Battery module

Abstract

The utility model provides a battery module which can reduce the welding time in the welding process of a bus and a plurality of electrode leads and can stabilize the bonding strength in the welding process. A battery module (11) is provided with: a plurality of battery cells (20) that are stacked on each other; a bus bar (30) that is electrically connected to electrode leads (26) of the plurality of battery cells; and a welded section (50) that joins the bus bar and the plurality of end sections to each other in an overlapping section (30A) in which the end sections of the plurality of electrode leads overlap each other on the bus bar. And a heat input part (60) formed at a position overlapping the welding part in at least one of the electrode lead and the bus bar, wherein the heat input property of the heat input part (60) in the bonding direction is higher than that of other parts.

Description

Technical Field

[0001] The utility model relates to a battery module. Background Art

[0002] The battery module disclosed in Japanese Patent Publication No. 7062162 includes a plurality of battery cells stacked on each other 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 converge on the bus bar unit and are joined by welding or the like.

[0003] However, when welding the ends of a plurality of electrode leads to the bus bar, from the viewpoint of reducing man-hours, simultaneous welding of a plurality of electrode leads is considered. On the other hand, in a battery module formed by stacking a plurality of battery cells on each other, stress may be generated at the welded portion between the electrode lead and the bus bar due to the expansion of the battery cells during the expansion of the battery module. When simultaneously welding a plurality of electrode leads, in order to prevent the electrode leads from detaching from the bus bar, it is desirable to stabilize the joining strength during welding. Summary of the Utility Model

[0004] In view of the above facts, the purpose of the present utility model is to provide a battery module that can reduce the man-hours of welding in the welding of a bus bar and a plurality of electrode leads and can stabilize the joining strength during welding.

[0005] The battery module of the first aspect includes: a plurality of battery cells stacked on each other; a bus bar electrically connected to electrode leads of the plurality of battery cells; a welding portion for joining the bus bar and the plurality of ends to each other in an overlapping portion where the ends of the plurality of electrode leads overlap each other on the bus bar; and a heat input portion formed at a position overlapping the welding portion in at least one of the electrode lead and the bus bar, the heat input portion having higher heat input property in the joining direction than other portions.

[0006] The battery module of the first aspect includes a plurality of battery cells stacked on each other. In addition, the electrode leads of each battery cell are electrically joined to the bus bar via a welding portion. On the bus bar, a welding portion for joining the bus bar and the ends of the plurality of electrode leads to each other is formed in an overlapping portion where the ends of the plurality of electrode leads overlap each other. Thereby, a plurality of electrode leads are simultaneously welded to the bus bar, reducing the man-hours of welding. In addition, in the first aspect, in at least one of the electrode lead and the bus bar, a heat input portion having higher heat input property in the joining direction than other portions is formed at a position overlapping the welding portion. As a result, when simultaneously welding a plurality of electrode leads to the bus bar side by laser welding or the like, the heat input property to the base material can be improved, and the joining strength of the welding portion can be stabilized.

[0007] In the battery module of the second method, in the first method, the heat input portion is formed by a visible surface treatment and is formed at least on the electrode lead wire on the processing surface constituting the welding portion.

[0008] In the battery module of the second method, the heat input portion is formed on the electrode lead wire on the processing surface constituting the welding portion in the overlapping portion on the bus bar. It should be noted that the "processing surface of the welding portion" here refers to the surface contacted by the welding machine when simultaneously welding the ends of a plurality of electrode lead wires.

[0009] Here, in the second method, the heat input portion is formed by a visible surface treatment. Therefore, even in a state where a plurality of electrode lead wires are overlapped, it is possible to easily align the folding position or welding position of the plurality of electrode lead wires with respect to the bus bar. As a result, a battery module with excellent productivity can be obtained.

[0010] In the battery module of the third method, in the first method or the second method, the heat input portion is constituted by a thin-walled portion having a thickness thinner than other portions on at least one of the electrode lead wires.

