Electricity storage device manufacturing method and electricity storage device

Abstract

To provide a power storage device manufacturing method and a power storage device that have reliability of dimensional accuracy by suppressing protrusion of a fusion solidified part to outward of the outer package.SOLUTION: The present disclosure pertains to a method for manufacturing a power storage device 100 that includes an outer package 12 having a bottom part, an opening and a side wall 12a, and a case 1 having an aperture sealing plate 18 that seals the opening. The method comprises an aperture seal fitting step for fitting the aperture sealing plate 18 to the opening of the outer package 12, and a laser welding step for laser welding the fitting part 11 of the outer package 12 and the aperture sealing plate 18. In the laser welding step, the case 1 is irradiated with a laser beam L while the aperture sealing plate 18 is placed in an attitude facing diagonally upward, horizontal, diagonally downward, or downward with respect to a vertical direction, and the melted metal having been melted by the laser beam L is tilted in a direction of the aperture sealing plate 18, or in the vertical direction with respect to the aperture sealing plate 18, by the dead weight of the melted metal and solidified, so as to form a fusion solidified part 50.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] In recent years, power storage devices such as lithium-ion secondary batteries have been suitably used as portable power sources for personal computers, mobile terminals, and the like, and as power sources for driving vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). Conventionally, power storage devices have been known that include an exterior body having a bottom, an opening facing the bottom, and a sidewall extending from the bottom to the opening, and a sealing plate that seals the opening, with a molten and solidified portion at the fitting portion between the exterior body and the sealing plate. For example, Patent Document 1 discloses a welding method for a prismatic battery container, in which, when laser welding a battery case (exterior body) and a lid (sealing plate), the incident angle of the laser beam is set to a predetermined angle that is not perpendicular to the surface of the welded portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-181666 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional electric storage devices, the molten solidified portion protrudes outward from the exterior of the outer casing, causing fluctuations in the dimensions of the electric storage device. As electric storage devices become more widespread, stable dimensional accuracy is required, and high reliability, including stable welding quality and high energy, is also required. Therefore, the present inventor believes that it is desirable to suppress the protrusion of the molten solidified portion of the electric storage device outward from the exterior.

[0005] The technology disclosed herein has been made in consideration of the above circumstances, and its purpose is to provide a method for manufacturing an electricity storage device and an electricity storage device that have reliable dimensional accuracy by suppressing the molten and solidified portion from protruding outside the outer casing. [Means for solving the problem]

[0006] The technology disclosed herein relates to a method for manufacturing an electric storage device including an electrode assembly and a case that houses the electrode assembly. The case includes an exterior body having a bottom, an opening facing the bottom, and a sidewall extending from the bottom to the opening, and a sealing plate that seals the opening. The manufacturing method disclosed herein includes a sealing plate fitting step of housing the electrode assembly in the case and fitting the sealing plate into the opening of the exterior body, and a laser welding step of laser-welding the fitting portion between the exterior body and the sealing plate after the sealing plate fitting step. Here, in the laser welding step, the case is oriented such that the sealing plate faces diagonally upward, horizontally, diagonally downward, or downward with respect to the vertical direction, and a laser beam is irradiated onto the case. The molten metal melted by the laser beam tilts toward the sealing plate or vertically relative to the sealing plate due to its own weight, and solidifies, forming a molten solidified portion.

[0007] With this configuration, by placing the case in the above-described position, the molten metal generated by the laser beam is tilted toward the sealing plate or vertically relative to the sealing plate due to its own weight. The molten metal then solidifies, forming a molten solidified portion, which can prevent the molten solidified portion from spilling out of the exterior case. Therefore, an electric storage device with reliable dimensional accuracy can be manufactured. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically illustrating an electricity storage device according to one embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Figure 3]FIG. 3 is a top view schematically showing the exterior body and the sealing plate. [Figure 4] FIG. 4 is a flow diagram showing a method for manufacturing an electricity storage device according to one embodiment. [Figure 5] 5A and 5B are longitudinal cross-sectional views of an electricity storage device according to one embodiment taken along the line AA in FIG. 3, where (a) shows the state of laser light irradiation and (b) shows the state of formation of a molten solidified portion. [Figure 6] 6A and 6B are longitudinal cross-sectional views of an electricity storage device according to one embodiment taken along the line AA in FIG. 3, where (a) shows the state of laser light irradiation and (b) shows the state of formation of a molten solidified portion. [Figure 7] 7A and 7B are longitudinal cross-sectional views of an electricity storage device according to one embodiment taken along the line AA in FIG. 3, where (a) shows the state of laser light irradiation and (b) shows the state of formation of a molten solidified portion. [Figure 8] 8A and 8B are longitudinal cross-sectional views of an electricity storage device according to one embodiment taken along the line AA in FIG. 3, where (a) shows the state of laser light irradiation and (b) shows the state of formation of a molten solidified portion. [Figure 9] FIG. 9 is a schematic diagram showing a laser welding process according to one embodiment. [Figure 10] FIG. 10 is a flowchart showing a method for manufacturing an electricity storage device according to one embodiment. [Figure 11] FIG. 11 is a flowchart showing a method for manufacturing an electricity storage device according to one embodiment. [Figure 12] FIG. 12 is a flowchart showing a method for manufacturing an electricity storage device according to a modified example. [Figure 13] FIG. 13 is a longitudinal cross-sectional view of a conventional electricity storage device taken along the line AA in FIG. 3, where (a) shows the state of laser light irradiation and (b) shows the state of formation of a molten solidified portion. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. Matters not mentioned in this specification but necessary for implementing the technology disclosed herein can be understood as design matters for those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. In this specification, a numerical range expressed as "A to B" includes A and B, and also encompasses the meanings of "preferably greater than A" and "preferably smaller than B."

