Method for manufacturing an electricity storage device

Abstract

To provide a method for manufacturing a power storage device in which an outer peripheral edge unit of a cap is uniformly welded to a circular recess section provided in a metal case over an entire circumference.SOLUTION: A power storage device 1 includes: a circular recess portion 4PR that is provided in a sidewall portion 4 of a metallic case 2, being recessed toward a thickness direction inner side HXI, and in which a liquid injection hole 4PH is bored in an annular recess portion 4PR; a recess peripheral portion 4PM that surrounds a periphery; and a cap portion 4PC that is welded to a recess peripheral portion 4PM and hermetically seals a liquid injection hole 4PH. A method for manufacturing the power storage device includes: an abutting step S61 of accommodating at least an annular cap outer peripheral edge portion 14CP of an unwelded cap 14C to be a cap portion 4PC in the annular recess portion 4PR of the metal case and abutting the cap outer peripheral edge portion 14CP to an inner peripheral surface 4PRI over an entire circumference; and an entire periphery welding process S64 for energy-beam-welding the cap outer peripheral edge portion 14CP to the recess peripheral portion 4PM over an entire circumference in a state where the cap outer peripheral edge portion 14CP abuts on the inner peripheral surface 4PRI of the circular recess portion 4PR over an entire circumference.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an electricity storage device having a cap portion that air-tightly seals a liquid injection hole of a metal case that contains an electrode body and an electrolyte. [Background technology]

[0002] Conventionally, in a power storage device such as a lithium ion secondary battery having a metal case containing an electrode body and an electrolyte, a power storage device in which a liquid inlet of the metal case is airtightly sealed with a cap part welded to the metal case and a manufacturing method thereof are known. For example, Patent Document 1 describes a technique in which an inlet provided on a lid of a housing, which is a battery can, is covered with an unwelded cap and the periphery of the cap is joined to the housing. Specifically, a cylindrical recess part is provided in the housing (lid body) one step lower than the outer surface, and a liquid inlet part is formed in the center of the bottom part. Then, an outer peripheral disk-shaped cap is inserted into the recess part, and the outer peripheral edge part of the cap is laser-welded to the wall part of the housing surrounding the recess part all around. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2009 / 128375 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to make the outer peripheral edge of the cap insertable into the cylindrical recess provided in the housing, the outer dimension of the outer peripheral edge of the cap must be smaller than the inner diameter of the recess. Therefore, when the outer peripheral edge of the cap is placed in the recess before welding, a gap is inevitably generated between the inner peripheral surface of the recess of the housing and the outer peripheral end surface of the sealing cap. Moreover, the size of the gap is not necessarily uniform over the entire circumference. In many cases, the outer peripheral end surface of the cap is positioned offset relative to the inner peripheral surface of the wall portion that forms the recess of the housing. In some cases, the outer peripheral end surface of the cap is positioned in a state in which a part of the circumferential direction of the outer peripheral end surface of the cap abuts against a part of the circumferential direction of the inner peripheral surface of the recess, while a large gap is generated on the opposite side.

[0005] When the outer peripheral edge of the cap is laser welded to the wall of the housing in this arrangement, the condition of the weld is likely to vary circumferentially due to variations in the size of the gap, which can lead to poor sealing or fluctuations in the strength of the seal. The present invention has been made in consideration of such problems, and aims to provide a method for manufacturing an electricity storage device in which the outer peripheral edge of a cap is welded evenly around the entire circumference to a circular recess formed in a metal case. [Means for solving the problem]

[0006] (1) One aspect of the present invention for solving the above problems is a method for manufacturing an electric storage device comprising: an electrode body, an electrolyte, and a metal case that accommodates them; the metal case having a circular recess provided in a sidewall portion that constitutes the metal case and recessed inward in a thickness direction of the sidewall portion, the circular recess being formed by drilling a liquid injection hole in an annular bottom portion that constitutes a bottom surface of the circular recess; a recess peripheral portion that surrounds a periphery of the circular recess; and a cap portion that is welded to the recess peripheral portion and hermetically seals the liquid injection hole, the method including: accommodating at least an annular cap outer peripheral edge portion of an unwelded cap that constitutes the cap portion within the circular recess portion of the metal case; The outer peripheral edge portion of the cap is expanded in diameter,The method for manufacturing an electricity storage device includes: a contacting step of contacting an outer circumferential edge portion of the cap with an inner circumferential surface of the circular recess portion over the entire circumference, and a full-circumference welding step of energy beam welding the outer circumferential edge portion of the cap to the periphery of the recess portion over the entire circumference in a state in which the outer circumferential edge portion of the cap is in contact with the inner circumferential surface of the circular recess portion over the entire circumference.

[0007] In the manufacturing method of the above-mentioned electricity storage device, in the abutting step, at least an outer peripheral edge portion of the unwelded cap is accommodated in a circular recess portion provided in the metal case, and then The outer periphery of the cap is expanded, The outer peripheral edge of the cap is brought into contact with the inner peripheral surface of the circular recess over the entire circumference. That is, a state is created in which no gap is generated between the inner peripheral surface of the circular recess and the outer peripheral end face of the unwelded cap over the entire circumference. Then, in the full circumference welding process, the outer peripheral edge of the cap is energy beam welded to the recess periphery over the entire circumference in this state in which the outer peripheral edge of the cap is in contact with the inner peripheral surface of the circular recess over the entire circumference. This prevents the welding condition from varying in the circumferential direction due to variations in the size of the gap, and allows the outer peripheral edge of the cap to be uniformly welded to the recess periphery over the entire circumference, thereby suppressing variations in the sealing strength of the cap portion.

[0008] As a method of accommodating at least the outer peripheral edge of the unwelded cap in a circular recess provided in the metal case and then abutting the entire outer peripheral edge of the cap against the inner peripheral surface of the circular recess, there may be mentioned a method of accommodating the outer peripheral edge of a cap of an expandable unwelded cap in the circular recess of the metal case, and then expanding the outer peripheral edge of the cap of the unwelded cap by a diameter expanding operation to abut the entire outer peripheral edge of the cap against the inner peripheral surface of the circular recess. There may also be mentioned a method of reducing the diameter of the cap outer peripheral edge of the unwelded cap in advance by a diameter reducing operation, accommodating the cap outer peripheral edge of the unwelded cap in the circular recess of the metal case, and then releasing the diameter reducing operation to expand the cap outer peripheral edge of the unwelded cap to abut the entire outer peripheral edge of the cap against the inner peripheral surface of the circular recess.

