Wb may also be wider. In the main welding, when welding case 11 and sealing plate 13, the laser is scanned along the welding trajectory to perform the welding. At this time, the temperature of case 11 gradually rises. As the temperature of case 11 rises, the opening of case 11 expands. If the opening of case 11 expands, the edge of the opening 11d of case 11 (the trailing edge 11d1 in Figure 4) may deform outward significantly, as schematically shown in Figure 4. As a result, the gap between the edge of the opening 11d of case 11 and the sealing plate 13 may widen locally.

[0024] According to the inventors of this application, the longer the distance between the temporary weld Wa and the temporary weld Wb, the more likely it is that the gap between the edge of the opening 11d of the case 11 and the sealing plate 13 will widen due to the heat acting on the case 11 during the main welding process, as described above. Specifically, the inventors of this application have found that the gap between the case 11 and the sealing plate 13 is particularly likely to widen in areas where the distance between the temporary weld Wa and the temporary weld Wb is longer than 40 mm.

[0025] If the gap between case 11 and sealing plate 13 is large, when laser welding case 11 and sealing plate 13, the molten pool may drip into the interior of case 11 through the gap. When the molten pool drips, laser leakage may occur at that location. Laser leakage is the phenomenon in which the laser light penetrates the gap between case 11 and sealing plate 13 and enters the interior of case 11. Laser leakage can lead to welding defects and reduce the strength of the joint. The inventors of this application have found that laser leakage is relatively likely to occur when the gap between the edge of the opening 11d of case 11 and the sealing plate 13 becomes approximately 0.1 mm or more after the case 11 has expanded.

[0026] The case preparation step S1 shown in Figure 3 is a step of preparing a rectangular case 11 having a rectangular opening 11d on one side. Figure 5 is a plan view of the case 11 prepared in the case preparation step S1 (see Figure 3). In the case 11 prepared in the case preparation step S1, the central parts of the rear edge 11d1 and front edge 11d2 along a pair of opposing wide surfaces 11c of the edge of the opening 11d are curved so as to be concave toward the inside of the opening 11d. That is, the rear edge 11d1 and front edge 11d2 are curved toward the inside of the thickness direction X as they are toward the center in the width direction Y. The length in the width direction Y of the case 11 prepared in the case preparation step S1 (see Figure 3) may be, for example, 30 cm or more. By preparing such a relatively large case 11, a relatively large electrode body 20 can be housed inside the case 11, so that a high-capacity energy storage device can be obtained.

[0027] Figure 6 is a schematic diagram of the formation of the case 11 prepared in the case preparation process S1 (see Figure 3). In Figure 6, the case 11 is formed in a substantially rectangular shape in plan view. The case 11 is formed, for example, by bending a single rectangular flat plate. As shown in Figure 6, the case 11 is formed into the shape shown in Figure 5 by, for example, inserting a spacer 200 inside the case 11 and roll-pressing a pair of wide surfaces 11c with a pair of rolling rolls 300. The spacer 200 is formed so that it can be inserted into the inside of the case 11 through an opening 11d. The length of the spacer 200 in the width direction Y is substantially the same as the length of the opening 11d in the width direction Y. The central part of the spacer 200 in the width direction Y is curved so as to be concave toward the inside of the opening 11d. That is, the length of the spacer 200 in the thickness direction X is substantially the same as the opening 11d at both ends in the width direction Y, and becomes shorter than the opening 11d toward the center in the width direction Y. The spacer 200 is formed from, for example, a metal material with relatively high rigidity.

[0028] The rolling roll 300 is, for example, a metal roll. The rolling roll 300 rotates while applying press pressure to the trailing edge 11d1 and the leading edge 11d2 to such an extent that the trailing edge 11d1 and the leading edge 11d2 plastically deform inward in the thickness direction X when the rolling roll presses them. The rolling roll 300 is connected to, for example, a pneumatic cylinder (not shown) or a hydraulic cylinder (not shown). The press pressure applied by the rolling roll 300 is controlled by the pneumatic cylinder or hydraulic cylinder. The rolling roll 300 is also connected to a drive device (not shown) such as a motor, and is configured to be rotatable by the drive device. When the trailing edge 11d1 and the leading edge 11d2 are roll-pressed by the rolling roll 300, a case 11 is formed in which the central parts of the trailing edge 11d1 and the leading edge 11d2 are curved so as to be recessed inward into the opening 11d, as shown in Figure 5.

