JP2020181725A - Battery pack - Google Patents

Abstract

To provide a battery pack capable of maintaining a voltage detection line in a safe condition even if abnormalities (for example, thermal runaway) of a battery pack occur.SOLUTION: A battery pack 10 including a plurality of battery cells 30 housed in a case 13 includes a metal holder 40 for fixing the battery cells 30 to the case 13. Voltage detection lines 50 connected to the respective battery cells 30 are provided in the proximity of the holder 40, and a thermal expansion material 70 that expands due to heat generated by the thermal runaway of the battery cells 30 is arranged between the holder 40 and the voltage detection lines 50.SELECTED DRAWING: Figure 5

Description

The present invention relates to, for example, a battery pack mounted on a vehicle or the like, and more particularly to a structure of a battery pack capable of further enhancing safety during thermal runaway (thermal chain) of a battery cell.

Electric vehicles such as electric vehicles and hybrid vehicles equipped with an electric motor as a power source are equipped with a battery pack for supplying electric power to the electric motor. The battery pack includes a plurality of battery cells and a case for accommodating the plurality of battery cells, and each battery cell is electrically connected in the case.

There are various structures of each battery cell, and for example, there is one in which a power generation element including a positive electrode plate, a negative electrode plate, and a separator is housed in a container together with an electrolytic solution, and the container is sealed by a lid member. In such a battery cell, for example, if foreign matter such as metal dust is mixed in the container, there is a possibility that an internal short circuit (short circuit) may occur due to the foreign matter.

When an internal short circuit occurs, the temperature inside the container rises and gas is generated, which may increase the pressure inside the container. For this reason, the battery cell is generally provided with a safety valve that opens when the pressure in the container rises to a predetermined value to suppress bursting due to the pressure rise.

Further, in a battery pack in which a plurality of battery cells are sealed in a container, when the safety valve is opened due to an internal short circuit, the internal pressure rises even in adjacent normal battery cells due to the influence of the heat of the battery cells. As a result, the safety valve may open (so-called thermal runaway, heat chain).

By the way, various structures of a battery pack including a plurality of battery cells have been proposed. For example, there is a battery pack in which a plurality of battery cells are held in a predetermined number by a metal holder and fixed to a case (. For example, see Patent Document 1).

JP-A-2017-27808

Some battery packs have a voltage detection line on such a metal holder. If thermal runaway occurs in such a structure, the heat of the battery cell is transmitted to the voltage detection line via the holder, the coating of the voltage detection line may be peeled off, and secondary damage such as a short circuit may occur.

The present invention has been made in view of such circumstances, and provides a battery pack capable of maintaining a voltage detection line in a safe state even when an abnormality (for example, thermal runaway) of the battery pack occurs. The purpose is to do.

One aspect of the present invention that solves the above problems is a battery pack including a plurality of battery cells housed in a case, the battery pack having a metal holder for fixing the battery cells to the case, and near the holder. Is provided with a voltage detection line connected to each battery cell, and a thermal expansion material that expands due to heat generated by the thermal runaway of the battery cell is arranged between the holder and the voltage detection line. It is in the battery pack, which is characterized by being.

Here, it is preferable that the connection portion of the voltage detection line with the battery cell is in a relaxed state so that the connection is maintained when the thermal expansion material expands.

Further, it is preferable that the side of the voltage detection line opposite to the battery cell is covered with the case, and a space portion is formed between the voltage detection line and the case. Further, the distance of the space portion is preferably at least the thickness of the thermal expansion material after thermal expansion.

Further, the connection portion of the voltage detection line with the battery cell may be in a tense state so as to be cut when the thermal expansion material expands. In this case, it is preferable that the thermal expansion material is formed with a plurality of insertion holes into which each voltage detection line connected to the battery cell is individually inserted.

According to the battery pack of the present invention, the voltage detection line can be maintained in a safe state even when an abnormality (for example, thermal runaway) of the battery pack occurs.

