Battery pack

Abstract

To suppress increase of a binding loading due to a long-term deterioration.SOLUTION: A battery pack comprises: a plurality of electric cells 10 having a rectangular-shaped outer shape, and is bound in a state of being arranged in a predetermined arrangement direction; plate-like spacers 21 and 22 which are provided between the electric cells 10 to insulate between the electric cells 10; and insulation rigid bodies 24, 25, and 26 provided between the spacers 21 and 22. The rigid bodies 24, 25, and 26 include a rigidity higher than that of the spacers 21 and 22, and is provided so as to be contacted to each of the spacers 21 and 22 nipping the rigid bodies 24, 25, and 26 at a plurality of places between the spacers 21 and 22, and includes a thickness of an arrangement direction in which the rigid bodies 24, 25, and 26 do not penetrate the spacers 21 and 22 even when a gap between the spacers 21 and 22 becomes the minimum by the increase of the binding load.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a configuration between a plurality of unit cells included in a battery pack. [Background technology]

[0002] The assembled battery is, for example, constructed by stacking a plurality of unit cells each having a rectangular parallelepiped outer shape, with spacers disposed between the unit cells to adjust the restraining load acting on the unit cells.

[0003] For example, JP 2019-128980 A (Patent Document 1) discloses a configuration in which a pressure adjustment member for adjusting a restraining load (restraining pressure) is provided between stacked single cells in a battery pack formed by stacking a plurality of single cells. The pressure adjustment member has a liquid holding portion capable of holding liquid and a liquid storage portion having a space capable of storing liquid. When a certain level of pressure or more is generated due to the expansion and contraction of the outer shape of the single cell caused by charging and discharging the single cell, the pressure adjustment member is deformed by the liquid moving from the storage portion to the holding portion. When the pressure or more is released, the liquid in the holding portion moves to the storage portion, thereby maintaining the restraining load constant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-128980 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned pressure adjustment member maintains the restraint load constant on the assumption that the deformation of the outer shape of the cell is contained within a certain range of change, and does not take into account the range of change in the direction of increasing the restraint load due to aging of the cell. As the cell deteriorates with age, gas is generated inside the cell, causing the outer shape of the cell to expand, and the pressure inside the cell increases, causing the restraint load to increase. For this reason, it may not be possible to maintain the restraint load constant.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a battery pack that suppresses an increase in binding load due to aging deterioration. [Means for solving the problem]

[0007] According to an aspect of the present disclosure, there is provided a battery pack having a rectangular shape, the battery pack including a plurality of unit cells arranged and restrained in a predetermined arrangement direction, a plurality of plate-shaped spacers provided between the unit cells to insulate the unit cells, and an insulating member provided between the spacers. The insulating member has a hardness higher than that of the spacers, is provided so as to contact each of the two spacers that sandwich the insulating member at a plurality of points between the spacers, and has a thickness in the arrangement direction such that the insulating member does not penetrate the spacers even when the distance between the two spacers is minimized due to an increase in the restraining load.

[0008] In this way, when the restraint load increases due to the expansion of the unit cells due to aging in addition to the expansion of the unit cells due to charging and discharging, the insulating member, which has a harder hardness than the spacer, sinks into the spacer, preventing the restraint load from increasing more than expected. This makes it possible to keep the restraint load constant.

[0009] According to an aspect of the present disclosure, there is provided a battery pack having a rectangular shape, the battery pack including a plurality of unit cells arranged in a predetermined arrangement direction and restrained therein, a plurality of plate-shaped spacers provided between the unit cells to insulate the unit cells, and a plurality of bracing members provided between the spacers and having a hardness higher than that of the spacers. The plurality of bracing members include a first bracing member arranged in a first region corresponding to a central region of the unit cells when viewed from the arrangement direction, and a second bracing member provided in a second region corresponding to outer regions located on both sides of the central region in a height direction of the unit cells perpendicular to the arrangement direction. The first bracing member is arranged to be embedded in the spacer without penetrating the spacer when the gap between the two spacers is minimized due to an increase in the restraining load.

[0010] Generally, when a cell expands, the central region of the cell expands more than the peripheral regions of the cell, so when the cell expands and the gap between the two spacers becomes smaller due to an increase in the restraining load, a large load is applied to the central region of the cell.

[0011] In the battery pack disclosed herein, when the gap between the two spacers becomes smaller due to an increase in the restraining load caused by the expansion of the cells due to aging, the first tensioning member disposed in the first region corresponding to the central region is pushed into the spacer. This causes the spacer to plastically deform and absorb the restraining load. This reduces the load applied to the central region of the cells, thereby making it possible to suppress the occurrence of a difference in the restraining load between the central region of the cells and the peripheral regions of the cells.

[0012] In the battery pack according to the aspect of the present disclosure, the first bracing member is preferably configured to sink into the spacer more than the second bracing member.

[0013] With this configuration, when the gap between the two spacers becomes smaller due to an increase in the restraining load, the load applied to the central region of the unit cell can be more reliably reduced.

[0014] In the battery pack according to the certain aspect of the present disclosure, an elastic body may be disposed between the first bracing member and the spacer.

[0015] By arranging the elastic body in this manner, the load applied to the central region of the cell can be further reduced, and the difference in restraining load between the central region of the cell and the peripheral region of the cell can be further suppressed.

[0016] The battery pack according to an aspect of the present disclosure may further include a holding member disposed between the spacers and holding the first and second bracing members. In this case, the first bracing member may be configured to be embedded into the holding member when the gap between the two spacers becomes smaller due to an increase in the restraining load.

[0017] With this configuration, the first bracing member sinks into the holding member, causing the holding member to undergo plastic deformation, thereby reducing the restraining load applied to the central region of the unit cell.

[0018] In the battery pack according to the aspect of the present disclosure described above, the second bracing member may be formed of an elastic member.

[0019] With this configuration, when the gap between the two spacers becomes smaller due to an increase in the restraining load, the elastic member applies a reaction force in a direction in which the gap between the two spacers widens, thereby increasing the load applied to the peripheral region of the unit cell. This makes it possible to prevent a difference in the restraining load between the central region of the unit cell and the peripheral region of the unit cell. Effect of the Invention

[0020] According to the present disclosure, it is possible to provide a battery pack that suppresses an increase in the restraining load due to aging. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram showing an example of a configuration of a battery pack in accordance with a first embodiment. [Diagram 2] 4 is a timing chart showing an example of a change in a restraining load acting on a battery pack in association with charging and discharging. [Diagram 3] 5 is a timing chart showing an example of a change in a restraining load acting on a battery pack due to aging. [Figure 4] 5 is a timing chart showing an example of a change in the overall restraining load acting on the battery pack. [Diagram 5] 4 is a cross-sectional view showing a detailed configuration of a load adjustment mechanism. FIG. [Figure 6] 5A to 5C are diagrams for explaining thicknesses of members constituting the load adjustment mechanism. [Figure 7] 10A and 10B are diagrams illustrating an example of an arrangement of a plurality of insulating rigid bodies provided on a positioning member. [Figure 8] 4 is a diagram for explaining the operation of a load adjustment mechanism of the battery pack 1. FIG. [Figure 9] 4 is a timing chart showing an example of a change in a restraining load acting on the battery pack according to the first embodiment in association with charging and discharging. [Figure 10] 4 is a timing chart showing an example of a change in a restraining load associated with aging acting on the battery pack according to the first embodiment. [Figure 11] 4 is a timing chart showing an example of a change in the overall restraining load acting on the battery pack according to the first embodiment. [Figure 12] 13 is a diagram for explaining a first example of an arrangement of a plurality of insulating rigid bodies in the modified example. FIG. [Figure 13] 13 is a diagram for explaining a second example of an arrangement of a plurality of insulating rigid bodies in the modified example. FIG. [Figure 14] FIG. 13 is a diagram for explaining a third example of an arrangement of a plurality of insulating rigid bodies in the modified example. [Figure 15] 13 is a diagram for explaining a fourth example of an arrangement of a plurality of insulating rigid bodies in the modified example. FIG. [Figure 16] FIG. 13 is a diagram for explaining a fifth example of an arrangement of a plurality of insulating rigid bodies in the modified example. [Figure 17] 13 is a diagram for explaining a first example of a cross-sectional shape of an insulating rigid body in a modified example. FIG. [Figure 18] 13 is a diagram for explaining a second example of a cross-sectional shape of an insulating rigid body in the modified example. FIG. [Figure 19] 13 is a diagram for explaining a third example of a cross-sectional shape of an insulating rigid body in a modified example. FIG. [Figure 20] 13 is a cross-sectional view showing a detailed configuration of a load adjustment mechanism in a modified example. FIG. [Figure 21] 13 is a diagram for explaining a first arrangement example of a plurality of insulating rigid bodies arranged on a second spacer in the modified example. FIG. [Figure 22] 13A and 13B are diagrams illustrating the configuration of a first spacer in a modified example. [Diagram 23] 10A and 10B are diagrams for explaining the operation of a load adjustment mechanism of a battery pack according to a modified example. [Figure 24] FIG. 11 is a cross-sectional view showing a detailed configuration of a load adjustment mechanism in another modified example. [Diagram 25] 13 is a diagram for explaining a second arrangement example of a plurality of insulating rigid bodies arranged on a second spacer in the modified example. FIG. [Figure 26] 13A and 13B are diagrams for explaining examples of arrangement of a plurality of insulating rigid bodies arranged on a first spacer in the modified example. [Figure 27] 13 is a diagram for explaining a fourth example of a cross-sectional shape of an insulating rigid body in a modified example. FIG. [Figure 28] 13 is a diagram for explaining a fifth example of a cross-sectional shape of an insulating rigid body in a modified example. FIG. [Figure 29] FIG. 11 is a vertical cross-sectional view of a battery pack according to a second embodiment. [Diagram 30] 30 is a cross-sectional view taken along the line XXX-XXX shown in FIG. 29. [Diagram 31] 10 is a diagram for explaining the thicknesses of the members constituting the load adjustment mechanism provided in the battery pack according to the second embodiment. FIG. [Diagram 32] 13 is a diagram showing a first example of a cross-sectional shape of a first bracing member in a modified example. FIG. [Diagram 33]13 is a diagram showing a second example of a cross-sectional shape of a first bracing member in a modified example. FIG. [Diagram 34] 4 is a cross-sectional view of a battery pack in Comparative Example 1, showing an initial state of the battery pack. FIG. [Diagram 35] 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell in the initial state of Comparative Example 1. FIG. [Diagram 36] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the initial state of Comparative Example 1. [Figure 37] FIG. 2 is a cross-sectional view showing the state of a single cell in Comparative Example 1 during intermediate use. [Figure 38] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 1 during the intermediate period of use. [Figure 39] FIG. 13 is a diagram showing the distribution of displacement of a unit cell in the height direction of the unit cell during intermediate use of Comparative Example 1. [Diagram 40] FIG. 2 is a cross-sectional view showing the state of a single cell in the final stage of use of Comparative Example 1. [Diagram 41] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 1 at the end of use. [Diagram 42] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells at the end of use in Comparative Example 1. [Diagram 43] 11 is a cross-sectional view showing an initial state of a battery pack in Comparative Example 2. FIG. [Diagram 44] 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell in the initial state of Comparative Example 2. FIG. [Diagram 45] 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the initial state of Comparative Example 2. FIG. [Figure 46] FIG. 11 is a cross-sectional view showing the state of a battery pack in Comparative Example 2 during intermediate use. [Figure 47] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 2 during the middle stage of use. [Figure 48] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the middle of use of Comparative Example 2. [Figure 49] FIG. 11 is a cross-sectional view showing the state of a single cell in the final stage of use of Comparative Example 2. [Figure 50] 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 2 at the end of use. FIG. [Figure 51] 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells at the end of use in Comparative Example 2. FIG. [Figure 52] 4 is a cross-sectional view showing an initial state of a battery pack in Reference Example 1. FIG. [Figure 53] 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell in the initial state of Reference Example 1. FIG. [Figure 54] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the initial state of Reference Example 1. [Figure 55] FIG. 4 is a cross-sectional view showing a state of the battery pack of Reference Example 1 in the middle stage of use. [Figure 56] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Reference Example 1 during the intermediate period of use. [Figure 57] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the middle stage of use of Reference Example 1. [Figure 58] FIG. 2 is a cross-sectional view showing the state of a single cell in Reference Example 1 at the end of its life. [Figure 59] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Reference Example 1 at the end of use. [Figure 60] FIG. 13 is a graph showing the distribution of displacement of unit cells in the height direction of the unit cells at the end of use in Reference Example 1. [Figure 61] 11 is a cross-sectional view showing an initial state of a battery pack in accordance with a second embodiment. FIG. [Figure 62]FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell in the initial state of the second embodiment. [Figure 63] FIG. 11 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the initial state of the second embodiment. [Figure 64] FIG. 11 is a cross-sectional view showing a state of a battery pack in the middle of use according to the second embodiment. [Figure 65] 13A and 13B are diagrams showing how the elastic body is deformed during the middle period of use of the second embodiment. [Figure 66] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell in the middle of use in the second embodiment. [Figure 67] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells during intermediate use in the second embodiment. [Figure 68] FIG. 11 is a cross-sectional view showing the state of a unit cell in the final stage of use according to the second embodiment. [Figure 69] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell in the final stage of use in accordance with the second embodiment. [Figure 70] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells at the end of use in the second embodiment. [Figure 71] FIG. 11 is a vertical cross-sectional view of a battery pack according to a third embodiment. [Figure 72] FIG. 11 is a vertical cross-sectional view of a battery pack according to a fourth embodiment. [Figure 73] FIG. 11 is a cross-sectional view showing the shapes of a first bracing member and a second bracing member in a first modified example. [Figure 74] 13 is a cross-sectional view showing the shapes of a first bracing member and a second bracing member in a second modified example. FIG. [Figure 75] FIG. 13 is a cross-sectional view showing an initial state of a battery pack in embodiment 5. [Figure 76] FIG. 13 is a diagram showing the distribution of restraining loads in the height direction of a unit cell in the height direction of the unit cell in the initial state of the fifth embodiment. [Figure 77]FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells in the initial state of the fifth embodiment. [Figure 78] FIG. 13 is a cross-sectional view showing a state of a battery pack in the final stage of use according to the fifth embodiment. [Figure 79] FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the height direction of the unit cell at the end of use in accordance with the fifth embodiment. [Figure 80] FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells at the end of use in embodiment 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0023] (Embodiment 1) FIG. 1 is a diagram showing an example of the configuration of a battery pack 1 according to the first embodiment. As shown in FIG. 1, the battery pack 1 includes end plates 7 and 8, a restraining band 9, and a plurality of unit cells 10. The plurality of unit cells 10 are arranged in a row along a predetermined arrangement direction (e.g., 10 units). The plurality of unit cells 10 are arranged such that an end face in the thickness direction of each unit cell 10 faces an end face in the thickness direction of an adjacent unit cell 10. A load adjustment mechanism 20 is provided between each of the plurality of unit cells 10. A battery string 40 is formed by the plurality of unit cells 10 and the load adjustment mechanisms 20.

