Battery module

Abstract

The present invention provides a battery module that can appropriately pressurize a stack and, when lithium-ion batteries are used, can absorb displacement of a pressurization load that occurs with charging and discharging of the stacked battery cells and can fix a pressurization plate at the end of the stacking direction of the lithium-ion battery stack to the case. To solve the above problem, a battery module has: a cell stack that stacks a plurality of battery cells having a power generating element and an outer body that covers the power generating element; a fastening member that fastens the cell stack; an end plate that is disposed at both ends of the stacking direction of the cell stack; a fastening nut that fastens the fastening member and the end plate on the outside of the cell stack; a brace that is fastened by the fastening nut; and a case that houses the cell stack; and the cell stack is fixed to the case by the brace.

Description

Technical Field

[0001] This invention relates to a battery module. Background Technology

[0002] In order for battery modules, which serve as power sources for electric vehicles, to function properly, pressure needs to be applied to the stacked battery cells in the stacking direction. Especially in solid-state secondary batteries using solid electrolytes, much greater pressure is required compared to liquid-state secondary batteries using liquid electrolytes. One method of pressurization involves initially pressurizing the stack from both ends of the battery cells, and then attaching end plates and side plates to the end faces and sides of the stack.

[0003] In the aforementioned pressurization method, the laminate needs to be initially pressurized to a pressure greater than the target pressure. Furthermore, due to the uneven elastic modulus along the lamination direction of the laminate, the residual load becomes uneven. Consequently, the strength and stiffness of the end plates and side plates are required, resulting in increased component space and a lower occupancy rate of individual battery cells in the battery module. As an alternative pressurization method, a technique is disclosed that uses a pair of pressure plates to clamp the laminate and uses connecting rods to pressurize the pair of pressure plates (for example, see Patent Document 1).

[0004] [Previous Technical Documents]

[0005] (Patent Documents)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-293771 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] The technology disclosed in Patent Document 1 involves arranging multiple prismatic lithium-ion batteries on the same plane and connecting a pair of pressure plates using a central connecting rod and peripheral connecting rods. The pair of pressure plates are pressurized by screws fastened to both ends of the peripheral connecting rods, thus bringing them closer together. However, in this technology, because the lithium-ion batteries expand or contract during charging and discharging, displacement occurs in the stacking direction of the individual cells. Therefore, when using lithium-ion batteries, it is difficult to fix the pressure plates at the stacking ends of the lithium-ion battery stack to the casing.

[0009] The present invention was made in view of the above circumstances, and aims to provide a battery module that can appropriately pressurize the laminate, and when using a lithium-ion battery, can absorb the displacement of the pressurized load that occurs with the charging and discharging of the laminated battery cells, and can fix the pressurized plate at the stacking end of the lithium-ion battery laminate to the housing.

[0010] [Technical means to solve the problem]

[0011] (1) The present invention relates to a battery module comprising: a single cell stack, which is formed by stacking multiple battery cells, wherein the battery cell has a power generation element and an outer casing covering the power generation element; a fastening member for fastening the single cell stack; an end plate disposed at both ends of the single cell stack in the stacking direction; a fastening nut on the outside of the single cell stack for fastening the fastening member to the end plate; a support bar for fastening by the fastening nut; and a housing for housing the single cell stack; wherein the single cell stack is fixed to the housing by the support bar.

[0012] According to the invention of (1), a battery module can be provided that can use struts to absorb displacement that occurs with the expansion and contraction of the single-cell laminate.

[0013] (2) According to the battery module described in (1), wherein the stiffness of the aforementioned support bar in the aforementioned stacking direction is lower than the stiffness of the aforementioned support bar in the direction orthogonal to the aforementioned stacking direction.

[0014] According to the invention of (2), struts can be used to better absorb the displacement that occurs with the expansion and contraction of the monomer laminate.

[0015] (3) The battery module according to (1) or (2), wherein the aforementioned support bar has a first inclined portion, which is inclined in a direction extending downward when viewed from the aforementioned stacking direction.

[0016] According to the invention of (3), struts can be used to better absorb the displacement that occurs with the expansion and contraction of the monomer laminate.

