JP7631866B2 - Battery pack - Google Patents

Description

This disclosure relates to the configuration between multiple cells included in a battery pack.

The battery pack is, for example, constructed by stacking multiple rectangular cells. Spacers are placed between the cells to adjust the restraining load acting on the cells.

For example, JP 2019-128980 A (Patent Document 1) discloses a configuration in which a pressure adjustment member that adjusts the restraining load (restraining pressure) is provided between stacked single cells in a battery pack formed by stacking multiple 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 pressure of a certain level or more is generated due to the expansion and contraction of the outer shape of the single cells caused by charging and discharging the single cells, the pressure adjustment member is deformed by the liquid moving from the storage portion to the holding portion. When pressure of a certain level or more is released, the liquid in the holding portion moves to the storage portion, thereby maintaining a constant restraining load.

JP 2019-128980 A

However, the above-mentioned maintenance of a constant restraint load by the pressure adjustment member is premised on the assumption that the deformation of the external 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 an increase in the restraint load due to deterioration of the cell over time. As the cell deteriorates over time, gas is generated inside, causing the external shape of the cell to expand, and the restraint load increases due to the increase in pressure inside the cell. As a result, it may not be possible to maintain a constant restraint load.

This disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a battery pack that suppresses an increase in restraining load due to aging.

The battery pack according to one aspect of the present disclosure has a rectangular shape and includes a plurality of unit cells that are constrained while arranged in a predetermined arrangement direction, a plurality of plate-shaped spacers that are provided between the unit cells and 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 that prevents the insulating member from penetrating the spacers even when the distance between the two spacers is minimized due to an increase in the constraining load.

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

The battery pack according to one aspect of the present disclosure includes a plurality of unit cells having a rectangular shape and constrained in a state in which they are arranged in a predetermined arrangement direction, a plurality of plate-shaped spacers provided between the unit cells to insulate the unit cells, and a plurality of tension members provided between the spacers and having a hardness higher than that of the spacers. The plurality of tension members include a first tension member arranged in a first region corresponding to a central region of the unit cells when viewed from the arrangement direction, and a second tension member provided in a second region corresponding to outer regions located on both outsides of the central region in a height direction of the unit cells perpendicular to the arrangement direction. The first tension member is arranged so as to be embedded in the spacer without penetrating it when the gap between the two spacers is minimized due to an increase in the restraining load.

Generally, when a cell expands, the central region of the cell expands more than the peripheral regions of the cell. Therefore, 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 placed on the central region of the cell.

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 single cells due to aging, the first tensioning member arranged in the first region corresponding to the central region sinks 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 single cells, thereby making it possible to suppress the occurrence of a difference in the restraining load between the central region of the single cells and the peripheral regions of the single cells.

In the battery pack according to one aspect of the present disclosure, it is preferable that the first tension member is configured to be embedded in the spacer more than the second tension member.

By configuring it in this way, 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 single cell can be more reliably reduced.

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

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.

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

By configuring it in this way, the first tension member sinks into the retaining member, causing the retaining member to undergo plastic deformation, thereby reducing the restraining load applied to the central region of the single cell.

In the battery pack according to one aspect of the present disclosure, the second tension member may be made of an elastic member.

By configuring it in this way, 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 the 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.

This disclosure makes it possible to provide a battery pack that suppresses the increase in restraining load caused by aging.

