Joint structure and battery module

Abstract

To improve joining strength of mutually different metallic materials by laser wobbling welding.SOLUTION: A joint structure includes a first conductive body C1 and a second conductive body C2 which are joined to each other via a joint portion JC having a laser weld mark circularly wobbled with respect to a predetermined weld direction WD and are made of different metallic materials to each other. A plurality of cavities CV are arranged at a predetermined pitch in the weld direction WD between the first conductive body C1 and the second conductive body C2.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a joint structure and a battery module. [Background technology]

[0002] In recent years, various techniques relating to laser welding have been developed.

[0003] Patent Document 1 describes joining metal and resin together by laser welding.

[0004] Patent Document 2 describes laser scanning processing of a metal surface in a predetermined scanning direction and in another scanning direction different from the predetermined scanning direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-117724 [Patent Document 2] International Publication No. 2007 / 072603 Summary of the Invention [Problem to be solved by the invention]

[0006] Laser wobbling welding is sometimes used to join different metal materials together, and in laser wobbling welding, it is desirable that the joining strength between the metal materials is high.

[0007] An example of an object of the present invention is to improve the joining strength of dissimilar metal materials by laser wobbling welding. Other objects of the present invention will become apparent from the description of this specification. [Means for solving the problem]

[0008] One aspect of the present invention is as follows. 1. A pair of conductors made of different metal materials are joined together via a joint having a laser welding mark that is circularly wobbled in a predetermined welding direction, A joining structure in which a plurality of cavities are arranged at a predetermined pitch in the welding direction between the pair of conductors. 2. The joint structure described in 1., wherein the metal material of one of the pair of conductors and the metal material of the other of the pair of conductors are aluminum and copper, respectively. 3. A battery module having the joining structure described in 1. or 2. [Effects of the Invention]

[0009] According to the above-described aspects of the present invention, it is possible to improve the joining strength of different metal materials by laser wobbling welding. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is an exploded top perspective view of the battery module according to the embodiment. [Figure 2] 1 is a side view of a joining structure comprising a first conductor and a second conductor joined together by laser welding. [Figure 3] FIG. 2 is a top view of a laser path in laser welding of the joining structure according to the embodiment. [Figure 4] FIG. 10 is a top view of a laser path in laser welding of a joining structure according to a comparative example. [Figure 5] 10 is a diagram showing the results of energy dispersive X-ray analysis (EDS) of laser welding according to an embodiment when the distance G between the opposing surfaces of the first conductor and the second conductor is 0.00 mm. FIG. [Figure 6] FIG. 10 is a diagram showing the results of EDS of laser welding according to an embodiment when the distance G between the opposing surfaces of the first conductor and the second conductor is 0.15 mm. [Figure 7] FIG. 10 is a diagram showing the results of EDS of laser welding according to an embodiment when the distance G between the opposing surfaces of the first conductor and the second conductor is 0.20 mm. [Figure 8]FIG. 10 is a diagram showing the results of EDS of laser welding according to an embodiment when the distance G between the opposing surfaces of the first conductor and the second conductor is 0.25 mm. [Figure 9] FIG. 10 is a diagram showing the results of EDS of laser welding according to a comparative example when the distance G between the opposing surfaces of the first conductor and the second conductor is 0.00 mm. [Figure 10] FIG. 10 is a diagram showing the results of EDS of laser welding according to a comparative example when the distance G between the opposing surfaces of the first conductor and the second conductor is 0.15 mm. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, similar components are designated by similar reference numerals, and the description thereof will be omitted as appropriate.

[0012] FIG. 1 is an exploded perspective view of a battery module 100 according to an embodiment.

[0013] For the sake of explanation, FIG. 1 shows the X, Y, and Z directions. The X direction indicates the front-to-rear direction of the battery module 100. The Y direction is perpendicular to the X direction. The Y direction indicates the left-to-right direction of the battery module 100. The Z direction is perpendicular to both the X and Y directions. The Z direction indicates the up-down direction of the battery module 100. The arrows pointing to the X direction, the Y direction, and the Z direction indicate the front, left, and up directions of the battery module 100, respectively. Hereinafter, as necessary, the tip side of an arrow indicating the X direction will be referred to as the +X side, the opposite side of the tip of the arrow indicating the X direction will be referred to as the -X side, the tip side of an arrow indicating the Y direction will be referred to as the +Y side, the opposite side of the tip of the arrow indicating the Y direction will be referred to as the -Y side, the tip side of an arrow indicating the Z direction will be referred to as the +Z side, and the opposite side of the tip of the arrow indicating the Z direction will be referred to as the -Z side. The relationship between the X direction, Y direction, and Z direction and the front-rear direction, left-right direction, and up-down direction of the battery module 100 is not limited to the above example.

