Battery module

Abstract

To provide a battery module that applies appropriate pressure to a laminate, absorbs the displacement of the pressurized load that accompanies charging and discharging of a stacked battery cells when using a lithium-ion battery, can fix a pressure plate at the end of the stacking direction of the lithium-ion battery stack to a case.SOLUTION: A battery module includes a cell laminate in which a plurality of battery cells are stacked, each having a power generation element and an outer body covering the power generation element, a fastening member that fastens the cell laminate, end plates arranged at both ends of the cell laminate in the stacking direction, a fastening nut that fastens the fastening member and the end plate on the outside of the cell laminate, a stay fastened by the fastening nut, and a case containing the cell laminate, and the cell laminate is fixed to the case by the stay.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery module.

Background Art

[0002] In order for a battery module serving as a power source for an electric vehicle or the like to function properly, it is necessary to apply pressure in the stacking direction to the stacked battery cells to pressurize them. In particular, in a solid secondary battery using a solid electrolyte as an electrolyte, it is necessary to apply a much larger pressure compared to a liquid secondary battery using a liquid electrolyte. As a pressurization method, there is a method of joining an end plate and a side plate to both end faces and side faces of a stacked body in a state where the stacked body of battery cells is initially pressurized from both end faces of the stacked body.

[0003] In the above pressurization method, it is necessary to perform initial pressurization on the stacked body that is larger than the target pressure. In addition, since there is variation in the elastic modulus in the stacking direction of the stacked body, there is a problem that the residual load becomes non-uniform. Furthermore, as a result of the need for the strength and rigidity of the end plate and side plate, the space for the members increases, and there is also a problem that the occupancy rate of the battery cells in the battery module becomes low. As a pressurization method other than the above, there is a technique of sandwiching a stacked body between a pair of pressurizing plates and pressurizing the pair of pressurizing plates with a connecting rod (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technology disclosed in Patent Document 1 arranges a plurality of rectangular lithium-ion batteries on the same plane and connects a pair of pressure plates by a central connecting rod and a peripheral connecting rod. The pair of pressure plates are pressed closer to each other by tightening screw members attached to both ends of the peripheral connecting rod. However, in the above technology, when the lithium-ion battery expands or contracts during charge and discharge, displacement occurs in the cell stacking direction. Therefore, when using the lithium-ion battery, it becomes difficult to fix the pressure plate at the stacking direction end of the lithium-ion battery stack to the case.

[0006] The present invention has been made in view of the above, and can preferably press the stack, absorb the displacement of the pressing load accompanying charge and discharge of the stacked battery cells when using the lithium-ion battery, and fix the pressure plate at the stacking direction end of the lithium-ion battery stack to the case. An object is to provide a battery module that can be used.

Means for Solving the Problems

[0007] (1) The present invention relates to a battery module having a cell stack in which a plurality of battery cells having a power generation element and an exterior body covering the power generation element are stacked, a fastening member for fastening the cell stack, and end plates disposed at both ends in the stacking direction of the cell stack. And a fastening nut for fastening the fastening member and the end plate outside the cell stack, a stay fastened by the fastening nut, and a case for accommodating the cell stack, and the cell stack is fixed to the case by the stay.

[0008] (1) According to the invention of (1), a battery module can be provided that can absorb displacement accompanying expansion and contraction of the cell stack by the stay.

[0009] (2) The battery module according to (1), wherein the rigidity of the stay in the stacking direction is lower than the rigidity in the direction orthogonal to the stacking direction of the stay.

[0010] According to the invention of (2), the displacement associated with the expansion and contraction of the cell stack can be preferably absorbed by the stay.

[0011] (3) The battery module according to (1) or (2), wherein the stay has a first inclined portion that inclines in a direction widening downward when viewed from the stacking direction.

[0012] According to the invention of (3), the displacement associated with the expansion and contraction of the cell stack can be preferably absorbed by the stay.

[0013] (4) The battery module according to any one of (1) to (3), wherein the stay has a second inclined portion that inclines downward from the fastening portion with the fastening nut toward the outside of the cell stack in the stacking direction.

[0014] According to the invention of (4), the displacement associated with the expansion and contraction of the cell stack can be preferably absorbed by the stay.

[0015] (5) The battery module according to any one of (1) to (4), wherein a plurality of the fastening members are arranged, the stay has a plurality of hole portions through which a part of the fastening members is inserted, and the stay is integrally formed.

[0016] According to the invention of (5), the rigidity of the stay can be designed more precisely, and the reliability of the battery module can be improved.

