Battery pack

Abstract

To provide a battery pack which inhibits local deterioration of a battery module and variations of internal resistances of batteries.SOLUTION: A battery pack 10 of the disclosure includes: a battery module 11 having a plurality of batteries 11a; and an exterior case 12 which houses the battery modules. At least a part of a surface, which faces the exterior case, of each battery module in the battery pack of the disclosure is covered with a heat insulation material layer 13. Further, the battery pack of the disclosure has an air layer 14 between the heat insulation material layer and the exterior case.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] There are known technologies for constructing battery packs that include battery modules each having a plurality of batteries. In such battery packs, it is anticipated that the batteries will generate heat, and therefore technologies have been developed to dissipate the heat inside the battery pack to the outside.

[0003] Patent Document 1 discloses a battery unit comprising a battery module having a plurality of cells, a control board having a control unit that controls the charging and discharging of the battery module, and a housing case that houses the battery module and the control board, with a restraint plate provided between the battery module and the control board that dissipates heat generated from the battery module and the control board to a standing wall portion by thermal conduction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-013725 Summary of the Invention [Problem to be solved by the invention]

[0005] In a battery pack, localized deterioration of the battery modules and variations in the internal resistance of the batteries may occur.

[0006] An object of the present disclosure is to provide a battery pack in which localized deterioration of battery modules and variations in internal resistance of batteries are suppressed. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> A battery pack comprising a battery module having a plurality of batteries and an exterior case that houses the battery module, At least a part of the surface of the battery module facing the exterior case is covered with a heat insulating material layer; and an air layer between the heat insulating material layer and the exterior case; Battery pack. <Aspect 2> The plurality of batteries are stacked on top of each other within the battery module; and The heat insulating layer is disposed on the outside of the outermost battery. The battery pack according to embodiment 1. <Aspect 3> the battery pack is for a vehicle, Within the battery module, the plurality of batteries are stacked on top of each other in the vehicle width direction; and The heat insulating layer is disposed on the outer side of the outermost battery. The battery pack according to embodiment 1. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a battery pack in which local deterioration of the battery module and variations in the internal resistance of the battery are suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a battery pack according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of a battery pack according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a graph showing the temperature of each cell when a current test was carried out on the battery packs of the example and the comparative example. [Figure 4] FIG. 4 is a graph showing the temperature of each cell after the battery pack of each example was left standing at 25° C. for 12 hours after the current test. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0011] Battery pack The battery pack of the present disclosure includes a battery module having a plurality of batteries and an exterior case that houses the battery module. Furthermore, at least a portion of the surface of the battery module facing the exterior case in the battery pack of the present disclosure is covered with a heat insulating layer. Furthermore, the battery pack of the present disclosure has an air layer between the heat insulating layer and the exterior case.

[0012] The present inventors believe that one of the causes of localized deterioration of the battery module and variations in the internal resistance of the battery is differences in heat dissipation within the battery pack. Specifically, without intending to be bound by any theory, this is thought to be because the battery temperature drops significantly locally in areas with high heat dissipation, such as the surface of the battery module facing the exterior case, resulting in variations in temperature within the battery pack.

[0013] In this regard, the present inventors have discovered that deterioration of the battery module and variations in the internal resistance of the battery can be suppressed by covering at least a portion of the surface of the battery module facing the exterior case with a heat insulating layer and providing an air layer between the heat insulating layer and the exterior case. Without intending to be bound by any theory, the reason for this is thought to be that the above-mentioned configuration suppresses heat dissipation from areas with high heat dissipation properties, such as the surface of the battery module facing the exterior case, and as a result, temperature variations within the battery pack can be suppressed.

[0014] A battery pack 10 according to the present disclosure will be described below with reference to Fig. 1. Fig. 1 is a schematic diagram showing an example of a battery pack 10 according to the present disclosure. Note that the dimensional relationships in Fig. 1 do not reflect the actual dimensional relationships.

[0015] As shown in FIG. 1, a battery pack 10 of the present disclosure includes a battery module 11 having a plurality of batteries 11a, and an exterior case 12 that houses the battery module 11.

[0016] The type and shape of the battery 11a are not particularly limited.

[0017] The number of batteries 11a is not particularly limited, but may be 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more, and may be 30 or less, 20 or less, or 15 or less.

[0018] The battery module 11 may include a plurality of batteries 11a and an inner case 11b that houses the batteries 11a.

[0019] The material of the interior case 11b is not particularly limited, but may be metal from the viewpoint of heat dissipation and strength.

[0020] The number of battery modules 11 may be one or more, and can be set appropriately depending on the required battery output, the use of the battery pack, and the like.

[0021] The material of the exterior case 12 is not particularly limited, but may be metal from the viewpoint of heat dissipation and strength, such as aluminum.

[0022] As shown in FIG. 1, the surface of the battery module 11 in the battery pack 10 of the present disclosure that faces the exterior case 12 is covered with a heat insulating layer 13.

[0023] The material for the heat insulating layer 13 is not particularly limited as long as it has a lower thermal conductivity than the material for the interior case 11b, and may be a resin. Examples of resin include, but are not limited to, polyethylene and polypropylene.