[0029] Case 11 is formed such that, for example, when the width Y of case 11 is 30 cm, the central portions of the rear edge 11d1 and the front edge 11d2 are recessed by approximately 4 mm each toward the inside of the opening 11d compared to the ends of the rear edge 11d1 and the front edge 11d2 toward the inside of the opening 11d. However, the amount of recession of case 11 is not limited to this. Furthermore, the method of curving the rear edge 11d1 and the front edge 11d2 is not limited to this. Note that case 11 does not necessarily have to be formed in a substantially rectangular shape and then have the rear edge 11d1 and the front edge 11d2 curved. For example, case 11 in the shape shown in Figure 5 may be formed using a pre-curved flat plate.

[0030] The sealing plate preparation step S2 shown in Figure 3 is a step of preparing a sealing plate 13 that seals the opening 11d of the case 11. The method of preparing the sealing plate 13 in the sealing plate preparation step S2 is not particularly limited. The sealing plate 13 can be prepared, for example, by machining a rectangular flat plate, such as by drilling holes, and then attaching electrode terminals 17, 18 (see Figure 2). Alternatively, the sealing plate 13 may be prepared by integrally molding it together with the electrode terminals 17, 18. The sealing plate preparation step S2 may be performed before or after the case preparation step S1. Alternatively, the sealing plate preparation step S2 may be performed simultaneously with the case preparation step S1.

[0031] The electrode preparation step S3 is a step in which a flat electrode body 20 (see Figure 2) to be housed in the case 11 is prepared. The method of preparing the electrode body 20 in the electrode preparation step S3 is not particularly limited. As described above, for example, the electrode body 20 is manufactured by stacking a positive electrode, a negative electrode, and a separator and winding them together. The electrode preparation step S3 may be performed before or after the case preparation step S1 and the sealing plate preparation step S2. Alternatively, the electrode preparation step S3 may be performed simultaneously with the case preparation step S1 and / or the sealing plate preparation step S2.

[0032] Assembly step S4 is the process of housing the electrode body 20 into the case 11 through the opening 11d and attaching the sealing plate 13 to the opening 11d of the case 11. In assembly step S4, the electrode body 20 is housed with its trailing edge 11d1 and leading edge 11d2 along a pair of wide surfaces 11c open outwards from the case 11. As shown in Figure 3, assembly step S4 includes a connection step S41, a can opening step S42, and a housing step S43.

[0033] In connection step S41, first, the electrode body 20 is connected to the electrode terminals 17 and 18, as shown in Figure 2. More specifically, the positive electrode of the electrode body 20 is connected to the internal terminal 17b of electrode terminal 17, and the negative electrode of the electrode body 20 is connected to the internal terminal 18b of electrode terminal 18. The electrode terminals 17 and 18 are connected to the electrode body 20 by welding, for example, by laser welding. However, the method of connecting the electrode terminals 17 and 18 is not particularly limited.

[0034] The can opening process S42 is a process of opening the trailing edge 11d1 and the leading edge 11d2 along a pair of wide surfaces 11c toward the outside of the case 11. In this process, the can opening process S42 involves attaching a pair of suction pads 61 (see Figure 7) to the pair of wide surfaces 11c from the outside of the pair of wide surfaces 11c in the thickness direction X, and moving the pair of suction pads 61 toward the outside of the case 11, thereby opening the trailing edge 11d1 and the leading edge 11d2 along the pair of wide surfaces 11c toward the outside of the case 11. Figure 7 is a schematic diagram before opening the trailing edge 11d1 and the leading edge 11d2. In the can opening process S42 (see Figure 3), first, suction jigs 60 are attached to each of the pair of wide surfaces 11c. Two suction jigs 60 are attached to one wide surface 11c. Two suction jigs 60 are attached side by side in the width direction Y. Furthermore, the suction fixtures 60 are mounted in pairs so as to be symmetrical with respect to the opening 11d in the thickness direction X. In other words, four suction fixtures 60 are mounted here. The position of the suction fixtures 60 in the vertical direction Z is not particularly limited, but it is preferable that they be mounted on the upper part of the pair of wide surfaces 11c in order to open the trailing edge 11d1 and the leading edge 11d2 (see Figure 9). However, the arrangement and number of suction fixtures 60 are not particularly limited.

