WO2016152189A1

WO2016152189A1 - Battery module

Info

Publication number: WO2016152189A1
Application number: PCT/JP2016/050565
Authority: WO
Inventors: 直人守作; 浩生植田; 加藤　崇行
Original assignee: 株式会社豊田自動織機
Priority date: 2015-03-25
Filing date: 2016-01-08
Publication date: 2016-09-29
Also published as: JP6488812B2; JP2016181475A

Abstract

The battery module 1 contains an array 2 comprising a plurality of battery cells 11 that have been arrayed. Housed inside a case 12 of each of the plurality of battery cells 11 are: an electrode assembly body 13 comprising a positive electrode 21 and a negative electrode 22 layered with a separator 23 interposed therebetween; an electrolyte solution added with an overcharge additive for generating a gas by starting a reaction when the battery cell 11 has reached an overcharged state; and a current interruption device 26 for interrupting a charging current when, due to the gas generation, the internal pressure of the case 12 has reached a threshold value or greater. Fixed on an outer side surface 12a of the case 12 is a rigid member 31 for restricting, with respect to a lower limit value of the amount of gas generated which has been set beforehand according to the amount of overcharge additive added, the expansion of the case 12 in such a manner that the internal pressure of the case 12 is equal to or greater than the operating pressure of the current interruption device 26.

Description

Battery module

The present invention relates to a battery module.

Conventionally, a battery module in which a plurality of battery cells such as lithium ion secondary batteries are arranged is known. As such a battery module, there is a configuration that suppresses fluctuations in characteristics such as internal resistance in a battery cell by sandwiching an array of battery cells with a restraint such as a metal plate and restraining it with a constant load. . For example, in the assembled battery described in Patent Document 1, a metal band having bent portions at both ends is fixed to an end plate, and the battery block is constrained in the stacking direction by the end plate.

JP 2013-055069 A

The battery cell incorporated in the battery module as described above includes a current interrupt device (CID: Current) that interrupts the current path of the battery cell when gas is generated in the battery cell case due to an abnormality such as overcharge. (Interrupt Device) is built-in. The current interrupt device operates to physically interrupt the current path of the battery cell when the internal pressure of the case reaches a preset threshold value due to generation of gas.

However, in a battery cell equipped with a current interrupt device, expansion of the case due to gas becomes a problem. That is, if the case expands easily when gas is generated, the increase in the internal pressure of the case with respect to the amount of gas generated becomes more gradual than the design value, and the current interrupt device may not operate at an appropriate timing. For such a problem, it is conceivable to simply increase the thickness of the case, but there is a problem in that the volume in the case is reduced and the design of electrodes and the like in the battery cell is limited.

The present invention has been made to solve the above-described problems, and provides a battery module capable of operating a current interrupting device at an appropriate timing even when a binding load is not applied to an array of battery cells. The purpose is to provide.

In order to solve the above problems, a battery module according to one aspect of the present invention is a battery module including an array formed by arranging a plurality of battery cells, and a battery cell case is provided with a separator interposed therebetween. An electrode assembly formed by laminating a positive electrode and a negative electrode, an electrolyte solution to which an overcharge additive that starts a reaction and generates gas when the battery cell is overcharged, and gas generation A current interrupting device that interrupts the charging current when the internal pressure of the case rises above a threshold, and a gas generation amount that is preset according to the amount of overcharge additive added to the outer surface of the case A rigid member that regulates the expansion of the case is fixed so that the internal pressure of the case becomes equal to or higher than the operating pressure of the current interrupting device with respect to the lower limit value.

In this battery module, a rigid member that restricts deformation of the case is fixed to the outer surface of the case in the battery cell. Since the rigidity of the case is increased by the rigid member, the expansion of the case when gas is generated is restricted. Therefore, the internal pressure of the case at the time of gas generation can be increased according to the set value, and the current interrupting device can be operated at an appropriate timing. In addition, since the rigid member is disposed on the outer surface of the case, the capacity in the case is not reduced, and the design of the electrodes and the like in the battery cell is prevented from being restricted.