[0011] In the battery module of the third method, by forming a thin-walled portion having a thickness thinner than other portions at a position overlapping the welding portion, a heat input portion having a higher heat input property in the joining direction to the welding portion than other portions can be constituted. As a result, when simultaneously welding a plurality of electrode lead wires to the bus bar side by laser welding or the like, the heat input property to the base material can be improved, and the joining strength of the welding portion can be stabilized.

[0012] In the battery module of the fourth method, in the first method or the second method, the welding 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 having a diameter smaller than the dot diameter of the welding portion on at least one of the electrode lead wires.

[0013] In the battery module of the fourth method, the welding portion is formed in a dot shape when viewed from the joining direction. In addition, in the second method, by providing a through hole having a diameter smaller than the dot diameter of the welding portion at a position overlapping the welding portion, the surface area of the welding portion is increased. Thus, a heat input portion having a higher heat input property in the joining direction to the welding portion than other portions is formed. In addition, by constituting the heat input portion with a through hole, the heat input property of the central portion of the welding portion can be effectively improved, and the penetration of the base material in the central portion of the welding portion can be deepened. As a result, when simultaneously welding a plurality of electrode lead wires to the bus bar side by spot welding using a laser or the like, the joining strength of the welding portion can be effectively stabilized.

[0014] In the battery module of the fifth method, in the first method or the second method, the heat input portion is constituted by roughening the surface of at least one of the electrode lead wires.

[0015] In the battery module of the fifth mode, at a position overlapping with the welding part, the surface of the electrode lead is roughened to increase the surface area of the welding part, and a heat input part with higher heat input property in the joining direction to the welding part than other parts is formed. As a result, when a plurality of electrode leads are simultaneously welded to the bus bar side by laser welding or the like, the joining strength of the welding part can be effectively stabilized.

[0016] In the battery module of the sixth mode, in the first mode or the second mode, the heat input part is formed by coating a black material on the surface of at least one of the electrode leads.

[0017] In the battery module of the sixth mode, by coating a black material on the surface of the electrode lead at a position overlapping with the welding part, a heat input part with higher heat input property in the joining direction to the welding part than other parts is formed. As a result, when a plurality of electrode leads are simultaneously welded to the bus bar side by laser welding or the like, the joining strength of the welding part can be effectively stabilized.

[0018] As described above, in the battery module of the present utility model, in the welding of the bus bar and a plurality of electrode leads, the working hours of welding can be reduced, and the joining strength during welding can be stabilized. Description of the Drawings

[0019] Figure 1 It is a schematic top view showing a main part of a vehicle to which the battery pack according to the embodiment is applied.

[0020] Figure 2 It is a schematic perspective view of the battery module according to the embodiment.

[0021] Figure 3 It is a top view of the battery module according to the embodiment in a state where the upper cover of the module case is removed.

[0022] Figure 4 It is a schematic view of the battery cell housed in the battery module as viewed from the thickness direction.

[0023] Figure 5 It is a schematic top view showing a partial enlargement of a state where a plurality of battery cells are housed in the module case.

[0024] Figure 6A and Figure 6B It is a view showing an enlarged view of the welding part for joining a plurality of electrode leads to the bus bar, Figure 6A is from Figure 5 an enlarged front view as viewed from the A direction of, Figure 6B is a view showing Figure 6A an enlarged cross-sectional view of a cross-section cut along the B-B line of.

[0025] Figures 7A to 7D is forFigure 6B The corresponding enlarged cross-sectional view shows an example of a heat input portion formed at a welded portion. DETAILED DESCRIPTION

[0026] The following refers to Figures 1 to 7D to describe an embodiment of the present invention.

