Battery pack

Abstract

This battery pack comprises: a pressing member having a rod-shaped portion and configured to be movable in the axial direction of the rod-shaped portion; a first laminated body configured to include a plurality of first cells of a first type that expand during charging, the first cells being stacked in the axial direction; a second laminated body configured to include a plurality of second cells of a second type that expand during discharging, the second cells being stacked in the axial direction; a first case that houses the first laminated body; and a second case that houses the second laminated body. A first end portion of the pressing member in the axial direction is located inside the first case and is in contact with a first side surface on one side in the axial direction of the first laminated body, and a second end portion of the pressing member opposite to the first end portion is located inside the second case and is in contact with a second side surface on one side in the axial direction of the second laminated body, the second side surface facing the first side surface.

Description

Battery pack

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

[0002] For example, Patent Document 1 discloses a battery module in which a laminate in which a plurality of cells are laminated is constrained by an end plate and a side plate. In such Patent Document 1, a displacement adjusting member including an elastic body is provided between an end portion of the laminate and the end plate.

[0003] Japanese Patent Application Laid-Open No. 2019-128979

[0004] In recent years, various types of cells have been researched and developed. For example, the practical application of a battery module including a cell having excellent energy density is desired. Generally, a cell repeats expansion and contraction when charging and discharging are repeated, and when putting a battery module into practical use, it is desirable to appropriately manage the expansion and contraction of the cell.

[0005] Therefore, an object of the present invention is to provide a battery pack capable of appropriately managing the expansion and contraction of cells.

[0006] In order to solve the above problems, a battery pack according to an embodiment of the present invention includes a pressing member having a rod-shaped portion and configured to be movable in the axial direction of the rod-shaped portion, a first laminate formed by laminating a plurality of first cells of a first type that expand during charging in the axial direction, a second laminate formed by laminating a plurality of second cells of a second type that expand during discharging in the axial direction, a first case that houses the first laminate, and a second case that houses the second laminate. The first end portion of the pressing member in the axial direction is located inside the first case and abuts against one first side surface of the first laminate in the axial direction, and the second end portion of the pressing member opposite to the first end portion is located inside the second case and abuts against a side surface facing the first side surface and one second side surface of the second laminate in the axial direction.

[0007] According to the present invention, it becomes possible to appropriately manage the expansion and contraction of cells.

[0008] Figure 1 is a schematic diagram showing an example of the configuration of a battery pack according to the first embodiment. Figure 2 is a partially enlarged view showing an example of charging the first and second cells. Figure 3 is a partially enlarged view showing an example of discharging the first and second cells. Figure 4 is a schematic diagram showing an example of the configuration of a battery pack according to the second embodiment. Figure 5 is a partially enlarged view showing an example of charging the first and second cells in the second embodiment. Figure 6 is a partially enlarged view showing an example of discharging the first and second cells in the second embodiment.

[0009] Embodiments of the present invention will be described in detail below with reference to the attached drawings. The specific dimensions, materials, numerical values, etc., shown in these embodiments are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustrations.

[0010] (First Embodiment) Figure 1 is a schematic diagram showing an example of the configuration of a battery pack 1 according to the first embodiment. The battery pack 1 is mounted on a vehicle 2, for example. However, the battery pack 1 is not limited to being mounted on a vehicle 2, and may be mounted on various devices.

[0011] The battery pack 1 comprises a pack case 10, a first battery module 12, a second battery module 14, and a pressing member 16.

[0012] The pack case 10 has an internal space. The first battery module 12, the second battery module 14, and the pressing member 16 are housed inside the pack case 10.

[0013] In the example shown in Figure 1, four sets of battery modules are provided, each set consisting of one first battery module 12, one second battery module 14, and one pressing member 16. However, the number of such sets is not limited to four; it could be one, two, three, or five or more. The number of first battery modules 12, the number of second battery modules 14, and the number of pressing members 16 should all be the same.

[0014] The first battery module 12 has a first case 20 and a first stack 22. The first case 20 is formed, for example, in the shape of a rectangular parallelepiped and has space inside. The first stack 22 is housed inside the first case 20.

[0015] The first laminate 22 includes a plurality of first cells 24 of a first type that expand during charging. The first cells 24 may be, for example, a flat laminate cell structure.

