Battery module, vehicle and bus bar

Abstract

To provide a battery module that can effectively prevent the spread of fire to other battery cells even if thermal runaway or the like occurs in one of a plurality of battery cells electrically connected to each other. [Solution] A battery module according to an embodiment includes two cell blocks connected in series and a bus bar, with multiple battery cells connected in parallel in each cell block. The bus bar forms one or more intra-block connection portions for each cell block, each connecting two corresponding battery cells belonging to the same cell block, and multiple inter-block connection portions, each connecting two corresponding battery cells belonging to different cell blocks. In the bus bar, the resistance of each intra-block connection portion is higher than the resistance of any of the inter-block connection portions.

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a battery module, a vehicle, and a bus bar. [Background technology]

[0002] In a battery module, a plurality of battery cells are electrically connected to one another by one or more bus bars. In a certain battery module, for example, in each of a plurality of cell blocks, a plurality of battery cells are electrically connected to one another in parallel, and a plurality of cell blocks are electrically connected to one another in series. In such a battery module, a plurality of battery cells that are electrically connected to one another are arranged side by side.

[0003] In the battery module described above, even if one of the multiple battery cells rises to an excessively high temperature due to thermal runaway or the like, it is required to effectively suppress excessive temperature rises in the other battery cells caused by heat from the battery cell that has experienced thermal runaway or the like. In other words, it is required to effectively suppress the spread of fire to the other battery cells due to thermal runaway or the like in one battery cell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5764911 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-65794 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that the present invention aims to solve is to provide a battery module, a vehicle, and a bus bar that can effectively prevent the spread of fire to other battery cells even if thermal runaway or the like occurs in one of multiple battery cells that are electrically connected to each other. [Means for solving the problem]

[0006] A battery module according to an embodiment includes two cell blocks and a bus bar. Each of the two cell blocks includes a plurality of battery cells electrically connected in parallel, and the two cell blocks are electrically connected in series. The bus bar is integrally formed from a conductive material and connects the battery cells of the two cell blocks to each other. The bus bar forms one or more intra-block connection portions for each of the two cell blocks, each connecting two corresponding battery cells belonging to the same cell block, and also forms a plurality of inter-block connection portions, each connecting two corresponding battery cells belonging to different cell blocks. In the bus bar, the resistance of each intra-block connection portion is higher than the resistance of any of the inter-block connection portions. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view that schematically shows an example of a single battery cell used in a battery module in the embodiments and the like. [Figure 2] FIG. 2 is a perspective view schematically showing an example of the configuration of a battery module in the embodiment and the like. [Figure 3] FIG. 3 is a schematic diagram showing an example of the configuration of any one of the bus bars used in the battery module in the embodiments and the like. [Figure 4] FIG. 4 is a schematic diagram showing an example of a configuration in which a plurality of battery cells in two cell blocks are connected to each other by any one of the bus bars in the battery module according to the embodiment etc. FIG. [Figure 5] FIG. 5 is a schematic diagram showing an example of a circuit model of a battery module according to the embodiment, etc. [Figure 6] FIG. 6 is a schematic diagram showing an example of a change in situation when thermal runaway occurs in one battery cell in a battery module according to the embodiment and the like. [Figure 7] FIG. 7 is a schematic diagram showing an example of a circuit model when thermal runaway occurs in one battery cell in a battery module according to the embodiment etc. [Figure 8] FIG. 8 is a schematic diagram showing an example of any one configuration of a bus bar used in a battery module in a modification of the embodiment or the like. [Figure 9] FIG. 9 is a schematic diagram showing an example of a vehicle in which a battery module according to the embodiment etc. is used. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the embodiments, a battery module including a plurality of battery cells is provided. In the battery module, the plurality of battery cells are electrically connected to each other by one or more bus bars.

[0009] (battery cell) First, the battery cell will be described. In the embodiments, each of the multiple battery cells used in the battery module has a configuration similar to one of the examples described below. FIG. 1 is a perspective view that schematically shows an example of a single battery cell 1 used in the battery module in the embodiments. In the example shown in FIG. 1, the battery cell 1 includes an electrode group 2, an outer container 3, and a lid member 5. In the battery cell 1, the outer container 3 and the lid member 5 form an exterior portion. The outer container 3 and the lid member 5 are each made of metal, and in one example, they are made of aluminum or an aluminum alloy.

[0010] Here, the battery cell 1 has a defined height direction (the direction indicated by arrows H1 and H2). One side of the battery cell 1 in the height direction is the upper side (the side indicated by arrow H1), and the side opposite the upper side in the height direction is the lower side (the side indicated by arrow H2). The outer casing 3 has a bottom wall 6 and a peripheral wall 7, which define an internal cavity inside the outer casing 3. In the battery cell 1, the electrode group 2 is housed in the internal cavity of the outer casing 3. In the outer casing 3, the bottom wall 6 covers the internal cavity from below in the height direction. The peripheral wall 7 covers the internal cavity from the outer periphery over the entire circumferential direction. The peripheral wall 7 is connected to the bottom wall 6 and extends upward in the height direction from the connection position to the bottom wall 6.

[0011] In the outer container 3, the internal cavity opens on the side opposite the bottom wall 6 in the height direction, i.e., upward in the height direction. In the battery cell 1, the lid member 5 is attached to the peripheral wall 7 of the outer container 3 at the end opposite the bottom wall 6. The lid member 5 then closes the opening of the internal cavity of the outer container 3. The lid member 5 is attached to the outer container 3, for example, by being welded to the peripheral wall 7.

[0012] In the battery cell 1, the electrode group 2 includes a positive electrode and a negative electrode, and in the electrode group 2, the positive electrode and the negative electrode are electrically insulated from each other. An electrolyte, such as an electrolytic solution, is held by the electrode group 2 in the internal cavity of the outer container 3. In the example shown in FIG. 1 , a pair of terminals 8 are attached to the cover member 5, and each of the terminals 8 is exposed on the outer surface of the cover member 5. The pair of terminals 8 are spaced apart from each other. In the battery cell 1, one of the pair of terminals 8 serves as a positive terminal, and the other of the pair of terminals 8 serves as a negative terminal.