[0027] The overall configuration of the vehicle 100 will be described below. Figure 1 It is a schematic top view showing the main part of the vehicle 100 to which the battery pack 10 according to the embodiment is applied. As Figure 1 shown, the vehicle 100 is an electric vehicle (BEV: Battery Electric Vehicle) with the battery pack 10 mounted under the floor. In addition, the arrows UP, FR, and LH in each figure respectively 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. When the directions of front, rear, left, right, up, and down are used for description, unless otherwise specified, front and rear in the vehicle front-rear direction, left and right in the vehicle width direction, and up and down in the vehicle up-down direction are meant.

[0028] As an example, in the vehicle 100 of the present embodiment, a DC / DC converter 102, an electric compressor 104, and a PTC (Positive Temperature Coefficient) heater 106 are arranged on the vehicle front side of the battery pack 10. In addition, a motor 108, a gearbox 110, an inverter 112, and a charger 114 are arranged on the vehicle rear side of the battery pack 10.

[0029] The DC current output from the battery pack 10 is supplied to the electric compressor 104, the PTC heater 106, the inverter 112, etc. after the voltage is adjusted by the DC / DC converter 102. In addition, by supplying power to the motor 108 via the inverter 112, the rear wheels rotate to make the vehicle 100 travel.

[0030] A charging port 116 is provided on the right side of the rear portion of the vehicle 100. By connecting a charging plug of an external charging device (not shown) to the charging port 116, the battery pack 10 can be charged via the in-vehicle charger 114.

[0031] In addition, the configurations, structures, etc. of the components constituting the vehicle 100 are not limited to those described above. For example, it can also be applied to a hybrid vehicle (HV: Hybrid Vehicle) or a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle) equipped with an engine. In addition, in the present embodiment, a vehicle with rear-wheel drive in which the motor 108 is mounted on the rear part of the vehicle is taken as an example for description, but it is not limited thereto. It can be a front-wheel drive vehicle in which the motor 108 is mounted on the front part of the vehicle, or a pair of motors 108 can be mounted on the front and rear of the vehicle. In addition, it can also be a vehicle having in-wheel motors on each wheel.

[0032] Here, the battery pack 10 is configured to include a plurality of battery modules 11. As an example in the present embodiment, 10 battery modules 11 are provided. Specifically, 5 battery modules 11 are arranged in the vehicle front-rear direction on the right side of the vehicle 100, and 5 battery modules 11 are arranged in the vehicle front-rear direction on the left side of the vehicle 100. In addition, the respective battery modules 11 are electrically connected.

[0033] Figure 2 is a schematic perspective view of the battery module 11. As Figure 2 shown, the battery module 11 has a module housing 16 that forms the outer shell. The module housing 16 is formed in a substantially rectangular parallelepiped shape with the vehicle width direction as the length direction. In addition, the module housing 16 is formed of aluminum alloy. For example, the module housing 16 is formed by joining aluminum die-castings to both ends of an extruded material of aluminum alloy by laser welding or the like.

[0034] A pair of voltage terminals 12 and connectors 14 are respectively provided at both ends in the vehicle width direction of the battery module 11. A flexible printed circuit board 21 described later is connected to the connector 14. In addition, a bus bar 30 (refer to Figure 4 ) is welded to both ends in the vehicle width direction of the battery module 11.

[0035] The length MW in the vehicle width direction of the battery module 11 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.

[0036] Figure 3 is a top view in a state where the upper cover of the battery module 11 is removed. As Figure 3 shown, battery cells 20 serving as batteries are housed inside the module housing 16. As an example, a plurality of battery cells 20 are housed in an arranged (stacked) state inside the module housing 16. In the present embodiment, 24 battery cells 20 are arranged in the vehicle front-rear direction and bonded to each other.

[0037] In addition, for ease of understanding of the description, inFigures 3 to 6B In each of the figures, the direction indicated by arrow W is defined as the width direction of the battery cell 20, the direction indicated by arrow H is defined as the height direction (vertical direction) of the battery cell 20, and the direction indicated by arrow D is defined as the thickness direction of the battery cell 20.