[0035] The suction jig 60 comprises a suction pad 61 and a drive device 62. The suction pad 61 is the part that adheres to a pair of wide surfaces 11c. The suction surface of the suction pad 61 is formed of nitrile rubber, silicone rubber, or the like. The suction jig 60 is configured to suck air between the suction pad 61 and the wide surfaces 11c, and by performing this suction, the wide surfaces 11c can be adsorbed. The drive device 62 is a device that moves the suction pad 61 in the thickness direction X. The drive device 62 may be, for example, an air cylinder.

[0036] Figure 8 is a schematic diagram of the opening of the trailing edge 11d1 and the leading edge 11d2. As shown in Figure 8, after the suction pads 61 are attached to the pair of wide surfaces 11c, the drive unit 62 moves the suction pads 61 toward the outside of the case 11. More specifically, the drive unit 62 of the suction fixture 60 attached to the front wide surface 11c of the pair of wide surfaces 11c moves the suction pad 61 toward the front, and the drive unit 62 of the suction fixture 60 attached to the rear wide surface 11c of the pair of wide surfaces 11c moves the suction pad 61 toward the rear. As a result, the trailing edge 11d1 and the leading edge 11d2 along the pair of wide surfaces 11c are opened toward the outside of the case 11. Here, the amount of movement of the drive unit 62 and the suction of the suction pads 61 are controlled so as not to cause plastic deformation in the direction that the trailing edge 11d1 and the leading edge 11d2 open toward the outside of the case 11.

[0037] The housing step S43 shown in Figure 3 is the process of housing the electrode body 20 inside the case 11 and attaching the sealing plate 13 to the opening 11d. Figure 9 is a schematic diagram of when the electrode body 20 is housing inside the case 11 and the sealing plate 13 is attached to the opening 11d. In the housing step S43 (see Figure 3), as shown in Figure 9, the electrode body 20 is moved from the opening 11d towards the inside of the case 11 with the rear edge 11d1 and front edge 11d2 open to the outside of the case 11. At this time, the sealing plate 13 attached to the electrode body 20 is attached to the case 11. The sealing plate 13 is positioned so that the upper surface of the sealing plate 13 is flush with the rear edge 11d1, front edge 11d2, left edge 11d3 (see Figure 2), and right edge 11d4 (see Figure 2). In other words, the sealing plate 13 is mounted so that it is at the upper end of the energy storage device 10 (see Figure 2). Note that, for example, a step (not shown) may be provided inside the case 11 to determine the vertical position Z of the sealing plate 13. In such a case, the sealing plate 13 is mounted by placing it on the step. Once the sealing plate 13 is mounted, the electrode body 20 connected to the sealing plate 13 is housed inside the case 11.

[0038] After the sealing plate 13 is attached to the opening 11d and the electrode body 20 is housed inside the case 11, the suction by the suction jig 60 is released. For example, the suction pad 61 is removed by introducing air between the suction pad 61 and the wide surface 11c, and the suction by the suction jig 60 is released. Figure 10 is a plan view of the case 11 and sealing plate 13 when the suction pad 61 has been removed. As described above, the case 11 prepared in the case preparation step S1 (see Figure 3) is curved such that the pair of wide surfaces 11c are recessed toward the inside of the opening 11d, as shown in Figure 5. Therefore, when the suction of the suction jig 60 (see Figure 10) is released in the housing step S43 (see Figure 3), the elasticity of the case 11 causes the pair of wide surfaces 11c to return to their recessed shape toward the inside of the opening 11d. At this time, since the sealing plate 13 is fitted into the opening 11d, the pair of wide surfaces 11c take on a shape that conforms to the outer shape of the sealing plate 13, as shown in Figure 10. At this time, the peripheral edge 13a of the sealing plate 13 is pressed toward the inside of the opening 11d by the rear edge 11d1 and the front edge 11d2. At this time, the pair of wide surfaces 11c maintain a substantially straight shape extending in the width direction Y.

