Rectangular secondary battery

Abstract

In a rectangular secondary battery (1, 10), a positive electrode terminal (302) electrically connected to a positive electrode sheet (250) is provided on a third wall (130) of a pair of third walls (120, 130) that faces the positive electrode sheet (250), a negative electrode terminal (301) electrically connected to a negative electrode sheet (220) is provided on a third wall (120) of the pair of third walls (120, 130) that faces the negative electrode sheet (220), and at least one of a pair of second walls (112) includes: a base part (112B0); and a protruding section (140) that protrudes from the base section (112B0) in a direction away from the first end surface (271B) of the electrode body (200), and that is provided with an exhaust valve (150) that breaks when the pressure within the case (100) is equal to or greater than a predetermined value.

Description

Technical Field The present technology relates to a square secondary battery. Background Art Japanese Patent Application Laid-Open Nos. 2021-89812, 2019-133854, and 2022-149950 disclose rectangular secondary batteries provided with exhaust valves that rupture when the pressure in the case reaches a predetermined value or more. From the viewpoint of the reliability of the exhaust valve, there is still room for improvement in the rectangular secondary batteries described in Japanese Patent Application Laid-Open Nos. 2021-89812, 2019-133854, and 2022-149950. Summary of the invention The present technology aims to provide a prismatic secondary battery having a highly reliable exhaust valve. The present technology provides the following square secondary batteries.

[0001] A square secondary battery comprises: an electrode body, the electrode body including a positive electrode and a negative electrode; and a shell, the shell accommodating the electrode body, the shell including a pair of first walls facing each other, a pair of second walls facing each other, and a pair of third walls facing each other, the electrode body having a positive electrode sheet electrically connected to the positive electrode on a surface facing one of the pair of third walls, the electrode body having a negative electrode sheet electrically connected to the negative electrode on a surface facing either of the pair of third walls, a positive terminal electrically connected to the positive electrode sheet is provided on the third wall facing the positive electrode sheet in the pair of third walls, a negative terminal electrically connected to the negative electrode sheet is provided on the third wall facing the negative electrode sheet in the pair of third walls, at least one of the pair of second walls comprises: a base; and a protrusion, the protrusion protruding from the base in a direction away from the first end face of the electrode body, an exhaust valve that breaks when the pressure in the shell becomes above a specified value is provided on the protrusion.

[0002] In the rectangular secondary battery described in [1], at least one of the pair of third walls is connected to a portion of the second wall where the protrusion is provided.

[0003] In the square secondary battery described in [2], the electrode body has a second end face on which at least one of the positive electrode sheet and the negative electrode sheet is provided, a first space is formed between the protrusion and the first end face of the electrode body, and a second space is formed between the third wall and the second end face of the electrode body, and the first space and the second space are connected.

[0004] The prismatic secondary battery according to any one of [1] to [3] further comprises an insulating sheet disposed between the protrusion and the first end face of the electrode body, the insulating sheet being disposed closer to the first end face of the electrode body than the inner surface of the protrusion.