Brief Description of the Drawings

[0017]

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Mode for Carrying Out the Invention

[0018] (First Embodiment) The battery module 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the following drawings, the same parts and corresponding parts are denoted by the same reference numerals.

[0019] [Cell Stack] As shown in FIG. 1, the battery module 10 according to the first embodiment has cell stacks 11a and 11b in which a plurality of battery cells 1 having a power generation element 2 and an exterior body 3 covering the power generation element 2 are stacked. The power generation element 2 is, for example, a solid battery in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are repeatedly stacked in this order. In the following description, the power generation element 2 will be described as a solid battery, but the power generation element 2 may be an electrolyte-based battery including a liquid electrolyte. In addition to the above, the battery module 10 has a fastening member 4, a central fixing member 5, an end plate 6, a pressing plate 7, a stay 8, and a fastening nut f1.

[0020] As materials for constituting the positive electrode layer, the solid electrolyte layer, and the negative electrode layer as the power generation element 2, known materials as materials for constituting a solid battery can be used.

[0021] The exterior body 3 houses the power generation element 2 inside. The exterior body 3 is not particularly limited, but is preferably a laminate film. By configuring the exterior body 3 with a laminate film, the volume of the exterior body 3 can be reduced, and the energy density of the battery module can be improved. The laminate cell has, for example, a multilayer structure in which a heat-sealable resin layer such as polyolefin is laminated on the outside of a metal layer made of aluminum, stainless steel (SUS), etc. As the exterior body 3, a metal can can also be used.

[0022] A plurality of battery cells 1 are laminated in the same direction as the lamination direction of the electrode layers constituting the power generation element 2 (the lamination direction L1 shown in FIG. 1) to form cell laminates 11a and 11b. The cell laminates 11a and 11b are sandwiched and held by end plates 6 from both ends in the lamination direction L1.

[0023] As shown in FIG. 2, in the central portion of the vertical cross-section along the lamination direction L1 of the plurality of battery cells 1, first through-holes h1 (hereinafter, may be simply referred to as "through-holes h1") are provided 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 together with the exterior body 3. The shape of the through-hole h1 is not particularly limited, but preferably has a circular cross-sectional shape similar to the cross-sectional shape of the fastening member 4 described later. As a method of forming the through-hole h1, for example, through-holes are opened for each electrode layer and solid electrolyte layer constituting the power generation element 2 to form a laminate, the laminate is enclosed in the exterior body 3, and the exterior bodies 3 at the locations corresponding to the through-holes are joined by welding the laminate film, and a through-hole slightly smaller than the through-hole is formed in the exterior body 3 by punching or the like on the inner peripheral side of the through-hole.

[0024] A plurality of battery cells 1 are arranged such that the through-holes h1 communicate with each other, and a fastening member 4 for fastening the cell laminates 11a and 11b is arranged in the through-hole h1. A pair of end plates 6 are tightened by the fastening member 4 in a direction to narrow the distance between them. Thereby, the cell laminates 11a and 11b can be pressurized without initial pressurization (preloading).

[0025] [Fastening member] The fastening member 4 has a shaft portion forming a main body, male screw portions 41 formed at both ends of the shaft portion, a diameter-expanded portion 42 formed in a central portion in the axial direction and forming a part of the shaft portion, and a rotation prevention portion 43 arranged between the male screw portion 41 and the shaft portion. The diameter-expanded portion 42 is arranged in a second through-hole h2 of a central fixing member 5 described later. The shaft portion of the fastening member 4 is inserted into the through-holes h1 of the cell laminates 11a and 11b, and the male screw portions 41 extend from the hole portions h3, h4, and h5 provided in the end plates 6, the pressure plates 7, and the stays 8, respectively, at both ends of the cell laminates 11a and 11b, and are screwed with fastening nuts f1. From the viewpoint of making the cross-sectional stress uniform, the cross-sectional shape of the fastening member 4 is preferably circular.

[0026] By inserting the fastening member 4 into the through-hole h1 provided in the central portion of the laminated surface of the cell laminates 11a and 11b and pressurizing the cell laminates 11a and 11b using the pair of end plates 6 and the fastening nuts f1, the surface pressure applied to the cell laminates 11a and 11b can be made uniform. In addition, an outer frame for fixing the cell laminate becomes unnecessary, and the volume ratio of the power generation element 2 in the battery module 10 can be improved, so the energy density of the battery module 10 can be improved. In the present invention, the fastening member 4 is not limited to being inserted into the through-hole h1 provided in the central portion of the laminated surface of the cell laminate. The fastening member 4 may be arranged at a location other than the central portion of the laminated surface of the cell laminate.

