Battery pack and manufacturing method thereof

Abstract

To provide a battery pack capable of more surely detecting a weld defect of a bus bar to an electrode.SOLUTION: The present invention relates to a battery pack comprising a battery stack 20 consisting of a laminate of a plurality of battery cells and a bus bar module 30 fixed to the battery stack. Electrodes 23m and 23p are provided on a specific surface 22s of each battery cell. The battery stack includes a surface consisting of the specific surfaces of the plurality of battery cells. The bus bar module includes a base member 40 and a bus bar. The base member is fixed onto the surface of the battery stack. The bus bar includes a fixed part fixed to the base member and a first extension part extending from the fixed part to a first electrode in the electrodes of the plurality of battery cells. The first extension part is welded to the first electrode in a state where a stress is applied to the first extension part in a direction away from the first electrode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a battery pack and a manufacturing method thereof.

[0002] The battery pack disclosed in Patent Document 1 includes a battery stack and a busbar module. The battery stack is configured by a stack of multiple battery cells. An electrode is provided on the surface of each battery cell. A busbar module is fixed onto the surface of the battery stack configured by the surfaces of each battery cell (i.e., the surfaces on which the electrodes are provided). The busbar module has busbars welded to the electrodes of the battery cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-008876 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the welding conditions when welding the busbar to the electrode of the battery cell are not appropriate, a welding defect may occur. For example, if a gap exists between the busbar and the electrode in the welding process, a welding defect may occur. In order to detect a welding defect, an electrical inspection can be performed after the welding process to detect whether the busbar and the electrode are electrically connected. If the busbar is not in contact with the electrode due to a welding defect, an abnormality is detected in the electrical inspection. However, there are cases where the busbar is not welded to the electrode due to a welding defect, but is in contact with the electrode. In this case, since the busbar is electrically connected to the electrode, an abnormality is not detected in the electrical inspection. As described above, in the conventional battery pack, it may be difficult to detect a welding defect of the busbar to the electrode. In this specification, a technology for more reliably detecting a welding defect of the busbar to the electrode is proposed. [Means for solving the problem]

[0005] The battery pack disclosed in this specification includes a battery stack formed by stacking a plurality of battery cells, and a busbar module fixed to the battery stack. An electrode is provided on a specific surface of each of the battery cells. The battery stack has a surface formed by the specific surfaces of the plurality of battery cells. The busbar module includes a base member and a busbar. The base member is fixed onto the surface of the battery stack. The busbar has a fixing portion fixed to the base member and a first extension portion extending from the fixing portion to a first electrode of the electrodes of the plurality of battery cells. The first extension portion is welded to the first electrode in a state where a stress is applied to the first extension portion in a direction away from the first electrode.

[0006] In this battery pack, the first extension is welded to the first electrode in a state where a stress is applied to the first extension in a direction away from the first electrode. Therefore, if a welding defect occurs when welding the first extension to the first electrode, the first extension is not in contact with the first electrode. Therefore, by electrically detecting whether or not the first extension and the first electrode are electrically connected, the welding defect can be detected.

[0007] The manufacturing method of a battery pack disclosed in the present specification includes a step of fixing a busbar module to a battery stack. The battery stack is configured by a stack of a plurality of battery cells. An electrode is provided on a specific surface of each of the battery cells. The battery stack has a surface configured by the specific surfaces of the plurality of battery cells. The busbar module includes a base member and a busbar. The busbar has a fixing portion fixed to the base member and a first extension portion extending from the fixing portion. The step of fixing the busbar module to the battery stack includes a first step and a second step. In the first step, the base member is fixed on the surface of the battery stack such that the first extension portion faces a first electrode of the electrodes of the plurality of battery cells with a gap therebetween. In the second step, the first extension portion is welded to the first electrode in a state in which the first extension portion is in contact with the first electrode by elastically deforming the first extension portion.

