Battery module

Abstract

This helps to prevent the battery module from becoming too large. [Solution] The present invention comprises a separator 20 having a plurality of battery cells 10 and a cooling gap G arranged between the battery cells, the separator containing expanded graphite.

Description

Technical Field

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

Background Art

[0002] Since the battery capacity of a single battery cell is small, a desired battery performance is obtained by using a battery module in which a plurality of battery cells are stacked. When the battery cells are stacked in this way to increase the energy density, there is a high possibility that the temperature of the battery cells will become too high.

[0003] Conventional techniques related to an undesirable high-temperature state of a battery module disclose that a sheet contains at least one of a mineral-based powder and a flame retardant, starts an endothermic reaction at 100 to 1000°C, and undergoes at least one structural change selected from the group consisting of a phase change, expansion, foaming, and curing due to the endothermic reaction to prevent the undesirable high-temperature state (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a separator is required to appropriately maintain a gap for air cooling between the battery cells included in the battery module, and setting the separator causes a problem that the battery size increases.

[0006] An object of the present invention is to suppress an increase in the size of a battery module.

Means for Solving the Problems

[0007] One aspect of the present invention that achieves the above objective is a battery module comprising a plurality of battery cells and a separator having cooling gaps disposed between the battery cells. The separator contains expanded graphite. [Effects of the Invention]

[0008] The battery module according to the present invention can suppress an increase in the size of the battery module. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the internal structure of a battery module according to an embodiment, including the case, adjacent battery cells, and separators arranged between the battery cells. [Figure 2] Figure 1 is a schematic diagram showing the state of the battery module at high temperatures. [Figure 3] This is a schematic diagram showing a modified battery module of Figure 1, including the case, battery cells, and separator. [Figure 4] This is a schematic diagram showing the normal state of a modified battery module according to Figure 1, including the case, battery cells, and separator. [Figure 5] Figure 4 is a schematic diagram showing the state of the battery module at high temperatures. [Figure 6] This is a schematic diagram showing a modified battery module of Figure 1, including a case, battery cells, separators, and an insulating sheet. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the attached drawings. In the drawings, the same reference numerals are used for identical components, and redundant descriptions are omitted. In the drawings, the size and proportions of each component are exaggerated to facilitate understanding of the embodiments and may differ from the actual size and proportions.

[0011] Figure 1 is a schematic diagram showing the internal structure of a battery module 100 according to one embodiment of the present invention, illustrating a case 10, adjacent battery cells 20, and separators 30 arranged between the battery cells 20. An outline of one embodiment of the present invention, using Figure 1, is a battery module 100 comprising battery cells 20, separators 30 arranged between adjacent battery cells 20, and a case 10 that houses the battery cells 20 and the separators 30, etc. The battery module 100 according to this embodiment can be used, for example, as a power source for a vehicle (not shown) that is an electric vehicle driven by an electric motor. The vehicle is not limited to an electric vehicle; for example, the battery module 100 may be applied as a power source for a hybrid vehicle. The following describes each configuration in detail.

[0012] (case) The battery module 100 is configured to house multiple battery cells 20 inside the case 10, and to house separators 30 between adjacent battery cells 20.

[0013] In addition to the case 10, battery cells 20, and separator 30, the battery module 100 includes components such as busbars (not shown). Busbars are used to electrically connect the battery cells to each other.

[0014] Case 10 can be made of a metal such as steel, for example. The shape of Case 10 can be a rectangular prism, but the specific shape is not particularly limited as long as it can accommodate the above-mentioned parts.

[0015] (Battery cell) A plurality of battery cells 20 are accommodated inside the case 10 and can include a positive electrode, a negative electrode, an in-cell separator, a positive electrode tab, a negative electrode tab, an insulating material, etc. The size of the battery cell 20 is not particularly limited, but for example, it can be configured to be 120 - 150 mm × 170 - 200 mm × 20 mm, etc. The battery cell 20 can be formed to include at least a partially flat surface 21 at a portion adjacent to the separator 30. Although the inside of the battery module 100 is shown in the drawing, for the sake of convenience, the battery cell 20 shows a schematic shape in an uncut state.

[0016] (Separator) The separator 30 is accommodated inside the case 10 and is disposed between adjacent battery cells 20, has a cooling gap G, and is configured to include expanded graphite. By configuring it in this way, the cooling performance can be ensured by the role of the separator 30 that holds the gap G between the battery cells 20 under normal conditions.

[0017] Figure 2 is a schematic diagram showing the state of the battery module 100 in FIG. 1 at high temperature. At high temperature, the separator 30 forms a heat insulation layer by the expanded graphite contained in the separator 30 expanding into a structure like a porous body or a foam and serves as a heat insulation material, thereby preventing heat from being transmitted between the battery cells 20. Also, by eliminating the need to dispose a member that functions as a heat insulation material separately from the separator 30 between the battery cells 20 as in the conventional case, the gap G between the battery cells 20 can be narrowed, and thereby the size of the battery module 100 can be reduced. The separator 30 can be configured to contact the battery cell 20.

[0018] Regarding expanded graphite, flake graphite is a naturally occurring mineral with a structure in which hexagonal plate-like crystals of carbon form layers. The layers are bonded by electrical forces (van der Waals forces) rather than chemical bonds and have the property of being easily peeled off. Thermally expandable graphite is an intercalation compound in which an oxidizing agent is pushed into the layers of this graphite using a chemical reaction. When this is heated, the intercalated substance decomposes and gasifies, and due to this pressure, it has the property of expanding greatly in the direction of the vertical axis of the hexagonal plate-like crystals.