[0009] (2) The method for manufacturing the electric storage device described in (1) may preferably include a temporary fixing step of temporarily fixing the outer peripheral edge portion of the cap to the surrounding area of ​​the recess in a state in which the outer peripheral edge portion of the cap is in contact with the inner peripheral surface of the circular recess over the entire circumference after the abutment step and before the full-circumference welding step.

[0010] In this manufacturing method, a temporary fixing process is provided after the contact process and before the full circumference welding process. Therefore, after the temporary fixing process, the outer peripheral edge of the cap can be maintained in contact with the inner peripheral surface of the circular recess over the entire circumference without continuing the diameter expanding operation, and the full circumference welding process can be performed. In addition, the occurrence of a problem in which the unwelded cap falls off from the circular recess before the full circumference welding process can be prevented.

[0011] The temporary fixing may be performed by energy beam welding the outer peripheral edge of the cap to the recess periphery at several points in the circumferential direction while the outer peripheral edge of the cap is in contact with the inner peripheral surface of the recess over the entire circumference, or by applying an adhesive to the outer peripheral edge of the cap and adhering the outer peripheral edge of the cap to the annular bottom of the recess while the outer peripheral edge of the cap is in contact with the inner peripheral surface of the recess over the entire circumference.

[0012] (3) In the method for manufacturing an electric storage device described in (1) or (2), the unwelded cap is configured so that the outer peripheral edge portion of the cap can be expanded by a diameter expanding operation, and the abutting step may include a positioning step of positioning the unwelded cap in a form in which at least the outer peripheral edge portion of the unwelded cap is accommodated within the circular recessed portion of the metal case, and an expanded diameter abutting step of expanding the outer peripheral edge portion of the cap by the diameter expanding operation to abut the outer peripheral edge portion of the cap against the inner peripheral surface of the circular recessed portion over its entire circumference.

[0013] In this manufacturing method, an unwelded cap configured to be expandable in diameter by a diameter expansion operation is used as the unwelded cap, and in the abutment process, the unwelded cap before expansion is placed in the placement process, and then the cap outer peripheral edge is expanded in diameter by a diameter expansion operation to abut against the inner peripheral surface of the circular recess over its entire circumference in the diameter expansion abutment process. Therefore, the cap outer peripheral edge of the unwelded cap before the diameter expansion operation can be easily placed within the circular recess.

[0014] An example of an unwelded cap configured so that the outer peripheral edge of the cap can be expanded by an expansion operation is an unwelded cap made of a metal plate whose outer shape is a two-dimensional bell curve (two-dimensional normal distribution curve) that is rotationally symmetric around the cap axis, and whose outer peripheral edge can be expanded by an expansion operation in which the top of the cap in the central portion is pressed inward in the axial direction of the cap along the cap axis. Another example is an unwelded cap which has a disk-shaped cap central portion and a cap outer peripheral edge portion which surrounds it in the shape of a truncated cone and expands gradually in the thickness direction, and the cap central portion can be selected by clicking between a spherically bulging state on the side away from the cap outer peripheral edge portion in the axial direction and a spherically dented state on the side approaching the cap outer peripheral edge portion in the axial direction, so that when the cap central portion is in either the bulging or dented state (diameter expansion operation), the cap outer peripheral edge portion is in an expanded state, and when the opposite state (release operation, diameter reduction operation) is selected, the cap outer peripheral edge portion is in a reduced state.

[0015] (4) A method for manufacturing an electric storage device as described in (3), wherein the unwelded cap is made of a metal plate, has an outer shape that is a two-dimensional bell curve that is rotationally symmetric around the cap axis, has a cap top and a cap outer peripheral edge portion that is located radially outward of the cap top, and the expanding operation is an operation of pressing the cap top inward in the cap axial direction from the cap top to the cap outer peripheral edge portion along the cap axis, thereby expanding the cap outer peripheral edge portion radially outward in the cap direction.

[0016] In this manufacturing method, an unwelded cap is used, which has a cap top and a cap outer peripheral edge in a two-dimensional bell curve shape that is rotationally symmetric about the cap axis. The diameter expansion operation is an operation in which the cap top is pressed inward in the cap axial direction to expand the cap outer peripheral edge outward in the cap radial direction. Therefore, in the arrangement step, the unwelded cap is arranged in a form in which the cap outer peripheral edge of the unwelded cap is accommodated in the circular recess of the metal case, and in the diameter expansion abutment step, the cap top of the unwelded cap is pressed inward in the cap axial direction, whereby the cap outer peripheral edge can be easily expanded in diameter and the cap outer peripheral edge can be abutted over the entire circumference against the inner peripheral surface of the circular recess.

[0017] (5) In the method for manufacturing an electric storage device described in (1) or (2), the unwelded cap is configured so that the outer peripheral edge portion of the cap can be elastically reduced in diameter by a diameter reduction operation, and the abutment step may include a diameter reduction step of elastically reducing the diameter of the outer peripheral edge portion of the cap by the diameter reduction operation, a positioning step of positioning the unwelded cap in a form in which at least the reduced outer peripheral edge portion of the unwelded cap is accommodated within the circular recess, and a release abutment step of releasing the diameter reduction operation to expand the outer peripheral edge portion of the cap and abut the outer peripheral edge portion of the cap against the inner surface of the circular recess over the entire circumference.

[0018] In this manufacturing method, an unwelded cap is used that is configured such that the outer circumferential edge of the cap can be elastically contracted by a diameter contraction operation, and in the abutment process, the elastically contracted unwelded cap is placed in the arrangement process, and then in the release abutment process, the diameter contraction operation is released to expand the outer circumferential edge of the cap so that it abuts against the inner circumferential surface of the circular recess over its entire circumference. fixed In the process, there are no obstacles such as jigs for diameter reduction operations, and welding can be performed easily.

