Secondary batteries

Abstract

According to one embodiment, this secondary battery comprises: an exterior container that has a lid body; an electrode body that has an electrode group, a positive electrode collector tab group, and a negative electrode collector tab group and that is accommodated within the exterior container; a pair of output terminals provided in the lid body; a positive electrode lead that has a first joining section joined to one of the output terminals and a second joining section joined to the positive electrode collector tab group and that electrically connects the positive electrode collector tab group and the output terminal; and a negative electrode lead that has a first joining section joined to the other output terminal and a second joining section joined to the negative electrode collector tab group and that electrically connects the negative electrode collector tab group and the output terminal. The second joining section has a first joining surface and a second joining surface that face one another, one portion of the collector tab group with the same polarity is joined to the first joining surface, and another portion of the collector tab group with the same polarity is joined to the second joining surface and faces the one portion of the collector tab group with the second joining section sandwiched therebetween.

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a secondary battery. [Background technology]

[0002] In recent years, high-energy-density secondary batteries, such as lithium-ion secondary batteries, have been widely used as power sources for electronic devices and electric vehicles. Such secondary batteries are constructed by housing an electrode assembly having a positive electrode and a negative electrode, and a nonaqueous electrolyte, in a rectangular outer container made of aluminum or an aluminum alloy. The lid of the outer container is provided with a positive electrode output terminal, a negative electrode output terminal, a sealing plate, a gas exhaust valve, etc., and the positive electrode output terminal and the negative electrode output terminal are connected to the positive electrode current collecting tab and the negative electrode current collecting tab of the electrode assembly, respectively, via a positive electrode lead and a negative electrode lead provided in the outer container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-84695 [Patent Document 2] International Publication No. 09 / 031442 [Patent Document 3] Special Publication No. 2013-534361 [Patent Document 4] Patent No. 4552237 [Patent Document 5] Patent No. 5157027 Summary of the Invention [Problem to be solved by the invention]

[0004] In the manufacturing process of the secondary battery described above, the current collecting tabs are joined to the leads by methods such as laser welding and ultrasonic bonding. In the manufacturing process, the joining step is a relatively cumbersome operation. In particular, in a secondary battery having multiple electrode assemblies and many current collecting tabs, the joining operation of the current collecting tabs can be even more cumbersome. An object of an embodiment of the present invention is to provide a secondary battery that can simplify the joining work of current collecting tabs. [Means for solving the problem]

[0005] According to an embodiment, the secondary battery includes an outer container having a lid, a positive electrode plate, and a negative electrode plate. It is wound around a winding axis. Electrode group and multiple positive electrode current collecting tabs and negative electrode current collecting tab Includes a first electrode body housed in the outer container and having a first positive electrode current collecting tab group and a first negative electrode current collecting tab group extending in the same direction from one axial end of the electrode group; an electrode group formed by winding the first electrode body housed in the outer container, a positive electrode plate and a negative electrode plate around a winding axis; and a second electrode body housed in the outer container and facing the first electrode body, the second electrode body including a plurality of positive electrode current collecting tabs and negative electrode current collecting tabs extending in the same direction from one axial end of the electrode group; a pair of output terminals provided on the cover body; and a first joint portion joined to one of the output terminals; joined to the first positive electrode current collecting tab group and the second positive electrode current collecting tab group a second joint portion; the first negative electrode current collecting tab group and the second negative electrode current collecting tab group a positive electrode lead electrically connecting the positive electrode lead to the output terminal, and a first joint portion joined to the other output terminal; joined to the first negative electrode current collecting tab group and the second negative electrode current collecting tab group a second joint portion; the first negative electrode current collecting tab group and the second negative electrode current collecting tab group and a negative electrode lead electrically connecting the second joint portion to the output terminal. The second joint portion has a first joint surface and a second joint surface facing each other, The first positive electrode current collector tab group is joined to the first joint surface of the positive electrode lead, the second positive electrode current collector tab group is joined to the second joint surface of the positive electrode lead and faces the first positive electrode current collector tab group across the second joint portion, the first negative electrode current collector tab group is joined to the first joint surface of the negative electrode lead, and the second negative electrode current collector tab group is joined to the second joint surface of the negative electrode lead and faces the first negative electrode current collector tab group across the second joint portion. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing the appearance of a secondary battery according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the secondary battery. [Figure 3] FIG. 3 is a perspective view of the electrode body of the secondary battery, showing the electrode body partially developed. [Figure 4] FIG. 4 is a front view of the secondary battery with the outer container omitted. [Figure 5] 5 is a cross-sectional view of the secondary battery taken along line AA in FIG. [Figure 6] 6 is a cross-sectional view of the secondary battery taken along line BB in FIG. [Figure 7] FIG. 7 is a diagram schematically showing a process of joining an electrode lead and a current collecting tab. [Figure 8] FIG. 8 is a schematic perspective view of the electrode lead and the current collecting tab in a joined state, viewed from different directions. [Figure 9] FIG. 9 is a cross-sectional view schematically showing an electrode lead and a current collecting tab. [Figure 10] FIG. 10 is a perspective view showing a secondary battery according to a second embodiment with an outer container omitted. [Figure 11] 11 is a cross-sectional view of the secondary battery according to the second embodiment, corresponding to FIG. 5. FIG. [Figure 12] 12 is a cross-sectional view of the secondary battery according to the second embodiment, corresponding to FIG. 6. FIG. [Figure 13] FIG. 13 is a perspective view of a branch of a secondary battery according to a third embodiment. [Figure 14] FIG. 14 is a perspective view of an electrode body of the secondary battery according to the third embodiment, showing the electrode body in a partially developed state. [Figure 15] FIG. 15 is a cross-sectional view of the secondary battery according to the third embodiment. [Figure 16] 16 is a cross-sectional view of the secondary battery according to the third embodiment, corresponding to FIG. 6. FIG. [Figure 17] 17A and 17B are diagrams schematically showing a joining step and a joined state of an electrode lead and a current collecting tab in the third embodiment. [Figure 18] FIG. 18 is a diagram schematically showing a process of joining an electrode lead and a current collecting tab of a secondary battery according to a first modified example. [Figure 19] FIG. 19 is a diagram schematically showing an electrode body and an electrode lead of a secondary battery according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. The disclosure is merely an example, and appropriate modifications that are easily conceivable by those skilled in the art while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual embodiment for the sake of clarity, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be appropriately simplified or omitted.

[0008] (First embodiment) The secondary battery according to the first embodiment will be described in detail. FIG. 1 is a perspective view showing the appearance of a secondary battery according to a first embodiment. As shown in the figure, the secondary battery 10 is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion battery, and includes a flat, approximately rectangular outer container 12 and an electrode assembly 30 (described below) housed together with a non-aqueous electrolyte solution in the outer container 12. The outer container 12 is, for example, an outer can (battery case) formed from a metal plate such as aluminum, an aluminum alloy, iron, or stainless steel.

[0009] The outer container 12 has a container body 16 with an open top end, and a rectangular plate-shaped lid 14 that is welded to the container body 16 and closes the opening of the container body 16, forming an airtight interior. The lid 14 is provided with a pair of output terminals, i.e., a positive electrode terminal 20 and a negative electrode terminal 21, a pressure release valve (safety valve) 22, and an injection port. The injection port is sealed with a disk-shaped sealing lid 25. Here, the longitudinal direction of the lid 14 and the container body 16 is defined as X, the width direction of the lid 14 and the container body 16 perpendicular to the longitudinal direction X is defined as Y, and the height direction of the container body 16 is defined as Z.

