Power storage device

Abstract

This power storage device comprises: a power storage element; an end plate disposed in a first direction of the power storage element; and a side plate extending in the first direction and connected to the end plate. At least one of the end plate and the side plate has a protrusion formed in at least one of the corners thereof, where the first direction and a second direction, which is orthogonal to the first direction, cross each other. The protrusion is formed by deforming at least one of the end plate and the side plate in a convex shape toward the outside, and as a result thereof, the protrusion has a space which is open on the power storage element side.

Description

Power storage device

[0001] The present invention relates to an electricity storage device.

[0002] Patent Literature 1 discloses a battery module including a plurality of battery cells, a pair of end plates, and a pair of restraining members. The plurality of battery cells are aligned in one direction, with a pair of end plates disposed at both ends of the battery cells. The pair of restraining members are disposed to sandwich the plurality of battery cells and the pair of end plates in a direction perpendicular to the alignment direction of the battery cells. The ends of the pair of restraining members are connected to the pair of end plates. As a result, the plurality of battery cells are fixed by the pair of end plates and the pair of restraining members.

[0003] Japanese Patent Application Laid-Open No. 2020-57520

[0004] In the conventional battery modules described above, battery cells expand during charging and discharging, and this expansion exerts a force on the end plates or restraining members. Increasing the rigidity of the end plates or restraining members is one way to prevent damage to the end plates or restraining members caused by this force. However, simply increasing the rigidity could increase the cost of the end plates or restraining members and the mass of the battery module. Therefore, it is necessary to absorb the force acting on the end plates or restraining members.

[0005] The present invention was made by the inventor of the present application by focusing on the above-mentioned problem, and aims to provide an energy storage device that can absorb the force acting on the end plate or side plate when the energy storage element expands.

[0006] A storage device according to one aspect of the present invention comprises a storage element, an end plate arranged in a first direction of the storage element, and a side plate extending in the first direction and connected to the end plate, wherein at least one of the end plate and the side plate has a protrusion formed at at least one corner where the first direction intersects with a second direction perpendicular to the first direction, and the protrusion is formed so as to have a space that opens toward the storage element by deforming at least one of the end plate and the side plate into a convex shape facing outward.

[0007] According to the electricity storage device of the present invention, it is possible to absorb the force acting on the end plates or the side plates when the electricity storage elements expand.

[0008] FIG. 1 is a perspective view showing a configuration of an energy storage device (with the exterior body removed) according to an embodiment. FIG. 2 is a plan view showing a configuration of an energy storage device (with the exterior body removed) according to an embodiment. FIG. 3 is a perspective view showing a configuration of an end plate according to an embodiment. FIG. 4 is a perspective view showing a configuration of a side plate according to an embodiment. FIG. 5 is a perspective view showing a configuration of an energy storage device (with the exterior body attached) according to an embodiment. FIG. 6 is a cross-sectional view showing a configuration of an energy storage device (with the exterior body attached) according to an embodiment. FIG. 7 is a cross-sectional view showing behavior of an end plate when an energy storage device according to an embodiment expands. FIG. 8 is a schematic diagram showing simulation results of stress distribution when force is applied to an end plate of a comparative example and an end plate according to an embodiment. FIG. 9 is a cross-sectional view showing configurations of an end plate and a side plate according to a first modified example of the embodiment. FIG. 10 is a cross-sectional view showing configurations of an end plate and a side plate according to a second modified example of the embodiment. FIG. 11 is a cross-sectional view showing configurations of an end plate and a side plate according to a third modified example of the embodiment. FIG. 12 is a cross-sectional view showing configurations of an end plate and a side plate according to a fourth modified example of the embodiment. FIG. 13 is a cross-sectional view showing the configuration of an end plate and a side plate according to a fifth modification of the embodiment.

[0009] (1) An energy storage device according to one aspect of the present invention comprises an energy storage element, an end plate arranged in a first direction of the energy storage element, and a side plate extending in the first direction and connected to the end plate, wherein at least one of the end plate and the side plate has a protrusion formed at at least one corner where the first direction intersects with a second direction perpendicular to the first direction, and the protrusion is formed to have a space that opens toward the energy storage element by deforming at least one of the end plate and the side plate into a convex shape facing outward.

