Energy storage cell

Abstract

To provide a fuse part which is not easily re-coupled.SOLUTION: A power storage cell includes a cell case and an electrode body. The cell case houses the electrode body. The cell case includes an electrode terminal. A current path is formed in the cell case. The current path electrically connects the electrode body with the electrode terminal. The current path includes a fuse part. Tensile stress is applied to the fuse part in a direction in which the fuse part is separated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an energy storage cell. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2015-103521 (Patent Document 1) discloses a secondary battery including a fuse portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-103521 Summary of the Invention [Problem to be solved by the invention]

[0004] It has been proposed to provide a fuse within a storage cell (secondary battery). When an overcurrent occurs within the storage cell, the fuse melts, cutting off the current path. However, after the fuse melts, the storage cell may be subjected to vibrations, etc. Vibrations, etc. may cause the tips of the melted fuse to reconnect.

[0005] The present disclosure aims to provide a fuse portion that is less susceptible to rebonding. [Means for solving the problem]

[0006] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action in this specification includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0007] 1. The energy storage cell includes a cell case and an electrode assembly. The cell case houses the electrode assembly. The cell case includes electrode terminals. A current path is formed within the cell case. The current path electrically connects the electrode assembly and the electrode terminals. The current path includes a fuse portion. Tensile stress is applied to the fuse portion in a direction that separates the fuse portion.

[0008] The fuse portion can be blown by an overcurrent. Tensile stress is applied in a direction that separates the fuse portion. When the fuse portion blows, the tensile stress acts to pull the blown tips apart. This makes it possible to provide a fuse portion that is difficult to recombine.

[0009] 2. In the energy storage cell described in the above item "1," for example, tensile stress may be generated by the electrode assembly's own weight.

[0010] 3. In the energy storage cell according to the above item "1" or "2," the current path may further include, for example, a welded portion. Tensile stress may remain in the welded portion.

[0011] 4. In the energy storage cell according to any one of the above items 1 to 3, the current path may further include, for example, a bent portion. Tensile stress may be generated by springback of the bent portion.

[0012] 5. In the energy storage cell according to any one of the above items "1" to "4," the tensile stress may be applied, for example, parallel to the direction of current flow.

[0013] 6. In the energy storage cell according to any one of the above items "1" to "5," the tensile stress may be applied, for example, perpendicular to the direction of current flow.

[0014] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") will be described. However, the present embodiment does not limit the technical scope of the present disclosure. The present embodiment is illustrative in all respects. The present embodiment is non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is also intended from the beginning that any configuration may be extracted from the present embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic perspective view of a first storage cell in this embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the first storage cell in this embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of the first storage cell in this embodiment. [Figure 4] FIG. 4 is a first conceptual diagram showing the fuse portion in this embodiment. [Figure 5] FIG. 5 is a second conceptual diagram showing the fuse portion in this embodiment. [Figure 6] FIG. 6 is a third conceptual diagram showing the fuse portion in this embodiment. [Figure 7] FIG. 7 is a fourth conceptual diagram showing the fuse portion in this embodiment. [Figure 8] FIG. 8 is a fifth conceptual diagram showing the fuse portion in this embodiment. [Figure 9] FIG. 9 is a sixth conceptual diagram showing the fuse portion in this embodiment. [Figure 10] FIG. 10 is a schematic perspective view of the second storage cell in this embodiment. [Figure 11] FIG. 11 is an exploded perspective view of the second storage cell in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Definitions of terms, etc.> The terms "comprise," "include," "have," and variations thereof (e.g., "consisting of") are open-ended. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even closed-ended terms do not exclude additional elements that are normally incidental impurities or unrelated to the disclosed technology. The term "consisting essentially of..." is semi-closed. Semi-closed terms allow for the addition of elements that do not substantially affect the basic and novel characteristics of the disclosed technology.

[0017] In this embodiment, geometric terms (e.g., "parallel," "perpendicular," and the like) should not be interpreted in a strict sense. For example, "parallel" may deviate slightly from the strict meaning of "parallel." Geometric terms may include, for example, tolerances, errors, and the like in design, work, and manufacturing. The dimensional relationships in each drawing may not match the actual dimensional relationships. To facilitate reader understanding, the dimensional relationships (length, width, thickness, and the like) in each drawing may be changed. Furthermore, some components may be omitted. In each drawing, functionally identical or equivalent components may be designated by the same reference numerals.

