Battery cell and method for manufacturing the same

Abstract

To provide a battery cell and a method for manufacturing the battery cell that can ensure the strength of a folded rectangular tubular case body and improve the product precision. [Solution] A battery cell 10 comprising a secondary battery ND having an electrode body 2, a rectangular cylindrical case body 11 housing the electrode body 2 with both ends 11T in the Z direction open, and a lid 12 sealing the ends 11T of the case body 11, wherein the case body 11 has a pair of long side portions 111 formed by bending a flat plate material HZ along the axial direction (Z direction) and a pair of short side portions 112 perpendicular to the long side portions 111, and in the bent portion 113 where the long side portions 111 and the short side portions 112 intersect, thick-walled portions N1 and thin-walled portions N2 are alternately formed along the axial direction (Z direction).

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a battery cell constituting a secondary battery used as a driving source for hybrid vehicles, electric vehicles and the like, and a method for manufacturing the same. [Background Art]

[0002] Secondary batteries used as driving sources for hybrid vehicles, electric vehicles and the like need to conduct high current at high voltage, and thus tend to use large prismatic battery cells. The battery cell includes, for example, a flatly wound electrode assembly, a square cylindrical case body accommodating the electrode assembly, and a lid sealing the case body. The case body is formed, for example, by bending a flat plate material made of an aluminum plate or a steel plate into a square cylindrical shape. However, compressive stress remains on the inner side of the plate and tensile stress remains on the outer side of the plate at the bent portion of the flat plate material, and the reaction force thereof causes a problem that the product accuracy of the bent case body decreases. In addition, for a large case body, there is a problem that the bending force increases when bending the flat plate material. To address this problem, for example, Patent Document 1 discloses a method of performing bending while irradiating a bent portion with laser light to heat-soften (weaken) the same, so as to reduce the bending force required for the flat plate material. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Laid-Open No. 2014-79796 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, in the technology of the aforementioned Patent Document 1, the heat-softened (weakened) bent portion is elongated during bending, so that the overall plate thickness becomes thin, which causes a problem that the strength of the case body tends to decrease.

[0005] This disclosed technology has been made in view of the aforementioned problems, and aims to provide a battery cell and a method for manufacturing the battery cell that can ensure the strength of a folded rectangular tubular case body and improve the product precision thereof. [Means for solving the problem]

[0006] (1) One aspect of the disclosed technology for solving the above problems is a battery cell comprising a metal battery case having an electrode body, a rectangular cylindrical case body housing the electrode body and having openings at both ends in the axial direction, and a lid that seals the ends of the case body, wherein the case body comprises a pair of long side portions formed by bending a flat plate material along the axial direction and a pair of short side portions perpendicular to the long side portions, and in the bent portion where the long side portions and the short side portions intersect, thick-walled portions and thin-walled portions are alternately formed along the axial direction.

[0007] (2) In the battery cell described in (1), it is preferable that the thick-walled portion and the thin-walled portion are formed alternately in multiple rows along the axial direction in the bent portion.

[0008] (3) In the battery cell described in (1) or (2), it is preferable that the thickened portion is formed on the axial central side of the bent portion with a higher area ratio than on the end sides.

[0009] (4) In a battery cell described in any one of (1) to (3), it is preferable that the thin-walled portion is formed in a location where either one or both of the inner surface and outer surface of the flat plate material are perforated in a concave shape by the heat of the laser beam.

[0010] (5) Another aspect of the disclosed technology for solving the above problems is a method for manufacturing a battery cell as described in any one of (1) to (4), wherein the manufacturing process of the case body includes a preparation step of forming a thickened portion corresponding to the thickened portion and a thinned portion corresponding to the thinned portion in the portion of the flat material that is to be bent. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view of a battery cell according to one aspect of this embodiment. [Figure 2] Figure 1 shows a schematic cross-sectional view of AA. [Figure 3] This is a view taken along arrow B, as shown in Figure 2. [Figure 4] Figure 1 is a flowchart illustrating the manufacturing method for the battery cell case body. [Figure 5] This is a plan view of a flat plate material in which a thin-walled section and a thick-walled section have been formed in the area to be bent, as shown in the preparation process in Figure 4. [Figure 6A] Figure 5 shows a cross-sectional view of CC. [Figure 6B] Figure 5 shows a cross-sectional view of the part of the flat plate material that is to be bent for use in Modification 1 of the battery cell shown in Figure 1, as shown in Figure 5. [Figure 7A] Figure 4 shows a cross-sectional view of the bending process in which a flat sheet material is set in the bending die device. [Figure 7B] Figure 4 shows a cross-sectional view of a flat sheet material after it has been bent using a bending die device during the bending process. [Figure 8] This is a view from arrow B in Figure 2, in a modified example 2 of the battery cell shown in Figure 1. [Modes for carrying out the invention]

