Battery modules and battery packs

Abstract

To obtain a battery module and a battery pack capable of absorbing the thermal expansion of a battery cell.SOLUTION: A battery module 11 includes a plurality of battery cells 20 arranged inside a housing, and buffer members 32, 34 arranged between adjacent battery cells 20 and at least one of the battery cells 20, with the arrangement direction of the battery cells 20 as the thickness direction, and are formed such that the reaction force acting on the battery cells 20 is smaller at the centers 32A, 34A than the peripheral ends 32B, 34B.SELECTED DRAWING: Figure 7

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a battery pack in which heat insulation buffer members are arranged between stacked battery cells. In the battery pack described in Patent Document 1, by arranging heat insulation buffer members between the battery cells, it is possible to prevent the battery cells from directly rubbing against each other during transportation of the product, and it is also possible to achieve thermal insulation between the battery cells.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in order to improve the power storage amount per unit area of the battery module, it is necessary to arrange the battery cells without gaps. However, in the battery pack described in Patent Document 1, the thermal expansion of the battery cells cannot be absorbed. In particular, when the battery cells thermally expand, the central portion bulges in the thickness direction. However, in the battery pack described in Patent Document 1, such thermal expansion of the battery cells is not considered, and there is room for improvement.

[0005] In consideration of the above facts, an object of the present invention is to obtain a battery module and a battery pack that can absorb the thermal expansion of battery cells.

Means for Solving the Problems

[0006] The battery module according to claim 1 includes a plurality of battery cells housed in an arranged state inside a housing, and with the arrangement direction of the battery cells as the thickness direction ,beforeThe battery cell and the inner wall of the housing in between A buffer member is positioned such that the reaction force acting on the battery cell is smaller in the central part than at the peripheral edges, A central thick-walled buffer member is positioned in the central part of the housing in the direction of arrangement of the battery cells, and its thickness is gradually increased from the peripheral edge to the central part. It has.

[0007] In the battery module according to claim 1, a plurality of battery cells are housed in an arranged state inside the housing. Furthermore, a buffer member is placed between adjacent battery cells and between a battery cell and the inner wall of the housing at least in one of these locations. Here, the buffer member is oriented with the arrangement direction of the battery cells in the thickness direction, and is formed such that the reaction force acting on the battery cells is smaller in the central part of the buffer member than at the peripheral edges. As a result, when a battery cell expands due to thermal expansion and the central part of the battery cell bulges out, the reaction force acting on the battery cell from the buffer member can be made substantially uniform between the central part and the peripheral edges, and the thermal expansion of the battery cell can be absorbed by the buffer member. Furthermore, by placing cushioning material between the inner walls on both sides of the housing and the battery cells, the reaction force acting from the inner walls of the housing to the battery cells can be reduced. Furthermore, a central thick-walled buffer member positioned in the center of the battery cell arrangement curves the central portion of the battery cell. This allows the terminals extending from the ends of the battery cell to bend towards the center in the battery cell arrangement direction, thereby suppressing stress concentration at the terminals.

[0010] Claim 2 In the battery module relating to claim 1, the buffer member is formed to be thinner in the central part than at the peripheral ends.

[0011] Claim 2 In the battery module relating to this, by making the thickness of the central part of the buffer member thinner than the peripheral part, the reaction force acting on the battery cell from the central part of the buffer member can be made smaller than the reaction force acting on the battery cell from the peripheral part of the buffer member.

[0012] Claim 3 In the battery module relating to claim 1, the buffer member is formed with a lower density in the central part than in the peripheral part.

[0013] Claim 3 In the battery module relating to this, by making the density of the central part of the buffering member smaller than that of the peripheral parts, the reaction force acting on the battery cell from the central part of the buffering member can be made smaller than the reaction force acting on the battery cell from the peripheral parts of the buffering member.

[0018] Claim 4 The battery pack according to Claim 3 includes a plurality of battery modules according to any one of Claims 1 to

[0019] Claim 4 In the battery pack according to Claim By absorbing the thermal expansion of the battery cells in a plurality of battery modules, the reliability of the entire battery pack can be improved.

