secondary batteries

Abstract

To provide a secondary battery having high capacity and high reliability.SOLUTION: A secondary battery includes: an electrode assembly including a first electrode and a second electrode having a polarity different from a polarity of the first electrode; and a case accommodating the electrode assembly. The case includes: a case body having a first opening at one end portion thereof in a first direction and a second opening at the other end portion thereof in the first direction; a first sealing plate sealing the first opening; and a second sealing plate sealing the second opening. The case body is provided with a joining portion extending from the first opening to the second opening, the joining portion having a shape of line. The joining portion has at least one bent portion at a position separated from the first opening and the second opening, and when pressure in the case becomes equal to or more than a predetermined value, the joining portion is fractured to discharge gas in the case to outside of the case.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present technology relates to a secondary battery. [Background technology]

[0002] Conventionally, a groove or a thin portion is formed in the wall surface of the case of a secondary battery to serve as a safety valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-148184 [Patent Document 2] Patent No. 5821605 Summary of the Invention [Problem to be solved by the invention]

[0004] As battery capacity increases, secondary batteries are also becoming larger. From the perspective of reliability in large secondary batteries, there is room for further improvement in conventional secondary batteries. The objective of this technology is to provide a high-capacity, highly reliable secondary battery. [Means for solving the problem]

[0005] The present technology provides the following secondary battery.

[0006] [1] A secondary battery comprising: an electrode assembly including a first electrode and a second electrode having a polarity opposite to that of the first electrode; and a case accommodating the electrode assembly, wherein the case includes a case 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 that seals the first opening, and a second sealing plate that seals the second opening, wherein the case body is 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 spaced apart from the first opening and the second opening, and wherein when the pressure inside the case reaches or exceeds a predetermined value, the joint breaks and gas inside the case is discharged to the outside of the case.

[0007] [2] The secondary battery described in [1], wherein the case body includes a pair of first wall portions facing each other in a second direction perpendicular to the first direction, and the bending portion is provided in the first wall portions.

[0008] [3] The secondary battery described in [2], wherein the joint portion includes a first region and a second region located on the opposite side of the first region with respect to the bent portion, the first region and the second region extending in the first direction, the first wall portion having a first center line extending in the first direction and passing through a center of the first wall portion in a third direction perpendicular to the first direction and the second direction, and the first region is located closer to the first center line of the first wall portion than the second region.

[0009] [4] The secondary battery described in [3], wherein the joint portion includes a plurality of the second regions and the first region formed between the plurality of the second regions in the first direction.

[0010] [5] The secondary battery described in [3], wherein the joint portion includes a plurality of the first regions and the second regions formed between the plurality of the first regions in the first direction.

[0011] [6] The secondary battery described in [2], wherein 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 in a third direction perpendicular to the first direction and the second direction, and the joint portion is formed substantially symmetrically with respect to the second center line.

[0012] [7] The case body is oriented in a third direction perpendicular to the first direction and the second direction. Opposing The secondary battery according to [2], further comprising a pair of second wall portions, wherein the area of ​​the first wall portions is smaller than the area of ​​the second wall portions.

[0013] [8] A secondary battery described in any one of [1] to [7], wherein the case body is composed 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.

[0014] [9] The secondary battery according to any one of [1] to [8], wherein the case has a substantially rectangular parallelepiped shape. [Effects of the Invention]

