Method for manufacturing case for secondary battery, and secondary battery

Abstract

The invention provides a method for manufacturing a secondary battery case and a secondary battery. This method for manufacturing a secondary battery case is provided with: a step for bending a metal plate, which has 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; a step for forming a joining section for joining the first end side and the second end side by irradiating the first end side and the second end side with a high-energy line; and a step for forming a fragile portion by irradiating a position of the metal plate separated from the first end side and the second end side with a high-energy line.

Description

Technical Field

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

[0002] As a prior art document disclosing a non-aqueous electrolyte secondary battery, there is Japanese Patent Publication No. 8-148184. In the non-aqueous electrolyte secondary battery described in Japanese Patent Publication No. 8-148184, grooves extending in multiple directions are formed on the side surfaces of the flat rectangular battery container that are not parallel to the positive electrode and the negative electrode.

[0003] As a prior art document that discloses a secondary battery, there is Japanese Patent No. 5821605. In the secondary battery described in Japanese Patent No. 5821605, a thin-walled portion in the housing that is thinner than other portions of the metal plate is formed as a safety valve at a location where the edges of the metal plates are welded to each other. The thin-walled portion is formed by rolling or grinding.

[0004] From the viewpoint of reliability of secondary batteries, there is room for efficiently manufacturing highly reliable secondary batteries in the secondary batteries described in Japanese Patent Application Laid-Open No. 8-148184 and Japanese Patent No. 5821605. Summary of the invention

[0005] The present technology has been made to solve the above-mentioned problems, and an object of the present technology is to provide a highly reliable secondary battery that can be manufactured efficiently.

[0006] The manufacturing method of the secondary battery shell based on the present technology includes the following steps, namely: bending a metal plate having a first end and a second end into a cylindrical cavity in a manner that the first end is close to the second end; forming a joint portion that joins the first end and the second end by irradiating high-energy rays to the first end and the second end; and forming a fragile portion by irradiating high-energy rays to a position in the metal plate that is away from the first end and the second end.

[0007] The secondary battery based on the present technology comprises an electrode body and a shell. The electrode body comprises a first electrode and a second electrode having a polarity different from that of the first electrode. The shell accommodates the electrode body. The shell comprises an outer body, a first sealing plate and a second sealing plate. The outer body has a first opening and a second opening. The first opening is located at the end of the first side in the first direction. The second opening is located at the end of the second side on the 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. A joint and a molten solidification portion are provided in the outer body. The joint extends from the first opening to the second opening. The molten solidification portion constitutes a fragile portion that breaks when the internal pressure of the shell becomes above a specified value and discharges the gas in the shell to the outside of the shell. The outer body has a first end side and a second end side that are joined at the joint. The molten solidification portion is provided at a position away from the first end side and the second end side.

[0008] The melted and solidified portion refers to a portion where a part of the metal plate constituting the exterior body is melted and solidified by irradiation with high-energy rays.

[0009] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a front view showing the structure of the secondary battery according to the first embodiment of the present technology.

[0011] Figure 2 It means observing from the direction of arrow II Figure 1 A diagram showing the state of a secondary battery.

[0012] Figure 3 It means observing from the direction of arrow III Figure 1 A diagram showing the state of a secondary battery.

[0013] Figure 4 It means observing from the direction of arrow IV Figure 1 A diagram showing the state of a secondary battery.

[0014] Figure 5 It means when viewed from the direction of arrow V Figure 1 A diagram showing the state of a secondary battery.

[0015] Figure 6 yes Figure 1 A front cross-sectional view of a secondary battery is shown.

[0016] Figure 7 It is a front view showing a negative electrode original plate before forming a negative electrode plate.

[0017] Figure 8 yes Figure 7The VIII-VIII cross-sectional view of the negative electrode original plate shown.

[0018] Fig. 9 It is a front view showing a negative electrode plate formed from a negative electrode original plate.

[0019] Fig.10 It is a front view showing a positive electrode original plate before forming a positive electrode plate.

[0020] Fig.11 yes Fig.10 XI-XI cross-sectional view of the positive electrode original plate shown.

[0021] Fig.12 It is a front view showing a positive electrode plate formed from a positive electrode original plate.

[0022] Fig.13 This is a flowchart showing a method for manufacturing a case body included in the secondary battery case according to the first embodiment.

[0023] Fig.14 It is a diagram showing a metal plate constituting the housing body.

[0024] Fig.15 It means that Fig.14 The figure shows the state of the metal plate after bending.

[0025] Fig.16 It is a perspective view showing a state where a joint portion is formed on the housing body.

[0026] Fig.17 It is a cross-sectional view showing a state where a joint portion is formed on the housing body.

[0027] Fig.18 It is a perspective view showing a state where a fragile portion is formed on the housing body.

[0028] Fig.19 yes Fig.18 A XIX-XIX cross-sectional view of the housing body is shown.

[0029] Fig. 20 yes Fig.18 XX-XX cross-sectional view of the shell body shown.

[0030] Fig.21 This is a cross-sectional view showing a state where a fragile portion and a first region are formed in the case body.

[0031] Fig. 22 It is a perspective view showing the structure of the case body when the fragile portion is broken.

[0032] Fig.23 It is a plan view showing the structure of a case body of a secondary battery according to the second embodiment.

[0033] Fig.24 It is a plan view showing the cleavage range of the shell body according to the second embodiment.

[0034] Fig.25 It is a plan view showing the structure of a case body of a secondary battery according to the third embodiment.

[0035] Fig.26 It is a plan view showing the cleavage range of the shell body according to the third embodiment.

[0036] Fig. 27 It is a plan view showing the structure of a case body of a secondary battery according to a fourth embodiment.

[0037] Fig.28 It is a plan view showing the cleavage range of the shell body according to the fourth embodiment. DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the present technology will be described. In addition, the same reference numerals are given to the same or corresponding parts, and description thereof may not be repeated.

[0039] In addition, in the embodiments described below, when the number, amount, etc. are mentioned, the scope of the present technology is not necessarily limited to the number, amount, etc., unless otherwise specified. In addition, in the following embodiments, except for the cases where there are special records, each component is not necessarily essential to the present technology. In addition, the present technology is not necessarily limited to the technology that has all the effects mentioned in the present embodiment.