[0010] 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 lithium polymer batteries and lithium ion capacitors. A secondary battery generally refers to a battery that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes. Here, a lithium ion secondary battery is exemplified as one form of electricity storage device.

[0011] <Electricity storage device 100> FIG. 1 is a perspective view schematically illustrating an electricity storage device 100. FIG. 2 is a schematic longitudinal sectional view taken along line II-II in FIG. 1. FIG. 3 is a top view schematically illustrating an outer casing 12 and a sealing plate 18. In FIGS. 2 and 3, the outer casing 12 and the sealing plate 18 are shown before being welded (before the molten solidified portion 50 is formed). In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom (the direction of gravity). In the drawings, the symbol X indicates the short side direction (also referred to as the thickness direction) of the electricity storage device 100, the symbol Y indicates the long side direction of the electricity storage device 100, and the symbol Z indicates the vertical direction. However, these directions are merely used for convenience of explanation and do not limit the installation form of the electricity storage device 100 in any way.

[0012] As shown in Fig. 1 and Fig. 2, the electricity storage device 100 includes a case 1, an electrode assembly 20, a positive electrode terminal 6, a negative electrode terminal 8, a positive electrode current collector 35, and a negative electrode current collector 45. Although not shown, the electricity storage device 100 further includes an electrolyte solution. The configuration of the electricity storage device 100 may be the same as that of a conventional device. The electricity storage device 100 is preferably a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

[0013] The case 1 is a housing that houses the electrode assembly 20. As shown in FIGS. 1 and 2, the case 1 includes an exterior body 12 having an opening 15 and a sealing plate 18 that seals the opening 15. The exterior body 12 and the sealing plate 18 have sizes that correspond to the number of electrode assemblies 20 (one or more) that will be housed, their sizes, etc. The case 1 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy mainly containing aluminum. Here, the case 1 is made of aluminum. As shown in FIG. 1, the case 1 has a flat, bottomed, and generally rectangular parallelepiped shape (square). However, the shape of the case 1 is not limited to this, and it may be, for example, cylindrical.

[0014] As shown in FIGS. 1 and 2, the exterior body 12 is a container with a bottom and a substantially rectangular parallelepiped shape, with an opening 15 on one side (here, the top surface). As shown in FIG. 1, the exterior body 12 includes a substantially rectangular bottom 12d having a pair of short sides and a pair of long sides, a pair of short side walls 12a and 12b extending upward from the short sides of the bottom 12d and facing each other, and a pair of long side walls 12e and 12f extending upward from the long sides of the bottom 12d and facing each other. The short side walls 12a and 12b have a smaller area than the long side walls 12e and 12f. In this specification, the term "substantially rectangular" is intended to encompass not only a perfect rectangular shape (rectangular shape) but also, for example, a shape in which the corners connecting the long and short sides of the rectangle are rounded or a shape in which the corners have notches. The short side walls 12a, 12b and the long side walls 12e, 12f are an example of the "side walls" disclosed herein. The short side walls 12a, 12b are an example of the "first side walls" disclosed herein, and the long side walls 12e, 12f are an example of the "second side walls" disclosed herein. One side of the exterior body 12 is formed with a substantially rectangular annular opening 15 surrounded by the pair of short side walls 12a, 12b and the pair of long side walls 12e, 12f. As shown in FIG. 2, the bottom 12d faces the opening 15.

[0015] As shown in Figures 1 and 2, sealing plate 18 is a member that seals opening 15 of exterior body 12. Here, sealing plate 18 is a plate-like member that is generally rectangular in plan view. As shown in Figure 2, sealing plate 18 is provided with a liquid injection hole 71, a gas exhaust valve 73, and terminal extraction holes 74 and 75. Sealing plate 18 faces bottom 12d of exterior body 12.

[0016] As shown in FIG. 3, the outer peripheral surface of sealing plate 18 and the inner surface of exterior body 12 (opening 15) are arranged (fitted) to face each other at fitting portion 11. Here, the upper ends of sealing plate 18 and exterior body 12 (upper end portion in FIG. 2) are flush in plan view. Fitting portion 11 has a pair of short sides 11a, 11b and a pair of long sides 11e, 11f. Short sides 11a, 11b correspond to short side walls 12a, 12b and extend parallel to each other in straight lines. Meanwhile, long sides 11e, 11f correspond to long side walls 12e, 12f and extend parallel to each other in straight lines. In the following description, of the pair of short sides 11a, 11b, one short side 11a (left side in FIG. 3) will be referred to as the "first side 11a," and the other short side 11b (right side in FIG. 3) will be referred to as the "second side 11b." Furthermore, of the pair of long sides 11e, 11f, one long side 11e (front side in FIG. 3) will be referred to as the "third side 11e," and the other long side 11f (rear side in FIG. 3) will be referred to as the "fourth side 11f." The first side 11a, the second side 11b, the third side 11e, and the fourth side 11f are examples of the "first side," "second side," "third side," and "fourth side" disclosed herein. 3, the fitting portion 11 has rounded portions 11g, 11h, 11i, and 11j provided between the short side portions 11a and 11b and the long side portions 11e and 11f. However, the rounded portions of the fitting portion 11 are not essential. As will be described in detail later, by laser welding the fitting portion 11 around its entire periphery, a ring-shaped molten solidification portion 50 (see FIG. 5) is formed and the sealing plate 18 and the exterior body 12 are joined. This hermetically seals (closes) the case 1.

[0017] Inlet hole 71 is a through-hole for injecting the electrolyte into case 1 after sealing plate 18 is attached to exterior body 12. In this case, inlet hole 71 is sealed with sealing member 72 after the electrolyte is injected. Gas release valve 73 is a thin-walled portion configured to break when the pressure inside case 1 reaches or exceeds a predetermined value, thereby releasing gas inside case 1 to the outside.