[0010] In an energy storage device according to one embodiment of the present invention, at least one of the end plates and the side plates includes a protruding portion that is deformed to have a convex shape facing outward, so that when the energy storage element expands in the first direction during charging and discharging, the force acting on the end plate or the side plate can be absorbed by the protruding portion. In other words, by deforming the protruding portion, the force acting on the end plate or the side plate can be absorbed.

[0011] (2) In the energy storage device described above in (1), the protrusion may be formed on the end plate.

[0012] According to the energy storage device described in (2) above, the protrusion is formed on the end plate disposed in the first direction of the energy storage element, so that when the energy storage element expands in the first direction, the protrusion is more likely to deform, and thus can absorb the force acting on the end plate.

[0013] (3) In the energy storage device described above in (2), the thickness of the end plate in the first direction may be greater than the thickness of the side plate in the second direction.

[0014] According to the energy storage device described in (3) above, since the thickness of the end plates in the first direction is greater than the thickness of the side plates in the second direction, excessive deformation of the protrusions can be suppressed when the energy storage element expands in the first direction. Also, since the thickness of the side plates in the second direction is smaller than the thickness of the end plates in the first direction, an increase in the mass of the energy storage device can be suppressed.

[0015] (4) In the energy storage device described above in (1), the protrusion may be formed on the side plate.

[0016] According to the energy storage device described in (4) above, the protrusion is formed on the side plate extending in the first direction, so that when the energy storage element expands in the first direction, the protrusion is more likely to deform, and thus can absorb the force acting on the side plate.

[0017] (5) In the energy storage device according to any one of (1) to (4) above, a cross section of the protruding portion parallel to the first direction and the second direction may be arc-shaped.

[0018] According to the electricity storage device described in (5) above, the cross section of the protruding portion is formed in an arc shape, so that it is possible to prevent the force acting on the protruding portion from concentrating locally.

[0019] (6) In the energy storage device described in any one of (1) to (5) above, the energy storage device may include an outer casing that houses the energy storage element, the end plate, and the side plate, and a gap may be formed between the end plate and the surface of the outer casing that faces the end plate.

[0020] According to the energy storage device described in (6) above, by forming a gap between the exterior body and the end plate, when the exterior body is deformed by an external impact, it is possible to prevent the load acting on the deformed exterior body from acting directly on the end plate. As a result, damage to the energy storage element can be suppressed. Furthermore, when the energy storage element expands in the first direction, this gap can be used as a space to accommodate the expansion. As a result, damage to the exterior body can be suppressed. At the same time, the exterior body can restrict the expansion of the energy storage element so that the energy storage element does not expand too much.

[0021] 1. Embodiment of the Power Storage Device 8 An embodiment of the power storage device 8 according to the present invention will be described below with reference to the drawings. Note that the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiment and its modified examples are merely examples and are not intended to limit the present invention. Each figure is a schematic diagram, and dimensions and the like are not necessarily depicted precisely. In each figure, the same or similar components are designated by the same reference numerals.

[0022] In the following description and in the drawings, for convenience of explanation, the explanation will be made according to the directions shown in Figures 1 to 4. However, these directions are set for convenience of explanation and do not limit the present invention.

[0023] Expressions indicating relative directions or attitudes, such as parallel and perpendicular, also include cases where the directions or attitudes are not strictly those. Two directions being perpendicular to each other does not only mean that the two directions are completely perpendicular to each other, but also means that the two directions are substantially perpendicular to each other, or that the two directions are shifted by a few degrees from 90 degrees. In the following description, when the term "insulation" is used, it means "electrical insulation." An insulating material has a volume resistivity of 1×10 ６ Ωm or more, more preferably 1×10 ７ Ωm or more, more preferably 1×10 １０ It is preferable that the material be made of a material with a resistance of Ωm or more.