[0039] The tack welding process S5 shown in Figure 3 is a process in which a laser beam is irradiated from the outer surface side of the sealing plate 13 to a predetermined portion of the boundary between the case 11 and the sealing plate 13, thereby tack welding the case 11 and the sealing plate 13. Figure 11 is a schematic diagram illustrating the tack welding process S5. In the tack welding process S5, the case 11 and the sealing plate 13 are tack welded with the sealing plate 13 installed in the opening 11d. Tack welding is performed to position the sealing plate 13 relative to the opening 11d. In the tack welding process S5, the case 11 and the sealing plate 13 are welded intermittently. In the tack welding process S5, the case 11 and the sealing plate 13 are tack welded at a plurality of predetermined positions on the boundary between the case 11 and the sealing plate 13. The symbols W1 to W16 in Figure 11 indicate the tack welded areas. The tack welds W1 to W16 are the parts where the case 11 and the sealing plate 13 are joined. In Figure 11, the tack welds W1 to W16 are shown in an exaggerated manner. Tack welding is performed, for example, with a laser beam diameter of 0.6 mm, a laser output of 3000 W, and a laser beam movement speed of 150 mm / s. However, the conditions for tack welding are not limited to these.

[0040] Here, as indicated by the symbols W1 to W4 in Figure 11, a predetermined position near the gas discharge valve 14 on the boundary between the case 11 and the sealing plate 13 is tack-welded. Also, as indicated by the symbols W5 to W16 in Figure 11, a predetermined position near the electrode terminals 17 and 18 on the boundary between the case 11 and the sealing plate 13 is tack-welded. However, the positions and number of tack-welded areas are not limited to the configuration shown in Figure 11, and can be appropriately changed according to the dimensions of the case 11 and the sealing plate 13. The welding equipment used in the tack-welding process S5 may be the same as or different from the equipment used in the main welding process S6 (see Figure 3) described later. Various conventionally known welding equipment may be used in the tack-welding process S5. Furthermore, the tack-welding process S5 may be performed with the boundary between the case 11 and the sealing plate 13 clamped.

[0041] In Figure 11, the symbol L1 indicates the spacing between temporary welds W1 and W2. In Figure 11, the symbol L2 indicates the spacing between temporary welds W1 and W6. In Figure 11, the symbol L3 indicates the spacing between temporary welds W5 and W6. In Figure 11, since temporary welds W1 to W16 are arranged symmetrically with respect to the X and Y directions, the spacing between temporary welds W3 and W4 is equal to the spacing L1 of temporary welds W1 and W2. The spacing between temporary welds W4 and W7, the spacing between temporary welds W2 and W9, and the spacing between temporary welds W3 and W12 are equal to the spacing L2 of temporary welds W1 and W6. The spacing between temporary welds W7 and W8, the spacing between temporary welds W9 and W10, and the spacing between temporary welds W11 and W12 are equal to the spacing L3 of temporary welds W5 and W6.

[0042] In Figure 11, the relative sizes of the spacing L1 between tack welds W1 and W2, L2 between tack welds W1 and W6, and L3 between tack welds W5 and W6 are L2 > L3 = L1. That is, in Figure 11, the spacing L1 between tack welds W1 and W2 is equal to the spacing L3 between tack welds W5 and W6. The spacing L2 between tack welds W1 and W6 is longer than the spacing L2 between tack welds W1 and W2 and the spacing L3 between tack welds W5 and W6. In this embodiment, L1 = 40 mm, L2 = 80 mm, and L3 = 40 mm. However, the lengths of the spacings L1, L2, and L3 are not limited to these values.

[0043] The welding process S6 shown in Figure 3 is a process in which the laser beam is manipulated along the boundary between the case 11 and the peripheral edge 13a of the sealing plate 13 to weld the case and the sealing plate 13 all around. In this welding process S6, the case 11 and the sealing plate 13 are welded while the case 11 is pressed against the electrode body 20 in the thickness direction X. Figure 12 is a schematic diagram illustrating this welding process S6. In Figure 12, the case 11 and the sealing plate 13 are shown as viewed from above. In this welding process S6, the edge of the opening 11d of the case 11 and the peripheral edge 13a of the sealing plate 13 are laser welded. The symbol WT2 in Figure 12 indicates a part of the welding trajectory in this welding process S6. Here, laser welding is performed in a clockwise direction in a plan view. However, the welding trajectory in this welding process S6 is not limited to this. The welding in welding process S6 is performed, for example, with a laser beam diameter of 0.8 to 1.0 mm, a laser output of 6000 W, and a laser beam movement speed of 300 mm / s. However, the welding conditions in welding process S6 are not limited to these.