[0018] For example, "at least one of A and B" includes "A or B" as well as "A and B." "at least one of A and B" can also be written as "A and / or B."

[0019] "Electrode" is a general term for positive electrodes and negative electrodes. Electrode may also refer to at least one of a positive electrode and a negative electrode. For example, an electrode terminal may refer to at least one of a positive electrode terminal and a negative electrode terminal.

[0020] <First storage cell> Fig. 1 is a schematic perspective view of a first storage cell in this embodiment. Fig. 2 is an exploded perspective view of the first storage cell in this embodiment. Fig. 3 is a schematic cross-sectional view of the first storage cell in this embodiment. The first storage cell 1 includes a cell case 200 and an electrode assembly 100.

[0021] 《Electrode body》 The electrode assembly 100 may include, for example, a plurality of unit electrode bodies 111 and an insulating film 120 (see FIG. 2). The electrode assembly 100 may include, for example, two to four unit electrode bodies 111. Each of the plurality of unit electrode bodies 111 may include a plurality of positive electrode tabs 110P and a plurality of negative electrode tabs 110N. Each of the plurality of unit electrode bodies 111 may have, for example, the same structure. Each of the plurality of unit electrode bodies 111 may have, for example, different structures from each other.

[0022] The unit electrode body 111 may have any structure. The unit electrode body 111 may be, for example, a laminated type. The unit electrode body 111 may be, for example, a wound type. The unit electrode body 111 may include, for example, a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet, the negative electrode sheet, and the separator may each have, for example, a strip-like planar shape.

[0023] The positive electrode sheet may include, for example, a metal foil and a positive electrode composite layer. The positive electrode composite layer may be disposed on the surface of the metal foil. For example, the positive electrode composite layer may be formed by coating the surface of the metal foil with a positive electrode slurry. An uncoated portion may be formed on the upper long side of the metal foil. The positive electrode composite layer is not formed on the uncoated portion. The metal foil is exposed in the uncoated portion. For example, a plurality of positive electrode tabs 110P may be joined to the uncoated portion. The plurality of positive electrode tabs 110P may be arranged at intervals from one another.

[0024] The negative electrode sheet may include, for example, a metal foil and a negative electrode composite layer. The negative electrode composite layer may be disposed on the surface of the metal foil. For example, the negative electrode composite layer may be formed by coating the surface of the metal foil with a negative electrode slurry. An uncoated portion may be formed on the upper long side of the metal foil. The negative electrode composite layer is not formed on the uncoated portion. The metal foil is exposed in the uncoated portion. For example, a plurality of negative electrode tabs 110N may be joined to the uncoated portion. The plurality of negative electrode tabs 110N may be arranged at intervals from one another.

[0025] The insulating film 120 may, for example, cover the peripheral and bottom surfaces of a plurality of unit electrode bodies 111 together (see FIG. 2).

[0026] Cell Case The cell case 200 houses the electrode assembly 100. The cell case 200 also houses an electrolyte (not shown). The cell case 200 is sealed. The cell case 200 includes a case body 210 and a lid 220.

[0027] The case body 210 has an opening 211 that opens upward (see FIG. 2). The case body 210 may be made of, for example, metal. The case body 210 may include, for example, aluminum (Al). The case body 210 includes a bottom wall 212 and a peripheral wall 214 (see FIG. 3). The bottom wall 212 may be, for example, rectangular and flat. The peripheral wall 214 stands upright from the bottom wall 212. The peripheral wall 214 may be, for example, rectangular tubular. The dimension of the peripheral wall 214 in the width direction (X-axis direction) may be larger than the dimension of the peripheral wall 214 in the thickness direction (Y-axis direction). The dimension of the peripheral wall 214 in the height direction (Z-axis direction) may be larger than the dimension of the peripheral wall 214 in the thickness direction.