[0014] The battery module 100 includes a plurality of battery cells 110 , a plurality of compression pads 120 , a front voltage detection device 130 , a rear voltage detection device 140 , and a container 150 .

[0015] The multiple battery cells 110 are stacked in the Y direction. The multiple compression pads 120 and the multiple battery cells 110 are stacked alternately in the Y direction. Each compression pad 120 is arranged between adjacent battery cells 110 in the Y direction and on both sides of the multiple battery cells 110 in the Y direction. Hereinafter, as necessary, the multiple battery cells 110 and the multiple compression pads 120 stacked alternately in the Y direction will be referred to as a stack of battery cells 110. The dimension of each battery cell 110 in the X direction is the dimension in the longitudinal direction of each battery cell 110. The dimension of each battery cell 110 in the Z direction is the dimension in the lateral direction of each battery cell 110. The dimension of each battery cell 110 in the Y direction is the dimension in the thickness direction of each battery cell 110. The shape of each battery cell 110 is not limited to this example.

[0016] Each battery cell 110 includes a battery element (not shown), an exterior material 112, a positive electrode tab 114, and a negative electrode tab 116. In one example, the battery element includes a plurality of positive electrodes and a plurality of negative electrodes (not shown) stacked alternately in the Y direction, and a separator (not shown) positioned between adjacent positive electrodes and negative electrodes in the Y direction. The exterior material 112 seals the battery element and an electrolyte (not shown). The positive electrode tab 114 is electrically connected to the positive electrode of the battery element. The positive electrode tab 114 is drawn out from one of both sides of the exterior material 112 in the X direction. The negative electrode tab 116 is electrically connected to the negative electrode of the battery element. The negative electrode tab 116 is drawn out from the other side of the exterior material 112 in the X direction. However, the structure of each battery cell 110 is not limited to this example.

[0017] Each battery cell 110 may be an all-solid-state battery. In an all-solid-state battery, a solid electrolyte layer is provided in the portion corresponding to the separator. An all-solid-state battery does not contain an electrolyte solution. Unless otherwise specified, the following description will be given assuming that each battery cell 110 is a battery cell containing an electrolyte solution.

[0018] The multiple battery cells 110 are electrically connected in a combination of series and parallel. Specifically, cell groups including at least two battery cells 110 adjacent to each other in the Y direction and connected in parallel are stacked in the Y direction and connected in series. A tab group 118 is located at the front side of the stack of battery cells 110. A positive electrode tab 114 drawn from a battery cell 110 of one cell group connected in parallel is electrically connected to a negative electrode tab 116 drawn from a battery cell 110 of another cell group connected in parallel, and the positive electrode tab 114 and the negative electrode tab 116 are electrically connected to each other. The positive electrode tab 114 and the negative electrode tab 116 in the tab group 118 are joined to each other by, for example, laser welding. A tab group 118 is also located at the rear of the stack of battery cells 110. Thus, multiple cell groups are connected in series from the cell group located at one end of the stack of battery cells 110 in the Y direction to the cell group located at the other end of the stack of battery cells 110 in the Y direction. Hereinafter, as necessary, the tab group 118 located on the front side of the stack of battery cells 110 will be referred to as the front tab group 118, and the tab group 118 located on the rear side of the stack of battery cells 110 will be referred to as the rear tab group 118.

[0019] The electrical connection of the plurality of battery cells 110 is not limited to the above example. For example, a stack of battery cells 110 may be formed by connecting single battery cells 110 in series.

[0020] The front voltage detection device 130 detects the voltages of the plurality of front tab groups 118. The front voltage detection device 130 includes a front protector 131, a plurality of front voltage detection terminals 132, a plurality of front voltage detection lines 133, a front connector 134, and a front bus bar 135.

[0021] The front protector 131 covers the front of the stack of battery cells 110. The front protector 131 is made of an insulating material such as resin. The front protector 131 defines multiple front openings 131a. Each of the multiple front tab groups 118 is exposed forward through each of the multiple front openings 131a.