[0040] In addition, in this specification, the descriptions of "comprise", "include", and "have" are open forms. That is, when a certain structure is included, other structures other than the structure may or may not be included.

[0041] In addition, in this specification, when geometric terms and terms indicating position and direction relationships are used, such as "parallel", "orthogonal", "oblique 45°", "coaxial", "along", etc., these terms allow for manufacturing errors or some changes. In this specification, when terms such as "upper side" and "lower side" are used to indicate relative positional relationships, these terms are used to indicate relative positional relationships in one state, and the relative positional relationship can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, turning the entire mechanism upside down, etc.).

[0042] In this specification, "secondary battery" is not limited to lithium ion batteries, and may include other secondary batteries such as nickel-hydrogen batteries and sodium ion batteries. In this specification, positive electrodes and negative electrodes may be collectively referred to as "electrodes".

[0043] In addition, in the drawings, the direction along the winding axis of the electrode body of the secondary battery is set as the X direction, the short side direction of the shell when viewed from the X direction is set as the Y direction, and the long side direction of the shell when viewed from the X direction is set as the Z direction. In addition, in order to facilitate the understanding of the present technology, there are parts where the dimensions of each structure in the drawings are changed from the actual dimensions. In addition, in the drawings, there is a case where the sealing plate joint between the shell body and the sealing plate is not illustrated.

[0044] In addition, in the present application specification, the X direction is set as the first direction in which the first opening and the second opening of the shell body are arranged, the Y direction is set as the third direction in which the first plate-like portion and the second plate-like portion of one of a pair of first wall portions (first side portions) are arranged, and the Z direction is set as the second direction in which a pair of first wall portions (first side portions) are arranged with respect to each other.

[0045] (Implementation Method 1)

[0046] (Overall structure of the battery)

[0047] Figure 1 It is a front view of the secondary battery 1 according to the present embodiment. Figure 2 to Figure 5 They are respectively viewed from the direction of arrow II, arrow III, arrow IV, and arrow V. Figure 1 The diagram shows the state of the secondary battery 1. Figure 6 yes Figure 1 The secondary battery 1 is shown in front cross-sectional view.

[0048] The secondary battery 1 can be mounted on an electric vehicle (BEV), a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), etc. However, the use of the secondary battery 1 is not limited to vehicle-mounted use.

[0049] like Figure 1 to Figure 6 As shown, the secondary battery 1 includes a case 100 , an electrode body 200 , an electrode terminal 300 , and a current collector 400 .

[0050] When forming a battery pack including secondary batteries 1, a plurality of secondary batteries 1 are stacked in their Y direction. The stacked secondary batteries 1 may be constrained in the stacking direction (Y direction) by a constraining member to form a battery module, or the battery pack may be directly supported by the side surface of the battery pack housing without using a constraining member.

[0051] The case 100 accommodates the electrode assembly 200 . The case 100 includes a case body 110 (external body), a first sealing plate 120 , and a second sealing plate 130 .

[0052] The shell body 110 is composed of a cylindrical, preferably square cylindrical component. Thus, a square secondary battery 1 can be obtained. The shell body 110 is made of metal. Specifically, the shell body 110 is composed of aluminum, aluminum alloy, iron or iron alloy. When the shell body 110 is composed of iron or iron alloy, the shell body 110 can also be plated with nickel, tin or zinc.

[0053] like Figure 1 , Figure 2 As shown in FIG. 1 , a first sealing plate 120 and a second sealing plate 130 are provided at both ends of the housing body. The housing body 110 is formed by, for example, bringing the ends of a plate-shaped member (metal plate) subjected to bending into contact with each other (at Figure 5 The square tube shape can be formed by joining the two members (for example, laser welding) to each other as shown in the joining portion 115 illustrated in FIG. The corners of the "square tube shape" may also have an R shape.

[0054] In the present embodiment, the shell body 110 is formed in such a manner that the X direction of the secondary battery 1 is longer than the Y direction and the Z direction of the secondary battery 1. The dimension of the shell body 110 in the X direction is preferably greater than 30 cm. Thus, a relatively large (high capacity) secondary battery 1 can be formed. The dimension of the shell body 110 in the Z direction is preferably less than 20 cm, more preferably less than 15 cm, and further preferably less than 10 cm. Thus, a secondary battery 1 with a relatively low height (low height) can be formed, for example, the mountability on a vehicle is improved.

[0055] The housing body 110 includes a pair of first side portions 111 (a pair of first wall portions) and a pair of second side portions 112 (a pair of second wall portions). The pair of first side portions 111 are opposed to each other in a second direction (Z direction) orthogonal to the first direction (X direction). The pair of first side portions 111 constitute the bottom surface portion and the top surface portion of the housing 100.

[0056] 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 surface of the housing 100 .

[0057] The pair of first side portions 111 and the pair of second side portions 112 are arranged to cross each other. The pair of first side portions 111 and the pair of second side portions 112 are connected at their respective ends. As in the present embodiment, the area of ​​each of the pair of first side portions 111 is preferably smaller than the area of ​​each of the pair of second side portions 112.

[0058] like Figure 5 As shown, a joint portion 115 is formed on one of the pair of first side portions 111A. The joint portion 115 extends from the first opening 113 to the second opening 114. That is, the joint portion 115 extends along the X direction of the secondary battery 1. At the joint portion 115, the edges of the metal plates constituting the case body 110 are joined to each other.

[0059] One of the pair of first side surfaces 111A is provided with a fragile portion 150. When the internal pressure of the housing 100 reaches a predetermined value or more, the fragile portion 150 is broken, thereby discharging the gas in the housing 100 to the outside of the housing 100.

[0060] In the present embodiment, the joint portion 115 and the fragile portion 150 are provided on one of the pair of first side portions 111A. The details of the joint portion 115 and the fragile portion 150 will be described later.