[0024] End plates 7, 8 are provided to sandwich the battery string 40 from a predetermined arrangement direction. Restraint bands 9 are provided to the battery string 40 and the end plates 7, 8 to prevent the distance between the end plates 7, 8 from increasing in the arrangement direction.

[0025] The restraint bands 9 are provided at four locations: on the upper surface side of the cell 10, at both ends in the width direction, and on the lower surface side of the cell 10, at both ends in the width direction.

[0026] The cell 10 is a sealed secondary battery, and includes a rectangular battery case 11 having an opening on the top surface, a lid 13 that closes (seals) the opening, and a flat electrode body (not shown) housed in the power source case 11. The lid 13 is provided with a safety valve 13j, a positive electrode external terminal 19b, and a negative electrode external terminal 19c. The entire periphery of the lid 13 is joined to the opening of the battery case 11 by welding. This makes the cell 10 sealed.

[0027] The electrode assembly is formed, for example, by winding a sheet-shaped positive electrode and a sheet-shaped negative electrode with a sheet-shaped separator (neither shown) between them. A positive electrode connecting member that electrically connects to the positive electrode external terminal 19b and a negative electrode connecting member that electrically connects to the negative electrode external terminal 19c are welded to this electrode assembly.

[0028] In the battery pack 1 of embodiment 1, a battery string 40 consisting of a plurality of single cells 10 and a load adjustment mechanism 20 is subjected to a predetermined restraining load (compressive load) in the arrangement direction by end plates 7, 8 sandwiching the battery string 40. The battery string 40 and the end plates 7, 8 are then integrally restrained by assembling four restraining bands 9.

[0029] As shown in FIG. 1, in the battery pack 1, the positive external terminals 19b and the negative external terminals 19c of the cells 10 adjacent to each other in the arrangement direction are electrically connected by a bus bar 3.

[0030] More specifically, the bus bar 3 is made of a rectangular metal plate and has two through holes formed therein, through which the positive external terminal 19b and the negative external terminal 19c can be inserted. With the positive external terminal 19b inserted into one of the through holes of the bus bar 3, a nut 5 is screwed onto the male thread of the positive external terminal 19b, thereby fastening the negative external terminal 19c to the bus bar 3. In this manner, adjacent cells 10 are connected by the bus bar 3, and the cells 10 constituting the battery pack 1 are electrically connected in series.

[0031] When the battery pack 1 having the above-described configuration is charged and discharged, the expansion and contraction of the cells 10 causes fluctuations in the restraining load.

[0032] FIG. 2 is a timing chart showing an example of changes in the restraint load acting on the battery pack 1 due to charging and discharging. The vertical axis of FIG. 2 indicates the restraint load. The horizontal axis of FIG. 2 indicates time. As shown in FIG. 2, when the single cell 10 expands due to charging and discharging, the restraint load increases. When the single cell 10 contracts due to, for example, the charging and discharging being stopped, the restraint load decreases. In this way, the restraint load associated with charging and discharging repeatedly increases and decreases within a certain range of change as charging and discharging are repeated.

[0033] Such fluctuations in the restraint load of the battery pack 1 can be accommodated by, for example, a load adjustment mechanism 20 disposed between the cells 10, which can keep the restraint load constant.

[0034] However, since the fluctuations in the restraint load during charging and discharging of such a battery pack 1 are contained within a certain range of change, if, in addition to these fluctuations, an increase in the restraint load occurs due to deterioration of the single battery 10 over time, it may not be possible to maintain the restraint load constant.

[0035] FIG. 3 is a timing chart showing an example of a change in the restraint load acting on the battery pack 1 due to deterioration over time. The vertical axis of FIG. 3 indicates the restraint load. The horizontal axis of FIG. 3 indicates time. As shown in FIG. 3, when gas is generated in the cell 10 due to deterioration over time and the external shape of the cell 10 expands, the pressure inside the cell 10 increases as the amount of gas increases, and the amount of expansion of the external shape of the cell 10 increases as the pressure increases. As a result of the expansion of the external shape of the cell 10, the restraint load increases.

[0036] As a result, the overall constraint load acting on the battery pack 1 tends to increase. FIG. 4 is a timing chart showing an example of changes in the overall constraint load acting on the battery pack 1. The vertical axis of FIG. 4 represents the constraint load. The horizontal axis of FIG. 4 represents time. As shown in FIG. 4, the overall constraint load acting on the battery pack 1 repeatedly increases and decreases within a certain range of change due to charging and discharging, while the range showing the certain range of change shifts in the direction of increasing the constraint load due to an increase in the constraint load associated with deterioration over time.

[0037] Therefore, in addition to fluctuations in the restraint load when the battery pack 1 is charged and discharged, the range of change due to deterioration over time of the battery cells also varies, and it may not be possible to maintain the restraint load constant.

[0038] Therefore, in the first embodiment, the load adjustment mechanism 20 of the battery pack 1 is configured as follows. That is, the load adjustment mechanism 20 is provided between the cells 10 and includes a plurality of plate-shaped spacers that insulate the cells 10, and an insulating member provided between the spacers. The insulating member has a hardness higher than that of the spacers, is provided so as to contact each of the two spacers that sandwich the insulating member at a plurality of points between the spacers, and has a thickness in the arrangement direction such that the insulating member does not penetrate the spacers even when the gap between the two spacers is minimized due to an increase in the restraining load.

[0039] In this way, when the restraining load increases due to the expansion of the cell 10 due to aging in addition to the expansion of the cell 10 due to charging and discharging, the insulating member having a hardness higher than that of the spacer is embedded in the spacer, and the restraining load is prevented from increasing more than expected. When the gap between the two spacers becomes small, the insulating member functions as a bracing member that braces the spacers. In the following description, the insulating member is referred to as an insulating rigid body.

[0040] Fig. 5 is a cross-sectional view showing a detailed configuration of the load adjustment mechanism 20. As shown in Fig. 5, the load adjustment mechanism 20 includes a first spacer 21, a second spacer 22, a positioning member (holding member) 23, and insulating rigid bodies 24, 25, and .

[0041] The first spacer 21 and the second spacer 22 are both plate-like members and have substantially the same rectangular shape as the end faces in the thickness direction of the unit cells 10. The first spacer 21 and the second spacer 22 are provided in contact with adjacent unit cells 10. Between the first spacer 21 and the second spacer 22, a positioning member 23 is provided, which has substantially the same rectangular shape as the first spacer 21 or the second spacer 22 when viewed from the arrangement direction.

[0042] A plurality of insulating rigid bodies including insulating rigid bodies 24, 25, and 26 are provided at a plurality of locations on positioning member 23. The positions of the plurality of insulating rigid bodies are restricted by positioning member 23. Positioning member 23 is provided with through holes at a plurality of locations. The plurality of insulating rigid bodies are press-fitted into through holes provided at predetermined locations on positioning member 23 to restrict their positions in the height direction and width direction. In addition to or instead of press-fitting, adhesion with an adhesive may be performed. FIG. 5 shows a cross section including insulating rigid bodies 24, 25, and 26 out of the plurality of insulating rigid bodies.