It is a figure which shows an example of the usage mode of a battery pack. It is a perspective view which shows the schematic structure of the battery pack. It is a perspective view which shows the schematic structure of the battery module included in the battery pack. It is a figure which shows the appearance of the battery cell which comprises the battery module. It is a figure explaining the voltage detection line and the thermal expansion sheet in the battery pack which concerns on this invention, and is the figure which shows typically the structure in the battery case. It is a figure explaining another example of the voltage detection line and the thermal expansion sheet in the battery pack which concerns on this invention, and is the figure which shows typically the structure in the battery case.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The battery pack according to the present invention is mounted on an electric vehicle, for example, and has a structure capable of maintaining a voltage detection line in a safe state even when a safety valve provided in a battery cell is opened and thermal runaway occurs. It has the characteristics of.

The vehicle 1 shown in FIG. 1 is, for example, an electric vehicle such as an electric vehicle or a hybrid vehicle, and is equipped with a battery pack 10 for supplying electric power to a motor (electric motor) (not shown).

As shown in FIG. 2, the battery pack 10 includes a battery case 13 including a pack tray 11 and a pack cover 12, and a battery module 20 housed in the battery case 13.

As shown in FIGS. 2 and 3, a plurality of battery modules 20 are housed in the battery case 13, and each battery module 20 has a plurality of battery cells (secondary batteries) 30 arranged side by side in close proximity to each other. It has. In this way, a plurality of battery cells 30 are housed in the battery case 13. Although not shown, the plurality of battery cells 30 are connected in series by a bus bar or the like. The number of battery cells 30 included in each battery module 20 is not particularly limited.

Here, each battery module 20 including the plurality of battery cells 30 is fixed to the pack tray 11 by a metal holder 40. In the present embodiment, the holder 40 includes an upper holder 41 provided so as to cover the upper portion of each battery cell 30 constituting the battery module 20, and the upper holder 41 is fixed to the pack tray 11 by bolts or the like.

Each battery cell 30 constituting the battery module 20 is, for example, a closed type secondary battery such as a lithium ion battery, and as shown in FIG. 4, a container 31, a lid member 32 for sealing the container 31, and a lid member 32. It has. Inside the container 31, an electrode body (power generation element) including a positive electrode plate, a negative electrode plate, and a separator is housed together with an electrolytic solution. Further, since the electrode body has a known structure, the description thereof is omitted here.

The lid member 32 is provided with a positive electrode terminal member 33 and a negative electrode terminal member 34, which are connected to the positive electrode plate or the negative electrode plate of the electrode body housed in the container 31, respectively. The lid member 32 is further provided with a safety valve 35 between the positive electrode terminal member 33 and the negative electrode terminal member 34.

The safety valve 35 is formed to be relatively fragile compared to other parts of the lid member 32. For example, when an internal short circuit occurs in the container 31, the internal pressure of the container 31 reaches a predetermined value. Then, it is configured to open the valve. As a result, even when the internal pressure of the container 31 rises, the gas in the container 31 is ejected to the outside from the opened safety valve 35. Therefore, the rupture of the container 31 due to the increase in the internal pressure can be suppressed.

By the way, as shown in FIG. 5, a voltage detection line 50 for detecting the voltage of each battery cell 30 is connected between the terminals of each battery cell (including a bus bar) 30 housed in the battery case 13. ing. Although not shown, the voltage detection line 50 is connected to a battery control unit (BMS). The battery control unit detects the voltage of each battery cell 30 via the voltage detection line 50, and monitors the charging state of each battery cell 30 and the presence or absence of abnormality based on the detection result and the like.

The voltage detection line 50 is arranged near the holder 40 for fixing the battery module 20 to the pack tray 11. For example, in this embodiment, the voltage detection line 50 is arranged on the holder 40 (upper holder 41). More specifically, the voltage detection line 50 is provided between a wiring portion 51 arranged on the holder 40 in a bundled state and between the terminals of the battery cells 30 extending from the wiring portion 51. It is composed of a connecting portion 52 to be connected.