[0013] The positive electrode terminal is electrically connected to the positive electrode of the electrode group 2 via a conductive member such as a lead, and the negative electrode terminal is electrically connected to the negative electrode of the electrode group 2 via a conductive member such as a lead. Each of the terminals 8 is prevented from contacting the lid member 5 by an insulating member 9 or the like, and is electrically insulated from the outer casing 3 and the lid member 5. In the internal cavity of the outer casing 3, the positive and negative electrodes of the electrode group 2 are prevented from contacting the outer casing 3 by an insulating member (not shown), and are electrically insulated from the outer casing 3 and the lid member 5.

[0014] The configuration of the battery cell is not limited to the example configuration shown in Fig. 1. For example, in the example shown in Fig. 1, the exterior part is formed from an exterior container 3 and a lid member 5, but the shape and dimensions of the members that form the exterior part can be changed as appropriate. In addition, the positions and dimensions of the pair of terminals that serve as the positive and negative terminals can also be changed as appropriate.

[0015] (battery module) Next, a battery module in which multiple battery cells are electrically connected will be described. Fig. 2 is a perspective view that schematically shows an example of the configuration of a battery module 10 in the embodiment etc. As shown in Fig. 2, the battery module 10 includes multiple battery cells 1, each of which has the same configuration as any of the battery cells 1 described above. The battery module 10 is provided with one or more bus bars 11, and the multiple battery cells 1 are electrically connected via the bus bars 11. Each of the one or more bus bars 11 is integrally formed from a conductive material, for example, aluminum or an aluminum alloy.

[0016] Furthermore, in the battery module 10 of the embodiment and the like, a plurality of cell blocks 12 are formed, and each of the plurality of cell blocks 12 is composed of a plurality of battery cells 1. In each of the plurality of cell blocks 12, the plurality of battery cells 1 are electrically connected in parallel to one another. Furthermore, in the battery module 10, the plurality of cell blocks 12 are electrically connected in series to one another. In the plurality of cell blocks 12, the number of parallel battery cells 1 electrically connected is the same for each. In the example of FIG. 2, in each of the plurality of cell blocks 12, two battery cells 1 are electrically connected in parallel to one another, and the number of parallel battery cells 1 in each cell block 12 is two. That is, in the battery module 10, a plurality of cell blocks 12, each of which has two battery cells 1 connected in parallel, are electrically connected in series to one another.

[0017] 2, the battery module 10 has a depth direction (the direction indicated by the arrow X), a horizontal direction (the direction indicated by the arrow Y) that intersects (is perpendicular or substantially perpendicular to) the depth direction, and a height direction (the directions indicated by the arrows Z1 and Z2) that intersect (is perpendicular or substantially perpendicular to) both the depth direction and the horizontal direction. The depth direction, the horizontal direction, and the height direction are also referred to as the "X direction," the "Y direction," and the "Z direction," respectively. In addition, in the battery module 10, one side in the height direction is the upper side (the arrow Z1 side), and the side opposite the upper side in the height direction is the lower side (the arrow Z2 side).

[0018] In the battery module 10, each of the multiple battery cells 1 is arranged with its height direction aligned with the height direction of the battery module 10. Each of the multiple battery cells 1 is arranged with its upper side in the height direction aligned or approximately aligned with the upper side of the battery module 10 in the height direction, that is, with the outer surface of the cover member 5 facing the upper side of the battery module 10 in the height direction.

[0019] In the battery module 10, a plurality of cell blocks 12 electrically connected in series are arranged in the lateral direction of the battery module 10. The plurality of cell blocks 12 are arranged with no or almost no misalignment relative to one another in the depth and height directions of the battery module 10. Furthermore, in each cell block 12, a plurality of battery cells 1 electrically connected in parallel are arranged in the depth direction of the battery module 10. In each of the plurality of cell blocks 12, the plurality of battery cells 1 are arranged with no or almost no misalignment relative to one another in the lateral and height directions of the battery module 10.

[0020] In the battery module 10 of the embodiment etc., the battery cells 1 of two corresponding cell blocks 12 among the plurality of cell blocks 12 are connected to each other by one bus bar 11. In the example of FIG. 2 , the battery cells 1 of two cell blocks 12 adjacent to each other in the arrangement direction of the plurality of cell blocks 12 (the horizontal direction of the battery module 10) are connected to each other by one bus bar 11.

[0021] FIG. 3 is a schematic diagram showing an example of the configuration of any one of the bus bars 11 used in the battery module 10 in the embodiments and the like. FIG. 4 is a schematic diagram showing an example of the configuration in which any one of the bus bars 11 connects multiple battery cells 1 in two cell blocks 12 to each other in the battery module 10 in the embodiments and the like. FIG. 4 shows the battery module 10 as viewed from above in the height direction. Below, any one of the bus bars 11 and the connection of multiple battery cells 1 in two cell blocks 12 by that bus bar 11 will be described. In the battery module 10, each of the bus bars 11 has the configuration described below, and each of the bus bars 11 connects multiple battery cells 1 in the corresponding two cell blocks 12 in the same manner as described below.

[0022] As shown in Figures 3 and 4, the busbar 11 includes multiple extended plate portions 15 and one or more bridging plate portions 16. The busbar 11 includes the same number of extended plate portions 15 as the number of parallel-connected battery cells 1 in each of the cell blocks 12. In the example shown in Figures 3 and 4, the busbar 11 includes two extended plate portions 15A and 15B. Furthermore, in the busbar 11, each of the one or more bridging plate portions 16 bridges between two corresponding ones of the multiple extended plate portions 15. The busbar 11 includes a number of bridging plate portions 16 equal to the number of parallel-connected battery cells 1 in each of the cell blocks 12 minus one. In the example shown in Figures 3 and 4, the busbar 11 includes only one bridging plate portion 16, which bridges between the extended plate portions 15A and 15B.