[0061] like Figure 3 As shown, a first opening 113 is provided at the end of the first side in the first direction (X direction) of the housing body 110. The first opening 113 is sealed by a first sealing plate 120. A sealing plate joint 125 is formed in the first opening 113 to seal the first opening 113. The first opening 113 and the first sealing plate 120 have a substantially rectangular shape with the Y direction being the short side direction and the Z direction being the long side direction.

[0062] A negative electrode terminal 301 (first electrode terminal) is provided on the first sealing plate 120. The negative electrode terminal 301 in this embodiment is located substantially at the center of the first sealing plate 120 in both the Y direction and the Z direction. The position of the negative electrode terminal 301 can be changed as appropriate.

[0063] like Figure 4 As shown, a second opening 114 is provided at the end of the second side on the side opposite to the first side in the first direction (X direction) of the housing body 110. That is, the second opening 114 is located at the end on the side opposite to the first opening 113. The second opening 114 is sealed by the 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 being the short side direction and the Z direction being the long side direction.

[0064] The second sealing plate 130 is provided with a positive terminal 302 (second electrode terminal) and a liquid injection hole 134. The positive terminal 302 in this embodiment is located substantially at the center of the second sealing plate 130 in the Y direction and the Z direction. In addition, the positions of the positive terminal 302 and the liquid injection hole 134 can be changed as appropriate.

[0065] 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, aluminum alloy, iron or iron alloy. When the first sealing plate 120 and the second sealing plate 130 are made of iron or iron alloy, the first sealing plate 120 and the second sealing plate 130 may be plated with nickel, tin or zinc.

[0066] 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 .

[0067] 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 .

[0068] The negative electrode terminal 301 is made of a conductive material (more specifically, a metal), for example, copper or a copper alloy, etc. A portion or layer made of aluminum or an aluminum alloy may be provided on the outer surface of the negative electrode terminal 301 .

[0069] The positive electrode terminal 302 is made of a conductive material (more specifically, a metal), and can be made of, for example, aluminum or an aluminum alloy.

[0070] The liquid injection hole 134 is sealed by a sealing member (not shown). As the sealing member, for example, a blind rivet or other metal member can be used.

[0071] The electrode body 200 is a flat electrode body having a positive electrode plate and a negative electrode plate described later. Specifically, the electrode body 200 is a wound electrode body formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate together via a strip-shaped separator not shown. However, in this specification, the "electrode body" is not limited to a wound electrode body, and may also be a stacked electrode body formed by alternately stacking a plurality of positive plates and a plurality of negative plates. The strip-shaped separator can be composed of a polyolefin microporous film, for example. The electrode body includes a plurality of positive plates and a plurality of negative plates, and may also be a positive electrode sheet group formed by stacking positive electrode sheets arranged on each positive plate, and a negative electrode sheet group formed by stacking negative electrode sheets arranged on each negative plate. In addition, the electrode body 200 may include a plurality of wound electrode bodies, or may include a plurality of stacked electrode bodies.

[0072] like Figure 6 As shown, the case 100 accommodates the electrode body 200. The electrode body 200 is accommodated in the case 100 so that the winding axis thereof is parallel to the X direction.

[0073] Specifically, a single or a plurality of wound electrode bodies and an electrolyte (electrolyte) (not shown) are housed inside an insulating sheet (not shown) disposed in the housing 100. As the electrolyte (non-aqueous electrolyte), for example, an electrolyte obtained by dissolving LiPF6 at a concentration of 1.2 mol / L in a non-aqueous solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio (25° C.) of 30:30:40 can be used. In addition, a solid electrolyte may be used instead of the electrolyte.

[0074] The electrode body 200 includes a main body (a portion in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween), a first electrode sheet group 220 (negative electrode sheet group), and a second electrode sheet group 250 (positive electrode sheet group).

[0075] The main body is composed of a negative electrode plate 210 (first electrode) and a positive electrode plate 240 (second electrode) described later. The first electrode sheet group 220 is located at an end of the main body on the first sealing plate 120 side in the X direction. The second electrode sheet group 250 is located at an end of the main body on the second sealing plate 130 side in the first direction (X direction).

[0076] The first electrode sheet group 220 and the second electrode sheet group 250 are formed so as to protrude from the center portion of the electrode body 200 toward the first sealing plate 120 or the second sealing plate 130 , respectively.

[0077] 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 formed of a plate-like member. The electrode body 200 is electrically connected to the negative electrode terminal 301 and the positive electrode terminal 302 via the current collector 400 .

[0078] 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 sheet group 220 and the negative electrode terminal 301. The negative electrode current collector 400A is made of a conductive material (more specifically, metal), such as copper or a copper alloy.

[0079] The positive electrode collector 400B is arranged on the second sealing plate 130 via an insulating member made of resin. The positive electrode collector 400B is electrically connected to the second electrode sheet group 250 and the positive terminal 302. The positive electrode collector 400B is composed of a conductive material (more specifically, a metal), for example, it can be composed of aluminum or an aluminum alloy. In addition, the second electrode sheet group 250 can also be electrically connected to the second sealing plate 130 directly, or electrically connected to the second sealing plate 130 via the positive electrode collector 400B. In this case, the second sealing plate 130 can also play the role of the positive terminal 302.

[0080] (Structure of Electrode Body 200)

[0081] Figure 7 is a front view showing a negative electrode original plate 210S before forming the negative electrode plate 210. Figure 8 yes Figure 7 The VIII-VIII cross-sectional view of the negative electrode original plate 210S shown in FIG. Fig. 9 1 is a front view showing a negative electrode plate 210 formed from a negative electrode original plate 210S.

[0082] The negative electrode plate 210 is manufactured by processing a negative electrode original plate 210S. Figure 7 and Figure 8 As shown, 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.

[0083] The negative electrode core 211 has a negative electrode active material layer 212 formed thereon except for one end portion of both surfaces. The negative electrode active material layer 212 is formed by applying a negative electrode active material layer slurry using a die coater.

[0084] The negative electrode active material layer slurry is prepared by kneading graphite as a 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 about 98:1:1.

[0085] 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 original plate 210S including the negative electrode core 211 and the negative electrode active material layer 212 is formed by compressing 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 based on energy line irradiation, metal mold processing, or tool processing.

