Battery pack

Abstract

To provide a battery pack capable of achieving secure adhesion and fixation between a cell stack and a case and excellent thermal conductivity between the cell stack and a cooling plate.SOLUTION: A battery pack comprises: a battery module; a case housing the battery module; and a cooling plate arranged in contact with an outside bottom face of the case. The battery module comprises: a cell stack whose whole shape is in a rectangular parallelepiped shape; a holding member for fixing the cell stack to the case; and a structure adhesive agent for adhering the cell stack to the holding member. The cell stack is configured by laminating rectangular plate-like cells in a thickness direction, being arranged so that its bottom face is directed to an inside bottom face the case. The holding member fixes the cell stack to the case via a fastening member. The structure adhesive agent is provided between an upper surface or one lateral face of the cell stack and the holding member. A heat conduction agent is provided between the bottom face of the cell stack and the cooling plate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a battery pack, and more particularly to a battery pack that can achieve reliable adhesive fixation between a cell stack and a case and excellent thermal conductivity between the cell stack and a cooling plate. [Background technology]

[0002] Conventionally, a battery module has been proposed that can reduce the number of fastening parts such as bolts used in order to increase the energy density of a battery pack (see Patent Document 1). In this battery module, a cooler, typically a cooling plate, that circulates a cooling medium is disposed below a thermally conductive lower plate of a module case, and further, an adhesive having a predetermined adhesive strength and thermal conductivity is provided between the bottom surface of the battery cell and the thermally conductive lower plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6681911 Summary of the Invention [Problem to be solved by the invention]

[0004] When an adhesive, typically a structural adhesive, is provided between the battery cell and the cooling plate, as in the battery module described in Patent Document 1, there is a problem in that the thermal conductivity from the battery cell to the cooling plate is reduced, causing a decrease in battery performance.

[0005] Therefore, the inventors attempted to ensure thermal conductivity by placing a thermal conductive agent between the bottom surface of the battery cell and the cooling plate, and further placing a structural adhesive between the side surface of the battery cell and the inner surface of the module case, but they discovered a new technical problem: it was not possible to secure a sufficient adhesive area for fixing the battery cell.

[0006] The present invention was made based on these new technical challenges, and aims to provide a battery pack that can reliably bond and fix the cell stack to the case and achieve excellent thermal conductivity between the cell stack and the cooling plate. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned objective could be achieved by providing a thermally conductive agent between the bottom surface of the rectangular parallelepiped cell stack and the cooling plate, and by providing a structural adhesive between the other surface of the cell stack and the retaining member, and thus completed the present invention.

[0008] That is, the battery pack of the present invention includes a battery module, a case that houses the battery module, and a cooling plate that is disposed in contact with the outer bottom surface of the case. The battery module includes a cell stack having an overall rectangular parallelepiped shape, a holding member that secures the cell stack to the case, and a structural adhesive that bonds them together. The cell stack is formed by stacking rectangular plate-shaped cells in the thickness direction, and is disposed with its bottom surface facing the inner bottom surface of the case. The holding member secures the cell stack to the case via fastening members. The structural adhesive is provided between the top surface or one side surface of the cell stack and the holding member. A thermally conductive agent is provided between the bottom surface of the cell stack and the cooling plate. [Effects of the Invention]

[0009] According to the present invention, a thermally conductive agent is provided between the bottom surface of the rectangular parallelepiped cell stack and the cooling plate, and a structural adhesive is provided between the other surface of the cell stack and the retaining member, thereby providing a battery pack that can reliably bond and fix the cell stack to the case and achieve excellent thermal conductivity between the cell stack and the cooling plate. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view schematically illustrating a state in which an upper portion of a case is cut away in one embodiment of the battery pack of the present invention. [Figure 2] 2 is a cross-sectional view of the battery pack shown in FIG. 1 taken along line II-II. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a battery pack according to the present invention will be described in detail with reference to the drawings. Note that the dimensional proportions of the drawings cited below are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0012] As shown in Fig. 1, the battery pack 1 of this embodiment includes a plurality of battery modules 10, 10, and a case 20 that houses these battery modules 10, 10. Furthermore, as shown in Fig. 2, the battery pack 1 includes a cooling plate 30 that is disposed integrally with the outer bottom surface 20A of the case 20, and a refrigerant 31 flows through this cooling plate 30. 2, for the sake of convenience, only a part of the flow path through which the coolant 31 flows is shown, and the upper part of the cut-out case is indicated by a two-dot chain line.