[0018] As the electrolyte, any known electrolyte may be used without any particular limitation. For example, a non-aqueous electrolyte in which a supporting salt (electrolyte salt) is dissolved in a non-aqueous solvent (organic solvent) is preferably used. Examples of non-aqueous solvents include carbonate-based solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorine-containing lithium salts such as LiPF6. The electrolyte may contain additives as needed.

[0019] The positive electrode terminal 6 is attached to one end of the sealing plate 18 in the long side direction Y (the left end in FIG. 2 ). The negative electrode terminal 8 is attached to the other end of the sealing plate 18 in the long side direction Y (the right end in FIG. 2 ). As shown in FIG. 2 , the positive electrode terminal 6 and the negative electrode terminal 8 are inserted through terminal lead-out holes 74, 75 and exposed on the outer surface of the sealing plate 18. As shown in FIG. 2 , the positive electrode terminal 6 is electrically connected to the positive electrode 3 of the electrode assembly 20 via a positive electrode current collecting member 35 inside the exterior body 12. The negative electrode terminal 8 is electrically connected to the negative electrode 4 of the electrode assembly 20 via a negative electrode current collecting member 45 inside the exterior body 12. The positive electrode terminal 6 and the negative electrode terminal 8 are insulated from the sealing plate 18 by a gasket 76 and an insulator 78. A current interrupter (CID) may be installed between the positive terminal 6 and the positive current collector 35 or between the negative terminal 8 and the negative current collector 45.

[0020] The positive electrode terminal 6 is preferably made of a metal, more preferably made of aluminum or an aluminum alloy, for example. The negative electrode terminal 8 is preferably made of a metal, more preferably made of copper or a copper alloy, for example. The negative electrode terminal 8 may be formed by joining two conductive members together. For example, the portion connected to the negative electrode current collecting member 45 may be made of copper or a copper alloy, and the portion exposed on the outer surface of the sealing plate 18 may be made of aluminum or an aluminum alloy.

[0021] It is preferable that a material having excellent chemical resistance and weather resistance be used for the gasket 76 and the insulator 78. The gasket 76 and the insulator 78 may be made of an electrically insulating and elastically deformable resin material, for example, a fluorinated resin such as perfluoroalkoxy fluorine resin (PFA), polyphenylene sulfide resin (PPS), aliphatic polyamide, or the like.

[0022] Here, the positive electrode terminal 6 is electrically connected to a plate-shaped positive electrode external conductive member 36 on the outside of the case 1. Similarly, the negative electrode terminal 8 is electrically connected to a plate-shaped negative electrode external conductive member 46 on the outside of the case 1. The positive electrode external conductive member 36 and the negative electrode external conductive member 46 are connected to other electricity storage devices or external equipment via external connection members such as bus bars. The positive electrode external conductive member 36 and the negative electrode external conductive member 46 are preferably made of a metal with excellent conductivity, such as aluminum, an aluminum alloy, copper, or a copper alloy. However, the positive electrode external conductive member 36 and the negative electrode external conductive member 46 are not essential and may be omitted in other embodiments.

[0023] The electrode assembly 20 may be the same as a conventional one and is not particularly limited. As shown in FIG. 2, the electrode assembly 20 has a positive electrode 3 and a negative electrode 4. Here, the electrode assembly 20 is a flat wound electrode assembly in which a strip-shaped positive electrode 3 and a strip-shaped negative electrode 4 are stacked in an insulated state via a strip-shaped separator 7 and wound around a winding axis. However, the electrode assembly 20 may also be a laminated electrode assembly in which a square-shaped (typically rectangular) positive electrode 3 and a square-shaped (typically rectangular) negative electrode 4 are stacked in an insulated state. In addition, the number of electrode assemblies 20 arranged inside one exterior package 12 is not particularly limited and may be two or more (plural). The positive electrode 3 and the negative electrode 4 are examples of "electrodes" in the technology disclosed herein.

[0024] As shown in Fig. 2, the positive electrode 3 has a positive electrode current collector 30 and a positive electrode active material layer 31 fixed onto the positive electrode current collector 30. The positive electrode current collector 30 is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode active material layer 31 is a layer containing a positive electrode active material (for example, a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide) that can reversibly store and release charge carriers.

[0025] The negative electrode 4 has a negative electrode current collector 40 and a negative electrode active material layer 41 fixed onto the negative electrode current collector 40. The negative electrode current collector 40 is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode active material layer 41 is a layer containing a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly store and release charge carriers.

[0026] The separator 7 is a member that insulates the positive electrode active material layer 31 of the positive electrode 3 from the negative electrode active material layer 41 of the negative electrode 4. A porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable as the separator 7. A heat resistance layer (HRL) containing an inorganic filler may be provided on the surface of the separator 7.

[0027] As shown in FIG. 2 , at the left end of the electrode body 20 in the long side direction Y, a portion of the positive electrode current collector 30 on which the positive electrode active material layer 31 is not formed (positive electrode current collector exposed portion) protrudes from the laminated portion. A positive electrode current collector 35 is attached to the positive electrode current collector exposed portion. The positive electrode current collector 35 may be made of the same metal material as the positive electrode current collector 30, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Furthermore, at the right end of the electrode body 20 in the long side direction Y, a portion of the negative electrode current collector 40 on which the negative electrode active material layer 41 is not formed (negative electrode current collector exposed portion) protrudes from the laminated portion. A negative electrode current collector 45 is attached to the negative electrode current collector exposed portion. The material (metal type) of the negative electrode current collector 45 may be different from that of the positive electrode current collector 35. The negative electrode current collecting member 45 may be made of the same metal as the negative electrode current collector 40, for example, a conductive metal such as copper, a copper alloy, nickel, or stainless steel.

