Battery module

Abstract

To obtain a battery module that can reduce the man hour of welding and stabilize bonding strength at welding between a bus bar and a plurality of electrode leads.SOLUTION: A battery module 11 includes a plurality of battery cells 20 stacked on each other, a bus bar 30 electrically connected to electrode leads 26 of the battery cells, a welding part 50 that, at an overlap part 30A where a plurality of end parts of the electrode leads are overlapped on the bus bar, bonds the end parts and the bus bar, and a heat input part 60 that is formed at a position overlapping with the welding part in at least one of the electrode lead and the bus bar, where the heat input property in a bonding direction is made higher than that in the other part.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] The battery module disclosed in the following Patent Document 1 includes a plurality of battery cells stacked on top of each other and a busbar unit electrically connected to electrode leads of the plurality of battery cells. In this battery module, ends of two electrode leads are gathered on the busbar unit and joined by welding or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7062162 Summary of the Invention [Problem to be solved by the invention]

[0004] When welding the ends of multiple electrode leads onto a bus bar, it is possible to simultaneously weld the multiple electrode leads from the viewpoint of reducing man-hours. However, in a battery module formed by stacking multiple battery cells on one another, stress may occur at the welded portion between the electrode lead and the bus bar due to expansion of the battery cells that occurs when the battery module swells, and therefore, when simultaneously welding multiple electrode leads, it is desirable to stabilize the joint strength during welding in order to prevent the electrode leads from coming off the bus bar.

[0005] In consideration of the above, an object of the present invention is to provide a battery module that can reduce the number of welding steps when welding a bus bar to a plurality of electrode leads and can stabilize the joint strength during welding. [Means for solving the problem]

[0006] A battery module of a first aspect includes a plurality of battery cells stacked on top of each other, a bus bar electrically connected to electrode leads of a plurality of the battery cells, a welding portion that joins the bus bar to the ends of the electrode leads at an overlapping portion where the ends of the electrode leads overlap each other on the bus bar, and a heat input portion that is formed in at least one of the electrode lead and the bus bar at a position that overlaps the welding portion and has a higher heat input property in the joining direction than other portions.

[0007] The battery module of the first aspect includes a plurality of battery cells stacked on top of each other. The electrode leads of each battery cell are electrically connected to the bus bar via welds. A weld is formed on the bus bar at an overlapping portion where the ends of the electrode leads overlap each other, joining the bus bar and the ends of the electrode leads. This allows the electrode leads to be simultaneously welded to the bus bar, reducing the number of welding steps. In the first aspect, a heat input portion having a higher heat input in the joining direction than other portions is formed at a position overlapping the weld in at least one of the electrode lead and the bus bar. As a result, when the electrode leads are simultaneously welded to the bus bar by laser welding or the like, the heat input to the base material can be increased and the joining strength of the weld can be stabilized.

[0008] A second aspect of the battery module is the same as the first aspect, wherein the heat input portion is configured with a visible surface treatment, and is formed at least on the electrode lead that constitutes the processed surface of the weld portion.

[0009] In the battery module of the second embodiment, the heat input portion is formed on the electrode lead that constitutes the processed surface of the weld at the overlapping portion on the bus bar. Note that the "processed surface of the weld" here means the surface that is contacted with a welder when simultaneously welding the ends of multiple electrode leads.

[0010] Here, in the second embodiment, the heat input portion is configured with a visible surface treatment. Therefore, even when the electrode leads are stacked, it is easy to align the folding positions and welding positions of the electrode leads 26 with respect to the bus bar. As a result, a battery module with excellent productivity can be obtained.

[0011] A battery module of a third aspect is the battery module of the first or second aspect, wherein the heat input portion is configured of a thin-walled portion of at least one of the electrode leads that is thinner than other portions of the electrode leads.

[0012] In the battery module of the third aspect, a thin-walled portion that is thinner than other portions is formed at a position that overlaps with the welded portion, thereby forming a heat input portion that has higher heat input in the joining direction of the welded portion than other portions. As a result, when multiple electrode leads are simultaneously welded to the bus bar side by laser welding or the like, the heat input to the base material can be increased and the joining strength of the welded portion can be stabilized.