1 is a diagram showing an example of a configuration of a battery pack according to a first embodiment; 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. 5 is a timing chart showing an example of a change in a restraining load acting on a battery pack due to aging. 5 is a timing chart showing an example of a change in the overall restraining load acting on the battery pack. 4 is a cross-sectional view showing a detailed configuration of a load adjustment mechanism. FIG. 5A to 5C are diagrams for explaining thicknesses of members constituting the load adjustment mechanism. 10A and 10B are diagrams illustrating an example of an arrangement of a plurality of insulating rigid bodies provided on a positioning member. 5A to 5C are diagrams for explaining the operation of a load adjustment mechanism of the battery pack 1. 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. 5 is a timing chart showing an example of a change in a restraining load due to aging acting on the battery pack according to the first embodiment; 5 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. 13A and 13B are diagrams for explaining a first example of an arrangement of a plurality of insulating rigid bodies in a modified example. 13A and 13B are diagrams for explaining a second example of an arrangement of a plurality of insulating rigid bodies in the modified example. FIG. 13 is a diagram for explaining a third example of an arrangement of a plurality of insulating rigid bodies in the modified example. FIG. 13 is a diagram for explaining a fourth example of an arrangement of a plurality of insulating rigid bodies in the modified example. FIG. 13 is a diagram for explaining a fifth example of an arrangement of a plurality of insulating rigid bodies in the modified example. 13A and 13B are diagrams for explaining a first example of a cross-sectional shape of an insulating rigid body in a modified example. 13A and 13B are diagrams for explaining a second example of a cross-sectional shape of an insulating rigid body in the modified example. 13A and 13B are diagrams for explaining a third example of a cross-sectional shape of an insulating rigid body in a modified example. 13 is a cross-sectional view showing a detailed configuration of a load adjustment mechanism in a modified example. FIG. 13A and 13B are diagrams for explaining a first arrangement example of a plurality of insulating rigid bodies arranged on a second spacer in the modified example. 13A and 13B are diagrams for explaining the configuration of a first spacer in a modified example. 10A and 10B are diagrams for explaining the operation of a load adjustment mechanism of a battery pack according to a modified example. FIG. 11 is a cross-sectional view showing a detailed configuration of a load adjustment mechanism in another modified example. 13A and 13B are diagrams for explaining a second arrangement example of a plurality of insulating rigid bodies arranged on a second spacer in the modified example. 13A and 13B are diagrams for explaining an example of an arrangement of a plurality of insulating rigid bodies arranged on a first spacer in a modified example. 13A and 13B are diagrams for explaining a fourth example of a cross-sectional shape of an insulating rigid body in a modified example. 13A and 13B are diagrams for explaining a fifth example of a cross-sectional shape of an insulating rigid body in a modified example. FIG. 11 is a vertical cross-sectional view of a battery pack according to a second embodiment. This is a cross-sectional view taken along line XXX-XXX shown in Figure 29. 10A and 10B are diagrams for explaining thicknesses of members constituting a load adjustment mechanism provided in a battery pack according to a second embodiment. 13A and 13B are diagrams showing a first example of a cross-sectional shape of a first bracing member in a modified example. 13A and 13B are diagrams showing a second example of a cross-sectional shape of a first bracing member in a modified example. 4 is a cross-sectional view of a battery pack showing an initial state of the battery pack in Comparative Example 1. FIG. 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 Comparative Example 1. 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. FIG. 2 is a cross-sectional view showing the state of a single cell in the middle of use of Comparative Example 1. FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in Comparative Example 1 during intermediate use. 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. FIG. 2 is a cross-sectional view showing the state of a single cell in the final stage of use of Comparative Example 1. 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. 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. FIG. 11 is a cross-sectional view showing an initial state of a battery pack in Comparative Example 2. 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 Comparative Example 2. FIG. 13 is a diagram showing the distribution of displacement of the unit cells in the height direction of the unit cells in the initial state of Comparative Example 2. FIG. 11 is a cross-sectional view showing the state of a battery pack in the middle of use of Comparative Example 2. 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. FIG. 13 is a diagram showing the distribution of displacement of unit cells in the height direction of the unit cells during intermediate use of Comparative Example 2. FIG. 11 is a cross-sectional view showing the state of a single cell in the final stage of use of Comparative Example 2. FIG. 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. 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. 2 is a cross-sectional view showing an initial state of a battery pack in Reference Example 1. 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 Reference Example 1. 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. FIG. 1 is a cross-sectional view showing a state of a battery pack in the middle of use according to Reference Example 1. 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 middle stage of use. 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 Reference Example 1. FIG. 2 is a cross-sectional view showing the state of a single cell in the final stage of use of Reference Example 1. 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. 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 Reference Example 1. FIG. 11 is a cross-sectional view showing an initial state of a battery pack in accordance with a second embodiment. 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 embodiment 2. FIG. 13 is a diagram showing the distribution of displacement amounts of unit cells in the height direction of the unit cells in the initial state of the second embodiment. FIG. FIG. 11 is a cross-sectional view showing a state of a battery pack in the middle of use according to the second embodiment. 13A and 13B are diagrams showing how the elastic body deforms during the middle stage of use of the second embodiment. FIG. 13 is a diagram showing the distribution of restraining load in the height direction of a unit cell in the middle of use in embodiment 2. FIG. 11 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. FIG. 11 is a cross-sectional view showing the state of a single cell in the final stage of use according to the second embodiment. 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 embodiment 2. 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 2. FIG. FIG. 11 is a vertical cross-sectional view of a battery pack according to a third embodiment. FIG. 13 is a vertical cross-sectional view of a battery pack according to a fourth embodiment. 11 is a cross-sectional view showing the shapes of a first bracing member and a second bracing member in a first modified example. FIG. 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. FIG. 13 is a cross-sectional view showing an initial state of a battery pack in embodiment 5. 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 embodiment 5. FIG. 13 is a diagram showing the distribution of displacement amounts of unit cells in the height direction of the unit cells in the initial state of embodiment 5. FIG. 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. 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 embodiment 5. FIG. 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.

The following describes in detail the embodiments of the present disclosure with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated.

(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. A plurality of the unit cells 10 (for example, 10 units) are arranged in a row along a predetermined arrangement direction. The 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 mechanism 20.

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

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

The cell 10 is a sealed secondary battery, and includes a rectangular battery case 11 with 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 supply 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 circumference of the lid 13 is joined to the opening of the battery case 11 by welding. This keeps the cell 10 sealed.

The electrode body 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 connection member that electrically connects to the positive electrode external terminal 19b and a negative electrode connection member that electrically connects to the negative electrode external terminal 19c are welded to this electrode body.

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

As shown in FIG. 1, in the battery pack 1, the positive external terminal 19b and the negative external terminal 19c of adjacent cells 10 in the arrangement direction are electrically connected by a bus bar 3.

More specifically, the busbar 3 is made of a rectangular metal plate and has two through holes 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 busbar 3, a nut 5 is screwed onto the male thread of the positive external terminal 19b to fasten the negative external terminal 19c to the busbar 3. In this way, adjacent cells 10 are connected by the busbar 3, and the cells 10 that make up the battery pack 1 are electrically connected in series.

When the battery pack 1 having the above-described configuration is charged and discharged, the restraint load fluctuates due to the expansion and contraction of the cells 10.

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

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

However, because 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 cells 10 over time, it may not be possible to maintain the restraint load constant.

Figure 3 is a timing chart showing an example of the change in the restraining load acting on the battery pack 1 due to deterioration over time. The vertical axis of Figure 3 indicates the restraining load. The horizontal axis of Figure 3 indicates time. As shown in Figure 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 restraining load increases.

As a result, the overall constraint load acting on the battery pack 1 tends to increase. Figure 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 Figure 4 indicates the constraint load. The horizontal axis of Figure 4 indicates time. As shown in Figure 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 moves in the direction of increasing constraint load due to an increase in the constraint load associated with aging.

As a result, in addition to fluctuations in the restraint load when the battery pack 1 is charged and discharged, the range of change due to deterioration of the battery cells over time may change, making it impossible to maintain the restraint load constant.