[0008] In this manufacturing method, in the second step, the first extension portion is elastically deformed to bring the first extension portion into contact with the first electrode, and the first extension portion is welded to the first electrode. Therefore, if a welding defect occurs in the second step, the first extension portion moves to a position where it is not in contact with the first electrode due to a reaction force caused by the elastic deformation after the welding step. Therefore, by electrically detecting whether or not the first extension portion and the first electrode are electrically connected, the welding defect can be detected. [Brief description of the drawings]

[0009] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] 4 is a cross-sectional view of the battery pack taken along line IV-IV in FIG. 3. [Diagram 5] 4 is a cross-sectional view of the battery pack taken along line VV in FIG. 3. [Figure 6]FIG. 4 is a plan view of the bus bar (with the base member not shown). [Figure 7] FIG. 6 is a cross-sectional view corresponding to FIGS. 4 and 5 of the busbar before the welding process. [Figure 8] FIG. 6 is a cross-sectional view corresponding to FIGS. 4 and 5 of the busbar during the welding process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the battery pack according to the embodiment disclosed herein, the first extension may have a welded portion welded to the first electrode and a connection portion connecting the welded portion and the fixed portion. The welded portion may be welded to the first electrode in a state where the connection portion is elastically deformed so that the welded portion approaches the first electrode.

[0011] According to this configuration, when a welding defect occurs, the reaction force of the connection portion causes the welded portion to be out of contact with the first electrode, making it possible to detect the welding defect.

[0012] In one example battery pack disclosed in the present specification, a height from the surface of the battery stack to the fixing portion may be greater than a height from the surface of the battery stack to the welded portion.

[0013] In the battery pack according to the embodiment disclosed herein, the bus bar may have a second extension extending from the fixing portion to an upper portion of a second electrode of the electrodes of the battery cells. The second extension may be welded to the second electrode in a state where a stress is applied to the second extension in a direction away from the second electrode.

[0014] In the battery pack manufacturing method according to the example disclosed in the present specification, the first extension portion may have a welded portion welded to the first electrode and a connection portion connecting the welded portion and the fixed portion. In the second step, the welded portion may be welded to the first electrode in a state in which the connection portion is elastically deformed so that the welded portion approaches the first electrode.

[0015] According to this configuration, when a welding defect occurs, the reaction force of the connection portion causes the welded portion to be out of contact with the first electrode, making it possible to detect the welding defect.

[0016] In the battery pack manufacturing method according to the example disclosed in the present specification, the first electrode may be an output electrode of the battery cell. The method may further include a step of detecting a potential of the bus bar after the second step.

[0017] According to this configuration, a welding defect can be detected based on the potential of the bus bar.

[0018] In the manufacturing method of a battery pack disclosed in the present specification as an example, the bus bar may have a second extension portion extending from the fixing portion. In the first step, the base member may be fixed on the surface of the battery stack such that the second extension portion faces a second electrode of the electrodes of the plurality of battery cells with a gap therebetween. In the second step, the second extension portion may be welded to the second electrode in a state in which the second extension portion is brought into contact with the second electrode by elastically deforming the second extension portion.

[0019] A battery pack 10 according to an embodiment shown in Fig. 1 is mounted on an electric vehicle. The battery pack 10 supplies power to a motor for driving the electric vehicle. As shown in Figs. 1 and 2, the battery pack 10 includes a battery stack 20, a bus bar module 30, a cover 70, and resin frames 80 and 82.

[0020] As shown in FIG. 2, the battery stack 20 is composed of a plurality of battery cells 22. Each battery cell 22 has a flat rectangular parallelepiped shape. The battery stack 20 is composed by stacking a plurality of battery cells 22 in their thickness direction. Each battery cell 22 has a surface 22s on which a positive electrode 23p and a negative electrode 23m are provided. The surface 22s of each battery cell 22 constitutes the upper surface 20u of the battery stack 20. In each battery cell 22, the positive electrode 23p and the negative electrode 23m are disposed at both ends of the surface 22s. On the upper surface 20u of the battery stack 20, the positive electrodes 23p and the negative electrodes 23m form columns 24a and 24b extending along the stacking direction of the battery stack 20. In the column 24a, the positive electrodes 23p and the negative electrodes 23m are alternately arranged along the stacking direction. In the column 24b, the positive electrodes 23p and the negative electrodes 23m are alternately arranged along the stacking direction. In the following, the positive electrode 23p and the negative electrode 23m may be collectively referred to as the electrodes 23. Each electrode 23 has a protrusion 26 provided at the center of its upper surface.