[0016] The first cell 24 may be, for example, a lithium-ion battery. In a lithium-ion battery, a carbon material is used for the negative electrode, and a lithium-containing oxide, such as lithium cobalt oxide, is used for the positive electrode.

[0017] During charging, lithium-ion batteries undergo an intercalation reaction in which lithium ions are inserted into the gaps in the carbon material of the negative electrode, causing the negative electrode to expand. As a result, lithium-ion batteries expand during charging. For example, the thickness of the flat first cell 24 increases.

[0018] Furthermore, during discharge, lithium-ion batteries cause the negative electrode to contract as lithium ions inserted into the gaps in the carbon material of the negative electrode are released. As a result, lithium-ion batteries contract during discharge.

[0019] The first cell 24 is not limited to a lithium-ion battery, but may be any cell that acts to expand during charging. For example, the first cell 24 may be a sodium-sulfur battery that is presumed to act to expand during charging. Alternatively, the first cell 24 may be a solid-state battery configured to expand during charging.

[0020] The first laminate 22 is composed of multiple first cells 24 stacked in the thickness direction of the first cells 24 (a direction perpendicular to the plane of the flat plate). For example, the multiple first cells 24 are stacked in the left-right direction indicated by arrow A10 in Figure 1.

[0021] As described above, since the first cell 24 expands in the thickness direction, the first laminate 22 expands and contracts along the stacking direction of the first cell 24 indicated by arrow A10.

[0022] The second battery module 14 has a second case 30 and a second stack 32. The second case 30 is formed, for example, in the shape of a rectangular parallelepiped and has space inside. The second stack 32 is housed inside the second case 30.

[0023] The second laminate 32 includes a plurality of second cells 34 of a second type that expand during discharge. The second cells 34 may be, for example, a flat laminate cell structure. The dimensions of the second cells 34 in a standard state that is not expanded or contracted may be substantially the same as the dimensions of the first cells 24 in that standard state.

[0024] The second cell 34 may be, for example, a lithium-sulfur battery. In a lithium-sulfur battery, the alkali metal lithium (Li) is used for the negative electrode and sulfur (S) is used for the positive electrode.

[0025] In lithium-sulfur batteries, during discharge, the sulfur at the positive electrode reacts with lithium ions to produce lithium sulfide (Li ２ S) is generated. Because the density of lithium sulfide is greater than the density of sulfur, it acts to cause the positive electrode to expand during discharge. As a result, the lithium-sulfur battery acts to expand during discharge. For example, it acts to cause the thickness of the flat second cell 34 to expand.

[0026] Furthermore, in lithium-sulfur batteries, during charging, sulfur and lithium ions are generated from lithium sulfide at the positive electrode. Since the density of sulfur is lower than the density of lithium sulfide, it acts to cause the positive electrode to contract during charging. As a result, lithium-sulfur batteries act to contract during charging.

[0027] The second cell 34 is not limited to a lithium-sulfur battery; it may be any cell that expands during discharge. For example, the second cell 34 may be an all-solid-state battery configured to expand during discharge.

[0028] The second laminate 32 is composed of a plurality of second cells 34 stacked in the thickness direction of the second cells 34. For example, the plurality of second cells 34 are stacked in the left-right direction in Figure 1. The stacking direction of the plurality of second cells 34 is substantially the same as the stacking direction of the plurality of first cells 24.

[0029] As described above, since the second cell 34 expands in the thickness direction, the second laminate 32 expands and contracts along the stacking direction of the second cell 34 indicated by arrow A10.

[0030] For the sake of clarity, the first cell 24 and the second cell 34 may be collectively referred to simply as "cells" without distinction. The first laminate 22 and the second laminate 32 may be collectively referred to simply as "laminated structures" without distinction. The first case 20 and the second case 30 may be collectively referred to simply as "cases" without distinction.

[0031] The first battery module 12 and the second battery module 14 are arranged facing each other such that the first stack 22 and the second stack 32 are aligned in a straight line in the stacking direction (direction of arrow A10 in Figure 1).

[0032] The pressing member 16 is provided between the first battery module 12 and the second battery module 14. The pressing member 16 has a rod-shaped portion 40, a first end portion 42, and a second end portion 44.

