JP7486273B2 - Battery Module - Google Patents

Description

The disclosed technology relates to a battery module having bus bars joined to the terminal surfaces of the battery cells.

In a battery module, a bus bar is generally connected to a terminal surface provided on the outer surface of the battery cell. The bus bar electrically connects the joined battery cell to, for example, other battery cells. An example of a conventional battery module in which a bus bar is joined to a battery cell is described in Patent Document 1. In the battery module in this document, an opening window is formed in the bus bar, and the terminal surface of the battery cell is exposed on the inside of the opening window, while the terminal surface and the bus bar are joined on the outside of the opening window.

International Publication No. 2017/130706

In the conventional technology described above, the weld marks, which are the joints between the terminal surfaces of the battery cells and the busbar, are formed large so as to surround the outside of the opening window of the busbar. When large weld marks are formed, for example, the time required for welding tends to be long, and the production efficiency of the battery module decreases. On the other hand, the shorter the welding time, the smaller the weld marks that can be formed, and the joint strength between the terminal surfaces and the busbar tends to decrease. In other words, it has been difficult to form weld marks in a short time that adequately suppress separation between the terminal surfaces and the busbar.

The disclosed technology has been developed to solve the problems of the conventional technology described above. In other words, the objective is to provide a battery module in which the terminal surfaces of the battery cells and the bus bars are joined in a short time and are not easily separated at the joints.

One aspect of the disclosed technology is a battery module having a battery cell with a portion of its outer surface serving as a terminal surface and a bus bar joined to the terminal surface, in which the bus bar has a cutout portion formed therein that penetrates the battery cell in the thickness direction and exposes a portion of the terminal surface, and a weld mark is formed at the portion where the bus bar and the terminal surface are joined by welding, and at least one end of the weld mark is attached to the cutout portion and to the terminal surface exposed at the cutout portion.

In the battery module of the above embodiment, a weld mark is formed in which at least one end of the weld mark is placed on the notch and on the terminal surface exposed at the notch. The end of such a weld mark is less likely to concentrate stress even when a force in a direction away from the terminal surface acts on the bus bar. Therefore, the terminal surface of the battery cell and the bus bar are less likely to separate at the weld mark. In addition, the weld mark can be formed by welding in a line and extending the end to the notch. By extending the weld end to the notch, the time required for welding is not particularly long. In other words, such a weld mark is formed in a short time. Therefore, the battery module of the above embodiment is a battery module in which the terminal surface of the battery cell and the bus bar are joined in a short time and are less likely to separate at the joint.

In the battery module of the above aspect, it is further preferable that the busbar has cutouts at multiple locations, and the weld mark is formed so as to extend from one cutout to another. In this way, separation of the busbar and the terminal surface at both ends of the weld mark can be prevented.

The battery module of the above aspect further has a plurality of battery cells, and it is desirable that the bus bar connects the terminal surfaces of two adjacent battery cells. In this way, a battery module can be configured in which the plurality of battery cells are appropriately connected and the desired capacity can be stably exhibited.

In the battery module of the above embodiment, it is further preferable that the cutout portion is a through hole. In this way, the through hole can be used as a marker or the like during the manufacturing process.

The disclosed technology provides a battery module in which the terminal surfaces of the battery cells and the bus bars are joined in a short time and are less likely to separate at the joints.

1 is an external perspective view of a battery module according to an embodiment; FIG. 2 is a perspective view of a battery cell and a bus bar in the battery module. FIG. FIG. FIG. 13 is a plan view of a bus bar on which a welding mark is formed according to a comparative example. FIG. 11 is a cross-sectional view of a welding mark according to a comparative example. 13A and 13B are diagrams illustrating a case where deformation occurs in a bus bar on which a welding mark is formed according to a comparative example. 11A and 11B are diagrams illustrating locations where stress occurs in a weld mark when deformation occurs in a bus bar on which a weld mark is formed according to a comparative example. 11A to 11C are diagrams illustrating locations where stress occurs in a weld mark when deformation occurs in the bus bar on which the weld mark is formed in the embodiment.

Below, an embodiment that embodies the disclosed technology will be described in detail with reference to the attached drawings. In this embodiment, the disclosed technology is applied to a battery module 1 shown in FIG. 1. The battery module 1 in FIG. 1 has a lower case 2 filled with multiple battery cells 3. The multiple battery cells 3 are arranged in a horizontally stacked manner inside the lower case 2. When the battery module 1 is actually used, an upper case and the like are further attached to the state shown in FIG. 1, but these are not characteristic of the disclosed technology and will not be described here.

