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 Art

[0002] The battery module disclosed in Patent Document 1 below includes a plurality of battery cells stacked on one another and a bus bar unit electrically connected to electrode leads of the plurality of battery cells. In this battery module, the ends of two electrode leads are gathered on the bus bar unit and joined by welding or the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when welding the ends of a plurality of electrode leads on a bus bar, it is desirable to simultaneously weld the plurality of electrode leads from the viewpoint of reducing man-hours.

[0005] However, when simultaneously welding the ends of two electrode leads by stacking them vertically as in the battery module disclosed in Patent Document 1 above, the cost increases due to an increase in the output of the welding machine.

[0006] In consideration of the above facts, an object of the present invention is to obtain a battery module capable of achieving both reduction of man-hours and cost reduction in the welded portion between a bus bar and a plurality of electrode leads.

Means for Solving the Problems

[0007] A battery module according to the first embodiment comprises a plurality of battery cells stacked on top of each other, electrode leads protruding from the battery cells, and a busbar electrically joined to the electrode leads via a weld, the busbar being formed across the ends of the plurality of electrode leads on a surface where the ends of the plurality of electrode leads are close together.

[0008] In the first embodiment of the battery module, a plurality of battery cells are stacked on top of each other. Electrode leads protruding from each battery cell are electrically joined to a busbar via a weld. Here, the weld connecting the electrode leads to the busbar is formed on the surface of the busbar where the ends of the multiple electrode leads are close together, spanning across the ends of the multiple electrode leads. This allows multiple electrode leads to be simultaneously joined to the busbar via a common weld, reducing the welding time. Furthermore, because the weld is formed spanning across the ends of multiple electrode leads, the welding machine output can be reduced compared to a configuration where the ends of multiple electrode leads are stacked vertically and welded along the joining direction, thereby reducing welding costs.

[0009] In this context, "the ends of multiple electrode leads approaching each other" is a broad concept that includes both the state in which the ends of multiple electrode leads are in contact with each other and the state in which the ends of multiple electrode leads are moving closer together while being separated from each other.

[0010] In the second embodiment of the battery module, the welded portion is formed in a dot shape when viewed from the joining direction of the welded portion, as in the first embodiment.

[0011] In the second embodiment of the battery module, the welded area is formed in a dot shape when viewed from the direction of the weld joint. Therefore, multiple electrode leads can be simultaneously joined to the busbar side via the dot-shaped welded area formed by laser welding or the like. This reduces the area of ​​the weld, suppresses distortion of the base material and welding burn caused by welding heat, and reduces the number of finishing steps.

[0012] In the third embodiment of the battery module, in the first or second embodiment, the welded portion has a heat input portion formed on at least one of the electrode lead and the busbar, which has higher heat input in the joining direction than other portions.

[0013] In the third embodiment of the battery module, the welded portion has a heat input section formed on at least one of the electrode lead and the busbar, which has a higher heat input in the joining direction than other parts. As a result, the heat input section allows for deeper penetration of the base material in the welded portion, thereby stabilizing the joint.

[0014] In the fourth embodiment of the battery module, the heat input portion is formed by a surface treatment that increases the surface area of ​​the welded portion, as in the third embodiment.

[0015] In the fourth embodiment of the battery module, the heat input in the joining direction is enhanced by increasing the surface area of ​​the weld through surface treatment of the heat input area. This allows for deeper penetration of the base material in the weld and stabilizes the joint.

[0016] In the fifth embodiment of the battery module, the heat input portion is formed by a surface treatment in which a black material is applied to the welded portion, as in the third embodiment.

[0017] In the fifth embodiment of the battery module, the heat input in the joining direction is enhanced by applying a black material to the welded area through surface treatment of the heat input area. This allows for deeper penetration of the base material in the welded area, thereby stabilizing the joint. [Effects of the Invention]

[0018] As described above, the battery module according to the present invention makes it possible to achieve both a reduction in man-hours and a reduction in cost in the welded joint between the busbar and the plurality of electrode leads. [Brief explanation of the drawing]

