Battery pack

Abstract

The present invention provides a battery pack in which excessive increases in the moment load acting on the end plate are suppressed. [Solution] Each of the multiple battery cells constituting the battery pack includes a case that houses the electrode body and has a substantially rectangular shape in which, when viewed from a first direction, the second direction perpendicular to the first direction is the longitudinal direction and the third direction perpendicular to the first and second directions is the short direction. The restraining member includes a pair of members provided to sandwich the multiple battery cells in the third direction, and the pair of members are fixed to the end plate from the third direction.

Description

Technical Field

[0001] The present technology relates to a battery pack.

Background Art

[0002] Conventionally, a battery pack has been known which is configured by arranging a plurality of battery cells along a stacking direction and restraining them in the stacking direction using end plates and restraining members.

[0003] Examples of the battery restraining structure in a conventional battery pack include those described in International Publication No. 2019 / 130936 (Patent Document 1) and International Publication No. 2019 / 130937 (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an expansion force is generated in the battery cell, a bending moment acts on the end plate provided at the end of the plurality of battery cells. With the increase in the size of the battery cell, the end plate is required to have a yield strength sufficient to receive the increased moment load. On the other hand, from the perspective of miniaturization of the battery pack, it is required to reduce the thickness of the end plate. From the viewpoint of achieving both of these problems, there is still room for improvement in the conventional battery pack.

[0006] An object of the present technology is to provide a battery pack in which an increase in the moment load acting on the end plate is suppressed.

Means for Solving the Problems

[0007] This technology provides the following battery pack.

[0008] [1] A battery pack comprising a plurality of battery cells arranged in a first direction, end plates provided at the ends of the plurality of battery cells in the first direction, and a restraining member that restrains the end plates and the plurality of battery cells in the first direction, wherein each of the plurality of battery cells includes a case that houses an electrode body and has a substantially rectangular shape such that, when viewed from the first direction, the second direction perpendicular to the first direction is the longitudinal direction and the third direction perpendicular to the first direction and the second direction is the short direction, and the restraining member includes a pair of members provided so as to sandwich the plurality of battery cells in the third direction, and the pair of members is fixed to the end plates from the third direction.

[0009] [2] The battery pack according to [1], wherein the plurality of battery cells have electrode terminals on a plane in the case perpendicular to the third direction.

[0010] [3] The battery pack according to [1], wherein the plurality of battery cells have electrode terminals on a plane in the case that is perpendicular to the second direction.

[0011] [4] The battery pack according to any one of [1] to [3], wherein the end plate has a stepped portion on at least one side in the third direction, is fixed to the restraining member, and further comprises a contact plate that abuts the stepped portion from the first direction.

[0012] [5] The battery pack according to any one of the items [1] to [4], wherein each of the pair of members is a plate-shaped member.

[0013] [6] The battery pack according to any one of [1] to [5], wherein each of the pair of members is provided at a position that includes the center of the plurality of battery cells in the second direction when viewed from the third direction.

[0014] [7] The dimension of each of the pair of members in the second direction varies along the first direction, The assembled battery according to any one of [1] to [6].

Advantages of the Invention

[0015] According to the present technology, it is possible to provide an assembled battery in which an excessive increase in the moment load acting on the end plate is suppressed.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective view of a battery constituting an assembled battery. [Figure 2] It is a front view showing a battery according to a modification. [Figure 3] It is a perspective view of the battery shown in FIG. 2. [Figure 4] It is a diagram showing a restraint structure of a battery in an assembled battery. [Figure 5] It is a diagram for explaining a load acting on an end plate. [Figure 6] It is a diagram for explaining the relationship between the width (B) and the height (H) of a battery. [Figure 7] It is a diagram showing an example of the shape of a restraint member in an assembled battery.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present technology will be described. In addition, the same reference numerals may be given to the same or corresponding parts, and the description thereof may not be repeated.

[0018] In the embodiments described below, when referring to the number, amount, etc., unless otherwise specified, the scope of the present technology is not necessarily limited to the number, amount, etc. Further, in the following embodiments, each component is not necessarily essential for the present technology unless otherwise specified. Further, the present technology is not limited to those that necessarily exhibit all the effects mentioned in the present embodiments.