The battery cell 3 in this embodiment is a rectangular flat plate as shown in FIG. 2. The battery cell 3 has a power generating element built inside the exterior body 4. A positive terminal 5 and a negative terminal 6 are provided at both ends of the upper surface of the exterior body 4. The battery cell 3 can be charged and discharged through the positive terminal 5 and the negative terminal 6. The upper surface of the positive terminal 5 is shown as the positive terminal surface 51, and the upper surface of the negative terminal 6 is shown as the negative terminal surface 61.

As shown in FIG. 2, the multiple battery cells 3 in the battery module 1 are arranged so that the positive electrode terminals 5 and the negative electrode terminals 6 are alternately arranged in the opposite directions. A bus bar 7 is arranged to connect the positive electrode terminals 5 and the negative electrode terminals 6 of adjacent battery cells 3. The bus bar 7 is a conductive metal plate. The bus bar 7 in this embodiment is flat. The bus bar 7 is connected to the positive electrode terminal surface 51 of the positive electrode terminal 5 and the negative electrode terminal surface 61 of the negative electrode terminal 6. The position of the bus bar 7 is shifted between the right column and the left column in FIG. 2. As a result, in the battery module 1 in this embodiment, the battery group consisting of the multiple battery cells 3 is electrically connected in series by the bus bar 7.

FIG. 3 is a plan view of the busbar 7. The busbar 7 has a positive electrode connection portion 71 connected to the positive electrode terminal surface 51 and a negative electrode connection portion 72 connected to the negative electrode terminal surface 61. The positive electrode connection portion 71 and the negative electrode connection portion 72 have through holes 75 formed therethrough that penetrate the busbar 7 in the thickness direction. The through holes 75 are cut-out portions formed by cutting out a portion of the busbar 7. Four through holes 75 are formed in each of the positive electrode connection portion 71 and the negative electrode connection portion 72. In this embodiment, the arrangement of the four through holes 75 in each of the positive electrode connection portion 71 and the negative electrode connection portion 72 is such that a rectangle is formed with these as vertices.

In addition, two weld marks 8 are formed on each of the positive electrode connection part 71 and the negative electrode connection part 72. The weld marks 8 are indicated by dot hatching. Each of the weld marks 8 is formed in a line connecting two through holes 75. The weld mark 8 on the positive electrode connection part 71 is formed by joining the positive electrode connection part 71 and the positive electrode terminal surface 51 by welding. The weld mark 8 on the negative electrode connection part 72 is formed by joining the negative electrode connection part 72 and the negative electrode terminal surface 61 by welding. Each of the linear weld marks 8 shown in FIG. 3 is formed to extend in the width direction of the battery cell 3.

Figure 4 is a cross-sectional view of the weld mark 8. The upper side of the end of the weld mark 8 hangs over the through hole 75. The lower side of the end of the weld mark 8 below the through hole 75 hangs over the positive terminal surface 51 or the negative terminal surface 61 exposed at the through hole 75. That is, both ends of the weld mark 8 formed between the through holes 75 hang over the through hole 75 and the positive terminal surface 51 or the negative terminal surface 61 exposed at the through hole 75. In addition, the weld mark 8 penetrates the bus bar 7 from the upper surface of the bus bar 7 in the thickness direction of the bus bar 7, and reaches the positive terminal 5 and the negative terminal 6. This joins the bus bar 7 to the positive terminal surface 51 or the negative terminal surface 61.

The weld mark 8 in this embodiment is formed by laser welding. That is, while the bus bar 7 is placed on the positive terminal surface 51 and the negative terminal surface 61, the irradiation position of the laser light is moved from one end of the area where the weld mark 8 is to be formed to the other end. As a result, the bus bar 7 and the positive terminal 5 or the negative terminal 6 melted by the laser irradiation mix with each other and then solidify to become the weld mark 8. The weld mark 8 in this embodiment is formed by moving the irradiation position of the laser light in a line so as to connect adjacent through holes 75. Therefore, the bus bar 7 can be joined in a short time compared to the case where a large planar weld mark is formed by irradiating the laser light.

In addition, in the case of the present embodiment, the weld mark 8 whose end reaches the through hole 75 makes it difficult for the bus bar 7 to separate from the positive terminal surface 51 and the negative terminal surface 61 at the end. This will be explained in comparison with a comparative example that is different from the weld mark 8 of the present embodiment.

