Battery pack

Abstract

The present invention relates to a battery pack that employs bus bars, and addresses the problem that if the straight-line distance between terminals of adjacent batteries is small, an overlapping area of the bus bars in a planar direction is small, and joint strength cannot be increased, and in order to resolve this problem the present invention is characterized in that, in a bus bar connecting a first positive electrode terminal of a first battery and an adjacent second negative electrode terminal of a second battery: a first conductive member of the bus bar includes a first joint portion that is joined to the first positive electrode terminal, and a first extended portion that extends from the first joint portion; a second conductive member of the bus bar includes a second joint portion that is joined to the second negative electrode terminal, and a second extended portion that extends from the second joint portion; the first conductive member and the second conductive member are mutually different materials and are connected at a third joint portion; and a distance from the third joint portion to one of the first joint portion and the second joint portion is less than to the other of the first joint portion and the second joint portion, and the third joint portion is formed in an overlapping portion of the first extended portion and the second extended portion.

Description

[Technical field]

[0001] The present invention relates to a bus bar for a battery pack and a battery pack. [Background technology]

[0002] In a battery pack that includes multiple secondary batteries such as lithium-ion secondary batteries, the positive and negative electrodes of adjacent secondary batteries are connected by a metal connection member called a bus bar. A bus bar is a flat plate-shaped member made of metal such as aluminum, copper, or iron, and is attached to the positive and negative electrodes of the secondary batteries by joining such as laser welding or ultrasonic welding, or by using fastening members.

[0003] The relative distance between the secondary battery cells in the battery pack may change to an undesired positional relationship during assembly or due to vibration during transportation. The relative distance between the secondary batteries may also change due to current flow or battery expansion and contraction. This may cause stress in the busbar or the positive and negative electrodes of the secondary batteries, raising concerns that this could lead to fatigue failure.

[0004] In order to relieve stress generated in a busbar or a secondary battery, it is known to form a stress relief portion in a middle portion in the longitudinal direction of the busbar by bending a flat plate perpendicular to the thickness direction by pressing, and protruding into a U-shape. In this structure, it is said that the stress relief portion deforms when the busbar thermally expands, thereby reducing the load transmitted to the positive and negative electrodes of the secondary battery. In addition, in such a structure, there is also a structure in which the stress relief portion formed in a U-shape is formed as a twisted portion twisted about 90° with respect to the thickness direction of the flat plate (for example, see Patent Document 1). However, there is almost no effect of relieving stress against a load applied perpendicular to the thickness direction, and even if the stress relief portion is formed as a twisted portion twisted about 90° with respect to the thickness direction of the flat plate, the rigidity of the twisted portion is large, so that it is basically the same as a busbar without a twisted portion, and it is not possible to expect an effect of relieving stress against a load applied perpendicular to the thickness direction.

[0005] In contrast, Patent Document 2 discloses a busbar for a battery pack that exhibits a stress relaxation effect, in which a first mounting surface 11 and a second mounting surface 12 are arranged parallel to an XY plane, a first rising surface 13 and a second rising surface 14 are arranged parallel to or inclined to a YZ plane, a connecting surface 15 is arranged parallel to or inclined to the XZ plane, the second rising surface is arranged parallel to or inclined to the YZ plane from a side portion of the second mounting surface on the same side as the first mounting surface in the X direction, the connecting surface has a recessed portion with a U-shaped cross section that is bent in a direction intersecting the Y direction, a first curved portion or inclined portion is formed between the first mounting surface and the first rising surface, and a second curved portion or inclined portion is formed between the second mounting surface and the second rising surface. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-73266 A [Patent Document 2] JP 2017-73398 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention relates to a busbar manufactured using USW, which is one of the joining methods in which multiple metal plates are laminated and joined in the thickness direction of the plates, and a battery pack using the same. USW does not require large-scale equipment, so USW-jointed busbars can be obtained at lower cost than pressure welding or FSW joining. However, as described above, these joining methods require a joint to be provided in the overlapping area of ​​multiple plates, so there is a problem that the upper limit of the joint strength is determined by the width of the overlapping area in the planar direction of the plates.

