Battery pack

Abstract

To provide a technology capable of suppressing the magnitude of short circuit current occurring when submerged in water.SOLUTION: A battery pack 1 includes a first battery 2-1, a second battery 2-2, and a bus bar connecting a positive terminal of the first battery and a negative terminal of the second battery. The bus bar includes a fusion portion 4 located below a short-circuit water level. The fusion portion is configured to dissolve in water to be cut off due to an electrochemical reaction when submerged in water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery pack.

Background Art

[0002] As a battery pack, one in which a plurality of batteries are connected in series is known. In such a battery pack, countermeasures against abnormal situations may be required.

[0003] For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2021-91283) describes a battery pack mounted on an electric vehicle, which includes a plurality of battery modules having a specific configuration. The plurality of battery modules are housed in a housing such that each terminal is disposed downward, and a conductive member and a relay are disposed below the outer peripheral portion of the battery case. According to the description of Patent Document 1, when the electric vehicle collides, the conductive member and the relay can be submerged with a small amount of water injection to discharge the battery module.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, the present inventors have been studying countermeasures against short circuits during submersion in a battery pack in which a plurality of batteries are connected in series. For example, a battery pack mounted on an electric vehicle may be unintentionally submerged during a flood or the like. During submersion, the battery pack may short-circuit through water, and a large current may flow as a short-circuit current. Such a large current may be accompanied by abnormal heat generation. Therefore, it is desirable to suppress the magnitude of the short-circuit current generated during submersion.

[0006] That is, an object of the present invention is to provide a technique capable of suppressing the magnitude of a short-circuit current generated during submersion.

Means for Solving the Problems

[0007] In one aspect, a battery pack according to the present invention includes a first battery and a second battery, and a bus bar connecting the positive electrode terminal of the first battery and the negative electrode terminal of the second battery. The first battery and the second battery each have a cell including a terminal. The bus bar has a fusing portion provided below the short-circuit water level. The short-circuit water level is the water level at which the terminal comes into contact with water during flooding. The fusing portion is configured to be dissolved in water by an electrochemical reaction and separated when flooded.

Advantages of the Invention

[0008] According to the present invention, there is provided a technique capable of suppressing the magnitude of a short-circuit current generated during submersion.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 8

Modes for Carrying Out the Invention

[0010] (Schematic) First, the basic configuration of the embodiment of the present invention will be described. FIG. 1 is a diagram showing the basic configuration of the assembled battery 1 according to this embodiment. This assembled battery 1 is used for applications that require countermeasures against submersion. Examples of such an assembled battery 1 include a battery mounted on an electric vehicle.

[0011] As shown in FIG. 1, the assembled battery 1 has a first battery 2-1, a second battery 2-2, and a bus bar 3. The first battery 2-1 and the second battery 2-2 are connected in series via the bus bar 3. Also, a bus bar 3 is connected to the negative electrode terminal of the first battery 2-1.

[0012] In the example shown in FIG. 1, the first battery 2-1 and the second battery 2-2 are each a cell 7 having a terminal 6. That is, the first battery 2-1 and the second battery 2-2 are each composed of a single cell 7. However, the first battery 2-1 may include a plurality of cells 7. Similarly, the second battery 2-2 may also include a plurality of cells 7.

[0013] The bus bar 3 is formed of a conductive member. Here, in this embodiment, a fusing portion 4 is provided on the bus bar 3 that connects the first battery 2-1 and the second battery 2-2. The fusing portion 4 is a portion provided below the short-circuit water level and is a portion that is disconnected during submersion. Note that the "short-circuit water level" is the water level at which the terminal 6 comes into contact with water during flooding. The fusing portion 4 is composed of a material that dissolves in water and is disconnected by an electrochemical reaction when it comes into contact with water (hereinafter, may be referred to as fusing).

[0014] Also, the lower end portion of the bus bar 3 connected to the negative electrode terminal of the first battery 2-1 is also located below the short-circuit water level.