[0028] <Method of manufacturing the electricity storage device 100> FIG. 4 is a flow diagram showing a manufacturing method for an electricity storage device 100 according to one embodiment. The electricity storage device 100 disclosed herein can be manufactured by a manufacturing method including, in order, a sealing plate fitting step S10 and a laser welding step S20, and is characterized by performing the laser welding step S20. The manufacturing method for the electricity storage device 100 disclosed herein may include other steps at any stage in addition to the steps described above, and the remaining manufacturing processes may be the same as conventional methods. FIGS. 5 to 8 are longitudinal cross-sectional views of the electricity storage device 100 including the laser welding step S20. FIG. 13 is a longitudinal cross-sectional view of an electricity storage device 100 according to a conventional example. In FIGS. 5 to 8 and 13, (a) shows the irradiation of laser light L, and (b) shows the formation of the molten and solidified portion 50. In FIGS. 5 to 8 and 13, the direction of gravity is indicated by an outline arrow, and portions of the sealing plate 18 and the exterior body 12 before melting are indicated by imaginary lines.

[0029] (Sealing plate fitting process S10) In the sealing plate fitting step S10, the electrode body 20 is housed inside the exterior body 12, and the sealing plate 18 is fitted into the opening 15 of the exterior body 12. This makes the upper end of the exterior body 12 flush with the sealing plate 18. In addition, the outer peripheral surface of the sealing plate 18 faces the inner surface of the exterior body 12 (opening 15), forming a fitting portion 11.

[0030] (Laser welding process S20) In the laser welding step S20, the fitting portion 11 between the exterior body 12 and the sealing plate 18, which was formed in the sealing plate fitting step S10, is laser welded. At this time, the case 1 is oriented so that the sealing plate 18 faces diagonally upward (see FIG. 5(a)), horizontally (see FIG. 6(a)), diagonally downward (see FIG. 7(a)), or downward (see FIG. 8(a)) with respect to the vertical direction.

[0031] During this welding, a portion of the sealing plate 18 and the outer casing 12 (shown by phantom lines) melts, and the molten portion solidifies, forming a molten solidified portion 50. The shape of the molten solidified portion 50 is determined, for example, by the flow of the molten metal and the influence of surface tension. Specifically, the molten solidified portion 50 is formed by solidifying in a raised shape due to the surface tension of the molten metal. Conventionally, welding is performed with the sealing plate 18 facing directly upward in the vertical direction Z (see FIG. 13(a)). Therefore, as shown in FIG. 13(b), there is a risk that a portion of the molten solidified portion 50 may protrude (project) outward from the outer casing 12. This protrusion of the molten solidified portion 50 causes variations in the size of the electricity storage device 100 (case 1) in the long side direction Y and the short side direction X. Therefore, the present inventors wish to suppress the protrusion of the molten solidified portion 50 outward from the outer casing 12. In this specification, "formed outside (protruding from) the exterior body" means that at least a part of the molten solidified portion 50 protrudes from the exterior body 12 in the long side direction Y or the short side direction X. Protrusion of at least a part of the molten solidified portion 50 in the vertical direction Z is not included in "protruding from the outside."

[0032] In contrast to the conventional example described above, here, the case 1 is oriented such that the sealing plate 18 faces diagonally upward (see FIG. 5(a)), horizontally (see FIG. 6(a)), diagonally downward (see FIG. 7(a)), or downward (see FIG. 8(a)) with respect to the vertical direction. That is, here, the case 1 is not oriented such that the sealing plate 18 faces directly upward with respect to the vertical direction Z (see FIG. 13(a)). Then, by irradiating the fitting portion 11 with laser light L while the case 1 is oriented as described above, a portion of the sealing plate 18 and the exterior body 12 melts and becomes molten metal. This molten metal solidifies while tilting toward the sealing plate 18 or in the vertical direction relative to the sealing plate 18 due to its own weight (according to the direction of gravity). As a result, a molten and solidified portion 50 is formed in a state in which protrusion outward from the exterior body 12 is suppressed (see FIGS. 5 to 8(b)). Therefore, the technology disclosed herein makes it possible to manufacture an electricity storage device with reliable dimensional accuracy. In a preferred embodiment, the molten solidified portion 50 does not protrude outward from the exterior body 12 .

[0033] In a preferred embodiment, as shown in Fig. 5, the case 1 is oriented such that the sealing plate 18 faces diagonally upward relative to the vertical direction. In this orientation, the molten solidified portion 50 is formed at an incline toward the sealing plate 18, as shown in Fig. 5(b). When the sealing plate 18 faces diagonally upward relative to the vertical direction, the manufacturing equipment can be simplified. Therefore, the electricity storage device 100 can be manufactured more efficiently.

[0034] In another preferred embodiment, as shown in Fig. 6, the case 1 is oriented such that the sealing plate 18 faces horizontally relative to the vertical direction. In this orientation, the molten solidified portion 50 is formed at an inclination toward the sealing plate 18, as shown in Fig. 6(b). The molten solidified portion 50 is also formed so as to be further away from the exterior of the outer casing 12. Therefore, when the sealing plate 18 faces horizontally relative to the vertical direction, the molten solidified portion 50 can be more suitably prevented from protruding outward from the exterior of the outer casing 12.

[0035] In another preferred embodiment, as shown in FIG. 7, the case 1 is oriented such that the sealing plate 18 faces diagonally downward relative to the vertical direction. In this position, the molten solidified portion 50 is formed and inclined toward the sealing plate 18, as shown in FIG. 7(b). In another preferred embodiment, as shown in FIG. 8, the case 1 is oriented such that the sealing plate 18 faces downward relative to the vertical direction. In this position, the molten solidified portion 50 is formed and inclined vertically relative to the sealing plate 18, as shown in FIG. 8(b). When the sealing plate 18 faces diagonally downward or downward relative to the vertical direction, adhesion of spatter generated during laser welding to the case 1 can be suitably suppressed.