[0008] The busbar is arranged to bridge the positive and negative electrode terminals of adjacent batteries. Generally, the shape of the busbar is roughly flat, connecting the positive and negative electrode terminals, but when making the USW busbar in a roughly flat shape, especially when the linear distance between the terminals is short, the overlapping area in the planar direction between the plates is small, which can easily cause problems with the joint strength. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention uses a bus bar with an increased overlap area on one side between the metal plates to be joined. According to a first aspect of the present invention, as a method for ensuring the joint strength of the joint surface while providing a three-dimensional structure that relieves stress, a first member and a second member are overlapped and the overlapped portion is joined by ultrasonic welding to increase the joint area and increase the likelihood of the joint strength, thereby reducing the risk of fatigue failure of the bus bar arranged in the battery pack.

[0010] Specifically, the present invention relates to a battery comprising a plurality of stacked single cells each including a positive terminal and a negative terminal, and a bus bar connecting the positive terminal of a first of the single cells and the negative terminal of a second of the single cells, the bus bar having a positive electrode side conductive member joined to the positive terminal of the first of the single cells and a negative electrode side conductive member joined to the negative electrode terminal of a second of the single cells located adjacent to the first of the single cells, the positive electrode terminal and the positive electrode side conductive member being made of a material different from the negative electrode terminal and the negative electrode side conductive member, the positive electrode side conductive member having a first joint portion joined to the positive electrode terminal and a first extension portion extending from the first joint portion, the negative electrode side conductive member having a second joint portion joined to the negative electrode terminal and a second extension portion extending from the first joint portion, the second extension portion extends from a second joint and extends to the same side as the first extension portion with respect to a virtual line passing through the first joint and the second joint, and the first extension portion and the second extension portion are joined together; when viewed from a direction in which the bus bar and the single cell overlap, an end of the positive electrode side conductive member is positioned away from an end of the negative electrode side conductive member that faces the positive electrode side conductive member on the virtual line connecting the first joint and the second joint, and the third joint is a region in which one of the distances from the first joint or the second joint to the third joint is closer than the other, and is formed at an overlapping portion where the first extension portion and the second extension portion are overlapped. Effect of the Invention

[0011] The bus bar of the present invention can be deformed in different directions in three dimensions, which provides a stress relief effect against loads from any direction, and has a wide joint area in the planar direction of the overlapping plates, which makes it possible to sufficiently increase the strength of the joint surface against stress, thereby making it possible to provide a battery pack with a low risk of fatigue failure of the bus bar. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is an exploded perspective view of the battery pack according to the present invention. [Diagram 2] FIG. 2 is a perspective view of a bus bar according to the first embodiment. [Diagram 3]FIG. 2 is an exploded perspective view of the bus bar according to the first embodiment. [Figure 4] FIG. 11 is a perspective view of a bus bar according to a comparative example. [Diagram 5] FIG. 11 is a perspective view of a bus bar according to a second embodiment. [Figure 6] FIG. 11 is an exploded perspective view of a bus bar according to a second embodiment. [Figure 7] FIG. 11 is a perspective view of a bus bar according to a third embodiment. [Figure 8] FIG. 11 is an exploded perspective view of a bus bar according to a third embodiment. [Figure 9] FIG. 11 is a perspective view of a bus bar according to a fourth embodiment. [Figure 10] FIG. 13 is a perspective view of a bus bar according to a fifth embodiment. [Figure 11] FIG. 13 is a perspective view of a bus bar according to a sixth embodiment. [Figure 12] FIG. 13 is a perspective view of a bus bar according to a seventh embodiment. [Figure 13] FIG. 13 is a perspective view of a bus bar according to an eighth embodiment. [Figure 14] FIG. 13 is a perspective view of a bus bar according to a ninth embodiment. [Figure 15] FIG. 23 is a perspective view of a bus bar according to a tenth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An example of a battery pack busbar and a battery pack according to the present invention will be described below with reference to the drawings. Fig. 1 is an exploded perspective view showing an example of a battery pack to which the present invention is applied. As shown in Fig. 1, the battery pack 1 has a structure in which a large number of unit cells 2 are fixed by a pair of end plates 4 and a pair of side plates 5. The unit cells 2 are, for example, prismatic secondary batteries such as lithium ion secondary batteries.