[0010] FIG. 2 is an exploded perspective view of the secondary battery. As shown in the figure, the container body 16 of the outer container 12 has a rectangular long side wall 16a, a rectangular long side wall 16b that faces the long side wall 16a in parallel and spaced apart relation, a pair of opposing short side walls 16c, and a bottom wall 16d. A rectangular upper opening 17 is defined by the upper edges of the pair of long side walls 16a, 16b and the upper edges of the pair of short side walls 16c. The lid 14 is formed in the shape of a rectangular plate having a size approximately equal to that of the upper opening 17. The outer peripheral edge of the lid 14 is welded to the upper peripheral edge of the container body 16, and the lid 14 is fixed to the container body 16 in a state in which the upper opening 17 is closed.

[0011] Rectangular recesses 26 are formed at both ends of the lid 14 in the longitudinal direction X, and sealing materials made of an insulating material such as synthetic resin or glass, e.g., gaskets 28, are fitted into the recesses 26. Through holes T1, T2 are formed in the center of each gasket 28 and recess 26. The positive terminal 20 integrally includes a substantially rectangular terminal body 20a and a connecting rod 20b extending downward from the bottom surface of the terminal body 20a. The positive terminal 20 is attached to the gasket 28 with the connecting rod 20b inserted through the gasket 28 and the through holes T1 and T2 of the recess 26. Similarly, the negative terminal 21 integrally includes a substantially rectangular terminal body 21a and a connecting rod 21b extending downward from the bottom surface of the terminal body 21a. The negative terminal 21 is attached to the gasket 28 with the connecting rod 21b inserted through the gasket 28 and the through holes T1 and T2 of the recess 26.

[0012] The lid 14 is formed with a safety valve (pressure release valve) 22 that functions as a gas exhaust mechanism, and a non-aqueous electrolyte injection port 29. The safety valve 22 is formed in the center of the lid 14 in the longitudinal direction X, and is provided between the positive electrode terminal 20 and the negative electrode terminal 21. The safety valve 22 is formed by making a portion of the lid 14 approximately half the thickness of the other portions. When gas is generated inside the outer casing 12 due to an abnormal mode of the secondary battery 10 or the like, and the internal pressure of the outer casing 12 rises to or exceeds a predetermined value, the safety valve 22 opens, reducing the internal pressure and preventing malfunctions such as rupture of the outer casing 12. The inlet 29 is formed in the lid 14 between the positive electrode terminal 20 and the safety valve 22. After the non-aqueous electrolyte solution is injected into the outer container 12 through the inlet 29, the inlet 29 is sealed with, for example, a disk-shaped sealing lid 25.

[0013] FIG. 3 is a perspective view showing an example of an electrode body. In one example, a so-called wound-type electrode assembly is used as the electrode assembly 30 housed in the outer container 12. As shown in Fig. 3, the electrode assembly 30 includes, for example, a sheet-like positive electrode plate 70 and a sheet-like negative electrode plate 72, which are spirally wound around a winding axis C with a sheet-like separator 73 interposed therebetween, and further includes an electrode group 74 formed into a flattened rectangle by radially compressing the electrode group 74 so that its cross-sectional shape becomes substantially the same quadrangular shape as the cross-sectional shape of the outer container 12. The separator 73 is disposed on the outermost layer (outermost periphery) of the electrode group 74. The electrode group 74 is held in the wound state by a stop tape (not shown) or the like.

[0014] The positive electrode plate 70 includes, for example, a strip-shaped positive electrode current collector 70a made of metal foil, a positive electrode active material layer 70b formed on at least one surface of the positive electrode current collector 70a, and a plurality of strip-shaped positive electrode current collector tabs 32 extending in a direction parallel to the winding axis C from multiple locations on the long side of the positive electrode current collector 70a. The negative electrode plate 72 has a strip-shaped negative electrode current collector 72a made of metal foil, a negative electrode active material layer 72b formed on at least one surface of the negative electrode current collector 72a, and a plurality of strip-shaped negative electrode current collector tabs 33 extending in a direction parallel to the winding axis C from multiple locations on the long side of the negative electrode current collector 72a.

[0015] The positive electrode current collecting tab 32 and the negative electrode current collecting tab 33 may each be formed by punching a current collector. That is, each current collector and current collecting tab is formed, for example, from a metal foil. The thickness of the metal foil, i.e., the thickness of each current collecting tab, is desirably 5 μm to 50 μm. A thickness of 5 μm or more prevents breakage of the current collector and current collecting tab during manufacturing and enables high current collection efficiency. It also prevents dissolution of the current collecting tab when a large current flows. Furthermore, a thickness of 50 μm or less allows the number of turns constituting the electrode body to be increased while suppressing an increase in the thickness of the electrode body. Preferably, the thickness of the metal foil is 10 μm to 20 μm. The material of the metal foil varies depending on the type of active material used in the positive and negative electrodes, but examples of usable materials include aluminum, aluminum alloys, copper, and copper alloys.

[0016] By overlapping and winding the positive electrode plate 70, separator 73, and negative electrode plate 72, the multiple positive electrode current collector tabs 32 are stacked side by side in the thickness direction of the electrode group 74 to form a positive electrode current collector tab group 32A. Similarly, the multiple negative electrode current collector tabs 33 are stacked side by side in the thickness direction of the electrode group 74 to form a negative electrode current collector tab group 33A. The positive electrode current collector tab group 32A and the negative electrode current collector tab group 33A extend in the same axial direction from one axial end of the electrode group 74 and are positioned apart from each other in the longitudinal direction of the electrode group 74, which is perpendicular to the axial direction.

[0017] 2, the electrode assembly 30 described above is housed in the container body 16 with the winding axis C aligned with the height direction Z of the outer container 12 and with one end face of the electrode group 74, the positive electrode current collector tab group 32A, and the negative electrode current collector tab group 33A facing the lid 14. One end face of the electrode group 74 faces the lid 14 at a predetermined distance. The positive electrode current collector tab group 32A is located at one end of the electrode assembly 30 in the longitudinal direction X and faces the positive electrode terminal 20. The negative electrode current collector tab group 33A is located at the other end of the electrode assembly 30 in the longitudinal direction X and faces the negative electrode terminal 21.

[0018] In this embodiment, the positive electrode current collector tab group 32A is divided into two tab groups in the stacking direction, here, the width direction Y. That is, the positive electrode current collector tab group 32A is divided into a first tab group 32A1 including a plurality of positive electrode current collector tabs 32 and a second tab group 32A2 including a plurality of positive electrode current collector tabs 32. The first tab group 32A1 faces the second tab group 32A2 with a gap in the width direction Y. The extending end portions of the first tab group 32A1 and the extending end portions of the second tab group 32A2 may be collectively held by backup leads bent into a U shape. Similarly, the negative electrode current collector tab group 33A is divided into a first tab group 33A1 including a plurality of negative electrode current collector tabs 33 and a second tab group 33A2 including a plurality of negative electrode current collector tabs 33. The first tab group 33A1 faces the second tab group 33A2 with a gap therebetween in the width direction Y. The extending ends of the first tab group 33A1 and the extending ends of the second tab group 33A2 may be collectively held by backup leads bent into a U shape.