[0043] Each of the first spacer 21, the second spacer 22, and the positioning member 23 is made of any one of materials such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polycarbonate (PC). The first spacer 21, the second spacer 22, and the positioning member 23 may all be made of the same material, may all be made of different materials, or at least one of them may be made of a material different from the others.

[0044] The plurality of insulating rigid bodies are each made of a material having a higher hardness than the first spacer 21 and the second spacer 22. Each of the plurality of insulating rigid bodies is made of a ceramic material, such as alumina or zirconia.

[0045] As shown in Fig. 5, the cross-section of the single cell 10 of the insulating rigid bodies 24, 25, and 26, viewed from the width direction, has a predetermined shape. In Embodiment 1, the cross-section of the single cell 10 of the insulating rigid bodies 24, 25, and 26, viewed from the width direction, is, for example, polygonal. Specifically, the cross-section of the insulating rigid bodies 24, 25, and 26 has, for example, an octagonal shape that is symmetric about the top, bottom, left, and right when viewed from the width direction. All of the plurality of insulating rigid bodies have the same shape. Note that the cross-section of the single cell 10 of the plurality of insulating rigid bodies, viewed from the thickness direction, is, for example, circular.

[0046] Fig. 6 is a diagram for explaining the thicknesses of the respective members constituting the load adjustment mechanism. Fig. 6 shows an enlarged view of the frame line portion of Fig. 5. As shown in Fig. 6, let the thicknesses (lengths in the arrangement direction, the same applies hereinafter) of the first spacer 21 and the second spacer 22 be tp1, the thickness of the positioning member be tp2, and the thickness of the insulating rigid body 25 be tr. In this case, the thicknesses of the respective members are set such that the magnitude relationship represented by the formula tp2 < tr < tp2 + 2×tp1 holds. The above formula is set such that the insulating rigid body 25 has a thickness in the arrangement direction that does not penetrate the first spacer 21 and the second spacer 22 even when the gap between the first spacer 21 and the second spacer 22 is minimized.

[0047] FIG. 7 is a diagram for explaining an example of the arrangement of a plurality of insulating rigid bodies provided in the positioning member 23. As shown in FIG. 7, the plurality of insulating rigid bodies (including the insulating rigid bodies 24, 25, 26) are arranged in a matrix of three in the height direction and ten in the width direction on the plane of the positioning member 23. That is, 30 insulating rigid bodies are arranged in the positioning member 23. The plurality of insulating rigid bodies are arranged at a first interval that is determined in advance in the height direction and at a second interval that is determined in advance in the width direction. In the first embodiment, the first interval is described as being larger than the second interval, but may be the same as the second interval or may be smaller than the second interval. In the present embodiment, the insulating rigid body 25 of the plurality of insulating rigid bodies 24, 25, 26 corresponds to a first bracing member arranged in a first region that corresponds to a central region of the unit cell 10 in the height direction. The insulating rigid bodies 24, 26 correspond to second bracing members provided in a second region corresponding to outer regions of the unit cells 10 located on both outer sides of the central region in the height direction.

[0048] The number of the multiple insulating rigid bodies in the width direction and height direction may be set so that the restraining load acting on the first spacer 21 and the second spacer 22 from each of the multiple insulating rigid bodies is diffused throughout, and is not limited to the arrangement shown in Fig. 7. The positions of the multiple insulating rigid bodies are set taking into consideration the state in which the unit cell 10 expands and contracts during charging and discharging, the state in which no expansion occurs due to aging deterioration in the early stages of use, and the state in which expansion occurs due to aging deterioration in the middle to later stages of use.

[0049] The battery pack 1 configured as described above is assembled by the following procedure. For example, the first spacer 21, the second spacer 22, and the positioning member 23 are formed into a predetermined rectangular shape. A through hole is formed at a predetermined position of the positioning member 23. A plurality of insulating rigid bodies are press-fitted into the through hole. Ten unit cells 10 are arranged such that the thickness direction of the unit cells 10 coincides with the arrangement direction. A load adjustment mechanism 20 including the first spacer 21, the positioning member 23, and the second spacer 22 is inserted between the unit cells 10. At this time, the positioning member 23 is arranged between the first spacer 21 and the second spacer 22. Then, a restraining load is applied to the battery string 40 by sandwiching it between the end plates 7 and 8. In this state, the battery string 40 is restrained by the restraining band 9 to form the battery pack 1.

[0050] The operation of the load adjustment mechanism 20 of the battery pack 1 according to the first embodiment based on the above-mentioned structure will be described. FIG. 8 is a diagram for explaining the operation of the load adjustment mechanism 20 of the battery pack 1. As shown in the load adjustment mechanism 20 of FIG. 8(A), in the initial state, the insulating rigid bodies 24, 25, and 26 are in contact with the first spacer 21 and the second spacer 22. When the single cell 10 expands and contracts due to charging and discharging while the single cell 10 is in the initial state, the first spacer 21, the second spacer 22, and the insulating rigid bodies 24, 25, and 26 each undergo elastic deformation to absorb the restraining load, thereby preventing the application of a restraining load greater than expected to the single cell 10.

[0051] As shown in the load adjustment mechanism 20 in FIG. 8(B), when gas is generated in the cell 10 after aging, the outer shape of the cell 10 expands with an increase in the amount of gas. As a result, the first spacer 21 and the second spacer 22 move so that the gap between them becomes smaller. Therefore, the gap between the first spacer 21 and the positioning member 23 and the gap between the second spacer 22 and the positioning member 23 become smaller. Since the insulating rigid bodies 24, 25, and 26 have a higher hardness than the first spacer 21 and the second spacer 22, they sink into the first spacer 21 and the second spacer 22. At this time, plastic deformation occurs in the first spacer 21 and the second spacer 22. Therefore, the restraining load increased by the expansion caused by the gas generation is absorbed by the plastic deformation of the first spacer 21 and the second spacer 22, and the application of a restraining load greater than expected to the cell 10 is suppressed.

[0052] Fig. 9 is a timing chart showing an example of a change in the restraint load acting on the battery pack 1 according to embodiment 1 in association with charging and discharging. The vertical axis in Fig. 9 indicates the restraint load. The horizontal axis in Fig. 2 indicates time. The change in the restraint load shown in Fig. 9 is similar to the change in the restraint load in association with charging and discharging described in Fig. 2. Therefore, detailed description thereof will not be repeated.

[0053] FIG. 10 is a timing chart showing an example of a change in the restraint load acting on the battery pack 1 according to embodiment 1 due to deterioration over time. The vertical axis of FIG. 10 indicates the restraint load. The horizontal axis of FIG. 10 indicates time. In the period up to time t(0), as shown by the solid line in FIG. 10, when gas is generated in the cell 10 due to deterioration over time and the external shape of the cell 10 expands, the pressure inside the cell 10 increases with the increase in the amount of gas, and the amount of expansion of the external shape of the cell 10 increases with the increase in pressure. As a result of the expansion of the external shape of the cell 10, the restraint load increases.

[0054] On the other hand, when time t(0) is reached, a plurality of insulating rigid bodies are embedded in the first spacer 21 and the second spacer 22, causing plastic deformation of the first spacer 21 and the second spacer 22. The constraint load is absorbed by the plastic deformation of the first spacer 21 and the second spacer 22, and no reaction force due to elastic deformation is generated, so that the constraint load decreases as shown by the dashed line in FIG.

[0055] Fig. 11 is a timing chart showing an example of a change in the overall constraint load acting on the battery pack 1 according to embodiment 1. The vertical axis in Fig. 11 represents the constraint load. The horizontal axis in Fig. 11 represents time. As shown by the solid line in Fig. 11, in the period up to time t(0), the overall constraint load acting on the battery pack 1 repeatedly increases and decreases within a certain range of change due to charging and discharging, while the range showing the certain range of change shifts in the direction in which the constraint load increases due to an increase in the constraint load associated with deterioration over time.

[0056] 11, when time t(0) is reached, the increased restraint load due to aging is absorbed by the plastic deformation of the first spacer 21 and the second spacer 22, and the range indicating the change range is prevented from moving in the direction in which the restraint load increases. This prevents the battery 10 from being subjected to a restraint load greater than expected.

[0057] As described above, according to the battery pack 1 of the first embodiment, in the case where the restraint load increases due to the expansion of the cells 10 due to aging in addition to the expansion of the cells 10 due to charging and discharging, the plurality of insulating rigid bodies including the insulating rigid bodies 24, 25, and 26 sink into the first spacer 21 and the second spacer 22, and the restraint load is prevented from increasing more than expected. This makes it possible to keep the restraint load constant. Therefore, it is possible to provide a battery pack that suppresses an increase in the restraint load due to aging.

[0058] Modifications will be described below. In the above-mentioned first embodiment, the insulating rigid bodies 24, 25, and 26 are described as being arranged in a matrix in the height direction and the width direction, but the arrangement is not particularly limited to being arranged in a matrix. Fig. 12 is a diagram for explaining a first example of an arrangement of a plurality of insulating rigid bodies in a modified example. As shown in Fig. 12, the insulating rigid bodies may be arranged on a diagonal line of a rectangular positioning member 23. Fig. 12 shows an example in which the insulating rigid bodies are arranged at equal intervals along the diagonal line, but the arrangement is not particularly limited to being arranged at equal intervals along the diagonal line.

[0059] Furthermore, in the above-mentioned first embodiment, the insulating rigid bodies 24, 25, and 26 have been described as being arranged in three in the height direction, but the number of insulating rigid bodies provided in the height direction is not particularly limited to three. Fig. 13 is a diagram for explaining a second example of the arrangement of a plurality of insulating rigid bodies in a modified example. As shown in Fig. 13, the insulating rigid bodies may be arranged in a matrix of four in the height direction and ten in the width direction with respect to the plane of the positioning member 23.

[0060] Furthermore, in the above-mentioned first embodiment, the interval between the insulating rigid bodies arranged in the height direction is described as being longer than the interval between the insulating rigid bodies arranged in the width direction, but this is not particularly limited. Fig. 14 is a diagram for explaining a third example of the arrangement of a plurality of insulating rigid bodies in the modified example. As shown in Fig. 14, the insulating rigid bodies may be arranged in a matrix of seven in the height direction and six in the width direction with respect to the plane of the positioning member 23. In this case, the interval between the insulating rigid bodies arranged in the height direction is shorter than the interval between the insulating rigid bodies arranged in the width direction.

[0061] Furthermore, in the above-mentioned first embodiment, the insulating rigid bodies are described as being arranged in a matrix, but the arrangement is not particularly limited to this. Fig. 15 is a diagram for explaining a fourth example of the arrangement of the insulating rigid bodies in the modified example. As shown in Fig. 15, the insulating rigid bodies may be arranged, for example, on a lattice line set on the plane of the positioning member 23. That is, the insulating rigid bodies may be arranged along a frame line set at a position a predetermined distance away from the outer edge of the positioning member 23, along a center line parallel to the horizontal line of the frame line in the height direction, and along two lines parallel to the vertical line of the frame line in the width direction.

