JP2018098074A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the expansion of thermal runaway among a plurality of single cells with a simple structure while securing cooling performance during the normal time.SOLUTION: Disclosed is a battery pack 1 which is constituted by arranging a plurality of single cells 3 in a case 2 and has a cooling air passage 4 extending in the vertical direction between single cells 3 adjacent to each other. Adiathermancy is provided upward of at least the cooling air passage 4 in the case 2 and a foam heat insulating material 10 is also provided, which is made of thermally expandable graphite thermally expanded at a predetermined temperature or higher to be flowed into the cooling air passage 4. Some of single batteries 3 has thermal runway, the foam heat insulating material 10 is thermally expanded by the heat and flowed into the cooling air passage 4, and the expansion of thermal runaway among a plurality of single cells 3 is prevented.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for preventing expansion of thermal runaway between single cells in an assembled battery in which a plurality of single cells are combined.

Many batteries with high output and high capacity, such as a battery for driving driving mounted on a vehicle, employ an assembled battery formed by combining a plurality of single cells.
For example, Patent Document 1 describes an assembled battery mounted on a vehicle such as a hybrid vehicle. The assembled battery is configured by combining a plurality of unit cells made of lithium ion batteries or the like, and the plurality of unit cells are housed in a case.

  Moreover, the assembled battery described in Patent Document 1 has a structure in which cooling air is introduced into the case from the outside by a blower fan in order to suppress a temperature rise during charging and discharging. In addition, when a thermal runaway occurs in a single cell in the case due to a short circuit, etc., the case's intake / exhaust port is automatically closed in order to suppress external influences, and the inflow of air into the case is blocked. ing.

JP2013-246920A

However, when some of the single cells in the case are thermally runaway, the assembled battery described in Patent Document 1 may transfer heat to the other single cells in the case, and the other single cells may also be thermally runaway. .
In order to prevent the thermal runaway from expanding, a method of inserting a flame retardant sheet or the like between the cells can be considered. However, as in Patent Document 1, a cooling air passage is provided between the cells. In the assembled battery, there is a problem that it becomes a factor that obstructs the passage of the cooling air in the cooling air passage, and the cooling performance is lowered during normal use.

  The present invention has been made to solve such problems, and the object of the present invention is to simplify the structure of thermal runaway between single cells while ensuring cooling performance during normal use. It is an object of the present invention to provide an assembled battery that can be prevented.

In order to achieve the above object, an assembled battery of the present invention is an assembled battery having a plurality of unit cells arranged in a case and having a cooling air passage extending in the vertical direction between the adjacent unit cells. A thermal expansion heat insulating material that has a heat insulating property and thermally expands at a predetermined temperature or more and flows into the cooling air passage is provided at least above the cooling air passage in the case.
Preferably, the thermal expansion heat insulating material is thermally expanded to the lower side of the unit cell in all the cooling air passages at the predetermined temperature or higher.

The thermal expansion heat insulating material may be formed of thermally expandable graphite.
Preferably, the unit cell is a lithium ion battery.
Preferably, a thermal expansion heat insulating material introduction member that guides the thermally expanded heat insulating material to the cooling air passage is provided below the installation position of the thermal expansion heat insulating material and above the unit cell.

  The assembled battery of the present invention includes a thermal expansion heat insulating material that thermally expands at a predetermined temperature or higher and flows into the cooling air passage at least above the cooling air passage in the case. And when the temperature in a case rises, the wall of the thermal expansion heat insulating material which has heat insulation is formed between adjacent unit cells. Thereby, the heat conduction from the unit cell which is in the case of thermal runaway to the other unit cell is suppressed, and the thermal runaway of the other unit cell can be prevented.

In addition, in the state where the unit cell is not thermally runaway and the temperature in the case is lower than the predetermined temperature and the thermal expansion insulation is not expanded, the thermal expansion insulation does not reach the cooling air passage. The cooling performance of the unit cell by the cooling air passing through the cooling air passage can be secured without hindering the passage of the cooling air in the air passage.
This ensures the cooling performance during normal use without thermal runaway, and prevents the thermal runaway from spreading to other cells in the case when at least some of the cells in the case run out of heat. This is possible with a simple structure.

