Secondary battery

Abstract

This secondary battery is provided with an electrode body (200) and a case (100), the case (100) including: a case main body (110) having a first opening (113) at one end and a second opening (114) at the other end; a first sealing plate (120) that seals the first opening (113); and a second sealing plate (130) for sealing the second opening (114), the housing main body (110) is provided with a linear joining part (115) extending from the first opening (113) to the second opening (114), the joining part (115) has at least one bent part (115A) at a position away from the first opening (113) and the second opening (114), and when the pressure in the housing (100) is equal to or greater than a predetermined value, the joining part (115) breaks, and the gas in the housing (100) is discharged to the outside of the housing (100).

Description

Technical Field The present technology relates to a secondary battery. Background Art Conventionally, a groove portion or a thin-walled portion is formed on the wall surface of the case of a secondary battery to serve as a safety valve. As the capacity of batteries increases, secondary batteries are becoming larger. From the perspective of reliability in large secondary batteries, there is room for further improvement in existing secondary batteries. The purpose of this technology is to provide a secondary battery with high capacity and high reliability. Summary of the invention The present technology provides the following secondary batteries.

[0001] A secondary battery comprises: an electrode body, the electrode body comprising a first electrode and a second electrode having a polarity different from that of the first electrode; and a shell, the shell accommodating the electrode body, the shell comprising: a shell body, the shell body having a first opening at one end in a first direction and a second opening at the other end in the first direction; a first sealing plate, the first sealing plate sealing the first opening; and a second sealing plate sealing the second opening, the shell body being provided with a linear joint extending from the first opening to the second opening, the joint having at least one bent portion at a position away from the first opening and the second opening, and when the pressure in the shell becomes greater than a specified value, the joint is broken, and the gas in the shell is discharged to the outside of the shell.

[0002] In the secondary battery described in [1], the case body includes a pair of first wall portions that face each other in a second direction orthogonal to the first direction, and the bent portion is provided on the first wall portions.

[0003] In the secondary battery described in [2], the joint portion includes a first region and a second region, the second region is located on the opposite side of the first region relative to the bending portion, the first region and the second region extend along the first direction, the first wall portion has a first center line, the first center line passes through the center of the first wall portion in a third direction orthogonal to the first direction and the second direction and extends along the first direction, and the first region is located closer to the first center line of the first wall portion than the second region.

[0004] In the secondary battery described in [3], the junction portion includes a plurality of the second regions and the first region formed between the plurality of the second regions in the first direction.

[0005] In the secondary battery described in [3], the junction portion includes a plurality of the first regions and the second region formed between the plurality of the first regions in the first direction.

[0006] In the secondary battery described in [2], the first wall portion has a second center line, which passes through the center of the first wall portion in the first direction and extends along a third direction orthogonal to the first direction and the second direction, and the joint portion is formed to be substantially symmetrical with respect to the second center line.

[0007] In the secondary battery described in [2], the case body includes a pair of second wall portions facing each other in a third direction orthogonal to the first direction and the second direction, and an area of ​​the first wall portion is smaller than an area of ​​the second wall portion.

[0008] In the secondary battery described in any one of [1] to [7], the case body is formed of a plate-shaped member including a first end and a second end, and the joint is formed by welding the first end and the second end.