[0062] Furthermore, in the above-mentioned first embodiment, the insulating rigid bodies are described as being arranged in a matrix, but are not limited to being arranged in a regular pattern. Fig. 16 is a diagram for explaining a fifth example of the arrangement of the insulating rigid bodies in the modified example. As shown in Fig. 16, the insulating rigid bodies may be arranged, for example, at predetermined positions that are set randomly.

[0063] Furthermore, in the above-mentioned first embodiment, the multiple insulating rigid bodies are arranged in groups of three at equal intervals in the height direction, but the multiple insulating rigid bodies are not limited to being arranged at equal intervals in the height direction. For example, the multiple insulating rigid bodies may be provided concentrated in the center of the cell 10 in the height direction where the restraining load is concentrated in the cell 10 that is in an expanded state during or at the end of use.

[0064] Furthermore, in the above-mentioned embodiment 1, the cross section of the insulating rigid body viewed from the width direction is described as an example of an octagonal shape, but the shape is not particularly limited to this. The insulating rigid body may be formed in a cross section such that, for example, when the gap between the first spacer 21 and the second spacer 22 becomes small due to the expansion of the single cell 10, the insulating rigid body does not penetrate either the first spacer 21 or the second spacer 22, and even if the insulating rigid body penetrates, the battery case 11 is protected. FIG. 17 is a diagram for explaining a first example of the cross section of the insulating rigid body in the modified example. As shown in FIG. 17, the insulating rigid body may have, for example, a rectangular cross section. In this way, the contact area with the battery case 11 is larger than when the insulating rigid body has a tapered cross section, so that even if the insulating rigid body penetrates, the force acting from the insulating rigid body to the battery case 11 is dispersed, and the battery case 11 is protected.

[0065] Furthermore, in the above-mentioned first embodiment, the cross section of the insulating rigid body viewed from the width direction is octagonal, but the shape is not particularly limited to this. Fig. 18 is a diagram for explaining a second example of the cross-sectional shape of the insulating rigid body in the modified example. As shown in Fig. 18, the insulating rigid body may have, for example, an elliptical cross section.

[0066] Furthermore, in the above-mentioned embodiment 1, the multiple insulating rigid bodies are described as all having the same cross-sectional shape, but the multiple insulating rigid bodies may be configured to have different cross-sectional shapes depending on the location (for example, when the position is different in the height direction or width direction).

[0067] Furthermore, in the above-mentioned first embodiment, the multiple insulating rigid bodies are described as being press-fitted into the through holes of the positioning member 23, but the present invention is not particularly limited to such a configuration. For example, the multiple insulating rigid bodies may be bonded to the surface of the positioning member 23. FIG. 19 is a diagram for explaining a third example of the cross-sectional shape of the insulating rigid body in the modified example. As shown in FIG. 19, the insulating rigid body may be made of two insulating members and bonded by an adhesive to the left surface and the right surface of the positioning member 23 at the same height and width positions as viewed in the width direction.

[0068] Furthermore, in the above-mentioned embodiment 1, the multiple insulating rigid bodies are described as being arranged on a positioning member 23 provided between the first spacer 21 and the second spacer 22, but, for example, the positioning member 23 may be omitted and the insulating rigid bodies may be arranged on at least one of the first spacer 21 and the second spacer 22.

[0069] Fig. 20 is a cross-sectional view showing a detailed configuration of the load adjustment mechanism 20 in the modified example. As shown in Fig. 20, the load adjustment mechanism 20 in this modified example includes a first spacer 21, a second spacer 22, and insulating rigid bodies 29, 30, and 31. The insulating rigid body 30 corresponds to the above-mentioned first strut member, and the insulating rigid bodies 29 and 31 correspond to the above-mentioned second strut member.

[0070] The first spacer 21 and the second spacer 22 have the same shapes and materials as the first spacer 21 and the second spacer 22 in the above-described first embodiment, except that the second spacer 22 has a plurality of insulating rigid bodies including insulating rigid bodies 29, 30, and 31 arranged therein. Therefore, detailed description thereof will not be repeated.

[0071] The material of the insulating rigid bodies provided in the second spacer 22 is the same as that of the insulating rigid bodies 24, 25, and 26 in the above-described first embodiment, so detailed description thereof will not be repeated.

[0072] The cross section of the insulating rigid bodies 29, 30, 31 has a predetermined shape, for example, a hexagonal shape. Specifically, the cross section of the insulating rigid bodies 29, 30, 31 has a hexagonal shape with a tapered end closer to the first spacer 21 so that the contact area with the second spacer 22 is larger than the contact area with the first spacer 21. The insulating rigid bodies 29, 30, 31 have a thickness in the arrangement direction that the first spacer 21 and the second spacer 22 do not penetrate even when the gap between the first spacer 21 and the second spacer 22 is minimized (i.e., even when the first spacer 21 and the second spacer 22 contact each other). The insulating rigid bodies 29, 30, 31 abut against the first spacer 21 and are bonded to the second spacer 22 using an adhesive.

[0073] Fig. 21 is a diagram for explaining a first arrangement example of a plurality of insulating rigid bodies arranged on the second spacer 22 in the modified example. As shown in Fig. 21, the plurality of insulating rigid bodies are arranged in a matrix of three in the height direction and ten in the width direction on the second spacer 22. As a result, 30 insulating rigid bodies are arranged on the second spacer 22. Fig. 22 is a diagram for explaining the configuration of the first spacer 21 in the modified example. As shown in Fig. 22, no insulating rigid body is arranged on the first spacer 21.

[0074] The battery pack 1 according to the above-described modified example is assembled in the following procedure. For example, the first spacer 21 and the second spacer 22 are formed into a predetermined rectangular shape. A plurality of insulating rigid bodies are attached to the surface of the second spacer 22 opposite to the surface that contacts the unit cells 10 at predetermined positions using an adhesive. Ten unit cells 10 are arranged such that the thickness direction of the unit cells 10 coincides with the arrangement direction. A load adjustment mechanism 20 including the first spacer 21 and the second spacer 22 is inserted between the unit cells 10. Then, a restraining load is applied to the battery string 40 by sandwiching it between the end plates 7 and 8. In this state, the battery string 40 is restrained by the restraining band 9, and the battery pack 1 is formed.

[0075] The operation of the load adjustment mechanism 20 of the battery pack 1 according to this modified example based on the above-mentioned structure will be described. Fig. 23 is a diagram for explaining the operation of the load adjustment mechanism 20 of the battery pack 1 according to the modified example. In the initial state, as shown in Fig. 20, the insulating rigid bodies 29, 30, 31 are in contact with the first spacer 21 and the second spacer 22. When the single cell 10 is in the initial state and expands and contracts due to charging and discharging, the first spacer 21, the second spacer 22, and the insulating rigid bodies 29, 30, 31 each elastically deform to absorb the restraining load, thereby preventing the application of a restraining load greater than expected to the single cell 10.

[0076] After aging, as shown in FIG. 23, when gas is generated in the cell 10, the outer shape of the cell 10 expands with an increase in the amount of gas. As a result, the first spacer 21 and the second spacer 22 move so that the gap between the first spacer 21 and the second spacer 22 becomes smaller. The insulating rigid bodies 29, 30, and 31 have a higher hardness than the first spacer 21 and the second spacer 22 and have a smaller contact area with the first spacer 21 than the contact area with the second spacer 22, so they sink into the first spacer 21. At this time, plastic deformation occurs in the first spacer 21. Therefore, the restraining load increased by the expansion caused by the gas generation is absorbed by the plastic deformation of the first spacer 21, and the application of a load greater than expected to the cell 10 is suppressed.

[0077] In this modified example, the multiple insulating rigid bodies are described as being arranged only on the surface of the second spacer 22 and not on the first spacer 21, but they may also be arranged on both the surface of the first spacer 21 and the surface of the second spacer 22 opposite the surface of the first spacer 21.

[0078] 24 is a cross-sectional view showing a detailed configuration of the load adjustment mechanism 20 in another modified example. The load adjustment mechanism 20 in this modified example includes a first spacer 21, a second spacer 22, and insulating rigid bodies 32, 33, 34, 35, 36, and 37. Note that the insulating rigid bodies 34 and 35 correspond to the above-mentioned first bracing member, and the insulating rigid bodies 32-33, 36-37 correspond to the above-mentioned second bracing member.

[0079] The first spacer 21 and the second spacer have the same shape and material as the first spacer 21 and the second spacer 22 in the above-described first embodiment, except that the insulating rigid bodies 32, 33, 34, 35, 36, and 37 are arranged, and therefore detailed description thereof will not be repeated.

[0080] Furthermore, the materials of the insulating rigid bodies 32, 33, 34, 35, 36, and 37 disposed in the first spacer 21 and the second spacer 22 are the same as those of the insulating rigid bodies 24, 25, and 26 in the above-described first embodiment, so detailed description thereof will not be repeated.

[0081] The cross sections of the insulating rigid bodies 32, 33, 34, 35, 36, and 37 have a predetermined shape, for example, a hexagonal shape. Specifically, the cross sections of the insulating rigid bodies 33, 35, and 37 have a hexagonal shape with a tapered end closer to the second spacer 22 so that the contact area with the first spacer 21 is larger than the contact area with the second spacer 22. Furthermore, the insulating rigid bodies 33, 35, and 37 abut against the second spacer 22 and are bonded to the first spacer 21 using an adhesive. Furthermore, the cross sections of the insulating rigid bodies 32, 34, and 36 have a hexagonal shape with a tapered end closer to the first spacer 21 so that the contact area with the second spacer 22 is larger than the contact area with the first spacer 21. The insulating rigid bodies 32, 34, and 36 abut against the first spacer 21 and are bonded to the second spacer 22 using an adhesive.

[0082] 25 is a diagram for explaining a second arrangement example of a plurality of insulating rigid bodies arranged on the second spacer 22 in the modified example. As shown in Fig. 25, the plurality of insulating rigid bodies are arranged in a matrix of three in the height direction and ten in the width direction on the second spacer 22. As a result, 30 insulating rigid bodies are arranged on the second spacer 22.

[0083] FIG. 26 is a diagram for explaining an example of the arrangement of a plurality of insulating rigid bodies arranged on the first spacer 21 in the modified example. As shown in FIG. 26, the plurality of insulating rigid bodies are arranged in a matrix with three in the height direction and ten in the width direction on the first spacer 21. As a result, 30 insulating rigid bodies are arranged on the first spacer 21. Furthermore, the plurality of insulating rigid bodies arranged on the first spacer 21 are arranged so as not to face the plurality of insulating rigid bodies arranged on the second spacer 22 in a state in which the first spacer 21 and the second spacer 22 are assembled between the unit cells 10. In FIG. 26, each of the plurality of insulating rigid bodies arranged on the first spacer 21 is arranged at a position shifted by a predetermined distance in the height direction from a position facing each of the plurality of insulating rigid bodies provided on the second spacer 22. Note that the plurality of insulating rigid bodies arranged on the first spacer 21 and the plurality of insulating rigid bodies arranged on the second spacer 22 may be arranged at positions not facing each other when assembled on the unit cells 10, and may be arranged at positions shifted in at least one of the height direction and the width direction.