[0027] As shown in FIG. 1, the anti-rotation portion 43 is disposed inside a hole portion h3 formed in the end plate 6, which is in the vicinity of the fastening nut f1. The anti-rotation portion 43 is, for example, a member having a polygonal or serrated shape in a cross-sectional view. The anti-rotation portion 43 may be integrally formed with the fastening member 4, may be constituted by a separate member from the fastening member 4, or may be fixed to the fastening member 4.

[0028] The anti-rotation portion 43 has a function of receiving torsional stress in the axial direction of the fastening member 4 by fitting into a hole portion h3 formed in the end plate 6, for example, and having an inner surface shape corresponding to the cross-sectional shape of the anti-rotation portion 43. Thereby, the torsional stress when the male screw portion 41 is screwed with the fastening nut f1 is transmitted only to the male screw portion 41 and the anti-rotation portion 43 of the fastening member 4, and is not transmitted from the anti-rotation portion 43 to the inner side of the cell laminate 11a, 11b. Therefore, loosening of the fastening nut f1 during use of the battery module 10 can be prevented over a long period of time. In addition, a larger axial force can be applied to the fastening member 4 by tightening the fastening nut f1. In addition to the above, it becomes possible to precisely adjust the surface pressure applied to the cell laminates 11a, 11b according to the degree of tightening of the fastening nut f1.

[0029] The diameter in the axial cross-section of the shaft portion 44 of the fastening member 4 shown in FIG. 2 can be designed according to the surface pressure applied to the cell laminates 11a, 11b. By reducing the above diameter, the stress per unit area applied to the shaft portion 44 increases, so that it becomes possible to reduce the elastic modulus for holding the distance between the end plates 6 in the compressing direction, and the change range of the surface pressure applied to the cell laminates 11a, 11b can be reduced.

[0030] [Central fixing member] The central fixing member 5 is a member disposed between a plurality of battery cells 1, and as shown in FIG. 1, it is a member disposed at the center in the stacking direction L1 of the battery module 10. By the central fixing member 5, the surface pressure applied to the cell stacks 11a and 11b is made uniform in the stacking direction L1. Since the central fixing member 5 only receives a force compressed in the stacking direction L1, it can be constituted by a lightweight metal such as aluminum, for example.

[0031] The central fixing member 5 is provided with a second through-hole h2 (hereinafter, may be simply referred to as "through-hole h2") in which the enlarged-diameter portion 42 of the fastening member 4 is disposed. As shown in FIG. 2, the central fixing member 5 is disposed such that the through-hole h2 communicates with the through-hole h1. The through-hole h2 may be fixed in a plane perpendicular to the axial direction by means of the enlarged-diameter portion 42 and inlay fixing or the like. Thereby, it becomes possible to position and fix the central fixing member 5 and the fastening member 4, and the central fixing member 5 can be easily disposed at the center in the stacking direction L1 of the battery module 10.

[0032] [End plate] The end plates 6 are a pair of members disposed at both ends in the stacking direction L1 of the cell stacks 11a and 11b. As shown in FIG. 2, the end plates 6 are formed with holes h3 through which the fastening members 4 can be inserted. By inserting the fastening members 4 into the holes h3 and fastening them with the fastening nuts f1, the end plates 6 sandwich and hold the cell stacks 11a and 11b.

[0033] As shown in FIG. 3, the end plate 6 has an inclined portion 61 and a load point 62. The load point 62 is a surface continuous with the inclined portion 61 and is a surface substantially perpendicular to the stacking direction L1. The end plate 6 is in contact with the pressing plate 7 at a plurality of load points 62. Thereby, the surface pressure applied from the end plate 6 to the cell stacks 11a and 11b is made uniform with respect to the stacking surface.

[0034] [Pressing plate] The pressing plate 7 is a pair of members fastened by a fastening nut f1 together with the end plate 6. The pressing plate 7 is disposed outside the end plate 6 in the stacking direction L1 at both ends of the cell stacks 11a and 11b in the stacking direction L1. The pressing plate 7 is a member capable of elastic deformation, for example, a leaf spring-like member made of metal. As shown in FIG. 2, a hole h4 through which the fastening member 4 can be inserted is formed in the pressing plate 7. When the fastening member 4 is inserted through the hole h4 and fastened by the fastening nut f1, the axial force due to the tightening of the fastening nut f1 is transmitted to the end plate 6 via the pressing plate 7.

[0035] As shown in FIG. 3, the pressing 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 substantially perpendicular to the stacking direction L1.

