Battery module

Abstract

To obtain a battery module that can achieve both reduction in labor and cost at the welded parts between a bus bar and a plurality of electrode leads.SOLUTION: A battery module 11 includes a plurality of battery cells 20 stacked on top of each other, electrode leads 26 protruding from the battery cells 20, and a bus bar 30 electrically joined to the electrode leads 26 via welds 50, the welds 50 being formed across the ends of the electrode leads 26 on a surface where the ends of the electrode leads 26 approach each other.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] Incidentally, when welding the ends of a plurality of electrode leads onto a bus bar, it is desirable to simultaneously weld the plurality of electrode leads from the viewpoint of reducing the number of steps.

[0005] However, when the ends of two electrode leads are stacked one above the other and welded simultaneously as in the battery module disclosed in Patent Document 1, the output of the welding machine becomes high, resulting in increased costs.

[0006] In consideration of the above, an object of the present invention is to provide a battery module that can achieve both reduction in the number of steps and reduction in costs at the welded joints between a bus bar and a plurality of 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, and a bus bar electrically joined to the electrode leads via welds, the welds being formed across ends of the electrode leads on a surface where the ends of the electrode leads approach each other.

[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. The welds connecting the electrode leads to the bus bar are formed across the ends of the electrode leads on the surface of the bus bar where the ends of the electrode leads are close to each other. This allows the electrode leads to be simultaneously connected to the bus bar via a common weld, reducing the number of welding steps. Since the welds are formed across the ends of the electrode leads, the output of the welding machine can be reduced compared to a configuration in which the ends of the electrode leads are welded one above the other along the joining direction, reducing the welding cost.

[0009] In addition, the term "the ends of the multiple electrode leads approaching each other" is a broad concept that includes both a state in which the ends of the multiple electrode leads abut each other, and a state in which the ends of the multiple electrode leads approach each other while being spaced apart.

[0010] A battery module of a second aspect is the battery module of the first aspect, wherein the welded portions are formed in a dot shape when viewed from a joining direction of the welded portions.

[0011] In the battery module of the second aspect, the welds are formed in a dot shape when viewed from the joining direction of the welds. Therefore, a plurality of electrode leads can be simultaneously joined to the bus bar side via the dot-shaped welds by laser welding or the like. This makes it possible to reduce the area of ​​the welds, suppress distortion of the base material and welding burns caused by welding heat, and reduce the number of steps in the finishing process.

[0012] The battery module of the third aspect is the battery module of the first or second aspect, wherein a heat input portion is formed in at least one of the electrode lead and the bus bar at the welded portion, the heat input portion having a higher heat input property in the joining direction than other portions.

[0013] In the battery module of the third aspect, a heat input portion is formed in at least one of the electrode lead and the bus bar in the welded portion, the heat input portion having a higher heat input in the joining direction than other portions, and as a result, the heat input portion can penetrate the base material of the welded portion deeply, thereby stabilizing the joining.

[0014] A fourth aspect of the battery module is the third aspect, wherein the heat input portion is formed by surface processing that increases the surface area of ​​the welded portion.

[0015] In the battery module of the fourth aspect, the heat input property of the welded portion is increased by increasing the surface area of ​​the welded portion through surface processing of the heat input portion, thereby increasing the heat input property in the joining direction, thereby enabling the welded portion to penetrate deeper into the base material, and stabilizing the joining.

[0016] A fifth aspect of the battery module is the third aspect, wherein the heat input portion is formed by surface processing in which a black material is applied to the welded portion.

[0017] In the battery module of the fifth aspect, the heat input property of the welded portion in the joining direction is improved by applying a black material to the welded portion through surface processing of the heat input portion, which allows the welded portion to penetrate deeper into the base material and stabilizes the joining. Effect of the Invention

[0018] As described above, in the battery module according to the present invention, it is possible to achieve both reduction in man-hours and cost at the welded portions between the bus bar and the multiple electrode leads. [Brief description of the drawings]

[0019] [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 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

[0020] Hereinafter, one embodiment of the present invention will be described with reference to FIGS.