[0005] In the square secondary battery described in any one of [1] to [4], the protrusion includes a first protrusion included in one of a pair of second walls, and a second protrusion included in the other of the pair of second walls, and the exhaust valve includes a first exhaust valve arranged on the first protrusion, and a second exhaust valve arranged on the second protrusion. 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 yes Figure 1 A front cross-sectional view of a secondary battery is shown. Figure 6 It is a front view showing a negative electrode original plate before forming a negative electrode plate. Figure 7 yes Figure 6 VII-VII cross-sectional view of the negative electrode original plate shown. Figure 8 It is a front view showing a negative electrode plate formed from a negative electrode original plate. Fig. 9 It is a front view showing a positive electrode original plate before forming a positive electrode plate. Fig.10 yes Fig. 9 XX cross-sectional view of the positive electrode original plate shown. Fig.11 It is a front view showing a positive electrode plate formed from a positive electrode original plate. Fig.12 It is a diagram showing an electrode body and a current collector taken out from a secondary battery. Fig.13 It is a front view of the connection structure between the negative electrode sheet group and the negative electrode collector. Fig.14 It is a cross-sectional view of the connection structure between the negative electrode sheet group and the negative electrode current collector. Fig.15 It is a perspective view showing an electrode body. Fig.16 This is an enlarged view of the vicinity of the upper surface of the wound electrode body. Fig.17 This is an enlarged cross-sectional view showing an example of the shape of the protruding portion. Fig.18 It is an enlarged cross-sectional view showing a modified example of the shape of the protrusion. Fig.19 It is a front cross-sectional view of the secondary battery according to the second embodiment. Fig. 20 This is a diagram for explaining the first space and the second space in the secondary battery according to the first embodiment. Fig.21 This is a diagram for explaining the first space and the second space in the secondary battery according to the second embodiment. Fig. 22 This is a perspective view showing a state where the secondary batteries of the first embodiment are stacked to form a battery pack. Fig.23 This is a diagram showing an example of arrangement of a protrusion and an exhaust valve (Part 1). Fig.24 This is a diagram showing an example of arrangement of the protrusion and the exhaust valve (part 2). Fig.25 This is a diagram (part 3) showing an example of the arrangement of the protrusion and the exhaust valve. Fig.26 This is a diagram (part 4) showing an example of the arrangement of the protrusion and the exhaust valve. Fig. 27 This is a diagram (part 5) showing an example of the arrangement of the protrusion and the exhaust valve. 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 the 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, sodium-ion batteries, and solid electrolyte secondary batteries. In this specification, "electrode" may be collectively referred to as positive electrode and negative electrode. In order to facilitate understanding of the invention, the dimensions of each structure in the drawings may be changed from the actual dimensions. (Implementation Method 1) Figure 1 It is a front view of the secondary battery 1 according to the first embodiment. Figure 2 to Figure 4 It indicates the observation from the direction of arrow II, arrow III and arrow IV respectively. Figure 1 The diagram shows the state of the secondary battery 1. Figure 5 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. In the first embodiment, Figures 1 to 18 In the diagram, the direction along the winding axis of the electrode body possessed by the secondary battery 1 is set as the X direction as the first direction, the short side direction of the electrode body perpendicular to the first direction and observed from the first direction is set as the Y direction as the second direction, and the long side direction of the electrode body perpendicular to the first direction and observed from the first direction is set as the Z direction as the third direction. In addition, in this embodiment, the first direction (X direction) is sometimes referred to as the "width direction" of the secondary battery or the shell body, and the second direction (Y direction) is similarly referred to as the "thickness direction" of the secondary battery or the shell body, and the third direction (Z direction) is similarly referred to as the "height direction" of the secondary battery or the shell body. like Figure 1 to Figure 5As 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 first sealing plate 120 , a second sealing plate 130 , a protrusion 140 , and a gas exhaust valve 150 . The case body 110 is made of a cylindrical, more specifically, square cylindrical member. This allows a square secondary battery 1 to be obtained. The case body 110 is made of metal. Specifically, the case body 110 is made of aluminum, aluminum alloy, iron, iron alloy, or the like. 