[0012] <Detailed description of this battery cell> Next, the overall configuration of a battery cell according to one aspect of an embodiment of the disclosed technology will be described in detail with reference to the drawings. FIG. 1 shows a side view of a battery cell according to one aspect of the present embodiment. FIG. 2 shows a schematic cross-sectional view taken along line A-A shown in FIG. 1. FIG. 3 shows a view from arrow B shown in FIG. 2. In each figure, the X direction indicates the width direction of the short side portion of the case body in the battery cell, the Y direction indicates the width direction of the long side portion of the case body in the battery cell, and the Z direction indicates the axial direction of the case body in the battery cell. The Z direction is also the axial direction of the electrode body.

[0013] A battery cell 10 according to one aspect of an embodiment of the technology disclosed herein is the battery cell 10 that constitutes a secondary battery ND including a battery case 1 and an electrode body 2, as shown in FIGS. 1 and 2. Among these, the battery case 1 includes a square cylindrical case body 11 that accommodates the electrode body 2 and has both ends 11T open in the axial direction (Z direction), and lid bodies 12 that seal both ends 11T of the case body 11.

[0014] Here, the electrode body 2 is an electrode body formed by flatly winding and laminating a strip-shaped positive electrode foil 2a, a strip-shaped negative electrode foil 2b, and a strip-shaped separator 2c interposed between the two electrode foils. However, the electrode body is not necessarily limited to this. For example, it may be an electrode body formed by laminating a plurality of sheet-shaped positive electrode foils, sheet-shaped negative electrode foils, and sheet-shaped separators interposed between the two electrode foils.

[0015] The present battery cell 10 constituting the secondary battery ND may be, for example, a lithium ion secondary battery. In this case, for example, an aluminum foil is used as the positive electrode foil 2a, and for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNiO2, etc.) can be used. Further, for example, a copper foil is used as the negative electrode foil 2b, and for example, graphite, hard carbon, soft carbon, etc. can be used as the active material fixed to the copper foil. Further, for example, a porous sheet made of polypropylene, polyethylene, or the like can be used as the separator 2c.

[0016] The lid 12 of the battery case 1 is formed of, for example, a plate material made of an aluminum material (including an aluminum alloy material), stainless steel, or the like. The end portion 11T of the case main body 11 and the lid body 12 are watertightly joined by, for example, laser welding. Current collector terminals 3 (a positive electrode current collector terminal 3a and a negative electrode current collector terminal 3b) connected to tab portions 2T formed at both ends of the electrode body 2 in the Z direction are fixed to the left and right lid bodies 12 via an insulating material 4.

[0017] Further, the case main body 11 of the battery case 1 is a square cylindrical body with a rectangular cross-section having a pair of wide long side surface portions 111 extending in the axial direction (Z direction) and a pair of narrow short side surface portions 112 (an upper short side surface portion 112a and a lower short side surface portion 112b) orthogonal to the long side surface portions 111. Among the short side surface portions 112, the upper short side surface portion 112a located at the upper position is formed with an injection port 114 for injecting an electrolyte into the battery case 1 and a safety valve 115. The case main body 11 is formed by bending a flat plate material HZ made of, for example, an aluminum material (including an aluminum alloy material), stainless steel, or the like along the axial direction (Z direction). Specifically, it is a square cylindrical body obtained by welding the tip end portions PZT of two bent plate materials PZ, each of which is obtained by bending the flat plate material HZ into a U-shaped (channel-shaped) cross-section in the bending step S2 described later.

