Battery pack

Abstract

The present invention provides a battery pack that can prevent the cell case of a battery cell from peeling off from a thermal conductive material that has adhesive force for connecting the battery cell to a heat dissipation member when the cell case of the battery cell expands in the stacking direction of the battery cells. [Solution] The device comprises a plurality of battery cells arranged in a first direction and having cell cases, a plurality of spacers provided between adjacent battery cells, a restraining member that brings adjacent battery cells and spacers into contact, a heat dissipation member facing the cell case, and a heat conductive material that adheres to the cell case and the heat dissipation member to connect the cell case and the heat dissipation member, wherein the Young's modulus of the central spacer, which is located in the center of the first direction, is the smallest among all spacers in the first direction, or the spring constant of the central spacer in the first direction is the smallest among all spacers, and the Young's modulus of the spacer is smaller than that of the cell case.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 below discloses a battery pack including a plurality of battery cells stacked in a first direction and a plurality of elastic bodies provided between adjacent battery cells. Each battery cell is in contact with an elastic body in a state of being displaced in a direction orthogonal to the first direction. When each battery cell expands, each elastic body is deformed, thereby reducing the amount of displacement of each battery cell in the orthogonal direction.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <了 A battery module having a plurality of battery cells and a plurality of elastic bodies and in which the battery cells and the elastic bodies are constrained by a constraining member can be housed in a battery case (lower case), and the bottom of the battery cell and the bottom of the battery case can be connected by a heat conductive material having an adhesive force. In this way, the heat of the battery cell is transmitted to the battery case through the heat conductive material.

[0005] However, when the battery cells of the battery module to which the technology of Patent Document 1 is applied expand, there is a risk that the battery cells (cell cases) are peeled off from the heat conductive material by the shearing force generated between the bottom of the battery cell and the bottom of the battery case.

[0006] In consideration of the above facts, the present invention aims to provide a battery pack that can suppress the peeling of the cell case of a battery cell from the heat conductive material having adhesive force for connecting the battery cell to the heat dissipation member when the cell case of the battery cell expands in the stacking direction of the battery cells. [Means for solving the problem]

[0007] The battery pack of the first embodiment comprises a plurality of battery cells having cell cases arranged in a first direction, a plurality of spacers provided between adjacent battery cells, a restraining member that restrains the battery cells and the spacers so as to bring adjacent battery cells and the spacers into contact, the cell case, a heat dissipation member facing a second direction perpendicular to the first direction, and a heat conductive material that adheres to the cell case and the heat dissipation member to connect the cell case and the heat dissipation member, wherein the Young's modulus of the central spacer, which is located in the center of the first direction, is the smallest among all the spacers in the first direction, or the spring constant of the central spacer in the first direction is the smallest among all the spacers, and the Young's modulus of the spacer is smaller than that of the cell case.

[0008] In the battery pack of the first embodiment, adjacent battery cells and spacers are brought into contact by a restraining member. As a result, the battery cells and spacers that are in contact with each other exert a force in the first direction. The Young's modulus of the spacer in the first direction is smaller than that of the cell case. Furthermore, the Young's modulus of the central spacer, which is located in the center in the first direction, is the smallest among all spacers in the first direction, or the spring constant of the central spacer in the first direction is the smallest among all spacers. Therefore, for example, when each battery cell expands in the first direction due to charging, the two battery cells in contact with the central spacer move toward the central spacer, and the amount of movement in the first direction of the neutral battery cells, which are predetermined battery cells located toward the ends of the battery module from these two battery cells, may become substantially zero. Furthermore, the amount of movement in the first direction of the battery cells located toward the ends of the battery module from the neutral battery cells is smaller than when the Young's modulus of the central spacer in the first direction is not the smallest among all spacers, and when the spring constant of the central spacer is not the smallest among all spacers.

[0009] Therefore, when viewed as a whole battery module, the amount of movement of the battery cell group in the first direction is reduced. Furthermore, the amount of movement of the battery cells located at both ends of the first direction, which are the most likely to move among the individual battery cells, is reduced. Consequently, large shear forces are less likely to occur between the heat dissipation member and the cell case. Therefore, in the first embodiment of the battery pack, when the cell case of the battery cell expands in the stacking direction of the battery cells, the cell case can be prevented from peeling off from the heat conductive material that has adhesive force for connecting the battery cell to the heat dissipation member.

