JP2018088356A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack which makes it possible to suppress an external short circuit that would be caused between unit cells to suitably suppress a rapid rise in unit cell temperature owing to a short-circuit current when a sharp conductive foreign material has stuck to the battery pack having a plurality of unit cells connected therein.SOLUTION: A battery pack 1 herein disclosed comprises a plurality of unit cells 10A to 10N arrayed in an array direction x, where positive electrode terminals 12 are connected to corresponding negative electrode terminals 14 through bus-bars 40. Out of the plurality of unit cells, the unit cell 10C having a positive electrode output terminal 12a is disposed at a position other than both ends in the array direction x; the positive electrode terminals 12 of the unit cells 10A and 10N at both ends in the array direction x are connected to the negative electrode terminals 14 of the unit cells 10B and 10M adjacent to the unit cells at both the end; and the negative electrode terminal 14 of the unit cell 10A disposed at one end is electrically connected to the positive electrode terminal 12 of the unit cell 10D separated therefrom through a bus-bar 42.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an assembled battery. Specifically, the present invention relates to a battery pack including a secondary battery as a single battery and a plurality of the single batteries.

  Lithium ion secondary batteries, nickel-metal hydride batteries and other secondary batteries or capacitors and other storage elements are used as single cells, and assembled batteries with multiple such cells are important as on-vehicle power supplies or power supplies for personal computers, portable terminals, etc. The nature is increasing. In particular, an assembled battery using a lithium-ion secondary battery that is lightweight and has a high energy density as a single battery is preferably used for a high-output power source mounted on a vehicle. Such an assembled battery is generally configured by arranging a plurality of rectangular secondary batteries (unit cells) adjacent to each other and electrically connecting the adjacent unit cells via a bus bar (for example, Patent Document 1). .

  An example of such an assembled battery is shown in FIG. The assembled battery 100 includes a plurality of flat rectangular cells 110A to 110E, and the plurality of cells 110A to 110E are arranged along the arrangement direction x so that the wide surfaces (flat surfaces) are adjacent to each other. Has been. In this assembled battery 100, the positive electrode terminal 112 and the negative electrode terminal 114 are electrically connected sequentially by the bus bar 140 between the single cells 110A to 110E. The positive terminal 112 of the unit cell 110A arranged at one end in the arrangement direction x is a positive output terminal 112a that is open so as to be connectable to the outside, and the unit cell 110E arranged at the other end. The negative electrode terminal 114 is a negative output terminal 114a that is open to be connectable to the outside.

  By the way, an assembled battery including this type of secondary battery as a constituent element (unit cell) is required to have a high level of safety as well as excellent battery performance. For this reason, various techniques for improving the safety of the assembled battery have been proposed. For example, if a unit cell generates heat during use, the unit cells may heat each other and the temperature of the entire assembled battery may increase rapidly. Various techniques have been proposed to suppress it.

Japanese Patent Laying-Open No. 2015-125859

However, when the assembled battery is mounted on a moving body such as a vehicle and used, a sharp conductive foreign substance F such as a nail is formed into each unit battery constituting the assembled battery 100 as shown in FIG. In some cases, a plurality of unit cells (unit cells 110A and 110B in FIG. 6) are penetrated so as to penetrate the positive electrode 132 and the negative electrode 135 accommodated in the inside in the stacking direction of the positive and negative electrodes. In such a case, a short-circuit current may be generated in each of the single cells 110A and 110B penetrated by the conductive foreign matter F, and the temperature of the single cells 110A and 110B may increase due to the Joule heat of the short-circuit current. .
At this time, the temperature rise that occurs in the first unit cell 110A arranged at the end in the arrangement direction x is about the same as the temperature rise that occurs when a conductive foreign object pierces the single secondary battery. In the second unit cell 110B adjacent to the first unit cell 110A, the temperature may rise more rapidly than in the first unit cell 110A.