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 single cells 10 and includes a plurality of plate-shaped spacers that insulate the single 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 multiple points between the spacers, and has a thickness in the arrangement direction that prevents the insulating member from penetrating the spacers even when the gap between the two spacers is minimized due to an increase in the restraining load.

In this way, when the restraining load increases due to the expansion of the cell 10 caused by aging in addition to the expansion of the cell 10 due to charging and discharging, the insulating member, which has a harder hardness than the spacer, sinks into the spacer, preventing the restraining load from increasing more than expected. When the gap between the two spacers becomes small, the insulating member functions as a tension member that tensions the spacers. In the following description, the insulating member is referred to as an insulating rigid body.

Figure 5 is a cross-sectional view showing the detailed configuration of the load adjustment mechanism 20. As shown in Figure 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 26.

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

A plurality of insulating rigid bodies, including insulating rigid bodies 24, 25, and 26, are provided at a plurality of locations on the positioning member 23. The positions of the insulating rigid bodies are restricted by the positioning member 23. The positioning member 23 is provided with through holes at a plurality of locations. The insulating rigid bodies are press-fitted into the through holes provided at predetermined locations on the positioning member 23, restricting their positions in the height direction and width direction. In addition to or instead of the 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.

Each of the first spacer 21, the second spacer 22, and the positioning member 23 is made of, for example, any one of the following materials: 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.

The multiple 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 multiple insulating rigid bodies is made of a ceramic material such as alumina or zirconia.

As shown in FIG. 5, the cross sections of the insulating rigid bodies 24, 25, 26 viewed from the width direction of the unit cell 10 have a predetermined shape. In the first embodiment, the cross sections of the insulating rigid bodies 24, 25, 26 viewed from the width direction of the unit cell 10 have, for example, a polygonal shape. Specifically, the cross sections of the insulating rigid bodies 24, 25, 26 have, for example, an octagonal shape that is symmetrical in the vertical and horizontal directions when viewed from the width direction. The multiple insulating rigid bodies all have the same shape. Note that the cross sections of the multiple insulating rigid bodies viewed from the thickness direction of the unit cell 10 have, for example, a circular shape.

Figure 6 is a diagram for explaining the thickness of each member constituting the load adjustment mechanism. Figure 6 shows an enlarged view of the framed portion of Figure 5. As shown in Figure 6, the thickness (length in the arrangement direction, the same applies below) of the first spacer 21 and the second spacer 22 is tp1, the thickness of the positioning member is tp2, and the thickness of the insulating rigid body 25 is tr. In this case, the thickness of each member is set so that the magnitude relationship shown by the formula tp2 < tr < tp2 + 2 × tp1 is established. The above formula is set so 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.

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 insulating rigid bodies 24, 25, and 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, and 26 corresponds to a first bracing member arranged in a first region corresponding to the central region of the single battery 10 in the height direction. The insulating rigid bodies 24, 26 correspond to second tension members provided in a second region corresponding to the outer regions of the unit cells 10 located on both sides of the central region in the height direction.

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

The assembled battery 1 configured as described above is assembled in the following procedure. For example, the first spacer 21, the second spacer 22, and the positioning member 23 are molded 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 single cells 10 are arranged so that the thickness direction of the single 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 single 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 assembled battery 1.

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 is in the initial state, when the single cell 10 expands and contracts due to charging and discharging, the first spacer 21, the second spacer 22, and the insulating rigid bodies 24, 25, and 26 each elastically deform to absorb the restraint load, thereby preventing the single cell 10 from being subjected to a restraint load greater than expected.

As shown in the load adjustment mechanism 20 in FIG. 8(B), after deterioration with time, when gas is generated in the single cell 10, the outer shape of the single cell 10 expands with the 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 due to 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 single cell 10 is suppressed.

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

Figure 10 is a timing chart showing an example of the change in the restraining load due to aging acting on the battery pack 1 according to embodiment 1. The vertical axis of Figure 10 indicates the restraining load. The horizontal axis of Figure 10 indicates time. In the period up to time t(0), as shown by the solid line in Figure 10, when gas is generated in the cell 10 due to aging 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 restraining load increases.

On the other hand, when time t(0) is reached, multiple insulating rigid bodies are embedded in the first spacer 21 and the second spacer 22, causing the first spacer 21 and the second spacer 22 to undergo plastic deformation. 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 the constraint load decreases, as shown by the dashed line in FIG. 10.

Figure 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 of Figure 11 indicates the constraint load. The horizontal axis of Figure 11 indicates time. As shown by the solid line in Figure 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 due to an increase in the constraint load associated with aging shifts in the direction in which the constraint load increases.

On the other hand, as shown by the dashed line in FIG. 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, so that the range indicating the change width is prevented from moving in the direction in which the restraint load increases. This prevents the single battery 10 from being subjected to a restraint load greater than expected.

As described above, according to the battery pack 1 of embodiment 1, in addition to the expansion of the single cells 10 due to charging and discharging, when the restraint load increases due to the expansion of the single cells 10 due to deterioration over time, the multiple insulating rigid bodies including the insulating rigid bodies 24, 25, and 26 can be suppressed from sinking into the first spacer 21 and the second spacer 22, preventing the restraint load from increasing more than expected. This makes it possible to maintain the restraint load constant. Therefore, it is possible to provide a battery pack that suppresses the increase in the restraint load due to deterioration over time.

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

Furthermore, in the above-mentioned embodiment 1, the insulating rigid bodies 24, 25, and 26 are described as being arranged in three in the height direction, but the number provided in the height direction is not limited to three. FIG. 13 is a diagram for explaining a second example of the arrangement of multiple insulating rigid bodies in the modified example. As shown in FIG. 13, the multiple 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.

Furthermore, in the above-mentioned embodiment 1, the spacing between the insulating rigid bodies arranged in the height direction is described as being longer than the spacing 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 multiple insulating rigid bodies in a modified example. As shown in FIG. 14, the multiple 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 spacing between the insulating rigid bodies arranged in the height direction is shorter than the spacing between the insulating rigid bodies arranged in the width direction.