[0015] The above is the basic configuration of the assembled battery 1 according to the present embodiment. According to the configuration as described above, when submerged, the lower end of the bus bar comes into contact with water before the terminal 6 of the cell 7. As a result, a closed circuit is formed through the fusing section 4. Specifically, a closed circuit is formed through the first battery 2-1, the bus bar 3 (fusing section 4) connecting the first battery 2-1 and the second battery 2-2, water, and the bus bar connected to the negative terminal of the first battery 2-1. As a result, a discharge current flows through the fusing section 4. At this time, an electrochemical reaction proceeds with the fusing section 4 as the positive electrode and the bus bar connected to the negative terminal of the first battery 2-1 as the negative electrode. In the fusing section 4 serving as the positive electrode, a chemical reaction in which the constituent material of the fusing section 4 dissolves proceeds, and the fusing section 4 is fused. Thereby, the voltage of the assembled battery 1 is divided. If the fusing section 4 is not provided, when the water level exceeds the short-circuit water level, the assembled battery 1 may short-circuit and a large current may flow as a short-circuit current. On the other hand, according to the present embodiment, the fusing section 4 is fused before such a large current flows. As a result, the voltage is divided. That is, the voltage of the assembled battery 1 becomes smaller. Therefore, even if the water level exceeds the short-circuit water level, the magnitude of the short-circuit current does not become so large. The assembled battery 1 is discharged in a mild state. It is possible to put the assembled battery 1 in a discharged state while preventing abnormal heat generation.

[0016] The above points have also been confirmed by simulation using a circuit model. Figure 2 is a graph showing the results of simulating the magnitude of the current flowing through each cell during a short circuit. Figure 2 shows the simulation results for a battery pack having 80 cells connected in series. It can be said that among the 80 cells, the 40 cells on the low potential side are the "first battery", and the 40 cells on the high potential side are the "second battery". That is, Figure 2 shows the simulation results when the first battery and the second battery each contain 40 cells. Figure 2 shows the relationship between the cell number (Cell No.) and the magnitude of the short circuit current (Current) flowing through each cell during submersion. The cell number is a number for identifying each cell, and is assigned in order from the low potential side to the high potential side. Figure 2(a) shows the results when the 80 cells are electrically disconnected at the middle part (that is, between the first battery and the second battery), and Figure 2(b) shows the results when the 80 cells remain connected in series. As shown in Figure 2, it can be understood that if the 80 cells are electrically disconnected at the middle part, the short circuit current decreases. Specifically, when disconnected at the middle part, the voltage is halved and the resistance is approximately doubled. As a result, the short circuit current is suppressed to about one-fourth of that when not disconnected.

[0017] The outline of the present embodiment has been described above with reference to the basic configuration.

[0018] In the example shown in Figure 1, the plurality of terminals 6 included in the first battery 2-1 and the second battery 2-2 are located at the same height. However, the heights of the plurality of terminals 6 may be different. In such a case, the water level at which any one of the plurality of terminals 6 comes into contact with water can be considered as the "short circuit water level". That is, the fusing part 4 may be arranged further below the terminal 6 arranged at the lowest position among the plurality of terminals 6.

[0019] Further, the fusing portion 4 may be made of a material that is fused by an electrochemical reaction when it comes into contact with water. Examples of such a material include copper and a metal material having a greater ionization tendency than copper. Note that the fusing portion 4 may be formed of the same material as the other portions of the bus bar 3, or may be formed of a different material.

[0020] Subsequently, the details of this embodiment will be described with reference to specific examples.

[0021] (First Embodiment) FIG. 3 is a perspective view showing the assembled battery 1 according to the first embodiment. This assembled battery 1 has a plurality of cells 7 (7-1 to 7-6). The plurality of cells 7 are arranged so as to be aligned in the horizontal direction. The plurality of cells 7 are electrically connected in series via a plurality of bus bars 3. The plurality of cells 7 are connected in series such that the cell 7-1 is on the negative electrode side (low potential side) and the cell 7-6 is on the positive electrode side (high potential side).

[0022] Each cell 7 is a so-called rectangular cell. Each cell 7 has a configuration in which a power generation element (not shown) is housed in a case. Each cell 7 has two terminals 6 (a positive electrode terminal and a negative electrode terminal) on the upper surface of the case. The positive electrode terminal and the negative electrode terminal of adjacent cells 7 are connected via a bus bar 3. The sizes of the plurality of cells 7 (7-1 to 7-6) are the same. Therefore, the heights of the plurality of terminals 6 present in the assembled battery 1 are aligned.

[0023] Here, each bus bar 3 extends downward from each terminal 6 such that an intermediate portion thereof is positioned below the short-circuit water level (the position where the terminal 6 is provided). Then, each bus bar 3 is folded back at its lower end portion (central portion).

[0024] The above is the configuration of the assembled battery 1 according to the first embodiment.