[0009] In the secondary battery described in any one of [1] to [8], the case has a substantially rectangular parallelepiped shape. 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 Figure 1 It is a front view showing the structure of the secondary battery according to the first embodiment. Figure 2 It means observing from the direction of arrow II Figure 1 A diagram showing the state of a secondary battery. Figure 3 It means observing from the direction of arrow III Figure 1 A diagram showing the state of a secondary battery. Figure 4 It means observing from the direction of arrow IV Figure 1 A diagram showing the state of a secondary battery. Figure 5 It means when viewed from the direction of arrow V Figure 1 A diagram showing the state of a secondary battery. Figure 6 yes Figure 1 A front cross-sectional view of a secondary battery is shown. Figure 7 It is a front view showing a negative electrode original plate before forming a negative electrode plate. Figure 8 yes Figure 7The VIII-VIII cross-sectional view of the negative electrode original plate shown. Fig. 9 It is a front view showing a negative electrode plate formed from a negative electrode original plate. Fig.10 It is a front view showing a positive electrode original plate before forming a positive electrode plate. Fig.11 yes Fig.10 XI-XI cross-sectional view of the positive electrode original plate shown. Fig.12 It is a front view showing a positive electrode plate formed from a positive electrode original plate. Fig.13 It is a figure (part 1) which shows the modification example of the bending part of a joining part. Fig.14 It is a figure (part 2) which shows the modification example of the bending part of a joining part. Fig.15 It is a figure (part 3) which shows the modification example of the bending part of a joining part. Fig.16 It is a figure (part 4) which shows the modification example of the bending part of a joining part. Fig.17 It is a figure (part 5) which shows the deformation example of the bending part of a joining part. Fig.18 It is a figure (part 6) which shows the deformation example of the bending part of a joining part. Fig.19 It is a figure (part 7) which shows the deformation example of the bending part of a joining part. Fig. 20 It is a figure (part 1) which shows the modification example of the shape of a joining part. Fig.21 It is a figure (part 2) which shows the modification example of the shape of a joining part. Fig. 22 It is a figure (part 3) which shows the modification example of the shape of a joining part. Fig.23 It means observing from the direction of arrow XXIII-XXIII Fig. 22 A diagram showing the state of a secondary battery. Fig.24 This is a schematic diagram showing an example of the arrangement of the exhaust valve (fragile portion). Fig.25 This is a diagram showing an example of a cross section of a joining portion (part 1). Fig.26 This is a diagram showing an example of a cross section of a joining portion (part 2). Fig. 27 This is a diagram showing an example of a cross section of a joining portion (part 3). Fig.28 This is a diagram showing an example of a cross section of a joining portion (part 4). Fig.29 This is a diagram showing an example of a cross section of a joining portion (part 5). DETAILED DESCRIPTION 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. 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. 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. In addition, in this specification, when geometrical terms and terms indicating position and direction relationships are used, such as "parallel", "orthogonal", "oblique 45 degrees", "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.). 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". In addition, the "secondary battery" in the present technology is not limited to a rectangular battery, and may be, for example, a cylindrical battery. 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 electrode body when viewed from the X direction is set as the Y direction, and the long side direction of the electrode body when viewed from the X direction is set as the Z direction. In addition, in order to facilitate the understanding of the invention, there are parts in which the dimensions of each structure in the drawings are changed from the actual dimensions. In the present application specification, the first direction (X direction) is sometimes referred to as the “width direction” of the secondary battery or the shell body, the second direction (Z direction) is similarly referred to as the “height direction” of the secondary battery or the shell body, and the third direction (Y direction) is similarly referred to as the “thickness direction” of the secondary battery or the shell body. (Overall structure of the battery) Figure 1It is a front view of the secondary battery 1 of this 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. 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. 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. The case 100 includes a case body 110, a sealing plate 120, and a sealing plate 130. The case 100 has a substantially rectangular parallelepiped shape. When forming a battery pack including secondary batteries 1, a plurality of secondary batteries 1 are stacked in their thickness 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. The case body 110 is made of a cylindrical, preferably rectangular, member. Thus, a rectangular secondary battery 1 can be obtained. The case body 110 is made of metal. Specifically, the case body 110 is made of aluminum, aluminum alloy, iron, or iron alloy. like Figure 1 , Figure 2 As shown in FIG. 1 , a sealing plate 120 and a 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 the plate-like members subjected to bending into contact with each other (at Figure 2 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. 1. The corners of the “square tube shape” may also have an R shape. In the present embodiment, the shell body 110 is formed in the width direction (X direction) of the secondary battery 1 to be longer than the thickness direction (Y direction) and the height direction (Z direction) of the secondary battery 1. The dimension (width) of the shell body 110 in the X direction is preferably greater than 15 cm, and more preferably greater than 30 cm. Thus, a relatively large (high-capacity) secondary battery 1 can be formed. The dimension (height) 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. The housing body 110 includes a pair of side portions 111 (second wall portion) and a pair of side portions 112 (first wall portion). The pair of side portions 111 constitute a portion of the side surface of the housing 100. The pair of side portions 112 constitute the bottom surface portion and the upper surface portion of the housing 100. The pair of side portions 111 and the pair of side portions 112 are arranged to intersect each other. The pair of side portions 111 and the pair of side portions 112 are adjacent to each other. Preferably, the area of ​​each of the pair of side portions 111 is larger than the area of ​​each of the pair of