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 the plate-like members subjected to bending into contact with each other (at Figure 2 The joint portion 115 shown in the example in the figure can be formed into a square tube shape by joining them together (for example, laser welding). The corner of the "square tube shape" can also have an R shape. The joint portion 115 in this embodiment extends along the first direction (X direction) on the outer peripheral surface of the shell body 110. 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 more 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 first side portions 111 (first wall) and a pair of second side portions 112 (second wall). The pair of first side portions 111 constitute a portion of the side of the housing 100. The pair of second side portions 112 constitute an upper surface portion 112A and a bottom surface portion 112B of the housing 100. The pair of first side portions 111 and the pair of second side portions 112 are arranged to intersect each other. The pair of first side portions 111 and the pair of second side portions 112 are connected at their respective ends. The area of ​​each of the pair of first side portions 111 is larger than the area of ​​each of the pair of second side portions 112. 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. 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. The first sealing plate 120 is provided with a negative electrode terminal 301 (first electrode terminal) and a liquid injection hole 121. The positions of the negative electrode terminal 301 and the liquid injection hole 121 can be changed as appropriate. The first sealing plate 120 can be joined to the case body 110 by laser welding, for example. like Figure 4 As shown, a second opening 114 is provided at the end of the second side opposite to the first side in the first direction (X direction) of the housing body 110. The second opening 114 is sealed by a second sealing plate 130. 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. The second sealing plate 130 is provided with a positive electrode terminal 302 (second electrode terminal) and a liquid injection hole 131. The positions of the positive electrode terminal 302 and the liquid injection hole 131 can be changed as appropriate. The second sealing plate 130 can be joined to the case body 110 by laser welding, for example. The first sealing plate 120 and the second sealing plate 130 (third wall) are made of metal. Specifically, the first sealing plate 120 and the second sealing plate 130 are made of aluminum, aluminum alloy, iron, iron alloy, or the like. In one example, the thickness of each of the first sealing plate 120 and the second sealing plate 130 is thicker than the thickness (plate thickness) of the case body 110 . The negative electrode terminal 301 is electrically connected to the negative electrode of the electrode body 200 . The negative electrode terminal 301 is attached to the first sealing plate 120 , that is, the case 100 . The positive electrode terminal 302 is electrically connected to the positive electrode of the electrode body 200 . The positive electrode terminal 302 is attached to the second 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 holes 121 and 131 are 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 can 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 provided on each positive plate can also be stacked to form a positive electrode sheet group, and the negative electrode sheets provided on each negative plate can also be stacked to form a negative electrode sheet group. like Figure 5 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 multiple wound electrode bodies and an electrolyte (electrolyte) not shown are housed together on the inner side of an insulating sheet arranged in the shell 100. The insulating sheet is arranged at a position closer to the lower surface 271B (described later) of the electrode body 200 than the inner surface of the protrusion 140 of the shell 100. The "insulating sheet" mentioned here is formed independently of the diaphragm constituting the electrode body 200. The "opposition" in the present technology also includes, for example, opposition via an "insulating sheet". However, the "insulating sheet" is not a necessary structure in the present technology. As an 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 can also be used instead of the electrolyte. The electrode body 200 includes a main body (a portion where the positive electrode plate and the negative electrode plate are stacked via a separator), a negative electrode sheet group 220 (a first electrode sheet group), and a positive electrode sheet group 250 (a second electrode sheet group). The main body of the electrode body 200 corresponds to the rectangular portion excluding the negative electrode sheet group 220 and the 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 first sealing plate 120 