[0019] In addition, in this specification, the descriptions of "comprise", "include", and "have" are in an open-ended form. That is, when including a certain component, other components outside the said component may or may not be included.

[0020] Also, in this specification, when geometric terms and terms representing positional and directional relationships, such as "parallel", "orthogonal", "diagonal 45°", "coaxial", "along", etc., are used, those terms allow for manufacturing errors or slight variations. When terms representing relative positional relationships such as "upper side" and "lower side" are used in this specification, those terms are used to indicate the relative positional relationship in one state, and depending on the installation direction of each mechanism (for example, reversing the entire mechanism up and down, etc.), the relative positional relationship can be reversed or rotated at an arbitrary angle.

[0021] In this specification, "battery" is not limited to lithium-ion batteries and may include other batteries such as nickel-metal hydride batteries and sodium-ion batteries. In this specification, "electrode" may be a general term for the positive electrode and the negative electrode.

[0022] In this specification, the "battery" can be mounted in a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a battery electric vehicle (BEV), etc. However, the use of the "battery cell" is not limited to in-vehicle use.

[0023] Figure 1 is a perspective view of the battery constituting the assembled battery. As shown in Figure 1, the battery 100 (battery cell) has a rectangular shape. The battery 100 has an electrode terminal 110, a housing 120, a gas discharge valve 130, and a liquid injection hole 140. A plurality of batteries 100 are arranged along the Y-axis direction (the first direction) to constitute the assembled battery.

[0024] The electrode terminals 110 are formed on the housing 120. The electrode terminals 110 have a positive electrode terminal 111 and a negative electrode terminal 112 that are aligned along the X-axis direction (second direction) perpendicular to the Y-axis direction (first direction). The positive electrode terminal 111 and the negative electrode terminal 112 are spaced apart from each other in the X-axis direction.

[0025] The housing 120 has a rectangular parallelepiped shape and forms the external appearance of the battery 100. The housing 120 includes a case body 120A that houses the electrode body 150 (see Figure 4) and electrolyte, and a sealing plate 120B that seals the opening of the case body 120A. The sealing plate 120B is joined to the case body 120A by welding.

[0026] The housing 120 has a top surface 121, a bottom surface 122, a first side surface 123, a second side surface 124, and two third side surfaces 125.

[0027] The upper surface 121 is a plane perpendicular to the Z-axis direction (third direction), which is perpendicular to the Y-axis direction and the X-axis direction. Electrode terminals 110 are arranged on the upper surface 121. That is, in the battery 100 illustrated in Figure 1, the electrode terminals 110 are provided on the plane of the housing 120 perpendicular to the Z-axis direction (third direction). The lower surface 122 faces the upper surface 121 along the Z-axis direction.

[0028] Each of the first side surface 123 and the second side surface 124 consists of a plane perpendicular to the Y-axis direction. Each of the first side surface 123 and the second side surface 124 has the largest area among the multiple sides of the housing 120. Each of the first side surface 123 and the second side surface 124 has a substantially rectangular shape, with the X-axis direction being the longitudinal direction and the Z-axis direction being the short direction when viewed from the Y-axis direction.

[0029] In one example of a battery pack configuration, adjacent batteries 100 in the Y-axis direction are stacked such that their first sides 123 and second sides 124 face each other. As a result, in the Y-axis direction where multiple batteries 100 are stacked, the positive terminals 111 and negative terminals 112 are arranged alternately.

[0030] The gas discharge valve 130 is located on the top surface 121. The gas discharge valve 130 discharges gas to the outside of the housing 120 when the temperature of the battery 100 rises (thermal runaway) and the internal pressure of the housing 120 exceeds a predetermined value due to the gas generated inside the housing 120.

[0031] The electrolyte injection hole 140 is provided on the top surface 121. The electrolyte is injected into the interior of the housing 120 through the electrolyte injection hole 140. The electrolyte injection hole 140 is sealed by a sealing member. As the sealing member, for example, a blind rivet or other metal member can be used.

[0032] The positions of the gas discharge valve 130 and the liquid injection hole 140 are not limited to those shown in Figure 1 and can be changed as appropriate.