[0015] According to this technology, by forming a bend in the linear joint extending from the first opening to the second opening in the case body, it becomes easier to limit the location of the rupture that will occur when the pressure inside the case exceeds a predetermined value, thereby improving the reliability of the battery. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a front view showing the configuration of a secondary battery according to Embodiment 1. FIG. [Figure 2] 2 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow II. [Figure 3] 3 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow III. [Figure 4] 4 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow IV. FIG. [Figure 5]2 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow V. FIG. [Figure 6] FIG. 2 is a front cross-sectional view of the secondary battery shown in FIG. [Figure 7] FIG. 2 is a front view showing a negative electrode blank before being formed into a negative electrode plate. [Figure 8] 8 is a cross-sectional view taken along the line VIII-VIII of the negative electrode plate shown in FIG. 7. [Figure 9] FIG. 2 is a front view showing a negative electrode plate formed from a negative electrode original plate. [Figure 10] FIG. 2 is a front view showing a positive electrode plate before it is formed into a positive electrode plate. [Figure 11] 11 is a cross-sectional view of the positive electrode plate taken along the line XI-XI in FIG. 10. [Figure 12] FIG. 2 is a front view showing a positive electrode plate formed from a positive electrode original plate. [Figure 13] FIG. 10 is a diagram (part 1) showing a modified example of the bent portion of the joint. [Figure 14] FIG. 2 is a diagram (part 2) showing a modified example of the bent portion of the joint. [Figure 15] FIG. 10 is a diagram (part 3) showing a modified example of the bent portion of the joint. [Figure 16] FIG. 4 is a diagram showing a modified example of the bent portion of the joint portion. [Figure 17] FIG. 5 is a diagram showing a modified example of the bent portion of the joint. [Figure 18] FIG. 6 is a diagram showing a modified example of the bent portion of the joint. [Figure 19] FIG. 7 is a diagram showing a modified example of the bent portion of the joint. [Figure 20] FIG. 10 is a diagram (part 1) showing a modified example of the shape of the joint portion. [Figure 21] FIG. 10 is a diagram (part 2) showing a modified example of the shape of the joint portion. [Figure 22] FIG. 10 is a diagram (part 3) showing a modified example of the shape of the joint portion. [Figure 23] 23 is a diagram showing the secondary battery shown in FIG. 22 as viewed from the direction of arrows XXIII-XXIII. FIG. [Figure 24]FIG. 2 is a schematic diagram showing an example of the arrangement of a gas release valve (weak portion). [Figure 25] FIG. 1 is a diagram (part 1) showing an example of a cross section of a joint. [Figure 26] FIG. 2 is a diagram (part 2) showing an example of a cross section of a joint. [Figure 27] FIG. 3 is a diagram (part 3) showing an example of a cross section of a joint. [Figure 28] FIG. 4 is a diagram showing an example of a cross section of a joint (part 4). [Figure 29] FIG. 5 is a diagram showing an example of a cross section of a joint. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof may not be repeated.

[0018] In the embodiments described below, when numbers, amounts, etc. are mentioned, the scope of the present technology is not necessarily limited to those numbers, amounts, etc., unless otherwise specified. Furthermore, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. Furthermore, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiments.

[0019] In this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a certain feature is included, other features may or may not be included.

[0020] Furthermore, when geometric terms and terms expressing positional and directional relationships are used in this specification, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along," these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in a single state, and the relative positional relationships can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0021] In this specification, the term "secondary battery" is not limited to lithium ion batteries, but may include other secondary batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0022] Furthermore, the "secondary battery" in the present technology is not limited to a prismatic battery, but may also be, for example, a cylindrical battery.

[0023] In the drawings, the direction along the winding axis of the electrode body provided in the secondary battery is the X direction, the shorter side direction of the electrode body as viewed from the X direction is the Y direction, and the longer side direction of the electrode body as viewed from the X direction is the Z direction. Also, to make the invention easier to understand, the dimensions of each component in the drawings may be shown differently from the actual dimensions.

[0024] In this specification, the first direction (X direction) may be referred to as the "width direction" of the secondary battery or the case body, the second direction (Z direction) may be referred to as the "height direction" of the secondary battery or the case body, and the third direction (Y direction) may be referred to as the "thickness direction" of the secondary battery or the case body.

[0025] (Overall battery configuration) Fig. 1 is a front view of a secondary battery 1 according to the present embodiment. Figs. 2 to 5 are views of the secondary battery 1 shown in Fig. 1 as viewed from the directions of arrows II, III, IV, and V, respectively. Fig. 6 is a front cross-sectional view of the secondary battery 1 shown in Fig. 1.

[0026] The secondary battery 1 can be mounted in an electric vehicle (BEV: Battery Electric Vehicle), a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle), a hybrid electric vehicle (HEV: Hybrid Electric Vehicle), etc. However, the use of the secondary battery 1 is not limited to being mounted in a vehicle.