[0013] 2, in this embodiment, the battery module 10 includes a cell stack 11 having an overall rectangular parallelepiped shape, a holding member 13 that fixes the cell stack 11 to the case 20, and a structural adhesive 15 that bonds the cell stack 11 and the holding member 13. The holding member 13 has a hat-shaped cross section that is made up of a top 131, edge portions 133, 133, and middle portions 135, 135 that connect the top 131 and the edge portions 133, 133. In this battery module 10, the bottom surface 11A of the cell stack 11 faces the inner bottom surface 20B of the case 20, and the upper portion of the cell stack 11 is held by middle portions 135, 135 of the holding member 13. In Fig. 2, the upward direction of the case 20 is indicated by arrow Z, and the thickness direction of the cells 12, which will be described later, is indicated by arrow X.

[0014] Furthermore, this cell stack 11 is configured by stacking a plurality of rectangular plate-shaped cells 12, . . . , 12 in the thickness direction of the cells 12 with the side surfaces 12A of the cells 12 facing the inner bottom surface 20B of the case 20.

[0015] In addition, in this battery pack 1, the holding member 13 is fixed to the strength member 21 of the case 20 by fastening members 17 such as bolts provided on the edges 133,133.

[0016] Furthermore, in this battery pack 1, a structural adhesive 15 is provided between the top surface 11B of the cell stack 11 and the holding member 13, and a thermal conductive agent 19 is provided between the bottom surface 11A of the cell stack 11 and the cooling plate 30.

[0017] Next, advantages of the battery pack of this embodiment will be described. According to the battery pack 1 of this embodiment, a structural adhesive 15 is provided between the top surface 11B of a given cell stack 11 and the holding member 13, and a thermally conductive agent 19 is provided between the bottom surface 11A and the cooling plate 30, thereby simultaneously improving the strength efficiency (adhesion area) in adhesive fixation and maintaining or improving thermal conductivity. This makes it possible to reliably adhesively fix the cell stack in the battery pack while suppressing or preventing a decrease in battery performance.

[0018] In particular, by providing the thermally conductive agent 19 between the cell stack and the cooling plate and fixing the battery module 10 to the case 20 with fastening members 17, the above-described battery pack can be produced with simple operations.

[0019] Furthermore, although not shown, it is also possible to provide structural adhesive 15 between the intermediate portions 135, 135 and the front and back surfaces of the cell stack (11C, 11D), thereby achieving further improvement (expansion) of the strength efficiency (adhesive area) in adhesive fixation.

[0020] Furthermore, in the battery pack 1 of this embodiment, as described above, the cell stack 11 is held by the intermediate portions 135, 135 of the holding member 13, and the fastening members (bolts) 17 are provided at the edge portions 133, 133. This prevents the bolt heads from protruding, and allows the battery module 10 to be efficiently housed in the case 20 while maintaining the fixing strength between the cell stack 11 and the case 20.

[0021] Furthermore, in the battery pack 1 of this embodiment, the cooling plate 30 is arranged integrally with the outer bottom surface 20A of the case 20, thereby further improving the thermal conductivity between the cell stack 11 and the cooling plate 30.

[0022] Here, the specifications, materials, etc. of the components in the above-described embodiment will be described in detail.

[0023] (case) A conventionally known case mounted on the bottom of a vehicle such as an electric vehicle can be used as the case 20. This case is a so-called pack case, and is usually made of a steel plate such as a high-tensile steel plate.

[0024] (Cooling plate) The cooling plate 30 is not particularly limited as long as it can dissipate heat generated in the cells 12. A suitable example of the cooling plate 30 is one in which a refrigerant 31 flows through a flow path formed of a metal material such as aluminum, copper, or stainless steel. While air can be used as the refrigerant, suitable examples include water and long-life coolant (LLC), which is water to which ethylene glycol or a rust inhibitor has been added. However, the refrigerant is not limited to these, and hydrocarbons such as carbon dioxide and isobutane can also be used as the refrigerant. As the metal material forming the flow path of the cooling plate, aluminum or copper is preferred from the viewpoint of excellent thermal conductivity, and stainless steel is preferred from the viewpoint of ease of integration with the case.

[0025] (cell stack) The cells 12 in the cell stack 11 may be, for example, conventionally known secondary batteries such as lithium ion secondary batteries. The exterior materials of the cells may be conventionally known rectangular metal cans or aluminum laminate films. The cells in the cell stack 11 may be sandwiched between end plates (not shown).

[0026] (holding member) As the holding member 17, for example, a so-called module top cover made of a steel plate can be used.