[0019] 2, the secondary battery 10 includes an insulator 36, a positive electrode lead 40A, and a negative electrode lead 40B, which are provided in the space between the electrode assembly 30 and the lid 14 within the outer container 12. The insulator 36 is formed in the shape of a rectangular plate having approximately the same dimensions as the lid 14. The insulator 36 is disposed opposite the inner surface of the lid 14. The insulator 36 is formed with a pair of through holes T3 that respectively face the pair of through holes T2 in the lid 14, and a through hole T5 that faces the injection port 29. The positive electrode lead 40A is disposed between the insulator 36 and the positive electrode current collector tab 32, and electrically connects the positive electrode terminal 20 and the positive electrode current collector tab 32. The negative electrode lead 40B is disposed between the insulator 36 and the negative electrode current collector tab 33, and electrically connects the negative electrode terminal 21 and the negative electrode current collector tab 33.

[0020] The positive electrode lead 40A is formed of a metal plate and integrally includes a rectangular plate-shaped first joint portion 42a and a rectangular plate-shaped second joint portion 42b that is perpendicular to the first joint portion 42a. The first joint portion 42a has a length slightly shorter than half the length of the lid 14 in the longitudinal direction X and a width slightly shorter than the width of the lid 14 in the width direction Y. The first joint portion 42a has a pair of long sides that extend in the longitudinal direction X and are arranged to face each other in parallel with the lid 14. The first joint portion 42a is provided with a through hole T4 for joining the connection rod 20b of the positive electrode terminal 20 and a through hole T6 that faces the injection port 29.

[0021] The second bonding portion 42b extends from the underside of the first bonding portion 42a, approximately perpendicular to the first bonding portion 42a. The second bonding portion 42b is located approximately in the center between the pair of long sides of the first bonding portion 42a. The second bonding portion 42b has the same length in the longitudinal direction X as the first bonding portion 42a and a width in the height direction Z that is equal to or greater than the width of the first bonding portion 42a. The second bonding portion 42b extends from one end to the other end of the first bonding portion 42a in the longitudinal direction X. Furthermore, both surfaces of the second bonding portion 42b form rectangular first bonding surfaces S1 and second bonding surfaces S2 that are parallel and face each other.

[0022] The negative electrode lead 40B has the same shape and dimensions as the positive electrode lead 40A. That is, the negative electrode lead 40B is formed of a metal plate and integrally includes a rectangular plate-shaped first joint portion 42a and a rectangular plate-shaped second joint portion 42b. The first joint portion 42a has a pair of long sides extending in the longitudinal direction X and is disposed so as to face the lid 14 in parallel. The first joint portion 42a is provided with only a through-hole T4 for joining the connection rod 21b of the negative electrode terminal 21. The second joint portion 42b extends from the lower surface side of the first joint portion 42a approximately perpendicular to the first joint portion 42a. The second joint portion 42b has rectangular first and second joint surfaces S1 and S2 that face each other in parallel. The metal plates that form the positive electrode lead 40A and the negative electrode lead 40B may be made of, for example, aluminum, an aluminum alloy, copper, or a copper alloy.

[0023] The internal structure of the assembled secondary battery 10 will now be described. 4 is a front view of the secondary battery with the container body 16 omitted, FIG. 5 is a cross-sectional view of the secondary battery taken along line AA in FIG. 1, and FIG. 6 is a cross-sectional view of the secondary battery taken along line BB in FIG. 1. As shown in FIG. 4 , the connection rod 20b of the positive terminal 20 passes through the through hole T1 of the gasket 28, the through hole T2 of the lid 14, and the through hole T3 of the insulator 36 and is fitted into the through hole T4 of the first joint portion 42a of the positive lead 40A. The connection rod 20b is then joined to the first joint portion 42a by laser welding, ultrasonic welding, or the like. This fixes the positive terminal 20 to the outer surface of the lid 14 via the gasket 28 and electrically connects it to the positive lead 40A. The first joint portion 42a of the positive lead 40A faces the inner surface of the lid 14 in parallel with the insulator 36 and extends in the longitudinal direction X from near the end of the lid 14 on the positive terminal 20 side toward the center of the lid 14 in the longitudinal direction X. The through hole T6 of the first joint portion 42a is aligned with the through hole T5 of the insulator 36 and the injection port 29 of the lid 14. The lid 14 and the positive electrode lead 40A are electrically insulated from each other by an insulator 36. The connection rod 21b of the negative electrode terminal 21 passes through the through hole T1 of the gasket 28, the through hole T2 of the lid 14, and the through hole T3 of the insulator 36 and is fitted into the through hole T4 of the first joint portion 42a of the negative electrode lead 40B, and is joined to the first joint portion 42a by laser welding, ultrasonic welding, or the like. As a result, the negative electrode terminal 21 is fixed to the outer surface of the lid 14 via the gasket 28 and is further electrically connected to the negative electrode lead 40B. The first joint portion 42a of the negative electrode lead 40B faces the inner surface of the lid 14 in parallel with each other, with the insulator 36 sandwiched therebetween, and extends in the longitudinal direction X from near the end of the lid 14 on the negative electrode terminal 21 side toward the center of the lid 14 in the longitudinal direction X. The lid 14 and the negative electrode lead 40B are electrically insulated from each other by the insulator 36.

[0024] 4, 5, and 6, the second joint portion 42b of the negative electrode lead 40B extends substantially perpendicular to the first joint portion 42a and the lid 14, and also extends in the longitudinal direction X. The second joint portion 42b extends between the first tab group 33A1 and the second tab group 33A2 of the negative electrode current collecting tab group 33, and is sandwiched between the first tab group 33A1 and the second tab group 33A2. That is, the first joint surface S1 of the second joint portion 42b faces the first tab group 33A1, and the second joint surface S2 faces the second tab group 33A2. The first tab group 33A1 is joined to the first bonding surface S1 of the second bonding portion 42b. The second tab group 33A2 is joined to the second bonding surface S2 of the second bonding portion 42b and faces the first tab group 33A1 across the second bonding portion 42b. This allows the negative electrode lead 40B to be electrically connected to the negative electrode tab group 32A.

[0025] 4 and 5, the second joint portion 42b of the positive electrode lead 40A extends substantially perpendicular to the first joint portion 42a and the lid 14, and also extends in the longitudinal direction X. The second joint portion 42b extends between the first tab group 32A1 and the second tab group 32A2 of the positive electrode current collecting tab group 32A, and is sandwiched between the first tab group 32A1 and the second tab group 32A2. The first joint surface S1 of the second joint portion 42b faces the first tab group 32A1, and the second joint surface S2 faces the second tab group 32A2. The first tab group 32A1 is joined to the first joint surface S1 of the second joint portion 42b. The second tab group 32A2 is joined to the second joint surface S2 of the second joint portion 42b and faces the first tab group 32A1 across the second joint portion 42b. This electrically connects the positive electrode lead 40A to the positive electrode current collecting tab group 32A.

[0026] Within the outer container 12, a rectangular frame-shaped insulating member 48 is provided between the electrode assembly 30 and the lid 14, surrounding the positive electrode lead 40A and the negative electrode lead 40B. The insulating member 48 is formed in a sheet or plate shape having a predetermined thickness from an insulating material such as synthetic resin. In one example, the insulating member 48 is attached to the inner surface of the container body 16, covering the entire periphery of the area between the end of the container body 16 on the top opening side and the end face of the electrode assembly 30. The positive electrode lead 40A and the negative electrode lead 40B are electrically insulated from the container body 16 by the insulating member 48.