[0010] In the second embodiment of the battery pack, all the spacers have the same shape, the Young's modulus of the central spacer is the smallest among all the spacers, and the Young's modulus of the spacers excluding the central spacer is the same.

[0011] In the battery pack of the second embodiment, all spacers have the same shape and the Young's modulus is the same for all spacers except the central spacer. Therefore, compared to cases where all spacers have different shapes or where the Young's modulus of each spacer is different, the battery pack can be manufactured at a lower cost and assembled more easily.

[0012] In the third embodiment of the battery pack, in the first embodiment, all the spacers have the same shape, the Young's modulus of the central spacer is the smallest among all the spacers, and the Young's modulus of the spacers other than the central spacer gradually decreases from the end side in the first direction toward the central spacer side.

[0013] In the third embodiment of the battery pack, the amount of movement of each battery cell in the first direction can be reduced compared to the case where the Young's modulus of the spacers, excluding the central spacer, is the same.

[0014] In the fourth embodiment of the battery pack, in the first embodiment, all the spacers have the same Young's modulus, the central spacer has the smallest spring constant among all the spacers, and the spacers excluding the central spacer have the same spring constant.

[0015] In the fourth embodiment of the battery pack, since all spacers have the same Young's modulus and all spacers except the central spacer have the same spring constant, the battery pack can be manufactured at a lower cost and assembled more easily compared to cases where all spacers have different Young's moduli or where each spacer has a different spring constant.

[0016] In the fifth embodiment of the battery pack, in the first embodiment, the Young's modulus of all the spacers is the same, the spring constant of the central spacer is the smallest among all the spacers, and the spring constants of the spacers other than the central spacer gradually decrease from the end side in the first direction toward the central spacer side.

[0017] In the battery pack of the fifth aspect, the amount of movement of each battery cell in the first direction can be reduced as compared with the case where the spring constants of the spacers except the central spacer are the same.

Advantages of the Invention

[0018] As described above, the battery pack according to the present invention has an excellent effect that when the cell case of the battery cell expands in the stacking direction of the battery cells, it can suppress the cell case from peeling off from the heat conductive material having an adhesive force for connecting the battery cell to the heat dissipation member.

Brief Description of the Drawings

[0019] <​​​​​​​​​​​​​​​​​​​​​​​​​​​Hereinafter, the battery pack (battery pack) according to the first embodiment will be described with reference to FIGS. 1 to 3. In each figure, the arrow UP, the arrow FR, and the arrow LH indicate the upper side in the vehicle up-down direction (second direction), the front side in the vehicle front-rear direction (first direction), and the left side in the vehicle left-right direction, respectively.

[0021] The battery pack 20 of the present embodiment is mounted on a vehicle. The vehicle of the present embodiment is a battery electric vehicle (BEV: Battery Electric Vehicle).

[0022] The battery pack 20 of the present embodiment includes a battery case 22 and a battery module 40. The power of the battery pack 20 (battery cell 43) is supplied to, for example, an electric motor (not shown) that applies driving force to the front and rear wheels of the vehicle.

[0023] The battery case 22 has a lower case (heat dissipation member) 24 (see FIG. 2) and an upper case (not shown).

[0024] The lower case 24 is a hollow body having an opening formed on the upper surface. The bottom (lower end) of the lower case 24 is composed of a substantially flat bottom plate portion 26. The lower case 24 has a peripheral wall portion (not shown) whose lower end is connected to the outer peripheral edge of the bottom plate portion 26, and an outer peripheral flange connected to the upper edge of the peripheral wall portion. The lower case 24 is made of, for example, metal.

[0025] A cooler (not shown) is fixed to the lower surface of the bottom plate portion 26 via a heat conductive material.

[0026] The upper case is a hollow body having an opening formed on the lower surface.

