Secondary battery

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] It has been conventional to form a groove or a thin portion in the wall 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 the capacity of batteries increases, the size of secondary batteries is also increasing. From the viewpoint of reliability of large secondary batteries, there is room for further improvement in conventional secondary batteries. The objective of this technology is to provide a secondary battery with high capacity and high reliability. [Means for solving the problem]

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

[0006] [1] A secondary battery comprising: an electrode body including a first electrode and a second electrode having a polarity opposite to that of the first electrode; and a case housing the electrode body, the case including 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 being provided with a linear joint extending from the first opening to the second opening, the joint having at least one bent portion at a position spaced apart from the first opening and the second opening, the joint breaking when pressure inside the case reaches or exceeds a predetermined value, and gas inside the case being 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 extend in the first direction, the first wall portion has a first center line 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, 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 passing through a center of the first wall portion in the first direction and extending 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 secondary battery described in [2], wherein the case body includes a pair of second wall portions perpendicular to each other in a third direction perpendicular to the first direction and the second direction, and 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. Effect of the Invention

[0015] According to the present 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 rupture that will occur when the pressure inside the case reaches or exceeds a predetermined value, thereby improving the reliability of the battery. [Brief description of the drawings]

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

[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 will not be repeated.

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

[0019] In this specification, the words "comprise", "include" and "have" are open-ended, i.e., when a certain configuration is included, other configurations may or may not be included.

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

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

[0023] In the drawings, the direction along the winding axis of the electrode body of the secondary battery is the X direction, the short side direction of the electrode body as viewed from the X direction is the Y direction, and the long side direction of the electrode body as viewed from the X direction is the Z direction. In addition, in order to make the invention easier to understand, the dimensions of each component in the drawings are sometimes 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 on a vehicle.

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

[0028] When configuring an assembled battery including the 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 restraining member to form a battery module, or the assembled battery may be directly supported on the side surface of a battery pack case without using a restraining 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 square tube shape, for example, by abutting the edges of bent plate-like members (joints 115 shown in Figure 2) and joining them together (for example, by laser welding). The corners of the "square tube" may have a rounded shape.

[0031] In this embodiment, the case body 110 is formed to be longer in the width direction (X direction) of the secondary battery 1 than 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 a relatively large (high capacity) secondary battery 1 to be configured. 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 a relatively low height (low height) secondary battery 1 to be configured, which improves the mountability in a vehicle, for example.

[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 form part of the side surfaces of the case 100. The pair of side surface portions 112 form 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 provided 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 an area larger 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 a base material by irradiation with a high-energy ray such as a laser beam and then solidifying the melted base material.

[0035] The joint 115 is formed linearly on the side surface portion 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 ends (edges) of the plate-like members constituting 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 of this embodiment, the joint 115 has the function of a gas exhaust valve (safety valve) that breaks when the pressure inside the case 100 reaches or exceeds a predetermined value, and exhausts gas inside the case 100 to the outside of the case 100.

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

[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) is torn 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 an increase in manufacturing costs.

[0041] Note that "preferentially cleaving the first region 1151" is not limited to "cleaving only the first region 1151" and 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 the case body 110 on the first side in the first direction (X direction). The opening 113 is sealed by a sealing plate 120. A joint 115 is formed in the opening 113 to seal the opening 113. The opening 113 and the sealing plate 120 have a substantially rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction. The rectangular shape includes a substantially rectangular shape, such as a rectangular shape or 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 to the first side in a first direction (X direction) of case body 110. That is, opening 114 is located at an end opposite to 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 plate 120 and the sealing plate 130 are made of metal. Specifically, the sealing plate 120 and the sealing plate 130 are made of aluminum, 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 body 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 134 is sealed by a sealing member (not shown). As the sealing member, for example, a blind rivet or other metal members can be used.

[0052] The electrode body 200 is a flat-shaped electrode body having a positive electrode plate and a negative electrode plate, which will be described later. Specifically, the electrode body 200 is a wound-type electrode body in which a band-shaped positive electrode plate and a band-shaped negative electrode plate are both wound via a band-shaped separator (not shown). However, in this specification, the "electrode body" is not limited to a wound-type electrode body, and may be a laminated electrode body in which a plurality of positive electrode plates and a plurality of negative electrode plates are alternately laminated. The belt-shaped separator may be composed of, for example, a polyolefin microporous film. The electrode body may include a plurality of positive electrode plates and a plurality of negative electrode plates, and the positive electrode tabs provided on each positive electrode plate may be laminated to form a positive electrode tab group, or the negative electrode tabs provided on each negative electrode plate may be laminated to form a negative electrode tab group. The electrode body 200 may include a plurality of wound-type electrode bodies, or may include a plurality of laminated electrode bodies.