[0019] [Figure 1]It is a schematic plan view showing a main part of a vehicle to which a battery pack according to an embodiment is applied. [Figure 2] It is a schematic perspective view of a battery module according to an embodiment. [Figure 3] It is a plan view of a battery module according to an embodiment with the upper lid of the module case removed. [Figure 4] It is a schematic view of a battery cell housed in a battery module as seen from the thickness direction. [Figure 5] It is a schematic plan view showing a state where a plurality of battery cells are housed in a module case, partially enlarged. [Figure 6] It is a view showing an enlarged welding part joining a plurality of electrode leads and a bus bar, (A) is an enlarged front view seen from the A direction of FIG. 5, and (B) is an enlarged cross-sectional view showing a cross-section cut along the B-B line of FIG. 6A. [Figure 7] (A) to (E) are enlarged cross-sectional views corresponding to FIG. 6(B), showing examples of heat input parts formed in the welding part.

Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

[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 a battery electric vehicle (BEV) in which the battery pack 10 is mounted under the floor. In addition, the arrows UP, FR, and LH in each figure indicate the upper side in the vehicle up-down direction, the front side in the vehicle front-rear direction, and the left side in the vehicle width direction, respectively. When explaining using the directions of front, rear, left, right, up, and down, unless otherwise specified, it shall indicate the front and rear in the vehicle front-rear direction, the left and right in the vehicle width direction, and the up and down in the vehicle up-down direction.

[0022] In this embodiment, the vehicle 100, as an example, has a DC / DC converter 102, an electric compressor 104, and a PTC (Positive Temperature Coefficient) heater 106 positioned in front of the battery pack 10. The motor 108, gearbox 110, inverter 112, and charger 114 are positioned behind the battery pack 10.

[0023] The DC current output from the battery pack 10 is voltage-adjusted by the DC / DC converter 102 and then supplied to the electric compressor 104, PTC heater 106, inverter 112, etc. Power is also supplied to the motor 108 via the inverter 112, causing the rear wheels to rotate and the vehicle 100 to move.

[0024] A charging port 116 is provided on the right side of the rear of the vehicle 100. By connecting a charging plug from an external charging device (not shown) to the charging port 116, power can be stored in the battery pack 10 via the onboard charger 114.

[0025] The arrangement and structure of the components constituting the vehicle 100 are not limited to the configuration described above. For example, it may be applied to a hybrid vehicle (HV) or a plug-in hybrid electric vehicle (PHEV) equipped with an engine. In this embodiment, the motor 108 is mounted at the rear of the vehicle and it is a rear-wheel drive vehicle, but it is not limited to this, and it may be a front-wheel drive vehicle with the motor 108 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, it may be a vehicle equipped with in-wheel motors for each wheel.

[0026] Here, the battery pack 10 is composed of multiple battery modules 11. In this embodiment, as an example, 10 battery modules 11 are provided. Specifically, 5 battery modules 11 are arranged in the longitudinal direction of the vehicle on the right side of the vehicle 100, and 5 battery modules 11 are arranged in the longitudinal direction of the vehicle on the left side of the vehicle 100. Furthermore, each battery module 11 is electrically connected.

[0027] Figure 2 is a schematic perspective view of the battery module 11. As shown in Figure 2, the battery module 11 includes a module case 16 that forms the outer shell. The module case 16 is formed in a substantially rectangular parallelepiped shape with the vehicle width direction as its longitudinal direction. The module case 16 is also formed of an aluminum alloy. For example, the module case 16 is formed by joining aluminum die-cast parts to both ends of an aluminum alloy extruded 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 Figure 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 longitudinal direction is, for example, 150 mm to 250 mm, and the height MH in the vehicle vertical direction is, for example, 80 mm to 110 mm.

[0030] Figure 3 is a plan view of the battery module 11 with the top cover removed. As shown in Figure 3, battery cells 20 are housed inside the module case 16. As an example, multiple battery cells 20 are housed inside the module case 16 in an arranged (stacked) state. In this embodiment, 24 battery cells 20 are arranged in the front-rear direction of the vehicle and bonded to each other.

[0031] For the sake of clarity, in Figures 3 to 6, the direction indicated by arrow W represents the width direction of the battery cell 20, the direction indicated by arrow H represents the height direction (up and down direction) of the battery cell 20, and the direction indicated by arrow D represents the thickness direction of the battery cell 20. The width direction of the battery case 22, as described later, coincides with the width direction W of the battery cell 20. The height direction of the battery case 22 coincides with the height direction H of the battery cell 20. The thickness direction of the battery case 22 coincides with the thickness direction D of the battery cell 20.