[0014] The rectangular cell 2 has a rectangular parallelepiped shape with an upper surface, a lower surface, a pair of flat surfaces with a large area, and a pair of side surfaces with a small area. The size of the cell 2 is, for example, a major axis of 12 cm, a minor axis of 1.2 cm, and a height of 6.5 cm, but this is merely an example and the cell can be of various sizes. The cells 2 are arranged in a row with the larger flat surfaces facing each other, and holders 3 are interposed between the cells 2, in front of the cell 2 at the top of the row, and behind the cell 2 at the bottom of the row.

[0015] The unit cells 2 have a positive electrode 2a and a negative electrode 2b on the upper side, and all have the same size, shape, and structure. Adjacent unit cells 2 are arranged with the positive electrode 2a and the negative electrode 2b facing each other, in other words, with the front and back planes alternately inverted. The positive electrode 2a is formed of an aluminum-based metal such as aluminum or an aluminum alloy, and the negative electrode 2b is formed of a copper-based metal such as copper or a copper alloy.

[0016] End plates 4 are disposed in front of the first holder 3 in the row and behind the last holder 3 in the row. The pair of end plates 4 are made of a metal material and have a substantially rectangular shape, with openings 4a at the four corners through which bolts 6 are inserted. A pair of side plates 5 are disposed on the sides of the cells 2 arranged in a row. Each side plate 5 is a rectangular frame having span sections spaced apart above and below and connecting sections that connect these span sections. Openings 5a are formed at each corner of the frame in correspondence with the openings 4a of the end plates 4.

[0017] The battery pack 1 is formed by placing the end plate 4 at the front of the row and the end plate 4 at the rear of the row inside the front and rear connecting parts of each side plate 5, and fastening the end plates 4 by inserting bolts 6 through openings 5a of the side plates 5 and openings 4a of the end plates 4. The bolts 6 are screwed into threaded holes (not shown) formed in the holder 3, or fastened by placing nuts (not shown) on the back sides of the end plates 4. Fastening with bolts 6 may be replaced by fastening with rivets.

[0018] An insulating cover 7 is disposed on the upper side of each cell 2 so as to surround the positive and negative electrodes 2a, 2b of the cells 2 arranged in a row. The positive electrodes 2a and negative electrodes 2b of adjacent cells 2 are connected by a bus bar 10. All the cells 2 are connected in series by the bus bar 10. An end bus bar 8 is connected to the positive electrode 2a1 of the first cell 2 in the row and the negative electrode 2b1 of the last cell 2 in the row. The bus bar 10 or the end bus bar 8 is joined to the positive and negative electrodes 2a, 2b by welding such as laser welding or ultrasonic welding. A structure in which the connection is made by screw fastening instead of welding may be used.