[0027] The current collecting tab group and the electrode lead are joined by methods such as laser welding, ultrasonic welding, resistance welding, etc. According to this embodiment, the current collecting tab group is joined to the electrode lead by ultrasonic welding. FIG. 7 is a diagram showing a schematic diagram of the joining step, and FIG. 8 is a perspective view of the joined current collecting tab group and electrode lead, viewed from different angles. As shown in FIG. 7 , in one example, the second joint portion 42b of the negative electrode lead 40B is sandwiched between the first tab group 33A1 and the second tab group 33A2, and the dual heads (a pair of horns H) of the ultrasonic bonding device are arranged to sandwich the first tab group 33A1, the second joint portion 42b of the negative electrode lead 40B, and the second tab group 33A2 from both sides. One horn H abuts against the outer surface of the first tab group 33A1 and presses the first tab group 33A1 toward the first joint surface S1 of the second joint portion 42b with a predetermined load. The other horn H abuts against the outer surface of the second tab group 33A2 and presses the second tab group 33A2 toward the second joint surface S2 of the second joint portion 42b with a predetermined load. In this state, the pair of horns H are ultrasonically vibrated in opposite phases. By applying a load and ultrasonic vibrations to the bonding interface, oxide films and dirt are removed from the bonding interface, and metal atoms are bonded together by electron-electron forces. That is, the first tab group 33A1 is bonded to the first bonding surface S1, and the second tab group 33A2 is bonded to the second bonding surface S2. Both the first tab group 33A1 and the second tab group 33A2 are simultaneously bonded to the negative electrode lead 40B in a single bonding operation. The first tab group 32A1 and the second tab group 32A2 of the positive electrode current collecting tab group 32A are simultaneously joined to the first joining surface S1 and the second joining surface S2 of the second joining portion 42b of the positive electrode lead 40A by the same ultrasonic joining method as described above.

[0028] When the above ultrasonic bonding is used, horn marks (pressed marks of the horn) T are left on the outer surfaces of the first tab group 33A1 and the second tab group 33A2, as shown in Figures 8(a) and 8(b). In one example, horn marks (pressed marks) T consisting of three rectangular recesses aligned in the longitudinal direction X are left on the outer surface of each tab group. Similarly, horn marks (pressed marks) T are left on the first tab group 32A1 and the second tab group 32A2 of the positive electrode current collecting tab group 32A.

[0029] The first tab group 32A1 (33A1) and the second tab group 32A2 (33A2) divided in the thickness direction may each be composed of the same number of current collecting tabs, or may each be composed of a different number of current collecting tabs. For example, as shown in FIG. 9(a), when the first tab group 33A1 and the second tab group 33A2 are each composed of the same number of current collecting tabs, the second joint portion 42b of the negative electrode lead 40B is provided at approximately the center of the first joint portion 42a in the width direction Y and extends between the first tab group 33A1 and the second tab group 33A2. As shown in FIG. 9(b), when the first tab group 33A1 and the second tab group 33A2 are composed of different numbers of current collecting tabs, for example, when the first tab group 33A1 is composed of a greater number of current collecting tabs than the second tab group 33A2, the second joint portion 42b of the negative electrode lead 40B is located at a position shifted from the center of the first joint portion 42a in the width direction Y toward the second tab group 33A2, which has fewer tabs, and extends between the first tab group 33A1 and the second tab group 33A2. The second joint portion 42b of the positive electrode lead 40A is configured similarly to the second joint portion 42b of the negative electrode lead 40B.

[0030] The secondary battery 10 according to the first embodiment configured as described above allows current collecting tab groups to be simultaneously bonded to both the first and second bonding surfaces of the electrode lead, simplifying the structure of the bonding portion and simplifying the bonding process. Furthermore, in the first embodiment, the current collecting tab group is divided into multiple tab groups, and each tab group is bonded to a common lead. This increases the bonding area between the current collecting tab and the lead, improving thermal conductivity. This allows for even greater current extraction. At the same time, the increased bonding area between the current collecting tab and the lead improves the vibration resistance of the current collecting tab. As described above, according to the first embodiment, a secondary battery can be provided that can simplify the joining work of the current collecting tabs.

[0031] Next, a secondary battery according to another embodiment of the present invention will be described. In the following embodiment, the same parts and components as those in the first embodiment will be assigned the same reference numerals as those in the first embodiment, and their description will be omitted or simplified. The following description will focus on the parts that are different from the first embodiment. (Second embodiment) FIG. 10 is a perspective view showing the secondary battery according to the second embodiment with the container body omitted, FIG. 11 is a cross-sectional view of the secondary battery according to the second embodiment corresponding to FIG. 5, and FIG. 12 is a cross-sectional view of the secondary battery according to the second embodiment corresponding to FIG. 6. As shown in the figure, the secondary battery 10 according to the second embodiment includes a plurality of electrode assemblies housed in an outer container 12, for example, two electrode assemblies 30A and 30B.

[0032] The electrode assembly 30A is configured similarly to the electrode assembly 30 in the first embodiment described above. However, the electrode assembly 30A is formed flatter than the electrode assembly 30, and has a thickness in the width direction Y that is approximately half the thickness of the electrode assembly 30. The electrode assembly 30A has an electrode group 74 and a positive electrode current collector tab group 32A and a negative electrode current collector tab group 33A that extend in the height direction Z from one axial end of the electrode group 74. The positive electrode current collector tab group 32A includes a plurality of positive electrode current collector tabs stacked in the thickness direction. The negative electrode current collector tab group 33A includes a plurality of negative electrode current collector tabs stacked in the thickness direction. The positive electrode current collector tab group 32A is located at one end of the electrode body 30A in the longitudinal direction X. The negative electrode current collector tab 33A is located at the other end of the electrode body 30A in the longitudinal direction X. In this way, the positive electrode current collector tab group 32A and the negative electrode current collector tab group 33A extend in the same direction from one end of the electrode group 74, and are located spaced apart from each other in the longitudinal direction X of the electrode body 30A. The electrode assembly 30A configured as described above is housed in the container body 16 with its winding axis aligned with the height direction Z of the outer container 12 and with the positive electrode current collector tab group 32A and the negative electrode current collector tab group 33A facing the lid 14. One end face of the electrode group 74 faces the lid 14 with a gap therebetween.

[0033] The electrode assembly 30B has the same configuration as the electrode assembly 30A. The electrode assembly 30B has an electrode group 74 and a positive electrode current collector tab group 32B and a negative electrode current collector tab group 33B that extend from the electrode group 74 in the height direction Z. The positive electrode current collector tab group 32B includes a plurality of positive electrode current collector tabs stacked in the thickness direction. The negative electrode current collector tab group 33B includes a plurality of negative electrode current collector tabs stacked in the thickness direction. The positive electrode current collecting tab group 32B is located at one end of the electrode body 30B in the longitudinal direction X. The negative electrode current collecting tab group 33B is located at the other end of the electrode body 30A in the longitudinal direction X. The positive electrode current collecting tab group 32B and the negative electrode current collecting tab group 33B extend in the same direction from one end of the electrode group 74 and are located spaced apart from each other in the longitudinal direction X of the electrode body 30A. The electrode assembly 30B configured as described above is housed in the container body 16 with its winding axis aligned with the height direction Z of the outer container 12 and with the positive electrode current collector tab group 32B and the negative electrode current collector tab 33B oriented toward the lid 14 side, and is arranged alongside the electrode assembly 30A in the width direction Y. The positive electrode current collector tab group 32B faces the positive electrode current collector tab group 32A in the width direction Y with a gap therebetween. The negative electrode current collector tab group 33B faces the negative electrode current collector tab group 33A in the width direction Y with a gap therebetween.