[0033] Figure 2 is a front view showing a modified battery 100. Figure 3 is a perspective view of the battery 100 shown in Figure 2. The battery 100 shown in Figures 2 and 3 has electrode terminals 110, a housing 120, and an electrolyte injection hole 140. A battery pack is formed by arranging the batteries 100 along the Y-axis direction (first direction). The housing 120 includes a case body 120A, a sealing plate 120B (first sealing plate), and a sealing plate 120C (second sealing plate). A battery pack is formed by arranging a plurality of batteries 100 along the Y-axis direction (first direction).

[0034] The case body 120A is made of a cylindrical, preferably rectangular, tubular member. This results in a rectangular battery 100.

[0035] As shown in Figures 2 and 3, sealing plates 120B and 120C are provided at both ends of the case body 120A, respectively. The case body 120A can be formed into a rectangular tube shape by, for example, bringing together the ends of bent plate-shaped members (joint portion 120D as illustrated in Figure 3) and joining them together (e.g., by laser welding). The corners of the "rectangular tube" may have a rounded shape.

[0036] The sealing plates 120B and 120C shown in Figures 2 and 3 have a substantially rectangular shape with the Y-axis direction being the short direction and the Z-axis direction being the long direction. The substantially rectangular shape includes a rectangular shape, or a rectangular shape with rounded corners, etc.

[0037] A positive electrode terminal 111 is provided on the sealing plate 120B. A negative electrode terminal 112 and an electrolyte injection hole 140 are provided on the sealing plate 120C. That is, in the battery 100 illustrated in Figures 2 and 3, the electrode terminals 110 are provided on a plane perpendicular to the X-axis direction (second direction) of the housing 120. The positions of the positive electrode terminal 111, the negative electrode terminal 112, and the electrolyte injection hole 140 can be changed as appropriate.

[0038] In the battery 100 shown in Figures 1 to 3, the case body 120A and the sealing plates 120B and 120C are made of metal. Specifically, the case body 120A and the sealing plates 120B and 120C are made of aluminum, aluminum alloy, iron, or iron alloy.

[0039] In the battery 100 shown in Figures 1 to 3, the case body 120A is formed to be longer in the width direction (X-axis direction) of the battery 100 than in the thickness direction (Y-axis direction) and height direction (Z-axis direction) of the battery 100. That is, when the battery 100 is viewed from the Y-axis direction, the housing 120 (case) of the battery 100 has a substantially rectangular shape in which the X-axis direction (second direction) is the longitudinal direction and the Z-axis direction (third direction) is the short direction.

[0040] Figure 4 shows the restraint structure of the battery 100 in the battery pack according to this embodiment. Although the example in the figure shows the battery 100 shown in Figure 1, the same restraint structure as shown in Figure 4 can also be applied to the battery 100 shown in Figures 2 and 3.

[0041] As shown in Figure 4, the battery pack includes a battery 100, an end plate 200, a separator 300, a restraining member 400, a contact plate 500, and a bolt 600.

[0042] The end plates 200 are provided at the ends of multiple batteries 100 in the Y-axis direction (first direction). When viewed from the Y-axis direction, the end plates 200 have a substantially rectangular shape with the X-axis direction (second direction) being the longitudinal direction and the Z-axis direction (third direction) being the short direction.

[0043] An insulating separator 300 is provided between the end plate 200 and the battery 100. Separators 300 are also provided between multiple batteries 100. A restraining member 400 restrains the end plate 200 and the multiple batteries 100 in the Y-axis direction.

[0044] The restraining member 400 includes a pair of plate-shaped members. As shown in Figure 4, the pair of plate-shaped members are arranged to sandwich a plurality of batteries 100 in the Z-axis direction. A contact plate 500 is fixed to the restraining member 400. The restraining member 400 and the contact plate 500 are fixed to the end plate 200 from the Z-axis direction by bolts 600.

[0045] The end plate 200 has stepped portions 210 on both sides in the Z-axis direction. The contact plate 500 abuts against the stepped portions 210 from the Y-axis direction. When a battery pack is assembled, the multiple batteries 100 are held in a compressed state in the Y-axis direction by the end plate 200 together with the separator 300. In reaction, a reaction force (cell reaction force) from the batteries 100 acts on the end plate 200.

[0046] When an expansion force is generated in the battery 100, this expansion force increases the force (cell reaction force) in the Y-axis direction from the battery 100. The cell reaction force is transmitted to the restraining member 400 via the stepped portion 210 of the end plate 200 and the contact plate 500. As a reaction, a compressive force in the Y-axis direction is applied to the battery 100, suppressing its expansion.