[0018] In the four bent sections 113 where the long side portion 111 and the short side portion 112 of the case body 11 intersect, thick-walled sections N1 and thin-walled sections N2 are alternately formed along the axial direction (Z direction). Specifically, as shown in Figures 2 and 3, multiple concave recesses DP are formed along the axial direction (Z direction) on the inner surface HZ1 side of the bent section 113. The minimum wall thickness t1 of the bent section 113 where the recesses DP are formed is smaller than the minimum wall thickness t2 of the section where the recesses DP are not formed. Therefore, the section of the bent section 113 where the recesses DP are formed is defined as the thin-walled section N2, and the section with a relatively larger wall thickness than the thin-walled section N2 is defined as the thick-walled section N1. Here, the thin-walled section N2 and the thick-walled section N1 are formed with approximately the same length along the axial direction (Z direction), but they may be formed with different lengths. Furthermore, the minimum wall thickness t1 of the thin-walled section N2 is preferably about 40-60% of the minimum wall thickness t2 of the thick-walled section N1. This is because if the minimum wall thickness t1 of the thin-walled section N2 is less than 40% of the minimum wall thickness t2 of the thick-walled section N1, the density of the thin-walled section N2 may decrease too much. Also, the recessed portion DP may be formed before or after the bending process.

[0019] In a case body 11 having a bent section 113 in which thick sections N1 and thin sections N2 are alternately formed, as shown in Figure 3, the reaction force between the compressive stress Q1 and tensile stress Q2 remaining between the inner surface HZ1 and outer surface HZ2 of the bent section 113 can be reduced in the thin section N2, thereby reducing the bending accuracy defects of the long side section 111 and short side section 112 that originate from the bent section 113. Furthermore, the connection strength between the long side section 111 and short side section 112 in the bent section 113 can be improved by the thick section N1, thereby ensuring the strength of the case body 11. Thus, the strength of the bent rectangular tubular case body 11 can be ensured, and a battery cell 10 with improved product accuracy of the case body 11 can be produced.

[0020] Furthermore, the thin-walled portion N2 is preferably formed in a location where either or both of the inner surface HZ1 and outer surface HZ2 of the flat plate material HZ have a pre-processing recess DY that has been drilled in a concave shape by the heat of the laser beam LS. In this case, a fine thin-walled portion N2 can be formed with precision at the required location on the inner surface HZ1 of the plate, further improving the product precision and strength of the case body 11. Here, each thin-walled portion N2 is formed on the inner surface HZ1 of the flat plate material HZ to the same size.

[0021] Furthermore, the thin-walled portion N2 is not formed at the axial (Z-direction) ends 11T of the bent portion 113 of the case body 11. Therefore, the ends 11T of the case body 11 and the lid 12 can be reliably welded in a watertight manner.

[0022] <Detailed explanation of the manufacturing method of this battery cell> Next, a method for manufacturing the battery cell 10 according to an embodiment of the disclosed technology described above will be explained in detail with reference to the drawings. Figure 4 shows a flowchart illustrating a method for manufacturing the case body of a battery cell according to one aspect of this embodiment. Figure 5 shows a plan view of a flat plate material in which a thin-walled portion and a thick-walled portion have been formed in the portion to be bent in the preparation step shown in Figure 4. Figure 6A shows a cross-sectional view of the CC shown in Figure 5. Figure 7A shows a cross-sectional view of the flat plate material set in the bending die device in the bending process shown in Figure 4. Figure 7B shows a cross-sectional view of the flat plate material bent in the bending die device in the bending process shown in Figure 4. In Figures 5 and 6, the first direction indicates the extension direction of the portion of the flat plate material intended for bending, and the second direction indicates the thickness direction of the flat plate material. In Figure 7, the left-right direction indicates, for example, the vertical direction perpendicular to the portion of the flat plate material intended for bending (bending portion), the up-down direction indicates, for example, the thickness direction of the flat plate material, and the depth-to-front direction indicates, for example, the extension direction of the portion of the flat plate material intended for bending (bending portion).

[0023] The manufacturing process for the case body 11 of the battery cell 10 comprises a preparation step S1, a bending step S2, and a joining step S3, as shown in Figure 4. In the preparation step S1, a thickened portion N1Y corresponding to a thickened portion N1 and a thinned portion N2Y corresponding to a thinned portion N2 are formed in the portion 113Y of the flat plate material HZ that is to be bent. Specifically, a pulsed laser is used to create multiple pre-processing recesses DY, for example, circular openings, that are recessed in a second direction (the thickness direction of the flat plate material HZ) on the first surface HZ1Y (the plate surface that will become the inner surface HZ1 mentioned above) of the portion 113Y of the flat plate material HZ that is to be bent in a first direction. The flat plate material HZ is, for example, a rectangular plate made of stainless steel with a constant thickness. Multiple pre-processing recesses DY are created so that the spacing between adjacent pre-processing recesses DY is approximately the same. Furthermore, no pre-processing recess DY is drilled on the second surface HZ2Y (the surface that will become the outer surface HZ2 of the plate as described above) of the bending portion 113Y. In addition, as shown in Figure 5, a pre-processing recess DY is drilled along both of the two bending portions 113Y. Furthermore, no pre-processing recess DY is drilled in the processing end portions 113YS located at both ends of the bending portion 113Y, but pre-processing recess DY is drilled in the intermediate processing portions 113YM of the bending portion 113Y, excluding the processing end portions 113YS.