[0022] Each of the front voltage detection terminals 132 is located in front of a corresponding one of the front tab groups 118. Each front voltage detection terminal 132 is made of a conductor such as metal. The rear surface of each front voltage detection terminal 132 is joined to the front surface of each front tab group 118 by a joining method such as laser welding. Therefore, each front voltage detection terminal 132 and each front tab group 118 are electrically connected to each other. Therefore, the front voltage detection device 130 can detect the voltage of each front tab group 118 using each front voltage detection terminal 132. The front voltage detection terminals 132 are held together by a front protector 131. Therefore, by placing the front protector 131 at an appropriate position relative to the stack of battery cells 110, each of the front voltage detection terminals 132 can be positioned appropriately relative to each of the front tab groups 118.

[0023] One end of each front voltage detection wire 133 is electrically connected to each front voltage detection terminal 132. The other end of each front voltage detection wire 133 is electrically connected to each front connector 134. Thus, the front voltage detection terminals 132 and the front connector 134 are electrically connected to each other via the front voltage detection wires 133. Each front voltage detection wire 133 is routed between one end of the front voltage detection wire 133 and the other end of the front voltage detection wire 133 via the front protector 131.

[0024] The front bus bar 135 is disposed at the right end of the front protector 131. The front bus bar 135 is electrically connected to the positive electrode tabs 114 that are pulled forward from the battery cells 110 of the cell group located at the right end of the stack of battery cells 110. The front bus bar 135 functions as an external terminal for electrically connecting the battery module 100 to an external device such as another battery module.

[0025] The rear voltage detection device 140 detects the voltages of the multiple rear tab groups 118. The rear voltage detection device 140 includes a rear protector 141, multiple rear voltage detection terminals 142, multiple rear voltage detection lines 143, a rear connector 144, and a rear bus bar 145.

[0026] The rear protector 141 covers the rear of the stack of battery cells 110. The rear protector 141 is made of an insulating material such as resin. The rear protector 141 defines multiple rear openings 141a. Each of the multiple rear tab groups 118 is exposed rearward through each of the multiple rear openings 141a.

[0027] Each of the rear voltage detection terminals 142 is located behind one of the rear tab groups 118. Each rear voltage detection terminal 142 is made of a conductor such as metal. The front surface of each rear voltage detection terminal 142 and the rear surface of each rear tab group 118 are joined together by a joining method such as laser welding. Therefore, each rear voltage detection terminal 142 and each rear tab group 118 are electrically connected to each other. Therefore, the rear voltage detection device 140 can detect the voltage of each rear tab group 118 using each rear voltage detection terminal 142. The rear voltage detection terminals 142 are held together by a rear protector 141. Therefore, by placing the rear protector 141 at an appropriate position relative to the stack of battery cells 110, each of the rear voltage detection terminals 142 can be positioned appropriately relative to each of the rear tab groups 118.

[0028] One end of each rear voltage detection line 143 is electrically connected to each rear voltage detection terminal 142. The other end of each rear voltage detection line 143 is electrically connected to each rear connector 144. Thus, the rear voltage detection terminals 142 and the rear connectors 144 are electrically connected to each other via the rear voltage detection lines 143. Each rear voltage detection line 143 is routed between one end of the rear voltage detection line 143 and the other end of the rear voltage detection line 143 via the rear protector 141.

[0029] The rear bus bar 145 is disposed at the left end of the rear protector 141. The rear bus bar 145 is electrically connected to the negative electrode tab 116 drawn rearward from the battery cell 110 of the cell group located at the left end of the stack of battery cells 110. The rear bus bar 145 functions as an external terminal for electrically connecting the battery module 100 to an external device such as another battery module.

