Method for manufacturing secondary battery case and secondary battery

Abstract

To provide a highly reliable secondary battery that can be efficiently manufactured.SOLUTION: A method for manufacturing a secondary battery case includes a step of bending a metal plate having a first end edge and a second end edge into a cylindrical shape such that the first end edge and the second end edge approach each other, a step of irradiating the first end edge and the second end edge with high-energy beam 2 to form a joint portion 115 for joining the first end edge and the second end edge, and a step of irradiating a position of the metal plate spaced apart from the first end edge and the second end edge with high-energy beam 2 to form a fragile portion 150.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] The present technology relates to a method for manufacturing a case for a secondary battery and a secondary battery. [Background technology]

[0002] A prior art document disclosing a nonaqueous electrolyte secondary battery is JP 8-148184 A (Patent Document 1). In the nonaqueous electrolyte secondary battery described in Patent Document 1, grooves extending in multiple directions are formed on a side surface of a flat rectangular battery container that is not parallel to the positive and negative electrodes.

[0003] Prior art documents disclosing secondary batteries include Japanese Patent No. 5821605 (Patent Document 2). In the secondary battery described in Patent Document 2, a thin-walled portion that is thinner than other metal plate portions in the case is formed as a safety valve at a location where the edges of the metal plates are welded together. The thin-walled portion is formed by rolling, grinding, or the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-148184 [Patent Document 2] Patent No. 5821605 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of reliability of secondary batteries, the secondary batteries described in Patent Documents 1 and 2 have room for efficient production of highly reliable secondary batteries.

[0006] The present technology has been made to solve the above-mentioned problems, and has an object to provide a highly reliable secondary battery that can be efficiently manufactured. [Means for solving the problem]

[0007] A manufacturing method for a secondary battery case based on the present technology includes the steps of bending a metal plate having a first end edge and a second end edge into a cylindrical shape so that the first end edge and the second end edge approach each other, forming a joint that joins the first end edge and the second end edge by irradiating the first end edge and the second end edge with high-energy rays, and forming a weak portion by irradiating the metal plate at a position spaced from the first end edge and the second end edge with high-energy rays.

[0008] A secondary battery based on the present technology includes an electrode body and a case. The electrode body includes a first electrode and a second electrode having a polarity different from that of the first electrode. The case accommodates the electrode body. The case includes an exterior body, a first sealing plate, and a second sealing plate. The exterior body has a first opening and a second opening. The first opening is located at an end of a first side in a first direction. The second opening is located at an end of a second side opposite to the first side in the first direction. The first sealing plate seals the first opening. The second sealing plate seals the second opening. The exterior body is provided with a joint and a molten solidified portion. The joint extends from the first opening to the second opening. The molten solidified portion constitutes a fragile portion that breaks when the internal pressure of the case reaches a predetermined value or higher and discharges gas in the case to the outside of the case. The exterior body has a first end side and a second end side that are joined at the joint. The melt-solidified portion is provided at a position spaced apart from the first end edge and the second end edge.

[0009] The molten and solidified portion refers to a portion of the metal plate constituting the exterior body that has melted and solidified due to irradiation with high-energy rays. Effect of the Invention

[0010] According to the present technology, it is possible to provide a highly reliable secondary battery that can be efficiently manufactured. [Brief description of the drawings]

[0011] [Figure 1] 1 is a front view showing a configuration of a secondary battery according to a first embodiment of the present technology. [Diagram 2] 2 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow II. [Diagram 3] 3 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow III. [Figure 4] 4 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow IV. [Diagram 5] 2 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow V. FIG. [Figure 6] 2 is a front cross-sectional view of the secondary battery shown in FIG. [Figure 7] FIG. 2 is a front view showing a negative electrode original plate before the negative electrode plate is formed. [Figure 8] 8 is a cross-sectional view taken along the line VIII-VIII of the negative electrode original plate shown in FIG. 7. [Figure 9] FIG. 2 is a front view showing a negative electrode plate formed from the negative electrode original plate. [Figure 10] FIG. 2 is a front view showing a positive electrode original plate before the positive electrode plate is formed. [Figure 11] 11 is a cross-sectional view taken along the line XI-XI of the positive electrode plate shown in FIG. [Figure 12] FIG. 2 is a front view showing a positive electrode plate formed from a positive electrode original plate. [Figure 13] 5 is a flowchart showing a method for manufacturing a case body provided in the secondary battery case according to the first embodiment. [Figure 14] FIG. 4 is a diagram showing a metal plate that constitutes a case main body. [Figure 15] 15 is a diagram showing a state in which the metal plate shown in FIG. 14 is bent. FIG. [Figure 16] FIG. 4 is a perspective view showing a state in which a joint is formed in a case main body. [Figure 17] 4 is a cross-sectional view showing a state in which a joint is formed in a case main body. FIG. [Figure 18] FIG. 4 is a perspective view showing a state in which a fragile portion is formed in a case main body. [Figure 19] 19 is a cross-sectional view of the case body shown in FIG. 18 taken along the line XIX-XIX. [Figure 20] 20 is a cross-sectional view of the case body shown in FIG. 18 taken along the line XX-XX. [Figure 21] 4 is a cross-sectional view showing a state in which a fragile portion and a first region are formed in a case body. FIG. [Figure 22] 11 is a perspective view showing the configuration of the case body when the fragile portion is broken. FIG. [Figure 23] 11 is a top view showing the configuration of a case body of a secondary battery according to Embodiment 2. FIG. [Figure 24] 11 is a top view showing a cleavage range of a case body according to embodiment 2. FIG. [Diagram 25] 11 is a top view showing the configuration of a case body of a secondary battery according to embodiment 3. FIG. [Figure 26] 13 is a top view showing the tearing range of the case body according to embodiment 3. FIG. [Figure 27] 13 is a top view showing the configuration of a case body of a secondary battery according to embodiment 4. FIG. [Figure 28] 13 is a top view showing the tearing range of the case body according to embodiment 4. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof will not be repeated.

[0013] In the embodiments described below, when referring to the number, amount, etc., the scope of the present technology is not necessarily limited to the number, amount, etc., unless otherwise specified. In addition, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. In addition, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiment.

[0014] In this specification, the words "comprise", "include" and "have" are open-ended, i.e., when a certain configuration is included, other configurations may or may not be included.