[0023] Each of the extended plate portions 15 of the busbar 11 has a length direction, a width direction that intersects (is perpendicular or substantially perpendicular to) the length direction, and a thickness direction that intersects (is perpendicular or substantially perpendicular to) both the length direction and the width direction. Each of the extended plate portions 15 has a length L1 that is the dimension along the length direction, a width W1 that is the dimension along the width direction, and a thickness D1 (see FIG. 2) that is the dimension along the thickness direction. In FIGS. 3 and 4, each of the extended plate portions 15 is shown as viewed from one side in the thickness direction.

[0024] Furthermore, for each of the one or more bridging plate portions 16, a plate length direction, a plate width direction intersecting (perpendicular or approximately perpendicular) with the plate length direction, and a plate thickness direction intersecting (perpendicular or approximately perpendicular) with both the plate length direction and the plate width direction are defined. Each of the bridging plate portions 16 also defines a plate length L2, which is the dimension along the plate length direction, a plate width W2, which is the dimension along the plate width direction, and a plate thickness D2 (see Figure 2), which is the dimension along the plate thickness direction. In Figures 3 and 4, the bridging plate portion 16 is shown as viewed from one side in the plate thickness direction.

[0025] In the busbar 11, the plate length direction of each of the extended plate portions 15 coincides or approximately coincides with the plate width direction of each of the bridging plate portions 16, and the plate width direction of each of the extended plate portions 15 coincides or approximately coincides with the plate length direction of each of the bridging plate portions 16. Furthermore, the plate thickness direction of each of the extended plate portions 15 coincides or approximately coincides with the plate thickness direction of each of the bridging plate portions 16. In an example such as Figures 3 and 4, the busbar 11 has an H-shape or approximately an H-shape when viewed from the plate thickness direction of the extended plate portions 15A, 15B and the bridging plate portion 16.

[0026] In this embodiment, the plate width W2 of each of the bridging plate portions 16 is smaller than the plate width W1 of any of the extended plate portions 15. In the busbar 11, the plate thickness D1 of the extended plate portion 15 and the plate thickness D2 of the bridging plate portion 16 are the same or approximately the same. Therefore, in the busbar 11, the cross-sectional area of ​​each of the bridging plate portions 16 is smaller than the cross-sectional area of ​​any of the extended plate portions 15, and the resistance per unit length of each of the bridging plate portions 16 is higher than the resistance per unit length of any of the extended plate portions 15.

[0027] In one example, similar to the example shown in FIG. 3 , two extension plate portions 15A, 15B and one bridging plate portion 16 are formed on the bus bar 11. The extension plate portions 15A, 15B each have a plate length L1 of approximately 60 mm and a plate width W1 of approximately 16 mm. The bridging plate portion 16 has a plate length L2 of approximately 8 mm and a plate width W2 that is smaller than the plate width W1. The plate thickness of the bus bar 11, which corresponds to the plate thickness D1 of each of the extension plate portions 15A, 15B and the plate thickness D2 of the bridging plate portion 16, is approximately 1 mm. In another example, the bus bar 11 is formed from aluminum or an aluminum alloy, and the bus bar 11 has an electrical conductivity of 38 mΩ. -1 mm -1 The specific heat is about 900 J·kg -1 ·K -1 The density is about 2.7 g cm -3 It will be about that level.

[0028] Each of the extended plate portions 15 is connected to a corresponding one of the bridging plate portions 16 at a center position or approximately a center position in the plate length direction. Furthermore, each of the extended plate portions 15 defines two divided regions 17, 18 that are divided in the plate length direction by the connection position of the bridging plate portion 16 as a boundary. In each of the extended plate portions 15, the divided region (first divided region) 17 corresponds to the region on one side in the plate length direction of the connection position of the bridging plate portion 16, and the divided region (second divided region) 18 corresponds to the region on the opposite side of the divided region 17 from the connection position of the bridging plate portion 16. In each of the extended plate portions 15, the dimension of the divided region 17 in the plate length direction matches or approximately matches the dimension of the divided region 18 in the plate length direction.

[0029] 4 and other figures, in the battery module 10, the plate thickness directions of the extended plate portions 15 and the bridging plate portions 16 coincide or approximately coincide with the height direction of the battery module 10 and are aligned along the height direction of each of the multiple battery cells 1. The plate length direction of the extended plate portions 15 and the plate width direction of the bridging plate portions 16 coincide or approximately coincide with the lateral direction of the battery module 10 and are aligned along the arrangement direction of the multiple cell blocks 12. The plate width direction of the extended plate portions 15 and the plate length direction of the bridging plate portions 16 coincide or approximately coincide with the depth direction of the battery module 10 and are aligned along the arrangement direction of the multiple battery cells 1 in each of the multiple cell blocks 12.

[0030] Here, two cell blocks 12 electrically connected in series by one arbitrary bus bar 11A are referred to as cell blocks 12A and 12B. The bus bar 11 is connected to the negative electrode terminals of the plurality of battery cells 1 that make up the cell block (first cell block) 12A, and is connected to the positive electrode terminals of the plurality of battery cells 1 that make up the cell block (second cell block) 12B. As a result, the two cell blocks 12A and 12B are electrically connected in series by the one bus bar 11, and the plurality of battery cells 1 in each of the cell blocks 12A and 12B are electrically connected in parallel.

[0031] In the busbar 11, one end in the plate length direction of each of the multiple extended plate portions 15, i.e., the dividing region 17, is connected to a corresponding one of the multiple battery cells 1 in the cell block 12A. In addition, in the busbar 11, the end in the plate length direction opposite the side connected to the cell block 12A, i.e., the dividing region 18, is connected to a corresponding one of the multiple battery cells 1 in the cell block 12B. Therefore, in the busbar 11, each of the multiple extended plate portions 15 connects two corresponding battery cells 1 belonging to different cell blocks 12A and 12B.