[0036] The inclination angle θ (see Figure 9) of the case 1 (sealing plate 18) with respect to the horizontal direction depends on factors such as the fluidity of the molten metal, but is preferably approximately 5° or more, and more preferably approximately 10° or more, from the standpoint of achieving the effect of forming the molten solidified portion 50.

[0037] The case 1 can be secured in place in the laser welding step S20 using a conventionally known method. For example, a rotating table or a robot arm can be used. Here, a method using a rotating table will be described in detail as an example. FIG. 9 is a schematic diagram illustrating the laser welding step S20 according to one embodiment. Note that in FIG. 9, the direction of rotation of the rotating shaft 126 is indicated by an arrow. Here, the case 1 is placed on the rotating table 120. The rotating table 120 includes a restraining jig 122, a turntable 124, and a rotating shaft 126. As shown in FIG. 9, the restraining jig 122, the turntable 124, and the rotating shaft 126 are inclined relative to the horizontal. As shown in FIG. 9, the scanner head 140 is positioned to face the sealing plate 18 of the case 1.

[0038] The restraining jig 122 is a jig that restrains the case 1. The shape of the restraining jig 122 need only be such that it can restrain the case 1. For example, it may be box-shaped with a recess that accommodates the case 1, or it may be band-shaped. As shown in FIG. 9, the case 1 that has undergone the sealing plate fitting step S10 is accommodated in the recess of the restraining jig 122. As shown in FIG. 9, the restraining jig 122 is placed (fixed) on a turntable 124. The turntable 124 is fixed on a rotating shaft 126, and thus moves in conjunction with the rotation of the rotating shaft 126. As shown in FIG. 9, the axis of the rotating shaft 126 coincides with the axis C of the case 1. As the rotating shaft 126 rotates, the turntable 124, the restraining jig 122 of the turntable 124, and the case 1 placed on the restraining jig 122 rotate around the axis (in the direction of the arrow in FIG. 9). In this case, the rotating shaft 126 rotates clockwise. The rotation direction of the rotary shaft 126 may be counterclockwise, or the rotation direction may be changed each time the rotary shaft 126 rotates.

[0039] The position of the scanner head 140 in the laser welding step S20 can be adjusted as appropriate depending on the shape of the case 1, the attitude of the case 1, the deflection angle of the laser light L, and the like. In FIG. 9, the scanner head 140 is disposed so that the axis C of the case 1 and the axis CL of the scanner head 140 are substantially aligned. Furthermore, without being limited thereto, for example, the scanner head 140 may be disposed such that the axis CL of the scanner head 140 is closer to the most upstream region of the fitting portion 11 (the uppermost region in the vertical direction Z) than the axis C of the case 1 as viewed in the direction of gravity. With such a configuration, the deflection angle of the laser light L can be further reduced. In other words, a scanner head with a small deflection angle of the laser light L can also be suitably employed in this embodiment.

[0040] 9, it is preferable that the scanner head 140 (laser irradiation surface) and the sealing plate 18 face each other, and that the scanner head 140 and the case 1 are inclined in the same direction. This suppresses changes in the profile at the processing point, making the welding quality more stable. Therefore, it is possible to more suitably suppress the protrusion of the molten solidified portion 50 outward from the outer casing 12. In this specification, "same orientation" means that the difference between the tilt angle θ of the case 1 relative to the horizontal plane and the tilt angle θL of the scanner head 140 relative to the horizontal plane is within ±5° (see FIG. 9).

[0041] The above-described configuration is merely an example and is not limiting. The method of fixing the case 1 can be changed as appropriate depending on the shape of the case 1, the position of the scanner head 140, etc. For example, to prevent misalignment between the exterior body 12 and the sealing plate 18, a jig (e.g., a clamp) may be used to fix the exterior body 12 and the sealing plate 18.

[0042] The type of laser beam used in the laser welding step S20 and the conditions for the laser welding may be the same as those used in the past and are not particularly limited. There are no particular limitations on the scanning path (scanning direction) of the laser beam, and the scanning locations of the laser beam may overlap in the fitting portion 11. The angle between the laser irradiation direction and the exterior body 12 and the sealing plate 18 (horizontal plane) is typically about 90±10°, for example about 90±5°.

[0043] In the laser welding step S20, laser welding can be performed on the fitting portion 11 except for the region located at the most downstream side in the direction of gravity (the lowest side in the vertical direction Z). In the laser welding step S20, laser welding can be performed in multiple steps, and the posture of the case 1 can be adjusted appropriately according to the region to be laser welded. For example, when welding the most downstream region of the fitting portion 11 in the direction of gravity, the posture of the case 1 can be adjusted so that the region is not located at the most downstream side in the direction of gravity, and then laser welding can be performed. The method of such adjustment is not particularly limited, but it is preferable to rotate the case 1 around its axis to adjust the position. This can suppress changes in the profile, thereby more stable the welding quality of the molten solidified portion 50.

[0044] First Embodiment Several examples of the technology disclosed herein will be described below, but it is not intended that the technology disclosed herein be limited to those examples. FIG. 10 is a flow diagram according to a first embodiment. In the first embodiment, the method includes a sealing plate fitting step S10, a first laser welding step S201, a second attitude adjustment step S202a, and a second laser welding step S202, in this order. The first laser welding step S201 and the second laser welding step S202 are aspects of the laser welding step S20 described above. In addition to the above steps, other steps may be included at any stage. Note that the sealing plate fitting step S10 may be the same as described above, and therefore will not be described here.