[0024] As shown in Figure 6A, in the bending portion 113Y, the portion where pre-processing recesses DY are formed by the heat of the irradiated laser beam LS has a relatively smaller plate thickness than the portion where the laser beam LS is not irradiated. Therefore, in this preparation step S1, by drilling multiple pre-processing recesses DY on the first surface HZ1Y side of the bending portion 113Y, a thin-walled portion N2Y is formed in the portion of the bending portion 113Y where the pre-processing recesses DY are drilled (formed), and a thick-walled portion N1Y, which has a relatively larger plate thickness than the thin-walled portion N2Y, is naturally formed in the portion where the pre-processing recesses DY are not drilled.

[0025] Next, in the bending process S2, a bending die device 50 is used to press-form a flat plate material HZ, which has multiple pre-processing recesses DY drilled along the bending target section 113Y, into a U-shaped cross section. The bending die device 50 comprises a first bending die 51 and a second bending die 52, as shown in Figure 7A. The first bending die 51 is a rectangular die that is movable in the vertical direction, as shown in Figure 7A, and the left-right dimension H1 shown in Figure 7A is the internal dimension in the X direction of the case body 11 described above. The second bending die 52 comprises a first body part 52A having a first inner wall surface 52AT perpendicular to the left-right direction shown in Figure 7A, a second body part 52B having a second inner wall surface 52BT parallel to the first inner wall surface 52AT, and a pressing part 53 positioned between the first inner wall surface 52AT and the second inner wall surface 52BT. The lateral separation distance H2 between the first inner wall surface 52AT of the first main body portion 52A and the second inner wall surface 52BT of the second main body portion 52B is the external dimension of the case body 11 in the X direction. The retaining portion 53 is a rectangular plate that is movable in the vertical direction, and a biasing means 54 consisting of a spring is provided on the lower side of the retaining portion 53 that can bias the retaining portion 53 from the lower side to the upper side in the vertical direction.

[0026] In the bending process S2, first, the flat sheet material HZ, from which the pre-processing recess DY was drilled in the preparation process S1, is placed on the pressing portion 53 located above the first main body portion 52A and the second main body portion 52B. Specifically, the flat sheet material HZ is placed on the pressing portion 53 such that the short side portion 112Y, sandwiched between the two bending portions 113Y on the flat sheet material HZ, fits between the extension surface extending upward in the vertical direction of the first inner wall surface 52AT of the first main body portion 52A and the extension surface extending upward of the second inner wall surface 52BT of the second main body portion 52B. Next, the first bending die 51 is moved downward from above the pressing portion 53, and the tip surface 51T of the first bending die 51 is brought into contact with the short side portion 112Y. The first bending die 51 is then moved downward. At this time, the press pressure P1 of the first bending die 51 is greater than the press pressure P2 of the clamping portion 53 in the vertical direction, from bottom to top. Therefore, with the flat plate material HZ held in place, the first bending die 51 moves downward together with the clamping portion 53 between the first inner wall surface 52AT and the second inner wall surface 52BT of the second bending die 52. Then, the short side portion 112Y of the held flat plate material HZ moves downward while remaining held, and the portion 113Y to be bent is bent at the corner portion 511 of the first bending die 51. Thus, a bent plate material PZ with a U-shaped cross-section is produced from the flat plate material HZ.

[0027] Next, in joining process S3, the case body 11 is formed from two bent sheet metal PZ by, for example, laser welding. Specifically, as shown in Figures 1 and 2, laser welding is performed with the ends PZT of the two bent sheet metal PZ butted together. This results in a rectangular tubular case body 11 having a welded section YS in the center of the long side portion 111.

