Secondary battery and method for manufacturing secondary battery

Abstract

To provide a secondary battery with a configuration capable of suppressing occurrence of damage to a tab group, and a method for manufacturing the secondary battery.SOLUTION: In a secondary battery 1, a current collector 431 is a first laminated body in which a plurality of metal plates 4300 are laminated, the current collector 431 includes a first region 431A and a second region 431B, a positive electrode tab group 250, 280 is joined to the first region 431A, a positive electrode current collecting portion 420 is joined to the second region 431B, and the current collector 431 is bent between the first region 431A and the second region 431B.SELECTED DRAWING: Figure 12

Description

[Technical Field]

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

[0002] Japanese Patent Publication No. 2021-099936 (Patent Document 1) relates to an invention of a power storage device, and discloses a configuration in which a group of tabs connected to a current collector are bent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-099936 Summary of the Invention [Problem to be solved by the invention]

[0004] To achieve a structure in which the tab group is bent, the length of the tab group needs to be increased, which may result in unintended folds or bends in the tab group during the secondary battery manufacturing process, etc., and may result in damage to the tab group.

[0005] An object of the present technology is to provide a secondary battery having a configuration capable of suppressing damage to a tab group, and a method for manufacturing the secondary battery. [Means for solving the problem]

[0006] The present technology provides the following secondary battery and secondary battery manufacturing method.

[0007] [1] A secondary battery comprising: an electrode assembly 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; a first tab group in which a plurality of first electrode tabs electrically connected to the first electrode are stacked; and a first current collector connected to the first tab group, wherein the first current collector is a first laminate in which a plurality of metal plates are stacked, the first current collector includes a first region and a second region, the first tab group is joined to the first region, and another conductive member is joined to the second region, and the first current collector is folded between the first region and the second region.

[0008] [2] The secondary battery according to [1], comprising: a second tab group in which a plurality of second electrode tabs electrically connected to the first electrode are stacked; and a second current collector connected to the second tab group, wherein the second current collector is a second laminate in which a plurality of metal plates are stacked; the second current collector includes a third region and a fourth region, the second tab group is joined to the third region, another conductive member is joined to the fourth region, and the second current collector is folded between the third region and the fourth region.

[0009] [3] The secondary battery according to [2], wherein the first current collector and the second current collector are stacked and joined to one of the other conductive members.

[0010] [4] The secondary battery according to [3], wherein the other conductive member, the first current collector, and the second current collector are stacked in this order, and a tip of the first current collector protrudes beyond a tip of the second current collector.

[0011] [5] The secondary battery according to any one of [2] to [4], wherein a first fuse portion is provided on the first current collector, a second fuse portion is provided on the second current collector, and the first fuse portion and the second fuse portion are arranged apart from each other.

[0012] [6] The secondary battery according to any one of [2] to [5], wherein the second region of the first current collector and the fourth region of the second current collector are joined to other conductive members in a non-opposing positional relationship.

[0013] [7] The secondary battery according to any one of [1] to [6], wherein the first current collector includes, in the first region, a region where a plurality of the metal plates are bonded to each other in a region not bonded to the first tab group.

[0014] [8] The secondary battery described in [7], wherein a plurality of first recesses are formed in the first region of the first current collector in a portion not joined to the first tab group, a plurality of second recesses are formed on the surface of the first tab group, and the depth of the first recesses is smaller than the depth of the second recesses.

[0015] [9] The secondary battery according to [7] or [8], wherein the first region of the first current collector has a plurality of first recesses in a portion not joined to the first tab group, and the first region has a plurality of second recesses on the surface of the first tab group, and the area of ​​one of the first recesses is smaller than the area of ​​one of the second recesses.

[0016]

[10] The secondary battery according to any one of [1] to [9], wherein the second region includes a region where a plurality of the metal plates are joined together in a region not joined to the other conductive member.

[0017]

[11] The secondary battery according to any one of [1] to

[10] , wherein the first current collector has a region in the region bent between the first region and the second region where the metal plates are not joined together.

[0018]

[12] The secondary battery according to any one of [1] to

[11] , wherein in the first current collector, in the folded region, the length of the metal plate arranged on the outermost side is longer than the length of the metal plate located inside it.

[0019]

[13] The secondary battery according to any one of [1] to

[12] , wherein the length of the first current collector from the joint with the first tab group to the joint with another conductive member is longer than the length from the base of the first tab group to the joint between the first current collector and the first tab group.

[0020]

[14] A method for manufacturing a secondary battery comprising: an electrode assembly including a first electrode and a second electrode having a polarity different from that of the first electrode; a case that houses the electrode assembly; a first tab group in which a plurality of first electrode tabs electrically connected to the first electrode are stacked; and a first current collector connected to the first tab group, wherein the first current collector is a first laminate in which a plurality of metal plates are stacked, the first current collector includes a first region and a second region, the first tab group is joined to the first region and another conductive member is joined to the second region, and the first current collector is folded between the first region and the second region, the method comprising: a first joining step of joining the first tab group to the first region; and a folding step of folding the first current collector between the first region and the second region.

[0021]

[15] A method for manufacturing a secondary battery as described in

[14] , comprising: a second tab group in which a plurality of second electrode tabs electrically connected to the first electrode are stacked; and a second current collector connected to the second tab group, wherein the second current collector is a second laminate in which a plurality of metal plates are stacked; the second current collector includes a third region and a fourth region, another conductive member is joined to the third region, the second tab group is joined to the fourth region, and the second current collector is folded between the third region and the fourth region.

[0022]

[16] A method for manufacturing a secondary battery according to

[15] , comprising a step of stacking the first current collector connected to the first tab group and the second current collector connected to the second tab group and connecting them to the other conductive member.

[0023]

[17] The method for manufacturing a secondary battery according to any one of

[14] to

[16] , further comprising the step of ultrasonically bonding the first tab group to the area in the first region where the metal plates are bonded together.

[0024]

[18] The method for manufacturing a secondary battery according to any one of

[14] to

[17] , further comprising a second joining step of joining the second region to the other conductive member by irradiating it with energy rays before the bending step.

[0025]

[19] The method for manufacturing a secondary battery according to

[18] , wherein the other conductive member is bonded to the region in the second region where the metal plates are bonded to each other. [Effects of the Invention]

[0026] According to the present technology, it is possible to provide a secondary battery having a configuration that can suppress damage to a tab group, and a method for manufacturing the secondary battery. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a front view showing the configuration of a secondary battery according to a first embodiment. [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] 8 is a cross-sectional view of the negative electrode (a cross-sectional view taken along line VII-VII in FIG. 8). [Figure 8] FIG. [Figure 9] 11 is a cross-sectional view of the positive electrode (cross-sectional view taken along line IX-IX in FIG. 10). [Figure 10] FIG. [Figure 11] FIG. 2 is a diagram showing the peripheral configuration of a negative electrode current collector. [Figure 12] FIG. 2 is a diagram showing the configuration of the periphery of a positive electrode current collector. [Figure 13] 1 is a flowchart showing a method for manufacturing a secondary battery. [Figure 14] FIG. 2 is a diagram showing a state in which current collectors are joined to a first electrode body and a second electrode body. [Figure 15] FIG. 10 is a view showing a state in which a sealing plate is attached to a negative electrode-side current collector. [Figure 16] FIG. 2 is a diagram showing a state in which the first electrode body and the second electrode body are superimposed. [Figure 17] 10A and 10B are diagrams showing a process of inserting the first electrode body and the second electrode body into the case body. [Figure 18] FIG. 10 is a view showing a state in which a sealing plate is attached to a current collector on the positive electrode side. [Figure 19] FIG. 10 is a view showing a state in which the opening of the case body is sealed. [Figure 20] FIG. 2 is a diagram showing a metal plate constituting a current collector. [Figure 21] FIG. 10 is a plan view of a current collector (first current collector) according to a second embodiment. [Figure 22] FIG. 10 is a side view of the current collector showing the state before joining in the second embodiment. [Figure 23] FIG. 10 is a side view of the current collector showing the state after joining in the second embodiment. [Figure 24] FIG. 10 is a plan view of a current collector after bonding of stacked metal plates according to a second embodiment. [Figure 25] FIG. 25 is a cross-sectional view taken along the line XXV-XXV in FIG. 24. [Figure 26] FIG. 26 is a cross-sectional view taken along the line XXVI-XXVI in FIG. 24. [Figure 27] FIG. 25 is a cross-sectional view taken along the line XXVII-XXVII in FIG. 24. [Figure 28] FIG. 2 is a development view showing a state in which the current collector is connected to a positive electrode tab group and a positive electrode current collector. [Figure 29] FIG. 29 is a cross-sectional view taken along the line XXIX-XXIX in FIG. 28. [Figure 30] FIG. 29 is a cross-sectional view taken along the line XXX-XXX in FIG. 28. [Figure 31] FIG. 29 is a cross-sectional view taken along the line XXXI-XXXI in FIG. 28. [Figure 32] FIG. 29 is a cross-sectional view of a modified example taken along the line XXXI-XXXI in FIG. 28. [Figure 33]FIG. 11 is a perspective view showing a state before the positive electrode side sealing plate of embodiment 3 is attached to the case. [Figure 34] FIG. 10 is a plan view showing a current collector according to a third embodiment. [Figure 35] FIG. 35 is a cross-sectional view taken along the line XXXV-XXXV in FIG. 34. [Figure 36] FIG. 36 is a cross-sectional view taken along the line XXXVI-XXXVI in FIG. 34. [Figure 37] FIG. 35 is a cross-sectional view taken along the line XXXVII-XXXVII in FIG. 34. [Figure 38] FIG. 10 is a plan view showing a current collector according to a third embodiment. [Figure 39] FIG. 10 is a development view showing a state in which the current collector of the third embodiment is connected to a positive electrode tab group and a positive electrode current collector. [Figure 40] FIG. 40 is a cross-sectional view taken along the line XL-XL in FIG. 39. [Figure 41] FIG. 40 is a cross-sectional view taken along the line XLI-XLI in FIG. 39. [Figure 42] FIG. 40 is a cross-sectional view taken along the line XLII-XLII in FIG. 39. [Figure 43] FIG. 10 is a diagram showing the configuration of a first modified current collector according to the fourth embodiment. [Figure 44] FIG. 10 is a diagram showing the configuration of a second modified current collector according to the fourth embodiment. [Figure 45] FIG. 10 is a diagram showing the configuration of a third modified current collector according to the fourth embodiment. [Figure 46] FIG. 10 is a diagram showing the configuration of a fourth modified current collector according to the fourth embodiment. [Figure 47] FIG. 10 is a diagram showing a form of a fifth modified current collector according to the fourth embodiment. [Figure 48] 13 is a cross-sectional view showing the effect when the fourth and fifth modified current collectors of the fourth embodiment are used. FIG. [Figure 49] FIG. 49 is a cross-sectional view taken along the line XLIX-XLIX in FIG. 43 according to the fifth embodiment. [Figure 50] 49 is a cross-sectional view corresponding to a cross section taken along line XLIX-XLIX in FIG. 43 according to the fifth embodiment. [Figure 51]FIG. 2 is a first development view showing a state in which the current collector is connected to a positive electrode tab group and a positive electrode current collector. [Figure 52] FIG. 2 is a second developed view showing a state in which the current collector is connected to the positive electrode tab group and the positive electrode current collector. [Figure 53] FIG. 1 is a side view showing the configuration of stacked metal plates. [Figure 54] FIG. 10 is a side view of the stacked metal plates in a folded state. [Figure 55] FIG. 10 is a side view showing two current collectors and two tab groups arranged in the following order: first current collector-first tab group-second current collector-second tab group. [Figure 56] FIG. 10 is a side view showing two current collectors and two tab groups arranged in the following order: first current collector-first tab group-second tab group-second current collector. DETAILED DESCRIPTION OF THE INVENTION