[0019] Illustrating the configuration of the separator 30, it is composed of a vertical wall portion 31 parallel to the plane direction YZ formed by the plane 21 of the battery cell 20 and a horizontal wall portion 32 extending in the direction X connecting between the battery cells 20. The expanded graphite is included in the vertical wall portion 31 as an example. By configuring it in this way, normally, an appropriate gap is ensured by the role of the separator 30 that holds the gap G between the battery cells 20, and at high temperatures, the expanded graphite in the vertical wall portion 31 expands to play the role of a heat insulating material. As a result, the amount of expanded graphite used can be saved, contributing to low cost and mass reduction. Also, the time for the expanded graphite to fill up the gap G can be made faster than when the expanded graphite is arranged in the horizontal wall portion 32 as will be described later. Examples of the material of the separator 30 other than the expanded graphite include thermoplastic resins. The separator 30 can be formed by configuring the vertical wall portion 31 with continuous fibers containing expanded graphite and overmolding the horizontal wall portion 32 by resin injection molding without expanded graphite. The vertical wall portion 31 can be arranged so as to pass through the approximate center of the horizontal wall portion 32 when viewed from the side as shown in FIG. 1. Although one vertical wall portion 31 and five (a plurality) horizontal wall portions 32 are shown in the drawing, the specific number does not have to be the same as in the drawing.

[0020] (Modified example of battery module) The following describes a modified version of the battery module. Components identical to those in the battery module 100 described above are denoted by the same reference numerals and their descriptions are omitted. In another embodiment of the battery module, the vertical wall portion 31 constituting the separator 30 does not contain expanded graphite, while the horizontal wall portion 32 is configured to contain expanded graphite by injection molding or the like. With this configuration, under normal conditions, the separator 30 maintains the air gap G between the battery cells 20, ensuring appropriate spacing, and at high temperatures, the expanded graphite in the horizontal wall portion 32 expands, acting as an insulating material. This reduces the amount of expanded graphite used, contributing to lower costs and reduced mass.

[0021] Figure 3 is a schematic diagram showing a modified battery module 100a of Figure 1, including the case 10, battery cell 20, and separator 30a. In the above, it was explained that the vertical wall portion 31 can be arranged to pass through approximately the center of the horizontal wall portion 32, but this is not the only option. In addition to the above, the separator 30a may be configured such that the position of the vertical wall portion 31a changes each time the horizontal wall portion 32 changes, as shown in the uneven shape of Figure 3.

[0022] Figure 4 is a schematic diagram showing a modified battery module 100b of Figure 1, including a case 10, a battery cell 20, and a separator 30b. As shown in Figure 4, the vertical wall portion 31b is positioned adjacent to one of the adjacent battery cells 20, the vertical wall portion 31b is made of a metal such as aluminum or iron, thermal conductive grease 33 is provided between the metal and the battery cell 20, and the horizontal wall portion 32 can be formed by overmolding.

[0023] Figure 5 is a schematic diagram showing the state of the battery module 100b in Figure 4 at high temperature. With the above configuration, even if the cells on the metal plate side become hot due to heat generation as shown in Figure 5, aluminum and the like have good thermal conductivity, so the expanded graphite in the side wall 32 can be expanded in a short time. In addition, since it is only necessary to include expanded graphite in the side wall 32, the amount of expanded graphite material used can be reduced. Furthermore, because the shape of the side wall 32 is simple, the effect of the reduced fluidity of the resin due to the expanded graphite can be minimized. The thermal conductive grease 33 can be made of known materials such as silicone.

[0024] Figure 6 is a schematic diagram showing a modified battery module 100c according to Figure 1, including a case 10, battery cells 20, separators 30, and a heat insulating sheet 40. Depending on the cooling requirements of the battery cells 20, the battery module 100c can be configured to include a heat insulating sheet 40 on the side portion 22 of the battery cell 20 where the separator 30 is not provided. By configuring it in this way, a battery module 100c having a separator 30 on only one side of the battery cell 20 can have its overall length shortened, which is expected to improve the energy density of the battery pack and the efficiency of the layout space. A known heat insulating sheet 40 can be used. Note that the specifications of the separator 30 in Figure 6 are not particularly limited and may be configured as shown in Figure 1, Figure 3, Figure 4, or other.

[0025] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. [Explanation of symbols]

[0026] 20 battery cells, 21 surfaces (flat surfaces), 22 side part, 30, 30a, 30b separators, 31, 31a, 31b vertical wall section, 32 Side wall section, 40 insulation sheets, 100, 100a, 100b, 100c battery modules, G void, X direction (direction connecting the battery cells), YZ plane direction.

Claims

1. Multiple battery cells, The battery cells are separated by a separator that includes a cooling gap, The aforementioned separator contains expanded graphite, and is a battery module.

2. The battery cell includes a surface that is at least partially flat in the portion adjacent to the separator. The separator is composed of vertical wall portions parallel to the plane direction of the battery cell and horizontal wall portions connecting adjacent battery cells. The battery module according to claim 1, wherein the expanded graphite is included in the vertical wall portion.

3. The battery cell includes a surface that is at least partially flat in the portion adjacent to the separator. The separator is composed of vertical wall portions parallel to the plane direction of the battery cell and horizontal wall portions connecting adjacent battery cells. The battery module according to claim 1, wherein the expanded graphite is included in the side wall portion.

4. The aforementioned vertical wall portion is in contact with one of the adjacent battery cells, The aforementioned vertical wall portion is made of metal. The battery module according to claim 3, wherein thermal conductive grease is provided between the metal and the battery cell.

5. The battery module according to claim 4, wherein a heat insulating sheet is provided on the side surface of the battery cell where the separator is not provided.

Images