[0030] 1 , the positive electrode tab 114 at the end of each of the plurality of serially connected cell groups is drawn forward from the battery cell 110 of the cell group located on the right end side of the stack of battery cells 110, and the negative electrode tab 116 at the end of each of the plurality of serially connected cell groups is drawn rearward from the battery cell 110 of the cell group located on the left end side of the stack of battery cells 110. Therefore, the front bus bar 135 is disposed on the right front side of the stack of battery cells 110, and the rear bus bar 145 is disposed on the left rear side of the stack of battery cells 110. However, the arrangement of the positive electrode tab 114 and the negative electrode tab 116 at the end of each of the plurality of serially connected cell groups may differ depending on the number of battery cells 110 included in the stack of battery cells 110. For example, there may be cases where the positive electrode tab 114 at the end of a group of multiple cells connected in series is pulled forward from the battery cell 110 of the cell group located on the right end side of the stack of battery cells 110, and the negative electrode tab 116 at the end of the group of multiple cells connected in series is pulled forward from the battery cell 110 of the cell group located on the left end side of the stack of battery cells 110. In this case, the bus bar electrically connected to the positive electrode tab 114 at the end of the group of multiple cells connected in series is arranged on the right front side of the stack of battery cells 110, and the bus bar electrically connected to the negative electrode tab 116 at the end of the group of multiple cells connected in series is arranged on the left front side of the stack of battery cells 110.

[0031] The housing 150 includes a front plate 151, a rear plate 152, a left plate 153, a right plate 154, an upper plate 155, and a lower plate 156. Each plate is, for example, a metal plate such as an aluminum plate.

[0032] The front plate 151 covers the +X side portion of the stack of battery cells 110 and the +X side portion of the front voltage detection device 130. The rear plate 152 covers the -X side portion of the stack of battery cells 110 and the -X side portion of the rear voltage detection device 140. The left plate 153 covers the +Y side portion of the stack of battery cells 110. The right plate 154 covers the -Y side portion of the stack of battery cells 110. The upper plate 155 covers the +Z side portion of the stack of battery cells 110. The lower plate 156 covers the -Z side portion of the stack of battery cells 110. A thermally conductive adhesive 160 is disposed between the upper surface of the lower plate 156 and the lower surface of the stack of battery cells 110. Therefore, heat generated from the stack of battery cells 110 can be dissipated downwards in the battery module 100 through the thermally conductive adhesive 160.

[0033] Fig. 2 is a side view of a joining structure including a first conductor C1 and a second conductor C2 joined together by laser welding. Fig. 3 is a top view of a laser path LP during laser welding of the joining structure according to the embodiment. Fig. 4 is a top view of a laser path LP during laser welding of a joining structure according to a comparative example.

[0034] For ease of explanation, the side where the first conductor C1 is located relative to the second conductor C2 will be referred to as the upper side, and the side where the second conductor C2 is located relative to the first conductor C1 will be referred to as the lower side. However, the relationship between the first conductor C1, the second conductor C2, and the up-down direction is not limited to this example. The first conductor C1 and the second conductor C2 may be upside down or oriented in a direction different from the up-down direction depending on the use of the first conductor C1 and the second conductor C2.

[0035] The first conductor C1 and the second conductor C2 are made of different metal materials. Metal materials refer to not only pure metals but also alloys. The metal materials used for the first conductor C1 and the second conductor C2 are not particularly limited, but include, for example, aluminum and copper. Unless otherwise specified, the following description will be given assuming that the metal material of the first conductor C1 is aluminum and the metal material of the second conductor C2 is copper. However, the metal materials of the first conductor C1 and the second conductor C2 are not limited to this example.

[0036] 2, the first conductor C1 and the second conductor C2 are joined to each other via a joint JC, which is formed by laser welding using a laser irradiated from above the first conductor C1.

[0037] The joint structure of the first conductor C1 and the second conductor C2 according to the embodiment can be used in various parts of the battery module 100 shown in FIG. 1 . In one example, the positive electrode tab 114 is made of aluminum, the negative electrode tab 116 is made of copper, the front bus bar 135 is made of copper, and the rear bus bar 145 is made of copper. In this example, for example, the positive electrode tab 114 and the front bus bar 135 can be the first conductor C1 and the second conductor C2, respectively, and the joint structure of the first conductor C1 and the second conductor C2 can be applied to the positive electrode tab 114 and the front bus bar 135. Alternatively, the positive electrode tab 114 and the negative electrode tab 116 in the tab group 118 can be the first conductor C1 and the second conductor C2, respectively, and the joint structure of the first conductor C1 and the second conductor C2 can be applied to the positive electrode tab 114 and the negative electrode tab 116 in the tab group 118.

[0038] As shown in Fig. 3, in laser welding according to the embodiment, multiple circular laser spots LS are formed along a laser path LP. As shown by the laser path LP in Fig. 3, the laser irradiated in laser welding is wobbled circularly with respect to the welding direction WD. Specifically, the laser is irradiated in a state in which a circular motion as wobbling is superimposed on a linear motion along a center line CL parallel to the welding direction WD. Therefore, when viewed from above the first conductor C1, the joint JC according to the embodiment has a laser weld mark that is wobbled circularly with respect to the welding direction WD.