[0032] A flexible printed circuit board (FPC) 21 is placed on top of the battery cell 20. The flexible printed circuit board 21 is formed in a strip shape with the vehicle width direction as its longitudinal direction, and thermistors 23 are provided at both ends of the flexible printed circuit board 21. The thermistors 23 are not bonded to the battery cell 20, but are pressed toward the battery cell 20 by the upper cover 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 material is a thin, elastically deformable plate-like member, and is placed between adjacent battery cells 20 with the arrangement direction of the battery cells 20 as the thickness direction. In this embodiment, as an example, cushioning material is placed at both ends in the longitudinal direction and in the longitudinal center of the module case 16.

[0034] Figure 4 is a schematic diagram of a battery cell 20 housed in a battery module 11, viewed from the thickness direction D. As shown in Figure 4, the battery cell 20 is formed in the shape of a long rectangular plate with the width direction W as the longitudinal direction, and is equipped with a battery case 22 that forms the outer shell. An electrode body 40 is housed inside the battery case 22. The electrode body 40 is constructed by laminating a positive electrode, a negative electrode, and a separator. In this embodiment, the battery case 22 is made of laminate film, and the electrode body 40 is sealed with laminate film.

[0035] The battery case 22 is embossed on at least one side in the thickness direction. The embossing creates a recessed housing portion 221 on the side surface in which the electrode body 40 is housed, and an outer end portion 223 provided outside the housing portion 221. The battery case 22 can employ either a single-cup embossed structure with one embossed area or a double-cup embossed structure with two embossed areas, but in this embodiment, it is a single-cup embossed structure with a recess depth of approximately 8 mm to 10 mm. Therefore, one first side surface 22A in the thickness direction of the battery case 22 is an embossed surface, and the other second side surface 22B (see Figure 5) in the thickness direction is a non-embossed surface.

[0036] The upper end of the battery case 22 in the width direction is bent, the corners are chamfered, and it has a roughly trapezoidal shape. In addition, the upper end of the battery case 22 is bent, and fixing tape 24 is wrapped around the upper end of the battery case 22 along the width direction.

[0037] Here, the battery cell 20 is equipped with electrode leads 26 that protrude from the end of the battery case 22. The electrode leads 26 are provided at both ends in the width direction of the battery cell. In this embodiment, as an example, the electrode leads 26 are provided at a position offset below the center of the height direction H of the battery cell 20. 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 width direction end of the battery case 22 and is electrically joined to the bus bar 30 via a weld 50 (see Figure 5). This electrode lead 26 is connected to the wiring outside the battery module 11 via the bus bar 30. The welding of the electrode lead 26 and the bus bar 30 can be performed using any known welding method, but in this example, the electrode lead 26 and the bus bar 30 are joined by laser welding.

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

[0039] Figure 5 is a schematic plan view showing a partially enlarged view of multiple battery cells 20 housed in a module case 16. As shown in this figure, within the module case 16, 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. In addition, plate-shaped busbars 30 are arranged on both the one and the other side in the width direction W of the battery cells 20.

[0040] Note that although Figure 5 shows the battery cells 20 spaced apart for ease of explanation, in reality, the stacked battery cells 20 are in contact either via a buffer material or directly, and are constrained from one another with a predetermined restraining pressure applied along the stacking direction (thickness direction D).

[0041] The busbar 30 extends along the stacking direction (thickness direction D) of the battery cell 20, with the width direction W of the battery cell 20 being the thickness direction. In addition, the busbar 30 has slot-shaped through holes 32 that penetrate through the busbar 30 in the thickness direction.

[0042] The other end of the electrode lead 26, which protrudes from the widthwise end W of the battery cell 20, is inserted into the through hole 32 of the bus bar 30. The end 261 protruding from the through hole 32 is folded back towards the bus bar 30 and overlapped with the surface of the bus bar 30.