[0013] A fourth aspect of the battery module is the first or second aspect, in which the welded portion is formed in a dot shape when viewed from the joining direction, and the heat input portion is formed by providing a through hole in at least one of the electrode leads, the through hole having a diameter smaller than the dot diameter of the welded portion.

[0014] In the battery module of the fourth aspect, the welded portion is formed in a dot shape when viewed from the joining direction. In the second aspect, a through hole having a diameter smaller than the dot diameter of the welded portion is provided at a position overlapping with the welded portion, thereby increasing the surface area of ​​the welded portion. This forms a heat input portion having a higher heat input in the joining direction of the welded portion than other portions. Furthermore, by forming the heat input portion as a through hole, the heat input at the center of the welded portion can be efficiently increased, and the melting of the base material at the center of the welded portion can be deepened. As a result, when multiple electrode leads are simultaneously welded to the bus bar side by spot welding using a laser or the like, the joining strength of the welded portion can be effectively stabilized.

[0015] A battery module of a fifth aspect is the battery module of the first or second aspect, wherein the heat input portion is formed by roughening a surface of at least one of the electrode leads.

[0016] In the battery module of the fifth aspect, the surface of the electrode lead is roughened at the position overlapping the welded portion to increase the surface area of ​​the welded portion, forming a heat input portion that has a higher heat input in the joining direction of the welded portion than other portions. As a result, when multiple electrode leads are simultaneously welded to the bus bar side by laser welding or the like, the joining strength of the welded portion can be effectively stabilized.

[0017] A battery module of a sixth aspect is the battery module of the first or second aspect, wherein the heat input portion is formed by applying a black material to a surface of at least one of the electrode leads.

[0018] In the battery module of the sixth aspect, a black material is applied to the surface of the electrode lead at a position overlapping the welded portion, forming a heat input portion that has a higher heat input in the joining direction of the welded portion than other portions. As a result, when multiple electrode leads are simultaneously welded to the bus bar side by laser welding or the like, the joining strength of the welded portion can be effectively stabilized. Effect of the Invention

[0019] As described above, in the battery module according to the present invention, the number of welding steps can be reduced when welding the bus bar to the multiple electrode leads, and the joint strength during welding can be stabilized. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic plan view showing a main part of a vehicle to which a battery pack according to an embodiment is applied; [Diagram 2] FIG. 1 is a schematic perspective view of a battery module according to an embodiment. [Diagram 3] FIG. 2 is a plan view of the battery module according to the embodiment with the top lid of the module case removed. [Figure 4] 3 is a schematic diagram of a battery cell accommodated in a battery module as viewed from the thickness direction. FIG. [Diagram 5] 4 is a schematic plan view showing, in a partially enlarged manner, a state in which a plurality of battery cells are housed in a module case. FIG. [Figure 6] 6A and 6B are enlarged views of welded portions joining multiple electrode leads and a bus bar, where (A) is an enlarged front view seen from direction A in FIG. 5, and (B) is an enlarged cross-sectional view showing a cross section cut along line BB in FIG. 6A. [Figure 7] 7(A) to (D) are enlarged cross-sectional views corresponding to FIG. 6(B), showing examples of a heat input portion formed in a welded portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, one embodiment of the present invention will be described with reference to Figs. 1 to 7(D).

[0022] (Overall configuration of vehicle 100) Fig. 1 is a schematic plan view showing a main part of a vehicle 100 to which a battery pack 10 according to an embodiment is applied. As shown in Fig. 1, the vehicle 100 is an electric vehicle (BEV: Battery Electric Vehicle) in which the battery pack 10 is mounted under the floor. Note that arrows UP and FR in each drawing indicate the battery pack 10 mounted under the floor. The arrows L and LH indicate the upper side in the vehicle vertical direction, the front side in the vehicle longitudinal direction, and the left side in the vehicle width direction, respectively. When the directions of front, rear, left, right, top and bottom are used in the description, they refer to the front and rear in the vehicle longitudinal direction, the left and right in the vehicle width direction, and the top and bottom in the vehicle vertical direction, unless otherwise specified.