Further, the rigid member is arranged on the outer surface of the case in the arrangement direction so as to overlap with the electrode assembly when viewed from the arrangement direction of the battery cells in the arrangement. In the portion where the electrode assembly is disposed, the case is likely to expand during overcharging. Therefore, by disposing the rigid member so as to overlap the electrode assembly, the expansion of the case can be more reliably regulated.

Further, the rigid member extends between a pair of edges that form opposite sides on the outer surface. A corner portion is formed at the edge of the outer surface by the adjacent outer surfaces. For this reason, the edge part of an outer surface is a part with high rigidity compared with the center part of an outer surface, and a deformation | transformation is hard to produce. Therefore, even when expansion occurs in the case, it is possible to prevent the rigid member from being detached from the outer surface of the case, and it is possible to maintain the regulation of expansion of the case.

Also, the rigid member extends between a pair of outer surfaces adjacent to the edge. In this case, it is possible to more suitably prevent the rigid member from being detached from the outer side surface of the case, and the effect of restricting the expansion of the case can be further maintained.

Also, the rigid member is fixed to the outer surface by adhesion. Thereby, a rigid member can be fixed to an outer surface easily and firmly.

According to this battery module, the current interrupting device can be operated at an appropriate timing even when a restraint load is not applied to the battery cell array.

It is the schematic which shows one Embodiment of a battery module. It is sectional drawing which shows the internal structure of the battery cell which comprises the battery module shown in FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 2. It is a schematic perspective view which shows the fixed state of the rigid member with respect to the case of a battery module. It is a graph which shows the effect of a battery module. It is a schematic perspective view which shows the modification of a battery module. It is a schematic perspective view which shows another modification of a battery module. It is a schematic perspective view which shows another modification of a battery module.

Hereinafter, preferred embodiments of the battery module will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a battery module. As shown in the figure, the battery module 1 includes an array 2 formed by arranging a plurality of battery cells 11. In the array body 2, a plurality (seven bodies in this embodiment) of battery cells 11 are arrayed via the heat transfer plate 5. The array body 2 is housed in a rectangular housing 4 made of metal without applying a restraining load due to an end plate or the like.

The battery cell 11 is, for example, a lithium ion secondary battery. For example, as shown in FIGS. 2 and 3, the battery cell 11 includes a hollow case 12 having a substantially rectangular parallelepiped shape and an electrode assembly 13 accommodated in the case 12. The case 12 is formed of a metal such as aluminum, for example, and an organic solvent-based or non-aqueous electrolyte is injected into the case 12, for example. As shown in FIG. 2, the positive terminal 15 and the negative terminal 16 are disposed on the top surface of the case 12 so as to be separated from each other. The positive electrode terminal 15 is fixed to one side in the width direction on the top surface of the case 12 via the insulating member 17, and the negative electrode terminal 16 is fixed to the other side in the width direction on the top surface of the case 12 via the insulating member 18. Has been.

As shown in FIG. 3, the electrode assembly 13 includes, for example, a positive electrode 21, a negative electrode 22, and a bag-like separator 23 disposed between the positive electrode 21 and the negative electrode 22. In the electrode assembly 13, the positive electrode 21 is accommodated in the separator 23, and the positive electrode 21 and the negative electrode 22 are alternately stacked via the separator 23 in this state.

The positive electrode 21 has a metal foil 21a made of, for example, aluminum foil, and a positive electrode active material layer 21b formed on both surfaces of the metal foil 21a. The positive electrode active material layer 21b is formed including a positive electrode active material and a binder. Examples of the positive electrode active material include composite oxide, metallic lithium, and sulfur. The composite oxide includes, for example, at least one of manganese, nickel, cobalt, and aluminum and lithium. A tab 21 c is formed on the upper edge portion of the positive electrode 21 corresponding to the position of the positive electrode terminal 15. The tab 21 c extends upward from the upper edge portion of the positive electrode 21 and is connected to the positive electrode terminal 15 via the conductive member 24.