[0024] 2. Overview of Energy Storage Device 8 FIG. 1 is a perspective view showing the configuration of an energy storage device 8 (with the exterior body 7 removed) according to this embodiment. FIG. 2 is a plan view showing the configuration of an energy storage device 8 (with the exterior body 7 removed) according to this embodiment. As shown in FIGS. 1 and 2 , the energy storage device 8 includes a plurality of energy storage elements 1 arranged in a front-to-rear direction (first direction), end plates 2 arranged at both ends of the plurality of energy storage elements 1 in the front-to-rear direction, and side plates 3 sandwiching the plurality of energy storage elements 1 from the left-to-right direction (second direction) perpendicular to the front-to-rear direction. In addition, a first spacer 4 or a second spacer 5 is arranged on the front or rear surface of the energy storage element 1. Each component will be described below.

[0025] 3. Energy Storage Element 1 The energy storage element 1 may be a primary battery, a secondary battery, a capacitor, or the like. In this embodiment, an example of the energy storage element 1 is a chargeable and dischargeable non-aqueous electrolyte secondary battery. More specifically, the energy storage element 1 is a lithium-ion secondary battery that utilizes electron transfer that occurs with the movement of lithium ions. The energy storage element 1 has a flattened rectangular parallelepiped (rectangular, square) shape that is long in the vertical and horizontal directions and short in the front-to-rear direction. In this embodiment, a plurality of (four) energy storage elements 1 are arranged side by side in the front-to-rear direction, but the number of energy storage elements 1 arranged is not particularly limited. The energy storage element 1 may be a single element. The size and shape of the energy storage element 1 are also not particularly limited, and it does not have to be long in the left-to-right direction or flat in the front-to-rear direction. The energy storage element 1 may have a shape other than a rectangular parallelepiped, such as an elongated cylinder, an elliptical cylinder, a cylindrical shape, or a polygonal prism shape other than a rectangular parallelepiped. The energy storage element 1 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery. The energy storage element 1 may be a battery using a solid electrolyte. The energy storage element 1 may be a pouch-type energy storage element.

[0026] The energy storage element 1 has an electrode body (not shown), a case 11 that houses the electrode body together with an electrolyte (not shown), and a pair of terminals 12 at least partially exposed to the outside of the case 11. The terminals 12 are provided on a surface of the case 11 in a vertical direction (third direction) that is perpendicular to the front-rear direction and the left-right direction.

[0027] The case 11 has a case body with an opening on the top in the vertical direction and a plate-shaped lid that closes the opening of the case body. Terminals 12 are arranged near both left and right ends of the lid. The case 11 has a flat rectangular parallelepiped shape (square or rectangular) that is long in the vertical and left and right directions and short in the front-to-back direction. The cases 11 are lined up in the front-to-back direction so that their front-to-back faces face each other.

[0028] <4. Spacers 4, 5> The first spacer 4 is a plate-shaped member disposed between two adjacent energy storage elements 1 and is made of an insulating material. The first spacer 4 has functions such as providing insulation between the two adjacent energy storage elements 1 and protecting the energy storage elements 1 from external impact. The second spacer 5 is a plate-shaped member disposed on one (front) side of the energy storage elements 1 disposed at one end (front end) in the front-to-rear direction of the plurality of energy storage elements 1 and on the other (rear) side of the energy storage elements 1 disposed at the other end (rear end) in the front-to-rear direction. The second spacer 5 is made of an insulating material. The second spacer 5 has functions such as providing insulation between the energy storage elements 1 and an end plate 2 (described later) and protecting the energy storage elements 1 from external impact.

[0029] 5. End Plate 2> Fig. 3 is a perspective view showing the configuration of an end plate 2 according to this embodiment. As shown in Fig. 2, the end plate 2 is disposed on one (front) side of the energy storage device 1 disposed at one end (front end) in the front-rear direction, and on the other (rear) side of the energy storage device 1 disposed at the other end (rear end) in the front-rear direction. In this embodiment, a pair of end plates 2 are used, which are symmetrical in shape in the front-rear direction. Therefore, with reference to Fig. 3, the end plate 2 in contact with the energy storage device 1 disposed at one end (front end) in the front-rear direction will be described. The above-mentioned second spacer 5 is disposed between the energy storage device 1 and the end plate 2 to insulate them from each other.

[0030] 3, the end plate 2 includes a rectangular main body 21, protrusions 22 connected to both left and right ends of the main body 21, and side surfaces 23 connected to the protrusions 22, which are integrally formed. The end plate 2 is formed by bending a metal plate.

