JP7697278B2 - Battery stack and restraining hoop member - Google Patents

Description

This disclosure relates to a battery stack and a restraining hoop member.

JP 2019-125444 A (Patent Document 1) discloses that the restraining mechanism that restrains multiple unit cells includes an annular restraining hoop portion. The restraining hoop portion applies a predetermined restraining pressure to the multiple unit cells in a direction that compresses them along the arrangement direction of the unit cells.

JP 2019-125444 A

When a single cell is restrained by a restraining hoop, a gap may form between the end plate and the restraining hoop due to variations in parts manufacturing. The inventors discovered that when a gap forms, stress is concentrated at the end of the curve of the restraining hoop.

This disclosure proposes a battery stack that can suppress stress concentration in the restraining hoop member, and a restraining hoop member that can suppress stress concentration.

According to one aspect of the present disclosure, a battery stack is proposed that includes a plurality of unit cells arranged in an arrangement direction and a restraining mechanism that restrains the plurality of unit cells. The restraining mechanism includes a pair of end plates arranged at both ends of the arrangement direction of the plurality of unit cells, and an annular restraining hoop member. The plurality of unit cells and the pair of end plates are arranged inside the ring of the restraining hoop member. The restraining hoop member has an easily deformable portion that partially facilitates deformation of the ring of the restraining hoop member in the circumferential direction.

The restraining hoop member has an easily deformable portion, which allows the restraining hoop member to undergo large elastic deformation in the circumferential direction of the ring. By allowing the restraining hoop member to undergo large elastic deformation during battery stack manufacturing, it is possible to prevent gaps from occurring between the end plates and the restraining hoop member in the assembled battery stack. By preventing gaps from occurring between the end plates and the restraining hoop member, it is possible to prevent stress from concentrating at the ends of the curve of the restraining hoop member.

In the above battery stack, the easily deformable portion may have a portion where the thickness of the restraining hoop member is smaller than the other portions of the easily deformable portion. By partially reducing the thickness of the restraining hoop member, the portion with the smaller thickness can be formed as the easily deformable portion.

In the above battery stack, the easily deformable portion may have a through hole formed through the restraining hoop member in the thickness direction. By forming a through hole in a portion of the restraining hoop member, the periphery of the through hole can be formed as the easily deformable portion.

In the above battery stack, the easily deformable portion may have a portion where the width of the restraining hoop member is smaller than the other portions of the easily deformable portion. By partially reducing the width of the restraining hoop member, the narrow portion can be formed as the easily deformable portion.

In the above battery stack, the pair of end plates may have a first surface facing the single battery cell and a second surface opposite the first surface, and the easily deformable portion may be in contact with the second surface. This makes it possible to prevent stress from concentrating on the easily deformable portion.

In the above battery stack, the second surface of the end plate may have curved chamfered portions on both circumferential edges of the ring of the restraining hoop member, a flat portion between the pair of chamfered portions, and the easily deformable portion may be in contact with the flat portion. With this arrangement, the restraining hoop member can continuously apply a high restraining force to the single cell.

In the above battery stack, the entire easily deformable portion of the ring of the restraining hoop member in the circumferential direction may be in contact with the flat portion. By arranging in this manner, the restraining hoop member can continuously apply a high restraining force to the single cell.

According to one aspect of the present disclosure, a ring-shaped restraining hoop member is proposed that restrains, in the arrangement direction, a plurality of unit cells arranged in an arrangement direction and a pair of end plates arranged at both ends of the arrangement direction of the plurality of unit cells. The plurality of unit cells and the pair of end plates are arranged inside the ring of the restraining hoop member. The restraining hoop member has an easily deformable portion that partially facilitates deformation of the ring of the restraining hoop member in the circumferential direction.

The restraining hoop member has an easily deformable portion, which allows the restraining hoop member to undergo large elastic deformation in the circumferential direction of the ring. By allowing the restraining hoop member to undergo large elastic deformation during battery stack manufacturing, it is possible to prevent gaps from occurring between the end plates and the restraining hoop member in the assembled battery stack. By preventing gaps from occurring between the end plates and the restraining hoop member, it is possible to prevent stress from concentrating at the ends of the curve of the restraining hoop member.