[0023] As an example, in the vehicle 100 of this embodiment, a DC / DC converter 102, an electric compressor 104, and a PTC (Positive Temperature Coefficient) heater 106 are disposed on the vehicle front side of the battery pack 10. In addition, a motor 108, a gear box 110, an inverter 112, and a charger 114 are disposed on the vehicle rear side of the battery pack 10.

[0024] The direct current output from the battery pack 10 has its voltage adjusted by a DC / DC converter 102, and is then supplied to an electric compressor 104, a PTC heater 106, an inverter 112, etc. In addition, power is supplied to a motor 108 via the inverter 112, causing the rear wheels to rotate and causing the vehicle 100 to run.

[0025] A charging port 116 is provided on the right side at the rear of the vehicle 100, and by connecting a charging plug of an external charging device (not shown) to the charging port 116, power can be stored in the battery pack 10 via the on-board charger 114.

[0026] The arrangement and structure of each component constituting the vehicle 100 are not limited to the above-mentioned configuration. For example, the present invention may be applied to a hybrid vehicle (HV: Hybrid Vehicle) equipped with an engine or a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle). In addition, in the present embodiment, the vehicle is a rear-wheel drive vehicle in which the motor 108 is mounted at the rear of the vehicle, but the present invention is not limited to this. The vehicle may be a front-wheel drive vehicle in which the motor 108 is mounted at the front of the vehicle, or a pair of motors 108 may be mounted at the front and rear of the vehicle. Furthermore, the vehicle may be equipped with an in-wheel motor on each wheel.

[0027] Here, the battery pack 10 is configured to include a plurality of battery modules 11. As an example in this embodiment, ten battery modules 11 are provided. Specifically, five battery modules 11 are arranged on the right side of the vehicle 100 in the vehicle front-rear direction, and five battery modules 11 are arranged on the left side of the vehicle 100 in the vehicle front-rear direction. In addition, each battery module 11 is electrically connected.

[0028] Fig. 2 is a schematic perspective view of the battery module 11. As shown in Fig. 2, the battery module 11 includes a module case 16 that forms an outer shell. The module case 16 is formed in a substantially rectangular parallelepiped shape with the vehicle width direction as the longitudinal direction. The module case 16 is made of an aluminum alloy. For example, the module case 16 is formed by joining aluminum die castings to both ends of an aluminum alloy extrusion material by laser welding or the like.

[0029] A pair of voltage terminals 12 and a connector 14 are provided at both ends of the battery module 11 in the vehicle width direction. A flexible printed circuit board 21, which will be described later, is connected to the connector 14. In addition, bus bars 30 (see FIG. 4) are welded to both ends of the battery module 11 in the vehicle width direction.

[0030] The length MW of the battery module 11 in the vehicle width direction is, for example, 350 mm to 600 mm, the length ML in the vehicle front-rear direction is, for example, 150 mm to 250 mm, and the height MH in the vehicle up-down direction is, for example, 80 mm to 110 mm.

[0031] Fig. 3 is a plan view of the battery module 11 with the top cover removed. As shown in Fig. 3, battery cells 20 serving as batteries are housed inside the module case 16. As an example, a plurality of battery cells 20 are housed in an arranged (stacked) state inside the module case 16. In this embodiment, 24 battery cells 20 are arranged in the front-rear direction of the vehicle and bonded to one another.

[0032] For ease of understanding, in each of Figures 3 to 6, the direction indicated by arrow W is the width direction of battery cell 20, the direction indicated by arrow H is the height direction (up and down direction) of battery cell 20, and the direction indicated by arrow D is the thickness direction of battery cell 20. The width direction of the battery case 22, which will be described later, coincides with the width direction W of the battery cells 20. The height direction of the battery case 22 coincides with the height direction H of the battery cells 20. The thickness direction of the battery case 22 coincides with the thickness direction D of the battery cells 20.