Meanwhile, the negative electrode 22 includes a metal foil 22a made of, for example, copper foil, and a negative electrode active material layer 22b formed on both surfaces of the metal foil 22a. The negative electrode active material layer 22b is formed including a negative electrode active material and a binder. Examples of the negative electrode active material include carbon such as graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, alkali metals such as lithium and sodium, metal compounds, SiOx (0.5 ≦ x ≦ 1.5 ) And the like, and boron-added carbon. A tab 22 c is formed at the upper edge of the negative electrode 22 in correspondence with the position of the negative electrode terminal 16. The tab 22 c extends upward from the upper edge portion of the negative electrode 22, and is connected to the negative electrode terminal 16 through the conductive member 25.

The separator 23 is formed in a bag shape, for example, and accommodates only the positive electrode 21 therein. Examples of the material for forming the separator 23 include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven fabric or a nonwoven fabric made of polypropylene, polyethylene terephthalate (PET), methylcellulose, and the like. The separator 23 is not limited to a bag shape, and a sheet shape may be used.

In the battery cell 11, an overcharge additive is added to the electrolyte injected into the case 12. The overcharge additive is an additive that starts a reaction and generates gas when the battery cell 11 is overcharged. As the overcharge additive, for example, cyclohexylbenzene (CHB), biphenyl (BP), or a mixture thereof is used.

In addition, as shown in FIG. 2, a current interrupt device 26 is provided in the case 12 to interrupt the charging current when the internal pressure of the case 12 rises above a threshold due to the gas generated by the reaction of the overcharge additive. ing. The current interrupt device 26 has an energization path (not shown), and the negative electrode terminal 16 and the conductive member 25 are connected in series by the energization path. When the internal pressure of the case 12 rises above a preset operating threshold value (operating pressure), the current interrupting device 26 physically interrupts the energization path and energizes the electrode assembly 13 and the negative electrode terminal 16. Cut off. The threshold value of the internal pressure of the case 12 set by the current interrupt device 26 is appropriately set based on conditions such as the amount of overcharge additive added to the battery cell 11 and the volume in the case 12.

In a battery cell equipped with such a current interrupting device, expansion of the case due to the generated gas becomes a problem. In a battery module of a type in which a restraint load by a restraint member is applied to the array body, expansion of the case is suppressed by the action of the restraint load even when gas is generated in the battery cell case. Therefore, the internal pressure of the case increases according to the amount of gas generated, and the current interrupt device operates when the internal pressure becomes equal to or greater than the threshold value.

On the other hand, in the battery module 1 that does not apply the restraining load by the restraining member to the array body 2 as in the present embodiment, it is considered that the case 12 easily expands when gas is generated. For this reason, the increase in the internal pressure of the case 12 with respect to the amount of gas generated becomes more gradual than the design value, and the current interrupt device 26 may not operate at an appropriate timing.

Therefore, in the battery module 1, as shown in FIG. 4, a rigid member 31 is disposed on the outer surface of the case 12 as a member that restricts the expansion of the case 12. As shown in the figure, the rigid member 31 is, for example, a flat plate formed in a rectangular shape. Examples of the material for forming the rigid member 31 include a metal material having a higher Young's modulus than the material for forming the case 12. For example, when the forming material of the case 12 is aluminum, iron can be used as the forming material of the rigid member 31. By using a metal material, the rigid member 31 itself can be provided with heat dissipation.

The length of one side 31a of the rigid member 31 is substantially the same as the lateral width W1 of the case 12. Further, the length of the other side 31b of the rigid member 31 is smaller than the height of the case 12, and for example, substantially coincides with the vertical width W2 (see FIG. 2) of the electrode assembly 13. The thickness of the rigid member 31 is approximately the same as the thickness W3 (see FIG. 3) of the wall portion of the case 12, for example.