[0032] Due to the configuration described above, in the battery module 10, a plurality of inter-block connection portions 21, each connecting two corresponding battery cells 1 belonging to different cell blocks 12A, 12B, are formed on the bus bar 11. The number of inter-block connection portions 21 formed on the bus bar 11 is the same as the number of parallel-connected battery cells 1 in each cell block 12. In the bus bar 11, each of the plurality of extension plate portions 15 constitutes a corresponding one of the inter-block connection portions 21, and the same number of inter-block connection portions 21 as the number of extension plate portions 15 are formed.

[0033] In addition, in the battery module 10, one or more intra-block connection portions 22 that connect two corresponding battery cells 1 that belong to the same cell block 12 are formed by the bus bar 11 for each of the two cell blocks 12A and 12B. That is, the bus bar 11 forms one or more intra-block connection portions 22A that connect two corresponding battery cells 1 that belong to the cell block 12A, and one or more intra-block connection portions 22B that connect two corresponding battery cells 1 that belong to the cell block 12B. The bus bar 11 forms intra-block connection portions 22 for each of the two cell blocks 12A and 12B, the number of which is the number of parallel-connected battery cells 1 in each of the cell blocks 12 minus one.

[0034] In the busbar 11, each of the intra-block connection portions (first intra-block connection portions) 22A is composed of two corresponding divided regions 17 of the multiple extended plate portions 15 and a bridging plate portion 16 bridging between the corresponding two extended plate portions 15. In addition, in the busbar 11, each of the intra-block connection portions (second intra-block connection portions) 22B is composed of two corresponding divided regions 18 of the multiple extended plate portions 15 and a bridging plate portion 16 bridging between the corresponding two extended plate portions 15.

[0035] In one example shown in FIG. 4 etc., in cell block (first cell block) 12A, two battery cells 1A, 1B are connected in parallel, and in cell block (second cell block) 12B, two battery cells 1C, 1D are connected in parallel. Two inter-block connection portions 21A, 21B are formed on bus bar 11. The inter-block connection portion (first inter-block connection portion) 21A is made up of an extended plate portion 15A and connects between the battery cell (first battery cell) 1A of cell block 12A and the battery cell (third battery cell) 1C of cell block 12B. The inter-block connection portion (second inter-block connection portion) 21B is made up of an extended plate portion 15B and connects between the battery cell (second battery cell) 1B of cell block 12A and the battery cell (fourth battery cell) 1D of cell block 12B.

[0036] In addition, in the example shown in FIG. 4 etc., the busbar 11 forms one intra-block connection portion 22A for the cell block 12A and one intra-block connection portion 22B for the cell block 12B. The intra-block connection portion 22A is composed of a dividing region 17 of the extended plate portions 15A, 15B and a bridging plate portion 16 bridging between the extended plate portions 15A, 15B. The intra-block connection portion 22A connects the battery cell (first battery cell) 1A and the battery cell (second battery cell) 1B of the cell block 12A. The intra-block connection portion 22B is composed of a dividing region 18 of the extended plate portions 15A, 15B and a bridging plate portion 16 bridging between the extended plate portions 15A, 15B. The intra-block connection portion 22B connects the battery cell (third battery cell) 1C and the battery cell (fourth battery cell) 1D of the cell block 12B.

[0037] In the embodiment and the like, in the bus bar 11, the resistance of each of the intra-block connection portions 22 (22A, 22B) is higher than the resistance of either of the inter-block connection portions 21. In one example shown in Figures 3 and 4 and the like, the resistance of the intra-block connection portion 22A connecting two battery cells 1A, 1B belonging to the cell block 12A and the resistance of the intra-block connection portion 22B connecting two battery cells 1C, 1D belonging to the cell block 12B are higher than the resistance of either of the inter-block connection portion 21A connecting the battery cell 1A of the cell block 12A and the battery cell 1C of the cell block 12B and the resistance of the inter-block connection portion 21B connecting the battery cell 1B of the cell block 12A and the battery cell 1D of the cell block 12B.

[0038] FIG. 5 is a schematic diagram showing an example of a circuit model of a battery module 10 according to an embodiment, etc. In the example of FIG. 5, similar to the examples of FIGS. 2 and 4, etc., two battery cells 1 are connected in parallel in each cell block 12. As shown in FIG. 5, etc., each battery cell 1 has a specified battery voltage V and internal resistance Rbat. In one example, each battery cell 1 includes lithium titanate as the negative electrode active material. Each battery cell 1 has a battery voltage V of approximately 2.6 V and an internal resistance Rbat of approximately 1 mΩ.

[0039] Furthermore, in each busbar 11, the resistance Rs of each of the divided regions 17, 18 in each extension plate portion 15 and the resistance Rp of each of the bridging plate portions 16 are defined. Therefore, in the busbar 11, the resistance of each of the multiple inter-block connection portions 21 is a resistance value 2Rs. Furthermore, in the busbar 11, the resistance of each of one or more intra-block connection portions 22A for the cell block 12A and one or more intra-block connection portions 22B for the cell block 12B is a resistance value 2Rs+Rp. In the embodiment, the resistance of each of the intra-block connection portions 22A, 22B is higher than the resistance of any of the inter-block connection portions 21. That is, the relationship of the following equation (1) is established.

[0040]

number

[0041] Here, when the battery module 10 is operated by charging and discharging, etc., one of the multiple battery cells 1 may rise to an excessively high temperature due to thermal runaway or the like. In this case, in the battery cell 1 experiencing thermal runaway or the like, one of the positive electrode, negative electrode, etc. may come into contact with the outer casing 3 or the lid member 5 due to, for example, melting of the insulating member, causing a short circuit. As a result, the battery cell 1 in which the short circuit has occurred due to thermal runaway or the like does not generate a battery voltage V, and a short-circuit current flows between the battery cell 1 in which the short circuit has occurred and battery cells 1 electrically connected in parallel to that battery cell 1. In other words, a short-circuit current flows between the battery cell 1 in which the short circuit has occurred and other battery cells 1 belonging to the same cell block 12 as that battery cell 1.