[0033] On the battery cell 20, a flexible printed circuit board (FPC) is The flexible printed circuit board 21 is formed in a strip shape with its longitudinal direction aligned with the vehicle width direction, and a thermistor 23 is provided at each end of the flexible printed circuit board 21. The thermistor 23 is not bonded to the battery cells 20, and is configured to be pressed towards the battery cells 20 by the upper lid of the battery module 11.

[0034] Furthermore, one or more cushioning materials (not shown) are housed inside the module case 16. For example, the cushioning materials are elastically deformable thin plate-like members, and are arranged between adjacent battery cells 20 with the arrangement direction of the battery cells 20 being the thickness direction. As an example in this embodiment, cushioning materials are arranged at both ends of the module case 16 in the longitudinal direction and in the central portion in the longitudinal direction.

[0035] Fig. 4 is a schematic diagram of a battery cell 20 accommodated in a battery module 11, as viewed from a thickness direction D. As shown in Fig. 4, the battery cell 20 is formed into a long rectangular plate shape with the width direction W as the longitudinal direction, and includes a battery case 22 forming an outer shell. An electrode body 40 is accommodated inside the battery case 22. The electrode body 40 is configured by laminating a positive electrode as an electrode, a negative electrode as an electrode, and a separator. In this embodiment, the battery case 22 is configured from a laminate film, and the electrode body 40 is sealed by the laminate film.

[0036] The battery case 22 is embossed on at least one side in the thickness direction of the battery case 22. By the embossing, a concave housing portion 221 in which the electrode body 40 is housed and an outer end portion 223 provided on the outside of the housing portion 221 are formed on the side. The battery case 22 may adopt both a single cup embossed structure in which one embossed portion is embossed and a double cup embossed structure in which two embossed portions are embossed, but the present embodiment adopts a single cup embossed structure with a drawing depth of about 8 mm to 10 mm. Therefore, the battery case 22 has a first side surface portion 22A on one side in the thickness direction as an embossed surface that forms an internal housing space of the battery cell 20. The battery case 22 has a second side surface portion 22B (see FIG. 5) on the other side in the thickness direction as a flat non-embossed surface that is not embossed.

[0037] The upper end of the battery case 22 in the width direction is bent and the corners are chamfered to form a generally trapezoidal shape. The upper end of the battery case 22 is also bent, and a fixing tape 24 is wound around the upper end of the battery case 22 along the width direction.

[0038] Here, the battery cell 20 is provided with an electrode lead 26 that protrudes from an end of the battery case 22. The electrode lead 26 is provided at both ends of the battery cell in the width direction. In the present embodiment, as an example, the electrode lead 26 is provided at a position offset downward from the center of the battery cell 20 in the height direction H. One end of the electrode lead 26 is connected to the electrode body 40 inside the battery case 22. The other end of the electrode lead 26 protrudes from the end of the battery case 22 in the width direction and is electrically joined to the bus bar 30 via a welded portion 50 (see FIG. 5). The electrode lead 26 is connected to external wiring of the battery module 11 via the bus bar 30. The electrode lead 26 and the bus bar 30 can be welded to each other by any known welding method as appropriate, but in one example of the present embodiment, the electrode lead 26 and the bus bar 30 are joined to each other by laser welding.

[0039] The length CW1 of the battery cell 20 in the vehicle width direction is, for example, 530 mm to 600 mm, 600 mm to 700 mm, 700 mm to 800 mm, 800 to 900 mm, 1000 mm or more, the length CW2 of the region in which the electrode body is housed is, for example, 500 mm to 520 mm, 600 mm to 700 mm, 700 mm to 800 mm, 800 to 900 mm, 1000 mm or more, and the height CH of the battery cell 20 is, for example, 80 mm to 110 mm, 110 mm to 140 mm. In addition, the thickness of the battery cell 20 is 5.0 mm to 7.0 mm, 7.0 mm to 9.0 mm, 9.0 mm to 11.0 mm, and the height TH of the electrode lead (terminal) 26 is 40 mm to 50 mm, 50 mm to 60 mm, 60 mm to 70 mm.