side portions 112. like Figure 2 and Figure 5 As shown, the side surface portion 112 includes a pair of side surface portions 112A and 112B. The side surface portions 112A and 112B each have a substantially rectangular shape with the X direction being the long side direction and the Y direction being the short side direction. like Figure 2 As shown, a joint portion 115 is formed on one side portion 112B of the pair of side portions 112. The joint portion 115 can be formed by melting a base material by irradiation with high-energy radiation such as laser light and then solidifying it. The joint 115 is formed linearly on the side surface 112B over the entire width direction (X direction) of the secondary battery 1, that is, from one end to the other end. At the joint 115, the edge sides (ends) of the plate-like members constituting the case body 110 are joined together. The joint portion 115 includes a first region 1151, a second region 1152, and a third region 1153. The first region 1151 and the second region 1152 extend along the X direction. The third region 1153 connects the first region 1151 and the second region 1152. The third region 1153 extends along the Y direction. A bending portion 115A (bending portion) is formed between the first region 1151 and the third region 1153 and between the second region 1152 and the third region 1153. The first region 1151 of the bonding portion 115 is located on the center line L (first center line) of the side surface 112B. The center line L passes through the center of the side surface 112B in the Y direction and extends in the X direction. The second region 1152 passes through a position offset from the center line L in the Y direction. In the secondary battery 1 of the present embodiment, the joint 115 has a function as a gas exhaust valve (safety valve) that ruptures when the pressure in the case 100 reaches a predetermined value or more to discharge the gas in the case 100 to the outside of the case 100 . Since the first region 1151 of the joint 115 is located on the center line L, it is displaced more when the pressure of the housing 100 increases, so that the stress is easily increased. Therefore, when the joint 115 functions as an exhaust valve (safety valve), the first region 1151 can be ruptured preferentially. By making the joint 115 function as an exhaust valve and providing the bent portion 115A, the rupture position of the joint 115 (exhaust valve) can be determined, thereby preventing damage to the battery pack during gas discharge. Therefore, the increase in manufacturing cost can be suppressed, and the secondary battery 1 with high reliability can be manufactured. Furthermore, “causally cleaving the first region 1151 preferentially” is not limited to “causally cleaving only the first region 1151 ”, and includes, for example, “causally cleaving the second region 1152 ” after initially “causally cleaving the first region 1151 ”. like Figure 3 As shown, an opening 113 (first opening) is provided at the end of the first side in the first direction (X direction) of the housing body 110. The opening 113 is sealed by a sealing plate 120. A joint 115 is formed in the opening 113 to seal the opening 113. The opening 113 and the sealing plate 120 have a generally rectangular shape with the Y direction being the short side direction and the Z direction being the long side direction. In addition, the rectangular shape includes a substantially rectangular shape such as a rectangular shape or a shape obtained by rounding the corners of a rectangular shape. The sealing plate 120 (first sealing plate) is provided with a negative electrode terminal 301. The position of the negative electrode terminal 301 can be changed as appropriate. like Figure 4 As shown, an opening 114 (second opening) is provided at the end of the second side of the housing body 110 on the first direction (X direction) and opposite to the first side. That is, the opening 114 is located at the end on the side opposite to the opening 113, and the openings 113 and 114 are opposite to each other. The opening 114 is sealed by the sealing plate 130. A joint 115 is formed in the opening 114 to seal the opening 114. The opening 114 and the sealing plate 130 have a generally rectangular shape with the Y direction being the short side direction and the Z direction being the long side direction. The sealing plate 130 (second sealing plate) is provided with a positive electrode terminal 302 and a liquid injection hole 134. The positions of the positive electrode terminal 302 and the liquid injection hole 134 can be changed as appropriate. The sealing plate 120 and the sealing plate 130 are made of metal. Specifically, the sealing plate 120 and the sealing plate 130 are made of aluminum, aluminum alloy, iron, iron alloy, or the like. The negative electrode terminal 301 (first electrode terminal) is electrically connected to the negative electrode of the electrode body 200 . The negative electrode terminal 301 is attached to the sealing plate 120 , that is, the case 100 . The positive electrode terminal 302 (second electrode terminal) is electrically connected to the positive electrode of the electrode body 200 . The positive electrode terminal 302 is attached to the sealing plate 130 , that is, the case 100 . 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 . 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. 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. 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 the positive electrode sheets arranged on each positive plate may also be stacked to form a positive electrode sheet group, and the negative electrode sheets arranged on each negative plate may also be stacked to form a negative electrode sheet group. In addition, the electrode body 200 may include a plurality of wound electrode bodies, or may include a plurality of stacked electrode bodies. 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. Specifically, a single or a plurality of wound electrode bodies and an electrolyte (electrolyte) not shown are housed together inside an insulating sheet to be described later and arranged 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. The electrode body 200 includes a main body portion (a portion in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween), a negative electrode sheet group 220 , and a positive electrode sheet group 250 . The main body is composed of a negative electrode plate 210 and a positive electrode plate 240 described later. The negative electrode sheet group 220 is located at the end of the electrode body 200 on the first side in the first direction (X direction) relative to the main body. The first side in this embodiment is the sealing plate 120 side. The positive electrode sheet group 250 is located at the end of the electrode body 200 on the second side in the first direction (X direction) relative to the main body. The second side in this embodiment is the sealing plate 130 side. The negative electrode sheet group 220 and the positive electrode sheet group 250 are formed to protrude from the central portion of the electrode body 200 toward the sealing plate 120 or the sealing plate 130 . 