[0084] Furthermore, the thickness of the insulating rigid body need only be such that it does not penetrate the first spacer 21 and the second spacer 22 even when the gap between the first spacer 21 and the second spacer 22 is at its smallest, and is, for example, smaller than the thickness of the first spacer 21 and the thickness of the second spacer 22.

[0085] In this modified example, the cross-sectional shape of the insulating rigid body as viewed in the width direction has been described as a hexagonal shape as shown in FIG. 24, but the cross-sectional shape is not particularly limited to this shape.

[0086] Fig. 27 is a diagram for explaining a fourth example of the cross-sectional shape of the insulating rigid body in the modified example. As shown in Fig. 27, the insulating rigid body 38 may have a semi-elliptical shape in which the surfaces other than the bonding surface are formed by curves. Fig. 28 is a diagram for explaining a fifth example of the cross-sectional shape of the insulating rigid body in the modified example. As shown in Fig. 28, the insulating rigid body 39 may have a shape that tapers toward the opposing first spacer 21.

[0087] The above-described modified examples may be implemented in whole or in part in appropriate combination. In general, when a wound electrode body is used as a battery element in a single cell, the amount of deformation of the single cell (more specifically, the amount of deformation of the battery element) due to charging / discharging or aging differs between the center and both ends in the height direction of the single cell. The center deforms more than the both ends. This causes variation in the restraining load in the height direction.

[0088] In the battery packs described in the second and subsequent embodiments, as will be described below, it is possible to suppress an increase in the restraint load due to deterioration over time, and further suppress variations in the restraint load in the height direction.

[0089] (Embodiment 2) Fig. 29 is a vertical cross-sectional view of a battery pack according to embodiment 2. Fig. 30 is a cross-sectional view taken along line XXX-XXX shown in Fig. 29. A battery pack 1A according to embodiment 2 will be described with reference to Figs. 29 and 30.

[0090] 29 and 30, the battery pack 1A according to the second embodiment differs from the battery pack 1 according to the first embodiment in the configuration of a load adjustment mechanism 20A. The other configurations are substantially the same.

[0091] The load adjustment mechanism 20A includes a first spacer 21, a second spacer 22, a positioning member (holding member) 23, a first elastic body 41, a second elastic body 42, and a plurality of bracing members 50.

[0092] The first spacer 21, the second spacer 22, and the positioning member 23 have substantially the same configuration as in the first embodiment.

[0093] The plurality of bracing members 50 are provided between the first spacer 21 and the second spacer 22, and have a higher hardness than the first spacer 21 and the second spacer 22. The plurality of bracing members 50 are made of an insulating rigid body. For example, the plurality of bracing members 50 are made of a ceramic material such as alumina or zirconia.

[0094] The plurality of bracing members 50 include a plurality of first bracing members 51 and a plurality of second bracing members 52.

[0095] The cross-sectional shape of the first bracing member 51 and the second bracing member 52 as viewed from the width direction is, for example, a polygonal shape. Specifically, the cross-sectional shape of the first bracing member 51 and the second bracing member 52 is an octagon that is symmetrical in the vertical and horizontal directions as viewed from the width direction. The thickness of the second bracing member 52 is thicker than the thickness of the first bracing member 51. Note that, as described later, the cross-sectional shapes of the first bracing member 51 and the second bracing member 52 can be changed as appropriate.

[0096] The multiple first tension members 51 are arranged in a first region R1 corresponding to a central region of the single cells 10 when viewed from an arrangement direction in which the multiple unit cells 10 are arranged in a row. The multiple first tension members 51 include, for example, those lined up along a direction parallel to the height direction of the unit cells 10 that is perpendicular to the arrangement direction, those lined up along a direction parallel to the width direction of the unit cells 10 that is perpendicular to the arrangement direction and the height direction, and those lined up along a diagonal line of the unit cells.

[0097] Among the multiple first tension members 51, those aligned along a direction parallel to the height direction are disposed approximately at the center in the width direction of the cell 10. Among the multiple first tension members 51, those aligned along a direction parallel to the width direction are disposed approximately at the center in the height direction of the cell 10.

[0098] When viewed from the above-mentioned arrangement direction, the multiple first bracing members 51 are arranged at positions that are line-symmetrical with respect to a center line of the cell that extends along the height direction through the center of the width direction of the cell 10.

[0099] As described below, the multiple first bracing members 51 are provided so as to be in a state where, when the gap between the first spacer 21 and the second spacer 22 is minimized by the restraining load, the first bracing members 51 do not penetrate the first spacer 21 and the second spacer 22 but are embedded in the first spacer 21 and the second spacer 22. Note that the state where the gap between the first spacer 21 and the second spacer 22 is minimized by the restraining load refers to a state where the unit cell has reached the end of its use and has expanded due to deterioration over time, as described below.

[0100] When viewed from the above-mentioned arrangement direction, the multiple second tension members 52 are arranged in second regions R2 corresponding to both outsides of the central region in the height direction of the unit cells 10. The multiple second tension members 52 include, for example, those aligned along a direction parallel to the above-mentioned height direction and those aligned along a diagonal line of the unit cells 10.

[0101] Among the multiple second tension members 52, those aligned in a direction parallel to the height direction are disposed approximately in the center in the width direction of the cell 10. When viewed from the above-mentioned arrangement direction, the multiple second tension members 52 are disposed at positions that are line-symmetrical with respect to the center line of the cell that extends along the height direction through the center in the width direction of the cell 10.

[0102] The arrangement of the first tension member 51 and the second tension member 52 is not limited to the above, and as long as they are distributed in the first region R1 and the second region R2, they may be arranged as shown in Figures 13 to 16 above, or can be changed as appropriate.

[0103] The first elastic body 41 and the second elastic body 42 have a plate-like shape and are arranged so as to overlap the central region of the above-mentioned single cell 10 when viewed from the arrangement direction. The first elastic body 41 and the second elastic body 42 have a hardness that allows a restraining load equivalent to that of the above-mentioned outer region to act on them in the initial assembly state of the battery pack 1, for example. The first elastic body 41 and the second elastic body 42 are preferably made of rubber or a foaming agent that deforms with an increase in the restraining load.

[0104] In the initial assembly state, the first elastic body 41 is disposed between the multiple first bracing members 51 and the first spacer 21. The first elastic body 41 is disposed adjacent to the first spacer 21. The first elastic body 41 is fixed to the first spacer 21 by an adhesive or the like. In the initial assembly state, the first elastic body 41 abuts against the first bracing members 51, thereby forming a gap between the first elastic body 41 and the positioning member 23.

[0105] In the initial assembly state, the second elastic body 42 is disposed between the multiple first bracing members 51 and the second spacer 22. The second elastic body 42 is disposed adjacent to the second spacer 22. The second elastic body 42 is fixed to the first spacer 21 by an adhesive or the like. In the initial assembly state, the second elastic body 42 abuts against the first bracing members 51, thereby forming a gap between the second elastic body 42 and the positioning member 23.

[0106] FIG. 31 is a diagram illustrating the thickness of each member constituting the load adjustment mechanism provided in the battery pack according to the second embodiment.

[0107] As shown in FIG. 31, the thickness of the first spacer 21 and the second spacer 22 is t p1 The thickness of the positioning member is t p2 The thickness of the first tension member 51 is t r1 The thickness of the second tension member 52 is t r2 The thickness t of the first tension member 51 is r1 is the thickness t of the second tension member 51 r2 is smaller by the thickness of the elastic body.

[0108] In this case, the first tension member 51 and the second tension member 52 are set to satisfy the following relational expression (1) so that they do not penetrate the first spacer 21 and the second spacer 22 even when the gap between the first spacer 21 and the second spacer 22 is at a minimum.

[0109] t p2 <t r2 <t p2 +2×t p1 ...(Formula 1) Here, the thickness of the first elastic body 41 and the second elastic body 42 before assembly is T0 (not shown in FIG. 31), the thickness of the first elastic body 41 and the second elastic body 42 in the initial assembly state is T1, the thickness of the first elastic body 41 and the second elastic body 42 after deformation due to creep or the like is T2, and an arbitrary thickness between T1 and T2 is T3. Also, the thickness of the unit cell 10 that can tolerate deformation when the unit cell 10 expands is Δt cell (not shown in FIG. 31).

[0110] In this case, it is preferable to satisfy the following relations (2), (3), and (4). 1 / 2(t r2 -t p2 )>T0>T1>T3>T2≧0...(Formula 2) t r1 +2×T1+t p1 =t r2 ...(Formula 3) t r1 +2×-t p2 <Δt cell ...(Formula 4) 32 and 33 are cross-sectional views showing first and second examples of the cross-sectional shape of a first bracing member in a modified example. With reference to Fig. 32, the shape of a first bracing member 51 according to embodiment 2 will be described.

[0111] The cross-sectional shape of the first bracing member 51 may be modified as shown in the following first and second examples.

[0112] 32, in the first modification, when viewed from the width direction, the cross-sectional shape of the first tension member 51 has an arc-shaped surface in which the surface that contacts the first elastic body 41 and the second elastic body 42 is arc-shaped. Specifically, the cross-sectional shape of the first tension member 51 has a circular shape. Note that the cross-sectional shape of the first tension member 51 is not limited to a circular shape, and may be an elliptical shape or an oval shape.

[0113] 33, in the second modified example, when viewed from the width direction, the cross-sectional shape of the first tension member 51 has an acute-angled tip portion protruding toward the first elastic body 41 and the second elastic body 42. Specifically, the cross-sectional shape of the first tension member 51 has a substantially rhombic shape.

[0114] The cross-sectional shape of the second bracing member 52 can also be changed as appropriate, and as described above with reference to Figs. 17 and 18, it may be a rectangular shape, an elliptical shape, or an oval shape.

[0115] Below, using Figures 34 to 70, we will explain the distribution of restraint load in the height direction of the cells and the distribution of displacement of the cells in the initial state, the intermediate state of use, and the final state of use for the assembled batteries 1X1, 1X2, and 1Y in Comparative Examples 1 and 2 and Reference Example 1, and the assembled battery 1A of this embodiment.

[0116] Fig. 34 is a cross-sectional view of a battery pack showing an initial state of the battery pack in Comparative Example 1. As shown in Fig. 34, the battery pack 1X1 in Comparative Example 1 is different from the battery packs 1, 1A according to the first and second embodiments in that it does not include the load adjustment mechanisms 20, 20A and a spacer 21X is disposed between two adjacent cells 10. The spacer 21X is sandwiched between the two cells 10. The spacer 21X is made of an insulating resin plate.

[0117] FIG. 35 is a diagram showing the distribution of the restraining load in the height direction of the unit cell in the height direction of the unit cell in the initial state of Comparative Example 1. As shown in FIG.

[0118] As shown in FIG. 35, in the initial state, the unit cell 10 is not expanded, and the restraining load applied to the unit cell 10 is approximately constant in the height direction of the unit cell.