[0039] In the laser welding according to the embodiment, the ratio of the area irradiated with the laser spot LS per unit length in the welding direction WD on the center line CL is adjusted. As shown in Fig. 3, in the laser welding according to the embodiment, multiple dense regions D where the laser spots LS are formed relatively densely because the laser paths LP intersect near the center line CL, and multiple sparse regions S where the laser spots LS are formed relatively sparsely between adjacent dense regions D, are alternately present in the welding direction WD.

[0040] The laser welding according to the comparative example is similar to the laser welding according to the embodiment, except for the following points.

[0041] The ratio of the irradiated area of ​​the laser spot LS per unit length in the welding direction WD on the center line CL of the laser welding according to the comparative example is higher than the ratio of the irradiated area of ​​the laser spot LS per unit length in the welding direction WD on the center line CL of the laser welding according to the embodiment. As shown in Fig. 4, in the laser welding according to the comparative example, a plurality of dense regions D and a plurality of sparse regions S alternate at a narrow pitch in the welding direction WD, compared to the laser welding according to the embodiment.

[0042] Fig. 5 is a diagram showing the results of energy dispersive X-ray analysis (EDS) of laser welding according to an embodiment in which the distance G between the opposing surfaces of the first conductor C1 and the second conductor C2 is 0.00 mm. Fig. 6 is a diagram showing the results of EDS of laser welding according to an embodiment in which the distance G between the opposing surfaces of the first conductor C1 and the second conductor C2 is 0.15 mm. Fig. 7 is a diagram showing the results of EDS of laser welding according to an embodiment in which the distance G between the opposing surfaces of the first conductor C1 and the second conductor C2 is 0.20 mm. Fig. 8 is a diagram showing the results of EDS of laser welding according to an embodiment in which the distance G between the opposing surfaces of the first conductor C1 and the second conductor C2 is 0.25 mm. Fig. 9 is a diagram showing the results of EDS of laser welding according to a comparative example in which the distance G between the opposing surfaces of the first conductor C1 and the second conductor C2 is 0.00 mm. FIG. 10 is a diagram showing the results of EDS of laser welding according to a comparative example in which the distance G between the opposing surfaces of the first conductors C1 and the second conductors C2 is 0.15 mm.

[0043] 2, the distance G between the opposing surfaces of the first conductor C1 and the second conductor C2 is the distance between the bottom surface of the first conductor C1 and the top surface of the second conductor C2. When the distance G is 0.00 mm, this means that the bottom surface of the first conductor C1 and the top surface of the second conductor C2 are in contact with each other.

[0044] The EDS shown in Figures 5 to 10 shows mapping of copper element. In each of Figures 5 to 10, the bars with "Cu 0%" and "Cu 100%" at the bottom and top, respectively, indicate the proportion of copper element.

[0045] In the laser welding according to the embodiment shown in FIGS. 5 to 8, the ratio of the area irradiated with the laser spot LS per unit length in the welding direction WD on the center line CL is adjusted.

[0046] In the laser welding according to the comparative example shown in FIGS. 9 and 10, the ratio of the area irradiated with the laser spot LS per unit length in the welding direction WD on the center line CL is adjusted.

[0047] In this embodiment, as shown in Figures 5 to 8, the second conductor C2 includes a plurality of aluminum-containing regions AL. The aluminum-containing regions AL are arranged at a predetermined pitch in the welding direction WD. The aluminum-containing regions AL are formed in the dense regions D shown in Figure 3.

[0048] In this embodiment, as shown in Figures 5 to 8, a plurality of cavities CV are present between the first conductor C1 and the second conductor C2. The plurality of cavities CV are arranged at a predetermined pitch in the welding direction WD. Each cavity CV does not contain either the aluminum contained in the first conductor C1 or the copper contained in the second conductor C2. The plurality of cavities CV are formed in a plurality of sparse regions S shown in Figure 3.

[0049] In the comparative example, as shown in FIGS. 9 and 10, regions corresponding to the aluminum-containing regions AL in the embodiment and regions corresponding to the cavities CV in the embodiment are not observed.

[0050] The EDS of the embodiment and the ESD of the comparative example will be compared with each other with reference to FIGS.