  Specifically, when the conductive foreign matter F penetrates the single cells 110A and 110B in the positive and negative electrode stacking direction, a short-circuit current is generated between the two single cells 110A and 110B via the bus bar 140 and the conductive foreign matter F. An external short circuit in which E1 flows occurs. In this case, two short-circuit currents (about 700 A in total) of the short-circuit current E2 generated inside the second unit cell 110B and the above-described external short-circuit current E1 flow into the negative electrode 135 of the second unit cell 110B. Thus, a rapid temperature rise may occur in the second unit cell 110B. When the conductive foreign substance F penetrates two or more single cells, the rapid temperature caused by the external short circuit also in the second and subsequent single cells (for example, the third single cell 110C). An increase can occur.

  The present invention has been made in view of such a point, and the main object of the present invention is between a plurality of single cells when a sharp conductive foreign object is pierced into an assembled battery in which the plurality of single cells are connected. It is an object of the present invention to provide an assembled battery that can suppress an external short circuit caused by the above-described problem and can suitably suppress an abrupt temperature increase of a single cell due to a short circuit current.

  In order to achieve the above object, an assembled battery having the following configuration is provided by the present invention.

The assembled battery disclosed herein is an assembled battery including a plurality of unit cells, each of which includes a battery in which an electrode body having a structure in which a positive electrode and a negative electrode are stacked is accommodated in a rectangular battery case, A plurality of single cells are arranged adjacent to each other in the same direction as the positive and negative electrode lamination direction of the electrode body of the laminated structure, and a positive electrode terminal and a negative electrode terminal between the plurality of single cells arranged in the arrangement direction are Each is electrically connected via a bus bar.
In the assembled battery disclosed herein, among the plurality of single cells, the single cells including the positive electrode output terminal which is a positive electrode terminal that is open so as to be connectable to the outside are arranged at positions other than both ends in the arrangement direction. The positive terminals of the single cells arranged at both ends in the arrangement direction are connected to the negative terminals of the single cells adjacent to the single cells at both ends via a bus bar and arranged at one end in the arrangement direction. The negative electrode terminal of the unit cell is electrically connected to the positive electrode terminal of the separated unit cell via the bus bar, excluding the unit cell adjacent to the unit cell at the one end.

As a result of repeated experiments and studies to solve the above-described problems, the present inventor conducted such conductivity when a sharp conductive foreign object such as a nail is stuck in an assembled battery including a plurality of unit cells. It has been found that the degree of temperature rise differs depending on the direction in which the foreign object is stuck.
Specifically, when the present inventor conducted an experiment, in the conventional assembled battery as shown in FIG. 5, from the end (the left side of FIG. 5) where the unit cell having the positive electrode output terminal is arranged. When conductive foreign objects are pierced along the arrangement direction, a rapid temperature rise due to an external short circuit is likely to occur, and the conductive material is connected from the end (the right side in FIG. 5) where the unit cell having the negative output terminal is disposed. As a result, a temperature increase due to an external short circuit was suppressed when the foreign object was stuck.

As a result of repeatedly examining the reason why such a result was obtained, the inventor connected the electrode terminal connected by the bus bar to the positive terminal and the negative terminal as in the case where a conductive foreign object was stuck from the right side of FIG. It was found that the short-circuit current of the external short circuit flowing through the bus bar is reduced when the conductive foreign matter is stuck from the direction in which they are arranged in order.
And based on such knowledge, even if conductive foreign matter pierces from any direction on both sides in the arrangement direction of the unit cells, the electrode terminals connected by the bus bar are arranged in the order of the positive electrode terminal and the negative electrode terminal. If the electrical connection of each unit cell can be constructed so that a conductive foreign object is pierced, it is considered that a rapid temperature rise due to an external short circuit can be suppressed, and the specific connection of each unit cell As a result of further examination of the method, an assembled battery having the structure described above has been completed.

It is a perspective view which shows typically the cell which comprises the assembled battery which concerns on one Embodiment of this invention. It is a figure which shows typically the electrode body of the cell which comprises the assembled battery which concerns on one Embodiment of this invention. It is a top view which shows typically the assembled battery which concerns on one Embodiment of this invention. It is a top view which shows typically the assembled battery which concerns on other embodiment of this invention. It is a top view which shows the conventional assembled battery typically. It is explanatory drawing which shows typically the state which the electroconductive foreign material stabbed into the conventional assembled battery.