[0020] As described above, according to the battery module and the battery pack according to the present invention, the thermal expansion of the battery cells can be absorbed.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic plan view showing a main part of a vehicle to which the battery pack according to the first embodiment is applied. [Figure 2] It is a schematic perspective view of a battery module. [Figure 3] It is a plan view of the battery module with the upper lid removed. [Figure 4] It is a schematic view of the battery cells housed in the battery module as viewed from the thickness direction. [Figure 5] It is a schematic perspective view showing a main part of the battery module in the first embodiment. [Figure 6] It is a schematic view of the buffer member in the first embodiment as viewed from the thickness direction. [Figure 7] It is a schematic plan view of the battery cells and the buffer member in the first embodiment. [Figure 8] It is a diagram schematically showing the state in which the battery cells have thermally expanded from the state of FIG. 7. [Figure 9] It is a schematic plan view of the battery cells and the buffer member in the second embodiment. [Figure 10] It is a diagram schematically showing the state in which the battery cells have thermally expanded from the state of FIG. 9.

Modes for Carrying Out the Invention

[0022] <First Embodiment> The battery pack 10 and battery module 11 according to the first embodiment will be described with reference to the drawings.

[0023] (Overall configuration of vehicle 100) Figure 1 is a schematic plan view showing the main parts of a vehicle 100 to which the battery pack 10 according to the embodiment is applied. As shown in Figure 1, the vehicle 100 is a battery electric vehicle (BEV) with the battery pack 10 mounted under the floor. In each figure, the arrows UP, FR, and LH indicate the upper side in the vertical direction of the vehicle, the front side in the longitudinal direction of the vehicle, and the left side in the vehicle width direction, respectively. When describing using the directions of front, rear, left, right, up, and down, unless otherwise specified, they refer to the front and rear in the longitudinal direction of the vehicle, the left and right in the vehicle width direction, and the up and down in the vehicle vertical direction.

[0024] In this embodiment, the vehicle 100, as an example, has a DC / DC converter 102, an electric compressor 104, and a PTC (Positive Temperature Coefficient) heater 106 positioned in front of the battery pack 10. The motor 108, gearbox 110, inverter 112, and charger 114 are positioned behind the battery pack 10.

[0025] The DC current output from the battery pack 10 is voltage-adjusted by the DC / DC converter 102 and then supplied to the electric compressor 104, PTC heater 106, inverter 112, etc. Power is also supplied to the motor 108 via the inverter 112, causing the rear wheels to rotate and the vehicle 100 to move.

[0026] A charging port 116 is provided on the right side of the rear of the vehicle 100. By connecting a charging plug from an external charging device (not shown) to the charging port 116, power can be stored in the battery pack 10 via the onboard charger 114.

[0027] The arrangement and structure of the components constituting the vehicle 100 are not limited to the configuration described above. For example, it may be applied to a hybrid vehicle (HV) or a plug-in hybrid electric vehicle (PHEV) equipped with an engine. In this embodiment, the motor 108 is mounted at the rear of the vehicle and it is a rear-wheel drive vehicle, but it is not limited to this, and it may be a front-wheel drive vehicle with the motor 108 mounted at the front of the vehicle, or a pair of motors 108 may be mounted at the front and rear of the vehicle. Furthermore, it may be a vehicle equipped with in-wheel motors for each wheel.

[0028] Here, the battery pack 10 is composed of multiple battery modules 11. In this embodiment, as an example, 10 battery modules 11 are provided. Specifically, 5 battery modules 11 are arranged in the longitudinal direction of the vehicle on the right side of the vehicle 100, and 5 battery modules 11 are arranged in the longitudinal direction of the vehicle on the left side of the vehicle 100. Furthermore, each battery module 11 is electrically connected.

[0029] Figure 2 is a schematic perspective view of the battery module 11. As shown in Figure 2, the battery module 11 is formed in a roughly rectangular parallelepiped shape with the vehicle width direction as the longitudinal direction. The outer shell of the battery module 11 is made of aluminum alloy. For example, the outer shell of the battery module 11 is formed by joining aluminum die-cast parts to both ends of an aluminum alloy extruded material by laser welding or the like.