[0027] As shown in FIG. 2, the battery module 40 is provided inside the lower case 24. As shown in FIG. 2, the battery module 40 includes a battery stack 41, a pair of end plates 54, and four restraint members 55.

[0028] In a plan view, the battery stack 41 extending in the front-to-back direction comprises a plurality of battery cells 43 and a plurality of spacers 53 positioned between adjacent battery cells 43. For convenience, as shown in Figure 1, the battery stack 41 has 12 battery cells 43. As shown in Figure 1, each battery cell 43 may be individually referred to as battery cell 43-1, battery cell 43-2, battery cell 43-3... battery cell 43-12, in order from the front. If it is not necessary to explain each battery cell individually, all battery cells are collectively referred to as battery cell 43.

[0029] As shown in Figure 2, the metal cell case 44 that constitutes the outer shape of the lithium-ion battery cell 43 is a rectangular parallelepiped. Each battery cell 43 has a positive electrode and a negative electrode (neither of which are shown). Each cell case 44 has a front plate portion 45 and a rear plate portion 46, both of which have a rectangular shape where the left-right dimension is greater than the top-down dimension. The cell cases 44 of each battery cell 43 are identical in specifications. That is, the Young's modulus of each cell case 44 is the same. The material constituting the cell case 44 in all embodiments and modifications is isotropic.

[0030] As shown in Figures 1 and 2, thirteen spacers 52 and 53 are provided between adjacent battery cells 43 (cell cases 44). Spacers 52 and 53 are integrally molded from resin. Spacers 52 and 53 are roughly rectangular in shape. The left-right width and top-down dimensions of spacers 52 and 53 are roughly the same as those of the battery cells 43, while the front-to-back dimensions of spacers 52 and 53 are smaller than those of the cell cases 44. All spacers 53 are identical in specifications (same shape). Also, spacers 52 have the same configuration as spacers 53 except for the material. As shown in Figure 1, each spacer 52 and 53 contacts the front plate portion 45 and the rear plate portion 46 of the cell case 44 of the battery cell 43, respectively. Here, the spacer 52 that contacts battery cells 43-6 and 43-7 may be referred to as the central spacer 52 in the following description. When it is not necessary to explain the central spacer 52 and spacers 53 individually, the central spacer 52 will be collectively referred to as spacer 52.

[0031] The Young's modulus of the resin material constituting the central spacer 52, which is located in the center of the longitudinal direction (stacking direction of the battery cells 43) of the battery module 40, is smaller than that of the resin material constituting the spacer 53. That is, as shown in Figure 3(a), the Young's modulus of the central spacer 52 in the front-to-back direction is smaller than that of the spacer 53 in the front-to-back direction. In other words, the Young's modulus of the central spacer 52 is the smallest among all the spacers 52 and 53. Furthermore, the Young's modulus of the spacers 52 and 53 in the front-to-back direction is smaller than the Young's modulus of the cell case 44 of each battery cell 43 in the front-to-back direction. Note that the materials constituting each spacer in all embodiments and modifications are isotropic.

[0032] As shown in Figures 1 and 2, the battery module 40 is equipped with a pair of front and rear end plates 54. The front end plate 54 is located directly in front of the foremost spacer 53, and the rear end plate 54 is located directly behind the rearmost spacer 53.

[0033] As shown in Figure 2, the four restraining members 55 extend in the front-rear direction, and their cross-sectional shape is approximately L-shaped. Each restraining member 55 overlaps the four corners of each battery cell 43 (cell case 44) and end plate 54, and is fixed to the front and rear end plates 54, respectively. As a result, the front-rear length of each restraining member 55 becomes shorter than when it is in a free state. That is, each restraining member 55 pulls the front and rear end plates 54 toward each other, and as a result the front and rear end plates 54 sandwich the battery stack 41 from the front and rear.

[0034] Therefore, adjacent cell cases 44 and spacers 52 and 53 in the front-to-back direction come into contact with each other with strong force in the front-to-back direction. In other words, a force in the front-to-back direction (first direction) is exerted between each adjacent spacer 52 and 53 and the front plate portion 45 and rear plate portion 46 of the cell case 44.