[0019] The busbars 10 arranged on one of the continuous insulating covers 7 have approximately the same shape and structure. The busbars 10 arranged on the other continuous insulating cover 7 have a shape that is approximately a mirror image of the busbars 10 arranged on one of the insulating covers 7. The end busbar 8 has an attachment surface that is connected to one of the positive and negative electrodes 2a, 2b of the cell 2, and a through hole for screw fastening is provided at the end opposite to the attachment surface. The present invention is characterized in the structure of the busbar 10, and one embodiment of the busbar 10 will be described below. EXAMPLES

[0020] Fig. 2 is an external perspective view of the battery pack busbar 10 according to the first embodiment shown in Fig. 1, and Fig. 3 is an exploded perspective view. The busbar 10 includes a first plate 11 formed by pressing a single sheet metal made of a metal such as aluminum or an aluminum alloy, a copper-based metal such as copper or a copper alloy, or iron, and a second plate 12 formed by pressing a single sheet metal made of a material different from that of the first plate 11, such as aluminum or an aluminum alloy, a copper-based metal such as copper or a copper alloy, or iron. In the following description, the X direction, the Y direction perpendicular to the X direction, and the Z direction perpendicular to the X and Y directions are as shown in Fig. 3.

[0021] The busbar 10 is composed of a first plate 11, which is a positive electrode side conductive member joined to the positive electrode terminal 2a of the first cell, and a second plate 12, which is a negative electrode side conductive member joined to the negative electrode terminal 2b of the second cell located adjacent to the first cell. The first plate 11, which is a positive electrode side conductive member, has a first joint portion 111 joined to the positive electrode terminal 2a and a first extension portion 112 extending from the first joint portion 111.

[0022] On the other hand, the second plate 12, which is the negative electrode side conductive member, has a second joint 121 joined to the negative electrode terminal 2b and a second extension portion 122 extending from the second joint portion 121 and extending to the same side as the first extension portion 112 with respect to a virtual line passing through the first joint portion 111 and the second joint portion 121.

[0023] In addition to these, the busbar 10 has a third extension portion 13 extending from at least one of the first extension portion 111 and the second extension portion 121, from an end face of the extension portion 112 or 122, and the third extension portion 13 extends almost parallel to the overlapping direction of the single cells 2, and has a third joint portion 131 in which at least a part of the face of the third extension portion 13 and the other extension portion 112 or 122 is joined by ultrasonic welding. The third joint portion 13 is located at a position perpendicular to a virtual line connecting the first joint portion 111 and the second joint portion 121. Also, the end portion of the first plate 11, which is a positive electrode side conductive member, and the end portion of the second plate 12, which is a negative electrode side conductive member, are located at a position apart. That is, the ends are not butted together. Furthermore, the third joint portion 131 is configured such that the distance between the third joint portion 131 and either the first joint portion 111 or the second joint portion 121 is shorter than the distance between the third joint portion 131 and the other.

[0024] The reason for using the busbar 10 having such a shape is that the flatness of the busbar 10 arranged at the upper part of the terminal is required. In other words, if the part of the busbar arranged at the upper part of the terminal is not flat, there is a problem that when the terminal and the busbar are joined in a subsequent process, there is a possibility that a problem occurs in pressing during joining, and a joining failure is likely to occur. On the other hand, in the case of USW (Ultrasonic welding) joining, joining marks specific to USW joining are generated. As a result, there is a problem that the upper surface and the lower surface of the busbar are not flat. In contrast, when the busbar 10 of the present invention is used, there is an advantage that the area for joining the first plate 11 and the second plate 12 can be made large while maintaining the flatness of the upper part of the terminal. Therefore, the joining strength of the first plate 11 and the second plate 12 can be increased.

[0025] That is, in a simple overlapping structure, when a third joint is used above and below the surface connecting the positive electrode terminal and the negative electrode terminal, the flatness is required, so that the joint area must be made small. By using the busbar 10 of the present invention, this problem can be solved. By using the busbar 10 of the present invention, no joint marks are left on the upper surface of the terminals of the busbar 10, so the joint area can be made large.

[0026] A concrete calculation of the joining area that can be adopted is as follows. Here, the area in the planar direction of the plates is described. That is, the width of the first plate 11 is A, the width of the second plate 12 is B, the distance between the first plate 11 and the second plate 12 is C, and the width of the third extension part is D. In this case, the maximum area S1 that can be ultrasonically joined in the bus bar of the present invention can be expressed as S1 = (A + B + C) x D. Examples of A, B, C, and D are A = 1 cm, B = 1 cm, C = 5 mm, and D = 2 mm to 10 mm. Examples of the plate thickness of the first plate 11 and the second plate 12 are, for example, 0.5 mm to 1.5 mm, and more preferably, about 0.6 mm to 0.8 mm.