[0042] In a battery module 10, when a short-circuit current flows in a cell block 12 to which a battery cell 1 experiencing thermal runaway or the like belongs, it is required that the short-circuit current be quickly shut off and the time during which the short-circuit current flows be kept short. Even if thermal runaway occurs in one battery cell 1, the time during which the short-circuit current flows is kept short, thereby minimizing Joule heat caused by the short-circuit current. This effectively prevents excessive temperature rise in battery cells 1 in cell blocks 12 other than the cell block 12 to which the battery cell 1 experiencing thermal runaway or the like belongs. Therefore, by shortening the time during which the short-circuit current flows in the cell block 12 to which the battery cell 1 experiencing thermal runaway or the like belongs, the spread of fire to other battery cells 1 due to thermal runaway or the like in one battery cell 1 is effectively prevented.

[0043] FIG. 6 is a schematic diagram showing an example of a change in situation when thermal runaway occurs in one battery cell 1 in a battery module 10 according to an embodiment or the like. In the example of FIG. 6, an example is shown in which two battery cells 1 are connected in parallel in each cell block 12. In addition, in the example of FIG. 6, the battery cell 1 in which thermal runaway has occurred is also shown as "battery cell 1α." As shown in FIG. 6 etc., when thermal runaway occurs in battery cell 1α, a short-circuit current Ishort flows between battery cell 1α and a battery cell 1 connected in parallel to battery cell 1α.

[0044] In the embodiment and the like, the resistance of each intra-block connection portion 22 in each bus bar 11 is higher than the resistance of any of the inter-block connection portions 21. Therefore, when a short-circuit current flows in the cell block 12 to which the battery cell 1α belongs, the intra-block connection portion 22 in each bus bar 11 that electrically connects the cell block 12 to which the battery cell 1α belongs to other cell blocks 12 melts down in a short period of time. This interrupts the short-circuit current in the cell block 12 to which the battery cell 1α belongs, and the time during which the short-circuit current flows is reduced to a short period of time.

[0045] Furthermore, in this embodiment, the plate width W2 of each of the bridging plate portions 16 in each of the bus bars 11 is smaller than the plate width W1 of any of the extension plate portions 15, and the resistance per unit length of each of the bridging plate portions 16 is higher than the resistance per unit length of any of the extension plate portions 15. Therefore, even if a short-circuit current flows in the cell block 12 to which the battery cell 1α belongs due to thermal runaway or the like of the battery cell 1α, as shown in FIG. 6 and other figures, the bridging plate portion 16 in one of the bus bars 11 electrically connecting the cell block 12 to which the battery cell 1α belongs to another cell block 12 will melt in a short time. As a result, the short-circuit current in the cell block 12 to which the battery cell 1α belongs is appropriately interrupted in a short time, and the time for which the short-circuit current flows is appropriately reduced in a short time.

[0046] Here, a preferred example of a bus bar 11 connecting the battery cells 1 of two cell blocks 12A and 12B in a configuration in which the battery cells 1 are connected in two parallel connections in each of a plurality of cell blocks 12 will be described. FIG. 7 is a schematic diagram showing an example of a circuit model when thermal runaway occurs in one battery cell 1 in a battery module 10 according to an embodiment or the like. In the example of FIG. 7, a cell block (first cell block) 12A in which two battery cells 1A and 1B are connected in two parallel connections is electrically connected by one bus bar 11 to a cell block (second cell block) 12B in which two battery cells 1C and 1D are connected in two parallel connections. The example of FIG. 7 also shows a state in which thermal runaway occurs in the battery cell 1B of the cell block 12A, and the battery voltage V is not generated in the battery cell 1B.

[0047] In the following description, one busbar 11 connecting the cell blocks 12A and 12B will also be referred to as the “busbar 11A.” The busbar 11 other than the busbar 11A connected to the cell block 12A will also be referred to as the “busbar 11B,” and the busbar 11 other than the busbar 11A connected to the cell block 12B will also be referred to as the “busbar 11C.” In the example shown in FIG. 7 , the busbar 11A is connected to the negative terminals of the battery cells 1A and 1B in the cell block 12A and the positive terminals of the battery cells 1C and 1D in the cell block 12B. The busbar 11B is connected to the positive terminals of the battery cells 1A and 1B in the cell block 12A, and the busbar 11C is connected to the negative terminals of the battery cells 1C and 1D in the cell block 12B. For the battery cell 1B that does not generate the battery voltage V, the internal resistance Rshort is specified instead of the internal resistance Rbat. In one example, in a battery cell 1 where no battery voltage V is generated, the internal resistance Rshort is about 1 mΩ.

[0048] 7, when a short circuit occurs in battery cell 1B due to thermal runaway or the like, the aforementioned short-circuit current flows between battery cell 1B and battery cell 1A connected in parallel to battery cell 1B, and the short-circuit current flows in cell block 12A to which battery cell 1B belongs. When a short-circuit current flows in cell block 12A, current I1 flows from battery cell 1A, passes through busbar 11C, battery cell 1B in which thermal runaway occurred, and divided region 17 of extension plate portion 15B of busbar 11A, in that order. Then, in extension plate portion 15B of busbar 11A, current I2 flows through bridging plate portion 16 of busbar 11A, and current I3 passes through divided region 18 of extension plate portion 15B of busbar 11A and flows through battery cells 1C, 1D, busbar 11C, etc. Then, at the extended plate portion 15A of the busbar 11A, the current I2 from the bridging plate portion 16 of the busbar 11A and the current I3 from the divided region 18 of the extended plate portion 15A of the busbar 11A join together, and the current I1 formed by the joining of the currents I2 and I3 passes through the divided region 17 of the extended plate portion 15A of the busbar 11A and flows toward the battery cell 1A.