[0040] 5 is a schematic plan view showing, in a partially enlarged manner, a state in which multiple battery cells 20 are housed in a module case 16. As shown in this figure, the other ends of the electrode leads 26 protrude from the ends in the width direction W of the multiple battery cells 20 that are stacked on top of each other inside the module case 16. In addition, plate-shaped bus bars 30 are arranged on both sides of the battery cells 20 in the width direction W.

[0041] For ease of explanation, FIG. 5 illustrates a state in which adjacent battery cells 20 are spaced apart; however, in reality, the stacked battery cells 20 are in contact with each other either directly or via a cushioning material, and are constrained to each other with a predetermined confining pressure applied along the stacking direction (thickness direction D).

[0042] The busbar 30 has a thickness direction that is the width direction W of the battery cells 20, and extends along the stacking direction (thickness direction D) of the battery cells 20. In addition, the busbar 30 has a slot-shaped through hole 32 formed therein that penetrates the busbar 30 in the thickness direction.

[0043] The other end of the electrode lead 26 protruding from the end of the battery cell 20 in the width direction W is inserted into the through hole 32 of the bus bar 30. In addition, the end 261 protruding from the through hole 32 is folded back towards the bus bar 30 and overlaps the surface of the bus bar 30.

[0044] The busbar 30 has a plurality of through holes 32 formed along the extension direction of the busbar 30 (thickness direction D in FIG. 5 ), and the electrode leads 26 protruding from the plurality of battery cells 20 are inserted into these through holes 32 and joined to the busbar 30. In this way, the plurality of battery cells 20 are electrically connected via the busbar 30. FIG. 5 shows a state in which the electrode leads 26 protruding from two battery cells 20 are joined to the busbar 30 via one welding part 50. As shown in FIG. 5 , the two electrode leads 26 are respectively inserted into different through holes 32 formed in the busbar 30. Then, the tip parts 261 of the two electrode leads 26 are folded back toward the busbar 30 in the direction in which they approach each other. As a result, an overlapping part 30A is formed on the surface of the busbar 30, where the end parts 261 of the two electrode leads 26 are overlapped. The electrode leads 26 are joined to the busbar 30 via the welding part 50 at the overlapping part 30A.

[0045] Fig. 6(A) is an enlarged front view of the welded portion 50 as viewed from the direction of the arrow A in Fig. 5. Fig. 6(B) is an enlarged cross-sectional view showing the cross section of the welded portion 50 taken along the line BB in Fig. 6(A).

[0046] 6(A) and 6(B), the welded portion 50 joins the ends 261 of the two electrode leads 26 stacked in the plate thickness direction to the surface of the busbar 30. Furthermore, a heat input portion 60 is formed on the surface of the end 261 of one of the two electrode leads 26 that is stacked on the upper side and constitutes the processed surface of the welded portion 50 at a position overlapping the welded portion 50. The heat input portion 60 is a region of the end 261 of the electrode lead 26 that has been surface-treated to increase heat input compared to other regions.

[0047] The term "heat input" used here refers to the ease with which heat (heat input) is transferred to the welded portion (base material) when welding.

[0048] In this embodiment, a heat input portion 60 is formed in a linear region extending on the surface of an end portion 261 of the electrode lead in the width direction of the electrode lead (height direction H in FIG. 6(A)).

[0049] The welded portion 50 can be formed by, for example, laser welding or arc welding. In one example of this embodiment, the welded portion 50 is formed by spot welding using a laser. Therefore, the welded portion 50 is formed in a circular dot shape when viewed from the joining direction (the plate thickness direction of the bus bar 30). In joining the electrode lead 26 and the bus bar 30, a plurality of welded portions 50 are formed along a heat input portion 60 formed in a linear region.