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 . The negative electrode current collector 400A is arranged on the sealing plate 120 via an insulating member made of resin. The negative electrode current collector 400A is electrically connected to the negative electrode sheet group 220 and the negative electrode terminal 301. The negative electrode current collector 400A is made of a conductive material (more specifically, a metal), for example, copper or a copper alloy. In addition, the details of the negative electrode current collector 400A will be described later. The positive electrode collector 400B is arranged on the sealing plate 130 via an insulating member made of resin. The positive electrode collector 400B is electrically connected to the positive 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 positive electrode sheet group 250 can also be electrically connected to the sealing plate 130 directly, or electrically connected to the sealing plate 130 via the positive electrode collector 400B. In this case, the sealing plate 130 can also play the role of the positive terminal 302. In addition, the details of the positive electrode collector 400B will be described later. (Structure of Electrode Body 200) Figure 7 2 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. The negative electrode plate 210 is manufactured by processing a negative electrode original plate 210S. Figure 7 and Figure 8As shown, the negative electrode original plate 210S includes a negative electrode core 211 (first electrode core) and a negative electrode active material layer 212. The negative electrode core 211 is a copper foil or a copper alloy foil. A negative electrode active material layer 212 is formed on the negative electrode core 211 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. 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. The negative electrode core 211 coated with the negative electrode active material layer slurry is dried and the water contained in the negative electrode active material layer slurry is removed to form 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. 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 (first electrode sheets) composed of a 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 a negative electrode sheet group 220. Thus, the negative electrode sheet group 220 is connected to the negative electrode plate 210. The positions of the respective plurality of negative electrode sheets 230 and the lengths in the protruding direction are appropriately adjusted in consideration of the connection state between the negative electrode sheet group 220 and the negative electrode collector 400A. In addition, the shape of the negative electrode sheet 230 is not limited to Figure 8 The shape illustrated in . 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. 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 (second electrode core), 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. 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. 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 such a manner that the mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material becomes approximately 97.5:1:1.5. 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. 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. 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 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 by compressing the positive electrode active material layer 242. The positive electrode plate 240 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. like Fig.12 As shown, at one end 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 (second electrode sheets) composed of a 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 a positive electrode sheet group 250. Thus, the positive electrode sheet group 250 is connected to the positive electrode plate 240. The positions of the plurality of positive electrode sheets 260 and the lengths in the protruding direction are appropriately adjusted in consideration of the connection state between the positive electrode sheet group 250 and 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 . 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. 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 negative electrode sheet group 220 is smaller than the thickness of the positive electrode sheet group 250. (Shape of the Joining Section 115 Including the Bend Section 115A) Figures 13 to 19 It is a diagram showing a modified example of the bent portion 115A of the joining portion 115 . like Figures 13 to 19 As shown, the first region 1151 of the bonding portion 115 does not necessarily need to be located on the center line L, and may be located closer to the center line L than the second region 1152 . For example, in Fig.13 In the example, the first region 1151 is located on one side of the center line L in the Y direction, and the second region 1152 is located on the other side of the center line L in the Y direction. When the distances between the center line L and the first region 1151 and the second region 1152 are respectively set to D1 and D2, the following relationship preferably holds, that is, D2 / D1>1.2. In this way, stress can be further concentrated in the first region 1151, and the priority cracking site can be determined more reliably. exist Fig.14 In the example of , the first region 1151 and the second region 1152 are located on the same side of the center line L in the Y direction, but the first region 1151 is closer to the center line L than the second region 1152. exist Fig.15 and Fig.16 In the example of , the bent portions 115A are formed at four locations. The number and positions of the bent portions 115A are not particularly limited and can be changed as appropriate. exist Fig.17 In the example of FIG. 1 , the intersection angle between the first region 1151 and the second region 1152 and the third region 1153 in the bent portion 115A is not 90°, but they intersect each other obliquely (at an angle other than 90°). The intersection angle ( Fig.17 The angle θ in θ is preferably 80° or less, and more preferably 60° or less. In this case, the crack generated in the first region 1151 can easily pass through the bent portion 115A and reach the second region 1152. exist Fig.18 In the example of , the first area 1151 close to the center line L is not formed in a linear shape but in a dot shape. Fig.19In the example of FIG. 1 , the first region 1151 sandwiched by the second region 1152 is formed in a substantially arc shape. exist Figures 13 to 19 In any of the examples, the shortest distance between the first region 1151 and the center line L is preferably about 5 mm or less, more preferably about 3 mm or less, and further preferably about 2 mm or less. (Configuration of the First Area 1151 and the Second Area 1152) Figure 20 to Figure 23 It is a diagram showing a modified example of the shape of the joining portion 115 . Fig.23 Indicates observation from the direction of arrow