[0045] (First laser welding process S201) In the first laser welding step S201, the first side portion 11a is laser-welded while the case 1 is maintained in a first position. In this specification, the term "first position" refers to a position in which the first side portion 11a is horizontal and higher than the second side portion 11b. Specifically, as shown in FIG. 9, the first side portion 11a and the second side portion 11b are horizontal to each other, and the first side portion 11a is positioned higher (on the U side) than the second side portion 11b in the vertical direction. Then, while the first position is maintained, laser light L is irradiated onto the first side portion 11a of the fitting portion of the case 1. As a result, the sealing plate 18 and a portion of the exterior body 12 melt as molten metal. Then, the molten metal solidifies under its own weight while tilted toward the sealing plate 18 (in other words, toward the second side portion 11b), forming a molten solidified portion 50.

[0046] In the first laser welding step S201, laser welding can be performed on the third side 11e and / or the fourth side 11f in addition to the first side 11a. However, it is not necessary to weld the entire area of ​​the third side 11e and / or the fourth side 11f in the first laser welding step S201. For example, in the first laser welding step S201, a portion of the third side 11e and / or the fourth side 11f may be laser welded, and then in the second laser welding step S202, the remaining area not laser welded in the first laser welding step S201 may be laser welded. Furthermore, if the fitting portion 11 has a rounded portion, the rounded portions 11h and 11g adjacent to the first side 11a may also be laser welded. However, it is preferable not to laser weld the second side 11b in the first laser welding step S201.

[0047] (Second posture adjustment step S202a) In some preferred embodiments, a second attitude adjustment step S202a may be performed before the second laser welding step S202. In the second attitude adjustment step S202a, the case 1 is rotated around its axis to adjust the case 1 to a second attitude. In this specification, the term "second attitude" refers to an attitude in which the second side 11b is horizontal and higher than the first side 11a. More specifically, the first side 11a and the second side 11b are horizontal to each other, and the second side 11b is positioned higher (toward the U side) than the first side 11a in the vertical direction. The rotation method may be, for example, the method exemplified in the laser welding step S20 described above. Here, as shown in FIG. 9 , the rotation shaft 126 of the turntable 120 is rotated around its axis (in the direction of the arrow) to rotate the case 1 placed on the restraining jig 122 around its axis. By rotating the case 1 in this configuration, the tilt angle of the case 1 can be maintained and fluctuations in the distance and angle between the case 1 and the scanner head 140 can be suppressed between the first and second positions. This suppresses changes in the profile, allowing for more stable welding in the subsequent second laser welding step S202. The direction of the axial rotation of the case 1 is not particularly limited and may be clockwise or counterclockwise. However, the second position adjustment step S202a is not required, and the case 1 can also be adjusted to the second position by a means other than the second position adjustment step S202a. Furthermore, as long as the second position is maintained, an additional step can be optionally performed between the second position adjustment step S202a and the second laser welding step S202.

[0048] (Second laser welding process S202) In the second laser welding step S202, while the case 1 is held in the second position, laser light L is irradiated onto the second side portion 11b of the fitting portion 11 of the case 1. As a result, the sealing plate 18 and a portion of the exterior body 12 are melted as molten metal. The molten metal then solidifies while tilted toward the sealing plate 18 (in other words, toward the first side portion 11a) due to its own weight, forming a molten solidified portion 50. Note that the second laser welding step S202 may be the same as the first laser welding step S201 except for the above-mentioned points. However, it is preferable that laser welding not be performed on the first side portion 11a in the second laser welding step S202. In addition, the irradiated portion (scanning path) of the laser light L may partially overlap between the first laser welding step S201 and the second laser welding step S202.

[0049] According to this embodiment, by performing the first laser welding step S201 and the second laser welding step S202, it is possible to more suitably prevent the molten solidified portion 50 from protruding outward from the outer casing 12 (more specifically, in the long side direction) with respect to the short side walls 12a, 12b. Therefore, it is possible to provide an electricity storage device 100 with improved reliability in the dimensional accuracy of the case 1. Furthermore, by performing the second attitude adjustment step S202a before the second laser welding step, it is possible to perform more stable welding in the second laser welding step S202 as well.

[0050] In the first embodiment described above, the first laser welding step S201 and the second laser welding step S202 were performed on the first side 11a and the second side 11b, which are the short side portions. However, this is not limited thereto. The manufacturing method of the energy storage device 100 according to the present disclosure can also be performed on the long side portions (the third side 11e and the fourth side 11f) of the energy storage device 100, following the first embodiment. In this case, for example, in the first embodiment, the "first side 11a" can be appropriately read as the "third side 11e" and the "second side 11b" can be appropriately read as the "fourth side 11f." This can more appropriately suppress the protrusion of the molten solidified portion 50 outward from the exterior body 12 (more specifically, in the short side direction) of the long side walls 12e and 12f. From the viewpoint of reliability of dimensional accuracy, it is more preferable to suppress the protrusion of the molten solidified portion 50 outward from the exterior body 12 in the long side direction. Therefore, it is more preferable to perform the first laser welding step S201 and the second laser welding step S202 on the first side portion 11a and the second side portion 11b (short side walls 12a, 12b).

[0051] <Second embodiment> FIG. 11 is a flow diagram according to the second embodiment. As shown in FIG. 11, the method for manufacturing the power storage device 100 according to the second embodiment includes a sealing plate fitting step S10, a first laser welding step S201, a second laser welding step S202, a third laser welding step S203, and a fourth laser welding step S204. The order of the steps following the sealing plate fitting step S10 may be changed, and other steps may be included as appropriate. The third laser welding step S203 and the fourth laser welding step S204 are one aspect of the laser welding step S20 described above. Note that in the second embodiment, the sealing plate fitting step S10, the first laser welding step S201, and the second laser welding step S202 may be the same as those in the first embodiment, and therefore description thereof will be omitted here.