The rigid member 31 is disposed on each of the two

outer surfaces

12a and 12a in the arrangement direction of the case 12 and overlaps with the electrode assembly 13 in the case 12 when viewed from the arrangement direction of the battery cells 11 in the arrangement 2. 12 is fixed at a position near the bottom. In the present embodiment, the rigid member 31 overlaps at least the region where the positive electrode active material layer 21b and the negative electrode active material layer 22b face each other (see FIG. 3) in the electrode assembly 13 when viewed from the arrangement direction of the array 2. Are arranged as follows. Since the rigid member 31 is disposed on each of the two

outer surfaces

12a and 12a in the arrangement direction of the case 12, when viewed from the width direction of the array 2, the electrode assembly 13 in the case 12 includes the rigid member 31, It is in the state located between 31.

Further, as described above, the length of the one side 31a of the rigid member 31 substantially matches the lateral width W1 of the case 12. For this reason, the rigid member 31 extends between a pair of edges forming opposite sides on the outer surface 12a, that is, over the

widthwise edges

12k and 12k on the outer surface 12a. The end surface 31c in the width direction of the rigid member 31 may be flush with the outer surface 12b (here, the outer surface in the width direction of the case 12) adjacent to the outer surface 12a, and the edge in the width direction of the outer surface 12a. It may be located slightly inside the portion 12k. When the end surface 31c in the width direction of the rigid member 31 is positioned inside the edge portion 12k in the width direction of the outer surface 12a, the distance from the end surface 31c to the edge portion 12k when viewed from the arrangement direction of the array 2 is The thickness of the wall portion of the case 12 is preferably equal to or less than W3.

Further, for example, a double-sided adhesive tape 32 is used for fixing the rigid member 31 and the outer surface 12a of the case 12. Examples of the double-sided adhesive tape 32 include a double-sided tape in which the base material is composed of a polyethylene terephthalate (PET) film, a polyamide film, and the like, and the adhesive is composed of an acrylic pressure-sensitive adhesive, a urethane-based adhesive, or the like. The double-sided adhesive tape 32 preferably has heat resistance. In the present embodiment, the double-sided adhesive tape 32 is attached to the inside of the edge of the rigid member 31 with a predetermined width along the one side 31 a and the other side 31 b of the rigid member 31. The outer surface 12a is firmly fixed. In the present embodiment, the double-sided adhesive tape 32 is attached only to the edge of the rigid member 31, and the central side of the rigid member 31 is free with respect to the outer surface 12 a of the case 12. .

As described above, in the battery module 1, the rigid member 31 that restricts deformation of the case 12 is fixed to the outer surface 12 a of the case 12 in each battery cell 11 constituting the array 2. Since the rigidity of the case 12 is enhanced by the rigid member 31, expansion of the case 12 when gas is generated is restricted. Therefore, it becomes possible to raise the internal pressure of the case 12 at the time of gas generation according to the set value, and the current interrupting device 26 can be operated at an appropriate timing. Further, since the rigid member 31 is disposed on the outer surface 12a of the case 12, the capacity in the case 12 is not reduced, and the design of the electrodes and the like in the battery cell 11 is also prevented from being restricted.

FIG. 5 is a graph showing the effect of the battery module. In the figure, the horizontal axis represents the gas generation amount and the vertical axis represents the internal pressure of the case. Assuming that the array is completely constrained (the case does not deform due to the constraining load from the constraining member), the volume of the case is always constant. For this reason, as shown in the graph A, the rate of increase of the internal pressure of the case with respect to the amount of gas generated is the highest. Note that when a restraining load is applied to the array, it is necessary to set a lower limit value of the gas generation amount smaller in advance than when a restraining load is not applied to the array.

On the other hand, when no restraining load is applied to the array and the rigid member is not fixed to the outer surface of the case, the case easily expands when gas is generated, and the volume of the case increases with expansion. For this reason, as shown in the graph B, the rate of increase of the internal pressure of the case with respect to the amount of gas generated is the lowest. Therefore, at the lower limit value of the gas generation amount, the internal pressure of the case does not reach the operating threshold value of the current interrupt device, and the current interrupt device may not operate.