[0044] As shown in Figure 12, in this embodiment, the case 11 is pressed in the thickness direction X by the clamping jig 50. The clamping jig 50 comprises a pressing part 51 and a drive device 52. The pressing part 51 is the part that is pressed against the case 11. In this embodiment, as shown in Figure 12, the pressing part 51 is formed so that it contacts a pair of wide surfaces 11c at four locations. Here, among the tack welds W1 to W16, the area where the distance between the tack welds W1 to W16 is relatively long (for example, between tack weld W2 and tack weld W9) is pressed. However, the shape of the pressing part 51 and the position where the case 11 is pressed are not particularly limited. The drive device 52 is a device that drives the pressing part 51. The type of drive device 52 is not particularly limited. The drive device 52 may be, for example, an air cylinder.

[0045] For example, when the width Y of case 11 is 30 cm, even if the opening 11d (see Figure 4) of case 11 expands during the main welding process S6 (see Figure 3), the gap between case 11 and sealing plate 13 (see Figure 4) was approximately 0.05 mm.

[0046] When the main welding process S6 (see Figure 3) is completed, the case 11 and the sealing plate 13 are welded together around the entire circumference of the peripheral edge 13a of the sealing plate 13. This seals the inside of the case 11. After the main welding process S6 is completed, an electrolyte injection process is performed to pour the electrolyte into the case 11, an aging process is performed to charge the energy storage device 10 and leave it for a predetermined time, and an inspection process is performed to check for internal short circuits in the energy storage device 10, etc., as appropriate, and the energy storage device 10 is manufactured.

[0047] As described above, according to the manufacturing method of the energy storage device 10 of this embodiment, the case 11 prepared in the case preparation step S1 has a curved shape in which the central parts of the rear edge 11d1 and the front edge 11d2 are recessed toward the inside of the opening 11d. Furthermore, in the can opening step S42 of the assembly step S4, the rear edge 11d1 and the front edge 11d2 along the pair of wide surfaces 11c are opened toward the outside of the case 11, and then in the housing step S43, the electrode body 20 is housed in the case 11 and the sealing plate 13 is attached to the case 11. At this time, due to the elasticity of the case 11, the rear edge 11d1 and the front edge 11d2 try to return to their recessed shape toward the inside of the opening 11d, so that the peripheral edge 13a of the sealing plate 13 is pressed toward the inside of the opening 11d by the rear edge 11d1 and the front edge 11d2. As a result, a gap is relatively unlikely to occur between the case 11 and the sealing plate 13. By performing welding in the tack welding process S5 and the main welding process S6 in this state, the molten pool is less likely to sag into the interior of the case 11. In other words, the occurrence of laser glitches during welding can be suppressed.

[0048] In the manufacturing method of the energy storage device 10 of this embodiment, the case 11 prepared in the case preparation step S1 has a bottom surface 11a, a pair of wide surfaces 11c, and a pair of narrow surfaces 11b. In the can opening step S42, the rear edge 11d1 and the front edge 11d2, which are edges along the pair of wide surfaces 11c, are opened outwards from the case 11. When there is a pair of wide surfaces 11c and a pair of narrow surfaces 11b as in this embodiment, the gap between tack welds is more likely to occur along the edges along the pair of wide surfaces 11c than along the pair of narrow surfaces 11b. Therefore, the gap between the case 11 and the sealing plate 13 is more likely to widen during welding along the pair of wide surfaces 11c compared with the pair of narrow surfaces 11b. In this embodiment, when the pair of wide surfaces 11c are shaped to be recessed toward the inside of the opening 11d, when the sealing plate 13 is attached to the case 11, the pair of wide surfaces 11c press the peripheral edge 13a of the sealing plate 13 toward the inside of the opening 11d. That is, in areas where there are likely to be relatively long gaps between tack welds, the peripheral edge 13a is pressed toward the inside of the opening 11d. As a result, gaps between the case 11 and the sealing plate 13 are less likely to occur.

[0049] According to the manufacturing method of the energy storage device 10 of this embodiment, in the welding process S6, the case 11 and the sealing plate 13 are welded together while the case 11 is pressed against the electrode body 20 in the thickness direction X by the clamping jig 50. This makes it less likely for a gap to form between the case 11 and the sealing plate 13.