[0047] By providing the contact plate 500, the force in the Y-axis direction from the battery 100 (cell reaction force) can be supported as shear stress. Alternatively, the connection strength between the restraining member 400 and the contact plate 500 may be improved by providing a hole in the restraining member 400 and fitting the contact plate 500 into the hole.

[0048] Figure 5 is a diagram illustrating the load acting on the end plate 200. As described above, the end plate 200 is connected to the restraining member 400 via the contact plate 500 at both ends in the Z-axis direction, and its displacement in the Y-axis direction is restricted.

[0049] As shown in Figure 5, a load in the Y-axis direction acts on the end plate 200 from the battery 100. Since the displacement in the Y-axis direction is restricted at both ends of the end plate 200 in the Z-axis direction, it is possible to schematically consider these parts as two support points and define the distance between them as the support distance (L).

[0050] As shown in Figure 5, if we schematically assume that the cell reaction force is a uniformly distributed load (w), the maximum value (δmax) of the deflection of the end plate 200 due to the cell reaction force is: δmax = 5 wL 4 / 384EI (w: distributed load, L: distance between supports, E: Young's modulus, I: second moment of area) Therefore, it is proportional to the fourth power of the distance between the supports (L).

[0051] As described above, the end plate 200 has the function of suppressing deformation of the battery 100. The end plate 200 is required to suppress the expansion of the battery 100 and reduce the deformation of the housing 120.

[0052] In this embodiment, the end plate 200 and the restraining member 400 are connected at both ends in the Z-axis direction, which is the short-side direction of the battery 100 when viewed from the Y-axis direction. Therefore, compared to a structure in which the end plate 200 and the restraining member 400 are connected at both ends in the X-axis direction, which is the long-side direction, the distance between the support points (L) shown in Figure 5 can be reduced.

[0053] Therefore, if the distributed load (w) from the battery, as well as the Young's modulus (E) and cross-sectional area (I) of the end plate 200 are constant, the maximum value (δmax) of the deflection (deformation) due to the cell reaction force can be reduced.

[0054] In other words, in this embodiment, if the allowable deformation amount of the end plate 200 is constant, even with a relatively small second moment of area (I), the deformation amount when subjected to a predetermined distributed load (w) can satisfy the conditions for the allowable deformation amount.

[0055] The inventors of this application have confirmed that, under specific conditions, the thickness of the end plate 200 required to satisfy the allowable deformation amount when subjected to the same cell reaction force is less than 1 / 3 of the thickness when the end plate 200 is supported at both ends in the short direction (Z-axis direction) compared to when the end plate 200 is supported at both ends in the long direction (X-axis direction) (a thickness of approximately 60 mm becomes approximately 19 mm). By making the end plate 200 thinner, it is possible to make the battery pack smaller or lighter.

[0056] In the battery pack according to this embodiment, by restraining the end plate 200 on the long side (both sides in the Z-axis direction) of the battery pack, rather than on the short side (both sides in the X-axis direction) of the battery pack, it is possible to suppress an excessive increase in the amount of deflection of the end plate 200 even when an expansion force is generated in the battery 100.

[0057] Figure 6 is a diagram illustrating the relationship between the width (B) and height (H) of the battery 100. As shown in Figure 6, the battery 100 constituting the battery pack according to this embodiment has a substantially rectangular shape in which the width (B) in the X-axis direction is greater than the height (H) in the Z-axis direction. In other words, the housing 120 of the battery 100 has a substantially rectangular shape in which the X-axis direction is the longitudinal direction and the Z-axis direction is the short direction.

[0058] The X-axis dimension (width: B) of the housing 120 is preferably about 200 mm or more, more preferably about 300 mm or more, and even more preferably about 500 mm or more. The X-axis dimension (width: B) of the housing 120 is preferably about 1200 mm or less. By setting the X-axis dimension (width: B) of the housing 120 within the above range, a relatively large (high capacity) battery 100 can be constructed.

[0059] The Z-axis dimension (height: H) of the housing 120 is preferably about 200 mm or less, more preferably about 150 mm or less, and even more preferably about 100 mm or less, and in one example about 90 mm. By setting the Z-axis dimension (height: H) of the housing 120 within the above range, a relatively low-height battery 100 can be constructed, which can improve, for example, its mountability in a vehicle.