side. The positive electrode sheet group 250 is located at the end of the second side in the first direction (X direction) relative to the main body. The second side in this embodiment is the second sealing plate 130 side. The negative electrode sheet group 220 and the positive 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. The current collector 400 includes a negative electrode current collector 410 (first current collector) and a positive electrode current collector 420 (second current collector). The negative electrode current collector 410 and the positive electrode current collector 420 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 410 is disposed on the first sealing plate 120 via a resin insulating member. The negative electrode current collector 410 is electrically connected to the negative electrode sheet group 220 and the negative electrode terminal 301. The negative electrode current collector 410 is made of a conductive material (more specifically, metal), such as copper or a copper alloy. The positive electrode collector 420 is arranged on the second sealing plate 130 via an insulating member made of resin. The positive electrode collector 420 is electrically connected to the positive electrode sheet group 250 and the positive terminal 302. The positive electrode collector 420 is composed of a conductive material (more specifically, a metal), for example, aluminum or an aluminum alloy. In addition, the positive electrode sheet group 250 can also be electrically connected to the second sealing plate 130 directly or via the positive electrode collector 420. In this case, the second sealing plate 130 can also play the role of the positive terminal 302. The bottom surface 112B of the case body 110 has a base portion 112B0 formed along the electrode body 200 at the center in the X direction, and protrusions 140 protruding away from the electrode body 200 are formed on both sides (both ends in the X direction). The shortest distance (gap) in the Z direction between the inner surface of the base portion 112B0 and a lower surface 271B (described later) of the electrode body 200 is, for example, preferably 5 mm or less, more preferably 3 mm or less, and further preferably 1 mm or less. The protrusion height of the protrusion 140 (the distance in the Z direction between the inner surface of the base 112B0 and the inner surface of the protrusion 140 ) is, for example, preferably about 1 mm or more, and more preferably about 3 mm or more. The protrusion 140 is provided with an exhaust valve 150. The exhaust valve 150 is formed on the bottom surface 112B separated from the winding axis of the wound electrode body 200. The exhaust valve 150 breaks when the pressure in the case 100 becomes equal to or higher than a predetermined value. The exhaust valve 150 can be formed by providing a thin wall portion or a groove portion in the protrusion 140. Figure 6 2 is a front view showing a negative electrode original plate 210S before forming a negative electrode plate 210 (first electrode). Figure 7 yes Figure 6 The VII-VII cross-sectional view of the negative electrode original plate 210S shown in FIG. Figure 8 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 the negative electrode original plate 210S. Figure 6 and Figure 7As 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. 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. 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 to remove the 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. like Figure 8 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 a negative electrode sheet group 220. As a result, the negative electrode sheet group 220 is connected to the negative electrode plate 210 (first electrode). 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 410. In addition, the shape of the negative electrode sheet 230 is not limited to Figure 8 The shape illustrated in . Fig. 9 2 is a front view showing a positive electrode original plate 240S before forming a positive electrode plate 240 (second electrode). Fig.10 yes Fig. 9 The XX-sectional view of the positive electrode original plate 240S shown in FIG. Fig.11 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. 9 and Fig.10 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. 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 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, a positive electrode original plate 240S including the positive electrode core 241, the positive electrode active material layer 242 and the positive electrode protective layer 243 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. like Fig.11 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 a positive electrode sheet group 250. Thus, the positive electrode sheet group 250 is in a state of being 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 positive electrode sheet group 250 is connected to the positive electrode collector 420. In addition, the shape of the positive electrode sheet 260 is not limited to Fig.11 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. Fig.12 