[0028] 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.

[0029] 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 mentioned in the present embodiments.

[0030] In this specification, the words "comprise," "include," and "have" are open-ended, meaning that when a certain feature is included, other features may or may not be included.

[0031] 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 a single state, and the relative positional relationships can be reversed or rotated to any angle by changing the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0032] In this specification, the term "secondary battery" may include not only lithium ion batteries but also nickel-metal hydride batteries, sodium ion batteries, etc. In this specification, the term "electrode" may collectively refer to positive electrodes and negative electrodes.

[0033] In the drawings, if the electrode body of the secondary battery is a laminated electrode body, the longitudinal direction of the laminated surface is the X direction, and if the electrode body is a wound electrode body, the direction along the winding axis 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. To facilitate understanding of the invention, the dimensions of each component in the drawings may be slightly different from the actual dimensions.

[0034] In this specification, the X direction may be referred to as the "width direction" of the secondary battery 1, the electrode body 200, and the case body 110, the Z direction may be referred to as the "height direction" of the secondary battery 1, the electrode body 200, and the case body 110, and the Y direction may be referred to as the "thickness direction" of the secondary battery 1, the electrode body 200, and the case body 110.

[0035] (Embodiment 1: Overall Configuration of Battery) Fig. 1 is a front view of a secondary battery 1 according to embodiment 1. Figs. 2 to 5 are diagrams showing 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.

[0036] 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.

[0037] 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 .

[0038] When configuring a battery pack including secondary batteries 1, multiple secondary batteries 1 are arranged in their thickness direction. The arranged secondary batteries 1 may be constrained in the arrangement 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 the battery pack case without using a constraining member.

[0039] 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.

[0040] As shown in Figures 1 and 2, sealing plates 120 and 130 are provided at both ends of case body 110. 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 have an R shape. Furthermore, the secondary battery in the present technology is not necessarily limited to a rectangular secondary battery.

[0041] 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 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.

[0042] The case main body 110 includes a pair of first side surface portions 111 and a pair of second side surface portions 112. The pair of first side surface portions 111 constitute part of the side surfaces of the case 100. The pair of second side surface portions 112 constitute the bottom surface portion and the top surface portion of the case 100. The pair of first side surface portions 111 and the pair of second side surface portions 112 are arranged to intersect with each other. The pair of first side surface portions 111 and the pair of second side surface portions 112 are connected at their respective ends. Each of the pair of first side surface portions 111 has a larger area than each of the pair of second side surface portions 112.

[0043] 5, a gas release valve 150 is provided on one second side surface portion 112A of the pair of second side surface portions 112. The gas release valve 150 extends in the width direction (X direction) of the secondary battery 1. The gas release valve 150 extends in the X direction from the center of the case body 110 in the X direction but does not reach both ends. The shape of the gas release valve 150 can be changed as appropriate.

[0044] The thickness of the plate-like member in the gas release valve 150 is thinner than the thickness of the plate-like members of the case body 110 other than the gas release valve 150. As a result, when the pressure inside the case 100 reaches or exceeds a predetermined value, the gas release valve 150 breaks preferentially compared to other parts of the case body 110, and releases gas inside the case 100 to the outside.

[0045] 2, a joint 115 is formed on the other second side surface portion 112B of the pair of second side surface portions 112. The joint 115 extends in the width direction (X direction) of the secondary battery 1. At the joint 115, the edges of the plate-like members that make up the case body 110 are joined together.

[0046] 3, an opening 113 (second opening) is provided at the end of case body 110 on the -X side in the X direction. Opening 113 is sealed with sealing plate 120 (second sealing plate). A joint 115 is formed in opening 113 to seal opening 113. Opening 113 and sealing plate 120 have a generally rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction. The generally rectangular shape includes a rectangular shape or a substantially rectangular shape such as a rectangular shape with rounded corners.

[0047] A negative electrode terminal 301 (second electrode terminal) is provided on the sealing plate 120. The position of the negative electrode terminal 301 can be changed as appropriate. The negative electrode terminal 301 is exposed to the outside of the sealing plate 120.

[0048] 4, an opening 114 (first opening) is provided at the end of case body 110 on the +X side in the X direction. Opening 114 is located at the end opposite opening 113, and openings 113 and 114 face each other. Opening 114 is sealed with sealing plate 130 (first sealing plate). 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.

[0049] A positive electrode terminal 302 (first electrode terminal) and a liquid injection hole 134 are provided on the sealing plate 130. The positions of the positive electrode terminal 302 and the liquid injection hole 134 can be changed as appropriate.

[0050] 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.

[0051] The negative electrode terminal 301 is electrically connected to the negative electrode of the electrode body 200. The negative electrode terminal 301 is attached to the sealing plate 120, i.e., the case 100. The negative electrode terminal 301 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. The negative electrode terminal 301 is connected to a plate-shaped member 303.

[0052] The plate-shaped member 303 is located outside the sealing plate 120. The plate-shaped member 303 is arranged so as to fit along the sealing plate 120. The plate-shaped member 303 is conductive. The plate-shaped member 303 is arranged to ensure a connection area with a bus bar or the like that electrically connects the secondary battery 1 to other adjacent secondary batteries. The connection between the negative electrode terminal 301 and the plate-shaped member 303 can be formed by, for example, laser welding.

[0053] 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. The positive electrode terminal 302 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 terminal 302 is exposed to the outside of the sealing plate 130. The positive electrode terminal 302 is connected to a plate-shaped member 304.

[0054] The plate-shaped member 304 is located outside the sealing plate 130. The plate-shaped member 304 is arranged so as to fit along the sealing plate 130. The plate-shaped member 304 is conductive. The plate-shaped member 304 is arranged to ensure a connection area with a bus bar or the like that electrically connects the secondary battery 1 to other adjacent secondary batteries. The connection between the positive electrode terminal 302 and the plate-shaped member 304 can be formed by, for example, laser welding.

[0055] 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.