On the other hand, when no rigid load is applied to the array body 2 and the rigid member 31 is fixed to the outer surface 12a of the case 12 as in the battery module 1 of the present embodiment, the expansion of the case 12 when gas is generated. Is restricted by the rigid member 31, and an increase in the volume of the case 12 is suppressed. For this reason, as shown in the graph C, the increase rate of the internal pressure of the case with respect to the amount of gas generated is higher than that in the graph B. Therefore, by restricting the expansion of the case 12 by the rigid member 31 so that the internal pressure of the case 12 becomes equal to or higher than the operating threshold value of the current interrupt device 26 at the lower limit value of the gas generation amount, no constraint load is applied to the array 2. Even in this case, the current interrupt device 26 can be operated at an appropriate timing.

In the battery module 1, the rigid member 31 is disposed on the outer surface 12 a so as to overlap the electrode assembly 13 when viewed from the arrangement direction of the battery cells 11 in the array 2. Since the area where the electrode assembly 13 is disposed has a larger area than the other surfaces, the case 12 is likely to expand during overcharging. Therefore, by disposing the rigid member 31 so as to overlap the electrode assembly 13, the expansion of the case 12 can be more reliably regulated.

Further, in the battery module 1, the rigid member 31 extends between the pair of

edge portions

12k, 12k that form opposite sides on the outer surface 12a. A corner portion is formed on the edge portion 12k of the outer side surface 12a by the adjacent

outer side surfaces

12a and 12b. For this reason, the edge part 12k of the outer side surface 12a is a part with high rigidity compared with the center part of the outer side surface 12a, and a deformation | transformation is hard to produce. In the battery module 1, the rigid member 31 extends between the

edges

12k and 12k and is fixed to the outer surface 12a at the positions of the

edges

12k and 12k. Therefore, even when the case 12 is inflated, it is possible to prevent the rigid member 31 from being detached from the outer surface 12a of the case 12, and the effect of restricting the expansion of the case 12 can be maintained.

In the battery module 1, the rigid member 31 is fixed to the outer surface 12 a by the double-sided adhesive tape 32. Thereby, the rigid member 31 can be fixed to the outer surface 12a easily and firmly. Moreover, in the battery module 1, the double-sided adhesive tape 32 is affixed only to the edge of the rigid member 31, and the central side of the rigid member 31 is free with respect to the outer surface 12a of the case 12 (see FIG. 4). With such a configuration, the rigidity member 31 can be fixed to the edge portion 12k of the outer surface 12a having a relatively high rigidity to substantially improve the rigidity of the case 12, while the center side of the rigidity member 31 is located with respect to the outer surface 12a. By being free, when the case 12 is inflated, the center side of the rigid member 31 can follow the deformation of the case 12. Therefore, stress concentration on the edge of the rigid member 31 can be suppressed, and the rigid member 31 can be more reliably prevented from being detached from the outer surface 12a of the case 12.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the rigid member 31 is formed of a metal material having a higher Young's modulus than the forming material of the case 12, but the rigid member 31 is formed of a metal material or a resin material having a lower Young's modulus than the forming material of the case 12. May be formed. When the rigid member 31 is formed of a metal material having a high Young's modulus, the deformation of the case 12 can be regulated by the rigidity of the rigid member 31 itself. On the other hand, when the rigid member 31 is formed of a metal material having a low Young's modulus, the deformation followability of the rigid member 31 with respect to the deformation of the case 12 can be ensured. Therefore, it is possible to prevent the rigid member 31 from being detached from the outer side surface 12a of the case 12, and the effect of restricting the expansion of the case 12 can be maintained.

