Bus bar and battery module using the bus bar

Abstract

To provide a bus bar which reliably connects electrode tabs while avoiding an increase in costs and has a structure capable of following expansion and contraction of battery cells due to charging and discharging, and a battery module using the bus bar.SOLUTION: There is provided a bus bar 5 to connect electrodes with different polarities. The bus bar includes a plurality of bus bar sheets 51 comprising dissimilar metals, one end portion 52 of the bus bar sheet 51 joined to a positive electrode, and the other end portion 53 of the bus bar sheet joined to a negative electrode. A metal of the same type of a metal constituting the positive electrode is arranged in a position facing the positive electrode at the one end portion 52 of the bus bar sheet 51, and a metal of the same type of a metal constituting the negative electrode is arranged in a position facing the negative electrode at the other end portion 53 of the bus bar sheet 51.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a bus bar and a battery module using the bus bar.

Background Art

[0002] Patent Document 1 discloses an invention related to an assembled battery including a plurality of battery cells having positive and negative electrode terminals made of different metals. For the positive and negative electrode terminals of each battery cell in the assembled battery, they are connected by a metal plate composed of a first metal plate and a second metal plate, which are the same kind of metal as the metals constituting the respective electrode terminals. Further, this metal plate is a clad material in which the first metal plate and the second metal plate are joined between the connection portions to the positive and negative electrode terminals.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, generally, since a clad material is a material formed by connecting different metals, it causes an increase in cost compared to a material made of a single metal. Further, when using a clad material joining different metals, variations may occur in the fastening strength when connecting the electrode terminals.

[0005] When a plurality of battery cells are connected to form a battery module, a so-called bus bar is used to connect the electrode tabs of adjacent battery cells. At this time, depending on the type of battery, the thickness in the stacking direction of the battery cell may change with charge and discharge.

[0006] That is, for example, in the case of a lithium-ion battery, when the thickness in the stacking direction of the battery cell after discharge is used as a reference, the thickness in the stacking direction of the battery cell after charging becomes thicker. That is, as the battery is charged and discharged, the battery cell repeatedly expands and contracts, and its thickness changes.

[0007] When such a change appears, if a metal plate as disclosed in Patent Document 1 described above is used, for example, the metal plate cannot follow the expansion and contraction of the battery cell accompanying charge and discharge, and excessive stress is particularly applied to the fastening portion. And when the fastening portion is damaged due to the application of such excessive stress, it becomes in a disconnected state, so that the function as a battery module cannot be achieved.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to securely connect an electrode tab while avoiding an increase in cost, and to have a structure that can follow the expansion and contraction of a battery cell accompanying charge and discharge. An object is to provide a bus bar and a battery module using the bus bar.

Means for Solving the Problems

[0009] The bus bar in the embodiment of the present invention is a bus bar that connects electrodes having different polarities, and includes a plurality of bus bar sheets made of different metals, one end of the bus bar sheet joined to the positive electrode, and the other end of the bus bar sheet joined to the negative electrode. At one end of the bus bar sheet, a metal of the same type as the metal constituting the positive electrode is arranged at a position facing the positive electrode, and at the other end of the bus bar sheet, a metal of the same type as the metal constituting the negative electrode is arranged at a position facing the negative electrode.

Effects of the Invention

[0010] Since the present invention adopts such a configuration, it is possible to securely connect the electrode tab while avoiding an increase in cost, and to follow the expansion and contraction of the battery cell accompanying charge and discharge.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each drawing is schematic and may be different from the actual one. Further, the embodiments of the present invention shown below are examples of devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the structure, arrangement, etc. of the components as the following. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0013] FIG. 1 is a schematic perspective view showing the overall configuration of the battery module 1 in the embodiment of the present invention. In the battery module 1 in the embodiment of the present invention, six battery cells 2 are stacked in the Y direction.

[0014] Note that various batteries are assumed as the battery, but in the embodiment of the present invention, for example, it is an all-solid-state lithium-ion battery that uses a solid electrolyte as the electrolyte and a lithium metal or a lithium-containing alloy as the negative electrode.

[0015] Further, in the following description, the stacking direction of the battery cells 2 is defined as the Y direction (the vertical direction in the drawings such as FIG. 1), and the directions perpendicular to the Y direction and perpendicular to each other are defined as the X direction and the Z direction.