[0086] like Fig. 9 As shown, at one end in the width direction of the negative electrode plate 210 formed by the negative electrode original plate 210S, a plurality of negative electrode sheets 230 formed by the negative electrode core 211 are provided. When the negative electrode plate 210 is wound, the plurality of negative electrode sheets 230 are stacked to form the first electrode sheet group 220. Thus, the first electrode sheet group 220 is connected to the negative electrode plate 210 (first electrode). Considering the state in which the first electrode sheet group 220 is connected to the negative electrode collector 400A, the positions of the respective plurality of negative electrode sheets 230 and the lengths in the protruding direction are appropriately adjusted. In addition, the shape of the negative electrode sheet 230 is not limited to Figure 8 The shape illustrated in .

[0087] Fig.10 is a front view showing a positive electrode original plate 240S before forming a positive electrode plate 240, Fig.11 yes Fig.10 The XI-XI cross-sectional view of the positive electrode original plate 240S shown in FIG. Fig.12 1 is a front view showing a positive electrode plate 240 formed of a positive electrode original plate 240S.

[0088] The positive electrode plate 240 as the second electrode has a different polarity from the negative electrode plate 210 as the first electrode. The positive electrode plate 240 is manufactured by processing a positive electrode original plate 240S. Fig.10 and Fig.11 As shown, 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.

[0089] The positive electrode core body 241 has a positive electrode active material layer 242 formed thereon except for one end portion of both surfaces. The positive electrode active material layer 242 is formed on the positive electrode core body 241 by applying a positive electrode active material layer slurry using a die coater.

[0090] The positive electrode active material layer slurry is prepared by kneading lithium nickel cobalt manganese composite oxide as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binding material, a carbon material as a conductive material, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium in a mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material of approximately 97.5:1:1.5.

[0091] The positive electrode protection layer 243 is in contact with the positive electrode core 241 and is formed at one end of the positive electrode active material layer 242 in the width direction. The positive electrode protection layer 243 is formed on the positive electrode core 241 by applying the positive electrode protection layer slurry using a die coater. The positive electrode protection layer 243 has a resistance greater than that of the positive electrode active material layer 242.

[0092] The positive electrode protective layer slurry was 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 was about 83:3:14.

[0093] The positive electrode core 241 coated with the positive electrode active material layer slurry and the positive electrode protective layer slurry is dried to remove the NMP contained in the positive electrode active material layer slurry and the positive electrode protective layer slurry, thereby forming the positive electrode active material layer 242 and the positive electrode protective layer 243. Furthermore, by compressing the positive electrode active material layer 242, the 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 is formed. The positive electrode original plate 240S is formed by cutting the positive electrode original plate 240S into a predetermined shape. The positive electrode original plate 240S can be cut by laser processing based on energy line irradiation, metal mold processing, or tool processing.

[0094] like Fig.12 As shown, at one end portion in the width direction of the positive electrode plate 240 formed by the positive electrode original plate 240S, a plurality of positive electrode sheets 260 formed by the positive electrode core 241 are provided. When the positive electrode plate 240 is wound, the plurality of positive electrode sheets 260 are stacked to form the second electrode sheet group 250. Thus, the second electrode sheet group 250 is connected to the positive electrode plate 240 (the second electrode). The positions of the respective plurality of positive electrode sheets 260 and the lengths in the protruding direction are appropriately adjusted in consideration of the state in which the second electrode sheet group 250 is connected to the positive electrode collector 400B. In addition, the shape of the positive electrode sheet 260 is not limited to Fig.12 The shape illustrated in .

[0095] The positive electrode protection layer 243 is provided at the root of each of the plurality of positive electrode sheets 260. The positive electrode protection layer 243 does not necessarily need to be provided at the root of the positive electrode sheet 260.

[0096] In a typical example, the thickness of the negative electrode sheet 230 (one sheet) is smaller than the thickness of the positive electrode sheet 260 (one sheet). In this case, the thickness of the first electrode sheet group 220 is smaller than the thickness of the second electrode sheet group 250.

[0097] (Manufacturing of the Housing Body 110)

[0098] Hereinafter, a method for manufacturing a case body (exterior body) included in the secondary battery case will be described. Fig.13 This is a flowchart showing a method for manufacturing a case body included in the secondary battery case according to the first embodiment. Fig.14 It is a diagram showing a metal plate constituting the housing body. Fig.15 It means that Fig.14 The figure shows the state of the metal plate after bending. Fig.16 It is a perspective view showing a state where a joint portion is formed on the housing body. Fig.17 It is a cross-sectional view showing a state where a joint portion is formed on the housing body.

[0099] like Fig.13 and Fig.14As shown, first, a metal plate 11 is prepared (step S1). The metal plate 11 is preferably rectangular. The metal plate 11 forms a cylindrical housing body 110 (external body). In this embodiment, the cylindrical housing body 110 (external body) is formed by one metal plate 11.

[0100] 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, Fig.13 and Fig.15 As shown, the metal plate 11 is bent into a tubular shape so that the first end side 13 and the second end side 14 are close to each other (step S2).

[0101] like Fig.13 , Figure 15 to Figure 17 As shown, next, the high energy line 2 is irradiated to the first end side 13 and the second end side 14 to form a joint 115 that joins the first end side 13 and the second end side 14 (S3 process). With respect to the metal plate 11, the first end side 13 and the second end side 14 parallel to the bent portion 12 are butted against each other, and the first plate-shaped portion 118 and the second plate-shaped portion 119 of one side 111A of the pair of first side portions are joined by the joint 115. Thus, a cylindrical shape having a pair of first side portions 111 is formed.

[0102] The high energy line 2 is, for example, a laser. However, the high energy line 2 is not limited to a laser, and may be an arc or the like. The high energy line 2 is along Fig.16 The joining portion 115 is a portion that is melted by irradiation with high energy beam 2 such as laser light and then solidified.