[0049] Here, the current I1 is calculated as shown in equation (2) using the battery voltage V and internal resistance Rbat of each battery cell 1, the resistances Rs and Rp defined in each bus bar 11, and the internal resistance Rshort of the battery cell 1 where no battery voltage V is generated. The current I2 is calculated as shown in equation (3) using the above-mentioned parameters and current I1, and the current I3 is calculated as shown in equation (4) using the above-mentioned parameters and current I1. When a short-circuit current flows through the cell block 12A as shown in the example of FIG. 7, the amount of heat generated by Joule heat, Win, in the bridging plate portion 16 of the bus bar 11A is calculated as shown in equation (5).

[0050]

number

[0051] Furthermore, when the temperature rise rate dT / dt of the bridging plate portion 16 of the busbar 11A when a short-circuit current is flowing through the cell block 12A is specified, the temperature rise rate dT / dt is calculated as shown in equation (6) using the heat release amount Wout in the bridging plate portion 16 and the heat capacity C of the bridging plate portion 16 in addition to the heat release amount Win calculated by equation (5). Note that the heat release amount Win and the heat release amount Wout are expressed in units such as W, and the heat capacity C is expressed in units such as J / K.

[0052] The amount of heat dissipation Wout at the bridging plate portion 16 is calculated as shown in Equation (7) using the heat transfer coefficient h between the busbar 11 and the atmosphere, the temperature Tbus of the bridging plate portion 16 of the busbar 11A, the environmental temperature Tatm where the battery module 10 is used, and the surface area Asurf of the bridging plate portion 16 of the busbar 11. The heat capacity C of the bridging plate portion 16 is calculated as shown in Equation (8) using the specific heat γ of the busbar 11 (bridging plate portion 16), the volume Vp of the bridging plate portion 16, and the density ρ of the busbar 11 (bridging plate portion 16). The surface area Asurf and volume Vp of the bridging plate portion 16 are each calculated using the plate length L2, plate width W2, and plate thickness D2 of the bridging plate portion 16 described above.

[0053]

number

[0054] Here, a simulation was performed on a situation where thermal runaway occurred in one battery cell 1α in a configuration in which two battery cells 1 were connected in parallel in each of a plurality of cell blocks 12, similar to the example in Figure 7. The simulation results showed that when a short-circuit current caused by thermal runaway flowed for 50 seconds in the cell block 12 to which battery cell 1α belonged, fire spread to battery cells 1 in cell blocks 12 other than the cell block 12 to which battery cell 1α incurring thermal runaway. On the other hand, when the time during which the short-circuit current caused by thermal runaway flowed in the cell block 12 to which battery cell 1α belonged was limited to 10 seconds, fire spread to battery cells 1 in cell blocks 12 other than the cell block 12 to which battery cell 1α incurring thermal runaway belonged.

[0055] From the results of the above simulations, the conditions under which the short-circuit current caused by thermal runaway is interrupted within 10 seconds with respect to the resistance component of the busbar 11, i.e., the conditions under which the bridging plate portion 16 melts down within 10 seconds after the short-circuit current starts to flow, were calculated. In this case, the conditions under which the temperature 10 seconds after the short-circuit current starts to flow is equal to or higher than the melting temperature (melting point) Tth of the bridging plate portion 16 (busbar 11) were calculated. The temperature 10 seconds after the short-circuit current starts to flow was calculated by calculating the temperature rise rate dT / dt of the bridging plate portion 16 using the above-mentioned formulas (2), (3), (5) to (8), etc. Note that the calculations were performed assuming that the temperature of the bridging plate portion 16 at the time the short-circuit current starts to flow was 25°C.

[0056] In addition, in the calculation of the condition that the short circuit current is interrupted within 10 seconds, the bus bar 11 is assumed to be made of aluminum, and the electrical conductivity of the bus bar 11 (bridge plate portion 16) is assumed to be 38 mΩ. -1 mm -1 and the specific heat γ is 900 J kg -1 ·K -1 and the density ρ is 2.7 g cm -3 The calculation was performed with the busbar 11 having a meltdown temperature Tth of 660°C and a plate thickness (plate thickness D2 of the bridging plate portion 16) of 1 mm. In addition, in the calculation under the condition that the short-circuit current is interrupted within 10 seconds, the heat transfer coefficient h between the busbar 11 and the atmosphere was set to 5 W m, which is the physical property of air when no flow is generated. -2 ·K -1 Then, for each battery cell 1, the battery voltage V was set to 2.6 V, the internal resistance Rbat was set to 1 mΩ, and for battery cells 1 where no battery voltage V was generated, the internal resistance Rshort was set to 1 mΩ, and calculations were performed.

[0057] As a result of the above calculations, it was calculated that the condition for interrupting the short-circuit current within 10 seconds is that the resistance value 2Rs+Rp of each resistor in the intra-block connection portion 22 in the busbar 11 is 1.2 times or more the resistance value 2Rs of each resistor in the inter-block connection portion 21. That is, in a configuration in which two battery cells 1 are connected in parallel in each of multiple cell blocks 12, the condition shown in equation (9) was calculated as the condition for interrupting the short-circuit current within 10 seconds. When the resistance of each intra-block connection portion 22 is 1.2 times or more the resistance of each inter-block connection portion 21, Joule heat is generated in the bridging plate portion 16 to the extent that the bridging plate portion 16 melts down within 10 seconds after the short-circuit current starts flowing.

[0058]

number

[0059] Furthermore, if a short-circuit current flows through the cell block 12A to which the battery cell 1B in which thermal runaway has occurred belongs, it is necessary not only to interrupt the short-circuit current in a short time, but also to reduce the short-circuit current flowing through the cell block 12 connected in series to the cell block 12A. That is, in the example of Figure 7, it is necessary to reduce the current I3 flowing through the battery cells 1C, 1D, etc. For example, it is necessary to reduce the current I3 to a level that is 1 / 10 or less of the current I2 flowing through the bridging plate portion 16 of the bus bar 11A.