[0015] Furthermore, when geometric terms and terms expressing positional and directional relationships, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along" are used in this specification, these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in one state, and the relative positional relationships can be inverted or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0016] In this specification, the term "secondary battery" is not limited to lithium ion batteries, but may include other secondary batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0017] In the drawings, the direction along the winding axis of the electrode body of the secondary battery is the X direction, the short side direction of the case as viewed from the X direction is the Y direction, and the long side direction of the case as viewed from the X direction is the Z direction. In addition, in order to facilitate understanding of the present technology, the dimensions of each component in the drawings may be changed from the actual dimensions. In addition, in the drawings, the sealing plate joint between the case body and the sealing plate may not be shown.

[0018] Furthermore, in this specification, the X direction is defined as the first direction in which the first opening and the second opening of the case body are aligned, the Y direction is defined as the third direction in which the first plate-like portion and the second plate-like portion of one of the pair of first wall portions (first side portions) are aligned, and the Z direction is defined as the second direction in which the pair of first wall portions (first side portions) are aligned.

[0019] (Embodiment 1) (Overall battery configuration) Fig. 1 is a front view of a secondary battery 1 according to the present embodiment. Figs. 2 to 5 are views of the secondary battery 1 shown in Fig. 1 as viewed from the directions of arrows II, III, IV, and V, respectively. Fig. 6 is a front cross-sectional view of the secondary battery 1 shown in Fig. 1.

[0020] The secondary battery 1 can be mounted in an electric vehicle (BEV: Battery Electric Vehicle), a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle), a hybrid electric vehicle (HEV: Hybrid Electric Vehicle), etc. However, the use of the secondary battery 1 is not limited to being mounted on a vehicle.

[0021] As shown in FIGS. 1 to 6, the secondary battery 1 includes a case 100, an electrode assembly 200, an electrode terminal 300, and a current collector 400. The case 100 includes a case 100, an electrode assembly 200, an electrode terminal 300, and a current collector 400.

[0022] When configuring an assembled battery including the secondary batteries 1, multiple secondary batteries 1 are stacked in the Y direction. The stacked secondary batteries 1 may be restrained in the stacking direction (Y direction) by a restraining member to form a battery module, or the assembled battery may be directly supported on the side of a battery pack case without using a restraining member.

[0023] The case 100 houses the electrode assembly 200. The case 100 includes a case body 110 (outer packaging body), a first sealing plate 120, and a second sealing plate .

[0024] The case body 110 is made of a cylindrical, preferably rectangular, member. This results in a rectangular secondary battery 1. The case body 110 is made of metal. Specifically, the case body 110 is made of aluminum, an aluminum alloy, iron, an iron alloy, or the like. When the case body 110 is made of iron or an iron alloy, the case body 110 may be plated with nickel, tin, zinc, or the like.

[0025] 1 and 2, a first sealing plate 120 and a second sealing plate 130 are provided at both ends of the case body. The case body 110 can be formed into a square tube shape, for example, by abutting the edges of a bent plate-like member (metal plate) (joint 115 shown in FIG. 5) and joining them together (for example, by laser welding). The corners of the "square tube" may have a rounded shape.

[0026] In this embodiment, the case body 110 is formed to be longer in the X direction of the secondary battery 1 than in the Y and Z directions of the secondary battery 1. The dimension of the case body 110 in the X direction is preferably about 30 cm or more. This allows a relatively large (high capacity) secondary battery 1 to be configured. The dimension of the case body 110 in the Z direction is preferably about 20 cm or less, more preferably about 15 cm or less, and even more preferably about 10 cm or less. This allows a relatively low height secondary battery 1 to be configured, improving the mountability in a vehicle, for example.

[0027] The case body 110 includes a pair of first side surface portions 111 (a pair of first wall portions) and a pair of second side surface portions 112 (a pair of second wall portions). The pair of first side surface portions 111 face each other in a second direction (Z direction) perpendicular to the first direction (X direction). The pair of first side surface portions 111 form the bottom surface portion and the top surface portion of the case 100.

[0028] The pair of second side surface portions 112 face each other in a third direction (Y direction) perpendicular to the first direction (X direction) and the second direction (Z direction). The pair of second side surface portions 112 constitute a part of the side surfaces of the case 100.

[0029] The pair of first side surface portions 111 and the pair of second side surface portions 112 are provided so as to intersect with each other. The pair of first side surface portions 111 and the pair of second side surface portions 112 are connected at their respective ends. As in this embodiment, it is desirable that the area of ​​each of the pair of first side surface portions 111 is smaller than the area of ​​each of the pair of second side surface portions 112.

[0030] 5, one 111A of the pair of first side surface portions is formed with a joint 115. The joint 115 extends from the first opening 113 to the second opening 114. That is, the joint 115 extends in the X direction of the secondary battery 1. At the joint 115, the ends of the metal plates that make up the case body 110 are joined together.

[0031] One 111A of the pair of first side surface portions is provided with a fragile portion 150. The fragile portion 150 breaks when the internal pressure of the case 100 reaches or exceeds a predetermined value, and discharges gas within the case 100 to the outside of the case 100.

[0032] In this embodiment, the joint portion 115 and the fragile portion 150 are provided on one 111A of the pair of first walls. The joint portion 115 and the fragile portion 150 will be described in detail later.

[0033] 3, a first opening 113 is provided at an end of a first side in a first direction (X direction) of case body 110. First opening 113 is sealed by a first sealing plate 120. A sealing plate joint 125 is formed in first opening 113 to seal first opening 113. First opening 113 and first sealing plate 120 have a substantially rectangular shape with a short side direction in the Y direction and a long side direction in the Z direction.

[0034] A negative electrode terminal 301 (first electrode terminal) is provided on the first sealing plate 120. In the present embodiment, the negative electrode terminal 301 is located approximately in the center of each of the Y direction and the Z direction of the first sealing plate 120. The position of the negative electrode terminal 301 can be changed as appropriate.

[0035] 4, a second opening 114 is provided at an end of a second side opposite to the first side in the first direction (X direction) of the case body 110. That is, the second opening 114 is located at an end opposite to the first opening 113. The second opening 114 is sealed by a second sealing plate 130. A sealing plate joint 135 is formed in the second opening 114 to seal the second opening 114. The second opening 114 and the second sealing plate 130 have a substantially rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction.

