Energy storage device

Abstract

This design aims to suppress the increase in the size of the battery cell while reducing the load on the electrode terminals when the battery cell expands. [Solution] The energy storage device comprises a plurality of battery cells, a busbar, a first roller, and a second roller. The plurality of battery cells include first and second battery cells adjacent to each other in the stacking direction. The busbar is provided to electrically connect a first electrode terminal, which is one of a pair of electrode terminals of the first battery cell, and a second electrode terminal, which is one of a pair of electrode terminals of the second battery cell. The first roller is rotatably mounted on the first electrode terminal, and the second roller is rotatably mounted on the second electrode terminal. The busbar is electrically connected to the first and second electrode terminals via the first and second rollers by being positioned in contact with each of the first and second rollers, and is positioned between the pair of electrode terminals in each of the first and second battery cells.

Description

Technical Field

[0001] The present disclosure relates to a power storage device having a plurality of battery cells.

Background Art

[0002] Patent Document 1 discloses a battery module. The connection bus bar has a pair of connection portions connected to the terminals of adjacent battery cells and a bent portion. The bent portion is formed between the pair of connection portions and is elastically deformable in the parallel arrangement direction in response to the expansion in the parallel arrangement direction of the battery cells.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the configuration described in Patent Document 1, the bus bar (connection bus bar) is directly connected to the electrode terminals of adjacent battery cells. More specifically, the bus bar is fixed to each electrode terminal by a fixing bolt. Therefore, even if the bent portion of the connection bus bar is deformed as the adjacent battery cells expand, a load is applied to the electrode terminals to which the bus bar is fixed. In addition, it is desirable that measures for making it difficult to apply a load to the electrode terminals be taken while suppressing an increase in the size of the battery cells in a state where the bus bar is assembled.

Means for Solving the Problems

[0005] The energy storage device according to this disclosure comprises a plurality of battery cells, a busbar, a first roller, and a second roller. The plurality of battery cells include first and second battery cells adjacent to each other in the stacking direction. The busbar is provided to electrically connect a first electrode terminal, which is one of a pair of electrode terminals of the first battery cell, and a second electrode terminal, which is one of a pair of electrode terminals of the second battery cell. The first roller is rotatably mounted on the first electrode terminal. The second roller is rotatably mounted on the second electrode terminal. The busbar is electrically connected to the first and second electrode terminals via the first and second rollers by being positioned to contact each of the first and second rollers. The busbar is positioned between the pair of electrode terminals in each of the first and second battery cells. [Effects of the Invention]

[0006] According to this disclosure, the increase in the size of the battery cell is suppressed, while reducing the load on the electrode terminals when the battery cell expands. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram illustrating the configuration of the energy storage device according to Embodiment 1. [Figure 2] This is a diagram illustrating the effects of the energy storage device according to Embodiment 1. [Figure 3] This is a diagram illustrating the configuration of the energy storage device according to Embodiment 2. [Modes for carrying out the invention]

[0008] 1. Embodiment 1 Figure 1 is a diagram illustrating the configuration of the energy storage device 1 according to Embodiment 1. More specifically, Figure 1 includes a perspective view of the energy storage device 1 (A), a view of the energy storage device 1 from the stacking direction D1 of the battery cells 10 (B), a view of the energy storage device 1 from the left-right direction D2 of the battery cells 10 (C), and various structural examples of the rollers 30 (D) to (G).

[0009] The energy storage device 1 is mounted on a vehicle, for example, and supplies power to the vehicle. The energy storage device 1 comprises a plurality of battery cells 10, which are secondary batteries, and a plurality of busbars 20 that electrically connect adjacent battery cells 10. For example, the energy storage device 1 is mounted on a vehicle as a battery module or battery pack having a housing C (not shown) that houses the plurality of battery cells 10. Alternatively, the energy storage device 1 may be configured using the vehicle's chassis or body as the housing C.