FIG. 2 is a diagram showing an electrode body 200 and a current collector 400 taken out of a secondary battery 1. Fig.12 As shown in FIG. 1 , the electrode body 200 is formed by stacking two electrode bodies 201 and 202, each of which is a wound electrode body. Fig.12 In the example shown, a structure in which two wound electrode bodies are stacked is shown, but the electrode body 200 may be composed of one wound electrode body, three or more wound electrode bodies, or a stacked electrode body. The negative electrode sheet group 220 is joined to the negative electrode current collector 410 at a joining portion 434 , and the positive electrode sheet group 250 is joined to the positive electrode current collector 420 at a joining portion 454 . Fig.13 It is a front view of the connection structure between the negative electrode sheet group and the negative electrode collector. Fig.14 It is a cross-sectional view of the connection structure between the negative electrode sheet group and the negative electrode current collector. like Fig.13 and Fig.14 As shown, the negative electrode current collector 410 electrically connects the negative electrode terminal 301 and the negative electrode sheet group 220. The negative electrode current collector 410 in this embodiment is connected to the negative electrode terminal 301 between the electrode body 200 and the first sealing plate 120. The negative electrode current collector 410 includes a first conductive member 430 and a second conductive member 440. The first conductive member 430 and the second conductive member 440 are joined at a joining portion 433. The first conductive member 430 and the second conductive member 440 are joined by, for example, laser welding. The first conductive member 430 is bonded to the negative electrode sheet group 220 at a bonding portion 434. The bonding portion 434 can be formed, for example, by ultrasonic welding, resistance welding, laser welding, riveting, etc. In this embodiment, the first conductive member 430 and the negative electrode sheet group 220 are bonded, for example, by ultrasonic bonding. The second conductive member 440 is connected to the negative terminal 301 at a joint portion 441. The joint portion 441 can be formed, for example, by ultrasonic welding, resistance welding, laser welding, riveting, etc. In the present embodiment, the negative terminal 301 and the second conductive member 440 are joined, for example, by providing a through hole in the second conductive member 440, inserting the negative terminal 301 into the through hole, riveting the negative terminal 301 to the second conductive member 440, and then welding the riveted portion and the second conductive member 440. The first conductive member 430 includes a first planar portion 431 and a second planar portion 432. The first planar portion 431 is connected to the second conductive member 440. The second planar portion 432 is connected to the negative electrode sheet group 220. The second planar portion 432 is disposed along the first sealing plate 120. A step portion 435 is provided between the first plane portion 431 and the second plane portion 432. With respect to the step portion 435, the first plane portion 431 and the second plane portion 432 are positioned differently in the first direction (X direction) when the secondary battery 1 is assembled. Thus, the first plane portion 431 and the second plane portion 432 can be arranged in one direction. The step portion 435 extends along the third direction (Z direction). A first insulating member 510 (resin member) is disposed between the negative electrode terminal 301 and the first sealing plate 120. A second insulating member 520 (resin member) is disposed between the first sealing plate 120 and the first conductive member 430 and the second conductive member 440. In addition, the first insulating member 510 and the second insulating member 520 may be an integral member. The negative electrode terminal 301 is attached to the first sealing plate 120 via the first insulating member 510 . The negative electrode terminal 301 is exposed outside the first sealing plate 120 and reaches the second conductive member 440 of the negative electrode collector 410 provided on the inner surface of the first sealing plate 120 . As the assembly order of each component, first, the negative electrode terminal 301 and the second conductive component 440 are mounted on the first sealing plate 120 together with the first insulating component 510 and the second insulating component 520. Next, the first conductive component 430 electrically connected to the electrode body 200 is mounted on the second conductive component 440. At this time, the first conductive component 430 is arranged on the first insulating component 510 in such a manner that a part of the first conductive component 430 overlaps with the second conductive component 440. Next, the first conductive component 430 and the second conductive component 440 are welded and connected at the joint 434. The negative electrode terminal 301 may be electrically connected