[0036] A positive electrode terminal 302 (second electrode terminal) and a liquid injection hole 134 are provided on the second sealing plate 130. The positive electrode terminal 302 in this embodiment is located approximately in the center of the second sealing plate 130 in both the Y direction and the Z direction. The positions of the positive electrode terminal 302 and the liquid injection hole 134 can be changed as appropriate.

[0037] The first sealing plate 120 and the second sealing plate 130 are made of metal. Specifically, the first sealing plate 120 and the second sealing plate 130 are made of aluminum, an aluminum alloy, iron, an iron alloy, etc. When the first sealing plate 120 and the second sealing plate 130 are made of iron or an iron alloy, the first sealing plate 120 and the second sealing plate 130 may be plated with nickel, tin, zinc, or the like.

[0038] The negative electrode terminal 301 is electrically connected to the negative electrode (first electrode) of the electrode body 200. The negative electrode terminal 301 is attached to the first sealing plate 120, that is, the case 100.

[0039] The positive electrode terminal 302 is electrically connected to the positive electrode (second electrode) of the electrode body 200. The positive electrode terminal 302 is attached to the second sealing plate 130, that is, the case 100.

[0040] The negative terminal 301 is made of a conductive material (more specifically, a metal), and may be made of, for example, copper or a copper alloy. The outer surface of the negative terminal 301 may be provided with a portion or layer made of aluminum or an aluminum alloy.

[0041] The positive terminal 302 is made of a conductive material (more specifically, a metal), and may be made of, for example, aluminum or an aluminum alloy.

[0042] The liquid inlet 134 is sealed by a sealing member (not shown). As the sealing member, for example, a blind rivet or other metal members can be used.

[0043] The electrode body 200 is a flat-shaped electrode body having a positive electrode plate and a negative electrode plate, which will be described later. Specifically, the electrode body 200 is a wound-type electrode body in which a band-shaped positive electrode plate and a band-shaped negative electrode plate are both wound via a band-shaped separator (not shown). However, in this specification, the "electrode body" is not limited to a wound-type electrode body, and may be a laminated electrode body in which a plurality of positive electrode plates and a plurality of negative electrode plates are alternately laminated. The belt-shaped separator may be composed of, for example, a polyolefin microporous film. The electrode body may include a plurality of positive electrode plates and a plurality of negative electrode plates, and the positive electrode tabs provided on each positive electrode plate may be laminated to form a positive electrode tab group, or the negative electrode tabs provided on each negative electrode plate may be laminated to form a negative electrode tab group. The electrode body 200 may include a plurality of wound-type electrode bodies, or may include a plurality of laminated electrode bodies.

[0044] 6, case 100 houses electrode assembly 200. Electrode assembly 200 is housed in case 100 so that its winding axis is parallel to the X direction.

[0045] Specifically, one or more wound electrode bodies are housed together with an electrolytic solution (electrolyte) (not shown) inside an insulating sheet (not shown) arranged in the case 100. The electrolytic solution (non-aqueous electrolytic solution) is, for example, a non-aqueous solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio (25° C.) of 30:30:40, and LiPF 6 A solution having a concentration of 1.2 mol / L can be used. Note that a solid electrolyte may be used instead of the electrolytic solution.

[0046] The electrode body 200 includes a main body portion (a portion in which positive electrode plates and negative electrode plates are stacked with a separator therebetween), a first electrode tab group 220 (negative electrode tab group), and a second electrode tab group 250 (positive electrode tab group).

[0047] The main body portion is composed of a negative electrode plate 210 (first electrode) and a positive electrode plate 240 (second electrode) described below. The first electrode tab group 220 is located at an end of the main body portion on the first sealing plate 120 side in the X direction. The second electrode tab group 250 is located at an end of the main body portion on the second sealing plate 130 side in the first direction (X direction).

[0048] The first electrode tab group 220 and the second electrode tab group 250 are formed so as to protrude from the central portion of the electrode body 200 towards the first sealing plate 120 or the second sealing plate 130, respectively.

[0049] The current collector 400 includes a negative electrode current collector 400A and a positive electrode current collector 400B. The negative electrode current collector 400A and the positive electrode current collector 400B are each made of a plate-shaped member. The electrode assembly 200 is electrically connected to a negative electrode terminal 301 and a positive electrode terminal 302 via the current collector 400.

[0050] The negative electrode current collector 400A is disposed on the first sealing plate 120 via a resin insulating member. The negative electrode current collector 400A is electrically connected to the first electrode tab group 220 and the negative electrode terminal 301. The negative electrode current collector 400A is made of a conductive material (more specifically, a metal), and may be made of, for example, copper or a copper alloy.

[0051] The positive electrode current collector 400B is disposed on the second sealing plate 130 via a resin insulating member. The positive electrode current collector 400B is electrically connected to the second electrode tab group 250 and the positive electrode terminal 302. The positive electrode current collector 400B is made of a conductive material (more specifically, a metal), and may be made of, for example, aluminum or an aluminum alloy. The second electrode tab group 250 may be electrically connected to the second sealing plate 130 directly or via the positive electrode current collector 400B. In this case, the second sealing plate 130 may play the role of the positive electrode terminal 302.

[0052] (Configuration of electrode body 200) FIG. 7 is a front view showing the negative electrode original plate 210S before the negative electrode plate 210 is formed, FIG. 8 is a cross-sectional view taken along line VIII-VIII of the negative electrode original plate 210S shown in FIG. 7, and FIG. 9 is a front view showing the negative electrode plate 210 formed from the negative electrode original plate 210S.

[0053] The negative electrode plate 210 is manufactured by processing a negative electrode original plate 210S. As shown in Figures 7 and 8, the negative electrode original plate 210S includes a negative electrode core 211 and a negative electrode active material layer 212. The negative electrode core 211 is a copper foil or a copper alloy foil.

[0054] A negative electrode active material layer 212 is formed on both sides of the negative electrode core 211 except for one end portion. The negative electrode active material layer 212 is formed by applying a negative electrode active material layer slurry with a die coater.

[0055] The negative electrode active material layer slurry is prepared by kneading graphite as the negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders, and water as a dispersion medium so that the mass ratio of graphite:SBR:CMC is approximately 98:1:1.