[0010] The battery storage device 1 comprises multiple battery cells 10, each having two or more battery cells 10 arranged side by side in the stacking direction (front-to-back direction) D1. Furthermore, the multiple battery cells 10 may also comprise multiple modules of these two or more battery cells 10. Each battery cell 10 has, for example, a rectangular shape. Each battery cell 10 has a pair of electrode terminals (positive terminal and negative terminal) 11. The pair of electrode terminals 11 protrude outward from a common terminal mounting surface (e.g., the top surface 12 of the battery cell 10). More specifically, the pair of electrode terminals 11 protrude upward from the top surface 12 in the height direction D3 of the battery cell 10 and are arranged side by side in the left-to-right direction D2.

[0011] The configuration of the energy storage device 1 will be explained below, focusing on two battery cells 10 that are adjacent to each other in the stacking direction D1 among the multiple battery cells 10 described above. Here, one of the two adjacent battery cells 10 will be called the "first battery cell 10A" and the other the "second battery cell 10B". In the case where the energy storage device 1 has multiple combinations of two battery cells 10 that are adjacent to each other in the stacking direction D1, the first battery cell 10A and the second battery cell 10B shown in Figure 1 represent typical configurations of multiple combinations of these two battery cells 10.

[0012] One of the pair of electrode terminals 11 of the first battery cell 10A is called the "first electrode terminal 11A," and one of the pair of electrode terminals 11 of the second battery cell 10B is called the "second electrode terminal 11B." Figure 1(A) shows one of several busbars 20. The busbar 20 shown in Figure 1(A) electrically connects the first electrode terminal 11A and the second electrode terminal 11B. More specifically, in the left-right direction D2, the first electrode terminal 11A and the second electrode terminal 11B are located on the same side. The busbar 20 is arranged to extend along the stacking direction D1.

[0013] The busbar 20 is used, for example, to electrically connect the first battery cell 10A and the second battery cell 10B in series. In this example, if the first battery cell 10A is the positive terminal, the second battery cell 10B is the negative terminal, and if the first battery cell 10A is the negative terminal, the second battery cell 10B is the positive terminal. Alternatively, the busbar 20 may be used to electrically connect the first battery cell 10A and the second battery cell 10B in parallel. In this example, both the first battery cell 10A and the second battery cell 10B are either the positive or negative terminals.

[0014] Battery cells can expand in the stacking direction due to aging (see, for example, Figure 2(B) below). If the busbar is fixed to the electrode terminals of the battery cells with bolts, the expansion of adjacent battery cells can cause changes in the distance between cells, which can put a load on the electrode terminals. Furthermore, measures to reduce the load on the electrode terminals should be implemented while suppressing the increase in the size of the battery cells when the busbar is assembled.

[0015] Therefore, the energy storage device 1 according to Embodiment 1 has the following configuration. That is, the energy storage device 1 includes a roller 30 (30A) rotatably provided on the first electrode terminal 11A and a roller 30 (30B) rotatably provided on the second electrode terminal 11B. More specifically, each roller 30 is integrated with the corresponding electrode terminal 11. In addition, rollers 30 are similarly provided on the electrode terminals 11 of battery cells 10 other than battery cells 10A and 10B among the plurality of battery cells 10 provided in the energy storage device 1, except for electrode terminals 11 that are not connected to the electrode terminals 11 of adjacent battery cells 10 using busbars 20.

[0016] The busbar 20 is positioned to contact the rollers 30A (first roller) and 30B (second roller) perpendicularly, thereby providing electrical contact with the electrode terminals 11A and 11B via the rollers 30A and 30B. As shown in Figure 1(B), the busbar 20 is positioned between the pair of electrode terminals 11 in each of the battery cells 10A and 10B. Additionally, in the example shown in Figure 1, the busbar 20 is positioned so as to remain within the height range of the electrode terminals 11A and 11B in the height direction D3 (in other words, so as not to protrude beyond each electrode terminal 11A and 11B).

[0017] Next, specific structural examples of the roller 30 (examples 1 to 4) will be described.