  Hereinafter, as an example of the assembled battery disclosed herein, a lithium ion secondary battery is used as a single battery, and an assembled battery including a plurality of the lithium ion secondary batteries will be described as an example. Note that in the assembled battery disclosed herein, a battery used as a single battery is not limited to a lithium ion secondary battery, and for example, a nickel hydrogen battery can be used.

  Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action. In addition, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. In addition, matters other than the matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, a configuration and manufacturing method of an electrolyte, a general technique related to construction of a lithium ion secondary battery, etc.) Therefore, it can be grasped as a design matter of a person skilled in the art based on the prior art in the field.

1. First, a single battery constituting the assembled battery according to this embodiment will be described. FIG. 1 is a perspective view schematically showing a unit cell constituting the assembled battery according to this embodiment, and FIG. 2 is a diagram schematically showing an electrode body of the unit battery constituting the assembled battery according to this embodiment. is there.
The unit cell 10 constituting the assembled battery according to the present embodiment is configured by housing the electrode body 30 illustrated in FIG. 2 in the rectangular battery case 50 illustrated in FIG. 1.

(1) Battery Case As shown in FIG. 1, the battery case 50 includes a flat rectangular case main body 52 having an open upper surface and a lid 54 that closes the opening of the upper surface. The battery case 50 is preferably made of, for example, metal or resin. Further, the positive electrode terminal 12 and the negative electrode terminal 14 are provided on the lid 54 that forms the upper surface of the battery case 50. Although not shown, the positive electrode terminal 12 is connected to the positive electrode of the electrode body in the battery case 50, and the negative electrode terminal 14 is connected to the negative electrode.

(2) Electrolytic Solution Inside the battery case 50 described above, an electrolytic solution is accommodated together with the electrode body 30 (see FIG. 2). As the electrolyte, the same electrolyte solution as that conventionally used for a lithium ion secondary battery can be used without particular limitation. For example, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). A non-aqueous electrolyte solution containing lithium hexafluorophosphate (LiPF ₆ ) at a concentration of about 1 mol / L in a mixed solvent (for example, volume ratio 3: 4: 3) can be used.

(3) Electrode body In this embodiment, an electrode body having a structure in which a positive electrode and a negative electrode are laminated is used. As shown in FIG. 2, the electrode body 30 in the present embodiment is configured by laminating a long sheet-like positive electrode 31 and a negative electrode 35 via a separator 38 and then winding the laminated body. It is a wound electrode body. The positive electrode 31 is configured by applying a positive electrode active material layer 33 to the surface of a positive electrode current collector 32 made of aluminum foil or the like, and the negative electrode 35 is formed on the surface of a negative electrode current collector 36 made of copper foil or the like. The negative electrode active material layer 37 containing the negative electrode active material is provided. For the separator 38, a resin porous sheet (film) having a function of electrically insulating the positive electrode 31 and the negative electrode 35, a function of holding a nonaqueous electrolyte, and the like is used.
About each material which comprises this positive electrode 31, the negative electrode 35, and the separator 38, the thing similar to what is used for the electrode body of the conventional general lithium ion secondary battery can be used without a restriction | limiting, and this invention is characterized. Since it is not attached, detailed description is omitted.
In addition, the electrode body should just be comprised by laminating | stacking a positive electrode and a negative electrode, and the laminated electrode body which laminated | stacked the rectangular sheet-like positive electrode and the negative electrode other than the winding electrode body mentioned above alternately Can also be used.

2. FIG. 3 is a plan view schematically showing the assembled battery according to the present embodiment. The assembled battery 1 according to the present embodiment includes a plurality (n) of the unit cells 10 having the above-described configuration, and the unit cells 10A to 10N are arranged adjacent to each other, and each unit cell that is arranged. It is constructed by electrically connecting the positive terminal 12 and the negative terminal 14 of 10A to 10N. Hereinafter, the configuration of the assembled battery according to the present embodiment will be specifically described.