[0031] The main body portion 21 is a rectangular portion that contacts the second spacer 5. The vertical length of the main body portion 21 is shorter than the vertical length of the energy storage element 1, and the horizontal length of the main body portion 21 is also shorter than the horizontal length of the energy storage element 1.

[0032] The protrusions 22 are connected to the upper portions of both ends of the main body 21. The upper end of the main body 21 and the upper end of the protrusions are aligned. That is, the upper end of the main body 21 and the upper end of the protrusions are aligned on the same straight line. As shown in FIG. 2 , the protrusions 22 are curved in an arc shape so as to be convex forward in the front-to-rear direction in a plan view (vertical direction). This forms a space S1 between the surface (rear surface) of the protrusions 22 facing the energy storage device 1 and the second spacer 5.

[0033] The side surface portion 23 is a rectangular portion extending rearward in the front-to-rear direction from the end of the protrusion 22 opposite the end on the main body portion 21 side. The vertical length of the side surface portion 23 is the same as the vertical length of the protrusion 22. The vertical length of the side surface portion 23 is shorter than the vertical length of the energy storage element 1. The side surface portion 23 is covered by the side plate 3, and is joined to the side plate 3 by welding, adhesive, bolting, or the like.

[0034] When the energy storage element 1 expands in the front-to-rear direction due to charging and discharging, the central portion of the front-to-rear surface of the energy storage element 1 expands the most. Therefore, in order to suppress the expansion of the energy storage element 1, it is preferable that the main body 21 is disposed in contact with the central portion of the front-to-rear surface of the energy storage element 1. Here, the central portion of the front-to-rear surface of the energy storage element 1 refers to the central region when the front-to-rear surface of the energy storage element 1 is divided into thirds in the vertical direction and the central region when the front-to-rear surface is divided into thirds in the horizontal direction.

[0035] The case 11 of the energy storage device 1 has a joint 13 that joins the case body and the lid. The joint 13 is a weak part of the case 11. Therefore, if the main body 21 comes into contact with the joint 13 in the front-to-rear direction, the joint 13 may be subjected to a load from the main body 21 and may be damaged. Therefore, it is preferable to position the main body 21 in a position where it does not come into contact with the joint 13 of the case 11.

[0036] 4 is a perspective view showing the configuration of the side plate 3 according to the present embodiment. In the present embodiment, a pair of side plates 3 are used, and since these have a symmetrical shape, only the side plate 3 disposed on the right side of the electric storage component 1 will be described.

[0037] As shown in FIG. 4 , the side plate 3 is formed by bending a single metal plate and includes a rectangular first portion 31 and a second portion 32 extending leftward from the upper end of the first portion 31. The vertical length of the first portion 31 is longer than the vertical length of the side portion 23 of the end plate 2. When the end plate 2 and the side plate 3 are joined, the first portion 31 extends upward beyond the upper end of the side portion 23. The second portion 32 is bent from the upper end of the first portion 31 and is configured to engage with the upper surface of the first spacer 4 or the second spacer 5. The second portion 32 has a notch 321 or a protrusion 322 formed to match the shape of the first spacer 4 or the second spacer 5 that contacts the second portion 32.

[0038] 7. Assembly of the Energy Storage Device 8 FIG. 5 is a perspective view showing the configuration of the energy storage device 8 (with the exterior body 7 attached) according to this embodiment. A method for assembling the energy storage device 8 will be described. First, a plurality of energy storage elements 1 are lined up in the front-to-rear direction. At this time, a first spacer 4 is placed between two adjacent energy storage elements 1. Next, a second spacer 5 and an end plate 2 are placed on one (front) side of the energy storage elements 1 placed at one end (front end) in the front-to-rear direction and on the other (rear) side of the energy storage elements 1 placed at the other end (rear end) in the front-to-rear direction. Next, a pair of side plates 3 are placed so as to sandwich the plurality of energy storage elements 1, the first spacer 4, the second spacer 5, and the pair of end plates 2 in the left-to-right direction, and the pair of side plates 3 are fixed to the pair of end plates 2. That is, the second portion 32 of the side plate 3 is engaged with the upper surface of the first spacer 4 or the second spacer 5, and the front and rear ends of the side plate 3 are joined to the side surface portions 23 of the pair of end plates 2, respectively, by welding, adhesive, bolting, or the like.