According to this disclosure, stress concentration in the restraining hoop member can be suppressed.

FIG. 2 is a schematic diagram of a battery stack. FIG. 2 is a schematic diagram showing a restraining hoop member as viewed from the front. FIG. 2 is an enlarged schematic view of region III in FIG. 1 .

The following describes the embodiment with reference to the drawings. In the following description, identical parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

Figure 1 is a schematic diagram of a battery stack 1. The battery stack 1 includes a plurality of single cells 10 and a restraining mechanism. The plurality of single cells 10 are arranged in a predetermined arrangement direction (the left-right direction in Figure 1). Hereinafter, the arrangement direction of the plurality of single cells 10 is also simply referred to as the arrangement direction. The restraining mechanism is a mechanism for restraining the plurality of single cells 10 so that they can be used as a set of batteries.

The single cell 10 is typically a secondary battery capable of repeated charging and discharging, such as a lithium ion secondary battery, a nickel-metal hydride battery, or an electric double layer capacitor. The single cell 10 has a battery case 12 and an external terminal 14. The battery case 12 houses therein a power generating element in which a solid electrolyte is arranged in layers between a positive electrode active material layer and a negative electrode active material layer. The external terminal 14 is disposed so as to protrude upward from the upper surface of the battery case 12. The external terminals 14 of adjacent single cells 10 are electrically connected to each other by a bus bar (not shown) to form a battery stack 1.

The restraining mechanism includes a pair of end plates, i.e., a first end plate 20 and a second end plate 30. The first end plate 20 and the second end plate 30 are plate-shaped members for evenly applying restraining pressure to the power generating element of the single cell 10. The pair of end plates are arranged at both ends of the arrangement direction of the multiple single cells 10. The pair of end plates are arranged at both ends of the arranged multiple single cells 10 so as to sandwich the arranged multiple single cells 10 in the arrangement direction. The first end plate 20 is arranged at one end of the arranged single cells 10 in the arrangement direction. The second end plate 30 is arranged at the other end of the arranged single cells 10 in the arrangement direction.

The first end plate 20 and the second end plate 30 are configured to be slightly larger than the dimensions of the single battery 10. If the direction in which the external terminal 14 protrudes from the battery case 12 of the single battery 10 is defined as the upward direction, and the opposite direction to the upward direction is defined as the downward direction, the upper end of the first end plate 20 is disposed above the tip of the external terminal 14. The upper end of the second end plate 30 is disposed above the tip of the external terminal 14. The lower end of the first end plate 20 is disposed below the lower surface (bottom surface) of the battery case 12. The lower end of the second end plate 30 is disposed below the lower surface of the battery case 12.

The dimensions of the first end plate 20 and the second end plate 30 in the direction in which the external terminal 14 of the cell 10 protrudes from the battery case 12 are made larger than the dimensions of the cell 10 in that direction. The dimensions of the first end plate 20 and the second end plate 30 in the direction in which the line segment connecting the tip of the external terminal 14 to the bottom surface of the battery case 12 at the shortest distance extends are made larger than the dimensions of the cell 10 in that direction.

The first end plate 20 has a first surface 21 facing the cells 10 and a second surface 22 opposite the first surface 21. The first surface 21 has a planar shape. The first end plate 20 is arranged so that the first surface 21 is perpendicular to the arrangement direction of the cells 10.

The second surface 22 of the first end plate 20 has a curved chamfered portion 23 on the upper edge. The second surface 22 has a curved chamfered portion 24 on the lower edge. The second surface 22 has a flat surface portion 25 between the pair of chamfered portions 23, 24. When viewed from the left in FIG. 1, the first end plate 20 has rounded, curved portions at the top and bottom corners.

The second end plate 30 has a first surface 31 facing the single cells 10 and a second surface 32 opposite the first surface 31. The first surface 31 has a planar shape. The second end plate 30 is arranged so that the first surface 31 is perpendicular to the arrangement direction of the single cells 10. The first end plate 20 and the second end plate 30 are arranged so that the first surface 21 of the first end plate 20 and the first surface 31 of the second end plate 30 are parallel to each other.