[0056] The negative electrode core 211 coated with the negative electrode active material layer slurry is dried to remove water contained in the negative electrode active material layer slurry, thereby forming the negative electrode active material layer 212. Furthermore, the negative electrode active material layer 212 is compressed to form a negative electrode original plate 210S including the negative electrode core 211 and the negative electrode active material layer 212. The negative electrode original plate 210S is cut into a predetermined shape to form the negative electrode plate 210. The negative electrode original plate 210S can be cut by laser processing using energy beam irradiation, die processing, cutter processing, or the like.

[0057] As shown in FIG. 9, a plurality of negative electrode tabs 230 made of a negative electrode core 211 are provided at one end in the width direction of the negative electrode plate 210 formed from the negative electrode original plate 210S. When the negative electrode plate 210 is wound, the plurality of negative electrode tabs 230 are stacked to form the first electrode tab group 220. As a result, the first electrode tab group 220 is connected to the negative electrode plate 210 (first electrode). The position and length in the protruding direction of each of the plurality of negative electrode tabs 230 are appropriately adjusted in consideration of the state in which the first electrode tab group 220 is connected to the negative electrode current collector 400A. The shape of the negative electrode tab 230 is not limited to the one exemplified in FIG. 8.

[0058] FIG. 10 is a front view showing the positive electrode original plate 240S before the positive electrode plate 240 is formed, FIG. 11 is a cross-sectional view taken along line XI-XI of the positive electrode original plate 240S shown in FIG. 10, and FIG. 12 is a front view showing the positive electrode plate 240 formed from the positive electrode original plate 240S.

[0059] The positive electrode plate 240, which is the second electrode, has a polarity different from that of the negative electrode plate 210, which is the first electrode. The positive electrode plate 240 is manufactured by processing a positive electrode original plate 240S. As shown in Fig. 10 and Fig. 11, the positive electrode original plate 240S includes a positive electrode core 241, a positive electrode active material layer 242, and a positive electrode protective layer 243. The positive electrode core 241 is an aluminum foil or an aluminum alloy foil.

[0060] A positive electrode active material layer 242 is formed on both sides of the positive electrode core 241 except for one end portion. The positive electrode active material layer 242 is formed on the positive electrode core 241 by applying a positive electrode active material layer slurry with a die coater.

[0061] The positive electrode active material layer slurry is prepared by kneading lithium nickel cobalt manganese composite oxide as the positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, a carbon material as a conductive material, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium, so that the mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material is approximately 97.5:1:1.5.

[0062] The positive electrode protective layer 243 is in contact with the positive electrode core 241 and is formed at one end in the width direction of the positive electrode active material layer 242. The positive electrode protective layer 243 is formed on the positive electrode core 241 by applying a positive electrode protective layer slurry with a die coater. The positive electrode protective layer 243 has a larger electric resistance than the positive electrode active material layer 242.

[0063] The positive electrode protective layer slurry is prepared by kneading alumina powder, a carbon material as a conductive material, PVdF as a binder, and NMP as a dispersion medium so that the mass ratio of alumina powder:carbon material:PVdF is approximately 83:3:14.

[0064] The positive electrode core 241 coated with the positive electrode active material layer slurry and the positive electrode protective layer slurry is dried, and the NMP contained in the positive electrode active material layer slurry and the positive electrode protective layer slurry is removed to form the positive electrode active material layer 242 and the positive electrode protective layer 243. Furthermore, the positive electrode active material layer 242 is compressed to form a positive electrode original plate 240S including the positive electrode core 241, the positive electrode active material layer 242, and the positive electrode protective layer 243. The positive electrode original plate 240S is cut into a predetermined shape to form the positive electrode plate 240. The positive electrode original plate 240S can be cut by laser processing using energy beam irradiation, die processing, cutter processing, or the like.

[0065] As shown in FIG. 12, a plurality of positive electrode tabs 260 made of a positive electrode core 241 are provided at one end in the width direction of the positive electrode plate 240 formed from the positive electrode original plate 240S. When the positive electrode plate 240 is wound, the plurality of positive electrode tabs 260 are stacked to form the second electrode tab group 250. As a result, the second electrode tab group 250 is connected to the positive electrode plate 240 (second electrode). The position and the length in the protruding direction of each of the plurality of positive electrode tabs 260 are appropriately adjusted in consideration of the state in which the second electrode tab group 250 is connected to the positive electrode current collector 400B. The shape of the positive electrode tab 260 is not limited to the one exemplified in FIG. 12.

[0066] A positive electrode protection layer 243 is provided at the base of each of the positive electrode tabs 260. The positive electrode protection layer 243 does not necessarily have to be provided at the base of the positive electrode tab 260.

[0067] In a typical example, the thickness of the negative electrode tab 230 (one piece) is smaller than the thickness of the positive electrode tab 260 (one piece). In this case, the thickness of the first electrode tab group 220 is smaller than the thickness of the second electrode tab group 250.

[0068] (Manufacture of case body 110) Hereinafter, a method for manufacturing the case body (exterior body) included in the secondary battery case will be described. Fig. 13 is a flowchart showing a method for manufacturing the case body included in the secondary battery case according to embodiment 1. Fig. 14 is a diagram showing a metal plate constituting the case body. Fig. 15 is a diagram showing a state in which the metal plate shown in Fig. 14 has been folded. Fig. 16 is a perspective view showing a state in which a joint is formed in the case body. Fig. 17 is a cross-sectional view showing a state in which a joint is formed in the case body.

[0069] As shown in Fig. 13 and Fig. 14, first, a metal plate 11 is prepared (S1 step). The metal plate 11 is preferably rectangular. A cylindrical case body 110 (exterior body) is formed by the metal plate 11. In the present embodiment, the cylindrical case body 110 (exterior body) is formed by one metal plate 11.

[0070] The metal plate 11 has a bent portion 12, a first end side 13, and a second end side 14. The metal plate 11 is bent along the bent portion 12. Specifically, as shown in Fig. 13 and Fig. 15, the metal plate 11 is bent into a cylindrical shape so that the first end side 13 and the second end side 14 approach each other (step S2).

[0071] 13 and 15 to 17, next, the first end side 13 and the second end side 14 are irradiated with high energy rays 2 to form joints 115 joining the first end side 13 and the second end side 14 (step S3). The first end side 13 and the second end side 14 of the metal plate 11, which are parallel to the bent portion 12, are butted together, so that the first plate-like portion 118 and the second plate-like portion 119 of the pair of first side surface portions 111A are joined by the joints 115. This forms a cylindrical shape having a pair of first side surface portions 111.