[0030] A pair of voltage terminals 12 and a connector 14 are provided at both ends of the battery module 11 in the vehicle width direction. A flexible printed circuit board 21, which will be described later, is connected to the connector 14. In addition, busbars (not shown) are welded to both ends of the battery module 11 in the vehicle width direction.

[0031] The length MW of the battery module 11 in the vehicle width direction is, for example, 350 mm to 600 mm, the length ML in the vehicle longitudinal direction is, for example, 150 mm to 250 mm, and the height MH in the vehicle vertical direction is, for example, 80 mm to 110 mm.

[0032] Figure 3 is a plan view of the battery module 11 with the top cover removed. As shown in Figure 3, multiple battery cells 20 are housed inside the battery module 11 in an arranged state. In this embodiment, as an example, 24 battery cells 20 are arranged in the front-rear direction of the vehicle and bonded to each other.

[0033] A flexible printed circuit board (FPC) 21 is placed on top of the battery cell 20. The flexible printed circuit board 21 is formed in a strip shape with the vehicle width direction as its longitudinal direction, and thermistors 23 are provided at both ends of the flexible printed circuit board 21. The thermistors 23 are not bonded to the battery cell 20, but are pressed toward the battery cell 20 by the upper cover of the battery module 11.

[0034] Figure 4 is a schematic view of a battery cell 20 housed in a battery module 11, viewed from the thickness direction. As shown in Figure 4, the battery cell 20 is formed in a roughly rectangular plate shape, and an electrode body (not shown) is housed inside. The electrode body is composed of a positive electrode, a negative electrode, and a separator stacked together, and is sealed with a laminate film 22.

[0035] In this embodiment, as an example, the electrode housing is formed by folding and bonding an embossed sheet-like laminate film 22. While both a single-cup embossed structure (with one embossed area) and a double-cup embossed structure (with two embossed areas) can be employed, this embodiment uses a single-cup embossed structure with a fold depth of approximately 8mm to 10mm.

[0036] The upper ends of both longitudinal ends of the battery cell 20 are bent, and the corners form the outer shape. In addition, the upper end of the battery cell 20 is bent, and a fixing tape 24 is wrapped around the upper end of the battery cell 20 along the longitudinal direction.

[0037] Here, terminals (tabs) 26 are provided at both longitudinal ends of the battery cell 20. In this embodiment, as an example, the terminals 26 are provided at a position offset below the vertical center of the battery cell 20. The terminals 26 are joined to a busbar (not shown) by laser welding or the like.

[0038] The length CW1 of the battery cell 20 in the vehicle width direction is, for example, 530mm~600mm, 600mm~700mm, 700mm~800mm, 800~900mm, and 1000mm or more. The length CW2 of the area where the electrode body is housed is, for example, 500mm~520mm, 600mm~700mm, 700mm~800mm, 800~900mm, and 1000mm or more. The height CH of the battery cell 20 is, for example, 80mm~110mm and 110mm~140mm. The thickness of the battery cell 20 is 5.0mm~7.0mm, 7.0mm~9.0mm, and 9.0mm~11.0mm. The height TH of the terminal 26 is 40mm~50mm, 50mm~60mm, and 60mm~70mm.

[0039] (cushioning members 32, 34) Figure 5 is a schematic perspective view showing the main parts of the battery module 11 in the embodiment. As shown in Figure 5, the 24 battery cells 20 are housed without gaps in the module case 30, which is the housing that constitutes the battery module 11, arranged in the longitudinal direction of the vehicle.

[0040] Furthermore, one or more cushioning materials are housed inside the module case 30. In this embodiment, as an example, a total of three cushioning materials, one cushioning member 32 and two cushioning members 34, are housed inside the module case 30.

[0041] The cushioning member 32 is positioned between adjacent battery cells 20, with the thickness direction being the same as the arrangement direction of the battery cells 20 (vehicle longitudinal direction), and is formed from an elastically deformable thin plate-like member. In particular, the cushioning member 32 is positioned in the central part of the module case 30 in the vehicle longitudinal direction. In this embodiment, as an example, 12 battery cells 20 are arranged on the vehicle longitudinal side of the cushioning member 32, and 12 battery cells 20 are arranged on the vehicle longitudinal side of the cushioning member 32. Therefore, the cushioning member 32 is positioned to equally divide the arranged plurality of battery cells 20.