[0018] In the first example, as shown in Figure 1(D), the roller 30 is provided together with a rotating shaft 31 and a pair of support parts 32. The rotating shaft 31 rotatably supports the roller 30. In the first embodiment, the rotating shaft 31 is parallel to the height direction D3 of the battery cell 10 and perpendicular to the upper surface 12 (terminal mounting surface) of the battery cell 10. One end of the pair of support parts 32 is fixed to the electrode terminals 11, and the other ends of the pair of support parts 32 are fixed to the respective ends of the rotating shaft 31. In the first example, the roller 30 is positioned in the middle of the height direction D3.

[0019] In the second example, as shown in FIG. 1(E), it is rotatably supported by a rotation axis 33 concentric with the electrode terminal 11. Similar to the first example, in this example as well, the rotation axis 33 is parallel to the height direction D3 and perpendicular to the upper surface 12. More specifically, in the second example, as can be seen from the cross-sectional view shown on the right side in FIG. 1(E), as an example, the rotation axis 33 has a large-diameter portion 34 that supports the roller 30 and a pair of small-diameter portions 35 located on both sides of the large-diameter portion 34. The electrode terminal 11 is formed by being divided into two cylindrical parts having the same outer shape as the diameter of the large-diameter portion 34 and covers the pair of small-diameter portions 35. Also, in the second example, the roller 30 is arranged in the middle in the height direction D3.

[0020] The third example has the same configuration as the first example, except that the position of the roller 30 in the height direction D3 is different, as shown in FIG. 1(F). In this example, the roller 30 is arranged to have the same height as the electrode terminal 11.

[0021] The fourth example has the same configuration as the second example, except that the position of the roller 30 in the height direction D3 is different, as shown in FIG. 1(G). In this example, the roller 30 is arranged to have the same height as the electrode terminal 11.

[0022] The roller 30 is interposed between each of the first electrode terminal 11A and the second electrode terminal 11B and the bus bar 20. Therefore, it is required that the roller 30 can be electrically connected to each of the first electrode terminal 11A, the second electrode terminal 11B, and the bus bar 20.

[0023] Therefore, various metals (e.g., iron) can be used as the material for the roller 30 as a general conductive material. More specifically, considering the effects of long-term vehicle use or vibration, it is desirable that the roller 30 be plated to prevent oxidation or rust. Alternatively, it is desirable that the roller 30 be made of a material that is less susceptible to changes due to oxidation such as rust. In addition, provided that it can maintain conductivity even after being worn down by abrasion, the roller 30 may be made of, for example, a conductive resin material. Furthermore, the members interposed between the roller 30 and the electrode terminals 11, namely the rotating shaft 31 (or 33) and the pair of support parts 32, are also made of a conductive material such as metal.

[0024] Furthermore, as shown in Figure 1, the busbar 20 is in contact with each of the battery cells 10A and 10B only at the rollers 30. In Embodiment 1, the elongated plate-shaped busbar 20 is arranged parallel to the respective electrode terminals 11A and 11B. More specifically, the busbar 20 is arranged such that its short side is perpendicular to the upper surface 12 of each battery cell 10, and its long side is parallel to the stacking direction D1. The busbar 20, arranged in this manner, is supported by the housing C of the energy storage device 1 (e.g., module case, pack case). In addition, with respect to the stacking direction D1, the busbar 20 has a length that allows it to maintain contact with each roller 30 when a change in the inter-cell distance DC occurs due to the expansion of the battery cells 10 (see Figure 2(B) described later).

[0025] Furthermore, as illustrated in Figure 1(B), if two busbars 20 are provided that are connected to a pair of electrode terminals 11 of a single battery cell 10 via rollers 30, the two busbars 20 may be supported by the housing C via an insulator 40 fixed to the housing C. The insulator 40 has the following function: In order to more reliably maintain contact between each busbar 20 and each roller 30, the insulator 40 is positioned between the two busbars 20 corresponding to the pair of electrode terminals 11 of the battery cell 10, as shown in Figure 1(B). More specifically, the insulator 40 may have a shape that matches the gap between the two busbars 20, or it may be formed using a rubbery material to have a width slightly larger than the gap between the two busbars 20. According to the latter example, the two busbars 20 are pressed against the respective electrode terminals 11. This allows for better maintenance of contact between each busbar 20 and each battery cell 10. Furthermore, in order to suppress an increase in the size of the battery cell 10, it is desirable that the insulator 40 be formed so as not to protrude upward in the height direction D3 as shown in Figure 1(B), or so as to minimize the amount of such protrusion. Additionally, instead of the insulator 40 made of rubber or the like, a metallic spring may be used, provided that an insulator is interposed between the spring and each busbar 20.