XXIII-XXIII Fig. 22 The state of the secondary battery 1 is shown. exist Fig. 20 In the example of , the joint portion 115 includes a plurality of (two) second regions 1152 and a first region 1151 formed between the two second regions 1152 in the X direction. The joint portion 115 is formed to be substantially symmetrical with respect to the center line L2 (second center line). The center line L2 passes through the center of the side portion 112B in the X direction and extends along the Y direction. exist Fig.21 In the example of , the junction 115 includes a plurality of (two) first regions 1151 and a second region 1152 formed in the X direction between the two first regions 1151. The junction 115 is formed substantially symmetrically with respect to the center line L2. exist Fig. 22 , Fig.23 In the example of , the joint portion 115 includes a plurality of (two) second regions 1152 and a first region 1151 formed between the two second regions 1152 in the X direction. Fig. 22 As shown in FIG. 1 , the first region 1151 is formed on the side portion 112B. On the side portion 112B, the joint portion 115 is formed substantially symmetrically with respect to the center line L2. Fig.23 As shown, the second region 1152 is formed on the side surface portion 111. The third region 1153 is formed so as to reach the side surface portion 111 from the side surface portion 112B. As mentioned above, in Figure 20 to Figure 23 In the three examples shown, the joining portion 115 (first region 1151 ) is formed substantially symmetrically with respect to the center line L2 passing through the center in the X direction. When a plurality of secondary batteries 1 are connected in series, the negative terminals 301 and the positive terminals 302 are arranged alternately in the Y direction, and the plurality of secondary batteries 1 are arranged in a state where their directions are alternately changed. At this time, since the first regions 1151 are arranged symmetrically with respect to the center line L2, even when the secondary batteries 1 are arranged in an alternately changed direction, the first regions 1151 are aligned in the Y direction, so that the gas discharge position (discharge position in the X direction) when the internal pressure of the housing 100 increases can be roughly consistent in the plurality of secondary batteries 1. exist Figure 20 to Figure 23 In any example, the total length of the first region 1151 in the X direction (when there are multiple first regions 1151, the total length of the multiple 1151) is preferably greater than 1 / 5 of the length of the shell body 110 in the X direction, and more preferably greater than 1 / 3. exist Figure 20 to Figure 23 In any of the examples, the first region 1151 is not formed near the openings 113 and 114 (a region that is 5 mm or less from the openings 113 and 114 in the X direction). Thus, it is preferred that the first region 1151 is separated from the openings 113 and 114 by a predetermined distance. By not providing the first region 1151 near the openings 113 and 114, it is possible to suppress the occurrence of undesired cracks between the housing body 110 and the sealing plates 120 and 130 when the internal pressure of the housing 100 increases. (Configuration of vulnerable parts) Fig.24 1 is a schematic diagram showing an example of the configuration of the fragile portion 1150 in the joint portion 115. Fig.24 As shown in FIG. 1 , when the electrode body 200 is a wound electrode body, the gas generated inside the electrode body 200 is discharged from both ends of the electrode body 200 in the X direction to the outside of the electrode body 200. Therefore, it is preferred to provide a fragile portion 1150 (exhaust valve) at both ends of the electrode body 200 in the X direction (above the negative electrode sheet group 220 and the positive electrode sheet group 250). For example, Fig.21 As shown in FIG. 1 , by adopting a configuration in which the first region 1151 is provided at both ends in the X direction, it is possible to realize Fig.24 The configuration of the fragile portion 1150 is shown in the schematic diagram. (Structure of the Joint 115) Figure 25 to Figure 29 115 is a diagram showing an example of a cross section of the joint portion 115. Figure 25 to Figure 29 In each of the examples, the first end portion 116 and the second end portion 117 of the plate-like member constituting the housing body 110 are joined by the joining portion 115. Thus, the housing body 110 is formed in a rectangular tube shape. exist Fig.25In the example of FIG. 1 , the first end portion 116 and the second end portion 117 are butted against each other in the region R and welded to form the joint portion 115. Fig.25 The weld depth D1 shown is different between the first region 1151 and the second region 1152 (eg, D1 is reduced in the first region 1151 compared to the second region 1152 ). exist Fig.26 In the example of FIG. 1 , the first end portion 116 and the second end portion 117 are overlapped in the region R and the region R is penetrated and welded to form the joint portion 115. Fig.26 The weld width W1 shown (the width at the boundary between the first end portion 116 and the second end portion 117 ) is different between the first region 1151 and the second region 1152 (for example, W1 is smaller in the first region 1151 than in the second region 1152 ). exist Fig. 27 In the example of FIG. 1 , the first end portion 116 and the second end portion 117 are overlapped in the region R, and the adjacent portions of the region R are fillet welded to form the joint portion 115. Fig. 27 The weld width W2 shown is different between the first region 1151 and the second region 1152 (eg, W2 is reduced in the first region 1151 compared to the second region 1152 ). exist Fig.28 , Fig.29 In the example of FIG. 1 , the joint 115 is formed by providing a concavo-convex shape at the first end 116 and the second end 117 and welding the region R formed by the meshing of the concavo-convex shape or its adjacent region. Fig.29 The weld width W3 shown (the width at the boundary between the first end portion 116 and the second end portion 117 ) is different between the first region 1151 and the second region 1152 (for example, W3 is smaller in the first region 1151 than in the second region 1152 ). 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 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: a housing body having a first opening at one end in a first direction and a second opening at another end in the first direction; a first sealing plate, the first sealing plate sealing the first opening; as well as a second sealing plate for sealing the second opening, The housing body is provided with a linear joint portion extending from the first opening to the second opening. The joining portion has at least one bent portion at a position away from the first opening and the second opening. When the pressure in the housing becomes equal to or higher than a predetermined value, the joint portion is broken, and the gas in the housing is discharged to the outside of the housing.