[0025] In this embodiment, when submerged, the lower ends of the plurality of bus bars 3 come into contact with water earlier than the plurality of terminals 6. As a result, a closed circuit is formed through the water and a discharge current flows. At this time, an electrochemical reaction using the bus bar 3 as an electrode proceeds. Specifically, among the plurality of bus bars 3, an electrochemical reaction proceeds in which the bus bar 3 located on the higher potential side than the middle serves as the positive electrode and the bus bar 3 located on the lower potential side than the middle serves as the negative electrode. As a result, the lower end of the bus bar 3 functioning as the positive electrode is melted as the melting part 4. Thereby, the voltage of the assembled battery 1 is divided and the assembled battery 1 discharges under mild conditions. In this embodiment, it can be said that the cell 7 located on the lower potential side than the middle functions as the first battery and the cell 7 located on the higher potential side than the middle functions as the second battery.

[0026] Note that the lower end of each bus bar 3 only needs to be located below the short-circuit water level. That is, the lower end of each bus bar 3 only needs to be located below the terminal 6. However, in a preferred embodiment, as shown in FIG. 3, the lower end of each bus bar 3 is located further below the lower end of the cell 7 (the lower surface of the case of each cell 7). For example, when the case of the cell 7 is made of metal, when the case of the cell 7 is flooded, a large short-circuit current may flow through the case. If the lower end of each bus bar 3 is located further below the lower end of the case of the cell 7, the voltage of the assembled battery 1 is divided before a large short-circuit current flows through the case. Thereby, it becomes possible to more reliably avoid the generation of a large current.

[0027] Also, in FIG. 3, the lower ends of the plurality of bus bars 3 are located at the same height. However, it is also possible to change the bus bar 3 that functions as the melting part 4 by changing the height of the plurality of bus bars 3. For example, if a configuration is adopted in which the bus bar 3 between the cells 7-1 to 7-2 and the bus bar 3 between the cells 7-2 to 7-3 are submerged earlier than the other bus bars, the lower end of the bus bar 3 between the cells 7-2 to 7-3 can be made to function as the melting part 4 and melted.

[0028] (Second Embodiment) Next, a second embodiment will be described. FIG. 4 is a perspective view showing the assembled battery 1 according to this embodiment. In this embodiment, the assembled battery 1 has a plurality of modules 8 (8-1 to 8-4). Each module 8 (8-1 to 8-4) has a plurality of cells 7 connected in series. The plurality of modules 8 are arranged side by side along the horizontal direction. Also, the plurality of cells 7 included in each module 8 are arranged side by side along the horizontal direction.

[0029] The plurality of modules 8 (8-1 to 8-4) are electrically connected in series via a plurality of bus bars 3 (3-1 to 3-3). The module 8-1 is the module on the lowest potential side, and the module 8-4 is the module on the highest potential side.

[0030] Here, the lower end of each bus bar 3 is located below the short-circuit water level. More specifically, the lower end of each bus bar 3 is located below the terminal 6 of the cell 7 included in each module 8 (8-1 to 8-4). Preferably, as shown in FIG. 4, the lower end of each bus bar 3 is located further below the lower end of the case of the cell 7.

[0031] In this embodiment, at the time of flooding, the lower end of each bus bar 3 is flooded before the terminal 6 is flooded. At this time, an electrochemical reaction proceeds with the lower end of the bus bar 3-3 on the highest potential side as the positive electrode and the lower end of the bus bar 3-1 on the lowest potential side as the negative electrode. As a result, the lower end of the bus bar 3-3 functions as the fusing portion 4 and fuses. In the intermediate bus bar 3-2, no particular reaction occurs. Thus, similar to the above-described embodiment, the voltage of the assembled battery 1 is divided, and the assembled battery 1 discharges under mild conditions.

[0032] If the height of the lower end of each bus bar 3 is adjusted so that the bus bars 3-1 and 3-2 are flooded earlier than the bus bar 3-3, the lower end of the bus bar 3-2 can be made to function as the fusing portion 4 and be fused.

[0033] (Third Embodiment) Next, a third embodiment will be described. Regarding the points where the same configuration as that of the first embodiment can be adopted, redundant explanations will be omitted. FIG. 5 is a perspective view showing the assembled battery 1 according to the third embodiment.

[0034] In this embodiment, similar to the first embodiment, the assembled battery 1 has a plurality of cells 7. The plurality of cells 7 are connected in series via the bus bar 3. However, different from the first embodiment, each cell 7 is a laminate type cell. That is, each cell 7 has a configuration in which a power generation element (not shown) is accommodated in a laminate film.