[0060] The ratio of the dimensions of the housing 120 in the X-axis direction to the dimensions in the Z-axis direction (width / height: B / H) is preferably 2 or more, more preferably 3 or more, and even more preferably 5 or more. The ratio of the dimensions of the housing 120 in the X-axis direction to the dimensions in the Z-axis direction (width / height: B / H) is approximately 12 or less.

[0061] The end plate 200 preferably has dimensions that allow it to contact the entire area of ​​the first side surface 123 and the second side surface 124 of the housing 120. The ratio of the X-axis dimension to the Z-axis dimension of the end plate 200 may be approximately the same as the ratio of the X-axis dimension to the Z-axis dimension of the housing 120, or they may be different. Furthermore, the dimensions (width: B, height: H) of the housing 120 and the end plate 200 are not limited to the above numerical ranges.

[0062] Figure 7 shows an example of the shape of the restraint member 400. In the example shown in Figure 7, the restraint member 400 includes a first portion 410 with a relatively wide width in the X-axis direction, a second portion 420 with a changing width in the X-axis direction, and a third portion 430 with a relatively narrow width in the X-axis direction. The first portion 410, the second portion 420, and the third portion 430 are aligned from the ends to the center of the battery pack in the Y-axis direction. That is, the dimensions of the restraint member 400 in the X-axis direction change along the Y-axis direction.

[0063] The first portion 410 is fixed to the end plate 200. By arranging the wide first portion 410, the cross-sectional rigidity of the restraining member 400 can be increased at the end of the battery pack. Furthermore, by providing a second portion 420 between the first portion 410 and the third portion 430 that continuously changes the width of the restraining member 400, excessive stress concentration in the restraining member 400 can be suppressed.

[0064] As shown in Figure 7, it is preferable that the restraint member 400 is positioned so as to include the center of the X-axis direction (second direction) of the multiple batteries 100 when viewed from the Z-axis direction (third direction). Furthermore, it is preferable that the restraint member 400 has a shape that is symmetrical with respect to the Y-axis direction (first direction) when viewed from the Z-axis direction (third direction).

[0065] While embodiments of the present technology have been described above, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present technology is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0066] 100 Battery, 110 Electrode terminal, 111 Positive terminal, 112 Negative terminal, 120 Housing, 120A Case body, 120B, 120C Sealing plate, 120D Joint, 121 Top surface, 122 Bottom surface, 123 First side surface, 124 Second side surface, 125 Third side surface, 130 Gas discharge valve, 140 Injection hole, 150 Electrode body, 200 End plate, 210 Stepped section, 300 Separator, 400 Restraining member, 410 First part, 420 Second part, 430 Third part, 500 Contact plate, 600 Volt.

Claims

1. Multiple battery cells arranged in a first direction, End plates provided at the ends of the plurality of battery cells in the first direction, The end plate and the restraining member that restrains the plurality of battery cells in the first direction are provided. Each of the plurality of battery cells includes a case that houses an electrode body and has a substantially rectangular shape, such that when viewed from the first direction, the second direction perpendicular to the first direction is the longitudinal direction, and the third direction perpendicular to the first and second directions is the short direction. The restraining member includes a pair of members provided to sandwich the plurality of battery cells in the third direction, The pair of members are fixed to the end plate from the third direction, forming a battery pack.

2. The battery pack according to claim 1, wherein the plurality of battery cells have electrode terminals on a plane in the case that is perpendicular to the third direction.

3. The battery pack according to claim 1, wherein the plurality of battery cells have electrode terminals on a plane in the case that is perpendicular to the second direction.

4. The end plate has a stepped portion on at least one side in the third direction, The battery pack according to any one of claims 1 to 3, further comprising a contact plate fixed to the restraining member and abutting the stepped portion from the first direction.

5. The battery pack according to any one of claims 1 to 3, wherein each of the pair of members is made of a plate-shaped member.

6. The battery pack according to any one of claims 1 to 3, wherein each of the pair of members is provided at a position that includes the center of the plurality of battery cells in the second direction when viewed from the third direction.

7. The battery pack according to any one of claims 1 to 3, wherein the dimensions of each of the pair of members in the second direction vary along the first direction.

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