[0027] 1 to 6, the secondary battery 1 includes a case 100, an electrode assembly 200, an electrode terminal 300, and a current collector 400. The case 100 includes a case body 110, a sealing plate 120, and a sealing plate 130. The case 100 has a substantially rectangular parallelepiped shape.

[0028] When configuring a battery pack including secondary batteries 1, multiple 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 on the side surface of a battery pack case without using a constraining member.

[0029] The case body 110 is made of a cylindrical, preferably rectangular, member. This results in a rectangular secondary battery 1. The case body 110 is made of metal. Specifically, the case body 110 is made of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0030] As shown in Figures 1 and 2, sealing plates 120 and 130 are provided at both ends of the case body. Case body 110 can be formed into a rectangular tube shape, for example, by abutting the edges of bent plate-like members (joint 115 shown in Figure 2) and joining them together (for example, by laser welding). The corners of the "rectangular tube" may be rounded.

[0031] In this embodiment, the case body 110 is formed so that it is longer in the width direction (X direction) of the secondary battery 1 than in the thickness direction (Y direction) and height direction (Z direction) of the secondary battery 1. The dimension (width) of the case body 110 in the X direction is preferably about 15 cm or more, and more preferably about 30 cm or more. This allows for the construction of a relatively large (high-capacity) secondary battery 1. The dimension (height) of the case body 110 in the Z direction is preferably about 20 cm or less, more preferably about 15 cm or less, and even more preferably about 10 cm or less. This allows for the construction of a relatively low-height secondary battery 1, which improves, for example, the mountability in a vehicle.

[0032] The case main body 110 includes a pair of side surface portions 111 (second wall portions) and a pair of side surface portions 112 (first wall portions). The pair of side surface portions 111 constitute part of the side surfaces of the case 100. The pair of side surface portions 112 constitute the bottom surface portion and the top surface portion of the case 100. The pair of side surface portions 111 and the pair of side surface portions 112 are arranged so as to intersect with each other. The pair of side surface portions 111 and the pair of side surface portions 112 are adjacent to each other. It is desirable that each of the pair of side surface portions 111 has a larger area than each of the pair of side surface portions 112.

[0033] 2 and 5, the side surface portion 112 includes a pair of side surface portions 112A and 112B. Each of the side surface portions 112A and 112B has a substantially rectangular shape with the X direction as the longitudinal direction and the Y direction as the lateral direction.

[0034] 2, a joint 115 is formed on one side surface portion 112B of the pair of side surface portions 112. The joint 115 can be formed by melting and then solidifying a base material by irradiation with high-energy rays such as laser light.

[0035] The joint 115 is formed linearly on the side surface 112B across the entire width (X direction) of the secondary battery 1, that is, from one end to the other end. At the joint 115, the edges (ends) of the plate-like members that make up the case body 110 are joined together.

[0036] 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 in the X direction. The third region 1153 connects the first region 1151 and the second region 1152. The third region 1153 extends in the Y direction. A bent portion 115A (bent portion) is formed between the first region 1151 and the third region 1153, and between the second region 1152 and the third region 1153.

[0037] The first region 1151 of the joint 115 is located on the center line L (first center line) of the side surface portion 112B. The center line L passes through the center of the side surface portion 112B in the Y direction and extends in the X direction. The second region 1152 passes through a position shifted from the center line L in the Y direction.

[0038] In the secondary battery 1 according to this embodiment, the joint 115 has the function of a gas exhaust valve (safety valve) that breaks when the pressure inside the case 100 exceeds a predetermined value, thereby discharging the gas inside the case 100 to the outside of the case 100.

[0039] Since first region 1151 of joint 115 is located on center line L, it is more likely to be displaced and stress increased when the pressure in case 100 increases. Therefore, when joint 115 is made to function as a gas release valve (safety valve), first region 1151 can be preferentially ruptured.

[0040] In this way, by providing joint 115 with the function of a gas release valve and providing bent portion 115A, the position at which joint 115 (gas release valve) breaks can be identified, thereby suppressing damage to the battery pack when gas is released. Therefore, it is possible to manufacture a highly reliable secondary battery 1 while suppressing increases in manufacturing costs.