[0039] The plurality of energy storage elements 1, the first spacer 4, the second spacer 5, the pair of end plates 2, and the pair of side plates 3 are then housed in an exterior body 7. The exterior body 7 includes a rectangular parallelepiped main body 71 having an opening on the upper side, and a lid 72 that closes the opening of the main body 71. The lid 72 is provided with external terminals 721. The plurality of energy storage elements 1, the first spacer 4, the second spacer 5, the pair of end plates 2, and the pair of side plates 3 are housed in the main body 71, and then the opening of the main body 71 is closed by the lid 72. The terminals 12 of the plurality of energy storage elements 1 are connected by bus bars (not shown). The terminals 12 are electrically connected to the external terminals 721 of the lid 72 by the bus bars.

[0040] Fig. 6 is a cross-sectional view showing the configuration of an electric storage device 8 (with an exterior body 7 attached) according to this embodiment. When the electric storage device 8 includes the exterior body 7, as shown in Fig. 6, a space S2 is formed between the main body portion 21 of the end plate 2 and the side wall of the main body 71. For ease of explanation, the first spacer 4 and the second spacer 5 are omitted from Fig. 6.

[0041] It is preferable that the thickness of the end plate 2 in the front-to-rear direction be greater than the thickness of the side plate 3 in the left-to-right direction. This prevents the protrusion 22 from being excessively deformed when the energy storage device 1 expands in the front-to-rear direction. Furthermore, because the thickness of the side plate 3 in the left-to-right direction is smaller than the thickness of the end plate 2 in the front-to-rear direction, an increase in the mass of the energy storage device 8 can be prevented. If the protrusion 22 is excessively deformed to the extent that it undergoes plastic deformation, the necessary restraining force for the energy storage device 1 is not generated, and the performance of the energy storage device 1 may deteriorate. Therefore, by providing the protrusion 22 on the end plate 2, which is thicker than the side plate 3, the maximum stress acting on the end plate 2 can be reduced without adversely affecting the performance of the energy storage device 1.

[0042] It is sufficient that the thickness of the end plate 2 in the front-rear direction is greater than the thickness of the side plate 3 in the left-right direction. It is sufficient that the thickness of one of the pair of end plates 2 is greater than the thickness of one of the pair of side plates 3.

[0043] 8. Features FIG. 7 is a cross-sectional view showing the behavior of the end plate 2 when the energy storage device 8 according to this embodiment expands. The energy storage device 8 configured as described above achieves the following effects. As shown in FIG. 7 , when the energy storage elements 1 expand in the front-to-rear direction due to charging and discharging, the force acting on the end plate 2 can be absorbed by the protrusion 22. At this time, a force acts on the end plate 2, causing it to expand outward. However, by providing the protrusion 22, a portion of this force can be applied to the protrusion 22. That is, the protrusion 22 can be deformed in conjunction with the deformation of the end plate 2 so that the space S1 of the protrusion 22 expands, thereby suppressing the local concentration of the force acting on the end plate 2 and dispersing it. This reduces the maximum stress acting on the end plate 2, enabling a design requiring a lower rigidity for the end plate 2. Another possible solution is to increase the rigidity of the end plate 2. Specifically, this can be achieved by increasing the Young's modulus of the material of the end plate 2 or by increasing the thickness of the end plate 2. In this case, disadvantages such as an increase in the cost of the end plates 2 and an increase in the mass of the energy storage device 8 arise. The energy storage device 8 of this embodiment can reduce the maximum stress acting on the end plates 2 while suppressing the concerns about the occurrence of the above disadvantages. Note that, for ease of explanation, the bulge of the energy storage element 1 is exaggerated in Figure 7. Also, the first spacers 4 and second spacers 5 are omitted.

[0044] Regarding the above points, the inventors conducted a simulation and the results are summarized in Figure 8. Figure 8 is a schematic diagram showing the results of a simulation of stress distribution when force is applied to an end plate 20 of a comparative example and an end plate 2 according to the present embodiment. Figure 8(a) shows a model (comparative example) in which an end plate 20 having no protrusions but a main body portion 201 and a side portion 202 is used and a side plate 3 is connected to this. Figure 8(b) shows a model in which a side plate 3 is connected to the end plate 2 according to the present embodiment.