[0042] Figure 6 is a schematic diagram of the buffer member 32 in the embodiment, viewed from the thickness direction. Figure 7 is a schematic plan view of the battery cell 20 and buffer members 32 and 34 in the embodiment. As shown in Figures 6 and 7, the buffer member 32 in this embodiment is formed with a thinner thickness in the central part 32A than in the peripheral part 32B. In other words, the buffer member 32 is formed such that the reaction force acting on the battery cell 20 is smaller in the central part 32A than in the peripheral part 32B. Note that in Figure 7, for the sake of explanation, the longitudinal lengths of the battery cell 20, buffer member 32, and buffer member 34 are shown to be shorter than they actually are, and do not reflect the relationship between thickness and length. The same applies to Figures 8 to 10, which will be described later.

[0043] In this embodiment, the cushioning member 32 is formed, for example, with the central portion 32A having a roughly oval shape when viewed from the thickness direction, and the thickness gradually decreasing towards the center. However, it is not limited to this, and the central portion 32A may also be roughly rectangular or elliptical when viewed from the thickness direction. Furthermore, although the outer shape of the cushioning member 32 is formed to be roughly rectangular when viewed from the thickness direction, it is not limited to this, and may also be formed to be roughly oval with rounded corners.

[0044] Here, the central portion 32A of the buffer member 32 is the region between the virtual lines L1 and L2 in Figure 7. In the battery cell 20, the region between the virtual lines L1 and L2 corresponds to the active material coated region where the electrode active material is applied.

[0045] As shown in Figure 5, the two buffer members 34 are positioned between the battery cells 20 and the inner walls of the front and rear side walls 30A of the module case 30, with the thickness direction of the battery cells 20 being the same as the arrangement direction of the battery cells 20 (vehicle longitudinal direction). Therefore, one surface of the buffer member 34 is in close contact with the battery cells 20, and the other surface of the buffer member 34 is in close contact with the side wall 30A.

[0046] The cushioning member 34 has substantially the same external shape as the cushioning member 32. That is, the cushioning member 34 in this embodiment is formed in a substantially rectangular shape when viewed in the thickness direction. Also, as shown in Figure 7, the cushioning member 34 is formed so that the thickness of the central part 34A is thinner than that of the peripheral part 34B. In other words, the cushioning member 34 is formed so that the reaction force acting on the battery cell 20 is smaller in the central part 34A than in the peripheral part 34B.

[0047] The cushioning member 34, located at the front of the vehicle, has a central portion 34A on the rear side of the vehicle, i.e., the side adjacent to the battery cell 20, that is recessed toward the front of the vehicle, and is formed in a shape in which the thickness gradually decreases toward the center. In addition, the front side of the cushioning member 34 is formed in a substantially flat shape along the inner wall (not shown) of the module case 30.

[0048] On the other hand, the cushioning member 34 located at the rear of the vehicle has a shape that is symmetrical to the cushioning member 34 located at the front of the vehicle. That is, the cushioning member 34 located at the rear of the vehicle has a central portion 34A on the front side of the vehicle, i.e., the side adjacent to the battery cell 20, that is recessed towards the rear of the vehicle, and is formed in a shape that gradually becomes thinner towards the center. In addition, the front side of the cushioning member 34 is formed in a substantially flat shape along the inner wall (not shown) of the module case 30. Note that in Figure 7, for the sake of explanation, the difference in thickness between the central portion 32A and the peripheral portion 32B of the cushioning member 32, and the difference in thickness between the central portion 34A and the peripheral portion 34B of the cushioning member 34 are exaggerated. In reality, there is no or almost no gap between the central portion 32A of the cushioning member 32 and the battery cell 20. Similarly, in reality, there is no or almost no gap between the central portion 34A of the cushioning member 34 and the battery cell 20.

[0049] Figure 8 schematically shows the state in which the battery cell 20, buffer member 32, and buffer member 34 are housed in the module case 30 and the battery cell 20 has undergone thermal expansion. As shown in Figure 8, the battery cell 20 expands due to repeated charging and discharging. In particular, the active material coated area of ​​the battery cell 20 expands due to thermal expansion, causing the central part of the battery cell 20 to bulge outwards.