[0052] (Third laser welding process S203) In the third laser welding step S203, the third side 11e is laser-welded while the case 1 is maintained in the third position. In this specification, the term "third position" refers to a position in which the third side 11e is horizontal and higher than the fourth side 11f. Specifically, the third side 11e and the fourth side 11f are horizontal to each other, and the third side 11e is positioned higher (toward the U side) than the fourth side 11f in the vertical direction. Then, while the third position is maintained, laser light L is irradiated onto the third side 11e of the fitting portion of the case 1. This causes the sealing plate 18 and a portion of the exterior body 12 to melt as molten metal. The molten metal then solidifies under its own weight while tilted toward the sealing plate 18 (in other words, toward the fourth side 11f), forming a molten solidified portion 50.

[0053] (Fourth laser welding process S204) In a fourth laser welding step S204, the fourth side 11f is laser-welded while the case 1 is maintained in the fourth position. In this specification, the term "fourth position" refers to a position in which the fourth side 11f is horizontal and higher than the third side 11e. Specifically, the third side 11e and the fourth side 11f are horizontal to each other, and the fourth side 11f is positioned higher (toward the U side) than the third side 11e in the vertical direction. Then, while the fourth position is maintained, laser light L is irradiated onto the fourth side 11f of the fitting portion of the case 1. This causes portions of the sealing plate 18 and the exterior body 12 to melt as molten metal. The molten metal then solidifies under its own weight while tilted toward the sealing plate 18 (in other words, toward the third side 11e), forming a molten solidified portion 50.

[0054] According to this example, by performing the third laser welding step S203 and the fourth laser welding step S204 described above in addition to the first laser welding step S201 and the second laser welding step S202, it is possible to more suitably suppress the protrusion of the molten solidified portion 50 outward from the outer casing 12 (more specifically, in the short side direction) also for the long side walls 12e and 12f. Therefore, it is possible to provide an electricity storage device 100 with more suitably improved reliability of the dimensional accuracy of the case 1. The welding methods for the third laser welding step S203 and the fourth laser welding step S204 may be the same as those for the first laser welding step S201 and the second laser welding step S202 described above. Furthermore, as in the first embodiment, when the fitting portion 11 has a rounded portion, adjacent rounded portions may be welded in each welding step.

[0055] In the second embodiment, the order in which the first to fourth laser welding steps S201 to S204 are performed is not limited to that shown in FIG. 11. FIG. 12 is a flow chart showing a modified example of the second embodiment. Here, the first laser welding step S201, the third laser welding step S203, the second laser welding step S202, and the fourth laser welding step S204 are performed in this order. This allows the posture of the case 1 to be adjusted efficiently (the case 1 to be rotated). However, the above

[0056] The manufacturing method for the electricity storage device 100 according to the present embodiment has been described above. Another aspect of the technology disclosed herein provides an electricity storage device 100. The electricity storage device 100 disclosed herein includes an electrode assembly 20, an outer casing 12, a sealing plate 18, and an annular molten solidified portion 50. The electricity storage device 100 is characterized by the molten solidified portion 50, but other configurations may be similar to those of conventional devices. In the electricity storage device 100, at least a portion of the molten solidified portion 50 is inclined toward the sealing plate 18 or in a vertical direction relative to the sealing plate 18. This prevents the molten solidified portion 50 from protruding outward from the outer casing 12, providing an electricity storage device 100 with reliable dimensional accuracy. In a preferred embodiment, an electricity storage device 100 is provided in which the molten solidified portion 50 does not protrude outward from the outer casing 12, improving the reliability of dimensional accuracy.

[0057] The electricity storage device 100 can be used for various purposes, but typically can be suitably used as a power source (driving power source) for motors mounted on various vehicles, such as passenger cars, trucks, etc. The type of vehicle is not particularly limited, and examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0058] Although several embodiments of the technology disclosed herein have been described above, the above embodiments are merely examples. The technology disclosed herein can be implemented in various other forms. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiments. For example, it is possible to replace part of the above-described embodiments with other modified embodiments, and it is also possible to add other modified embodiments to the above-described embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0059] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A method for manufacturing an electricity storage device comprising: an electrode assembly; and a case that houses the electrode assembly, wherein the case comprises an exterior body having a bottom, an opening that faces the bottom, and a sidewall that extends from the bottom to the opening; and a sealing plate that seals the opening, the method comprising: a sealing plate fitting step of accommodating the electrode assembly within the case and fitting the sealing plate into the opening of the exterior body; and a laser welding step, after the sealing plate fitting step, of laser-welding a fitting portion between the exterior body and the sealing plate, wherein the laser welding step comprises irradiating the case with laser light while the sealing plate is oriented such that the sealing plate faces diagonally upward, horizontally, diagonally downward, or downward with respect to the vertical direction, and causing the molten metal melted by the laser light to tilt toward the sealing plate or vertically relative to the sealing plate due to its own weight and solidify, thereby forming a molten and solidified portion. Item 2: The method for producing an electricity storage device according to Item 1, wherein the melt-solidified portion does not protrude outward from the exterior body. Item 3: The method for manufacturing an electricity storage device according to Item 1 or 2, wherein the bottom is generally rectangular, the sealing plate is generally rectangular and plate-like, the side walls include a pair of first side walls and a pair of second side walls, the opening is generally rectangular and annular, the fitting portion has a first side portion and a second side portion that correspond to the first side walls and that extend parallel to each other and in a straight line, a first position is an attitude in which the first side portion is horizontal and higher than the second side portion, and a second position is an attitude in which the second side portion is horizontal and higher than the first side portion, and the laser welding step includes a first laser welding step of laser-welding the first side portion while the case is held in the first position, and a second laser welding step of laser-welding the second side portion while the case is held in the second position. Item 4: The method for manufacturing an electricity storage device according to Item 3, further comprising a second attitude adjustment step of rotating the case around an axis and adjusting the case to take the second attitude before the second laser welding step. Item 5: The method for producing an electricity storage device according to Item 3 or 4, wherein the first side wall is a short side wall having a smaller area than the second side wall. Item 6: The method for manufacturing an electricity storage device according to any one of Items 3 to 5, wherein the fitting portion has a third side portion and a fourth side portion that correspond to the second side wall and that extend parallel to each other in a straight line, a third position is defined as an attitude in which the third side portion is horizontal and higher than the fourth side portion, and a fourth position is defined as an attitude in which the fourth side portion is horizontal and higher than the third side portion, and the laser welding step further includes a third laser welding step of laser welding the third side portion while maintaining the third position, and a fourth laser welding step of laser welding the fourth side portion while maintaining the fourth position. Item 7: The method for manufacturing an electricity storage device according to any one of items 1 to 6, wherein in the laser welding step, the laser light is irradiated by a scanner head, the scanner head facing the sealing plate and tilted in the same direction as the case. Item 8: The method for manufacturing an electricity storage device according to any one of Items 1 to 7, wherein in the laser welding step, the laser light is irradiated to the case in a state where the sealing plate is oriented obliquely upward relative to the vertical direction. Item 9: An electricity storage device comprising: an electrode body having electrodes; an exterior body having an opening and housing the electrode body; a sealing plate that seals the opening; and an annular molten solidified portion formed at a fitting portion between the opening of the exterior body and the sealing plate, wherein at least a portion of the molten solidified portion is inclined toward the sealing plate or in a direction vertical to the sealing plate. Item 10: The electricity storage device according to Item 9, wherein the melt-solidified portion does not protrude outward from the exterior body. [Explanation of symbols]