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 arrangement. 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 lattice lines 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.

Furthermore, in the above-mentioned first embodiment, the multiple 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 an arrangement of multiple insulating rigid bodies in a modified example. As shown in FIG. 16, the multiple insulating rigid bodies may be arranged, for example, at predetermined positions that are set randomly.

Furthermore, in the above-mentioned embodiment 1, the multiple insulating rigid bodies are described as being arranged in groups of three at equal intervals in the height direction, but the arrangement is not limited to being arranged at equal intervals in the height direction. For example, the multiple insulating rigid bodies may be 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 the middle or final stages of use.

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 shape. For example, when the gap between the first spacer 21 and the second spacer 22 becomes smaller due to the expansion of the single cell 10, the insulating rigid body may be formed into a cross-sectional shape that does not penetrate either the first spacer 21 or the second spacer 22, and protects the battery case 11 even if the insulating rigid body penetrates. Figure 17 is a diagram for explaining a first example of the cross-sectional shape of the insulating rigid body in the modified example. As shown in Figure 17, the insulating rigid body may have a rectangular cross section, for example. In this way, the contact area with the battery case 11 is larger than in the case of a tapered cross-sectional shape, 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.

Furthermore, in the above-mentioned embodiment 1, the cross section of the insulating rigid body viewed in the width direction is octagonal, but the shape is not particularly limited to this. Figure 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 Figure 18, the insulating rigid body may have, for example, an elliptical cross section.

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 positions are different in the height direction or width direction).

Furthermore, in the above-mentioned embodiment 1, the insulating rigid bodies are described as being arranged by being pressed into the through holes of the positioning member 23, but the present invention is not particularly limited to such a configuration. For example, the insulating rigid bodies may be adhered 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 composed of two insulating members, and may be adhered with an adhesive at the same height and width positions on the left and right surfaces of the positioning member 23 as viewed in the width direction.

Furthermore, in the above-mentioned embodiment 1, the multiple insulating rigid bodies are described as being arranged on the 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.

Figure 20 is a cross-sectional view showing the detailed configuration of the load adjustment mechanism 20 in the modified example. As shown in Figure 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. Note that the insulating rigid body 30 corresponds to the first bracing member described above, and the insulating rigid bodies 29 and 31 correspond to the second bracing member described above.

The first spacer 21 and the second spacer 22 have the same shape and material as the first spacer 21 and the second spacer 22 in the above-mentioned embodiment 1, 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.

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 first embodiment described above. Therefore, a detailed description thereof will not be repeated.

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 such 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.

Figure 21 is a diagram for explaining a first arrangement example of multiple insulating rigid bodies arranged on the second spacer 22 in the modified example. As shown in Figure 21, multiple insulating rigid bodies are arranged in a matrix with 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. Figure 22 is a diagram for explaining the configuration of the first spacer 21 in the modified example. As shown in Figure 22, no insulating rigid bodies are arranged on the first spacer 21.

The battery pack 1 according to the above-mentioned 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 single cells 10 at predetermined positions using an adhesive. Ten single cells 10 are arranged so that the thickness direction of the single 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 single 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.

The operation of the load adjustment mechanism 20 of the battery pack 1 according to this modified example based on the above 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 single cell 10 from being subjected to a restraining load greater than expected.

After aging, as shown in FIG. 23, when gas is generated in the single cell 10, the outer shape of the single cell 10 expands with the increase in the amount of gas. As a result, the first spacer 21 and the second spacer 22 each move so that the gap between them 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 the contact area with the first spacer 21 is smaller 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 due to gas generation is absorbed by the plastic deformation of the first spacer 21, and the application of a load greater than expected to the single cell 10 is suppressed.

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 be arranged on both the surface of the first spacer 21 and the surface of the second spacer 22 facing the surface of the first spacer 21.

Figure 24 is a cross-sectional view showing the 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 insulating rigid bodies 34 and 35 correspond to the first bracing member described above, and insulating rigid bodies 32-33, 36-37 correspond to the second bracing member described above.

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-mentioned embodiment 1, except that insulating rigid bodies 32, 33, 34, 35, 36, and 37 are arranged. Therefore, detailed description thereof will not be repeated.

Furthermore, the materials of the insulating rigid bodies 32, 33, 34, 35, 36, and 37 arranged 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-mentioned first embodiment. Therefore, detailed description thereof will not be repeated.

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.

Figure 25 is a diagram for explaining a second arrangement example of multiple insulating rigid bodies arranged on the second spacer 22 in the modified example. As shown in Figure 25, the multiple 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.

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 when 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 a position not facing each other when assembled on the unit cell 10, and may be arranged at a position shifted in at least one of the height direction and the width direction.

The thickness of the insulating rigid body may 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.

In this modified example, the cross-sectional shape of the insulating rigid body as viewed in the width direction is described as being hexagonal as shown in FIG. 24, but is not limited to this shape.

Figure 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 Figure 27, the insulating rigid body 38 may have a semi-elliptical shape in which the surfaces other than the adhesive surface are curved. Figure 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 Figure 28, the insulating rigid body 39 may have a shape that tapers toward the opposing first spacer 21.

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 cell, the deformation of the cell (more specifically, the deformation of the battery element) due to charging/discharging or aging differs between the center and both ends in the height direction of the cell. The deformation of the center is large, whereas the deformation of both ends is small. This causes a variation in the restraining load in the height direction.

As described below, in the battery packs described in the second and subsequent embodiments, it is possible to suppress the increase in the restraint load due to aging while also suppressing the variation in the restraint load in the height direction.

(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.