[0021] The resin frame 80 is fixed to one side surface of the battery stack 20. The resin frame 80 is made up of a plurality of resin connection members 80a. Each resin connection member 80a connects two adjacent battery cells 22. The resin frame 82 is fixed to the other side surface of the battery stack 20. The resin frame 82 is made up of a plurality of resin connection members 82a. Each resin connection member 82a connects two adjacent battery cells 22. The resin frames 80, 82 fix the multiple battery cells 22 to each other.

[0022] The bus bar module 30 is fixed onto an upper surface 20u of the battery stack 20. The cover 70 is fixed to the bus bar module 30 in a state where the cover 70 covers the upper surface of the bus bar module 30.

[0023] As shown in FIGS. 2 and 3, the bus bar module 30 has a base member 40 and a plurality of bus bars 50. In FIG. 3, the bus bars 50 are indicated by gray hatching. The base member 40 is made of insulating resin. As shown in FIG. 2, the base member 40 has a plurality of frame portions 42 provided along both edges of the base member 40. As shown in FIGS. 2 and 3, clips 45 are provided on the outer side surfaces of the frame portions 42. Protrusions 80b are provided on the upper surface of each resin connection member 80a of the resin frame 80. As shown in FIG. 3, each protrusion 80b is engaged with each clip 45 of the base member 40. Also, as shown in FIG. 2, protrusions 82b are provided on the upper surface of each resin connection member 82a of the resin frame 82. Although not shown, each protrusion 82b is engaged with each clip 45 of the base member 40. The base member 40 is fixed to the resin frames 80 and 82 by the protrusions 80b and 82b engaging with the clips 45. Therefore, the base member 40 is fixed to the battery stack 20 via the resin frames 80, 82. The base member 40 is fixed onto the upper surface 20u of the battery stack 20.

[0024] Next, the structure inside each frame portion 42 will be described. FIG. 4 shows a cross-sectional view of the battery pack 10 taken along line IV-IV in FIG. 3. As shown in FIG. 4, a support portion 44 is formed inside the frame portion 42 of the base member 40. The support portion 44 is fixed on the upper surface 20u of the battery stack 20. An opening 48a is provided at a position adjacent to the support portion 44 inside the frame portion 42. FIG. 5 shows a cross-sectional view of the battery pack 10 taken along line VV in FIG. 3. As shown in FIG. 5, a support portion 44 is also formed at the position of line VV. An opening 48b is provided at a position adjacent to the support portion 44 inside the frame portion 42. As shown in FIG. 3, the openings 48a and 48b are arranged with a gap between them inside the frame portion 42. As shown in FIGS. 3 to 5, the positive electrode 23p is arranged inside the opening 48a, and the negative electrode 23m is arranged inside the opening 48b. As shown in FIG. 3, the openings 48a and 48b are arranged with a gap between them. are separated by an intermediate partition 46 .

[0025] As shown in Figs. 2 and 3, each bus bar 50 is disposed in a corresponding frame portion 42. Bus bar 50 is a conductive member made of metal. Bus bar 50 has a fixed portion 54, a first extending portion 51, and a second extending portion 52. As shown in Figs. 3 to 5, fixed portion 54 is fixed onto support portion 44.