[0041] Note that "preferentially cleaving the first region 1151" is not limited to "cleaving only the first region 1151," but includes, for example, first "cleaving the first region 1151" and then "cleaving the second region 1152."

[0042] 3, an opening 113 (second opening) is provided at an end of a first side in a first direction (X direction) of case body 110. Opening 113 is sealed by sealing plate 120. A joint 115 is formed in opening 113 to seal opening 113. Opening 113 and sealing plate 120 have a substantially rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction. Note that the rectangular shape includes a rectangular shape or a substantially rectangular shape such as a rectangular shape with rounded corners.

[0043] A negative electrode terminal 301 is provided on the sealing plate 120 (second sealing plate). The position of the negative electrode terminal 301 can be changed as appropriate.

[0044] 4, an opening 114 (first opening) is provided at an end of a second side opposite the first side in a first direction (X direction) of case body 110. That is, opening 114 is located at an end opposite opening 113, and openings 113 and 114 face each other. Opening 114 is sealed by sealing plate 130. A joint 115 is formed in opening 114 to seal opening 114. Opening 114 and sealing plate 130 have a substantially rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction.

[0045] A positive electrode terminal 302 and a liquid injection hole 134 are provided on the sealing plate 130 (first sealing plate). The positions of the positive electrode terminal 302 and the liquid injection hole 134 can be changed as appropriate.

[0046] The sealing plates 120 and 130 are made of metal. Specifically, the sealing plates 120 and 130 are made of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0047] The negative electrode terminal 301 (second 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.

[0048] The positive electrode terminal 302 is electrically connected to the positive electrode of the electrode assembly 200. The positive electrode terminal 302 is attached to the sealing plate 130, i.e., the case 100.

[0049] The negative electrode terminal 301 (first electrode terminal) is made of a conductive material (more specifically, a metal), and may be made of, for example, copper or a copper alloy. The outer surface of the negative electrode terminal 301 may be provided with a portion or layer made of aluminum or an aluminum alloy.

[0050] The positive terminal 302 is made of a conductive material (more specifically, a metal), and may be made of, for example, aluminum or an aluminum alloy.

[0051] The liquid inlet hole 134 is sealed with a sealing member (not shown), which may be, for example, a blind rivet or other metal member.

[0052] The electrode assembly 200 is a flat-shaped electrode assembly having positive and negative electrode plates, as described below. Specifically, the electrode assembly 200 is a wound-type electrode assembly in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound together via a strip-shaped separator (not shown). However, in this specification, the term "electrode assembly" is not limited to a wound-type electrode assembly and may also be a stacked-type electrode assembly in which multiple positive electrode plates and multiple negative electrode plates are alternately stacked. The strip-shaped separator may be formed, for example, of a polyolefin microporous membrane. The electrode assembly may include multiple positive electrode plates and multiple negative electrode plates, and the positive electrode tabs provided on each positive electrode plate may be stacked to form a positive electrode tab group, or the negative electrode tabs provided on each negative electrode plate may be stacked to form a negative electrode tab group. The electrode assembly 200 may include multiple wound-type electrode bodies or multiple stacked-type electrode bodies.

[0053] 6, case 100 houses electrode assembly 200. Electrode assembly 200 is housed in case 100 so that its winding axis is parallel to the X direction.

[0054] Specifically, one or more wound electrode bodies are housed together with an electrolytic solution (electrolyte), not shown, inside an insulating sheet (described below) placed inside the case 100. The electrolytic solution (nonaqueous electrolytic solution) can be, for example, a nonaqueous solvent made by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio (25°C) of 30:30:40, in which LiPF6 is dissolved at a concentration of 1.2 mol / L. Note that a solid electrolyte may be used instead of the electrolytic solution.

[0055] The electrode assembly 200 includes a main body portion (a portion in which positive electrode plates and negative electrode plates are stacked with a separator interposed therebetween), a negative electrode tab group 220, and a positive electrode tab group 250.

[0056] The main body is composed of a negative electrode plate 210 and a positive electrode plate 240, which will be described later. The negative electrode tab group 220 is located at the end of a first side of the electrode assembly 200 in a first direction (X direction) relative to the main body. In this embodiment, the first side is the sealing plate 120 side. The positive electrode tab group 250 is located at the end of a second side of the electrode assembly 200 in the first direction (X direction) relative to the main body. In this embodiment, the second side is the sealing plate 130 side.