[0035] Tabs 9 are provided at both end portions in the horizontal direction of each cell 7. In this embodiment, it can be said that this tab 9 is the terminal 6 of the cell 7. The plurality of cells 7 are connected in series via the bus bar 3 at the tabs 9.

[0036] In this embodiment, it can be said that the water level at which the tab 9 is flooded is the short - circuit water level. That is, the lower end portion of each bus bar 3 is located below the lower end portion of the tab 9.

[0037] Also in this embodiment, before the tab 9 is flooded, the lower end portions of the respective bus bars 3 are submerged. As a result, among the submerged bus bars 3, the bus bar 3 functioning as the positive electrode is blown. Thereby, before a large short - circuit current is generated through the tab 9, the voltage of the assembled battery 1 is divided. As a result, while avoiding abnormal heat generation during short - circuit, the assembled battery 1 can be put into a discharged state.

[0038] In a preferred aspect, as shown in FIG. 5, the lower end portion of each bus bar 3 is located further below the lower end portion of the cell 7 (the lower end portion of the laminate film of the cell 7). By adopting such a configuration, even if there is a possibility that a short - circuit current flows through the laminate film during flooding, the fusing portion 4 is blown before such a short - circuit current flows. Thereby, it is possible to more reliably avoid the flow of a large short - circuit current.

[0039] (Fourth Embodiment) Next, a fourth embodiment will be described. Note that detailed descriptions will be omitted for components that can adopt the same configurations as those in the previously described embodiments.

[0040] In this embodiment, the configuration of the bus bar 3 is devised. FIG. 6 is a perspective view showing the bus bar 3 according to this embodiment. The bus bar 3 includes a metallic conductive member. As shown in FIG. 7, the bus bar 3 has a covered portion 11 and an exposed portion 10. In the covered portion 11, the metallic conductive member is covered with a covering material (for example, an insulating member). On the other hand, in the exposed portion 10, the metallic conductive member is exposed. The exposed portion 10 is provided at the lower end portion of the bus bar 3.

[0041] According to this embodiment, when the lower end portion of the bus bar 3 is flooded, current flows intensively in the exposed portion 10. Therefore, an electrochemical reaction is more likely to proceed in the exposed portion 10. Accordingly, it becomes possible to more surely melt the bus bar 3 at the exposed portion 10 (fuse portion 4).

[0042] (Fifth Embodiment) Next, a fifth embodiment will be described. Note that detailed descriptions will be omitted for components that can adopt the same configurations as those in the previously described embodiments.

[0043] Also in this embodiment, as in the fourth embodiment, the configuration of the bus bar 3 is devised. FIG. 7 is a perspective view showing the bus bar 3 according to this embodiment. As shown in FIG. 7, this bus bar 3 has a thin line portion 13. The thin line portion 13 is a portion that is thinner than the portions before and after it (see the thick line portion 12 in FIG. 7). The thin line portion 13 is provided at the lower end portion of the bus bar 3.

[0044] In this embodiment, the thin line portion 13 functions as the fuse portion 4. According to this embodiment, since the fuse portion 4 is thin, the fuse portion 4 melts more promptly when flooded. Accordingly, it becomes possible to more surely melt the bus bar 3 when flooded.

[0045] (Sixth Embodiment) Next, a sixth embodiment will be described. Note that detailed descriptions will be omitted for points where the same configurations as those in the above-described embodiments can be adopted.

[0046] Also in this embodiment, the configuration of the bus bar 3 is devised. FIG. 8 is a perspective view showing the bus bar 3. As shown in FIG. 8, this bus bar 3 has a high ionization tendency portion 15. The high ionization tendency portion 15 is a portion formed of a material having a higher ionization tendency than the portions before and after it (see FIG. 8, low ionization tendency portion 14). The high ionization tendency portion 15 is provided at the lower end portion of the bus bar 3.

[0047] In this embodiment, the high ionization tendency portion 15 functions as the fusing portion 4. According to this embodiment, since the fusing portion 4 is formed of a material having a high ionization tendency, the fusing portion 4 fuses more quickly when immersed in water. Therefore, it becomes possible to more surely fuse the bus bar 3 when immersed in water.

[0048] Note that the specific constituent materials of the low ionization tendency portion 14 and the high ionization tendency portion 15 are not particularly limited. For example, when the constituent material of the low ionization tendency portion 14 is copper, a conductive metal material having a higher ionization tendency than copper can be used as the constituent material of the high ionization tendency portion 15.