[0016] The battery cell 2 is formed by housing a laminated electrode body, which is formed by laminating a predetermined number of flat single cells each having a positive electrode, an electrolyte, and a negative electrode (not shown in FIG. 1) in the thickness direction (Y direction), in an exterior material such as a laminate film.

[0017] The battery cell 2 includes a main body 3 that houses such a laminated electrode body and electrode tabs 4 that protrude from both sides of the main body 3 in a direction (X direction) orthogonal to the lamination direction. The electrode tabs 4 are joined to a current collector of an electrode (positive electrode or negative electrode) of the battery cell 2. Therefore, the positive electrode tab 4a is connected to each positive electrode in the battery cell 2, and the negative electrode tab 4b is connected to each negative electrode, thereby having the role of extracting current from each electrode (moving electrons outside the battery cell 2).

[0018] Here, since the current collector of the positive electrode mainly uses aluminum as a base material, the positive electrode tab 4a is also formed of aluminum. On the other hand, since the current collector of the negative electrode mainly uses copper as a base material, the negative electrode tab 4b is also formed of copper.

[0019] Both the positive electrode tab 4a and the negative electrode tab 4b protrude in the X direction from between the upper main body 3a and the lower main body 3b. Also, in the battery cell 2 in the embodiment of the present invention shown in FIG. 1, the positive electrode tab 4a and the negative electrode tab 4b are formed so as to protrude from both sides of the main body 3 in the X direction. When it is not necessary to distinguish between the positive electrode tab 4a and the negative electrode tab 4b, they are collectively referred to as the "electrode tab 4" as appropriate as described above.

[0020] The battery cell 2 is used in a state where a plurality of sheets are laminated in the thickness direction (Y direction). As described above, in the battery module 1 in the embodiment of the present invention, six battery cells 2 are laminated, but the number of battery cells 2 to be laminated depends on the battery design.

[0021] Each battery cell 2 is stacked such that the positive electrode tab 4a of one battery cell 2 adjacent to the other battery cell 2 and the negative electrode tab 4b of the other battery cell 2 face each other in the stacking direction. Then, the stacked battery cells 2 are connected in series using the bus bar 5. That is, electrodes with different polarities facing each other in the stacking direction are connected by the bus bar 5.

[0022] The bus bar 5 connects electrodes (electrode tabs 4) with different polarities in adjacent battery cells 2 in the stacking direction (Y direction). Specifically, it is used to join the positive electrode tab 4a of one battery cell 2 and the negative electrode tab 4b of the other battery cell 2. By joining the bus bar 5 to the positive electrode tab 4a or the negative electrode tab 4b, the stacked battery cells 2 are mechanically connected to each other, and a plurality of battery cells 2 are electrically connected.

[0023] The bus bar 5 includes a plurality of bus bar sheets 51, one end 52 of the bus bar sheet 51 joined to the positive electrode, and the other end 53 of the bus bar sheet 51 joined to the negative electrode. FIG. 2 is a perspective view showing an enlarged view of the bus bar 5 in the embodiment of the present invention shown in the region surrounded by the square shown in FIG. 1.

[0024] Here, for convenience of explanation, the end of the bus bar sheet 51 joined to the positive electrode is referred to as the "one end", and the end of the bus bar sheet 51 joined to the negative electrode is referred to as the "other end". However, as will be described later, if the metal disposed at the end of the bus bar sheet 51 matches the metal constituting the positive electrode tab 4a or the metal constituting the negative electrode tab 4b, respectively, the end of the bus bar sheet 51 joined to the positive electrode may be referred to as the "other end", and the end of the bus bar sheet 51 joined to the negative electrode may be referred to as the "one end".

[0025] In the embodiment of the present invention, the bus bar 5 is composed of a plurality of bus bar sheets 51. And these plurality of bus bar sheets 51 are formed of different metals. Therefore, the bus bar 5 in the embodiment of the present invention is formed by laminating a plurality of metals. Here, the different metals used are, for example, aluminum that constitutes the positive electrode tab 4a and, for example, copper that constitutes the negative electrode tab 4b.

[0026] That is, the bus bar 5 is joined to the positive electrode tab 4a or the negative electrode tab 4b at one end portion 52 of the bus bar sheet 51 or the other end portion 53 of the bus bar sheet 51. As described above, the positive electrode tab 4a is formed of aluminum and the negative electrode tab 4b is formed of copper. When joining such a positive electrode tab 4a or negative electrode tab 4b and the bus bar 5, if joining between different metals is performed, variations in joining strength may occur. And as a result, for example, when a strong impact is applied to the battery module 2, the joined portion between the electrode tab 4 and the bus bar 5 may be damaged.

