Battery module

Abstract

To obtain a battery module that can stabilize bonding strength at welding in a welding part to bond a bus bar and an electrode lead.SOLUTION: A battery module 11 includes a plurality of battery cells 20 stacked on each other, an electrode lead 26 projecting from the battery cell, a bus bar 30 electrically bonded to the electrode lead through a welding part 50 at an overlap part 30A where end parts of the electrode leads are overlapped, 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 6

Description

[Technical field]

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

[0002] 2. Description of the Related Art There is known a battery module in which a plurality of battery cells are stacked on one another to form an assembled battery. In such a battery module, electrode leads extending from the plurality of battery cells are electrically connected to a bus bar.

[0003] Furthermore, in electric power devices, a joining method by welding is known as a method for electrically connecting an electrode lead and a bus bar (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 03313062 Summary of the Invention [Problem to be solved by the invention]

[0005] In a battery module formed by stacking a plurality of battery cells on one another, as described above, the electrode leads extending from the plurality of battery cells are electrically connected to the bus bar. Therefore, stress may be generated at the welded portion between the electrode lead and the bus bar due to the expansion of the battery cells that occurs when the battery module swells, and it is desirable to stabilize the joint strength during welding in order to prevent the electrode lead from coming off the bus bar.

[0006] In consideration of the above, an object of the present invention is to provide a battery module that can stabilize the joint strength during welding at the welds that join the bus bars and the electrode leads. [Means for solving the problem]

[0007] A battery module of a first aspect includes a plurality of battery cells stacked on top of each other, electrode leads protruding from the battery cells, a bus bar having an overlapping portion where ends of the electrode leads overlap and are electrically joined to the electrode leads at the overlapping portion via a welded portion, and 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 property in the joining direction than other portions.

[0008] The battery module of the first aspect includes a plurality of battery cells stacked on top of each other. The electrode leads protruding from each battery cell are electrically connected to the bus bar via welds. In the first aspect, a heat input portion is formed in at least one of the electrode lead and the bus bar at a position overlapping the weld. The heat input portion has a higher heat input in the joining direction of the weld than other portions. This increases the heat input to the base material when the electrode leads extending from the plurality of battery cells are welded to the bus bar by laser welding or the like, and stabilizes the joining strength of the weld.

[0009] The battery module of the second aspect is the battery module of the first aspect, wherein the heat input portion is configured of a thin-walled portion having a plate thickness smaller than that of other portions.

[0010] In the battery module of the second 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. This makes it possible to increase heat input to the base material and stabilize the joining strength of the welded portion when welding the electrode leads extending from the multiple battery cells to the bus bar by laser welding or the like.

[0011] A third aspect of the battery module is the same as the second aspect, wherein the thin-walled portion defines a groove portion extending linearly in at least one of the electrode lead and the bus bar, and a plurality of the welds are formed along the groove portion so as to form a dot shape when viewed from the joining direction.

[0012] In the battery module of the third aspect, the thin-walled portion constituting the heat input portion forms a linearly extending groove in at least one of the electrode lead and the bus bar. A plurality of welds are formed along the linearly extending groove so as to form a dot shape when viewed from the joining direction. In this way, the thin-walled portion formed by the linear groove can accommodate the plurality of welds when joining the electrode lead to the bus bar side via dot-shaped welds by laser welding or the like. This allows the joining strength of the plurality of welds to be stabilized by easy processing, thereby improving productivity.

[0013] A fourth aspect of the battery module is based on the third aspect, and wherein the groove has a V-shaped cross section.

[0014] In the battery module of the fourth aspect, the cross-sectional shape of the groove is V-shaped, so that when the electrode leads extending from the multiple battery cells are welded to the bus bar by laser welding or the like, the penetration of the base material can be deepened toward the center of the weld, thereby more effectively stabilizing the joint strength of the weld.

[0015] A fifth aspect of the battery module is based on the third aspect, wherein the groove has a cross-sectional shape that is a concave curved surface.

