JP2021193651A - Battery pack - Google Patents

Abstract

To provide a battery pack capable of appropriately suppressing the occurrence of a chain of overheating from among a plurality of secondary batteries.SOLUTION: A set of two secondary batteries 10A to 10E adjacent to each other and connected in series is referred to as a series connection unit. Series connection bus bars 20A to 20D electrically connect positive electrode terminals 15A to 15E of one secondary battery and negative electrode terminals 16A to 16E of the other secondary battery in the series connection unit. A short-circuit bus bar 30 is installed between the negative electrode terminal of one secondary battery and the positive electrode terminal of the other secondary battery in the series connection unit, and is installed between the positive electrode terminal and the negative electrode terminal of each secondary battery. The short-circuit bus bar passes through a flow path of the gas discharged from safety valves 14A to 14E. An insulating portion 40 cuts off the conduction between the terminals by the short-circuiting bus bar while being installed in the short-circuiting bus bar, and short-circuits the secondary battery by being heated and melted.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an assembled battery in which a plurality of secondary batteries are stacked.

An assembled battery in which a plurality of secondary batteries (also referred to as battery cells or short batteries) are stacked and connected is a portable power source such as a personal computer or a mobile terminal, or an EV (electric vehicle), HV (hybrid vehicle), PHV ( It is widely used as a power source for driving vehicles such as plug-in hybrid vehicles. Excessive temperature rise (hereinafter referred to as “overheating”) due to overcharging, heating, or the like may occur in each of the secondary batteries constituting the assembled battery. The larger the amount of charge of the secondary battery, the more likely it is that overheating will occur. Therefore, it is desirable to short-circuit the secondary battery, which may cause excessive temperature rise.

For example, in the assembled battery described in Patent Document 1, of a pair of adjacent secondary batteries, electricity is supplied between the positive electrode charged portion and the negative electrode charged portion, which are not normally connected, according to the temperature rise of the secondary battery. A short-circuit member is provided. As a result, the excessive temperature rise of the secondary battery is suppressed.

JP-A-2017-157274

When an overheating occurs in one of the plurality of secondary batteries constituting the assembled battery, heat is transferred from the secondary battery in which the overheating occurs to the adjacent secondary battery, and as a result, the adjacent secondary battery also becomes excessive. A temperature rise may occur. If excessive temperature rise occurs in a chain among a plurality of secondary batteries, the effect spreads to a large number of secondary batteries constituting the assembled battery. In the assembled battery described in Patent Document 1, the heat generated from the secondary battery is transferred to the adjacent secondary battery before being transferred to the short-circuit member, and as a result, the temperature rises excessively among the plurality of secondary batteries. It can occur in a chain.

A typical object of the present invention is to provide an assembled battery capable of appropriately suppressing the occurrence of chained overheating among a plurality of secondary batteries.

The assembled battery of one aspect disclosed herein is an assembled battery in which a plurality of secondary batteries are stacked, and the secondary battery is provided in a battery case for accommodating a power generation element inside and the battery case. Two two terminals that are adjacent to each other and are connected in series with a positive and negative terminals and a safety valve that discharges gas from the inside of the battery case to the outside when the internal pressure of the battery case rises. When the set of secondary batteries is a series connection unit, the series connection bus bar that electrically connects the positive terminal of one secondary battery and the negative terminal of the other secondary battery in the series connection unit, and the series connection unit. In addition to being installed between the negative terminal of the one secondary battery and the positive terminal of the other secondary battery in the above, the positive terminal and the negative terminal of each of the one secondary battery and the other secondary battery in the above. While being installed between the short-circuit bus bar that is installed between the batteries and passing through the flow path of the gas discharged from the safety valve, and the short-circuit bus bar that is installed in the short-circuit bus bar, the conduction between the terminals of the short-circuit bus bar is cut off. It is provided with an insulating portion that short-circuits the secondary battery by being heated and melted by the gas discharged from the safety valve.