[0028] The lid 220 closes the opening 211. For example, the lid 220 may be joined to the case body 210 by laser welding. The lid 220 may be, for example, flat. The lid 220 may be made of, for example, metal. The lid 220 may include, for example, Al. The lid 220 includes a positive electrode terminal 300P, a positive electrode terminal block 320, a lid body 222, an insulating gasket 520, and a negative electrode terminal 300N (see FIG. 3). That is, the cell casing 200 includes the electrode terminal 300. For example, the lid body 222 may also be provided with a pressure release valve 222a, a liquid injection hole 222b, a sealing member 222c, a pair of through holes 222d, etc.

[0029] Current Path The first storage cell 1 may include a connecting member 400. The connecting member 400 is conductive. The connecting member 400 includes a current collector 410. The current collector 410 is connected to a plurality of tabs. The current collector 410 includes a positive current collector 410P and a negative current collector 410N. The positive current collector 410P connects a plurality of positive tabs 110P to the positive connecting pin 420P. In other words, the connecting member 400 electrically connects the electrode assembly 100 and the electrode terminal 300. The positive current collector 410P forms a "first current path."

[0030] The positive terminal 300P includes a positive terminal plate 310, a positive terminal block 320, and a positive connecting pin 420P (see FIG. 3). The positive terminal plate 310 may have, for example, a rectangular parallelepiped outer shape. The positive terminal plate 310 may be made of, for example, a metal. The positive terminal plate 310 may contain, for example, Al or the like. The positive terminal block 320 may be made of, for example, a metal. The positive terminal block 320 may be made of, for example, a different material from that of the positive terminal plate 310. The positive terminal block 320 may have a lower melting point than the positive terminal plate 310. The positive terminal block 320 may contain, for example, iron (Fe) or the like. The positive terminal block 320 is joined to the upper surface of the lid main body 222. The positive terminal plate 310 is joined to the upper surface of the positive terminal block 320.

[0031] The positive electrode connecting pin 420P may have, for example, a cylindrical outer shape. A through hole is formed in each of the positive electrode terminal plate 310 and the positive electrode terminal block 320. The positive electrode connecting pin 420P is inserted into the through hole. With the positive electrode connecting pin 420P inserted into the connecting hole 412h, the lower end of the positive electrode connecting pin 420P is connected to the second flat plate portion 412. The upper end of the positive electrode connecting pin 420P may be fixed to the positive electrode terminal plate 310 by, for example, crimping.

[0032] The negative electrode current collector 410N connects the negative electrode tabs 110N and the negative electrode connecting pin 420N. In other words, the connecting member 400 electrically connects the electrode body 100 and the negative electrode terminal 300N. The negative electrode current collector 410N forms a "second current path."

[0033] The negative electrode connecting pin 420N connects the negative electrode current collector plate 410N and the negative electrode terminal plate 330. The negative electrode connecting pin 420N may have, for example, a cylindrical outer shape. When the negative electrode connecting pin 420N is inserted into the connecting hole 412h, the lower end of the negative electrode connecting pin 420N is connected to the second flat plate portion 412. The upper end of the negative electrode connecting pin 420N may be fixed to the negative electrode terminal plate 330 by, for example, crimping.

[0034] <<Fuse Section>> At least one of the first current path and the second current path includes a fuse portion. For example, the positive electrode current collector plate 410P may include the fuse portion 413. The positive electrode current collector plate 410P may include, for example, a first flat plate portion 411, a fuse portion 413, and a second flat plate portion 412. The fuse portion 413 may be disposed between the first flat plate portion 411 and the second flat plate portion 412. The fuse portion 413 may connect the first flat plate portion 411 and the second flat plate portion 412. The fuse portion 413, the first flat plate portion 411, and the second flat plate portion 412 may all be made of the same material, or may be made of different materials.