[0038] The width direction of the battery case 22 described later is the same as the width direction W of the battery cell 20. The height direction of the battery case 22 is the same as the height direction H of the battery cell 20. The thickness direction of the battery case 22 is the same as the thickness direction D of the battery cell 20.

[0039] A flexible printed circuit (FPC) 21 is disposed above the battery cell 20. The flexible printed circuit 21 is formed in a strip shape with the vehicle width direction as the length direction, and thermistors 23 are provided at both end portions of the flexible printed circuit 21. The thermistors 23 are not adhered to the battery cell 20 and are configured to be pressed toward the battery cell 20 side by the upper cover of the battery module 11.

[0040] In addition, one or more buffer materials (not shown) are housed inside the module case 16. For example, the buffer material is a thin plate-shaped member that can elastically deform and is disposed between adjacent battery cells 20 with the arrangement direction of the battery cells 20 as the thickness direction. In the present embodiment, as an example, buffer materials are disposed at both end portions in the length direction and the central portion in the length direction of the module case 16.

[0041] Figure 4 It is a schematic view of the battery cell 20 housed in the battery module 11 as viewed from the thickness direction D. As Figure 4 shown, the battery cell 20 is formed in a long rectangular plate shape with the width direction W as the length direction and includes a battery case 22 that constitutes the outer shell. An electrode body 40 is housed inside the battery case 22. The electrode body 40 is formed by laminating a positive electrode as an electrode, a negative electrode as an electrode, and a separator. In the present embodiment, the battery case 22 is formed of a laminated film, and the electrode body 40 is sealed with a laminated film.

[0042] The battery case 22 is embossed on at least one side in the thickness direction of the battery case 22. By performing the embossing process, a concave housing portion 221 for housing the electrode body 40 therein and an outer end portion 223 provided outside the housing portion 221 are formed on the side surface. In addition, the battery case 22 can adopt both a single-cup embossed structure with one embossing process and a double-cup embossed structure with two embossing processes. In the present embodiment, it is a single-cup embossed structure with a drawing depth of about 8 mm to 10 mm. Therefore, the first side surface 22A on one side in the thickness direction of the battery case 22 is an embossed surface that forms the internal housing space of the battery cell 20. In addition, the second side surface 22B (refer to Figure 5 ) on the other side in the thickness direction of the battery case 22 is a flat non-embossed surface without embossing.

[0043] The upper end in the width direction of the battery case 22 is bent, and the corner is chamfered to form a substantially trapezoidal shape. In addition, the upper end portion of the battery case 22 is bent, and a fixing band 24 is wound along the width direction at the upper end portion of the battery case 22.

[0044] Here, the battery cell 20 includes electrode leads 26 protruding from the end portion of the battery case 22. The electrode leads 26 are respectively provided at both end portions in the width direction of the battery cell. As an example in the present embodiment, the electrode leads 26 are provided at positions offset downward from the center in 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 end portion in the width direction of the battery case 22 and is electrically joined to the bus bar 30 via a welding portion 50 (refer to Figure 5 ). The 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 to the bus bar 30 can be appropriately performed by a known welding method. In an example of the present embodiment, the electrode lead 26 is joined to the bus bar 30 by laser welding.

[0045] 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 for housing the electrode body 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. The height CH of the battery cell 20 is, for example, 80 mm to 110 mm, 110 m 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.

[0046] Figure 5 This is a schematic top view showing a partial enlargement of the state in which a plurality of battery cells 20 are housed in the module housing 16. As shown in this figure, inside the module housing 16, the other end of the electrode lead 26 protrudes from the end in the width direction W of the plurality of battery cells 20 stacked on top of each other. In addition, plate-shaped bus bars 30 are respectively arranged on one side and the other side in the width direction W of the battery cell 20.

[0047] In addition, for the convenience of explanation, Figure 5 a state in which a gap is provided between adjacent battery cells 20 is shown. Actually, the plurality of stacked battery cells 20 are in contact with each other via a buffer material or directly, and are mutually constrained in a state where a predetermined restraint pressure is applied in the stacking direction (thickness direction D).