In the assembled battery according to the present disclosure, when an excessive temperature rise occurs in one of the secondary batteries included in the series connection unit, the insulating portion installed in the short-circuit bus bar is heated and melted by the high-temperature gas discharged from the safety valve. Will be done. As a result, the plurality of terminals on which the short-circuit bus bar is erected are conducted, and the other secondary battery included in the series connection unit (that is, the adjacent secondary battery adjacent to the secondary battery in which the overheating has occurred) is conducted. ) Is short-circuited externally. Since the SOC of the adjacent secondary battery short-circuited externally decreases, the temperature rise of the adjacent secondary battery is suppressed. Therefore, it is appropriately suppressed that the overheating occurs in a chain among the plurality of secondary batteries.

It is a top view of the assembled battery 1 of this embodiment. FIG. 1 is a cross-sectional view taken along the line AA in FIG. It is a figure which shows an example of the temperature transition of each secondary battery 10 when the overheating occurs in the 3rd secondary battery 10C in the assembled battery of the comparative example. It is a figure which shows an example of the temperature transition of each secondary battery 10 when the overheating occurs in the 3rd secondary battery 10C in the assembled battery of an Example.

Hereinafter, one of the typical embodiments in the present disclosure will be described in detail with reference to the drawings. Matters other than those specifically mentioned in the present specification and necessary for implementation can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art. In the following drawings, members / parts having the same function are described with the same reference numerals. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations.

As used herein, the term "battery" refers to a general storage device capable of extracting electrical energy, and is a concept including a primary battery and a secondary battery. "Secondary battery" refers to a general storage device that can be charged and discharged repeatedly, and includes so-called storage batteries (that is, chemical batteries) such as lithium ion secondary batteries, nickel hydrogen batteries, and nickel cadmium batteries, as well as electric double layer capacitors and the like. Includes capacitors (ie, physical batteries).

The configuration of the assembled battery 1 of the present embodiment will be described with reference to FIGS. 1 and 2. The assembled battery 1 includes a plurality of secondary batteries (battery cells) 10 (10A to 10E). Each secondary battery 10 is formed in a flat shape (in this embodiment, a substantially rectangular plate shape). The plurality of flat secondary batteries 10 are stacked in a predetermined stacking direction (left-right direction in FIGS. 1 and 2). In the present embodiment, the thickness direction of the flat secondary battery 10 is the stacking direction. In addition, in FIGS. 1 and 2, a gap is provided between the plurality of stacked secondary batteries 10 in order to facilitate understanding of the structure of the assembled battery 1. However, in reality, the plurality of secondary batteries 10 are stacked in close contact with each other without any gaps.

In the present embodiment, the assembled battery 1 provided with the five secondary batteries 10 (secondary batteries 10A, 10B, 10C, 10D, 10E in order from the left side of FIGS. 1 and 2) will be illustrated and described. However, it goes without saying that the number of secondary batteries 10 included in the assembled battery 1 is not limited to five. Further, in the present embodiment, a case where all of the plurality of secondary batteries 10 are connected in series is illustrated. However, the plurality of secondary batteries 10 may include both a set of a plurality of secondary batteries 10 connected in series and a set of secondary batteries 10 connected in parallel.

The secondary battery 10 will be described. In the present embodiment, the configurations of the plurality of secondary batteries 10 are the same, and thus the description will be given collectively. In addition, in FIGS. 1 and 2, the code of the primary secondary battery 10A is "A", the code of each configuration of the secondary battery 10B is "B" at the end, and each configuration of the third secondary battery 10C. "C" is added to the end of the code, "D" is added to the end of the code of each configuration of the 4th secondary battery 10D, and "E" is added to the end of the code of each configuration of the 5th secondary battery 10E. Further, in the present embodiment, a case where a lithium ion secondary battery, which is a kind of secondary battery, is used for the assembled battery 1 is exemplified. However, the secondary battery 10 is not limited to the lithium ion secondary battery. Each secondary battery 10 includes a battery case 11 (11A to 11E), a power generation element 13 (13A to 13E) (see FIG. 2), a positive electrode terminal 15 (15A to 15E), and a negative electrode terminal 16 (16A to 16E). Be prepared.