[0027] (Structural adhesives) Examples of the structural adhesive 15 include epoxy adhesives, acrylic adhesives, urethane adhesives, and phenol adhesives.

[0028] (thermal conductive agent) A suitable example of the thermally conductive agent 19 is a thermally conductive adhesive having higher thermal conductivity and lower adhesiveness than the structural adhesive 15. Examples of thermally conductive agents include resins such as urea resin, melamine resin, phenolic resin, resorcinol resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, polyimide resin, vinyl acetate resin, vinyl chloride resin, polyvinyl alcohol resin, acrylic resin, polyolefin resin, and silicone resin, and rubbers such as chloroprene rubber, nitrile rubber, SBR, natural rubber, reclaimed rubber, butyl rubber, block rubber, polysulfide, and silicone. Among these, acrylic resin, polyurethane resin, silicone resin, epoxy resin, and polyolefin resin are preferred, epoxy resin and polyolefin resin are more preferred, and polyolefin resin is even more preferred. Furthermore, suitable examples include those in which a thermally conductive inorganic filler is added to improve thermal conductivity. Examples of such inorganic fillers include aluminum oxide, magnesium oxide, zinc oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide, boron carbide, titanium carbide, diamond, etc. Furthermore, typical examples of thermally conductive adhesives include those obtained by adding the above-mentioned inorganic fillers having thermal conductivity to the above-mentioned structural adhesives.

[0029] Although the present invention has been described above with reference to one embodiment, the present invention is not limited to this embodiment, and various modifications are possible within the scope of the gist of the present invention.

[0030] In the present invention, in order to achieve efficient heat transfer from the cell stack 11 to the cooling plate 30, a thermal conductive agent 19 is placed between the bottom surface 11A of the cell stack 11 and the cooling plate 30, and a structure is adopted in which no structural adhesive 15 is interposed between the cell stack 11 and the cooling plate 30.

[0031] Therefore, if such an arrangement of the thermally conductive agent 19 can be realized, it is possible to adopt a different position, such as an inverted configuration from the structure shown in FIG. 2. In the structure shown in FIG. 2, the bottom and top surfaces of the cell stack have the largest areas of the surfaces forming the cell stack. However, this is not limited to this. For example, if one side surface (not shown) of the cell stack has a larger area than the top surface, a structural adhesive may be provided between the holding member arranged on one side surface of the cell stack and that side surface. Furthermore, the outer bottom surface of the case and the cooling plate may be in direct contact or may be in contact via a thermally conductive agent, or the case and the cooling plate may be integrated by sharing a common outer bottom surface.

[0032] In the battery pack 1 of the above embodiment, a portion of the cell stack 11 is held by intermediate portions 135, 135 of the holding member 13 having a hat-shaped cross section, and fastening members 17 are provided at the edge portions 133, 133. However, in the battery pack of the present invention, there are no particular limitations on the holding member as long as it adheres the cell stack at least via a structural adhesive and is fixed to the case by fastening members. Therefore, for example, the holding member 13 may be flat. [Explanation of symbols]

[0033] 1 battery pack 10 Battery Module 11 Cell stack 11A Bottom 11B Top surface 11C Front 11D back 12 cells 12A side 13 Retaining member 131 Top 133 Edge 135 Middle section 15 Structural adhesives 17 Fastening members 19 Thermal Conductive Agent 20 cases 20A outer bottom 20B Inner bottom surface 21 Strength members 30 Cooling Plate 31 Refrigerant

Claims

1. A battery pack including a battery module, a case accommodating the battery module, and a cooling plate disposed in contact with an outer bottom surface of the case, the battery module includes a cell stack having an overall rectangular parallelepiped shape, a holding member for fixing the cell stack to the case, and a structural adhesive for bonding the cell stack and the holding member to the case; the cell stack is formed by stacking rectangular plate-shaped cells in a thickness direction, and is disposed with its bottom surface facing the inner bottom surface of the case; the holding member fixes the cell stack to the case via a fastening member, the structural adhesive is provided between an upper surface or one side surface of the cell stack and the holding member, A thermally conductive agent is provided between the bottom surface of the cell stack and the cooling plate. A battery pack characterized by:

2. the holding member has a hat-shaped cross section consisting of a top portion, an edge portion, and an intermediate portion connecting the top portion and the edge portion, an upper surface side portion of the cell stack is held by the intermediate portion, The fastening member is provided on the edge portion.

2. The battery pack according to claim 1.

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