[0017] (4) The battery module according to any one of (1) to (3), wherein the aforementioned support bar has a second inclined portion, the second inclined portion being inclined downward from the fastening portion with the aforementioned fastening nut toward the outside of the aforementioned stacking direction of the aforementioned single-unit laminate.

[0018] According to the invention of (4), struts can be used to better absorb the displacement that occurs with the expansion and contraction of the monomer laminate.

[0019] (5) The battery module according to any one of (1) to (4), wherein the aforementioned fastening member is provided in a plurality of such portions, and the aforementioned support bar has a plurality of holes through which a portion of the aforementioned fastening member is inserted, and is formed as a single unit.

[0020] According to the invention of (5), the stiffness of the support bar can be designed more precisely, thereby improving the reliability of the battery module. Attached Figure Description

[0021] Figure 1 This is a partial cross-sectional view of the battery module according to the first embodiment of the present invention, shown from a side view.

[0022] Figure 2 It is a drawing Figure 1 An exploded view of the structure of the battery module.

[0023] Figure 3 It is a magnified drawing Figure 2 A diagram of the main parts.

[0024] Figure 4 This is a partial cross-sectional view of the battery module according to the second embodiment of the present invention, drawn from a top view.

[0025] Figure 5 It is drawn in the side view. Figure 4 A partial cross-sectional view of the battery module.

[0026] Figure 6 Viewed from one of the stacked layers. Figure 4 A diagram of a battery module.

[0027] Figure 7 Viewed from one of the stacked layers. Figure 4 A diagram of the support bars for the battery module.

[0028] Figure 8 Viewed from the side Figure 7 A diagram of the support bars for the battery module.

[0029] Figure 9 Viewed from one of the stacked layers. Figure 7 A diagram showing the overall structure of the support bars for the battery module.

[0030] Figure 10 It is a drawing Figure 7 The diagram shows an example of the variation in the support bars of the battery module.

[0031] Figure 11 Viewed from the side Figure 10 The diagram of the support strip. Detailed Implementation

[0032] (First Implementation)

[0033] Regarding the battery module of the first embodiment of the present invention, refer to Figures 1 to 3 This will be explained in detail. In the following diagrams, the same symbols are used to label the same parts and their corresponding parts.

[0034] [Monomeric laminate]

[0035] like Figure 1 As shown, the battery module 10 of the first embodiment has a stack of multiple battery cells 1, forming a stack of cells 11a and 11b. Each battery cell 1 has a power generation element 2 and an outer casing 3 covering the power generation element 2. The power generation element 2 is, for example, a solid-state battery formed by repeatedly stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. In the following description, the power generation element 2 is described as a solid-state battery, but the power generation element 2 can also be an electrolyte-based battery with a liquid electrolyte. In addition to the above, the battery module 10 also has a fastening component 4, a central fixing component 5, an end plate 6, a pressure plate 7, a support bar 8, and a fastening nut f1.

[0036] Materials used to form the positive electrode layer, solid electrolyte layer, and negative electrode layer of the power generation element 2 can be materials known as materials for solid batteries.

[0037] The outer casing 3 internally houses the power generation element 2. The outer casing 3 is not particularly limited, but a laminated film is preferred. By using a laminated film to construct the outer casing 3, the volume of the outer casing 3 can be reduced, thereby increasing the energy density of the battery module. The laminated monomer, for example, has a multi-layer structure formed by laminating a thermosetting resin layer such as polyolefin onto a metal layer made of aluminum, stainless steel (SUS), etc. A metal can may also be used as the outer casing 3.

[0038] Multiple battery cells 1 are arranged in the same direction as the stacking direction of the electrode layers constituting the power generation element 2. Figure 1 Multiple units are stacked in the stacking direction L1 shown to form a single-unit laminate 11a and 11b. The single-unit laminates 11a and 11b are clamped and held by end plates 6 from both ends of the stacking direction L1.