[0019] An example of an unwelded cap configured to elastically contract the outer circumferential edge of the cap by a diameter contraction operation is an unwelded cap made of a metal plate having a two-dimensional bell curve outer shape that is rotationally symmetrical about the cap axis, and in which the outer circumferential edge of the cap elastically contracts by a diameter contraction operation in which an inner part of the cap that is radially inward of the outer circumferential edge of the cap that forms the bottom part is sucked along the cap axis toward a side away from the outer circumferential edge of the cap.Another example is an unwelded cap configured such that the outer circumferential edge of the cap expands in diameter when the central part of the cap is in either the expanded or recessed state described above, and the outer circumferential edge of the cap contracts in the opposite state.

[0020] (6) A method for manufacturing an electric storage device as described in (5) may be provided, in which the unwelded cap is made of a metal plate and has an outer shape that is a two-dimensional bell curve that is rotationally symmetric around the cap axis, and has the cap outer peripheral edge portion and a cap inner portion that is located radially inward of the cap perpendicular to the axial direction of the unwelded cap than the cap outer peripheral edge portion, and the diameter reduction operation is an operation of sucking the cap inner portion outward in the cap axial direction from the cap outer peripheral edge portion side toward the cap inner portion side along the cap axis, thereby elastically reducing the diameter of the cap outer peripheral edge portion radially inward in the cap direction.

[0021] In this manufacturing method, an unwelded cap is used, which has a two-dimensional bell curve shape that is rotationally symmetrical about the cap axis and has a cap outer peripheral edge and a cap inner part. The diameter reduction operation is an operation in which the cap inner part is sucked outward in the cap axial direction, and the cap outer peripheral edge is elastically reduced in diameter inward in the cap radial direction. Therefore, in the diameter reduction arrangement step, the unwelded cap is arranged in a form in which the cap outer peripheral edge of the reduced diameter unwelded cap is accommodated in the circular recess of the metal case, and then in the release abutment step, the diameter reduction operation is released, i.e., the suction is stopped, so that the cap outer peripheral edge can be easily expanded in diameter and the cap outer peripheral edge can be abutted against the inner surface of the circular recess over the entire circumference.

[0022] (7) A method for manufacturing an electric storage device as described in any one of (1) to (6), wherein the inner circumferential surface of the circular recessed portion of the metal case has a shape that increases in diameter toward the inside in the thickness direction, and the cap outer circumferential end face of the unwelded cap has a shape that increases in diameter toward the inside in the thickness direction when the cap outer circumferential edge portion of the unwelded cap is accommodated within the circular recessed portion.

[0023] In this manufacturing method, the inner peripheral surface of the circular recess of the metal case and the outer peripheral end surface of the cap of the unwelded cap are shaped so that their diameters increase toward the inside in the thickness direction, so that in the abutting step, when the outer peripheral edge of the unwelded cap is expanded in diameter and abutted against the inner peripheral surface of the circular recess over its entire circumference, the unwelded cap engages with the circular recess and becomes difficult to fall off. Therefore, after the abutting step, it is possible to reliably prevent the unwelded cap from falling off the circular recess until the full circumference welding step or the temporary fixing step. [Brief description of the drawings]

[0024] [Figure 1] FIG. 2 is a partially cutaway longitudinal sectional view of the batteries according to the first and second embodiments and a modified embodiment. [Diagram 2] 1 is a flowchart showing each step of manufacturing the battery according to the first embodiment and a modified embodiment. [Diagram 3] FIG. 2 is a partially enlarged cross-sectional view showing a state in which an unwelded cap is placed in a circular recess of a lid body of a battery and welded in the first and second embodiments and a modified embodiment. [Figure 4] 4 is a partially enlarged cross-sectional view showing a state in which an unwelded cap is placed in a circular recess in a lid body of a battery according to the first embodiment. FIG. [Diagram 5] FIG. 11 is a partially enlarged cross-sectional view in accordance with the first embodiment, showing the state in which an unwelded cap placed in a circular recess of a battery lid is pressed and expanded in diameter so that the outer peripheral edge abuts against the inner peripheral surface of the circular recess over the entire circumference. [Figure 6] FIG. 11 is an explanatory diagram relating to embodiment 1, showing how the outer peripheral edge of the unwelded cap is temporarily fixed to the surrounding area of ​​the recess by laser welding while the outer peripheral edge is in contact with the inner peripheral surface of the circular recess over the entire circumference. [Figure 7] 10 is an explanatory diagram showing the shape of an outer peripheral edge portion of an unwelded cap and an inner peripheral surface of a circular recess portion of a lid body in a modified embodiment. FIG. [Figure 8] 5 is a flowchart showing steps for manufacturing a battery according to a second embodiment. [Figure 9] FIG. 11 is an explanatory view showing the relationship in diameter between a circular recess in a lid body of a battery and an unwelded cap according to a second embodiment. [Figure 10] FIG. 11 is a partially enlarged cross-sectional view showing a state in which the unwelded cap is sucked and reduced in diameter in the second embodiment. [Figure 11] FIG. 11 is a partially enlarged cross-sectional view illustrating a state in which an unwelded cap with a reduced diameter is placed in a circular recess in a lid body of a battery according to a second embodiment. [Figure 12] 13 is a partially enlarged cross-sectional view according to the second embodiment, showing a state in which the suction of the unwelded cap is released to expand the diameter thereof so that the outer circumferential edge portion is in contact with the inner circumferential surface of the circular recess portion over the entire circumference. FIG. [Figure 13] FIG. 11 is an explanatory diagram relating to embodiment 2, showing how the outer peripheral edge of the unwelded cap is temporarily fixed to the surrounding area of ​​the recess by laser welding while the outer peripheral edge is in contact with the inner peripheral surface of the circular recess over its entire circumference. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] <Embodiment 1> A method for manufacturing a lithium ion secondary battery (hereinafter, simply referred to as a battery) 1 according to a first embodiment of the present invention will be described below with reference to Figs. 1 to 6. The square battery 1 manufactured in the first embodiment shown in Fig. 1 is composed of a flat wound electrode body (hereinafter, simply referred to as an electrode body) 7, a rectangular box-shaped case 2 made of metal (made of aluminum in this embodiment) that houses the electrode body 7 therein, and a positive electrode terminal 5 and a negative electrode terminal 6 supported by the case 2. An electrolyte 8 is contained in the case 2, a part of which is impregnated in the electrode body 7 and a part of which is pooled at the bottom of the case 2.