[0035] In this way, the battery stack 41 and the end plate 54 are integrated by each restraining member 55. That is, a battery module 40 comprising the battery stack 41, a pair of end plates 54, and four restraining members 55 is completed.

[0036] Furthermore, the battery module 40 includes a number of busbars (not shown) connected to the positive and negative electrodes of each battery cell 43.

[0037] A battery module 40 is housed inside the lower case 24, and the battery module 40 is fixed to the bottom plate 26. That is, as shown in Figure 2, a liquid (viscous) thermal conductive material 60, which is an adhesive, is applied to a predetermined area extending in the front-to-back direction on the upper surface of the bottom plate 26. The left-to-right dimensions of this predetermined area are approximately the same as the left-to-right dimensions of the battery cell 43 (cell case 44), and the front-to-back dimensions of each area are approximately the same as the front-to-back dimensions of the battery module 40. The thermal conductive material 60 has high thermal conductivity.

[0038] Although not shown in the diagram, the bottom of the battery module 40 rests on the thermal conductive material 60. That is, the battery module 40 and the bottom plate portion 26 face each other in the vertical direction. As a result, the bottom plate portion 50 of the cell case 44 of each battery cell 43 comes into contact with the thermal conductive material 60. Once the thermal conductive material 60 solidifies, the battery module 40 is fixed to the bottom plate portion 26 by the thermal conductive material 60. The Young's modulus of the solidified thermal conductive material 60 is lower than the Young's modulus of the lower case 24 and the Young's modulus of the cell case 44, and the solidified thermal conductive material 60 is deformable.

[0039] Furthermore, the end plate 54 of the battery module 40 is fixed to the bottom plate portion 26 via a metal bracket (see Figure 1) 65 having an L-shaped cross-section.

[0040] Furthermore, the upper case is placed over the entire upper surface of the outer flange of the lower case 24, which houses the battery module 40, and the lower case 24 and the upper case are fixed to each other. This completes the battery pack 20. The battery case 22 of the completed battery pack 20 is then supported by the vehicle's body frame member.

[0041] (Mechanism of action and effect) Next, the operation and effects of the first embodiment will be described.

[0042] For example, when each battery cell 43 of the battery module 40 of the battery pack 20 mounted on a vehicle is charged, the front plate portion 45 and the rear plate portion 46 of the cell case 44 of each battery cell 43 bulge. Also, the front plate portion 45 and the rear plate portion 46 of each cell case 44 bulge due to aging deterioration. When the front plate portion 45 and the rear plate portion 46 of each cell case 44 bulge in the front-rear direction in this way, a force in the front-rear direction (first direction) is exerted between the adjacent spacers 52, 53 and the front plate portion 45 and the rear plate portion 46 of the cell case 44 due to this bulging.

[0043] Incidentally, the Young's modulus of spacers 52 and 53 in the front-to-back direction is smaller than that of the cell case 44. Furthermore, as shown in Figure 3(a), the Young's modulus of the central spacer 52, which is located in the center in the front-to-back direction, is the smallest among all the spacers 52 and 53. Therefore, for example, when each battery cell 43 (front plate portion 45, rear plate portion 46) expands in the front-to-back direction due to charging, as shown in Figure 3(b), the two battery cells 43-6 and 43-7 that are in contact with the central spacer 52 move toward the central spacer 52, and the amount of movement in the front-to-back direction of the neutral battery cells 43-5 and 43-8, which are predetermined battery cells located toward the ends of the battery module 40, respectively, becomes substantially zero.

[0044] Furthermore, the amount of movement in the front-to-back direction of the battery cell 43 located closer to the end of the battery module 40 than the neutral battery cells 43-5 and 43-8 becomes smaller compared to the case where the Young's modulus of the central spacer 52 in the front-to-back direction is not the smallest among all the spacers 52 and 53.