[0039] like Figure 2As shown, on each of the multiple battery cells 1, a first through hole h1 (hereinafter sometimes simply referred to as "through hole h1") is provided at the center of the cross-section along the vertical direction of the stacking direction L1 and in the direction of penetrating each electrode layer constituting the power generation element 2. The through hole h1 is a hole that penetrates the battery cell 1 and also penetrates the outer casing 3. The shape of the through hole h1 is not particularly limited, but it is preferable to have a circular cross-sectional shape that is the same as the cross-sectional shape of the fastening member 4 described later. As a method of forming the through hole h1, for example, it can be formed by: forming through holes on each electrode layer and solid electrolyte layer constituting the power generation element 2 and forming a laminate; sealing the laminate into the outer casing 3; joining the outer casing 3 to the portions corresponding to the through holes by welding the laminate film; and forming a through hole smaller than the through hole on the outer casing 3 by punching or the like on the inner circumference side of the through hole.

[0040] Multiple battery cells 1 are arranged in a manner that connects them via through holes h1. Fastening components 4 for fastening the cell stacks 11a and 11b are disposed in the through holes h1. A pair of end plates 6 are fastened by the fastening components 4 in a direction that reduces the distance between them. Thus, the cell stacks 11a and 11b can be pressurized without initial pressurization (pre-pressurization).

[0041] [Fastening components]

[0042] The fastening member 4 has a shaft portion constituting the main body, externally threaded portions 41 formed at both ends of the shaft portion, an enlarged diameter portion 42 forming part of the shaft portion and in the axial direction of the central portion, and an anti-rotation portion 43 disposed between the externally threaded portion 41 and the shaft portion. The enlarged diameter portion 42 is disposed in the second through hole h2 of the central fixing member 5 described later. In the fastening member 4, the shaft portion is inserted into the through hole h1 of the single-unit laminate 11a and 11b, and the externally threaded portions 41 extend from the holes h3, h4, and h5 respectively provided on the end plate 6, the pressure plate 7, and the support bar 8 at both ends of the single-unit laminate 11a and 11b, and are screwed into the fastening nut f1. From the viewpoint of uniformizing the cross-sectional stress, the cross-sectional shape of the fastening member 4 is preferably circular.

[0043] By inserting the fastening member 4 into the through hole h1 located in the central part of the lamination surface of the individual laminates 11a and 11b, and using a pair of end plates 6 and fastening nuts f1 to pressurize the individual laminates 11a and 11b, the surface pressure applied to the individual laminates 11a and 11b can be uniformized. Furthermore, since an outer frame for fixing the individual laminates is not required, the volume ratio of the power generation element 2 in the battery module 10 can be increased, thereby improving the energy density of the battery module 10. Moreover, in this invention, the fastening member 4 is not limited to being inserted into the through hole h1 located in the central part of the lamination surface of the individual laminate. The fastening member 4 can also be disposed at a location other than the central part of the lamination surface of the individual laminate.

[0044] like Figure 1 As shown, the anti-rotation part 43 is disposed near the fastening nut f1, i.e., inside the hole h3 formed on the end plate 6. The anti-rotation part 43 is, for example, a component with a polygonal or serrated shape in cross-section. The anti-rotation part 43 can be integrally formed with the fastening member 4, or it can be constituted by a component separate from the fastening member 4 and fixed to the fastening member 4.

[0045] The anti-rotation portion 43, for example, functions by engaging with a hole h3 formed on the end plate 6, which has an inner surface shape corresponding to the cross-sectional shape of the anti-rotation portion 43, to absorb the axial torsional stress of the fastening member 4. Thus, the torsional stress when the external thread portion 41 is screwed onto the fastening nut f1 is transmitted only to the external thread portion 41 and the anti-rotation portion 43 of the fastening member 4, and not from the anti-rotation portion 43 to the inner side of the cell laminates 11a and 11b. Therefore, loosening of the fastening nut f1 during the use of the battery module 10 can be prevented for a long period. Furthermore, by tightening the fastening nut f1, a larger axial force can be applied to the fastening member 4. In addition to the above, the surface pressure applied to the cell laminates 11a and 11b can be precisely adjusted by the tightness of the fastening nut f1.

[0046] Figure 2 The diameter of the axial section of the shaft portion 44 of the fastening member 4 shown can be designed according to the surface pressure applied to the monomer laminates 11a and 11b. By reducing the diameter, the stress per unit area applied to the shaft portion 44 increases, thus reducing the elastic modulus maintained in the direction of the distance between the compression end plates 6, thereby reducing the variation in surface pressure applied to the monomer laminates 11a and 11b.