[0056] The electrode assembly 200 is a flat-shaped electrode assembly in which positive electrodes and negative electrodes, which will be described later, are stacked. Specifically, the electrode assembly 200 is a laminated electrode assembly in which multiple positive electrodes and multiple negative electrodes are alternately stacked with a separator (not shown) interposed therebetween. However, in this specification, the term "electrode assembly" is not limited to a laminated electrode assembly, but may also be a wound electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound together with a strip-shaped separator interposed therebetween. The separator may be formed, for example, of a polyolefin microporous film. When the electrode assembly is a laminated electrode assembly including multiple positive electrodes and multiple negative electrodes, the positive electrode tabs provided on each positive electrode may be stacked to form a positive electrode tab group, and the negative electrode tabs provided on each negative electrode may be stacked to form a negative electrode tab group.

[0057] As shown in Fig. 6, the case 100 houses the electrode assembly 200. Fig. 6 illustrates a first electrode assembly 201, which will be described later. The first electrode assembly 201 is housed in the case 100 so that its longitudinal direction is parallel to the X direction.

[0058] Specifically, one or more stacked electrode bodies are housed together with an electrolytic solution (electrolyte) (not shown) inside an insulating sheet (not shown) arranged in the case 100. A solid electrolyte may be used instead of the electrolytic solution.

[0059] The first electrode body 201 includes a substantially rectangular main body, a negative electrode tab group 220, and a positive electrode tab group 250. The negative electrode tab group 220 is located at the end of the main body on the -X side in the X direction. The positive electrode tab group 250 is located at the end of the main body on the +X side in the X direction.

[0060] 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.

[0061] The current collectors 400 include a negative electrode current collector 400 A and a positive electrode current collector 400 B. The electrode assembly 200 is electrically connected to a negative electrode terminal 301 and a positive electrode terminal 302 via the current collectors 400 .

[0062] 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 can be made of a conductive material (more specifically, a metal such as copper or a copper alloy).

[0063] 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 can be made of a conductive material (more specifically, a metal such as aluminum or an aluminum alloy).

[0064] (Configuration of electrode body 200) 7 and 8, the negative electrode 210 includes a negative electrode core 211 and a negative electrode active material layer 212. The negative electrode core 211 is a copper foil or a copper alloy foil. The negative electrode active material layer 212 is formed by applying a negative electrode active material layer slurry using a die coater.

[0065] A plurality of negative electrode tabs 230 each made of a negative electrode core 211 are provided at one end in the width direction of the negative electrode 210. When the negative electrodes 210 are stacked, the plurality of negative electrode tabs 230 are stacked to form a negative electrode tab group 220. The length in the protruding direction of each of the negative electrode tabs 230 in the plurality of negative electrodes 210 is adjusted as appropriate, taking into consideration 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 the example shown in FIG. 8.

[0066] 9 and 10, the positive electrode 240 has a polarity different from that of the negative electrode 210. The positive electrode 240 includes a positive electrode core 241, a positive electrode active material layer 242, and a positive electrode protective layer 243. The positive electrode core 241 is an aluminum foil or an aluminum alloy foil. The positive electrode 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.

[0067] A plurality of positive electrode tabs 260 each made of a positive electrode core 241 are provided at one end in the width direction of the positive electrode 240. When the positive electrodes 240 are stacked, the plurality of positive electrode tabs 260 are stacked to form a positive electrode tab group 250. The length of each of the positive electrode tabs 260 in the protruding direction of the plurality of positive electrodes 240 is adjusted as appropriate, taking into consideration 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 example shown in FIG. 10.

[0068] The positive electrode protective layer 243 is provided at the base of the positive electrode tab 260. However, the positive electrode protective layer 243 does not necessarily have to be provided.

[0069] 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.

[0070] (Connection structure between electrode body 200 and current collector 400) 11 and 12, the electrode assembly 200 includes a first electrode assembly 201 and a second electrode assembly 202. Each of the first electrode assembly 201 and the second electrode assembly 202 includes a positive electrode 240 and a negative electrode 210. The electrode assembly 200 may be composed of three or more electrode assemblies.

[0071] The electrode body 200 is formed by stacking a first electrode body 201 and a second electrode body 202. The first electrode body 201 and the second electrode body 202 are aligned in the thickness direction (Y direction) of the first electrode body 201 and the second electrode body 202.

[0072] The first electrode body 201 includes a positive electrode tab group 250 (first electrode tabs) that are arranged at one end of the first electrode body 201 (FIG. 12) and are electrically connected to the positive electrode 240, and a negative electrode tab group 220 (second electrode tabs) that are arranged at the other end of the first electrode body 201 (FIG. 11) and are electrically connected to the negative electrode 210.

[0073] The second electrode body 202 includes a positive electrode tab group 280 (third electrode tabs) that are arranged at one end of the second electrode body 202 (FIG. 12) and are electrically connected to the positive electrode 240, and a negative electrode tab group 270 (fourth electrode tabs) that are arranged at the other end of the second electrode body 202 (FIG. 11) and are electrically connected to the negative electrode 210.

[0074] 11 (negative electrode side structure), the negative electrode tab groups 220, 270 are electrically connected to a current collector 410 (negative electrode current collector 400A). The current collector 410 (second current collector) to which the negative electrode tab groups 220 and 270 are joined can be made of a metal plate-like member. The current collector 410 can also be made of a single member.

[0075] The negative electrode tab group 220 has a curved portion 221. The curved portion 221 is a curved portion of the negative electrode tab group 220. The negative electrode tab group 270 has a curved portion 271. The curved portion 271 is a curved portion of the negative electrode tab group 270.

[0076] Negative electrode tab group 220 and negative electrode tab group 270 are curved in opposite directions so that their leading ends approach each other.

[0077] Furthermore, in the embodiment, the tip portions of the negative electrode tab group 220 and the negative electrode tab group 270 are spaced apart from each other, but the present technology is not limited to this configuration, and the tip portions of the negative electrode tab group 220 and the negative electrode tab group 270 may be in contact with each other.

[0078] The current collector 410 electrically connects the negative electrode terminal 301 to the negative electrode tab group 220 and the negative electrode tab group 270. The current collector 410 has a longitudinal direction in the Z direction and a lateral direction in the Y direction.

[0079] Negative electrode tab group 220 and negative electrode tab group 270 are each joined to current collector 410 at joint 410A (see FIG. 14) described below. Joint 410A can be formed by, for example, ultrasonic bonding, resistance welding, laser welding, caulking, or the like.

[0080] An insulating member 510 is disposed between the plate-shaped member 303 and the sealing plate 120. An insulating member 530 is disposed between the current collector 410 and the sealing plate 120. However, the negative electrode terminal 301 may be electrically connected to the sealing plate 120, and the sealing plate 120 may serve as the negative electrode terminal 301.

[0081] A spacer (not shown) may be disposed between the sealing plate 120 and the main body of the electrode assembly 200 (excluding the negative electrode tab groups 220, 270). The spacer may be made of an insulating resin material. The negative electrode tab groups 220, 270 are protected by passing through the interior of the spacer.

[0082] 12 (structure on the positive electrode side), the positive electrode tab group 250 and the positive electrode tab group 280 are each electrically connected to a current collector 430 (positive electrode current collector 400B). More specifically, the positive electrode tab group 250 is joined to a current collector 431, and the positive electrode tab group 280 is joined to a current collector 432.

[0083] The lengths of the positive electrode tab groups 250, 280 can be changed as appropriate. The lengths of the positive electrode tab groups 250, 280 are preferably the same, but may be different. The lengths of the positive electrode tab groups 250, 280 may be shorter or longer than the negative electrode tab groups 220, 270.

[0084] The current collector 431 (first current collector) to which the positive electrode tab group 250 is joined is made of a laminate (first laminate) in which a plurality of metal plates 4300 (see FIG. 20) described below are stacked. Similarly, the current collector 432 (third current collector) to which the positive electrode tab group 280 is joined is made of a laminate (second laminate) in which a plurality of metal plates 4300 (see FIG. 20) are stacked. In the current collectors 431 and 432, the number of stacked metal plates 4300 is two or more, preferably three or more, and more preferably five or more. Also, for example, the number can be 20 or less, preferably 15 or less, and more preferably 10 or less. Note that the same can be applied when a current collector in which metal plates are stacked is used on the negative electrode side.

[0085] The current collectors 431 and 432 electrically connect the positive electrode terminal 302 to the positive electrode tab group 250 and the positive electrode tab group 280. The current collectors 431 and 432 are each joined to the positive electrode current collecting portion 420 in a folded state, and are electrically connected to the positive electrode terminal 302.

[0086] A more stable current collection structure can be configured by dividing the current collector 430 into two current collectors 431 and 432. However, the scope of the present technology is not limited to this, and, for example, the positive electrode tab group 250 and the positive electrode tab group 280 may be joined to one current collector 430. By joining the positive electrode tab group 250 and the positive electrode tab group 280 to one current collector 430, the joining process can be simplified (reduced in number of times).

[0087] 12, the current collectors 431, 432 are joined to the positive electrode current collecting part 420 at a portion where the current collectors 431, 432 overlap each other (joining region 420A in FIG. 18). However, the scope of the present technology is not limited thereto, and the current collectors 431, 432 may be joined to the positive electrode current collecting part 420 at positions spaced apart or adjacent to each other on the positive electrode current collecting part 420.