The battery case 11 houses the power generation element 13 (electrode body and electrolytic solution) in a sealed state inside. The shape of the battery case 11 in this embodiment is a flat square shape. The battery case 11 is provided with a safety valve 14, a positive electrode terminal 15 for external connection, and a negative electrode terminal 16. When the internal pressure of the battery case 11 rises above a predetermined level, the safety valve 14 releases the internal pressure by discharging gas from the inside of the battery case 11 to the outside. The safety valves 14 (14A to 14E) of the present embodiment are formed on the upper lid of the flat square battery case 11. Therefore, the flow path of the gas discharged from the safety valve 14 extends upward from the safety valve 14. In the assembled battery 1 of the present embodiment, the safety valve 14 is provided directly under the short-circuit bus bar 30, which will be described later. Therefore, in FIG. 1, the safety valve 14 is shown by a dotted line. Further, in the present embodiment, the positive electrode terminal 15 and the negative electrode terminal 16 are also provided on the upper lid of the battery case 11. The material of the battery case 11 is preferably a material that is lightweight and has good thermal conductivity. As an example, aluminum having high thermal conductivity and appropriate rigidity is used as the material of the battery case 11 of the present embodiment. However, it is also possible to change the configuration of the battery case. For example, a flexible laminate may be used as the battery case.

In the electrode body, a positive electrode, a negative electrode, and a separator are superposed. In the positive electrode, a positive electrode active material layer is applied to one side or both sides of the positive electrode current collector. A positive electrode current collector terminal is joined to a portion where the positive electrode current collector is exposed without being coated with the positive electrode active material layer. The positive electrode terminal 15 is electrically connected to the positive electrode current collector terminal. In the negative electrode, a negative electrode active material layer is coated on one side or both sides of the negative electrode current collector. A negative electrode current collector terminal is bonded to a portion where the negative electrode current collector is exposed without coating the negative electrode active material layer. The negative electrode terminal 16 is electrically connected to the negative electrode current collector terminal. As the materials and members constituting the electrode body, the same materials and members as those used for a conventional general secondary battery (lithium ion secondary battery in this embodiment) can be used without limitation. Further, the electrolytic solution housed in the battery case 11 together with the electrode body contains a supporting salt in an appropriate non-aqueous solvent, and a conventionally known electrolytic solution can be adopted without particular limitation.

The connection relationship between the plurality of secondary batteries 10 in the assembled battery 1 will be described. Of the plurality of secondary batteries 10 constituting the assembled battery 1, a set of two secondary batteries 10 adjacent to each other and connected in series is called a series connection unit. As described above, the present embodiment illustrates the case where all five secondary batteries 10 are connected in series. In this case, all the sets of the secondary batteries 10 adjacent to each other form the series connection unit. That is, the assembled battery 1 of the present embodiment includes a set of the primary secondary battery 10A and the secondary secondary battery 10B, a set of the secondary secondary battery 10B and the third secondary battery 10C, and a set of the third secondary battery 10C. And a set of 4th secondary battery 10D, and a set of 4th secondary battery 10D and 5th secondary battery 10E are included in 5 series connection units.

Each series connection unit includes a series connection bus bar 20 (20A to 20D). The series connection bus bar 20 electrically connects the positive electrode terminal 15 of one secondary battery 10 and the negative electrode terminal 16 of the other secondary battery 10 in each series connection unit. Specifically, in the example shown in FIG. 1, in the series connection unit including the primary secondary battery 10A and the secondary secondary battery 10B, the positive electrode terminal 15A of the primary secondary battery 10A and the secondary secondary battery 10B The negative electrode terminal 16B is connected by the series connection bus bar 20A. In the series connection unit including the second secondary battery 10B and the third secondary battery 10C, the positive electrode terminal 15B of the secondary battery 10B and the negative electrode terminal 16C of the third secondary battery 10C are connected by the series connection bus bar 20B. Will be done. In the series connection unit including the third secondary battery 10C and the fourth secondary battery 10D, the positive electrode terminal 15C of the third secondary battery 10C and the negative electrode terminal 16D of the fourth secondary battery 10D are connected by the series connection bus bar 20C. Will be done. In the series connection unit including the 4th secondary battery 10D and the 5th secondary battery 10E, the positive electrode terminal 15D of the 4th secondary battery 10D and the negative electrode terminal 16E of the 5th secondary battery 10E are connected by the series connection bus bar 20D. Will be done. In the example shown in FIG. 1, the negative electrode terminal 16A of the primary secondary battery 10A and the positive electrode terminal 15E of the fifth secondary battery 10E are electrically connected to an external device by an external connection bus bar 22.