[0026] The rectangular box-shaped case 2 is composed of a case body 3 in the form of a bottomed square cylinder having an opening 3C, and a rectangular plate-shaped lid body 4 welded in a form that closes the opening 3C of the case body 3. A positive terminal 5 and a negative terminal 6 are fixed to the lid body 4 via an insulating material not shown. In addition, a non-returnable safety valve 4S is provided in the center part of the lid body 4, which is thinner than other parts of the lid body 4 and breaks and opens when the internal pressure of the case 2 exceeds the valve opening pressure, thereby releasing the gas generated in the case 2 to the outside of the case 2. In addition, the lid body 4 has a liquid injection hole 4PH that penetrates the lid body 4 in its thickness direction between the safety valve 4S and the positive terminal 5, and a liquid injection part 4P that hermetically seals the liquid injection hole 4PH. The hole axis X1 of the liquid injection hole 4PH coincides with the thickness direction of the lid body 4.

[0027] The electrode body 7 is a flat wound type electrode body in which strip-shaped positive electrode plates 7P and strip-shaped negative electrode plates 7N are alternately stacked and wound with two strip-shaped separators 7S made of porous resin film interposed therebetween, and then flattened. The electrode body 7 is housed in the case 2 via a bottomed rectangular cylindrical resin film (not shown) with the winding axis 7X laid down on its side. On one side (the right side in FIG. 1) 7X1 of the electrode body 7 in the winding axis direction, a positive electrode current collecting portion 7P is wound with the positive electrode current collecting foil 7Pa of the positive electrode plate 7P exposed. s is provided, and this positive electrode current collecting portion 7P s A positive electrode terminal 5 is welded to the negative electrode plate 7N. The electrode body 7 has a negative electrode current collector portion 7N on the other side (the left side in FIG. 1) 7X2 in the winding axis direction, in which the negative electrode current collector foil 7Na of the negative electrode plate 7N is exposed and wound. s is provided, and this negative electrode current collecting portion 7N s A negative electrode terminal 6 is welded to the electrode.

[0028] Next, the manufacturing procedure of the battery 1 will be described with reference to the flowchart of FIG. 2. The flat wound electrode body 7 described above is formed separately by a known method. Separately, the positive electrode terminal 5 and the negative electrode terminal 6 are fixed to the lid 4. Then, in the electrode body connecting step S1, the positive electrode current collecting portion 7P of the electrode body 7 is s The positive electrode terminal 5 is welded to the negative electrode current collector 7N. sThen, in an insertion process S2, a resin film (not shown) folded into a bottomed rectangular tube is placed around the electrode body 7, and the resin film and the electrode body 7 are inserted into the case body 3 through the opening 3C, and the opening 3C is closed with the lid 4. Next, in a sealing welding process S3, the opening 3C portion of the case body 3 and the peripheral portion of the lid 4 are laser-welded all around to seal the opening 3C and to integrate the case body 3 and the lid 4 into a single unit to form the case 2.

[0029] In the subsequent liquid injection temporary sealing step S4, electrolyte 8 is injected into case 2 through liquid injection hole 4PH of lid 4, and liquid injection hole 4PH is temporarily sealed with a rubber plug (not shown). The injected electrolyte 8 is impregnated into electrode body 7 and also pools at the bottom of case 2. Then, in initial charge aging step S5, a voltage is applied between positive electrode terminal 5 and negative electrode terminal 6 to initially charge battery 1, and the battery is then held in a high-temperature environment for a predetermined time.

[0030] Then, in a sealing step S6, the temporary sealing is released, and an unwelded cap 14C, which will be described below, is welded to the entire periphery of the liquid injection hole 4PH to air-tightly seal the liquid injection hole 4PH.

[0031] Next, the sealing of the liquid inlet 4PH with the unwelded cap 14C in the sealing step S6 will be described in detail. Prior to the description of the sealing step S6, the unwelded cap 14C and the configuration of the vicinity of the liquid inlet 4PH in the lid body 4 of the case 2 before welding the unwelded cap 14C and the configuration of the liquid inlet portion 4P after sealing will be described.

[0032] As shown in FIG. 4, the cover 4, which forms one of the six side walls of the rectangular parallelepiped case 2, has a cover outer surface 4OS facing the outside (upward in FIG. 1 and FIG. 4). The cover 4 further has a circular recess 4PR. Specifically, the cover outer surface 4OS has a circular recess 4PR that is cylindrically recessed toward the inside HXI in the hole axis direction. The aforementioned liquid injection hole 4PH is drilled in the center of the annular bottom 4PS that forms the bottom surface 4PRB of the circular recess 4PR. That is, in this embodiment, the circular recess 4PR is concentric with the liquid injection hole 4PH, and the central axis of the circular recess 4PR coincides with the hole axis X1 of the liquid injection hole 4PH. The portion of the cover 4 that surrounds the circular recess 4PR is called the recess peripheral portion 4PM. The inner diameter of the circular recess 4PR is called the recess inner diameter D4.

[0033] On the other hand, as shown in FIG. 4, the unwelded cap 14C is made of a metal plate (aluminum plate in this embodiment), and has a two-dimensional bell curve shape (normal distribution curve shape, bell curve shape) that is rotationally symmetric around the cap axis X2. That is, the unwelded cap 14C has a three-dimensional shape obtained by rotating a bell curve (normal distribution curve, bell curve) 1 / 2 around the cap axis X2, which is the center line. The unwelded cap 14C has a top (one example of a cap top) 14CT that is located in the center and has a convex shape toward the cap axial direction outer side CXO (upward in FIG. 1 and FIG. 4), and an annular outer peripheral edge portion (one example of a cap outer peripheral edge portion) 14CP that is located on the cap radial direction outer side CRO beyond the top 14CT and expands toward the cap radial direction outer side CRO. The outer diameter of the unwelded cap 14C is a cap outer diameter 14D. As shown in FIG. 4, the cap outer diameter 14D of the unwelded cap 14C in a free state is smaller than the recess inner diameter D4 of the circular recess portion 4PR (14D<4D).