[0072] The high energy beam 2 is, for example, a laser. However, the high energy beam 2 is not limited to a laser and may be an arc or the like. The high energy beam 2 moves along the DR1 direction in Fig. 16. The joint 115 refers to a portion that is melted by irradiation of the high energy beam 2 such as a laser and then solidified.

[0073] As shown in Fig. 17, the metal plates 11 are preferably joined in a state in which the first end side 13 and the second end side 14 are in contact with each other. The metal plates 11 may be joined in a state in which there is a gap between the first end side 13 and the second end side 14. The gap is preferably less than 0.2 mm. The metal plates 11 may also be joined by overlapping the vicinity of the first end side 13 and the vicinity of the second end side 14 in the thickness direction of the metal plates 11.

[0074] Fig. 18 is a perspective view showing a state in which a weak portion is formed in the case main body. As shown in Fig. 13 and Fig. 18, next, the metal plate 11 is irradiated with high energy rays 2 to form a weak portion 150 (step S4). The weak portion 150 is composed of a melted and solidified portion that is melted by irradiation with the high energy rays 2 and then solidified.

[0075] The bonded portion 115 includes a first region 155. The first region 155 is a portion that is irradiated again with high-energy radiation 2 after the bonded portion 115 is formed. In this embodiment, the first region 155 is located in the center of the bonded portion 115 in the first direction (X direction). The first region 155 extends linearly in the first direction (X direction).

[0076] The fragile portion 150 (melted and solidified portion) is formed at a position spaced apart from the first end side 13 and the second end side 14. In the present embodiment, the fragile portion 150 is formed such that a portion thereof is connected to the first region 155.

[0077] It is not necessary that the entire weak portion 150 is spaced apart from the first end side 13 and the second end side 14. However, the entire weak portion 150 may be provided at a position spaced apart from the first end side 13 and the second end side 14. Alternatively, the first region 155 may not be provided, and a part of the weak portion 150 may be connected to the joint portion 115.

[0078] The weak portion 150 and the first region 155 are formed by a single stroke of the high energy beam 2 (in a direction along the DR2 direction in FIG. 18). The weak portion 150 and the first region 155 can be efficiently formed by a single stroke of the high energy beam 2. The weak portion 150 and the first region 155 may be formed separately by the high energy beam 2. When the weak portion 150 and the first region 155 are formed separately, either the joint portion 115 or the weak portion 150 may be formed first. In addition, when forming the weak portion 150 by the high energy beam 2, it is not necessarily required to form the weak portion 150 by a single stroke.

[0079] At least a part of the fragile portion 150 is located on a center line C that passes through the center of one 111A of the pair of first wall portions in a third direction (Y direction) perpendicular to the first direction (X direction) and the second direction (Z direction) and extends along the first direction (X direction). When the internal pressure in the case 100 increases, each surface of the case 100 expands spherically (arcuately). In one 111A of the first side surface portions where the joint portion 115 is located, stress is most likely to concentrate on the center line C in the Y direction due to the internal pressure, and the amount of deformation is large. By providing the fragile portion 150 on this center line C in the X direction, it is possible to make the fragile portion 150 easier to break.

[0080] In this embodiment, the fragile portion 150 is located at the center of one 111A of the pair of first walls in the first direction (X direction). In one 111A of the first side surface portions where the joint portion 115 is located, the center in the X direction is most susceptible to stress concentration due to internal pressure and has the largest amount of deformation. By providing the fragile portion 150 at this center in the X direction, it is possible to make the fragile portion 150 easier to break.

[0081] In this embodiment, the first region 155 breaks before the weak portion 150. In this embodiment, the joint 115 is a first molten solidified portion, the weak portion 150 is a second molten solidified portion, and the first region 155 constitutes a third molten solidified portion.

[0082] The portion constituted by the fragile portion 150 and the first region 155 is substantially annular when viewed from the second direction (Z direction). The portion constituted by the fragile portion 150 and the first region 155 has no corners, so stress concentration during deformation during breakage is suppressed. For this reason, breakage is likely to occur along the shape of the fragile portion 150. In other words, the fragile portion 150 is likely to break along the shape intended by design.

[0083] Fig. 19 is a cross-sectional view taken along line XIX-XIX of the case main body shown in Fig. 18. Fig. 20 is a cross-sectional view taken along line XX-XX of the case main body shown in Fig. 18.

[0084] 19, the junction depth of the junction 115 is adjusted by conditions such as the output or operation speed of the high energy ray 2. Specifically, the thickness t 0 In contrast, the thickness t of the joint 115 1 But, t 0 ≧t 1 The depth of the joint 115 is adjusted so as to satisfy the relationship:

[0085] As shown in Fig. 20, the fragile portion 150 is recessed on the outer surface side of one 111A of the pair of first side surface portions. 2 is the thickness t of the joint 115 1 Thinner.

[0086] The first region 155 is recessed on the outer surface side of one 111A of the pair of first side surface portions, similar to the fragile portion 150. 3 is the thickness t of the fragile portion 150 2 Same as or thinner.

[0087] From the above, the thickness t 0 , the thickness t of the joint 115 1 , the thickness t of the weak portion 150 2 and the thickness t of the first region 155 3 t 0 ≧t 1 >t 2 ≧t 3 Satisfy the relationship.

[0088] The depth of the recess in the weak portion 150 and the first region 155 is set to a value equal to or larger than the thickness t 0 It is preferably 5% or more and 40% or less, and more preferably 25%.

[0089] FIG. 21 is a cross-sectional view showing a state in which a first region is formed in a case main body. As shown in FIG. 21, in order to make the thickness of the first region 155 thinner than other portions, the high energy beam 2 is wobbled (in this embodiment, the high energy beam 2 is swung from side to side) to form the first region 155. The laser is moved in the forming direction (X direction) of the first region 155 while reciprocating in the DR3 direction in FIG. 21. By intentionally forming an undercut, which is originally considered to be a welding defect, a portion thinner than the thickness of one 111A of the pair of first side surface portions can be formed. The fragile portion 150 is also formed by the same laser irradiation as the first region 155.