It is a longitudinal cross-sectional view which shows schematic structure of the assembled battery of the 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the state inside an assembled battery when thermal runaway occurs. It is a longitudinal cross-sectional view which shows schematic structure of the assembled battery of the 2nd Embodiment of this invention.

Hereinafter, an embodiment of a battery pack embodying the present invention will be described.
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an assembled battery 1 according to a first embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing an internal state of the assembled battery 1 when a thermal runaway occurs.
The assembled battery 1 of the present embodiment is a high-voltage, high-capacity battery such as a battery that supplies electric power to a driving motor for an electric vehicle or a hybrid vehicle, and is configured by combining a plurality of single cells made of lithium ion batteries. ing.

As shown in FIG. 1, the assembled battery 1 is configured by housing a plurality of single cells 3 in a rectangular box-shaped case 2. In FIG. 1, three unit cells 3 are illustrated in a simplified manner in the case 2, but a large number of unit cells 3 may be arranged in the front, rear, left, and right.
Cooling air passages 4 extending in the vertical direction are formed between the adjacent unit cells 3 and between the side wall 2a of the case 2 and the unit cell 3, respectively. In addition, in the lower part and the upper part of the unit cell 3, spaces (upper space 5 and lower space 6) through which the cooling air can pass are spread in the case 2 in the front-rear and left-right directions. The upper space 5 and the lower space 6 communicate with each other through the cooling air passages 4.

The side wall 2a of the case 2 is provided with an intake port 7 for introducing cooling air from the outside to the inside of the case 2 and an exhaust port 8 for discharging cooling air from the inside of the case 2 to the outside. The intake port 7 is arranged facing the lower space 6, and the exhaust port 8 is arranged facing the upper space 5 on the side wall 2 a on the left and right or opposite to the front and rear sides of the intake port 7.
In addition, cooling air is introduced into the intake port 7 by vehicle driving air or a blower fan (not shown).

As shown by the arrows in FIG. 1, the cooling air introduced from the intake port 7 is diverted from the lower space 6, passes through each cooling air passage 4, joins in the upper space 5, and is discharged from the exhaust port 8. The
Furthermore, in the assembled battery 1 of the present embodiment, a foam heat insulating material 10 (thermal expansion heat insulating material) formed of thermally expandable graphite is provided inside the upper wall 2b of the case 2. The foam heat insulating material 10 may be applied, for example, on the inner side of the upper wall 2b, or a foam heat insulating material formed by preliminarily solidifying thermally expandable graphite in a thin plate shape may be installed on the inner side of the upper wall 2b.

Thermally expansive graphite is a known substance that imparts thermal expansibility to graphite. For example, it expands at 200 to 300 degrees Celsius (predetermined temperature) or higher, and has high flame retardancy and heat insulation. In addition, the foam heat insulating material 10 made of this thermally expandable graphite has high fluidity at the time of thermal expansion.
The foam heat insulating material 10 is disposed over the entire inner surface of the upper wall 2 b of the case 2, and in particular, is disposed so as to be positioned above all the cooling air passages 4.

  In the assembled battery 1 having the above-described configuration, when at least one unit cell 3 is thermally runaway due to a short circuit accident or the like, as shown in FIG. 2, the foam heat insulating material 10 expands due to the heat. Since the foam heat insulating material 10 is disposed above all the cooling air passages 4 and has high fluidity at the time of thermal expansion, the heated foam heat insulating material 10 faces all the cooling air toward the lower side. It expands to flow into the passage 4. The foam heat insulating material 10 is set to an amount that reaches the lower wall 2c of the case 2 in all the cooling air passages 4 during thermal expansion.

Therefore, at the time of thermal expansion, the wall 11 of the foam heat insulating material 10 formed of thermally expandable graphite extending from the upper space 5 to the lower space 6 is formed in all the cooling air passages 4.
Thereby, when the thermal runaway occurs in at least a part of the single cells 3 in the case 2, the foam heat insulating material 10 expands due to the heat, and the single cell 3 and the adjacent single cells 3 have flame retardancy and Since it is blocked by the wall 11 of the foam insulation 10 having excellent heat insulating properties, heat conduction from the unit cell 3 that is thermally runaway to the other unit cell 3 that is not thermally runaway is suppressed, and expansion of the thermal runaway is suppressed. It is done. In this way, it is possible to suppress the expansion of the thermal runaway between the single cells 3 with a simple configuration in which the foam heat insulating material 10 made of thermally expandable graphite is installed above the cooling air passage 4 in the case 2. Become.