As shown in FIG. 3, in the assembled battery 1 according to the present embodiment, the square unit cells 10 </ b> A to 10 </ b> N are arranged along the arrangement direction x so as to be adjacent to each other. The arrangement direction x of the unit cells 10A to 10N is the same direction as the positive and negative electrode stacking direction (perpendicular to the paper surface of FIG. 2) of the electrode body 30 having the above-described stacked structure.
The unit cells 10A to 10N arranged in the arrangement direction x are electrically connected in series by connecting the positive electrode terminal 12 and the negative electrode terminal 14 to each other by the bus bars 40 and 42. In addition, although illustration is abbreviate | omitted, each cell 10A-10N is restrained along the sequence direction x by the restraint member.

  In the assembled battery 1 according to the present embodiment, the negative electrode terminal 14 of the unit cell 10N arranged at one end in the arrangement direction x is a negative output terminal 14a that is open so as to be connected to the outside. In the present specification, the end portion on which the unit cell 10N having the negative output terminal 14a is disposed is the downstream side in the arrangement direction x, and the opposite end portion is the upstream side in the arrangement direction x. That is, the left side in FIG. 3 is the upstream side in the arrangement direction x, and the right side is the downstream side. And the unit cell arrange | positioned at the edge part of the upstream of the arrangement direction x is called 1st cell unit 10A, and the unit cell arrange | positioned at the edge part of the downstream side is called nth unit cell 10N.

In the assembled battery 1 according to the present embodiment, first, among the plurality of single cells 10A to 10N, the single cell 10C including the positive electrode output terminal 12a that is the positive electrode terminal 12 that is open so as to be connectable to the outside is arranged in the arrangement direction x. Are arranged at positions other than both ends. Specifically, in the present embodiment, unlike the conventional assembled battery shown in FIG. 5, the first unit cell 10A arranged at the end in the arrangement direction x is not provided with a positive electrode output terminal. The positive electrode output terminal 12a is provided in the unit cell 10C arranged third from the upstream side in the arrangement direction x.
As described above, by arranging the unit cells 10C including the positive electrode output terminals 12a at positions other than both ends in the arrangement direction x, the first unit cell 10A arranged at the end on the upstream side in the arrangement direction x. The positive terminal 12 and the negative terminal 14 of the second unit cell 10B adjacent to the first unit cell 10A can be connected via the bus bar 40. Thus, on the upstream side of the assembled battery 1 according to the present embodiment, the electrical connection by the bus bar 40 is constructed so that the positive electrode terminal 12 and the negative electrode terminal 14 are arranged in this order from the upstream side to the downstream side in the arrangement direction x. can do.

  And in the assembled battery 1 which concerns on this embodiment, in order to avoid that the connection by a bus bar is constructed | assembled in order of the negative electrode terminal 14 and the positive electrode terminal 12 in the uppermost stream side of the arrangement direction x, the upstream of the arrangement direction x The negative electrode terminal 14 of the first unit cell 10A disposed at the end of the first cell is not the second unit cell 10B disposed adjacently, but the fourth unit disposed away from the first unit cell 10A. Is electrically connected to the positive electrode terminal 12 of the unit cell 10D via a bus bar 42 extending obliquely.

On the other hand, on the downstream side of the assembled battery 1 according to the present embodiment, the positive electrode terminal 12 of the nth unit cell 10N disposed at the downstream end in the arrangement direction x is adjacent to the nth unit cell 10N. To the negative terminal 14 of the (n-1) th cell 10M.
And on the downstream side of the assembled battery 1 according to the present embodiment, as in the connection between the nth unit cell 10N and the n−1th unit cell 10M, a positive terminal from the downstream side toward the upstream side, Each unit cell is connected via the bus bar 40 so as to be electrically connected in order of the negative electrode terminal, and such electrical connection is repeatedly performed up to the fourth unit cell 10D.

  As described above, in the assembled battery 1 according to the present embodiment, the first cell 10A and the fourth cell 10D are connected to each other in the arrangement direction x from the center except for the connection between the first cell 10A and the fourth cell 10D via the diagonally extending bus bar 42. Each of the unit cells 10A to 10N is sequentially electrically connected in order of the positive electrode terminal 12 and the negative electrode terminal 14.