[0034] The unwelded cap 14C of the present embodiment 1 is configured to be able to expand the outer circumferential edge portion 14CP by a "diameter expanding operation." In the unwelded cap 14C, the "diameter expanding operation" is an operation in which the apex 14CT is pressed toward the cap axially inward CXI (downward in FIG. 5) from the apex 14CT toward the outer circumferential edge portion 14CP along the cap axis X2, thereby expanding the outer circumferential edge portion 14CP toward the cap radially outward CRO.

[0035] Therefore, the outer peripheral edge portion 14CP of the unwelded cap 14C is accommodated in the circular recess portion 4PR of the lid body 4, and the outer peripheral edge portion 14CP is expanded in diameter so that the outer peripheral end face 14CPe of the unwelded cap 14C is in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference. Then, the outer peripheral edge portion 14CP is welded to the recess peripheral portion 4PM over the entire circumference by a laser beam LB (an example of an energy beam) to form an annular melted and solidified portion 4PW. This forms the liquid injection portion 4P that hermetically seals the liquid injection hole 4PH (see Figures 1 and 3). This liquid injection portion 4P originates from the unwelded cap 14C and has a cap portion 4PC that is rotationally symmetrical about the cap axis X2 welded to the recess peripheral portion 4PM.

[0036] The sealing step S6 will be described. In the abutting step S61 of the sealing step S6, the outer peripheral edge portion 14CP of the unwelded cap 14C that becomes the cap portion 4PC is accommodated in the circular recessed portion 4PR of the case 2, and the outer peripheral edge portion 14CP is abutted over the entire circumference against the inner peripheral surface 4PRI of the circular recessed portion 4PR.

[0037] In detail, the arrangement step in the contact step S61 SIn step 61A, the unwelded cap 14C is first arranged so that the outer peripheral edge 14CP of the unwelded cap 14C is accommodated in the circular recess 4PR, that is, the outer peripheral edge 14CP is in contact with the annular bottom 4PS over the entire circumference, as shown in Fig. 4. As described above, the cap outer diameter 14D of the unwelded cap 14C in the free state is smaller than the recess inner diameter D4 of the circular recess 4PR (14D<4D), so that the outer peripheral edge 14CP can be easily accommodated in the circular recess 4PR. In addition, a gap GP is generated between the outer peripheral end surface 14CPe of the unwelded cap 14C and the inner peripheral surface 4PRI of the circular recess 4PR.

[0038] Next, in the diameter expansion contact step S61B, the unwelded cap 14C is subjected to a "diameter expansion operation" to expand the outer peripheral edge portion 14CP, i.e., the outer diameter of the outer peripheral edge portion 14CP is increased from the cap outer diameter 14D in the free state, and the outer peripheral edge portion 14CP is contacted over the entire circumference with the inner peripheral surface 4PRI of the circular recess portion 4PR. That is, the outer peripheral end face 14CPe of the unwelded cap 14C is contacted over the entire circumference with the inner peripheral surface 4PRI of the circular recess portion 4PR. At this time, the unwelded cap 14C moves and its position is adjusted so that the cap axis X2 coincides with the circular recess portion 4PR and the hole axis X1 of the liquid injection hole 4PH. That is, it is automatically centered.

[0039] As described above, the unwelded cap 14C can have its outer circumferential edge portion 14CP expanded radially outwardly CRO by a "diameter expanding operation" in which the top portion 14CT is pressed inwardly CXI in the cap axial direction (downward in FIG. 5).

[0040] In the diameter expansion contact step S61B, the top 14CT of the unwelded cap 14C is pressed with a pressing force PF toward the cap axial inside CXI (downward in FIG. 5) as shown by the black arrow in FIG. 5, and the outer peripheral edge 14CP is expanded toward the cap radial outside CRO as shown by the white arrow, and the outer peripheral edge 14CP is contacted over the entire circumference with the inner peripheral surface 4PRI of the circular recess 4PR. Specifically, the top 14CT is pressed toward the cap axial inside CXI using a rod-shaped pressing tool PJ.

[0041] Next, in the temporary fixing step S62 prior to the full circumference welding step S64, the outer peripheral edge portion 14CP of the unwelded cap 14C and the recess peripheral portion 4PM are welded in a scattered manner at a suitable number of points while maintaining the pressing force PF as shown by the black arrow in FIG. In the present embodiment 1, the outer peripheral edge portion 14CP and the recess peripheral portion 4PM are laser welded in a scattered manner at three points spaced at an angle of about 120 degrees in the circumferential direction by using the temporary fixing laser beam LBH. As a result, the outer peripheral edge portion 14CP is temporarily fixed to the recess peripheral portion 4PM while maintaining the state in which the outer peripheral edge portion 14CP is in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference. As a result, even if the diameter expanding operation is not continued, that is, even if the pressing force PF is released, the outer peripheral edge portion 14CP can be maintained in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference, and the full circumference welding step S64 described later can be performed. In addition, the occurrence of a problem in which the unwelded cap 14C falls off from the circular recess 4PR of the lid 4 can also be prevented.

[0042] Therefore, in the pressure releasing step S63, the pressing force PF indicated by the black arrow in Fig. 6 is released. Specifically, the rod-shaped pressing tool PJ is removed.

[0043] Furthermore, in the full circumference welding process S64, the outer peripheral edge portion 14CP is welded to the recess peripheral portion 4PM over the entire circumference by the laser beam LB while the outer peripheral edge portion 14CP is in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference. Thus, the liquid injection hole 4PH can be airtightly sealed by the cap portion 4PC (see FIG. 3). Moreover, the cap portion 4PC of the first embodiment prevents the welding condition from varying in the circumferential direction due to variations in the size of the gap GP, and the outer peripheral edge portion 14CP can be uniformly welded to the recess peripheral portion 4PM over the entire circumference, thereby suppressing variations in the strength of the seal by the cap portion 4PC.

[0044] (Variations) Next, a manufacturing method of the battery 101 according to a modified embodiment of the first embodiment will be described with reference to Fig. 7. In the manufacturing method of the battery 101 according to this modified embodiment, the shape of the inner circumferential surface 104PRI of the circular recessed portion 104PR of the lid body 4 used in the sealing step S6 and the shape of the outer circumferential end surface 114CPe of the unwelded cap 114C are different from those of the embodiment, but the rest are similar. Therefore, the description will be centered on the different parts, and the same reference numerals will be used for the similar parts, and the description of the similar parts will be omitted or simplified.