[0027] Therefore, in the bus bar 5 in the embodiment of the present invention, at one end portion 52 of the bus bar sheet 51, a metal of the same kind as the metal constituting the positive electrode (positive electrode tab 4a) is arranged at a position facing the positive electrode (positive electrode tab 4a). Also, at the other end portion 53 of the bus bar sheet 51, a metal of the same kind as the metal constituting the negative electrode (negative electrode tab 4b) is arranged at a position facing the negative electrode (negative electrode tab 4b).

[0028] In FIG. 2, the negative electrode tab 4b is shown at the upper part of the drawing, and the positive electrode tab 4a is shown at the lower part of the drawing. And the bus bar 5 is arranged so as to be sandwiched between these positive electrode tab 4a and negative electrode tab 4b.

[0029] That is, the bus bar 5 is arranged (fastened) between the positive electrode tab 4a and the negative electrode tab 4b, and on that, one end portion 51 of the bus bar 5 and the positive electrode tab 4a, and the other end portion 53 and the negative electrode tab 4b are joined respectively.

[0030] Also, in the bus bar 5 shown in FIG. 2, three bus bar sheets 51 are used. For the sake of convenience of explanation, in these three bus bar sheets 51, they are represented as the first bus bar sheet 51a, the second bus bar sheet 51b, and the third bus bar sheet 51c in order from the main body 3 side. Further, it is assumed here that both the first bus bar sheet 51a and the second bus bar sheet 51b are formed of aluminum, and the third bus bar sheet 51c is formed of the same material.

[0031] As described above, in the bus bar 5 disposed between the positive electrode tab 4a and the negative electrode tab 4b, when joining with the positive electrode tab 4a and the negative electrode tab 4b, in order to avoid variations in joining strength, joining between the same kind of metals is preferable. Therefore, in the bus bar 5 in the embodiment of the present invention, one end portion 52 of the bus bar sheet 51 that joins with the positive electrode tab 4a is configured such that aluminum, which is the metal constituting the positive electrode tab 4a, is disposed.

[0032] Specifically, as shown in FIG. 2, one end portion 52 of the bus bar sheet 51 has a shape in which the first bus bar sheet 51a sandwiches the second bus bar sheet 51b and the third bus bar sheet 51c among the three bus bar sheets 51 and is folded back. In addition, as a method for creating such a shape, various methods can be adopted. For example, so-called hemming processing can be performed on the one end portion 52.

[0033] In this way, one end portion 51 and the other end portion 52 of the bus bar 5 in the embodiment of the present invention are processed in this manner. Therefore, it becomes easy to fasten the bus bar 5 between the positive electrode tab 4a and the negative electrode tab 4b.

[0034] Furthermore, at one end 51 of the bus bar 5, the first bus bar sheet 51a is folded back so as to sandwich the ends of the second bus bar sheet 51b and the third bus bar sheet 51c, and is, for example, caulked. By performing such processing, the third bus bar sheet 51c made of a metal different from that of the positive tab 4a is fixed inside the first bus bar sheet 51a. And at a position facing the positive tab 4a, the first bus bar sheet 51a formed of the same kind of metal as the positive tab 4a is arranged.

[0035] That is, one end 52 arranged at a position facing the positive tab 4a is formed of the first bus bar sheet 51a formed of the same kind of metal as the positive tab 4a. And since the joining of the one end 52 and the positive tab 4a is the joining of the same kind of metals, the variation in the joining strength can be suppressed.

[0036] Also, by adopting such a structure for the one end 52, when fastening and then joining the one ends 52 of the plurality of bus bar sheets 51 constituting the bus bar 5 to the positive tab 4a respectively, compared with the case of joining after fastening, it is more advantageous to perform hemming processing etc. in advance on the one end 52 of the bus bar 5 in the embodiment of the present invention so that the three bus bar sheets 51 are integrated, and then fasten and join to the positive tab 4a.