3. Next, a case where conductive foreign matter is stuck in the assembled battery 1 having the above structure will be described.
According to the assembled battery 1 having such a structure, even when a conductive foreign object is stuck from the upstream side in the arrangement direction x, or when a conductive foreign object is stuck from the downstream side, the occurrence of an external short circuit via the bus bar 40 is prevented. Since it can suppress, generation | occurrence | production of the rapid temperature rise by the said external short circuit can be suppressed. Hereinafter, a case where a conductive foreign material is stuck from the upstream side in the arrangement direction x and a case where a conductive foreign matter is stuck from the downstream side will be described separately.

(1) When conductive foreign matter is stuck from the upstream side in the arrangement direction The conductive foreign matter is stuck in the assembled battery 1 according to the present embodiment from the upstream side in the arrangement direction x. The case where the third cells 10A to 10C are penetrated will be described. At this time, the first to third unit cells 10A to 10C are all electrically connected in order of the positive terminal 12 and the negative terminal 14 from the upstream side to the downstream side in the arrangement direction x. A large short-circuit current through 40 does not flow, and a rapid temperature rise can be prevented.

  In the assembled battery 1 according to this embodiment, as described above, only the first unit cell 10A and the fourth unit cell 10D are in the order of the negative electrode terminal 14 and the positive electrode terminal 12 from the upstream side toward the downstream side. Connected with. However, since two unit cells (second unit cell 10B and third unit cell 10C) are arranged between the first unit cell 10A and the fourth unit cell 10D, the conductive unit It takes some time for the foreign object to reach the fourth unit cell 10D after passing through the first unit cell 10A. Until the conductive foreign matter reaches the fourth unit cell 10D, an internal short circuit occurs in the first unit cell 10A, and the positive and negative electrodes of the first unit cell 10A are damaged. The short circuit current of the external short circuit flowing through the first cell 10A receives a large resistance. Thus, in this embodiment, it is possible to suppress a large external short-circuit current from flowing through the bus bar 42 even in the connection portion between the first unit cell 10A and the fourth unit cell 10D. .

(2) When stuck from the downstream side Next, a conductive foreign matter is stuck from the downstream side in the arrangement direction x, and the conductive foreign matter causes the nth unit cell N and the (n−1) th unit cell 10M. The case where it penetrates will be described. At this time, the n-th unit cell N and the (n-1) -th unit cell 10M are connected in order of the positive electrode terminal 12 and the negative electrode terminal 14 from the downstream side in the arrangement direction x toward the upstream side. Similar to the case where a conductive foreign object is stuck from the upstream side, a rapid temperature increase due to an external short circuit via the bus bar 40 can be suppressed.

  As described above, in the assembled battery 1 according to the present embodiment, a large external short-circuit current via the bus bar 40 even when conductive foreign matter is pierced from either the upstream side or the downstream side in the arrangement direction x. Therefore, it is possible to suppress a rapid temperature rise due to the external short circuit, and to ensure a high level of safety.

  Further, in the assembled battery 1 according to the present embodiment, a location where the connection order of the electrode terminals is switched in the order of the negative electrode terminal 14 and the positive electrode terminal 12 at the central portion in the arrangement direction x, as in the downstream side of the fourth unit cell 10D. When a conductive foreign matter reaches such a location, an external short circuit through the bus bar can occur. However, when a nail, which is a general conductive foreign material, pierces an assembled battery, the possibility that the nail reaches the center of the arrangement direction x is very low, and the arrangement direction in which the connection order of the electrode terminals is temporarily switched. Even when the central portion of x is reached, in the assembled battery according to the present embodiment, a sudden temperature increase does not occur in all the second and subsequent cells as in the conventional assembled battery shown in FIG. Therefore, the temperature rise due to the external short circuit is suppressed more than in the past.

In the present embodiment, the number of unit cells constituting the assembled battery is not particularly limited. However, when adding a unit cell to the assembled battery 1 having the configuration shown in FIG. It is preferable to arrange between the unit cell 10C and the fourth unit cell 10D. As a result, the distance between the first unit cell 10A and the fourth unit cell 10D connected by the bus bar 42 extending obliquely can be further increased, and an external short circuit via the bus bar 42 can be more appropriately suppressed. .
Further, in order to appropriately prevent the conductive foreign matter from reaching the unit cell up to the place where the connection order of the electrode terminals is switched, it is between the third unit cell 10C and the fourth unit cell 10D, or 4 It is preferable to add a cell between the 10th cell 10D and the (n-1) th cell 10M.