[0033] The rod-shaped portion 40 is formed in the shape of a rod extending in the axial direction. The rod-shaped portion 40 may be formed in the shape of a cylinder or a cylindrical shape. The cross-sectional shape of the rod-shaped portion 40 perpendicular to the axial direction is equal along the axial direction. The rod-shaped portion 40 is made of, for example, a metal material.

[0034] The rod-shaped portion 40 is positioned between the first laminate 22 and the second laminate 32 in such a orientation that the axial direction of the rod-shaped portion 40 is substantially the same as the stacking direction of the first laminate 22 and the second laminate 32. In other words, the plurality of first cells 24 of the first laminate 22 and the plurality of second cells 34 of the second laminate 32 are stacked in the axial direction of the rod-shaped portion 40.

[0035] A first communication hole 50 is provided on the side of the first case 20 facing the second battery module 14, which connects the inside and outside of the first case 20. A second communication hole 52 is provided on the side of the second case 30 facing the first battery module 12, which connects the inside and outside of the second case 30.

[0036] The first communication hole 50 and the second communication hole 52 are formed, for example, in a circular shape. The inner diameter of the first communication hole 50 and the inner diameter of the second communication hole 52 are substantially equal. The inner diameters of the first communication hole 50 and the inner diameters of the second communication hole 52 are larger than the outer diameter of the rod-shaped portion 40 of the pressing member 16 by a predetermined clearance. The first communication hole 50 and the second communication hole 52 are provided such that the central axis of the first communication hole 50 and the central axis of the second communication hole 52 are substantially aligned in the same straight line.

[0037] The rod-shaped portion 40 is inserted into the first communication hole 50 and also into the second communication hole 52. The rod-shaped portion 40 is supported so as to be movable in the axial direction by the first communication hole 50 and the second communication hole 52. In other words, the pressing member 16 is configured to be movable in the axial direction (in the direction of arrow A10 in Figure 1).

[0038] The first end portion 42 is provided at one axial end of the rod-shaped portion 40. The first end portion 42 is located inside the first case 20. The first end portion 42 is formed, for example, in a flat plate shape. The first end portion 42 has a planar first contact surface 60 on the side opposite to the surface connected to the rod-shaped portion 40.

[0039] The first abutting surface 60 abuts against one first side surface 70 in the stacking direction of the first laminate 22 (in other words, the axial direction of the rod-shaped portion 40). More specifically, the first abutting surface 60 abuts against the first cell 24 located at one end in the axial direction of the rod-shaped portion 40 among the plurality of first cells 24.

[0040] At least the first abutting surface 60 of the first end portion 42 is made of an insulating material. The insulating material may be, for example, a thermosetting resin such as an epoxy resin.

[0041] The pressing member 16 and the first cell 24 contact each other via the insulating first abutting surface 60. Thereby, the pressing member 16 can be insulated from the first cell 24, and the safety of the battery pack 1 can be improved.

[0042] In addition to the first abutting surface 60, other side surfaces of the first end portion 42 may be made of an insulating material, or the entire first end portion 42 may be made of an insulating material.

[0043] The side surface opposite to the first side surface 70 where the first end portion 42 in the first laminate 22 abuts is supported by the inner surface of the first case 20. An insulating sheet or the like may be provided between the side surface of the first laminate 22 and the inner surface of the first case 20.

[0044] The second end portion 44 is provided at the other end in the axial direction of the rod-shaped portion 40. That is, the second end portion 44 is provided on the side opposite to the first end portion 42 in the rod-shaped portion 40. The second end portion 44 is located inside the second case 30. The second end portion 44 is formed in a flat plate shape, for example. The second end portion 44 has a flat second abutting surface 62 on the side opposite to the surface connected to the rod-shaped portion 40.

[0045] The second abutting surface 62 abuts against one second side surface 72 in the stacking direction of the second laminate 32 (in other words, the axial direction of the rod-shaped portion 40). The second side surface 72 of the second laminate 32 is the side surface facing the first side surface 70 of the first laminate 22. More specifically, the first abutting surface 60 abuts against the second cell 34 located at one end in the axial direction of the rod-shaped portion 40 among the plurality of second cells 34.