to the first sealing plate 120 . In addition, the first sealing plate 120 may also play the role of the negative electrode terminal 301 . In addition, Fig.13 and Fig.14 In FIG. 4 , the negative electrode current collector 410 is exemplified as being composed of two members (the first conductive member 430 and the second conductive member 440 ), but the negative electrode current collector 410 may be composed of a single member. exist Fig.13 and Fig.14 , the connection structure on the negative electrode side is shown, but the basic connection structure on the positive electrode side is also the same as that on the negative electrode side. Fig.15 2 is a perspective view showing the electrode body 200. Fig.15 As shown, the main body of the electrode body 200 has an upper surface 271A and a lower surface 271B (first end surface), short side surfaces 272A, 272B (second end surface), and long side surfaces 273A, 273B (third end surface). The upper surface 271A and the lower surface 271B are respectively opposite to the first side surface 111 of the shell body 110. The short side surfaces 272A, 272B are respectively opposite to the first sealing plate 120 and the second sealing plate 130. The long side surfaces 273A, 273B are respectively opposite to the second side surface 112 of the shell body 110. Fig.16 2 is an enlarged view of the vicinity of the upper surface 271A of the electrode body 200. Fig.16 As shown, when wound electrode bodies 201 and 202 are stacked to form electrode body 200 , curved surfaces 201A and 202A of the electrode bodies 201 and 202 are combined to form upper surface 271A of electrode body 200 . according to Fig.16 The shape of the upper surface 271A shown can make the cavity between the curved surfaces 201A and 202A serve as a passage for the gas in the housing 100 . In addition, the shape of the lower surface 271B is not shown in the figure, but can be Fig.16 The upper surface 271A shown has the same shape. Fig.17 It is an enlarged cross-sectional view showing the shape of the protrusion 140 . Fig.18 It is an enlarged cross-sectional view showing a modified example of the shape of the protrusion 140 . exist Fig.17 In the example shown, the first sealing plate 120 (third wall) is connected to a portion of the bottom surface portion 112B (second wall) of the housing body 110 where the protrusion 140 is provided. Fig.18 In the illustrated example, the first sealing plate 120 (third wall) and a portion of the bottom surface portion 112B (second wall) of the case body 110 where the protrusion 140 is provided are separated in the X direction. exist Fig.17 , Fig.18 In any of the examples, the space (first space) formed between the protrusion 140 and the lower surface 271B (first end face) of the electrode body 200 is connected to the space (second space) formed between the first sealing plate 120 and the short side surface 272A (second end face) of the electrode body 200. In this way, it is possible to stably ensure the exhaust path to the exhaust valve 150 in the housing 100. Specifically, the gas exhausted from the short side surface 272A of the wound electrode body 200 to the outside of the electrode body 200 can be guided to the space formed inside the protrusion 140, and exhausted to the outside of the housing 100 through the exhaust valve 150 formed in the protrusion 140. However, in the present technology, the above two spaces (the first space and the second space) are not necessarily directly connected. (Implementation Method 2) Fig.19 2 is a front cross-sectional view of a secondary battery 10 according to Embodiment 2. Fig.19 As shown, the secondary battery 10 includes a case 1000 , an electrode body 2000 , an electrode terminal 3000 , and a current collector 4000 . The housing 1000 includes a housing body having a bottom including a side surface portion 1100 and a bottom surface portion 1300 , a sealing plate 1200 , a protruding portion 1400 , and an exhaust valve 1500 . The electrode body 2000 has a pair of side surfaces 2710 (first end surfaces) and an upper surface 2720 (second end surface). The negative electrode sheet group 2200 and the positive electrode sheet group 2500 are provided on the upper surface 2720. The electrode body 2000 is wound along Fig.19 The electrode body 2000 is a wound electrode body in which the positive electrode plate and the negative electrode plate are wound about a winding axis extending in the vertical direction. However, the electrode body 2000 may be a stacked electrode body. The negative electrode sheet group 2200 is electrically connected to the negative electrode terminal 3010 via the negative electrode current collector 4100 . The positive electrode sheet group 2500 is electrically connected to the positive electrode terminal 3020 via the positive electrode current collector 4200 . The side surface 2710 of the electrode body 2000 includes side surfaces 2710A and 2710B formed on the left and right sides of the figure, respectively. The protrusion 1400 includes: a protrusion 1400 on the left side (first protrusion), which is provided at a position