A sheet-shaped thermal expansion material (thermal expansion sheet) 70 is provided between the voltage detection line 50 and the holder 40 (upper holder 41) (gap). That is, a thermal expansion sheet 70 is provided on the holder 40 in a predetermined region excluding the portion where the connection portion 52 of the voltage detection line 50 extends, and the wiring portion 51 of the voltage detection line 50 is provided on the thermal expansion sheet 70. Is fixed.

The thermal expansion sheet 70 is a sheet-like thermal expansion material having a relatively thin thickness, and when the battery cell 30 is in a normal state, the voltage detection line 50 is arranged close to the holder 40 (FIG. 5 (FIG. 5). a)). On the other hand, when an abnormality occurs in the battery cell 30 and heat is generated (for example, when thermal runaway occurs), the heat expands the thermal expansion sheet 70 to increase its thickness, and the holder 40 and the voltage detection line 50 (wiring). The gap with the part 51) is widened (FIG. 5 (b)).

When an abnormality occurs in the battery cell 30 in this way, the gap between the holder 40 and the voltage detection line 50 is widened, so that the heat of the battery cell 30 is transferred to the voltage detection line 50 via the metal holder 40. It can be suppressed from being transmitted. Therefore, it is possible to suppress the occurrence of secondary damage such as the coating of the voltage detection lines 50 being peeled off by the heat of the battery cell 30 and the voltage detection lines 50 coming into contact with each other or the voltage detection lines 50 and the holder 40 being short-circuited. it can. That is, even if an abnormality (for example, thermal runaway) occurs in the battery pack, the voltage detection line 50 can be maintained in a safe state.

Here, the connection portion 52 of the voltage detection line 50 with each battery cell 30 is in a relaxed state under normal conditions, for example, so that the connection with the battery cell 30 is maintained when the thermal expansion sheet 70 expands. It is preferable to have. That is, it is preferable that the connecting portion 52 extending from the wiring portion 51 of the voltage detection line 50 fixed on the thermal expansion sheet 70 and connected to each battery cell 30 is in a loosened state under normal conditions. In other words, it is preferable that the length of the connecting portion 52 of the voltage detection line 50 is longer than the thickness of the thermal expansion sheet 70 after thermal expansion.

As a result, even when the thermal expansion sheet 70 is thermally expanded due to an abnormality in the battery cell 30, the connection state between the voltage detection line 50 and the battery cell 30 can be maintained while suppressing secondary damage. Therefore, even if an abnormality occurs in the battery cell 30, the battery control unit (BMS) can continue to monitor the battery cell 30.

The upper portion of the voltage detection line 50 (opposite to the battery cell 30) is covered with the pack cover 12, but a space 80 is formed between the voltage detection line 50 and the pack cover 12. .. The space 80 is preferably formed as large (high) as possible, and is preferably formed at a distance (height) equal to or greater than the thickness of the thermal expansion sheet 70 after thermal expansion.

As a result, when an abnormality occurs in the battery cell 30, the expansion of the thermal expansion sheet 70 makes it possible to sufficiently secure a gap between the holder 40 and the voltage detection line 50. Further, when the battery cell 30 is in a normal state, the space 80 can suppress the voltage detection line 50 from being affected by heat from the outside of the battery case 13.

Here, the material of the thermal expansion sheet (thermal expansion material) 70 is not particularly limited as long as it expands by the heat of the battery cell 30, and an existing one may be adopted, but the battery cell 30 is normal due to heat. It is preferable that the battery expands to about 5 to 10 times the time.

Although described above as one embodiment of the present invention, the present invention is not limited to the above-described embodiment.

For example, in the above-described embodiment, the connection portion 52 of the voltage detection line 50 is configured to maintain the connection with the battery cell 30 when the thermal expansion sheet 70 thermally expands due to an abnormality in the battery cell 30. However, the thermal expansion sheet 70 may be configured to be cut when it is thermally expanded.