[0057] The negative electrode tab group 220 and the positive electrode tab group 250 are formed so as to protrude from the center portion of the electrode body 200 toward the sealing plate 120 or the sealing plate 130, respectively.

[0058] The current collectors 400 include a negative electrode current collector 400A and a positive electrode current collector 400B. The negative electrode current collector 400A and the positive electrode current collector 400B are each made of a plate-shaped member. The electrode assembly 200 is electrically connected to a negative electrode terminal 301 and a positive electrode terminal 302 via the current collectors 400.

[0059] The negative electrode current collector 400A is disposed on the sealing plate 120 via a resin insulating member. The negative electrode current collector 400A is electrically connected to the negative electrode tab group 220 and the negative electrode terminal 301. The negative electrode current collector 400A is made of a conductive material (more specifically, a metal), and may be made of, for example, copper or a copper alloy. Details of the negative electrode current collector 400A will be described later.

[0060] The positive electrode current collector 400B is disposed on the sealing plate 130 via a resin insulating member. The positive electrode current collector 400B is electrically connected to the positive electrode tab group 250 and the positive electrode terminal 302. The positive electrode current collector 400B is made of a conductive material (more specifically, a metal), and may be made of aluminum or an aluminum alloy, for example. The positive electrode tab group 250 may be electrically connected to the sealing plate 130 directly or via the positive electrode current collector 400B. In this case, the sealing plate 130 may serve as the positive electrode terminal 302. The positive electrode current collector 400B will be described in detail later.

[0061] (Configuration of electrode body 200) FIG. 7 is a front view showing the negative electrode plate 210S before the negative electrode plate 210 is formed, FIG. 8 is a cross-sectional view taken along line VIII-VIII of the negative electrode plate 210S shown in FIG. 7, and FIG. 9 is a front view showing the negative electrode plate 210 formed from the negative electrode plate 210S.

[0062] The negative electrode plate 210 is manufactured by processing a negative electrode original plate 210S. As shown in Figures 7 and 8, the negative electrode original plate 210S includes a negative electrode core 211 (second electrode core) and a negative electrode active material layer 212. The negative electrode core 211 is a copper foil or a copper alloy foil.

[0063] A negative electrode active material layer 212 is formed on both surfaces of the negative electrode substrate 211 except for one end portion. The negative electrode active material layer 212 is formed by applying a negative electrode active material layer slurry using a die coater.

[0064] The negative electrode active material layer slurry is prepared by kneading graphite as the negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders, and water as a dispersion medium so that the mass ratio of graphite:SBR:CMC is approximately 98:1:1.

[0065] The negative electrode substrate 211 coated with the negative electrode active material layer slurry is dried to remove water contained in the negative electrode active material layer slurry, thereby forming the negative electrode active material layer 212. The negative electrode active material layer 212 is then compressed to form a negative electrode base plate 210S including the negative electrode substrate 211 and the negative electrode active material layer 212. The negative electrode base plate 210S is cut into a predetermined shape to form the negative electrode plate 210. The negative electrode base plate 210S can be cut by laser processing using energy beam irradiation, mold processing, cutter processing, or the like.

[0066] As shown in FIG. 9 , a plurality of negative electrode tabs 230 (second electrode tabs) made of negative electrode cores 211 are provided at one end in the width direction of a negative electrode plate 210 formed from a negative electrode original plate 210S. When the negative electrode plate 210 is wound, the plurality of negative electrode tabs 230 are stacked to form a negative electrode tab group 220. As a result, the negative electrode tab group 220 is connected to the negative electrode plate 210. The position and length in the protruding direction of each of the plurality of negative electrode tabs 230 are appropriately adjusted taking into account the state in which the negative electrode tab group 220 is connected to the negative electrode current collector 400A. Note that the shape of the negative electrode tab 230 is not limited to the example shown in FIG. 8 .

[0067] FIG. 10 is a front view showing a positive electrode plate 240S before the positive electrode plate 240 is formed, FIG. 11 is a cross-sectional view taken along line XI-XI of the positive electrode plate 240S shown in FIG. 10, and FIG. 12 is a front view showing a positive electrode plate 240 formed from the positive electrode plate 240S.