[0037] On the other hand, the same configuration as that of the one end 52 is adopted also for the other end 53 of the bus bar sheet 51. That is, at the other end 52 of the bus bar 5, the third bus bar sheet 51c is folded back so as to sandwich the ends of the first bus bar sheet 51a and the second bus bar sheet 51b, and is, for example, caulked. By performing such processing, the first bus bar sheet 51a and the second bus bar sheet 51b made of metals different from that of the negative tab 4b are fixed inside the third bus bar sheet 51c. And at a position facing the negative tab 4b, the third bus bar sheet 51c formed of the same kind of metal as the negative tab 4b is arranged.

[0038] Therefore, even when fastening and joining the other end portion 53 of the bus bar sheet 51 to the negative electrode tab 4b, it is possible to avoid the labor of fastening the three bus bar sheets 51 to the negative electrode tab 4b separately and the variation in joining strength due to joining between dissimilar metals.

[0039] The bus bar 5 in the embodiment of the present invention includes a plurality of bus bar sheets 51. As shown in FIGS. 1 and 2, or as described so far, here, the case where there are three bus bar sheets 51 is taken as an example for explanation, but the number of sheets is not limited to three as long as there are a plurality of sheets. Since there are a plurality of bus bar sheets 51, one end portion 52 and the other end portion 53 can be formed in the above-described shapes.

[0040] Also, the shape of the bus bar 5 may be generally formed in an "m shape" as shown in FIGS. 1 and 2, for example. Or, it may be other shapes. Here, FIG. 3 is an explanatory diagram showing various forms of the bus bar 5 in the embodiment of the present invention.

[0041] In FIG. 3, three types of shapes are shown. Also, in order to clarify the difference in the shape of the bus bar 5, a state of viewing the bus bar 5 in the Z direction is shown. In each case, the negative electrode tab 4b extends in the X direction at the upper part of the drawing. Also, in each case, the positive electrode tab 4a extends in the X direction at the lower part of the drawing. Furthermore, in each case, a bus bar 5 having three bus bar sheets 51 is taken as an example and shown.

[0042] The three types of shapes are shown as FIG. 3(A), FIG. 3(B), and FIG. 3(C) from top to bottom, and the shape gradually becomes more complex from FIG. 3(A) to FIG. 3(C). First, the bus bar sheet 51A shown in FIG. 3(A) is formed in a "u shape". On the other hand, the bus bar sheet 51B shown in FIG. 3(B) is formed in the above-described "m shape". The bus bar sheet 51C shown in FIG. 3(C) is formed in a "spring shape".

[0043] When a plurality of bus bar sheets 51 are used in the bus bar 5 in this way, a gap G is provided between adjacent bus bar sheets 51. As will be described later, the shape of the bus bar 5 changes in accordance with the expansion and contraction of the battery cell 2 accompanying charge and discharge. However, if no gap G is provided between the plurality of bus bar sheets 51 at that time, it becomes difficult to change the shape of the bus bar 5 following the change of the battery cell 2.

[0044] Specifically, when the shape of the bus bar 5 changes in accordance with the expansion and contraction of the battery cell 2, it is preferable that the gap G is provided so that adjacent bus bar sheets 51 do not come into contact with each other. Therefore, it is considered that the gap G is small in terms of the thickness of the bus bar sheet 51, and it is better to secure a distance of at least the thickness of the bus bar sheet 51 or more as the gap G.

[0045] Furthermore, a plurality of bent portions 51d are provided in all three bus bar sheets 51. For example, in the bus bar sheet 51A shown in FIG. 3(A), bent portions 51d are provided at two locations, and in the bus bar sheet 51B shown in FIG. 3(B), bent portions 51d are provided at three locations.

[0046] For the spring-shaped bus bar sheet 51C (FIG. 3(C)), five or more odd-numbered bent portions 51d are provided. That is, the shape of the bus bar 5 is determined by the number of bent portions 51d provided.

[0047] And among the plurality of bus bar sheets 51, a gap G is provided between adjacent bus bar sheets 51, and a plurality of bent portions 51d are provided in each bus bar sheet 51. As described above for the bus bar sheet 51, flexibility and stretchability are added to the bus bar sheet 51 according to the number of sheets, the number of bent portions 51d, and the shape based on the gap G. The reasons why flexibility and stretchability are required for the bus bar 5 are as follows.