[0045] When these models were used and forces were applied to the end plates 2 and 20 in the direction of the arrows, the model in FIG. 8( a) experienced the greatest stress at the connection between the main body portion 201 and the side portion 202 of the end plate 20. On the other hand, the model in FIG. 8( b) experienced the greatest stress at the protrusion 22 of the end plate 2. Furthermore, the model in FIG. 8( b) had a wider area S where the maximum stress value was present than the model in FIG. 8( a). This indicates that the stress acting on the end plate 2 was more dispersed than the stress acting on the end plate 20. Furthermore, the maximum stress acting on the model in FIG. 8( b) was approximately 20% smaller than the maximum stress acting on the model in FIG. 8( a).

[0046] Because the thickness of the end plates 2 in the front-rear direction is greater than the thickness of the side plates 3 in the left-right direction, excessive deformation of the protrusions 22 can be suppressed when the energy storage device 1 expands in the front-rear direction. Furthermore, because the thickness of the side plates 3 in the left-right direction is smaller than the thickness of the end plates 2 in the front-rear direction, an increase in the mass of the energy storage device 8 can be suppressed. If the protrusions 22 were to deform excessively to the extent that they would undergo plastic deformation, the necessary restraining force for the energy storage device 1 would not be generated, and the performance of the energy storage device 1 may deteriorate. Therefore, by providing the protrusions 22 on the end plates 2 that are thicker than the side plates 3, the maximum stress acting on the end plates 2 can be reduced without adversely affecting the performance of the energy storage device 1.

[0047] Since the cross-sectional shape of the protrusion 22 is formed in an arc shape, it is possible to prevent the force acting on the protrusion 22 from concentrating locally.

[0048] As shown in FIG. 6 , when the energy storage device 8 includes an exterior body 7, forming a space S2 between the side wall 71 of the exterior body 7 and the main body portion 21 of the end plate 2 prevents a load acting on the deformed exterior body 7 from acting directly on the end plate 2 when the exterior body 7 is deformed by an external impact. As a result, damage to the energy storage element 1 can be suppressed. Furthermore, by forming the space S2, this space S2 can be used to accommodate the expansion of the energy storage element 1 when it expands in the front-to-rear direction. As a result, damage to the exterior body 7 can be suppressed. On the other hand, the side wall 71 of the exterior body 7 can restrict the expansion of the energy storage element 1 so that it does not expand too much.

[0049] 9. Modifications Although the power storage device 8 according to the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. Note that the following modifications can be combined with the above embodiment, and modifications can also be combined with each other as appropriate.

[0050] In the above embodiment, the protrusion 22 is provided on the end plate 2, but the position or orientation of the protrusion is not particularly limited and various configurations are possible. That is, it is sufficient that the protrusion is formed near the corner where the end plate 2 and the side plate 3 intersect.

[0051] (Variation 1) As shown in FIG. 9 , the end plate 2 can be formed only with a flat main body portion, and a protrusion 35 can be provided on the side plate 3. More specifically, the side plate 3 is composed of a plate-shaped main body portion 34, a protrusion 35 that curves forward in the front-to-rear direction from the front end of the main body portion 34, and a front surface portion 36 that extends in the left-to-right direction from the end of the protrusion 35 opposite the main body portion 34. The rear surface or front surface of the front surface portion 36 is joined to the end plate 2 by welding, adhesive bonding, bolting, or the like. Even in this configuration, the protrusion 35 of the side plate 3 can absorb forces acting on the side plate 3. That is, the space S1 of the protrusion 35 deforms to expand, allowing the force acting on the side plate 3 to be absorbed.

[0052] 10 , the protrusions provided on the end plates 2 extend not forward in the front-rear direction but in the left-right direction along which the main body 24 extends, and are curved so as to be convex to the side. Even in this configuration, the force acting on the end plates 2 can be absorbed by the protrusions 25.

[0053] 11, the side plate 3 is provided with a protrusion 38 that is curved so as to be convex in the left-right direction. Even in this configuration, the force acting on the side plate 3 can be absorbed by the protrusion 38 of the side plate 3.