As shown in Figures 29 and 30, the battery pack 1A according to embodiment 2 differs from the battery pack 1 according to embodiment 1 in the configuration of the load adjustment mechanism 20A. The other configurations are almost the same.

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 tension members 50.

The first spacer 21, the second spacer 22, and the positioning member 23 have a configuration substantially similar to that of embodiment 1.

The multiple 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 multiple bracing members 50 are made of an insulating rigid body. For example, the multiple bracing members 50 are made of a ceramic material such as alumina or zirconia.

The multiple tension members 50 include multiple first tension members 51 and multiple second tension members 52.

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

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

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

When viewed from the above-mentioned arrangement direction, the multiple first tension members 51 are arranged in positions that are linearly symmetrical with respect to the center line of the cell 10 that extends along the height direction through the center of the width direction of the cell 10.

As described below, the first tension members 51 are arranged so that when the gap between the first spacer 21 and the second spacer 22 is minimized by the restraining load, the tension members 51 are embedded in the first spacer 21 and the second spacer 22 without penetrating the first spacer 21 and the second spacer 22. Note that the state in which the gap between the first spacer 21 and the second spacer 22 is minimized by the restraining load refers to a state in which the single cell is in the final stage of use and has expanded due to deterioration over time, as described below.

When viewed from the above-mentioned arrangement direction, the multiple second tension members 52 are arranged in a second region R2 that corresponds to both outsides of the central region in the height direction of the single battery 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 single battery 10.

The second tension members 52 arranged in a direction parallel to the height direction are disposed at approximately the center of the width direction of the cell 10. When viewed from the above-mentioned arrangement direction, the second tension members 52 are disposed in positions that are linearly symmetrical with respect to the center line of the cell 10 that extends along the height direction through the center of the width direction of the cell 10.

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 may be changed as appropriate.

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 single battery 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 outer region to act, for example, in the initial assembly state of the battery pack 1. The first elastic body 41 and the second elastic body 42 are preferably made of rubber or a foaming agent that deforms as the restraining load increases.

In the initial assembly state, the first elastic body 41 is disposed between the first tension 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 adhesive or the like. In the initial assembly state, the first elastic body 41 abuts against the first tension members 51, thereby forming a gap between the first elastic body 41 and the positioning member 23.

In the initial assembly state, the second elastic body 42 is disposed between the multiple first tension 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 adhesive or the like. In the initial assembly state, the second elastic body 42 abuts against the first tension members 51, thereby forming a gap between the second elastic body 42 and the positioning member 23.

Figure 31 is a diagram illustrating the thickness of each member constituting the load adjustment mechanism provided in the battery pack according to embodiment 2.

31 , the thickness of the first spacer 21 and the second spacer 22 is _tp1 , the thickness of the positioning member is _tp2 , the thickness of the first strut member 51 is _tr1 , and the thickness of the second strut member 52 is _tr2 . The thickness _tr1 of the first strut member 51 is smaller than the thickness _tr2 of the second strut member 51 by the thickness of the elastic body.

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 minimized.

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 any thickness between _T1 and _T2 is _T3 . In addition, the thickness of the unit cell 10 that can tolerate deformation when the unit cell 10 expands is _Δtcell (not shown in FIG. 31).

In this case, it is preferable to satisfy the following relations (2), (3), and (4).
1/2(t _r2 -t _p2 )>T ₀ >T ₁ >T ₃ >T ₂ ≧0...(Formula 2)
t _r1 +2×T ₁ +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 the first bracing member in the modified example. The shape of the first bracing member 51 according to the second embodiment will be described with reference to FIG.

The cross-sectional shape of the first tension member 51 may be modified as shown in the first and second examples below.

As shown in FIG. 32, in the first modified example, 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 abuts against 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.

As shown in FIG. 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 that protrudes toward the first elastic body 41 and the second elastic body 42. Specifically, the cross-sectional shape of the first tension member 51 is substantially rhombic.

The cross-sectional shape of the second tension member 52 can also be changed as appropriate, and may be rectangular, elliptical, or oval, as described above with reference to Figures 17 and 18.

The following describes the distribution of restraint loads in the height direction of the cells and the distribution of displacement of the cells in the initial state, the intermediate state, 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 according to this embodiment, with reference to Figures 34 to 70.

Figure 34 is a cross-sectional view of a battery pack in Comparative Example 1, showing the initial state of the battery pack. As shown in Figure 34, the battery pack 1X1 in Comparative Example 1 does not include the load adjustment mechanisms 20, 20A, unlike the battery packs 1, 1A in the first and second embodiments, 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.

Figure 35 shows the distribution of restraining load in the height direction of a single cell in the initial state of Comparative Example 1.

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

Figure 36 shows the distribution of 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. 36, in the initial state, the cell 10 is not expanded, and the displacement of the cell 10 in the height direction is 0.

Figure 37 is a cross-sectional view showing the state of a single cell in the middle of use of Comparative Example 1. Note that the middle of use refers to, for example, the state from time t(0) shown in Figures 10 and 11 until a certain period of time has passed.

As shown in FIG. 37, during intermediate use, the center of the battery element expands, causing the center of the cell to expand more than both ends in the height direction. However, in Comparative Example 1, the spacer 21X disposed between the two cells 10 does not deform, preventing the cells 10 from deforming.

Figure 38 shows the distribution of restraining load in the height direction of a single cell during the middle period of use in Comparative Example 1.

As shown in Figure 38, in the middle of use of Comparative Example 1, as described above, the center of the single cell tends to expand more than both ends in the height direction, so the load (constraint load) applied to the center in the height direction becomes larger, as shown by the thick line. Also, compared to the initial state, the load applied to the entire height direction increases overall.

Figure 39 shows the distribution of displacement of the cells in the height direction during the middle of use of Comparative Example 1.