The assembled battery 1 includes a short-circuit bus bar 30. The short-circuit bus bar 30 is adjacent to the secondary battery 10 in which the overheating has occurred in order to prevent the overheating from occurring in a chain among the plurality of secondary batteries 10 in the assembled battery 1. Moreover, the secondary batteries 10 (adjacent secondary batteries) connected in series are externally short-circuited.

As shown in FIG. 1, the short-circuit bus bar 30 is installed between the negative electrode terminal 16 of one secondary battery 10 and the positive electrode terminal 15 of the other secondary battery 10 in each series connection unit. Specifically, in the example shown in FIG. 1, in the series connection unit including the primary secondary battery 10A and the secondary secondary battery 10B, the negative electrode terminal 16A of the primary secondary battery 10A and the positive electrode of the secondary secondary battery 10B are used. A short-circuit bus bar 30 is installed between the terminals 15B. In the series connection unit including the secondary battery 10B and the tertiary secondary battery 10C, the short-circuit bus bar 30 is erected between the negative electrode terminal 16B of the secondary battery 10B and the positive electrode terminal 15C of the tertiary secondary battery 10C. Will be done. In the series connection unit including the third secondary battery 10C and the fourth secondary battery 10D, the short-circuit bus bar 30 is erected between the negative electrode terminal 16C of the third secondary battery 10C and the positive electrode terminal 15D of the fourth secondary battery 10D. Will be done. In the series connection unit including the 4th secondary battery 10D and the 5th secondary battery 10E, the short-circuit bus bar 30 is erected between the negative electrode terminal 16D of the 4th secondary battery 10D and the positive electrode terminal 15E of the 5th secondary battery 10E. Will be done.

Further, the short-circuit bus bar 30 is installed between the positive electrode terminal 15 and the negative electrode terminal 16 in each secondary battery 10 in each series connection unit. For example, in the series connection unit including the primary secondary battery 10A and the secondary secondary battery 10B, the short-circuit bus bar 30 is installed between the positive electrode terminal 15A and the negative electrode terminal 16A of the primary secondary battery 10A, and is installed. It is installed between the positive electrode terminal 15B and the negative electrode terminal 16B of the secondary secondary battery 10B.

Further, the short-circuit bus bar 30 passes through a flow path of gas discharged from the two safety valves 14 in each series connection unit. For example, in the series connection unit including the primary secondary battery 10A and the secondary secondary battery 10B, the short-circuit bus bar 30 is a flow path of gas discharged from the safety valve 14A of the primary secondary battery 10A (in the present embodiment). , Above the safety valve 14A) and through the flow path of the gas discharged from the safety valve 14B of the secondary battery 10B (above the safety valve 14B in this embodiment).

As shown in FIG. 2, the short-circuit bus bar 30 is provided with an insulating portion 40. The insulating portion 40 cuts off (insulates) the continuity between the terminals of the short-circuit bus bar 30 while being installed in the short-circuit bus bar 30. Further, the insulating portion 40 is heated and melted by the high-temperature gas discharged from the safety valve 14 to start conduction between the terminals by the short-circuit bus bar 30. As a result, the secondary battery 10 is short-circuited externally. The insulating portion 40 has an insulating property and is formed of a material (for example, resin or the like) that melts when heated. In a state where the insulating portion 40 is installed in the short-circuit bus bar 30 (that is, in a state where the insulating portion 40 is not melted), the insulating portion 40 is interposed between the short-circuit bus bar 30 having electrical conductivity and the terminal. As a result of the short-circuit bus bar 30 and the terminals not contacting each other, the conduction between the terminals by the short-circuit bus bar 30 is cut off. When the insulating portion 40 is melted, the short-circuit bus bar 30 and the terminal come into contact with each other, and the terminals are made conductive.