[0049] The basic configuration of the present invention and the first to sixth embodiments have been described above. Note that these embodiments and examples are not independent of each other, and it is also possible to use them in combination within a non-contradictory range.

[0050] [Appendix] Hereinafter, the main configurations of the present invention and their effects will be summarized as an appendix.

[0051] (Appendix 1) A battery pack includes a first battery 2-1 and a second battery 2-2, and a bus bar 3 that connects the positive electrode terminal of the first battery and the negative electrode terminal of the second battery. The first battery and the second battery each have a cell 7 including a terminal 6. The bus bar has a fusing portion 4 provided below the short-circuit water level, where the short-circuit water level is the water level at which the terminal 6 comes into contact with water during flooding. The fusing portion 4 is configured to be dissolved in water and disconnected by an electrochemical reaction when flooded.

[0052] According to the above configuration, when flooded, the voltage of the battery pack is divided before a large current flows as a short-circuit current. Therefore, the short-circuit current can be reduced, and the battery pack can be discharged under mild conditions.

[0053] (Appendix 2) A battery pack according to Appendix 1, wherein the fusing portion is disposed below the lower end of the cell 7.

[0054] According to such a configuration, the fusing portion can be more reliably fused before a large short-circuit current flows.

[0055] (Appendix 3) A battery pack according to Appendix 1 or 2, wherein the bus bar has a metallic conductive member and a covering member that covers the conductive member, and at the fusing portion 4, the conductive member is exposed.

[0056] According to such a configuration, the fusing portion 4 can be more reliably fused when flooded.

[0057] (Appendix 4) A battery pack according to any one of Appendices 1 to 3, wherein the fusing portion 4 has a thin wire portion 13, and the thin wire portion is a portion thinner than the portions before and after it.

[0058] According to such a configuration, the fusing portion 4 can be more reliably fused when flooded.

[0059] (Appendix 5) The assembled battery according to any one of Supplementary Notes 1 to 4, wherein the fusing part 4 has a high ionization tendency part 15, and the high ionization tendency part 15 is a part constituted by a material having a higher ionization tendency than the parts before and after it.

[0060] According to such a configuration, when waterlogging occurs, the fusing part 4 can be more surely fused.

[0061] (Supplementary Note 6) The assembled battery according to any one of Supplementary Notes 1 to 5, wherein the fusing part 4 is arranged at the lower end part of the bus bar 3.

[0062] According to such a configuration, when waterlogging occurs, the fusing part 4 can be more surely fused.

[0063] (Supplementary Note 7) The assembled battery according to any one of Supplementary Notes 1 to 6, wherein the bus bar contains copper.

[0064] According to such a configuration, when waterlogging occurs, the fusing part 4 can be fused.

Explanation of Reference Numerals

[0065] 1... assembled battery, 2... battery, 2-1... first battery, 2-2... second battery, 3... bus bar, 4... fusing part, 6... terminal, 7... cell, 8... module, 9... tab, 10... exposed part, 11... covering part, 12... thick line part, 13... thin line part, 14... low ionization tendency part, 15... high ionization tendency part

Claims

1. A first battery and a second battery, a bus bar connecting the positive electrode terminal of the first battery and the negative electrode terminal of the second battery, and comprising the first battery and the second battery each have a cell including a terminal, the bus bar has a fusing portion provided below the short - circuit water level, the short - circuit water level is a water level at which the terminal comes into contact with water during flooding, the fusing portion is configured to dissolve in water and be severed by an electrochemical reaction when flooded, a battery pack.

2. The battery pack according to claim 1, wherein the fusing portion is disposed below the lower end of the cell, a battery pack.

3. The battery pack according to claim 1 or 2, wherein the bus bar has a metallic conductive member and a covering member covering the conductive member, and in the fusing portion, the conductive member is exposed, a battery pack.

4. The battery pack according to claim 1 or 2, wherein the fusing portion has a thin - wire portion, and the thin - wire portion is a portion thinner than the portions before and after it, a battery pack.

5. The battery pack according to claim 1 or 2, wherein the fusing portion has a high - ionization - tendency portion, and the high - ionization - tendency portion is a portion formed of a material having a higher ionization tendency than the portions before and after it, a battery pack.

6. The battery pack according to claim 1 or 2, wherein the fusing portion is disposed at the lower end of the bus bar, Combined battery.

7. The combined battery according to claim 1 or 2, wherein the bus bar contains copper. Combined battery.

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