Battery pack

Abstract

The utility model provides a battery pack which suppresses local deterioration of a battery module or deviation of internal resistance of a battery. A battery pack (10) according to the present disclosure includes a battery module (11) having a plurality of batteries (11a), and an exterior case (12) housing the plurality of battery modules. In addition, at least a part 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 material layer (13). Further, the battery pack according to the present disclosure has an air layer (14) between the heat insulating material layer and the exterior case.

Description

Technical Field

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

[0002] Currently, a battery pack is configured as a battery module having a plurality of batteries. In such a battery pack, the batteries generate heat, and therefore a technology has been developed to release the heat inside the battery pack to the outside.

[0003] Japanese Patent Gazette No. 2014-013725 discloses a battery unit, which includes a battery pack module having multiple single cells, a control substrate having a control unit that performs charge and discharge-related controls on the battery pack module, and a housing that accommodates these battery pack modules and the control substrate. A limiting plate is provided between the battery pack module and the control substrate, and the limiting plate releases heat generated from the battery pack module and the control substrate to the vertical wall portion through heat conduction.

[0004] In a battery pack, local degradation of a battery module or variations in the internal resistance of the battery may occur. Utility Model Content

[0005] An object of the present disclosure is to provide a battery pack that can suppress local degradation of a battery module and variations in the internal resistance of batteries.

[0006] The present inventors have discovered that the above-mentioned problems can be solved by the following means.

[0007] A first embodiment of the battery pack disclosed herein includes a battery module having a plurality of batteries and an outer casing for accommodating the battery module, wherein at least a portion of a surface of the battery module facing the outer casing is covered with a heat insulating material layer, and an air layer is provided between the heat insulating material layer and the outer casing.

[0008] A battery pack according to a second aspect of the present disclosure is the battery pack according to the first aspect, wherein the plurality of batteries are stacked one on another in the battery module, and the heat insulating material layer is disposed outside the outermost battery.

[0009] A third aspect of the present disclosure is a battery pack according to the first aspect, wherein the battery pack is used in a vehicle, wherein the plurality of batteries are stacked one on another in the vehicle width direction within the battery module, and the heat insulating material layer is arranged outside the outermost battery.

[0010] According to the present disclosure, it is possible to provide a battery pack that suppresses local degradation of a battery module and variations in the internal resistance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram showing an example of the battery pack disclosed herein.

[0012] Figure 2 Schematic diagram of a battery pack according to an embodiment of the present disclosure.

[0013] Figure 3 This is a graph showing the temperature of each battery cell when a power-on test was performed on the battery packs of the example and the comparative example.

[0014] Figure 4 This is a graph showing the temperature of each battery cell after the battery pack of each example was left to stand at 25° C. for 12 hours after the power-on test. DETAILED DESCRIPTION

[0015] The following describes the embodiments of the present disclosure in detail. However, the present disclosure is not limited to the following embodiments, and can be implemented with various modifications within the scope of the disclosed gist.

[0016] The battery pack disclosed herein includes a battery module comprising a plurality of batteries and an outer casing housing the battery module. Furthermore, at least a portion of the surface of the battery module facing the outer casing in the battery pack disclosed herein is covered with a layer of thermal insulation material. Furthermore, the battery pack disclosed herein has an air layer between the thermal insulation material layer and the outer casing.

[0017] The authors believe that one of the causes of localized degradation of battery modules and variations in the internal resistance of the batteries is variations in heat dissipation within the battery pack. Specifically (without wishing to be bound by any theory), this is because the battery temperature can drop significantly in areas with high heat dissipation, such as the surface of the battery module facing the exterior casing, causing temperature variations within the battery pack.

[0018] In this regard, the present authors have discovered that by covering at least a portion of the surface of the battery module facing the exterior casing with a thermal insulation layer and providing an air layer between the thermal insulation layer and the exterior casing, it is possible to suppress degradation of the battery module and variations in the internal resistance of the battery. The reason for this (without wishing to be bound by any theory) is that this structure suppresses heat dissipation from areas with high heat dissipation properties, such as the surface of the battery module facing the exterior casing, thereby suppressing temperature variations within the battery pack.

[0019] The following reference Figure 1 The battery pack 10 of the present disclosure will be described. Figure 1 Schematic diagram showing an example of the battery pack 10 of the present disclosure. Figure 1 The dimensional relationships in the diagram do not reflect the actual dimensional relationships.

[0020] like Figure 1 As shown, the battery pack 10 of the present disclosure includes a battery module 11 including a plurality of batteries 11 a and an exterior case 12 that houses the battery module 11 .

[0021] The type, shape, etc. of the battery 11 a are not particularly limited.

[0022] The number of batteries 11 a is not particularly limited and 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, or 30 or less, 20 or less, or 15 or less.

[0023] The battery module 11 may include, in addition to a plurality of batteries 11 a , an inner case 11 b for housing the batteries 11 a .

[0024] The material of the inner case 11b is not particularly limited, and may be metal from the viewpoint of heat dissipation and strength.

[0025] The number of battery modules 11 may be one or more, and can be appropriately set according to the required battery output, the purpose of the battery pack, and the like.

[0026] The material of the outer case 12 is not particularly limited, and may be metal from the viewpoint of heat dissipation and strength. An example of the metal material is aluminum.