[0103] like Fig.17 As shown, the metal plates 11 are preferably joined in a state where the first end edge 13 and the second end edge 14 are in contact with each other. In addition, the metal plates 11 may be joined in a state where there is a gap between the first end edge 13 and the second end edge 14. The gap is preferably less than 0.2 mm. In addition, the first end edge 13 and the second end edge 14 may be joined so that the vicinity thereof overlap each other in the thickness direction of the metal plates 11.

[0104] Fig.18 2 is a perspective view showing a state where a fragile portion is formed in the shell body. Fig.13 and Fig.18 As shown, next, the metal plate 11 is irradiated with the high energy beam 2 to form the fragile portion 150 (step S4). The fragile portion 150 is composed of a molten solidified portion that is melted by the irradiation of the high energy beam 2 and then solidified.

[0105] The bonding portion 115 includes a first region 155. The first region 155 is a portion formed by irradiating the high energy beam 2 again after forming the bonding portion 115. The first region 155 in this embodiment is located at the center of the bonding portion 115 in the first direction (X direction). The first region 155 extends linearly in the first direction (X direction).

[0106] The fragile portion 150 (melted and solidified portion) is formed at a position away from the first end side 13 and the second end side 14. In the present embodiment, the fragile portion 150 is formed so that a part thereof is connected to the first region 155.

[0107] Furthermore, the fragile portion 150 does not need to be entirely separated from the first end side 13 and the second end side 14. However, the entire fragile portion 150 may be provided at a position separated from the first end side 13 and the second end side 14. Alternatively, the first region 155 may not be provided, and a portion of the fragile portion 150 may be connected to the joint portion 115.

[0108] The fragile portion 150 and the first region 155 are irradiated with the high energy line 2 once (along the Fig.18 The fragile portion 150 and the first region 155 can be formed efficiently by one continuous irradiation of the high energy line 2. In addition, the fragile portion 150 and the first region 155 can also be formed separately by the high energy line 2. In the case of forming the fragile portion 150 and the first region 155 separately, either the junction 115 or the fragile portion 150 can be formed first. In addition, when the fragile portion 150 is formed by the high energy line 2, it is not necessary to perform one continuous irradiation.

[0109] At least a portion of the fragile portion 150 is located on a center line C that passes through the center of one of the pair of first side portions 111A in the third direction (Y direction) orthogonal to the first direction (X direction) and the second direction (Z direction) and extends along the first direction (X direction). If the internal pressure in the housing 100 rises, each surface of the housing 100 expands in a spherical (arc-shaped) shape. In one of the pair of first side portions 111A where the joint 115 is located, stress is most likely to be concentrated on the center line C in the Y direction with respect to the internal pressure, and the amount of deformation becomes large. By providing the fragile portion 150 on the center line C in the X direction, the fragile portion 150 can be easily broken.

[0110] The fragile portion 150 in this embodiment is located at the center of one of the pair of first side portions 111A in the first direction (X direction). In one of the pair of first side portions 111A where the joint portion 115 is located, stress is most likely to be concentrated in the center of the X direction with respect to internal pressure, and the amount of deformation becomes large. By providing the fragile portion 150 in the center of the X direction, the fragile portion 150 can be easily broken.

[0111] In the present embodiment, the first region 155 breaks earlier than the fragile portion 150. In the present embodiment, the joining portion 115 is a first melted and solidified portion, the fragile portion 150 is a second melted and solidified portion, and the first region 155 constitutes a third melted and solidified portion.

[0112] The portion formed by the fragile portion 150 and the first region 155 is generally annular when viewed from the second direction (Z direction). Since the portion formed by the fragile portion 150 and the first region 155 has no corners, stress concentration is suppressed during deformation during fracture. Therefore, it is easy to fracture along the shape of the fragile portion 150. That is, the fragile portion 150 is easy to fracture in the design target shape.

[0113] Fig.19 yes Fig.18 A XIX-XIX cross-sectional view of the housing body is shown. Fig. 20 yes Fig.18 XX-XX cross-sectional view of the shell body shown.

[0114] like Fig.19 As shown, the depth of the joint 115 is adjusted according to the output and movement speed of the high energy line 2. Specifically, the depth of the joint 115 is adjusted so that the thickness t1 of the joint 115 satisfies the relationship t0≧t1 with respect to the thickness t0 of the first plate-shaped portion 118 and the second plate-shaped portion 119.

[0115] like Fig. 20 As shown in FIG. 1 , the fragile portion 150 is recessed on the outer surface side of one of the pair of first side portions 111A. The thickness t2 of the fragile portion 150 is thinner than the thickness t1 of the bonding portion 115.

[0116] The first region 155 is recessed on the outer surface side of one of the pair of first side surfaces 111A, similarly to the fragile portion 150 . The thickness t3 of the first region 155 is the same as or thinner than the thickness t2 of the fragile portion 150 .

[0117] As described above, the thickness t0 of one of the pair of first side surfaces 111A, the thickness t1 of the bonding portion 115 , the thickness t2 of the fragile portion 150 , and the thickness t3 of the first region 155 satisfy the relationship t0≧t1>t2≧t3.

[0118] The depth of the depression of the fragile portion 150 and the first region 155 is preferably 5% to 40% of the thickness t0 of one 111A of the pair of first side surfaces, and more preferably 25% of the thickness t0.

[0119] Fig.21 2 is a cross-sectional view showing a state where the first region is formed in the shell body. Fig.21As shown in FIG. 1 , in order to make the thickness of the first region 155 thinner than other parts, the first region 155 is formed while the high energy line 2 is swung (in this embodiment, the high energy line 2 is swung left and right). Fig.21 The welding process reciprocates in the DR3 direction of the welding line while moving in the formation direction (X direction) of the first region 155. By intentionally forming an undercut that would otherwise be a welding defect, a portion thinner than the thickness of one of the pair of first side portions 111A can be formed. In addition, the fragile portion 150 is also formed by the same laser irradiation as the first region 155.

[0120] Fig. 22 2 is a perspective view showing the structure of the housing body when the fragile portion is broken. Fig. 22 As shown, when the pressure inside the housing 100 increases, the first region 155 becomes the rupture start position P1. The first region 155 becomes the rupture start position P1 because the first region 155 is the thinnest in the housing body 110.