[0016] In the battery module of the fifth aspect, the cross-sectional shape of the groove is made concavely curved, so that when the electrode leads extending from the multiple battery cells are welded to the bus bar by laser welding or the like, the penetration of the base material can be deepened toward the center of the weld. Furthermore, the surface area of ​​the groove is further increased, and the heat input can be efficiently increased. This makes it possible to more effectively stabilize the joint strength of the weld. Effect of the Invention

[0017] As described above, in the battery module according to the present invention, the joint strength during welding can be stabilized at the welded portions that join the bus bars and the electrode leads. [Brief description of the drawings]

[0018] [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 a welded portion joining an electrode lead 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 7(E) are enlarged cross-sectional views corresponding to FIG. 6(B), showing examples of heat input parts formed in the welded parts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, one embodiment of the present invention will be described with reference to Figs. 1 to 7(E).

[0020] (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 the arrows UP, FR, and LH in each figure 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 describing using the front-rear, left-right, up-down directions, they refer to the front-rear in the vehicle longitudinal direction, the left-right in the vehicle width direction, and the up-down in the vehicle vertical direction, unless otherwise specified.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] For ease of explanation, FIG. 5 illustrates only one battery cell 20 inside the battery case 16; however, in reality, multiple 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).

[0040] 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.

[0041] 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.

[0042] A plurality of through holes 32 are formed in the bus bar 30 along the extension direction of the bus bar 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 bus bar 30. In this way, the plurality of battery cells 20 are electrically connected via the bus bar 30. As shown in FIG. 5 , the electrode lead 26 is inserted into the through hole 32 formed in the bus bar 30. Then, the tip portion 261 of the electrode lead 26 is folded back towards the bus bar 30. In this way, an overlapping portion 30A is formed on the surface of the bus bar 30, where the end portion 261 of the electrode lead 26 overlaps. The electrode lead 26 is joined to the bus bar 30 at the overlapping portion 30A via a welding portion 50.

[0043] 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).

[0044] 6(A) and 6(B), the welded portion 50 is formed on the end 261 of the electrode lead 26 at the overlapping portion 30A of the busbar 30 where the end 261 of the electrode lead 26 overlaps. Furthermore, the end 261 of the electrode lead 26 has a heat input portion 60 formed at a position overlapping the welded portion 50 on the surface constituting the processed surface of the welded portion 50. The heat input portion 60 is a region of the end 261 of the electrode lead 26 that has been subjected to surface processing to enhance heat input compared to other portions.

[0045] 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.

[0046] 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)).

[0047] 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.

[0048] When the heat input property of the welded portion 50 is increased by the heat input portion 60, the penetration of the base material of the welded portion 50 becomes deeper, and the joining between the electrode lead 26 and the bus bar 30 can be stabilized.

[0049] 7(A) to 7(E), 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 each heat input portion 60 may be provided on bus bar 30, or may be provided on both electrode lead 26 and bus bar 30. 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.

[0050] In the example shown in Figs. 7(A) to 7(D), the heat input section 60 is configured to have an improved heat input property by performing surface processing to increase the surface area of ​​the processed surface of the welded section 50.

[0051] 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.

[0052] The groove 61 constituting the first heat input portion 60A has a V-shaped cross section. Therefore, the plate thickness of the end 261 of the electrode lead 26 becomes thinner toward the center of the welding area P. This increases the heat input at the center of the welded portion 50 compared to the outer periphery, and the base material is melted deeper at the center. As a result, the joint strength can be effectively increased.

[0053] The second heat input section 60B shown in Fig. 7(B) is configured by forming a linear groove 62 in the end 261 of the electrode lead 26. The groove 62 increases the surface area of ​​the machined surface of the welded section 50, improving the heat input. The groove 61 also forms a thin-walled section that is thinner than other sections. This also improves the heat input.

[0054] The groove 62 constituting the second heat input part 60B has a cross-sectional shape of a concave curved surface. The cross-sectional shape of the groove 62 may be rephrased as U-shaped. Therefore, like the first heat input part 60A, 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 part 50 compared to the outer periphery, and the penetration of the base material at the center becomes deeper. As a result, the joint strength can be effectively increased. In addition, by making the cross-sectional shape of the groove 62 concave, the surface area is increased compared to the V-shaped cross section, so that the penetration depth of the base material can be deepened even at the outer periphery of the welded part 50.

[0055] In a third heat input portion 60C shown in FIG. 7(C), 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] The fourth heat input section 60D shown in FIG. 7(D) 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 sections. 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.

[0057] 7(E) 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.