[0026] As shown in FIGS. 3 and 4, the first extension 51 extends from the fixed portion 54 to the upper portion of the positive electrode 23p in the opening 48a. The first extension 51 is provided with a through hole 51a. With the protrusion 26 of the positive electrode 23p inserted into the through hole 51a, the first extension 51 is welded to the positive electrode 23p. Hereinafter, the portion of the first extension 51 on the positive electrode 23p is referred to as a welded portion 51b, and the portion connecting the welded portion 51b and the fixed portion 54 is referred to as a connection portion 51c. As shown in FIG. 6, the welded portion 51b is welded to the positive electrode 23p within a welding range X1 provided on both sides of the through hole 51a. As shown in FIG. 4, the upper surface of the support 44 is disposed above the upper surface of the positive electrode 23p. Therefore, the height H1 from the upper surface 20u of the battery stack 20 to the fixed portion 54 is higher than the height H2 from the upper surface 20u to the welded portion 51b. Therefore, the connection portion 51c extends obliquely downward from the fixed portion 54 toward the welded portion 51b. The connection portion 51c is elastically deformed so that the welded portion 51b approaches the positive electrode 23p, and the welded portion 51b is welded to the positive electrode 23p in this state of the connection portion 51c being elastically deformed. Therefore, an elastic stress is generated in the connection portion 51c in a direction that moves the welded portion 51b away from the positive electrode 23p (i.e., upward).

[0027] As shown in FIGS. 3 and 5, the second extension 52 extends from the fixed portion 54 to the upper portion of the negative electrode 23m in the opening 48b. The second extension 52 is provided with a through hole 52a. With the protrusion 26 of the negative electrode 23m inserted into the through hole 52a, the second extension 52 is welded to the negative electrode 23m. Hereinafter, the portion of the second extension 52 on the negative electrode 23m is referred to as the welded portion 52b, and the portion connecting the welded portion 52b and the fixed portion 54 is referred to as the connection portion 52c. As shown in FIG. 6, the welded portion 52b is welded to the negative electrode 23m in a welding range X2 provided on both sides of the through hole 52a. As shown in FIG. 5, the upper surface of the support 44 is disposed above the upper surface of the negative electrode 23m. Therefore, the height H3 from the upper surface 20u of the battery stack 20 to the fixed portion 54 is higher than the height H4 from the upper surface 20u to the welded portion 52b. Therefore, the connection portion 52c extends obliquely downward from the fixed portion 54 toward the welded portion 52b. The connection portion 52c is elastically deformed so that the welded portion 52b approaches the negative electrode 23m, and the welded portion 52b is welded to the negative electrode 23m in this state in which the connection portion 52c is elastically deformed. Therefore, an elastic stress is generated in the connection portion 52c in a direction that moves the welded portion 52b away from the negative electrode 23m (i.e., upward).

[0028] As described above, adjacent pairs of positive electrode 23p and negative electrode 23m are connected by the bus bar 50. As shown in FIG. 2, the bus bars 50 are arranged along the rows 24a and 24b of the electrodes 23. Each pair of adjacent pairs of positive electrode 23p and negative electrode 23m is connected to each other by each bus bar 50. This connects each battery cell 22 in series. Therefore, the battery stack 20 outputs a voltage obtained by integrating the output voltages of each battery cell 22.

[0029] Next, a manufacturing method of the battery pack 10 will be described. First, the battery cells 22 are connected via the resin frames 80 and 82 to form the battery stack 20. Next, the base member 40 of the busbar module 30 is fixed to the resin frames 80 and 82. That is, the protrusions 80b and 82b of the resin frames 80 and 82 are engaged with the clips 45 of the base member 40 to fix the base member 40 of the busbar module 30 to the resin frames 80 and 82. As a result, the busbar module 30 is fixed on the upper surface 20u of the battery stack 20. When the busbar module 30 is fixed to the upper surface 20u of the battery stack 20, the first extension portion 51 of each busbar 50 is disposed above the positive electrode 23p as shown in FIG. 7. In this state, a gap 98 exists between the first extension portion 51 and the positive electrode 23p. In addition, in a manner substantially similar to the first extension portion 51, the second extension portion 52 of each busbar 50 is disposed above the negative electrode 23m as shown in FIG. 7. In this state, a gap 98 exists between the second extension portion 52 and the negative electrode 23m.