In the above embodiment, the double-sided adhesive tape 32 is attached only to the edge side of the rigid member 31, but the entire surface of the rigid member 31 may be attached to the outer surface 12 a by the double-sided adhesive tape 32. Further, when the entire surface of the rigid member 31 is attached to the outer surface 12a by the double-sided adhesive tape 32, the adhesive force of the double-sided adhesive tape 32 on the edge side of the rigid member 31 is set to the adhesive force of the double-sided adhesive tape 32 on the center side. Can be high. The fixing of the rigid member 31 and the case 12 is not limited to the double-sided adhesive tape 32, and may be performed using other fixing methods such as welding.

Also, various deformations can be applied to the shape of the rigid member 31. For example, as shown in FIG. 6, a plurality (here, two) of strip-shaped rigid members 31 may be arranged at a predetermined interval in the height direction of the outer surface 12a. Also in this case, it is preferable that each rigid member 31 overlaps the electrode assembly 13 when viewed from the arrangement direction of the battery cells 11 in the arrangement 2. In addition, the double-sided adhesive tape 32 is preferably disposed only at the edge of each rigid member 31. Thereby, the effect similar to the said embodiment is obtained. In the example of FIG. 6, the band-shaped rigid members 31 extend substantially parallel to each other, but may be extended so that the rigid members 31 intersect each other.

For example, as shown in FIG. 7, a flange 33 along the outer surface 12b is provided on the rigid member 31, and the rigid member 31 extends between a pair of

outer surfaces

12b and 12b adjacent to the outer surface 12a with the edge 12k interposed therebetween. It may be extended. Even in such a configuration, the rigid member 31 and the case 12 can be fixed in the vicinity of the corner formed by the adjacent

outer surfaces

12a and 12b. In addition, in this configuration, the adhesive surface between the main surface 34 and the outer surface 12a of the rigid member 31 and the adhesive surface between the flange 33 and the outer surface 12b intersect each other. Therefore, the rigid member 31 can be more preferably prevented from being detached from the case 12, and the effect of restricting the expansion of the case 12 can be further maintained.

Further, when the heat transfer plate 5 is not interposed between the

battery cells

11 and 11, for example, as shown in FIG. 8, the flange portion 33 of the rigid member 31 extends along the outer surface 12 b of the adjacent battery cell 11. It may be provided. In this case, the same effect as that of the embodiment shown in FIG. 7 is obtained. Further, since the number of parts of the rigid member 31 can be reduced, the battery module 1 can be reduced in size and cost.

DESCRIPTION OF SYMBOLS 1 ... Battery module, 2 ... Array, 11 ... Battery cell, 12 ... Case, 12a ... Outer surface, 12b ... Outer surface, 12k ... Edge, 13 ... Electrode assembly, 21 ... Positive electrode, 22 ... Negative electrode, 23 ... Separator, 26 ... current interrupt device, 31 ... rigid member.

Claims

A battery module comprising an array formed by arranging a plurality of battery cells,
In the case of the battery cell,
An electrode assembly formed by laminating a positive electrode and a negative electrode via a separator;
An electrolyte solution to which an overcharge additive that starts a reaction and generates gas when the battery cell is overcharged, and
A current interrupt device that interrupts a charging current when the internal pressure of the case rises above a threshold value due to the generation of the gas,
On the outer surface of the case,
The expansion of the case is regulated so that the internal pressure of the case becomes equal to or higher than the operating pressure of the current interrupting device with respect to a lower limit value of the gas generation amount set in advance according to the addition amount of the overcharge additive. A battery module in which a rigid member is fixed.
2. The battery module according to claim 1, wherein the rigid member is disposed on an outer surface of the case in the arrangement direction so as to overlap the electrode assembly when viewed from the arrangement direction of the battery cells in the array.
The battery module according to claim 1 or 2, wherein the rigid member extends between a pair of edges forming opposite sides on the outer surface.
The battery module according to claim 3, wherein the rigid member extends between a pair of outer surfaces adjacent to the edge.
The battery module according to any one of claims 1 to 4, wherein the rigid member is fixed to the outer surface by adhesion.