[0088] The positive electrode tab group 250 and the positive electrode tab group 280 are respectively joined to current collectors 431, 432 in a positive electrode joining region 200R (see FIG. 14) described later. The positive electrode joining region 200R can be formed by, for example, ultrasonic joining, resistance welding, laser welding, caulking, or the like.

[0089] The positive electrode bonding region 200R between the current collector 431 and the positive electrode tab group 250 and the positive electrode bonding region 200R between the current collector 432 and the positive electrode tab group 280 are formed at positions spaced apart from each other on the XY plane.

[0090] 12 , a positive electrode tab group 250 is disposed in the X direction between the end of the current collector 431 on the electrode body 200 side (left side in the figure) and the end of the current collector 432 on the electrode body 200 side (left side in the figure) (the gap between the current collectors 431, 432). A positive electrode tab group 280 may be disposed in the gap between the current collectors 431, 432, or both the positive electrode tab groups 250, 280 may be disposed in the gap between the current collectors 431, 432. This allows the gap between the current collectors 431, 432 to be used effectively.

[0091] An insulating member 520 is disposed between the plate-shaped member 304 and the sealing plate 130. An insulating member 540 is disposed between the positive electrode terminal 302 and the sealing plate 130. However, the positive electrode terminal 302 may be electrically connected to the sealing plate 130, and the sealing plate 130 may serve as the positive electrode terminal 302.

[0092] A spacer (not shown) may be disposed between the sealing plate 130 and the main body of the electrode assembly 200 (excluding the positive electrode tab groups 250, 280). The spacer may be made of an insulating resin material. The positive electrode tab groups 250, 280 are protected by passing through the interior of the spacer.

[0093] (Manufacturing process of secondary battery 1) A method for manufacturing the secondary battery according to this embodiment will now be described. Fig. 13 is a flowchart showing the method for manufacturing the secondary battery 1.

[0094] As shown in FIG. 13, the method for manufacturing the secondary battery 1 includes a step (S1) of preparing the first electrode body 201 and the second electrode body 202, a step (S2) of joining the negative electrode tab group 220 and the negative electrode tab group 270 to the current collector 410, a step (S3) of joining the positive electrode tab group 250 to the current collector 431, a step (S4) of joining the positive electrode tab group 280 to the current collector 432, a step (S5) of electrically connecting the current collector 410 joined to the negative electrode tab group 220 and the negative electrode tab group 270 to the negative electrode terminal 301, and a step (S6) of electrically connecting the first electrode body 201 and the second electrode body 202 to the negative electrode tab group 220. The process includes a step (S6) of overlapping the first electrode body 201 and the second electrode body 202, a step (S7) of assembling a spacer and an insulating sheet to the electrode body 200, a step (S8) of inserting the first electrode body 201 and the second electrode body 202 into the case body 110, a step (S9) of electrically connecting the current collectors 431, 432 joined to the positive electrode tab groups 250, 280 to the positive electrode terminal 302, a step (S10) of joining the sealing plates 120, 130 to the case body 110 to seal the openings 113, 114, and a step (S11) of conducting a leak test.

[0095] 14 to 19 are diagrams showing the steps in the method for manufacturing the secondary battery 1. FIG.

[0096] In the step (S1) of producing the first electrode body 201 and the second electrode body 202, it is preferable that a portion of the tip of each of the negative electrode tab group 220, the positive electrode tab group 250, the negative electrode tab group 270, and the positive electrode tab group 280 is cut off so that the lengths of the tips are the same when bundled.

[0097] As shown in FIG. 14, after the first electrode body 201 and the second electrode body 202 are fabricated, the negative electrode tab groups 220, 270 are joined to the current collector 410 (S2), the positive electrode tab group 250 is joined to the current collector 431 (S3), and the positive electrode tab group 280 is joined to the current collector 432 (S4).

[0098] The negative electrode tab groups 220, 270 are joined to the current collector 410 at a joint 410A. The positive electrode tab group 250 is joined to the current collector 431 in the positive electrode joining region 200R. The positive electrode tab group 280 is joined to the current collector 432 in the positive electrode joining region 200R.

[0099] The current collector 431, the first electrode body 201, the current collector 410, the second electrode body 202, and the current collector 432 are arranged in this order in the direction of the arrow DR1.

[0100] 14 , in the height direction of the first electrode body 201 and the second electrode body 202, the current collector 410 and the current collectors 431, 432 are arranged to be biased to one side from the center of the first electrode body 201 and the second electrode body 202. In addition, in the height direction of the first electrode body 201 and the second electrode body 202, the negative electrode tab group 220, the positive electrode tab group 250, the negative electrode tab group 270, and the positive electrode tab group 280 are each arranged to be biased to one side from the center of the first electrode body 201 and the second electrode body 202.

[0101] However, the scope of the present technology is not limited thereto, and the current collector 410 and the current collectors 431, 432 may be disposed at the center of the first electrode body 201 and the second electrode body 202 in the height direction of the first electrode body 201 and the second electrode body 202. Furthermore, the negative electrode tab group 220, the positive electrode tab group 250, the negative electrode tab group 270, and the positive electrode tab group 280 may each be disposed at the center of the first electrode body 201 and the second electrode body 202 in the height direction of the first electrode body 201 and the second electrode body 202.

[0102] As shown in FIG. 15 , the current collector 410 joined to the negative electrode tab group 220 and the negative electrode tab group 270 is assembled to the sealing plate 120. A current collector 440 and a negative electrode terminal 301 have been attached to the sealing plate 120 in advance. The current collector 410 is assembled to the sealing plate 120 via the current collector 440. The current collector 410 is joined to the current collector 440 at a joint 440A. The joint 440A can be formed by, for example, laser welding. As a result of the above, the current collector 410 is electrically connected to the negative electrode terminal 301 (S5).

[0103] 16, the negative electrode tab group 220 and the negative electrode tab group 270 are folded in the thickness direction of the first electrode body 201 and the second electrode body 202 (a direction perpendicular to the DR1 direction in FIGS. 14 and 15), and the first electrode body 201 and the second electrode body 202 are overlapped (S6). Here, the negative electrode tab group 220 and the negative electrode tab group 270 are folded so that their leading ends face each other.

[0104] When the first electrode body 201 and the second electrode body 202 are "superimposed", the first electrode body 201 and the second electrode body 202 may be directly superimposed on each other, or another member may be disposed between the first electrode body 201 and the second electrode body 202. Furthermore, the first electrode body 201 and the second electrode body 202 may or may not be fixed by tape or the like.

[0105] The above-mentioned spacer and insulating sheet are assembled to the electrode assembly 200 (S7). However, the spacer and insulating sheet are not necessarily required components in the present technology. The insulating sheet does not necessarily need to cover the entire surface of the electrode assembly 200. When the electrode assembly 200 is covered with the insulating sheet, it is preferable that the spacer is also covered with the insulating sheet.

[0106] As shown in FIG. 17, the first electrode body 201 and the second electrode body 202 stacked on top of each other are inserted into the case body 110 with the current collector 430 side at the top (S8).

[0107] When inserting the electrode assembly 200 into the case body 110, the electrode assembly 200 may be pulled from the positive electrode side or pushed from the negative electrode side. When the electrode assembly 200 is pushed from the negative electrode side, the negative electrode tab group 220 and the negative electrode tab group 270 can be bent at the same time.

[0108] As shown in FIG. 18 , after the electrode assembly 200 is inserted into the case body 110, the current collector 430 joined to the positive electrode tab group 250 and the positive electrode tab group 280 is assembled to the sealing plate 130. A positive electrode current collecting part 420 and a positive electrode terminal 302 are attached to the sealing plate 130 in advance. The current collector 430 is assembled to the sealing plate 130 via the positive electrode current collecting part 420. The current collector 410 is joined to the positive electrode current collecting part 420 in a joining region 420A. The joining region 420A can be formed by, for example, laser welding or the like. As a result of the above, the current collector 430 is electrically connected to the positive electrode terminal 302 (S9).

[0109] The current collectors 431, 432 joined to the positive electrode tab groups 250, 280 are electrically connected to the positive electrode terminal 302, and then bent together with the positive electrode tab groups 250, 280 into the shape shown in Fig. 12. It is preferable that the current collectors 431, 432 are bent simultaneously, but the current collectors 431, 432 may be bent sequentially.

[0110] 19, sealing plates 120 and 130 are joined to case body 110 (S10). Sealing plate 120 seals opening 113 of case body 110, and sealing plate 130 seals opening 114 of case body 110. In this way, first electrode body 201 and second electrode body 202 are housed in case 100.

[0111] After the above steps are completed, inspections such as a leak inspection are performed (S11). After the leak inspection, the secondary battery 1 is dried to remove moisture from inside the case 100. Then, electrolyte is injected into the inside of the case 100 through the liquid injection hole 134. When injecting the electrolyte, the case 100 is tilted with the sealing plate 130 facing up and the sealing plate 120 facing down, and the electrolyte is injected into the inside of the case 100 through the liquid injection hole 134 in the sealing plate 130. Then, degassing charging is performed. The liquid injection hole 134 may be temporarily sealed during degassing charging. The liquid injection hole 134 is then sealed, and the secondary battery 1 is completed.