[0048] The bus bar 30 extends along the stacking direction (thickness direction D) of the battery cells 20 with the width direction W of the battery cell 20 as the plate thickness direction. In addition, a groove-shaped through hole 32 penetrating the bus bar 30 in the plate thickness direction is formed in the bus bar 30.

[0049] The other end of the electrode lead 26 protruding from the end in the width direction W of the battery cell 20 is inserted into the through hole 32 of the bus bar 30. In addition, the end portion 261 protruding from the through hole 32 is folded back toward the bus bar 30 side and overlaps the surface of the bus bar 30.

[0050] On the bus bar 30, a plurality of through holes 32 are formed along the extending direction of the bus bar 30 (in the Figure 5 is the thickness direction D). The electrode leads 26 protruding from the plurality of battery cells 20 are inserted through these through holes 32 and joined to the bus bar 30. Thus, the plurality of battery cells 20 are electrically connected via the bus bar 30. In the Figure 5 a state in which the electrode leads 26 protruding from two battery cells 20 are joined to the bus bar 30 via one welding portion 50 is shown. As Figure 5 shown, the two electrode leads 26 are respectively inserted through different through holes 32 formed in the bus bar 30. And the end portions 261 of the two electrode leads 26 are folded back toward the bus bar 30 side in directions approaching each other. Thus, an overlapping portion 30A where the end portions 261 of the two electrode leads 26 overlap is formed on the surface of the bus bar 30. The electrode lead 26 is joined to the bus bar 30 via the welding portion 50 in this overlapping portion 30A.

[0051] Figure 6A is a magnified front view of the welding portion 50 as viewed from the arrow A direction in the Figure 5 . Figure 6B is a magnified cross-sectional view showing the cross-section of the welding portion 50 cut along the B-B line in the Figure 6A .

[0052] As Figure 6AAnd Figure 6B As shown in Figure 6B , the welding portion 50 joins the ends 261 of two electrode leads 26 that overlap in the plate thickness direction to the surface of the bus bar 30. Further, on the surface of the end 261 of the electrode lead 26 that overlaps on the upper side among the ends 261 of the two electrode leads 26 and constitutes one side of the processing surface of the welding portion 50, a heat input portion 60 is formed at a position overlapping the welding portion 50. The heat input portion 60 is a region where surface processing has been performed on the end 261 of the electrode lead 26 in order to improve the heat input property compared to other portions.

[0053] In addition, the "heat input property" mentioned here refers to the ease of heat (heat input) transfer to the welding portion (base material) during welding.

[0054] In the present embodiment, the heat input portion 60 is formed in a linear region where the surface of the end 261 of the electrode lead 26 extends in the width direction of the electrode lead 26 (in Figure 6A it is the height direction H). Figure 6A In the present embodiment, the heat input portion 60 is formed in a linear region where the surface of the end 261 of the electrode lead 26 extends in the width direction of the electrode lead 26 (in Figure 6A it is the height direction H).

[0055] The welding portion 50 can be formed, for example, by laser welding or arc welding. In an example of the present embodiment, the welding portion 50 is formed by spot welding using a laser. Therefore, the welding 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 the joining of the electrode lead 26 and the bus bar 30, a plurality of welding portions 50 are formed along the heat input portion 60 formed in the linear region.

[0056] Refer to Figures 7A to 7D Examples of the heat input portion 60 will be described. Here, although a plurality of examples of forming the heat input portion 60 by surface processing of the electrode lead 26 are described, when the processing surface of the welding portion 50 is constituted by the surface of the bus bar 30, a configuration in which the heat input portion 60 is provided on the bus bar 30 can be adopted, or a configuration provided on both the electrode lead 26 and the bus bar 30 can be adopted. In addition, a structure in which the heat input portion 60 is provided at the end 261 of another electrode lead 26 disposed between the bus bar 30 and the upper-side electrode lead 26 can also be adopted.