[0121] If the fracture starts from the fracture start position P1, a through hole 151 is formed in the shell body 110. Specifically, the fracture develops 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, so that the internal pressure of the shell 100 is reduced. The internal pressure of the shell 100 is reduced, and the force that expands the fractured portion when the gas is discharged acts on the periphery of the fractured portion. As a result, the fracture of the fragile portion 150 adjacent to the first region 155 develops until the through hole 151 has a certain area ( Fig. 22 The gas is discharged from the through hole 151 to the outside of the housing 100.

[0122] In this embodiment, the portion of the housing body 110 surrounded by the first region 155 and the fragile portion 150 is not cut away from the housing body 110, but the through hole 151 is formed in a state connected to the housing body 110. Thus, the direction of gas discharge can be made directional. In addition, the portion of the housing body 110 surrounded by the first region 155 and the fragile portion 150 may also be cut away from the housing body 110.

[0123] On the other hand, the bonding portion 115 adjacent to the broken portion may be slightly broken, but since it is a shape that does not easily contribute to the enlargement of the cross-sectional area of ​​the gas exhaust path, it is only slightly broken compared to the fragile portion 150 .

[0124] In the manufacturing method of the secondary battery case and the secondary battery 1 of the first embodiment of the present technology, the metal plate 11 constituting the case body 110 (external body) is irradiated with high energy rays 2 to form the joint 115 and the fragile portion 150, wherein the joint 115 joins the first end side 13 and the second end side 14 of the metal plate 11, the fragile portion 150 is separated from the first end side 13 and the second end side 14, and when the pressure inside the case 100 is increased, the gas is discharged to improve the reliability of the secondary battery 1. Compared with the case where the fragile portion such as the groove is formed by a method other than the high energy rays 2, since the joint of the case body 110 (external body) and the formation of the fragile portion 150 can be performed by the same processing method based on the high energy rays 2, the fragile portion 150 can be efficiently provided. As a result, a secondary battery 1 that can be efficiently manufactured and has high reliability can be provided.

[0125] In the manufacturing method of a secondary battery shell and the secondary battery 1 of embodiment 1 of the present technology, by setting the joining portion 115 and the fragile portion 150 on the same plane in the shell body 110 (external body), the joining portion 115 and the fragile portion 150 can be efficiently set by the high-energy line 2 without changing the posture of the shell body 110, so that the secondary battery 1 can be efficiently manufactured.

[0126] In the method for manufacturing a secondary battery case and the secondary battery 1 according to the first embodiment of the present technology, the joint portion 115 is formed so as to include the first region 155 formed by irradiating the high energy beam 2 again after the joint portion 115 is formed, and the fragile portion 150 is formed so as to be connected to the first region 155. Thus, since the first region 155 is made the fracture start position P1 of the case body 110 (exterior body), the case body 110 is easily fractured, and the gas in the case 100 can be easily discharged.

[0127] In the manufacturing method of the secondary battery shell and the secondary battery 1 of embodiment 1 of the present technology, the part composed of the fragile portion 150 and the first area 155 is roughly annular when viewed from the second direction (Z direction), thereby making it easier to ensure a larger opening area of ​​the through hole 151 for gas discharge caused by rupture of the fragile portion 150 and the first area 155 compared to other shapes (such as linear shapes).

[0128] In the manufacturing method of a secondary battery shell and the secondary battery 1 of embodiment 1 of the present technology, at least a portion of the fragile portion 150 is located on a center line C that passes through the center of one side 111A of a pair of first side portions (first wall portion) in the third direction (Y direction) and extends along the first direction (X direction), so that the fragile portion 150 is set at a position in the shell 100 where the deformation caused by the pressure of the gas is large, thereby making it easy to break the fragile portion 150.

[0129] In the manufacturing method of a secondary battery shell and the secondary battery 1 of embodiment 1 of the present technology, a fragile portion 150 is provided on one of the pair of first side portions (first wall portions) in the shell body 110, the area of ​​which is smaller than the respective areas of the pair of second side portions 112 (second wall portions), so that when gas is generated in the shell 100, even if a plurality of secondary batteries 1 are stacked by cooperating with each other through the pair of second side portions 112, the generated gas can be easily discharged without interfering with other secondary batteries 1.

[0130] In the secondary battery case manufacturing method and the secondary battery 1 according to the first embodiment of the present technology, the area and position of the broken case 100 can be determined by providing the fragile portion 150 , so that the gas discharge design of the secondary battery 1 can be easily performed.

[0131] In the method for manufacturing a secondary battery case and the secondary battery 1 according to the first embodiment of the present technology, when manufacturing secondary batteries 1 having the same physique and different gas emission amounts by changing the specifications of the secondary battery 1, the secondary battery 1 can be manufactured by only changing the processing conditions of the high-energy wires 2 that form the fragile portion 150 and the first region 155. As a result, the development speed of the secondary battery 1 is increased, and the cost of the metal mold used to manufacture the case 100 can be suppressed.

[0132] Secondary batteries according to Embodiments 2 to 4 are described below. The secondary batteries according to these embodiments differ from the secondary battery 1 according to Embodiment 1 of the present technology in the structures of the joint and the fragile portion of the case body, and therefore the same structures as those of the secondary battery 1 according to Embodiment 1 of the present technology will not be described repeatedly.

[0133] (Implementation Method 2)

[0134] Fig.23 It is a plan view showing the structure of a case body of a secondary battery according to the second embodiment. Fig.24 It is a plan view showing the cleavage range of the shell body according to the second embodiment.

[0135] like Fig.23 and Fig.24 As shown, the secondary battery of this embodiment includes a shell body 110A (external body). The shell body 110A is provided with a fragile portion 150A and a first region 155A. The portion consisting of the fragile portion 150A and the first region 155A is rectangular when viewed from the second direction (Z direction). The first region 155A is one of the four sides of the rectangular shape.