[0050] In this embodiment, because the central portion 32A of the buffer member 32 is thin, the central portion of the battery cell 20 fits into this thinned portion, making the reaction force acting from the buffer member 32 to the battery cell 20 roughly equal in the central portion and the peripheral portion. Similarly, because the central portion 34A of the buffer member 34 is thin, the central portion of the battery cell 20 fits into this thinned portion, making the reaction force acting from the buffer member 34 to the battery cell 20 roughly equal in the central portion and the peripheral portion.

[0051] (action) Next, the operation of the battery module 11 and battery pack 10 according to this embodiment will be described.

[0052] In the battery module 11 according to this embodiment, a plurality of battery cells 20 are housed in an arrangement inside the module case 30. In addition, a buffer member 32 is placed between adjacent battery cells 20, and a buffer member 34 is placed between the battery cells 20 and the inner wall of the module case 30.

[0053] Here, the buffer members 32 and 34 are oriented with the battery cell arrangement direction in the thickness direction, and are formed such that the reaction force acting on the battery cell 20 is smaller in the central portions 32A and 34A than in the peripheral portions 32B and 34B of each buffer member 32 and 34. As a result, when the battery cell 20 expands due to thermal expansion and the central portion of the battery cell 20 bulges out, the reaction force acting on the battery cell 20 from the buffer members 32 and 34 can be made substantially uniform between the central portion and the peripheral portion, and the thermal expansion of the battery cell 20 can be absorbed by the buffer members 32 and 34.

[0054] Furthermore, because the thermal expansion of the battery cells 20 causes the greatest stress to act on the central part of the battery module 11 in the front-to-back direction, placing the buffer member 32 in this central part of the battery module 11 allows the entire battery module 11 to effectively absorb the thermal expansion of the battery cells 20.

[0055] Furthermore, in this embodiment, by making the thickness of the central portions 32A and 34A of the cushioning members 32 and 34 thinner than the peripheral portions 32B and 34B, the reaction force acting from the peripheral portions 32B and 34B of the cushioning members 32 and 34 to the battery cell 20 can be made smaller than the reaction force acting from the peripheral portions 32B and 34B of the cushioning members 32 and 34 to the battery cell 20.

[0056] Furthermore, in this embodiment, by arranging a buffer member 34 between the inner walls of the side walls 30A on both sides of the module case 30 and the battery cell 20, the reaction force acting from the inner wall of the module case 30 to the battery cell 20 can be reduced.

[0057] <Second Embodiment> Next, the battery module 50 according to the second embodiment will be described with reference to the drawings. Components similar to those in the first embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0058] Figure 9 is a schematic plan view of the battery cell and buffer member in the second embodiment. As shown in Figure 9, the battery module 50 of this embodiment has the same structure as the first embodiment, except for the central thick buffer member 52.

[0059] The central thick-walled buffer member 52 is positioned in the central part of the battery module 50 in the direction of the arrangement of the battery cells 20, with the arrangement direction of the battery cells 20 being the thickness direction. Furthermore, the central thick-walled buffer member 52 is formed in a substantially rectangular shape when viewed from the thickness direction.

[0060] In this embodiment, the central thick-walled buffer member 52 is formed with a greater thickness in the central portion 52A than in the peripheral portion 52B.

[0061] (action) Next, the operation of the battery module 50 according to this embodiment will be explained.

[0062] Figure 10 schematically shows the state in which the battery cell 20 has undergone thermal expansion from the state shown in Figure 9. As shown in Figure 10, in this embodiment, the thermal expansion of the battery cell 20 is absorbed by the buffer members 34 arranged on both the front and rear sides of the battery module 50.

[0063] Furthermore, the central thick cushioning member 52 positioned in the center of the vehicle in the longitudinal direction causes the central portion of the battery cell 20 to curve. This allows the terminals 26 extending from the ends of the battery cell 20 to be bent towards the center in the direction of the battery cell arrangement, thereby suppressing stress concentration on the terminals 26.

[0064] In other words, if only terminal 26 is bent, stress will concentrate at the base of terminal 26, potentially damaging it. However, by curving the battery cell 20 itself, as in this embodiment, the concentration of stress at the base of terminal 26 can be suppressed. Other functions are the same as in the first embodiment.