[0045] Therefore, when viewed as a whole, the amount of movement of the battery cell group 43 in the front-to-back direction is reduced. Furthermore, the amount of movement of battery cells 43-1 and 43-12, which are located at both ends in the front-to-back direction and tend to have the largest amount of movement in that direction among the individual battery cells 43, is reduced. As a result, in the battery pack 20 of this embodiment, when the cell case 44 of each battery cell 43 expands in the front-to-back direction, the shear force generated between each battery cell 43 and the thermal conductive material 60 does not tend to become large, thus suppressing the peeling of each cell case 44 from the thermal conductive material 60.

[0046] Therefore, when the battery cells 43 become hot due to the vehicle's operation after charging is complete, the heat from each battery cell 43 is efficiently transferred from the bottom plate portion 50 of the cell case 44 to the bottom plate portion 26 via the heat conductive material 60, and the heat from the bottom plate portion 26 is further absorbed by the cooler.

[0047] Furthermore, in the battery pack 20, all spacers 52 and 53 have the same shape, and the Young's modulus of each spacer 53 is the same except for the central spacer 52. Therefore, compared to cases where all spacers 52 and 53 have different shapes, or where the Young's modulus of each spacer 53 is different from one another, the battery pack 20 can be manufactured at a lower cost and assembled more easily.

[0048] Next, a second embodiment of the present invention will be described with reference to Figures 4 and 5. Note that the same reference numerals will be used for the same components as in the first embodiment, and their detailed descriptions will be omitted.

[0049] The battery pack 20 of the second embodiment differs from that of the first embodiment in the configuration of the battery module. More specifically, the configuration of the spacers differs from that of the first embodiment.

[0050] As shown in Figure 4, the battery module 70 of the second embodiment has spacers 72 and 73 instead of spacers 52 and 53.

[0051] As shown in Figure 4, thirteen roughly rectangular spacers 72 and 73 are provided between adjacent battery cells 43 in the battery module 70. The width and height dimensions of the spacers 72 and 73 are approximately the same as those of the battery cells 43, and the front-to-back dimensions of the spacers 72 and 73 are smaller than those of the cell case 44. The spacers 72 and 73 are integrally molded products made of the same resin material. That is, the Young's modulus in the front-to-back direction is the same for all spacers 72 and 73. Furthermore, the Young's modulus in the front-to-back direction of the spacers 72 and 73 is smaller than the Young's modulus in the front-to-back direction of the cell case 44 of each battery cell 43. As shown in Figure 4, each spacer 72 and 73 contacts the front plate portion 45 and the rear plate portion 46 of the cell case 44 of the battery cell 43, respectively. Here, the spacer 72 that contacts battery cell 43-6 and battery cell 43-7 may be referred to as the central spacer 72 in the following description.

[0052] The front-to-back dimension (thickness) of the central spacer 72 is greater than the front-to-back dimension of the other spacers 73. As is well known, the following equation (1) holds between Young's modulus E, spring constant k, the thickness (front-to-back dimension) L of the spacer in the free state, and the cross-sectional area S of the cross section perpendicular to the front-to-back direction of the spacer. k=S×E÷L...Equation (1)

[0053] As described above, the central spacer 72 has the same configuration (material) as spacer 73, except that its thickness (front-to-back dimension L) is greater than that of spacer 73. Therefore, the spring constant (k) of the central spacer 72 in the front-to-back direction is smaller than that of spacer 73. In other words, the spring constant of the central spacer 72 is the smallest among all spacers 72 and 73. The spring constants of each spacer 73 are the same as those of the other spacers 73.

[0054] (Mechanism of action and effect) Next, the operation and effects of the second embodiment will be described.

[0055] For example, when each battery cell 43 of the battery module 70 is charged, the front plate 45 and rear plate 46 of the cell case 44 of each battery cell 43 bulge. As a result of this bulging, a force in the front-to-back direction is exerted between the adjacent spacers 72, 73 and the front plate 45 and rear plate 46 of the cell case 44.