[0035] FIG. 4 is a first conceptual diagram illustrating the fuse portion of this embodiment. FIG. 5 is a second conceptual diagram illustrating the fuse portion of this embodiment. The fuse portion 413 includes a fusible material. The fuse portion 413 may be made of a fusible material. The fuse portion 413 may include any fusible material. The fuse portion 413 may include, for example, a metal material. The fuse portion 413 may have a smaller cross-sectional area than the first plate portion 411 and the second plate portion 412. The cross-sectional area here refers to the area of ​​a cross section perpendicular to the current flow direction. In FIGS. 4 and 5, the current flow direction corresponds to the X-axis direction. The smaller cross-sectional area may increase the resistance of the fuse portion 413 compared to other portions. Therefore, when an overcurrent flows through the positive electrode current collector 410P, the fuse portion 413 is expected to selectively melt. The portion with the smaller cross-sectional area may also be referred to as a thin-walled portion.

[0036] In this embodiment, the tensile stress TS is applied in a direction that separates the fuse portion 413. The tensile stress TS may be applied, for example, parallel to the direction of current flow. For example, the tensile stress may be applied in the X-axis direction. When the fuse portion 413 melts, the tensile stress TS may act to separate the melted tips. Therefore, it is expected that recombination will be less likely to occur.

[0037] FIG. 6 is a third conceptual diagram showing the fuse portion in this embodiment. FIG. 7 is a fourth conceptual diagram showing the fuse portion in this embodiment. The tensile stress TS may be applied, for example, perpendicular to the direction of current flow. For example, the tensile stress may be applied in the Z-axis direction. For example, the tensile stress may be applied in the Y-axis direction. When the fuse portion 413 melts, the tensile stress TS may act to separate the melted tips. Therefore, it is expected that recombination will be less likely to occur.

[0038] 8 is a fifth conceptual diagram showing the fuse portion in this embodiment. The tensile stress TS may include, for example, multiple directional components. For example, the tensile stress TS may include a first component TS1 and a second component TS2. The first component TS1 may act, for example, in the X-axis direction. The second component TS2 may act, for example, in the Z-axis direction (vertical direction). The second component TS2 may act, for example, in the Y-axis direction. The first component TS1 and the second component TS2 may act in a composite manner in a direction that separates the fuse portion 413.

[0039] The tensile stress TS can be applied by any structure. For example, the tensile stress TS may be generated by the weight of the electrode assembly 100. For example, the electrode assembly 100 is not supported by the bottom wall 212, the peripheral wall 214, the insulating film 120, etc. (see FIGS. 2 and 3 ), and is suspended from the current collector plates 410 (positive current collector plate 410P and negative current collector plate 410N), so that the weight of the electrode assembly 100 can act on the fuse portion 413.

[0040] For example, the positive current collector plate 410P may include a welded portion. Tensile stress TS may remain in the welded portion. For example, a welded portion may be formed between the first flat plate portion 411 and the positive electrode tab 110P. For example, a welded portion may be formed between the second flat plate portion 412 and the positive electrode connecting pin 420P.

[0041] For example, welding may be performed with bending deformation. That is, the positive electrode current collector plate 410P may include a bending deformation portion. A tensile stress TS may be generated by springback of the bending deformation portion. The bending deformation portion may include, for example, an elongation deformation portion.

[0042] FIG. 9 is a sixth conceptual diagram illustrating the fuse portion in this embodiment. For example, a tension member 415 may be disposed within the cell casing 200. The tension member 415 may include, for example, an insulating material, a heat-resistant material, or the like. The tension member 415 may include, for example, a resin material, or the like. The tension member 415 may be, for example, an elastic body. The tension member 415 may be, for example, wire-shaped, coil spring-shaped, or the like. For example, at least a portion of the tension member 415 may be fixed to the inner surface of the cell casing 200. For example, at least a portion of the tension member 415 may be physically connected to at least one of the first flat plate portion 411 and the second flat plate portion 412. For example, a heat insulating material may be interposed between the tension member 415 and at least one of the first flat plate portion 411 and the second flat plate portion 412.

[0043] For example, the tensile stress TS may be generated by the tensile force of the tensile member 415. For example, the tensile stress TS may be generated by the elastic recovery of the tensile member 415. The tensile stress TS may include a component in the X-axis direction, a component in the Y-axis direction, or a component in the Z-axis direction. When the fuse portion 413 melts, the tensile stress TS may separate the first flat plate portion 411 and the second flat plate portion 412.