[0048] That is, in a lithium-ion battery using lithium metal or the like for the negative electrode, when discharging, the volume of the negative electrode decreases due to the dissolution of lithium, and when charging, the volume of the negative electrode increases due to the precipitation of lithium. Due to this volume change, the thickness of the battery cell 2 (the dimension in the Y direction shown in FIG. 1) changes. And if the dimension of the battery cell 2 in the Y direction changes, the distance between the adjacent electrode tabs 4 (the positive electrode tab 4a and the negative electrode tab 4b) also changes. Therefore, in order to follow the change in the distance between the adjacent electrode tabs 4 based on the volume change of the lithium-ion battery accompanying charge and discharge, it is necessary to give the bus bar 5 that connects the adjacent electrode tabs 4 flexibility and stretchability.

[0049] Furthermore, as described above, the bus bar 5 is composed of a plurality of bus bar sheets 51, and a gap G is provided between the respective bus bar sheets 51. Here, when the battery cell 2 is charged and discharged, a large amount of current flows through the positive electrode tab 4a and the negative electrode tab 4b. This is because, as a function of the electrode tab 4, current flows through the electrode tab 4 both when discharging from the battery cell 2 and when charging the battery cell 2. And when current flows, heat is generated, but a large amount of heat is generated in the electrode tab 4 accompanying charge and discharge of the battery cell 2.

[0050] However, as described above, since the bus bar 5 in the embodiment of the present invention is composed of a plurality of bus bar sheets 51, the surface area of the bus bar sheet 51 expands, and a gap G is provided between the plurality of bus bar sheets 51. Therefore, for example, the bus bar sheet 51 has better cooling performance than a single bus bar 5.

[0051] [Operation] Next, the movement of the bus bar 5 accompanying charge and discharge of the battery cell 2 will be described with reference to FIG. 4. FIG. 4 is an explanatory diagram showing the change of the bus bar 5 when expansion and contraction occur in the battery cell 2 in the embodiment of the present invention.

[0052] Figure 4 is divided into Figure 4(A) and Figure 4(B). The battery cell 2 shown in Figure 4(A) shows, for example, a newly manufactured battery cell 2 or a discharged battery cell 2, and it is in a state of not being charged at all. Such a state can be said to be "t soc = 0%". Here, "SOC" refers to "State Of Charge". Also, the thickness in the Y direction in the state of the battery cell 2 shown in Figure 4(A) is represented as "L1".

[0053] On the other hand, the battery cell 2 shown in Figure 4(B) shows a fully charged battery cell 2 in a fully charged state (maximum allowable charge state). Since the battery cell 2 shown in Figure 4(B) is in a fully charged state like this, it can be expressed as "t soc = 100%". Also, the thickness in the Y direction in the fully charged state of the battery cell 2 shown in Figure 4(B) is represented as "L2".

[0054] As the battery cell 2 is charged from the uncharged state (thickness L1), the thickness in the Y direction gradually increases. This is because, as described above, when charging, the volume of the negative electrode increases due to the precipitation of lithium. And when it reaches the fully charged state, the thickness of the battery cell 2 becomes L2.

[0055] On the other hand, when the charged battery cell 2 is discharged, for example, by running, the volume of the negative electrode decreases due to the dissolution of lithium. In this case, since the overall volume of the battery cell 2 also becomes smaller, the thickness of the battery cell 2 in the Y direction gradually decreases.

[0056] As the thickness of the battery cell 2 increases and decreases due to charging and discharging like this, the distance in the Y direction between the positive electrode tab 4a and the negative electrode tab 4b also changes. That is, when the battery cell 2 shown in Figure 4(A) is charged from the uncharged state, the thickness of the battery cell 2 in the Y direction gradually increases. Along with this change in the battery cell 2, the space between the positive electrode tab 4a and the negative electrode tab 4b protruding in the X direction from the adjacent battery cell 2 also gradually expands.

[0057] Then, when the battery cell 2 shown in FIG. 4(B) is fully charged, the thickness L2 of the battery cell 2 in the Y direction becomes maximum. Accordingly, the distance between the positive electrode tab 4a and the negative electrode tab 4b also becomes maximum. In accordance with the length between the positive electrode tab 4a and the negative electrode tab 4b in this state, the bus bar 5 also extends in the Y direction.