Figure 5 is a plan view of a busbar 7 on which a weld mark 9 according to a comparative example is formed. The configuration of the comparative example is the same as that of the above embodiment except for the weld mark 9. The weld mark 9 according to the comparative example is shorter than the weld mark 8 according to this embodiment. Specifically, the weld mark 9 according to the comparative example is long enough that both ends of the weld mark 9 do not reach the through hole 75. Figure 6 is a cross-sectional view of the weld mark 9 according to the comparative example. Both ends of the weld mark 9 do not overlap the through hole 75 or the positive terminal surface 51 or the negative terminal surface 61 exposed at the through hole 75.

Figure 7 is a diagram showing a case where a force is applied to a busbar 7 on which a weld mark 9 according to a comparative example is formed, moving the busbar 7 away from the positive electrode terminal surface 51 and the negative electrode terminal surface 61. In the busbar 7 of Figure 7, a force is applied to move the busbar 7 away from the positive electrode terminal surface 51 and the negative electrode terminal surface 61, the closer to the end (right side) of the busbar 7 in the longitudinal direction of the weld mark 9. For example, if one of adjacent battery cells 3 moves relative to the other, the busbar 7 may be deformed in a twisted manner, causing such a force to act.

Figure 8 shows a plan view of the weld mark 9 according to the comparative example. Figure 8 also shows position A where stress occurs when the busbar 7 is deformed so that the busbar 7 is further away from the positive terminal surface 51 and the negative terminal surface 61 toward the upper end side of the busbar 7. As shown in Figure 8, position A is located at the longitudinal end of the weld mark 9. That is, in the weld mark 9 according to the comparative example, stress may be concentrated at position A at the longitudinal end. Position A where this stress is concentrated is the thick part of the weld mark 9 as shown in Figure 7, and is the middle point in the thickness direction. At position A of the weld mark 9, repeated stress concentration may occur, which may cause fatigue failure.

In contrast, in the weld mark 8 according to this embodiment, as shown in the cross-sectional view of FIG. 4, the upper surface becomes gentler as it approaches the longitudinal end. The weld mark 8 according to this embodiment is shaped so that it becomes thinner as it approaches the end, and sinks below the positive terminal surface 51 and the negative terminal surface 61 inside the through hole 75. This shape of the weld mark 8 makes it difficult for stress to concentrate at the longitudinal end, even if the busbar 7 is deformed so that it is farther away from the positive terminal surface 51 and the negative terminal surface 61 as it approaches the end of the busbar 7.

9 shows a plan view of the weld mark 8 according to this embodiment. FIG. 9 also shows positions B1 to B3 and C1 to C3 where stress occurs when the busbar 7 is deformed so as to move away from the positive terminal surface 51 and the negative terminal surface 61 toward the upper end of the busbar 7. Positions B1 to B3 and positions C1 to C3 are located on the sides near the upper end of the weld mark 8. The stress generated is smaller at positions B3 and C3, which are farther from the upper end, than at positions B1 and C1, which are closer to the upper end of the weld mark 8. That is, in the weld mark 8 according to this embodiment, as shown in FIG. 9, when the busbar 7 is deformed so as to move away from the positive terminal surface 51 and the negative terminal surface 61 toward the upper end of the busbar 7, stress is distributed along the side of the weld mark 8. This prevents large stress from concentrating on the longitudinal end of the weld mark 8. Therefore, the weld mark 8 according to this embodiment is less susceptible to fatigue failure even in a situation where the busbar 7 is repeatedly deformed. This prevents the busbar 7 from being separated from the positive terminal surface 51 and the negative terminal surface 61.

The through hole 75 can also be effectively used in the welding process of the bus bar 7. That is, for example, during laser welding, the through hole 75 can be used as a mark for the start or end point of the laser irradiation. This makes it possible to accurately determine the laser irradiation position and form an appropriate weld mark 8. Furthermore, since the laser irradiation position and the marks for the start and end points are close to each other, the laser irradiation can be performed accurately from the start point to the end point.

The through holes 75 can be effectively used in the welding process of the busbar 7, which allows the miniaturization of each component, such as the busbar 7. This is because there is no need to provide a separate through hole to be used as a marker in the welding process. Also, the weld marks 8 can be formed large within the limited area of the busbar 7, the positive terminal surface 51, and the negative terminal surface 61. This allows the weld marks 8 to be formed with sufficient joint strength while miniaturizing each component.