On the other hand, because the spacer 21X prevents deformation of the single cell, during the intermediate period of use of Comparative Example 1, as shown in FIG. 39, the displacement of the single cell remains zero in the height direction.

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

As shown in FIG. 40, in the final stage of use of Comparative Example 1, the cell 10 tends to expand more overall than in the middle stage of use, and in particular, the center of the cell tends to expand even more.

Figure 41 shows the distribution of restraining load in the height direction of a single cell at the end of use in Comparative Example 1.

As shown in FIG. 41, in the final stage of use of Comparative Example 1, the cell 10 further expands as described above, and the restraint load increases overall compared to the distribution of the restraint load in the middle stage of use shown by the dashed line. In particular, the restraint load increases significantly in the center of the cell 10 in the height direction.

Figure 42 shows the distribution of displacement of the cells in the height direction at the end of use in Comparative Example 1.

On the other hand, because the spacer 21X prevents deformation of the single cell, during the middle period of use of Comparative Example 1, as shown in Figure 42, the displacement of the single cell remains zero in the height direction.

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.

If the restraint load exceeds a specified value or if there is a large variation in the restraint load, this is likely to cause a deterioration in Li precipitation resistance and an increase in electrical resistance. This will result in a deterioration in the safety and lifespan of the battery pack 1X1.

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

Figure 44 shows the distribution of the restraining load in the height direction of the single cell in the initial state of Comparative Example 2.

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

Figure 45 shows the distribution of 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. 45, in the initial state, the cell 10 is not expanded, and the displacement of the cell 10 in the height direction is 0.

Figure 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 Figure 46, in the middle of use, the center of the battery element expands, and the center of the 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 cell 10. Specifically, the elastic body 60 is compressed by the expanded cell.

Figure 47 shows the distribution of restraining load in the height direction of a single cell during the middle period of use of Comparative Example 2.

As shown in FIG. 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 remains almost the same as the load in the initial state and is approximately constant in the height direction.

Figure 48 shows the distribution of displacement of the cells in the height direction during the middle of use of Comparative Example 2.

As shown in FIG. 48, during the middle period of use of Comparative Example 2, the deformation of the single cell as described above results in a distribution in which the center of the cell in the height direction bulges more than both ends in the height direction in response to the deformation of the single cell.

Figure 49 is a cross-sectional view showing the state of the cell at the end of use of Comparative Example 2. As shown in Figure 49, at the end of use of Comparative Example 2, the cell 10 as a whole expands more than in the middle of use, and in particular, the center of the cell expands more significantly.

Figure 50 shows the distribution of restraining load in the height direction of a single cell at the end of use in Comparative Example 2.

As shown in FIG. 50, at the end of use, the elastic body 60 is further compressed due to the deformation of the single cell 10, and the overall restraining load increases in the height direction. On the other hand, the elastic body 60 deforms to follow the expansion of the single cell 10, so that the restraining load applied to the single cell 10 becomes approximately constant in the height direction.

Figure 51 shows the distribution of displacement of the cells in the height direction at the end of use in Comparative Example 2.

As shown in FIG. 51, in the final stage of use of Comparative Example 2, the deformation of the single cells as described above results in a distribution in which the center of the cell in the height direction bulges more than both ends in the height direction, compared to the middle stage of use.

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

Figure 52 is a cross-sectional view showing the initial state of the battery pack in Reference Example 1. As shown in Figure 52, the battery pack 1Y in Reference Example 1 has a configuration substantially similar to that of the battery pack 1 in embodiment 1. That is, in Reference Examples 1 and 2, the first tension member 51 and the second tension member 52 have the same shape and are also substantially the same thickness.

Figure 53 shows the distribution of the restraining load in the height direction of the single cell in the initial state of Reference Example 1.

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

Figure 54 shows the distribution of displacement of the single cells in the height direction of the single cells in the initial state of Reference Example 1.

As shown in FIG. 54, in the initial state, the cell 10 is not expanded, and the displacement of the cell 10 in the height direction is 0.

Figure 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 Figure 55, in the middle of use, the center of the battery element expands, and the center of the height of the single 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 single cell 10 so that the gap between them becomes narrower. In this state, both the first tension member 51 and the second tension member 52, or the first tension member 51, slightly sinks 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.

Figure 56 shows the distribution of restraining load in the height direction of a single cell during the middle period of use of Reference Example 1.

As shown in FIG. 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.

Figure 57 shows the distribution of displacement of the cells in the height direction during the middle period of use of Reference Example 1.

As shown in FIG. 57, the amount of displacement of the single cell in the height direction is distributed such that the center of the cell in the height direction bulges more than both ends of the cell in the height direction due to deformation of the single cell.

Figure 58 is a cross-sectional view showing the state of the cell at the end of use of Reference Example 1. As shown in Figure 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.

Figure 59 shows the distribution of restraining load in the height direction of a single cell at the end of use in Reference Example 1.

As shown in FIG. 59, the center of the battery cell 10 expands more than both ends in the height direction, so the load (restraint load) applied to the center in the height direction increases, as shown by the thick line. Also, compared to the intermediate state, the load applied to the entire height direction increases overall.

On the other hand, as described above, the first spacer 21 and the second spacer 22 are plastically deformed, and the increased restraint load due to 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 single cell 10, the first bracing member 51 is deeply embedded in the first spacer 21 and the second spacer 22, so that the restraint load can be greatly reduced. In addition, the second bracing member 52 is embedded in the first spacer 21 and the second spacer 22 at both ends of the single cell 10 in the height direction, 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 single cell 10 can be suppressed compared to Comparative Examples 1 and 2.

Figure 60 shows the distribution of displacement of the cells in the height direction at the end of use in Reference Example 1.

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 cell in the height direction bulges 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, damage to the bus bars connecting the single cells 10 and the case housing the battery pack 1X2 can be suppressed.