[0047] [Central fixed component]

[0048] The central fixing component 5 is a component disposed between multiple battery cells 1, and as... Figure 1The part shown is located at the center of the stacking direction L1 in the battery module 10. The surface pressure applied to the cell stacks 11a and 11b is homogenized along the stacking direction L1 by the central fixing part 5. Since the central fixing part 5 is only subjected to the force of compression in the stacking direction L1, it can be made of a lightweight metal such as aluminum.

[0049] The central fixing component 5 is provided with a second through hole h2 (hereinafter sometimes simply referred to as "through hole h2"), and the second through hole h2 is provided with an enlarged diameter portion 42 of the fastening component 4. Figure 2 As shown, the central fixing member 5 is arranged with through holes h2 and h1 connected. The through hole h2 can also be fixed to the enlarged diameter portion 42 on a surface perpendicular to the axial direction by means of an insert fixing or similar method. As a result, the central fixing member 5 and the fastening member 4 can be positioned and fixed, so that the central fixing member 5 can be easily arranged in the center of the stacking direction L1 in the battery module 10.

[0050] [Endplate]

[0051] End plates 6 are a pair of components disposed at both ends of the lamination direction L1 of the single-unit laminates 11a and 11b. For example... Figure 2 As shown, a hole h3 is formed on the end plate 6 through which the fastening member 4 can be inserted. By inserting the fastening member 4 into the hole h3 and fastening it with the fastening nut f1, the end plate 6 clamps and holds the individual laminates 11a and 11b.

[0052] like Figure 3 As shown, the end plate 6 has an inclined portion 61 and load points 62. The load points 62 are surfaces continuous with the inclined portion 61 and are surfaces substantially perpendicular to the lamination direction L1. The end plate 6 abuts against the pressure plate 7 at a plurality of load points 62. Thus, the surface pressure applied from the end plate 6 to the monolayers 11a, 11b is homogenized relative to the lamination surfaces.

[0053] [Pressure plate]

[0054] The pressure plate 7 is a pair of components fastened together with the end plate 6 by the fastening nut f1. The pressure plate 7 is located on the outer side of the end plate 6 in the lamination direction L1 at both ends of the single-unit laminates 11a and 11b. The pressure plate 7 is a component capable of elastic deformation, for example, a metal leaf spring-like component. Figure 2 As shown, a hole h4 is formed in the pressure plate 7 through which the fastening member 4 can be inserted. By inserting the fastening member 4 into the hole h4 and fastening it with the fastening nut f1, the axial force generated by the fastening of the fastening nut f1 is transmitted to the end plate 6 through the pressure plate 7.

[0055] like Figure 3As shown, the pressure plate 7 has an inclined portion 71 and a load point 72. The inclined portion 71 is a surface inclined along the inclined portion 61. The load point 72 is a surface continuous with the inclined portion 71 and is a surface that is substantially perpendicular to the lamination direction L1.

[0056] [Support strip]

[0057] The support bar 8 is a pair of components fastened together with the end plate 6 and the pressure plate 7 by the fastening nut f1. The support bar 8 is used to fix the individual laminates 11a and 11b. The support bar 8 is located at both ends of the individual laminates 11a and 11b in the lamination direction L1, outside the pressure plate 7 in the lamination direction L1. Figure 2 As shown, a hole h5 is formed in the support bar 8 through which the fastening member 4 can be inserted. The fastening member 4 is inserted into the hole h5 and fastened using a fastening nut f1. By fixing the support bar 8 with the fastening member 4, the installation space and number of parts of the support bar 8 can be reduced. Details of the construction of the support bar 8 will be described in the following second embodiment.

[0058] (Second Implementation)

[0059] Next, referring to the second embodiment of the present invention... Figures 4-9 The following description will be provided. In the following description, for structures that are the same as those in the first embodiment described above, the same symbols will sometimes be used in the drawings and the description will be omitted.