[0027] However, the above dimensions are examples, and there are no particular limitations on the widths of A, B, C, and D, and any size is acceptable as long as they can be installed in a module or pack. Also, as long as the joining surface is in the area where the extension part and the other plate overlap, the effects of the present invention can be obtained regardless of the area and location of the joining surface.

[0028] In this case, the third extension portion 13 or the fourth extension portion may be provided extending from the end face of the first extension portion 112 and the second extension portion 122, and in this case as well, the maximum area S1 is as shown in Fig. 2. Note that a voltage detection wire can be attached to the first extension portion 112, the third extension portion 131, and the second extension portion 122 of the busbar 10 at a location where no USW joint is provided.

[0029] At least one of the first plate 11 and the second plate 12 in the busbar 10 may be nickel-plated on a surface where the first plate 11 and the second plate 12 are physically connected to each other. Both the first plate 11 and the second plate 12 may be nickel-plated. The surface to be nickel-plated may be only a part of the surface where the first plate 11 and the second plate 12 are physically connected to each other, or the entire surface. In addition, the surface to be nickel-plated may be only the surface where the first plate 11 and the second plate 12 are physically connected to each other, or the nickel plating may be applied to other surfaces of the plates as well.

[0030] By applying nickel plating to the surface where the first plate 11 and the second plate 12 are physically connected to each other, the process margin of the joining can be increased when joining an aluminum-based metal and a copper-based metal, and as a result, the joining strength of the joining surface can be increased. In addition, the effect of suppressing corrosion of the aluminum-based metal can be expected. The thickness of the applied nickel plating is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and most preferably 4 μm or more and 10 μm or less. The process margin of the USW joining can also be increased by increasing the thickness of this nickel plating. The glossiness of the nickel plating can be matte, semi-gloss, or glossy plating, and any glossiness can be selected according to the joining conditions.

[0031] Glossiness can be measured using a glossmeter. Specifically, the glossiness is measured by measuring the intensity of light incident from directly above the plate surface, I in And the light is at 45 degrees to the incident light. is the intensity of the reflected light out log(I in / I o ut ) is defined as the glossiness, the glossiness is preferably 0.2 to 2.5, more preferably 0.3 to 2.5, and most preferably 0.6 to 2.5. By keeping the glossiness in this range, the process margin of USW joining can be increased.

[0032] A specific example of the combination of this embodiment 1 will be shown. The first plate 11 can be made of pure aluminum, the second plate 12 can be made of oxygen-free copper, and the surface of the second plate 12 can be nickel-plated. The thickness of the nickel plating can be 5 μm, and the glossiness can be 2.0. Nickel plating methods include electroplating and electroless plating. Either method can be used as long as USW bonding can be achieved, but electroplating is preferred.

[0033] FIG. 4 is a perspective view showing a comparative example of the busbar 10. In FIG. 4, a flat first plate 11 and a flat second plate 12 are butt-jointed at their end faces. Hereinafter, this configuration is called a flat clad material. In FIG. 4, the first plate 11 and the second plate are joined at a joint surface 30. A mixed region 31 of the material constituting the first plate 11 and the material constituting the second plate is formed over a width w in the planar direction of the plates, centered on the joint surface 30. The width w is, for example, 1 mm. In the configuration shown in FIG. 4, since there is no impression by USW, the reliability of the connection at the positive electrode or the negative electrode can be ensured. However, the flat clad material as shown in FIG. 4 has a problem of high cost. EXAMPLES