[0045] As can be easily understood from Figure 7, the circular recess portion 104PR provided in the lid body 4 used in this modified embodiment has a truncated conical shape whose inner surface 104PRI becomes larger in diameter as it moves inward in the hole axis direction HXI (downward in Figure 7), i.e., as it approaches the bottom surface 104PRB of the annular bottom portion 104PS.

[0046] On the other hand, the outer peripheral end surface 114CPe of the unwelded cap 114C has a shape that increases in diameter toward the inside CXI in the cap axial direction (downward in FIG. 7). Therefore, when the outer peripheral edge portion 114CP of the unwelded cap 114C is accommodated in the circular recess portion 104PR, the outer peripheral end surface 114CPe has a truncated cone shape that increases in diameter toward the inside HXI in the hole axial direction.

[0047] Therefore, in the above-mentioned contact step S61, specifically in the diameter expansion contact step S61B, the top 114CT of the unwelded cap 114C is pressed inward in the cap axial direction CXI to expand the outer peripheral edge 114CP, and the outer peripheral edge 114CP is brought into contact with the inner peripheral surface 104PRI of the circular recess 104PR over the entire circumference, so that the unwelded cap 114C engages with the circular recess 104PR and becomes difficult to come off. Therefore, after the contact step S61, it is possible to reliably prevent the unwelded cap 114C from falling off the circular recess 104PR before the temporary fixing step S62.

[0048] The first angle θ1 between the bottom surface 104PRB of the circular recess 104PR and the inner peripheral surface 104PRI, and the second angle θ2 between the bottom surface 104PRB of the circular recess 104PR and the outer peripheral end surface 114CPe of the unwelded cap 114C are preferably 60 to 85 degrees. Also, it is preferable to make the second angle θ2 larger than the first angle θ1 (θ1<θ2). This is because the diameter expansion generates a force that presses the outer peripheral edge portion 114CP of the unwelded cap 114C against the annular bottom portion 104PS, and the arrangement of the unwelded cap 114C in the circular recess 104PR can be more stabilized.

[0049] (Embodiment 2) Next, a manufacturing method of the battery 201 according to the second embodiment will be described with reference to Fig. 1, Fig. 2, and Fig. 8 to Fig. 13. In the manufacturing method of the battery 1 according to the first embodiment described above, an example has been shown in which an unwelded cap 14C capable of expanding the outer circumferential edge portion 14CP by a diameter expanding operation of pressing the top portion 14CT is used and welded to the circular recess portion 4PR of the lid body 4. In contrast, the manufacturing method of the battery 201 of the present embodiment 2 is different in that an unwelded cap 214C is used that can elastically reduce the diameter of the outer peripheral edge portion 214CP by a diameter reduction operation of sucking the inner portion 214CI including the top portion 214CT. Therefore, the following description will focus on the different parts, and similar parts will be given the same reference numerals and descriptions of similar parts will be omitted or simplified.

[0050] In the configuration and manufacturing method of the battery 201 of the present embodiment 2, the electrode assembly connection step S1 to the initial charge aging step S5 are similar to those of the embodiment 1 (see FIG. 3), and therefore the description thereof will be omitted. On the other hand, the sealing step S260 is different from the sealing step S6 of the embodiment 1, and therefore will be described below (see FIG. 8).

[0051] As shown in FIG. 9, the unwelded cap 214C is also made of a metal plate (aluminum plate in this embodiment), and has a two-dimensional bell curve shape (normal distribution curve shape, bell curve shape) that is rotationally symmetric around the cap axis X2. That is, the unwelded cap 214C also has a three-dimensional shape obtained by rotating a bell curve (normal distribution curve, bell curve) around the cap axis X2, which is the center line, one revolution. The unwelded cap 214C also has an apex (an example of a cap apex) 214CT that is located in the center and has a convex shape toward the cap axial direction outer side CXO (upward in FIG. 1 and FIG. 9), and an annular outer peripheral edge portion (an example of a cap outer peripheral edge portion) 214CP that is located on the cap radially outer side CRO beyond the apex 214CT and expands toward the cap radially outer side CRO. The portion of the cap radially inner side CRI beyond the outer peripheral edge portion 214CP is defined as an inner portion (an example of a cap inner portion) 214CI. The outer diameter of the unwelded cap 214C is defined as a cap outer diameter 214D. As shown in Fig. 9, the cap outer diameter 214D of the unwelded cap 214C in a free state is larger than the recess inner diameter D4 of the circular recess portion 4PR (214D>4D).

[0052] The unwelded cap 214C of the second embodiment is configured to be able to elastically reduce the diameter of the outer circumferential edge portion 214CP by a "diameter reduction operation." In the unwelded cap 214C, the "diameter reduction operation" is an operation in which the inner portion 214CI is elastically attracted toward the cap axial outer side CXO (upward in FIG. 9) from the outer circumferential edge portion 214CP toward the apex 214CT along the cap axis X2, thereby elastically reducing the diameter of the outer circumferential edge portion 214CP toward the cap radial inner side CRI.

[0053] The outer peripheral edge 214CP of the unwelded cap 214C, the diameter of which has been reduced in advance, is accommodated in the circular recess 4PR of the lid 4. 2The diameter of the cap 14CP is released and elastically expanded, so that the outer peripheral end surface 214CPe of the unwelded cap 214C is in contact with the inner peripheral surface 4PRI of the circular recessed portion 4PR over the entire circumference. Then, as in the first embodiment, the outer peripheral edge portion 214CP is welded to the recessed peripheral portion 4PM over the entire circumference by the laser beam LB to form the annular melted and solidified portion 4PW. This forms the liquid injection portion 4P that hermetically seals the liquid injection hole 4PH (see Figs. 1 and 3). As in the first embodiment, the liquid injection portion 4P of the second embodiment also has a cap portion 4PC that originates from the unwelded cap 214C and is rotationally symmetrical around the cap axis X2 welded to the recessed peripheral portion 4PM.