[0060] Figure 4 This is a top view of the battery module 100 according to the second embodiment. The battery module 100 is a larger battery module manufactured by combining the battery module 10. Figure 4 and Figure 5 As shown, in each of the multiple battery cells 1a, multiple holes are formed at the center of the cross-section along the vertical direction of the stacking direction L1, and multiple fastening members 4 (three in this embodiment) are inserted through each hole. The number of fastening members 4 is not limited to the above number; for example, there may be two or four. Figure 5 and Figure 6 As shown, the battery module 100 has a housing 9 that houses the stack of battery cells 1a.

[0061] The central fixing member 5a of this embodiment has multiple through holes h2 through which the fastening member 4 is inserted. Furthermore, the central fixing member 5a has a connection portion 51 to the housing 9. The central fixing member 5a is connected to the housing 9 by screwing a fastening bolt f2 into the connection portion 51. This further improves the rigidity of the stacked battery cell 1a.

[0062] like Figure 6As shown, in this embodiment, the pressure plate 7 has three parts arranged in the direction L2, which is orthogonal to the stacking direction L1. In addition, in this embodiment, the load points 72a, 72b, 72c and 72d where the pressure plate 7 abuts against the end plate 6 are arranged symmetrically with respect to the fastening nut f1.

[0063] [Support strip]

[0064] like Figure 6 and Figure 7 As shown, the support bar 8a of this embodiment has connecting portions 83 to the housing 9 at both ends and / or between the fastening members 4 in the direction L2 orthogonal to the stacking direction L1. The support bar 8a is connected to the housing 9 by screwing the fastening bolts f3 into the connecting portions 83. This further improves the rigidity of the stack of battery cells 1a. In addition, the support bar 8a is made of a component capable of elastic deformation, and the rigidity in the stacking direction L1 is set to be lower than the rigidity in the direction orthogonal to the stacking direction L1. As a result, the support bar 8a can absorb the displacement that occurs with the expansion and contraction of the stack of battery cells 1a. Therefore, even when the battery cell 1a expands and contracts when using the battery module 10, the pressure plate 7 can still be fixed to the housing 9 via the support bar 8a.

[0065] Figure 7 Therefore, with Figure 6 A view from the same perspective, viewed from the stacking direction L1, of a portion of the support bar 8a disposed on the stacked end side of the battery module 100. (See figure) Figure 7 As shown, the support bar 8a has a first inclined portion 81, which, when viewed from the stacking direction L1, is inclined in a direction extending downwards. Additionally, as... Figure 8 As shown, the support bar 8a has a second inclined portion 82, which slopes downwards outwards from the fastening portion (hole h5) with the fastening nut f1 in the stacking direction L1. With this structure, the support bar 8a can absorb displacement caused by the expansion and contraction of the stacked battery cells 1a by flexing and deforming in the stacking direction L1. Furthermore, its high stiffness relative to the stacked surface of the battery cells 1a allows for better fixation of the stacked battery cells 1a.

[0066] Figure 9 Therefore, with Figure 6 Viewed from the same perspective, an overall diagram of the support bar 8a used in the battery module 100 is shown. The support bar 8a is preferably as follows: Figure 9As shown, the fastening members 4 and holes h5 are integrally formed regardless of their number, rather than being provided separately according to the number of fastening members 4 and holes h5. By integrally forming the support bar 8a, the connection portion 83a between each hole h5 and the housing 9 can be individually formed. Therefore, compared to the case where the support bars 8a are provided separately and the connection portions 83a are overlapped and fastened together using fastening bolts f3, no step difference is generated in the connection portions 83a. Therefore, the stiffness of the support bar 8a, which absorbs the displacement that occurs with the expansion and contraction of each individual laminate, can be designed more precisely, thus improving the reliability of the battery module 100. In addition, the number of parts in the battery module 100 can be reduced, improving assembly operability. Furthermore, by inserting the fastening members 4 through the multiple holes h5 and fastening them with fastening nuts f1, the same effect as the anti-rotation portion 43 of the fastening member 4 can be obtained, so the fastening member 4 can be constructed without the need to provide the anti-rotation portion 43.

[0067] (Third Implementation)

[0068] Figure 10 Therefore with Figure 7 A portion of the support bar 8b in the third embodiment is viewed from the same viewpoint. The support bar 8b can be applied to the same battery module as the battery module 100 that uses the support bar 8a.