[0054] (Variations 4 and 5) In the above embodiment, the cross-sectional shape of the protrusion 22 is curved in an arc shape, but this is not limited to this. As shown in FIG. 12, the cross-section of the protrusion 22 may be shaped to be convex at an acute angle. As shown in FIG. 13, the cross-section of the protrusion 22 may be shaped to be convex in a rectangular shape. That is, the cross-sectional shape may have a flat surface that is generally parallel to the main body 21. Even if the protrusion 22 is formed as a convex at an acute angle or a convex in a rectangular shape, it deforms to expand the space S1, and therefore can absorb the force acting on the end plate 2. However, a curved cross-section of the protrusion 22 is preferable because it can suppress the local application of force.

[0055] (Other Modifications) As described above, the direction in which the protruding portion 22 protrudes is not particularly limited and can be determined appropriately in relation to the exterior body 7. However, it is preferable that the protruding portion 22 protrude in the direction in which the energy storage devices 1 are arranged.

[0056] In the above embodiment, the protrusions 22 are provided at the four corners formed by the pair of end plates 2 and the pair of side plates 3, but this is not limiting. The protrusions 22 may be provided at only two corners at either one end in the front-rear direction, or at only two corners at either one end in the left-right direction. Furthermore, the protrusion 22 may be provided at only one of the four corners.

[0057] There are no particular limitations on the configuration of the energy storage device 1, and any known configuration of an energy storage device can be adopted. The shapes of the first spacer 4, the second spacer 5, and the exterior body 7 can be changed as appropriate.

[0058] In the above embodiment, a pair of end plates 2 and a pair of side plates 3 are used, but an end plate 2 may be provided only at one end of each of the energy storage elements 1. Alternatively, only one side plate 3 may be provided. Furthermore, the end plate 2 and the side plate 3 do not necessarily have to be formed as separate bodies, and may be formed integrally with no joints.

[0059] In the above embodiment, the thickness of the end plates 2 in the front-rear direction is greater than the thickness of the side plates 3 in the left-right direction, but this configuration is not essential. The thickness of the end plates 2 may be the same as the thickness of the side plates 3, or the thickness of the end plates 2 may be smaller than the thickness of the side plates 3.

[0060] In the above embodiment, the energy storage device 8 includes the exterior body 7, but it is not essential that the energy storage device 8 includes the exterior body 7. In other words, the plurality of energy storage elements 1, the first spacer 4, the second spacer 5, the pair of end plates 2, and the pair of side plates 3 may be disposed directly inside the housing of the vehicle.

[0061] The present invention can be applied to an electricity storage device including an electricity storage element such as a lithium ion secondary battery.

[0062] REFERENCE SIGNS LIST 1 Energy storage element 11 Case 12 Terminal 13 Joint 2, 20 End plate 21, 201 Main body 22 Protrusion 23, 202 Side surface 3 Side plate 31 First portion 32 Second portion 36 Front surface 321 Notch 322 Protrusion 4 First spacer 5 Second spacer 7 Exterior body 71 Main body 72 Lid 721 External terminal 8 Energy storage device S1 Space S2 Space

Claims

1. An energy storage device comprising: an energy storage element; an end plate arranged in a first direction of the energy storage element; and a side plate extending in the first direction and connected to the end plate, wherein at least one of the end plate and the side plate has a protrusion formed at at least one corner where the first direction intersects with a second direction perpendicular to the first direction, and the protrusion is formed so as to have a space that opens towards the energy storage element by deforming at least one of the end plate and the side plate into a convex shape facing outward.

2. The energy storage device according to claim 1, wherein the protrusion is formed on the end plate.

3. The energy storage device according to claim 2, wherein a thickness of the end plates in the first direction is greater than a thickness of the side plates in the second direction.

4. The energy storage device according to claim 1, wherein the protrusion is formed on the side plate.

5. The energy storage device according to any one of claims 1 to 4, wherein a cross section of the protrusion parallel to the first direction and the second direction is arc-shaped.

6. The energy storage device according to any one of claims 1 to 4, comprising an exterior body that houses the energy storage element, the end plate, and the side plate, and a gap is formed between the end plate and a surface of the exterior body that faces the end plate.