[0026] Furthermore, similar to the roller 30, the busbar 20 is also made of, for example, metal. Additionally, with respect to the contact area between the roller 30 and the busbar 20, the materials of the roller 30 and the busbar 20 may be the same or different. However, from a safety standpoint, the parts of the busbar 20 other than the contact area with the roller 30 may be made of an insulating material.

[0027] Furthermore, since the busbar 20 contacts the roller 30 and causes the roller 30 to roll, it has a smooth, plate-like shape. However, the busbar 20 may have a guide (e.g., a groove 21 shown in Figure 1(B)) on the contact surface with the roller 30 to restrict the vertical position of the roller 30 (height direction D3). In addition, it is desirable that the groove 21 has a concave cross-sectional shape when viewed from the stacking direction D1 and is formed to support the roller 30 from above and below (in other words, in the height direction D3). Also, the groove 21 is formed to extend along the longitudinal direction (stacking direction D1) of the busbar 20.

[0028] Furthermore, the multiple battery cells 10 provided in the energy storage device 1 may be arranged such that there is a plate-shaped insulator between adjacent battery cells 10 in the stacking direction D1. In this example, instead of providing the insulator 40 described above (see Figure 1(B)), the plate-shaped insulator may be formed to extend to the same location as the insulator 40 in order to maintain contact between each busbar 20 facing a pair of electrode terminals 11 and the roller 30 in each battery cell.

[0029] Figure 2 is a diagram illustrating the effects of the energy storage device 1 according to Embodiment 1. More specifically, Figure 2(A) shows the energy storage device 1 in its initial stage, and Figure 2(B) shows the energy storage device 1 when it is expanding due to deterioration. As can be seen by comparing Figure 2(A) and Figure 2(B), when each battery cell 10A and 10B expands due to deterioration, the inter-cell distance DC increases due to the expansion of each battery cell 10A and 10B. In addition, in a battery module in which a predetermined number of battery cells 10 are arranged along the stacking direction D1, the inter-cell distance DC increases particularly in battery cells 10 that are adjacent to each other near the center of the battery module.

[0030] According to the energy storage device 1 described above, of the bus bar 20 and each battery cell 10A and 10B, only each battery cell 10A and 10B have degrees of freedom in the stacking direction D1, allowing for conductivity between the battery cells 10A and 10B. Therefore, with this energy storage device 1, when the distance DC between cells increases, the movement of each battery cell 10A and 10B is not hindered by the bus bar 20. That is, deformation of each battery cell 10 and fluctuations in the distance DC between cells can be tolerated while maintaining conductivity between the bus bar 20 and each electrode terminal 11 via the roller 30. The bus bar 20 is positioned between the pair of electrode terminals 11 in each of the battery cells 10A and 10B. Therefore, with this energy storage device 1, the increase in the size of each battery cell 10 is suppressed, and the load on the electrode terminals 11 is reduced when the battery cells 10 expand.

[0031] 2. Embodiment 2 Figure 3 is a diagram illustrating the configuration of the energy storage device 2 according to Embodiment 2. More specifically, Figure 3 includes a perspective view of the energy storage device 2 (A), an enlarged view of the roller 36 and terminal 11 (B), and various specific examples of the arrangement around the busbar 22 or 23 (C) and (D).