[0034] FIG. 5 is a perspective view showing Example 2. In Example 2, in contrast to the first embodiment, in addition to the third extension portion 13, a protrusion 113 for attaching a voltage detection line is provided on an end face of the extension portion 112 extending from the first plate 11. FIG. 6 is an exploded perspective view of FIG. 5. The rest of the configuration is the same as that of Example 1. Although not shown here, a protrusion 113 for attaching a voltage detection line may be provided on the extension portion 122 extending from the second plate 12. In this case, too, the maximum area S2 in the planar direction of the plate that can be ultrasonically bonded in the bus bar of the present invention is S2=(A+B+C)×D, and the bonding area can be increased in the same manner. EXAMPLES

[0035] FIG. 7 is a perspective view showing Example 3. In FIG. 7, the first extension portion 112 and the second extension portion 122 present on the first plate 11 and the second plate 12 are bent in comparison with the configuration of Example 1, and a third extension portion 13 is provided extending from both the extension portions 112 and 122. FIG. 8 is an exploded perspective view of FIG. 7. The rest of the configuration is the same as that of Example 1. The maximum area S3 in the planar direction of the plate that can be ultrasonically bonded in the busbar 10 in Example 3 is S3=(A+B+C)×D, and can be made large. In this case, the bending angle may be any angle as long as it can be attached inside the module or pack. In this embodiment, an angle of 45 degrees is shown, but even if it is 90 degrees, the maximum area that can be ultrasonically bonded does not change. Note that a voltage detection line can be attached to the first extension portion 112 and the second extension portion 122 of the busbar 10 at the portion where the USW joint portion is not provided. EXAMPLES

[0036] Fig. 9 is a perspective view showing Example 4. Fig. 9 shows a configuration in which a protrusion 114 for attaching a voltage detection line is added to the first plate 11 in the opposite direction to the first extension portion in the configuration of Example 3. The other configurations are the same as those of Example 3. In Example 4 as well, the maximum area S4 in the planar direction of the plate that can be ultrasonically joined with the bus bar of the present invention can be expressed as S4 = (A + B + C) × D, and the joining area can be made large. EXAMPLES

[0037] FIG. 10 is a perspective view of Example 5. FIG. 10 shows a configuration in Example 3 in which the first extension 112 and the second extension 122 present on the first plate 11 and the second plate 12 are bent, a third extension 13 is extended from one of the extensions 112 or 122, and the third extension 13 is provided with a scaled structure 14 for relieving stress. In Example 5, the bending angle of the third extension with respect to the first extension and the second extension is set to 90 degrees, but similar effects can be obtained with other angles. The other configurations are the same as those of Example 3. In this case, if the length of the scaled structure 14 is E, the maximum area S5 in the planar direction of the plate that can be ultrasonically bonded in the busbar 10 of the present invention can be expressed as S5=(A+CE)×D or S5=(B+CE)×D, and the bonding area can be made large. EXAMPLES

[0038] Fig. 11 is a perspective view showing Example 6. Fig. 11 shows a configuration in which, in the configuration of Example 1, a third extension portion 13 is provided extending in the second direction from one of the first extension portion 112 or the second extension portion 122 present on the first plate 11 and the second plate 12 in plan view. The other configurations are the same as those of Example 1. In Example 6 as well, the maximum area S6 in the planar direction of the plates that can be ultrasonically joined in the busbar 10 can be expressed as S6 = A x D or S6 = B x D, and the joining area can be made large. EXAMPLES

[0039] Fig. 12 is a perspective view showing Example 7. Fig. 12 shows a configuration in which the first extension portion 112 and the second extension portion 122 present on the first plate 11 and the second plate 12 in the configuration of Example 1 are bent, a third extension portion 13 is provided extending from one of the extension portions, and a scaled structure 14 is provided on a part of the third extension portion 13. The rest of the configuration is the same as that of Example 1. In this case, the maximum area S7 in the planar direction of the plates that can be ultrasonically joined in the bus bar of the present invention can be expressed as S7 = (A + CE) × D or S7 = (B + CE) × D, and the joining area can be made large. EXAMPLES