[0054] The sealing step S260 will be described. In the abutting step S261 of the sealing step S260, the outer peripheral edge portion 214CP of the unwelded cap 214C that becomes the cap portion 4PC is accommodated in the circular recessed portion 4PR of the case 2, and the entire outer peripheral edge portion 214CP is abutted against the inner peripheral surface 4PRI of the circular recessed portion 4PR.

[0055] In detail, in the suction diameter reduction step S261A of the contact step S261, first, as shown in Fig. 10, the suction pipe SS is arranged so that the tip SSS of the suction pipe SS contacts the inside part 214CI of the unwelded cap 214C and the top part 214CT is located inside the tip SSS. The suction pipe SS is connected to a vacuum pump (not shown) to exhaust the air inside the suction pipe SS, generating a suction force SF indicated by a black arrow, and the tip SSS of the suction pipe SS sucks the inside part 214CI of the unwelded cap 214C. This causes the inside part 214CI of the unwelded cap 214C to deform so as to be narrowed, and the outer peripheral edge part 214CP is elastically reduced in diameter to the cap radial direction inside CRI as indicated by a white arrow, and the cap outer diameter 214Ds in the reduced diameter state is made smaller than the cap outer diameter 214D in the free state and further smaller than the recess inner diameter D4 of the circular recess part 4PR (214Ds<4D<214D).

[0056] Next, the placement process SIn 261B, as shown in Fig. 11, the unwelded cap 214C is moved together with the suction pipe SS, and the unwelded cap 214C is arranged in a state in which the outer peripheral edge 214CP is accommodated in the circular recess 4PR, that is, the outer peripheral edge 214CP is in contact with the annular bottom 4PS over the entire circumference. As described above, the cap outer diameter 214Ds of the unwelded cap 214C in the reduced diameter state is smaller than the recess inner diameter D4 of the circular recess 4PR (214Ds<4D), so that the outer peripheral edge 214CP can be easily accommodated in the circular recess 4PR. In addition, a gap GP is generated between the outer peripheral end surface 214CPe of the unwelded cap 214C and the inner peripheral surface 4PRI of the circular recess 4PR.

[0057] Thereafter, in the release contact step S261C, the "diameter reduction operation" is released, specifically, the suction force SF of the suction tube SS is eliminated, and the outer peripheral edge portion 214CP is elastically expanded in diameter, so that the outer peripheral edge portion 214CP is contacted over the entire circumference with the inner peripheral surface 4PRI of the circular recessed portion 4PR. That is, the outer peripheral end face 214CPe of the unwelded cap 214C is contacted over the entire circumference with the inner peripheral surface 4PRI of the circular recessed portion 4PR. At this time, the unwelded cap 214C moves and its position is adjusted so that the cap axis X2 coincides with the circular recessed portion 4PR and the hole axis X1 of the liquid injection hole 4PH. That is, the center is automatically adjusted. In this embodiment 2, the outer peripheral edge portion 214CP of the unwelded cap 214C elastically presses the inner peripheral surface 4PRI of the circular recess portion 4PR, so that the unwelded cap 214C can be held in the circular recess portion 4PR without applying a pressing force PF or the like to the unwelded cap 214C as in embodiment 1. After the diameter reduction operation is released, the suction pipe SS is moved.

[0058] Next, in the temporary fixing step S262 prior to the full circumference welding step S264, unlike the first embodiment, the outer peripheral edge portion 214CP of the unwelded cap 214C and the recess peripheral portion 4PM are welded in a scattered manner at a suitable number of points without applying a pressing force PF as shown in FIG. 2The 14CP and the recess peripheral portion 4PM are laser-welded at three points spaced at an angle of approximately 120 degrees in the circumferential direction. This temporarily fixes the outer peripheral edge portion 214CP to the recess peripheral portion 4PM while maintaining the outer peripheral edge portion 214CP in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference. This allows the entire circumference welding step S264 described below to be performed while maintaining the outer peripheral edge portion 214CP in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference. This also prevents the unwelded cap 214C from falling off the circular recess portion 4PR of the lid body 4.

[0059] Furthermore, in a full circumference welding process S264, with the outer peripheral edge portion 214CP in contact with the inner peripheral surface 4PRI of the circular recess portion 4PR over the entire circumference, the outer peripheral edge portion 214CP is welded over the entire circumference to the recess peripheral portion 4PM by the laser beam LB. In this way, the liquid injection hole 4PH can be airtightly sealed by the cap portion 4PC (see FIG. 3). Moreover, with the cap portion 4PC of this embodiment 2, the welding condition is prevented from varying in the circumferential direction due to the variation in the size of the gap GP, and the outer peripheral edge portion 214CP is welded to the recess peripheral portion 4PM over the entire circumference. 2 The 14CP can be welded uniformly all around, and fluctuations in the strength of the seal provided by the cap portion 4PC can be suppressed.

[0060] The present invention has been described above in accordance with embodiments 1 and 2 and modified forms. However, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that the present invention can be modified and applied as appropriate without departing from the spirit of the present invention. For example, in the embodiment, the arrangement step S 61A, S In 261B, the outer peripheral edge portions 14CP, 214CP of the unwelded caps 14C, 214C are accommodated in the circular recessed portion 4PR of the case 2 (see FIGS. 4 and 11). Therefore, the top portions 14CT, 214CT protrude outward from the lid outer surface 4OS of the lid body 4. However, it is also possible to prevent the top of the cap from protruding from the outer surface of the lid body by increasing the depth of the circular recess of the lid body or by using a low-height unwelded cap so that the entire unwelded cap is contained within the circular recess.

[0061] In the embodiment, the temporary fixing steps S62, S262 are performed prior to the full circumference welding steps S64, S264, but the full circumference welding step may be performed without temporary fixing the unwelded cap. However, when using an unwelded cap that is expanded in diameter as in the first embodiment, the pressure is not released in the pressure release step S63, and the full circumference welding is performed while continuing to press the top of the cap.