[0057] In addition, each figure shows the state before the welding portion 50 is formed on the electrode lead 26 and the bus bar 30 as the base materials, and the welding range is represented by the region P surrounded by a double-dashed line.

[0058] In Figures 7A to 7C In the example shown in Figures 7A to 7C , the heat input portion 60 is formed by surface processing that increases the surface area of the welding portion.

[0059] Figure 7AThe illustrated first heat input portion 60A is formed by forming a linear groove portion 61 extending in the width direction of the electrode lead 26 at the end portion 261 of the electrode lead 26. Through this groove portion 61, the surface area of the processing surface of the welding portion 50 is increased, improving the heat input property. In addition, the groove portion 61 forms a thin wall portion having a plate thickness thinner than other portions. In this regard, the heat input property is also improved.

[0060] In the illustrated example, the cross-sectional shape of the groove portion 61 is V-shaped. Therefore, the plate thickness of the end portion 261 of the electrode lead 26 becomes thinner toward the center side of the welding range P. As a result, the heat input property on the center side of the welding portion 50 is higher than that on the outer peripheral side, and the penetration of the base material on the center side becomes deeper. As a result, the bonding strength can be effectively improved. In addition, the cross-sectional shape of the groove portion 61 is not limited to the V shape, and may be a rectangular shape or a concave curved surface shape (U shape).

[0061] Figure 7B The illustrated second heat input portion 60B is constituted by a through hole 63 provided in the end portion 261 of the electrode lead 26. The diameter of the through hole 63 is set to be smaller than the diameter of the dot-shaped welding portion 50. The surface area of the welding portion is increased by the inner surface of the through hole 63. As a result, the heat input property in the bonding direction of the welding portion 50 is higher than that of other portions. In addition, according to the shape of the through hole 63, the heat input property can be effectively improved toward the center side of the welding portion 50, and the penetration of the base material on the center side of the welding portion 50 becomes deeper. As a result, the bonding strength can be effectively improved.

[0062] Figure 7C The illustrated third heat input portion 60C roughens the surface of the end portion 261 of the electrode lead 26 more than other portions, increasing the surface area of the welding portion 50.

[0063] Figure 7D The illustrated fourth heat input portion 60D is formed by a surface treatment in which a black material 68 is coated on the surface of the end portion 261 of the electrode lead 26. Thereby, the black material 68 absorbs the laser, improving the heat input property of the welding portion 50 and enabling deeper penetration of the base material.

[0064] The above-mentioned Figures 7A to 7D Each of the heat input portions 60 (60A to 60D) listed above is constituted by a surface treatment that can be visually observed from the processing surface of the welding portion 50.

[0065] As described above, in the battery module 11 according to the embodiment, a plurality of battery cells 20 are stacked on one another. In addition, the electrode leads 26 of each battery cell 20 are electrically joined to the bus bar 30 via the welding portion 50. On the bus bar 30, a welding portion 50 that joins the bus bar 30 and the end portions 261 of the plurality of electrode leads 26 to each other is formed on an overlapping portion 30A where the end portions 261 of the plurality of electrode leads 26 overlap each other. Thereby, the plurality of electrode leads 26 are welded to the bus bar 30 simultaneously, reducing the man-hours for welding. In addition, in the present embodiment, in at least one of the electrode lead 26 and the bus bar 30, a heat input portion 60 having a higher heat input property in the joining direction than other portions is formed at a position overlapping the welding portion 50. As a result, when the plurality of electrode leads 26 are simultaneously welded to the bus bar 30 side by laser welding or the like, the heat input property to the base material can be improved, and the joining strength of the welding portion 50 can be stabilized.