[0021] (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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] A flexible printed circuit (FPC) 21 is disposed on the battery cells 20. The flexible printed circuit 21 is formed in a strip shape with the vehicle width direction as the longitudinal direction, and a thermistor 23 is provided on each of both ends of the flexible printed circuit 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.

[0033] 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.

[0034] 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.

[0035] 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 22A on one side in the thickness direction that is an embossed surface that has been embossed, and a second side surface 22B (see FIG. 5) on the other side in the thickness direction that is a non-embossed surface that has not been embossed.

[0036] 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.

[0037] 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.

[0038] The length CW1 of the battery cell 20 in the vehicle width direction is, for example, 530 mm to 600 mm, the length CW2 of the area in which the electrode body is housed is, for example, 500 mm to 520 mm, and the height CH of the battery cell 20 is, for example, 80 mm to 110 mm. The thickness of the battery cell 20 is 7.0 mm to 9.0 mm, and the height TH of the electrode lead (terminal) 26 is 40 mm to 50 mm.

[0039] 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.

[0040] For ease of explanation, FIG. 5 illustrates the battery cells 20 with gaps between them; 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).

[0041] 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.

[0042] 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.

[0043] A plurality of through holes 32 are formed in the bus bar 30, 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. FIG. 5 shows a state in which the electrode leads 26 protruding from two battery cells 20 are joined to the bus bar 30 via a welding part 50. As shown in FIG. 5, the two electrode leads 26 are each inserted into a through hole 32 formed in the bus bar 30. Then, the tip parts 261 of the two electrode leads 26 are folded back toward the bus bar 30 in a direction approaching each other. As a result, the ends of the two electrode leads 26 are arranged close to each other on the surface of the bus bar 30. Then, the ends 261 of the two electrode leads 26 are joined to the bus bar 30 via the welding part 50.

[0044] In the illustrated example, the ends of the two electrode leads 26 are close to each other but spaced apart from each other, but the ends of the two electrode leads 26 may also abut against each other.

[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 weld 50 is formed across the ends of the two electrode leads 26 on the surface of the busbar 30 where the ends of the two electrode leads 26 approach each other. As a result, the ends 261 of the two electrode leads 26 are simultaneously joined with the joining direction being the plate thickness direction of the busbar 30. In addition, since the weld 50 is formed by spot welding using a laser, it is formed in the shape of a circular dot when viewed from the joining direction of the weld 50 (the plate thickness direction of the busbar 30).

[0047] In this embodiment, the ends 261 of the two electrode leads 26 are disposed facing each other in the thickness direction D of the battery cell 20, and a plurality of welds 50 are formed along the center line C1 between the ends 261.

[0048] Here, in the welded portion 50, a heat input portion 60 having a higher heat input property in the joining direction than other portions is formed in at least one of the electrode lead 26 and the bus bar 30. As an example, the heat input portion 60 is formed by surface processing of at least one of the electrode lead 26 and the bus bar 30. 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 portion 60 is formed by surface processing that increases the surface area of ​​the welded portion 50.

[0051] 7(A), a first heat input part 60A forms an inclined surface 61 on the end 261 of the electrode lead 26, thereby increasing the surface area of ​​the welded part 50. Furthermore, by forming the inclined surface 61, the plate thickness of the end 261 of the electrode lead 26 becomes thinner toward the center of the welding range P. This allows the heat input on the center side of the welded part 50 to be higher than that on the outer periphery side, and efficiently increases the joining strength.

[0052] 7(B), a step 62 is formed on the end 261 of the electrode lead 26, thereby increasing the surface area of ​​the welded portion 50. Furthermore, by forming the step 62, the plate thickness of the end 261 of the electrode lead 26 closer to the center of the welding range P becomes thinner than the plate thickness on the outer periphery. This allows the heat input on the center side of the welded portion 50 to be higher than that on the outer periphery, thereby efficiently increasing the joining strength.

[0053] 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.