[0056] Incidentally, the Young's modulus of spacers 72 and 73 in the front-to-back direction is smaller than that of the cell case 44. Furthermore, as shown in Figure 5(a), the front-to-back dimension (thickness) of the central spacer 72 is the thickest. In other words, the spring constant of the central spacer 72 in the front-to-back direction is the smallest among all the spacers 52 and 53. Therefore, for example, when each battery cell 43 (front plate portion 45, rear plate portion 46) expands in the front-to-back direction due to charging, as shown in Figure 5(b), the two battery cells 43-6 and 43-7 that are in contact with the central spacer 72 move toward the central spacer 72, and the amount of front-to-back movement of the neutral battery cells 43-5 and 43-8, which are predetermined battery cells located on the end side of the battery module 70, respectively, becomes substantially zero.

[0057] Furthermore, the amount of movement in the front-to-back direction of the battery cell 43 located closer to the end of the battery module 70 than the neutral battery cells 43-5 and 43-8 is smaller compared to the case where the spring constant of the central spacer 72 is not the smallest among all the spacers 72 and 73.

[0058] Therefore, when considering the battery module 70 as a whole, the amount of movement of the battery cell group 43 in the front-to-back direction is reduced. Furthermore, the amount of movement of battery cells 43-1 and 43-12, which tend to have the largest amount of movement in the front-to-back direction among the battery cells 43, is reduced. As a result, the battery pack 20 of this embodiment can suppress the separation of each cell case 44 from the thermal conductive material 60 when the cell case 44 of each battery cell 43 expands in the front-to-back direction.

[0059] Furthermore, since all spacers 72 and 73 have the same Young's modulus and all spacers 73 except the central spacer 72 have the same spring constant, the battery pack 20 can be manufactured at a lower cost and assembled more easily compared to cases where all spacers 72 and 73 have different Young's moduli or where the spring constants of each spacer 73 are different.

[0060] Next, a third embodiment of the present invention will be described with reference to Figures 6 and 7. Note that the same reference numerals will be used for the same components as in the first embodiment, and their detailed descriptions will be omitted.

[0061] The battery pack 20 of the third embodiment differs from that of the first embodiment in the configuration of the battery module. More specifically, the configuration of the spacers differs from that of the first embodiment.

[0062] As shown in Figure 6, thirteen spacers 82 and 83 are provided between adjacent battery cells 43 (cell cases 44). The spacers 82 and 83 are integrally molded from resin, and each spacer 82 and 83 has the same approximately rectangular parallelepiped shape. The left-right width and top-down dimensions of the spacers 82 and 83 are approximately the same as those of the battery cells 43, while the front-to-back dimensions of the spacers 82 and 83 are smaller than those of the cell cases 44. As shown in Figure 6, each spacer 82 and 83 contacts the front plate portion 45 and the rear plate portion 46 of the cell case 44 of the battery cell 43, respectively. In the following description, the spacer 82 that contacts battery cells 43-6 and 43-7 may be referred to as the central spacer 82. When it is not necessary to explain the central spacer 82 and spacers 83 individually, the central spacer 82 will be collectively referred to as spacer 82.

[0063] The Young's modulus of the resin material constituting the central spacer 82 is smaller than that of the resin material constituting the spacer 83 and the Young's modulus of the cell case 44. Furthermore, as shown in Figure 7(a), the Young's modulus of each spacer 83 gradually increases from the center (central spacer 82) towards the end of the battery module 80. That is, the Young's modulus of spacers 82 and 83 gradually decreases from the end of the battery module 80 towards the center (central spacer 82). The Young's modulus of spacer 83 is smaller than that of the cell case 44.

[0064] (Mechanism of action and effect) Next, the operation and effects of the third embodiment will be described.

[0065] For example, when each battery cell 43 of the battery module 80 is charged, the front plate 45 and rear plate 46 of the cell case 44 of each battery cell 43 bulge. As a result of this bulging, a force in the front-to-back direction (first direction) is exerted between the adjacent spacers 82, 83 and the front plate 45 and rear plate 46 of the cell case 44.