[0112] The order of the electrode assembly 200 insertion step and the current collector connection step is not limited to the above example. For example, the order of the current collectors 410, 431, and 432 joining steps (S2 to S4) can be changed as appropriate.

[0113] In this embodiment, an example has been described in which, after the step (S8) of inserting the first electrode body 201 and the second electrode body 202 into the case 100 body is completed, the current collector 430 is electrically connected (S9) to the positive electrode terminal 302 with the first electrode body 201 and the second electrode body 202 completely positioned within the case body 110; however, the positive electrode terminal 302 and the electrode body 200 may also be electrically connected (S9) before the step (S8) of inserting the electrode body 200 into the case body 110 is completely completed (during the insertion step).

[0114] In this embodiment, an example has been described in which the current collectors 431, 432 are bent after the step (S9) of electrically connecting the current collectors 431, 432 to the positive electrode terminal 302, but the current collectors 431, 432 may be deformed before the step (S9) of electrically connecting the current collectors 431, 432 to the positive electrode terminal 302.

[0115] (Configuration of metal plate 4300) As shown in FIG. 20, the metal plate 4300 includes a first region 430A joined to the positive electrode tab groups 250, 280, a second region 430B joined to the positive electrode current collecting portion 420, and a connection portion 430C, a hole portion 430D, and a notch 430E provided between the first region 430A and the second region 430B.

[0116] When forming the current collector 430, the plurality of metal plates 4300 may be bonded to one another in the first region 430A and the second region 430B (first portion). The bonding of the plurality of metal plates 4300 is preferably performed by, for example, ultrasonic bonding, diffusion bonding, or the like. In the case of diffusion bonding, the metal plates 4300 are preferably bonded to one another by applying pressure to the stacked metal plates 4300 while being heated at a temperature lower than the melting point of the metal plates 4300. The bonding of the plurality of metal plates 4300 to one another is performed before other conductive members (positive electrode tab groups 250, 280 and positive electrode current collecting portion 420) are bonded to the first region 430A and the second region 430B.

[0117] It is preferable that the connection portion 430C (second portion) of the current collector 430 includes a region where the multiple metal plates 4300 are not joined to one another. This makes it easier to bend the current collector 430 at the connection portion 430C. It is preferable that the bent portion of the metal plate 4300 includes a region where the multiple metal plates 4300 are not joined to one another. It is also preferable that the multiple metal plates 4300 are not joined to one another over the entire bent portion of the metal plate 4300. There may also be portions in regions other than the connection portion 430C (the first region 430A and the second region 430B) where the multiple metal plates 4300 are not joined to one another.

[0118] In regions where the metal plates 4300 are not joined to each other, the metal plates 4300 may abut against each other. Also, a small gap may exist between the metal plates 4300. In regions where the metal plates 4300 are not joined to each other, the metal plates 4300 are not welded to each other, and a clear boundary exists between each metal plate 4300. For example, a natural oxide film may exist on the surface of each metal plate 4300.

[0119] By providing hole 430D and notch 430E in connection portion 430C, the cross-sectional area of ​​connection portion 430C can be reduced, making it easier to bend current collector 430 at connection portion 430C. Connection portion 430C can also function as a fuse portion.

[0120] The metal plate 4300 can be made of, for example, aluminum or an aluminum alloy. The metal plate 4300 can also be made of copper, a copper alloy, nickel, a nickel alloy, iron, or an iron alloy. The thickness of one metal plate 4300 is preferably greater than the thickness of one positive electrode tab 260, and is preferably about three times or more (more preferably about five times or more) the thickness of one positive electrode tab 260. The thickness of one metal plate 4300 is preferably, for example, 0.05 mm or more, and more preferably 0.08 mm or more. It is also preferably 0.5 mm or less, more preferably 0.3 mm or less, and even more preferably 0.2 mm or less. The thickness of one metal plate 4300 is preferably ½ or less, and more preferably ⅕ or less, of the thickness of the positive electrode current collecting part 420. The same can be applied when a current collector in which metal plates are stacked is used on the negative electrode side.

[0121] The number of metal plates 4300 constituting the current collectors 431, 432 can be changed as appropriate. The total thickness (first thickness: T1) of the current collectors 431, 432 is preferably greater than the total thickness (second thickness: T2) of the positive electrode tab groups 250, 280 joined to the current collectors 431, 432. More preferably, T1 / T2 is approximately 1.5 or greater, and even more preferably, T1 / T2 is approximately 2 or greater.

[0122] The "total thickness of the current collectors 431, 432" refers to the total thickness of the portions of the current collectors 431, 432 where there are no irregularities. The "total thickness of the positive electrode tab groups 250, 280" refers to the total thickness of the portions where the positive electrode tab groups 250, 280 are gathered together and other than the positive electrode bonding region 200R.

[0123] In the present embodiment, by using current collector 430 formed of a laminate of multiple metal plates 4300, it is possible to provide current collector 430 that is easy to deform stably while suppressing an increase in resistance. As a result, positive electrode current collector 400B can be made smaller, and the energy density of secondary battery 1 can be improved.

[0124] In a state in which the first electrode body 201 and the second electrode body 202 are disposed in the case body 110, the current collector 430 connected to the positive electrode tab groups 250, 280 is electrically connected to the positive electrode terminal 302, and then the current collector 430 is folded, a secondary battery 1 with high energy density and high reliability can be manufactured more stably and efficiently by configuring the current collector 430 as a laminate of multiple metal plates 4300. In this case, it is particularly preferable that the negative electrode tab groups 220, 270 are configured so that they are each joined to one surface of the current collector 410 in a curved state, as shown in FIG. 11 . Note that the positive and negative electrode sides may be configured in reverse.

[0125] In the present embodiment, in the step (S2) of joining the current collector 410 to the negative electrode tab groups 220, 270, the first electrode body 201 is placed on one side of the current collector 410, and the second electrode body 202 is placed on the other side of the current collector 410, as shown in FIG. 14 , the negative electrode tab groups 220, 270 are joined to the current collector 410 in this state. In this state, the main bodies of the first electrode body 201 and the second electrode body 202 are positioned relatively far from the current collector 410, which provides many options for joining techniques and also allows the negative electrode tab groups 220, 270 to be made relatively short. By shortening the negative electrode tab groups 220, 270, the internal space of the case 100 can be effectively utilized, further improving the energy density of the secondary battery 1.

[0126] Furthermore, in the present embodiment, current collector 431 and current collector 432 are curved in the same direction when first electrode body 201 and second electrode body 202 are stacked together, so it is possible to arrange current collector 432 by efficiently utilizing the space on the inner periphery of the curved portion of current collector 431. As a result, positive electrode collector 400B can be further miniaturized, and the energy density of secondary battery 1 can be improved.

[0127] Furthermore, in the present embodiment, by joining the current collectors 431, 432 to the positive electrode tab groups 250, 280 in advance (S3, S4), it is possible to protect the positive electrode tab groups 250, 280 and suppress damage thereto (deformation, breakage, etc.) in the subsequent step (S6) of stacking the first electrode body 201 and the second electrode body 202 and the step (S8) of inserting the first electrode body 201 and the second electrode body 202 into the case body 110. As a result, it is possible to provide a highly reliable secondary battery 1.

[0128] (supplement) In this embodiment, as shown in FIG. 12, when the first electrode body 201 and the second electrode body 202 are stacked together, the current collectors 431 and 432 are bent so as to curve in the same direction, but the current collectors 431 and 432 may also be bent so as to curve in opposite directions.

[0129] In the present embodiment, an example has been described in which the current collectors 431, 432 are joined to the positive electrode tab groups 250, 280 from the same side (both are on the left side in the figure with respect to the positive electrode tab groups 250, 280) in the state shown in Fig. 12. In this case, in the state before the first electrode body 201 and the second electrode body 202 are superimposed (Figs. 14 and 15), the current collectors 431, 432 are joined to the positive electrode tab groups 250, 280 from different sides.

[0130] However, the scope of the present technology is not limited to the above, and the current collectors 431, 432 may be joined to the positive electrode tab groups 250, 280 from different sides in the state shown in Fig. 12. In this case, in the state before the first electrode body 201 and the second electrode body 202 are superimposed (Figs. 14 and 15), the current collectors 431, 432 are joined to the positive electrode tab groups 250, 280 from the same side.

[0131] In the present embodiment, an example has been described in which a folded current collector 430 made of a metal plate laminate is used on the positive electrode side (FIG. 12) and a current collector 410 made of a single metal member is used on the negative electrode side (FIG. 11), but the scope of the present technology is not limited to this, and the positive electrode side and the negative electrode side may have opposite structures to the above. Also, instead of a single member, a current collector 410 made of an integrated plurality of members may be used.

[0132] (Embodiment 2: Configuration of current collector) 21 to 23, the configuration of current collectors 431 and 432 will be described. Current collector 431 (first current collector) is connected to positive electrode tab group 250, and current collector 432 (second current collector) is connected to positive electrode tab group 280. Current collector 431 and current collector 432 have the same configuration, so the following description will focus on the configuration of current collector 431.