The second surface 32 of the second end plate 30 has a curved chamfered portion 33 on the upper edge. The second surface 32 has a curved chamfered portion 34 on the lower edge. The second surface 32 has a flat surface portion 35 between the pair of chamfered portions 33, 34. When viewed from the right in FIG. 1, the second end plate 30 has rounded, curved portions at the top and bottom corners.

The restraining mechanism includes a restraining hoop member 40. The restraining hoop member 40 has an annular shape. The restraining hoop member 40 has a flat belt shape. The restraining hoop member 40 has a first support portion 41 arranged along the second surface 22 of the first end plate 20. The restraining hoop member 40 has a second support portion 42 arranged along the second surface 32 of the second end plate 30. The restraining hoop member 40 has a connecting portion 43 that continuously connects the first support portion 41 and the second support portion 42 along the arrangement direction of the single cells 10 so as to extend from the upper end of the first end plate 20 to the upper end of the second end plate 30. The restraining hoop member 40 has a connecting portion 44 that continuously connects the first support portion 41 and the second support portion 42 along the arrangement direction of the single cells 10 so as to extend from the lower end of the first end plate 20 to the lower end of the second end plate 30.

The restraining hoop member 40 surrounds the stack, which is made up of the first end plate 20, the array of the plurality of single cells 10, and the second end plate 30, in an annular shape along its outer periphery. The plurality of single cells 10, the first end plate 20, and the second end plate 30 are arranged inside the ring of the restraining hoop member 40. The restraining hoop member 40 is in contact with the second surface 22 of the first end plate 20. The restraining hoop member 40 is in contact with the second surface 32 of the second end plate 30.

The restraining hoop member 40 is closed in a ring shape, thereby restricting the distance between the first end plate 20 and the second end plate 30. The dimension in the arrangement direction of the connecting parts 43, 44 of the restraining hoop member 40 is equal to the dimension in the arrangement direction of the multiple unit cells 10 that are restrained in the arranged state. The dimension in the arrangement direction of the connecting parts 43, 44 of the restraining hoop member 40 is determined so that the restraining pressure applied to the unit cells 10 is a predetermined magnitude. The restraining hoop member 40 is configured so that the dimension in the arrangement direction of the connecting parts 43, 44 is smaller than the dimension in the arrangement direction of the multiple unit cells 10 in an unrestrained state.

When the restraining hoop member 40 is assembled around the first end plate 20, the multiple single cells 10, and the second end plate 30, a tensile stress acts on the restraining hoop member 40 in the circumferential direction of the ring of the restraining hoop member 40. The restraining hoop member 40 applies a force to the first end plate 20 and the second end plate 30 in a direction that reduces the distance between the first end plate 20 and the second end plate 30. This causes the restraining hoop member 40 to generate a restraining pressure on the single cells 10, restraining the multiple single cells 10.

The dimensions of the first end plate 20 and the second end plate 30 are larger than the dimensions of the cells 10 in the vertical direction of the cells 10, so that as shown in FIG. 1, a gap is formed between the connecting portion 43 of the restraining hoop member 40 and the external terminal 14, and a gap is formed between the connecting portion 44 and the battery case 12. The restraining hoop member 40 assembled around the first end plate 20, the multiple cells 10, and the second end plate 30 is positioned away from the cells 10, preventing interference between the restraining hoop member 40 and the cells 10. This allows the restraining hoop member 40 to firmly restrain the cells 10 in the arrangement direction.

The material from which the restraining hoop member 40 is formed may be, for example, a metal material, a resin material, an inorganic material, or a composite material. The restraining hoop member 40 may have a seamless ring structure made of a single material. Alternatively, the restraining hoop member 40 may have a ring structure with a seam, for example, formed by overlapping and joining the ends of two semi-ring-shaped members together.

The restraining mechanism may include only one restraining hoop member 40. The restraining mechanism may include two or more restraining hoop members 40. When the restraining mechanism includes only one restraining hoop member 40, the restraining hoop member 40 may be formed wider than when the restraining mechanism includes two or more restraining hoop members 40.