For example, as shown in FIG. 6, the connection portion 52 of the voltage detection line 50 may be in a tense state (a state without slack) in the normal state of the battery cell 30 (FIG. 6A). Specifically, the length of the connecting portion 52 of the voltage detection line 50 is set to be substantially the same length as the thickness of the thermal expansion sheet 70 before thermal expansion.

Even in such a configuration, the voltage detection line 50 is normally arranged close to the holder 40 (FIG. 6A), and when an abnormality occurs in the battery cell 30, the heat of the battery cell 30 causes the thermal expansion sheet 70. Expands to increase the thickness, and the gap between the holder 40 and the voltage detection line 50 is widened (FIG. 6 (b)). However, in this configuration, the gap between the holder 40 and the voltage detection line 50 is widened, so that the connection portion 52 of each voltage detection line 50 is broken and the voltage detection line 50 and each battery cell 30 are electrically connected. Is disconnected.

Even with such a configuration, it is possible to suppress the occurrence of secondary damage such as the voltage detection lines 50 coming into contact with each other or the voltage detection lines 50 and the holder 40 coming into contact with each other to cause a short circuit.

Further, when the connection portion 52 of the voltage detection line 50 is broken in this way, the thermal expansion sheet 70 has a plurality of insertion holes into which the connection portion 52 of each voltage detection line 50 connected to the battery cell 30 is individually inserted. It is preferable that 71 is formed. That is, it is preferable that the connection portion 52 of each voltage detection line 50 is inserted into separate insertion holes 71 formed in the thermal expansion sheet 70.

As a result, when the thermal expansion sheet 70 is thermally expanded and the connection portion 52 of each voltage detection line 50 is broken, the tip end portion of the voltage detection line 50 is housed in the insertion hole 71 of the thermal expansion sheet 70. Therefore, contact between the voltage detection lines 50 or between the voltage detection lines 50 and the holder 40 can be more reliably suppressed.

Further, in the above-described embodiment, the configuration in which the upper holder covering the upper part of the battery cell is provided as the holder is illustrated, but the holder may have a configuration in which the battery module can be placed in the battery case. The holder may be provided on the side or bottom side of the battery module, for example. Even in that case, the contact between the holder and the voltage detection line can be suppressed by arranging the thermal expansion sheet between the holder and the voltage detection line provided near the holder.

Further, in the above-described embodiment, the present invention has been described by taking a battery pack mounted on an electric vehicle as an example, but the present invention can also be applied to a battery pack other than that for a vehicle.

1 Vehicle (electric vehicle)
10 Battery pack 11 Pack tray 12 Pack cover 13 Battery case 20 Battery module 30 Battery cell 31 Container 32 Lid member 33 Positive terminal member 34 Negative terminal member 35 Safety valve 40 Holder 41 Upper holder 50 Voltage detection line 51 Wiring part 52 Connection part 70 Thermal expansion Sheet 71 Insertion hole 80 Space

Claims (4)

A battery pack with multiple battery cells housed in a case.
A metal holder for fixing the battery cell to the case is provided, and a voltage detection line connected to each battery cell is provided in the vicinity of the holder, and a voltage detection line is provided between the holder and the voltage detection line. , A battery pack characterized in that a thermal expansion material that expands due to heat generated by the thermal runaway of the battery cell is arranged. The battery pack according to claim 1.
A battery pack characterized in that the connection portion of the voltage detection line with the battery cell is in a relaxed state so that the connection is maintained when the thermal expansion material expands. The battery pack according to claim 1 or 2.
The side of the voltage detection line opposite to the battery cell is covered by the case.
A battery pack characterized in that a space is formed between the voltage detection line and the case. The battery pack according to claim 3.
A battery pack characterized in that the distance between the spaces is at least the thickness of the thermal expansion material after thermal expansion.

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