[0119] FIG. 36 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the initial state of Comparative Example 1. As shown in FIG.

[0120] As shown in FIG. 36, in the initial state, the unit cell 10 is not expanded, and the displacement of the unit cell 10 in the height direction is zero.

[0121] 37 is a cross-sectional view showing the state of a cell in the middle of use of Comparative Example 1. Note that the middle of use refers to the state until a certain period of time has elapsed from time t(0) shown in FIGS.

[0122] 37, during the middle of use, the central portion of the battery element expands, causing the central portion of the unit cell to expand more in the height direction than both ends in the height direction. However, in Comparative Example 1, the spacer 21X disposed between the two unit cells 10 does not deform, and thus deformation of the unit cells 10 is prevented.

[0123] FIG. 38 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 1 during the middle of use.

[0124] 38, in the middle of use of Comparative Example 1, the central part of the cell tends to expand more than both ends in the height direction as described above, so the load (constraint load) applied to the central part in the height direction becomes large as shown by the thick line. Also, compared to the initial state, the load applied to the entire height direction increases overall.

[0125] FIG. 39 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the middle of use of Comparative Example 1. As shown in FIG.

[0126] On the other hand, since the spacers 21X prevent deformation of the unit cells, during the intermediate period of use of Comparative Example 1, as shown in FIG. 39, the displacement of the unit cells remains zero in the height direction.

[0127] 40 is a cross-sectional view showing the state of a cell at the end of use in Comparative Example 1. The end of use refers to a state in which a long period of time has passed since the above-mentioned middle period of use.

[0128] As shown in FIG. 40, in the final stage of use of Comparative Example 1, the unit cell 10 tends to expand more overall than in the middle stage of use, and in particular, the central portion of the unit cell tends to expand more significantly.

[0129] FIG. 41 is a diagram showing the distribution of restraining load in the height direction of a cell in Comparative Example 1 at the end of use.

[0130] 41, in the final stage of use of Comparative Example 1, the cell 10 further expands as described above, and as a result, the restraint load increases overall compared to the distribution of the restraint load in the middle stage of use, which is indicated by the dashed line. In particular, the restraint load increases significantly in the center of the cell 10 in the height direction.

[0131] FIG. 42 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells at the end of use in Comparative Example 1. As shown in FIG.

[0132] On the other hand, since the spacers 21X prevent deformation of the unit cells, during the intermediate period of use of Comparative Example 1, the displacement of the unit cells in the height direction remains zero, as shown in FIG.

[0133] Thus, in Comparative Example 1, although the spacer 21X can suppress the displacement of the unit cell, the load applied to the center of the unit cell in the height direction increases toward the end of use, and the restraining load varies greatly in the height direction.

[0134] If the restraint load exceeds a predetermined value or if the restraint load varies greatly, the Li precipitation resistance is likely to deteriorate and the electrical resistance is likely to increase, which will deteriorate the safety and lifespan of the battery pack 1X1.

[0135] Fig. 43 is a cross-sectional view showing an initial state of a battery pack in Comparative Example 2. As shown in Fig. 43, in a battery pack 1X2 in Comparative Example 2, compared to the battery packs 1 and 1A according to embodiments 1 and 2, a load adjustment mechanism 20X2 is configured with an elastic body 60. The elastic body 60 is sandwiched between two single cells 10.

[0136] FIG. 44 is a diagram showing the distribution of the restraining load in the height direction of the unit cell in the height direction of the unit cell in the initial state of Comparative Example 2. As shown in FIG.

[0137] As shown in FIG. 44, in the initial state, the unit cell 10 is not expanded, and the restraining load applied to the unit cell 10 is approximately constant in the height direction of the unit cell.

[0138] FIG. 45 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the initial state of Comparative Example 2. As shown in FIG.

[0139] As shown in FIG. 45, in the initial state, the unit cell 10 is not expanded, and the displacement of the unit cell 10 in the height direction is zero.

[0140] Fig. 46 is a cross-sectional view showing the state of the battery pack in the middle of use of Comparative Example 2. As shown in Fig. 46, in the middle of use, the center of the battery element expands, and the center of the battery cell 10 also expands more in the height direction than both ends in the height direction. The elastic body 60 deforms in response to the expansion of the battery cell 10. Specifically, the elastic body 60 is compressed by the expanded battery cell.

[0141] FIG. 47 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 2 during the middle of use.

[0142] 47, in the middle of use of Comparative Example 2, as described above, the center of the cell 10 expands more than both ends in the height direction. At this time, the elastic body 60 deforms to follow the expansion of the cell, thereby mitigating the load caused by the expansion. Therefore, the restraint load applied to the cell 10 does not change much from the load in the initial state and remains approximately constant in the height direction.

[0143] FIG. 48 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the middle of use of Comparative Example 2.

[0144] As shown in Figure 48, during the middle of use of Comparative Example 2, due to the deformation of the single cell as described above, the displacement of the single cell in the height direction is distributed such that the central part in the height direction bulges more than both ends in the height direction in response to the deformation of the single cell.

[0145] Fig. 49 is a cross-sectional view showing the state of a cell at the end of use of Comparative Example 2. As shown in Fig. 49, at the end of use of Comparative Example 2, the cell 10 as a whole is more swollen than in the middle of use, and in particular, the central part of the cell is more swollen.

[0146] FIG. 50 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 2 at the end of use.

[0147] 50, at the end of use, the elastic body 60 is further compressed due to the deformation of the battery cell 10, and the overall restraint load increases in the height direction. On the other hand, the elastic body 60 deforms to follow the expansion of the battery cell 10, so that the restraint load applied to the battery cell 10 becomes approximately constant in the height direction.

[0148] FIG. 51 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells at the end of use in Comparative Example 2. As shown in FIG.

[0149] As shown in Figure 51, at the end of use of Comparative Example 2, due to the deformation of the single cells as described above, the displacement of the single cells in the height direction is distributed such that the central part in the height direction bulges more than both ends in the height direction, compared to the middle stage of use.

[0150] Thus, in Comparative Example 2, the bias in the load caused by the deformation of the cells 10 is alleviated with the deformation of the elastic body 60, and the restraining load applied to the cells 10 becomes substantially constant in the height direction, but the displacement occurring in the cells 10 cannot be suppressed. In such a case, the large displacement of the cells 10 causes the battery pack 1X2 to also deform significantly from its initial state. If the cells 10 and the battery pack 1X2 deform beyond the allowable value, there is a risk that the bus bars connecting the cells 10 to each other and the housing case housing the battery pack 1X2 will be damaged.

[0151] Fig. 52 is a cross-sectional view showing an initial state of the battery pack in Reference Example 1. As shown in Fig. 52, the battery pack 1Y in Reference Example 1 has a configuration substantially similar to that of the battery pack 1 according to Embodiment 1. That is, in Reference Examples 1 and 2, the first strut member 51 and the second strut member 52 have the same shape and also have substantially the same thickness.

[0152] FIG. 53 is a diagram showing the distribution of the restraining load in the height direction of the unit cell in the height direction of the unit cell in the initial state of Reference Example 1. As shown in FIG.

[0153] As shown in FIG. 53, in the initial state, the unit cell 10 is not expanded, and the restraining load applied to the unit cell 10 is approximately constant in the height direction of the unit cell.

[0154] FIG. 54 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the initial state of Reference Example 1. In FIG.

[0155] As shown in FIG. 54, in the initial state, the unit cell 10 is not expanded, and the displacement of the unit cell 10 in the height direction is zero.

[0156] FIG. 55 is a cross-sectional view showing the state of the battery pack in the middle of use of Reference Example 1. As shown in FIG. 55, in the middle of use, the center of the battery element expands, and the center of the height direction of the unit cell also expands more than both ends in the height direction. At this time, the first spacer 21 and the second spacer 22 are pressed against the unit cell 10 so that the gap between them becomes narrower. In this state, both the first strut member 51 and the second strut member 52, or the first strut member 51, is slightly depressed into the first spacer 21 and the second spacer 22. As a result, the first spacer 21 and the second spacer 22 are plastically deformed, and the restraining load increased by the expansion is absorbed.

[0157] FIG. 56 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Reference Example 1 during the intermediate period of use.

[0158] 56, in the middle of use of Reference Example 1, the center of the cell expands more than both ends in the height direction, so the load (constraint load) applied to the center in the height direction increases as shown by the thick line. Also, compared to the initial state, the load applied to the entire height direction increases overall.

[0159] FIG. 57 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the middle of use of Reference Example 1. In FIG.

[0160] As shown in FIG. 57, the displacement of the unit cells in the height direction is distributed such that the center part in the height direction bulges more than both ends in the height direction due to deformation of the unit cells.

[0161] Fig. 58 is a cross-sectional view showing the state of the cell at the end of use of Reference Example 1. As shown in Fig. 58, at the end of use of Reference Example 1, the cell 10 expands more overall compared to the middle of use, and in particular, the center of the cell 10 expands more significantly. At this time, the first tension member 51 is deeply embedded in the first spacer 21 and the second spacer 22. This causes the first spacer 21 and the second spacer to plastically deform, and the restraining load increased by the expansion is largely absorbed.

[0162] FIG. 59 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Reference Example 1 at the end of use.

[0163] 59, the central portion of the cell 10 expands more than both ends in the height direction, so the load (constraint load) applied to the central portion in the height direction becomes larger as shown by the thick line. Also, compared to the intermediate state, the load applied to the entire height direction increases overall.

[0164] On the other hand, as described above, the first spacer 21 and the second spacer 22 are plastically deformed, and the restraint load increased by expansion is largely absorbed, so that the overall restraint load can be reduced compared to Comparative Example 1. In particular, in the center of the unit cell 10, the first strut member 51 is largely embedded in the first spacer 21 and the second spacer 22, so that the restraint load can be greatly reduced. Also, at both ends of the unit cell 10 in the height direction, the second strut member 52 is embedded in the first spacer 21 and the second spacer 22, so that the restraint load can be reduced. As a result, in Reference Example 1, the variation in the restraint load in the height direction of the unit cell 10 can be suppressed compared to Comparative Examples 1 and 2.

[0165] FIG. 60 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells at the end of use of Reference Example 1. As shown in FIG.

[0166] As shown in FIG. 60, in the final stage of use of Reference Example 1, the deformation of the single cells 10 as described above results in a distribution in which the center of the cells in the height direction bulges out more than both ends in the height direction compared to the middle stage of use. Here, in Reference Example 1, due to the presence of the first tension member 51, the displacement of the center of the single cells 10 is a value just before reaching the first tension member 51. Therefore, in Reference Example 1, the displacement of the single cells can be reduced compared to Comparative Example 2. This makes it possible to suppress the displacement of the single cells 10 and the battery pack 1 to be equal to or less than the deformation tolerance. As a result, it is possible to suppress damage to the bus bars connecting the single cells 10 and the storage case that stores the battery pack 1X2.

[0167] Fig. 61 is a cross-sectional view showing an initial state of the battery pack in embodiment 2. As shown in Fig. 61, the battery pack 1A in embodiment 2 has the above-mentioned configuration.