[0036] [Stay] The stay 8 is a pair of members fastened by a fastening nut f1 together with the end plate 6 and the pressing plate 7. The stay 8 is a member for fixing the cell stacks 11a and 11b. The stay 8 is disposed outside the pressing plate 7 in the stacking direction L1 at both ends of the cell stacks 11a and 11b in the stacking direction L1. As shown in FIG. 2, a hole h5 through which the fastening member 4 can be inserted is formed in the stay 8. The fastening member 4 is inserted through the hole h5 and fastened by the fastening nut f1. By using the fastening member 4 to fix the stay 8, the installation space and the number of components of the stay 8 can be reduced. Details of the configuration of the stay 8 will be described in the following second embodiment.

[0037] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 4 to 9. In the following description, for components having the same configuration as those in the first embodiment, the same reference numerals may be given in the drawings and the description thereof may be omitted.

[0038] FIG. 4 is a top view of the battery module 100 according to the second embodiment. The battery module 100 is formed by combining the battery modules 10 to form a larger battery module. As shown in FIGS. 4 and 5, in a plurality of battery cells 1a, a plurality of holes are formed in the central portion of the vertical cross-section along the stacking direction L1, and a plurality of fastening members 4 (three in this embodiment) are inserted and arranged therein. The number of the arranged fastening members 4 is not limited to the above, and may be, for example, two or four. As shown in FIGS. 5 and 6, the battery module 100 includes a case 9 that houses the stacked body of the battery cells 1a.

[0039] The central fixing member 5a according to this embodiment has a plurality of through holes h2 through which the fastening members 4 are inserted. Further, the central fixing member 5a has a connecting portion 51 with the case 9. A fastening bolt f2 is screwed into the connecting portion 51 to connect the central fixing member 5a and the case 9. Thereby, the rigidity of the stacked body of the battery cells 1a can be further increased.

[0040] As shown in FIG. 6, three pressing plates 7 according to this embodiment are arranged in the direction L2, which is a direction orthogonal to the stacking direction L1. Further, in this embodiment, four load points 72a, 72b, 72c, and 72d where the pressing plate 7 abuts against the end plate 6 are arranged at symmetric positions with reference to the fastening nut f1.

[0041] [Stay] As shown in FIGS. 6 and 7, the stay 8a according to this embodiment has a connecting portion 83 with the case 9 at both ends in the direction L2 orthogonal to the stacking direction L1 and / or between the fastening members 4. A fastening bolt f3 is screwed into the connecting portion 83 to connect the stay 8a and the case 9. Thereby, the rigidity of the stacked body of the battery cells 1a can be further increased. Further, the stay 8a is composed of an elastically deformable member, 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. Thereby, the stay 8a can absorb the displacement accompanying the expansion and contraction of the stacked body of the battery cells 1a. Therefore, even though the battery cells 1a expand and contract during the use of the battery module 10, the pressure plate 7 can be fixed to the case 9 via the stay 8a.

[0042] FIG. 7 is a view of a part of the stay 8a arranged on the stacked end side of the battery module 100 from the stacking direction L1 at the same viewing angle as FIG. 6. As shown in FIG. 7, the stay 8a has a first inclined portion 81 that inclines in a direction that widens downward when viewed from the stacking direction L1. Further, as shown in FIG. 8, the stay 8a has a second inclined portion 82 that inclines downward toward the outside of the stacking direction L1 from a hole portion h5 that is a fastening portion with the fastening nut f1. With the above configuration, the stay 8a can absorb the displacement accompanying the expansion and contraction of the stacked body of the battery cells 1a by bending and deforming in the stacking direction L1. On the other hand, the rigidity with respect to the stacking surface of the battery cells 1a is high, and the stacked body of the battery cells 1a can be preferably fixed.

[0043] FIG. 9 is a view of the entire stay 8a used for the battery module 100 from the same perspective as FIG. 6. The stay 8a is not provided individually according to the number of fastening members 4 and holes h5. As shown in FIG. 9, it is preferable that the stay 8a is integrally formed regardless of the number of fastening members 4 and holes h5. By integrally forming the stay 8a, the connecting portion 83a with the case 9 provided between each hole h5 can be made into a single one. Therefore, compared with the case where the stays 8a are provided individually and the connecting portions 83a are overlapped and fastened together with the fastening bolts f3, no step is generated in the connecting portion 83a. Therefore, the rigidity of the stay 8a for absorbing the displacement accompanying the expansion and contraction of each cell laminate can be designed more precisely, so that the reliability of the battery module 100 can be improved. In addition, the number of parts of the battery module 100 can be reduced, and the assembly workability can be improved. Further, by inserting the fastening member 4 through a plurality of holes h5 and fastening it with the fastening nut f1, the same effect as that of the anti-rotation portion 43 of the fastening member 4 can be obtained. Therefore, the fastening member 4 can be configured without providing the anti-rotation portion 43.