[0034] 10, 11, and 12, the second joint portion 42b of the negative electrode lead 40B extends substantially perpendicular to the first joint portion 42a and the lid 14, and also extends in the longitudinal direction X. The second joint portion 42b extends between the negative electrode current collector tab group 33A of the electrode body 30A and the negative electrode current collector tab group 33B of the electrode body 30B, and is sandwiched between the negative electrode current collector tab group 33A and the negative electrode current collector tab group 33B. That is, the first joint surface S1 of the second joint portion 42b faces the negative electrode current collector tab group 33A, and the second joint surface S2 faces the negative electrode current collector tab group 33B. The negative electrode current collector tab group 33A is joined to the first joint surface S1 of the second joint portion 42b. The negative electrode current collector tab group 33B is joined to the second joint surface S2 of the second joint portion 42b and faces the negative electrode current collector tab group 33A across the second joint portion 42b. As a result, the negative electrode lead 40B is electrically connected to the negative electrode current collector tab groups 33A and 33B.

[0035] 10 and 11, the second joint portion 42b of the positive electrode lead 40A extends substantially perpendicular to the first joint portion 42a and the lid 14, and also extends in the longitudinal direction X. The second joint portion 42b extends between the positive electrode current collector tab group 32A of the electrode body 30A and the positive electrode current collector tab group 32B of the electrode body 30B, and is sandwiched between the positive electrode current collector tab group 32A and the positive electrode current collector tab group 32B. The first joint surface S1 of the second joint portion 42b faces the positive electrode current collector tab group 32A, and the second joint surface S2 faces the positive electrode current collector tab group 32B. The positive electrode current collector tab group 32A is joined to the first joint surface S1 of the second joint portion 42b. The positive electrode current collector tab group 32B is joined to the second joint surface S2 of the second joint portion 42b and faces the positive electrode current collector tab group 32A across the second joint portion 42b. In this way, the positive electrode lead 40A is electrically connected to the positive electrode current collector tab groups 32A and 32B.

[0036] In the second embodiment, the current collecting tab group and the leads are joined by ultrasonic bonding, similar to that in the first embodiment. That is, with the positive electrode current collecting tab group 32A, the second joint portion 42b of the positive electrode lead, and the positive electrode current collecting tab group 32B sandwiched between the pair of horns H, the positive electrode current collecting tab group 32A is ultrasonically bonded simultaneously to the first joint surface S1 of the second joint portion 42b, and the positive electrode current collecting tab group 32B is ultrasonically bonded simultaneously to the second joint surface S2 of the second joint portion 42b. Both positive electrode current collecting tab groups 32A and 32B are simultaneously bonded to the positive electrode lead 40A in a single bonding operation. Similarly, on the negative electrode side, the negative electrode current collector tab group 33A, the second joint portion 42b of the negative electrode lead, and the negative electrode current collector tab group 33B are sandwiched between a pair of horns H, and then the negative electrode current collector tab group 33A is ultrasonically bonded simultaneously to the first joint surface S1 of the second joint portion 42b, and the negative electrode current collector tab group 33B is ultrasonically bonded simultaneously to the second joint surface S2 of the second joint portion 42b. Both negative electrode current collector tab groups 33A and 33B are simultaneously bonded to the negative electrode lead 40B in a single bonding operation. Horn marks (pressing marks) T remain on the outer surfaces of the positive electrode current collecting tab groups 32A, 32B and the outer surfaces of the negative electrode current collecting tabs 33A, 33B.

[0037] In the second embodiment, the other configurations of the secondary battery 10 are the same as those of the secondary battery 10 according to the first embodiment. The secondary battery 10 according to the second embodiment configured as described above can also achieve the same effects as the secondary battery according to the first embodiment. According to the second embodiment, by providing multiple electrode bodies, the capacity of the secondary battery can be increased. Furthermore, according to the second embodiment, by joining multiple current collecting tab groups of multiple electrode bodies to both sides of a common lead, the joining structure between the current collecting tabs and the lead can be simplified, thereby improving the weight energy density of the secondary battery and simplifying the manufacturing process.

[0038] (Third embodiment) FIG. 13 is an exploded perspective view of a secondary battery according to a third embodiment, and FIG. 14 is a perspective view showing a partially developed electrode body according to the third embodiment. 13, the secondary battery 10 according to the third embodiment includes a plurality of electrode bodies, for example, two electrode bodies 30A and 30B, housed in an outer container 12. Each electrode body is a so-called horizontal tab type wound electrode body in which a positive electrode current collecting tab and a negative electrode current collecting tab extend in opposite directions from an electrode group.

[0039] An example will be described using the electrode assembly 30A as a representative example. As shown in Fig. 14, the electrode assembly 30A has an electrode group 74 formed into a flat rectangular shape by spirally winding sheet-like positive electrode plates 70 and negative electrode plates 72 around a winding axis C with a sheet-like separator 73 interposed therebetween and further compressing them in the radial direction so that the cross-sectional shape becomes a substantially rectangular shape. The separator 73 is arranged on the outermost layer (outermost periphery) of the electrode group 74. The positive electrode plate 70 includes a strip-shaped positive electrode current collector 70a made of, for example, a metal foil and a strip-shaped positive electrode active material layer 70b formed on at least one surface of the positive electrode current collector 70a. The positive electrode active material layer 70b has a width smaller than that of the positive electrode current collector 70a, one side edge aligned with one side edge of the positive electrode current collector 70a, and the other side edge extending parallel to and spaced apart from the other side edge of the positive electrode current collector 70a. The portion of the positive electrode current collector 70a that does not support the positive electrode active material layer 70b forms the positive electrode current collector tab 32 of the positive electrode plate 70. The positive electrode current collector tab 32 has a constant width in a direction parallel to the winding axis C and extends continuously along the other side edge of the positive electrode current collector 70a.

[0040] The negative electrode plate 72 includes a strip-shaped negative electrode current collector 72a made of metal foil and a strip-shaped negative electrode active material layer 72b formed on at least one surface of the negative electrode current collector 72a. The negative electrode active material layer 72b has a width smaller than that of the negative electrode current collector 72a and substantially the same width as that of the positive electrode active material layer 72b. One side edge of the negative electrode active material layer 72b is aligned with one side edge of the negative electrode current collector 72a, and the other side edge extends parallel to and spaced apart from the other side edge of the negative electrode current collector 72a. The portion of the negative electrode current collector 72a that does not support the negative electrode active material layer 72b forms the negative electrode current collector tab 33 of the negative electrode plate 72. The negative electrode current collector tab 33 has a constant width in a direction parallel to the winding axis C and extends continuously along the other side edge of the negative electrode current collector 72a. The negative electrode plate 72 is disposed offset by the above-mentioned predetermined distance from the positive electrode plate 70 in one direction parallel to the winding axis C. As a result, the negative electrode active material layer 72b of the negative electrode plate 72 is aligned and faces the positive electrode active material layer 70b of the positive electrode plate 70, and the negative electrode current collector tab 33 does not overlap with the positive electrode plate 70 and extends in the opposite direction from the positive electrode current collector tab 32. Similarly, the positive electrode current collector tab 32 of the positive electrode plate 70 does not overlap with the negative electrode plate 72 and extends in the opposite direction from the negative electrode current collector tab 33.

[0041] Each separator 73 is formed to have approximately the same width as the positive electrode active material layer 74a and the negative electrode active material layer 74b. Each separator 73 is positioned to face only the positive electrode active material layer 74a and the negative electrode active material layer 74b, and does not overlap the positive electrode current collector tab 32 and the negative electrode current collector tab 33.