[0068] The positive electrode plate 240, which is the second electrode, has a polarity different from that of the negative electrode plate 210, which is the first electrode. The positive electrode plate 240 is manufactured by processing a positive electrode base plate 240S. As shown in FIGS. 10 and 11, the positive electrode base plate 240S includes a positive electrode core 241 (first 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.

[0069] A positive electrode active material layer 242 is formed on both surfaces of the positive electrode core 241 except for one end portion. The positive electrode active material layer 242 is formed on the positive electrode core 241 by applying a positive electrode active material layer slurry using a die coater.

[0070] The positive electrode active material layer slurry is prepared by kneading lithium nickel cobalt manganese composite oxide as the positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, a carbon material as a conductive material, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium so that the mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material is approximately 97.5:1:1.5.

[0071] The positive electrode protective layer 243 is in contact with the positive electrode core 241 and is formed on one end of the positive electrode active material layer 242 in the width direction. The positive electrode protective layer 243 is formed on the positive electrode core 241 by applying a positive electrode protective layer slurry using a die coater. The positive electrode protective layer 243 has a larger electrical resistance than the positive electrode active material layer 242.

[0072] The positive electrode protective layer slurry is prepared by kneading alumina powder, a carbon material as a conductive material, PVdF as a binder, and NMP as a dispersion medium so that the mass ratio of alumina powder:carbon material:PVdF is approximately 83:3:14.

[0073] The positive electrode substrate 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, thereby forming the positive electrode active material layer 242 and the positive electrode protective layer 243. The positive electrode active material layer 242 is then compressed to form a positive electrode base plate 240S including the positive electrode substrate 241, the positive electrode active material layer 242, and the positive electrode protective layer 243. The positive electrode base plate 240S is cut into a predetermined shape to form the positive electrode plate 240. The positive electrode base plate 240S can be cut by laser processing using energy beam irradiation, mold processing, cutter processing, or the like.

[0074] As shown in FIG. 12, a plurality of positive electrode tabs 260 (first electrode tabs) made of positive electrode cores 241 are provided at one end in the width direction of a positive electrode plate 240 formed from a positive electrode original plate 240S. When the positive electrode plate 240 is wound, the plurality of positive electrode tabs 260 are stacked to form a positive electrode tab group 250. As a result, the positive electrode tab group 250 is connected to the positive electrode plate 240. The position and length in the protruding direction of each of the plurality of positive electrode tabs 260 are appropriately adjusted taking into account the state in which the positive electrode tab group 250 is connected to the positive electrode current collector 400B. The shape of the positive electrode tabs 260 is not limited to the example shown in FIG. 12.

[0075] A positive electrode protective layer 243 is provided at the base of each of the positive electrode tabs 260. The positive electrode protective layer 243 does not necessarily have to be provided at the base of the positive electrode tab 260.

[0076] In a typical example, the thickness of the negative electrode tab 230 (one piece) is smaller than the thickness of the positive electrode tab 260 (one piece). In this case, the thickness of the negative electrode tab group 220 is smaller than the thickness of the positive electrode tab group 250.

[0077] (Shape of joint 115 including bent portion 115A) 13 to 19 are diagrams showing modified examples of the bent portion 115A of the joint portion 115. FIG.

[0078] As shown in FIGS. 13 to 19, the first region 1151 of the joint 115 does not necessarily have to be located on the center line L, but may be located closer to the center line L than the second region 1152.

[0079] 13, 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 D1 and D2, respectively, D2 / D1>1.2 It is preferable that the following relationship holds: By doing so, stress can be generated more concentratedly in the first region 1151, and the preferential cleavage location can be more reliably identified.

[0080] In the example of FIG. 14, 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.

[0081] 15 and 16, four bent portions 115A are formed. The number and positions of the bent portions 115A are not particularly limited and can be changed as appropriate.