The first end plate 20 and the second end plate 30 may have upper and lower corners entirely formed into curved surfaces. Alternatively, the first end plate 20 and the second end plate 30 may have groove shapes at the upper and lower corners, the restraining hoop member 40 may be housed inside the groove shapes, and the bottom surface of the groove shapes may be formed into a curved surface to form a chamfered portion. In the latter case, it is possible to suppress misalignment of the restraining hoop member 40 in the width direction of the battery stack 1 (the direction perpendicular to the paper surface in FIG. 1).

Figure 2 is a schematic diagram of the restraining hoop member 40 as viewed from the front. Figure 2 illustrates the restraining hoop member 40 as viewed in the direction of arrow II in Figure 1, and therefore illustrates the first support portion 41 of the restraining hoop member 40. As shown in Figure 2, the restraining hoop member 40 has an easily deformable portion 50 in a portion in the circumferential direction of the ring, which is easier to deform in the circumferential direction of the ring than other portions. The easily deformable portion 50 is a portion of the restraining hoop member 40 that makes it easier to deform in the circumferential direction of the ring of the restraining hoop member 40 than other portions. The easily deformable portion 50 is configured to be more easily deformable in the circumferential direction of the ring of the restraining hoop member 40 than the portion of the restraining hoop member 40 that is not the easily deformable portion 50.

The boundary line 51 shown in FIG. 2 indicates a position on the second surface 22 of the first end plate 20 that corresponds to the boundary between the chamfered portion 23 and the flat portion 25. The boundary line 52 shown in FIG. 2 indicates a position on the second surface 22 of the first end plate 20 that corresponds to the boundary between the chamfered portion 24 and the flat portion 25. In the circumferential direction of the ring of the restraining hoop member 40, the easily deformable portion 50 is formed between the boundary line 51 and the boundary line 52.

As explained with reference to FIG. 1, the restraining hoop member 40 is in contact with the second surface 22 of the first end plate 20. Therefore, the easily deformable portion 50 shown in FIG. 2 is in contact with the second surface 22 of the first end plate 20. The easily deformable portion 50 is in contact with the flat surface portion 25 of the second surface 22 of the first end plate 20. The entire easily deformable portion 50 in the circumferential direction of the ring of the restraining hoop member 40 is in contact with the flat surface portion 25 of the second surface 22 of the first end plate 20.

The easily deformable portion 50 has a width-reducing portion 53. The width of the flat belt-shaped restraining hoop member 40 is smaller at the width-reducing portion 53. The easily deformable portion 50 has a portion where the width of the restraining hoop member 40 is smaller than the restraining hoop member 40 other than the easily deformable portion 50. The width of the restraining hoop member 40 gradually decreases from the boundary line 51 toward the width-reducing portion 53 shown in FIG. 2, and the width of the restraining hoop member 40 gradually decreases from the boundary line 52 toward the width-reducing portion 53. The width-reducing portion 53 is formed in the central portion of the easily deformable portion 50 in the circumferential direction of the ring of the restraining hoop member 40. The width of the restraining hoop member 40 is smallest at the width-reducing portion 53.

By providing the width reducing portion 53, the cross-sectional area perpendicular to the circumferential direction of the ring of the restraining hoop member 40 is reduced in the easily deformable portion 50. As a result, the rigidity of the easily deformable portion 50 is reduced compared to the restraining hoop member 40 other than the easily deformable portion 50. Because the easily deformable portion 50 has a low rigidity structure, the circumferential deformation of the ring of the restraining hoop member 40 in the easily deformable portion 50 is made easier than in other parts of the restraining hoop member 40.

The easily deformable portion 50 has a portion where the thickness of the restraining hoop member 40 is smaller than the restraining hoop member 40 other than the easily deformable portion 50. Typically, the easily deformable portion 50 has through holes 54, 55 that penetrate the restraining hoop member 40 in the thickness direction. That is, the thickness of the restraining hoop member 40 is zero at the through holes 54, 55. In the circumferential direction of the ring of the restraining hoop member 40, the through hole 54 is formed between the boundary line 51 and the width reduction portion 53, and the through hole 55 is formed between the boundary line 52 and the width reduction portion 53. By forming the through holes 54, 55 in the restraining hoop member 40, a narrow portion 56 with a small width is formed around the through holes 54, 55.