[0042] The current collectors and current collecting tabs of the positive electrode plate 70 and the negative electrode plate 72 may be formed, for example, by punching metal foil. The thickness of the metal foil, i.e., the thickness of each current collecting tab, is preferably 5 μm to 50 μm. A thickness of 5 μm or more prevents breakage of the current collectors and current collecting tabs during manufacturing and enables high current collection efficiency. It also prevents dissolution of the current collecting tabs when a large current flows. A thickness of 50 μm or less allows the number of turns constituting the electrode body to be increased while suppressing an increase in the thickness of the electrode body. Preferably, the thickness of the metal foil is 10 μm to 20 μm. The material of the metal foil varies depending on the type of active material used in the positive and negative electrodes, but examples of suitable materials include aluminum, aluminum alloys, copper, and copper alloys.

[0043] By overlapping and winding the positive electrode plate 70, separator 73, and negative electrode plate 72, the positive electrode current collector tab 32 is also wound around the winding axis C and sequentially stacked in the thickness direction to form an annular positive electrode current collector tab group 32A. The positive electrode current collector tab group 32A extends in one direction parallel to the winding axis C from one axial end face of the electrode group 74. In this embodiment, the positive electrode current collector tab group 32A is formed in a flat track shape including a pair of straight strip portions SL1, SL2 facing each other with a gap between them. Similarly, the negative electrode current collector tabs 33 are wound around the winding axis C and sequentially stacked in the thickness direction to form an annular negative electrode current collector tab group 33A. The negative electrode current collector tab group 33A extends from the other axial end face of the electrode group 74 in the opposite direction parallel to the winding axis C, that is, in the opposite direction to the extension direction of the positive electrode current collector tab group 32A. In this embodiment, the negative electrode current collector tab group 33A is formed in a flat track shape including a pair of straight strip portions SL1, SL2 facing each other with a gap between them.

[0044] The other electrode body 30B is configured in the same manner as the above-mentioned electrode body 30A. That is, the electrode body 30B has an electrode group 74 formed in a flat rectangular shape, a positive electrode current collector tab group 32B extending from one axial end face of the electrode group 74 in one direction parallel to the winding axis C, and a negative electrode current collector tab group 33B extending from the other axial end face of the electrode group 74 in the opposite direction parallel to the winding axis C.

[0045] 13 , the electrode assembly 30A configured as described above is housed in the container body 16 with the winding axis C coinciding with the longitudinal direction X of the outer container 12 and with the positive electrode current collector tab group 32A and the negative electrode current collector tab group 33A each extending in the height direction Z. The positive electrode current collector tab group 32A is disposed on the positive electrode terminal 20 side, and the negative electrode current collector tab group 33A is disposed on the negative electrode terminal 21 side. The electrode assembly 30B is housed within the container body 16 with its winding axis C aligned with the longitudinal direction X of the outer container 12, and with the positive electrode current collector tab group 32A and negative electrode current collector tab group 33A each extending in the height direction Z, and is arranged side by side with the electrode assembly 30A in the width direction Y. The positive electrode current collector tab group 32B is arranged on the positive electrode terminal 20 side, and the negative electrode current collector tab group 33B is arranged on the negative electrode terminal 21 side. The positive electrode current collector tab group 32B faces the positive electrode current collector tab group 32A of the electrode assembly 30A in a substantially parallel relationship, with a gap in the width direction Y between them. The negative electrode current collector tab group 33B faces the negative electrode current collector tab group 33A of the electrode assembly 30A in a substantially parallel relationship, with a gap in the width direction Y between them.

[0046] As shown in FIG. 13 , insulating members 47a and 47b are provided inside the container body 16 to electrically insulate the container body 16 from the positive electrode current collector tab groups 32A and 32B and from the negative electrode current collector tab groups 33A and 33B, respectively. In one example, the insulating members 47a and 47b are each formed in a sheet or plate shape having a predetermined thickness from an insulating material such as synthetic resin. The insulating member 47a is attached to the inner surface of the container body 16 on the side of one sidewall 16c and covers the periphery of the positive electrode current collector tab groups 32A and 32B. The insulating member 47b is attached to the inner surface of the container body 16 on the side of the other sidewall 16c and covers the periphery of the negative electrode current collector tab groups 33A and 33B.

[0047] As shown in Fig. 13, the secondary battery 10 includes two insulators 36, a positive electrode lead 40A, and a negative electrode lead 40B, which are provided in the space between the electrode assemblies 30A and 30B and the lid 14 within the outer casing 12. Each insulator 36 is formed in a rectangular plate shape. One insulator 36 is disposed opposite the inner surface of the lid 14 at a position opposite the positive electrode terminal 20. The other insulator 36 is disposed opposite the inner surface of the lid 14 at a position opposite the negative electrode terminal 21. The insulators 36 are formed with through holes T3 that respectively face the pair of through holes T2 in the lid 14. The positive electrode lead 40A is disposed between the insulator 36 and the positive electrode current collector tab groups 32A and 32B, and electrically connects the positive electrode terminal 20 to the positive electrode current collector tab groups 32A and 32B. The negative electrode lead 40B is disposed between the insulator 36 and the negative electrode current collector tab groups 33A and 33B, and electrically connects the negative electrode terminal 21 to the negative electrode current collector tab groups 33A and 33B.

[0048] The positive electrode lead 40A is formed of a metal plate and integrally includes a rectangular plate-shaped first joint portion 42a and a narrow rectangular plate-shaped second joint portion 42b that is perpendicular to the first joint portion 42a. The first joint portion 42a has a length slightly shorter than half the length of the lid 14 in the longitudinal direction X and a width slightly shorter than the width of the lid 14 in the width direction Y. A pair of long sides of the first joint portion 42a extend in the longitudinal direction X and are disposed so as to face the lid 14 in parallel with the insulator 36 interposed therebetween. A through hole T4 is provided in the first joint portion 42a for joining the connection rod 20b of the positive electrode terminal 20. The second joint portion 42b extends from the lower surface of the first joint portion 42a in the height direction Z, approximately perpendicular to the first joint portion 42a. The second joint portion 42b is located at one end of the first joint portion 42a in the longitudinal direction X (here, the end on the side of the sidewall 16c), approximately in the center between the pair of long sides of the first joint portion 42a. The second joint portion 42b has a width W1 in the longitudinal direction X and a length L1 in the height direction Z. The width W1 is slightly smaller than the width in the longitudinal direction X of the current collecting tab groups 32A and 33A of the electrode assemblies 30A and 30B described above. The length L1 is slightly shorter than the length in the height direction Z of the current collecting tab groups 32A and 33A. Both surfaces of the second joint portion 42b constitute a first joint surface S1 and an opposing second joint surface S2.

[0049] The negative electrode lead 40B has the same shape and dimensions as the positive electrode lead 40A. Specifically, the negative electrode lead 40B is formed of a metal plate and integrally includes a rectangular plate-shaped first joint portion 42a and an elongated rectangular plate-shaped second joint portion 42b. The first joint portion 42a has a pair of long sides extending in the longitudinal direction X and is disposed parallel to and facing the lid 14 with the insulator 36 interposed therebetween. The first joint portion 42a has a through-hole T4 for joining the connection rod 21b of the negative electrode terminal 21. The second joint portion 42b extends in the height direction Z from one end of the first joint portion 42a in the longitudinal direction X (here, the end on the side of the sidewall 1c) approximately perpendicular to the first joint portion 42a. The second joint portion 42b has rectangular first and second joint surfaces S1 and S2 that are parallel to and facing each other. The metal plates that form the positive electrode lead 40A and the negative electrode lead 40B may be made of, for example, aluminum, an aluminum alloy, copper, or a copper alloy.