[0030] Next, as shown in FIG. 8, the welded portion 51b of the first extension portion 51 is pressed toward the positive electrode 23p by a pressing jig 90. The pressing jig 90 has a pair of protrusions 90a, 90b. The protrusions 90a, 90b of the pressing jig 90 press the first extension portion 51 toward the positive electrode 23p in the range Y1 (i.e., the range provided on both sides of the through hole 51a) shown in FIG. 6. This causes the connection portion 51c to elastically deform, and the welded portion 51b comes into contact with the positive electrode 23p as shown in FIG. 8. Next, while the first extension portion 51 is being pressed, a laser is irradiated from above onto the welded portion 51b (more specifically, within the welding range X1 in FIG. 6), thereby welding the welded portion 51b to the positive electrode 23p. When the welded portion 51b is welded to the positive electrode 23p in this manner, the welded portion 51b is welded to the positive electrode 23p in a state in which the connection portion 51c is elastically deformed. That is, the welded portion 51b is fixed to the positive electrode 23p in a state in which a stress is generated in the connection portion 51c in a direction that moves the welded portion 51b away from the positive electrode 23p.

[0031] In addition, the second extension portion 52 is welded to the negative electrode 23m in the same manner as the first extension portion 51 is welded to the positive electrode 23p. That is, as shown in FIG. 8, the welded portion 52b of the second extension portion 52 is pressed toward the negative electrode 23m by a pressing jig 90. The protrusions 90a and 90b of the pressing jig 90 press the second extension portion 52 toward the negative electrode 23m in the range Y2 shown in FIG. 6 (i.e., the range provided on both sides of the through hole 52a). This causes the connection portion 52c to elastically deform, and the welded portion 52b comes into contact with the negative electrode 23m as shown in FIG. 8. Next, while the second extension portion 52 is being pressed, a laser is irradiated from above to the welded portion 52b (more specifically, within the welding range X2 in FIG. 6), thereby welding the welded portion 52b to the negative electrode 23m. When the welded portion 52b is welded to the negative electrode 23m in this manner, the welded portion 52b is welded to the negative electrode 23m in a state in which the connection portion 52c is elastically deformed. That is, the welded portion 52b is fixed to the negative electrode 23m in a state in which a stress is generated in the connection portion 52c in a direction that moves the welded portion 52b away from the negative electrode 23m.

[0032] By the welding method described above, each bus bar 50 is welded to the corresponding positive electrode 23p and negative electrode 23m.

[0033] Next, an inspection process is performed to detect the potential of each bus bar 50. Since the battery stack 20 is a stack of a plurality of battery cells 22, dimensional errors due to misalignment of the battery cells 22 during stacking are likely to occur in the battery stack 20. For this reason, the dimensional errors may cause welding conditions for each bus bar 50 to be inappropriate, resulting in defective welding. In the above-described manufacturing method, a gap 98 exists between the welded portion 51b and the positive electrode 23p before pressure is applied, as shown in FIG. 7. In the welding process, as shown in FIG. 8, the welded portion 51b is pressurized by the pressure jig 90, so that the connection portion 51c is elastically deformed and the welded portion 51b comes into contact with the positive electrode 23p. In this state in which the connection portion 51c is elastically deformed, the welded portion 51b is welded to the positive electrode 23p. If defective welding occurs in this welding process, the welded portion 51b is not connected to the positive electrode 23p. In the case where a welding defect occurs in this way, when the pressure jig 90 is removed from the welded portion 51b after the welding process, the stress of the connection portion 51c is released, and the connection portion 51c returns to the original shape shown in FIG. 7. Therefore, the welded portion 51b is not in contact with the positive electrode 23p. That is, the welded portion 51b is insulated from the positive electrode 23p. Therefore, in the subsequent inspection process, an abnormal potential is detected in the bus bar 50 where the welding defect occurs. Similarly, even if a welding defect occurs between the welded portion 52b and the negative electrode 23m, when the pressure jig 90 is removed from the welded portion 52b, the welded portion 52b is not in contact with the negative electrode 23m. Therefore, in the subsequent inspection process, an abnormal potential is detected. In this way, in this manufacturing method, since the bus bar 50 is not in contact with the electrode 23 when a welding defect occurs, the welding defect can be detected by the potential of the bus bar 50. In this manufacturing method, the welding defect can be detected more reliably than in the past.