[0069] Like support bar 8a, support bar 8b has connection portions 83 to housing 9 at both ends and / or between fastening members 4 in the direction L2 orthogonal to the stacking direction L1. Support bar 8b is connected to housing 9 by screwing fastening bolts f3 into connection portions 83. Additionally, as... Figure 10 As shown, it has a first inclined portion 81a. Figure 11 and Figure 8 Similarly, this is a view of the support bar 8b viewed from the direction along the stacking direction L1. Like the support bar 8a, the support bar 8b has a second inclined portion 82.

[0070] like Figure 10 As shown, the support bar 8b has a hole h6. By providing the hole h6 on the support bar 8b, it is easy to design the stiffness of the support bar 8b in the stacking direction L1. This is because the stiffness of the support bar 8b in the stacking direction L1 can be adjusted by adjusting the size of the hole h6. In addition to the above, by having the hole h6 on the support bar 8b, the allowable deflection in the stacking direction L1 can also be increased. Therefore, the displacement that occurs with the expansion and contraction of the stack of battery cells 1a can be better absorbed. Figure 10 In the middle, the shape of the hole h6 has a roughly square opening, but the shape of the hole h6 is not particularly limited.

[0071] The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and can be modified appropriately.

[0072] In the above embodiment, it was explained that the anti-rotation portions 4 and 3, for example, engage with a hole h3 formed on the end plate 6 having an inner surface shape corresponding to the cross-sectional shape of the anti-rotation portion 43. This is not limited to the above. The anti-rotation portion 43 may also be provided at the end of the external thread portion 41 to fix the end of the external thread portion 41.

[0073] In the above embodiment, it is described that the support bars 8 and 8a have holes h5 through which the fastening member 4 can be inserted, and are fastened by the fastening nut f1. This is not limited to the above description. The support bars in this invention may also be connected to the pressure plate at one or more locations.

[0074] Figure Labels

[0075] 10, 100 battery modules

[0076] 1. 1A battery cell

[0077] 11a, 11b Monomer laminates

[0078] 2. Power generation components

[0079] 3 outer body

[0080] 4 Fastening components

[0081] 43 Anti-rotation part

[0082] 5.5a Central fixed component

[0083] 51 Connecting Part

[0084] 6 end plates

[0085] 8 support bars

[0086] 81 First Inclined Section

[0087] 82 Second Inclined Section

[0088] 9. Shell

[0089] f1 Fastening nut

[0090] h1 First through hole

[0091] h2 Second through hole

[0092] h5 Hole

[0093] L1 stacking direction

Claims

1. A battery module, comprising: A single-cell stack is formed by stacking multiple battery cells, wherein each battery cell has a power generation element and an outer casing covering the aforementioned power generation element; Fastening components, for fastening the aforementioned monolithic laminate; End plates are disposed at both ends of the aforementioned monolithic laminate in the lamination direction; A fastening nut is used to fasten the fastening component to the end plate on the outside of the aforementioned monolithic laminate. The support bar is fastened by the aforementioned fastening nuts; and, The shell contains the aforementioned monolithic laminate; Furthermore, the aforementioned monolayer is fixed to the aforementioned shell using the aforementioned support bars. The aforementioned fastening components are configured in multiple ways. The aforementioned support bar has multiple holes through which portions of the aforementioned fastening components are respectively inserted, and these holes are integrally formed. The aforementioned support bar also has a hole for adjusting the stiffness of the aforementioned support bar in the aforementioned stacking direction.

2. The battery module according to claim 1, wherein, The stiffness of the aforementioned support bar in the aforementioned stacking direction is lower than the stiffness of the aforementioned support bar in the direction orthogonal to the aforementioned stacking direction.

3. The battery module according to claim 1, wherein, The aforementioned support bar has a first inclined portion, which, when viewed from the aforementioned stacking direction, is inclined in a direction that extends downward.

4. The battery module according to claim 1, wherein, The aforementioned support bar has a second inclined portion, which is inclined downward from the fastening portion with the aforementioned fastening nut toward the outside of the aforementioned stacking direction of the aforementioned single-unit laminate.

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