[0090] Fig. 22 is a perspective view showing the configuration of the case body when the fragile portion breaks. As shown in Fig. 22, when the pressure inside the case 100 increases, the first region 155 becomes the break start position P1. The reason that the first region 155 becomes the break start position P1 is because the first region 155 is the thinnest part of the case body 110.

[0091] When the fracture starts from the fracture start position P1, a through hole 151 is formed in the case body 110. Specifically, the fracture progresses from the fracture start position P1 to the entire area of ​​the first region 155. Immediately after the fracture, gas is discharged from the fractured portion, and the internal pressure of the case 100 decreases. While the internal pressure of the case 100 decreases, a force that tries to expand the fractured portion when the gas is discharged is applied to the periphery of the fractured portion. This causes the fracture of the weak portion 150 adjacent to the first region 155 to progress (in the direction DR4 in FIG. 22) until the through hole 151 has a certain area. Gas is discharged from the through hole 151 to the outside of the case 100.

[0092] In this embodiment, the through hole 151 is formed in the portion of the case body 110 surrounded by the first region 155 and the fragile portion 150 while it is connected to the case body 110 without being cut off from the case body 110. This allows the gas to escape in a direction that is directivity. Note that the portion of the case body 110 surrounded by the first region 155 and the fragile portion 150 may be cut off from the case body 110.

[0093] On the other hand, the joint 115 adjacent to the broken portion may break to some extent, but since its shape is unlikely to contribute to increasing the cross-sectional area of ​​the gas discharge path, the breakage will be small compared to the fragile portion 150.

[0094] In the manufacturing method for a secondary battery case and the secondary battery 1 according to the first embodiment of the present technology, a joint 115 that joins a first end edge 13 and a second end edge 14 of the metal plate 11 and a weak part 150 that is spaced apart from the first end edge 13 and the second end edge 14 and that discharges gas when the pressure inside the case 100 increases are formed by irradiating a high-energy ray 2 to the metal plate 11 that constitutes the case body 110 (exterior body). Compared to the case where a weak part such as a groove is formed by a method other than the high-energy ray 2, the joint between the case bodies 110 (exterior body) and the formation of the weak part 150 can be performed by the same processing method using the high-energy ray 2, so that the weak part 150 can be provided efficiently. As a result, a highly reliable secondary battery 1 that can be efficiently manufactured can be provided.

[0095] In the manufacturing method for a secondary battery case and the secondary battery 1 relating to embodiment 1 of the present technology, by providing the joint portion 115 and the weak portion 150 on the same plane of the case body 110 (outer body), the joint portion 115 and the weak portion 150 can be efficiently provided by high-energy beam 2 without changing the posture of the case body 110, and therefore the secondary battery 1 can be efficiently manufactured.

[0096] In the manufacturing method for a secondary battery case and the secondary battery 1 according to the first embodiment of the present technology, the joint 115 is formed including a first region 155 that is irradiated again with high-energy rays 2 after the joint 115 is formed, and the fragile portion 150 is formed connected to the first region 155. This makes it easier for the case body 110 to break with the first region 155 being the break start position P1 of the case body 110 (exterior body), and therefore makes it easier to discharge gas within the case 100.

[0097] In the manufacturing method for a secondary battery case and the secondary battery 1 relating to embodiment 1 of the present technology, the portion formed by the fragile portion 150 and the first region 155 is approximately annular when viewed from the second direction (Z direction), which makes it easier to ensure a large opening area of ​​the through hole 151 for discharging gas when the fragile portion 150 and the first region 155 break, compared to other shapes (e.g., linear).

[0098] In the manufacturing method for a secondary battery case and the secondary battery 1 relating to embodiment 1 of the present technology, at least a portion of the fragile portion 150 passes through the center of one 111A of a pair of first side portions (first wall portions) in the third direction (Y direction) and is positioned on a center line C extending along the first direction (X direction). By providing the fragile portion 150 at a position in the case 100 where the amount of deformation due to gas pressure is large, the fragile portion 150 can be made to break easily.

[0099] In the manufacturing method for a secondary battery case and the secondary battery 1 relating to embodiment 1 of the present technology, a weak portion 150 is provided in one 111A of a pair of first side portions (first wall portions) of the case body 110, which has an area smaller than each of the pair of second side portions 112 (first wall portions).Therefore, when gas is generated within the case 100, even if multiple secondary batteries 1 are stacked with their pairs of second side portions 112 aligned together, the generated gas can be easily discharged without interfering with the other secondary batteries 1.

[0100] In the manufacturing method for a secondary battery case and the secondary battery 1 relating to embodiment 1 of the present technology, by providing a fragile portion 150, the area and position of the case 100 that will break can be identified, making it easier to design the gas exhaust of the secondary battery 1.

[0101] In the manufacturing method for a secondary battery case and the secondary battery 1 according to the first embodiment of the present technology, when manufacturing a secondary battery 1 with a different gas emission amount while keeping the physical size of the secondary battery 1 the same due to a change in the specifications of the secondary battery 1, the secondary battery 1 can be manufactured simply by changing the processing conditions of the high-energy beam 2 that forms the fragile portion 150 and the first region 155. This increases the development speed of the secondary battery 1 and reduces the cost of a mold for manufacturing the case 100.

[0102] Hereinafter, secondary batteries according to embodiments 2 to 6 will be described. Since the secondary batteries according to these embodiments have different configurations of the joints and fragile parts of the case body from secondary battery 1 according to embodiment 1 of the present technology, the description of the configurations that are similar to those of secondary battery 1 according to embodiment 1 of the present technology will not be repeated.

[0103] (Embodiment 2) Fig. 23 is a top view showing the configuration of a case body of a secondary battery according to embodiment 2. Fig. 24 is a top view showing a tear-open range of the case body according to embodiment 2.

[0104] 23 and 24, the secondary battery according to the present embodiment includes a case body 110A (exterior body). Case body 110A is provided with a fragile portion 150A and a first region 155A. A portion formed by fragile portion 150A and first region 155A has a rectangular shape when viewed from the second direction (Z direction). First region 155A is one of four sides of the rectangular shape.

[0105] When the pressure inside the case rises, the first region 155A becomes the fracture start position P2. When fracture starts from the fracture start position P2, the fracture progresses throughout the first region 155A, and the fracture progresses along the DR5 direction of the fragile portion 150A. The fracture of the fragile portion 150A causes gas to be discharged to the outside of the case. Since the portion formed by the fragile portion 150A and the first region 155A has a rectangular shape, the cleavage range 153A is the range of the rectangular portion.