[0044] For example, the positive electrode current collector 410P may include a process-affected layer. Tensile stress TS may remain in the process-affected layer. For example, the first flat plate portion 411 has a first main surface. The first main surface faces the bottom wall 212 (see FIG. 3). The second flat plate portion 412 has a second main surface. The second main surface faces the lid 220 (see FIG. 3). For example, a process-affected layer may be formed on each of the first and second main surfaces. Due to the residual stress of the process-affected layer, it is expected that the first flat plate portion 411 and the second flat plate portion 412 will warp in directions away from each other when the fuse portion 413 is blown. For example, the process-affected layer may be formed by laser processing or the like.

[0045] Other configurations The first energy storage cell 1 may include an insulator 500. The insulator 500 provides insulation between the connecting member 400 and the cell case 200. The insulator 500 includes an insulating sheet 510 and an insulating gasket 520.

[0046] Insulating sheet 510 is connected to the underside of lid main body 222. Through holes are formed in insulating sheet 510 in the height direction at a portion overlapping pressure release valve 222a, a portion overlapping liquid injection hole 222b, a portion overlapping each through-hole 222d, and a portion overlapping reversal plate 224.

[0047] The insulating gasket 520 has a shape that surrounds the connecting pin 420. The insulating gasket 520 provides insulation between the connecting pin 420 and the cell casing 200. The insulating gasket 520 includes a positive electrode gasket 520P and a negative electrode gasket 520N.

[0048] The positive electrode gasket 520P covers the positive electrode connecting pin 420P. The positive electrode gasket 520P has a cylindrical outer shape. The negative electrode gasket 520N covers the negative electrode connecting pin 420N. The negative electrode gasket 520N may have the same structure as the positive electrode gasket 520P. The negative electrode gasket 520N (insulating member) electrically insulates the lid main body 222 from the negative electrode terminal 300N.

[0049] The negative electrode terminal 300N includes a negative electrode terminal plate 330 and a negative electrode connecting pin 420N. The negative electrode terminal plate 330 may be made of, for example, metal. The negative electrode terminal plate 330 may contain, for example, copper (Cu), nickel (Ni), or the like. The insulating member 340 electrically insulates the negative electrode terminal 300N from the lid main body 222. The insulating member 340 may be made of, for example, a resin material. The reversal plate 224 may have an outer shape such as a dish shape or a bowl shape. When the internal pressure of the cell case 200 increases, the reversal plate 224 may be reversed. When the reversal plate 224 is reversed, the lid main body 222 and the negative electrode terminal 300N may be electrically connected.

[0050] <Second storage cell> Fig. 10 is a schematic perspective view of a second energy storage cell in this embodiment. Fig. 11 is an exploded perspective view of the second energy storage cell in this embodiment. Below, differences between the second energy storage cell 2 and the first energy storage cell 1 will be mainly described. Description of commonalities between the second energy storage cell 2 and the first energy storage cell 1 may be omitted.

[0051] The second storage cell 2 includes an inner insulator 610 and an outer insulator 620. The inner insulator 610 is disposed inside the cell case 200. That is, the inner insulator 610 is disposed between the electrode assembly 100 and the current collector plate 410. The positive electrode tab 110P and the negative electrode tab 110N are connected to the current collector plate 410 above the inner insulator 610. A through hole is formed in the inner insulator 610 at a position that overlaps with the through hole of the first flat plate portion 411 in the height direction. The electrode assembly 100 includes a unit electrode assembly 111, a unit electrode assembly 112, a unit electrode assembly 113, and a unit electrode assembly 114 (see FIG. 11 ).

[0052] The outer insulator 620 is disposed on the outside of the cell casing 200. That is, the outer insulator 620 is disposed on the upper surface of the lid 220. Through holes are formed in the outer insulator 620 at a portion overlapping in the height direction with the positive electrode terminal 300P, a portion overlapping with the negative electrode terminal 300N, a portion overlapping with the pressure release valve 222a, and a portion overlapping with the liquid injection hole 222b.

[0053] The insulator 500 further includes a pair of side sheets 511 connected to the insulating sheet 510 (see FIG. 11). Each of the pair of side sheets 511 has a shape that extends downward from an edge of the insulating sheet 510 in the thickness direction. The pair of side sheets 511 are disposed between the sides of the electrode body 100 and the case body 210.