[0058] On the other hand, when the battery cell 2 is discharged, since the volume of the battery cell 2 gradually decreases, the thickness of the battery cell 2 in the Y direction also gradually contracts. Along with this contraction, the distance between the positive electrode tab 4a and the negative electrode tab 4b also gradually shrinks. Therefore, the bus bar 5 disposed between the positive electrode tab 4a and the negative electrode tab 4b, with one end 52 joined to the positive electrode tab 4a and the other end 53 joined to the negative electrode tab 4b, also contracts.

[0059] Finally, it reaches the state of thickness L1 as shown in FIG. 4(A). From this, the change in the distance in the Y direction between the positive electrode tab 4a and the negative electrode tab 4b corresponds to the expansion and contraction changes in the Y direction of the battery cell 2. Therefore, the thickness of the battery cell 2 shown in FIG. 4 has the relationship of "L1 < L2".

[0060] Note that one end 52 of the bus bar 5 is joined to the positive electrode tab 4a, and the other end 53 is joined to the negative electrode tab 4b. Therefore, in the state shown in FIG. 4(B), although the bus bar 5 extends in accordance with the charging state with respect to the battery cell 2, these joining states are maintained. Therefore, the electrode tab 4 bends in a direction to reduce the distance in the Y direction at the joining portion with the bus bar 5.

[0061] Also, the gap G between the three bus bar sheets 51 of the bus bar 5 in the state shown in FIG. 4(B) is narrower than the gap G between the bus bar sheets 51 when the battery cell 2 shown in FIG. 4(A) is in the initial state (discharged state), but the adjacent bus bar sheets 51 do not contact each other.

[0062] On the one hand, as the battery cell 2 gradually discharges due to use from a fully charged state, its state changes from the state shown in FIG. 4(B) to the state shown in FIG. 4(A) finally. Accordingly, the bus bar 5 fastened and joined between the positive electrode tab 4a and the negative electrode tab 4b also gradually contracts. The bus bar 5 disposed between the positive electrode tab 4a and the negative electrode tab 4b expands and contracts following the change in thickness due to charge and discharge of the battery cell 2.

[0063] This is because, as described above, the bus bar 5 in the embodiment of the present invention has flexibility and stretchability. Therefore, even if the thickness of the battery cell 2 in the Y direction changes, it is possible to avoid breakage due to the bus bar 5 not expanding and contracting.

[0064] Further, the bus bar 5 in the embodiment of the present invention has the structure as described above. Therefore, in the joining between the positive electrode tab 4a and the negative electrode tab 4b in the bus bar 5, in any case, joining between the same kind of metals can be performed. Therefore, since a clad material in which different metals are joined is not used, an increase in cost can be avoided and variation in joining strength can also be avoided.

[0065] Regarding the orientation when fastening the bus bar 5 to the electrode tab 4, heretofore, for example, as shown in FIG. 3, it has been described on the premise that the bus bar sheet 51 is arranged in such a manner as to be accommodated in the space between the positive electrode tab 4a and the negative electrode tab 4b.

[0066] However, the orientation of the bus bar 5 is not limited to such an orientation. For example, the bus bar sheet 51 may be arranged in such a manner that it is not accommodated in the space between the positive electrode tab 4a and the negative electrode tab 4b and protrudes from between them, that is, the bus bar sheet 51 is arranged at a position away from the main body 3.

[0067] In addition, regarding the joining method between the bus bar 5 and the electrode tab 4, various methods such as caulking, screwing, riveting, welding, etc. can be adopted. Among these joining methods, welding is preferable from the viewpoint of ensuring reliable electrical conductivity.

[0068] [Effects of the Embodiment] (1) A bus bar that connects electrodes with different polarities, comprising a plurality of bus bar sheets made of different metals, one end of the bus bar sheet joined to the positive electrode, and the other end of the bus bar sheet joined to the negative electrode. At one end of the bus bar sheet, a metal of the same type as the metal constituting the positive electrode is arranged at a position facing the positive electrode, and at the other end of the bus bar sheet, a metal of the same type as the metal constituting the negative electrode is arranged at a position facing the negative electrode.

[0069] By adopting such a bus bar, the metal constituting one end of the bus bar can be made of the same type as the metal constituting the positive electrode tab, and the metal constituting the other end can be made of the same type as the metal constituting the negative electrode tab. Therefore, the connection of the electrode tabs can be surely performed while avoiding an increase in cost.

[0070] (2) One end of the bus bar sheet and the other end of the bus bar sheet are hemmed. Therefore, the fastening and joining of the bus bar sheet and the electrode tab are facilitated, and reliable joining of the one end and the other end of the bus bar sheet with the electrode tab becomes possible.