2. The secondary battery according to claim 1, characterized in that: The housing body includes a pair of first wall portions facing each other in a second direction orthogonal to the first direction. The bent portion is provided on the first wall portion.

3. The secondary battery according to claim 2, characterized in that: The joining portion includes a first region and a second region, wherein the second region is located on a side opposite to the first region with respect to the bent portion. The first region and the second region extend along the first direction, The first wall portion has a first center line that passes through the center of the first wall portion in a third direction that is orthogonal to the first direction and the second direction and extends along the first direction. The first region is located closer to the first center line of the first wall portion than the second region.

4. The secondary battery according to claim 3, characterized in that: The bonding portion includes a plurality of the second regions and the first region formed between the plurality of the second regions in the first direction.

5. The secondary battery according to claim 3, characterized in that: The bonding portion includes a plurality of the first regions and the second region formed between the plurality of the first regions in the first direction.

6. The secondary battery according to claim 2, characterized in that: The first wall portion has a second center line that passes through the center of the first wall portion in the first direction and extends along a third direction that is orthogonal to the first direction and the second direction. The joining portion is formed substantially symmetrically with respect to the second center line.

7. The secondary battery according to claim 2, characterized in that: The housing body includes 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 ​​the first wall portion is smaller than the area of ​​the second wall portion.

8. The secondary battery according to any one of claims 1 to 7, characterized in that The housing body is composed of a plate-shaped member including a first end and a second end. The joining portion is formed by welding the first end portion and the second end portion.

9. The secondary battery according to any one of claims 1 to 7, characterized in that The housing has a substantially rectangular parallelepiped shape.

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