[0054] The negative terminal 300N further includes an insulating plate 350 (see FIGS. 10 and 11). The negative terminal plate 330 includes a negative terminal block 331 and a conductive plate 335. The conductive plate 335 is fixed on an insulating member 340. The negative terminal block 331 is connected onto the conductive plate 335. The negative terminal block 331 may be welded to the conductive plate 335. A through hole is formed in each of the conductive plate 335 and the negative terminal block 331. The negative connecting pin 420N is inserted through the through hole. The conductive plate 335 includes a facing portion 332. The insulating plate 350 covers a portion of the conductive plate 335 that is located above the reversal plate 224.

[0055] The positive current collector 410P forms a first current path. The negative current collector 410N forms a second current path. At least one of the positive current collector 410P and the negative current collector 410N includes a fuse portion. For example, the positive current collector 410P may include the fuse portion (not shown in FIG. 11). In this embodiment, a tensile stress (not shown in FIG. 11) is applied to the fuse portion. The tensile stress acts in a direction that separates the fuse portion. [Explanation of symbols]

[0056] 1 First storage cell, 2 Second storage cell, 100 Electrode body, 110N Negative electrode tab, 110P Positive electrode tab, 111, 112, 113, 114 Unit electrode body, 120 Insulating film, 200 Cell case, 210 Case body, 211 Opening, 212 Bottom wall, 214 Surrounding wall, 220 Lid, 222 Lid body, 222a Pressure release valve, 222b Injection hole, 222c Sealing member, 222d Through hole, 224 Reversal plate, 300 Electrode terminal, 300N Negative electrode terminal, 300P Positive electrode terminal, 310 Positive electrode terminal plate, 320 Positive electrode terminal block, 330 Negative electrode terminal plate, 331 Negative electrode terminal block, 332 Opposing portion, 335 Conductive plate, 340 Insulating member, 350 Insulating plate, 400 Connecting member, 410 current collecting plate, 410N negative electrode current collecting plate, 410P positive electrode current collecting plate, 411 first flat plate portion, 412 second flat plate portion, 412h connecting hole, 413 fuse portion, 415 tensile member, 420 connecting pin, 420N negative electrode connecting pin, 420P positive electrode connecting pin, 500 insulator, 510 insulating sheet, 511 side sheet, 520 insulating gasket, 520N negative electrode gasket, 520P positive electrode gasket, 610 inner insulator, 620 outer insulator, TS tensile stress, TS1 first component, TS2 second component.

Claims

1. Cell case, and electrode body, Including, the cell case accommodates the electrode body, the cell casing includes an electrode terminal; A current path is formed within the cell casing, the current path electrically connects the electrode body and the electrode terminal, the current path includes a first plate portion, a fuse portion, and a second plate portion; the fuse portion connects the first flat plate portion and the second flat plate portion, the fuse portion has a thickness smaller than that of the first flat plate portion and the second flat plate portion; The current path further includes a weld. the first flat plate portion is joined to a positive electrode tab or a negative electrode tab by the welded portion, the second flat plate portion is connected to the electrode terminal, The welding portion is provided above the electrode body, the electrode body is suspended from the first flat plate portion by the positive electrode tab and the negative electrode tab, the first flat plate portion, the fuse portion, or the second flat plate portion further includes a bending deformation portion; a tensile stress is applied to the fuse portion in a direction separating the fuse portion due to springback of the bent deformation portion and the weight of the electrode body; Energy storage cell.

2. The tensile stress remains in the welded portion. The energy storage cell according to claim 1 .

3. The tensile stress is applied perpendicular to the direction of current flow. The energy storage cell according to claim 1 .

4. the cell case includes a bottom wall and a peripheral wall extending from the bottom wall; There is a gap between the bottom wall and the peripheral wall and the electrode body. The energy storage cell according to claim 1 .

5. The tensile stress remains in the welded portion, The tensile stress is applied perpendicular to the direction of current flow. The energy storage cell according to claim 1 .

6. The welded portion includes a bent portion. The energy storage cell according to claim 1 .

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