4). Assembly Battery According to Other Embodiments Another embodiment of the assembly battery disclosed herein includes an assembly battery 1A having a structure shown in FIG. In the assembled battery 1A having such a structure, a plurality of single cells 10 are arranged adjacent to each other, and the positive cells 12 and the negative electrodes 14 of the adjacent single cells 10 are directly connected via a bus bar 40. Two arrangement units 20A and 20B are provided. Positive electrode output terminals 12a and 12b and negative electrode output terminals 14a and 14b are provided at both ends in the arrangement direction x of each of the unit cell arrangement units 20A and 20B.
In the assembled battery 1 shown in FIG. 4, the unit cell arrangement units 20A and 20B are inverted and arranged so that the positive electrode output terminals 12a and 12b are adjacent to each other, and the negative electrode of one unit cell arrangement unit 20A The output terminal 14a and the positive electrode output terminal 12b of the other unit cell array unit 20B are electrically connected directly via an obliquely extending bus bar 42.

By connecting the two unit cell arrangement units 20A and 20B in this way, the positive electrode output terminals 12a are arranged at positions other than both ends in the arrangement direction x and arranged at both ends in the arrangement direction x, as in the above-described embodiment. The positive electrode terminal 12 of the unit cell 10 is connected to the negative electrode terminal 14 of the unit cell 10 adjacent to the unit cell 10 at both ends via the bus bar 40 and is disposed at one end in the arrangement direction x. The negative electrode terminal 14 of the unit cell 10 (the negative electrode output terminal 14a of the unit cell array unit 20A) is electrically connected to the separated positive electrode terminal 12 (the positive electrode output terminal 12b of the unit cell array unit 20B) via the bus bar 42. The assembled battery 1 </ b> A can be constructed.
Thereby, even when a conductive foreign object is stuck from any direction of the arrangement direction x, it is possible to suppress a large short circuit current from flowing through the bus bar 40.

  In FIG. 4, each single cell array unit 20A, 20B includes five single cells 10. However, the number of single cells constituting the single cell array unit is not particularly limited. For example, an assembled battery used as a general on-vehicle power source is composed of 20 to 40 (for example, 30) unit cells, and when constructing such an assembled battery, each unit cell array unit Is preferably composed of 10 to 20 (for example, 15) single cells. When a single cell arrangement unit is constructed with such a large number of single cells, it is possible to prevent conductive foreign matter from reaching the central part of the assembled battery where the connection order of the electrode terminals is switched in the order of the negative electrode terminal and the positive electrode terminal. it can.

[Test example]
Hereinafter, test examples relating to the present invention will be described, but the following test examples are not intended to limit the present invention.

1. Production of battery pack of test example (1) Test examples 1 and 2
A positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), a conductive material (acetylene black), and a binder (PVDF) were mixed at a mass ratio of 94: 3: 3. A rectangular positive electrode was produced in which the positive electrode active material layer was formed on both surfaces of a positive electrode current collector (aluminum foil) having a thickness of 12 μm. On the other hand, a negative electrode active material layer in which a negative electrode active material (graphite), a thickener (CMC), and a binder (SBR) are mixed at a mass ratio of 98: 1: 1 is a negative electrode having a thickness of 10 μm. A rectangular negative electrode formed on both surfaces of the current collector (copper foil) was produced.
Next, a wound electrode body including the positive electrode, the negative electrode, and the separator described above is manufactured, and the wound electrode body is housed in a rectangular battery case as shown in FIG. A single cell was prepared. Then, five unit cells prepared in the above-described procedure are prepared, and the five unit cells are connected through the bus bar in the same procedure as in the embodiment shown in FIG. Built.

(2) Test examples 3, 4
After producing five unit cells in the same procedure as in Test Examples 1 and 2, the assembled cells of Test Examples 3 and 4 were connected by connecting the five unit cells via a bus bar as shown in FIG. It was constructed.