[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 later) arranged in the case 100. As the electrolytic solution (non-aqueous electrolytic solution), for example, LiPF6 dissolved at a concentration of 1.2 mol / L in a non-aqueous solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio (25°C) of 30:30:40 can be used. Note that a solid electrolyte may be used instead of the electrolytic solution.

[0055] The electrode body 200 includes a main body portion (a portion in which positive electrode plates and negative electrode plates are laminated with a separator 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 an end of a first side of the electrode body 200 in a first direction (X direction) relative to the main body. The first side in this embodiment is the sealing plate 120 side. The positive electrode tab group 250 is located at an end of a second side of the electrode body 200 in the first direction (X direction) relative to the main body. The second side in this embodiment 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 central portion of the electrode body 200 towards the sealing plate 120 or the sealing plate 130, respectively.

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

[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, for example, aluminum or an aluminum alloy. 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 play the role of 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 original plate 210S before the negative electrode plate 210 is formed, FIG. 8 is a cross-sectional view taken along line VIII-VIII of the negative electrode original plate 210S shown in FIG. 7, and FIG. 9 is a front view showing the negative electrode plate 210 formed from the negative electrode original plate 210S.

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

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

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

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

[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 original plate 240S. As shown in Fig. 10 and Fig. 11, the positive electrode original 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 sides of the positive electrode core 241 except for one end portion. The positive electrode active material layer 242 is formed on the positive electrode core 241 by applying a positive electrode active material layer slurry with a die coater.

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

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

[0074] As shown in FIG. 12, a plurality of positive electrode tabs 260 (first electrode tabs) made of a positive electrode core 241 are provided at one end in the width direction of the positive electrode plate 240 formed from the positive electrode original plate 240S. When the positive electrode plate 240 is wound, the plurality of positive electrode tabs 260 are stacked to form 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 in consideration of 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 tab 260 is not limited to the one exemplified 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 need 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 in the Y direction with respect to the center line L, and the second region 1152 is located on the other side in the Y direction with respect to the center line L. 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 intensively in the first region 1151, and the preferential cleavage site 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 in the Y direction with respect to the center line L, 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 they intersect obliquely (at an angle other than 90°). The intersection angle (θ in FIG. 17) of the third region 1153 with respect to the X direction (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 from 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 dot shape rather than a line shape. Also, 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 in 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) Figures 20 to 23 are diagrams showing modified shapes of the joint portion 115. Figure 23 shows the secondary battery 1 shown in Figure 22 as viewed from the direction of the arrows XXIII-XXIII.

[0086] 20, the joint 115 includes a plurality (two) of 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 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 a center line L2.

[0088] In the example of Figs. 22 and 23, the joint 115 includes a plurality (two) of 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 in the side portion 112B. On the side 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 in the side portion 111. The third region 1153 is formed so as to reach the side portion 111 from the side portion 112B.

[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 the positive electrode terminals 302 are lined up alternately in the Y direction. In this case, since the first regions 1151 are arranged symmetrically with respect to the center line L2, even if the secondary batteries 1 are arranged with their orientations alternated, 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 substantially consistent for the multiple secondary batteries 1.

[0091] In any of the examples in Figures 20 to 23, the total length of 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 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 in the vicinity of openings 113, 114 (a region approximately 5 mm or less from openings 113, 114 in the X direction). In this manner, first region 1151 is preferably spaced a predetermined distance from openings 113, 114. By not providing first region 1151 in the vicinity of openings 113, 114, unintended cleavage between case body 110 and sealing plates 120, 130 can be suppressed when the internal pressure of case 100 increases.

[0093] (Location of the weak part) Fig. 24 is a schematic diagram showing an example of the arrangement of the fragile portion 1150 in the joint portion 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 the 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, a first end portion 116 and a second end portion 117 of a plate-like member 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 first end 116 and the second end 117 are butt-welded in the region R to form the joint 115. It is possible to make the weld depth D1 shown in FIG. 25 different between the first region 1151 and the second region 1152 (for example, to make D1 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 welded to form the joint 115. It is possible to make the weld width W1 (the width at the boundary between the first end 116 and the second end 117) shown in FIG. 26 different between the first region 1151 and the second region 1152 (for example, make W1 smaller in the first region 1151 than in the second region 1152).

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

[0099] 28 and 29, first end 116 and second end 117 are provided with uneven shapes, and the uneven shapes are engaged to form region R or an adjacent region, thereby forming joint 115. It is possible to make weld width W3 (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, make W3 smaller in first region 1151 than in second region 1152).

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

[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 body, 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 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 an 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 the first regions in the first direction.

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

7. the case body includes a pair of second walls perpendicular to 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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