[0066] Incidentally, the Young's modulus of spacers 82 and 83 in the front-to-back direction is smaller than that of the cell case 44. Furthermore, as shown in Figure 7(a), the Young's modulus of spacers 82 and 83 gradually decreases as you move from the end side of the battery module 80 towards the center (central spacer 82). Therefore, for example, when each battery cell 43 (front plate portion 45, rear plate portion 46) expands in the front-to-back direction due to charging, as shown in Figure 7(b), the two battery cells 43-6 and 43-7 that are in contact with the central spacer 82, and the two battery cells 43-5 and 43-8 adjacent to them move towards the central spacer 82, and the amount of front-to-back movement of the neutral battery cells 43-4 and 43-9, which are predetermined battery cells located closer to the ends of the battery module 80 than these four battery cells 43-5, 43-6, 43-7, and 43-8, can become substantially zero.

[0067] Furthermore, the amount of movement in the front-to-back direction of the battery cell 43 located closer to the end of the battery module 80 than the neutral battery cells 43-4 and 43-9 is smaller compared to the case where the Young's modulus of the spacers 83, excluding the central spacer 82, is the same.

[0068] Therefore, when considering the battery module 80 as a whole, the amount of movement of the battery cell group 43 in the front-to-back direction tends to be smaller than in the first and second embodiments. Furthermore, the amount of movement of battery cells 43-1 and 43-12, which tend to have the largest amount of movement in the front-to-back direction among the battery cells 43, tends to be smaller than in the first and second embodiments. As a result, the battery pack 20 of this embodiment can more effectively suppress the peeling of each cell case 44 from the thermal conductive material 60 when the cell case 44 of each battery cell 43 expands in the front-to-back direction.

[0069] Although battery packs according to each embodiment have been described above, these can be modified as appropriate without departing from the spirit of the present invention.

[0070] For example, the material (Young's modulus) of all spacers may be the same, the spring constant of the central spacer may be made the smallest among all spacers, and the spring constants of the spacers other than the central spacer may gradually decrease as they move from the end of the battery molding towards the central spacer. This modified battery module can exhibit the same effects as the third embodiment.

[0071] The battery module can contain any number of battery cells, as long as there are multiple cells. However, if the number of battery cells is odd, the number of central spacers will be two.

[0072] The vehicle may be an electric vehicle that is different from an electric vehicle and is equipped with an electric motor that utilizes power from a battery pack. For example, the vehicle may be a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV). [Explanation of Symbols]

[0073] 20 battery packs 24 Lower case (heat dissipation component) 43 battery cells 44-cell case 52 Spacer (Center Spacer) 53 Spacer 55 Restraining member 60 Thermal conductive material 72 Spacer (Center Spacer) 73 Spacers 80 Battery Modules 82 Spacer (Center Spacer) 83 Spacer

Claims

1. Multiple battery cells having cell cases arranged in a first direction, Multiple spacers are provided between adjacent battery cells, A restraining member that restrains the battery cells and the spacers so as to bring adjacent battery cells and the spacers into contact, The cell case and the heat dissipation member facing the second direction perpendicular to the first direction, A thermal conductive material is bonded to the cell case and the heat dissipation member to connect the cell case and the heat dissipation member, Equipped with, The Young's modulus of the central spacer, which is located in the center in the first direction, is the smallest among all the spacers in the first direction, or the spring constant of the central spacer in the first direction is the smallest among all the spacers. A battery pack in which the Young's modulus of the spacer is smaller than that of the cell case.

2. All of the aforementioned spacers have the same shape, The Young's modulus of the central spacer is the smallest among all the spacers. The battery pack according to claim 1, wherein the Young's modulus of the spacers, excluding the central spacer, is the same.

3. All of the aforementioned spacers have the same shape, The Young's modulus of the central spacer is the smallest among all the spacers. The battery pack according to claim 1, wherein the Young's modulus of the spacers, excluding the central spacer, gradually decreases as you move from the end side in the first direction toward the central spacer side.

4. The Young's modulus of all the spacers is the same, The spring constant of the central spacer is the smallest among all the spacers. The battery pack according to claim 1, wherein the spring constants of the spacers, excluding the central spacer, are the same.

5. The Young's modulus of all the spacers is the same, The spring constant of the central spacer is the smallest among all the spacers. The battery pack according to claim 1, wherein the spring constant of the spacers, excluding the central spacer, gradually decreases as you move from the end in the first direction toward the central spacer.

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