[0133] Current collector 431 is formed by laminating a plurality of, for example, about 15 metal plates 4300 each having a thickness of about 0.1 mm (the number of plates is omitted in the drawing). Current collector 431 includes a first region 431A connected to positive electrode tab group 250 and a second region 431B connected to positive electrode current collecting portion 420 as another conductive member.

[0134] The width W1 of the first region 431A and the second region 431B is set to be the same.

[0135] In current collector 431, first fuse portion 431C and second fuse portion 431D are provided as connection portions that melt when a current equal to or greater than a predetermined value flows between first region 431A and second region 431B. Width W2 of first fuse portion 431C and second fuse portion 431D is set smaller than width W1 of first region 431A and second region 431B.

[0136] A first hole 431E is provided between the first fuse portion 431C and the second fuse portion 431D. A first U-shaped cutout 431F recessed inward is provided on both ends of the first fuse portion 431C and the second fuse portion 431D. The shape of the first hole 431E is not limited to an ellipse and may be rectangular, circular, or the like. The shape of the first cutout 431F is also not limited to a U-shape.

[0137] When viewed unfolded as shown in Figure 24, the ratio of "area of ​​the region where the metal plates are joined together in the portion that will become the bending portion" to "area of ​​the portion that will become the bending portion (excluding the area of ​​first cutout 431F and first hole portion 431E)" is preferably 0.5 or less, more preferably 0.3 or less, and most preferably 0.1 or less.

[0138] It is most preferable that the metal plates are not joined together at the portion that becomes the bent portion. Here, the portion that becomes the bent portion is the portion that is bent and curved when current collector 431 is bent. For example, in FIG. 24, this is the portion located between two first cutouts 431F.

[0139] (bonded state) Next, the bonding state of the current collector 431 will be described with reference to FIGS.

[0140] Before being connected to the tab group of the electrode body 200, the second region 431B connected to the positive electrode current collecting portion 420 of the current collector 431 may be previously joined by ultrasonic bonding, diffusion bonding, or the like, and the first joining region 431R is provided (first joining step). When joining is performed using ultrasonic bonding, marks (multiple recesses) of the anvil or horn used during ultrasonic bonding, which will be described later, are left on the surface of the first joining region 431R. In addition to ultrasonic bonding and diffusion bonding, the first joining region 431R of the second region 431B may also be formed by irradiation of high-energy rays, such as laser welding.

[0141] 26 and 27, first region 431A, first fuse portion 431C, and second fuse portion 431D are not joined together in advance, which makes it easier to bend current collector 431 in this region, particularly since first fuse portion 431C and second fuse portion 431D are not joined together.

[0142] In the present embodiment, first region 431A and second region 431B are provided to have the same area, but the area of ​​the second region may be larger than the area of ​​the first region, as shown in current collector 430 of Embodiment 1. For example, the area of ​​the second region may be 1.5 times or more larger than the area of ​​the first region (the embodiment shown in FIG. 20).

[0143] 21 to 27, the description has been given of current collector 431, but the same applies to current collector 432. Metal plate 4300, first region 431A, second region 431B, first fuse portion 431C, second fuse portion 431D, first hole portion 431E, first cutout 4300, and first joint region 431R described for current collector 431 correspond to metal plate 4300, third region 432A, fourth region 432B, third fuse portion 432C, fourth fuse portion 432D, second hole portion 432E, second cutout 432F, and second joint region 432R, respectively, in current collector 432 (see FIG. 24).

[0144] (Connection to positive electrode tab group 250, 280 / positive electrode current collecting portion 420) Next, with reference to FIGS. 28 to 32, the connection of current collectors 431, 432 to positive electrode tab groups 250, 280 and positive electrode current collecting portion 420 will be described (second connection step).

[0145] As shown in Fig. 28, in an unfolded planar state, current collectors 431 and 432 are stacked in the same position. As shown in Fig. 28 to Fig. 30, second region 431B of current collector 431 (first current collector) and fourth region 432B of current collector 432 (second current collector) are stacked on top of positive electrode current collector 420, and first bonding region 431R and second bonding region 432R are bonded to positive electrode current collector 420 by laser welding or the like to provide bonding region 420A (second connection step).

[0146] In the second region 431B, even in a region not joined to the positive electrode current collecting portion 420, the metal plates 4300 of the second region 431B are joined together at the first joining region 431R. In this case, the area of ​​the first joining region 431R where the metal plates 4300 are joined together (the area when viewed along the stacking direction of the metal plates 4300) is preferably larger than the area of ​​the joining region 420A. Preferably, it is at least two times, more preferably at least five times, and even more preferably at least ten times. The same applies to the relationship between the joining region 420A and the second joining region 432R.

[0147] When the first junction region 431R and the second junction region 432R are arranged to overlap on the positive electrode current collecting part 420, the first junction region 431R and the second junction region 432R are arranged so that their tip portions ST are aligned in the drawing, but the tip of the first junction region 431R may be arranged to protrude further than the tip of the second junction region 432R. This allows the first junction region 431R to be confirmed in a plan view.

[0148] On the other hand, as shown in Figures 28 and 31, the positive electrode tab group 250 is joined to one surface of the first region 431A of the current collector 431 (first current collector) by ultrasonic bonding or the like to form the positive electrode joining region 200R, and the positive electrode tab group 280 is joined to one surface of the third region 432A of the current collector 432 (second current collector) by ultrasonic bonding or the like to form the positive electrode joining region 200R (the state shown in Figure 12).

[0149] As shown in FIG. 32, a positive electrode bonding region 200R with the positive electrode tab group 250 may be formed on one surface of the first region 431A of the current collector 431, and a positive electrode bonding region 200R with the positive electrode tab group 280 may be formed on the other surface of the third region 432A of the current collector 432.

[0150] 28 again, the current collector 431 may include a region in the first region 431A where the metal plates of the first region 431A are joined together at a position where the positive electrode tab group 250 and the joined positive electrode joining region 200R do not overlap in a plan view, in order to stabilize the stacked state of the current collector 431. The same applies to the current collector 432.

[0151] 12, when assembled into secondary battery 1, the region between first region 431A and second region 431B of current collector 431 (first fuse portion 431C and second fuse portion 431D) is bent, so that first region 431A and second region 431B of current collector 431 face each other. Similarly, the region between third region 432A and fourth region 432B of current collector 432 (third fuse portion 432C and fourth fuse portion 432D) is bent, so that third region 432A and fourth region 432B of current collector 432 face each other.

[0152] The folded regions of the current collectors 431, 432 include regions where the metal plates are not previously bonded to each other. As a result, the current collectors are easily bent while maintaining a certain level of cross-sectional area. As a result, the bending of the positive electrode tab group 250 and the positive electrode tab group 280 is minimized, making it possible to prevent unintended folding or bending of the tab groups. Furthermore, it is possible to reduce the space required for current collection. Although not essential, it is more preferable that the folded regions be narrower than the other regions.

[0153] As a result, for example, it is possible to provide a secondary battery with high volumetric energy density while maintaining excellent output characteristics (or suppressing heat generation).

[0154] (Embodiment 3) Next, other configurations of the current collector will be described with reference to Fig. 33 to Fig. 42. In the above-described embodiment, the first current collector and the second current collector are provided so as to have the same shape and to overlap each other, but in this embodiment, a configuration is shown in which the second region of the first current collector and the fourth region of the second current collector are joined to other conductive members in a positional relationship in which they do not face each other.

[0155] 33, a first region 531A of a current collector 531 (first current collector) is joined to the positive electrode tab group 250 by a positive electrode joining region 200R, and a second region 531B is joined to the positive electrode current collecting portion 420 by a joining region 420A. A third region 532A of a current collector 532 (second current collector) is joined to the positive electrode tab group 280 by a positive electrode joining region 200R, and a fourth region 532B is joined to the positive electrode current collecting portion 420 by a joining region 420A. The joining state and the like are the same as in the second embodiment.

[0156] 34 to 36, the basic configuration of current collector 531 is similar to that of current collector 431 described in embodiment 2, but the shape of the developed state is different. Like current collector 431, current collector 531 is provided with first region 531A, second region 531B, first fuse portion 531C, second fuse portion 531D, first hole portion 531E, first cutout 531F, and first joint region 531R.

[0157] This current collector 531 is provided so that the area of ​​the first region 531A is larger than the area of ​​the second region 531B, and in the drawing, the left end of the first region 531A is aligned with the left end of the second region 531B.

[0158] On the other hand, as shown in FIG. 38, current collector 532 is provided with third region 532A, fourth region 532B, third fuse portion 532C, fourth fuse portion 532D, second hole portion 532E, second cutout 532F, and second bonding region 532R.

[0159] Current collector 531 and current collector 532 have a symmetrical shape that becomes the same when rotated 180 degrees about an axis perpendicular to the width direction in the figure, and when they are overlapped, second region 531B of current collector 531 and fourth region 532B of current collector 532 are positioned so that they do not overlap.

[0160] In current collector 531, when first region 531A has a width W11 and second region 531B has a width W21, the dimensional relationship W21≦0.5×W11 should be satisfied.