By forming through holes 54, 55 that reduce the thickness of the restraining hoop member 40 in the easily deformable portion 50, typically making the thickness of the restraining hoop member 40 zero, the cross-sectional area perpendicular to the circumferential direction of the ring of the restraining hoop member 40 is reduced in the easily deformable portion 50. This reduces the rigidity of the easily deformable portion 50 compared to the restraining hoop member 40 other than the easily deformable portion 50. Because the easily deformable portion 50 has a low rigidity structure, the circumferential deformation of the ring of the restraining hoop member 40 in the easily deformable portion 50 is made easier than in other parts of the restraining hoop member 40.

The restraining hoop member 40 of the embodiment described above has an easily deformable portion 50, which makes the elastic deformation of the ring in the circumferential direction easier than a conventional restraining hoop member that does not have an easily deformable portion 50. When the restraining hoop member 40 of the embodiment is deformed to increase the circumferential dimension of the ring, the amount of elastic deformation until the yield point is reached is larger than that of a conventional restraining hoop member that does not have an easily deformable portion 50.

When manufacturing the battery stack 1 using the restraining hoop member 40, first, the annular restraining hoop member 40 is placed so as to surround the first end plate 20 and the second end plate 30. Next, the first end plate 20 and the second end plate 30 are moved relative to each other to increase the distance between the first end plate 20 and the second end plate 30. At this time, the restraining hoop member 40 elastically deforms so as to increase the circumferential dimension of the ring. In this state, multiple single cells 10 are placed between the first end plate 20 and the second end plate 30. Then, the force applied for the relative movement between the first end plate 20 and the second end plate 30 is released.

The restraining hoop member 40 of the embodiment is capable of undergoing greater elastic deformation than conventional restraining hoop members when manufacturing the battery stack 1. When the force applied to the first end plate 20 and/or the second end plate 30 to assemble the unit cells 10 is released, the restraining hoop member 40 elastically deforms to reduce the circumferential dimension of the ring, and a restraining pressure is applied from the restraining hoop member 40 to the unit cells 10.

At this time, due to the large amount of elastic deformation of the restraining hoop member 40, which reduces the circumferential dimension of the ring, the restraining hoop member 40 is positioned along the curved surface of the chamfered portion 24 of the second surface 22 of the first end plate 20, as shown in Figure 3. The restraining hoop member 40 is in surface contact with the chamfered portion 24, and no gap is generated between the restraining hoop member 40 and the second surface 22 of the first end plate 20. Note that Figure 3 is a schematic diagram showing an enlarged view of region III in Figure 1.

Even if the dimensions of the first end plate 20 fluctuate due to manufacturing variance, the restraining hoop member 40 can be made to closely conform to the actual shape of the first end plate 20, and can be positioned with no gap between it and the first end plate 20. By eliminating any gap between the first end plate 20 and the restraining hoop member 40, stress concentration at the end of the curve of the restraining hoop member 40 can be suppressed.

With reference to Figure 3, the arrangement of the restraining hoop member 40 along the chamfered portion 24 at the lower end of the first end plate 20 has been representatively explained, but the restraining hoop member 40 is similarly arranged at the chamfered portion 23 at the upper end of the first end plate 20 with no gap between the chamfered portion 23. A configuration in which no gaps are formed between the first end plate 20 and the restraining hoop member 40 can be reliably realized.

Although the easily deformable portion 50 formed in the first support portion 41 of the restraining hoop member 40 has been described, a similar easily deformable portion 50 can also be provided in the second support portion 42. By arranging the restraining hoop member 40 without any gap between it and the chamfered portions 33, 34 of the second end plate 30, it is possible to suppress stress concentration at the end of the curve of the restraining hoop member 40. By providing easily deformable portions 50 at multiple locations in the circumferential direction of the ring of the restraining hoop member 40, it is possible to increase the amount of elastic deformation of the restraining hoop member 40. By configuring the restraining hoop member 40 to have easily deformable portions 50 at two equally spaced locations in the circumferential direction of the ring, it is possible to reliably elastically deform the restraining hoop member 40 in the circumferential direction of the ring, and to suppress stress concentration in the restraining hoop member 40.