[0066] In addition, the heat input portion 60 is formed at the end portion 261 of the electrode lead 26 that constitutes the processing surface of the welding portion 50 in the overlapping portion 30A on the bus bar 30. In addition, the heat input portion 60 is formed by a surface processing that can be visually observed. Therefore, even in a state where a plurality of electrode leads 26 are overlapped, the alignment of the folding position or the welding position of the plurality of electrode leads 26 with respect to the bus bar 30 can be easily performed. As a result, a battery module with excellent productivity can be obtained.

[0067] In addition, when the heat input portions 60 are formed on both the electrode lead 26 and the bus bar 30, in order to be configured such that both heat input portions 60 can be visually observed when viewed from the joining direction, the length in the width direction of the heat input portion on the bus bar side may be formed to be longer than the width of the electrode lead 26.

[0068] For example Figure 7A As shown, the heat input portion 60 can be constituted by a thin wall portion having a plate thickness thinner than other portions. By forming a thin wall portion (groove portion 61) having a plate thickness thinner than other portions at a position overlapping the welding portion 50, the heat input property in the joining direction of the welding portion 50 is higher than other portions, and the joining strength of the welding portion 50 can be stabilized.

[0069] In addition, the heat input portion 60 may also be as Figure 7B As shown, it is constituted by providing a through hole 63 having a diameter smaller than the dot diameter of the welding portion 50 at the end portion 261 of the electrode lead 26. The surface area of the welding portion is increased by the inner surface of the through hole 63, and the heat input property can be increased toward the center side of the welding portion 50 by the shape of the through hole 63. Therefore, the heat input property of the welding portion can be improved, and the penetration of the base material can be made deeper toward the center of the welding portion 50. Thereby, the joining strength of the welding portion 50 can be stabilized more effectively.

[0070] In addition, the heat input portion 60 is asFigure 7C As shown, it can also be formed by roughening the surface of the electrode lead at a position overlapping with the welding part 50. By roughening the surface of the electrode lead 26, the surface area of the welding part can be increased, and the heat input property in the joining direction to the welding part can be improved compared with other parts. Thereby, the joining strength of the welding part 50 can be effectively stabilized.

[0071] In addition, the heat input part 60 can also be as Figure 7D shown. At a position overlapping with the welding part 50, the heat input property is improved by coating the surface of the end part 261 of the electrode lead 26 with a black material 68, and the joining strength of the welding part 50 is stabilized.

[0072] In addition, in the present embodiment, the welding part 50 is formed in a dot shape when observed from the joining direction of the welding part 50 by spot welding using a laser. Thereby, the surface range of the welding part 50 where the base material is melted in can be reduced, the deformation of the base material or welding burn caused by welding heat can be suppressed, and the man-hours for finishing treatment can be reduced.

[0073] The above has described one embodiment and one modification example, but the present utility model can be implemented with various changes without departing from its gist. For example, in the above embodiment, the end parts of the two electrode leads are joined to the bus bar 30 at the same time, but it is not limited thereto. On the surface of the bus bar, the end parts of three or more electrode leads 26 can also be overlapped with each other, and their end parts can be joined at the same time via the welding part.

Claims

1. A battery module, characterized in that: have: A plurality of battery cells stacked one on top of the other; A bus bar electrically connected to the electrode leads of the plurality of battery cells; A welding portion, in an overlapping portion of the bus bar where the ends of the plurality of electrode leads overlap with each other, for joining the bus bar and the plurality of ends to each other; as well as A heat input portion is formed in at least one of the electrode lead and the bus bar at a position overlapping the weld portion, and the heat input property of the heat input portion in the joining direction is higher than that of other portions.

2. The battery module according to claim 1, characterized in that: The heat input portion is formed by a surface processing that can be visually seen, and is formed at least on the processed surface of the electrode lead that constitutes the weld portion.

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

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

5. The battery module according to claim 1 or 2, characterized in that: The heat input portion is formed by roughening a surface of at least one of the electrode leads.

6. The battery module according to claim 1 or 2, characterized in that: The heat input portion is formed by coating a black material on a surface of at least one of the electrode leads.

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