opposite to the side surface 2710A of the electrode body 2000; and a protrusion 1400 on the right side (second protrusion), which is provided at a position opposite to the side surface 2710B of the electrode body 2000. The exhaust valve 1500 includes an exhaust valve 1500 (first exhaust valve) provided on the left side of the protrusion 1400 on the left side, and an exhaust valve 1500 (second exhaust valve) provided on the right side of the protrusion 1400 on the right side. That is, in the present embodiment, a pair of exhaust valves 1500 are both formed on the side surface portion 1100 separated from the winding axis of the wound electrode body 2000. However, the protrusion 1400 and the exhaust valve 1500 are not limited to being formed on both the left and right sides, and the protrusion 1400 and the exhaust valve 1500 may be provided only on one side of the side surface 1100 . As other matters are the same as those in Implementation 1, detailed descriptions will not be repeated. (1st space and 2nd space) Fig. 20 , Fig.21 These are diagrams for explaining the space inside the case of the secondary batteries 1 and 10 according to the first and second embodiments, respectively. Fig. 20 , Fig.21 The dotted line in is an imaginary straight line obtained by stretching the inner surface of the base along its extending direction. exist Fig. 20 In the example (Embodiment 1), the first space 11 is formed between the protrusion 140 and the electrode body 200 , and the second space 12 is formed between the first sealing plate 120 (third wall) and the electrode body 200 . exist Fig.21 In the example (Embodiment 2), the first space 11 is formed between the protrusion 1400 and the electrode body 200 , and the second space 12 is formed between the sealing plate 1200 (third wall) and the electrode body 200 . exist Fig. 20 In the example of , the width of the second space 12, that is, the distance between the short side 272A of the electrode body 200 and the first sealing plate 120 is preferably 5 mm or more, and more preferably 8 mm or more. Fig.21 In the example, the width of the second space 12, that is, the distance between the upper surface 2720 of the electrode body 2000 and the sealing plate 1200 is also preferably about 5 mm or more, and more preferably about 8 mm or more. exist Fig. 20 , Fig.21 In the example of FIG. 1 , the length L of the protrusions 140 and 1400 is 140 , L 1400 Each is, for example, about 1 / 10 or more of the total length of the housings 100 and 1000 in the same direction. In addition, Fig. 20 , Fig.21 In the example, the volume of the first space 11 is preferably 120 mm 3 More than 200 mm (more preferably 200 mm 3 More preferably, 300 mm 3 More preferably, 400 mm 3 The volume of the first space 11 is preferably 1100 mm or more, and the ratio (volume percentage) of the volume of the first space 11 to the internal volume of the housing 100, 100 is preferably 0.05% or more. In addition, the volume of the second space 12 is preferably 1100 mm or more. 3 The ratio (volume percentage) of the volume of the second space 12 to the internal volume of the housing 100 , 1000 is preferably about 1.5 percent or more. The internal volumes of the cases 100 , 100 and the volumes of the first space 11 and the second space 12 mentioned here are values ​​calculated by including the portions occupied by the electrode bodies 200 , 2000 or other components as the volumes of the spaces. According to Fig. 20 , Fig.21 The first space 11 and the second space 12 illustrated in the figure can reliably connect the first space 11 formed inside the protrusions 140, 1400 with the second space 12 adjacent to the short side surface 272A or the upper surface 2720 of the electrode body 200, thereby reliably ensuring an exhaust path in the shell that guides the gas ejected from the electrode body 200 to the exhaust valve 150. (Battery Pack Structure) Fig. 22 It is a perspective view showing a state where the secondary batteries 1 according to the first embodiment are stacked to form a battery pack. like Fig. 22 As shown, when forming a battery pack including secondary batteries 1, multiple secondary batteries 1 are stacked in their thickness direction. End plates 2 are provided at both ends of the stacked secondary batteries 1. The battery pack can be formed by constraining the stack of secondary batteries 1 and end plates 2 in the stacking direction (Y direction) using a restraining member 3. Both ends of the restraining member 3 are fixed to the end plates 2 by fastening members 4. Multiple secondary batteries 1 are electrically connected by bus bars 5. Fig. 22 In the figure, the secondary batteries 1 in the center portion in the Y direction are omitted, but the number of stacked secondary batteries 1 can be changed appropriately. The duct through which the gas exhausted from the exhaust valve 150 and the like flows in the Y direction can be provided at a position avoiding the restraining member 3 . In addition, the structure of the battery pack is not limited to Fig. 22 In the structure illustrated in FIG. 1 , for example, the