The first support portion 41, which contacts the second surface 22 of the first end plate 20, and the second support portion 42, which contacts the second surface 32 of the second end plate 30, are formed with easily deformable portions 50, which are configured to contact the second surfaces 22, 32. This makes it possible to prevent the easily deformable portions 50 from becoming a stress concentration point, and more reliably achieves the effect of preventing stress concentration from occurring in the restraining hoop member 40.

The restraining hoop member 40 receives a reaction force by applying a restraining pressure to the single battery 10. The parts of the restraining hoop member 40 that contact the flat surface 25 of the first end plate 20 and the flat surface 35 of the second end plate 30 are the parts where the stress acting on the restraining hoop member 40 due to the reaction force is the smallest. Therefore, the restraining hoop member 40 is arranged with respect to the first end plate 20 and the second end plate 30 so that the easily deformable part 50 contacts the flat surface parts 25, 35, more typically, the entire easily deformable part 50 contacts the flat surface parts 25, 35. By arranging in this way, it is possible to prevent the easily deformable part 50, which has low rigidity, from reducing the function of the restraining hoop member 40, and the restraining hoop member 40 can reliably continue to apply a high load restraining force to the single battery 10.

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

1 Battery stack, 10 Single cell, 12 Battery case, 14 External terminal, 20 First end plate, 21, 31 First surface, 22, 32 Second surface, 23, 24, 33, 34 Chamfered portion, 25, 35 Planar portion, 30 Second end plate, 40 Restraining hoop member, 41 First support portion, 42 Second support portion, 43, 44 Connecting portion, 50 Deformable portion, 51, 52 Boundary line, 53 Width reduction portion, 54, 55 Through hole, 56 Details.

Claims (8)

A plurality of unit cells arranged in an arrangement direction;
a restraining mechanism for restraining the plurality of unit cells,
the restraint mechanism includes a pair of end plates arranged at both ends of the plurality of unit cells in the arrangement direction, and an annular restraint hoop member,
the plurality of unit cells and the pair of end plates are disposed inside a ring of the restraining hoop member,
The restraining hoop member has an easily deformable portion that partially facilitates deformation of the ring of the restraining hoop member in the circumferential direction,
The pair of end plates each have a first surface facing the battery cell and a second surface opposite to the first surface,
The easily deformable portion contacts the second surface . The battery stack according to claim 1, wherein the easily deformable portion has a portion where the thickness of the restraining hoop member is smaller than the thickness of the other portion. The battery stack according to claim 2, wherein the easily deformable portion has a through hole that penetrates the restraining hoop member in the thickness direction. The battery stack according to any one of claims 1 to 3, wherein the easily deformable portion has a portion in which the restraining hoop member has a smaller width than the other portions of the easily deformable portion. the second surface has curved chamfered portions on both edges in the circumferential direction of the ring of the restraining hoop member, and has a flat portion between the pair of chamfered portions;
The battery stack according to claim 1 , wherein the easily deformable portion is in contact with the flat portion. The battery stack according to claim 5 , wherein the entirety of the easily deformable portion in the circumferential direction of the ring of the restraining hoop member contacts the flat portion. a ring-shaped restraining hoop member that restrains, in the arrangement direction, a plurality of unit cells arranged in an arrangement direction and a pair of end plates that are disposed at both ends of the plurality of unit cells in the arrangement direction and have a first surface facing the unit cells and a second surface opposite to the first surface ,
the plurality of unit cells and the pair of end plates are disposed inside a ring of the restraining hoop member,
a deformation-prone portion that partially facilitates deformation of the ring of the restraining hoop member in the circumferential direction ;
The easily deformable portion contacts the second surface . The restraining hoop member according to claim 7 , wherein the easily deformable portions are provided at two locations equidistantly spaced in the circumferential direction.

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