[0050] The internal structure of the assembled secondary battery 10 will now be described. FIG. 15 is a cross-sectional view of the secondary battery according to the third embodiment, and FIG. 16 is a cross-sectional view of the secondary battery according to the third embodiment, corresponding to FIG. As shown in FIG. 15 , the connection rod 20b of the positive terminal 20 passes through the through hole T1 of the gasket 28, the through hole T2 of the lid 14, and the through hole T3 of the insulator 36 and is fitted into the through hole T4 of the first joint portion 42a of the positive lead 40A. The connection rod 20b is then joined to the first joint portion 42a by laser welding, ultrasonic welding, or the like. As a result, the positive terminal 20 is fixed to the outer surface of the lid 14 via the gasket 28 and is electrically connected to the positive lead 40A. The first joint portion 42a of the positive lead 40A faces the inner surface of the lid 14 in parallel with the insulator 36, and extends in the longitudinal direction X from near the end of the lid 14 on the positive terminal 20 side toward the center of the lid 14 in the longitudinal direction X. The lid 14 and the positive lead 40A are electrically insulated by the insulator 36. The connection rod 21b of the negative electrode terminal 21 passes through the through hole T1 of the gasket 28, the through hole T2 of the lid 14, and the through hole T3 of the insulator 36 and is fitted into the through hole T4 of the first joint portion 42a of the negative electrode lead 40B, and is joined to the first joint portion 42a by laser welding, ultrasonic welding, or the like. As a result, the negative electrode terminal 21 is fixed to the outer surface of the lid 14 via the gasket 28 and is further electrically connected to the negative electrode lead 40B. The first joint portion 42a of the negative electrode lead 40B faces the inner surface of the lid 14 in parallel with each other, with the insulator 36 sandwiched therebetween, and extends in the longitudinal direction X from near the end of the lid 14 on the negative electrode terminal 21 side toward the center of the lid 14 in the longitudinal direction X. The lid 14 and the negative electrode lead 40B are electrically insulated from each other by the insulator 36.

[0051] 15 and 16, the second joint portion 42b of the negative electrode lead 40B extends substantially perpendicular to the first joint portion 42a and the lid 14 and extends between the negative electrode current collector tab group 33A of the electrode assembly 30A and the negative electrode current collector tab group 33B of the electrode assembly 30B. As a result, the second joint portion 42b is sandwiched between the negative electrode current collector tab group 33A and the negative electrode current collector tab group 33B. In one example, the second joint portion 42b is sandwiched between the straight strip portion SL1 of the negative electrode current collector tab group 33A and the straight strip portion SL2 of the negative electrode current collector tab group 33B. The first joint surface S1 of the second joint portion 42b faces the straight strip portion SL1 of the negative electrode current collector tab group 33A, and the second joint surface S2 faces the straight strip portion SL2 of the negative electrode current collector tab group 33B. The straight line portion SL1 of the negative electrode current collector tab group 33A is joined to the first joint surface S1 of the second joint portion 42b. The straight line portion SL2 of the negative electrode current collector tab group 33B is joined to the second joint surface S2 of the second joint portion 42b and faces the straight line portion SL1 of the negative electrode current collector tab group 33A across the second joint portion 42b. In this way, the negative electrode lead 40B is electrically connected to the negative electrode current collector tab groups 33A and 33B.

[0052] As shown in FIG. 15, the second joint portion 42b of the positive electrode lead 40A extends substantially perpendicular to the first joint portion 42a and the lid 14 and extends between the positive electrode current collector tab group 32A of the electrode assembly 30A and the positive electrode current collector tab group 32B of the electrode assembly 30B. The second joint portion 42b is sandwiched between the positive electrode current collector tab group 32A and the positive electrode current collector tab group 32B. In one example, similar to the negative electrode side, the second joint portion 42b is sandwiched between the straight strip portion SL1 of the positive electrode current collector tab group 32A and the straight strip portion SL2 of the positive electrode current collector tab group 32B (see FIG. 14 for the straight strip portions SL1 and SL2). As a result, the first joint surface S1 of the second joint portion 42b faces the straight strip portion SL1 of the positive electrode current collector tab group 32A, and the second joint surface S2 faces the straight strip portion SL2 of the positive electrode current collector tab group 32B. The straight strip portion SL1 of the positive electrode current collector tab group 32A is joined to the first joint surface S1 of the second joint portion 42b. The straight strip portion SL2 of the positive electrode current collector tab group 32B is joined to the second joint surface S2 of the second joint portion 42b and faces the straight strip portion SL1 of the positive electrode current collector tab group 32A across the second joint portion 42b. In this way, the positive electrode lead 40A is electrically connected to the positive electrode current collector tab groups 32A and 32B.

[0053] In the third embodiment, the current collecting tab group and the leads are joined by ultrasonic bonding, similar to that in the first embodiment. FIG. 17 is a diagram schematically showing a joining step and a joined state of the current collecting tab group and the electrode lead in the third embodiment. 17(a), the straight strip portion SL1 of the negative electrode current collecting tab group 33A, the second joint portion 42b of the negative electrode lead 40B, and the straight strip portion SL2 of the negative electrode current collecting tab group 33B are sandwiched between a pair of horns, and the straight strip portion SL1 is ultrasonically bonded to the first joint surface S1 of the second joint portion 42b, and the straight strip portion SL2 is ultrasonically bonded to the second joint surface S2 of the second joint portion 42b simultaneously using each horn. In a single bonding operation, both the negative electrode current collecting tab groups 33A and 33B are simultaneously bonded to the negative electrode lead 40B. The positive electrode current collecting tab group is also bonded to the positive electrode lead 40A by similar ultrasonic bonding. Similarly, on the positive electrode side, the straight strip portion SL1 of the positive electrode current collecting tab group 32A, the second joint portion 42b of the positive electrode lead 40A, and the straight strip portion SL2 of the positive electrode current collecting tab group 32B are sandwiched between a pair of horns, and the straight strip portion SL1 is ultrasonically bonded to the first joint surface S1 of the second joint portion 42b, and the straight strip portion SL2 is ultrasonically bonded to the second joint surface S2 of the second joint portion 42b simultaneously, using each horn. 17(b), horn marks (press marks) T remain on each of the straight strip portions SL1 and SL2 joined to the second joint portion 42b. In one example, four rectangular horn marks T remain aligned in the longitudinal direction of the current collecting tab group.

[0054] The secondary battery 10 according to the third embodiment configured as described above can also achieve the same effects as the secondary battery according to the first embodiment. According to the third embodiment, by providing multiple electrode bodies, the capacity of the secondary battery can be increased. Furthermore, according to the third embodiment, it is possible to simultaneously bond multiple current collecting tab groups of multiple electrode bodies to both sides of a common lead, simplifying the bonding structure between the current collecting tabs and the lead and simplifying the manufacturing process. Furthermore, the electrode lead only needs to have one second bonding portion for two electrode bodies, which allows for simplification and miniaturization of the electrode lead. Miniaturizing the electrode lead can improve the weight energy density of the secondary battery.