[0054] 7(D) is formed by alternately forming convex portions 64 protruding along the surface of the busbar 30 and concave portions 65 recessed from the convex portions 64 on the end portions 261 of the electrode lead 26, and arranging the convex portions 64 and concave portions 65 of the two electrode leads 26 to mesh with each other. In this heat input portion 60E, for example, by providing a welding range P at the position where the convex portions 64 and concave portions 65 mesh with each other, the opposing area (surface area) of the end portions 261 can be increased.

[0055] 7(E), the heat input part 60 is formed by surface processing in which a black material 68 is applied to the end 261 (welded part 50) of the electrode lead 26. This allows the black material 68 to absorb the laser light, increasing the heat input of the welded part 50 and allowing deeper penetration of the base material.

[0056] (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 welds 50. The welds 50 joining the electrode leads 26 to the bus bar 30 are formed across the ends 261 of the electrode leads 26 on the surface of the bus bar 30 where the ends 261 of the electrode leads 26 are close to each other. This allows the electrode leads 26 to be simultaneously joined to the bus bar 30 via the common welds 50, reducing the number of welding steps. In addition, since the welds 50 are formed across the ends 261 of the electrode leads 26, the output of the welding machine can be reduced compared to a configuration in which the ends of the electrode leads are welded by overlapping them vertically along the joining direction, and the welding costs can be reduced.

[0057] In this embodiment, the welds 50 are formed in a dot shape when viewed from the joining direction of the welds 50. Therefore, the electrode leads 26 can be simultaneously joined to the bus bar 30 side via the dot-shaped welds formed by laser welding or the like. This makes it possible to reduce the area of ​​the welds 50, suppress distortion of the base material and welding burns caused by welding heat, and reduce the number of steps in the finishing process.

[0058] 7(A) to 7(E), in the present embodiment, a heat input portion 60 having a higher heat input property in the joining direction than other portions is formed in at least one of the electrode lead 26 and the bus bar 30 in the welded portion 50. As a result, the heat input portion 60 can deepen the penetration of the base material of the welded portion 50, and the joining can be stabilized.

[0059] 7(A) to 7(D), the heat input in the joining direction of the welded portion 50 is improved by increasing the surface area of ​​the welded portion 50 through surface processing of the heat input portions 60 (A to D). This allows the welded portion 50 to penetrate deeper into the base material, resulting in a stable joint.

[0060] 7(E), the heat input in the joining direction of the welded portion 50 is improved by coating the welded portion 50 with a black material 68 through surface treatment of the heat input portion 60E. This allows the welded portion 50 to penetrate deeper into the base material, stabilizing the joining.

[0061] Although one embodiment and one modified example have been described above, the present invention can be practiced with various modifications without departing from the spirit and scope of the present invention. It goes without saying that the scope of the present invention is not limited to the above embodiment.

[0062] For example, in the above embodiment, the ends of two electrode leads are joined together at the same time, but the present invention is not limited to this. On the surface of the bus bar, the ends of three or more electrode leads 26 may be brought close to each other, and a weld may be formed across these ends. [Explanation of symbols]

[0063] 11 Battery module 20 Battery Cells 30 Busbar 26 Electrode Lead 261 End 40 Electrode body 50 Welding 60 Heat input section (60A~60E)

Claims

1. A plurality of battery cells stacked on top of each other; an electrode lead protruding from the battery cell; a bus bar that is electrically connected to the electrode leads via welds, the welds being formed across the ends of the electrode leads on a surface where the ends of the electrode leads approach each other; A battery module comprising:

2. The welded portion is formed in a dot shape when viewed from a joining direction of the welded portion. The battery module according to claim 1 .

3. In the welded portion, a heat input portion is formed in at least one of the electrode lead and the bus bar, the heat input portion having a higher heat input property in a joining direction than other portions. The battery module according to claim 1 or 2.

4. The heat input portion is formed by surface processing to increase the surface area of ​​the welded portion. The battery module according to claim 3 .

5. The heat input portion is formed by surface processing in which a black material is applied to the weld portion. The battery module according to claim 3 .

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