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

Figure 62 shows the distribution of the restraining load in the height direction of the cell in the cell height direction in the initial state of embodiment 2.

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

Figure 63 shows the distribution of displacement of the cells in the height direction of the cells in the initial state of embodiment 2.

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

Figure 64 is a cross-sectional view showing the state of the battery pack in the middle of use of the second embodiment. As shown in Figure 64, in the middle of use, the center of the battery element expands, and the center of the height of the single 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 single 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 single cell 10 progresses over time.

Figure 65 is a diagram showing how the elastic body deforms during the middle of use in embodiment 2. 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 Figure 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 remains in contact with the first spacer 21 and the second spacer 22 or is slightly biting into them. At this time, the first elastic body 41 and the second elastic body 42 deform, dispersing the restraining load that has increased due to expansion. As a result, in embodiment 2, the variation in the restraining load in the height direction is suppressed more than in comparative example 1 and reference example 1.

Figure 66 shows the distribution of restraining load in the height direction of a single cell during intermediate use in embodiment 2.

As shown in FIG. 66, during the middle of use, the load adjustment mechanism 20A is compressed due to the deformation of the single cell, and the overall restraint load increases in the height direction. On the other hand, as described above, the first elastic body 41 and the second elastic body 42 are deformed, so that the restraint load applied to the single cell 10 becomes approximately constant in the height direction.

Figure 67 shows the distribution of displacement of the cells in the height direction during intermediate use of embodiment 2.

As shown in FIG. 67, during intermediate use, the deformation of the single cell 10 as described above results in a distribution in which the center of the cell in the height direction bulges more than both ends in the height direction.

Figure 68 is a cross-sectional view showing the state of a single cell at the end of use of embodiment 2. As shown in Figure 68, at the end of use of embodiment 2, the single cell 10 as a whole expands more than when it is in the middle of use, and in particular, the center of the single cell expands more significantly.

At this time, the first tension 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 through the first elastic body 41 and the second elastic body 42, which have been thinned to the limit. In addition, the second tension 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 undergo plastic deformation at the center and both ends in the height direction.

Figure 69 shows the distribution of restraining load in the height direction of a single cell at the end of use in embodiment 2.

As shown in FIG. 69, in the final stage 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.

Figure 70 shows the distribution of displacement of the cells in the height direction at the end of use in embodiment 2.

As described above, in the second embodiment, due to the presence of the first tension member 51, the amount of displacement of the center of the single cell 10 is a value just before it reaches the first tension member 51. Therefore, as shown in FIG. 70, in the second embodiment, the amount of displacement of the single cell can be reduced compared to the second comparative example. This makes it possible to suppress the amount of displacement of the single cell 10 and the battery pack 1 to be less than the deformation tolerance. As a result, damage to the bus bars connecting the single cells 10 and the case housing the battery pack 1X2 can be suppressed.

(Embodiment 3)
Fig. 71 is a vertical cross-sectional view of a battery pack according to embodiment 3. A battery pack 1B according to embodiment 3 will be described with reference to Fig. 71.

As shown in FIG. 71, the battery pack 1B according to the third embodiment differs from the battery pack 1A according to the second embodiment in that the first elastic body 41 and the second elastic body 42 are omitted, and the first tension member 51 is configured to be more easily embedded into the first spacer 21 and the second spacer 22 than the second tension member 52. The other configurations are substantially the same.

The cross-sectional shape of the first tension member 51 has an elliptical shape with a short axis in the height direction and a long axis in the arrangement direction (thickness direction). The cross-sectional shape of the first tension member 51 is not limited to an ellipse, and may be an oval shape. The cross-sectional shape of the first tension 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 with an acute angle, and more specifically, the cross-sectional shape of the first tension member 51 may be a rhombus.

The cross-sectional shape of the second tension 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 tension member 52 that contacts the first spacer 21 and the second spacer 22 may be formed in an arc shape so that the second tension member 52 is less likely to sink into the first spacer 21 and the second spacer 22 than the first tension member 51.

When configured in this manner, when the single 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, causing the first spacer 21 and the second spacer 22 to undergo large plastic deformation on the first bracing member 51 side. This allows the central portion of the single cell 10 to absorb more of the restraining load, thereby suppressing the variation in the restraining load between the central portion and both ends in the height direction.

(Embodiment 4)
Fig. 72 is a vertical cross-sectional view of a battery pack according to embodiment 4. A battery pack 1C according to embodiment 4 will be described with reference to Fig. 72.

As shown in FIG. 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 arranged so as to be able to be embedded in the positioning member 23. The other configurations are substantially the same.

The multiple first tension 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.

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.

The first member 511 and the fourth member 514 have approximately the same shape and are arranged so as to be point symmetrical with respect to a predetermined point on the positioning member 23.

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) to the tip portion. The thickness of the first member 511 from the tip portion to the flat portion is denoted by _tr3 .

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) to the tip portion. The thickness of the first member 511 from the tip portion to the flat portion is represented as _tr2 .

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 _{r 2-3} .

In this case, the following relations (4), (5), and (6) hold.
t _r2-3 = t _r1 ...Formula (4)
t _r2 < t _r1 ...Formula (5)
t _r3 <t _{t_r3} ...Formula (6)
The second member 512 and the fifth member 515 have substantially the same shape, and are disposed so as to be point symmetrical with respect to a predetermined point on the positioning member 23 .

The cross-sectional shape of the second member 512 is polygonal. The second member 512 includes a first planar portion that contacts the positioning member 23 in a planar manner and a second planar portion that contacts the first spacer 21 in a planar manner. The thickness of the second member 512 is smaller than the thickness of the first member 511.

The cross-sectional shape of the fifth member 515 is polygonal. The fifth member 515 includes a first planar portion that contacts the positioning member 23 in a planar manner and a second planar portion that contacts the second spacer 22 in a planar manner. The thickness of the fifth member 515 is smaller than the thickness of the fourth member 514.