[0106] In the manufacturing method for a secondary battery case and the secondary battery according to the second embodiment of the present technology, the portion constituted by the fragile portion 150A and the first region 155A has a rectangular shape when viewed from the second direction (Z direction), and therefore the fragile portion 150A and the first region 155A can be formed by drawing the high-energy beam in one stroke, and therefore the fragile portion 150A and the first region 155A can be formed efficiently. Note that the high-energy beam does not necessarily have to be drawn in one stroke.

[0107] In the manufacturing method for a secondary battery case and the secondary battery according to embodiment 2 of the present technology, the portion formed by fragile portion 150A and first region 155A has a rectangular shape, so that case body 110A breaks in a straight line, making it easier to design the rupture area.

[0108] In the manufacturing method for a secondary battery case and the secondary battery according to embodiment 2 of the present technology, the portion formed by fragile portion 150A and first region 155A has a rectangular shape, which makes it easier to ensure a large tear range 153A compared to other shapes (e.g., linear).

[0109] (Embodiment 3) Fig. 25 is a top view showing the configuration of a case body of a secondary battery according to embodiment 3. Fig. 26 is a top view showing a tear-open range of the case body according to embodiment 3.

[0110] 25 and 26, the secondary battery according to the present embodiment includes a case body 110B (exterior body). Case body 110B is provided with a fragile portion 150B and a first region 155B. A portion formed by fragile portion 150B and first region 155B is substantially N-shaped when viewed from the second direction (Z direction).

[0111] The fragile portion 150B is composed of one side that spans a part of the joint 115B in a direction inclined from the X direction, and two sides that intersect the joint 115B approximately perpendicularly in the Y direction from both ends of the one side. The first region 155B is located at the intersection of the joint 115B extending in the first direction (X direction) and the fragile portion 150B formed in an approximately N shape.

[0112] When the pressure inside the case rises, the first region 155B becomes the fracture start position P3. In this embodiment, fracture occurs at the fracture start position P3 near the center of the first region 155B in the first direction (X direction). When fracture starts from the fracture start position P3, the fracture progresses along the DR6 direction of the weak portion 150B. The fracture of the weak portion 150B causes gas to be discharged to the outside of the case. Since the portion formed by the weak portion 150B and the first region 155B is substantially N-shaped, the cleavage range 153B becomes a substantially rectangular range surrounded by the substantially N-shape.

[0113] In the manufacturing method for a secondary battery case and the secondary battery according to the third embodiment of the present technology, the portion constituted by the fragile portion 150B and the first region 155B is substantially N-shaped when viewed from the second direction (Z direction), and therefore the fragile portion 150B and the first region 155B can be formed by a single stroke of the high-energy beam, and therefore the fragile portion 150B and the first region 155B can be formed efficiently. Note that it is not necessarily required to form the fragile portion 150B and the first region 155B by a single stroke of the high-energy beam.

[0114] In the manufacturing method for a secondary battery case and the secondary battery according to the third embodiment of the present technology, the portion constituted by the fragile portion 150B and the first region 155B is substantially N-shaped when viewed from the second direction (Z direction), and therefore the cleavage range 153B is not entirely surrounded by the fragile portion 150B and the first region 155B, so that it is possible to suppress breakage that separates the fragile portion 150B and the first region 155B from the case body 110B, thereby reducing the risk of the case bursting.

[0115] In the manufacturing method for a secondary battery case and the secondary battery relating to embodiment 3 of the present technology, the portion formed by the fragile portion 150B and the first region 155B is approximately N-shaped when viewed from the second direction (Z direction), which makes it easier to ensure a large tearing range 153B compared to other shapes (e.g., linear).

[0116] (Embodiment 4) Fig. 27 is a top view showing the configuration of a case body of a secondary battery according to embodiment 4. Fig. 28 is a top view showing a tear-open range of the case body according to embodiment 4.

[0117] 27 and 28, the secondary battery according to the present embodiment includes a case body 110C (exterior body). The case body 110C is provided with a fragile portion 150C and a first region 155C. The portion formed by the fragile portion 150C and the first region 155C is substantially X-shaped when viewed from the second direction (Z direction).

[0118] The fragile portion 150C is configured by four sides extending in four directions from near the center in the third direction (Y direction) and inclined from the first direction (X direction) and the third direction (Y direction). The fragile portion 150C extends from near the center in the Y direction of the pair of first side surface portions 111 to both ends. The first region 155C is located at the intersection of the joint portion 115C extending in the first direction (X direction) and the fragile portion 150C formed in a substantially X-shape.

[0119] The first region 155C is preferably disposed so as to be located at the center in the X direction. Moreover, the fragile portion 150C is preferably symmetrical with respect to a center line in the X direction passing through the center in the Y direction of the pair of first side surface portions 111. This makes it easier to break the case body 110C uniformly in the pair of first side surface portions 111.

[0120] When the pressure inside the case rises, the first region 155C becomes the rupture start position P4. When the rupture starts from the rupture start position P4, the rupture progresses along the DR7 direction of the fragile portion 150C. The rupture of the fragile portion 150C causes gas to be discharged to the outside of the case. Since the portion formed by the fragile portion 150C and the first region 155C is substantially X-shaped, the rupture range 153C becomes a substantially rectangular portion surrounded by the substantially X-shape.

[0121] In the manufacturing method for a secondary battery case and the secondary battery according to the fourth embodiment of the present technology, the portion constituted by the fragile portion 150C and the first region 155C is substantially X-shaped when viewed from the second direction (Z direction), and therefore the cleavage range 153C is not entirely surrounded by the fragile portion 150C and the first region 155C, so that it is possible to suppress breakage that separates the fragile portion 150C and the first region 155C from the case body 110C. This reduces the risk of the case bursting.

[0122] In the manufacturing method for a secondary battery case and the secondary battery according to embodiment 4 of the present technology, the portion formed by the fragile portion 150C and the first region 155C is approximately X-shaped when viewed from the second direction (Z direction), which makes it easier to ensure a large tearing range 153C compared to other shapes (e.g., linear).

[0123] In the manufacturing method for a secondary battery case and the secondary battery according to embodiment 4 of the present technology, the portion formed by the fragile portion 150C and the first region 155C is approximately X-shaped when viewed from the second direction (Z direction), so that the fragile portion 150C can be broken simultaneously in four places, thereby improving the breaking speed.