[0071] (3) The plurality of bus bar sheets are arranged so as to provide a gap between one end of the bus bar sheet and the other end of the bus bar sheet.

[0072] Therefore, even if the distance between the positive electrode tab and the negative electrode tab expands or contracts in the stacking direction due to charging and discharging of the battery cell, a gap is provided between the plurality of bus bar sheets, so that adjacent bus bar sheets can be prevented from contacting each other. Further, since a gap is provided between the plurality of bus bar sheets, the flexibility and stretchability of the bus bar are improved, and a bus bar that can follow the changes of the battery cell can be provided.

[0073] (4) The plurality of bus bar sheets are provided with a plurality of bent portions between one end portion and the other end portion of the bus bar sheet.

[0074] Since the plurality of bus bar sheets each have a plurality of bent portions, the flexibility and stretchability of the bus bar are improved, and a bus bar that can follow the changes of the battery cell can be provided.

[0075] (5) The battery module according to the embodiment of the present invention includes a positive electrode, an electrolyte, and a negative electrode, and a battery cell including a positive electrode tab and a negative electrode tab that protrude in a direction orthogonal to the stacking direction as electrode tabs, and in the stacking direction, a plurality of bus bar sheets made of different metals that join the positive electrode tab of one battery cell and the negative electrode tab of the other adjacent battery cell, one end portion of the bus bar sheet joined to the positive electrode, and the other end portion of the bus bar sheet joined to the negative electrode, and at one end portion of the bus bar sheet, a metal of the same type as the metal constituting the positive electrode is disposed at a position facing the positive electrode, and at the other end portion of the bus bar sheet, a metal of the same type as the metal constituting the negative electrode is disposed at a position facing the negative electrode.

[0076] By adopting such a battery module, it is possible to join the positive electrode tab or the negative electrode tab, which are the same type of metal, at one end portion and the other end portion of the bus bar. Therefore, the connection of the electrode tabs can be surely performed while avoiding an increase in cost, and the flexibility and stretchability of the bus bar are improved, and the bus bar can follow the changes of the battery cell.

Description of Reference Numerals

[0077] 1... battery module, 2... battery cell, 3... main body, 3a... upper part of the main body, 3b... lower part of the main body, 4... electrode tab, 4a... positive electrode tab, 4b... negative electrode tab, 5... bus bar, 51... bus bar sheet, 51a... bus bar sheet, 51b... bus bar sheet, 51c... bus bar sheet, 51d... bent part, 52... one end, 53... the other end, L1... thickness, L2... thickness

Claims

1. A bus bar for connecting electrodes with different polarities, comprising: a plurality of bus bar sheets made of different metals; one end of the bus bar sheet joined to the positive electrode; and the other end of the bus bar sheet joined to the negative electrode, wherein at one end of the bus bar sheet, a metal of the same type as the metal constituting the positive electrode is arranged at a position facing the positive electrode, and at the other end of the bus bar sheet, a metal of the same type as the metal constituting the negative electrode is arranged at a position facing the negative electrode.

2. The bus bar according to claim 1, wherein one end of the bus bar sheet and the other end of the bus bar sheet are hemmed.

3. The bus bar according to claim 1, wherein the plurality of bus bar sheets are arranged so as to provide a gap between one end of the bus bar sheet and the other end of the bus bar sheet.

4. The bus bar according to claim 2, wherein the plurality of bus bar sheets are arranged so as to provide a gap between one end of the bus bar sheet and the other end of the bus bar sheet.

5. The bus bar according to claim 3, wherein the plurality of bus bar sheets include a plurality of bent portions between one end of the bus bar sheet and the other end of the bus bar sheet.

6. The bus bar according to claim 4, wherein the plurality of bus bar sheets include a plurality of bent portions between one end of the bus bar sheet and the other end of the bus bar sheet.

7. A battery cell having a positive electrode, an electrolyte, and a negative electrode, and including a positive electrode tab and a negative electrode tab protruding in a direction orthogonal to the stacking direction as electrode tabs; the bus bar according to any one of claims 1 to 4 for joining the positive electrode tab of one of the battery cells and the negative electrode tab of the other battery cell in the battery cells adjacent in the stacking direction; and A battery module characterized by comprising the same.

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