[0055] Next, a modification of the third embodiment will be described. (First Modification) FIG. 18 is a diagram schematically showing a process of joining a current collecting tab group and an electrode lead of a secondary battery according to a first modified example. As shown in the figure, in the first modified example, the straight strip portions SL1 and SL2 of the negative electrode current collecting tab group 33A, the second joint portion 42b of the negative electrode lead 40B, and the straight strip portions SL1 and SL2 of the negative electrode current collecting tab group 33B are sandwiched between a pair of horns, and the straight strip portions SL1 and SL2 are simultaneously ultrasonically bonded to the first joint surface S1 of the second joint portion 42b and the second joint surface S2 of the second joint portion 42b using each horn. In a single bonding operation, both of the negative electrode current collecting tab groups 33A and 33B are simultaneously bonded to the negative electrode lead 40B. The positive electrode current collecting tab group is also bonded to the positive electrode lead 40A by similar ultrasonic bonding. According to the first modification, by joining both linear stripes of the current collecting tab group to the electrode lead, the joining area between the current collecting tab and the lead is increased, improving thermal conductivity, and thereby enabling extraction of even larger currents.

[0056] (Second Modification) FIG. 19 is a diagram schematically showing the configuration of the electrode body and electrode leads of a secondary battery according to a first modified example, and a process for joining the current collecting tab group and the electrode leads. As shown in the figure, according to the third modification, the secondary battery includes three electrode bodies 30A, 30B, and 30C. The electrode bodies 30A, 30B, and 30C are formed with the same configuration, shape, and dimensions and are arranged side by side in the thickness direction. An electrode lead, for example, a negative electrode lead 40B, integrally includes a first joint portion 42a and two second joint portions 42b and 42c that extend substantially perpendicularly from the first joint portion 42a and face each other in parallel with a gap between them. Each of the second joint portions 42b and 42c has a first joint surface S1 and a second joint surface S2 that face each other.

[0057] One of the second joint portions 42b is sandwiched between the negative electrode current collector tab group 33A of the electrode body 30A and the negative electrode current collector tab group 33B of the electrode body 30B. The negative electrode current collector tab group 33A is joined to the first joint surface S1 of the second joint portion 42b, and the negative electrode current collector tab group 33B is joined to the second joint surface S2, and they face the negative electrode current collector tab group 33A across the second joint portion 42b. The other second joint portion 42c is sandwiched between the negative electrode current collector tab group 33B of the electrode body 30B and the negative electrode current collector tab group 33C of the electrode body 30C. The negative electrode current collector tab group 33B is joined to the first joint surface S1 of the second joint portion 42c, and the negative electrode current collector tab group 33C is joined to the second joint surface S2 of the second joint portion 42c, facing the negative electrode current collector tab group 33B across the second joint portion 42c. The second bonding portions 42b, 42c are bonded to the negative electrode current collecting tab group by ultrasonic bonding, similar to the third embodiment described above.

[0058] According to the second modified example of the above configuration, by providing multiple electrode bodies, the capacity of the secondary battery can be increased. Furthermore, it is possible to simultaneously bond multiple current collecting tab groups of multiple electrode bodies to both sides of a common lead, simplifying the bonding structure between the current collecting tabs and the lead and simplifying the manufacturing process. Furthermore, the electrode lead only needs to have one second bonding portion for two electrode bodies, which allows for simplification and miniaturization of the electrode lead.

[0059] The present invention is not limited to the above-described embodiments or modifications, and can be embodied by modifying the components within the scope of the gist of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. For example, the electrode body is not limited to a so-called wound-type electrode body in which electrode plates are wound, but a so-called stacked-type electrode body in which multiple electrode plates are stacked in the thickness direction may also be applied. The forming materials, shapes, sizes, etc. of the elements constituting the secondary battery are not limited to the above-described embodiments, and can be variously changed as necessary.

Claims

1. an outer container having a lid; a first electrode body that includes an electrode group formed by winding a positive electrode plate and a negative electrode plate around a winding axis, and a first positive electrode current collecting tab group and a first negative electrode current collecting tab group that include a plurality of positive electrode current collecting tabs and a plurality of negative electrode current collecting tabs and extend in the same direction from one end in the axial direction of the electrode group, and is housed in the outer container; a second electrode body that is accommodated in the outer container and faces the first electrode body, the second electrode body including an electrode group formed by winding a positive electrode plate and a negative electrode plate around a winding axis, and a second positive electrode current collecting tab group and a second negative electrode current collecting tab group that include a plurality of positive electrode current collecting tabs and a plurality of negative electrode current collecting tabs and extend in the same direction from one end of the electrode group in the axial direction; a pair of output terminals provided on the cover; a positive electrode lead having a first joint portion joined to one of the output terminals and a second joint portion joined to the first positive electrode current collector tab group and the second positive electrode current collector tab group, electrically connecting the first positive electrode current collector tab group and the second positive electrode current collector tab group to the output terminal; a negative electrode lead having a first joint portion joined to the other output terminal and a second joint portion joined to the first negative electrode current collector tab group and the second negative electrode current collector tab group, and electrically connecting the first negative electrode current collector tab group and the second negative electrode current collector tab group to the output terminal, the second joint portion has a first joint surface and a second joint surface facing each other, the first positive electrode current collecting tab group is joined to the first joint surface of the positive electrode lead, and the second positive electrode current collecting tab group is joined to the second joint surface of the positive electrode lead and faces the first positive electrode current collecting tab group across the second joint portion, the first negative electrode current collecting tab group is joined to the first joint surface of the negative electrode lead, and the second negative electrode current collecting tab group is joined to the second joint surface of the negative electrode lead and faces the first negative electrode current collecting tab group with the second joint portion interposed therebetween; Secondary battery.

2. the first positive electrode current collecting tab group and the second positive electrode current collecting tab group include the same number of positive electrode current collecting tabs, The secondary battery according to claim 1 , wherein the first negative electrode current collector tab group and the second negative electrode current collector tab group include the same number of negative electrode current collector tabs.

3. the first positive electrode current collecting tab group and the second positive electrode current collecting tab group include a different number of positive electrode current collecting tabs, The secondary battery according to claim 1 , wherein the first negative electrode current collector tab group and the second negative electrode current collector tab group include different numbers of negative electrode current collector tabs.

4. 2. The secondary battery according to claim 1, wherein the first positive electrode current collector tab group and the second positive electrode current collector tab group each have horn press marks, and the first negative electrode current collector tab group and the second negative electrode current collector tab group each have horn press marks.

5. the first positive electrode current collecting tab group extends in the axial direction from one end of the electrode group in the axial direction, and the first negative electrode current collecting tab group extends in the opposite direction to the first positive electrode current collecting tab group from the other end of the electrode group in the axial direction, 2. The secondary battery according to claim 1, wherein the second positive electrode current collecting tab group extends in the axial direction from one axial end of the electrode group, and the second negative electrode current collecting tab group extends in the opposite direction from the second positive electrode current collecting tab group from the other axial end of the electrode group.

6. 6. The secondary battery according to claim 5, wherein the first positive electrode current collector tab group has a pair of straight stripe portions facing each other, one of which is joined to the first joint surface of the positive electrode lead, and the second positive electrode current collector tab group has a pair of straight stripe portions facing each other, one of which is joined to the second joint surface of the positive electrode lead.

7. 6. The secondary battery according to claim 5, wherein the first positive electrode current collector tab group has a pair of linear stripes facing each other, the pair of linear stripes being joined to the first joining surface of the positive electrode lead, and the second positive electrode current collector tab group has a pair of linear stripes facing each other, the pair of linear stripes being joined to the second joining surface of the positive electrode lead.

Images