[0046] The second end portion 44 is configured such that at least the second contact surface 62 is made of an insulating material. The insulating material may be, for example, a thermosetting resin such as an epoxy resin.

[0047] The pressing member 16 and the second cell 34 are in contact with each other via the insulating second contact surface 62. Thereby, the pressing member 16 can be insulated from the second cell 34, and the safety of the battery pack 1 can be improved.

[0048] In addition to the second contact surface 62, other side surfaces of the second end portion 44 may be made of an insulating material, or the entire second end portion 44 may be made of an insulating material.

[0049] The side surface of the second laminate 32 opposite to the second side surface 72 against which the second end portion 44 abuts is supported by the inner surface of the second case 30. An insulating sheet or the like may be provided between the side surface of the second laminate 32 and the inner surface of the second case 30.

[0050] The length of the rod-shaped portion 40 may be set according to the relationship between the initial positions of the first end portion 4 at the initial position of the second end portion 44.

[0051] In the battery pack 1, when charging the plurality of first cells 24 of the first laminate 22, the plurality of second cells 34 of the second laminate 32 are also charged. In the battery pack 1, when discharging the plurality of first cells 24 of the first laminate 22, the plurality of second cells 34 of the second laminate 32 are also discharged.

[0052] FIG. 2 is a partially enlarged view showing an example when charging the first cell 24 and the second cell 34. When the first cell and the second cell 34 are charged, the first cell 24 expands and the second cell shrinks. In FIG. 2, by making the thickness of the first cell 24 larger than the thickness of the second cell 34, it is shown that the first cell 24 is expanded.

[0053] When the first cell 24 is charged, it expands, and the length of the first laminate 22 in the stacking direction becomes longer than before the expansion. As a result, the first laminate 22 presses the pressing member 16 toward the second battery module 14, as indicated by the white arrow A20.

[0054] Since the pressing member 16 is configured to be movable in the axial direction, it is slid by the first stack 22 toward the second battery module 14. At this time, the pressing member 16 presses the second side surface 72 of the second stack 32 in the stacking direction with its second end 44. As a result, a restraining force is applied to the second stack 32 from the first stack 22 via the pressing member 16 in a direction that causes the second stack 32 to contract along the stacking direction.

[0055] In other words, in the battery pack 1, the expansion force of the first cell 24 is used to apply a restraining force to the second cell 34.

[0056] Here, when the second cell 34 is charged and contracts, the length of the second laminate 32 in the stacking direction becomes shorter compared to when it was expanded. As a result, gaps are created between adjacent second cells 34 in the second laminate 32 compared to when the second cell 34 was expanded.

[0057] In the battery pack 1 of the first embodiment, when the second cell 34 contracts, a restraining force is applied to the second cell 34 by the expansion of the first cell 24.

[0058] Therefore, in the battery pack 1 of the first embodiment, it is possible to suppress the occurrence of gaps between adjacent second cells 34 caused by the contraction of the second cells 34. As a result, in the battery pack 1 of the first embodiment, the mechanical strength of the second laminate 32 during charging can be improved.

[0059] Furthermore, when the first cell 24 expands, the first end 42 of the pressing member 16 moves towards the second battery module 14 inside the first case 20. The first laminate 22 is capable of expanding until the first end 42 contacts the first case 20. That is, once the first end 42 of the first laminate 22 contacts the first case 20, further expansion of the first laminate 22 is suppressed.

[0060] Therefore, in the battery pack 1 of the first embodiment, it is possible to suppress excessive expansion of the first cell 24 of the first laminate 22.

[0061] Figure 3 is a partially enlarged view showing an example of the discharge of the first cell 24 and the second cell 34. When the first cell 24 and the second cell 34 are discharged, the first cell 24 contracts and the second cell 34 expands. In Figure 3, the expansion of the second cell 34 is shown by making the thickness of the second cell 34 greater than the thickness of the first cell 24.

[0062] When the second cell 34 is discharged and expands, the length of the second laminate 32 in the stacking direction becomes longer than before the expansion. As a result, the second laminate 32 presses the pressing member 16 toward the first battery module 12, as indicated by the white arrow A30.