[0065] Although the battery pack 10 and battery module 11 according to this embodiment have been described above, the invention is not limited thereto and can be implemented in various forms without departing from the spirit of the present invention. For example, in the first embodiment described above, as shown in Figure 7, the cushioning members 32 and 34 are shaped so that their thickness gradually decreases from the peripheral ends 32B and 34B toward the central parts 32A and 34A, but the invention is not limited thereto. For example, they may be shaped so that their thickness decreases in a stepped manner.

[0066] Furthermore, although the central portions 32A and 34A of the buffer members 32 and 34 are formed to be thinner than the peripheral portions 32B and 34B, the buffer members are not limited to this. In other embodiments, buffer members may be used in which the density of the central portion is lower than that of the peripheral portions. For example, when the buffer member is formed from foamed resin, the amount of foaming can be controlled to form a buffer member in which the density of the central portion is lower than that of the peripheral portions. By making the density of the central portion of the buffer member lower than that of the peripheral portions, the reaction force acting from the central portion of the buffer member to the battery cell can be made smaller than the reaction force acting from the peripheral portions of the buffer member to the battery cell. As a result, similar to the above embodiment, when the battery cell 20 undergoes thermal expansion, the reaction force acting from the buffer member to the battery cell 20 can be made substantially uniform between the central portion and the peripheral portions, and the effect of absorbing the thermal expansion of the battery cell 20 by the buffer member can be obtained.

[0067] Furthermore, materials with different elastic moduli may be used for the central part and the peripheral part of the cushioning member. Specifically, by using a material with a lower elastic moduli for the central part of the cushioning member than for the peripheral part, the reaction force acting from the central part of the cushioning member to the battery cell can be made smaller than the reaction force acting from the peripheral part of the cushioning member to the battery cell, similar to the embodiment described above.

[0068] The following additional information is disclosed regarding the above embodiment.

[0069] (Note 1) Multiple battery cells are housed in an arrangement inside the casing, A buffer member is provided, with the arrangement direction of the battery cells being the thickness direction, and is positioned between adjacent battery cells and between the battery cells and the inner wall of the housing, such that the reaction force acting on the battery cells is smaller in the central part than at the peripheral edges. A battery module having (Note 2) The battery module according to Appendix 1, wherein the buffer member is located at least in the central portion of the housing in the direction of arrangement of the battery cells. (Note 3) The battery module according to Appendix 1 or Appendix 2, wherein the buffer member is formed to be thinner in the central part than at the peripheral ends. (Note 4) The aforementioned buffer member is formed with a lower density in the central part than in the peripheral part, as described in any one of Appendix 1 to Appendix 3 of the battery module. (Note 5) The buffer member is disposed at least between the inner walls on both sides of the housing and the battery cell, as described in any one of Appendix 1 to Appendix 4 of the battery module. (Note 6) The battery module as described in Appendix 5, wherein a central thick-walled buffer member is arranged in the central portion of the housing in the direction of arrangement of the battery cells, the central portion being thicker than the peripheral edges. (Note 7) A battery pack comprising multiple battery modules as described in any one of the appendices 1 to 6. [Explanation of Symbols]

[0070] 10 battery packs 11.50 Battery Module 20 battery cells 30 Module Cases (Enclosures) 32,34 Cushioning material 32A,34A central part 32B,34B Peripheral end 52 Central thick cushioning member 52A Central part 52B Peripheral end

Claims

1. Multiple battery cells are housed in an arrangement inside the casing, A buffer member is disposed between the battery cells and the inner wall of the housing, with the arrangement direction of the battery cells being the thickness direction, and is formed such that the reaction force acting on the battery cells is smaller in the central part than at the peripheral edges. A central thick-walled buffer member is positioned in the central part of the housing in the direction of arrangement of the battery cells, and its thickness is gradually increased from the peripheral edge to the central part. A battery module having

2. The battery module according to claim 1, wherein the buffer member is formed to be thinner in the central part than at the peripheral ends.

3. The battery module according to claim 1, wherein the buffer member is formed with a lower density in the central part than in the peripheral part.

4. A battery pack comprising a plurality of battery modules as described in any one of claims 1 to 3.

Images