[0082] 17, the intersection angle between the first region 1151 and the second region 1152 and the third region 1153 at the bent portion 115A is not 90°, but rather they intersect obliquely (at an angle other than 90°). The intersection angle (θ in FIG. 17) of the third region 1153 with the X direction (the extension direction of the first region 1151 and the second region 1152) is preferably 80° or less, and more preferably 60° or less. This makes it easier for the cleavage occurring in the first region 1151 to pass through the bent portion 115A and reach the second region 1152.

[0083] In the example of Fig. 18, the first region 1151 close to the center line L is formed in a dotted shape rather than a linear shape. In the example of Fig. 19, the first region 1151 sandwiched between the second regions 1152 is formed in a substantially arc shape.

[0084] In any of the examples of FIGS. 13 to 19, 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 even more preferably about 2 mm or less.

[0085] (Arrangement of first region 1151 and second region 1152) 20 to 23 are diagrams showing modified shapes of the joint portion 115. Fig. 23 shows the secondary battery 1 shown in Fig. 22 as viewed from the direction of arrow XXIII-XXIII.

[0086] 20, the joint 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 115 is formed substantially symmetrically with respect to a center line L2 (second center line). The center line L2 passes through the center of the side surface portion 112B in the X direction and extends in the Y direction.

[0087] 21, the joint 115 includes a plurality of (two) first regions 1151 and a second region 1152 formed between the two first regions 1151 in the X direction. The joint 115 is formed substantially symmetrically with respect to the center line L2.

[0088] 22 and 23, the joint 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. As shown in FIG. 22, the first region 1151 is formed on the side surface portion 112B. On the side surface portion 112B, the joint 115 is formed substantially symmetrically with respect to the center line L2. As shown in FIG. 23, the second region 1152 is formed on the side surface portion 111. The third region 1153 is formed so as to extend from the side surface portion 112B to the side surface portion 111.

[0089] As described above, in all three examples shown in FIGS. 20 to 23, the joint 115 (first region 1151) is formed substantially symmetrically with respect to the center line L2 passing through the center in the X direction.

[0090] When multiple secondary batteries 1 are connected in series, the multiple secondary batteries 1 are arranged with their orientations alternated so that the negative electrode terminals 301 and positive electrode terminals 302 are lined up alternately in the Y direction. In this case, because the first regions 1151 are arranged symmetrically with respect to the center line L2, even when the orientations of the secondary batteries 1 are alternately switched, the first regions 1151 are aligned in the Y direction, and the gas discharge positions (discharge positions in the X direction) when the internal pressure of the case 100 increases can be made approximately the same for the multiple secondary batteries 1.

[0091] In any of the examples shown in Figures 20 to 23, the total length of the first region 1151 in the X direction (if there are multiple first regions 1151, the total length of the multiple first regions 1151) is preferably at least about 1 / 5 of the length of the case body 110 in the X direction, and more preferably at least about 1 / 3.

[0092] 20 to 23, first region 1151 is not formed near openings 113, 114 (regions approximately 5 mm or less in the X direction from openings 113, 114). In this way, it is preferable to separate first region 1151 by a predetermined distance from openings 113, 114. By not providing first region 1151 near openings 113, 114, it is possible to prevent unintended rupture between case body 110 and sealing plates 120, 130 when the internal pressure of case 100 increases.

[0093] (Position of weak parts) Fig. 24 is a schematic diagram showing an example of the arrangement of a fragile portion 1150 in a joint 115. As shown in Fig. 24, when the electrode body 200 is a wound-type electrode body, gas generated inside the electrode body 200 is discharged to the outside of the electrode body 200 from both ends in the X direction of the electrode body 200. Therefore, it is preferable to provide fragile portions 1150 (gas discharge valves) at both ends in the X direction of the electrode body 200 (above the negative electrode tab group 220 and the positive electrode tab group 250).

[0094] For example, as shown in FIG. 21, by adopting an arrangement in which first regions 1151 are provided at both ends in the X direction, it is possible to realize the arrangement of fragile portions 1150 shown in the schematic diagram of FIG.

[0095] (Structure of joint 115) 25 to 29 are diagrams showing examples of cross sections of joint portion 115. In all of the examples shown in Fig. 25 to 29, first end portion 116 and second end portion 117 of plate-like members constituting case body 110 are joined by joint portion 115. This forms case body 110 in the shape of a rectangular tube.