The third member 513 and the sixth member 516 have approximately the same shape and are arranged so as to be point symmetrical with respect to a predetermined point on the positioning member 23.

The third member 513 has a recessed portion that recesses into the positioning member 23 and a flat portion that contacts the first spacer 21 in a planar manner. The third member 513 also has a recessed portion to avoid interference with the recessed portion of the sixth member 516 described below. The recessed portion is provided so as to be continuous with the recessed portion, and is recessed toward the first spacer 21.

The sixth member 516 has a recessed portion that recesses into the positioning member 23 and a flat portion that contacts the second spacer 22 in a planar manner. The sixth member 516 also has a recessed portion to avoid interference with the recessed portion of the third member 513. The recessed portion is provided so as to be continuous with the recessed portion, and is recessed toward the second spacer 22.

The recessed portion of the sixth member 516 is arranged to face the retracted portion of the third member 513. The recessed portion of the sixth member 516 is arranged to face the recessed portion of the third member 513.

When configured in this manner, when the battery cell 10 expands due to deterioration over time, the first tensioning 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 central side of the battery cell 10 to absorb more of the restraining load, thereby suppressing variation in the restraining load at the center and both ends in the height direction.

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

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

As shown in FIG. 73, in the first modified example, the multiple first tension members 51 include a first member 511A, a second member 512A, a third member 513A, and a fourth member 514A.

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.

The first member 511A and the third member 513A have substantially the same shape and are arranged so as to be symmetrical with respect to a predetermined center line of the positioning member 23.

The first member 511A has an acute-angled tip (protrusion) that protrudes toward the positioning member 23. The first member 511A has a flat portion that makes planar contact with the first spacer 21.

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

The second member 512A and the fourth member 514A have substantially the same shape and are arranged so as to be symmetrical with respect to a predetermined center line of the positioning member 23.

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

The fourth member 514A has a first planar portion that contacts the positioning member 23 in a planar manner, and a second planar portion that contacts the second spacer 22 in a planar manner.

Even when configured in this manner, when the battery cell 10 expands due to deterioration over time, the first tensioning member 51 (more specifically, the first member 511A and the third member 513A) 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 central side of the battery cell 10 to absorb more of the restraining load, thereby suppressing the variation in the restraining load at the center and both ends in the height direction.

As shown in FIG. 74, in the second modified example, the multiple first tension members 51 include a first member 511B, a second member 512B, a third member 513B, and a fourth member 514B.

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.

The first member 511B has a recessed portion that recesses into the positioning member 23 and a flat portion that contacts the first spacer 21 in a planar manner. The first member 511B also has a recessed portion to avoid interference with the recessed portion of the third member 513B described below. The recessed portion and the recessed portion are located on the opposite side (the positioning member 23 side) from the side where the flat portion is located.

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.

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

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

The second member 512B has a recessed portion that recesses into the positioning member 23 and a flat portion that contacts the first spacer 21 in a planar manner. 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 (the positioning member 23 side) from the side where the flat portion is located.

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 (the positioning member 23 side) to the side where the flat portion is located.

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

Even when configured in this manner, if the battery cell 10 expands due to deterioration over time, the first tension member 51 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 central side of the battery cell 10 to absorb more of the restraining load, making it possible to suppress variation in the restraining load at the center and both ends in the height direction.

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

As shown in FIG. 75, the battery pack 1D according to embodiment 5 differs from the battery pack 1A according to embodiment 2 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 tension member 52D is made of an elastic material. The other configurations are almost the same. Note that the elastic member used for the second tension member 52D can be, for example, a coil spring.

Figure 76 shows the distribution of the restraining load in the height direction of the cell in the initial state of embodiment 5.

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

Figure 77 shows the distribution of displacement of the cells in the height direction of the cells in the initial state of embodiment 5.

As shown in FIG. 77, the battery cell 10 is not expanded, and the displacement of the battery cell 10 in the height direction is zero.

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

At this time, the first tension member 51 sinks into the first spacer 21 and the second spacer 22. This causes the first spacer 21 and the second spacer 22 to plastically deform at the center in the height direction. Meanwhile, the second tension member 52D, which is made of an elastic material, applies an elastic force to the first spacer 21 and the second spacer 22 against the compression direction. In other words, the second tension member 52D applies an elastic force to move the first spacer 21 and the second spacer 22 away from each other.

Figure 79 shows the distribution of restraining load in the height direction of a single cell at the end of use in embodiment 5.

As shown in FIG. 79, at the end of use, as described above, the first spacer 21 and the second spacer 22 undergo plastic deformation at the center in the height direction, absorbing the restraining load at the center. In addition, as described above, at both ends in the height direction, the second tension 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 tension 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.

Figure 80 shows the distribution of displacement of the cells in the height direction at the end of use in embodiment 5.

As shown in FIG. 80, due to the presence of the first tension member 51, the amount of displacement of the center of the single cell 10 in the height direction is a value just before it reaches the first tension member 51. On the other hand, at both ends of the single cell 10 in the height direction, the displacement of the single cell 10 is suppressed by the elastic biasing force of the second tension member 52D. Therefore, as shown in FIG. 80, in embodiment 5, the amount of displacement of the single cell can be reduced compared to comparative example 2.

As described above, even in embodiment 5, it is possible to suppress the variation in the restraining load at the center and both ends in the height direction.

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

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 external terminal, 19c Negative 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 member, 512, 512A, 512B second member, 513, 513A, 513B third member, 514, 514A, 514B fourth member, 515 fifth member, 516 sixth member.

Claims (5)

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 . 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 . 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. the plurality of tension members are disposed on the plate-shaped holding 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 . the plurality of tension members are disposed on the plate-shaped holding 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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