[0168] FIG. 62 is a diagram showing distribution of restraining load in the height direction of a cell in the height direction of the cell in the initial state of the second embodiment.

[0169] As shown in FIG. 62, in the initial state, the unit cell 10 is not expanded, and the restraining load applied to the unit cell 10 is approximately constant in the height direction of the unit cell.

[0170] FIG. 63 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the initial state of the second embodiment.

[0171] As shown in FIG. 63, in the initial state, the unit cell 10 is not expanded, and the amount of displacement of the unit cell 10 is approximately constant in the height direction of the unit cell.

[0172] Fig. 64 is a cross-sectional view showing the state of the battery pack in the middle of use according to the second embodiment. As shown in Fig. 64, in the middle of use, the center of the battery element expands, and the center of the height of the battery cell 10 also expands more than both ends in the height direction. At this time, the center portions of the first spacer 21 and the second spacer 22 pressed by the expansion of the battery cell 10 are easily deformed by the first elastic body 41 and the second elastic body 42, and are displaced toward the positioning member 23 as deterioration of the battery cell 10 progresses.

[0173] Fig. 65 is a diagram showing the state in which the elastic body is deformed in the middle of use of the second embodiment. As described above, when the central portion of the first spacer 21 and the second spacer 22 is displaced toward the positioning member 23, as shown in Fig. 65, the first tension member 51 bites into the first elastic body 41 and the second elastic body 42 while the second tension member 52 maintains a state of abutment against the first spacer 21 and the second spacer 22 or while slightly biting into them. At this time, the first elastic body 41 and the second elastic body 42 are deformed, and the restraining load that has increased due to the expansion is dispersed. As a result, in the second embodiment, the variation in the restraining load in the height direction is suppressed more than in the first comparative example and the first reference example.

[0174] FIG. 66 is a diagram showing distribution of restraining load in the height direction of a cell in the middle of use according to the second embodiment.

[0175] 66, in the intermediate stage of use, the load adjustment mechanism 20A is compressed due to the deformation of the battery cell, and the overall restraining load increases in the height direction. Meanwhile, as described above, the first elastic body 41 and the second elastic body 42 are deformed, and the restraining load applied to the battery cell 10 becomes substantially constant in the height direction.

[0176] FIG. 67 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells during intermediate use according to the second embodiment.

[0177] As shown in FIG. 67, during intermediate use, the unit cells 10 deform as described above, and the displacement of the unit cells in the height direction is distributed such that the central part in the height direction bulges more than both ends in the height direction.

[0178] Fig. 68 is a cross-sectional view showing the state of the cell at the end of use of embodiment 2. As shown in Fig. 68, at the end of use of embodiment 2, cell 10 as a whole is more swollen than in the middle of use, and in particular, the central part of the cell is more swollen.

[0179] At this time, the first bracing member 51 penetrates the first elastic body 41 and the second elastic body 42, or penetrates into the first spacer 21 and the second spacer 22 via the first elastic body 41 and the second elastic body 42 that have been thinned to the limit. In addition, the second bracing member 52 also penetrates into the first spacer 21 and the second spacer 22. As a result, while the first elastic body 41 and the second elastic body 42 deform, the first spacer 21 and the second spacer 22 plastically deform at the center and both ends in the height direction.

[0180] FIG. 69 is a diagram showing distribution of restraining load in the height direction of a cell in the height direction of the cell at the end of use according to the second embodiment.

[0181] 69, at the end of use, as described above, the constraint load is absorbed by the deformation of the first elastic body 41 and the second elastic body 42, while the constraint load is also absorbed by the plastic deformation of the first spacer 21 and the second spacer 22, so that the constraint load can be reduced overall compared to Comparative Example 1 and Reference Example 1. In addition, as described above, the first spacer 21 and the second spacer 22 plastically deform at the center and both ends in the height direction, so that the variation in the constraint load can be suppressed at the center and both ends in the height direction.

[0182] FIG. 70 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells at the end of use according to the second embodiment.

[0183] As described above, in the second embodiment, due to the presence of the first bracing member 51, the amount of displacement of the center of the cell 10 is a value just before it reaches the first bracing member 51. For this reason, as shown in FIG. 70, in the second embodiment, the amount of displacement of the cell can be reduced compared to the second comparative example. This makes it possible to suppress the amount of displacement of the cell 10 and the battery pack 1 to be equal to or less than the allowable deformation amount. As a result, it is possible to suppress damage to the bus bars connecting the cells 10 to each other and damage to the housing case that houses the battery pack 1X2.

[0184] (Embodiment 3) Fig. 71 is a vertical cross-sectional view of a battery pack according to embodiment 3. With reference to Fig. 71, a battery pack 1B according to embodiment 3 will be described.

[0185] 71, the battery pack 1B according to embodiment 3 differs from the battery pack 1A according to embodiment 2 in that the first elastic body 41 and the second elastic body 42 are omitted and the first bracing member 51 is configured to be more likely to sink into the first spacer 21 and the second spacer 22 than the second bracing member 52. The other configurations are substantially the same.

[0186] The cross-sectional shape of the first bracing member 51 has an elliptical shape with a minor axis in the height direction and a major axis in the arrangement direction (thickness direction). The cross-sectional shape of the first bracing member 51 is not limited to an ellipse, and may be an oval shape. The cross-sectional shape of the first bracing member 51 may also have a shape that tapers toward the tip in the thickness direction. In this case, the tip may have a vertex portion with an acute angle, and more specifically, the cross-sectional shape of the first bracing member 51 may be a rhombus shape.

[0187] The cross-sectional shape of the second bracing member 52 is polygonal, and in this case, a pair of sides of the polygonal shape that are parallel to the height direction contact the first spacer 21 and the second spacer 22. In this case, each vertex of the polygonal shape may be chamfered. The polygonal shape may be, for example, a rectangle or an octagon. In addition, the surface of the second bracing member 52 that contacts the first spacer 21 and the second spacer 22 may be formed in an arc shape so that the second bracing member 52 is less likely to sink into the first spacer 21 and the second spacer 22 than the first bracing member 51.

[0188] In this configuration, when the unit cell 10 expands due to deterioration over time, the first bracing member 51 sinks into the first spacer 21 and the second spacer 22 more than the second bracing member 52, and the first spacer 21 and the second spacer 22 undergo large plastic deformation on the side of the first bracing member 51. This makes it possible to absorb more of the restraint load on the central side of the unit cell 10, thereby suppressing variation in the restraint load between the central part and both ends in the height direction.

[0189] (Embodiment 4) Fig. 72 is a vertical cross-sectional view of a battery pack according to embodiment 4. With reference to Fig. 72, a battery pack 1C according to embodiment 4 will be described.

[0190] 72, the battery pack 1C according to embodiment 4 differs from the battery pack 1B according to embodiment 3 in that the shape of the first tension member 51 is different and the first tension member 51 is provided so as to be able to be embedded in the positioning member 23. The other configurations are substantially the same.

[0191] The multiple first bracing members 51 include a first member 511 , a second member 512 , a third member 513 , a fourth member 514 , a fifth member 515 , and a sixth member 516 .

[0192] The first member 511, the second member 512, and the third member 513, and the fourth member 514, the fifth member 515, and the sixth member 516 are arranged to sandwich the positioning member 23. The first member 511, the second member 512, and the third member 513 are arranged on the side of the positioning member 23 where the first spacer 21 is located. The fourth member 514, the fifth member 515, and the sixth member 516 are arranged on the side of the positioning member 23 where the second spacer 22 is located.

[0193] The first member 511 and the fourth member 514 have substantially the same shape, and are arranged to be point-symmetric with respect to a predetermined point on the positioning member 23.

[0194] The first member 511 includes a tip portion having an acute angle that is engaged with the positioning member 23, and a flat portion that is in planar contact with the first spacer 21. The flat portion is provided on the opposite side (first spacer 21 side) of the tip portion. The thickness of the first member 511 from the tip portion to the flat portion is t r3 Let us assume that.

[0195] The fourth member 514 includes a tip portion having an acute angle that is engaged with the positioning member 23, and a flat portion that is in planar contact with the second spacer 22. The flat portion is provided on the opposite side (the second spacer 22 side) of the tip portion. The thickness of the first member 511 from the tip portion to the flat portion is t r2 Let us assume that.

[0196] The thickness of the second bracing member 52 is t r 1, and the thickness between the first spacer 21 and the second spacer 22 in the initial state is t r2-3 Let us assume that.

[0197] In this case, the following relations (4), (5), and (6) hold. t r2-3 =t r1 ...Equation (4) t r2 <t r1 ...Equation (5) t r3 <t t_r3 ...Equation (6) The second member 512 and the fifth member 515 have substantially the same shape, and are arranged to be point-symmetric with respect to a predetermined point on the positioning member 23.

[0198] The cross-sectional shape of the second member 512 is polygonal. The second member 512 includes a first flat portion that is in planar contact with the positioning member 23 and a second flat portion that is in planar contact with the first spacer 21. The thickness of the second member 512 is smaller than the thickness of the first member 511.

[0199] The cross-sectional shape of the fifth member 515 is polygonal. The fifth member 515 includes a first flat portion that is in planar contact with the positioning member 23 and a second flat portion that is in planar contact with the second spacer 22. The thickness of the fifth member 515 is smaller than the thickness of the fourth member 514.

[0200] The third member 513 and the sixth member 516 have substantially the same shape, and are arranged to be point-symmetric with respect to a predetermined point on the positioning member 23.

[0201] The third member 513 has a recessed portion that recesses into the positioning member 23 and a flat portion that comes into planar contact with the first spacer 21. The third member 513 also has a retracted portion to avoid interference with the recessed portion of a sixth member 516, which will be described later. The retracted portion is provided so as to be continuous with the recessed portion, and is provided so as to be recessed toward the first spacer 21 side.

[0202] The sixth member 516 has a recessed portion that recesses into the positioning member 23 and a flat portion that comes into planar contact with the second spacer 22. The sixth member 516 also has a retracted portion to avoid interference with the recessed portion of the third member 513. The retracted portion is provided so as to be continuous with the recessed portion, and is provided so as to be recessed toward the second spacer 22 side.

[0203] The recessed portion of the sixth member 516 is disposed so as to face the retreated portion of the third member 513. The recessed portion of the sixth member 516 is disposed so as to face the recessed portion of the third member 513.

[0204] In this configuration, when the cell 10 expands due to deterioration over time, the first bracing member 51 (more specifically, the first member 511, the third member 513, the fourth member 514, and the sixth member 516) sinks into the positioning member 23, causing the positioning member 23 to plastically deform at the center side in the height direction. This allows the restraint load to be absorbed more at the center side of the cell 10, making it possible to suppress variation in the restraint load between the center and both ends in the height direction.

[0205] As will be described below with reference to Figs. 73 and 74, the first tension member 51 may be modified as follows.

[0206] Figures 73 and 74 are cross-sectional views showing the shapes of the first and second bracing members in the first and second modified examples. The shapes of the first bracing members in the first and second modified examples will be described with reference to Figures 73 to 74.