[0063] Since the pressing member 16 is configured to be movable in the axial direction, it is slid by the second laminate 32 in the direction toward the first battery module 12. At this time, the pressing member 16 presses the first side surface 70 of the first laminate 22 in the stacking direction with its first end 42. As a result, a restraining force is applied to the first laminate 22 from the second laminate 32 via the pressing member 16 in a direction that causes the first laminate 22 to contract along the stacking direction.

[0064] In other words, in the battery pack 1, a restraining force is applied to the first cell 24 by utilizing the expansion force of the second cell 34 as it expands.

[0065] Here, when the first cell 24 is discharged and contracts, the length of the first laminate 22 in the stacking direction becomes shorter compared to when it was expanded. As a result, gaps are created between adjacent first cells 24 in the first laminate 22 compared to when the first cells 24 were expanded.

[0066] In the battery pack 1 of the first embodiment, when the first cell 24 contracts, a restraining force is applied to the first cell 24 by the expansion of the second cell 34.

[0067] Therefore, in the battery pack 1 of the first embodiment, the occurrence of gaps between adjacent first cells 24 caused by the contraction of the first cells 24 can be suppressed. As a result, in the battery pack 1 of the first embodiment, the mechanical strength of the first laminate 22 during discharge can be improved.

[0068] Furthermore, when the second cell 34 expands, the second end 44 of the pressing member 16 moves towards the first battery module 12 inside the second case 30. The second laminate 32 is capable of expanding until the second end 44 contacts the second case 30. That is, once the second end 44 of the second laminate 32 contacts the second case 30, further expansion of the second laminate 32 is suppressed.

[0069] Therefore, in the battery pack 1 of the first embodiment, it is possible to suppress excessive expansion of the second cell 34 of the second laminate 32.

[0070] As described above, the battery pack 1 of the first embodiment includes a pressing member 16 having a rod-shaped portion 40 and configured to be movable in the axial direction of the rod-shaped portion 40. The battery pack 1 of the first embodiment includes a first laminate 22 composed of a plurality of first cells 24 of a first type that expand when charged, arranged in an axial direction. The battery pack 1 of the first embodiment includes a second laminate 32 composed of a plurality of second cells 34 of a second type that expand when discharged, arranged in an axial direction. The battery pack 1 of the first embodiment includes a first case 20 that houses the first laminate 22. The battery pack 1 of the first embodiment includes a second case 30 that houses the second laminate 32. In the battery pack 1 of the first embodiment, the axial first end 42 of the pressing member 16 is located inside the first case 20 and abuts against one axial first side surface 70 of the first laminate 22. In the battery pack 1 of the first embodiment, the second end 44 of the pressing member 16, opposite to the first end 42, is located inside the second case 30 and is the side facing the first side 70, and is in contact with one of the axial second side 72 of the second laminate 32.

[0071] As a result, in the battery pack 1 of the first embodiment, when the second cell 34 contracts, a restraining force is applied to the second cell 34 by the expansion of the first cell 24, and when the first cell 24 contracts, a restraining force is applied to the first cell 24 by the expansion of the second cell 34. Furthermore, in the battery pack 1 of the first embodiment, it is possible to suppress excessive expansion of the first cell 24 of the first laminate 22 and the second cell 34 of the second laminate 32.

[0072] Therefore, in the battery pack 1 of the first embodiment, it is possible to appropriately manage the expansion and contraction of the cells.

[0073] Let's return to Figure 1 and explain in more detail. For the sake of explanation, the amount of expansion when the first cell 24 expands is sometimes referred to as the first expansion amount. The amount of expansion when the second cell 34 expands is sometimes referred to as the second expansion amount. Since the types of the first cell 24 and the second cell 34 are different, the relationship between the first expansion amount and the second expansion amount will also differ depending on the combination of the types of the first cell 24 and the second cell 34. In addition, cells that have a relatively large expansion amount when they expand among the first cell 24 and the second cell 34 are sometimes referred to as large-expansion cells.

[0074] The following describes an example where the second expansion amount of the second cell 34 is relatively larger than the first expansion amount of the first cell 24; in other words, an example where the second cell 34 is a highly expanded cell. For example, if the second cell 34 is a lithium-sulfur battery and the first cell 24 is a lithium-ion battery, the second expansion amount is, for example, about twice as large as the first expansion amount.