[0040] Fig. 13 is a perspective view showing Example 8. Fig. 13 shows a configuration in which the first extension portion 112 and the second extension portion 122 present on the first plate 11 and the second plate 12 in Example 3 are bent, and a third extension portion 13 is extended from one of the extension portions. In Example 8, the bending angle is set to 90 degrees, but similar effects can be obtained with other angles. The other configurations are the same as those of Example 3. In this case, the maximum area S8 in the planar direction of the plate that can be ultrasonically bonded in the busbar 10 in Example 8 can be expressed as S8 = A x D or S8 = B x D, and the bonding area can be made large. EXAMPLES

[0041] Fig. 14 is a perspective view showing Example 9. In Fig. 14, protrusions 114 for attaching a voltage detector are provided on one of first plate 11 and second plate 12, and the other configuration is the same as that of Example 5. In Example 9, the bending angle of third extension portion 13 with respect to first extension portion 112 or second extension portion 122 is set to 90 degrees, but similar effects can be obtained with other angles. In this case, if the length of scaled structure 14 is E, the maximum area S9 in the planar direction of the plate that can be ultrasonically joined with the busbar of the present invention can be expressed as S9 = (A + CE) × D or S9 = (B + CE) × D, and the joining area can be made large. EXAMPLES

[0042] FIG. 15 is a perspective view showing Example 10. FIG. 15 shows a configuration in which the first extension portion 112 and the second extension portion 122 present on the first plate 11 and the second plate 12 are bent, and a third extension portion 13 is extended from one of the extension portions 112 or 122, and the extension portion 13 has a reversed relationship to that of Example 8. The horn and anvil of the USW may be applied in such a way that the horn is on the first plate 11 side and the anvil is on the second plate 12 side, or the horn is on the second plate 12 side and the anvil is on the first plate 11 side. In either case, the effect of the present invention can be obtained. In Example 10, the bending angle is set to 90 degrees, but the same effect can be obtained with other angles. The other configurations are the same as those of Example 3. In the busbar 10 of Example 10, the maximum area S3 in the planar direction of the plate that can be ultrasonically bonded can also be expressed as S3=(A+B+C)×D, and the bonding area can be made large.

[0043] It should be noted that the above-described embodiments are merely examples. For example, the effects of the present invention can be obtained even when the thicknesses of the first plate 11 and the second plate 12 are changed. The position and area of ​​the connecting surface of the busbar 10 can be changed in various ways according to the length of each extension portion 3. Furthermore, curved portions, bent portions, and inclined portions may be added to the flat portions of each extension portion, or steps may be added, as appropriate. Furthermore, the structures shown in the above-described embodiments may be combined.

[0044] The method of attaching the bus bar and the voltage detection wire in the present invention is not particularly limited, but examples include ultrasonic bonding, laser welding, screw fastening, crimping, etc. Furthermore, the structure provided on the bus bar for extracting the voltage detection wire can be provided at any desired location on the bus bar as long as it does not interfere with other components of the battery pack. Furthermore, the shape of the structure may also vary.

[0045] For example, as shown in the embodiment, the protrusion may be provided as an extension in a direction parallel to the plate surface of the bus bar, or may be provided as a protrusion structure in a direction perpendicular to the plate surface of the bus bar. The protrusion structure may not only be flat, but also have a complex three-dimensional structure. A press-fit connector may be attached to the protrusion structure to attach a voltage detection line. The protrusion structure may be freely three-dimensional in accordance with the size of the press-fit connector and the handling of the connector inside the battery pack.

[0046] The present invention is not limited to the busbar 10 for connecting a lithium-ion secondary battery, but can also be applied to a busbar for connecting a secondary battery that uses a water-soluble electrolyte, such as a nickel-metal hydride battery, a nickel-cadmium battery, or a lead-acid battery. The present invention can also be applied to a busbar for connecting a storage element, such as a lithium-ion capacitor or an electrolytic double layer capacitor.