[0161] (Connection to positive electrode tab group 250, 280 / positive electrode current collecting portion 420) 39 to 42, a description will be given of connection of current collector 531 and current collector 532 to positive electrode tab groups 250, 280 and positive electrode current collecting part 420. When current collector 531 and current collector 532 having this configuration are used, second region 531B of current collector 531 and fourth region 532B of current collector 532 are arranged so as to be shifted without overlapping, and are each joined to positive electrode current collecting part 420 by laser welding or the like to provide joining region 420A.

[0162] Regarding the connection to the positive electrode tab groups 250, 280, as shown in Figure 42 (similar to Figure 31), the positive electrode tab group 250 of the first electrode body 201 is joined to one surface of the first region 531A of the current collector 531 by ultrasonic bonding or the like to form a positive electrode joining region 200R, and the positive electrode tab group 280 of the second electrode body 202 is joined to one surface of the third region 532A of the current collector 532 by ultrasonic bonding or the like to form a positive electrode joining region 200R.

[0163] Similar to the connection structure shown in FIG. 32, a positive electrode joining region 200R with the positive electrode tab group 250 may be formed on one surface of the first region 531A of the current collector 531, and a positive electrode joining region 200R with the positive electrode tab group 280 may be formed on the other surface of the third region 532A of the current collector 532.

[0164] In this way, by disposing the second region 531B of the current collector 531 and the fourth region 532B of the current collector 532 so that they do not overlap but are offset, the two positive electrode bonding regions 200R are dispersed and welded, which makes welding easier and improves workability. Furthermore, since welding is easier, a bonded portion can be formed more stably, which reduces resistance and effectively suppresses heat generation during charging and discharging. As a result, for example, it is possible to provide a secondary battery with a high volumetric energy density while maintaining excellent output characteristics (or suppressing heat generation).

[0165] (Fourth embodiment) Other current collector configurations that can be employed for the first current collector and the second current collector will be described with reference to FIGS.

[0166] The basic configurations of the first to fifth modified current collectors are the same as current collector 431 described in embodiment 2, so only the planar forms will be described below.

[0167] 43, deformed current collector 631 includes first region 631A and second region 631B, which are connected at both ends by first fuse portion 631C and second fuse portion 631D. Providing first fuse portion 631C and second fuse portion 631D at both ends in this manner provides a current collector that is resistant to torsion. Dimensional control is easier than with deformed current collector 831, which will be described later.

[0168] 44, deformed current collector 731 includes first region 731A and second region 731B, which are connected at the center by first fuse portion 731C. With this configuration, dimensional control is easier than with deformed current collector 631.

[0169] 45, modified current collector 831 includes first region 831A and second region 831B, which are connected at both ends by first fuse portion 831C and second fuse portion 831D and connected at the center by third fuse portion 831E. With this configuration, a current collector that is resistant to torsion is obtained.

[0170] As shown in FIG. 46, the deformed current collector 931 includes a first region 931A and a second region 931B, and the first region 931A and the second region 931B are connected by a first fuse portion 931C at offset positions. By offsetting the first region 931A and the second region 931B in this manner, it is possible to design an arrangement that effectively utilizes the internal space of the case body 110. Furthermore, as shown in FIG. 48, when the deformed current collector 931 is used, it is possible to distance the electrical connection position from the electrolyte solution DW accumulated inside the case body 110. As a result, the reliability of the secondary battery can be improved.

[0171] As shown in Fig. 47, deformed current collector 1031 includes first region 1031A and second region 1031B, and first region 1031A and second region 1031B are offset from each other and connected by first fuse portion 1031C and second fuse portion 1031D. By offsetting first region 1031A and second region 1031B in this way, it is possible to obtain the same effects as deformed current collector 931, as explained in Fig. 48. Furthermore, because there are two fuse portions, it is possible to obtain a current collector that is resistant to twisting.

[0172] (Embodiment 5) The first bonding region between the metal plates that make up the current collector will be described with reference to Figures 49 and 50. This applies to any of the current collectors (first current collector, second current collector) described in each of the above-mentioned embodiments, but here we will describe first bonding region 631R formed in second region 631B of modified current collector 631 described in Figure 43.

[0173] When observing the structure of the final product, the following pressing marks can be seen in areas other than the area where the bonding area 420A is provided.

[0174] 49, when metal plates 4300 are stacked and ultrasonically bonded, vibration and load are applied to first bonding region 631R formed in second region 631B of deformed current collector 631 while it is sandwiched between an anvil and a horn used during ultrasonic bonding. The anvil (receiving jig) is a jig that positions and fixes second region 631B to prevent the vibration energy from escaping, and the horn resonates with the vibration of the vibrator to apply vibration and load to second region 631B.

[0175] In this case, the different patterns of protrusions and recesses (indentations from the anvil and horn) formed on the front and back of second region 631B make it easy to determine which side is the front and which side is the back, and a specific side can be reliably brought into contact with positive electrode current collecting portion 420. In FIG. 49, it can be determined that indentations A1 are multiple indentations from the horn (multiple first recesses), and indentations B1 are multiple indentations from the anvil (multiple second recesses). This makes it easy to determine which side is the front and which side is the back of second region 631B, improving the productivity of secondary battery 1.

[0176] Furthermore, the differences in the shapes of the indentation marks A1 and B1 include (A) the difference in the diameter of the indentation marks (first recesses) and (B) the difference in the arrangement of the indentation marks (second recesses), which causes a localized high-load area HP (the area surrounded by HP in the figure) to occur between the front and back of the second region 631B, thereby enabling the bonding strength between the metal plates to be structured.

[0177] Furthermore, by abutting the surface of the second region 631B having a large number of flat portions (the region indicated by FP in the figure) with the positive electrode current collecting portion 420 and providing a laser joint between the second region 631B and the positive electrode current collecting portion 420, the joint area can be increased and the joint strength can be improved.

[0178] Furthermore, in the laser irradiation area of ​​the second region 631B, the surface that will have a larger contact area when abutted against the positive electrode current collecting portion 420 is abutted against the positive electrode current collecting portion 420, and laser irradiation L is performed from the opposite surface, thereby improving the joint strength by through-hole welding.

[0179] 50, when two metal plate laminates, the second region 631B of the deformed current collector 631 (first current collector) and the fourth region 632B of the deformed current collector 632 (second current collector), are laminated, the respective ultrasonic joints are overlapped and laser welded to the positive electrode current collector 420. In this case, it is preferable that the press marks B1 and A2 formed on the front and back surfaces of each current collector mesh with each other, increasing the contact area between the second region 631B and the fourth region 632B when pressed from above.

[0180] If the current collector placed on the upper surface is the first current collector and the one placed on the lower surface that comes into contact with another conductive member is the second current collector, it is desirable that the convex portion of the surface of the first current collector facing the second current collector enters the concave portion of the surface of the second current collector facing the first current collector, and when the first current collector is pressed from the opposite direction to the surface on which the second current collector is located, the area of ​​contact between the first current collector and the second current collector on the surface parallel to the conductive member becomes large.

[0181] The ultrasonic bonding marks provided on the first current collector and the second current collector may be the same or different.

[0182] Note that multiple pressure marks (depressions) generated when clamped between an anvil and a horn during ultrasonic bonding may be formed on the surfaces of positive electrode tab groups 250, 280. In this case, when first depressions are formed as multiple pressure marks in a portion of first region 431A of current collector 431 that is not bonded to current collector 431, and second depressions are formed as multiple pressure marks on the surface of positive electrode tab group 250, the depth of the first depressions is preferably smaller than the depth of the second depressions. The area of ​​one first depression in a plan view is preferably smaller than the area of ​​one second depression. The same applies to the area between third region 432A of current collector 432 and positive electrode tab group 280.

[0183] When observing the structure of the final product, the above-mentioned configuration can be confirmed in the region other than the region where the positive electrode bonding region 200R is provided. With this configuration, it is possible to obtain the same effects as those described in Fig. 49 and Fig. 50.

[0184] (Other preferred forms) 51 and 52, a preferred embodiment of the connection of current collectors 431, 432 to positive electrode tab groups 250, 280 and positive electrode current collecting portion 420, which was described with reference to FIG. 28, will be described.

[0185] In the developed view of Figure 51, if the shortest distance between the bonding area 420A and the positive electrode bonding area 200R is distance L1, and the shortest distance between the root 200t of the positive electrode tab group 250 of the electrode body 200 and the positive electrode bonding area 200R is distance L2, it is preferable that L1≧L2, more preferably L1≧1.1×L2, and more preferably L1≧1.2×L2.

[0186] For example, as shown in the developed view of FIG. 52, when the bonding region 420A and the positive electrode bonding region 200R are provided misaligned, the shortest distance between the corner of the bonding region 420A and the corner of the positive electrode bonding region 200R is the distance L1, as shown in the figure.

[0187] Regarding the distance L1, if there is a misalignment among multiple metal plates, the position closest to the positive electrode bonding region 200R is used as the reference, and regarding the distance L2, if there is a misalignment among multiple tabs, the position closest to the base 200t of the positive electrode tab group 250 is used as the reference.