[0043] Multiple through holes 32 are formed in the busbar 30, and electrode leads 26 protruding from multiple battery cells 20 are inserted through these through holes 32 and joined to the busbar 30. In this way, the multiple battery cells 20 are electrically connected via the busbar 30. Figure 5 shows a state in which electrode leads 26 protruding from two battery cells 20 are joined to the busbar 30 via a weld 50. As shown in Figure 5, the two electrode leads 26 are each inserted through a through hole 32 formed in the busbar 30. The tips 261 of the two electrode leads 26 are folded back toward the busbar 30 in a direction that brings them closer together. As a result, the ends of the two electrode leads 26 are positioned close together on the surface of the busbar 30. The ends 261 of the two electrode leads 26 are joined to the busbar 30 via a weld 50.

[0044] In the illustrated example, the ends of the two electrode leads 26 are close together but spaced apart, however, the ends of the two electrode leads 26 may be in contact with each other.

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

[0046] As shown in Figures 6(A) and 6(B), the welded portion 50 is formed on the surface of the busbar 30 where the ends of the two electrode leads 26 are close together, straddling the ends of the two electrode leads 26. As a result, the ends 261 of the two electrode leads 26 are simultaneously joined with the thickness direction of the busbar 30 as the joining direction. Furthermore, since the welded portion 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 welded portion 50 (the thickness direction of the busbar 30).

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

[0048] Here, in the welded joint 50, a heat input portion 60 is formed on at least one of the electrode lead 26 and the busbar 30, which has a higher heat input in the joining direction than other parts. The heat input portion 60 is formed, for example, by surface treatment on at least one of the electrode lead 26 and the busbar 30. When the heat input of the welded joint 50 is increased by the heat input portion 60, the penetration of the base material of the welded joint 50 becomes deeper, and the joint between the electrode lead 26 and the busbar 30 can be stabilized.

[0049] Referring to Figures 7(A) to 7(E), examples of the heat input section 60 will be described. Here, several examples of forming the heat input section 60 by surface processing on the electrode lead 26 will be listed and described, but each heat input section 60 may be provided on the bus bar 30, or it may be provided on both the electrode lead 26 and the bus bar 30. Each figure shows the state before the weld 50 is formed on the base material, which consists of the electrode lead 26 and busbar 30, and the welding area is indicated by the region P enclosed by the dashed line.

[0050] In the examples shown in Figures 7(A) to 7(D), the heat input section 60 is formed by surface treatment that increases the surface area of ​​the welded section 50.

[0051] The first heat input section 60A shown in Figure 7(A) has an inclined surface 61 formed on the end 261 of the electrode lead 26, increasing the surface area of ​​the welded section 50. Furthermore, the formation of the inclined surface 61 causes the plate thickness of the end 261 of the electrode lead 26 to decrease toward the center of the welded area P. As a result, the heat input on the center side of the welded section 50 can be increased compared to the outer circumference side, and the joint strength can be efficiently increased.

[0052] The second heat input section 60B shown in Figure 7(B) has a stepped section 62 formed at the end 261 of the electrode lead 26, increasing the surface area of ​​the welded section 50. Furthermore, the formation of the stepped section 62 makes the plate thickness of the end 261 of the electrode lead 26 closer to the center of the welding range P thinner than the plate thickness on the outer circumference. As a result, the heat input on the center side of the welded section 50 can be increased compared to the outer circumference, and the joint strength can be efficiently increased.

[0053] The third heat input section 60C shown in Figure 7(C) has a rougher surface at the end 261 of the electrode lead 26 compared to other parts, thereby increasing the surface area of ​​the welded section 50.

[0054] Furthermore, the fifth heat input section 60E shown in Figure 7(D) is formed by alternately forming protrusions 64 that project along the surface of the busbar 30 and recesses 65 that are recessed relative to the protrusions 64 on the end 261 of the electrode lead 26, and arranging the two electrode leads 26 so that the protrusions 64 and recesses 65 interlock. In this heat input section 60E, for example, by providing a welding range P at the position where the protrusions 64 and recesses 65 interlock, the opposing surface area (surface area) of the end 261 can be increased.

[0055] On the other hand, the fourth heat input section 60D shown in Figure 7(E) is formed by a surface treatment in which a black material 68 is applied to the end 261 (welded section 50) of the electrode lead 26. As a result, the black material 68 absorbs the laser light, increasing the heat input to the welded section 50 and allowing for deeper penetration into the base material.