As an example, in the present embodiment, the entire short-circuit bus bar 30 is covered (coated) by the insulating portion 40, so that the conduction by the short-circuit bus bar 30 is cut off. However, it is also possible to change the method of installing the insulating portion 40 on the short-circuit bus bar 30. For example, the insulating portion 40 may be installed not only at the entire short-circuit bus bar 30, but only at a position where the short-circuit bus bar 30 and the terminal are close to each other.

The principle that the chain of overheating is suppressed by the short-circuit bus bar 30 will be described in detail. In the following, of the two secondary batteries 10 included in the series connection unit, the secondary battery 10 in which the overheating has occurred is referred to as an "overheating secondary battery", and the other secondary battery 10 is referred to as an "adjacent secondary battery". It is called "next battery". When high-temperature gas is discharged from the safety valve 14 of the overheated secondary battery, the portion of the short-circuit bus bar 30 installed between the positive electrode terminal 15 and the negative electrode terminal 16 of the overheated secondary battery becomes hot. It is heated by the gas of. The heat is conducted through the short-circuit bus bar 30 to the positive electrode terminal 15 and the negative electrode terminal 16 of the overheated secondary battery, and further to the terminals of the adjacent secondary battery (positive electrode terminal 15 or the negative electrode terminal 16). As a result, at least both terminals of the overheated secondary battery and the insulating portion 40 provided at the terminal portion of the adjacent secondary battery of the short-circuit bus bar 30 are melted. Therefore, both terminals of the overheated secondary battery and the terminals of the adjacent secondary battery are conducted by the short-circuit bus bar 30, and the adjacent secondary battery is short-circuited externally. Since the SOC (State Of Charge) of the adjacent secondary battery short-circuited externally decreases, even if the heat generated by the overheated secondary battery is conducted to the adjacent secondary battery, the excessive temperature rise occurs in the adjacent secondary battery. It's hard to do. Therefore, it is possible to prevent the overheating from occurring in a chain among the plurality of secondary batteries.

For example, when an excessive temperature rise occurs in the primary secondary battery 10A, a secondary battery constituting a series connection unit together with the positive electrode terminal 15A and the negative electrode terminal 16A of the primary secondary battery 10A and the primary secondary battery 10A. The short-circuit bus bar 30 conducts electricity between the positive electrode terminals 15B of 10B. As a result, the secondary secondary battery 10B constituting the series connection unit together with the primary secondary battery 10A is externally short-circuited.

Further, it is assumed that an excessive temperature rise occurs in the third secondary battery 10C. The third secondary battery 10C and the second secondary battery 10B both form a series connection unit. Further, the third secondary battery 10C and the fourth secondary battery 10D also form a series connection unit. Therefore, when an excessive temperature rise occurs in the third secondary battery 10C, the positive electrode terminal 15C and the negative electrode terminal 16C of the third secondary battery 10C, the negative electrode terminal 16B of the secondary secondary battery 10B, and the fourth secondary battery 10D Between the positive electrode terminals 15D of the above, the short-circuit bus bar 30 conducts the conduction. As a result, the secondary secondary battery 10B and the fourth secondary battery 10D adjacent to the tertiary secondary battery 10C are short-circuited externally.