[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 protruding from each battery cell 20 are electrically joined to the bus bar 30 via the welded portion 50. In this embodiment, the electrode lead 26 has a heat input portion 60 formed at a position overlapping the welded portion 50. The heat input portion 60 has a higher heat input in the joining direction of the welded portion 50 than other portions. This increases the heat input to the base material when the electrode leads 26 extending from the plurality of battery cells 20 and the bus bar 30 are welded by laser welding or the like, and stabilizes the joining strength of the welded portion. As a result, it is possible to suppress the electrode lead 26 from coming off the bus bar 30 due to the stress generated in the welded portion 50 between the electrode lead 26 and the bus bar 30 caused by the expansion of the battery cells 20 that occurs when the battery module 11 swells.

[0059] 7(A) and 7(B), the heat input portion 60 can be configured with a thin-walled portion having a thinner plate thickness than other portions. By forming a thin-walled portion (groove portions 61, 62) having a thinner plate thickness than other portions at a position overlapping the welded portion 50, the heat input in the joining direction of the welded portion 50 is higher than other portions, and the joining strength of the welded portion 50 can be stabilized.

[0060] 7(A) and 7(B), when the heat input portion 60 is configured with a thin-walled portion having a plate thickness thinner than other portions, it may be formed as linearly extending grooves 61, 62. Then, a plurality of welds 50 may be formed along the linearly extending grooves 61, 62 so as to form a dot shape when viewed from the joining direction. In this case, the thin-walled portion formed by the linear grooves 61, 62 can accommodate the plurality of welds 50 when the electrode lead 26 is joined to the bus bar 30 side via the dot-shaped welds 50 by laser welding or the like. This allows the joining strength of the plurality of welds 50 to be stabilized by easy processing, thereby improving productivity.

[0061] 7(A), by forming the cross-sectional shape of the groove 61 into a V-shape, it is possible to deepen the penetration of the base material toward the center of the welded portion 50. This makes it possible to more effectively stabilize the joining strength of the welded portion 50.

[0062] 7(B), by making the cross-sectional shape of the groove 62 a concave curved shape, the penetration of the base metal toward the center of the weld is deepened, and the surface area can be increased without widening the groove width, thereby efficiently increasing the heat input. This makes it possible to more effectively stabilize the joining strength of the weld 50.

[0063] 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 other parts. This effectively stabilizes the joining strength of the welded section 50.

[0064] 7(D), 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 in the end section 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 makes it possible to more effectively stabilize the joint strength of the welded section 50.

[0065] 7(E), the heat input portion 60 may be provided with a black material 68 applied to the surface of the end portion 261 of the electrode lead 26 to enhance heat input and stabilize the joining strength of the welded portion 50. In the embodiment shown in FIG.

[0066] In addition, in the heat input portion 60 (60A to 60D) shown in Figures 7(A) to 7(E), the width of the heat input portion 60 may be set smaller than the width of the welded portion 50 in order to suppress a decrease in the mechanical strength of the end portion 261 of the electrode lead 26.

[0067] Moreover, in the heat input parts 60 (60A to 60D) shown in Figs. 7(A) to 7(E), the heat input parts 60 are configured by surface processing that is visible from the processed surface of the welded part 50. Therefore, the heat input parts can facilitate alignment of the folded back position of the electrode lead 26 with respect to the busbar 30. Furthermore, when the heat input parts 60 are formed on both the electrode lead 26 and the busbar 30, the heat input part on the busbar side may be formed so that its length in the width direction is longer than the width of the electrode lead 26. In this way, by configuring both heat input parts 60 to be visible when viewed from the joining direction, it becomes even easier to align the electrode lead with the busbar 30. [Explanation of symbols]

[0068] 11 Battery module 20 Battery Cells 30 Busbar 26 Electrode Lead 261 End 50 Welding 60 Heat input section (60A~60D) 61 Groove 62 Groove

Claims

1. A plurality of battery cells stacked on top of each other; an electrode lead protruding from the battery cell; a bus bar electrically joined to the electrode lead via a welded portion at an overlapping portion where an end of the electrode lead overlaps; 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 composed of a thin-walled portion having a plate thickness thinner than other portions. The battery module according to claim 1 .

3. the thin-walled portion defines a groove portion extending linearly in at least one of the electrode lead and the bus bar, A plurality of the welds are formed along the grooves so as to form a dot shape when viewed from the joining direction. The battery module according to claim 2 .

4. The groove portion has a V-shaped cross-sectional shape. The battery module according to claim 3 .

5. The groove portion has a cross-sectional shape of a concave curved surface. The battery module according to claim 3 .

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