battery pack may be directly supported on the side surface of the battery pack case without using the end plate 2 , the restraining member 3 , and the fastening member 4 . (Arrangement of the protrusion 140 and the exhaust valve 150) Figure 23 to Figure 27 1 is a diagram showing an example of the arrangement of the protrusion 140 and the exhaust valve 150 in the secondary battery 1 according to the first embodiment. like Figure 23 to Figure 26 As shown in the example, on the bottom surface 112B of the housing body 110, a pair of protrusions 140 and the exhaust valve 150 can also be set to be symmetrical on the left and right, such as Fig. 27 As shown in the example of FIG. 1 , one protrusion 140 extending along the longitudinal direction of the bottom surface portion 112B may be provided, and one exhaust valve 150 may be provided at the center thereof. exist Figure 23 to Figure 27In any of the examples, the first space 11 formed inside the protrusion 140 can be connected to the second space 12 formed on both sides of the electrode body 200 to reliably ensure that the gas discharged from the short side 272A of the electrode body 200 reaches the exhaust path of the exhaust valve 150. The arrangement of the protrusion 140 and the exhaust valve 150 is not limited to Figure 23 to Figure 27 In the arrangement illustrated in FIG. 1 , for example, a plurality of exhaust valves 150 may be arranged on one protrusion 140. In addition, the shapes and sizes of the protrusion 140 and the exhaust valve 150 may be changed as appropriate. (Function and Effect) According to the secondary battery 1, 10, by providing the exhaust valve 150, 1500 on the protrusion 140, 1400 protruding in the direction away from the electrode body 200, 2000, it is possible to stably ensure that the high-temperature gas generated in the housing 100, 1000 reaches the exhaust valve. Therefore, when the internal pressure of the housing 100, 1000 rises and the gas needs to be exhausted, the exhaust valve 150, 1500 can be operated stably to suppress the cracking of the undesired part. In this way, according to the secondary battery 1, 10, the reliability of the exhaust valve 150, 1500 can be improved. 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 square secondary battery, characterized in that: have: an electrode body comprising a positive electrode and a negative electrode; and a shell that accommodates the electrode body, The housing includes a pair of first walls facing each other, a pair of second walls facing each other, and a pair of third walls facing each other. The electrode body has a positive electrode sheet electrically connected to the positive electrode on a surface facing one of the pair of third walls. The electrode body has a negative electrode sheet electrically connected to the negative electrode on a surface facing one of the pair of third walls. The third wall of the pair of third walls, which is opposite to the positive electrode sheet, is provided with a positive terminal electrically connected to the positive electrode sheet. The third wall of the pair of third walls that is opposite to the negative electrode sheet is provided with a negative electrode terminal that is electrically connected to the negative electrode sheet. At least one of the pair of second walls comprises: base; as well as a protrusion that protrudes from the base in a direction away from the first end surface of the electrode body, The protruding portion is provided with an exhaust valve that breaks when the pressure in the housing becomes equal to or higher than a predetermined value.

2. The square secondary battery according to claim 1, characterized in that: At least one of the pair of third walls is connected to a portion of the second wall where the protrusion is provided.

3. The square secondary battery according to claim 2, characterized in that: The electrode body has a second end surface on which at least one of the positive electrode sheet and the negative electrode sheet is provided. A first space is formed between the protruding portion and the first end surface of the electrode body. A second space is formed between the third wall and the second end surface of the electrode body. The first space is communicated with the second space.

4. The square secondary battery according to any one of claims 1 to 3, characterized in that: further comprising an insulating sheet disposed between the protruding portion and the first end surface of the electrode body, The insulating sheet is arranged at a position closer to the first end surface of the electrode body than the inner surface of the protrusion.

5. The square secondary battery according to any one of claims 1 to 3, characterized in that: The protrusion includes a first protrusion included in one of the pair of second walls and a second protrusion included in the other of the pair of second walls. The exhaust valve includes a first exhaust valve provided at the first protrusion, and a second exhaust valve provided at the second protrusion.

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