[0060] From this perspective, in a configuration in which two battery cells 1 are connected in parallel in each of a plurality of cell blocks 12, in addition to the above-mentioned condition that short-circuit current is interrupted within 10 seconds, the condition that current I3 is 1 / 10 or less of current I2 (condition that satisfies I3≦0.1×I2) was calculated. In this case, the condition that current I3 is 1 / 10 or less of current I2 was calculated using the above-mentioned equations (2) to (4), etc. In addition, the battery voltage V and internal resistance Rbat of each battery cell 1, and the internal resistance Rshort of a battery cell 1 in which battery voltage V is not generated, etc. were set to the same values ​​as those used in the calculation of the condition that short-circuit current is interrupted within 10 seconds.

[0061] As a result of the above calculations, the condition for current I3 to be 1 / 10 or less of current I2 was calculated as the condition for the resistance value 2Rs+Rp of each resistor of the intra-block connection portion 22 in the busbar 11 to be 4.2 times or less the resistance value 2Rs of each resistor of the inter-block connection portion 21. That is, in a configuration in which two battery cells 1 are connected in parallel in each of multiple cell blocks 12, the condition shown in equation (10) was calculated as the condition for current I3 to be 1 / 10 or less of current I2. By making the resistance of each intra-block connection portion 22 4.2 times or less the resistance of each inter-block connection portion 21, the short-circuit current flowing in the cell block 12 connected in series to the cell block 12 to which the battery cell 1 experiencing thermal runaway belongs is appropriately reduced.

[0062]

number

[0063] As described above, in a configuration in which two cell blocks 12 are connected in series by one bus bar 11 and two battery cells 1 are connected in parallel in each of the two cell blocks 12, it is preferable that the resistance of each intra-block connection portion 22 be 1.2 times or more and 4.2 times or less than the resistance of each inter-block connection portion 21.

[0064] By making the resistance of each intra-block connection part 22 at least 1.2 times the resistance of each inter-block connection part 21, even if a short-circuit current flows in the cell block 12 to which the battery cell 1 in which thermal runaway occurred belongs, the time for which the short-circuit current flows is appropriately reduced to a short time. This appropriately prevents the spread of fire to battery cells 1 other than the battery cell 1 in which thermal runaway or the like occurred. Furthermore, by making the resistance of each intra-block connection part 22 at most 4.2 times the resistance of each inter-block connection part 21, the short-circuit current flowing in the cell block 12 connected in series to the cell block 12 to which the battery cell 1 in which thermal runaway occurred belongs is reduced.

[0065] In the above-described embodiments, the plate width W2 of each bridging plate portion 16 in the busbar 11 is smaller than the plate width W1 of any of the extended plate portions 15, so that the resistance per unit length of each bridging plate portion 16 is higher than the resistance per unit length of any of the extended plate portions 15. FIG. 8 is a schematic diagram showing an example of any one configuration of a busbar 11 used in a battery module 10 in a modification of the embodiments. As shown in FIG. 8, this modification also includes multiple extended plate portions 15 and one or more bridging plate portions 16, as in the above-described embodiments. The example in FIG. 8 includes two extended plate portions 15A, 15B and one bridging plate portion 16, as in the examples in FIGS. 3 and 4.

[0066] In this modified example, as in the above-described embodiment, the direction, dimensions, etc. are specified for each of the extended plate portions 15 and the bridging plate portions 16. In the busbar 11, as in the above-described embodiment, the plate length direction of each of the extended plate portions 15 coincides or approximately coincides with the plate width direction of each of the bridging plate portions 16, and the plate width direction of each of the extended plate portions 15 coincides or approximately coincides with the plate length direction of each of the bridging plate portions 16. Furthermore, the plate thickness direction of each of the extended plate portions 15 coincides or approximately coincides with the plate thickness direction of each of the bridging plate portions 16. In Figure 8, each of the extended plate portions 15 is shown as viewed from one side in the plate length direction, and the bridging plate portion 16 is shown as viewed from one side in the plate width direction.

[0067] However, in the busbar 11 of this modified example, unlike the above-described embodiment, the plate thickness D2 of each of the bridging plate portions 16 is smaller (thinner) than the plate thickness D1 of any of the extended plate portions 15. Furthermore, in the busbar 11 of this modified example, the plate width W1 of the extended plate portion 15 and the plate width W2 of the bridging plate portion 16 are the same or approximately the same. By adopting such a configuration, in the busbar 11 of this modified example, the cross-sectional area of ​​each of the bridging plate portions 16 is smaller than the cross-sectional area of ​​any of the extended plate portions 15, and the resistance per unit length of each of the bridging plate portions 16 is higher than the resistance per unit length of any of the extended plate portions 15.

[0068] As described above, in the busbar 11 of this modified example, the resistance per unit length of each of the bridging plate portions 16 is higher than the resistance per unit length of any of the extension plate portions 15. Therefore, even if a short-circuit current flows in the cell block 12 to which the battery cell 1α belongs due to thermal runaway or the like in one battery cell 1α, the bridging plate portion 16 in one of the busbars 11 electrically connecting the cell block 12 to which the battery cell 1α belongs to another cell block 12 will melt in a short time. As a result, in the cell block 12 to which the battery cell 1α belongs, the short-circuit current is appropriately interrupted in a short time and the time for which the short-circuit current flows is appropriately reduced in a short time.

[0069] Furthermore, in a certain modified busbar 11, the plate thickness D2 of each of the bridging plate portions 16 is smaller than the plate thickness D1 of any of the extended plate portions 15, and the plate width W2 of each of the bridging plate portions 16 is smaller than the plate width W2 of any of the extended plate portions 15. In this case as well, in the busbar 11, the cross-sectional area of ​​each of the bridging plate portions 16 is smaller than the cross-sectional area of ​​any of the extended plate portions 15, and the resistance per unit length of each of the bridging plate portions 16 is higher than the resistance per unit length of any of the extended plate portions 15. Therefore, this modified example also achieves the same functions and effects as the above-described embodiment and the like.