[0028] As explained in detail above, the manufacturing process of the case body 11 includes a preparation step S1 in which a thickened portion N1Y corresponding to the thickened portion N1 and a thinned portion N2Y corresponding to the thinned portion N2 are formed in the portion 113Y of the flat material HZ that is to be bent. Therefore, since the thickened portion N1Y and the thinned portion N2Y are formed in advance in the portion 113Y of the flat material HZ that is to be bent, the thickened portion N1 and the thinned portion N2 can be easily formed in the bent portion 113 of the case body 11, and a case body 11 that can achieve both product accuracy and strength can be manufactured.

[0029] <Variation> The embodiments described in detail above are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can be improved and modified in various ways without departing from its essence. Figure 6B shows a cross-sectional view of CC shown in Figure 5 at the part of the flat plate material to be bent for use in Modification 1 of the battery cell shown in Figure 1. Figure 8 shows a view taken along arrow B shown in Figure 2 in Modification 2 of the battery cell shown in Figure 1.

[0030] In the above-described embodiment, the battery cell 10 is shown in which, of the inner surface HZ1 side and outer surface HZ2 side of the folded portion 113 of the case body 11, the recess DP is present only on the inner surface HZ1 side, the portion of the folded portion 113 without the recess DP is defined as a thick portion N1, and the portion of the folded portion 113 with the recess DP is defined as a thin portion N2. However, for example, a battery cell may also be used in which, of the inner surface HZ1 side and outer surface HZ2 side of the folded portion, the recess DP is present only on the outer surface HZ2 side, the portion of the folded portion 113 without the recess DP is defined as a thick portion N1, and the portion of the folded portion with the recess DP is defined as a thin portion N2. Alternatively, for example, a battery cell may have recesses DP on both the inner surface HZ1 and outer surface HZ2 of the bent portion of the case body, with the portion of the bent portion without recesses DP being a thick-walled portion N1 and the portion of the bent portion with recesses DP being a thin-walled portion N2. In such a battery cell, the reaction force between the compressive stress Q1 and tensile stress Q2 remaining in and around the bent portion can be more reliably reduced in the thin-walled portion N2, and the bending accuracy defects of the long and short sides that occur starting from the bent portion can be reduced. In the case of such a battery cell, an example of the flat plate material HZ is shown in Figure 6B, in which pre-processing recesses DY are drilled on both the first surface HZ1Y, which becomes the inner surface HZ1, and the second surface HZ2Y, which becomes the outer surface HZ2, of the portion 213Y to be bent (modified example 1). In this modified example 1, the flat plate material HZ is also formed in the same way as in the embodiment described above. In the preparation step S1, a thin-walled portion N2Y is formed in the area where the two pre-processing recesses DY overlap when viewed in the second direction (plate thickness direction), and a thick-walled portion N1Y is formed in the area where no pre-processing recesses DY are drilled.

[0031] Furthermore, in the above-described embodiment, a battery cell 10 was shown in which a plurality of recesses DP were drilled in a row along the axial direction (Z direction) on the bent portion 113, and the thin-walled portion N2 of the bent portion 113 where the recesses DP were located and the thick-walled portion N1 of the bent portion 113 where the recesses DP were not located were alternately formed in a row along the Z direction. However, for example, a battery cell may also be provided in which a plurality of recesses DP were drilled in two or more rows (three rows in modified example 2 shown in Figure 8) along the axial direction (Z direction) on the bent portion 113, and the thin-walled portion N2 of the bent portion 113 where the recesses DP were located and the thick-walled portion N1 of the bent portion 113 where the recesses DP were not located are alternately formed over multiple rows (three rows in modified example 2 shown in Figure 8) along the axial direction (Z direction). With such a battery cell, multiple thick-walled portions N1 and thin-walled portions N2 can be densely distributed along the arc cross-section of the bent portion 113. Therefore, by bending the flat plate material HZ, the reaction force between the compressive stress Q1 and tensile stress Q2 remaining between the inner surface HZ1 and outer surface HZ2 of the bent portion 113 is reduced more uniformly, and the surface accuracy of the long side portion 111 and the short side portion 112 can be further improved. In addition, the number of rows of recesses DP drilled along the axial direction (Z direction) on the inner surface HZ1 of the bent portion 113 and the number of rows of recesses DP on the outer surface HZ2 may be the same (for example, two rows of recesses DP on both the inner surface HZ1 and outer surface HZ2), or they may be different (for example, one row of recesses DP on the inner surface HZ1 and two rows of recesses DP on the outer surface HZ2).