<Comparative test>
With reference to FIGS. 3 and 4, the results of a comparative test for confirming the effect of providing the short-circuit bus bar 30 and the insulating portion 40 on the assembled battery 1 will be described. In this test, two assembled batteries were prepared. The assembled battery of the embodiment is the assembled battery 1 (see FIGS. 1 and 2) of the present embodiment described above. The other comparative example battery does not include the short-circuit bus bar 30 and the insulating portion 40 described above, but all other configurations are the same as those of the battery 1 of the present embodiment. In this test, first, for both the assembled battery of the example and the assembled battery of the comparative example, the SOC of all the secondary batteries was set to 100% in an environment of 25 ° C. Next, by piercing the middle third secondary battery 10C in the five stacked secondary batteries 10 with a nail, the tertiary secondary battery 10C was forcibly overheated. FIG. 3 shows the temperature transition of each secondary battery in the assembled battery of the comparative example. FIG. 4 shows the temperature transition of each secondary battery in the assembled battery of the embodiment.

As shown in FIG. 3, in the assembled battery of the comparative example, the heat generated in the third secondary battery 10C is conducted to the adjacent secondary secondary battery 10B and the fourth secondary battery 10D to conduct the second secondary battery. Overheating also occurred in the secondary battery 10B and the fourth secondary battery 10D. Further, after that, the heat generated in the secondary secondary battery 10B was conducted to the adjacent primary secondary battery 10A, so that the overheating also occurred in the primary secondary battery 10A. Further, the heat generated in the 4th secondary battery 10D is conducted to the adjacent 5th secondary battery 10E, so that the overheating also occurs in the 5th secondary battery 10E. As described above, in the assembled battery of the comparative example, overheating occurred in a chain among the plurality of secondary batteries 10.

As shown in FIG. 4, in the assembled battery of the embodiment, the heat generated in the third secondary battery 10C was conducted to the adjacent secondary secondary battery 10B and the fourth secondary battery 10D, but the secondary secondary battery 10C. In the battery 10B and the fourth secondary battery 10D, an external short circuit occurred due to the short circuit bus bar 30 and the insulating portion 40. Therefore, in the second secondary battery 10B and the fourth secondary battery 10D, the overheating did not occur. Therefore, the overheating did not occur even in the primary secondary battery 10A adjacent to the secondary secondary battery 10B and the fifth secondary battery 10E adjacent to the fourth secondary battery 10D. As described above, it can be seen that in the assembled battery of the embodiment, the chain of overheating was suppressed by using the short-circuit bus bar 30 and the insulating portion 40.

Although the detailed description has been given with reference to specific embodiments, these are merely examples and do not limit the scope of the claims. The techniques described in the claims include various modifications and modifications of the above-described embodiments. For example, in the assembled battery 1 of the above embodiment, a case where all of the plurality of secondary batteries 10 are connected in series is illustrated. However, the plurality of secondary batteries 10 may include both a set of a plurality of secondary batteries 10 connected in series and a set of secondary batteries 10 connected in parallel. Even in this case, the chain of overheating is appropriately suppressed by installing the short-circuit bus bar and the insulating portion in the series connection unit connected in series among the two secondary batteries 10 adjacent to each other. ..

1 set battery 10 secondary battery 11 battery case 13 power generation element 14 safety valve 15 positive electrode terminal 16 negative electrode terminal 20 series connection bus bar 30 short circuit bus bar 40 insulation

Claims (1)

It is an assembled battery in which multiple secondary batteries are stacked.
The secondary battery is
A battery case that houses the power generation element inside,
The positive electrode terminal and the negative electrode terminal provided in the battery case,
A safety valve that discharges gas from the inside of the battery case to the outside when the internal pressure of the battery case rises.
Equipped with
When a set of two secondary batteries adjacent to each other and connected in series is used as a series connection unit,
A series connection bus bar that electrically connects the positive electrode terminal of one secondary battery and the negative electrode terminal of the other secondary battery in the series connection unit.
It is installed between the negative electrode terminal of the one secondary battery and the positive electrode terminal of the other secondary battery in the series connection unit, and the positive electrode terminal of each of the one secondary battery and the other secondary battery. A short-circuit bus bar installed between the and the negative electrode terminal and passing through the flow path of the gas discharged from the safety valve.
An insulating portion that cuts off the conduction between the terminals by the short-circuit bus bar while being installed in the short-circuit bus bar and short-circuits the secondary battery by being heated and melted by the gas discharged from the safety valve.
With a built-in battery.

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