[0075] The amount of cell expansion is related to the amount of movement of the pressing member 16, and if the amount of cell expansion is large, the amount of movement of the pressing member 16 will also be large. Considering this, for example, if the number of stacked second cells 34, which have a relatively large amount of expansion, is relatively large, the amount of movement of the pressing member 16 in response to the expansion of the second cells 34 may become excessively large, which may impose an excessive restraining force on the first stacked body 22.

[0076] In the battery pack 1 of the first embodiment, the number of stacked cells among the first cell 24 and second cell 34 that expand relatively large when expanded may be less than the number of stacked cells that expand relatively small. For example, as shown in Figure 1, in the case where the second cell 34 is a highly expandable cell, the number of stacked second cells 34 may be less than the number of stacked first cells 24.

[0077] Suppose we determine the number of layers for the first cell 24 by subtracting a first subtraction number (e.g., 3) from a predetermined standard number of layers (e.g., 20) to get a number (e.g., 17). In this case, if the second expansion amount is about twice as large as the first expansion amount, we may determine the number of layers for the second cell 34 by subtracting a second subtraction number (e.g., 6), which is twice the first subtraction number, from the standard number of layers to get a number (e.g., 14). In addition, if the second expansion amount is about twice as large as the first expansion amount, the number of layers for the second cell 34 may be half the number of layers for the first cell 24.

[0078] As a result, in the battery pack 1 of the first embodiment, it is possible to suppress the excessive movement of the pressing member 16 in response to the expansion of the laminate containing cells with a relatively large expansion amount. Consequently, in the battery pack 1 of the first embodiment, it is possible to suppress the application of excessive restraining force to the laminate with a relatively small expansion amount, thereby preventing damage to the cells.

[0079] Furthermore, the difference between the number of layers of the second cell 34 and the number of layers of the first cell 24 may be determined based on the difference between the second expansion amount and the first expansion amount. For example, the larger the difference between the second expansion amount and the first expansion amount, the larger the difference between the number of layers of the second cell 34 and the number of layers of the first cell 24 may be.

[0080] Furthermore, if the difference between the second expansion amount and the first expansion amount is relatively small, the number of layers of the second cell 34 and the number of layers of the first cell 24 may be the same.

[0081] For the sake of explanation, the maximum amount that the pressing member 16 can move is sometimes referred to as the movable amount. The movable amount of the pressing member 16 may be set based on either or both of the restraining force applied to the first laminate 22 and the restraining force applied to the second laminate 32. The distance between the first end 42 and the side surface of the first case 20 facing the second battery module 14, and the distance between the second end 44 and the side surface of the second case 30 facing the first battery module 12 may be determined based on the movable amount of the pressing member 16.

[0082] (Second Embodiment) Figure 4 is a schematic diagram showing an example of the configuration of the battery pack 100 according to the second embodiment. The battery pack 100 of the second embodiment differs from the battery pack 1 of the first embodiment in that it further has a spacer 110, but in other respects it has the same configuration as the battery pack 1 of the first embodiment. The differences from the first embodiment will be described in detail below, and for convenience, the same aspects as the first embodiment will be omitted from the explanation.

[0083] The spacer 110 is formed, for example, in the shape of a flat plate having a predetermined thickness. The spacer 110 may be made of a metal material. The spacer 110 has a through hole 112 that penetrates through the spacer 110.

[0084] The spacer 110 is housed in one of the first case 20 and second case 30, which houses the laminate containing the large-expansion cell. The spacer 110 is provided between the inner surface of the case in which the spacer 110 is housed and the first end 42 and second end 44 of the pressing member 16 that contact the large-expansion cell. The rod-shaped portion 40 of the pressing member 16 is inserted through the through hole 112 of the spacer 110.

[0085] For example, in the case where the second cell 34 is a highly expanding cell, the spacer 110 is provided between the inner surface of the second case 30 and the surface of the second end 44 opposite to the second contact surface 62.

[0086] The thickness of the spacer 110 may be determined, for example, based on the difference between the expansion force generated by the laminate containing the large expansion cell and the maximum allowable limit of the restraining force to be applied.