[0136] When the pressure inside the housing has risen, the first region 155A becomes the fracture start position P2. When the fracture starts from the fracture start position P2, the fracture progresses to the entire area of ​​the first region 155A, and the fracture progresses along the DR5 direction of the fragile portion 150A. The gas is discharged to the outside of the housing by the fracture of the fragile portion 150A. Since the portion formed by the fragile portion 150A and the first region 155A is rectangular, the crack range 153A is the range of the rectangular portion.

[0137] In the method for manufacturing a secondary battery case and the secondary battery according to the second embodiment of the present technology, the portion consisting of the fragile portion 150A and the first region 155A has a rectangular shape when viewed from the second direction (Z direction), so that the fragile portion 150A and the first region 155A can be formed by a single continuous irradiation of high-energy rays, and thus the fragile portion 150A and the first region 155A can be formed efficiently. In addition, a single continuous irradiation of high-energy rays is not necessarily required.

[0138] In the secondary battery case manufacturing method and the secondary battery according to the second embodiment of the present technology, the portion composed of the fragile portion 150A and the first region 155A is rectangular, so that the case body 110A breaks linearly, and thus the cleavage area can be easily designed.

[0139] In the secondary battery case manufacturing method and the secondary battery according to the second embodiment of the present technology, the portion composed of the fragile portion 150A and the first region 155A is rectangular, and a larger cleavage range 153A can be easily ensured compared with other shapes (eg, linear shapes).

[0140] (Implementation 3)

[0141] Fig.25 It is a plan view showing the structure of a case body of a secondary battery according to the third embodiment. Fig.26 It is a plan view showing the cleavage range of the shell body according to the third embodiment.

[0142] like Fig.25 and Fig.26 As shown, the secondary battery of this embodiment includes a case body 110B (external body). The case body 110B is provided with a fragile portion 150B and a first region 155B. The portion composed of the fragile portion 150B and the first region 155B is substantially N-shaped when viewed from the second direction (Z direction).

[0143] The fragile portion 150B is composed of one side that crosses a portion of the bonding portion 115B in a direction inclined from the X direction, and two sides that intersect the bonding portion 115B approximately orthogonally in the Y direction from both ends of the one side. The first region 155B is located at the intersection of the bonding portion 115B extending in the first direction (X direction) and the fragile portion 150B formed approximately in an N-shape.

[0144] When the pressure inside the housing has risen, the first region 155B becomes the fracture start position P3. In the present embodiment, fracture is performed at the fracture start position P3 close to the center of the first direction (X direction) in the first region 155B. If the fracture starts from the fracture start position P3, the fracture develops along the DR6 direction of the fragile portion 150B. By the fracture of the fragile portion 150B, the gas is discharged to the outside of the housing. The portion formed by the fragile portion 150B and the first region 155B is roughly N-shaped, so that the crack range 153B becomes the range of a roughly rectangular portion surrounded by a roughly N-shaped shape.

[0145] In the method for manufacturing a secondary battery case and the secondary battery according to the third embodiment of the present technology, the portion composed of the fragile portion 150B and the first region 155B is substantially N-shaped when viewed from the second direction (Z direction), so that the fragile portion 150B and the first region 155B can be formed by a single continuous irradiation of high-energy rays, and thus the fragile portion 150B and the first region 155B can be formed efficiently. In addition, a single continuous irradiation of high-energy rays is not necessarily required.

[0146] In the manufacturing method of the secondary battery case and the secondary battery according to the third embodiment of the present technology, the portion composed of the fragile portion 150B and the first region 155B is roughly N-shaped when viewed from the second direction (Z direction), and the crack range 153B is not completely surrounded by the fragile portion 150B and the first region 155B, so it is possible to suppress the fracture that causes the fragile portion 150B and the first region 155B to separate from the case body 110B. As a result, the risk of the case rupture can be reduced.

[0147] In the manufacturing method of the secondary battery casing and the secondary battery of the third embodiment of the present technology, the part composed of the fragile portion 150B and the first area 155B is roughly N-shaped when viewed from the second direction (Z direction), and compared with other shapes (such as linear shapes), it is easy to ensure a larger crack range 153B.

[0148] (Implementation 4)

[0149] Fig. 27 It is a plan view showing the structure of a case body of a secondary battery according to a fourth embodiment. Fig.28It is a plan view showing the cleavage range of the shell body according to the fourth embodiment.

[0150] like Fig. 27 and Fig.28 As shown, the secondary battery of this embodiment includes a case body 110C (external body). The case body 110C is provided with a fragile portion 150C and a first region 155C. The portion composed of the fragile portion 150C and the first region 155C is substantially X-shaped when viewed from the second direction (Z direction).

[0151] The fragile portion 150C is composed of four sides extending in four directions obliquely from the first direction (X direction) and the third direction (Y direction) from the vicinity of the center in the third direction (Y direction). The fragile portion 150C extends from the vicinity of the center in the Y direction of the pair of first side 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.

[0152] The first region 155C is preferably arranged to be located at the center in the X direction. In addition, the fragile portion 150C is preferably line-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 portions 111. Thus, the housing body 110C can be easily and uniformly broken in the pair of first side portions 111.

[0153] When the pressure inside the housing has risen, the first region 155C becomes the fracture start position P4. When the fracture starts from the fracture start position P4, the fracture progresses along the DR7 direction of the fragile portion 150C. The gas is discharged to the outside of the housing by the fracture of the fragile portion 150C. The portion formed by the fragile portion 150C and the first region 155C is roughly X-shaped, so that the cleavage range 153C is a range of a roughly rectangular portion surrounded by a roughly X-shape.

[0154] In the method for manufacturing a secondary battery case and the secondary battery according to the fourth embodiment of the present technology, the portion composed of the fragile portion 150C and the first region 155C is substantially X-shaped when viewed from the second direction (Z direction), so that the crack range 153C is not completely surrounded by the fragile portion 150C and the first region 155C, and thus it is possible to suppress the fracture that causes the fragile portion 150C and the first region 155C to separate from the case body 110C. As a result, the risk of the case rupture can be reduced.

[0155] In the manufacturing method of the secondary battery case and the secondary battery of the fourth embodiment of the present technology, the part composed of the fragile portion 150C and the first area 155C is roughly X-shaped when viewed from the second direction (Z direction), and compared with other shapes (such as linear shapes), it is easy to ensure a larger crack range 153C.