[0124] In the secondary battery in the above-mentioned embodiment, the joint portion and the fragile portion of the case body are connected by the first region, but the present invention is not limited to this configuration. The joint portion and the fragile portion of the case body may be formed apart from each other on the same plane of the case body. The joint portion and the fragile portion of the case body may be formed apart from each other on different planes of the case body. Even when the joint portion and the fragile portion are formed apart from each other on the same plane of the case body, or when the joint portion and the fragile portion are formed apart from each other on different planes of the case body, the joint portion and the fragile portion can be provided by the same processing method using high energy rays, so that a highly reliable secondary battery can be efficiently provided.

[0125] Although the embodiment of the present technology has been described above, the embodiment disclosed herein should be considered as illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0126] 1 secondary battery, 2 high energy ray, 11 metal plate, 12 bent portion, 13 first end edge, 14 second end edge, 100 case, 110, 110A, 110B, 110C case body, 111 pair of first side portions (pair of first wall portions), 111A one of the pair of first side portions (pair of first wall portions), 112 pair of second side portions (pair of second wall portions), 113 first opening, 114 second opening, 115, 115B, 115C joint portion, 118 first plate-shaped portion, 119 second plate-shaped portion, 120 first sealing plate, 125, 135 sealing plate joint portion, 130 second sealing plate, 134 liquid injection hole, 150, 150A, 150B, 150C fragile portion, 151 Through hole, 153A, 153B, 153C cleavage range, 155, 155A, 155B, 155C first region, 200 electrode body, 210 negative electrode plate, 210S negative electrode base plate, 211 negative electrode core, 212 negative electrode active material layer, 220 first electrode tab group, 230 negative electrode tab, 240 positive electrode plate, 240S positive electrode base plate, 241 positive electrode core, 242 positive electrode active material layer, 243 positive electrode protective layer, 250 second electrode tab group, 260 positive electrode tab, 300 electrode terminal, 301 negative electrode terminal, 302 positive electrode terminal, 400 current collector, 400A negative electrode current collector, 400B positive electrode current collector, C center line, P1, P2, P3, P4 fracture start position.

Claims

1. a step of bending a metal plate having a first end side and a second end side into a cylindrical shape such that the first end side and the second end side approach each other; forming a joint portion that joins the first end side and the second end side by irradiating the first end side and the second end side with a high-energy beam; and forming a fragile portion by irradiating the metal plate with high-energy rays at a position spaced from the first end edge and the second end edge.

2. A cylindrical exterior body is formed by the metal plate, The exterior body is a first opening located at an end of a first side in a first direction; a second opening located at an end of a second side opposite the first side in the first direction; a pair of first walls facing each other in a second direction perpendicular to the first direction; The method for manufacturing a secondary battery case according to claim 1 , wherein the joint portion and the fragile portion are provided on one of the pair of first walls.

3. The method for manufacturing a secondary battery case according to claim 2 , wherein the fragile portion is formed so as to be connected to the joint portion.

4. the bonded portion includes a first region that is irradiated again with high-energy radiation after the bonded portion is formed, The method for manufacturing a secondary battery case according to claim 2 , wherein the fragile portion is formed so as to be connected to the first region.

5. The method for manufacturing a secondary battery case according to claim 4 , wherein a portion formed by the fragile portion and the first region is substantially annular when viewed from the second direction.

6. The method for manufacturing a secondary battery case according to claim 4 , wherein a portion formed by the fragile portion and the first region is substantially N-shaped when viewed from the second direction.

7. The method for manufacturing a secondary battery case according to claim 4 , wherein a portion formed by the fragile portion and the first region is substantially X-shaped when viewed from the second direction.

8. 8. The method for manufacturing a secondary battery case according to claim 2, wherein at least a portion of the fragile portion is located on a center line that passes through a center of one of the pair of first wall portions in a third direction perpendicular to the first direction and the second direction and extends along the first direction.

9. the exterior body has a pair of second wall portions opposed to each other in a third direction perpendicular to the first direction and the second direction, The method for manufacturing a secondary battery case according to claim 2 , wherein an area of ​​each of the pair of first walls is smaller than an area of ​​each of the pair of second walls.

10. An electrode body including a first electrode and a second electrode having a polarity different from that of the first electrode; A case that houses the electrode body, The case is an exterior body having a first opening located at an end of a first side in a first direction and a second opening located at an end of a second side opposite to the first side in the first direction; a first sealing plate that seals the first opening; a second sealing plate that seals the second opening, The exterior body is provided with a joint extending from the first opening to the second opening, and a molten solidified portion constituting a fragile portion that breaks when the internal pressure of the case becomes equal to or greater than a predetermined value and discharges gas in the case to the outside of the case; The exterior body has a first end edge and a second end edge joined at the joint portion, The molten and solidified portion is provided at a position spaced apart from the first end edge and the second end edge.

11. The exterior body has a pair of first walls facing each other in a second direction perpendicular to the first direction, The secondary battery according to claim 10 , wherein the joint portion and the fragile portion are provided on one of the pair of first walls.

12. The secondary battery according to claim 11 , wherein the fragile portion is formed to be connected to the joint portion.

13. the bonded portion includes a first region that is irradiated again with high-energy radiation after the bonded portion is formed, The secondary battery according to claim 11 , wherein the fragile portion is formed to be connected to the first region.

14. The secondary battery according to claim 13 , wherein a portion formed by the fragile portion and the first region is substantially annular when viewed from the second direction.

15. The secondary battery according to claim 13 , wherein a portion formed by the fragile portion and the first region is substantially N-shaped when viewed from the second direction.

16. The secondary battery according to claim 13 , wherein a portion formed by the fragile portion and the first region is substantially X-shaped when viewed from the second direction.

17. 17. The secondary battery of claim 11, wherein at least a portion of the weak portion passes through a center of one of the pair of first wall portions in a third direction perpendicular to the first direction and the second direction and is located on a center line extending along the first direction.

18. the exterior body has a pair of second wall portions opposed to each other in a third direction perpendicular to the first direction and the second direction, 17. The secondary battery according to claim 11, wherein an area of ​​each of the pair of first walls is smaller than an area of ​​each of the pair of second walls.

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