[0047] In addition, the battery pack bus bar 10 of the present invention can be modified in various ways and applied. [Explanation of symbols]

[0048] REFERENCE SIGNS LIST 1...battery assembly, 2...cell, 2a...positive electrode, 2b...negative electrode, 3...holder, 4...end plate, 4a...opening, 5...side plate, 5b...opening, 6...bolt, 7...insulating cover, 8...end bus bar, 10...bus bar, 10...display panel, 11...first plate (positive electrode side conductive member), 12...second plate (negative electrode side conductive member), 13...third extension, 14...scale structure, 20...end of electrode terminal, 30...joint surface, 31...mixed region, 111...first joint, 112...first extension, 113...first projection, 114...second projection, 121...second joint, 122...second extension, 131...third joint

Claims

1. A first battery having a first positive terminal and a first negative terminal arranged at a first interval in a first direction, and a second battery having a second positive terminal and a second negative terminal arranged at a second interval in the first direction are arranged in a second direction intersecting the first direction, a battery pack in which the first positive electrode terminal and the second negative electrode terminal are arranged adjacent to each other in the second direction, and a bus bar connects the first positive electrode terminal and the second negative electrode terminal, the first conductive member of the bus bar has a first joint portion joined to the first positive terminal and a first extension portion extending from the first joint portion in the first direction, the second conductive member of the bus bar has a second joint portion joined to the second negative terminal and a second extension portion extending from the second joint portion in the first direction, the first conductive member and the second conductive member are made of different materials, the first conductive member and the second conductive member are connected at a third joint; an end of the first extension portion and an end of the second extension portion are spaced apart from a line connecting the first joint portion and the second joint portion in the first direction; the third joint portion is formed at an overlapping portion of the first extension portion and the second extension portion, with one of the third joint portion and the first joint portion being closer to the first joint portion or the second joint portion than the other.

2. The first extension portion further includes a third extension portion extending in the second direction, 2 . The battery pack according to claim 1 , wherein the third joint portion is present at an overlapping portion of the second extension portion and the third extension portion.

3. The second extension portion further includes a fourth extension portion extending in the second direction, 2 . The battery pack according to claim 1 , wherein the third joint portion is present in an overlapping portion of the first extension portion and the fourth extension portion.

4. The second extension portion further includes a fourth extension portion extending in the second direction, 3. The battery pack according to claim 2, wherein the third joint portion is present at an overlapping portion of the third extension portion and the fourth extension portion.

5. 2 . The battery pack according to claim 1 , wherein the first conductive member or the second conductive member has a projection for voltage detection in the first direction in a plan view.

6. 5. The battery pack according to claim 2, wherein a surface on which the third joint portion is formed is angled with respect to a surface on which the first joint portion and the second joint portion are formed.

7. The assembled battery according to any one of claims 1 to 6, wherein the first extending portion and the second extending portion are joined via nickel or a nickel alloy.

8. The assembled battery according to claim 2, wherein the third extending portion has a telescopic structure in a region other than the region where the third joining portion is formed.

9. The assembled battery according to claim 3, wherein the fourth extending portion has a telescopic structure in a region other than the region where the third joining portion is formed.

10. The assembled battery according to claim 4, wherein the third extending portion or the fourth extending portion has a telescopic structure in a region other than the region where the third joining portion is formed.

11. The first battery and the second battery are rectangular parallelepipeds, the first positive electrode terminal and the first negative electrode terminal of the first battery are formed on the same surface of the rectangular parallelepiped, and the second positive electrode terminal and the second negative electrode terminal of the second battery are formed on the same surface of the rectangular parallelepiped. The assembled battery according to claim 1, characterized in that.

12. The assembled battery according to claim 1, wherein a plurality of sets of the first battery and the second battery are arranged in the second direction.

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