[0050] According to this embodiment, the sealing plate 13 prepared in the sealing plate preparation step S2 is provided with electrode terminals 17 and 18. In the tack welding step S5, tack welding is performed in the tack welding sections W5 to W16. Here, when multiple energy storage devices 10 are electrically connected, the electrode terminals 17 and 18 of each of the multiple energy storage devices 10 are connected, for example, by a busbar. The electrode terminals 17 and 18 and the busbar are connected, for example, by ultrasonic welding. In order to perform ultrasonic welding or the like appropriately, the positions of the electrode terminals 17 and 18 must be appropriately positioned. That is, it is preferable to suppress variations in the positions of the electrode terminals 17 and 18 during the manufacturing of the energy storage device 10. According to the manufacturing method of the energy storage device 10 of this embodiment, in the tack welding step S5, tack welding is performed in the tack welding sections W5 to W16, and after the positions near the electrode terminals 17 and 18 are in a state where they are relatively unlikely to shift, the main welding step S6 is performed. Therefore, the positions of the electrode terminals 17 and 18 after the main welding step S6 can be made relatively less likely to vary.

[0051] In the manufacturing method of the energy storage device 10 of this embodiment, the sealing plate 13 prepared in the sealing plate preparation step S2 has a gas discharge valve 14. In the tack welding step S5, tack welding is performed at the tack welded sections W1 to W4 near the gas discharge valve 14, which are part of the boundary between the case 11 and the sealing plate 13. When the case 11 and the sealing plate 13 are welded in the main welding step S6, if the position of the gas discharge valve 14 in the vertical Z direction shifts from a predetermined position and the gas discharge valve 14 comes into contact with the electrode body 20, there is a possibility that the gas discharge valve 14 may be damaged or that electrical conductivity between the electrode body 20 and the sealing plate 13 may occur via the gas discharge valve 14. Therefore, it is preferable to suppress variations in the position of the gas discharge valve 14 in the vertical Z direction during the manufacturing of the energy storage device 10. In this embodiment, tack welding is performed at the tack welded sections W1 to W4 near the gas discharge valve 14, and the main welding step S6 is performed in a state where the position of the gas discharge valve 14 in the vertical Z direction is relatively unlikely to shift. Therefore, the position of the gas discharge valve 14 in the vertical Z direction after the main welding process S6 can be made relatively less prone to variation.

[0052] According to the manufacturing method of the energy storage device 10 of this embodiment, the can opening step S42 involves attaching a pair of suction pads 61 to a pair of wide surfaces 11c and moving the suction pads 61 toward the outside of the case 11 to open the rear edge 11d1 and the front edge 11d2. This allows the rear edge 11d1 and the front edge 11d2 to be opened with a relatively simple configuration.

[0053] The technologies disclosed herein have been described in detail above. Unless otherwise specified, the embodiments and other details mentioned herein do not limit the present invention. Furthermore, the technologies disclosed herein can be modified in various ways, and each component and each process mentioned herein may be omitted or combined as appropriate, unless no particular problems arise. This specification also includes the disclosures described in the following sections.

[0054] Section 1: The process involves preparing a rectangular case having a rectangular opening on one side, A step of preparing a sealing plate to seal the opening, A step of preparing a flat electrode body to be housed in the aforementioned case, An assembly step of housing the electrode body inside the case through the opening and attaching the sealing plate to the opening of the case, A temporary welding step is performed by irradiating a predetermined portion of the boundary between the case and the sealing plate with laser light from the outer surface side of the sealing plate, thereby temporarily welding the case and the sealing plate. The main welding process involves manipulating a laser beam along the boundary between the case and the peripheral edge of the sealing plate to weld the case and the sealing plate all around. Includes, The case prepared in the process of preparing the case is such that the central part of the edge of the opening along the pair of opposing side walls is curved so as to be recessed toward the inside of the opening. The assembly step is a method for manufacturing an energy storage device, comprising housing the electrode body with its edges along the pair of opposing side walls open toward the outside of the case.

[0055] Section 2: The method for manufacturing an energy storage device according to item 1, wherein the case prepared in the step of preparing the case has a rectangular bottom surface facing the opening, a pair of wide surfaces extending from the long side of the bottom surface, and a pair of narrow surfaces extending from the short side of the bottom surface, and the pair of side walls are the pair of wide surfaces.

[0056] Section 3: The method for manufacturing an energy storage device according to item 1 or 2, wherein the welding step involves welding the case and the sealing plate while pressing the case against the electrode body in the thickness direction.