[0032] The energy storage device 2 is configured similarly to the energy storage device 1 according to Embodiment 1, except that the direction of rotation of the rollers is different, and consequently the arrangement of the busbars is different. Specifically, in the energy storage device 1, the rotation axis 31 (or 33) of the roller 30 is parallel to the height direction D3. In contrast, in the energy storage device 2, the rotation axis 37 of the roller 36 is parallel to the left-right direction D2 (in other words, the direction in which the pair of electrode terminals 11 in each battery cell 10 face each other), as shown in Figure 2(A). In the following description, the roller 36 provided on the first electrode terminal 11A will be called roller 36A (first roller), and the roller 36 provided on the second electrode terminal 11B will be called roller 36B (second roller).

[0033] Due to the difference in the rotation direction of the rollers 36 described above, the busbars 22 are arranged as follows. Here, the busbar 22 for connecting the first battery cell 10A and the second battery cell 10B (see Figure 3(A)) will be described. The busbar 22 is positioned between the rollers 36A and 36B and the upper surfaces 12 of each battery cell 10A and 10B. The busbar 22 has an elongated plate shape and is positioned parallel to the upper surface 12 of each battery cell 10. More specifically, similar to the busbar 20, the busbar 22 is positioned so that its longitudinal direction is parallel to the stacking direction D1.

[0034] As shown in the right-hand diagram in Figure 3(C), the upper surface of the busbar 22, positioned in the above orientation, contacts each of the rollers 36 (36A and 36B). The lower surface of the busbar 22 is supported by the upper surface 12 of each battery cell 10 via an elastic insulator 41. In other words, the busbar 22 is held by each upper surface 12 and each roller 36 by utilizing the elasticity of the insulator 41 interposed between it and the upper surface 12 of each battery cell 10. Additionally, the insulator 41, which is press-fitted between the busbar 22 and the upper surface 12 of each battery cell 10, has a height H1 that makes the distance from the upper surface of the busbar 22 to the lower surface of the insulator 41 longer than the distance between the rollers 36 and the upper surface 12 before the busbar 22 is assembled (see the left-hand diagram in Figure 3(C)). After the busbar 22 is assembled, the height of the insulator 40 decreases to a height H2 (see the right-hand diagram in Figure 3(C)). As a result, the elasticity of the insulator 41 maintains contact between the busbar 22 and each roller 36, while fixing the position of the busbar 22 in the height direction D3.

[0035] Furthermore, as shown in Figure 3(A), similar to the busbar 20 in Embodiment 1, the busbar 22 is also positioned between the pair of electrode terminals 11 in each of the battery cells 10A and 10B. The busbar 22 is also positioned so that it fits within the height range of the electrode terminals 11 (11A and 11B, respectively) in the height direction D3 (see Figure 3(C)).

[0036] Furthermore, the energy storage device 2 according to Embodiment 2 may also include a busbar 23 shown in Figure 3(D) instead of the busbar 22. The busbar 23 differs from the busbar 22 in that it has grooves 24 on the contact surface (upper surface) with each roller 36. The grooves 24 are examples of guides for regulating the position of the rollers 36 in the left-right direction D2, and are formed to extend along the longitudinal direction (stacking direction D1) of the busbar 23.

[0037] The energy storage device 2 according to Embodiment 2 also suppresses the increase in the size of each battery cell 10, while reducing the load on the electrode terminals 11 when the battery cells 10 expand. [Explanation of symbols]

[0038] 1, 2 Energy storage device, 10 Battery cell, 11 Electrode terminal, 20, 22, 23 Busbar, 21, 24 Groove, 30, 36 Roller, 40, 41 Insulator

Claims

[Claim 1] A plurality of battery cells, including first and second battery cells adjacent to each other in the stacking direction, A busbar for electrically connecting a first electrode terminal, which is one of a pair of electrode terminals of the first battery cell, and a second electrode terminal, which is one of a pair of electrode terminals of the second battery cell, A first roller is rotatably mounted on the first electrode terminal, A second roller is rotatably mounted on the second electrode terminal, Equipped with, The busbar is positioned to contact each of the first and second rollers, thereby providing electrical contact with each of the first and second electrode terminals via the first and second rollers, and is positioned between the pair of electrode terminals in each of the first and second battery cells. Energy storage device.

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