[0027] like Figure 1 As shown, 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 material layer 13 .

[0028] The material constituting the heat insulating layer 13 is not particularly limited as long as it has a lower thermal conductivity than the material constituting the inner case 11b, and may be a resin. Examples of the resin include, but are not limited to, polyethylene and polypropylene.

[0029] The thermal conductivity of the material constituting the thermal insulating layer 13 may be 0.50 W / m·K or less. This thermal conductivity may be greater than 0.001 W / m·K, 0.01 W / m·K or greater, 0.05 W / m·K or greater, or 0.10 W / m·K or greater, and may be 0.40 W / m·K or less, 0.35 W / m·K or less, 0.30 W / m·K or less, 0.25 W / m·K or less, 0.20 W / m·K or less, or 0.15 W / m·K or less. When the thermal conductivity is within this range, temperature fluctuations in the battery due to heat generation can be effectively suppressed.

[0030] The density of the thermal insulation material layer 13 can be 1.5 g / cm 3 Below. The density is 0.5g / cm 3 Above, 0.7g / cm 3 Above or 0.9g / cm 3 Above, it can be 1.3g / cm 3Below, 1.1g / cm 3 Below or 1.0g / cm 3 the following.

[0031] The thickness of the thermal insulation layer 13 can be appropriately set based on the thermal conductivity of the material constituting the thermal insulation layer 13 and the thermal conductivity of the inner casing 11b. For example, the thickness of the thermal insulation layer 13 can be 0.1 mm or greater, 0.5 mm or greater, 1 mm or greater, 2 mm or greater, 3 mm or greater, or 4 mm or greater, and can be 10 mm or less, 8 mm or less, 7 mm or less, or 6 mm or less. Furthermore, the thickness of the thermal insulation layer 13 can be 5 mm.

[0032] like Figure 1 As shown, the battery pack 10 of the present disclosure has an air layer 14 between the heat insulating material layer 13 and the outer case 12 .

[0033] The air layer 14 can be formed, for example, by placing the battery module 11 inside the outer casing 12 so that the heat insulating layer 13 does not come into contact with the outer casing 12 .

[0034] The thickness of the air layer 14 can be appropriately set based on the thermal conductivity and thickness of the heat insulating layer 13 . The thickness of the air layer 14 can be set to the length from the surface of the heat insulating layer 13 to the surface of the outer case 12 .

[0035] like Figure 1 As shown, in the battery module 11 of the battery pack 10 of the present disclosure, a plurality of batteries 11a may be stacked one on top of the other. In this case, a heat insulating material layer 13 may be disposed outside the outermost battery 11a.

[0036] The battery pack disclosed herein can be used in a vehicle. In this case, within the battery module 11, a plurality of batteries 11a can be stacked one on top of the other in the vehicle width direction, and a heat insulating layer 13 can be disposed outside the outermost battery 11a.

[0037] The following describes an example. Ten batteries (battery cells) were stacked and housed in an inner casing to create a battery module. This battery module was then placed inside the outer casing, without contact with the outer casing, to create an air layer, thereby creating a comparative battery pack.

[0038] In the inner casing of the battery module, the outermost layer that contacts the outside of the battery is made of polypropylene (thermal conductivity: 0.12 W / (m·K), density: 0.94 g / cm 3 , thickness: 5mm) of the heat insulating material layer, except that the same method as the comparative example was used to prepare Figure 2 The battery pack of Example 1 is shown.

[0039] In addition to changing the insulation material layer to polyethylene (thermal conductivity: 0.33W / (m·K), density: 0.95g / cm 3 , thickness: 5 mm), the battery pack of Example 2 was produced in the same manner as Example 1.

[0040] The evaluation is described below. A power-on test was performed on the battery packs of the Examples and Comparative Examples, and the maximum temperature reached in each battery cell was measured. Furthermore, after the power-on test, the temperature of each battery cell was measured after the battery packs of each example were left at 25°C for 12 hours.

[0041] The results of the above evaluation are shown in Figure 3 and Figure 4 In addition, Figure 3 and Figure 4 In the figures, the results are shown as relative values based on the fifth battery cell from the end in each battery pack.

[0042] like Figure 3 As shown in FIG. 1 , the temperature variation between the battery cells in the battery pack of the embodiment is smaller than that of the battery cells in the comparative example. Figure 4 As shown, when left at 25°C for a specified time, the difference in the magnitude of temperature variation between the battery cells was more pronounced in the Examples and Comparative Examples. In particular, in Example 1, which used a heat-insulating material layer with low thermal conductivity, temperature variation between the battery cells was effectively suppressed even after leaving the battery cells at rest under these conditions.

Claims

1. A battery pack comprising a battery module having a plurality of batteries and an outer casing for accommodating the battery module, characterized in that: At least a portion of a surface of the battery module facing the outer case is covered with a heat insulating layer, and an air layer is present between the heat insulating layer and the outer case.

2. The battery pack according to claim 1, wherein: In the battery module, the plurality of batteries are stacked one on another, and the heat insulating material layer is arranged outside the outermost battery.

3. The battery pack according to claim 1, wherein: The battery pack is used in a vehicle. In the battery module, the plurality of batteries are stacked one on another in the vehicle width direction, and the heat insulating material layer is arranged outside the outermost battery.

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