[0057] Section 4: The sealing plate prepared in the step of preparing the sealing plate is provided with electrode terminals. The method for manufacturing an energy storage device according to any one of claims 1 to 3, wherein the temporary welding step involves temporarily welding a predetermined position near the electrode terminals within the boundary portion between the case and the sealing plate.

[0058] Section 5: The sealing plate prepared in the step of preparing the sealing plate is provided with a gas discharge valve in the center in a direction perpendicular to the thickness direction of the electrode body. The method for manufacturing an energy storage device according to any one of claims 1 to 4, wherein the temporary welding step involves temporarily welding a predetermined position near the gas discharge valve within the boundary portion between the case and the sealing plate.

[0059] Item 6: The method for manufacturing an energy storage device according to any one of claims 1 to 5, wherein the assembly step involves attaching a pair of suction pads to the pair of side walls that adsorb to the pair of side walls from the outside of the pair of side walls in the thickness direction of the electrode body, and moving the pair of suction pads toward the outside of the case so that the edges along the opposing pair of side walls are opened toward the outside of the case. [Explanation of symbols]

[0060] 10 Energy Storage Devices 11 cases 11a Bottom part 11b Narrow side 11c wide surface 11d aperture 11d1 Trailing edge 11d2 Anterior edge 11d3 Left border 11d4 Right edge 13 Sealing plate 13a Peripheral area 14 Gas discharge valve 17,18 Electrode terminal 17a,18a External terminal 17b,18b Internal terminal 20 Electrode body 50 Clamping fixtures 51 Pressing part 52 Drive unit 60 Suction jigs 61 Suction pads 62 Drive unit 200 Spacer 300 rolling mill rolls S1 Case preparation process S2 Sealing plate preparation process S3 Electrode body preparation process S4 Assembly process S41 Connection process S42 Can opening process S43 Accommodation Process S5 Temporary welding process S6 Main welding process W1~W16 Temporary Welds WT1, WT2 welding orbital Wa, Wb tack weld

Claims

1. The process involves preparing a rectangular case having a rectangular opening on one side, A step of preparing a sealing plate to seal the opening, A step of preparing a flat electrode body to be housed in the aforementioned case, An assembly step of housing the electrode body inside the case through the opening and attaching the sealing plate to the opening of the case, A temporary welding step is performed by irradiating a predetermined portion of the boundary between the case and the sealing plate with laser light from the outer surface side of the sealing plate, thereby temporarily welding the case and the sealing plate. The main welding process involves manipulating a laser beam along the boundary between the case and the peripheral edge of the sealing plate to weld the case and the sealing plate all around. Includes, The case prepared in the process of preparing the case is such that the central part of the edge of the opening along the pair of opposing side walls is curved so as to be recessed toward the inside of the opening. The assembly step is a method for manufacturing an energy storage device, comprising housing the electrode body with its edges along the pair of opposing side walls open toward the outside of the case.

2. The method for manufacturing an energy storage device according to claim 1, wherein the case prepared in the step of preparing the case has a rectangular bottom surface facing the opening, a pair of wide surfaces extending from the long side of the bottom surface, and a pair of narrow surfaces extending from the short side of the bottom surface, and the pair of side walls are the pair of wide surfaces.

3. The method for manufacturing an energy storage device according to claim 1, wherein the welding step involves welding the case and the sealing plate while pressing the case against the electrode body in the thickness direction.

4. The sealing plate prepared in the step of preparing the sealing plate is provided with electrode terminals. The method for manufacturing an energy storage device according to claim 1, wherein the temporary welding step involves temporarily welding a predetermined position near the electrode terminals within the boundary portion between the case and the sealing plate.

5. The sealing plate prepared in the step of preparing the sealing plate is provided with a gas discharge valve in the center in a direction perpendicular to the thickness direction of the electrode body. The method for manufacturing an energy storage device according to claim 1, wherein the temporary welding step involves temporarily welding a predetermined position near the gas discharge valve within the boundary portion between the case and the sealing plate.

6. The method for manufacturing an energy storage device according to claim 1, wherein the assembly step involves attaching a pair of suction pads to the pair of side walls that adsorb to the pair of side walls from the outside of the pair of side walls in the thickness direction of the electrode body, and moving the pair of suction pads toward the outside of the case so that the edges along the opposing pair of side walls open toward the outside of the case.

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