[0050] 7(A) to 7(D), examples of heat input portion 60 will be described. Here, several examples of forming heat input portion 60 by surface processing of electrode lead 26 will be described, but when the processed surface of welded portion 50 is configured as the surface of busbar 30, heat input portion 60 may be provided on busbar 30, or may be provided on both electrode lead 26 and busbar 30. Also, heat input portion 60 may be provided on end portion 261 of another electrode lead 26 arranged between busbar 30 and upper electrode lead 26. Each figure shows a state before the welded portion 50 is formed on the base materials, the electrode lead 26 and the bus bar 30, and the welded area is indicated by an area P surrounded by a two-dot chain line.

[0051] In the example shown in Figs. 7(A) to 7(C), the heat input portion 60 is formed by surface treatment that increases the surface area of ​​the welding portion.

[0052] 7(A) is configured by forming a linear groove 61 extending in the width direction of the electrode lead 26 in the end 261 of the electrode lead 26. This groove 61 increases the surface area of ​​the processed surface of the welded portion 50, improving the heat input. The groove 61 also forms a thin-walled portion that is thinner than other portions. This also improves the heat input.

[0053] In the illustrated example, the cross-sectional shape of the groove 61 is V-shaped. Therefore, the plate thickness of the end 261 of the electrode lead 26 becomes thinner toward the center of the welding range P. This increases the heat input at the center of the welded portion 50 compared to the outer periphery, and the melting of the base material becomes deeper at the center. As a result, the joint strength can be effectively increased. Note that the cross-sectional shape of the groove 61 is not limited to a V-shape, and may be a rectangle or a concave curved shape (U-shape).

[0054] The second heat input section 60B shown in FIG. 7(B) is composed of a through hole 63 provided in the end 261 of the electrode lead 26. The diameter of the through hole 63 is set smaller than the diameter of the dot-shaped welded section 50. The inner surface of the through hole 63 increases the surface area of ​​the welded section. This increases the heat input in the joining direction of the welded section 50 compared to other parts. In addition, the shape of the through hole 63 can efficiently increase the heat input toward the center of the welded section 50, and the melting of the base material becomes deeper on the center side of the welded section 50. As a result, the joining strength can be effectively increased.

[0055] In a third heat input portion 60C shown in FIG. 7(C), the surface of the end portion 261 of the electrode lead 26 is roughened more than other portions, thereby increasing the surface area of ​​the welded portion 50.

[0056] 7(D) is formed by surface processing in which a black material 68 is applied to the surface of the end 261 of the electrode lead 26. This allows the black material 68 to absorb the laser light, increasing the heat input of the welded portion 50 and allowing deeper penetration into the base material.

[0057] Each of the heat input sections 60 (60A to 60D) listed in the above-mentioned FIGS. 7(A) to 7(D) is configured by surface processing that is visible from the processed surface of the welded section 50.

[0058] (Action and Effects) As described above, the battery module 11 according to the embodiment includes a plurality of battery cells 20 stacked on top of each other. The electrode leads 26 of each battery cell 20 are electrically joined to the bus bar 30 via the welds 50. The welds 50 that join the bus bar 30 and the ends 261 of the electrode leads 26 to each other are formed on the bus bar 30 at overlapping portions 30A where the ends 261 of the electrode leads 26 overlap each other. This allows the electrode leads 26 to be simultaneously welded to the bus bar 30, reducing the number of welding steps. In this embodiment, at least one of the electrode leads 26 and the bus bar 30 has a heat input portion 60 that has a higher heat input in the joining direction than other portions, formed at a position that overlaps with the welds 50. As a result, when the electrode leads 26 are simultaneously welded to the bus bar 30 by laser welding or the like, the heat input to the base material can be increased, and the joining strength of the welds 50 can be stabilized.