[0188] (About the length of the metal plate 4300) The lengths of the current collector 431 (first current collector) and the metal plate 4300 used in the second region 431B and current collector 432 (second current collector) will be described with reference to FIGS.

[0189] As shown in Figure 53, it is preferable that the length of the metal plate located on the outermost side (the lowest position in Figure 53) when folded is longer than the length of metal plate 4300 located on the inner side when folded.

[0190] More specifically, in the case of current collector 431 (see FIG. 21), it is preferable that when folded, metal plate 4300 located on the outermost side is the longest in the length from first region 431A to second region 431B, and that metal plates 4300 located closer to the inside are shorter, with the innermost metal plate being the shortest. However, some of the metal plates may be the same length, or the order of the lengths may be reversed.

[0191] 54, when the stacked metal plates 4300 are folded, the current collectors can be easily folded, improving the productivity of the secondary battery. Furthermore, the current collectors can be efficiently housed inside the case body 110, improving the energy density of the secondary battery.

[0192] (Arrangement of the first current collector, the first tab group, the second current collector, and the second tab group in the stacking direction) With reference to Figures 55 and 56, the arrangement in the stacking direction of current collector 431 (first current collector), positive electrode tab group 250 (first tab group), current collector 432 (second current collector), and positive electrode tab group 280 (second tab group) will be described.

[0193] Either the configuration shown in FIG. 55 or FIG. 56 can be adopted, but when either configuration is adopted, the following effects can be obtained.

[0194] The configuration shown in Figure 55 shows a configuration in which a current collector 431 (first current collector), a positive electrode tab group 250 (first tab group), a current collector 432 (second current collector), and a positive electrode tab group 280 (second tab group) are connected in a line.

[0195] This configuration makes it easier to shorten the length of the tab group and to increase the proportion of the first current collector and the second current collector in the conductive path, which reduces foil tearing in the tab group and allows for the production of a more reliable secondary battery.

[0196] The configuration shown in Figure 56 shows a configuration in which a current collector 431 (first current collector), a positive electrode tab group 250 (first tab group), a positive electrode tab group 280 (second tab group), and a current collector 432 (second current collector) are connected in a line. The total length of the first current collector and the first tab group, and the total length of the second current collector and the second tab group, can be shortened, allowing the current collectors and the tab groups to be accommodated in a space-saving secondary battery. As a result, it is possible to manufacture a secondary battery with higher energy density.

[0197] (More preferred forms) 55, in current collector 431, in the region surrounded by A in the figure, it is preferable that a chamfer or a rounded portion is formed on the end (corner) facing positive electrode tab group 250. This configuration can prevent damage to positive electrode tab group 250. The same applies to the region surrounded by B in the figure in current collector 432.

[0198] Although the above embodiment has been described taking the positive electrode side as an example, the same configuration can also be applied to the negative electrode side.

[0199] 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]

[0200] 1 secondary battery, 100 case, 110 case body, 111 first side portion, 112, 112A, 112B second side portion, 113, 114 opening, 115, 410A, 431A, 440A joint portion, 120, 130 sealing plate, 134 liquid hole, 150 gas release valve, 200 electrode body, 200R positive electrode joint region, 200t base, 201 first electrode body, 202 second electrode body, 210 negative electrode, 211 negative electrode core body, 212 negative electrode active material layer, 220, 270 negative electrode tab group, 221, 271 curved portion, 230 negative electrode tab, 240 positive electrode, 241 positive electrode core body, 242 positive electrode active material layer, 243 positive electrode protective layer, 250, 280 Positive electrode tab group, 260 Positive electrode tab, 300 Electrode terminal, 301 Negative electrode terminal, 302 Positive electrode terminal, 303, 304 Plate-shaped member, 400, 410, 430, 431, 432, 440, 531, 532 Current collector, 400A Negative electrode current collector, 400B Positive electrode current collector, 420 Positive electrode current collector, 420A Bonding region, 430A, 431A, 531A, 631A, 731A, 831A, 931A, 1031A First region, 430B, 431B, 531B, 631B, 731B, 831B, 931B, 1031B Second region, 430C Connection portion, 430D hole portion, 431C, 531C, 631C, 731C, 831C, 931C, 1031C; first fuse portion, 431D, 531D, 631D, 831D, 1031D; second fuse portion, 431E, 531E; first hole portion, 431R, 531R, 631R; first bonding region, 432A, 532A; third region, 432B, 532B, 632B; fourth region, 432C, 532C, 831E; third fuse portion, 432D, 532D; fourth fuse portion, 432E, 532E; second hole portion, 432R, 532R; second bonding region, 510, 520, 530, 540; insulating member, 631, 632, 731, 831, 931, 1031 Deformed current collector, 4300 metal plate.

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; a first tab group in which a plurality of first electrode tabs electrically connected to the first electrodes are stacked; a first current collector connected to the first group of tabs; Equipped with the first current collector is a first laminate in which a plurality of metal plates are laminated, the first current collector includes a first region and a second region; the first tab group is joined to the first region; Another conductive member is joined to the second region, The first current collector is bent between the first region and the second region. Secondary battery.

2. a second tab group in which a plurality of second electrode tabs electrically connected to the first electrodes are stacked; a second current collector connected to the second group of tabs; the second current collector is a second laminate in which a plurality of metal plates are laminated, the second current collector includes a third region and a fourth region; the second tab group is joined to the third region; Another conductive member is joined to the fourth region, the second current collector is bent between the third region and the fourth region; The secondary battery according to claim 1 .

3. the first current collector and the second current collector are stacked and joined to one of the other conductive members; The secondary battery according to claim 2 .

4. the other conductive member, the first current collector, and the second current collector are stacked in this order, The tip of the first current collector protrudes beyond the tip of the second current collector. The secondary battery according to claim 3 .

5. a first fuse portion is provided on the first current collector; a second fuse portion is provided on the second current collector; The first fuse portion and the second fuse portion are disposed apart from each other. The secondary battery according to claim 2 .

6. the second region of the first current collector and the fourth region of the second current collector are joined to another conductive member in a positional relationship in which they do not face each other; The secondary battery according to claim 2 .

7. The first current collector is In the first region, a region where the plurality of metal plates are joined to each other in a region not joined to the first tab group is included. The secondary battery according to claim 1 .

8. a plurality of first recesses are formed in a portion of the first region of the first current collector that is not joined to the first tab group; a plurality of second recesses are formed on the surface of the first tab group; The depth of the first recess is smaller than the depth of the second recess. The secondary battery according to claim 7 .

9. a plurality of first recesses are formed in a portion of the first region of the first current collector that is not joined to the first tab group; a plurality of second recesses on the surface of the first group of tabs; an area of ​​one of the first recesses is smaller than an area of ​​one of the second recesses; The secondary battery according to claim 7 .

10. The first current collector is the second region includes a region where the plurality of metal plates are joined together in a region not joined to the other conductive member, The secondary battery according to claim 1 .

11. The first current collector is In the region bent between the first region and the second region, there is a region where the metal plates are not joined to each other. The secondary battery according to claim 1 .

12. In the first current collector, the length of the metal plate arranged on the outermost side in the folded region is longer than the length of the metal plate located inside thereof. The secondary battery according to claim 1 .

13. The length of the first current collector from the joint with the first tab group to the joint with another conductive member is a length longer than the length from the base of the first tab group to the joint between the first current collector and the first tab group; The secondary battery according to claim 1 .

14. 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; a first tab group in which a plurality of first electrode tabs electrically connected to the first electrodes are stacked; a first current collector connected to the first group of tabs; Equipped with the first current collector is a first laminate in which a plurality of metal plates are laminated, the first current collector includes a first region and a second region; the first tab group is joined to the first region; Another conductive member is joined to the second region, The first current collector is bent between the first region and the second region. A method for manufacturing a secondary battery, a first joining step of joining the first tab group to the first region; a bending step of bending the first current collector between the first region and the second region; A method for manufacturing a secondary battery comprising the steps of:

15. a second tab group in which a plurality of second electrode tabs electrically connected to the first electrodes are stacked; a second current collector connected to the second group of tabs; Equipped with the second current collector is a second laminate in which a plurality of metal plates are laminated, the second current collector includes a third region and a fourth region; Another conductive member is joined to the third region, the second tab group is joined to the fourth region; the second current collector is bent between the third region and the fourth region; The method for manufacturing a secondary battery according to claim 14.

16. a step of overlapping the first current collector connected to the first tab group and the second current collector connected to the second tab group and connecting them to the other conductive member, The method for manufacturing a secondary battery according to claim 15.

17. a step of ultrasonically bonding the first tab group to the region where the metal plates are bonded in the first region, The method for manufacturing a secondary battery according to claim 14.

18. a second bonding step of bonding the second region to the other conductive member by irradiating the second region with an energy beam before the bending step; The method for manufacturing a secondary battery according to claim 14.

19. In the second region, the other conductive member is joined to the region where the metal plates are joined. The method for manufacturing a secondary battery according to claim 18.

Images