2. Evaluation Test The following nail penetration test was performed on the assembled batteries of Test Examples 1 to 4.
First, in a temperature environment of 25 ° C., the assembled battery of each of the above-described test examples is adjusted to a SOC 100% charge state, two thermocouples are attached to the outer surface of the battery case, and the cell arrangement direction x A tungsten nail was stabbed along. The nail had a diameter of 6 mm and a tip angle of 60 °, and was pierced perpendicularly at a speed of 25 mm / sec near the center of the wide surface of the rectangular battery case. In Test Examples 1 and 3, a nail is pierced from the upstream side in the arrangement direction to penetrate the first unit cell and the second unit cell. In Test Examples 2 and 4, a nail is pierced from the downstream side to the fifth cell. The unit cell and the fourth unit cell were passed through.
And while the nail was pierced, the temperature of each single cell which comprises an assembled battery was measured with the above-mentioned thermocouple. Of the measured temperatures, the highest temperature is shown in Table 1 as the maximum temperature of the cell.

3. Evaluation Results From the results shown in Table 1, in Test Example 2 and Test Example 4 where the nail was pierced from the downstream side to the upstream side in the arrangement direction x, the maximum temperature of the unit cell was about 450 ° C. in both test examples. The temperature rise was similar to that caused when a nail was stuck in a single secondary battery. Therefore, in both the assembled battery shown in FIG. 3 and the assembled battery shown in FIG. 5, when a conductive foreign object is stuck from the downstream side in the arrangement direction, a large external short circuit does not occur, and a rapid temperature It was confirmed that the increase was suppressed.

  On the other hand, when the test example 1 in which the nail was stabbed from the upstream side to the downstream side in the arrangement direction x was compared with the test example 3, the maximum temperature was 440 ° C. in the test example 1, and the test example 2 in which the nail was stabbed from the downstream side In contrast to Test Example 4, the temperature increased rapidly to 630 ° C. in Test Example 3. From this, when a conductive foreign object such as a nail is pierced from the direction in which the electrode terminal is connected in the order of the negative electrode terminal and the positive electrode terminal as in Test Example 3, the temperature rises rapidly due to an external short circuit. It was found that there is a risk of occurrence. And in the assembled battery in which the electrical connection by the bus bar is constructed as shown in FIG. 3, even if the nail is pierced from either the upstream side or the downstream side in the arrangement direction, the temperature rises rapidly due to the external short circuit. It was confirmed that it could be prevented.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1, 1A, 100 assembled battery 10, 10A-10N, 110A-110E single battery 12, 112 positive terminal 12a, 12b, 112a positive output terminal 14, 114 negative terminal 14a, 14b, 114a negative output terminal 20A, 20B single battery array Unit 30 Electrode body 31, 132 Positive electrode 32 Positive electrode current collector 33 Positive electrode active material layer 35, 135 Negative electrode 36 Negative electrode current collector 37 Negative electrode active material layer 38 Separator 40, 42, 140 Bus bar 50 Battery case 52 Case body 54 Lid body E1 External short-circuit current E2 Internal short-circuit current x arrangement direction

Claims (1)

A battery in which an electrode body having a structure in which a positive electrode and a negative electrode are stacked is housed in a rectangular battery case is a single battery, and an assembled battery including a plurality of the single batteries,
The plurality of single cells are arranged adjacent to each other in the same direction as the positive and negative electrode lamination direction of the electrode body of the laminated structure, and a positive electrode terminal and a negative electrode between the plurality of single cells arranged in the arrangement direction The terminals are electrically connected to each other via the bus bar,
Here, out of the plurality of unit cells, the unit cell provided with a positive electrode output terminal that is a positive electrode terminal that is open to be connectable to the outside, is arranged at a position other than both ends in the arrangement direction,
The positive terminals of the single cells arranged at both ends in the arrangement direction are connected to the negative terminals of the single cells adjacent to the single cells at both ends via the bus bar,
The negative terminal of the unit cell arranged at one end in the arrangement direction is electrically connected to the positive terminal of the separated unit cell via the bus bar, excluding the unit cell adjacent to the unit cell at the one end. Assembled battery.

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