As described above in detail, the battery module according to this embodiment has the battery cell 3 and the bus bar 7 joined to the positive terminal surface 51 and the negative terminal surface 61 of the battery cell 3. The bus bar 7 has a through hole 75 penetrating in the thickness direction. Inside the through hole 75, a part of the positive terminal surface 51 and the negative terminal surface 61 is exposed. In addition, a welding mark 8 is formed at a point where the bus bar 7 and the positive terminal surface 51 and the negative terminal surface 61 are joined by welding. The end of the welding mark 8 hangs on the through hole 75 and the positive terminal surface 51 and the negative terminal surface 61 exposed at the through hole 75. At the end of such a welding mark 8, stress is unlikely to concentrate even when a force acting in a direction away from the positive terminal surface 51 and the negative terminal surface 61 acts on the bus bar 7. Therefore, the bus bar 7 is prevented from being separated from the positive terminal surface 51 and the negative terminal surface 61. In addition, the weld mark 8 can be formed by joining the wires in a line and extending the end of the line to the through hole 75. By extending the end of the weld to the through hole 75, the time required for welding is not significantly increased. In other words, the weld mark 8 is formed in a short time. Therefore, the terminal surface of the battery cell and the bus bar are joined in a short time, resulting in a battery module in which they are unlikely to separate at the joint.

In addition, a plurality of through holes 75 are formed in the bus bar 7. The welding mark 8 is formed so that both ends reach two through holes 75. Therefore, separation between the bus bar 7 and the positive terminal surface 51 and the negative terminal surface 61 at both ends of the welding mark 8 can be suppressed. The bus bar 7 also connects the positive terminal surface 51 and the negative terminal surface 61 of two adjacently arranged battery cells 3. This allows the battery module 1 to be configured so that the multiple battery cells 3 are properly connected and can stably exhibit the desired capacity. In addition, by making the points where the ends of the welding marks 8 reach into through holes 75, the through holes 75 can be used as markers or the like in the manufacturing process. For example, by using the through holes 75 as markers for the start or end points of laser welding, the laser irradiation position can be accurately determined.

The above embodiments are merely examples and do not limit the disclosed technology in any way. Naturally, the disclosed technology can be improved and modified in various ways without departing from the spirit of the technology.

For example, in the above embodiment, an example was described in which both ends of the weld mark 8 reach the two through holes 75. However, if the purpose is to suppress only the stress concentration on one end side of the weld mark, it is sufficient that the weld mark only reaches the through hole on that one end side. Also, for example, in the above embodiment, an example was described in which the notch part where the end of the weld mark 8 is hung is a round through hole 75. However, the shape of the notch part where the end of the weld mark is hung may be, for example, a triangular or rectangular through hole. Also, for example, the notch part where the end of the weld mark is hung may be a U-shape with a part connected to the outer edge of the bus bar.

For example, in the above embodiment, two weld marks 8 are provided on each of the positive terminal surface 51 and the negative terminal surface 61. However, one weld mark 8 may be provided on each of the positive terminal surface 51 and the negative terminal surface 61. For example, in the above embodiment, two weld marks 8 are provided in parallel, with both ends reaching two of the four through holes 75. However, when providing multiple weld marks, they do not necessarily have to be parallel. For example, the weld marks may be provided so as to connect the diagonal ones of the four through holes 75 arranged to form the vertices of a rectangle. In other words, multiple weld marks may be provided so as to intersect.

In the above embodiment, an example of a battery module 1 in which multiple battery cells 3 are electrically connected in series has been described. However, for example, a battery module in which multiple battery cells 3 are electrically connected in parallel can also be applied. In other words, there are no restrictions on the electrical connection mode. In the above embodiment, a bus bar 7 is described in which both ends are connected to the terminal surfaces of the battery cells 3. However, for example, a weld mark 8 may be formed on one end of a bus bar whose one end is connected to the terminal surface of the battery cell 3 and whose other end is connected to an external terminal of the battery module. In addition, there is no particular limitation on the type of battery (nickel-metal hydride battery, lithium-ion battery, etc.) that can be applied to the above embodiment.

1 Battery module 3 Battery cell 7 Bus bar 51 Positive electrode terminal surface 61 Negative electrode terminal surface 75 Through hole (cutout portion)

Claims (3)

A battery module including a battery cell having a terminal surface as a part of an outer surface thereof and a bus bar joined to the terminal surface,
The bus bar has a cutout portion formed therein, the cutout portion penetrating the bus bar in a thickness direction and exposing a part of the terminal surface,
a weld mark is formed at a location where the bus bar and the terminal surface are joined by welding;
At least one end of the weld mark is in contact with the notch and the terminal surface exposed at the notch ,
The bus bar has a plurality of cutout portions formed therein,
The battery module , wherein the weld mark is formed so as to extend from one of the cutout locations to another of the cutout locations . The battery module according to claim 1 ,
A battery cell is provided.
The bus bar connects the terminal surfaces of two adjacent battery cells to each other. The battery module according to claim 1 or 2 ,
The battery module, wherein the cutout portion is a through hole.

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