[0056] (Mechanism of action and effect) As described above, the battery module 11 according to the embodiment includes a plurality of battery cells 20 stacked on top of each other. Furthermore, electrode leads 26 protruding from each battery cell 20 are electrically joined to the busbar 30 via a welded joint 50. Here, the welded joint 50 joining the electrode leads 26 to the busbar 30 is formed on the surface of the busbar 30 where the ends 261 of the plurality of electrode leads 26 are close together, straddling the ends 261 of the plurality of electrode leads 26. This allows for the simultaneous joining of multiple electrode leads 26 to the busbar 30 via a common welded joint 50, reducing the welding time. Additionally, since the welded joint 50 is formed straddling the ends 261 of the plurality of electrode leads 26, the output of the welding machine can be reduced compared to a configuration where the ends of the plurality of electrode leads are stacked vertically and welded along the joining direction, thereby reducing welding costs.

[0057] In this embodiment, the welded portion 50 is formed in a dot shape when viewed from the joining direction of the welded portion 50. Therefore, multiple electrode leads 26 can be simultaneously joined to the busbar 30 side via the dot-shaped welded portion formed by laser welding or the like. This reduces the area of ​​the welded portion 50, suppresses distortion of the base material and welding burn caused by welding heat, and reduces the number of finishing steps.

[0058] In this embodiment, as shown in Figures 7(A) to 7(E), the welded portion 50 has a heat input portion 60 formed on at least one of the electrode lead 26 and the busbar 30, which has higher heat input in the joining direction than other parts. As a result, the heat input portion 60 allows for deeper penetration of the base material in the welded portion 50, thereby stabilizing the joint.

[0059] In the example shown in Figures 7(A) to 7(D), the heat input in the joining direction is enhanced by increasing the surface area of ​​the welded joint 50 through surface treatment of the heat input areas 60 (A to D). This allows for deeper penetration of the base material into the welded joint 50, thereby stabilizing the joint.

[0060] On the other hand, in the example shown in Figure 7(E), the heat input in the joining direction is enhanced in the welded joint 50 by applying a black material 68 to the welded joint 50 through surface treatment of the heat input section 60E. This allows for deeper penetration of the base material in the welded joint 50, thereby stabilizing the joint.

[0061] Although one embodiment and one modification have been described above, the present invention can be implemented with various modifications without departing from its spirit. Of course, the scope of the present invention is not limited to the above-described embodiment.

[0062] For example, in the above embodiment, the ends of two electrode leads were joined together simultaneously, but the invention is not limited to this. On the surface of the busbar, the ends of three or more electrode leads 26 may be brought close together, and a welded portion may be formed to span these ends. [Explanation of Symbols]

[0063] 11 Battery Modules 20 battery cells 30 Bus Bar 26 electrode leads 261 End 40 Electrode body 50 Welded section 60 Heat input section (60A~60E)

Claims

1. Multiple battery cells stacked on top of each other, The electrode leads protruding from the aforementioned battery cell, The system comprises an electrode lead electrically joined to a busbar formed across the ends of multiple electrode leads on a surface where the ends of multiple electrode leads are close together, the welded portion being electrically connected to the electrode lead via a welded portion, and the busbar being formed across the ends of multiple electrode leads on a surface where the ends of multiple electrode leads are close together. In the welded portion, a heat input portion is formed at the end of each of the multiple electrode leads, in which the heat input in the joining direction is higher than in other parts. The heat input portion is composed of a stepped portion connecting a first flat surface along the upper surface in the joining direction of the electrode lead and a second flat surface that is thinner in thickness. Battery module.

2. Multiple battery cells stacked on top of each other, The electrode leads protruding from the aforementioned battery cell, The system comprises an electrode lead electrically joined to a busbar formed across the ends of multiple electrode leads on a surface where the ends of multiple electrode leads are close together, the welded portion being electrically connected to the electrode lead via a welded portion, and the busbar being formed across the ends of multiple electrode leads on a surface where the ends of multiple electrode leads are close together. In the welded portion, a heat input portion is formed at the end of each of the multiple electrode leads, in which the heat input in the joining direction is higher than in other parts. The heat input portion is composed of a protrusion that projects along the surface of the busbar and a recess that is recessed relative to the protrusion at the end of the electrode lead, and the protrusions and recesses are formed alternately along the tip edge of the end of the electrode lead, and are arranged so that the protrusions and recesses formed on the ends of adjacent electrode leads interlock. Battery module.

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

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