[0059] Moreover, the heat input portion 60 is formed at the end 261 of the electrode lead 26 that constitutes the processed surface of the welded portion 50 at the overlapping portion 30A on the busbar 30. Moreover, the heat input portion 60 is configured with a visible surface treatment. Therefore, even in a state where the multiple electrode leads 26 are overlapped, it is possible to easily align the folding positions and welding positions of the multiple electrode leads 26 with respect to the busbar 30. As a result, a battery module with excellent productivity can be obtained. When heat input portions 60 are formed on both the electrode lead 26 and the bus bar 30, the widthwise length of the heat input portion on the bus bar side may be formed to be longer than the width of the electrode lead 26 so that both heat input portions 60 are visible when viewed from the joining direction.

[0060] 7(A), the heat input portion 60 can be configured with a thin-walled portion having a thickness thinner than other portions. By forming a thin-walled portion (groove portion 61) having a thickness thinner than other portions at a position overlapping the welded portion 50, the heat input in the joining direction of the welded portion 50 is increased compared to other portions, and the joining strength of the welded portion 50 can be stabilized.

[0061] 7(B), the heat input section 60 may be configured by providing a through hole 63 having a diameter smaller than the dot diameter of the welded section 50 at the end 261 of the electrode lead 26. The inner surface of the through hole 63 increases the surface area of ​​the welded section, and the shape of the through hole 63 can increase the heat input toward the center of the welded section 50. Therefore, the penetration of the base material can be deepened toward the center of the welded section 50 while increasing the heat input of the welded section. This can more effectively stabilize the joint strength of the welded section 50.

[0062] 7(C), the heat input section 60 may be formed by roughening the surface of the electrode lead at the position overlapping the welded section 50. Roughening the surface of the electrode lead 26 increases the surface area of ​​the welded section, and the heat input in the joining direction of the welded section can be increased more than in other areas. This effectively stabilizes the joining strength of the welded section 50.

[0063] In addition, as shown in FIG. 7(D), the heat input portion 60 may be improved by applying a black material 68 to the surface of the end portion 261 of the electrode lead 26 at the position overlapping with the welded portion 50, thereby stabilizing the bonding strength of the welded portion 50.

[0064] In this embodiment, the welded portion 50 is formed by spot welding using a laser in a dot shape when viewed from the joining direction of the welded portion 50. This reduces the surface area of ​​the welded portion 50 into which the base material is melted, suppresses distortion of the base material and welding burns caused by welding heat, and reduces the number of steps in the finishing process.

[0065] Although one embodiment and one modified example have been described above, the present invention can be modified in various ways without departing from the spirit and scope of the present invention. For example, in the above embodiment, the ends of the two electrode leads are simultaneously joined together with the bus bar 30, but this is not limited to this. Ends of three or more electrode leads 26 may be overlapped on the surface of the bus bar, and these ends may be simultaneously joined via welds. [Explanation of symbols]

[0066] 11 Battery module 20 Battery Cells 30 Busbar 26 Electrode Lead 261 End 50 Welding 60 Heat input section (60A~60D) 61 Groove (thin wall) 63 Through hole 68 Black material

Claims

1. A plurality of battery cells stacked on top of each other; a bus bar electrically connected to the electrode leads of the plurality of battery cells; a welded portion that joins the ends of the electrode leads to the bus bar at an overlapping portion where the ends of the electrode leads are overlapped on the bus bar; a heat input portion formed in at least one of the electrode lead and the bus bar at a position overlapping the welded portion and having a higher heat input in a joining direction than other portions; A battery module comprising:

2. The heat input portion is configured with a visible surface treatment, which is formed at least on the electrode lead that constitutes the treatment surface of the weld portion. The battery module according to claim 1 .

3. The heat input portion is configured of a thin-walled portion having a plate thickness thinner than other portions of at least one of the electrode leads. The battery module according to claim 1 or 2.

4. The welded portion is formed in a dot shape when viewed from the joining direction, The heat input portion is formed by providing a through hole having a diameter smaller than a dot diameter of the welded portion in at least one of the electrode leads. The battery module according to claim 1 or 2.

5. The heat input portion is configured by roughening a surface of at least one of the electrode leads. The battery module according to claim 1 or 2.

6. The heat input portion is formed by applying a black material to a surface of at least one of the electrode leads. The battery module according to claim 1 or 2.

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