[0034] Although in the above-described embodiment, the bus bar 50 is welded to the electrode 23 by laser welding, the bus bar 50 may be welded to the electrode 23 by another welding method.

[0035] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0036] 10: Battery pack 20: Battery stack 22: Battery cell 23m: Negative electrode 23p: positive electrode 30: Busbar module 40: Base material 44: Support part 50: Busbar 51: 1st extension part 52:Second extension part 70: Cover 80: Resin frame

Claims

1. 1. A battery pack comprising: A battery stack formed by stacking a plurality of battery cells; A bus bar module fixed to the battery stack; having An electrode is provided on a specific surface of each of the battery cells; the battery stack has a surface defined by the particular surfaces of the plurality of battery cells; The bus bar module comprises: a base member fixed onto the surface of the battery stack; a bus bar including a fixed portion fixed to the base member and a first extension portion extending from the fixed portion to a first electrode among the electrodes of the plurality of battery cells; having the first extension portion is welded to the first electrode in a state in which a stress is applied to the first extension portion in a direction away from the first electrode; Battery pack.

2. The first extension portion has a welded portion welded to the first electrode and a connection portion connecting the welded portion and the fixed portion, the welding portion is welded to the first electrode in a state in which the connection portion is elastically deformed so that the welding portion approaches the first electrode; The battery pack according to claim 1 .

3. The battery pack according to claim 2 , wherein a height from the surface of the battery stack to the fixing portion is greater than a height from the surface of the battery stack to the welded portion.

4. the bus bar has a second extension portion extending from the fixed portion to an upper portion of a second electrode among the electrodes of the plurality of battery cells, the second extension portion is welded to the second electrode in a state in which a stress is applied to the second extension portion in a direction away from the second electrode; The battery pack according to any one of claims 1 to 3.

5. A method for manufacturing a battery pack, comprising: Attaching the bus bar module to the battery stack; The battery stack is formed by stacking a plurality of battery cells, An electrode is provided on a specific surface of each of the battery cells; the battery stack has a surface defined by the particular surfaces of the plurality of battery cells; the bus bar module includes a base member and a bus bar; the bus bar has a fixed portion fixed to the base member and a first extension portion extending from the fixed portion, The step of fixing the bus bar module to the battery stack further comprises: a first step of fixing the base member on the surface of the battery stack such that the first extension portion faces a first electrode of the electrodes of the plurality of battery cells with a gap therebetween; a second step of elastically deforming the first extension portion to bring the first extension portion into contact with the first electrode, and welding the first extension portion to the first electrode in a state where the first extension portion is in contact with the first electrode; The manufacturing method according to claim 1,

6. The first extension portion has a welded portion welded to the first electrode and a connection portion connecting the welded portion and the fixed portion, In the second step, the welding portion is welded to the first electrode in a state in which the connection portion is elastically deformed so that the welding portion approaches the first electrode. The method according to claim 5 .

7. the first electrode is an output electrode of the battery cell; The method further includes a step of detecting a potential of the bus bar after the second step. The method according to claim 5 or 6.

8. the bus bar has a second extension portion extending from the fixed portion, In the first step, the base member is fixed on the surface of the battery stack such that the second extension portion faces second electrodes of the electrodes of the plurality of battery cells with a gap therebetween; In the second step, the second extension portion is elastically deformed to bring the second extension portion into contact with the second electrode, and the second extension portion is welded to the second electrode in this state. The method according to any one of claims 5 to 7.

Images