[0070] (Battery equipped equipment) The battery module 10 described above is used by being mounted in a battery-equipped device. Examples of battery-equipped devices that can be equipped with the battery module 10 include vehicles, large-scale power storage devices for power systems, smartphones, stationary power supply devices, robots, drones, etc. Examples of vehicles that can be used as battery-equipped devices include electric vehicles, railroad cars, electric buses, plug-in hybrid vehicles, and electric motorcycles.

[0071] FIG. 9 is a schematic diagram showing an example of a vehicle 30 in which a battery module 10 according to an embodiment or the like is used. As shown in FIG. 9, the vehicle 30, which serves as a battery-equipped device, includes a vehicle body 31. The battery module 10 is mounted on the vehicle body 31. In addition to the battery module 10, a drive circuit, a control circuit, a power supply, a load, and the like (none of which are shown) are mounted on the vehicle body 31. The battery module 10 is charged by power from either a power supply mounted on the vehicle body 31 or a charger (not shown) external to the vehicle 30. At this time, after AC / DC conversion or voltage transformation is performed in the drive circuit, DC power within a voltage range compatible with the battery module 10 is input from the drive circuit to the battery module 10. Examples of power sources mounted on the vehicle body 31 include a charger mounted on the vehicle and a storage battery separate from the battery module 10.

[0072] The power discharged from the battery module 10 is supplied to either a load mounted on the vehicle body 31 or to devices external to the vehicle 30. An example of a load mounted on the vehicle body 31 is an electric motor that drives the vehicle 30. The DC power discharged from the battery module 10 is converted into power corresponding to the load and devices in the drive circuit, and then supplied to the load and devices. The control circuit is composed of either a processor or an integrated circuit mounted on the vehicle body 31. The control circuit controls the charging and discharging of the battery module 10 by controlling the operation of the drive circuit, etc.

[0073] In at least one of the above-described embodiments or examples, a plurality of battery cells are connected in parallel in each of two cell blocks connected in series. The bus bar has at least one intra-block connection portion for each of the two cell blocks, each connecting two corresponding battery cells belonging to the same cell block, and a plurality of inter-block connection portions for each connecting two corresponding battery cells belonging to different cell blocks. The bus bar has a higher resistance in each of the intra-block connection portions than in any of the inter-block connection portions. This makes it possible to provide a battery module, vehicle, and bus bar that can effectively prevent the spread of fire to other battery cells, even if thermal runaway or the like occurs in one of the electrically connected battery cells.

[0074] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0075] 1 (1A to 1D, 1α)...battery cell, 10...battery module, 11 (11A to 11C)...bus bar, 12 (12A, 12B)...cell block, 15 (15A, 15B)...extension plate portion, 16...bridging plate portion, 21 (21A, 21B)...inter-block connection portion, 22 (22A, 22B)...intra-block connection portion, 30...vehicle, 31...vehicle body.

Claims

1. two cell blocks each including a plurality of battery cells electrically connected in parallel to each other and electrically connected in series to each other; a bus bar formed integrally from a conductive material and connecting the plurality of battery cells of the two cell blocks to each other, the bus bar having one or more intra-block connection portions for each of the two cell blocks, each connecting two corresponding battery cells belonging to the same cell block, and a plurality of inter-block connection portions for each of the two cell blocks, each connecting two corresponding battery cells belonging to different cell blocks, the resistance of each of the intra-block connection portions being higher than the resistance of any of the inter-block connection portions; A battery module comprising:

2. the two cell blocks include a first cell block including a first battery cell and a second battery cell as the plurality of battery cells, and a second cell block including a third battery cell and a fourth battery cell as the plurality of battery cells; the bus bar forms, as the intra-block connection portions, a first intra-block connection portion that connects the first battery cell and the second battery cell and a second intra-block connection portion that connects the third battery cell and the fourth battery cell; and, as the inter-block connection portions, a first inter-block connection portion that connects the first battery cell and the third battery cell and a second inter-block connection portion that connects the second battery cell and the fourth battery cell; a resistance of each of the first intra-block connection portion and the second intra-block connection portion is 1.2 times or more and 4.2 times or less than a resistance of each of the first inter-block connection portion and the second inter-block connection portion; The battery module of claim 1 .

3. The bus bar is a plurality of extension plate portions each connecting two corresponding battery cells belonging to different cell blocks and constituting a corresponding one of the plurality of inter-block connection portions; One or more bridging plate portions each bridging two corresponding ones of the plurality of extending plate portions and each having a plate width smaller than the plate width of any of the plurality of extending plate portions; The battery module of claim 1 .

4. The bus bar is a plurality of extension plate portions each connecting two corresponding battery cells belonging to different cell blocks and constituting a corresponding one of the plurality of inter-block connection portions; One or more bridging plate portions each bridging two corresponding ones of the plurality of extending plate portions and each having a plate thickness thinner than any of the plurality of extending plate portions; The battery module of claim 1 .

5. The battery module according to any one of claims 1 to 4; a vehicle body on which the battery module is mounted; A vehicle equipped with the above.

6. In a battery module in which two cell blocks are electrically connected in series with each other and a plurality of batteries are electrically connected in parallel with each other in each of the two cell blocks, a bus bar connecting the plurality of batteries in the two cell blocks with each other, integrally formed from a conductive material; forming one or more intra-block connection portions for each of the two cell blocks, each of which connects two corresponding battery cells belonging to the same cell block; forming a plurality of inter-block connection portions each connecting two corresponding battery cells belonging to different cell blocks; a resistance of each of the intra-block connection portions is higher than a resistance of any of the inter-block connection portions; Busbar.

Images