[0062] In the above-described modified embodiment, the inner peripheral surface 104PRI of the circular recess 104PR provided in the lid 4 is formed into a truncated cone shape that increases in diameter toward the inside HXI in the hole axis direction (downward in FIG. 7). In addition, an unwelded cap 114C that can be expanded by a diameter expansion operation is used as the unwelded cap 114C, and its outer peripheral end surface 114CPe is formed into a shape that increases in diameter toward the inside CXI in the cap axis direction (downward in FIG. 7). However, as in the second embodiment, an unwelded cap that can be reduced in diameter by a diameter reduction operation may be used, and its outer peripheral end surface may be formed into a shape that increases in diameter toward the inside CXI in the cap axis direction. [Explanation of symbols]

[0063] 1,101,201 Battery (energy storage device) 2 Case (metal case) 4 Lid (side wall) 4OS Lid outer surface (outer wall surface) 4P,104P Liquid injection part 4PH,104PH Liquid injection hole 4PR, 104PR circular recess 4PRI,104PRI Inner surface D4 Inner diameter of recess 4PM, 104PM Around the recess 4PRB, 104PRB Bottom 4PS, 104PS Circular bottom 4PC Cap 4PW Melting and solidification section 4PHW Temporary stop 14C, 114C, 214C Unwelded Cap D14, D214, 214Ds Cap outer diameter 14CT, 114CT, 214CT Top (top of cap) 14CP, 114CP, 214CP Outer edge (outer edge of cap) 214CI Inner part (inner part of cap) 14CPe, 114CPe, 214CPe Outer end face (cap outer end face) X1 hole axis HXI Hole axis direction inside (thickness direction inside) HRI radial inside X2 Cap axis CXI Cap Axial Inner CXO Cap axial direction outside CRI Cap Radial Inner Side CRO Cap radial outer side PF pressing force SF attraction power S6,S260 Sealing process S61,S261 Contact process S61A placement process S261A Diameter reduction process S261B placement process S61B Diameter expansion contact process S261C Release contact process S62, S262 Temporary fixing process S63 Pressure release process S64, S264 All-around welding process LB Laser beam (energy beam)

Claims

1. The battery includes an electrode body, an electrolyte, and a metal case that contains these. The metal case is A circular recessed portion is provided in a side wall portion constituting the metal case and recessed toward an inner side in a thickness direction of the side wall portion, A liquid injection hole is formed in the annular bottom portion that forms the bottom surface of the circular recess portion. The circular recessed portion; a recess peripheral portion surrounding the circular recess portion; a cap portion welded to the periphery of the recess and airtightly sealing the liquid injection hole. A method for manufacturing an electricity storage device, comprising: a contacting step of accommodating at least an annular outer peripheral edge portion of the unwelded cap that becomes the cap portion into the circular recessed portion of the metal case, expanding the diameter of the outer peripheral edge portion of the cap, and contacting the entire outer peripheral edge portion of the cap against an inner peripheral surface of the circular recessed portion; and a full-circumferential welding process of energy beam welding the outer circumferential edge portion of the cap to the periphery of the recess in a state in which the outer circumferential edge portion of the cap is in contact with the inner circumferential surface of the circular recess over the entire circumference. A method for manufacturing an electricity storage device.

2. A method for producing the electricity storage device according to claim 1, comprising the steps of: After the abutting step and before the circumferential welding step, a temporary fixing step of temporarily fixing the outer circumferential edge portion of the cap to the peripheral portion of the recess in a state in which the outer circumferential edge portion of the cap is in contact with the inner circumferential surface of the circular recess over the entire circumference thereof; A method for manufacturing an electricity storage device.

3. A method for producing the electricity storage device according to claim 1 or 2, comprising the steps of: The unwelded cap is configured so that the outer peripheral edge of the cap can be expanded by a diameter expanding operation, The contacting step includes: a positioning step of positioning the unwelded cap such that at least the outer peripheral edge of the unwelded cap is accommodated in the circular recess of the metal case; and a diameter expansion contact process for expanding the outer peripheral edge portion of the cap by the diameter expansion operation, so that the outer peripheral edge portion of the cap is brought into contact with the inner peripheral surface of the circular recess over the entire circumference thereof. A method for manufacturing an electricity storage device.

4. A method for producing the electricity storage device according to claim 3, comprising the steps of: The unwelded cap is It is made of a metal plate, The outer shape is a two-dimensional bell curve that is rotationally symmetric about the cap axis, A cap top portion, and the cap outer peripheral edge portion is located radially outward of the cap top portion, The diameter expansion operation is The cap top is pressed inward in the cap axial direction from the cap top toward the cap outer peripheral edge along the cap axis, This is an operation for expanding the outer peripheral edge portion of the cap radially outward. A method for manufacturing an electricity storage device.

5. A method for producing the electricity storage device according to claim 1 or 2, comprising the steps of: The unwelded cap is configured such that the outer peripheral edge of the cap can be elastically contracted by a diameter contracting operation, The contacting step includes: a diameter reducing step of elastically reducing the diameter of the outer peripheral edge portion of the cap by the diameter reducing operation; a positioning step of positioning the unwelded cap such that at least the reduced outer peripheral edge portion of the unwelded cap is accommodated in the circular recess; and a release abutment process for releasing the diameter reduction operation to expand the outer peripheral edge portion of the cap and abutting the outer peripheral edge portion of the cap against the inner peripheral surface of the circular recessed portion over the entire circumference thereof. A method for manufacturing an electricity storage device.

6. A method for producing the electricity storage device according to claim 5, comprising the steps of: The unwelded cap is It is made of a metal plate, The outer shape is a two-dimensional bell curve that is rotationally symmetric about the cap axis, The cap outer periphery, and a cap inner portion located radially inward of the cap in a direction perpendicular to the axial direction of the unwelded cap relative to the cap outer peripheral edge portion; The diameter reduction operation is The cap inner portion is sucked outward in the cap axial direction from the cap outer peripheral edge portion side toward the cap inner portion side along the cap axis, The outer circumferential edge of the cap is elastically contracted inward in the radial direction of the cap. A method for manufacturing an electricity storage device.

7. A method for producing the electricity storage device according to claim 1 or 2, comprising the steps of: The inner circumferential surface of the circular recess of the metal case is The diameter of the shape increases toward the inside in the thickness direction, The outer peripheral end surface of the unwelded cap is When the outer peripheral edge of the unwelded cap is accommodated in the circular recess, the outer peripheral edge of the unwelded cap has a shape that increases in diameter toward the inside in the thickness direction. A method for manufacturing an electricity storage device.

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