[0060] 1 case 3 Positive electrode 4 Negative electrode 6 Positive terminal 7 Separator 8 Negative terminal 11 Fitting part 11a First side (short side) 11b Second side (short side) 11e Third side (long side) 11f Fourth side (long side) 11g, 11h, 11i, 11j R section 12 Exterior body 12d bottom 12a, 12b short side wall 12e, 12f long side wall 15 Opening 18 Sealing plate 20 Electrode body 30 Positive electrode current collector 31 Cathode active material layer 35 Positive electrode current collecting member 36 Positive electrode external conductive member 40 Negative electrode current collector 41 Negative electrode active material layer 45 Negative electrode current collecting member 46 Negative electrode external conductive member 50 Melting and solidification area 71 Liquid injection hole 74,75 Terminal extraction hole 76 Gasket 78 Insulator 100 Energy storage device 120 Rotating Platform 122 Restraint Jig 124 Turntable 126 Rotation Axis L laser light S10 Sealing plate fitting process S20 Laser Welding Process S201 First laser welding process S202 Second laser welding process S203 Third laser welding process S204 4th laser welding process S202a 2nd attitude adjustment process

Claims

1. A method for manufacturing an electricity storage device including an electrode assembly and a case that houses the electrode assembly, The case is an exterior body having a bottom, an opening facing the bottom, and a sidewall extending from the bottom to the opening; a sealing plate that seals the opening; Equipped with a sealing plate fitting step of accommodating the electrode body in the case and fitting the sealing plate into the opening of the exterior body; a laser welding step of laser-welding a fitting portion between the exterior body and the sealing plate after the sealing plate fitting step, The laser welding process includes: irradiating the case with laser light while the sealing plate is oriented in a direction obliquely upward, horizontally, obliquely downward, or downward with respect to the vertical direction; The molten metal melted by the laser light is tilted toward the sealing plate or in a direction vertical to the sealing plate by its own weight, and solidified to form a molten solidified portion. A method for manufacturing an electricity storage device.

2. The molten and solidified portion does not protrude outward from the outer casing. The method for manufacturing the electricity storage device according to claim 1 .

3. The bottom is generally rectangular, The sealing plate is substantially rectangular and plate-shaped, The side walls include a pair of first side walls and a pair of second side walls, The opening is generally rectangular and annular. the fitting portion has a first side portion and a second side portion that correspond to the first side wall and extend parallel to each other in a straight line; a first posture in which the first side portion is horizontal and higher than the second side portion; a second posture in which the second side portion is horizontal and higher than the first side portion; The laser welding process includes: a first laser welding step of laser welding the first side portion while the case is maintained in the first position; a second laser welding step of laser welding the second side portion while the case is maintained in the second position; The method for manufacturing the electricity storage device according to claim 1 or 2, comprising:

4. Before the second laser welding step, a second attitude adjustment step of rotating the case around an axis to adjust the case to the second attitude, The method for manufacturing the electricity storage device according to claim 3 .

5. The first side wall is a short side wall having an area smaller than that of the second side wall. The method for manufacturing the electricity storage device according to claim 4 .

6. the fitting portion has a third side portion and a fourth side portion that correspond to the second side wall and extend parallel to each other in a straight line; a third posture in which the third side portion is horizontal and higher than the fourth side portion; a fourth posture in which the fourth side portion is horizontal and higher than the third side portion; The laser welding process includes: a third laser welding step of laser welding the third side portion while maintaining the third posture; a fourth laser welding step of laser welding the fourth side portion while maintaining the fourth posture; The method for manufacturing an electricity storage device according to claim 3 , further comprising:

7. In the laser welding step, The laser light is irradiated by a scanner head; the scanner head faces the sealing plate and is inclined in the same direction as the case; The method for manufacturing the electricity storage device according to claim 1 or 2.

8. In the laser welding step, The case is irradiated with laser light while the sealing plate is oriented so as to face obliquely upward with respect to the vertical direction. The method for manufacturing the electricity storage device according to claim 1 or 2.

9. an electrode body having electrodes; an exterior body having an opening and accommodating the electrode body; a sealing plate that seals the opening; An annular molten and solidified portion formed at a fitting portion between the opening of the exterior body and the sealing plate, At least a portion of the molten and solidified portion is inclined toward the sealing plate or in a direction vertical to the sealing plate, The molten and solidified portion does not protrude outward from the outer casing. Energy storage device.

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