[0156] In the manufacturing method of the secondary battery case and the secondary battery of the fourth embodiment of the present technology, the part composed of the fragile portion 150C and the first region 155C is roughly X-shaped when viewed from the second direction (Z direction), and the fragile portion 150C can be broken at four locations simultaneously, thereby increasing the breaking speed.

[0157] In addition, the structure in which the joint and the fragile portion of the shell body in the secondary battery in the above-mentioned embodiment are connected by the first region is described, but it is not limited to this structure. The joint and the fragile portion of the shell body can also be formed on the same plane of the shell body in a manner separated from each other. In addition, the joint and the fragile portion of the shell body can also be formed on different planes in the shell body in a manner separated from each other. Even in the case where the joint and the fragile portion are formed on the same plane of the shell body in a manner separated from each other, or the joint and the fragile portion are formed on different planes in the shell body in a manner separated from each other, the joint and the fragile portion can be set using the same processing method based on high-energy lines, so a secondary battery with high reliability can be efficiently provided.

[0158] Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims, and it is intended to include all changes within the meaning and scope equivalent to the claims.

Claims

1. A method for manufacturing a secondary battery casing, characterized in that: The following processes are available, namely: A step of bending a metal plate having a first end side and a second end side into a cylindrical shape so that the first end side is close to the second end side; a step of forming a joint portion where the first end side and the second end side are joined by irradiating the first end side and the second end side with a high energy beam; and The step of forming a fragile portion by irradiating a position of the metal plate away from the first end side and the second end side with a high-energy beam.

2. The method for manufacturing a secondary battery casing according to claim 1, wherein: The metal plate forms a cylindrical outer body. The outer casing has: a first opening located at an end portion of a first side in a first direction; a second opening located at an end portion of a second side opposite to the first side in the first direction; and a pair of first wall portions, the pair of first wall portions facing each other in a second direction orthogonal to the first direction, The joining portion and the fragile portion are provided on one of the pair of first wall portions.

3. The method for manufacturing a secondary battery casing according to claim 2, wherein: The fragile portion is formed in a manner connected to the joining portion.

4. The method for manufacturing a secondary battery casing according to claim 2, wherein: The bonding portion includes a first region formed by irradiating the bonding portion with a high energy beam again after the bonding portion is formed. The fragile portion is formed so as to be continuous with the first region.

5. The method for manufacturing a secondary battery casing according to claim 4, characterized in that: When the portion consisting of the fragile portion and the first region is viewed from the second direction, the portion consisting of the fragile portion and the first region has a substantially ring shape.

6. The method for manufacturing a secondary battery casing according to claim 4, wherein: When the portion composed of the fragile portion and the first region is viewed from the second direction, the portion composed of the fragile portion and the first region has a substantially N-shape.

7. The method for manufacturing a secondary battery casing according to claim 4, wherein: When the portion composed of the fragile portion and the first region is viewed from the second direction, the portion composed of the fragile portion and the first region is substantially in an X-shape.

8. The method for manufacturing a secondary battery case according to any one of claims 2 to 7, characterized in that: At least a portion of the fragile portion is located on a center line that passes through the center of one of the pair of first wall portions in a third direction that is orthogonal to the first direction and the second direction and extends along the first direction.

9. The method for manufacturing a secondary battery case according to any one of claims 2 to 7, characterized in that: The outer casing has a pair of second wall portions facing each other in a third direction orthogonal to the first direction and the second direction. The area of ​​each of the pair of first wall portions is smaller than the area of ​​each of the pair of second wall portions.

10. A secondary battery, characterized in that: have: an electrode body including a first electrode and a second electrode having a polarity different from that of the first electrode; and a shell that accommodates the electrode body, The housing comprises: an outer casing having a first opening located at an end portion on a first side in a first direction, and a second opening located at an end portion on a second side opposite to the first side in the first direction; a first sealing plate for sealing the first opening; and a second sealing plate for sealing the second opening, The outer casing is provided with a joint portion and a melt-solidified portion, the joint portion extending from the first opening to the second opening, the melt-solidified portion constituting a fragile portion that breaks when the internal pressure of the shell becomes equal to or higher than a predetermined value and discharges the gas in the shell to the outside of the shell, The outer casing has a first end side and a second end side joined at the joining portion, The melted and solidified portion is provided at a position separated from the first end side and the second end side.

11. The secondary battery according to claim 10, characterized in that: The outer casing has a pair of first wall portions facing each other in a second direction orthogonal to the first direction. The joining portion and the fragile portion are provided on one of the pair of first wall portions.

12. The secondary battery according to claim 11, characterized in that: The fragile portion is formed in a manner connected to the joining portion.

13. The secondary battery according to claim 11, characterized in that: The bonding portion includes a first region formed by irradiating the bonding portion with a high energy beam again after the bonding portion is formed. The fragile portion is formed so as to be continuous with the first region.

14. The secondary battery according to claim 13, characterized in that: When the portion consisting of the fragile portion and the first region is viewed from the second direction, the portion consisting of the fragile portion and the first region has a substantially ring shape.

15. The secondary battery according to claim 13, characterized in that: When the portion composed of the fragile portion and the first region is viewed from the second direction, the portion composed of the fragile portion and the first region has a substantially N-shape.

16. The secondary battery according to claim 13, characterized in that: When the portion composed of the fragile portion and the first region is viewed from the second direction, the portion composed of the fragile portion and the first region is substantially in an X-shape.

17. The secondary battery according to any one of claims 11 to 16, characterized in that: At least a portion of the fragile portion is located on a center line that passes through the center of one of the pair of first wall portions in a third direction that is orthogonal to the first direction and the second direction and extends along the first direction.

18. The secondary battery according to any one of claims 11 to 16, characterized in that: The outer casing has a pair of second wall portions facing each other in a third direction orthogonal to the first direction and the second direction. The area of ​​each of the pair of first wall portions is smaller than the area of ​​each of the pair of second wall portions.

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