[0032] Furthermore, in the above-described embodiment, a pre-processing recess DY having a circular opening was shown on the first surface HZ1Y (plate surface) of the flat plate material HZ. However, the plate surface of the flat plate material may also have a groove-shaped pre-processing recess with an opening other than a circle, such as an elliptical or rectangular shape extending along the first direction as shown in Figure 5. Also, in the embodiment, a case body 11 made of two bent plate materials PZ was shown. In other words, one case body made using two flat plate materials HZ was shown. However, one case body made using one flat plate material may also be shown. As a method for manufacturing a battery cell in such a case, for example, four bending sections are provided on one flat plate material, and in the preparation step, a thick section N1Y and a thin section N2Y are formed on the four bending sections of the flat plate material, in the bending step, all four bending sections of the flat plate material are bent to form bent sections, and in the joining step, a rectangular cylindrical case body is formed.

[0033] Furthermore, in the above-described embodiment, the portion of the bent section 113 with a recess DP was designated as a thin-walled portion N2, and the portion without a recess DP was designated as a thick-walled portion N1. However, it is sufficient for the thickness of the bent section 113 to be relatively greater in the thick-walled portion N1 than in the thin-walled portion N2. For example, a recess DP may be formed along the entire length of the bent section 113 in the axial direction (Z direction), and the portion of the recess DP with a relatively larger thickness may be designated as a thick-walled portion N1, and the portion with a relatively smaller thickness may be designated as a thin-walled portion N2. Also, in the embodiment, a pre-processing recess DY formed in a concave shape by the heat of a laser beam LS was shown, but a pre-processing recess formed in a concave shape by drilling or grinding, or a pre-processing recess formed in a concave shape by press working may also be used.

[0034] Furthermore, in the above-described embodiment, the case body 11 is shown in which the thin-walled portion N2 and the thick-walled portion N1 are formed at approximately the same interval in the bent portion 113. However, it is not necessarily limited to this. For example, the thick-walled portion N1 may be formed in a larger area ratio on the central portion 113M (see Figure 1) in the axial direction (Z direction) of the bent portion 113 than on the end portions 113S. In this case, the strength of the central portion 113M in the axial direction (Z direction) of the case body 11 can be further increased, so that the central portion 113M of the bent portion 113 can be made even less susceptible to deformation, for example, when the pressure inside the battery case 1 increases due to the temperature rise of the battery cell 10 during rapid charging of the battery cell 10, or when the electrode body 2 expands in volume due to the aging of the battery cell 10.

[0035] Furthermore, in the preparation step S1 of the above embodiment, multiple pre-processing recesses DY were drilled using a pulsed laser, but lasers other than pulsed lasers may also be used. Also, in the embodiment, a flat plate material HZ made of aluminum (including aluminum alloy) or stainless steel was shown, but a flat plate material made of other metals may also be used. [Explanation of Symbols]

[0036] 1 Battery case 2 Electrode body 10 battery cells 11 Case body 11T end 12 Lid 111 Long side part 112 Short side part 113 Bending section 113M central part 113S Both ends HZ flat plate material HZ1 plate inner surface HZ2 plate outer surface LS laser light N1 Thick part N1Y Thick-walled section N2 thin section N2Y Thin-walled section ND secondary battery S1 Preparation process

Claims

1. A battery cell comprising a metal battery case having an electrode body, a rectangular cylindrical case body housing the electrode body with both ends open in the axial direction, and a lid that seals the ends of the case body, The case body comprises a pair of long side portions formed by bending a flat plate material along the axial direction, and a pair of short side portions perpendicular to the long side portions. In the bent portion where the long side portion and the short side portion intersect, thick-walled portions and thin-walled portions are alternately formed along the axial direction. Battery cell.

2. In the battery cell described in claim 1, The thick-walled portion and the thin-walled portion are formed alternately in multiple rows along the axial direction in the bending portion. Battery cell.

3. In the battery cell described in claim 1, The thickened portion is formed on the axial central side of the bent portion with a higher area ratio than on the ends. Battery cell.

4. In the battery cell described in claim 1, The thin-walled portion is formed in a location where either or both of the inner and outer surfaces of the flat plate material are concave due to the heat of the laser beam. Battery cell.

5. A method for manufacturing a battery cell according to any one of claims 1 to 4, The manufacturing process for the case body includes a preparatory step of forming a thickened portion corresponding to the thickened portion and a thinned portion corresponding to the thinned portion in the portion of the flat material that is to be bent. A method for manufacturing battery cells.

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