Further, since the foam heat insulating material 10 flows into the cooling air passage 4 between the side wall 2a of the case and the unit cell 3 when the unit cell 3 is thermally runaway, the intake port 7 and the exhaust port 8 can be closed. . Thereby, it becomes possible to prevent the case 2 from being affected.
On the other hand, at the normal time when no thermal runaway of the unit cell 3 occurs, the foam heat insulating material 10 does not expand. Therefore, the foam heat insulating material 10 does not exist in the cooling air passage 4, and cooling that passes through the cooling air passage 4 is performed. The cooling performance of the cell 3 by wind is ensured. As described above, since the foamed heat insulating material 10 does not exist in the cooling air passage 4 in the normal state, the width of the cooling air passage 4 can be set to the minimum that ensures the cooling efficiency, and the assembled battery 1 can be made compact. Can be configured.

FIG. 3 is a longitudinal sectional view showing a schematic configuration of the assembled battery 20 of the second embodiment.
As shown in FIG. 3, the assembled battery 20 of the present embodiment is provided with a foam heat insulating material introduction bracket 21 (thermal expansion heat insulating material introducing member) in the case 2 with respect to the assembled battery 1 of the first embodiment. It is different. The foam heat insulating material introduction bracket 21 is provided in the upper space 5 above the unit cell 3. The foam heat insulating material introduction bracket 21 is formed, for example, by bending a plate material, and the width thereof is substantially the width of one unit cell 3. And it arrange | positions so that the intermediate part 21a may protrude upwards so that the left-right position of the foam heat insulating material introduction bracket 21 may correspond with the left-right position of the cell 3. The foam heat insulating material introduction bracket 21 has a function of introducing the foam heat insulating material 10 that expands downward from the upper side of the single cell 3 toward the single cell 3 into the cooling air passage 4 when the foamed heat insulating material 10 expands. Have.

Thereby, the thermally expanded foam heat insulating material 10 is easily introduced into the cooling air passage 4 along the upper surface of the foam heat insulating material introduction bracket 21. Therefore, when thermal runaway of the unit cell 3 occurs, the wall 11 of the foam heat insulating material 10 can be quickly formed in the cooling air passage 4, and the expansion of the thermal runaway can be quickly suppressed to reduce damage.
The description of the embodiment is finished as above, but the aspect of the present invention is not limited to the above embodiment. For example, the foam heat insulating material 10 may be formed of a material that has heat insulating properties and thermally expands even if it is other than thermally expandable graphite. The present invention can be widely applied to an assembled battery including a cooling air passage between a plurality of single cells.

1, 20 Battery pack 2 Case 3 Cell 4 Cooling air passage 10 Foam insulation (thermal expansion insulation)
21 Foam insulation introduction bracket (thermal expansion insulation introduction member)

Claims (5)

A battery assembly comprising a plurality of single cells arranged in a case, and having a cooling air passage extending in the vertical direction between the adjacent single cells,
A battery assembly comprising: a thermal expansion heat insulating material that has a heat insulating property and thermally expands at a predetermined temperature or higher and flows into the cooling air passage at least above the cooling air passage in the case.   2. The assembled battery according to claim 1, wherein the thermal expansion heat insulating material thermally expands below the unit cell in all the cooling air passages at the predetermined temperature or higher.   The assembled battery according to claim 1, wherein the thermally expandable heat insulating material is formed of thermally expandable graphite.   The assembled battery according to any one of claims 1 to 3, wherein the single battery is a lithium ion battery.   The thermal expansion heat insulating material introduction member which guides the thermally expanded heat insulating material thermally expanded to the cooling air passage is provided below the installation position of the thermal expansion heat insulating material and above the unit cell. 5. The assembled battery according to any one of items 1 to 4.

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