[0024] The thermal conductivity of the material constituting the thermal insulation layer 13 may be 0.50 W / m·K or less. This thermal conductivity may be greater than 0.001 W / m·K, greater than or equal to 0.01 W / m·K, greater than or equal to 0.05 W / m·K, or greater than or equal to 0.10 W / m·K, and may be less than or equal to 0.40 W / m·K, less than or equal to 0.35 W / m·K, less than or equal to 0.30 W / m·K, less than or equal to 0.25 W / m·K, less than or equal to 0.20 W / m·K, or less than or equal to 0.15 W / m·K. When the thermal conductivity is within the above range, variations in battery temperature due to heat generation can be efficiently suppressed.

[0025] The density of the heat insulating layer 13 is 1.5 g / cm 3 The density may be 0.5 g / cm or less. 3 More than 0.7g / cm 3 or more, or 0.9 g / cm 3 may be 1.3 g / cm or more, 3 Below, 1.1g / cm 3 or less, or 1.0 g / cm 3 It may be the following:

[0026] The thickness of the insulating material layer 13 can be set appropriately based on the thermal conductivity of the material constituting the insulating material layer 13 and the thermal conductivity of the interior case 11b. The thickness of the insulating material layer 13 may be, for example, 0.1 mm or more, 0.5 mm or more, 1 mm or more, 2 mm or more, 3 mm or more, or 4 mm or more, and may be 10 mm or less, 8 mm or less, 7 mm or less, or 6 mm or less. The thickness of the insulating material layer 13 may also be 5 mm.

[0027] As shown in FIG. 1, a battery pack 10 of the present disclosure has an air layer 14 between a heat insulating material layer 13 and an exterior case 12.

[0028] The air layer 14 can be formed, for example, by placing the battery module 11 inside the exterior case 12 so that the heat insulating material layer 13 does not come into contact with the exterior case 12.

[0029] The thickness of the air layer 14 can be set appropriately based on the thermal conductivity and thickness of the heat insulating material layer 13. The thickness of the air layer 14 can be the length from the surface of the heat insulating material layer 13 to the surface of the exterior case 12.

[0030] 1, a plurality of batteries 11a may be stacked on one another in a battery module 11 of a battery pack 10 of the present disclosure. In this case, a heat insulating layer 13 may be disposed on the outside of the outermost battery 11a.

[0031] The battery pack of the present disclosure may be for use in a vehicle. In this case, a plurality of batteries 11a may be stacked in the vehicle width direction within the battery module 11, and a heat insulating layer 13 may be disposed on the outside of the outermost battery 11a. [Example]

[0032] <<Making a battery pack>> Comparative Example Ten batteries (cells) were stacked on top of each other and housed in an inner case to create a battery module. This battery module was then placed inside the outer case so as not to come into contact with the outer case, forming an air layer, thereby creating a battery pack for the comparative example.

[0033] Example 1 The outermost layer of the battery module's interior case, which comes into contact with the outside of the battery, is made of polypropylene (thermal conductivity: 0.12 W / (m K), density: 0.94 g / cm 3 A battery pack of Example 1 as shown in FIG. 2 was produced in the same manner as in the comparative example, except that a heat insulating layer made of a cellulose acylate film (thickness: 5 mm) was placed.

[0034] Example 2 The insulation layer is made of polyethylene (thermal conductivity: 0.33 W / (m K), density: 0.95 g / cm 3 A battery pack of Example 2 was produced in the same manner as in Example 1, except that the thickness was changed to 5 mm.

[0035] "evaluation" A current test was conducted on the battery packs of the examples and comparative examples, and the maximum temperature reached in each cell was measured. After the current test, the battery packs of each example were left standing at 25°C for 12 hours, and the temperature of each cell was then measured.

[0036] "result" The results of the above evaluation are shown in Figures 3 and 4. In both Figures 3 and 4, the results are shown as relative values ​​with the fifth cell from the end of each battery pack as the reference.

[0037] As shown in Figure 3, the cells in the battery pack of the Example had smaller temperature variation between cells than the cells of the Comparative Example. Furthermore, as shown in Figure 4, when left standing at 25°C for a predetermined time, the difference in the magnitude of temperature variation between cells became more pronounced between the Example and the Comparative Example. In particular, in Example 1, which used a heat insulating layer with low thermal conductivity, the temperature variation between cells was effectively suppressed even after being left standing under the above conditions. [Explanation of symbols]

[0038] 10 Battery pack 11 Battery module 11a battery 11b Inner case 12 Outer case 13 Insulation layer 14 Air Layer

Claims

1. A battery pack comprising a battery module having a plurality of batteries and an exterior case that houses the battery module, the battery module includes an interior case that houses the battery; a surface of the battery module facing the exterior case is covered with a heat insulating layer; The material constituting the heat insulating layer has a lower thermal conductivity than the material constituting the interior case, and an air layer between the heat insulating material layer and the exterior case; Battery pack.

2. The thermal conductivity of the material constituting the thermal insulation layer is 0.35 W / m·K or less, and The thickness of the heat insulating layer is 1 mm or more and 10 mm or less. The battery pack according to claim 1 .

3. A battery pack as described in claim 2, wherein the number of batteries is 5 or more and 20 or less.

4. The plurality of batteries are stacked on top of each other within the battery module; and The heat insulating layer is disposed on the outer side of the outermost battery. The battery pack according to claim 1 .

5. the battery pack is for a vehicle, Within the battery module, the plurality of batteries are stacked on top of each other in the vehicle width direction; and The heat insulating layer is disposed on the outer side of the outermost battery. The battery pack according to claim 1 .

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