[0087] Figure 5 is a partially enlarged view showing an example of charging the first cell 24 and the second cell 34 in the second embodiment. When the first cell 24 and the second cell 34 are charged, the first cell 24 expands and the second cell 34 contracts.

[0088] As the first cell 24 is charged and expands, the first laminate 22 presses the pressing member 16 toward the second battery module 14, as indicated by the white arrow A50. The pressing member 16 is slid toward the second battery module 14 by the first laminate 22, pressing the second side surface 72 of the second laminate 32 in the stacking direction. In other words, in the battery pack 100 of the second embodiment, as in the first embodiment, a restraining force is applied to the second cell 34 by the expansion of the first cell 24.

[0089] Since the spacer 110 is positioned on the opposite side of the second laminate 32 from the second end 44, it does not obstruct the restraining force applied to the second cell 34.

[0090] Figure 6 is a partially enlarged view showing an example of the second embodiment in which the first cell 24 and the second cell 34 are discharged. When the first cell 24 and the second cell 34 are discharged, the first cell 24 contracts and the second cell 34 expands.

[0091] When the second cell 34 is discharged and expands, the second laminate 32 presses the pressing member 16 toward the first battery module 12, as indicated by the white arrow A60. The pressing member 16 is slid toward the first battery module 12 by the second laminate 32, pressing the first side surface 70 of the first laminate 22 in the stacking direction.

[0092] Since the spacer 110 is positioned between the inner surface of the second case 30 and the surface of the second end 44 opposite to the second contact surface 62, the second laminate 32 can expand until the second end 44 contacts the spacer 110. That is, once the second end 44 of the second laminate 32 contacts the spacer 110, further expansion of the second laminate 32 is suppressed.

[0093] In the battery pack 100 of the second embodiment, compared to the embodiment without the spacer 110, the amount of expansion of the second laminate 32 is more restricted, thereby further restricting the amount of movement of the pressing member 16.

[0094] Therefore, in the battery pack 100 of the second embodiment, it is possible to suppress excessive expansion of the second laminate 32 and to suppress excessive restraining force applied to the first laminate 22.

[0095] In the second embodiment, the amount of movement of the pressing member 16 was precisely adjusted by providing a spacer 110. However, the embodiment is not limited to providing a spacer 110; for example, the thickness of the second end portion 44 may be increased by the amount of the spacer 110 to provide the pressing member 16 with the same function as the spacer 110.

[0096] Embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these embodiments. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention.

[0097] For example, in the first and second embodiments described above, an example was described in which the second cell 34 is a highly expanded cell. However, depending on the type of cell, the first cell 24 may also be a highly expanded cell.

[0098] 1,100 Battery pack 16 Pressing member 20 First case 22 First laminate 24 First cell 30 Second case 32 Second laminate 34 Second cell 40 Rod-shaped portion 42 First end 44 Second end 110 Spacer

Claims

1. A battery pack comprising: a pressing member having a rod-shaped portion and configured to be movable in the axial direction of the rod-shaped portion; a first laminate composed of a plurality of first cells of a first type that expand when charged, arranged in a stack in the axial direction; a second laminate composed of a plurality of second cells of a second type that expand when discharged, arranged in a stack in the axial direction; a first case housing the first laminate; and a second case housing the second laminate, wherein the first end of the pressing member in the axial direction is located inside the first case and abuts against one first side surface of the first laminate in the axial direction; and the second end of the pressing member opposite to the first end is located inside the second case and abuts against one second side surface of the second laminate in the axial direction, which is opposite to the first side surface.

2. The battery pack according to claim 1, wherein the contact surface of the first end and the contact surface of the second end of the pressing member are made of an insulating material.

3. The battery pack according to claim 1, wherein the number of stacked cells among the first and second cells that expand relatively large when expanded is less than the number of stacked cells that expand relatively small.

4. The battery pack according to claim 1, further comprising a spacer having a predetermined thickness, wherein the cell among the first and second cells that expands relatively more when expanded is a large-expansion cell, and the spacer is provided between the inner surface of the case among the first and second cases that houses the large-expansion cell and the end of the first and second ends of the pressing member that abuts the large-expansion cell.

5. The battery pack according to claim 1, wherein the first cell is a lithium-ion battery and the second cell is a lithium-sulfur battery.

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