[0044] (Third Embodiment) FIG. 10 is a view of a part of the stay 8b according to the third embodiment from the same perspective as FIG. 7. The stay 8b can be applied to a battery module similar to the battery module 100 to which the stay 8a is applied.

[0045] Similar to the stay 8a, the stay 8b has a connecting portion 83 with the case 9 at both ends and / or between the fastening members 4 in the direction L2 orthogonal to the stacking direction L1. A fastening bolt f3 is screwed into the connecting portion 83 to connect the stay 8b and the case 9. Also, as shown in FIG. 10, it has a first inclined portion 81a. FIG. 11 is a view of the stay 8b from the direction along the stacking direction L1, similar to FIG. 8. Similar to the stay 8a, the stay 8b has a second inclined portion 82.

[0046] As shown in FIG. 10, the stay 8b has a hole portion h6. By providing the hole portion h6 in the stay 8b, it is easy to design the rigidity of the stay 8b in the stacking direction L1. This is because the rigidity of the stay 8b in the stacking direction L1 can be adjusted by adjusting the size of the hole portion h6. In addition to the above, since the stay 8b has the hole portion h6, the allowable amount of deflection in the stacking direction L1 can be increased. Therefore, the displacement associated with the expansion and contraction of the stacked body of the battery cells 1a can be absorbed more preferably. In FIG. 10, the shape of the hole portion h6 has a substantially rectangular opening, but the shape of the hole portion h6 is not particularly limited.

[0047] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments and can be appropriately modified.

[0048] In the above embodiment, the anti-rotation portion 43 has been described as being fitted into a hole portion h3 formed in the end plate 6, for example, having an inner surface shape corresponding to the cross-sectional shape of the anti-rotation portion 43. It is not limited to the above. The anti-rotation portion 43 may be provided at the end of the male screw portion 41 and fix the end of the male screw portion 41.

[0049] In the above embodiment, the stays 8 and 8a have been described as having a hole portion h5 through which the fastening member 4 can be inserted and being fastened by a fastening nut f1. It is not limited to the above. The stay in the present invention may be connected to the pressure plate at one or more locations.

Explanation of Reference Numerals

[0050] 10, 100 Battery module 1, 1a Battery cell 11a, 11b Cell stack 2 Power generation element 3 Exterior body 4 Fastening member 43 Anti-rotation portion 5, 5a Central fixing member 51 Connecting portion 6 End plate 8 Stay 81 First inclined part 82 Second inclined part 9 Case f1 Fastening nut h1 First through-hole h2 Second through-hole h5 Hole part L1 Laminating direction

Claims

1. A cell stack in which a plurality of battery cells each having a power generation element and an exterior body covering the power generation element are stacked; A fastening member for fastening the cell stack; End plates disposed at both ends of the cell stack in the stacking direction; A fastening nut for fastening the fastening member and the end plate outside the cell stack at a central portion of the stacking surface of the cell stack; A stay fastened by the fastening nut; A case for housing the cell stack, and having, The cell stack is fixed to the case by the stay, The stay has a first inclined portion that inclines in a direction widening from the fastening portion with the fastening nut toward the connecting portion with the case when viewed from the stacking direction, a battery module.

2. A cell stack in which a plurality of battery cells each having a power generation element and an exterior body covering the power generation element are stacked; A fastening member for fastening the cell stack; End plates disposed at both ends of the cell stack in the stacking direction; A fastening nut for fastening the fastening member and the end plate outside the cell stack; A stay fastened by the fastening nut; A case for housing the cell stack, and having, The cell stack is fixed to the case by the stay, A plurality of the fastening members are arranged, The stay has a plurality of holes through which a part of the plurality of fastening members are respectively inserted and is integrally formed, A connecting portion between the stay and the case provided between adjacent holes is a single connecting portion, a battery module.

3. The rigidity of the stay in the stacking direction is lower than the rigidity in a direction orthogonal to the stacking direction of the stay, the battery module according to claim 1 or 2.

4. The stay has a first inclined portion that inclines in a direction widening downward when viewed from the stacking direction, the battery module according to claim 2 or 3.

5. The stay has a second inclined portion that inclines downward from the fastening portion with the fastening nut toward the outside of the cell stack in the stacking direction, the battery module according to any one of claims 1 to 4.

6. A plurality of the fastening members are arranged, The stay has a plurality of holes through which a part of the fastening members are inserted and is integrally formed, the battery module according to any one of claims 1, 3 to 5.

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