[0207] As shown in FIG. 73, in the first modified example, the plurality of first bracing members 51 include a first member 511A, a second member 512A, a third member 513A, and a fourth member 514A.

[0208] The first member 511A, the second member 512A, the third member 513A, and the fourth member 514A are arranged to sandwich the positioning member 23. The first member 511A and the second member 512A are arranged on the side of the positioning member 23 where the first spacer 21 is located. The third member 513A, the fifth member 515, and the sixth member 516 are arranged on the side of the positioning member 23 where the second spacer 22 is located.

[0209] The first member 511A and the third member 513A have substantially the same shape, and are disposed so as to be symmetrical with respect to a predetermined center line of the positioning member .

[0210] The first member 511A has an acute-angled tip portion (protruding portion) that protrudes toward the positioning member 23. The first member 511A has a flat portion that comes into planar contact with the first spacer 21.

[0211] The third member 513A has an acute-angled tip portion (protruding portion) that protrudes toward the positioning member 23 3. The third member 513A has a flat portion that contacts the second spacer 22 in a planar manner.

[0212] The second member 512A and the fourth member 514A have substantially the same shape, and are disposed so as to be symmetrical with respect to a predetermined center line of the positioning member .

[0213] The second member 512A has a first flat portion that contacts the positioning member 23 in a planar manner, and a second flat portion that contacts the first spacer 21 in a planar manner.

[0214] The fourth member 514A has a first flat portion that contacts the positioning member 23 in a flat plane, and a second flat portion that contacts the second spacer 22 in a flat plane.

[0215] Even in this configuration, when the cell 10 expands due to aging, the first bracing member 51 (more specifically, the first member 511A and the third member 513A) sinks into the positioning member 23, causing plastic deformation of the positioning member 23 at the center side in the height direction. This allows the restraint load to be absorbed more at the center side of the cell 10, making it possible to suppress variation in the restraint load between the center and both ends in the height direction.

[0216] As shown in FIG. 74, in the second modified example, the plurality of first bracing members 51 include a first member 511B, a second member 512B, a third member 513B, and a fourth member 514B.

[0217] The first member 511B, the second member 512B, the third member 513B, and the fourth member 514B are arranged to sandwich the positioning member 23 therebetween.

[0218] The first member 511B has a recessed portion that recesses into the positioning member 23 and a flat portion that comes into planar contact with the first spacer 21. The first member 511B also has a retracted portion to avoid interference with the recessed portion of a third member 513B, which will be described later. The recessed portion and the retracted portion are located on the opposite side (the positioning member 23 side) to the side where the flat portion is located.

[0219] The recessed portion of the first member 511B is provided on both ends in the height direction. The retreated portion of the first member 511B is provided in the center in the height direction, and is provided between the recessed portions provided on both ends in the height direction.

[0220] The third member 513B has a recessed portion that recesses into the positioning member 23 and a flat portion that comes into planar contact with the second spacer 22. The third member 513B also has a retracted portion to avoid interference with the recessed portion of the first member 511B described above. The recessed portion and the retracted portion are located on the opposite side (positioning member 23 side) to the side where the flat portion is located.

[0221] The recessed portion of the third member 513B is provided in the center in the height direction, and the retracted portions of the third member 513B are provided on both ends in the height direction.

[0222] The second member 512B has a recessed portion that recesses into the positioning member 23 and a flat portion that comes into planar contact with the first spacer 21. The recessed portion of the first member 511B is provided in the center in the height direction. The recessed portion is located on the opposite side (positioning member 23 side) to the side where the flat portion is located.

[0223] The fourth member 514B has a flat portion that comes into planar contact with the second spacer 22. The fourth member 514B also has a retracted portion to avoid interference with the recessed portion of the second member 512B described above. The retracted portion is located on the opposite side (positioning member 23 side) to the side where the flat portion is located.

[0224] The recessed portion of the third member 513B is provided in the center in the height direction, and the retracted portions of the third member 513B are provided on both ends in the height direction.

[0225] Even in this configuration, when the cell 10 expands due to aging, the first bracing member 51 sinks into the positioning member 23, causing plastic deformation of the positioning member 23 at the center side in the height direction. This allows the central side of the cell 10 to absorb the restraint load more effectively, making it possible to suppress variation in the restraint load between the center and both ends in the height direction.

[0226] (Embodiment 5) Fig. 75 is a cross-sectional view showing an initial state of the battery pack in embodiment 5. With reference to Fig. 75, a battery pack 1D according to embodiment 5 will be described.

[0227] As shown in Fig. 75, the battery pack 1D according to the fifth embodiment differs from the battery pack 1A according to the second embodiment in the configuration of the load adjustment mechanism 20D, specifically, in that the first elastic body 41 and the second elastic body 42 are omitted, and the second bracing member 52D is made of an elastic member. The other configurations are almost the same. For example, a coil spring can be used as the elastic member used for the second bracing member 52D.

[0228] FIG. 76 is a diagram showing distribution of restraining load in the height direction of a cell in the height direction of the cell in the initial state of the fifth embodiment.

[0229] As shown in FIG. 76, in the initial state, the unit cell 10 is not expanded, and the restraining load applied to the unit cell 10 is approximately constant in the height direction of the unit cell.

[0230] FIG. 77 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells in the initial state of the fifth embodiment.

[0231] As shown in FIG. 77, the unit cell 10 is not expanded, and the amount of displacement of the unit cell 10 in the height direction is zero.

[0232] Fig. 78 is a cross-sectional view showing the state of the battery pack at the end of use of embodiment 5. As shown in Fig. 78, at the end of use of embodiment 5, the unit cells 10 swell significantly overall, and in particular, the central parts of the unit cells swell most significantly.

[0233] At this time, the first bracing member 51 sinks into the first spacer 21 and the second spacer 22. As a result, the first spacer 21 and the second spacer 22 undergo plastic deformation at the center in the height direction. Meanwhile, the second bracing member 52D made of an elastic member applies an elastic biasing force to the first spacer 21 and the second spacer 22 against the compression direction. That is, the second bracing member 52D applies an elastic biasing force to move the first spacer 21 and the second spacer 22 away from each other.

[0234] FIG. 79 is a diagram showing distribution of restraining load in the height direction of a cell in the height direction of the cell in the final stage of use of the fifth embodiment.

[0235] As shown in FIG. 79, in the final stage of use, as described above, the first spacer 21 and the second spacer 22 undergo plastic deformation at the center in the height direction, and absorb the restraining load at the center. In addition, as described above, at both ends in the height direction, the second bracing member 52D applies an elastic force to the first spacer 21 and the second spacer 22 against the compression direction. Therefore, in the fifth embodiment, the restraining load can be significantly reduced at the center in the height direction compared to the first comparative example. In addition, at both ends in the height direction, the restraining load increases due to the elastic force of the second bracing member 52D. As a result, the variation in the restraining load can be suppressed at the center in the height direction and at both ends.

[0236] FIG. 80 is a diagram showing the distribution of the displacement of the unit cells in the height direction of the unit cells at the end of use according to the fifth embodiment.

[0237] As shown in Fig. 80, due to the presence of the first bracing member 51, the amount of displacement of the center of the cell 10 in the height direction is a value just before it reaches the first bracing member 51. On the other hand, at both ends of the cell 10 in the height direction, the displacement of the cell 10 is suppressed by the elastic biasing force of the second bracing member 52D. Therefore, as shown in Fig. 80, in the fifth embodiment, the amount of displacement of the cell can be reduced compared to the second comparative example.

[0238] As described above, in the fifth embodiment as well, it is possible to suppress the variation in the restraining load at the center portion and both ends in the height direction.

[0239] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0240] 1, 1A, 1B, 1C, 1D, 1X1, 1X2, 1Y battery pack, 3 bus bar, 5 nut, 7, 8 end plate, 9 restraint band, 10 single cell, 11 battery case, 13 lid, 13j safety valve, 19b positive electrode external terminal, 19c negative electrode external terminal, 20, 20A, 20D, 20X2 load adjustment mechanism, 21 first spacer, 21X spacer, 22 second spacer, 23 positioning member, 24, 25, 26, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 insulating rigid body, 40 battery string, 41 first elastic body, 42 second elastic body, 50 bracing member, 51 first bracing member, 52, 52D second bracing member, 60 Elastic body, 511, 511A, 511B first members, 512, 512A, 512B second members, 513, 513A, 513B third members, 514, 514A, 514B fourth members, 515 fifth members, and 516 sixth members.

Claims

1. A plurality of unit cells having a rectangular parallelepiped outer shape and arranged and restrained in a predetermined arrangement direction; a plate-shaped first spacer and a plate-shaped second spacer that are disposed between each pair of adjacent unit cells in the arrangement direction and that insulate the adjacent unit cells from each other; an insulating member provided between the first spacer and the second spacer, the insulating member has a hardness higher than that of the first spacer and the second spacer, is provided so as to contact each of the first spacer and the second spacer that sandwich the insulating member at a plurality of points between the first spacer and the second spacer, and has a thickness in the arrangement direction such that the insulating member does not penetrate the first spacer and the second spacer even when a gap between the first spacer and the second spacer is minimized due to an increase in a restraining load; the insulating member is disposed on a plate-shaped retaining member disposed between the first spacer and the second spacer at a distance from the first spacer and the second spacer, or is disposed on at least one of the first spacer and the second spacer.

2. A plurality of unit cells having a rectangular parallelepiped outer shape and arranged and restrained in a predetermined arrangement direction; a plate-shaped first spacer and a plate-shaped second spacer that are disposed between each pair of adjacent unit cells in the arrangement direction and that insulate the adjacent unit cells from each other; a plurality of bracing members provided between the first spacer and the second spacer and having a hardness higher than that of the first spacer and the second spacer; the plurality of tension members include a first tension member disposed in a first region corresponding to a central region of the battery cell when viewed from the arrangement direction, and a second tension member provided in a second region corresponding to outer regions located on both outer sides of the central region in a height direction of the battery cell perpendicular to the arrangement direction, the first bracing member is provided so as to be embedded in the first spacer and the second spacer without penetrating the first spacer and the second spacer when a gap between the first spacer and the second spacer is minimized due to an increase in the restraining load, The plurality of bracing members are arranged on a plate-shaped retaining member disposed between the first spacer and the second spacer at a distance from the first spacer and the second spacer, or are arranged on at least one of the first spacer and the second spacer.

3. The battery pack according to claim 2 , wherein the first bracing member is configured to be embedded into the first spacer and the second spacer more than the second bracing member.

4. The plurality of tension members are arranged on the plate-shaped retaining member disposed between the first spacer and the second spacer at a distance from the first spacer and the second spacer, The battery pack according to claim 2 , wherein an elastic body is disposed between the first bracing member and the first spacer and between the first bracing member and the second spacer.

5. The plurality of tension members are arranged on the plate-shaped retaining member disposed between the first spacer and the second spacer at a distance from the first spacer and the second spacer, 3 . The battery pack according to claim 2 , wherein the first bracing member is disposed so as to be embedded into the holding member when a gap between the first spacer and the second spacer becomes smaller due to an increase in a restraining load.

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