[0051] The upper surface of the first conductor C1 in the embodiment is flatter than in the comparative example. This result suggests that the aggregation and movement of the first conductor C1 during laser welding is suppressed more in the embodiment than in the comparative example. Therefore, it can be said that the bonding strength between the first conductor C1 and the second conductor C2 can be improved by the amount that the aggregation and movement of the first conductor C1 is suppressed more in the embodiment than in the comparative example.

[0052] The reason why the aggregation and movement of the first conductors C1 can be suppressed more effectively in the embodiment than in the comparative example will be explained.

[0053] As shown in FIGS. 3 and 4 , in the embodiment, multiple dense regions D and multiple sparse regions S are alternately arranged at a wider pitch in the welding direction WD than in the comparative example. Therefore, in the embodiment, when multiple laser spots LS are formed along the laser path LP, it is estimated that the temperature at the center of each sparse region S and its vicinity is lower than the temperature at the center of each sparse region S and its vicinity. It is estimated that the higher the temperature of the first conductors C1, the more likely the first conductors C1 are to aggregate and move. Therefore, in the embodiment, it is estimated that the first conductors C1 are less likely to aggregate and move at the center of each sparse region S and its vicinity than at the center of each sparse region S and its vicinity. Therefore, as shown in FIGS. 6 to 8 , when the lower surface of the first conductor C1 and the upper surface of the second conductor C2 are separated from each other in advance, a cavity CV remains between the first conductor C1 and the second conductor C2. Alternatively, as shown in FIG. 5 , when the lower surface of the first conductor C1 and the upper surface of the second conductor C2 are in contact with each other in advance, the first conductors C1 partially move to form a cavity CV between the first conductor C1 and the second conductor C2. The reason why a cavity CV is formed even when the lower surface of the first conductor C1 and the upper surface of the second conductor C2 are in contact with each other beforehand is presumably because the temperature between the contact surfaces of the first conductor C1 and the second conductor C2 becomes relatively high during laser welding, causing the first conductor C1 to partially move near the interface between the first conductor C1 and the second conductor C2 at the center of each sparse region S and its vicinity.

[0054] 3 and 4, in the comparative example, a plurality of dense regions D and a plurality of sparse regions S are alternately arranged at narrower intervals in the welding direction WD than in the embodiment. Therefore, in the comparative example, it is estimated that the temperature of the first conductors C1 during laser welding is relatively high throughout the entire laser path LP, regardless of the position in the welding direction WD. Therefore, it is estimated that in the comparative example, the first conductors C1 are more likely to aggregate and move toward the periphery of the laser-irradiated portion than in the embodiment.

[0055] A comparison between the embodiments and comparative examples reveals that when multiple aluminum-containing regions AL and multiple cavities CV are arranged alternately at a predetermined pitch in the welding direction WD, the bonding strength of the first conductor C1 and the second conductor C2 is improved compared to when there are no regions corresponding to the aluminum-containing regions AL and the cavities CV.

[0056] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various other configurations can also be adopted. [Explanation of symbols]

[0057] 100 battery module, 110 battery cell, 112 exterior material, 114 positive electrode tab, 116 negative electrode tab, 118 tab group, 120 compression pad, 130 front voltage detection device, 131 front protector, 131a front opening, 132 front voltage detection terminal, 133 front voltage detection line, 134 front connector, 135 front bus bar, 140 rear voltage detection device, 141 rear protector, 141a rear opening, 142 rear voltage detection terminal, 143 rear voltage detection line, 144 rear connector, 145 rear bus bar, 150 housing, 151 front plate, 152 rear plate, 153 left plate, 154 right plate, 155 upper plate, 156 lower plate, 160 thermally conductive adhesive, AL aluminum-containing area, C1 first conductor, C2 Second conductor, CL centerline, CV cavity, D dense area, JC joint, LP laser path, LS laser spot, S sparse area, WD welding direction

Claims

1. a pair of conductors made of different metal materials and joined to each other via a joint having a laser welding mark that is circularly wobbled in a predetermined welding direction; A joining structure in which a plurality of cavities are arranged at a predetermined pitch in the welding direction between the pair of conductors.

2. The joint structure according to claim 1 , wherein the metal material of one of the pair of conductors and the metal material of the other of the pair of conductors are aluminum and copper, respectively.

3. A battery module having the joining structure according to claim 1 or 2.

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