[0096] 25, the joint 115 is formed by butt-welding the first end 116 and the second end 117 in the region R. The weld depth D1 shown in FIG. 25 can be made different between the first region 1151 and the second region 1152 (for example, D1 can be made smaller in the first region 1151 than in the second region 1152).

[0097] 26, the first end 116 and the second end 117 are overlapped in the region R, and the region R is fully welded to form the joint 115. The weld width W1 (the width at the boundary between the first end 116 and the second end 117) shown in FIG. 26 can be made different between the first region 1151 and the second region 1152 (for example, W1 can be made smaller in the first region 1151 than in the second region 1152).

[0098] 27, first end 116 and second end 117 are overlapped in region R, and adjacent portions of region R are fillet welded to form joint 115. The weld width W2 shown in FIG. 27 can be made different between first region 1151 and second region 1152 (for example, W2 can be made smaller in first region 1151 than in second region 1152).

[0099] 28 and 29, concave and convex shapes are provided on first end 116 and second end 117, and region R formed by the meshing of these concave and convex shapes or an adjacent region is welded to form joint 115. It is possible to make weld width W3 (the width at the boundary between first end 116 and second end 117) shown in Fig. 29 different between first region 1151 and second region 1152 (for example, W3 in first region 1151 is smaller than W3 in second region 1152).

[0100] Although the embodiments of the present technology have been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0101] 1 secondary battery, 100 case, 110 case body, 111, 112, 112A, 112B side portion, 113, 114 opening, 115 joint portion, 115A bent portion, 116 first end portion, 117 second end portion, 120, 130 sealing plate, 134 liquid injection hole, 200 electrode body, 210 negative electrode plate, 210S negative electrode base plate, 211 negative electrode core body, 212 negative electrode active material layer, 220 negative electrode tab group, 230 negative electrode tab, 240 positive electrode plate, 240S positive electrode base plate, 241 positive electrode core body, 242 positive electrode active material layer, 243 positive electrode protective layer, 250 positive electrode tab group, 260 positive electrode tab, 300 electrode terminal, 301 negative electrode terminal, 302 Positive electrode terminal, 400 current collector, 400A negative electrode current collector, 400B positive electrode current collector, 1150 fragile portion, 1151 first region, 1152 second region, 1153 third region.

Claims

1. an electrode body including a first electrode and a second electrode having a polarity different from that of the first electrode; a case for accommodating the electrode assembly; the case includes a case 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 that seals the first opening, and a second sealing plate that seals the second opening; The case body is provided with a linear joint portion extending from the first opening to the second opening, the joint portion has at least one bent portion at a position spaced apart from the first opening and the second opening, When the pressure inside the case reaches or exceeds a predetermined value, the joint breaks and the gas inside the case is discharged to the outside of the case.

2. the case body includes a pair of first walls facing each other in a second direction perpendicular to the first direction, The secondary battery according to claim 1 , wherein the bent portion is provided in the first wall portion.

3. the joint portion includes a first region and a second region located on the opposite side of the first region with respect to the bent portion, the first region and the second region extend in the first direction; the first wall portion has a first centerline that passes through a center of the first wall portion in a third direction perpendicular to the first direction and the second direction and extends in the first direction; The secondary battery according to claim 2 , wherein 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 , wherein the joint 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 , wherein the joint portion includes a plurality of the first regions and the second regions formed between the plurality of first regions in the first direction.

6. the first wall portion has a second center line that passes through a center of the first wall portion in the first direction and extends in a third direction that is perpendicular to the first direction and the second direction; The secondary battery according to claim 2 , wherein the joint portion is formed substantially symmetrically with respect to the second center line.

7. the case body includes a pair of second wall portions facing each other in a third direction perpendicular to the first direction and the second direction, The secondary battery according to claim 2 , wherein an area of ​​the first wall portion is smaller than an area of ​​the second wall portion.

8. the case body is formed of a plate-like member including a first end and a second end, The secondary battery according to claim 1 , wherein the joint portion is formed by welding the first end portion and the second end portion.

9. The secondary battery according to claim 1 , wherein the case has a substantially rectangular parallelepiped shape.

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